Evaluation and Significance of Cytomegalovirus-Specific Cellular Immune Response in Lung Transplant Recipients

QuantiFERON® Monitor Test as a Potential Tool for Stratifying Patients by Infection Risk and Tailoring Follow-Up Care in Lung Transplant Recipients: A Single-Center Retrospective Experience

BACKGROUND

Lung transplantation is a life-saving option for patients with end-stage respiratory diseases, but risk of infections remains critical for ensuring long-term organ function. This study aimed to assess immune recovery in lung transplant recipients by measuring IFN-γ levels using the QuantiFERON Monitor Test (QFM). Results were correlated with episodes of infection and organ rejection to explore the assay's predictive potential.

METHODS

A retrospective study was conducted on 15 lung transplant recipients at the Lung Transplant Centre of Turin (Città della Salute e della Scienza di Torino, Italy) between December 2019 and January 2023. Patients were divided into a High Infection (HI) group (with >3 infections) and Low Infection (LI) group (with ≤3 infections). QFM assays were performed after 18 months post-transplant.

RESULTS

HI patients had lower QFM levels compared to LI (68.84 ± 21.98 vs. 380.54 ± 104.64 UI/mL, p = 0.033). A QFM value <89.5 UI/mL was associated with increased infection risk (p < 0.05). Patients with lower QFM levels also exhibited higher rates of MRSA bacteremia during hospitalization (50% HI vs. 0% LI, p = 0.04). No differences were observed in acute or chronic rejection rates, but LI patients showed more frequent alveolar neutrophilia at the fourth month post-transplant (0% HI vs. 55.5% LI, p = 0.04).

CONCLUSION

lower QFM values were associated with higher infection risk, highlighting the assay's potential for immune monitoring. In this study, a QFM value of 89.5 UI/mL showed good predictive accuracy for infections beyond 18 months. Further studies are needed to refine QFM's role in post-transplant care.

QuantiFERON CMV Test and CMV Serostatus in Lung Transplant: Stratification Risk for Infection, Chronic and Acute Allograft Rejection

The QuantiFERON CMV (QCMV) test evaluates specific adaptive immune system activity against CMV by measuring IFN-γ released by activated CD8+ T lymphocytes. We aimed to evaluate the QCMV test as a predictive tool for CMV manifestations and acute or chronic lung allograft rejection (AR and CLAD) in lung transplant (LTx) patients. A total of 73 patients were divided into four groups based on donor and recipient (D/R) serology for CMV and QCMV assay: group A low-risk for CMV infection and disease (D-/R-); group B and C at intermediate-risk (R+), group B with non-reactive QCMV and group C with reactive QCMV; group D at high-risk (D+/R-). Group D patients experienced higher viral replication; no differences were observed among R+ patients of groups B and C. D+/R- patients had a higher number of AR events and group C presented a lower incidence of AR. Prevalence of CLAD at 24 months was higher in group B with a higher risk of CLAD development (OR 6.33). The QCMV test allows us to identify R+ non-reactive QCMV population as the most exposed to onset of CLAD. This population had a higher, although non-significant, susceptibility to AR compared to the R+ population with reactive QCMV.

Herpes Virus Infection in Lung Transplantation: Diagnosis, Treatment and Prevention Strategies

Lung transplantation is an ultimate treatment option for some end-stage lung diseases; due to the intense immunosuppression needed to reduce the risk of developing acute and chronic allograft failure, infectious complications are highly incident. Viral infections represent nearly 30% of all infectious complications, with herpes viruses playing an important role in the development of acute and chronic diseases. Among them, cytomegalovirus (CMV) is a major cause of morbidity and mortality, being associated with an increased risk of chronic lung allograft failure. Epstein-Barr virus (EBV) is associated with transformation of infected B cells with the development of post-transplantation lymphoproliferative disorders (PTLDs). Similarly, herpes simplex virus (HSV), varicella zoster virus and human herpesviruses 6 and 7 can also be responsible for acute manifestations in lung transplant patients. During these last years, new, highly sensitive and specific diagnostic tests have been developed, and preventive and prophylactic strategies have been studied aiming to reduce and prevent the incidence of these viral infections. In this narrative review, we explore epidemiology, diagnosis and treatment options for more frequent herpes virus infections in lung transplant patients.

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.

Cytomegalovirus Immunity Assays Predict Viremia but not Replication Within the Lung Allograft

Cytomegalovirus (CMV) infection causes significant morbidity and mortality in lung transplant recipients. Current guidelines use pretransplant donor and recipient CMV serostatus to predict the risk of subsequent CMV replication and length of antiviral prophylaxis. Immunological monitoring may better inform the risk of CMV infection in patients, thereby allowing for improved tailoring of antiviral prophylaxis. In this study, we compared 2 commercially available assays, the QuantiFERON-CMV (QFN-CMV) and T-Track-CMV (enzyme-linked immunosorbent spot assay), to predict the risk of CMV disease in lung transplant recipients.

Methods

We performed CMV immunity assays on 32 lung transplant recipients at risk of CMV disease as defined by serostatus (CMV-seropositive recipients, n = 26; or CMV-seronegative lung transplant recipient receiving a CMV-seropositive donor organ, n = 6). QFN-CMV and T-Track were performed on peripheral blood mononuclear cells, and episodes of CMV replication in both serum and bronchoalveolar lavage were found to be correlated to the CMV immune assays. The predictive ability of the assays was determined using Kaplan-Meier curves.

Results

There was a degree of concordance between tests, with 44% of recipients positive for both tests and 28% negative for both tests; however, test results were discordant in 28% of cases. A negative result in either the QFN-CMV (P < 0.01) or T-Track (P < 0.05) assays was obtained in a significantly higher number of recipients who experienced CMV replication in the blood. Using these assays together gave higher predictability of CMV replication, with only 1 recipient experiencing CMV replication in the blood who obtained a positive test result for both assays. Neither assay was able to predict recipients who experienced CMV replication in the lung allograft.

Conclusions

Our study demonstrates that CMV immunity assays can predict viremia; however, the lack of association with allograft infection suggests that CMV-specific T-cell immunity in the circulation is not associated with the control of CMV replication within the transplanted lung allograft.

CMV antiviral stewardship: navigating obstacles to facilitate target attainment

PURPOSE OF REVIEW

Despite the availability of potent antivirals, consensus guidelines and decades of research, cytomegalovirus (CMV) continues to be associated with negative outcomes after solid organ transplant. This has been attributed to postprophylaxis CMV infection and a lack of development of CMV-specific cell mediated immunity (CMI). A shift from a focus on antiviral prevention to a focus on CMI target attainment is needed to improve CMV outcomes after transplantation.

RECENT FINDINGS

There are many obstacles to CMI target attainment. Antiviral stewardship programs (AVS) have been employed to improve patient outcomes through appropriate antiviral use, reduction of unnecessary exposure and resistance mitigation. By focusing on the patient's unique substrate of conglomerate risk factors and addressing these factors specifically with evidenced based methodology, the AVS can address these obstacles, increasing rates of CMI and subsequently reducing risk of future CMV infection and negative outcomes.

SUMMARY

With its multidisciplinary composition utilizing decades of experience from antimicrobial stewardship principles and practices, the AVS is uniquely poised to facilitate the shift from a focus on prevention to CMI target attainment and be the supporting pillar for the frontline transplant clinician caring for transplant patients with CMV.

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.

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.

Tailored combined cytomegalovirus management in lung transplantation: a retrospective analysis

BACKGROUND

There is no univocal prophylactic regimen to prevent cytomegalovirus (CMV) infection/disease in lung transplantation (LT) recipients. The aim of this study is to evaluate short-term clinical outcomes of a tailored combined CMV management approach.

METHODS

After 1-year follow up, 43 LT patients receiving combined CMV prophylaxis with antiviral agents and CMV-specific IgG were evaluated in a retrospective observational study. Systemic and lung viral infections were investigated by molecular methods on a total of 1134 whole blood and 167 bronchoalveolar lavage (BAL) and biopsy specimens. CMV immunity was assessed by ELISPOT assay. Clinical and therapeutic data were also evaluated.

RESULTS

We found 2/167 cases of CMV pneumonia (1.2%), both in the donor-positive/recipient-positive (D⁺/R⁺) population, and 51/167 cases of CMV pulmonary infection (BAL positivity 30.5%). However, only 32/167 patients (19.1%) were treated due to their weak immunological response at CMV ELISPOT assay. Viremia ⩾100,000 copies/mL occurred in 33/1134 specimens (2.9%). Regarding CMV-serological matching (D/R), the D⁺/R^- population had more CMV viremia episodes (p < 0.05) and fewer viremia-free days (p < 0.001).

CONCLUSIONS

Compared to previous findings, our study shows a lower incidence of CMV pneumonia and viremia despite the presence of a substantial CMV load. In addition, our findings further confirm the D⁺/R^- group to be a high-risk population for CMV viremia. Overall, a good immunological response seems to protect patients from CMV viremia and pneumonia but not from CMV alveolar replication. The reviews of this paper are available via the supplemental material section.

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).

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.

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.

Comparison of the Commercial QuantiFERON-CMV and Overlapping Peptide-based ELISPOT Assays for Predicting CMV Infection in Kidney Transplant Recipients

Cytomegalovirus (CMV) is one of the most important opportunistic infections in transplant recipients. Tests for CMV-specific T cell responses have been proposed to change the current risk stratification strategy using CMV assays. We evaluated the usefulness of pre-transplant CMV-specific T cell assays in kidney transplant (KT) candidates for predicting the development of CMV infection after transplantation comparing the results of the overlapping peptides (OLPs)-based enzyme-linked immunospot (ELISPOT) assay and the commercial QuantiFERON-CMV assay. We prospectively enrolled all cases of KT over a 5-month period, except donor CMV-seropositive and recipient seronegative transplants that are at highest risk of CMV infection. All the patients underwent QuantiFERON-CMV, CMV OLPs-based pp65, and immediate-early 1 (IE-1)-specific ELISPOT assays before transplantation. The primary outcome was the incidence of CMV infection at 6 months after transplant. The total of 47 KT recipients consisted of 45 living-donor KTs and 2 deceased-donor KTs. There was no association between positive QuantiFERON-CMV results and CMV infection. However, 10 of 34 patients with phosphoprotein 65 (pp65)- or IE-1-specific ELISPOT results higher than cut-off value developed CMV infections compared with none of 13 patients with results lower than cut-off value developed CMV. The OLPs-based ELISPOT assays are more useful than the QuantiFERON-CMV assay for predicting CMV infection. Patients with higher CMV-specific T cell immunity at baseline appear to be more likely to develop CMV infections after KT, suggesting that the abrupt decline in CMV-specific T cell responses after immunosuppression, or high CMV-specific T cell responses due to frequent CMV activation before KT, may promote CMV infection.

Enzyme-Linked Immunospot Assay as a Complementary Method to Assess and Monitor Cytomegalovirus Infection in Kidney Transplant Recipients on Pre-emptive Antiviral Therapy: A Single-Center Experience

BACKGROUND

Cytomegalovirus (CMV) disease represents a major cause of post-transplantation morbidity and mortality. To estimate the risk of infection and monitor response to antiviral therapy, current guidelines suggest combination of viral load monitoring with direct assessment of CMV-specific immune response. We used enzyme-linked immunospot (ELISpot) for the evaluation of CMV-specific T-cell response in kidney transplant recipients with CMV viremia and investigated how information gained could help manage CMV infection.

METHODS

Seventeen patients on pre-emptive antiviral therapy and CMV quantitative polymerase chain reaction (qPCR) ≥500 copies/mL (first episode after transplantation) were assessed using ELISpot and divided into Weak (9 patients with baseline ELISpot <25 spot-forming colonies [SFCs]/200,000 peripheral blood mononuclear cells [PBMCs]) and Strong Responders (8 patients with baseline ELISpot ≥25 SFCs/200,000 PBMCs). CMV-specific T-cell response, infection severity, viral load, and antiviral therapy were prospectively recorded and compared between groups at 1, 2, and 24 months of follow-up.

RESULTS

Demographic and transplant characteristics of Weak and Strong Responders were similar. No episodes of CMV disease were observed. Weak Responders were more likely to experience CMV syndrome (56% vs 36.5%) and late virus reactivation (56% vs 25%) than Strong Responders. Weak Responders showed higher baseline median viral loads (19,700 vs 9265 copies/mL) and needed antiviral therapy for longer (179 vs 59.5 days). T-cell response showed 2 main patterns: early and delayed.

CONCLUSIONS

ELISpot provides prognostic information about infection severity, risk of late reactivation, and response to therapy. Randomized trials, evaluating the need for antiviral therapy in kidney transplant recipients with asymptomatic infection and effective virus-specific T-cell immune response, are warranted.

An optimized IFN-γ ELISpot assay for the sensitive and standardized monitoring of CMV protein-reactive effector cells of cell-mediated immunity

Background

In healthy individuals, Cytomegalovirus (CMV) infection is efficiently controlled by CMV-specific cell-mediated immunity (CMI). Functional impairment of CMI in immunocompromized individuals however can lead to uncontrolled CMV replication and severe clinical complications. Close monitoring of CMV-specific CMI is therefore clinically relevant and might allow a reliable prognosis of CMV disease as well as assist personalized therapeutic decisions.

Methods

Objective of this work was the optimization and technical validation of an IFN-γ ELISpot assay for a standardized, sensitive and reliable quantification of CMV-reactive effector cells. T-activated® immunodominant CMV IE-1 and pp65 proteins were used as stimulants. All basic assay parameters and reagents were tested and optimized to establish a user-friendly protocol and maximize the signal-to-noise ratio of the ELISpot assay.

Results

Optimized and standardized ELISpot revealed low intra-assay, inter-assay and inter-operator variability (coefficient of variation CV below 22%) and CV inter-site was lower than 40%. Good assay linearity was obtained between 6 × 10⁴ and 2 × 10⁵ PBMC per well upon stimulation with T-activated® IE-1 (R² = 0.97) and pp65 (R² = 0.99) antigens. Remarkably, stimulation of peripheral blood mononuclear cells (PBMC) with T-activated® IE-1 and pp65 proteins resulted in the activation of a broad range of CMV-reactive effector cells, including CD3⁺CD4⁺ (Th), CD3⁺CD8⁺ (CTL), CD3⁻CD56⁺ (NK) and CD3⁺CD56⁺ (NKT-like) cells. Accordingly, the optimized IFN-γ ELISpot assay revealed very high sensitivity (97%) in a cohort of 45 healthy donors, of which 32 were CMV IgG-seropositive.

Conclusion

The combined use of T-activated® IE-1 and pp65 proteins for the stimulation of PBMC with the optimized IFN-γ ELISpot assay represents a highly standardized, valuable tool to monitor the functionality of CMV-specific CMI with great sensitivity and reliability.

Electronic supplementary material

The online version of this article (doi:10.1186/s12865-017-0195-y) contains supplementary material, which is available to authorized users.

Immunological Prediction of Cytomegalovirus (CMV) Replication Risk in Solid Organ Transplantation Recipients: Approaches for Regulating the Targeted Anti-CMV Prevention Strategies

The current cytomegalovirus (CMV) prevention strategies in solid organ transplantation (SOT) recipients have contributed towards overcoming the detrimental effects caused by CMV lytic infection, and improving the long-term success rate of graft survival. Although the quantification of CMV in peripheral blood is the standard method, and an excellent end-point for diagnosing CMV replication and modulating the anti-CMV prevention strategies in SOT recipients, a novel biomarker mimicking the CMV control mechanism is required. CMV-specific immune monitoring can be employed as a basic tool predicting CMV infection or disease after SOT, since uncontrolled CMV replication mostly originates from the impairment of immune responses against CMV under immunosuppressive conditions in SOT recipients. Several studies conducted during the past few decades have indicated the possibility of measuring the CMV-specific cell-mediated immune response in clinical situations. Among several analytical assays, the most advancing standardized tool is the QuantiFERON®-CMV assay. The T-Track® CMV kit that uses the standardized enzyme-linked immunospot assay is also widely employed. In addition to these assays, immunophenotyping and intracellular cytokine analysis using flow cytometry (with fluorescence-labeled monoclonal antibodies or peptide-major histocompatibility complex multimers) needs to be adequately standardized and validated for potential clinical applications.

Immune-based monitoring for cytomegalovirus infection in solid organ transplantation: is it ready for clinical primetime?

The impact of CMV infection and disease in solid organ transplant (SOT) recipients continues despite remarkable improvements in its prevention and management with antiviral drugs. Studies that have investigated the host immune response to CMV have paved way for the development of novel immune-based assays that are anticipated to complement the current antiviral-based strategies for CMV management after transplantation. In this article, we review the emerging data on the clinical application of innovative CMV-specific T-cell assays, including their role in risk-stratification, prognostication, prevention and treatment of CMV infection and disease in SOT recipients.

Evaluation of Epstein-Barr virus-specific immunologic response in solid organ transplant recipients with an enzyme-linked ImmunoSpot assay

Epstein-Barr virus (EBV) is a γ-herpes virus, responsible for infectious mononucleosis in immunocompetent hosts. Cellular immunity appears rapidly during EBV primary infection, keeping it silent despite long-life persistence in B lymphocytes. Defects of the EBV-specific cellular immunity are supposed to be the basis of post-transplantation lymphoproliferative disorders, promoted by high levels of immunosuppression. We retrospectively reviewed 197 solid organ transplant recipients to investigate EBV-specific lymphocyte responsiveness using Enzyme-linked ImmunoSpot assay (EliSpot), which assesses the EBV-specific interferon (IFN)-γ producing peripheral blood mononuclear cells, and kinetics of EBV infection/reactivation post-transplantation using quantitative real-time polymerase chain reaction (PCR) on whole blood. Overall, 102 of the 197 patients (51.8%) showed EBV responsiveness at the EBV-EliSpot assay: 68 (66.6%) showed a persistently positive EBV response in 3 or more determinations and 34 (33.3%) had transient episodes of nonresponsiveness. Ninety-five (48.2%) patients were persistently EBV nonresponders. EBV-DNAemia data were available for 58 patients: 27.6% presented at least one episode of EBV-DNA occurrence. No differences were found in EBV-EliSpot response stratification between the groups of patients who experienced episodes of EBV reactivation and those without EBV-DNAemia. However, EBV DNAemia peak values tended to be higher in the first year post-transplantation in the group of patients with a persistent positive EBV-specific immune response. EBV viral load quantitation in blood and EliSpot EBV-specific immune response determination may represent a powerful tool for monitoring solid organ transplant recipients, guiding immunosuppression modulation in patients with active EBV replication.

Updated international consensus guidelines on the management of cytomegalovirus in solid-organ transplantation

Cytomegalovirus (CMV) continues to be one of the most common infections after solid-organ transplantation, resulting in significant morbidity, graft loss, and adverse outcomes. Management of CMV varies considerably among transplant centers but has been become more standardized by publication of consensus guidelines by the Infectious Diseases Section of The Transplantation Society. An international panel of experts was reconvened in October 2012 to revise and expand evidence and expert opinion-based consensus guidelines on CMV management, including diagnostics, immunology, prevention, treatment, drug resistance, and pediatric issues. The following report summarizes the recommendations.

Late-onset cytomegalovirus (CMV) in lung transplant recipients: can CMV serostatus guide the duration of prophylaxis?

Evidence supports the use of 12 months of cytomegalovirus prophylaxis in all at-risk lung transplants; whether cytomegalovirus serostatus can be used to further optimize this duration remains to be determined. The purpose of this retrospective study was to determine if cytomegalovirus serostatus of both donor and recipient were associated with late-onset cytomegalovirus. The primary outcome was the proportion of lung transplants that developed cytomegalovirus infection or disease during the 180-day period following 6 months of prophylaxis in each at-risk serotype. Two hundred forty-four consecutive lung transplants were evaluated, 131 were included. The proportion of recipients with cytomegalovirus differed significantly between serotypes (20 of 41 [48.8%] D+/R- vs. 19 of 56 [33.9%] D+/R+ vs. 2 of 34 [5.9%] D-/R+; p < 0.001). In a multivariate model, older age (odds ratio [OR], 1.05, 95% confidence interval [CI] 1.004-1.099; p = 0.03) and D+/R- serostatus (OR, 3.83; 95% CI 1.674-8.770; p = 0.002) were associated with cytomegalovirus. Among R+ lung transplants, D- serostatus was associated with the absence of cytomegalovirus (OR, 0.12; 95% CI 0.0263-0.563; p = 0.007). These findings suggest that in the valganciclovir era, cytomegalovirus serostatus of both donor and recipient may identify lung transplants at heightened risk for late-onset cytomegalovirus.

Vaccination with synthetic constructs expressing cytomegalovirus immunogens is highly T cell immunogenic in mice

There is no licensed vaccine or cure for human cytomegalovirus (CMV), a ubiquitous β-herpesvirus infecting 60-95% of adults worldwide. Infection can cause congenital abnormalities, result in severe disease in immunocompromised patients, and is a major impediment during successful organ transplantation. In addition, it has been associated with numerous inflammatory diseases and cancers, as well as being implicated in the development of essential hypertension, a major risk factor for heart disease. To date, limited data regarding the identification of immunogenic viral targets has frustrated CMV vaccine development. Based upon promising clinical data suggesting an important role for T cells in protecting against disease in the transplantation setting, we designed a novel panel of highly-optimized synthetic vaccines encoding major CMV proteins and evaluated their immune potential in murine studies. Vaccination induced robust CD8+ and CD4+ T cells of great epitopic breadth as extensively analyzed using a novel modified T cell assay described herein. Together with improved levels of CMV-specific T cells as driven by a vaccine, further immune evaluation of each target is warranted. The present model provides an important tool for guiding future immunization strategies against CMV.

The Lack and Cytomegalovirus-Specific Cellular Immune Response May Contribute to the Onset of Organ Infection and Disease in Lung Transplant Recipients

Cellular immune response has been demonstrated to play a role in the control of human cytomegalovirus (HCMV) replication in organ transplant recipients. Herein, HCMV-specific T-cell response and association to the onset of organ infection/disease were prospectively evaluated by EliSPOT assay in a population of 46 lung transplant (LT) recipients at 1, 3, 6, 9 and 12 months post-transplantation. According to our centre's practice, a combined prolonged antiviral prophylaxis (HCMV-IG for 12 months and ganciclovir or valganciclovir for 3 weeks from postoperative day 21) was given to all LT recipients. HCMV-DNA was concomitantly detected on bronchoalveolar lavage (BAL) and whole blood by real-time PCR. Approximately one third of patients resulted HCMV persistently non-responder; the rate of HCMV infection, as evaluated by HCMV-DNA positivity, tended to be higher in non-responders. Mean viral load on BAL was significantly higher in non-responders vs other patients (p <0.001). Temporal profile of infections appeared related to the HCMV responder status with a shorter time to onset of infection post-transplantation and a longer duration in non-responders. The occurrence of organ disease (i.e. pneumonia) tended to be higher in non-responders, with poor prognosis, as death occurred in one of three non-responder patients that developed HCMV pneumonia. The lack of HCMV-specific cellular response can contribute to the onset of organ infection and disease also in patients in which antiviral prophylaxis was adopted; this could be due to the potential occurrence of incomplete control of replication in lungs or a delayed priming of T-cell reconstitution.

Right place, right time: the evolving role of herpesvirus infection as a "second hit" in idiopathic pulmonary fibrosis

Over the course of the past decade, increasing evidence has implicated alveolar epithelial cell injury and dysfunction in the pathogenesis of idiopathic pulmonary fibrosis (IPF). Genetic factors, cigarette smoking, and other environmental exposures have been identified as potential factors leading to a population of vulnerable alveolar epithelial cells. In addition, molecular techniques have demonstrated herpesviruses are commonly detectable in the lungs of patients with IPF, raising suspicion that, in the setting of a vulnerable alveolar epithelium, lytic (or latent) herpesvirus infection may act as a "second hit" leading to the development of pulmonary fibrosis. Intriguingly, in vivo modeling has shown that herpesvirus infection induces or worsens lung fibrosis when combined with immunodeficiency or other injurious stimuli. Here, we discuss potential mechanisms through which herpesvirus infection may contribute to the pathogenesis of IPF. Ultimately, antiviral therapy may hold promise for halting the progression of this deadly disease.