Maher K. Gandhi

Human cytomegalovirus: clinical aspects, immune regulation, and emerging treatments

After initial infection, human cytomegalovirus remains in a persistent state with the host. Immunity against the virus controls replication, although intermitent viral shedding can still take place in the seropositive immunocompetent person. Replication of cytomegalovirus in the absence of an effective immune response is central to the pathogenesis of disease. Therefore, complications are primarily seen in individuals whose immune system is immature, or is suppressed by drug treatment or coinfection with other pathogens. Although our increasing knowledge of the host-virus relationship has lead to the development of new pharmacological strategies for cytomegalovirus-associated infections, these strategies all have limitations-eg, drug toxicities, development of resistance, poor oral bioavailability, and low potency. Immune-based therapies to complement pharmacological strategies for the successful treatment of virus-associated complications should be prospectively investigated.

Identification of Naive or Antigen-Experienced Human CD8 + T Cells by Expression of Costimulation and Chemokine Receptors: Analysis of the Human Cytomegalovirus-Specific CD8 + T Cell Response

Human CMV (HCMV) infection provides an informative model of how long term human CD8+ T cell memory is maintained in the presence of Ag. To clarify the phenotypic identity of Ag-experienced human CD8+ T cells in vivo, we determined the expression of costimulation and chemokine receptors on Ag-specific CD8+ T cells by quantifying individual virus-specific clones in different cell populations using TCR clonotypic probing. In healthy HCMV carriers, expanded CD8+ clones specific for either HCMV tegument protein pp65 or immediate-early protein IE72 are found in both CD45ROhigh cells and the subpopulation of CD45RAhigh cells that lack the costimulatory molecule CD28. In contrast to previous suggested models of CD8+ T cell memory, we found that in healthy virus carriers highly purified CD28−CD45RAhighCCR7− cells are not terminally differentiated, because following stimulation in vitro with specific HCMV peptide these cells underwent sustained clonal proliferation, up-regulated CD45RO and CCR5, and showed strong peptide-specific cytotoxic activity. In an individual with acute primary HCMV infection, HCMV pp65-specific CD8+ T cells are predominantly CD28−CD45ROhighCCR7−. During convalescence, an increasing proportion of pp65-specific CD8+ T cells were CD28−CD45RAhighCCR7−. We conclude that naive human CD8+ T cells are CD28+CD45RAhigh, express CCR7 but not CCR6, and are predominantly CD27+ and L-selectin CD62 ligand-positive. The phenotype CD27+CD45RAhigh should not be used to identify naive human CD8+ T cells, because CD27+CD45RAhigh cells also contain a significant subpopulation of CD28−CD27+ Ag-experienced expanded clones. Thus CD8+ T cell memory to HCMV is maintained by cells of expanded HCMV-specific clones that show heterogeneity of activation state and costimulation molecular expression within both CD45ROhigh and CD28−CD45RAhigh T cell pools.

Epstein–Barr virus-associated Hodgkin's lymphoma

Survivors of Hodgkins lymphoma (HL) frequently have many years to experience the long‐term toxicities of combined modality therapies. Also, a significant proportion of HL patients will relapse or have refractory disease, and less than half of these patients will respond to current salvage strategies. 30–50% of HL cases are Epstein–Barr virus associated (EBV‐positive HL). The virus is localized to the malignant cells and is clonal. EBV‐positive HL is more frequent in childhood, in older adults (>45 years) and in mixed cellularity cases. The survival of EBV‐positive HL in the elderly and the immunosuppressed is particularly poor. Despite improvements in our understanding of EBV‐positive HL, the true contribution of EBV to the pathogenesis of HL remains unknown. Increased knowledge of the virus’ role in the basic biology of HL may generate novel therapeutic strategies for EBV‐positive HL and the presence of EBV‐latent antigens in the malignant HL cells may represent a target for cellular immunotherapy.

Plasma Epstein-Barr Virus (EBV) DNA Is a Biomarker for EBV-Positive Hodgkin's Lymphoma

Purpose: Latent Epstein-Barr virus (EBV) genomes are found in the malignant cells of approximately one-third of Hodgkins lymphoma (HL) cases. Detection and quantitation of EBV viral DNA could potentially be used as a biomarker of disease activity. Experimental Design: Initially, EBV-DNA viral load was prospectively monitored from peripheral blood mononuclear cells (PBMC) in patients with HL. Subsequently, we analyzed viral load in plasma from a second cohort of patients. A total of 58 patients with HL (31 newly diagnosed, 6 relapsed, and 21 in long-term remission) were tested. Using real-time PCR, 43 PBMC and 52 plasma samples were analyzed. Results: EBV-DNA was detectable in the plasma of all EBV-positive patients with HL prior to therapy. However, viral DNA was undetectable following therapy in responding patients (P = 0.0156), EBV-positive HL patients in long-term remission (P = 0.0011), and in all patients with EBV-negative HL (P = 0.0238). Conversely, there was no association seen for the EBV-DNA load measured from PBMC in patients with active EBV-positive HL patients as compared with EBV-negative HL, or patients in long-term remission. EBV-DNA load in matched plasma/PBMC samples were not correlated. Conclusions: We show that free plasma EBV-DNA has excellent sensitivity and specificity, and can be used as a noninvasive biomarker for EBV-positive HL and that serial monitoring could predict response to therapy. Additional prospective studies are required to further evaluate the use of free plasma EBV-DNA as a biomarker for monitoring response to treatment in patients with EBV-positive HL.

EBNA3B-deficient EBV promotes B cell lymphomagenesis in humanized mice and is found in human tumors

Epstein-Barr virus (EBV) persistently infects more than 90% of the human population and is etiologically linked to several B cell malignancies, including Burkitt lymphoma (BL), Hodgkin lymphoma (HL), and diffuse large B cell lymphoma (DLBCL). Despite its growth transforming properties, most immune-competent individuals control EBV infection throughout their lives. EBV encodes various oncogenes, and of the 6 latency-associated EBV-encoded nuclear antigens, only EBNA3B is completely dispensable for B cell transformation in vitro. Here, we report that infection with EBV lacking EBNA3B leads to aggressive, immune-evading monomorphic DLBCL-like tumors in NOD/SCID/γc-/- mice with reconstituted human immune system components. Infection with EBNA3B-knockout EBV (EBNA3BKO) induced expansion of EBV-specific T cells that failed to infiltrate the tumors. EBNA3BKO-infected B cells expanded more rapidly and secreted less T cell-chemoattractant CXCL10, reducing T cell recruitment in vitro and T cell-mediated killing in vivo. B cell lines from 2 EBV-positive human lymphomas encoding truncated EBNA3B exhibited gene expression profiles and phenotypic characteristics similar to those of tumor-derived lines from the humanized mice, including reduced CXCL10 secretion. Screening EBV-positive DLBCL, HL, and BL human samples identified additional EBNA3B mutations. Thus, EBNA3B is a virus-encoded tumor suppressor whose inactivation promotes immune evasion and virus-driven lymphomagenesis.

Epstein–Barr Virus‐Related Post‐Transplant Lymphoproliferative Disorders: Pathogenetic Insights for Targeted Therapy

Post‐transplant lymphoproliferative disorder (PTLD) is a spectrum of major, life‐threatening lymphoproliferative diseases occurring in the post‐transplant setting. The majority of PTLD is of B‐cell origin and is associated with several risk factors, the most significant being Epstein‐Barr virus (EBV) infection. EBVs in vitro transforming abilities, distinctive latency, clonality within the malignant cells and response to targeted therapies implicate a critical role in the biology of PTLD. This minireview focuses on EBV‐related PTLD pathogenesis, in particular the interplay between aspects of the EBV life cycle and latency with nonviral factors resulting in the wide spectrum of histology and clinical presentations encountered in PTLD. With the increased prevalence of transplantation a rise in the incidence of PTLD may be expected. Therefore the importance of laboratory and animal models in the understanding of PTLD and the development of novel therapeutic approaches is discussed.

Noninvasive monitoring of diffuse large B-cell lymphoma by immunoglobulin high-throughput sequencing

Recent studies have shown limited utility of routine surveillance imaging for diffuse large B-cell lymphoma (DLBCL) patients achieving remission. Detection of molecular disease by immunoglobulin high-throughput sequencing (Ig-HTS) from peripheral blood provides an alternate strategy for surveillance. We prospectively evaluated the utility of Ig-HTS within 311 blood and 105 tumor samples from 75 patients with DLBCL, comparing Ig-HTS from the cellular (circulating leukocytes) and acellular (plasma cell-free DNA) compartments of peripheral blood to clinical outcomes and (18)fluoro-deoxyglucose positron emission tomography combined with computed tomography (PET/CT; n = 173). Clonotypic immunoglobulin rearrangements were detected in 83% of patients with adequate tumor samples to enable subsequent monitoring in peripheral blood. Molecular disease measured from plasma, compared with circulating leukocytes, was more abundant and better correlated with radiographic disease burden. Before treatment, molecular disease was detected in the plasma of 82% of patients compared with 71% in circulating cells (P = .68). However, molecular disease was detected significantly more frequently in the plasma at time of relapse (100% vs 30%; P = .001). Detection of molecular disease in the plasma often preceded PET/CT detection of relapse in patients initially achieving remission. During surveillance time points before relapse, plasma Ig-HTS demonstrated improved specificity (100% vs 56%, P < .0001) and similar sensitivity (31% vs 55%, P = .4) compared with PET/CT. Given its high specificity, Ig-HTS from plasma has potential clinical utility for surveillance after complete remission.

Antibody responses to vaccinations given within the first two years after transplant are similar between autologous peripheral blood stem cell and bone marrow transplant recipients.

As a consequence of the significantly larger inoculum of lymphoid cells present in peripheral blood stem cell (PBSC) harvests compared to bone marrow (BM), it is possible that autoPBSCT recipients may have an earlier and*or enhanced response to vaccines. Until data to confirm this become available, the European Blood and Marrow Transplantation Association (EBMT) recommend that all transplant recipients be immunized in the same way regardless of stem cell source. We performed a prospective study comparing serological responses to influenza, pneumococcal polysaccharide and tetanus toxoid vaccines between autoPBSCT with autoBMT recipients. Antibody responses in sibling HLA-matched allogeneic BMT (alloBMT) survivors were also evaluated. All vaccines were administered within the first 2 years after stem cell transplantation. Fifty patients were enrolled. The time of vaccination after transplant was similar between autoPBSCT (mean 11 months for each vaccine) and autoBMT recipients (mean 12 months except 13 months for tetanus toxoid) (P = NS). Serological responses were poor and no significant difference in response to any of the vaccines used was seen between the three transplant cohorts. We provide no evidence that current EBMT guidelines be modified. Large prospective vaccine studies are needed to address the issue more fully. Bone Marrow Transplantation (2001) 28, 775–781.

Primary CNS Posttransplant Lymphoproliferative Disease (PTLD): An International Report of 84 Cases in the Modern Era

We performed a multicenter, International analysis of solid organ transplant (SOT)‐related primary central nervous system (PCNS) posttransplant lymphoproliferative disease (PTLD). Among 84 PCNS PTLD patients, median time of SOT‐to‐PTLD was 54 months, 79% had kidney SOT, histology was monomorphic in 83% and tumor was EBV+ in 94%. Further, 33% had deep brain involvement, 10% had CSF involvement, while none had ocular disease. Immunosuppression was reduced in 93%; additional first‐line therapy included high‐dose methotrexate (48%), high‐dose cytarabine (33%), brain radiation (24%) and/or rituximab (44%). The overall response rate was 60%, while treatment‐related mortality was 13%. With 42‐month median follow‐up, three‐year progression‐free survival (PFS) and overall survival (OS) were 32% and 43%, respectively. There was a trend on univariable analysis for improved PFS for patients who received rituximab and/or high‐dose cytarabine. On multivariable Cox regression, poor performance status predicted inferior PFS (HR 2.61, 95% CI 1.32–5.17, p = 0.006), while increased LDH portended inferior OS (HR 4.16, 95% CI 1.29–13.46, p = 0.02). Moreover, lack of response to first‐line therapy was the most dominant prognostic factor on multivariable analysis (HR 8.70, 95% CI 2.56–29.57, p = 0.0005). Altogether, PCNS PTLD appears to represent a distinct clinicopathologic entity within the PTLD spectrum that is associated with renal SOT, occurs late, is monomorphic and retains EBV positivity.

Plasma microRNA are disease response biomarkers in classical Hodgkin lymphoma

Purpose: Although microRNAs (miRNA) show potential as diagnostic biomarkers in cancer, their role as circulating cell-free disease response biomarkers remains unknown. Candidate circulating miRNA biomarkers for classical Hodgkin lymphoma (cHL) might arise from Hodgkin–Reed–Sternberg (HRS) cells and/or nonmalignant tumor-infiltrating cells. HRS cells are sparse within the diseased node, embedded within a benign microenvironment, the composition of which is distinct from that seen in healthy lymph nodes. Experimental Design: Microarray profiling of more than 1,000 human miRNAs in 14 cHL primary tissues and eight healthy lymph nodes revealed a number of new disease node–associated miRNAs, including miR-494 and miR-1973. Using quantitative real-time PCR (qRT-PCR), we tested the utility of these, as well as previously identified disease node–associated plasma miRNAs (including miR-21 and miR-155), as disease response biomarkers in a prospective cohort of 42 patients with cHL. Blood samples were taken in conjunction with radiologic imaging at fixed time points before, during, and after therapy. Absolute quantification was used so as to facilitate implementation in diagnostic laboratories. Results: Levels of miR-494, miR-1973, and miR-21 were higher in patients than control (n = 20) plasma (P = 0.004, P = 0.007, and P < 0.0001, respectively). MiR-494 and miR-21 associated with Hasenclever scores ≥3. Strikingly, all three miRNAs returned to normal at remission (P = 0.0006, P = 0.0002, and P < 0.0001 respectively). However, only miR-494 and miR-1973 reflected interim therapy response with reduction being more pronounced in patients achieving complete versus partial responses (P = 0.043 and P = 0.0012, respectively). Conclusion: Our results demonstrate that in patients with cHL, circulating cell-free miRNAs can reflect disease response once therapy has commenced. Clin Cancer Res; 20(1); 253–64. ©2013 AACR.