Interplay between IL-10, IFN-γ, IL-17A and PD-1 Expressing EBNA1-Specific CD4(+) and CD8(+) T Cell Responses in the Etiologic Pathway to Endemic Burkitt Lymphoma

SIMPLE SUMMARY: Endemic Burkitt lymphoma (eBL) is a common pediatric cancer in sub-Saharan Africa. The incidence of this aggressive B-cell cancer is linked to Plasmodium falciparum (Pf) malaria and Epstein–Barr virus (EBV) co-infections during childhood. Most eBL tumors contain EBV and are characterized by the Epstein–Barr Nuclear Antigen 1 (EBNA1) latency I pattern of viral gene expression. The aim of our study was to compare the phenotypes and functions of CD4(+) and CD8(+) T cell responses to EBNA1 in children diagnosed with eBL and in healthy EBV-seropositive children to highlight differences that contribute to the balance between anti-viral immunity and eBL pathogenesis. ABSTRACT: Children diagnosed with endemic Burkitt lymphoma (eBL) are deficient in interferon-γ (IFN-γ) responses to Epstein–Barr Nuclear Antigen1 (EBNA1), the viral protein that defines the latency I pattern in this B cell tumor. However, the contributions of immune-regulatory cytokines and phenotypes of the EBNA1-specific T cells have not been characterized for eBL. Using a bespoke flow cytometry assay we measured intracellular IFN-γ, IL-10, IL-17A expression and phenotyped CD4(+) and CD8(+) T cell effector memory subsets specific to EBNA1 for eBL patients compared to two groups of healthy children with divergent malaria exposures. In response to EBNA1 and a malaria antigen (PfSEA-1A), the three study groups exhibited strikingly different cytokine expression and T cell memory profiles. EBNA1-specific IFN-γ-producing CD4(+) T cell response rates were lowest in eBL (40%) compared to children with high malaria (84%) and low malaria (66%) exposures (p < 0.0001 and p = 0.0004, respectively). However, eBL patients did not differ in CD8(+) T cell response rates or the magnitude of IFN-γ expression. In contrast, eBL children were more likely to have EBNA1-specific CD4(+) T cells expressing IL-10, and less likely to have polyfunctional IFN-γ(+)IL-10(+) CD4(+) T cells (p = 0.02). They were also more likely to have IFN-γ(+)IL-17A(+), IFN-γ(+) and IL-17A(+) CD8(+) T cell subsets compared to healthy children. Cytokine-producing T cell subsets were predominantly CD45RA(+)CCR7(+) T(NAIVE-LIKE) cells, yet PD-1, a marker of persistent activation/exhaustion, was more highly expressed by the central memory (T(CM)) and effector memory (T(EM)) T cell subsets. In summary, our study suggests that IL-10 mediated immune regulation and depletion of IFN-γ(+) EBNA1-specific CD4(+) T cells are complementary mechanisms that contribute to impaired T cell cytotoxicity in eBL pathogenesis.