Ebook Transplant infections (3rd edition): Part 2

58202_ch22.qxd

2/1/10

SECTION

8:49 PM

Page 311

V ■ Viral Infections

CHAPTER

Cytomegalovirus Infection after
Stem Cell Transplantation

22

MORGAN HAKKI, MICHAEL J. BOECKH, PER LJUNGMAN

VIRUS STRUCTURE AND REPLICATION
Human cytomegalovirus (HCMV) is a member of the beta
(␤ ) subfamily of the herpesviridae, along with human herpesvirus (HHV)-6 and HHV-7. The CMV virion is composed
of a double-stranded DNA genome encased in an icosahedral
capsid. Surrounding the capsid is a region known as the tegument (or matrix) and an outermost lipid membrane containing
viral glycoproteins, which mediate viral binding to and entry
into the host cell.
The genome contains approximately 230 thousand base
pairs of DNA that encode approximately 200 proteins, and is
organized into long and short unique segments that are

flanked by inverted repeats (1,2). CMV genes are named based
on their position within each segment of the genome. For example, UL97 is the 97th open reading frame (ORF) in the
unique long segment. Some genes also have names based on
historical usage or homologies to genes of other herpesviruses;
UL55, for example, is also known as glycoprotein B.
CMV grows in a limited number of cell lines in the laboratory, such as diploid human fibroblasts, endothelial cells,
and macrophages. During human infection, however, CMV
has been found in a wide range of cells, including endothelial
cells, epithelial cells, blood cells including neutrophils, and
smooth muscle cells (3). The presence of CMV in these cells
may be due to active replication within the cell, phagocytosis
of CMV proteins, or abortive (incomplete) replication, and
likely contributes to dissemination and transmission.
The ability to persist in a latent state in which evidence of
viral replication is undetectable but replication-competent
virus is present is a hallmark of herpesviruses. In the case of
CMV, little is known about the site or mechanisms of latency.
Since CMV can be transmitted from seropositive blood donors,
a blood component is likely to be one site of latency. Several
studies support the idea that cells of the granulocyte–monocyte
lineage harbor latent CMV (4–6). Transplantation of solid organs clearly can transmit CMV, so it is possible that cells other
than those mentioned above can harbor and transmit latent
CMV. However, whether the latently infected cell type in these
organs is transitory blood cells, macrophages, or permanent
cells is not yet clear.

INTERACTION OF CMV WITH
THE HOST IMMUNE SYSTEM
Adaptive Immunity
The importance of a competent immune system in controlling

CMV replication is manifested by the clear association of immunosuppression with CMV disease. The role of humoral immunity in controlling CMV replication is not clear. Antibodies
to multiple different CMV proteins, primarily glycoproteins B
(gB) and H (gH), develop during infection (7–9). Although
antibodies to gB and gH can neutralize the virus in cell culture, they do not appear to prevent primary infection in adults,
but rather may function to limit disease severity (10,11).
Paramount in controlling CMV replication is T-cell mediated cellular immunity. CMV provokes a robust CD8ϩ cytotoxic T lymphocyte (CTL) response, and the proportion of
circulating CD8ϩ T-cells in healthy individuals that are specific
for CMV antigens ranges from 10% to 40%, depending on the
age of the person (12–17). Numerous CMV proteins are targeted
by the CD8ϩ T-cell response, the most immunodominant ones
being the gene products of UL123 (IE-1), UL122 (IE-2), and
UL83 (pp65) (14,17–23). Lack of CMV-specific CD8ϩ CTL responses predispose to CMV infection, whereas reconstitution of
CMV-specific CD8ϩ CTL responses after hematopoietic cell
transplantation (HCT) correlates with protection from CMV
and improved outcome of CMV disease (24–28).
After HCT, detectable CMV-specific CD4ϩ responses
are associated with protection from CMV disease (24,29–31).
The lack of CMV-specific CD4ϩ cells is associated with late
CMV disease and death in patients who have undergone HCT
(32). CMV-specific CD4ϩ cells likely function at least in part
by helping to maintain robust CMV-specific CD8ϩ cell responses (28,33).
Innate Immunity
Innate immunity also functions to control CMV replication.
CMV triggers cellular inflammatory cytokine production
upon binding to the target cell, mediated in part by the interaction of gB and gH with toll-like receptor (TLR) 2 (34–36).
Polymorphisms in TLR2 have been associated with CMV
311


58202_ch22.qxd

312

2/1/10

Section V

8:49 PM

■

Page 312

Viral Infections

infection after liver transplantation (37). In mouse studies,
TLR3 and TLR9 proved to be important components in limiting
murine cytomegalovirus (MCMV) replication (38,39).
Natural killer (NK) cells represent another arm of the innate immune response and have been shown to limit MCMV
replication in mice (25,40–44). In humans, NK cell responses
increase during CMV infection after renal transplantation,
and a deficiency in NK cells is associated with severe CMV
infection (among other herpesviruses) (45,46). The genotype of
the donor activating killer immunoglobulin-like receptor (aKIR),
which regulates NK cell function, has recently been demonstrated to influence the development of CMV infection after allogeneic HCT (47–49). The mechanisms behind these associations
are not fully understood and these findings require validation in
independent cohorts.
Finally, polymorphisms in chemokine receptor 5 (CCR5)
and interleukin (IL)-10 have been associated with CMV disease, whereas polymorphisms in monocyte chemoattractant
protein 1 (MCP-1) are associated with reactivation after allogeneic HCT (50). Much more work needs to be done to determine the role(s) of these components of innate immunity in

regulating CMV replication in humans.
Immune Evasion
An array of CMV genes has been found to function in immune
evasion. For example, CMV has genes that inhibit apoptosis (51),
major histocompatibility complex (MHC)-I-restricted antigen
presentation (52), and interferon-mediated pathways (53–56).
CMV also encodes several homologues of cellular proteins, including MHC class-I molecules, CCRs, IL-10, TNF receptors,
and CXC-1 homologues, that function to evade the host immune
response (57–61).

DIAGNOSTIC METHODS
The serologic determination of IgG and IgM has an important
role in determining a patient’s risk for CMV infection after
transplantation (see “Risk Factors” section) or during immunosuppressive therapy, but is not useful in the diagnosis of
CMV infection or disease.
Growth of CMV in tissue culture takes several weeks, limiting its clinical usefulness as a diagnostic tool. Culture-proven
viremia is highly predictive of CMV disease, but is of limited utility for screening since this finding frequently coincides with the
onset of symptomatic disease (62–64).
The shell-vial technique, in which monoclonal antibodies
are used to detect CMV immediate-early proteins in cultured
cells, can be performed within 18 to 24 h after inoculation. This
assay is not sensitive enough to use for routine blood monitoring
(63), but is highly useful on bronchoalveolar lavage (BAL) fluid
in the diagnosis of CMV pneumonia (65).

The detection of the CMV pp65 tegument phosphoprotein in peripheral blood leukocytes offers a rapid, sensitive, and
specific method of diagnosing CMV viremia. In this assay, peripheral leukocytes are spread on a glass slide, stained with a
fluorescent antibody directed against pp65, and the number of
positive cells is reported per number of total leukocytes on the
slide, thereby providing a rough quantitative assessment of the

circulating viral load. In the transplant setting, a positive CMV
pp65 assay has been shown to predict the development of invasive disease (66,67). Since this assay relies on the detection of
pp65 in circulating leukocytes, it may not be reliable in patients with profound leukopenia. The predictive value of this
assay has not been validated when performed on other body
fluids such as BAL fluid.
Quantitative polymerase chain reaction (qPCR) relies on
the amplification and quantitative measurement of CMV
DNA. PCR is the most sensitive method for detecting CMV
(68), whereas at the same time maintaining high specificity. In
addition, it is very rapid, with results usually available within
24 h. qPCR provides a direct quantitative measurement of
CMV viral load, which is an accurate predictor of CMV disease after transplantation (32,69–72). qPCR testing has become
the standard method for detecting CMV in blood (either
whole blood or plasma) and spinal fluid at many, if not most,
institutions. Although PCR has been used on BAL fluid (73),
viral-load cut-offs have not been defined. And even though
the sensitivity and negative predictive values are very high, the
specificity and positive predictive values are not known.
The detection of CMV mRNA by nucleic acid sequencebased amplification (NASBA) on blood samples has proven to
be as useful as DNA PCR or p65 antigenemia for guiding preemptive therapy after HCT (74,75). However, this method has
not been as widely adopted as the pp65 antigenemia- or PCRbased assays.
The presence of characteristic CMV “owl’s eye” nuclear
inclusions in histopathology specimens is useful in the diagnosis of invasive CMV disease. This method has relatively low
sensitivity, but can be enhanced by use of immunohistochemical techniques to identify CMV antigens even when classic inclusions may not be evident.

CLINICAL MANIFESTATIONS
Care must be taken to distinguish CMV “infection” from
CMV “disease.” CMV infection simply indicates the detection
of CMV, typically by DNA PCR, pp65 antigenemia, or mRNA
NASBA, from plasma or whole blood in a CMV-seronegative

patient (primary infection) or a CMV-seropositive patient (reactivation of latent virus or superinfection with another strain
of CMV) (76,77).
International definitions of CMV disease, broadly defined
as the presence of symptoms and signs compatible with CMV


58202_ch22.qxd

2/1/10

8:49 PM

Page 313

Chapter 22

end-organ involvement along with the detection of CMV
using a validated method in the appropriate clinical specimen,
have been published (78). Fever is a common manifestation,
but may be absent in patients receiving high-dose immunosuppression. Almost any organ can be involved in CMV disease and therefore CMV infection has protean manifestations.
Pneumonia is the most important clinical manifestation
of CMV disease due to its high associated mortality. Patients
who have undergone autologous or allogeneic HCT have
mortality rates of 60% to 90% (79–81). This unacceptably high
mortality rate has not changed much in the past 20 years, indicating that much more work needs to be done in order to optimize the management of these patients.
CMV pneumonia often manifests with fever, nonproductive cough, hypoxia, and interstitial infiltrates on radiography.
Rarely, nodules may be observed on radiography. The onset of
symptoms can occur over 1 to 2 weeks, often times with rapid
progression to respiratory failure and the requirement for
mechanical ventilation. The diagnosis of CMV pneumonia is

established by detection of CMV by shell-vial culture, or histology in BAL or lung biopsy specimens in the presence of
compatible clinical signs and symptoms. Pulmonary shedding
of CMV is common, but CMV detection in BAL from asymptomatic patients who underwent routine BAL screening at
day 35 after HCT was predictive of subsequent CMV pneumonia in approximately two thirds of cases (82). Therefore,
the presence of CMV in a BAL specimen in the absence of
clinical evidence of CMV disease must be interpreted with
caution. We do not recommend PCR testing on BAL fluid
since there is little data correlating CMV DNA detection by
PCR in BAL fluid with CMV pneumonia. However, due to
the high negative predictive value afforded by its high sensitivity, a negative PCR result can be used to rule out the diagnosis of CMV pneumonia (73).
CMV can affect any part of the gastrointestinal tract from
the esophagus to the colon. Esophagitis typically results in
odynophagia, whereas abdominal pain and hematochezia
occur with colitis. Ulcers extending deep into the submucosal
layers are seen on endoscopy, and visual differentiation of
these lesions from other processes that may affect the gastrointestinal tract in these populations, such as graft-versus-host
(GVHD) disease, is often difficult. The diagnosis of gastrointestinal disease relies on detection of CMV in biopsy specimens
by culture and/or histology. Given the relative lack of sensitivity of each method, both methods should be used on biopsy
specimens to diagnose CMV disease. Notably, gastrointestinal
disease can occur in the absence of CMV detection in the blood
(83,84).
Retinitis is relatively uncommon after HCT (85–88).
Decreased visual acuity or blurred vision are typical presenting symptoms, and approximately 60% of patients will have
involvement of both eyes (86). Most cases present later than
day 100 after transplantation and are associated with prior

■

Cytomegalovirus Infection after Stem Cell Transplantation

313

CMV reactivation, delayed lymphocyte engraftment, and
GVHD (86).
Other manifestations, including hepatitis, encephalitis,
and infection of the bone marrow resulting in myelosuppression, are all rare with current preventative strategies.

RISK FACTORS
Allogeneic HCT Recipients
In the setting of allogeneic HCT, the most important risk
factor is the serological status of the donor and recipient.
CMV-seronegative patients who receive stem cells from a
CMV-seronegative donor (DϪ/RϪ) have a very low risk of
primary infection. Primary infection can still occur if CMV
is transmitted in transfused blood products or is acquired via
sexual contact or through contact with another individual
with primary CMV infection.
Approximately 30% of seronegative recipients who receive stem cells from a seropositive donor (Dϩ/RϪ) will develop primary CMV infection due to transmission of latent
CMV via the allograft. Although the risk of CMV disease is
low due to pre-emptive treatment of CMV infection, mortality
due to bacterial and fungal infections in these patients is
higher than in similarly matched DϪ/RϪ transplants (18.3%
vs. 9.7%, respectively) (89). The reason for this is not entirely
clear, one hypothesis being that CMV infection after HCT has
additional immunomodulating effects (indirect effects) that
increase a patient’s susceptibility to infection with other, unrelated organisms.
Without prophylaxis, approximately 80% of CMVseropositive patients will experience CMV infection after allogeneic HCT. Again, current preventative strategies have
resulted in a substantial decrease in the incidence of CMV disease, which had historically occurred in 20% to 35% of these
patients (90). Although a CMV-seropositive recipient is at
higher risk for transplant-related mortality (TRM) than a

seronegative recipient (91,92), the impact of donor serostatus
when the recipient in seropositive remains controversial. Some
studies have reported a beneficial effect of having seropositive
donor with regards to a reduction in relapse- or nonrelapserelated mortality (NRM), whereas other studies have found no
such benefit (93–104). A large CIBMTR study is presently underway to reconcile these controversial findings. However, although
the effects on NRM and overall survival are controversial, this
serological combination has been reported as a risk factor for
delayed CMV-specific immune reconstitution (105–108), CMV
reactivation (106,109), late CMV recurrence (110), and CMV disease (72,106,111).
Other risk factors for CMV infection after allogeneic HCT
include the use of steroids at doses greater than 1 mg/kg body
weight/day, T-cell depletion, acute and chronic GVHD, and the
use of mismatched or unrelated donors (69,72,111–115).


58202_ch22.qxd

314

2/1/10

8:49 PM

Section V

■

Page 314

Viral Infections

Whether the source of stem cells (peripheral blood vs. bone marrow) has a significant impact on the development of CMV infection and disease is not clear, as several studies have yielded
conflicting results (111,115–117). Interestingly, the use of
sirolimus for GVHD prophylaxis appears to protect against
CMV infection, possibly due to the inhibition of cellular signaling pathways that are co-opted by CMV during infection for
synthesis of viral proteins (111,118).
Late CMV Infection after Allogeneic HCT
Whereas CMV was typically seen by 100 days after allogeneic
HCT (119), in the current era of pre-emptive ganciclovir therapy, it has become a significant problem after day 100 following
allogeneic HCT (32,110,120). In the absence of specific preventative measures, 15% to 30% of allogeneic HCT patients will
experience late CMV infection and 6% to 18% will consequently develop the disease (32,69,110,121–123). Late CMV infection is strongly associated with NRM (110). Several factors
predict the development of late CMV infection (Table 22.1)
(24,30,32,110,112). Measures such as prolonged courses of therapy and continued weekly surveillance (Table 22.1) are warranted in these patients in order to reduce the risk of late CMV
disease (32,123,124).
Nonmyeloablative HCT
The use of matched, related nonmyeloablative conditioning
regimens generally results in a less CMV infection and disease
early after HCT compared to standard myeloablative regimens (113,124). However, by 1 year after HCT, the risk of
CMV infection and disease is equal among nonmyeloablative
and myeloablative groups (124,125). Conditioning regimens
that include T-cell depletion show no reduction in CMV after
nonmyeloablative transplantation compared to myeloablative
regimens (126), and matched, unrelated nonmyeloablative
TABLE 22.1

transplantation carries the same risk of CMV infection and
disease as does myeloablative transplantation (124).
Autologous HCT and Umbilical Cord Blood
Transplantation
After autologous transplantation, approximately 40% of

seropositive patients will have detectable CMV infection
(79,127). Although CMV disease is rare after autologous transplantation (116,128–130), the outcome of CMV pneumonia is
similar to that after allogeneic HCT (79,131,132). Risk factors
for CMV disease after autologous transplantation include
CD34ϩ selection, high-dose corticosteroids, and the use of
total-body irradiation or fludarabine as a part of the conditioning regimen (116). Therefore, although CMV is not typically
considered a significant pathogen after autologous HCT, certain patients who are at high risk for CMV in this setting merit
routine surveillance and pre-emptive therapy.
Umbilical cord blood transplantation (CBT) is a technique
that is now utilized when a suitable donor for bone marrow or
peripheral blood stem cell transplantation is not available (133).
Since most infants are born without CMV infection, the transplanted allograft is almost always CMV-negative. Among
CMV-seropositive recipients who do not receive antiviral prophylaxis, the rate of CMV infection after CBT is 40% to 80%,
with one study reporting 100% (134–138). When patients receive prophylaxis with high-dose valacyclovir after CBT, it
does not appear that CBT entails a significantly greater risk of
CMV infection and disease than does peripheral blood stem
cell or bone marrow transplantation (115).
Impact of Novel Immunosuppressive Agents
The increasing use of immunomodulating monoclonal antibodies in the setting of HCT and hematological malignancies
poses a new risk for CMV infection (139). Alemtuzumab is an

CMV Infection and Disease after Day 100 Following Allogeneic HCT:
Risk Factors, Surveillance Strategies, and Treatment

• Risk factors
-CMV infection or disease before day 100, or use of prophylaxis (ganciclovir, valganciclovir,
foscarnet, and cidofovir), PLUS any one of
• Lack of CMV-specific T-cell immune reconstitution
• Acute or chronic GVHD requiring systemic immunosuppression
• Lymphopenia

• Mismatched/unrelated transplant
• Surveillance
-Weekly PCR screening until
• Immunosuppression tapered (Ͻ0.5 mg/kg/day prednisone, no further
anti-T-cell therapy), and
• Three consecutive negative assays
• Pre-emptive therapy
-IV ganciclovir or oral valganciclovir (if oral absorption is reliable) induction until viral load
declines (at least 1 week) or foscarnet in the setting of neutropenia
-Maintenance therapy until viremia is cleared


58202_ch22.qxd

2/1/10

8:49 PM

Page 315

Chapter 22

anti-CD52 monoclonal antibody that results in CD4ϩ and
CD8ϩ lymphopenia that can last for up to 9 months after administration. CMV infection typically occurs during the period of maximal immunosuppression, which is 3 to 6 weeks
after alemtuzumab therapy (140,141). Patients who received
alemtuzumab as a part of the conditioning regimen or for
GVHD prophylaxis during HCT experienced a higher rate of
CMV infection compared to matched controls not receiving
alemtuzumab (142,143).

PREVENTION OF CYTOMEGALOVIRUS
INFECTION AND DISEASE
Pre- and Posttransplant Risk Reduction
CMV serological status of the recipient and donor should be
assessed as early as possible prior to HCT, as this is the most
important predictor of subsequent CMV infection. For the
seronegative recipient, the main goal is to prevent primary
CMV infection. Therefore, recipients who are CMV seronegative before allogeneic HCT should ideally receive a graft from
a CMV-negative donor. Weighing the factor of donor CMVserostatus compared to other relevant donor factors, such as
human leukocyte antigen (HLA)-match, is difficult. No data
exist indicating whether study HLA-matching is more important compared to CMV-serostatus in affecting a good outcome
for the patient. Given the choice, an antigen-matched donor
for HLA-A, B, or DR would most likely be preferred to a
CMV-negative donor. For lesser degrees of mismatch (allelemismatches or mismatches on HLA-C, DQ, or DP), the
CMV-serostatus of donor should be considered a factor even if
the match was poorer. Compared to other donor factors such
as age or blood group, a CMV-seronegative donor would have
preference.
The transfusion of blood products represents a significant
source for CMV transmission in D−/R− patients (144). To reduce this risk, blood products from CMV seronegative donors
or leukocyte-reduced, filtered blood products should be used
in this setting (145–147). It is not clear which strategy is the
most effective (148,149), and no controlled study has investigated whether there is an extra benefit from the use of both
methods.
Immunoprophylaxis
Intravenous immune globulin (IVIG) is not reliably effective
as prophylaxis against primary CMV infection. One study
demonstrated a reduction in the rate of CMV infection but not
disease with the use of CMV-specific immunoglobulin (150),
whereas another study was unable to confirm protection from

infection using anti-CMV hyperimmune globulin (151).
Similarly negative results were observed using a CMV-specific

■

Cytomegalovirus Infection after Stem Cell Transplantation

315

monoclonal antibody (152). Likewise, the effect of immunoglobulin on reducing CMV infection in seropositive patients is modest, and no survival benefit among those receiving
immunoglobulin has been reported in any study or metaanalysis (153–158). Therefore, the prophylactic use of immune
globulin is not recommended.
Antiviral Prophylaxis and Pre-Emptive Therapy
The prophylactic or pre-emptive use of antiviral agents after
HCT has markedly reduced the incidence of early CMV disease
and has improved survival among certain high-risk populations
(63,112,159). Prophylaxis denotes the routine administration of
antivirals to all at-risk patients regardless of the presence of active CMV infection. Pre-emptive therapy, on the other hand,
withholds antiviral therapy until CMV infection is detected, but
prior to the development of CMV disease.
Both prophylaxis and pre-emptive therapy have their benefits and drawbacks. Since prophylaxis involves the treatment
of all at-risk patients, close monitoring is not required when
ganciclovir or foscarnet are used, making this the easier strategy conceptually and useful in situations where rapid, sensitive
CMV diagnostic methods are not available. Additionally, prophylaxis may prevent the indirect effects associated with CMV
infection. However, since not all at-risk patients will experience CMV infection, prophylaxis strategies result in some patients receiving the drug unnecessarily, thereby exposing the
patient to potential drug-related toxicities without discernable
benefit. This is not an issue with pre-emptive treatment, since
by definition all patients who receive treatment will have active CMV infection.
The success of the pre-emptive treatment strategy is
largely dependent on the early detection of viremia. This, in

turn, depends on access to rapid, sensitive CMV surveillance
methods and on strict adherence to a surveillance-testing
schedule. By allowing a limited amount of viral replication,
pre-emptive therapy may stimulate immune responses and
thereby promote CMV-specific immune reconstitution (24).
Since both strategies are equally effective in preventing CMV
disease (159), most transplant centers have moved toward
pre-emptive strategies as pp65 antigenemia and DNA PCRbased diagnostics techniques have become readily available
(160–162).
More recently, there has been great interest in utilizing
methods to determine CMV-specific immune reconstitution
after HCT as an additional means to stratify risk of CMV infection and disease (immune monitoring) and further tailor
surveillance and pre-emptive therapy strategies. The types of
assays used, their strengths and limitations, and their predictive value in terms of CMV infection and disease after transplantation have been extensively reviewed elsewhere (12,163).
The utility of measuring T-cell responses as a guide for withholding therapy was evaluated in a small pilot study involving


58202_ch22.qxd

2/1/10

316

Section V

8:49 PM

■

Page 316

Viral Infections

HCT recipients more than 100 days after transplant (105).
Although promising, the use of immune monitoring in this
fashion requires validation in larger, randomized trials before
it can be recommended.
Antiviral Agents
Several antiviral drugs that demonstrate activity against CMV
are available once the decision is made to employ either prophylaxis or pre-emptive treatment (Table 22.2). High-dose
acyclovir reduces the risk for CMV infection and possibly disease (164,165). Valacyclovir is the valin-ester prodrug of acyclovir and is better absorbed, thereby attaining higher serum
concentrations than acyclovir. High-dose valacyclovir is more
effective than acyclovir in reducing CMV infection and the
need for pre-emptive therapy with ganciclovir after HCT, although the impact of this on survival after HCT is not clear
(166). Routine monitoring for CMV infection is still required
if valacyclovir or acyclovir prophylaxis is used.
TABLE 22.2

Ganciclovir is a nucleoside analogue of guanosine that
acts as a competitive inhibitor of deoxyguanosine triphosphate incorporation into viral DNA. A CMV gene, UL97,
encodes a phosphotransferase that converts ganciclovir to
ganciclovir monophosphate. Cellular enzymes then convert
ganciclovir monophosphate to the active triphosphate form.
Ganciclovir is currently the first-line agent for CMV prophylaxis and pre-emptive treatment barring contraindications.
Intravenous ganciclovir has been demonstrated to reduce the
risk of CMV infection and disease compared to placebo, but
did not improve overall survival (159,167–169). Neutropenia
occurs in up to 30% of HCT recipients during ganciclovir
therapy (170), thereby placing the patient at risk of invasive
bacterial and fungal infections (159,167,170). Neutropenia

often responds to dose reduction and support with granulocyte-colony stimulating factor, but occasionally discontinuation of ganciclovir is required, in which case foscarnet is
typically the second-line agent of choice. Measurement of
ganciclovir concentrations can be helpful to guide therapy

Antiviral Agents used for Prophylaxis, Pre-Emptive Therapy, and Treatment of
CMV Disease after HCT
Dose Based on Reason for Use

Agents

Toxicities

Prophylaxis

Pre-emptive Therapy

Treatment of
Disease

Acyclovir

Local injection
reactions (IV),
nephrotoxicity,
headache, and nausea

IV: 500 mg/m2 t.i.d.,
PO: 800 mg q.i.d.
(ജ40 kg) or 600
mg/m2 q.i.d. (Ͻ40 kg)

Not recommended

Not recommended

Valacyclovir

Gastrointestinal upset,
neutropenia, and
TTP/HUSa

2 g t.i.d. to q.i.d. (ജ40 kg) Not recommended

Not recommended

Ganciclovir

Neutropenia,
thrombocytopenia,
and nephrotoxicityb

Induction: 5 mg/kg
b.i.d., maintenance:
5 mg/kg/day

Induction: 5 mg/kg
b.i.d., maintenance:
5 mg/kg/day

Induction: 5

mg/kg b.i.d.,
maintenance:
5 mg/kg/day

Valganciclovir

Neutropenia,
headache, nausea, and
diarrhea

Not established

Induction: 900 mg
b.i.d. (ജ40 kg),
maintenance:
900 mg/kg/day (ജ40 kg)

Not established

Cidofovir

Nephrotoxicity

Not established

Induction:
Induction:
3–5 mg/kg/week ϫ 2–3 doses 3–5 mg/kg/week
for 3 doses
maintenance not established

maintenance
3–5 mg/kg/every
other week

Foscarnet

Nephrotoxicity,
metabolic

Induction: 60 mg/kg
b.i.d., maintenance:

Induction: 60 mg/kg
b.i.d., maintenance:

abnormalities c, and
anemia
aCausality
bTypically

90–120 mg/kg/day

90 mg/kg/day

remains to be determined.

observed with the concomitant use of nephrotoxic immunosuppressive agents.

cHypercalcemia,

hypomagnesemia, hypokalemia, and hypo- or hyperphosphatemia. Requires careful monitoring.

Induction:
60 mg/kg
b.i.d. or t.i.d.
maintenance:
90 mg/kg/day


58202_ch22.qxd

2/1/10

8:49 PM

Page 317

Chapter 22

and reduce the risk for toxicity especially in the situation of
pre-existing renal impairment.
Valganciclovir is the orally available prodrug of ganciclovir and achieves serum concentrations at least equivalent to
intravenous ganciclovir (171–173). The results of several uncontrolled studies suggest that valganciclovir is comparable to
intravenous ganciclovir in terms of efficacy and safety when
used as pre-emptive therapy after allogeneic HCT (171,
174–176). As of the writing of this chapter, no data comparing
valganciclovir to intravenous ganciclovir in the setting of a
randomized, controlled trial have been published. Preliminary
data from a randomized trial have been presented indicating
little or no difference in efficacy or toxicity compared to intravenous ganciclovir (177). Until more data are available, caution should be exercised when choosing valganciclovir as

pre-emptive therapy.
Foscarnet is a pyrophosphate analogue that binds directly
to and competitively inhibits the CMV DNA polymerase.
Foscarnet is generally considered to be as effective as ganciclovir for pre-emptive therapy after allogeneic transplantation
(178). However, three uncontrolled studies have documented
cases of breakthrough CMV disease during foscarnet therapy
(179–181). These findings, combined with commonly encountered toxicities of foscarnet, have led to the use of foscarnet as a
second-line agent when ganciclovir is contraindicated or not
tolerated.
Cidofovir is a cytosine nucleotide analogue that does not
require phosphorylation by viral enzymes for antiviral activity.
Cellular enzymes convert cidofovir to cidofovir triphosphate,
which then inhibits the CMV DNA polymerase. The long
half-life of cidofovir allows a once-per-week dosing schedule.
However, the major toxicity with cidofovir—acute renal tubular necrosis—limits its utility after HCT, and it should
therefore be considered third-line therapy after ganciclovir
and foscarnet (182).
Monitoring for CMV Infection and Initiation of
Pre-Emptive Therapy
qPCR assays for CMV DNA are increasingly used for surveillance because they offer two advantages. First, they are more
sensitive than pp65 antigenemia, thereby prompting treatment
initiation in cases of CMV disease that have been missed with
the pp65 antigenemia assay (159). Additionally, the quantitative
nature of the assay may enable the development of institutionspecific viral load thresholds for beginning treatment,
thereby avoiding unnecessary treatment of patients who are
at low risk of progression to disease. It has been reported that
the initial viral load as well as the viral load kinetics are important as risk factors for CMV disease (183). Currently,
there are no validated universal viral load thresholds, and
such thresholds would be difficult to establish due to differences in assay performance and testing material (whole blood
vs. plasma) (184).

■

Cytomegalovirus Infection after Stem Cell Transplantation

317

With the exception of those receiving ganciclovir prophylaxis, all patients who have undergone allogeneic HCT, regardless of pretransplant donor and recipient serostatus,
should be monitored on a weekly basis for CMV infection
using pp65 antigenemia, DNA PCR, or mRNA NASBA.
Although CMV infection is rare in DϪ/RϪpatients, routine
monitoring was effective in identifying CMV infection and
preventing disease in a large cohort (185). Monitoring is generally performed until day 100 after engraftment or longer in patients at risk for late CMV disease (Table 22.1). The ideal
duration and frequency of CMV monitoring in the later transplantation periods have not been determined (123,124).
Routine monitoring of autograft recipients is not recommended, with the exception being high-risk patients as described above (161,162,186).
A general approach to prophylaxis and pre-emptive
therapy is presented in Table 22.3. If a pre-emptive strategy is
used, the initial detection of CMV in peripheral blood after
allogeneic HCT should prompt the initiation of antiviral
therapy and a thorough evaluation of the patient in order to
assess for signs and symptoms concerning for CMV disease
(186). Various durations of pre-emptive antiviral treatment
have been explored. Initial studies administered ganciclovir
until day 100 after engraftment, which ultimately entailed
approximately 6 to 8 weeks of therapy in the average recipient. Studies from the mid-1990s using short courses (2 to 3
week) of ganciclovir based on negative PCR assays at the end
of therapy were generally effective; however, resumption of
pre-emptive therapy was necessary in approximately 30% of
patients (63,178,188). Most centers now continue antiviral
treatment until the designated viral marker is negative and

the patient has received at least 2 weeks of antiviral therapy.
If less sensitive markers than DNA PCR, such as the pp65
antigenemia assay, are used, then pre-emptive therapy
should be continued until two negative assays are obtained
(178). If a patient is still viremic by PCR or pp65 antigenemia
assay after 2 weeks of therapy, treatment should be extended
at maintenance dosing until clearance is achieved. It has been
shown that a low rate of viral load decrease is a risk factor for
later-occurring CMV disease (72).

SPECIAL POPULATIONS
Patients with CMV infection occurring prior to planned allogeneic HCT have a very high risk of death after transplantation (189). After transplantation, a patient with documented
pretransplant CMV infection should either be monitored for
CMV very closely (i.e., twice weekly), or be given prophylaxis
with ganciclovir or foscarnet.
The optimal approach to CMV after CBT is not clear.
One study described successful pre-emptive treatment with
ganciclovir (138), whereas another combined high-dose
valacyclovir prophylaxis with continued monitoring and


318
pp65 Ag у 5
cells/slide (or
at any level if
CD34ϩselected
graph)
At engraftment

Ͻ100 days

Ͻ100 days

GCV 5 mg/kg
IV q.d.

GCV 5 mg/kg
IV q.d.

GCV 5 mg/kg
IV q.d.

GCV 5 mg/kg
IV q.d.

First Line Choice:
Maintenance

be combined with active surveillance for CMV infection.

use of total body irradiation (TBI) in conditioning, recent fludarabine or 2-chlorodeoxyadenosine, high-dose corticosteroids.

GCV 5 mg/kg IV
b.i.d. ϫ 5–7 days

GCV 5 mg/kg IV
b.i.d. ϫ 7 days and
declining viral load

GCV 5 mg/kg IV

b.i.d. ϫ 7–14 days
and declining viral
load
GCV 5 mg/kg IV
b.i.d. ϫ 7–14 days
and declining viral
load

First-Line
Choice: Induction

Foscarnet,
acycyclovir,b and
valacyclovirb

Foscarnet,
valganciclovir
and cidofovir

Valganciclovir,
foscarnet

Foscarnet,
valganciclovir,
and cidofovir

Alternative

Day 100 after
HCT

Until in dicator
assay negative
and min. 2 weeks
therapy

Until in dicator
assay negative
and min. 2–3
weeks therapy

Indicator test
negative and
2–3 weeks

Duration

Transplant. 2009;15(10):1143–1238; Bone Marrow Transplant. 2009;44(8):part 2.

Association of Medical Microbiology and Infectious Diseases Canada (AMMI), the Centers for Disease Control and Prevention (CDC), and the Health Resources and Services Administration (HRSA). Biol Blood Marrow

Marrow Transplantation (ASBMT), the Canadian Blood and Marrow Transplant Group (CBMTG), the Infectious Disease Society of America (IDSA), the Society for Healthcare Epidemiology of America (SHEA), the

International Blood and Marrow Transplant Research (CIBMTR®), the National Marrow Donor Program (NMDP), the European Blood and Marrow Transplant Group (EBMT), the American Society of Blood and

Modified from Tomblyn M, Chiller T, EinseleH, et al. Guidelines for Preventing Infectious Complications among Hematopoietic Cell Transplant Recipients: A Global Perspective. Recommendations of the Center for

bMust

aIncludes

Allogeneic
HCT
recipients

pp65 Ag у 5
cells/slide or у 2
consecutively
positive
PCR / viremia

Ͼ100 days

Allogeneic
HCT or GVHD
requiring
steroid therapy
or early CMV
infection
Autologous
HCT and CMVseropositive
and at high
riska

Prophylaxis

At first
detection of
CMV infection

Ͻ100 days

Allogeneic
HCT
recipients

Initiation

Pre-emptive

Timing
Post-HCT

8:49 PM

Patient
Population

Strategies for Pre-Emptive Therapy and Prophylaxis after HCT

2/1/10

Prevention
Strategy

TABLE 22.3

58202_ch22.qxd
Page 318

58202_ch22.qxd

2/1/10

8:49 PM

Page 319

Chapter 22

pre-emptive therapy (115). Due to initial experience in Seattle
suggesting a high rate of infection and disease early posttransplant, the latter approach, coupled with ganciclovir prophylaxis for the week prior to transplant and continued CMV
surveillance posttransplant, has been adopted.
Antiviral Resistance
Drug resistance is relatively uncommon after HCT but can
occur with all drugs used for the treatment and prophylaxis of
CMV. Risk factors for drug resistance include prolonged
(months) antiviral therapy, intermittent low-level viral replication in the presence of drug due to profound immunosuppression or suboptimal drug levels, and lack of prior immunity
to CMV (190). Drug resistance should be suspected in patients
that are on an appropriate dosage of an antiviral drug and who
have increasing quantitative viral loads for more than 2 weeks.
After start of antiviral therapy in treatment-naïve patients, an
increase in the viral load will occur in approximately one third
of patients and is likely due to the underlying immunosuppression, not true drug resistance (67). If a patient has received
ganciclovir before transplantation or if viral load increases
occur in the late setting where most patients are not antiviral
drug naïve anymore, drug resistance should be suspected.
An approach to the patient with suspected drug-resistant
CMV is presented in Figure 22.1. Since ganciclovir is used as a

first-line agent in most cases of CMV infection, resistance to

■

Cytomegalovirus Infection after Stem Cell Transplantation

this antiviral is the most commonly encountered problem.
Resistance is most often due to mutations in the UL97 gene,
and less often to mutations in the UL54-encoded DNA polymerase. UL97 mutations that confer resistance have been described and genotypic assays are available for diagnostic
analysis in reference laboratories (191). Phenotypic testing can
be performed, but this type of assay is time-consuming and is
therefore not as helpful as rapid genotypic testing in guiding
patient management. However, since different UL97 mutations confer varying degrees of ganciclovir resistance, some
cases of genotypically defined ganciclovir-resistant CMV may
still respond to ganciclovir therapy (192) and therefore care
must be taken in interpreting genotype results.
If ganciclovir resistance is documented or suspected, foscarnet is generally the second-line agent of choice. Unlike ganciclovir, foscarnet activity is not dependent on phosphorylation
by the UL97 gene product; thus, CMV that has acquired ganciclovir resistance due to UL97 mutations will still be susceptible to foscarnet (193). Studies evaluating the utility of
combination therapy of foscarnet and ganciclovir for ganciclovir-resistant CMV disease have been inconclusive and
therefore this strategy is not routinely recommended (194).
Resistance to foscarnet can occur and is due to mutations in
UL54. Interestingly, cross-resistance between foscarnet and
ganciclovir does not occur, as mutations in UL54 conferring
resistance to foscarnet occur in regions distinct from those conferring ganciclovir resistance (195).

Suspicion of ganciclovir (GCV) or valganciclovir (VGCV)resistance:
Rising viral load after two weeks of ongoing GCV or VGCV therapy
Prior GCV or VGCV exposure
Symptomatic disease after or during extended GCV or VGCV therapy

UL97 genotyping

Presence of UL97 mutations conferring resistance?

yes

Change to foscarnet
Less commonly used (input from expert recommended):
Cidofovira
Combination GCV+Foscamet
HIgh-dose GCV
Leflunomide
Artesunate
a Genotyping

319

No

UL54 genotyping
Pending UL54 genotyping results:
If high-risk patient, symptomatic disease,
or rapidly increasing viral load, switch to foscamet
If stable viral load and clinically silent infection,
continue GCV or VGCV at current dose or consider
higher-dose GCV therapy

of UL54 DNA polymerase is recommended to evaluate for mutations conferring cross-resistance to cidofovir

FIGURE 22.1. Approach to the patient with suspected ganciclovir–valganciclovir-resistant CMV.

58202_ch22.qxd

320

2/1/10

Section V

8:49 PM

■

Page 320

Viral Infections

Since cidofovir is not phosphorylated by the CMV UL97
gene product, it is active against ganciclovir-resistant UL97 mutants. However, certain UL54 mutations can confer causes crossresistance between ganciclovir and cidofovir (193,195). Therefore,
additional genotype testing of UL54 is indicated to evaluate for
potential cross-resistance conferring mutations. There is limited
experience with cidofovir for treatment of ganciclovir-resistant
CMV, and its toxicity profile precludes its routine use as secondline treatment for ganciclovir-resistant CMV.
Drugs presently under evaluation, such as maribavir, may
also provide therapeutic options in the future. Maribavir inhibits the CMV UL97 kinase and is active and against wild-type
and ganciclovir-resistant CMV strains (196). Other drugs with
possible anti-CMV activity include the arthritis drug leflunomide and the antimalaria compound artesunate (197–199).
None of these are approved by European or American regulatory authorities for the treatment of CMV. Another potentially
useful approach is to use the immunosuppressive drug sirolimus

as adjunct therapy since it may impair CMV replication by regulating cellular signaling pathways, and has in fact been shown
to reduce the risk of CMV reactivation after HCT and renal
transplantation (111,118).
Vaccination
Given the costs and toxicities associated with antiviral therapy, a
vaccine to prevent CMV infection would be of substantial benefit. Indeed, the Institute of Medicine has given the development
of a CMV vaccine the highest priority (200). Thus far, most vaccine candidates have yielded mixed results (201). Recently, a
phase I trial of a bivalent vaccine containing plasmids encoding
gB and pp65 showed promising results in CMV-seronegative
vaccine recipients, but not CMV-seropositive recipients, which
is a limitation common to many CMV vaccine candidates (202).
Since it is the seropositive transplant patient who is at greatest
risk for CMV infection, more work is required to provide protective immunity in these patients after HCT.
Management of CMV Disease
As mentioned earlier, the diagnosis of CMV disease requires
documenting the presence of CMV in the appropriate diagnostic specimen, coupled with symptoms and signs consistent with
CMV. For gastrointestinal disease, standard therapy generally
entails induction treatment with an intravenous antiviral, most
often ganciclovir, for 3 to 4 weeks followed by several weeks of
maintenance. Shorter courses of induction therapy (2 weeks)
are not as effective (203). There is no role for concomitant
IVIG in the treatment of gastrointestinal disease (204).
Recurrence of gastrointestinal disease may occur in approximately 30% of patients in the setting of continued immunosuppression and such patients may benefit from secondary
prophylaxis with maintenance antivirals until immunosuppression has been reduced. Foscarnet can be used as an

alternative if neutropenia is present. Valganciclovir as maintenance treatment for gastrointestinal disease has not been well
studied but may be reasonable if symptoms are improved, systemic viremia is suppressed, and there are no factors that
would impair the absorption of an orally administered medication, such as severe gastrointestinal GVHD.
Several studies established the current standard of care for
CMV pneumonia, which is treated with ganciclovir (or foscarnet as an alternative agent) in combination with IVIG

(205–208). These studies showed improved survival rates compared to historical outcome results. There does not appear to be
a specific advantage of CMV-specific immune globulin (CMVIg) compared to pooled immunoglobulin (206). However, in
specific clinical situations, such as volume overload, CMV-Ig
may be preferred. Several studies have raised doubt regarding
the beneficial effect of concomitant IVIG (209,210). However,
although the use of IVIG remains a controversial topic, it is still
considered as standard of care at many centers until more data
regarding its utility are available.
CMV retinitis is typically treated with systemic ganciclovir, foscarnet, or cidofovir, with or without intraocular ganciclovir injections or implants (86,211–213). Fomivirsen is an
antisense RNA molecule that targets mRNA encoded by
CMV and is approved as second-line therapy for CMV retinitis in patients with AIDS (214).
Other manifestations of CMV disease, such as hepatitis
and encephalitis, are uncommon and are typically managed
with intravenous ganciclovir. The duration of therapy for
these manifestations has not been well established and should
be tailored to the individual patient.
Adoptive Immunotherapy
HCMV-specific T-cells can be generated via several different
mechanisms in attempts to passively restore cellular immunity after transplantation (12). Several groups have reported a
beneficial impact of adoptive immunotherapy on HCMV
viral loads in patients who had undergone HCT (215).
Despite these seemingly promising results, scientific questions remain unanswered (such as the optimal cell type and
dose for infusion) and technical hurdles persist (availability of
clinical grade reagents) that preclude adoptive immunotherapy from becoming a routine clinical procedure at the current
time. This topic is discussed in more detail in chapter 46.

CONCLUSIONS AND FUTURE
DIRECTIONS
Although much progress has been made in the prevention of
CMV disease after HCT over the past decade, several issues

remain. Increasing the specificity of pre-emptive therapy by
combining detection of viremia with monitoring of CMVspecific T-cell immunity merits evaluation in a randomized


58202_ch22.qxd

2/1/10

8:49 PM

Page 321

Chapter 22

trial. CMV pneumonia still carries a poor prognosis that has not
changed in 20 years. Therefore, other strategies, such as combination antiviral therapy, should be studied in this setting in
order to improve outcome. Additionally, the benefit provided
by IVIG in the treatment of CMV pneumonia needs to be determined. New treatment and vaccination options for CMV
are urgently needed because the currently available drugs have
major limitations, such as toxicity and resistance. Novel drugs
such as lipid cidofovir (216), a novel nonnucleoside inhibitor
(217), as well as leflunomide and artesunate, deserve a systematic evaluation. Vaccination may also play an increasing role in
the future prevention of CMV infection and disease.

ACKNOWLEDGMENTS
Per Ljungman had support from Karolinska Institutet
Research Funds and the Swedish Children’s Cancer Fund.
Michael Boeckh had support from the National Institute of
Health (NIH CA 18029).

REFERENCES
1. Mocarski ES, Shenk T, Pass RF. Cytomegaloviruses. In: Knipe
DM, Howley PM, eds. Fields Virology. Vol 2. 5th ed. Philadelphia:
Lippincott Williams & Wilkins; 2007:2701–2772.
2. Murphy E, Yu D, Grimwood J, et al. Coding potential of laboratory and clinical strains of human cytomegalovirus. Proc Natl
Acad Sci U S A. 2003;100:14976–14981.
3. Sinzger C, Digel M, Jahn G. Cytomegalovirus cell tropism. Curr
Top Microbiol Immunol. 2008;325:63–83.
4. Bolovan-Fritts CA, Mocarski ES, Wiedeman JA. Peripheral
blood CD14(ϩ) cells from healthy subjects carry a circular
conformation of latent cytomegalovirus genome. Blood.
1999;93:394–398.
5. Kondo K, Kaneshima H, Mocarski ES. Human cytomegalovirus
latent infection of granulocyte-macrophage progenitors. Proc Natl
Acad Sci U S A. 1994;91:11879–11883.
6. Taylor-Wiedeman J, Sissons JG, Borysiewicz LK, et al. Monocytes
are a major site of persistence of human cytomegalovirus in peripheral blood mononuclear cells. J Gen Virol. 1991;72(pt 9):
2059–2064.
7. Britt WJ, Vugler L, Butfiloski EJ, et al. Cell surface expression of
human cytomegalovirus (HCMV) gp55-116 (gB): use of HCMVrecombinant vaccinia virus-infected cells in analysis of the human
neutralizing antibody response. J Virol. 1990;64:1079–1085.
8. Marshall GS, Rabalais GP, Stout GG, et al. Antibodies to recombinant-derived glycoprotein B after natural human cytomegalovirus
infection correlate with neutralizing activity. J Infect Dis. 1992;165:
381–384.
9. Rasmussen L, Matkin C, Spaete R, et al. Antibody response to
human cytomegalovirus glycoproteins gB and gH after natural
infection in humans. J Infect Dis. 1991;164:835–842.
10. Boppana SB, Britt WJ. Antiviral antibody responses and intrauterine transmission after primary maternal cytomegalovirus
infection. J Infect Dis. 1995;171:1115–1121.
11. Jonjic S, Pavic I, Lucin P, et al. Efficacious control of cytomegalovirus infection after long-term depletion of CD8ϩ T

lymphocytes. J Virol. 1990;64:5457–5464.

■

Cytomegalovirus Infection after Stem Cell Transplantation

321

12. Crough T, Khanna R. Immunobiology of human cytomegalovirus:
from bench to bedside. Clin Microbiol Rev. 2009;22:76–98. Table of
contents.
13. Gillespie GM, Wills MR, Appay V, et al. Functional heterogeneity
and high frequencies of cytomegalovirus-specific CD8(ϩ) T lymphocytes in healthy seropositive donors. J Virol. 2000;74:8140–8150.
14. Khan N, Cobbold M, Keenan R, et al. Comparative analysis of
CD8ϩ T cell responses against human cytomegalovirus proteins
pp65 and immediate early 1 shows similarities in precursor frequency, oligoclonality, and phenotype. J Infect Dis. 2002;185:
1025–1034.
15. Khan N, Hislop A, Gudgeon N, et al. Herpesvirus-specific CD8
T cell immunity in old age: cytomegalovirus impairs the response
to a coresident EBV infection. J Immunol. 2004;173:7481–7489.
16. Ouyang Q, Wagner WM, Wikby A, et al. Large numbers of dysfunctional CD8ϩ T lymphocytes bearing receptors for a single
dominant CMV epitope in the very old. J Clin Immunol. 2003;23:
247–257.
17. Sylwester AW, Mitchell BL, Edgar JB, et al. Broadly targeted
human cytomegalovirus-specific CD4ϩ and CD8ϩ T cells dominate the memory compartments of exposed subjects. J Exp Med.
2005;202:673–685.
18. Elkington R, Walker S, Crough T, et al. Ex vivo profiling of
CD8ϩ-T-cell responses to human cytomegalovirus reveals broad
and multispecific reactivities in healthy virus carriers. J Virol.
2003;77:5226–5240.

19. Kern F, Bunde T, Faulhaber N, et al. Cytomegalovirus (CMV)
phosphoprotein 65 makes a large contribution to shaping the T
cell repertoire in CMV-exposed individuals. J Infect Dis. 2002;
185:1709–1716.
20. Kern F, Surel IP, Faulhaber N, et al. Target structures of the
CD8(ϩ)-T-cell response to human cytomegalovirus: the 72-kilodalton major immediate-early protein revisited. J Virol. 1999;73:
8179–8184.
21. Khan N, Best D, Bruton R, et al. T cell recognition patterns of immunodominant cytomegalovirus antigens in primary and persistent infection. J. Immunol. 2007;178:4455–4465.
22. Khan N, Bruton R, Taylor GS, et al. Identification of cytomegalovirus-specific cytotoxic T lymphocytes in vitro is greatly
enhanced by the use of recombinant virus lacking the US2 to
US11 region or modified vaccinia virus Ankara expressing individual viral genes. J Virol. 2005;79:2869–2879.
23. Kondo E, Akatsuka Y, Kuzushima K, et al. Identification of novel
CTL epitopes of CMV-pp65 presented by a variety of HLA alleles. Blood. 2004;103:630–638.
24. Li CR, Greenberg PD, Gilbert MJ, et al. Recovery of HLArestricted cytomegalovirus (CMV)-specific T-cell responses after
allogeneic bone marrow transplant: correlation with CMV disease
and effect of ganciclovir prophylaxis. Blood. 1994;83:1971–1979.
25. Polic B, Hengel H, Krmpotic A, et al. Hierarchical and redundant lymphocyte subset control precludes cytomegalovirus replication during latent infection. J Exp Med. 1998;188:1047–1054.
26. Quinnan GV, Kirmani N Jr, Rook AH, et al. Cytotoxic T cells in
cytomegalovirus infection: HLA-restricted T-lymphocyte and
non-T-lymphocyte cytotoxic responses correlate with recovery
from cytomegalovirus infection in bone-marrow-transplant recipients. N Engl J Med. 1982;307:7–13.
27. Reusser P, Cathomas G, Attenhofer R, et al. Cytomegalovirus
(CMV)-specific T cell immunity after renal transplantation mediates protection from CMV disease by limiting the systemic virus
load. J Infect Dis. 1999;180:247–253.
28. Reusser P, Riddell SR, Meyers JD, et al. Cytotoxic T-lymphocyte
response to cytomegalovirus after human allogeneic bone marrow


58202_ch22.qxd

322

29.

30.

31.

32.

33.

34.

35.

36.

37.

38.

39.

40.

41.

42.

43.

44.

45.

2/1/10

Section V

8:49 PM

■

Page 322

Viral Infections

transplantation: pattern of recovery and correlation with
cytomegalovirus infection and disease. Blood. 1991;78:1373–1380.
Hebart H, Daginik S, Stevanovic S, et al. Sensitive detection of
human cytomegalovirus peptide-specific cytotoxic T-lymphocyte
responses by interferon-gamma-enzyme-linked immunospot
assay and flow cytometry in healthy individuals and in patients
after allogeneic stem cell transplantation. Blood. 2002;99:
3830–3837.
Krause H, Hebart H, Jahn G, et al. Screening for CMV-specific T
cell proliferation to identify patients at risk of developing late
onset CMV disease. Bone Marrow Transplant. 1997;19:1111–1116.
Ljungman P, Aschan J, Azinge JN, et al. Cytomegalovirus viraemia and specific T-helper cell responses as predictors of disease

after allogeneic marrow transplantation. Br J Haematol. 1993;83:
118–124.
Boeckh M, Leisenring W, Riddell SR, et al. Late cytomegalovirus
disease and mortality in recipients of allogeneic hematopoietic
stem cell transplants: importance of viral load and T-cell immunity. Blood. 2003;101:407–414.
Einsele H, Roosnek E, Rufer N, et al. Infusion of cytomegalovirus (CMV)-specific T cells for the treatment of CMV infection not responding to antiviral chemotherapy. Blood. 2002;99:
3916–3922.
Boehme KW, Guerrero M, Compton T. Human cytomegalovirus
envelope glycoproteins B and H are necessary for TLR2 activation in permissive cells. J Immunol. 2006;177:7094–7102.
Compton T, Kurt-Jones EA, Boehme KW, et al. Human cytomegalovirus activates inflammatory cytokine responses via
CD14 and Toll-like receptor 2. J Virol. 2003;77:4588–4596.
Juckem LK, Boehme KW, Feire AL, et al. Differential initiation
of innate immune responses induced by human cytomegalovirus
entry into fibroblast cells. J Immunol. 2008;180:4965–4977.
Kijpittayarit S, Eid AJ, Brown RA, et al. Relationship between
toll-like receptor 2 polymorphism and cytomegalovirus disease
after liver transplantation. Clin Infect Dis. 2007;44:1315–1320.
Delale T, Paquin A, Asselin-Paturel C, et al. MyD88-dependent
and -independent murine cytomegalovirus sensing for IFN-alpha
release and initiation of immune responses in vivo. J Immunol.
2005;175:6723–6732.
Tabeta K, Georgel P, Janssen E, et al. Toll-like receptors 9 and 3
as essential components of innate immune defense against
mouse cytomegalovirus infection. Proc Natl Acad Sci USA.
2004;101:3516–3521.
Brown MG, Dokun AO, Heusel JW, et al. Vital involvement of a
natural killer cell activation receptor in resistance to viral infection. Science. 2001;292:934–937.
Bukowski JF, Warner JF, Dennert G, et al. Adoptive transfer
studies demonstrating the antiviral effect of natural killer cells in
vivo. J Exp Med. 1985;161:40–52.

Bukowski JF, Woda BA, Habu S, et al. Natural killer cell depletion enhances virus synthesis and virus-induced hepatitis in vivo.
J Immunol. 1983;131:1531–1538.
Scalzo AA, Fitzgerald NA, Simmons A, et al. Cmv-1, a genetic
locus that controls murine cytomegalovirus replication in the
spleen. J Exp Med. 1990;171:1469–1483.
Scalzo AA, Fitzgerald NA, Wallace CR, et al. The effect of the
CMV-1 resistance gene, which is linked to the natural killer cell
gene complex, is mediated by natural killer cells. J Immunol.
1992;149:581–589.
Biron CA, Byron KS, Sullivan JL. Severe herpesvirus infections
in an adolescent without natural killer cells. N Engl J Med.
1989;320:1731–1735.

46. Venema H, van den Berg AP, van Zanten C, et al. Natural killer
cell responses in renal transplant patients with cytomegalovirus
infection. J Med Virol. 1994;42:188–192.
47. Chen C, Busson M, Rocha V, et al. Activating KIR genes are associated with CMV reactivation and survival after non-T-cell depleted HLA-identical sibling bone marrow transplantation for
malignant disorders. Bone Marrow Transplant. 2006;38:437–444.
48. Cook M, Briggs D, Craddock C, et al. Donor KIR genotype has a
major influence on the rate of cytomegalovirus reactivation following T-cell replete stem cell transplantation. Blood. 2006;107:
1230–1232.
49. Zaia JA, Sun JY, Gallez-Hawkins GM, et al. The effect of single and
combined activating killer immunoglobulin-like receptor genotypes
on cytomegalovirus infection and immunity after hematopoietic cell
transplantation. Biol Blood Marrow Transplant. 2009;15:315–325.
50. Loeffler J, Steffens M, Arlt EM, et al. Polymorphisms in the genes
encoding chemokine receptor 5, interleukin-10, and monocyte
chemoattractant protein 1 contribute to cytomegalovirus reactivation and disease after allogeneic stem cell transplantation. J Clin
Microbiol. 2006;44:1847–1850.
51. Goldmacher VS, Bartle LM, Skaletskaya A, et al. A

cytomegalovirus-encoded mitochondria-localized inhibitor of apoptosis structurally unrelated to Bcl-2. Proc Natl Acad Sci USA.
1999;96:12536–12541.
52. Basta S, Bennink JR. A survival game of hide and seek: cytomegaloviruses and MHC class I antigen presentation pathways.
Viral Immunol. 2003;16:231–242.
53. Abate DA, Watanabe S, Mocarski ES. Major human cytomegalovirus structural protein pp65 (ppUL83) prevents interferon response factor 3 activation in the interferon response.
J Virol. 2004;78:10995–11006.
54. Child SJ, Hakki M, De Niro KL, et al. Evasion of cellular antiviral responses by human cytomegalovirus TRS1 and IRS1. J Virol.
2004;78:197–205.
55. Taylor RT, Bresnahan WA. Human cytomegalovirus immediateearly 2 gene expression blocks virus-induced beta interferon production. J Virol. 2005;79:3873–3877.
56. Taylor RT, Bresnahan WA. Human cytomegalovirus immediateearly 2 protein IE86 blocks virus-induced chemokine expression.
J Virol. 2006;80:920–928.
57. Benedict CA, Butrovich KD, Lurain NS, et al. Cutting edge: a
novel viral TNF receptor superfamily member in virulent strains
of human cytomegalovirus. J Immunol. 1999;162:6967–6970.
58. Chapman TL, Heikeman AP, Bjorkman PJ. The inhibitory receptor
LIR-1 uses a common binding interaction to recognize class I MHC
molecules and the viral homolog UL18. Immunity. 1999;11:603–613.
59. Gao JL, Murphy PM. Human cytomegalovirus open reading
frame US28 encodes a functional beta chemokine receptor. J Biol
Chem. 1994;269:28539–28542.
60. Kotenko SV, Saccani S, Izotova LS, et al. Human cytomegalovirus harbors its own unique IL-10 homolog (cmvIL10). Proc Natl Acad Sci USA. 2000;97:1695–1700.
61. Penfold ME, Dairaghi DJ, Duke GM, et al. Cytomegalovirus encodes a potent alpha chemokine. Proc Natl Acad Sci USA.
1999;96:9839–9844.
62. Boeckh M, Boivin G. Quantitation of cytomegalovirus: methodologic aspects and clinical applications. Clin Microbiol Rev.
1998;11:533–554.
63. Einsele H, Ehninger G, Hebart H, et al. Polymerase chain reaction monitoring reduces the incidence of cytomegalovirus disease
and the duration and side effects of antiviral therapy after bone
marrow transplantation. Blood. 1995;86:2815–2820.

58202_ch22.qxd

2/1/10

8:49 PM

Page 323

Chapter 22

64. Meyers JD, Ljungman P, Fisher LD. Cytomegalovirus excretion as a
predictor of cytomegalovirus disease after marrow transplantation:
importance of cytomegalovirus viremia. J Infect Dis. 1990;162:373–380.
65. Crawford SW, Bowden RA, Hackman RC, et al. Rapid detection
of cytomegalovirus pulmonary infection by bronchoalveolar lavage
and centrifugation culture. Ann Intern Med. 1988;108:180–185.
66. Boeckh M, Bowden RA, Goodrich JM, et al. Cytomegalovirus
antigen detection in peripheral blood leukocytes after allogeneic
marrow transplantation. Blood. 1992;80:1358–1364.
67. Nichols WG, Corey L, Gooley T, et al. Rising pp65 antigenemia
during preemptive anticytomegalovirus therapy after allogeneic
hematopoietic stem cell transplantation: risk factors, correlation
with DNA load, and outcomes. Blood. 2001;97:867–874.
68. Boeckh M, Huang M, Ferrenberg J, et al. Optimization of quantitative detection of cytomegalovirus DNA in plasma by real-time
PCR. J Clin Microbiol. 2004;42:1142–1148.
69. Einsele H, Hebart H, Kauffmann-Schneider C, et al. Risk factors for
treatment failures in patients receiving PCR-based preemptive therapy for CMV infection. Bone Marrow Transplant. 2000;25:757–763.
70. Emery VC, Griffiths PD. Prediction of cytomegalovirus load and
resistance patterns after antiviral chemotherapy. Proc Natl Acad
Sci USA. 2000;97:8039–8044.

71. Gor D, Sabin C, Prentice HG, et al. Longitudinal fluctuations in cytomegalovirus load in bone marrow transplant patients: relationship
between peak virus load, donor/recipient serostatus, acute GVHD
and CMV disease. Bone Marrow Transplant. 1998;21:597–605.
72. Ljungman P, Perez-Bercoff L, Jonsson J, et al. Risk factors for the
development of cytomegalovirus disease after allogeneic stem cell
transplantation. Haematologica. 2006;91:78–83.
73. Cathomas G, Morris P, Pekle K, et al. Rapid diagnosis of cytomegalovirus pneumonia in marrow transplant recipients by
bronchoalveolar lavage using the polymerase chain reaction, virus
culture, and the direct immunostaining of alveolar cells. Blood.
1993;81:1909–1914.
74. Gerna G, Lilleri D, Baldanti F, et al. Human cytomegalovirus
immediate-early mRNAemia versus pp65 antigenemia for guiding pre-emptive therapy in children and young adults undergoing
hematopoietic stem cell transplantation: a prospective, randomized, open-label trial. Blood. 2003;101:5053–5060.
75. Hebart H, Ljungman P, Klingebiel T, et al. Prospective comparison of PCR-based versus late mRNA-based preemptive antiviral
therapy for HCMV infection in patients after allogeneic stem cell
transplantation. Blood. 2003;102:195a.
76. Collier AC, Chandler SH, Handsfield HH, et al. Identification of
multiple strains of cytomegalovirus in homosexual men. J Infect
Dis. 1989;159:123–126.
77. Manuel O, Pang XL, Humar A, et al. An assessment of donor-torecipient transmission patterns of human cytomegalovirus by
analysis of viral genomic variants. J Infect Dis. 2009;199:1621–1628.
78. Ljungman P, Griffiths P, Paya C. Definitions of cytomegalovirus
infection and disease in transplant recipients. Clin Infect Dis.
2002;34:1094–1097.
79. Boeckh M, Stevens-Ayers T, Bowden RA. Cytomegalovirus pp65
antigenemia after autologous marrow and peripheral blood stem
cell transplantation. J Infect Dis. 1996;174:907–912.
80. Konoplev S, Champlin RE, Giralt S, et al. Cytomegalovirus pneumonia in adult autologous blood and marrow transplant recipients. Bone Marrow Transplant. 2001;27:877–881.
81. Ljungman P. Cytomegalovirus pneumonia: presentation, diagnosis, and treatment. Semin Respir Infect. 1995;10:209–215.
82. Schmidt GM, Horak DA, Niland JC, et al. A randomized,

controlled trial of prophylactic ganciclovir for cytomegalovirus

■

Cytomegalovirus Infection after Stem Cell Transplantation

83.

84.

85.

86.

87.

88.

89.

90.

91.

92.

93.

94.

95.

96.
97.

98.

99.

323

pulmonary infection in recipients of allogeneic bone marrow
transplants; The City of Hope-Stanford-Syntex CMV Study
Group. N Engl J Med. 1991;324:1005–1011.
Jang EY, Park SY, Lee EJ, et al. Diagnostic performance of the cytomegalovirus (CMV) antigenemia assay in patients with CMV
gastrointestinal disease. Clin Infect Dis. 2009;48:e121–e124.
Mori T, Okamoto S, Matsuoka S, et al. Risk-adapted pre-emptive
therapy for cytomegalovirus disease in patients undergoing allogeneic bone marrow transplantation. Bone Marrow Transplant.
2000;25:765–769.
Coskuncan NM, Jabs DA, Dunn JP, et al. The eye in bone marrow transplantation. VI. Retinal complications. Arch Ophthalmol.
1994;112:372–379.
Crippa F, Corey L, Chuang EL, et al. Virological, clinical, and ophthalmologic features of cytomegalovirus retinitis after hematopoietic stem cell transplantation. Clin Infect Dis. 2001;32:214–219.
Eid AJ, Bakri SJ, Kijpittayarit S, et al. Clinical features and outcomes of cytomegalovirus retinitis after transplantation. Transpl
Infect Dis. 2008;10:13–18.
Larsson K, Lonnqvist B, Ringden O, et al. CMV retinitis after allogeneic bone marrow transplantation: a report of five cases.
Transpl Infect Dis. 2002;4:75–79.
Nichols WG, Corey L, Gooley T, et al. High risk of death due to
bacterial and fungal infection among cytomegalovirus (CMV)seronegative recipients of stem cell transplants from seropositive
donors: evidence for indirect effects of primary CMV infection.
J Infect Dis. 2002;185:273–282.

Boeckh M. Current antiviral strategies for controlling cytomegalovirus in hematopoietic stem cell transplant recipients:
prevention and therapy. Transpl Infect Dis. 1999;1:165–178.
Broers AE, van Der Holt R, van Esser JW, et al. Increased transplantrelated morbidity and mortality in CMV-seropositive patients despite
highly effective prevention of CMV disease after allogeneic T-cell-depleted stem cell transplantation. Blood. 2000;95:2240–2245.
Craddock C, Szydlo RM, Dazzi F, et al. Cytomegalovirus seropositivity adversely influences outcome after T-depleted unrelated
donor transplant in patients with chronic myeloid leukaemia: the
case for tailored graft-versus-host disease prophylaxis. Br J
Haematol. 2001;112:228–236.
Behrendt CE, Rosenthal J, Bolotin E, et al. Donor and recipient
CMV serostatus and outcome of pediatric allogeneic HSCT for
acute leukemia in the era of CMV-preemptive therapy. Biol Blood
Marrow Transplant. 2009;15:54–60.
Boeckh M, Nichols WG. The impact of cytomegalovirus serostatus of donor and recipient before hematopoietic stem cell transplantation in the era of antiviral prophylaxis and preemptive
therapy. Blood. 2004;103:2003–2008.
Bordon V, Bravo S, Van Renterghem L, et al. Surveillance of cytomegalovirus (CMV) DNAemia in pediatric allogeneic stem cell
transplantation: incidence and outcome of CMV infection and
disease. Transpl Infect Dis. 2008;10:19–23.
Cwynarski K, Roberts IA, Iacobelli S, et al. Stem cell transplantation
for chronic myeloid leukemia in children. Blood. 2003;102:1224–1231.
Erard V, Guthrie KA, Riddell S, et al. Impact of HLA A2 and cytomegalovirus serostatus on outcomes in patients with leukemia
following matched-sibling myeloablative allogeneic hematopoietic cell transplantation. Haematologica. 2006;91:1377–1383.
Grob JP, Grundy JE, Prentice HG, et al. Immune donors can protect marrow-transplant recipients from severe cytomegalovirus
infections. Lancet. 1987;1:774–776.
Jacobsen N, Badsberg JH, Lonnqvist B, et al. Graft-versusleukaemia activity associated with CMV-seropositive donor,


58202_ch22.qxd

324

100.

101.

102.

103.

104.

105.

106.

107.

108.

109.

110.

111.

112.

113.

114.

115.

2/1/10

Section V

8:49 PM

■

Page 324

Viral Infections

post-transplant CMV infection, young donor age and chronic
graft-versus-host disease in bone marrow allograft recipients. The
Nordic Bone Marrow Transplantation Group. Bone Marrow
Transplant. 1990;5:413–418.
Kollman C, Howe CW, Anasetti C, et al. Donor characteristics as
risk factors in recipients after transplantation of bone marrow
from unrelated donors: the effect of donor age. Blood.
2001;98:2043–2051.
Ljungman P, Einsele H, Frassoni F, et al. Donor CMV serological
status influences the outcome of CMV-seropositive recipients after
unrelated donor stem cell transplantation; an EBMT megafile
analysis. Blood. 2003;102:4255–4260.
Nachbaur D, Clausen J, Kircher B. Donor cytomegalovirus
seropositivity and the risk of leukemic relapse after reducedintensity transplants. Eur J Haematol. 2006;76:414–419.
Ringden O, Schaffer M, Le Blanc K, et al. Which donor should be
chosen for hematopoietic stem cell transplantation among unrelated HLA-A, -B, and -DRB1 genomically identical volunteers?

Biol Blood Marrow Transplant. 2004;10:128–134.
Gustafsson Jernberg A, Remberger M, Ringden O, et al. Risk factors in pediatric stem cell transplantation for leukemia. Pediatr
Transplant. 2004;8:464–474.
Avetisyan G, Aschan J, Hagglund H, et al. Evaluation of intervention strategy based on CMV-specific immune responses after
allogeneic SCT. Bone Marrow Transplant. 2007;40:865–869.
Ganepola S, Gentilini C, Hilbers U, et al. Patients at high risk for
CMV infection and disease show delayed CD8ϩ T-cell immune
recovery after allogeneic stem cell transplantation. Bone Marrow
Transplant. 2007;39:293–299.
Lilleri D, Fornara C, Chiesa A, et al. Human cytomegalovirusspecific CD4ϩ and CD8ϩ T-cell reconstitution in adult allogeneic hematopoietic stem cell transplant recipients and immune
control of viral infection. Haematologica. 2008;93:248–256.
Moins-Teisserenc H, Busson M, Scieux C, et al. Patterns of cytomegalovirus reactivation are associated with distinct evolutive
profiles of immune reconstitution after allogeneic hematopoeitic
stem cell transplantation. J Infect Dis. 2008;198:818–826.
Lin TS, Zahrieh D, Weller E, et al. Risk factors for cytomegalovirus reactivation after CD6ϩ T-cell-depleted allogeneic
bone marrow transplantation. Transplantation. 2002;74:49–54.
Ozdemir E, Saliba R, Champlin R, et al. Risk factors associated
with late cytomegalovirus reactivation after allogeneic stem cell
transplantation for hematological malignancies. Bone Marrow
Transplant. 2007;40:125–136.
Marty FM, Bryar J, Browne SK, et al. Sirolimus-based graft-versus-host disease prophylaxis protects against cytomegalovirus reactivation after allogeneic hematopoietic stem cell transplantation:
a cohort analysis. Blood. 2007;110:490–500.
Ljungman P, Aschan J, Lewensohn-Fuchs I, et al. Results of different strategies for reducing cytomegalovirus-associated mortality in allogeneic stem cell transplant recipients. Transplantation.
1998;66:1330–1334.
Martino R, Rovira M, Carreras E, et al. Severe infections after allogeneic peripheral blood stem cell transplantation: a matchedpair comparison of unmanipulated and CD34ϩ cell-selected
transplantation. Haematologica. 2001;86:1075–1086.
Miller W, Flynn P, McCullough J, et al. Cytomegalovirus infection after bone marrow transplantation: an association with acute
graft-v-host disease. Blood. 1986;67:1162–1167.
Walker CM, van Burik JA, De For TE, et al. Cytomegalovirus infection after allogeneic transplantation: comparison of cord blood
with peripheral blood and marrow graft sources. Biol Blood

Marrow Transplant. 2007;13:1106–1115.

116. Holmberg LA, Boeckh M, Hooper H, et al. Increased incidence of
cytomegalovirus disease after autologous CD34-selected peripheral blood stem cell transplantation. Blood. 1999;94:4029–4035.
117. Trenschel R, Ross S, Husing J, et al. Reduced risk of persisting cytomegalovirus pp65 antigenemia and cytomegalovirus interstitial
pneumonia following allogeneic PBSCT. Bone Marrow Transplant.
2000;25:665–672.
118. Kudchodkar SB, Yu Y, Maguire TG, et al. Human cytomegalovirus infection alters the substrate specificities and rapamycin sensitivities of raptor- and rictor-containing complexes.
Proc Natl Acad Sci USA. 2006;103:14182–14187.
119. Einsele H, Steidle M, Vallbracht A, et al. Early occurrence of
human cytomegalovirus infection after bone marrow transplantation as demonstrated by the polymerase chain reaction technique.
Blood. 1991;77:1104–1110.
120. Nguyen Q, Champlin R, Giralt S, et al. Late cytomegalovirus
pneumonia in adult allogeneic blood and marrow transplant recipients. Clin Infect Dis. 1999;28:618–623.
121. Machado CM, Menezes RX, Macedo MC, et al. Extended antigenemia surveillance and late cytomegalovirus infection after allogeneic BMT. Bone Marrow Transplant. 2001;28:1053–1059.
122. Osarogiagbon RU, Defor TE, Weisdorf MA, et al. CMV antigenemia following bone marrow transplantation: risk factors and
outcomes. Biol Blood Marrow Transplant. 2000;6:280–288.
123. Peggs KS, Preiser W, Kottaridis PD, et al. Extended routine polymerase chain reaction surveillance and pre-emptive antiviral therapy for cytomegalovirus after allogeneic transplantation. Br J
Haematol. 2000;111:782–790.
124. Junghanss C, Boeckh M, Carter RA, et al. Incidence and outcome
of cytomegalovirus infections following nonmyeloablative compared with myeloablative allogeneic stem cell transplantation, a
matched control study. Blood. 2002;99:1978–1985.
125. Nakamae H, Kirby KA, Sandmaier BM, et al. Effect of conditioning regimen intensity on CMV infection in allogeneic hematopoietic
cell transplantation. Biol Blood Marrow Transplant. 2009;15:694–703.
126. Chakrabarti S, Mackinnon S, Chopra R, et al. High incidence of
cytomegalovirus infection after nonmyeloablative stem cell transplantation: potential role of Campath-1H in delaying immune reconstitution. Blood. 2002;99:4357–4363.
127. Hebart H, Schroder A, Loffler J, et al. Cytomegalovirus monitoring by polymerase chain reaction of whole blood samples from patients undergoing autologous bone marrow or peripheral blood
progenitor cell transplantation. J Infect Dis. 1997;175:1490–1493.
128. Bilgrami S, Aslanzadeh J, Feingold JM, et al. Cytomegalovirus
viremia, viruria and disease after autologous peripheral blood

stem cell transplantation: no need for surveillance. Bone Marrow
Transplant. 1999;24:69–73.
129. Boeckh M, Gooley TA, Reusser P, et al. Failure of high-dose acyclovir to prevent cytomegalovirus disease after autologous marrow transplantation. J Infect Dis. 1995;172:939–943.
130. Singhal S, Powles R, Treleaven J, et al. Cytomegaloviremia after
autografting for leukemia: clinical significance and lack of effect
on engraftment. Leukemia. 1997;11:835–838.
131. Enright H, Haake R, Weisdorf D, et al. Cytomegalovirus pneumonia after bone marrow transplantation. Risk factors and response to therapy. Transplantation. 1993;55:1339–1346.
132. Reusser P, Fisher LD, Buckner CD, et al. Cytomegalovirus infection after autologous bone marrow transplantation: occurrence of
cytomegalovirus disease and effect on engraftment. Blood. 1990;
75:1888–1894.
133. Schoemans H, Theunissen K, Maertens J, et al. Adult umbilical
cord blood transplantation: a comprehensive review. Bone Marrow
Transplant. 2006;38:83–93.


58202_ch22.qxd

2/1/10

8:49 PM

Page 325

Chapter 22

134. Albano MS, Taylor P, Pass RF, et al. Umbilical cord blood transplantation and cytomegalovirus: posttransplantation infection and
donor screening. Blood. 2006;108:4275–4282.
135. Matsumura T, Narimatsu H, Kami M, et al. Cytomegalovirus infections following umbilical cord blood transplantation using reduced intensity conditioning regimens for adult patients. Biol
Blood Marrow Transplant. 2007;13:577–583.
136. Saavedra S, Sanz GF, Jarque I, et al. Early infections in adult patients undergoing unrelated donor cord blood transplantation.

Bone Marrow Transplant. 2002;30:937–943.
137. Takami A, Mochizuki K, Asakura H, et al. High incidence of cytomegalovirus reactivation in adult recipients of an unrelated cord
blood transplant. Haematologica. 2005;90:1290–1292.
138. Tomonari A, Takahashi S, Ooi J, et al. Preemptive therapy with ganciclovir 5 mg/kg once daily for cytomegalovirus infection after unrelated
cord blood transplantation. Bone Marrow Transplant. 2008;41:371–376.
139. Koo S, Baden LR. Infectious complications associated with immunomodulating monoclonal antibodies used in the treatment
of hematologic malignancy. J Natl Compr Canc Netw. 2008;6:
202–213.
140. O’Brien SM, Keating MJ, Mocarski ES. Updated guidelines on
the management of cytomegalovirus reactivation in patients with
chronic lymphocytic leukemia treated with alemtuzumab. Clin
Lymphoma Myeloma. 2006;7:125–130.
141. Orlandi EM, Baldanti F, Citro A, et al. Monitoring for cytomegalovirus and Epstein–Barr virus infection in chronic lymphocytic leukemia patients receiving i.v. fludarabine-cyclophosphamide
combination and alemtuzumab as consolidation therapy.
Haematologica. 2008;93:1758–1760.
142. Delgado J, Pillai S, Benjamin R, et al. The effect of in vivo T cell
depletion with alemtuzumab on reduced-intensity allogeneic
hematopoietic cell transplantation for chronic lymphocytic
leukemia. Biol Blood Marrow Transplant. 2008;14:1288–1297.
143. Martin SI, Marty FM, Fiumara K, et al. Infectious complications
associated with alemtuzumab use for lymphoproliferative disorders. Clin Infect Dis. 2006;43:16–24.
144. Bowden RA, Sayers M, Flournoy N, et al. Cytomegalovirus immune globulin and seronegative blood products to prevent primary cytomegalovirus infection after marrow transplantation.
N Engl J Med. 1986;314:1006–1010.
145. Bowden R, Cays M, Schoch G, et al. Comparison of filtered blood
(FB) to seronegative blood products (SB) for prevention of cytomegalovirus (CMV) infection after marrow transplant. Blood.
1995;86:3598–3603.
146. Ljungman P, Larsson K, Kumlien G, et al. Leukocyte depleted,
unscreened blood products give a low risk for CMV infection and
disease in CMV seronegative allogeneic stem cell transplant recipients with seronegative stem cell donors. Scand J Infect Dis.
2002;34:347–350.

147. Nichols WG, Price TH, Gooley T, et al. Transfusion-transmitted
cytomegalovirus infection after receipt of leukoreduced blood
products. Blood. 2003;101:4195–4200.
148. Blajchman MA, Goldman M, Freedman JJ, et al. Proceedings of
a consensus conference: prevention of post-transfusion CMV in
the era of universal leukoreduction. Transfus Med Rev. 2001;15:
1–20.
149. Ratko TA, Cummings JP, Oberman HA, et al. Evidence-based
recommendations for the use of WBC-reduced cellular blood
components. Transfusion. 2001;41:1310–1319.
150. Bowden RA, Fisher LD, Rogers K, et al. Cytomegalovirus
(CMV)-specific intravenous immunoglobulin for the prevention
of primary CMV infection and disease after marrow transplant
[see comments]. J Infect Dis. 1991;164:483–487.

■

Cytomegalovirus Infection after Stem Cell Transplantation

325

151. Ruutu T, Ljungman P, Brinch L, et al. No prevention of cytomegalovirus infection by anti-cytomegalovirus hyperimmune
globulin in seronegative bone marrow transplant recipients.
The Nordic BMT Group. Bone Marrow Transplant. 1997;19:
233–236.
152. Boeckh M, Bowden R, Storer B, et al. Randomized, placebocontrolled, double-blind study of a cytomegalovirus-specific
monoclonal antibody (MSL-109) for prevention of cytomegalovirus
infection after allogeneic hematopoietic stem cell transplantation.
Biol Blood Marrow Transplant. 2001;7:343–351.
153. Bass E, Powe N, Goodman S, et al. Efficacy of immune globulin

in preventing complications of bone marrow transplantation: a
meta-analysis. Bone Marrow Transplant. 1993;12:179–183.
154. Messori A, Rampazzo R, Scroccaro G, et al. Efficacy of hyperimmune anti-cytomegalovirus immunoglobulins for the prevention
of cytomegalovirus infection in recipients of allogeneic bone marrow transplantation: a meta analysis. Bone Marrow Transplant.
1994;13:163–168.
155. Raanani P, Gafter-Gvili A, Paul M, et al. Immunoglobulin prophylaxis in patients undergoing haematopoietic stem cell transplantation: systematic review and meta-analysis, [abstract O267].
Bone Marrow Transplant. 2008;41:s46.
156. Sullivan KM, Kopecky KJ, Jocom J, et al. Immunomodulatory
and antimicrobial efficacy of intravenous immunoglobulin in
bone marrow transplantation. N Engl J Med. 1990;323:705–712.
157. Winston DJ, Ho WG, Lin CH, et al. Intravenous immune globulin for prevention of cytomegalovirus infection and interstitial
pneumonia after bone marrow transplantation. Ann Intern Med.
1987;106:12–18.
158. Zikos P, Van Lint MT, Lamparelli T, et al. A randomized trial of
high dose polyvalent intravenous immunoglobulin (HDIgG) vs.
Cytomegalovirus (CMV) hyperimmune IgG in allogeneic hemopoietic stem cell transplants (HSCT). Haematologica. 1998;83:
132–137.
159. Boeckh M, Gooley TA, Myerson D, et al. Cytomegalovirus pp65
antigenemia-guided early treatment with ganciclovir versus ganciclovir at engraftment after allogeneic marrow transplantation:
a randomized double-blind study. Blood. 1996;88:4063–4071.
160. Avery RK, Adal KA, Longworth DL, et al. A survey of allogeneic
bone marrow transplant programs in the United States regarding
cytomegalovirus prophylaxis and pre-emptive therapy. Bone
Marrow Transplant. 2000;26:763–767.
161. Ljungman P. CMV infections after hematopoietic stem cell transplantation. Bone Marrow Transplant. 2008;42(suppl 1):S70–S72.
162. Ljungman P, Reusser P, de la Camara R, et al. Management of CMV
infections: recommendations from the infectious diseases working
party of the EBMT. Bone Marrow Transplant. 2004;33:1075–1081.
163. Lacey SF, Diamond DJ, Zaia JA. Assessment of cellular immunity
to human cytomegalovirus in recipients of allogeneic stem cell

transplants. Biol Blood Marrow Transplant. 2004;10:433–447.
164. Meyers JD, Reed EC, Shepp DH, et al. Acyclovir for prevention
of cytomegalovirus infection and disease after allogeneic marrow
transplantation. N Engl J Med. 1988;318:70–75.
165. Prentice HG, Gluckman E, Powles RL, et al. Impact of long-term
acyclovir on cytomegalovirus infection and survival after allogeneic bone marrow transplantation. European Acyclovir for
CMV Prophylaxis Study Group. Lancet. 1994;343:749–753.
166. Ljungman P, De La Camara R, Milpied N, et al. A randomised
study of valaciclovir as prophylaxis against CMV reactivation in allogeneic bone marrow transplant recipients. Blood. 2002;73:930–936.
167. Goodrich JM, Bowden RA, Fisher L, et al. Ganciclovir prophylaxis to prevent cytomegalovirus disease after allogeneic marrow
transplant. Ann Intern Med. 1993;118:173–178.


58202_ch22.qxd

326

2/1/10

Section V

8:49 PM

■

Page 326

Viral Infections

168. Winston DJ, Ho WG, Bartoni K, et al. Ganciclovir prophylaxis of

cytomegalovirus infection and disease in allogeneic bone marrow
transplant recipients. Results of a placebo-controlled, doubleblind trial. Ann Intern Med. 1993;118:179–184.
169. Winston DJ, Yeager AM, Chandrasekar PH, et al. Randomized
comparison of oral valacyclovir and intravenous ganciclovir for
prevention of cytomegalovirus disease after allogeneic bone marrow transplantation. Clin Infect Dis. 2003;36:749–758.
170. Salzberger B, Bowden RA, Hackman RC, et al. Neutropenia in
allogeneic marrow transplant recipients receiving ganciclovir for
prevention of cytomegalovirus disease: risk factors and outcome.
Blood. 1997;90:2502–2508.
171. Busca A, de Fabritiis P, Ghisetti V, et al. Oral valganciclovir as
preemptive therapy for cytomegalovirus infection post allogeneic
stem cell transplantation. Transpl Infect Dis. 2007;9:102–107.
172. Einsele H, Reusser P, Bornhauser M, et al. Oral valganciclovir
leads to higher exposure to ganciclovir than intravenous ganciclovir in patients following allogeneic stem cell transplantation.
Blood. 2006;107:3002–3008.
173. Winston DJ, Baden LR, Gabriel DA, et al. Pharmacokinetics of
ganciclovir after oral valganciclovir versus intravenous ganciclovir in allogeneic stem cell transplant patients with graft-versushost disease of the gastrointestinal tract. Biol Blood Marrow
Transplant. 2006;12:635–640.
174. Allice T, Busca A, Locatelli F, et al. Valganciclovir as pre-emptive
therapy for cytomegalovirus infection post-allogenic stem cell
transplantation: implications for the emergence of drug-resistant
cytomegalovirus. J Antimicrob Chemother. 2009;63:600–608.
175. Ayala E, Greene J, Sandin R, et al. Valganciclovir is safe and effective as pre-emptive therapy for CMV infection in allogeneic
hematopoietic stem cell transplantation. Bone Marrow Transplant.
2006;37:851–856.
176. Takenaka K, Eto T, Nagafuji K, et al. Oral valganciclovir as preemptive therapy is effective for cytomegalovirus infection in allogeneic hematopoietic stem cell transplant recipients. Int J Hematol.
2009;89:231–237.
177. Volin L, Barkholt L, Nihtinen A, et al. An open-label randomised study of oral valganciclovir versus intravenous ganciclovir for pre-emptive therapy of cytomegalovirus infection after
allogeneic stem cell transplantation. In: 34th Annual Meeting of
the European Group for Blood and Marrow Transplantation.

Florence, Italy; 2008.
178. Reusser P, Einsele H, Lee J, et al. Randomized multicenter trial of
foscarnet versus ganciclovir for preemptive therapy of cytomegalovirus infection after allogeneic stem cell transplantation.
Blood. 2002;99:1159–1164.
179. Bacigalupo A, Tedone E, Van Lint MT, et al. CMV prophylaxis
with foscarnet in allogeneic bone marrow transplant recipients at
high risk of developing CMV infections. Bone Marrow Transplant.
1994;13:783–788.
180. Bregante S, Bertilson S, Tedone E, et al. Foscarnet prophylaxis of
cytomegalovirus infections in patients undergoing allogeneic bone
marrow transplantation (BMT): a dose-finding study. Bone
Marrow Transplant. 2000;26:23–29.
181. Reusser P, Gambertoglio JG, Lilleby K, et al. Phase I-II trial of
foscarnet for prevention of cytomegalovirus infection in autologous and allogeneic marrow transplant recipients [see comments].
J Infect Dis. 1992;166:473–479.
182. Ljungman P, Deliliers GL, Platzbecker U, et al. Cidofovir for cytomegalovirus infection and disease in allogeneic stem cell transplant
recipients. The Infectious Diseases Working Party of the European
Group for Blood and Marrow Transplantation. Blood. 2001;97:
388–392.

183. Emery VC, Sabin CA, Cope AV, et al. Application of viral-load
kinetics to identify patients who develop cytomegalovirus disease
after transplantation. Lancet. 2000;355:2032–2036.
184. Pang XL, Fox JD, Fenton JM, et al. Interlaboratory comparison of
cytomegalovirus viral load assays. Am J Transplant. 2009;9:258–268.
185. Nichols WG, Price T, Boeckh M. Donor serostatus and CMV infection and disease among recipients of prophylactic granulocyte
transfusions. Blood. 2003;101:5091–5092; author reply 5092.
186. Ljungman P, de la Camara R, Cordonnier C, et al. Management
of CMV, HHV-6, HHV-7 and Kaposi-sarcoma herpesvirus
(HHV-8) infections in patients with hematological malignancies

and after SCT. Bone Marrow Transplant. 2008;42:227–240.
187. Tomblyn M, Chiller T, EinseleH, et al. Guidelines for Preventing
Infectious Complications among Hematopoietic Cell Transplant
Recipients: A Global Perspective. Recommendations of the Center
for International Blood and Marrow Transplant Research
(CIBMTR®), the National Marrow Donor Program (NMDP), the
European Blood and Marrow Transplant Group (EBMT), the
American Society of Blood and Marrow Transplantation (ASBMT),
the Canadian Blood and Marrow Transplant Group (CBMTG), the
Infectious Disease Society of America (IDSA), the Society for
Healthcare Epidemiology of America (SHEA), the Association of
Medical Microbiology and Infectious Diseases Canada (AMMI), the
Centers for Disease Control and Prevention (CDC), and the Health
Resources and Services Administration (HRSA). Biol Blood Marrow
Transplant. 2009;15(10):1143–1238; Bone Marrow Transplant.
2009;44(8):part 2.
188. Ljungman P, Lore K, Aschan J, et al. Use of a semi-quantitative
PCR for cytomegalovirus DNA as a basis for pre-emptive antiviral therapy in allogeneic bone marrow transplant patients. Bone
Marrow Transplant. 1986;17:583–587.
189. Fries BC, Riddell SR, Kim HW, et al. Cytomegalovirus disease
before hematopoietic cell transplantation as a risk for complications after transplantation. Biol Blood Marrow Transplant.
2005;11:136–148.
190. Chou SW. Cytomegalovirus drug resistance and clinical implications. Transpl Infect Dis. 2001;3(suppl 2):20–24.
191. Chou S. Cytomegalovirus UL97 mutations in the era of ganciclovir and maribavir. Rev Med Virol. 2008;18:233–246.
192. Iwasenko JM, Scott GM, Rawlinson WD, et al. Successful valganciclovir treatment of post-transplant cytomegalovirus infection in the
presence of UL97 mutation N597D. J Med Virol. 2009;81:507–510.
193. Prichard MN, Britt WJ, Daily SL, et al. Human cytomegalovirus UL97 Kinase is required for the normal intranuclear distribution of pp65 and virion morphogenesis. J Virol.
2005;79:15494–15502.
194. Drew WL. Is combination antiviral therapy for CMV superior to
monotherapy? J Clin Virol. 2006;35:485–488.

195. Chou S, Lurain NS, Thompson KD, et al. Viral DNA polymerase
mutations associated with drug resistance in human cytomegalovirus. J Infect Dis. 2003;188:32–39.
196. Drew WL, Miner RC, Marousek GI, et al. Maribavir sensitivity of
cytomegalovirus isolates resistant to ganciclovir, cidofovir or foscarnet. J Clin Virol. 2006;37:124–127.
197. Avery RK, Bolwell BJ, Yen-Lieberman B, et al. Use of leflunomide in
an allogeneic bone marrow transplant recipient with refractory cytomegalovirus infection. Bone Marrow Transplant. 2004;34:1071–1075.
198. Battiwalla M, Paplham P, Almyroudis NG, et al. Leflunomide
failure to control recurrent cytomegalovirus infection in the setting of renal failure after allogeneic stem cell transplantation.
Transpl Infect Dis. 2007;9:28–32.
199. Efferth T, Romero M, Wolf D, et al. The antiviral activities of
artemisinin and artesunate. Clin Infect Dis. 2008;47:804–811.


58202_ch22.qxd

2/1/10

8:49 PM

Page 327

Chapter 22

200. Arvin AM, Fast P, Myers M, et al. Vaccine development to prevent cytomegalovirus disease: report from the National Vaccine
Advisory Committee. Clin Infect Dis. 2004;39:233–239.
201. Adler SP. Human CMV vaccine trials: what if CMV caused a
rash? J Clin Virol. 2008;41:231–236.
202. Wloch MK, Smith LR, Boutsaboualoy S, et al. Safety and immunogenicity of a bivalent cytomegalovirus DNA vaccine in
healthy adult subjects. J Infect Dis. 2008;197:1634–1642.
203. Reed EC, Wolford JL, Kopecky KJ, et al. Ganciclovir for the

treatment of cytomegalovirus gastroenteritis in bone marrow
transplant patients. A randomized, placebo-controlled trial. Ann
Intern Med. 1990;112:505–510.
204. Ljungman P, Cordonnier C, Einsele H, et al. Use of intravenous
immune globulin in addition to antiviral therapy in the treatment
of CMV gastrointestinal disease in allogeneic bone marrow transplant patients: a report from the European Group for Blood and
Marrow Transplantation (EBMT). Infectious Diseases Working
Party of the EBMT. Bone Marrow Transplant. 1998;21:473–476.
205. Emanuel D, Cunningham I, Jules-Elysee K, et al. Cytomegalovirus
pneumonia after bone marrow transplantation successfully treated
with the combination of ganciclovir and high-dose intravenous immune globulin. Ann Intern Med. 1998;109:777–782.
206. Ljungman P, Engelhard D, Link H, et al. Treatment of interstitial
pneumonitis due to cytomegalovirus with ganciclovir and intravenous immune globulin: experience of European Bone Marrow
Transplant Group. Clin Infect Dis. 1992;14:831–835.
207. Reed EC, Bowden RA, Dandliker PS, et al. Treatment of cytomegalovirus pneumonia with ganciclovir and intravenous
cytomegalovirus immunoglobulin in patients with bone marrow transplants. Ann Intern Med. 1988;109:783–788.
208. Schmidt GM, Kovacs A, Zaia JA, et al. Ganciclovir/immunoglobulin combination therapy for the treatment of human

■

Cytomegalovirus Infection after Stem Cell Transplantation

209.

210.

211.

212.

213.

214.
215.
216.

217.

327

cytomegalovirus-associated interstitial pneumonia in bone marrow allograft recipients. Transplantation. 1988;46:905–907.
Erard V, Gutherie KA, Smith J, et al. Cytomegalovirus pneumonia (CMV-IP) after hematopoeitic cell transplantation (HCT):
outcomes and factors associated with mortality (abstract V-1379).
In: 47th Interscience Conference on Antimicrobial Agents and
Chemotherapy. Chicago, IL; 2007.
Machado CM, Dulley FL, Boas LS, et al. CMV pneumonia in allogeneic BMT recipients undergoing early treatment of pre-emptive
ganciclovir therapy. Bone Marrow Transplant. 2000;26:413–417.
Chang M, Dunn JP. Ganciclovir implant in the treatment of
cytomegalovirus retinitis. Expert Rev Med Devices. 2005;2:
421–427.
Okamoto T, Okada M, Mori A, et al. Successful treatment of severe
cytomegalovirus retinitis with foscarnet and intraocular infection
of ganciclovir in a myelosuppressed unrelated bone marrow transplant patient. Bone Marrow Transplant. 1997;20:801–803.
Ganly PS, Arthur C, Goldman JM, et al. Foscarnet as treatment
for cytomegalovirus retinitis following bone marrow transplantation. Postgrad Med J. 1988;64:389–391.
Biron KK. Antiviral drugs for cytomegalovirus diseases. Antiviral
Res. 2006;71:154–163.
Einsele H, Kapp M, Grigoleit GU. CMV-specific T cell therapy.
Blood Cells Mol Dis. 2008;40:71–75.
Williams-Aziz SL, Hartline CB, Harden EA, et al. Comparative

activities of lipid esters of cidofovir and cyclic cidofovir against
replication of herpesviruses in vitro. Antimicrob Agents Chemother.
2005;49:3724–3733.
Schleiss MR, Bernstein DI, McVoy MA, et al. The non-nucleoside
antiviral, BAY 38-4766, protects against cytomegalovirus (CMV)
disease and mortality in immunocompromised guinea pigs.
Antiviral Res. 2005;65:35–43.


58202_ch23.qxd

2/1/10

8:50 PM

Page 328

CHAPTER

23

Cytomegalovirus Infection
after Solid Organ Transplantation
RAYMUND R. RAZONABLE, AJIT P. LIMAYE

EPIDEMIOLOGY AND PATHOGENESIS
Cytomegalovirus (CMV) is the major pathogen that affects the
outcome of solid organ transplantation (1). Not only is CMV a
common infection among all solid organ transplant populations, but also its clinical impact translates into significant
morbidity and mortality (1). CMV is a ubiquitous ␤-herpesvirus

that infects most humans (2). The prevalence rate of CMV
seropositivity in the United States is estimated to be 60% among
individuals who are at least 6 years old (2). The seroprevalence
rate increases directly with age, so that 90% of adults who are at
least 80 years old are CMV seropositive (2). Primary infection
with CMV is acquired through contact with infected body fluids such as saliva, urine, or genital secretions from CMVinfected individuals (3). The vast majority of primary CMV
infections occur during childhood through early adulthood
(3). Clinically, primary CMV infection in immunocompetent
individuals is manifested either as an asymptomatic illness in
the majority of individuals or occasionally as a benign infectious mononucleosis-like syndrome characterized by fever and
lymphadenopathy (3).
The immune response to CMV is initiated upon the recognition of CMV virions and antigens by pathogen-recognition
receptors, such as the Toll-like receptors, which are expressed
on macrophages, dendritic cells, and other innate immune cells
(4–6). The outcome of this interaction between CMV and innate immune cells is the secretion of interferon-␥, tumor necrosis factor (TNF)-␣, interleukins, and other cytokines involved
in the control of the earliest stages of viral infection (4–6). In
addition, innate immune activation leads to the upregulation of
costimulatory molecules that direct the development, maturation, and proliferation of lymphocytes responsible for CMVspecific cell-mediated and humoral immunity (4–8). However,
CMV has developed immune evasion mechanisms so that
CMV-specific cellular and humoral immune responses do not
completely eliminate the virus. Instead, CMV infection universally leads to lifelong latency, with intermittent periods of reactivation and low-level persistence (9–11).
Cells that allow for CMV latency and/or viral persistence
are widely distributed in the human body, including the hematopoietic progenitor cells (12), peripheral blood mononuclear
328

cells (3,13), polymorphonuclear leukocytes (14), and macrophages (15). CMV also infects and may persist in fibroblasts,
smooth muscle cells, and endothelial cells (16). The wide distribution of CMV-infected cells in the various tissues and organs,
such as the bone marrow, liver, kidney, lungs, and gastrointestinal tract (17–20), allows for the efficient transmission of CMV
to susceptible hosts during organ and tissue transplantation.
Mechanisms of Acquiring Cytomegalovirus

Infection after Solid Organ Transplantation
The three major mechanisms of acquiring CMV infection after
solid organ transplantation are (i) primary infection, (ii) reactivation infection, and (iii) superinfection.
Primary Cytomegalovirus Infection (CMV Dϩ/RϪ)
Primary CMV infection occurs when a CMV-seronegative patient (CMV RϪ) receives an allograft from a CMV seropositive
donor (CMV Dϩ). This CMV Dϩ/RϪ serologic mismatch is
estimated to occur in 15% to 25% of all solid organ transplantation (1). In the absence of antiviral prophylaxis, a CMV Dϩ/RϪ
serologic mismatch will almost always result in the transmission
of CMV to the susceptible transplant recipient, where it can
cause clinically severe primary CMV disease. Less commonly,
primary CMV infection may occur in a CMV RϪ transplant recipient when CMV is transmitted through transfusion of blood
products from CMV seropositive donors or through natural
transmission routes in the community (21,22); these latter two
mechanisms account for the occurrence of CMV infection and
disease in CMV DϪ/RϪ solid organ transplant recipients.
Reactivation Infection (CMV DϪ/Rϩ)
Reactivation infection occurs when endogenous latent CMV in
a CMV seropositive (CMV Rϩ) transplant recipient reactivates during the periods of impaired immunity after solid
organ transplantation. Because patients have preexisting CMVspecific cell-mediated and humoral immunity, the degree of
CMV reactivation and replication in CMV Rϩ patients is relatively lower when compared to the primary CMV infection in
CMV Dϩ/RϪ patients and hence a relatively lower risk of
developing symptomatic CMV disease (23,24).


58202_ch23.qxd

2/1/10

8:50 PM

Page 329

Chapter 23

■

Superinfection (CMV Dϩ/Rϩ)
Superinfection (also known as reinfection) occurs when a
CMV Rϩ transplant recipient is infected with an exogenous
CMV strain from a CMV seropositive donor (or other exogenous source), and subsequently, either the donor allografttransmitted exogenous CMV or recipient-derived endogenous
CMV, or both, reactivate to cause clinical disease after solid
organ transplantation (25). In the majority of cases, donorderived CMV is the predominant virus that reactivates in
CMV Dϩ/Rϩ patients (25–27), suggesting a potentially incomplete degree of cross-protection against other viral strains.
Mechanisms of Cytomegalovirus Reactivation
after Solid Organ Transplantation
Table 23.1 lists some of the risk factors associated with CMV
infection and disease after solid organ transplantation (1).
Central to many of these factors is the secretion of various
proinflammatory cytokines and catecholamines (28–30),
most notably TNF-␣, which has been implicated in many
studies as a potent transactivator of CMV reactivation (31).
In vitro, TNF-␣ stimulated the activity of CMV immediate-early (CMV-IE) enhancer/promoter region in a human
monocytic cell line (32,33). Stimulation of the TNF-␣1
receptor results in the activation of protein kinase C and nuclear factor-kappa B (NF-␬B), which undergoes nuclear
translocation and binds within the CMV-IE enhancer/promoter region (28,34,35), triggering a cascade of events that
lead to CMV reactivation (36). Likewise, catecholamines released during periods of stress, whether physiologic or in
response to medical illness, could stimulate CMV-IE enhancer/
promoter activity (34,35) through the cyclic adenosine mono-

TABLE 23.1

Cytomegalovirus Infection after Solid Organ Transplantation

329

phosphate (cAMP) pathway. Collectively, inflammation,
stress, and other factors that influence cAMP and NF-␬B signaling pathways contribute to the reactivation of CMV from
latency after solid organ transplantation. Indeed, clinical
conditions characterized by high levels of TNF-␣, such as
bacterial sepsis and allograft rejection, have been significantly associated with CMV infection in the transplant and
nontransplant settings (37–40).

Risk Factors for Cytomegalovirus Infection
after Solid Organ Transplantation
Without antiviral therapy, up to 55% of solid organ transplant
recipients with CMV reactivation will progress to develop
CMV disease (41–43). The rates of CMV disease vary according
to the type of organ transplantation (Table 23.2) (1). In general,
the occurrence of CMV disease after solid organ transplantation
is influenced by many interrelated factors that are categorized
into (i) those that favor disease progression (e.g., delayed immune recovery, immunosuppressive drugs, viral load, viral
coinfections) and (ii) those that control viral replication (e.g.,
CMV-specific immunity, antiviral therapy) (Table 23.1).
Cytomegalovirus Dϩ/RϪ Serologic Mismatch
A CMV Dϩ/RϪ serologic mismatch is considered as the most
important variable that predicts CMV disease after solid organ
transplantation. It is therefore imperative that CMV immunoglobulin G screening is performed on all transplant donors
and potential transplant candidates so as to allow for risk stratification and guide the intensity of CMV prevention strategy after
transplantation (44). Historical data suggest that up to 70% of all
CMV Dϩ/RϪ solid organ transplant recipients, which lack

Factors that Influence the Reactivation of CMV and the Risk of Clinical
Disease after Solid Organ Transplantation
Factors that Influence Progression to CMV Disease

Factors that Influence
CMV Reactivation

Increase Risk of CMV Disease

Diminish Risk of CMV Disease

Allogeneic stimulation

Lack of preexisting CMV-specific immunity
(i.e., Dϩ/RϪ)

Preexisting CMV-specific
immunity (Rϩ)

Allograft rejection

Pharmacologic immunosuppression
OKT3, ATG, and ALG
Alemtuzumab
Mycophenolate mofetil (Ͼ2 g/d)
High-dose methylprednisolone

Antiviral prophylaxis
Preemptive antiviral therapy

Viral burden (viral load)

Immunotherapy

Lymphocyte-depleting agents
OKT3, ATG, ALG

Stress
Critical illness
Surgical procedure
Bacterial and fungal sepsis

Abbreviations: CMV, cytomegalovirus; OKT3, muromonab-CD3; ATG, antithymocyte globulin; ALG, antilymphocyte globulin; Dϩ/RϪ, donor positive/recipient negative;
Rϩ, recipient positive.


58202_ch23.qxd

330

2/1/10

Section V

TABLE 23.2

8:50 PM

■

Page 330

Viral Infections

Estimated Incidence Rates of CMV Disease after Solid Organ Transplantation
CMV D؉/R؊

CMV R؉

No Prophylaxis
(%)

With Prophylaxisb,d
(%)

No Prophylaxis
(%)

With Prophylaxisb,d
(%)

Kidney and/or pancreas

45–65

6–29

8–10

1–2

Liver

45–65

6–29

8–19

4–13

Heart

29–74

19–30

20–40

2

Lung and lung–heart

50–91

36–40b

35–59

5–15b

Type of Solid Organ
Transplanta

10c

1–5c

Abbreviations: CMV, cytomegalovirus; Dϩ/RϪ, donor positive/recipient negative; Rϩ, recipient positive.
aThe

estimated incidence after small bowel transplantation is 22% of all patients, including all donor and recipient CMV serostatus.

bAntiviral

prophylaxis is given for a duration of 3 months unless otherwise indicated.

cIndicates

6 months of prophylaxis after lung transplantation.

dCMV

disease in patients, who received prophylaxis, generally occurs after the completion of antiviral prophylaxis (delayed-onset CMV disease).

CMV-specific cellular and humoral immunity, will develop primary CMV disease if they do not receive any CMV prevention
strategy (Table 23.2) (1). The absence of preexisting CMV-specific immunity in CMV Dϩ/RϪ solid organ transplant recipients allows for a very rapid CMV replication dynamics, with an
estimated CMV doubling rate of 1 day (23,24). Clinically, this
translates to a high rate of clinical CMV disease. In contrast, the

presence of preexisting immunity in CMV Rϩ solid organ
transplant recipients dampens CMV replication dynamics
(23,24). This lower degree of CMV replication
dynamics could explain the relatively lower incidence and potentially lesser severity of CMV disease in CMV Rϩ transplant
patients when compared to CMV Dϩ/RϪ patients (23,24,45,46).
Defects in Cytomegalovirus-Specific
T-Cell Immunity
Optimal functioning of CMV-specific T cells is essential for
adequate control of CMV infection (45–48). Expectedly,
CMV-specific CD4ϩ and CD8ϩ T lymphocytes are absent at
the time of organ transplantation in CMV Dϩ/RϪ patients,
thereby predisposing these patients to a high rate of CMV disease (47,49,50). On the contrary, CMV-specific CD4ϩ and
CD8ϩ T lymphocytes are present among CMV Rϩ solid
organ transplant recipients, although the use of lymphocytedepleting immunosuppressive drugs such as OKT3 or thymoglobulin decreases the absolute levels, percentages, and
function of these cells to a level that results in incomplete protection and hence increased predisposition to CMV reactivation, replication, and clinical disease (47,48,50,51). In this regard,
the severity of immunosuppression induced by lymphocytedepleting drugs is a major factor that determines who develops CMV viremia and clinical disease. Several studies have
been conducted to estimate the threshold of CD4ϩ and

CD8ϩ T cells that confer protection or risk, but this level has
not been precisely defined (47,48,50,51).
Defects in Innate Immunity
Since CMV is initially recognized by cells of the innate immune system, through pathogen-recognition receptors, deficiencies in cells and molecules of innate immunity have been
implicated as factors that increase the risk of CMV infection
and disease after solid organ transplantation (52–57). Among
these are deficiencies in various Toll-like receptors, mannosebinding lectin, mannose-associated serine protease-2, and activating and inhibitory killer cell immunoglobulin-like
receptors, all of which have been reported to be associated
with a higher incidence of CMV disease after solid organ
transplantation (52–57).
Pharmacologic Immunosuppression
Immunosuppressive drugs, which are administered as induction or maintenance therapy for the prevention and treatment

of allograft rejection, impair the immune responses to CMV
and other pathogens. These drugs, especially the lymphocytedepleting agents, could dampen and delay the reconstitution
of CMV-specific, cell-mediated, and humoral immune responses and lead to uncontrolled CMV replication and disease
(40,58). Among the drugs that are most commonly associated
with CMV disease are OKT3, antilymphocyte globulin
(ALG), antithymocyte globulin (ATG), and alemtuzumab
(59–69). Administration of certain lymphocyte-depleting antibodies is often complicated by a cytokine release syndrome,
characterized by high fevers and rigors. Theoretically, cytokine (TNF-␣) release syndrome could induce CMV reactivation, which in the presence of global suppression of T-cell
function could lead to uncontrolled CMV replication and


58202_ch23.qxd

2/1/10

8:50 PM

Page 331

Chapter 23

clinical disease (59). Several studies have also implicated high
doses of steroids and mycophenolate mofetil in the development of CMV disease (59–69). In addition to the individual
effects and risks associated with specific immunosuppressive
drugs, the overall combined net state of drug immunosuppression is likely playing a major role in the predisposition to develop CMV disease after solid organ transplantation.
Allograft Rejection
Acute rejection is a well-defined major risk factor for CMV
disease after solid organ transplantation (40,58,70,71). Proinflammatory cytokines, such as TNF-␣, released during an
episode of allograft rejection serve as potent transactivators of
CMV from a state of latency to one of active replication. In one

study, acute rejection increased the risk of CMV disease by
sixfold in a cohort of CMV Dϩ/RϪ liver and renal transplant
recipients (40). In another study, CMV disease occurred in
three-quarters of patients during the month following an
episode of acute rejection (72). Conversely, CMV is implicated
as a major risk factor for the occurrence of acute and chronic
allograft rejection after solid organ transplantation, thereby
establishing a bidirectional relationship between CMV and rejection (58). Indeed, antiviral prophylaxis with ganciclovir or
valacyclovir has been associated not only with a reduction in
CMV disease but also with reduction in acute rejection (73,74).
Type of Organ Transplant

■

Cytomegalovirus Infection after Solid Organ Transplantation

331

Viral Load and Genotype
Peak viral load and antigenemia levels have been shown to be
independent predictors of CMV disease after solid organ
transplantation (23,24,89–92). In one study, the risk of CMV
disease is increased 8-fold in patients with detectable viral
load, and 50-fold in patients with viral load greater than 2860
copies per 10 (6) peripheral blood mononuclear cells (92).
Additionally, genetic variability of viral strains (i.e., the viral
genotype) may influence the pathogenesis of CMV disease
(93), and this could potentially account for the higher rate of
CMV disease among CMV Dϩ/Rϩ compared to CMV
DϪ/Rϩ patients. Studies in CMV Rϩ solid organ transplant

recipients demonstrate that the majority of reactivated CMV
strains originated from donor instead of the recipient (25–27).
Bacterial and Fungal Infections
Invasive bacterial and fungal infections have been associated
with a higher incidence of CMV disease after solid organ
transplantation (39,94). The proinflammatory condition associated with invasive bacterial and fungal infections would
favor for the reactivation of CMV from latency, and this could
lead to clinical disease. Conversely, CMV disease per se increases the risk of opportunistic bacterial and fungal infections
after solid organ transplantation, possibly as a result of CMVinduced immunomodulation (94–96) or as a marker of an
overimmunosuppressed state.

The predisposition to develop CMV disease varies depending
on the type of organ transplant. Lung, small intestinal, and
pancreas transplant recipients generally have the highest risk,
whereas liver and heart transplant have intermediate risk, and
kidney transplant have the lowest risk for CMV disease
(1,44,75). Although this may be due to the intensity of immunosuppression, it has been postulated that the amount of
CMV harbored in the transplanted allograft may contribute to
the increased predisposition of lung and small intestinal transplant recipients to develop CMV disease (1,75).

Other Factors

Viral Interactions

In solid organ transplant recipients in whom no specific CMV
prevention strategy is used, the onset of CMV infection occurs
during the first 3 months after transplantation, when the degree
of pharmacologic immunosuppression is most intense (59,98,99).
However, this traditional onset has been delayed, particularly
among CMV Dϩ/RϪ solid organ transplant recipients who are

receiving anti-CMV prophylaxis, so that, in these patients, CMV
disease now occurs most commonly during the first 3 months
after completion of anti-CMV prophylaxis (39,74,100–104).
CMV infection in solid organ transplant recipients exhibits a wide spectrum of clinical manifestations, ranging from
asymptomatic infection to severe and occasionally lethal CMV
disease (105). Based on the clinical manifestations, CMV infection is generally classified either as an asymptomatic infection
(termed subclinical CMV infection) or symptomatic infection

Observational studies demonstrate that liver and kidney transplant recipients with human herpesvirus (HHV)-6 and HHV-7
infections were more likely to develop CMV disease after
transplantation (70,76–79). The underlying mechanisms for
this association is not clearly defined, although it has been
postulated that HHV-6 and HHV-7 have immunomodulating properties (80–87) that could enhance immune dysfunction, thereby predisposing to a higher incidence of CMV
disease (76,77,79,88). Alternatively, the reactivation of multiple
viruses including HHV-6 and HHV-7 may only serve as an indicator of a more impaired net state of immune dysfunction,
and hence the reported clinical associations between these
virus infections may be coincidental and not causal.

Other factors that have been significantly associated with CMV
disease after solid organ transplantation are (i) a higher Charlson
comorbidity index (39), (ii) a low creatinine clearance (97), (iii) an
ABO blood group A (97), and (iv) female gender (97). The mechanisms underlying the significant associations between these clinical factors and CMV infection and disease remain undefined.

CLINICAL SYNDROMES


58202_ch23.qxd

332

2/1/10

Section V

TABLE 23.3

8:50 PM

■

Page 332

Viral Infections

Impact of CMV on Solid Organ Transplantation

Direct Effects

Indirect Effects

Nonclinical Effects

CMV syndrome

Acute allograft rejection

Tissue-invasive CMV disease
Gastrointestinal disease
Hepatitis
Pneumonitis

CNS disease
Retinitis
Nephritis
Pancreatitis
Carditis
Othersa
Mortality

Chronic rejection and allograft failure
Bronchiolitis obliterans
Transplant vasculopathy
Tubulointerstitial fibrosis

Increased total cost
Increased resource utilization
Prolonged hospitalization

Opportunistic and other infections
Fungi (Aspergillus, Pneumocystis)
Bacteria (i.e., Nocardia)
Epstein–Barr virus–associated PTLD
Hepatitis C recurrence
Other viruses (HHV-6, HHV-7)
New-onset diabetes
Mortality

Abbreviations: CMV, cytomegalovirus; PTLD, posttransplant lymphoproliferative diseases; HHV, human herpesvirus.
aAny

organ system may be affected by cytomegalovirus.

(termed CMV disease). CMV disease, which is characterized
by the presence of clinical signs and symptoms, can be further
classified into an infection with organ involvement (termed
tissue-invasive CMV disease) and without organ involvement
(termed CMV syndrome) (Table 23.3) (44,106,107).
The clinical impact of CMV extends beyond these “direct”
syndromes to a myriad of indirect effects, such as the influence
of CMV on acute rejection, chronic rejection, chronic allograft
failure, allograft dysfunction, patient and allograft survival,
lymphomas and other malignancies, and increased predisposition to other opportunistic infections (Table 23.3) (1,107–109).
Collectively, these direct and indirect effects of CMV contribute significantly to increased resource utilization and overall cost of solid organ transplantation (110–112).
Direct Cytomegalovirus Effects
The direct effects of CMV in solid organ transplantation result
from the reactivation of the virus in latently infected cells (including the allograft), its dissemination in the blood, and its invasion and replication in target organs (such as the transplanted
allograft and other organs, most commonly the gastrointestinal
tract). These events produce a characteristic febrile illness, often
accompanied by bone marrow suppression, and various endorgan invasive diseases such as pneumonitis, gastritis, enteritis,
colitis, encephalitis, hepatitis, and retinitis, among others (Table
23.3). The diagnosis of CMV disease is confirmed by demonstrating the virus in the blood, other body fluids, or tissue specimens (107). Table 23.4 lists the various laboratory methods used
for the diagnosis of CMV infection and disease after solid organ
transplantation (113). Most laboratories utilize CMV nucleic acid
detection assay (such as polymerase chain reaction [PCR]) or
CMV pp65 antigenemia to confirm the clinical suspicion of

CMV infection and disease (113). The slow turn-around time
and poor sensitivity of virus cultures have limited their clinical
utility in the real-time diagnosis of CMV disease after transplantation (113). CMV serology is not particularly useful for the
diagnosis of CMV disease after transplantation, since immunosuppressive therapy delays the generation of immunoglobulin
response in many transplant recipients (113).

Cytomegalovirus Syndrome
CMV syndrome is the term for clinical disease in the absence of
tissue or end-organ involvement (107). CMV syndrome accounts for approximately 60% of all cases of CMV disease
occurring after solid organ transplantation (39,100,102,107).
Clinically, CMV syndrome is manifested as fever with constitutional symptoms, such as malaise, weakness, myalgia, and
arthralgia (107). Many cases of CMV syndrome are accompanied by myelosuppression, most commonly with leukopenia
and thrombocytopenia (107). In all cases of CMV syndrome,
CMV DNA or antigenemia is detected in the blood (107). In
some cases, coinfections with HHV-6 and HHV-7 may be
demonstrated (114–118). However, the role of these other herpesviruses in the clinical symptomatology of CMV syndrome
has not been conclusively demonstrated (118). Nonetheless, the
term “viral syndrome” has been suggested to account for the
presence of viral coinfections (107).
End-Organ (Tissue-Invasive)
Cytomegalovirus Disease
Approximately 40% of CMV disease cases after solid organ
transplantation are manifested clinically as tissue-invasive
disease and are characterized by signs and symptoms of endorgan dysfunction (1,39,74,100–102,119). The clinical diagnosis


58202_ch23.qxd

2/1/10

8:50 PM

Page 333

Chapter 23

TABLE 23.4

■

Cytomegalovirus Infection after Solid Organ Transplantation

333

Laboratory Methods for the Diagnosis of CMV Infection and Disease after
Solid Organ Transplantation

Method

Examples

Principle

Clinical Use

Comments

Viral culture

Tube culture
Shell vial assay

Virus isolation

Diagnosis of CMV
infection and disease

High specificity
but poor sensitivity
Virus isolate may be used
for phenotypic drug
susceptibility

Serology

ELISA

Antibody
detection
(IgG, IgM)

Pretransplant assessment
of CMV exposure
Not used for real-time
diagnosis of acute disease
after transplantation

IgM suggests acute
infection
Majority of patients are
IgG seropositive

Antigenemia

Slide method

pp65 antigen
detection

Rapid diagnosis of CMV
infection and disease
Guide for preemptive
therapy (e.g., Ͼ10 positive
cells per 2 ϫ 105 cells)
Guide for duration of
antiviral therapy

More sensitive than
shell vial assay
Lacks standardization
Operator-dependent
(subjective interpretation)
Requires immediate
processing

Nucleic acid
detection and
amplification

COBAS Amplicor
CMV Monitor
LightCycler assay
NucliSens assay
Digene assay

Viral nucleic acid

(DNA or RNA)
detection

Rapid diagnosis of CMV
infection and disease
Guide for antiviral therapy
(e.g., 1000–5000 copies/mL
of plasma using COBAS)
Guide for duration
of antiviral therapy

Qualitative assay does
not distinguish latency
from active replication
Virus quantification can
guide duration of
antiviral therapy
Surrogate marker for
antiviral resistence.

Abbreviations: ELISA, enzyme-linked immunosorbent assay; CMV, cytomegalovirus.

of tissue-invasive CMV disease is confirmed by the demonstration of CMV in tissue specimens by viral culture, histopathology
(i.e., inclusion bodies), immunohistochemistry, or in situ DNA
hybridization (107). In most cases of tissue-invasive disease,
CMV is demonstrated in the peripheral blood by PCR or pp65
antigenemia. However, a small number of cases may present as
a compartmentalized CMV disease with no detectable virus in
the blood (1); in these cases, a tissue specimen is needed to confirm the diagnosis of tissue-invasive disease (1).
The most common tissue-invasive form is gastrointestinal

CMV disease, which can involve any part of the gastrointestinal tract and manifests clinically as mucositis, diarrhea, and
hemorrhagic ulcerative disease (1,39,74,100–102,119). The
most severe forms of tissue-invasive CMV disease are pneumonia and central nervous system disease (e.g., encephalitis).
In some cases, multiple organ systems may be involved, such
as concomitant CMV colitis and hepatitis. Very rarely, CMV
may involve the retina to cause retinochoroiditis that can lead
to permanent blindness if not detected and treated early and
aggressively (75). Virtually any organ system can be affected by
CMV, and some of the less common sites of tissue involvement
are the gallbladder and biliary tree, epididymis, skin, and
endometrium (120–125). Congenital CMV has also been reported
to occur in the offspring of female transplant recipients (126).

It is not uncommon for CMV disease to involve the transplanted allograft, especially among CMV Dϩ/RϪ patients. This
clinical observation is not unexpected since the virus in CMV
Dϩ/RϪ solid organ transplant recipients is present initially only
in the transplanted allograft. Accordingly, CMV is expected to
reactivate initially in the transplanted organ and cause graft dysfunction and allograft tissue-invasive CMV disease prior to its
systemic dissemination. CMV reactivation in the transplanted
allograft could potentially explain the vulnerability of the transplanted allograft to develop end-organ CMV disease (127–131).
Hence, compared to other organ transplant recipients, CMV
hepatitis occurs relatively more frequently among liver transplant recipients (132), CMV pancreatitis among pancreas transplant recipients (127), and CMV pneumonitis among lung and
heart–lung transplant recipients (128–130). Although CMV myocarditis is rare, it is also typically observed among heart transplant
recipients (131). Because many of the clinical manifestations of
tissue-invasive CMV disease are difficult to differentiate from allograft rejection, performing tissue biopsy for definitive diagnosis is imperative to guide appropriate therapy.
The clinical manifestations of tissue-invasive CMV disease
depend on the involved organ and the severity of involvement.
In addition to fever, CMV hepatitis typically manifests as elevated serum levels of gamma-glutamyl transferase, alkaline

58202_ch23.qxd

334

2/1/10

Section V

8:50 PM

■

Page 334

Viral Infections

phosphatase, and aminotransferases, with minimal elevations in
serum bilirubin levels (132). CMV pneumonitis manifests as
fever, dyspnea, and cough, accompanied by hypoxemia and radiographic findings of bilateral interstitial, unilateral lobar, or
nodular pulmonary infiltrates (133). CMV can affect any segment of the gastrointestinal tract, including the esophagus,
stomach, and small and large intestines (134). Depending on the
segment involved, gastrointestinal CMV disease may manifest
with symptoms such as dysphagia and odynophagia (CMV
esophagitis), nausea, vomiting, delayed gastric emptying, and
abdominal pain (CMV gastritis), gastrointestinal hemorrhage
(CMV gastritis, enteritis, or colitis), and diarrhea (CMV enterocolitis) (135–137). A high index of suspicion should be maintained for CMV colitis in any transplant recipient who presents
with lower gastrointestinal bleeding even at later periods after
transplantation (136). The endoscopic findings of gastrointestinal CMV disease could be nonspecific, such as erythema and
diffuse, shallow erosions, although characteristic ulcerations are
typically observed (136). Histopathologic examination to

demonstrate CMV inclusion bodies in tissue specimens, the use
of in situ hybridization or CMV-specific immunochemical
stains to demonstrate the presence of the virus in biopsy specimens, or the use of viral culture of tissue are necessary to confirm the presence of tissue-invasive CMV disease (135). CMV
has also been reported to cause vasculitis that resulted in ischemic colitis (138), or thrombosis of the hepatobiliary system
(139,140). CMV retinitis usually presents at a late stage, usually
more than 6 months after solid organ transplantation (75).
Patients with CMV retinitis may be asymptomatic, or they may
experience blurring of vision, scotomata, or decreased visual
acuity (75). Characteristic fundoscopic findings often reveal the
diagnosis of CMV retinitis, although the demonstration of
CMV by PCR or culture of vitreous humor may be necessary in
atypical cases (75). Central nervous system involvement by
CMV occurs very rarely, and it is manifested as change in mental function and confirmed by the demonstration of CMV by
PCR or viral culture of the cerebrospinal fluid (124).
Indirect Cytomegalovirus Effects
In addition to its well-characterized direct effects, CMV is associated with numerous indirect effects (Table 23.3), which
occur as a result of the ability of the virus to modulate the immune system, either directly or through the upregulation of
cytokines, chemokines, growth factors, and other immune
molecules (109). Some of the indirect effects may be delayed
direct effects of persistent subclinical CMV infection in the
transplanted allograft (e.g., chronic allograft failure) (141).
Increased Opportunistic Infections
CMV causes immunomodulation that could account for the
predisposition to develop bacterial and opportunistic fungal
infections after solid organ transplantation (95,142,143). Some
studies have even shown that the incidence of bacterial and

fungal infections were lower among solid organ transplant recipients who received ganciclovir prophylaxis (96,144,145).
The immunomodulatory property of CMV is also postulated
to account for the higher risk of Epstein–Barr virus(EBV)induced posttransplantation lymphoproliferative diseases

(PTLD) among patients with CMV disease (146).
Allograft Rejection
CMV has been associated with reduced short- and long-term
survival and function of liver, kidney, lung, pancreas, and
heart allografts (39,147,148). Early-onset acute allograft rejection was found to be significantly higher among CMV-infected
transplant recipients (149). Prolonged CMV replication has
also been associated with an increased risk of chronic rejection
after liver transplantation (150). Although the mechanisms
underlying these clinical associations have not been fully elucidated, persistent CMV replication may, even at subclinical levels, mediate a persistent T-cell stimulation, either directly or
indirectly by increasing the immunogenicity of the transplanted allograft (i.e., interferon-␥–mediated upregulation of
major histocompatibility complex antigens), hence resulting in
a chronic inflammatory process (151).
Chronic Allograft Failure
The most common cause of long-term allograft loss, chronic
allograft failure, has been associated with CMV infection.
Among lung transplant recipients, CMV has been significantly associated with bronchiolitis obliterans syndrome, a
form of chronic lung rejection characterized by bronchiolar
inflammation and granulation (130). Ganciclovir prophylaxis
has been associated with a significant reduction in the incidence
of bronchiolitis obliterans after lung transplantation (152).
Among heart transplant recipients, CMV has been implicated
in the pathogenesis of accelerated vasculopathy leading to cardiac dysfunction (discussed later in the chapter) (152–154). An
association between CMV and left ventricular dysfunction has
also been reported in heart transplant recipients (155). CMV
disease has also been implicated as a factor for the development of vanishing bile duct syndrome, which is characterized
by ductopenia, severe jaundice, and pruritus after liver transplantation (156–158). Among kidney transplant recipients,
CMV has been significantly associated with tubulointerstitial
fibrosis and glomerulopathy, characterized by enlargement
and necrosis of endothelial cells and accumulation of mononuclear cell infiltration and fibrillary material deposition in
glomerular capillaries (39,125).

Vasculopathy and Procoagulation
A significant association between CMV and accelerated vasculopathy has been reported after heart transplantation
(153,154,159–161). This clinical association is supported by in
vitro experimental data showing the ability of CMV to infect
endothelial cells, influence smooth muscle cell migration and


58202_ch23.qxd

2/1/10

8:50 PM

Page 335

Chapter 23

growth in vitro, and induce neointimal proliferation in rat aortic allografts (162). Experimental in vivo data demonstrate that
rat CMV causes endothelial inflammation that results in intimal
thickening in aortic and cardiac allografts, and this effect was
diminished or abolished by ganciclovir (163,164). In addition,
CMV-enhanced allograft vasculopathy may be mediated by a
proliferative effect on the smooth muscle cells and/or inflammatory cells with enhanced production of growth factors
(159,163–166). CMV infection of endothelial cells may also lead
to a procoagulant response that could account for the clinical association between CMV and vascular thrombosis (140,167,168).
Anti-CMV drugs together with CMV-hyperimmune globulins
have been suggested to reduce the predisposition to develop accelerated vasculopathy after heart transplantation (153,154).
Viral Interactions
Circumstances after solid organ transplantation predispose not
only the reactivation of CMV but also of other latent viruses,

thus allowing for the potential for microbial interactions
(79,115–117). The potential interactions among reactivated
viruses have been suggested to modify the clinical presentation of these infections (79,88,115–117,147,169,170). Examples
of this phenomenon are the proposed interactions among ␤herpesviruses, which may be manifested as an increased incidence and severity of CMV disease (79,88), the proposed association between CMV and EBV-associated PTLD (146), and the
ability of CMV to accelerate the clinical course of recurrent
hepatitis C virus infection, resulting in allograft failure and
mortality after liver transplantation (169,170).
Mortality
Solid organ transplant recipients who develop CMV disease
have a significantly higher mortality rate when compared to
those who did not develop CMV disease (39,103,171–173).
Causes of death may be directly due to CMV disease or could
result from non-CMV–related causes. The use of effective
anti-CMV drugs for prophylaxis has been shown to reduce allcause mortality after solid organ transplantation (174–177).

PREVENTION OF CYTOMEGALOVIRUS
INFECTION AND DISEASE
Because of the negative impact of CMV on clinical outcomes,
its prevention is considered one of the most important management strategies after solid organ transplantation. Among the
various anti-CMV prevention strategies, the most common is
the use of antiviral drugs either as antiviral prophylaxis or preemptive therapy. Also a common practice is the use of CMVseronegative, filtered, or leukocyte-reduced blood products
when blood transfusion is necessary for patient care. CMVseronegative donor and recipient matching, which would pair a
CMV-seronegative donor and recipient is logistically difficult.

■

Cytomegalovirus Infection after Solid Organ Transplantation

335

Awaiting a CMV-seronegative donor may result in an unnecessarily prolonged waiting time for a patient who needs a lifesaving transplant procedure. Currently, passive immunization
with CMV immunoglobulin is less commonly used, partly because of its expense, modest efficacy, and the availability of
more effective antiviral drug strategies. There is no vaccine that
is available clinically for active immunization against CMV in
humans, although some are in early clinical development.
Antiviral Drug Strategies
The two major antiviral drug strategies for the prevention of
CMV disease after solid organ transplantation are (i) antiviral
prophylaxis and (ii) preemptive therapy (44,106,178). Antiviral
prophylaxis entails the administration of an antiviral drug for a
fixed duration of time (usually 3 months) to all patients or to
“at-risk” patients after solid organ transplantation (44,106,178).
In contrast, preemptive therapy involves the administration
of antiviral drug only to transplant recipients with evidence of
early asymptomatic CMV replication (44,106,178). The goal of
preemptive therapy is to treat early CMV reactivation prior to
the onset of clinical manifestations. A variant of preemptive
therapy is targeted prophylaxis, which entails the administration of antiviral drugs during periods highly associated
with CMV reactivation, such as those times when ATG, ALG,
OKT3, and alemtuzumab are administered for the treatment of
acute graft rejection (44,106,178).
There is an ongoing debate whether antiviral prophylaxis
or preemptive therapy is the optimal strategy for preventing
CMV disease after solid organ transplantation. It is generally
believed, however, that both strategies are effective for CMV
disease prevention (179–181). Several meta-analyses concluded
that antiviral prophylaxis and preemptive therapy are both
effective in preventing the direct effects of CMV disease
(174–177). However, a significant reduction in the incidence of
indirect CMV effects was more evident with antiviral prophylaxis compared to preemptive therapy (Table 23.5) (174–177).

Specifically, a reduction in the all-cause mortality was demonstrated with antiviral prophylaxis but not with preemptive
therapy (1,144,182). In recent head-to-head clinical trials that
directly compared the efficacy of both antiviral strategies in
cohorts of kidney transplant recipients, it appears that both are
equally effective in preventing CMV disease (179–181), although a reduction in the incidence of acute allograft rejection
and a better long-term survival was observed with antiviral
prophylaxis (180), suggesting the potential advantage of antiviral prophylaxis over preemptive therapy in reducing the
indirect effects of CMV (Table 23.6). The overall cost of both
antiviral strategies appears to be similar, with cost of drug
(for antiviral prophylaxis) being counter-balanced by the
cost of laboratory monitoring (for preemptive therapy) (181).
Table 23.7 summarizes the potential benefits and disadvantages of the two antiviral strategies (1). Which of these two