EBV-positive lymphoma patients have a selective deficiency in EBV immunity

Abstract

21032 Background: Epstein-Barr virus (EBV) asymptomatically establishes persistent infections in more than 90% of the adult population. However, due to effective immune control, only a minority of infected carriers develops spontaneous EBV-associated lymphomas. Since EBV nuclear antigen-1 (EBNA1) is the only protein expressed in all proliferating EBV infected cells we hypothesize that EBNA1 specific immune response is critical in preventing EBV-positive lymphomas. Methods: After informed consent, peripheral blood from healthy volunteers and lymphoma patients (prior to therapy- no evidence of cytopenia) were stimulated (ex vivo) with overlapping peptides covering the immunogenic EBNA1 (aa400–641) sequence. Frequency of EBNA1-specific T-cells were assessed by intracellular cytokine staining and flow cytometric proliferation assays. Cytokine pattern, surface marker phenotype and functional reactivity against EBV specific and control antigens were analyzed. Results: Patient and volunteer immune responses to control antigens and other viruses were assessed and statistically indistinguishable. EBNA1 specific CD4+ T cell responses were detected among 18 of 20 healthy carriers, and among 10 of 16 patients with EBV-negative lymphoma (relative to healthy volunteers p=0.145 via paired student T test). None of the patients with EBV-positive lymphomas (n=8) had a detectable EBNA1-specific CD4+ T-cell response (p<0.003 relative to healthy volunteers and patients with EBV-negative lymphomas). Conclusions: Healthy volunteers and patients with EBV-negative lymphoma have statistically similar EBNA1-specific CD4+ T cell responses. Although patients with EBV-positive lymphoma have intact immune responses to common viruses and antigens, they selectively lack an EBNA1-specific CD4+ T cell response. An intact EBNA1 specific immune response among patients with EBV-negaitve lymphoma implies that lymphoma is not a cause of a selective immune deficiency. On the contrary, these findings suggest that EBNA1-specific CD4+ T cells are critical in the prevention of EBV mediated lymphomas, and a defect in EBNA1 specific immunity may leave EBV carriers suseptible to EBV-positive lymphomas. EBNA1- specific CD4+ T cell function may be a new target for therapies of EBV-associated malignancies. No significant financial relationships to disclose.