Cytomegalovirus in hematopoietic stem cell transplant recipients. Infect Dis Clin North Am. 2010;24:319-337. [PMID: 20466273 DOI: 10.1016/j.idc.2010.01.008]

Impact of cytomegalovirus gastrointestinal disease on the clinical outcomes in patients with gastrointestinal graft-versus-host disease in the era of preemptive therapy

Cytomegalovirus gastrointestinal (CMV-GI) disease in GI graft-versus-host disease (GI-GVHD) has not been properly evaluated in the era of preemptive therapy for CMV infection. We investigated 103 patients with GI-GVHD who underwent endoscopic biopsies with immunohistochemical staining for CMV. All recipients and/or donors were seropositive for CMV and monitored with a strategy of preemptive therapy based on real-time quantitative polymerase chain reaction. Twenty-six patients (25 %) developed CMV-GI disease, especially in HLA-mismatched transplants (P = 0.023) and with initial gut involvement of GVHD (P = 0.009). The CMV-GI diseases were diagnosed at follow-up endoscopies (n = 10, 39 %), comprising 19 % of 52 patients who underwent follow-up endoscopies, as well as initial endoscopies (n = 16, 61 %), comprising 16 % of all GI-GVHD patients. In seven cases, either at initial (n = 5) or follow-up endoscopies (n = 2), CMV-GI disease was diagnosed in the absence of histopathologic evidence for GI-GVHD. Notably, only 11 patients (42 %) had prior CMV DNAemia before the diagnosis of CMV-GI disease, while 12 (46 %) and three (12 %) had concurrent and no CMV DNAemia, respectively. Sixty-five percent of CMV-GI disease was resolved by additional antiviral therapies, but CMV-GI disease (P = 0.032) as well as severity of GVHD (P = 0.001) negatively affected GVHD-specific survival. In conclusion, our data demonstrate that CMV-GI disease was a cause of initial or persistent GI manifestations after the initiation of therapy in a considerable proportion of GI-GVHD. These suggest the necessity of novel strategies to reduce CMV-GI disease as well as an effort to confirm CMV with repeated endoscopies.

Treatment with mesenchymal stromal cells is a risk factor for pneumonia-related death after allogeneic hematopoietic stem cell transplantation

We performed a retrospective cohort study to find out whether the use of reduced-intensity conditioning (RIC) might reduce the risk of early death from pneumonia. Pneumonia-associated deaths were evaluated in 691 hematopoietic stem cell transplantation (HSCT) patients. The majority had a hematological malignancy (n = 504) and an HLA-matched donor (n = 584). RIC was given to 336 patients and myeloablative conditioning (MAC) to 355. Data concerning radiology, culture and autopsy results were evaluated together with risk factors for death related to pneumonia within or after 100 d after HSCT (early and overall pneumonia). In 60 patients, pneumonia contributed to death (early n = 17). The cumulative incidence of early pneumonia-related death was 2.8% and 2.1% in MAC and RIC patients, respectively. The cumulative incidence of overall pneumonia-related death was 8.2% and 10.5%, respectively. In 40 patients, (67%) an etiology could be established, with 19 patients having proven or probable mold infection. In the multivariate analyses, acute graft-versus-host disease (GVHD) grades II-IV, cytomegalovirus (CMV) infection and having received mesenchymal stromal cells (MSCs) were factors associated with overall pneumonia-related death. Bacteremia and a previous HSCT were associated with early pneumonia-related death. RIC did not reduce the incidence of early death associated with pneumonia. Acute GVHD II-IV, CMV infection and MSC treatment were factors associated with pneumonia-related death. Mold infection was the most common contributor to pneumonia-related death in HSCT patients.

Reconstitution of protective immune responses against cytomegalovirus and varicella zoster virus does not require disease development in pediatric recipients of umbilical cord blood transplantation

CMV and varicella zoster virus (VZV) are significant causes of morbidity and mortality following umbilical cord blood transplantation (UCBT). However, the kinetics of reconstitution and protective potential of antiviral cell-mediated immune responses following UCBT remain poorly characterized. In this study, the reconstitution of CMV- and VZV-specific T cell responses was assessed using IFN-γ ELISPOT in 28 children who underwent UCBT to treat hematological or inherited disorders. Barely detectable in the first 3 mo posttransplantation, CMV- and VZV-specific T cell responses were observed in 30.4% and 40.3% of study subjects after 36 mo of follow-up. Four of five CMV-seropositive subjects developed detectable levels of circulating CMV DNA (DNAemia), and 5 of 17 VZV-seropositive patients experienced herpes zoster during the posttransplant period. Four CMV-seronegative subjects developed IFN-γ responses against CMV, and four subjects developed a VZV-specific IFN-γ response without clinical signs of infection. No CMV- or VZV-related events were observed in study subjects following the development of CMV- or VZV-specific responses > 150 spot-forming units/10(6) PBMCs, consistent with T cell-mediated protection. Finally, famciclovir prophylaxis did not strictly prevent the reconstitution of the VZV-specific T cell repertoire, because the frequency of T cells producing IFN-γ in response to VZV Ags reached levels consistent with protection in two nonzoster subjects. Monitoring of CMV- and VZV-specific cell-mediated immunity could inform immunocompetence and guide the initiation and cessation of antiherpetic prophylaxis in UCBT recipients.

Molecular diagnosis and management of viral infections in hematopoietic stem cell transplant recipients

Viral infections after allogeneic hematopoietic stem cell transplantation (HSCT) are important complications associated with high morbidity and mortality. In this setting, reactivations of persisting latent viral pathogens from donor and/or recipient cells play a central role whereas the sterile environment of transplant units renders new infections less likely. The viruses currently regarded as most relevant in the HSCT setting include particularly the herpes virus family--specifically cytomegalovirus (CMV), Epstein-Barr virus (EBV), and human herpesvirus 6 (HHV-6)--as well as human adenoviruses (AdVs) and the polyoma virus BK (BKV). Timely detection and monitoring of virus copy numbers are prerequisites for successful preemptive treatment approaches. Pre- and post-transplant surveillance by sensitive and quantitative molecular methods has therefore become an essential part of the diagnostic routine. In this review, we discuss diagnostic aspects and the clinical management of the most important viral infections in HSCT recipients, with a focus on pediatric patients.

The immune response to human CMV

This review will summarize and interpret recent literature regarding the human CMV immune response, which is among the strongest measured and is the focus of attention for numerous research groups. CMV is a highly prevalent, globally occurring infection that rarely elicits disease in healthy immunocompetent hosts. The human immune system is unable to clear CMV infection and latency, but mounts a spirited immune-defense targeting multiple immune-evasion genes encoded by this dsDNA β-herpes virus. Additionally, the magnitude of cellular immune response devoted to CMV may cause premature immune senescence, and the high frequencies of cytolytic T cells may aggravate vascular pathologies. However, uncontrolled CMV viremia and life-threatening symptoms, which occur readily after immunosuppression and in the immature host, clearly indicate the essential role of immunity in maintaining asymptomatic co-existence with CMV. Approaches for harnessing the host immune response to CMV are needed to reduce the burden of CMV complications in immunocompromised individuals.

Efficacy and safety of low-dose ganciclovir preemptive therapy in allogeneic haematopoietic stem cell transplant recipients compared with conventional-dose ganciclovir: a prospective observational study

OBJECTIVES

We performed a prospective observational study comparing the efficacy and safety of low-dose ganciclovir (5 mg/kg/day) as initial preemptive therapy in allogeneic haematopoietic stem cell transplantation (HSCT) recipients with conventional-dose ganciclovir (10 mg/kg/day).

METHODS

All adult patients undergoing allogeneic HSCT were enrolled at a transplant centre over a 24 month period. The decision to use low-dose or conventional-dose ganciclovir was at the discretion of each attending haematologist. A logistic regression model with inverse probability of treatment weighting (IPTW) using propensity scores was performed to reduce the effect of the selection bias in assignment for ganciclovir preemptive therapy.

RESULTS

Of the 252 HSCT recipients, 97 (38%) received preemptive ganciclovir therapy. Of these, 53 (55%) and 44 (45%) received low-dose and conventional-dose ganciclovir, respectively. The viral clearance rate was higher in the low-dose ganciclovir group [98% (52/53)] than in the conventional-dose ganciclovir group [86% (38/44), P = 0.04], while the low-dose ganciclovir group exhibited a longer viral clearance time (median 21.0 days) than the conventional-dose ganciclovir group (median 14.0 days, P = 0.05). The rate of discontinuation of therapy due to neutropenia or nephrotoxicity was similar in the two groups, although conventional-dose ganciclovir was changed to another regimen more frequently than low-dose ganciclovir. There were three cases of cytomegalovirus (CMV) disease in each group after the initial preemptive therapy. The logistic regression models using propensity scores also revealed that there were no significant differences in viral clearance, secondary episodes of CMV infection, CMV disease and overall mortality between the two groups.

CONCLUSIONS

Low-dose ganciclovir appears to be safe, and to be at least as effective as conventional-dose ganciclovir for CMV viraemia in allogeneic HSCT recipients.

The novel anticytomegalovirus compound AIC246 (Letermovir) inhibits human cytomegalovirus replication through a specific antiviral mechanism that involves the viral terminase

Human cytomegalovirus (HCMV) remains the leading viral cause of birth defects and life-threatening disease in transplant recipients. All approved antiviral drugs target the viral DNA polymerase and are associated with severe toxicity issues and the emergence of drug resistance. Attempts to discover improved anti-HCMV drugs led to the identification of the small-molecular-weight compound AIC246 (Letermovir). AIC246 exhibits outstanding anti-HCMV activity in vitro and in vivo and currently is undergoing a clinical phase IIb trial. The initial mode-of-action studies suggested that the drug acts late in the HCMV replication cycle via a mechanism distinct from that of polymerase inhibitors. Here, we extend our mode-of-action analyses and report that AIC246 blocks viral replication without inhibiting the synthesis of progeny HCMV DNA or viral proteins. The genotyping of mutant viruses that escaped AIC246 inhibition uncovered distinct point mutations in the UL56 subunit of the viral terminase complex. Marker transfer analyses confirmed that these mutations were sufficient to mediate AIC246 resistance. The mapping of drug resistance to open reading frame UL56 suggests that viral DNA processing and/or packaging is targeted by AIC246. In line with this, we demonstrate that AIC246 affects the formation of proper unit-length genomes from viral DNA concatemers and interferes with virion maturation. However, since AIC246-resistant viruses do not exhibit cross-resistance to previously published terminase inhibitors, our data suggest that AIC246 interferes with HCMV DNA cleavage/packaging via a molecular mechanism that is distinct from that of other compound classes known to target the viral terminase.

The EBMT risk score

The European Group for Blood and Marrow Transplantation (EBMT) risk score provides a simple tool to assess instantly chances and risks of hematopoietic SCT(HSCT) for an individual patient pre-transplant. Five factors, age of the patient, stage of the disease, time from diagnosis, donor type and donor recipient gender combination augment risk for an individual patient with increasing score from 0 as best to 7 as worst in an additive way. The score holds for all acquired hematological disorders, for allogeneic and autologous HSCT (score 0-5), is independent of the HSCT technology and is valid for standard or reduced intensity conditioning. Survival is uniformly worse for older patients, transplanted in advanced disease stage after a long-time interval and with a mismatched donor than for younger patients, transplanted soon in early stage with a well matched donor. Additional risk factors such as performance score, CMV serostatus or cytokine polymorphisms improve prediction but to different extents for low or high-risk patients. Comparative assessment of disease risk and global pre-transplant risk should guide decisions for each patient with his/her specific disease between HSCT and a non-transplant approach and replace the traditional 'donor vs no donor' with such a risk-adapted individualized strategy.

CMV infection after transplant from cord blood compared to other alternative donors: the importance of donor-negative CMV serostatus

Cytomegalovirus (CMV) infection and disease are important complications after hematopoietic stem cell transplant, particularly after transplant from alternative donors. Allogeneic cord blood transplantation (CBT) is being increasingly used, but immune recovery may be delayed. The aim of this study was to compare CMV infection in CBT with transplants from unrelated or mismatched related donors, from now on defined as alternative donors. A total of 165 consecutive transplants were divided in 2 groups: (1) alternative donors transplants (n = 85) and (2) CBT recipients (n = 80). Donor and recipient (D/R) CMV serostatus were recorded. The incidence of CMV infection, its severity, timing, and outcome were compared. Median follow-up was 257 days (1-1328). CMV infection was monitored by CMV antigenemia and expressed as CMV Ag positive cell/2 × 10(5) polymorphonuclear blood cells. There was a trend toward a higher cumulative incidence of CMV infection among CBT than alternative donor transplant recipients (64% vs 51%, P = .12). The median time to CMV reactivation was 35 days, and was comparable in the 2 groups (P = .8). The maximum number of CMV-positive cells was similar in the 2 groups (11 versus 16, P = .2). The time interval between the first and the last positive CMV antigenemia was almost 4 times longer in CBT compared with alternative donor transplants (109 vs 29 days, respectively, P = .008). The incidence of late CMV infection was also higher in CBT (62% vs 24%, P < .001). The incidence of early and late CMV infection in CBT was similar to D-/R+ alternative transplants, and higher than in D+/R+ alternative transplants: early infection, 72% in CBT versus 69% in D-/R+ alternative versus 55% in D+/R+ alternative (P = .21); and late infection, 67% in CBT versus 60% in D-/R+ alternative versus 7% in D+/R+ alternative (P < .001). Transplant-related mortality and overall survival were similar between the groups: 34% versus 36% (P = .6) and 54% versus 46% (P = .3) for alternative transplant and CBT, respectively. Longer duration and higher incidence of late CMV infection was seen in CBT patients, when compared with alternative donor transplants, whereas no difference in mortality was observed. The duration and incidence of late CMV infection were similar when D-/R+ CBT were compared with D-/R+ alternative donor transplants.

Cytomegalovirus DNA quantification using an automated platform for nucleic acid extraction and real-time PCR assay setup

Analytical performance characteristics of the QIAsymphony RGQ system with artus cytomegalovirus (CMV) reagents were determined. Measurable range spanned 2.0 to ≥ 7.0 log(10) copies/ml. The detection limit was 23 copies/ml. Intrarun and interrun coefficients of variation were ≤ 2.1% at 3.0 and 5.0 log(10) copies/ml. In clinical specimens, RGQ values were ~0.2 log(10) copies/ml higher than those in an assay using a BioRobot M48 extraction/manual reaction setup/7500 Real-Time PCR instrument. No cross-contamination was observed.

Recent developments in antiviral drugs for cytomegalovirus

Human cytomegalovirus continues to impact adversely on the outcome of solid organ and stem cell transplantation and remains a major cause of congenital abnormalities. In the absence of a vaccine, antiviral drugs have been the mainstay of therapy. Although very few anticytomegalovirus drugs are currently licensed, there are multiple opportunities within the viral life cycle for drug development. In this article we summarize some of the key new antiviral agents undergoing preclinical and clinical development against a range of targets in the viral life cycle, highlighting those where further development is warranted or being undertaken.

Cytomegalovirus: pathogen, paradigm, and puzzle

Human cytomegalovirus (CMV), one of the eight herpesviruses that commonly infect humans, is best known for its propensity to cause disease in immunocompromised patients, especially transplant recipients, patients with advanced AIDS, and congenitally infected newborns. Advances in molecular virology coupled with improvements in diagnostic methods and treatment options have vastly improved our understanding of and ability to manage CMV, but many uncertainties remain, including the mechanisms of persistence and pathogenesis and its hypothesized roles in a variety of human illnesses. Here we review recent advances that are reshaping our view and approach to this fascinating virus.