Epstein-Barr Virus Gene Expression, Human Leukocyte Antigen Alleles and Chronic High Viral Loads in Pediatric Renal Transplant Patients

The IPTA Nashville Consensus Conference on Post-Transplant lymphoproliferative disorders after solid organ transplantation in children: III - Consensus guidelines for Epstein-Barr virus load and other biomarker monitoring

The International Pediatric Transplant Association convened an expert consensus conference to assess current evidence and develop recommendations for various aspects of care relating to post-transplant lymphoproliferative disorders after solid organ transplantation in children. In this report from the Viral Load and Biomarker Monitoring Working Group, we reviewed the existing literature regarding the role of Epstein-Barr viral load and other biomarkers in peripheral blood for predicting the development of PTLD, for PTLD diagnosis, and for monitoring of response to treatment. Key recommendations from the group highlighted the strong recommendation for use of the term EBV DNAemia instead of "viremia" to describe EBV DNA levels in peripheral blood as well as concerns with comparison of EBV DNAemia measurement results performed at different institutions even when tests are calibrated using the WHO international standard. The working group concluded that either whole blood or plasma could be used as matrices for EBV DNA measurement; optimal specimen type may be clinical context dependent. Whole blood testing has some advantages for surveillance to inform pre-emptive interventions while plasma testing may be preferred in the setting of clinical symptoms and treatment monitoring. However, EBV DNAemia testing alone was not recommended for PTLD diagnosis. Quantitative EBV DNAemia surveillance to identify patients at risk for PTLD and to inform pre-emptive interventions in patients who are EBV seronegative pre-transplant was recommended. In contrast, with the exception of intestinal transplant recipients or those with recent primary EBV infection prior to SOT, surveillance was not recommended in pediatric SOT recipients EBV seropositive pre-transplant. Implications of viral load kinetic parameters including peak load and viral set point on pre-emptive PTLD prevention monitoring algorithms were discussed. Use of additional markers, including measurements of EBV specific cell mediated immunity was discussed but not recommended though the importance of obtaining additional data from prospective multicenter studies was highlighted as a key research priority.

Screening and Management of PTLD

Posttransplant lymphoproliferative disorder (PTLD) represents a heterogeneous group of lymphoproliferative diseases occurring in the setting of immunosuppression following hematopoietic stem cells transplant and solid organ transplantation. Despite its overall low incidence, PTLD is a serious complication following transplantation, with a mortality rate as high as 50% in transplant recipients. Therefore, it is important to establish for each transplant recipient a personalized risk evaluation for the development of PTLD based on the determination of Epstein-Barr virus serostatus and viral load following the initiation of immunosuppression. Due to the dynamic progression of PTLD, reflected in the diverse pathological features, different therapeutic approaches have been used to treat this disorder. Moreover, new therapeutic strategies based on the administration of virus-specific cytotoxic T cells have been developed. In this review, we summarize the available data on screening and treatment to suggest a strategy to identify transplant recipients at a higher risk for PTLD development and to review the current therapeutic options for PTLD.

Classic Hodgkin lymphoma post-transplant lymphoproliferative disorders (PTLD) are often preceded by discordant PTLD subtypes

Classic Hodgkin lymphoma (CHL) is the rarest post-transplant lymphoproliferative disorder (PTLD) subtype. Few cases of patients with metachronous discordant PTLD episodes including CHL-PTLD have been reported, but the incidence of and risk factors for this phenomenon are unknown. Patients with CHL-PTLD were identified from an institutional PTLD database. Of 13 patients identified with CHL-PTLD six (46%) had antecedent non-CHL-PTLD: three had polymorphic PTLD, two monomorphic PTLD, and one nondestructive PTLD. Patients with prior metachronous non-CHL-PTLD were younger at transplant and had a longer latency time to CHL-PTLD post-transplant. The prevalence of EBV seronegativity at transplant was high in both groups, but prolonged high-level EBV DNAemia only occurred in some with metachronous non-CHL-PTLD. In conclusion, patients with CHL-PTLD have metachronous non-CHL-PTLD diagnoses with discordant histology more commonly than previously recognized. Primary EBV infection with chronically elevated EBV viral loads may represent unique risk factors for CHL-PTLD following an initial non-CHL-PTLD event.

Post-transplant lymphoproliferative disorders, Epstein-Barr virus infection, and disease in solid organ transplantation: Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

PTLD with the response-dependent sequential use of RIS, rituximab, and cytotoxic chemotherapy is recommended. Evidence gaps requiring future research and alternate treatment strategies including immunotherapy are highlighted.

Plasma EBV microRNAs in paediatric renal transplant recipients

BACKGROUND

Epstein-Barr virus (EBV) was the first human virus identified to express microRNA (miRNA). To date, 44 mature miRNAs are encoded for within the EBV genome. EBV miRNAs have not been profiled in paediatric renal transplant recipients. In this study, we investigated circulating EBV miRNA profiles as novel biomarkers in paediatric renal transplant patients.

METHODS

Forty-two microRNAs encoded within 2 EBV open reading frames (BART and BHRF) were examined in renal transplant recipients who resolved EBV infection (REI) or maintained chronic high viral loads (CHL), and in non-transplant patients with acute infectious mononucleosis (IM).

RESULTS

Plasma EBV-miR-BART2-5p was present in higher numbers of IM (7/8) and CHL (7/10) compared to REI (7/12) patients. A trend was observed between the numbers of plasma EBV miRNAs expressed and EBV viral load (p < 0.07). Several EBV-miRs including BART7-3p, 15, 9-3p, 11-3p, 1-3p and 3-3p were detected in IM and CHL patients only. The lytic EBV-miRs, BHRF1-2-3p and 1-1, indicating active viral replication, were detected in IM patients only. One CHL patient developed post-transplant lymphoproliferative disease (PTLD) after several years and analysis of 10 samples over a 30-month period showed an average 24-fold higher change in plasma EBV-miR-BART2-5p compared to the CHL group and 110-fold higher change compared to the REI group.

CONCLUSIONS

Our results suggest that EBV-miR-BART2-5p, which targets the stress-induced immune ligand MICB to escape recognition and elimination by NK cells, may have a role in sustaining high EBV viral loads in CHL paediatric kidney transplant recipients.

Carcinogenesis of nasopharyngeal carcinoma: an alternate hypothetical mechanism

Current proposed mechanisms implicate both early and latent Epstein-Barr virus (EBV) infection in the carcinogenic cascade, whereas epidemiological studies have always associated nasopharyngeal carcinoma (NPC) with early childhood EBV infection and with chronic ear, nose, and sinus conditions. Moreover, most patients with NPC present with IgA antibody titers to EBV capsid antigen (VCA-IgA), which can precede actual tumor presentation by several years. If early childhood EBV infection indeed constitutes a key event in NPC carcinogenesis, one would have to explain the inability to detect the virus in normal nasopharyngeal epithelium of patients at a high risk for EBV infection. It is perhaps possible that EBV resides within the salivary glands, instead of the epithelium, during latency. This claim is indirectly supported by observations that the East Asian phenotype shares the characteristics of an increased susceptibility to NPC and immature salivary gland morphogenesis, the latter of which is influenced by the association of salivary gland morphogenesis with an evolutionary variant of the human ectodysplasin receptor gene (EDAR), EDARV370A. Whether the immature salivary gland represents a more favorable nidus for EBV is uncertain, but in patients with infectious mononucleosis, EBV has been isolated in this anatomical organ. The presence of EBV-induced lymphoepitheliomas in the salivary glands and lungs further addresses the possibility of submucosal spread of the virus. Adding to the fact that the fossa of Rosen Müller contains a transformative zone active only in the first decade of life, one might be tempted to speculate the possibility of an alternative carcinogenic cascade for NPC that is perhaps not dissimilar to the model of human papillomavirus and cervical cancer.

Host genetics of Epstein-Barr virus infection, latency and disease

Epstein–Barr virus (EBV) infects 95% of the adult population and is the cause of infectious mononucleosis. It is also associated with 1% of cancers worldwide, such as nasopharyngeal carcinoma, Hodgkin's lymphoma and Burkitt's lymphoma. Human and cancer genetic studies are now major forces determining gene variants associated with many cancers, including nasopharyngeal carcinoma and Hodgkin's lymphoma. Host genetics is also important in infectious disease; however, there have been no large-scale efforts towards understanding the contribution that human genetic variation plays in primary EBV infection and latency. This review covers 25 years of studies into host genetic susceptibility to EBV infection and disease, from candidate gene studies, to the first genome-wide association study of EBV antibody response, and an EBV-status stratified genome-wide association study of Hodgkin's lymphoma. Although many genes are implicated in EBV-related disease, studies are often small, not replicated or followed up in a different disease. Larger, appropriately powered genomic studies to understand the host response to EBV will be needed to move our understanding of the biology of EBV infection beyond the handful of genes currently identified. Fifty years since the discovery of EBV and its identification as a human oncogenic virus, a glimpse of the future is shown by the first whole-genome and whole-exome studies, revealing new human genes at the heart of the host–EBV interaction. © 2014 The Authors. Reviews in Medical Virology published by John Wiley & Sons Ltd.

Increased levels of PD-1 expression on CD8 T cells in patients post-renal transplant irrespective of chronic high EBV viral load

Studies have identified solid organ transplant recipients who remain asymptomatic despite maintaining CHL. Factors which determine the CHL state remain poorly understood but are likely to involve immunological control of the viral infection. We monitored expression of PD-1, a marker of T-cell exhaustion and viral persistence, on CD8 T cells in patients who resolved EBV infection as determined by undetectable EBV DNA (REI) and CHL patients. PD-1 expression on CD8 T cells was increased in the first year post-transplant irrespective of EBV outcome, and most CD8 T cells continued to express PD-1 for up to three yr post-transplant. Although all patient groups showed similar frequencies of EBV-specific CD8+ T cells, PD-1 expression on these cells increased in the post-transplant groups compared with the pretransplant patients. Functional studies of EBV-specific CD8+ T cells stimulated with BZLF or LMP2 peptide pools revealed monofunctional IFN-γ responses. Our results indicate that PD-1 expression on CD8 T cells post-transplant may result from factors other than antigenic stimulation.

Determining EBV load: current best practice and future requirements

EBV, a gammaherpesvirus and the pathogenic agent for infectious mononucleosis, is also associated with a broad spectrum of lymphoid and epithelial malignancies in immunocompetent and immunosuppressed individuals. EBV-DNA-load measurement by PCR has been shown to be a potential tool for the diagnosis of these diseases, a prognostic factor of their outcome and a successful method to monitor immunosuppressed patients. Since the end of 2011, there is an international WHO standard reference for EBV quantification available; however, many questions still remain; for instance about the optimal amplified region of the EBV genome, or the best-used specimen for EBV detection. Additionally, the optimal specimen and amplified region may vary in different malignancies. In this article, the authors review the different methods to measure EBV load, focus on the best-used specimen for the different EBV-associated malignancies and discuss future requirements and opportunities for EBV-load measurement.