Meet in the middle: Could cell mediated-immunity assays be the answer for ideal Cytomegalovirus prophylaxis after lung transplantation? Observational study from a single center with intermittent antiviral prophylaxis

BACKGROUND

Cytomegalovirus (CMV) can cause tissue-invasive disease and indirect effects after lung transplantation (LTx) such as acute rejection episodes and chronic lung allograft dysfunction. Monitoring CMV-specific cell immune recovery (CMV-CIR) after LTx can individualize CMV risks and establish better antiviral approach. This study evaluated the dynamics of CMV-CIR, using QuantiFERON-CMV assay (Qiagen Group), in the first year after LTx.

METHODS

Prospective observational cohort study included lung transplant recipients from December/2015 to December/2016. Universal antiviral prophylaxis with intravenous ganciclovir 5 mg/kg/day 3 days/week for 3 months was given for CMV-seropositive recipients (R+) and only CMV-seropositive donor and negative recipient (D+/R-) received a 6-month-prophylaxis with ganciclovir and valganciclovir, on alternate days, in the first 3 months and then, 3 more months of valganciclovir. QuantiFERON-CMV was measured at the same time points of surveillance bronchoscopies. CMV infection was defined as any DNAemia detected and CMV disease with proven biopsy or antigenemia pp65 above 10 cells/300.000 neutrophils.

RESULTS

Thirty-eight patients were included. On days 45, 90, and 365 days post-LTx, 60%, 72%, and 81% QuantiFERON-CMV were reactive, respectively. Eleven patients (28.9%) presented CMV-disease and 27 DNAemia/CMV infections. Reactive tests were able to predict CMV disease only at 90 days after LTx (p = .027) but failed on DNAemia/CMV infection (p = .148). Daily prophylaxis, for D+/R- patients (13.2%), remained as an independently associated factor for not achieving reactive QuantiFERON-CMV (adjusted OR .27, 95%CI .12-.60, p = .02).

CONCLUSION

QuantiFERON-CMV may be another diagnostic tool to help stratify CMV-disease risk and individualized antiviral prophylaxis after LTx.

QuantiFERON monitor predicts early cytomegalovirus infection and viral burden in allogeneic hematopoietic stem cell transplantation

INTRODUCTION

Cytomegalovirus (CMV) infection is a major cause of transplantation-related morbidity and mortality. This study assessed the utility of the QuantiFERON monitor (QFM; Qiagen) for the prediction of early CMV infection and viral burden.

METHODS

QuantiFERON-CMV (QF-CMV; Qiagen) and QFM were measured at the post-allogeneic hematopoietic stem cell transplantation (HSCT) week 4. CMV DNA was measured at every visit until post-HSCT week 24. The QFM cutoff specific to CMV infection was established.

RESULT

At the post-HSCT week 4, the QFM cutoff predicting CMV infection was 86.95 IU/mL. While QF-CMV results at the post-HSCT week 4 were associated with high-level CMV infection (CMV DNA ≥ 5,000 IU/mL) but not with CMV infection (CMV DNA ≥ 500 IU/mL), QFM was associated with both CMV infection and high-level CMV infection. Both indeterminate QF-CMV and nonreactive QFM were associated with increased peak CMV DNA.

CONCLUSION

Low QFM is a risk factor for CMV infection and increased CMV viral loads. QFM at post-HSCT week 4 can be utilized as an assay to predict the risk and burden of early CMV infection in HSCT recipients, in conjunction with other risk factors.

Human cytomegalovirus UL23 exploits PD-L1 inhibitory signaling pathway to evade T cell-mediated cytotoxicity

Human cytomegalovirus (HCMV), a widely prevalent human beta-herpesvirus, establishes lifelong persistence in the host following primary infection. In healthy individuals, the virus is effectively controlled by HCMV-specific T cells and typically exhibits asymptomatic. The T cell immune response plays a pivotal role in combating HCMV infection, while HCMV employs various strategies to counteract it within the host. Previously, we reported that UL23, a tegument protein of HCMV, facilitates viral immune evasion from interferon-gamma (IFN-γ) responses, and it is well known that IFN-γ is mainly derived from T cells. However, the involvement of UL23 in viral immune evasion from T cell-mediated immunity remains unclear. Herein, we present compelling evidence that UL23 significantly enhances viral resistance against T cell-mediated cytotoxicity during HCMV infection from the co-culture assays of HCMV-infected cells with T cells. We found that IFN-γ plays a major role in regulating T cell cytotoxicity mediated by UL23. More interestingly, we demonstrated that UL23 not only regulates the IFN-γ downstream responses but also modulates the IFN-γ secretion by regulating T cell activities. Further experiments indicate that UL23 upregulates the expression and signaling of programmed death ligand 1 (PD-L1), which is responsible for inhibiting multiple aspects of T cell activities, including activation, apoptosis, and IFN-γ secretion, as determined through RNA-seq analysis and inhibitor-blocking experiments, ultimately facilitating viral replication and spread. Our findings highlight the potential role of UL23 as an alternative antagonist in suppressing T cell cytotoxicity and unveil a novel strategy for HCMV to evade T cell immunity.

IMPORTANCE

T cell immunity is pivotal in controlling primary human cytomegalovirus (HCMV) infection, restricting periodic reactivation, and preventing HCMV-associated diseases. Despite inducing a robust T cell immune response, HCMV has developed sophisticated immune evasion mechanisms that specifically target T cell responses. Although numerous studies have been conducted on HCMV-specific T cells, the primary focus has been on the impact of HCMV on T cell recognition via major histocompatibility complex molecules. Our studies show for the first time that HCMV exploits the programmed death ligand 1 (PD-L1) inhibitory signaling pathway to evade T cell immunity by modulating the activities of T cells and thereby blocking the secretion of IFN-γ, which is directly mediated by HCMV-encoded tegument protein UL23. While PD-L1 has been extensively studied in the context of tumors and viruses, its involvement in HCMV infection and viral immune evasion is rarely reported. We observed an upregulation of PD-L1 in normal cells during HCMV infection and provided strong evidence supporting its critical role in UL23-induced inhibition of T cell-mediated cytotoxicity. The novel strategy employed by HCMV to manipulate the inhibitory signaling pathway of T cell immune activation for viral evasion through its encoded protein offers valuable insights for the understanding of HCMV-mediated T cell immunomodulation and developing innovative antiviral treatment strategies.

Cellular immunity against cytomegalovirus and risk of infection after kidney transplantation

Introduction

Cytomegalovirus (CMV) infection remains a challenge following kidney transplantation (KTx). Currently, CMV-IgG serostatus at transplantation is used to individualize CMV preventive strategies. We assessed the clinical utility of CMV-IGRA for predicting CMV infection following KTx.

Methods

We performed a nationwide prospective cohort study from August 2016 until December 2022. Data from all adult KTx recipients in Norway, n=1,546 (R+; n=1,157, D+/R-; n=260, D-/R-; 129), were included with a total of 3,556 CMV-IGRA analyses (1,375 at KTx, 1,188 at eight weeks, 993 one-year after KTx) and 35,782 CMV DNAemia analyses.

Results

In R+ recipients CMV-IGRA status, measured at any of the time-points, could not identify any differential risk of later CMV infection. D+/R- recipients remaining CMV-IGRA negative 1-year after transplantation (regardless of positive CMV DNAemia and/or CMV IgG status at that time) had increased risk of developing later CMV infection compared to D+/R- recipients who had become CMV-IGRA positive (14% vs. 2%, p=0.01).

Conclusion

Knowledge of pre-transplant CMV-IGRA status did not provide additional information to CMV-IgG serostatus that could improve current post-transplant CMV treatment algorithms. However, D+/R- recipients with a persisting negative CMV-IGRA one-year after transplantation remained at increased risk of experiencing later CMV infection. Therefore we advocate post-transplant CMV-IGRA monitoring in these patients.

Dynamics and Clinical Significance of Cytomegalovirus-Specific Neutralizing Antibodies in Kidney Transplant Recipients Treated with T-Cell-Depleting Agents

We measured cytomegalovirus (CMV)-specific antibodies that neutralize epithelial cell infection (CMV-AbNEIs) in 101 CMV-seropositive kidney transplant recipients (KTRs) at baseline and posttransplant months 3 and 6. All the patients received antithymocyte globulin and 3-month valganciclovir prophylaxis. There were no significant differences in pretransplant AbNEIs titers between KTRs that developed or did not develop any-level CMV infection or the composite of high-level infection and/or disease. One-year CMV infection-free survival was comparable between KTRs with or without pretransplant CMV-AbNEIs. No differences were observed by months 3 and 6. We observed no protective role for CMV-AbNEIs among CMV-seropositive KTRs undergoing T-cell-depleting induction.

Clinical utility of a cytomegalovirus-specific T cell assay in assessing the risk of post-prophylaxis cytomegalovirus infection and post-treatment relapse

INTRODUCTION

Cytomegalovirus (CMV) causes significant morbidity in solid organ transplant recipients (SOTR). Measuring cell-mediated immunity (CMI) may inform the risk of CMV infection after antiviral prophylaxis and predict relapse after CMV treatment.

METHODS

We serially assessed CMV CMI using the QuantiFERON-CMV assay (QF-CMV; Qiagen, Germantown, MD) in two cohorts of SOTRs: during valganciclovir prophylaxis and during treatment of CMV viremia. Results of CMI were correlated with post-prophylaxis CMV infection and post-treatment relapse, respectively.

RESULTS

Only one (4.2%) of 24 CMV D+/R- patients demonstrated positive QF-CMV by the end of valganciclovir prophylaxis. Four (16.6%) patients developed post-prophylaxis CMV infection; all four had undetectable QF-CMV at end of prophylaxis. Among 20 patients treated for CMV infection, 18 (90%) developed QF-CMV levels >.2 IU/mL by end of antiviral treatment and none developed CMV relapse. In contrast, the single patient who relapsed after completing treatment had a CMV CMI <.2 IU/ml (p = .0036).

CONCLUSION

Since CMV D+/R- SOTRs are unlikely to develop adequate CMV CMI while receiving valganciclovir prophylaxis, the utility of CMV CMI monitoring for risk stratification during time of prophylaxis had limited value. Conversely, CMV CMI testing may be a useful marker of the risk of CMV relapse after antiviral treatment.

The influence of HLA A, B, C, DR alleles and HLA haplotypes on cytomegalovirus-specific cell mediated immunity in seropositive Korean kidney transplant candidates

We evaluated the effect of specific HLA alleles and haplotypes on cytomegalovirus (CMV)-specific cell mediated immunity (CMI) in kidney transplant (KT) candidates. CMV-specific ELISPOT against pp65 and IE-1 antigens (hereafter referred to as pp65 and IE-1, respectively) was performed in 229 seropositive KT candidates. We analyzed the results related to 44 selected HLA alleles (9 HLA-A, 15 HLA-B, 9 HLA-C, and 11 HLA-DR) and 13 HLA haplotypes commonly found in study participants. The pp65 and IE-1 results in 229 seropositive candidates were 227.5 (114.5-471.5) and 41.0 (8.8-185.8) (median [interquartile range]) spots/2 × 105 PBMCs, respectively. The pp65 and IE-1 results showed significant differences between candidates with different HLA alleles (A*02 vs. A*26 [p = 0.016], A*24 vs. A*30 [p = 0.031], B*07 vs. B*46 [p = 0.005], B*54 vs. B*35 [p = 0.041], B*54 vs. B*44 [p = 0.018], B*54 vs. B*51 [p = 0.025], and C*06 vs. C*14 [p = 0.034]). HLA-A*02 and B*54 were associated with increased pp65 and IE-1 results, respectively (p = 0.005 and p < 0.001, respectively). In contrast, the HLA-A*26 and B*46 alleles were associated with a decreased pp65 response, whereas the A*30 allele was associated with a decreased IE-1 response (p < 0.05). The pp65 results correlated with the HLA-A allele frequencies (R = 0.7546, p = 0.019) and the IE-1 results correlated with the HLA-C allele frequencies of the study participants (R = 0.7882, p = 0.012). Among 13 haplotypes, HLA-A*30 ~ B*13 ~ C*06 ~ DRB1*07 showed decreased CMV-CMIs compared to the other HLA haplotypes, probably due to a combination of HLA alleles associated with lower CMV-CMIs. Our results demonstrated that CMV-specific CMIs may be influenced by the HLA allele as well as the HLA haplotype. To better predict CMV reactivation, it is important to estimate risk in the context of HLA allele and haplotype information.

Advances and Challenges in Cytomegalovirus Detection Methods for Liver Transplant Donors

Cytomegalovirus (CMV) infection is a highly prevalent opportunistic infection among liver transplant recipients. When the liver donor is infected with CMV, there is a risk of transmission to the recipient, leading to CMV infection. To improve the postoperative outcome of liver transplantation, it is crucial to shift the focus of CMV detection to the donor and achieve early diagnosis, as well as implement effective preventative and therapeutic measures. However, the commonly used CMV detection methods in the past had limitations that prevented their early and accurate diagnosis in liver transplant donors. This review focuses on the latest advancements in CMV detection methods that can potentially be applied to liver transplant donors. The objective is to compare and evaluate their clinical utility, thereby providing guidance and support for rapid and accurate diagnosis of CMV infection in the clinic. The clustered regularly interspaced short palindromic repeats-associated proteins (CRISPR-Cas) system-based assay emerges as a promising method for detecting the virus, offering great prospects for early and expedient CMV infection diagnosis in clinical settings.

Gaining consensus around patient risk groups and prognostic profiles to guide CMV management among patients with solid organ transplant: Insights from a Delphi panel with SOT experts

INTRODUCTION

This study aimed to characterize patient risk groups and respective prognostic profiles to optimize clinical decision-making and guide appropriate medical cytomegalovirus (CMV) management among patients with solid organ transplant (SOT).

METHODS

Between September 2021 and February 2022, a three-round modified Delphi study was conducted to generate consensus among 14 international experts in virology and organ transplantation. Experts were asked about treatment and prognoses for patients in seven distinct clinical scenarios. Furthermore, experts were asked to risk-stratify patients by pre-/post-transplant characteristics. Consensus around opting for/against a treatment was observed if ≥75% or <25% of experts reported ≥50% likelihood to recommend or if treatments were ranked inside/outside the top two options and ≥75% of experts were within 1 standard deviation of the mean rank.

RESULTS

Experts agreed on several unmet needs in CMV disease management post-SOT, particularly avoidance of treatment-limiting toxicities with conventional CMV therapy and emergence of both primary refractory and drug resistant treatment failures. Experts considered CMV viral load, resistance profile, and route of administration as critical to treatment selection. For newer CMV therapeutic options, experts listed lack of long-term use data, concerns over potential resistance, high cost and limited availability as challenges restricting adoption, and successful patient management.

CONCLUSION

Experts achieved consensus around patient risk stratifications and factors influencing therapeutic options. Recommendations emerging from this Delphi study may support practicing physicians when confronted with challenging CMV scenarios in SOT patients, but additional experiences with newer anti-CMV agents are needed to re-validate expert consensus and update post-transplant CMV guidelines.

Contemporary Biomarkers for Renal Transplantation: A Narrative Overview

Renal transplantation (RT) is the preferred treatment for end-stage renal disease. However, clinical challenges persist, i.e., early detection of graft dysfunction, timely identification of rejection episodes, personalization of immunosuppressive therapy, and prediction of long-term graft survival. Biomarkers have emerged as valuable tools to address these challenges and revolutionize RT patient care. Our review synthesizes the existing scientific literature to highlight promising biomarkers, their biological characteristics, and their potential roles in enhancing clinical decision-making and patient outcomes. Emerging non-invasive biomarkers seemingly provide valuable insights into the immunopathology of nephron injury and allograft rejection. Moreover, we analyzed biomarkers with intra-nephron specificities, i.e., glomerular vs. tubular (proximal vs. distal), which can localize an injury in different nephron areas. Additionally, this paper provides a comprehensive analysis of the potential clinical applications of biomarkers in the prediction, detection, differential diagnosis and assessment of post-RT non-surgical allograft complications. Lastly, we focus on the pursuit of immune tolerance biomarkers, which aims to reclassify transplant recipients based on immune risk thresholds, guide personalized immunosuppression strategies, and ultimately identify patients for whom immunosuppression may safely be reduced. Further research, validation, standardization, and prospective studies are necessary to fully harness the clinical utility of RT biomarkers and guide the development of targeted therapies.

Prospects of Cytomegalovirus-Specific T-Cell Receptors in Clinical Diagnosis and Therapy

Human cytomegalovirus (HCMV) is responsible for widespread infections worldwide. In immunocompetent individuals it is typically latent, while infection or reactivation in immunocompromised individuals can result in severe clinical symptoms or even death. Although there has been significant progress in the treatment and diagnosis of HCMV infection in recent years, numerous shortcomings and developmental limitations persist. There is an urgent need to develop innovative, safe, and effective treatments, as well as to explore early and timely diagnostic strategies for HCMV infection. Cell-mediated immune responses are the primary factor controlling HCMV infection and replication, but the protective role of humoral immune responses remains controversial. T-cells, key effector cells of the cellular immune system, are critical for clearing and preventing HCMV infection. The T-cell receptor (TCR) lies at the heart of T-cell immune responses, and its diversity enables the immune system to differentiate between self and non-self. Given the significant influence of cellular immunity on human health and the indispensable role of the TCR in T-cell immune responses, we posit that the impact of TCR on the development of novel diagnostic and prognostic methods, as well as on patient monitoring and management of clinical HCMV infection, will be far-reaching and profound. High-throughput and single-cell sequencing technologies have facilitated unprecedented quantitative detection of TCR diversity. With these current sequencing technologies, researchers have already obtained a vast number of TCR sequences. It is plausible that in the near future studies on TCR repertoires will be instrumental in assessing vaccine efficacy, immunotherapeutic strategies, and the early diagnosis of HCMV infection.

Comparison of intracellular cytokine staining versus an ELISA-based assay to assess CMV-specific cell-mediated immunity in high-risk kidney transplant recipients

The best method for monitoring cytomegalovirus (CMV)-specific cell-mediated immunity (CMV-CMI) among high-risk kidney transplant (KT) recipients remains uncertain. We assessed CMV-CMI by intracellular cytokine staining (ICS) by flow cytometry and a commercial interferon (IFN)-γ release assay (QuantiFERON®-CMV [QTF-CMV]) at posttransplant months 3, 4, and 5 in 53 CMV-seropositive KT recipients that had received induction therapy with antithymocyte globulin (ATG) and a 3-month course of valganciclovir prophylaxis. The discriminative capacity (areas under receiver operating characteristics curve [auROCs]) and diagnostic accuracy to predict immune protection against CMV infection from the discontinuation of prophylaxis to month 12 were compared between both methods. There was significant although moderate correlations between CMV-specific IFN-γ-producing CD8⁺ T-cell counts enumerated by ICS and IFN-γ levels by QTF-CMV at months 3 (rho: 0.493; p = 0.005) and 4 (rho: 0.440; p = 0.077). The auROCs for CMV-specific CD4⁺ and CD8⁺ T-cells by ICS were nonsignificantly higher than that of QTF-CMV (0.696 and 0.733 vs. 0.678; p = 0.900 and 0.692, respectively). The optimal cut-off of ≥0.395 CMV-specific CD8⁺ T-cells yielded a sensitivity of 86.4%, specificity of 54.6%, positive predictive value of 79.2% and negative predictive value of 66.7% to predict protection. The corresponding estimates for QTF-CMV (IFN-γ levels ≥0.2 IU/mL) were 78.9%, 37.5%, 75.0%, and 42.9%, respectively. The enumeration of CMV-specific IFN-γ-producing CD8⁺ T-cells at the time of cessation of prophylaxis performed slightly better than the QTF-CMV assay to predict immune protection in seropositive KT recipients previously treated with ATG.

Fifteen-Year Surveillance of LTR Receiving Pre-Emptive Therapy for CMV Infection: Prevention of CMV Disease and Incidence of CLAD

The efficacy of pre-emptive therapy in the prevention of cytomegalovirus (CMV) disease and the potential association of CMV infection with the occurrence of chronic lung allograft dysfunction (CLAD) was evaluated in 129 lung transplant recipients receiving pre-emptive therapy based on pp65-antigenemia or CMV-DNA in the blood and in the bronchoalveolar lavage. Seventy-one (55%) patients received pre-emptive ganciclovir/valganciclovir (GCV/VGCV) for CMV infection for a median of 28 (9-191) days. Possible CMV disease occurred in six (5%) patients and was healed after the GCV/VGCV therapy. The cumulative incidence of CLAD was 38% and 54% at 5 and 10 years. Acute rejection and CMV load in the blood (but not in the lung) were independent predictors of the occurrence of CLAD. Pre-emptive therapy is highly effective in preventing CMV disease in lung recipients and does not induce a superior incidence of CLAD compared to what reported for other cohorts of patients who received an extended antiviral prophylaxis.

Diagnosis and treatment for the early stage of cytomegalovirus infection during hematopoietic stem cell transplantation

Cytomegalovirus (CMV) infection remains a frequent complication after hematopoietic stem cell transplantation (HSCT) and causes significant morbidity and mortality in transplantation recipients. In this review, we highlight the role of major risk factors that are associated with the incidence of CMV infection. Advances in immunosurveillance may predict CMV infection, allowing early interventions to prevent severe infection. Furthermore, numerous therapeutic strategies against CMV infection after HSCT are summarized. A comprehensive understanding of the current situation of CMV treatment may provide a hint for clinical practice and even promote the development of novel strategies for precision medicine.

Utility of Cytomegalovirus Cell-Mediated Immunity Assays in Solid Organ Transplantation

Cytomegalovirus (CMV) is one of the most important viral complications after solid organ transplantation (SOT). Current preventive and management strategies rely primarily on serologic and viral load testing and remain suboptimal. To address these issues, multiple techniques to measure CMV-specific cell-mediated immunity (CMI) have been developed and evaluated in clinical studies over the past two decades. These assays show significant promise for the personalization of CMV management. For example, CMI assays can be used to help determine the optimal duration of antiviral prophylaxis or whether antiviral therapy is indicated in patients with low levels of CMV reactivation. However, despite numerous studies showing potential utility, these assays are not yet in widespread routine clinical use. Barriers to adoption include variations in test complexity, standardization, and thresholds for positivity and insufficient interventional clinical trials. Here, we provide an updated assessment of commonly available tests and the clinical utility of CMV-specific CMI testing in SOT recipients.

Development of CMV-specific cytotoxic T cells (CMV-Tc) in pediatric renal transplant recipients with CMV viremia

BACKGROUND

Viral infections are controlled primarily by viral-specific T cells, raising concern for adequate T-cell response to clear CMV infection in transplant recipients receiving lymphocyte-depleting agents (LDA). We examined the rates of CMV viremia and clearance, seroconversion, and CMV-specific CD8+ T cell (CMV-Tc) activity with class of induction agent received.

METHODS

Retrospective review of 45 pediatric renal transplant recipients who received induction with LDA (n = 31) or non-LDA (NLDA; n = 14) received valganciclovir prophylaxis for 6 months post-transplant and CMV-PCR monitoring. CMV-Tc was measured by intracellular IFNγ flow cytometry, when possible, at baseline, 1 month after CMV viremia (>5 copies/PCR) and serially until CMV-Tc was positive (≥0.2%).

RESULTS

Viremia rates at 1, 2, and 4 years post-transplant were higher in LDA vs. NLDA (46.3% vs. 7.2%, 64.2% vs. 7.2%, and 64.2% vs. 7.2%, respectively; p = .002). Viremia rates at these time points in seronegative LDA (50.3%, 71.6%, 71.6%) were significantly or near significantly higher than seronegative NLDA (9.1%, 9.1%, 9.1%; p = .004), seropositive-LDA (22.3%, 22.3%, 22.3%; p = .07), or seropositive NLDA (0%, 0%, 0%; p = .07). Eleven of 17 (64.7%) viremic subjects required valganciclovir dose reduction during the prophylaxis period for leukopenia. All viremic LDA patients developed CMV-Tc. One viremic NLDA patient did not develop CMV-Tc. No patients developed CMV disease.

CONCLUSION

CMV seronegative pediatric renal transplant patients receiving LDA are more likely to have valganciclovir prophylaxis dose reduction and develop subclinical CMV viremia; however, all developed CMV-Tc. Larger prospective studies are needed to further understand the effects of induction agents on CMV-Tc and CMV-Tc's role post-transplant.

A Multi-Factorial Observational Study on Sequential Fecal Microbiota Transplant in Patients with Medically Refractory Clostridioides difficile Infection

Fecal microbiota transplantation (FMT) is highly effective in recurrent Clostridioides difficile infection (CDI); increasing evidence supports FMT in severe or fulminant Clostridioides difficile infection (SFCDI). However, the multifactorial mechanisms that underpin the efficacy of FMT are not fully understood. Systems biology approaches using high-throughput technologies may help with mechanistic dissection of host-microbial interactions. Here, we have undertaken a deep phenomics study on four adults receiving sequential FMT for SFCDI, in which we performed a longitudinal, integrative analysis of multiple host factors and intestinal microbiome changes. Stool samples were profiled for changes in gut microbiota and metabolites and blood samples for alterations in targeted epigenomic, metabonomic, glycomic, immune proteomic, immunophenotyping, immune functional assays, and T-cell receptor (TCR) repertoires, respectively. We characterised temporal trajectories in gut microbial and host immunometabolic data sets in three responders and one non-responder to sequential FMT. A total of 562 features were used for analysis, of which 78 features were identified, which differed between the responders and the non-responder. The observed dynamic phenotypic changes may potentially suggest immunosenescent signals in the non-responder and may help to underpin the mechanisms accompanying successful FMT, although our study is limited by a small sample size and significant heterogeneity in patient baseline characteristics. Our multi-omics integrative longitudinal analytical approach extends the knowledge regarding mechanisms of efficacy of FMT and highlights preliminary novel signatures, which should be validated in larger studies.

Cytomegalovirus specific polyfunctional T-cell responses expressing CD107a predict control of CMV infection after liver transplantation

Cytomegalovirus (CMV) viral load after liver transplantation (LT) is controlled by cell mediated immune responses (CMI). Quantification of CMV-specific T-cells may identify patients who control CMV spontaneously and avoid expensive and potentially toxic antiviral therapies. Prospective post-LT clinical, virological and immunological monitoring was carried out up to 1-year post-LT in a cohort of adult recipients. The CMV-specific T-cell response was characterized using flow cytometry intracellular cytokine staining in 49 LT recipients-R (79.6% R+, 20.4% R-). CMV infection occurred in 24 patients (18 D+/R+ and 6 D+/R-). Only patients with undetectable polyfunctional CMV-specific CD4+ T-cells developed CMV infection. Predictive models showed that polyfunctional CMV-specific CD4+ T-cells pre-existing before LT are protective for CMV reactivation posttransplantation. Quantitation of CD4+ T-cell responses to CMV may be a useful marker for spontaneous control of viral replication to tailor antiviral prophylaxis after LT.

Blood transfusion and the risk for infections in kidney transplant patients

BACKGROUND

Receipt of a red blood cell transfusion (RBCT) post-kidney transplantation may alter immunity which could predispose to subsequent infection.

METHODS

We carried out a single-center, retrospective cohort study of 1,258 adult kidney transplant recipients from 2002 to 2018 (mean age 52, 64% male). The receipt of RBCT post-transplant (468 participants transfused, total 2,373 RBCT) was analyzed as a time-varying, cumulative exposure. Adjusted cox proportional hazards models were used to calculate hazard ratios (HR) for outcomes of bacterial or viral (BK or CMV) infection.

RESULTS

Over a median follow-up of 3.8 years, bacterial infection occurred in 34% of participants at a median of 409 days post-transplant and viral infection occurred in 25% at a median of 154 days post-transplant. Transfusion was associated with a step-wise higher risk of bacterial infection (HR 1.35, 95%CI 0.95-1.91; HR 1.29, 95%CI 0.92-1.82; HR 2.63, 95%CI 1.94-3.56; HR 3.38, 95%CI 2.30-4.95, for 1, 2, 3-5 and >5 RBCT respectively), but not viral infection. These findings were consistent in multiple additional analyses, including accounting for reverse causality.

CONCLUSION

Blood transfusion after kidney transplant is associated with a higher risk for bacterial infection, emphasizing the need to use transfusions judiciously in this population already at risk for infections.

American Society for Transplantation and Cellular Therapy Series: #3-Prevention of Cytomegalovirus Infection and Disease After Hematopoietic Cell Transplantation

The Practice Guidelines Committee of the American Society for Transplantation and Cellular Therapy partnered with its Transplant Infectious Disease Special Interest Group to update its 2009 compendium-style infectious diseases guidelines for the care of hematopoietic cell transplant (HCT) recipients. A new approach was taken with the goal of better serving clinical providers by publishing each standalone topic in the infectious disease series as a concise format of frequently asked questions (FAQ), tables, and figures. Adult and pediatric infectious disease and HCT content experts developed and answered FAQs. Topics were finalized with harmonized recommendations that were made by assigning an A through E strength of recommendation paired with a level of supporting evidence graded I through III. The third topic in the series focuses on the prevention of cytomegalovirus infection and disease in HCT recipients by reviewing prophylaxis and preemptive therapy approaches; key definitions, relevant risk factors, and diagnostic monitoring considerations are also reviewed.

Immune Monitoring Using QuantiFERON®-CMV Assay in Congenital Cytomegalovirus Infection: Correlation With Clinical Presentation and CMV DNA Load

BACKGROUND

Cytomegalovirus (CMV)-specific CD8 + T-cell responses can be detected early in fetal life, but their role in the manifestations of congenital CMV (cCMV) infection remains largely unknown.

METHODS

CMV-specific CD8 + T-cell responses were assessed in neonates with cCMV using QuantiFERON®-CMV assay, within day 14 of life (T0) and during the second month of life (T1). Detection and quantification of CMV DNA in whole blood and urine samples were performed at both time points. QuantiFERON®-CMV results were evaluated in relation to timing of maternal infection, clinical manifestations of cCMV and CMV DNA levels.

RESULTS

Thirty neonates were enrolled (10/30 [33%] symptomatic; 20/30 [67%] asymptomatic). At T0 16/30 (53%) subjects had a reactive QuantiFERON®-CMV result and 16/16 (100%) were asymptomatic, whereas 14/30 (47%) had a nonreactive or indeterminate QuantiFERON®-CMV result and 4/14 (29%) were asymptomatic. At T1, 17/29 (59%) subjects had a reactive QuantiFERON®-CMV result, and 17/17 (100%) were asymptomatic, whereas 12/29 (41%) had a nonreactive or indeterminate result and 3/12 (25%) were asymptomatic. At both T0 and T1 reactive QuantiFERON®-CMV results correlated with lack of symptoms (P = .0001). At T1 median CMV DNAemia was lower in subjects with reactive QuantiFERON®-CMV results as compared with subjects with nonreactive or indeterminate results (1.82 log IU/mL [1.82-2.89] vs 2.55 log IU/mL [1.82-4.42], P = .009). No correlation was found between QuantiFERON®-CMV results and gestational age at maternal infection nor with urine CMV DNA levels.

CONCLUSIONS

A detectable CMV-specific CD8 + T-cell response, evaluated using the QuantiFERON®-CMV assay, correlates with the lack of CMV-related symptoms and the control of CMV DNAemia.

Cellular Immunity to Predict the Risk of Cytomegalovirus Infection in Kidney Transplantation: A Prospective, Interventional, Multicenter Clinical Trial

BACKGROUND

Improving cytomegalovirus (CMV) immune-risk stratification in kidney transplantation is highly needed to establish guided preventive strategies.

METHODS

This prospective, interventional, multicenter clinical trial assessed the value of monitoring pretransplant CMV-specific cell-mediated immunity (CMI) using an interferon-γ release assay to predict CMV infection in kidney transplantation. One hundred sixty donor/recipient CMV-seropositive (D+/R+) patients, stratified by their baseline CMV (immediate-early protein 1)-specific CMI risk, were randomized to receive either preemptive or 3-month antiviral prophylaxis. Also, 15-day posttransplant CMI risk stratification and CMI specific to the 65 kDa phosphoprotein (pp65) CMV antigen were investigated. Immunosuppression consisted of basiliximab, tacrolimus, mycophenolate mofetil, and corticosteroids in 80% of patients, whereas 20% received thymoglobulin induction therapy.

RESULTS

Patients at high risk for CMV based on pretransplant CMI developed significantly higher CMV infection rates than those deemed to be at low risk with both preemptive (73.3% vs 44.4%; odds ratio [OR], 3.44 [95% confidence interval {CI}, 1.30-9.08]) and prophylaxis (33.3% vs 4.1%; OR, 11.75 [95% CI, 2.31-59.71]) approaches. The predictive capacity for CMV-specific CMI was only found in basiliximab-treated patients for both preemptive and prophylaxis therapy. Fifteen-day CMI risk stratification better predicted CMV infection (81.3% vs 9.1%; OR, 43.33 [95% CI, 7.89-237.96]).

CONCLUSIONS

Pretransplant CMV-specific CMI identifies D+/R+ kidney recipients at high risk of developing CMV infection if not receiving T-cell-depleting antibodies. Monitoring CMV-specific CMI soon after transplantation further defines the CMV infection prediction risk. Monitoring CMV-specific CMI may guide decision making regarding the type of CMV preventive strategy in kidney transplantation.

CLINICAL TRIALS REGISTRATION

NCT02550639.

Immunologic monitoring of cytomegalovirus (CMV) enzyme-linked immune absorbent spot (ELISPOT) for controlling clinically significant CMV infection in pediatric allogeneic hematopoietic stem cell transplant recipients

The dynamics of recovery of cytomegalovirus (CMV)-specific cell-mediated immunity (CMI) and its impact on controlling clinically significant CMV infections following hematopoietic stem cell transplant (HSCT) are rarely reported in pediatric HSCT recipients. In this study, dynamics of recovery of CMV-specific CMI and its clinical significance in controlling CMV viremia and clinically significant CMV infections were assessed in pediatric allogeneic HSCT recipients. All subjects underwent CMV pp65- and IE1-specific enzyme-linked immune absorbent spot (ELISPOT) assays just before transplantation and then monthly until the detection of CMV-specific CMI with ≥ 5 spot-forming cells (SFC) / 2.0 × 105 cells. Clinically significant CMV infections were defined as CMV diseases, prolonged CMV infections, recurrent CMV infections or late onset CMV infections. Among 52 recipients, 88.5% of recipients recovered CMV-specific CMI with ≥ 5 SFC/ 2.0 × 105 cells at a median of 34 days (interquartile range [IQR]: 29-95 days) following HSCT, 55.8% at 30 days following HSCT, and 73.1% at 90 days following HSCT. The presence of CMV-specific CMI before HSCT was the significant factors for the reconstitution of CMV specific CMI after HSCT (adjusted odds ratio [aOR] = 13.33; 95% confidence interval [CI] = 1.21-142.86). After HSCT, 30 recipients experienced CMV viremia, of which 20 were clinically significant CMV infections. The full recovery of CMV-specific CMI with ≥ 50 SFC / 2.0 × 105 cells after HSCT was the protective factor for the development of clinically significant CMV infections (aOR = 0.13; 95% CI = 0.22-0.71). In the haploidentical HSCT recipients, 82.1% recovered CMV-specific CMI at a median of 65 days after HSCT (IQR: 34-118 days) with a tendency to recover their CMV-specific CMI later than did those from non-haploidentical donors (65 days vs. 30 days; P = 0.001). Clinically significant CMV infections tended to occur more frequently in the haploidentical HSCT recipients compared to those with matched donor HSCT (46.4% vs. 29.2%; P = 0.205). The full recovery of CMV-specific CMI with ≥ 50 SFC/2.0 × 105 cells after HSCT also lowered the risk of development of clinically significant CMV infections (aOR = 0.08; 95% CI = 0.01-0.90). However, transplantation from haploidentical donors was a significant risk factor hampering recovery of CMV-specific CMI (aOR = 0.08; 95% CI = 0.01-0.86) and full recovery of CMV-specific CMI (aOR = 0.05; 95% CI = 0.01-0.50). Pre-transplant CMV-specific CMI influenced the recovery of CMV-specific CMI, and the full recovery of CMV-specific CMI could be a surrogate marker for preventing clinically significant CMV infections in pediatric HSCT recipients. Immunologic monitoring using ELISPOT assay before and after HSCT helps in identifying patients with a high risk of CMV infection and in controlling CMV infection.

Early cytomegalovirus DNAemia and antiviral dose adjustment in high vs intermediate risk kidney transplant recipients

BACKGROUND

Cytomegalovirus (CMV) infection continues to negatively affect outcomes for solid organ transplant recipients, despite the advent of strategies for preemptive surveillance and prophylaxis. The impact is especially great for CMV seronegative recipients of donor seropositive organs, who typically lack the ability to control CMV infection at the time of transplantation.

METHODS

We reviewed episodes of CMV DNAemia in a modern cohort of kidney transplant recipients over a 3-year period at a high-volume transplant center to investigate the frequency of DNAemia during antiviral prophylaxis.

RESULTS

Despite receipt of antiviral prophylaxis per current guidelines, 75 cases of CMV DNAemia were observed in the first 100 days after transplantation. For high risk patients, median time to DNAemia was 75 days after transplantation, and the majority of patients had experienced dose-reduction of valganciclovir due to renal insufficiency. Review of CMV seropositive intermediate risk patients demonstrated DNAemia occurring earlier after transplantation compared with high risk patients with a median time of 64 days (P = .029). The impact of valganciclovir dose adjustment was less notable in the intermediate risk group.

CONCLUSIONS

Guidelines recommend beginning routine surveillance for CMV after the completion of antiviral prophylaxis. Our findings suggest that closer monitoring may be beneficial, especially for high risk patients at risk for DNAemia. Patients requiring dose adjustment of valganciclovir due to renal insufficiency may be at increased risk for CMV DNAemia. Improved methods for CMV prophylaxis and evaluation of immunologic risk for CMV DNAemia and disease are needed to improve patient outcomes after kidney transplantation.

Comparison of Three Cellular Assays to Predict the Course of CMV Infection in Liver Transplant Recipients

To estimate protection from cytomegalovirus (CMV) replication after solid organ transplantation, CMV serology has been considered insufficient and thus CMV immunity is increasingly assessed by cellular in vitro methods. We compared two commercially available IFN-γ ELISpot assays (T-Track CMV and T-SPOT.CMV) and an IFN-γ ELISA (QuantiFERON-CMV). Currently, there is no study comparing these three assays. The assays were performed in 56 liver transplant recipients at the end of antiviral prophylaxis and one month thereafter. In CMV high- or intermediate-risk patients the two ELISpot assays showed significant correlation (p < 0.0001, r > 0.6) but the correlation of the ELISpot assays with QuantiFERON-CMV was weaker. Results of both ELISpot assays were similarly predictive of protection from CMV-DNAemia ≥500 copies/mL [CMV pp65 T-SPOT.CMV at the end of prophylaxis: area under curve (AUC) = 0.744, cut-off 142 spot forming units (SFU), sensitivity set to 100%, specificity 46%; CMV IE-1 T-Track CMV at month 1: AUC = 0.762, cut-off 3.5 SFU, sensitivity set to 100%, specificity 59%]. The QuantiFERON-CMV assay was inferior, reaching a specificity of 23% when setting the sensitivity to 100%. In conclusion, both CMV-specific ELISpot assays appear suitable to assess protection from CMV infection/reactivation in liver transplant recipients.

Early T cell reconstitution and cytokine profile may help to guide a personalized management of human cytomegalovirus infection after allogeneic hematopoietic stem cell transplantation

Human cytomegalovirus (HCMV) infection is one of the major causes of mortality and morbidity after allo-hematopoietic stem cell transplantation (HSCT). Antiviral therapies are associated with toxicity and high economic burden. The aim of this retrospective study was to identify allo-HSCT HCMV-seropositive recipients at low risk of clinically significant HCMV infection who could avoid antiviral therapies. Sixty adult patients who underwent allo-HSCT were clustered in two groups: i) 22 (37%) spontaneously controlling HCMV reactivation (Controllers); ii) 38 (63%) developing clinically significant HCMV infection and receiving pre-emptive therapy (Non-Controllers). We analyzed several patient baseline characteristics, total/HCMV-specific CD4⁺ and CD8⁺ T-cell counts and their cytokine production (IFNγ, TNFα, IL2). Controllers presented a higher number of total/HCMV-specific CD4⁺ and CD8⁺ T-cells (P=0.001 and P=0.017 for total CD4⁺ and CD8⁺ T-cells respectively; P<0.001 for HCMV-specific T-cells) and a lower percentage of mono-functional IFNγ-producing HCMV-specific CD8⁺ T-cells (P=0.002). In bi-variable models, the prognostic impact of the percentage of mono-functional HCMV-specific CD8⁺ T-cells on treatment-free survival, adjusted for total/HCMVspecific CD4⁺ and CD8⁺ T-cells, was confirmed. An HCMV-seronegative donor was the only baseline characteristic associated with a clinically significant infection. These data, when confirmed by a larger prospective study, may provide information for guiding the personalized management of HCMV infection in allo-HSCT recipients.

Post-transplant absolute lymphocyte count predicts early cytomegalovirus infection after heart transplantation

Immunosuppressive therapy can decrease rejection episodes and increase the risk of severe and fatal infections in heart transplantation (HT) recipients. Immunosuppressive therapy can also decrease the absolute lymphocyte count (ALC), but the relationship between early post-transplant ALC and early cytomegalovirus (CMV) infection is largely unknown, especially in HT. We retrospectively analyzed 58 HT recipients who tested positive for CMV IgG antibody and received basiliximab induction therapy. We collected preoperative and 2-month postoperative data on ALC and CMV load. The CMV load > 1200 IU/mL was used as the cutoff value to define early CMV infection. Post-transplant lymphopenia was defined as an ALC of < 500 cells/μL at postoperative day (POD) #7. On POD #7, 29 (50.0%) patients had post-transplant lymphopenia and 29 (50.0%) patients did not. The incidence of CMV infection within 1 or 2 months of HT was higher in the post-transplant lymphopenia group than in the non-lymphopenia group (82.8% vs. 48.3%, P = 0.013; 89.7% vs. 65.5%, P = 0.028, respectively). ALC < 500 cells/μL on POD #7 was an independent risk factor for early CMV infection within 1 month of HT (odds ratio, 4.14; 95% confidence interval, 1.16-14.77; P = 0.029). A low ALC after HT was associated with a high risk of early CMV infection. Post-transplant ALC monitoring is simple and inexpensive and can help identify patients at high risk of early CMV infection.

Recent Approaches and Strategies in the Generation of Anti-human Cytomegalovirus Vaccines

Human cytomegalovirus is the largest human herpesvirus and shares many core features of other herpesviruses such as tightly regulated gene expression during genome replication and latency as well as the establishment of lifelong persistence following infection. In contrast to stereotypic clinical syndromes associated with alpha-herpesvirus infections, almost all primary HCMV infections are asymptomatic and acquired early in life in most populations in the world. Although asymptomatic in most individuals, HCMV is a major cause of disease in hosts with deficits in adaptive and innate immunity such as infants who are infected in utero and allograft recipients following transplantation. Congenital HCMV is a commonly acquired infection in the developing fetus that can result in a number of neurodevelopmental abnormalities. Similarly, HCMV is a major cause of disease in allograft recipients in the immediate and late posttransplant period and is thought to be a major contributor to chronic allograft rejection. Even though HCMV induces robust innate and adaptive immune responses, it also encodes a vast array of immune evasion functions that are thought aid in its persistence. Immune correlates of protective immunity that prevent or modify intrauterine HCMV infection remain incompletely defined but are thought to consist primarily of adaptive responses in the pregnant mother, thus making congenital HCMV a potentially vaccine modifiable disease. Similarly, HCMV infection in allograft recipients is often more severe in recipients without preexisting adaptive immunity to HCMV. Thus, there has been a considerable effort to modify HCMV specific immunity in transplant recipient either through active immunization or passive transfer of adaptive effector functions. Although efforts to develop an efficacious vaccine and/or passive immunotherapy to limit HCMV disease have been underway for nearly six decades, most have met with limited success at best. In contrast to previous efforts, current HCMV vaccine development has relied on observations of unique properties of HCMV in hopes of reproducing immune responses that at a minimum will be similar to that following natural infection. However, more recent findings have suggested that immunity following naturally acquired HCMV infection may have limited protective activity and almost certainly, is not sterilizing. Such observations suggest that either the induction of natural immunity must be specifically tailored to generate protective activity or alternatively, that providing targeted passive immunity to susceptible populations could be prove to be more efficacious.

Flow cytometric measurement of STAT5 phosphorylation in cytomegalovirus-stimulated T cells

Cytomegalovirus (CMV)-specific T cells expand with CMV reactivation and are probably prerequisite for control and protection. Given the critical role STAT5A phosphorylation (pSTAT5A) in T cell proliferation, this study presents a simple and sensitive flow cytometric-based pSTAT5A assay to quickly identify CMV-specific T cell proliferation. We determined pSTAT5A in T cells treated with CMV-specific peptide mix (pp65 + IE1 peptides) from 20 healthy adult subjects and three immunodeficient patients with CARMIL-2 mutation. After stimulation, the percentage of pSTAT5A⁺ T cells in CMV-seropositive (CMV⁺ ) subjects significantly increased from 3.0% ± 1.9% (unstimulated) to 11.4% ± 5.9% (stimulated) for 24 h. After 7 days of stimulation, the percentage of expanded T cells amounted to 26% ± 17.2%. Conversely, the percentage of pSTAT5A⁺ T cells and T cell proliferation from CMV-seronegative (CMV^- ) subjects hardly changed (from 3.0% ± 1.3% to 3.7% ± 1.8% and from 4.3% ± 2.1% to 5.7% ± 1.7%, respectively). We analyzed the correlation between the percentage of pSTAT5A⁺ T cells versus (1) CMV-IgG concentrations versus (2) the percentage of expanded T cells and versus (3) the percentage of initial CMV-specific T cells. In immunodeficient patients with CARMIL-2 mutation, CMV-specific pSTAT5A and T cell proliferation were completely deficient. In conclusion, flow cytometric-based pSTAT5A assay represents an appropriate tool to quickly identify CMV-specific T cell proliferation and helps to understand dysfunctions in controlling other pathogens. Flow cytometric-based pSTAT5A assay may be a useful test in clinical practice and merits further validation in large studies.

Pretransplant CMV-Specific T-Cell Immunity But Not Dose of Antithymocyte Globulin Is Associated With Recovery of Specific Immunity After Kidney Transplantation

BACKGROUND

This is a prospective, multicenter, observational study in cytomegalovirus (CMV)-seropositive kidney transplant recipients with pretransplant CMV-specific cell-mediated immunity (CMV-CMI) receiving antithymocyte globulin (ATG). We aimed to investigate posttransplant CMV-CMI over time and the impact of the dose-dependent ATG.

METHODS

CMV-CMI was assessed at days +30, +45, +60, and +90 after transplantation with the QuantiFERON-CMV assay. A reactive result (interferon-γ [IFN-γ] ≥ 0.2 IU/mL) indicated a positive CMV-CMI.

RESULTS

A total of 78 positive CMV-CMI patients were enrolled in the study, of which 59.5% had a positive CMV-CMI at day +30 and 82.7% at day +90. Multivariate logistic regression analysis showed that ATG dose was not associated with positive CMV-CMI at any point. However, pretransplant IFN-γ level (>12 IU/mL vs ≤12 IU/mL) was associated with positive CMV-CMI at day +30 (odds ratio, 12.9; 95% confidence interval, 3.1-53.3; P < .001). In addition, all the patients who did not recover CMV-CMI at day +90 had a pretransplant IFN-γ level ≤12 IU/mL.

CONCLUSIONS

More than half of CMV-seropositive kidney transplant recipients receiving ATG recover (or maintain) CMV-CMI by the first month after transplantation. The pretransplant IFN-γ level, but not the ATG dose, shows a strong association with the kinetics of this recovery.

Monitoring of CMV-specific cell-mediated immunity with a commercial ELISA-based interferon-γ release assay in kidney transplant recipients treated with antithymocyte globulin

Monitoring for cytomegalovirus (CMV)-specific cell-mediated immunity (CMV-CMI) may be useful for individualizing valganciclovir (VGCV) prophylaxis after kidney transplantation (KT). We performed a commercial ELISA-based interferon (IFN)-γ release assay (QTF-CMV) from posttransplant months 2-5 (362 points) in 120 CMV-seropositive KT recipients that received antithymocyte globulin as induction therapy and VGCV prophylaxis (median of 92 days). Forty-seven patients (39.3%) had CMV infection after discontinuation of prophylaxis. The QTF-CMV assay was reactive, nonreactive, and indeterminate in 264 (72.9%), 90 (24.9%), and 8 points (2.2%). The QTF-CMV assay at prophylaxis discontinuation exhibited suboptimal accuracy for predicting protective CMV-CMI (sensitivity: 77.4%; specificity: 34.3%; positive predictive value [PPV]: 64.1%; negative predictive value [NPV]: 50.0%), with no differences in 1-year CMV infection rates between patients with negative (nonreactive or indeterminate) or reactive results (45.8% vs 36.1%; P = .244). Specificity and PPV to predict protective CMV-CMI improved by elevating the IFN-γ cutoff value to 1.13 IU/mL (65.7% and 71.4%) and 7.0 IU/mL (85.7% and 76.2%), although NPVs decreased. The QTF-CMV assay as per manufacturer's interpretative criteria performed poorly to predict protection from CMV infection following discontinuation of VGCV prophylaxis among ATG-treated CMV-seropositive KT recipients. This performance is slightly improved by modifying the IFN-γ positivity threshold.

Lack of cytomegalovirus (CMV)-specific cell-mediated immune response using QuantiFERON-CMV assay in CMV-seropositive healthy volunteers: fact not artifact

The QuantiFERON-CMV (QF) assay measures cell-mediated immunity against cytomegalovirus (CMV-CMI), which is particularly useful in individuals susceptible to CMV infection such as transplant patients. A positive QF result identifies patients that are better protected against CMV infection. However, the significance of a negative QF result in CMV-seropositive individuals needs to be clarified. CMV-CMI was analyzed in healthy subjects using the QF assay, and, in parallel, the Flow-cytometric Assay of Specific Cell-mediated Immune response in Activated whole blood (FASCIA). FASCIA assay measures T-cell proliferation using CMV lysate as stimulus whereas QF assay use a mix of peptides. A total of 93 healthy volunteers were enrolled, and 13/71 CMV-seropositive individuals (18.3%) showed humoral/cellular discordance using QF assay (CMV+ QF-). Interestingly, with FASCIA assay CD4+ and CD8+ T-cell proliferations were lower in CMV+ QF- than in CMV+ QF+ individuals. Furthermore, CMV+ QF- volunteers had a lower level of anti-CMV IgG than CMV+ QF+ subjects. Discordant CMV+ QF- volunteers can be defined as low responder individuals since they show lower CMV-specific humoral and cellular immune responses in comparison to CMV+ QF+ individuals. Immune discordance shows the high heterogeneity of immunity to CMV in healthy subjects.

Prevention and therapy of viral infections in patients with solid organ transplantation

Solid organ transplantation (SOT) is the best treatment option for end-stage organ disease. The number of SOT procedures has been steadily increasing worldwide during the past decades. This trend has been accompanied by the continuous incorporation of new antimicrobial drugs and by the refinement of strategies aimed at minimizing the risk of opportunistic infection. Nonetheless, viral infections, which can occur at any stage of the post-transplant period, remain a clinical challenge that negatively impacts both patient and graft outcomes. This review offers an overview of the most relevant viral infections in the SOT population, with a focus on herpesviruses (cytomegalovirus, Epstein-Barr virus, varicella-zoster virus, and herpes simplex virus 1 and 2) and polyomaviruses (human BK polyomavirus). In addition, the currently recommended prophylactic and treatment approaches are summarized, as well as the new antiviral agents in different phases of clinical development.

Diagnostic usefulness of the cytomegalovirus (CMV)-specific T cell-based assay for predicting CMV infection after kidney transplant

BACKGROUND/AIMS

We evaluated the usefulness in kidney transplant (KT) candidates of cytomegalovirus (CMV)-specific enzyme-linked immunospot (ELISPOT) assays for predicting the development of post-transplant CMV infections.

METHODS

All adult recipients admitted for living-donor KT between March 2014 and March 2015 were prospectively enrolled except donor CMV-seropositive and recipient seronegative (D+/R-) recipients. All the enrolled patients underwent CMV-specific ELISPOT assays before transplant, and a researcher blinded to the results of these assays examined the patients for CMV infection at least 6 months post-transplant.

RESULTS

Of 133 KT recipients, 44 (33%) developed CMV infections. When we used the cut-off determined by receiver operator characteristic curve, 16 of the 34 patients (47%) with negative pp65-specific ELISPOT results (< 11 spots/200,000 cells) developed CMV infections, whereas 28 of the 99 patients (39%) with positive pp65-specific ELISPOT results at baseline (≥ 11 spots/200,000 cells) developed CMV infections after KT (p = 0.02). Based on the multivariable Cox regression model, negative pp65-specific ELISPOT assay results was an independent risk factor for CMV infection (adjusted hazard ratio [AHR], 1.87; 95% confidence interval [CI], 1.01 to 3.46; p = 0.047) as well as age (AHR, 1.05; 95% CI, 1.01 to 1.08; p = 0.007).

CONCLUSION

Pre-transplant CMV-specific ELISPOT assay appears to predict the development of CMV infections after KT in recipients at moderate risk such as CMV-seropositive recipients (Clinical Trial Registration Number NCT02025335).

Predictive tools to determine risk of infection in kidney transplant recipients

Introduction: Infection represents a major complication after kidney transplantation (KT). Therapeutic drug monitoring is essentially the only approach for the adjustment of immunosuppression in current practice, with suboptimal results. The implementation of immune monitoring strategies may contribute to minimizing the risk of adverse events attributable to over-immunosuppression without compromising graft outcomes.Areas covered: The present review (based on PubMed/MEDLINE searches from database inception to November 2019) is focused on immune biomarkers with no antigen specificity (non-pathogen-specific), including serum levels of immunoglobulins and complement factors, peripheral blood lymphocyte subpopulations, soluble CD30, intracellular ATP production by stimulated CD4⁺ T-cells, and other cell-based immune assays. We also summarized recent advances in the use of replication kinetics of latent viruses to assess the functionality of T-cell immunity, with focus on the nonpathogenic anelloviruses. Finally, the composite risk scores reported in the literature are critically discussed.Expert opinion: Notable efforts have been made to develop an enlarging repertoire of immune biomarkers and prediction models, although most of them still lack technical standardization and external validation. Preventive interventions based on these tools (prolongation of prophylaxis, tapering of immunosuppression, or immunoglobulin replacement therapy in hypogammaglobulinemic patients) remain to be defined, ideally in the context of controlled trials.

The Ability of a Cytomegalovirus ELISPOT Assay to Predict Outcome of Low-Level CMV Reactivation in Hematopoietic Cell Transplant Recipients

BACKGROUND

Cytomegalovirus (CMV) infections in hematopoietic cell transplant (HCT) recipients cause substantial morbidity and mortality. CMV cell-mediated immunity (CMV-CMI) can be determined by levels of interferon gamma (IFN-γ) production using an enzyme-linked immunospot (ELISPOT) CMV assay (T-SPOT.CMV assay). In this study, we evaluated the ability of this assay to predict the outcome of low-level CMV reactivation in HCT recipients.

METHODS

We followed 55 HCT recipients with low-level CMV reactivation up to 8 weeks from enrollment. Progression to clinically significant CMV infection (CS-CMVi) was defined as a CMV load >1000 IU/mL or > 500 IU/mL in patients receiving matched related/autologous or matched unrelated transplants, respectively, and initiation of antiviral treatment.

RESULTS

Progression to CS-CMVi occurred in 31 (56%) of the HCT recipients. Spot counts of CMV-specific pp65 and IE1 antigens were significantly lower in patients who had CS-CMVi than in patients who did not. On multivariate analysis, the ELISPOT CMV responses and steroids use were the only predictors of progression to CS-CMVi.

CONCLUSIONS

A strong association between low CMV-CMI and progression to CS-CMVi was observed in HCT recipients. The implementation of serial monitoring of CMV-CMI may identify patients at risk of progression to CS-CMVi that require antiviral therapy.

CMV Prevention and Treatment in Transplantation: What's New in 2019

PURPOSE OF REVIEW

Transplant recipients are at risk for cytomegalovirus (CMV) infection and associated morbidity and mortality. We summarize recently introduced or currently investigated modalities for prevention and treatment of CMV infection in hematopoietic cell (HCT) and solid organ transplant (SOT) recipients.

RECENT FINDINGS

Letermovir was recently approved for CMV prevention in HCT recipients. Data from real world studies support its role to improve outcomes in this population. Letermovir is currently under investigation for broader patient populations and indications. Maribavir is in late stages of development for CMV treatment and may provide a safer alternative to currently available anti-CMV drugs. Promising CMV vaccine candidates and adoptive cell therapy approaches are under evaluation. CMV immune monitoring assays are predicted to play a more central role in our clinical decision making. In recent years, major advances have been made in CMV prevention and treatment in transplant recipients. Rigorous research is ongoing and is anticipated to further impact our ability to improve outcomes in this population.

Human cytomegalovirus seroprevalence and titres in solid organ transplant recipients and transplant donors in Seoul, South Korea

Background

Human cytomegalovirus (HCMV) can cause poor outcomes in solid organ transplant (SOT) recipients; moreover, it is associated with cardiovascular diseases (CVD) in the general population. Accordingly, anti-HCMV immunoglobulin G (IgG) seroepidemiology may be useful in identifying the risk of post-SOT HCMV infection or disease as well as immunosenescence or CVD. However, HCMV seroprevalence and titre have not been fully evaluated with regard to age distribution or compared between SOT recipients and healthy individuals in South Korea.

Methods

We retrospectively retrieved all unduplicated anti-HCMV IgG results of individuals aged > 1 year evaluated between July 2006 and November 2017 at Severance Hospital in Seoul. The cohort, excluding haematopoietic stem cell transplant recipients and subjects with equivocal values, included 2184 SOT recipients and 3015 healthy transplant donors. All IgG results in the SOT recipients were measured during the pre-transplant period.

Results

The overall IgG seroprevalence and titres were significantly higher among SOT recipients than among healthy donors (98.7% vs. 88.6%, p < 0.001, and 64.7 ± 44.3 vs. 49.8 ± 20.6 arbitrary units/mL, p < 0.001, respectively). The lowest seropositive rate in the SOT group was observed in recipients aged between 11 and 15 years (70.6%). The frequency of seropositivity among adults aged ≥41 years increased to ≥90% in SOT recipients and healthy donors. Age was independently associated with higher HCMV seroprevalence (41–60 years, OR, 76.4, 95% CI, 24.5–238.9, p < 0.001; ≥ 61 years, OR, 4.4, 95% CI, 1.3–14.9, p < 0.001, compared to ≤40 years). The healthy donor group had an independently low HCMV seropositive rate (OR, 0.1, 95% CI, 0.1–0.2, p < 0.001).

Conclusions

HCMV seropositivity was the lowest among school-aged children and adolescents. IgG testing revealed an intermediate serostatus risk of post-transplant HCMV infection and disease for most adult SOT recipients in South Korea.

A prospective multicenter observational study of cell-mediated immunity as a predictor for cytomegalovirus infection in kidney transplant recipients

T cell immunity is essential for the control of cytomegalovirus (CMV) infection after transplantation. We evaluated a CMV-specific peptide-based enzyme-linked immunosorbent spot (ELISPOT) assay to determine whether assay results could predict subsequent CMV events. Adult kidney transplant recipients at 43 centers underwent ELISPOT testing to enumerate interferon gamma (IFN-γ) binding spot-forming units (sfu) after stimulation of cells with an overlapping peptide pool of CMV phosphoprotein 65 (pp65) and immediate early-1 (IE-1) protein at the end of antiviral prophylaxis (EOP) and various time points thereafter. The primary outcome was a CMV event in the first posttransplant year. In 583 kidney transplant recipients (260 seropositive donor [D+]/seronegative recipient [R-] and 277 R+), CMV events occurred in 44 of 368 eligible patients (11.8%) at a median of 227 days (range 92-360) posttransplant. A cutoff value of >40 sfu/2.5 × 10⁵  cells for either IE-1 or pp65 was derived as a threshold for positivity, with a negative predictive value of >97% for CMV events. CMV events were significantly lower in assay positive vs assay negative patients (3.0% vs 19.5%, P < .0001 for pp65). Time to CMV event post-EOP was significantly greater in those with sfu >40 at EOP (P < .0001). In this large, multicenter trial of kidney transplant recipients, we show that an assessment of CMV-specific immunity using a novel ELISPOT assay is able to predict protection from CMV infection.

Clinical Correlation of Cytomegalovirus Infection With CMV-specific CD8+ T-cell Immune Competence Score and Lymphocyte Subsets in Solid Organ Transplant Recipients

BACKGROUND

Control of cytomegalovirus (CMV) infection after solid organ transplantation (SOT) requires a functional immune system. We assessed the association between quantitation and function of CMV-specific CD8+ T cells and CMV infection in SOT recipients.

METHODS

During a 10-year period, selected kidney, heart, lung, pancreas, liver, and composite tissue recipients were tested for CMV-specific CD8+ T cells immune competence (CMV-CD8+), as measured by enumeration, interferon-gamma production, and CD107a/b degranulation. Quantitative and functional data were used to assemble T-cell immune competence (TIC) score. CMV infection was diagnosed by polymerase chain reaction in blood and other samples or histopathology.

RESULTS

Of 130 patients tested, 59 had CMV infection or disease. The median onset to CMV infection was 10.5 months (interquartile range [IQR], 5.5-18.7). Gastrointestinal disease (28.8%), pneumonia (20.3%), and CMV syndrome (17%) were most common presentation. An impaired nonspecific or CMV-CD8+ TIC score was associated with tissue-invasive disease (hazard risk, 2.84, 95% confidence interval, 1.03-11.81; P = 0.04). Patients with impaired CMV-CD8+ TIC score had longer viremia duration (42.4 days vs 18.8 d; P < 0.001). Patients with impaired nonspecific or CMV-CD8+ TIC score had higher risk of relapse (68.8% vs 27.9%; hazard risk, 2.56; 95% confidence interval, 1.09-5.89; P = 0.03). Patients with CMV infection or disease had lower median absolute lymphocyte count (380 [IQR, 240-540] vs 940 [IQR, 551-1210] cells/mm; P < 0.0001) and CD4+ T cell count (29 cells/mm [IQR, 1.3-116.0] vs 325.5 cells/mm [IQR, 151.5-589.8]; P < 0.0001).

CONCLUSIONS

Nonspecific and CMV-specific CD8+ T-cell function correlated with the course of CMV after SOT, and measuring these has the potential to assist in its clinical management.

Efficacy and safety of the combination of reduced duration prophylaxis followed by immuno-guided prophylaxis to prevent cytomegalovirus disease in lung transplant recipients (CYTOCOR STUDY): an open-label, randomised, non-inferiority clinical trial

INTRODUCTION

Prolonged use of antivirals to prevent the development of cytomegalovirus (CMV) disease in lung transplant patients has been shown to have significant side effects, for which alternatives are being sought to reduce their use. The monitoring of cell immunity against CMV could be an alternative as it has shown to be useful in identifying transplant patients at low risk of infection, who could benefit from shorter prophylaxis. The aim of the CYTOCOR study is to demonstrate that the combination of a reduced prophylaxis strategy with subsequent CMV-specific immunological monitoring would allow CMV infection to be controlled in lung transplant patients as effectively as the usual strategy (prophylaxis followed by pre-emptive therapy), while reducing the side effects of antivirals due to the shorter duration of prophylaxis.

METHODS AND ANALYSIS

Phase III randomised, open, multicentre, parallel, non-inferiority clinical trial to study the efficacy and safety of the combination of a prophylaxis strategy up to month +3 post-transplant followed by immuno-guided prophylaxis using the QuantiFERON-CMV technique up to month +12 post-transplant to prevent CMV disease in CMV-seropositive lung transplant recipients. This strategy will be compared with a combination of a usual prophylaxis strategy up to month +6 post-transplant followed by pre-emptive therapy up to month +12. To study the incidence of CMV disease, patients will be followed up to 18 months post-transplantation. A total of 150 patients are expected to be recruited for the study.

ETHICS AND PUBLIC DISSEMINATION

The clinical trial has been approved by the Research Ethics Committees and authorised by the Spanish Agency of Medicines and Medical Devices (AEMPS).If the hypothesis of this clinical trial is verified, the dissemination of the results could change clinical practice by increasing knowledge about the safety and efficacy of discontinuing valganciclovir prophylaxis in lung transplant recipients.

TRIAL REGISTRATION NUMBER

NCT03699254.

IL28B rs12979860 T allele protects against CMV disease in liver transplant recipients in the post-prophylaxis and late period

BACKGROUND

Cytomegalovirus (CMV) disease represents a serious complication in liver transplant (OLT) recipients. CMV prophylaxis reduces incidence of CMV disease in the early post-transplant period (on-prophylaxis disease, OPD) but may postpone its manifestation after the completion of prophylaxis. Post-prophylaxis disease (PPD) incidence after prophylaxis cessation may be modified by genetic factors.

METHODS

We analyzed impact of IL28B rs1297986 variants on CMV disease incidence in 743 adult OLT recipients receiving universal prophylaxis.

RESULTS

One hundred and forty-four (19.4%) patients had at least one CMV disease episode. One hundred and two of them (70.8%) had at least one OPD and 36 (25%) patients had PPD, six (4.2%) patients had both. The rate of IL28B T allele carriers was lower in PPD group (38.9%) in comparison with OPD group (66.7%, P = 0.005) and group without CMV disease (61.4%, P = 0.009). The impact of IL28B genotype on the risk of CMV OPD was significant neither in the allelic (TT + CT vs CC, P = 0.32) nor in the recessive model (TT vs CT + CC, P = 0.79). Contrarily, in the PPD group, T allele (TT + CT vs CC) had a protective effect, OR 0.4 (95% CI 0.2-0.8, P = 0.008). Further risk factors of PPD were age <55 years and valganciclovir prophylaxis, whereas the risk factors of OPD were age <55 years, cyclosporine A therapy and pre-transplant CMV serostatus (donor +/recipient -).

CONCLUSIONS

IL28B rs12979860 T allele carriers had a lower risk of CMV PPD.

Impacts of Interleukin-18 Polymorphisms on the Incidence of Delayed-Onset Cytomegalovirus Infection in a Cohort of Kidney Transplant Recipients

Background

The incidence of cytomegalovirus (CMV) infection in solid organ transplant recipients may be reduced by antiviral prophylaxis, but this strategy may lead to delayed-onset CMV infection. The proinflammatory cytokine interleukin (IL)-18 plays a major role in viral host defense responses. This study examines the impacts of 2 single-nucleotide polymorphisms (SNPs) in the promoter region of the IL-18 gene, -607C/A (rs1946518) and -137G/C (rs187238), on the incidence of delayed-onset CMV infection in patients undergoing kidney transplant.

Methods

This retrospective study analyzed 2 IL-18 SNPs in consecutive adult kidney transplant recipients using real-time polymerase chain reaction with TaqMan probes. Participants were enrolled over the period 2005–2013 and stratified according to their IL-18 SNP genotype. The concordance index (Harrell’s c-index) was used as a measure of the discriminatory power of the predictive models constructed with bootstrapping to correct for optimistic bias.

Results

Seven hundred nine patients received transplants in the study period, and 498 met selection criteria. Cytomegalovirus infection and disease incidence were 38% and 7.5%, respectively. In multivariate competing risk regression models, carriers of the -607C/-137G haplotype who received prophylaxis showed a higher incidence of CMV replication after antiviral agent discontinuation (hazard ratio = 2.42 [95% confidence interval, 1.11–5.26]; P = .026), whereas CMV disease was not observed in those given prophylaxis who were noncarriers of this polymorphism (P = .009).

Conclusions

Our findings suggest that the -607C/-137G IL-18 haplotype is associated with a higher incidence of postprophylaxis CMV replication. The prior identification of this polymorphism could help select alternative measures to prevent delayed-onset CMV infection in these patients.

Persistent primary cytomegalovirus infection in a kidney transplant recipient: Multi-drug resistant and compartmentalized infection leading to graft loss

Cytomegalovirus (CMV) is one of the most common opportunistic infections after transplantation. To prevent CMV infections, universal prophylaxis and pre-emptive therapy with ganciclovir or its prodrug valganciclovir is applied. However, prolonged antiviral therapy may result in drug-resistance emergence. We describe a case of a 43-year-old CMV-seronegative patient who underwent kidney transplantation from a CMV-seropositive donor and developed CMV disease despite valganciclovir prophylaxis. CMV viral load increased even though valgangiclovir dose was augmented and immunosuppressive therapy reduced. CMV genotyping revealed mutations in the viral UL97 protein kinase, explaining ganciclovir-resistant CMV infection. The viral load failed to respond to foscavir, cidofovir and CMV-neutralizing immunoglobulins. Kidney allograft dysfunction developed 3 months post-transplantation with a histopathologic diagnosis of CMV nephropathy and potentially concomitant T-cell mediated rejection. A transplantectomy was performed on day 164 post-transplantation since the patient had uncontrollable CMV disease associated with a circulating multidrug-resistant DNA polymerase-mutant virus. Detailed monitoring in this patient demonstrated hallmarks of complicated CMV disease: (i) relatively rapid evolution of drug-resistant CMV mutants in the setting of persistent high blood viral loads, (ii) emergence of viral drug-resistance linked to acute graft rejection, (iii) transient and, thereafter, lack of response to various anti-CMV treatments, (iv) compartmentalization and heterogeneity of CMV viral populations, (v) possible differential ability of viral mutants to cause disease in the graft, and (vi) detection of minor viral variants by next generation sequencing. Translational research platforms that provide rapid molecular genotyping for detection of CMV drug-resistance are essential in guiding CMV disease management in high-risk transplant recipients.

New Developments in the Management of Cytomegalovirus Infection After Transplantation

Cytomegalovirus (CMV) continues to be one of the most important pathogens that universally affect solid organ and allogeneic hematopoietic stem cell transplant recipients. Lack of effective CMV-specific immunity is the common factor that predisposes to the risk of CMV reactivation and clinical disease after transplantation. Antiviral drugs are the cornerstone for prevention and treatment of CMV infection and disease. Over the years, the CMV DNA polymerase inhibitor, ganciclovir (and valganciclovir), have served as the backbone for management, while foscarnet and cidofovir are reserved for the management of CMV infection that is refractory or resistant to ganciclovir treatment. In this review, we highlight the role of the newly approved drug, letermovir, a viral terminase inhibitor, for CMV prevention after allogeneic hematopoietic stem cell transplantation. Advances in immunologic monitoring may allow for an individualized approach to management of CMV after transplantation. Specifically, the potential role of CMV-specific T-cell measurements in guiding the need for the treatment of asymptomatic CMV infection and the duration of treatment of CMV disease is discussed. The role of adoptive immunotherapy, using ex vivo-generated CMV-specific T cells, is highlighted. This article provides a review of novel drugs, tests, and strategies in optimizing our current approaches to prevention and treatment of CMV in transplant recipients.

The Third International Consensus Guidelines on the Management of Cytomegalovirus in Solid-organ Transplantation

Despite recent advances, cytomegalovirus (CMV) infections remain one of the most common complications affecting solid organ transplant recipients, conveying higher risks of complications, graft loss, morbidity, and mortality. Research in the field and development of prior consensus guidelines supported by The Transplantation Society has allowed a more standardized approach to CMV management. An international multidisciplinary panel of experts was convened to expand and revise evidence and expert opinion-based consensus guidelines on CMV management including prevention, treatment, diagnostics, immunology, drug resistance, and pediatric issues. Highlights include advances in molecular and immunologic diagnostics, improved understanding of diagnostic thresholds, optimized methods of prevention, advances in the use of novel antiviral therapies and certain immunosuppressive agents, and more savvy approaches to treatment resistant/refractory disease. The following report summarizes the updated recommendations.

Prevention and Treatment of Cytomegalovirus Infections in Solid Organ Transplant Recipients

Despite advances in prevention and treatment, cytomegalovirus (CMV) infection and disease remain an expected problem in solid organ transplant recipients. Because of the effect of immunosuppressing medications, CMV primary, secondary, and reactivated infection requires antiviral medications to prevent serious direct and indirect effects of the virus. Side effects and drug resistance, however, often limit the capacity of traditional antiviral therapies. This article updates the clinician on current and promising approaches to the management and control of CMV in the solid organ transplant recipient.

Late cytomegalovirus (CMV) infections after kidney transplantation under the preemptive strategy: Risk factors and clinical aspects

BACKGROUND

Late cytomegalovirus infections (LCMV) after the cessation of prophylaxis are well described. We aimed to assess clinical and epidemiological data on late-occurring cytomegalovirus (CMV) infections in the absence of CMV prophylaxis in a cohort of kidney transplant patients.

METHODS

In a cohort of kidney transplant recipients not employing CMV-specific prophylaxis, patients with CMV infections occurring after 6 months of transplantation were compared to patients with CMV infections diagnosed within the first 6 months (early infections). The main objectives were to compare clinical outcomes and evaluate risk factors for late CMV infection.

RESULTS

A total of 556 patients were evaluated. Forty-three patients with LCMV infections were compared to 513 patients with early CMV infections. LCMV infections occurred after a median of 473 days of transplantation and had a more severe course, with a statistically significant higher rate of invasive disease and graft loss (60.5% vs 21.6% and 11.6% vs 3.1% respectively). Thirty-day mortality was twice as high for patients with LCMV, but did not reach statistical significance (9.3% vs 4.3%). By multivariate analysis, employment of antilymphocyte therapy early after transplantation and tacrolimus as initial immunosuppressive therapy were significantly protective for the occurrence of LCMV infections.

CONCLUSION

Late CMV infections in the absence of specific prophylaxis after kidney transplantation have a more severe outcome when compared to early infections and occur in patients less immunosuppressed early after transplantation.

Treatment and Prevention of CMV Disease in Transplant Recipients: Current Knowledge and Future Perspectives

This review summarizes the significant impact of cytomegalovirus (CMV) infection on solid organ and hematopoietic stem cell transplant recipients. A discussion of the various CMV prevention and treatment strategies is provided, including a detailed description of each of the available CMV antiviral drugs.