Cytomegalovirus (CMV) immune monitoring with ELISPOT and QuantiFERON-CMV assay in seropositive kidney transplant recipients

Pathogen-specific cell-mediated immunity to guide the management of cytomegalovirus in solid organ transplantation: state of the art clinical review

INTRODUCTION

Cytomegalovirus (CMV) is a common opportunistic infection after solid organ transplantation, with significant impact on morbidity and long-term survival. Despite advances in diagnostics and therapeutics, the management of CMV remains very challenging.

AREAS COVERED

This article reviews emerging data on the clinical utility of laboratory assays that quantify cell-mediated immune responses to CMV. Observational studies have consistently demonstrated that a deficiency in pathogen-specific cell-mediated immunity is correlated with a heightened risk of primary, reactivation or recurrent CMV after transplantation. A limited number of interventional studies have recently investigated cell-mediated immune assays in guiding the prevention and treatment of CMV infection after solid organ transplantation.

EXPERT OPINION

The pathogenesis and outcome of CMV after solid organ transplantion reflect the interplay between viral replication and CMV-specific immune reconstitution. Research in CMV-specific cell-mediated immunity paved way for the development of several laboratory assays that may assist clinicians in predicting the risk of CMV after transplantation, individualize the approach to CMV disease prevention, guide the need and duration of treatment of CMV infection, and predict the risk of relapse after treatment. More interventional studies are needed to further solidify the role of cell-mediated immune assays in various clinical situations after transplantation.

COVID-19 Vaccine in Lung and Liver Transplant Recipients Exceeds Expectations: An Italian Real-Life Experience on Immunogenicity and Clinical Efficacy of BNT162b2 Vaccine

This study assessed humoral and T cell-mediated immune responses to the BNT162b2 vaccine in orthotopic liver transplant (OLT) and lung transplant (LUT) recipients who received three doses of the vaccine from March 2021 at our institution. Serum samples were collected 60 days post-second and third dose to quantify antibodies against the spike region of SARS-CoV-2 while whole blood samples were collected to analyze the SARS-CoV-2-specific T-cell response using an IFN-γ ELISpot assay. We enrolled 244 OLT and 120 LUT recipients. The third dose increased antibody titres in OLT recipients (from a median value of 131 after the second dose to 5523 IU/mL, p < 0.001) and LUT recipients (from 14.8 to 1729 IU/mL, p < 0.001). T-cell response also increased in OLT recipients (from 8.5 to 23 IFN-γ SFU per 250,000 PBMC, p < 0.001) and LUT recipients (from 8 to 15 IFN-γ SFU per 250,000 PBMC, p < 0.001). A total of 128 breakthrough infections were observed: two (0.8%) OLT recipients were hospitalized due to COVID-19 and one died (0.4%); among LUT recipients, seven were hospitalized (5.8%) and two patients died (1.7%). In conclusion, the three-dose schedule of the BNT162b2 vaccine elicited both humoral and T cell-mediated responses in solid organ transplant recipients. The risk of severe COVID-19 post-vaccination was low in this population.

Advancing cytomegalovirus prevention in solid organ transplant recipients: The promise of cell-mediated immune assays

Cytomegalovirus (CMV) infections are a major source of morbidity and mortality in solid organ transplant recipients. Prophylactic, preemptive, and hybrid prevention strategies have traditionally been the mainstay of CMV prevention but there is growing interest in the use of CMV cell-mediated immune assays to inform novel approaches to risk stratification. Recent evidence suggests that CMV interferon-gamma release assays can offer predictive insights into the risk for CMV-related illnesses, raising the potential for tailored CMV prevention strategies anchored to each individual's unique CMV immune profile. However, the predictive capacity of these assays for CMV-related illnesses can be profoundly influenced by when they are performed relative to transplant, and the induction immunosuppressive regimen the patient has received. In this review, we explore the relevant literature shaping our understanding of the optimal use of these assays. Furthermore, we also highlight the benefits of quantifying the CD4+ and CD8+ T-Cell responses to CMV, which is offered by some interferon-gamma release assays utilizing intracellular cytokine staining, for providing a holistic assessment of the recovery of cell-mediated immunity post-induction immunosuppression.

Cytomegalovirus Cell-mediated Immunity Assays in Pediatric Transplantation

Cytomegalovirus (CMV) is a significant cause of morbidity and mortality in pediatric transplantation. However, currently utilized CMV prevention paradigms have limitations, leading to research aimed at novel strategies for mitigation of CMV infection. Cell-mediated immunity (CMI) is crucial in controlling CMV infection and the use of CMV-specific CMI assays to guide prevention and treatment of CMV infection in both solid organ transplant and hematopoietic cell transplant recipients shows great promise. In this article, we review the immune response to CMV infection to highlight the rationale for CMI assays, describe available commercial assays and strategies for their use, and summarize relevant literature regarding the use of CMI assays in transplant recipients.

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.

QuantiFERON-CMV and monitor predict cytomegalovirus, mortality, and graft-versus-host disease in transplant recipients

Cytomegalovirus (CMV) is the most prevalent infection in recipients of hematopoietic stem cell transplant (HSCT). QuantiFERON-CMV (QF-CMV) and QuantiFERON-Monitor (QFM) assays were used to test whether immune-competent adult allogeneic HSCT recipients with CMV-specific T cells can control CMV infection or reactivation. Our data demonstrated a significant correlation between CMV infection measured by CMV-antigenemia test and QF-CMV results, graft versus host disease (GvHD), and mortality rates. The QF-CMV test revealed that CMV-specific T cells with higher interferon-γ (IFN-γ) release were correlated with lower CMV infection rates. There was a significant negative association between QF-CMV results, GvHD, and mortality rates. Data showed that a one-unit rise in IFN-γ was linked with a 12.7% reduction in GvHD and a 20.7% reduction in the mortality odds ratio. In addition, a negative correlation was found between QF-M results and CMV infection, with the QFM test predicting protection against CMV infection by 1.9%. This is one of the few studies establishing the QF-CMV test's predictive value for GvHD and mortality, its use to monitor HSCT patients for pre-emptive therapy, and the use of the QFM test to predict CMV infection and mortality in HSCT patients. Thus, these assays could be utilized to optimize preventive and pre-emptive therapy procedures to reduce transplant recipient adverse effects and posttransplant therapy costs.

Antiviral Approach to Cytomegalovirus Infection: An Overview of Conventional and Novel Strategies

Human cytomegalovirus (HCMV) is a herpesvirus capable of establishing a lifelong persistence in the host through a chronic state of infection and remains an essential global concern due to its distinct life cycle, mutations, and latency. It represents a life-threatening pathogen for immunocompromised patients, such as solid organ transplanted patients, HIV-positive individuals, and hematopoietic stem cell recipients. Multiple antiviral approaches are currently available and administered in order to prevent or manage viral infections in the early stages. However, limitations due to side effects and the onset of antidrug resistance are a hurdle to their efficacy, especially for long-term therapies. Novel antiviral molecules, together with innovative approaches (e.g., genetic editing and RNA interference) are currently in study, with promising results performed in vitro and in vivo. Since HCMV is a virus able to establish latent infection, with a consequential risk of reactivation, infection management could benefit from preventive treatment for critical patients, such as immunocompromised individuals and seronegative pregnant women. This review will provide an overview of conventional antiviral clinical approaches and their mechanisms of action. Additionally, an overview of proposed and developing new molecules is provided, including nucleic-acid-based therapies and immune-mediated approaches.

Pretransplant BKV-IgG serostatus and BKV-specific ELISPOT assays to predict BKV infection after kidney transplantation

Introduction

Polyomavirus (BKV) infection can lead to major complications and damage to the graft in kidney transplant recipients (KTRs). We investigated whether pretransplant BK serostatus and BK-specific cell-mediated immunity (CMI) predicts post-transplant BK infection.

Methods

A total of 93 donor-recipient pairs who underwent kidney transplantation (KT) and 44 healthy controls were examined. Assessment of donor and recipient BKV serostatus and BKV-CMI in recipients was performed prior to transplantation using BKV-IgG ELISA and BKV-specific IFN-g ELISPOT assays against five BK viral antigens (LT, St, VP1, VP2, and VP3). BK viremia was diagnosed when blood BKV-DNA of 104 copies/mL or more was detected during follow-up periods.

Results

Anti-BKV IgG antibody was detected in 74 (79.6%) of 93 KTRs and in 68 (73.1%) of 93 KT donors. A greater percentage of KTRs who received allograft from donors with high levels of anti-BKV IgG had posttransplant BK viremia (+) than KTRs from donors with low anti-BKV IgG (25.5% [12/47] vs. 4.3% [2/46], respectively; P = 0.007). Pretransplant total BKV-ELISPOT results were lower in BK viremia (+) patients than in patients without viremia (-) 20.5 [range 9.9-63.6] vs. 72.0 [43.2 - 110.8]; P = 0. 027). The sensitivity and specificity of the total BKV-ELISPOT assay (cut-off ≤ 53 spots/3×105 cells) for prediction of posttransplant BK viremia were 71.4 (95% CI: 41.9-91.6) and 54.4 (42.8-65.7), respectively. The combination of high donor BKV-IgG, low recipient BKV-IgG, and low total BKV-ELISPOT results improved specificity to 91.1%.

Discussion

Our study highlights the importance of pretransplant BKV-IgG serostatus and BKV-specific CMI in predicting posttransplant BKV infection in KTRs. The combination of high donor BKV-IgG, low recipient BKV-IgG, and low total BKV-ELISPOT results predicted BK viremia after KT. Pretransplant identification of patients at highrisk for BK viremia could enable timely interventions and improve clinical outcomes of KTRs.

Torque teno virus viremia and QuantiFERON®-CMV assay in prediction of cytomegalovirus reactivation in R+ kidney transplant recipients

Introduction

Cytomegalovirus (CMV) is the most frequent infectious complication following solid organ transplantation. Torque teno viruses (TTV) viremia has been proposed as a biomarker of functional immunity in the management of kidney transplant recipients (KTR). The QuantiFERON^®-CMV (QF-CMV) is a commercially available assay that allows the assessment of CD8⁺ T-cell responses in routine diagnostic laboratories.

Methods

In a prospective national multicenter cohort of 64 CMV-seropositive (R+) KTR, we analyzed the value of TTV load and the two markers of the QF-CMV assay [QF-Ag (CMV-specific T-cell responses) and QF-Mg (overall T-cell responses)], alone and in combination, in prediction of CMV reactivation (≥3 log₁₀ IU/ ml) in the first post-transplant year. We compared previously published cut-offs and specific cut-offs optimized from ROC curves for our population.

Results

Using the conventional cut-off (3.45 log₁₀ copies/ml), TTV load at D0 [inclusion visit on the day of transplantation before induction (D0)], or at M1 (1-month post-transplant visit) perform better in predicting CMV viremia control than CMV reactivation. Survival analyses suggest a better performance of our optimized TTV cut-offs (3.78 log₁₀ copies/ml at D0 and 4.23 log₁₀ copies/ml at M1) for risk stratification of CMV reactivation in our R+ KTR cohort. The QF-CMV (QF-Ag = 0.2 IU/ml, and QF-Mg = 0.5 IU/ml) also appears to better predict CMV viremia control than CMV reactivation. Moreover, survival analyses suggest that the QF-Mg would perform better than the QF-Ag in stratifying the risk of CMV reactivation. The use of our optimized QF-Mg cut-off (1.27 IU/ml) at M1 further improved risk stratification of CMV reactivation. Using conventional cut-offs, the combination of TTV load and QF-Ag or TTV load and QF-Mg did not improve prediction of CMV viremia control compared to separate analysis of each marker but resulted in an increase of positive predictive values. The use of our cut-offs slightly improved risk prediction of CMV reactivation.

Conclusion

The combination of TTV load and QF-Ag or TTV load and QF-Mg could be useful in stratifying the risk of CMV reactivation in R+ KTR during the first post-transplant year and thereby have an impact on the duration of prophylaxis in these patients.

Clinical trial registration

ClinicalTrials.gov registry, identifier NCT02064699.

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.

A consensus conference to define the utility of advanced infectious disease diagnostics in solid organ transplant recipients

The last decade has seen an explosion of advanced assays for the diagnosis of infectious diseases, yet evidence-based recommendations to inform their optimal use in the care of transplant recipients are lacking. A consensus conference sponsored by the American Society of Transplantation (AST) was convened on December 7, 2021, to define the utility of novel infectious disease diagnostics in organ transplant recipients. The conference represented a collaborative effort by experts in transplant infectious diseases, diagnostic stewardship, and clinical microbiology from centers across North America to evaluate current uses, unmet needs, and future directions for assays in 5 categories including (1) multiplex molecular assays, (2) rapid antimicrobial resistance detection methods, (3) pathogen-specific T-cell reactivity assays, (4) next-generation sequencing assays, and (5) mass spectrometry-based assays. Participants reviewed and appraised available literature, determined assay advantages and limitations, developed best practice guidance largely based on expert opinion for clinical use, and identified areas of future investigation in the setting of transplantation. In addition, attendees emphasized the need for well-designed studies to generate high-quality evidence needed to guide care, identified regulatory and financial barriers, and discussed the role of regulatory agencies in facilitating research and implementation of these assays. Findings and consensus statements are presented.

Intra-host diversity of drug-resistant cytomegalovirus: A case report of cytomegalovirus infection after allogeneic hematopoietic cell transplantation

Cytomegalovirus (CMV) is a major infectious agent causing severe complications in allogeneic hematopoietic cell transplantation (HCT) recipients, thereby warranting the need for aggressive preemptive or targeted antiviral therapy. However, prolonged or repeated use of antiviral agents, such as ganciclovir (GCV), foscarnet (FOS), and cidofovir (CDV), can result in drug-resistant CMV infection, posing challenges to successful outcomes. Here, we report a case of a patient with acute myeloid leukemia and drug-resistant CMV infection who presented with persistent CMV DNAemia, colitis, pneumonia, and encephalitis. An intra-host diversity of UL97 and UL54 mutations were detected through the genotypic resistance testing conducted on two blood samples (D+199 and D+224) and a cerebrospinal fluid (CSF) specimen (D+260) collected from the patient. UL97 L595W/L595F and L595W mutations were detected in the blood and CSF samples, respectively, that conferred GCV resistance. UL54 F412L mutation detected in all three samples conferred GCV/CDV resistance. However, the V787L mutation of UL54, conferring GCV/FOS resistance, was observed only in the D+224 blood sample. Despite combination therapy with FOS and high dose GCV and adjunctive therapy with leflunomide, the patient died from CMV infection and multiple organ failure on D+279. Further data on resistant mutations and intra-host diversity of CMV should be accumulated to elucidate the antiviral resistance and related outcomes.

QuantiFERON-Cytomegalovirus Assay for Prediction of Cytomegalovirus Viremia in Kidney Transplant Recipients: Study From High Cytomegalovirus Seroprevalence Country

Background

Early studies showed the utility of pretransplant QuantiFERON-Cytomegalovirus (QF-CMV) assays for CMV-disease prediction post kidney transplant (KT). However, recent data are conflicting.

Methods

This prospective cohort study enrolled adult patients undergoing KT between July 2017 and May 2019. Patients with antithymocyte globulin therapy or negative pretransplant CMV IgG were excluded. QF-CMV assays were performed on transplantation day and one month thereafter, and CMV viral loads were obtained 1, 3, and 6 months posttransplantation. The primary outcome was CMV viremia within 6 months. The QF-CMV assay–posttransplant CMV viremia association was analyzed.

Results

Fifty-five patients were enrolled (male, 58.2%; mean (SD) age, 46.5 (10.2) years). Fifty-two (94.5%) received CMV-seropositive donor kidneys. Over 6 months, 29 patients developed CMV viremia (52.7%), with 14 (25.5%) having significant viremia requiring antiviral therapy. The CMV-viremia incidence of patients with nonreactive and reactive baseline QF-CMV assays did not differ significantly (55.3% and 47.1%; p = 0.573). Among patients with reactive pretransplant QF-CMV assays, there was a trend toward a lower incidence of CMV viremia for those who were persistently reactive at 1 month after KTs, although there was no statistically significant difference (50% vs 83%; p = 0.132).

Conclusions

Our study could not support the use of single-timepoint pretransplant or 1-month posttransplant QF-CMV assays as a predictor for posttransplant CMV viremia in CMV seropositive KT recipients. Investigation of the association between dynamic QF-CMV-status changes and CMV-viremia incidence are needed.

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.

Laboratory diagnostic testing for cytomegalovirus infection in solid organ transplant patients

Human cytomegalovirus (CMV) infection, which is one of the most common complications in transplant recipients, increases the risk of graft loss and rejection. Laboratory strategies for diagnosing CMV infection rely on the measurement of viral DNAemia and CMV-specific cell-mediated immunity (CMV-CMI). The CMV quantitative nucleic acid amplification test (QNAT) enabled the spread of preemptive therapy and prompted recommendations for surveillance, diagnosis, and monitoring. Despite the implementation of the World Health Organization international standard for calibration, variability of QNAT persists due to technical issues. CMV immunoglobulin G serology is the standard method for CMV immune screening of transplant candidates and donors. Assays for CMV-CMI play an important role in helping to predict the risk and to develop an individualized CMV management plan. Genotypic testing for resistance is needed when drug-resistant CMV infection is suspected. Here, we review the state of the art of laboratory tests for CMV infection in solid organ transplantation.

Cytomegalovirus infection in liver-transplanted children

Cytomegalovirus (CMV) infection is a common complication of liver trans-plantation in children. The CMV serostatus of recipients and donors is the primary risk factor, and prophylaxis or pre-emptive strategies are recommended for high-risk patients. Graft rejection, coinfection and Epstein-Bar virus reactivation, which can lead to post-transplant lymphoproliferative disease, are indirect effects of CMV infection. Assessment of CMV infection viral load should be routinely performed upon clinical suspicion. However, tissue-invasive CMV disease is not associated with CMV viraemia and requires confirmation by tissue pathology. Oral valganciclovir and intravenous ganciclovir are equivalent treatments, and the duration of treatment depends on factors including CMV viral load, tissue pathology, and clinical response. Risk stratification by donor and recipient status prior to transplantation and post-transplantation antiviral prophylaxis or pre-emptive therapy are recommended. Adult guidelines have been established but additional study of the effectiveness of the preventive guidelines in children is needed. This review summarizes the burden, risk factors, clinical manifestations, laboratory evaluation, treatment, and prevention of CMV infection in children after liver transplantation.

Utility of CMV-Specific Immune Monitoring for the Management of CMV in Solid Organ Transplant Recipients: A Clinical Update

Cytomegalovirus (CMV) is one of the most important opportunistic infections in solid organ transplant (SOT) recipients. However, current techniques used to predict risk for CMV infection fall short. CMV-specific cell mediated immunity (CMI) plays an important role in protecting against CMV infection. There is evidence that assays measuring CMV-CMI might better identify SOT recipients at risk of complications from CMV compared to anti-CMV IgG, which is our current standard of care. Here, we review recently published studies that utilize CMV-CMI, at various points before and after transplantation, to help predict risk and guide the management of CMV infection following organ transplantation. The evidence supports the use of these novel assays to help identify SOT recipients at increased risk and highlights the need for larger prospective trials evaluating these modalities in this high-risk population.

Human cytomegalovirus infection: A considerable issue following allogeneic hematopoietic stem cell transplantation

Cytomegalovirus (CMV) is an opportunistic virus, whereby recipients are most susceptible following allogeneic hematopoietic stem cell transplantation (allo-HSCT). With the development of novel immunosuppressive agents and antiviral drugs, accompanied with the widespread application of prophylaxis and preemptive treatment, significant developments have been made in transplant recipients with human (H)CMV infection. However, HCMV remains an important cause of short- and long-term morbidity and mortality in transplant recipients. The present review summarizes the molecular mechanism and risk factors of HCMV reactivation following allo-HSCT, the diagnosis of CMV infection following allo-HSCT, prophylaxis and treatment of HCMV infection, and future perspectives. All relevant literature were retrieved from PubMed and have been reviewed.

CMV high-risk status and posttransplant outcomes in kidney transplant recipients treated with belatacept

INTRODUCTION

Cytomegalovirus (CMV) remains associated with poor outcomes after kidney transplantation (kTx). The impact of belatacept on CMV infection remains understudied. In this study, we assessed the impact of belatacept on patient and graft survivals.

METHODS

CMV seronegative kTx recipients were included. Patient and graft survival were studied using Kaplan-Meier method, log-rank test. Cox models were used to compare outcomes by CMV risk and immunosuppressive regimen. Incidence and persistence of CMV viremia under belatacept vs tacrolimus were compared.

RESULTS

Among 308 CMV seronegative recipients, 168 CMV high-risk and 203 belatacept-treated patients were included. High-risk CMV status was associated with lower patient survival and graft survival. Among the CMV high-risk group, patients treated with belatacept presented a higher incidence of CMV viremia, a higher rate of first-line treatment failure and a longer time to virus clearance. They had a nonsignificant trend toward a lower graft survival.

CONCLUSION

Belatacept-based maintenance immunosuppression is associated with an increased risk of CMV primary-infection and a prolonged course of viral replication in CMV high-risk patients. Further studies are needed to confirm the nonsignificant trend towards a lower graft survival in CMV high-risk patients treated with belatacept and whether it is explained by the higher risk of CMV reactivation and infection.

Usefulness of BK virus-specific interferon-γ enzyme-linked immunospot assay for predicting the outcome of BK virus infection in kidney transplant recipients

BACKGROUND/AIMS

To investigate if BK virus (BKV)-specific T cell immunity measured by an interferon-γ enzyme-linked immunospot (ELISPOT) assay can predict the outcome of BK virus infection in kidney transplant recipients (KTRs).

METHODS

We included 68 KTRs with different viremia status (no viremia [n = 17], BK viremia [n = 27], and cleared viremia [n = 24]) and 44 healthy controls (HCs). The BK viremia group was divided into controller (< 3 months) and noncontroller (> 3 months) according to sustained duration of BKV infection. We compared BKV-ELISPOT results against five BKV peptides (large tumor antigen [LT], St, VP1-3).

RESULTS

BKV-ELISPOT results were higher in three KTRs groups with different BKV infection status than the HCs group (p < 0.05). In KTR groups, they were higher in cleared viremia group than no viremia or BK viremia group. Within the BK viremia group, controller group had higher LT-ELISPOT results compared to noncontroller group (p = 0.032). Also, KTRs without BK virus-associated nephropathy (BKVN) had higher LT, St, VP1, and VP2-ELISPOT results than those with BKVN (p < 0.05).

CONCLUSION

BKV-ELISPOT assay may be effective in predicting clinical outcomes of BKV infection in terms of clearance of BK virus and development of BKVN.

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.

Cellular and humoral cytomegalovirus immunity changes in one-year combined prophylaxis after lung transplantation: suggestions from and for clinical practice

Background:

Immune responses, both cellular and humoral, against cytomegalovirus (CMV) are used to predict CMV manifestations in solid organ recipients. The aim of this study is to evaluate CMV enzyme-linked immunospot (ELISPOT) assay and serology during CMV infections, their concordance and variations after lung transplantation (LTx).

Methods:

We retrospectively analysed in one year the follow-up data of 43 patients receiving combined CMV prophylaxis with antiviral agents and CMV-specific immunoglobulin G (IgG). CMV infections were investigated by using molecular analyses on both 167 bronchoalveolar lavage and biopsy specimens and 1134 blood samples. Cellular CMV immunity was assessed with specific ELISPOT whereas the humoral one was assessed by quantifying specific immunoglobulins.

Results:

At the first month after LTx the majority of patients were ELISPOT responders (52.3%) and 30.9% were non-responders. ELISPOT responders had a lower incidence of CMV viremia (p = 0.047), whereas neither effects on CMV pulmonary asymptomatic infection nor on acute rejection were observed. Responders had a higher CMV IgG titre (p < 0.0001) in particular at the first month after LTx (p = 0.0001). Concordance among CMV ELISPOT assay and IgG levels was moderate (Cohen’s K 0.524), with an agreement of 89.8%. All ELISPOT responders maintained their status and almost all non-responders became responders during follow-up (92.3%); the percentage of IgG seropositive subjects increased from 74.4% at the first month of follow-up to 97.4% after 1 year.

Conclusions:

Despite a moderate concordance with serology, ELISPOT response predicted a lower incidence of CMV viremia in LTx patients; no effects were reported on pulmonary clinical manifestations nor on acute rejection. The ELISPOT response as well as serology changed during the follow-up, not only after first CMV contact.

The reviews of this paper are available via the supplemental material section.

Progress and Challenges in the Prevention, Diagnosis, and Management of Cytomegalovirus Infection in Transplantation

Hosts with compromised or naive immune systems, such as individuals living with HIV/AIDS, transplant recipients, and fetuses, are at the highest risk for complications from cytomegalovirus (CMV) infection. Despite substantial progress in prevention, diagnostics, and treatment, CMV continues to negatively impact both solid-organ transplant (SOT) and hematologic cell transplant (HCT) recipients. In this article, we summarize important developments in the field over the past 10 years and highlight new approaches and remaining challenges to the optimal control of CMV infection and disease in transplant settings.

Cytomegalovirus (CMV) Cell-Mediated Immunity and CMV Infection After Allogeneic Hematopoietic Cell Transplantation: The REACT Study

BACKGROUND

Cytomegalovirus (CMV) infection remains an important cause of morbidity and mortality in allogeneic hematopoietic cell transplant (allo-HCT) recipients. CMV cell-mediated immunity (CMV-CMI) as determined by a peptide-based enzyme-linked immunospot (ELISPOT) CMV assay may identify patients at risk for clinically significant CMV infection (CS-CMVi).

METHODS

The CS-CMVi was defined as CMV viremia and/or disease necessitating antiviral therapy. CMV-CMI was characterized as high when the intermediate-early 1 (IE-1) antigen spot counts (SPCs) were >100 (cutoff 1) or when the IE-1 and phosphoprotein 65 antigen SPCs were both >100 SPCs per 250 000 cells (cutoff 2), and a low CMV-CMI when SPCs were below these thresholds. In this prospective multicenter study, we evaluated CMV-CMI every 2 weeks from the pretransplant period until 6 months posttransplantation in 241 allo-HCT recipients with positive CMV serostatus. The primary endpoint was CS-CMVi occurring within 2 weeks of the last measurement of CMV-CMI.

RESULTS

CS-CMVi occurred in 70 allo-HCT recipients (29%). CMV-CMI was low in patients who experienced CS-CMVi (94%), whereas those who had a high CMV-CMI were less likely to have CS-CMVi (P < .0001). Patients with CS-CMVi had higher all-cause mortality (P = .007), especially those with low CMV-CMI (P = .035). On multivariable analysis, CMV-CMI, sex, race, antithymocyte globulin, and steroid use were independent predictors of CS-CMVi, and the time from transplant to engraftment was the only predictor of mortality.

CONCLUSIONS

Measurement of CMV-CMI using a novel ELISPOT assay would be useful clinically to monitor allo-HCT recipients and distinguish between those at risk of developing CS-CMVi and requiring antiviral prophylaxis or therapy and those who are protected.

Cytomegalovirus-Specific T Cell Epitope Recognition in Congenital Cytomegalovirus Mother-Infant Pairs

Background: Congenital cytomegalovirus (cCMV) infection is the most common infection acquired before birth and from which about 20% of infants develop permanent neurodevelopmental effects regardless of presence or absence of symptoms at birth. Viral escape from host immune control may be a mechanism of CMV transmission and infant disease severity. We sought to identify and compare CMV epitopes recognized by mother-infant pairs. We also hypothesized that if immune escape were occurring, then one pattern of longitudinal CD8 T cell responses restricted by shared HLA alleles would be maternal loss (by viral escape) and infant gain (by viral reversion to wildtype) of CMV epitope recognition. Methods: The study population consisted of 6 women with primary CMV infection during pregnancy and their infants with cCMV infection. CMV UL83 and UL123 peptides with known or predicted restriction by maternal MHC class I alleles were identified, and a subset was selected for testing based on several criteria. Maternal or infant cells were stimulated with CMV peptides in the IFN-γ ELISpot assay. Results: Overall, 14 of 25 (56%; 8 UL83 and 6 UL123) peptides recognized by mother-infant pairs were not previously reported as CD8 T cell epitopes. Of three pairs with longitudinal samples, one showed maternal loss and infant gain of responses to a CMV epitope restricted by a shared HLA allele. Conclusions: CD8 T cell responses to multiple novel CMV epitopes were identified, particularly in infants. Moreover, the hypothesized pattern of CMV immune escape was observed in one mother-infant pair. These findings emphasize that knowledge of paired CMV epitope recognition allows exploration of viral immune escape that may operate within the maternal-fetal system. Our work provides rationale for future studies of this potential mechanism of CMV transmission during pregnancy or clinical outcomes of infants with cCMV infection.

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.

[Functional immunoassays in the setting of infectious risk and immunosuppressive therapy of non-HIV immunocompromised patients]

The holistic approach of the human immune system is based on the study of its components collectively driving a functional response to an immunogenic stimulus. To appreciate a specific immune dysfunction, a condition is mimicked ex vivo and the immune response induced is assessed. The application field of such assays are broad and expanding, from the diagnosis of primary and secondary immunodeficiencies, immunotherapy for cancer to the management of patients at-risk for infections and vaccination. These assays are immune monitoring tools that may contribute to a personalised and precision medicine. The purpose of this review is to describe immune functional assays available in the setting of non-HIV acquired immune deficiency. First, we will address the use of theses assays in the diagnosis of opportunistic infections such as viral reactivation. Secondly, we will report the usefulness of these assays to assess vaccine efficacy and to manage immunosuppressive therapies.

The development and implementation of stewardship initiatives to optimize the prevention and treatment of cytomegalovirus infection in solid-organ transplant recipients

Classical stewardship efforts have targeted immunocompetent patients; however, appropriate use of antimicrobials in the immunocompromised host has become a target of interest. Cytomegalovirus (CMV) infection is one of the most common and significant complications after solid-organ transplant (SOT). The treatment of CMV requires a dual approach of antiviral drug therapy and reduction of immunosuppression for optimal outcomes. This dual approach to CMV management increases complexity and requires individualization of therapy to balance antiviral efficacy with the risk of allograft rejection. In this review, we focus on the development and implementation of CMV stewardship initiatives, as a component of antimicrobial stewardship in the immunocompromised host, to optimize the management of prevention and treatment of CMV in SOT recipients. These initiatives have the potential not only to improve judicious use of antivirals and prevent resistance but also to improve patient and graft survival given the interconnection between CMV infection and allograft function.

Delayed NK Cell Reconstitution and Reduced NK Activity Increased the Risks of CMV Disease in Allogeneic-Hematopoietic Stem Cell Transplantation

Cytomegalovirus (CMV) infection has a significant impact in patients after allogeneic hematopoietic stem cell transplantation (HSCT). We investigated natural killer (NK) cell reconstitution and cytotoxic/cytokine production in controlling CMV infection, especially severe CMV disease in HSCT patients. Fifty-eight patients with acute myeloid leukemia (AML) who received allo-HSCT were included. We monitored NK reconstitution and NK function at baseline, 30, 60, 90, 120, 150, and 180 days after HSCT, and compared the results in recipients stratified on post-HSCT CMV reactivation (n = 23), non-reactivation (n = 24) versus CMV disease (n = 11) groups. The CMV disease group had a significantly delayed recovery of CD56dim NK cells and expansion of FcRγ-CD3ζ+NK cells started post-HSCT 150 days. Sequential results of NK cytotoxicity, NK cell-mediated antibody-dependent cellular cytotoxicity (NK-ADCC), and NK-Interferon-gamma (NK-IFNγ) production for 180 days demonstrated delayed recovery and decreased levels in the CMV disease group compared with the other groups. The results within 1 month after CMV viremia also showed a significant decrease in NK function in the CMV disease group compared to the CMV reactivation group. It suggests that NK cells' maturation and cytotoxic/IFNγ production contributes to CMV protection, thereby revealing the NK phenotype and functional NK monitoring as a biomarker for CMV risk prediction, especially CMV disease.

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.

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.

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.

Assessment and prevention of cytomegalovirus infection in allogeneic hematopoietic stem cell transplant and in solid organ transplant: A multidisciplinary consensus conference by the Italian GITMO, SITO, and AMCLI societies

Cytomegalovirus (CMV) remains a major cause of morbidity and mortality in allogeneic hematopoietic stem cell transplantation (allo-HSCT) and solid organ transplantation (SOT) recipients. In view of the uncertainties on the assessment and prevention of CMV infection in both transplant procedures, three Italian scientific societies for HSCT and SOT and for Clinical Microbiology appointed a panel of experts to compose a framework of recommendations. Recommendations were derived from a comprehensive analysis of the scientific literature and from a multidisciplinary consensus conference process. The lack of adequate clinical trials focused on certain diagnostic procedures, and antiviral intervention forced the panel to use the methods of consensus for shaping some recommendations. Recommendations concerning the two types of transplant were given for the following issues: assessment of pretransplant CMV serostatus, immunological monitoring after transplant, CMV prophylaxis with antivirals, CMV preemptive strategy, and CMV prophylaxis with immunoglobulin infusion and with adoptive immunotherapy. The questions raised by and the recommendations resulting from this consensus conference project may contribute to the improvement of certain crucial aspects of the management of CMV infections in allo-HSCT and in SOT populations.

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.

Diagnostic performance of cytomegalovirus (CMV) immune monitoring with ELISPOT and QuantiFERON-CMV assay in kidney transplantation: A PRISMA-compliant article

BACKGROUND

Cytomegalovirus (CMV) infection is part of major infection complications following kidney transplantation. However, more rapid and low-complexity assays are needed for CMV infection. Our study is to investigate the diagnostic efficacy of 2 novel tests, CMV-ELISPOT and QuantiFERON-CMV tests, in CMV DNA viremia and CMV infection following renal transplant.

METHODS

We searched MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials and the Web of Science. Case-control or cohort study designed to explore the CMV-ELISPOT and/or QuantiFERON-CMV tests in the recipients with CMV infection was considered to be eligible for this study. Sensitivity (SEN), specificity (SPE), diagnostic odds ratio (DOR), and summary receiver-operating characteristic (SROC) curves were calculated.

RESULTS

We selected a total of 12 articles for systematic review and 11 of them were included in meta-analysis. For CMV-pp65 assay, the pooled SEN, SPE, and DOR were 0.73 (95% confidence interval [CI], 0.67-0.78), 0.61 (95% CI, 0.56-0.65), and 4.46 (95% CI, 3.11-6.39), respectively. For CMV-IE-1 assay, the pooled SEN, SPE, and DOR were 0.84 (95% CI, 0.78-0.88), 0.46 (95% CI, 0.42-0.51), and 5.07 (95% CI, 3.26-7.89), respectively, whereas the pooled SEN, SPE, and DOR of QuantiFERON-CMV test were 0.38 (95% CI, 0.28-0.49), 0.38 (95% CI, 0.32-0.44), and 1.02 (95% CI, 0.17-6.00).

CONCLUSIONS

We reported that CMV-ELISPOT tests, including CMV-pp65 and CMV-IE-1, perform well in the diagnosis and prediction of CMV infection in renal transplant recipients, whereas QuantiFERON-CMV test needs further exploration.

Early Post-Transplant Torquetenovirus Viremia Predicts Cytomegalovirus Reactivations In Solid Organ Transplant Recipients

Monitoring the human virome has been recently suggested as a promising and novel area of research for identifying new biomarkers which would help physicians in the management of transplant patients. Imbalance of the immune system in transplant recipients has a significant impact on replication of Torquetenovirus (TTV), the most representative and abundant virus of human virome. TTV kinetic was studied by real-time PCR in 280 liver or kidney transplant recipients who underwent different drug regimens to maintain immunosuppression. During one-year post-transplant follow-up, TTV viremia fluctuated irrespective of transplanted organ type but consistent with the immunosuppression regimen. TTV kinetic in patients who manifested cytomegalovirus (CMV) reactivation within the first four months post-transplant differed from that observed in patients who did not experience CMV complications. Importantly, plasma TTV load measured between day 0 and 10 post-transplant was significantly higher in CMV DNA positive than in CMV DNA negative patients. TTV viremia above 3.45 log DNA copies/ml within the first 10 days post-transplant correlates with higher propensity to CMV reactivation following transplantation. This study provides further evidence for using early post-transplant TTV viremia to predict CMV reactivation in liver or kidney transplant recipients.

Immune Monitoring of Infectious Complications in Transplant Patients: an Important Step towards Improved Clinical Management

Immune reconstitution following organ transplantation is absolutely critical in preventing infectious complications. However, understanding the kinetics of immune reconstitution and its potential impact on the clinical management of transplant patients remains a significant challenge. Over the last decade, various platform technologies have emerged which have provided important insights into the immune reconstitution kinetics in transplant patients. However, many of these technologies are too complicated and cumbersome to implement in a clinical setting. In this issue of the Journal of Clinical Microbiology, Chiereghin et al. (J. Clin. Microbiol. 56:e01040-17, 2018, https://doi.org/10.1128/JCM.01040-17) report the results of their evaluation of the QuantiFERON-CMV (QFN-CMV) assay to assess human cytomegalovirus (CMV)-specific CD8⁺ T-cell immunity in heart transplant recipients as a prognostic tool. These studies showed that patients with absence of global immune reactivity in the QFN-CMV assay were at a higher risk of developing CMV after discontinuing antiviral prophylaxis. Furthermore, failure to reconstitute CMV-specific immunity after resolution of the first episode of viremia was associated with viral relapse. These observations, along with other recent clinical studies utilizing the QFN-CMV assay, demonstrate that systematic monitoring of antiviral immunity can be successfully used as a prognostic tool and also to guide changes to the clinical management of transplant patients.

Infectious complications after hematopoietic stem cell transplantation: current status and future perspectives in Korea

Hematopoietic stem cell transplantation (HSCT) is a treatment for hematologic malignancies, immune deficiencies, or genetic diseases, ect. Recently, the number of HSCTs performed in Korea has increased and the outcomes have improved. However, infectious complications account for most of the morbidity and mortality after HSCT. Post-HSCT infectious complications are usually classified according to the time after HSCT: pre-engraftment, immediate post-engraftment, and late post-engraftment period. In addition, the types and risk factors of infectious complications differ according to the stem cell source, donor type, conditioning intensity, region, prophylaxis strategy, and comorbidities, such as graft-versushost disease and invasive fungal infection. In this review, we summarize infectious complications after HSCT, focusing on the Korean perspectives.