The effect of Epstein-Barr virus DNA on T-helper 17 and regulatory T-cell selected marker expression in mice

Abstract

Introduction: Epstein-Barr Virus (EBV) establishes latency following a primary infection mainly in B-lymphocytes and is capable of reactivating at any time potentially shedding its viral DNA. A previous study at the Department of Experimental Pathology, Immunology and Microbiology indicated that EBV DNA increased the levels of the autoimmune-related proinflammatory cytokine interleukin-17 (IL-17) in mice suggesting that EBV DNA may trigger autoimmune pathways. IL-17 is produced mainly by the CD4+ T helper 17 (Th17) lymphocytes and is associated with various autoimmune diseases. On the other hand, regulatory T cells (Treg), possess suppressor and anti-inflammatory properties and play a role in the maintenance of immune homeostasis in contrast with the function of Th17 cells. The main objective of this study was to investigate whether regulatory T cell activities are affected by EBV DNA. Methods: To assess the effect of EBV DNA on the activity of Th17 and regulatory T cell pathways, 27 BALB-c mice divided into three groups, each containing 9 mice, were used. Mouse groups were intraperitoneally injected with sterile distilled water as a negative control, EBV DNA (144×103 copies) or Staphylococcus epidermidis DNA (28.3 pg) as a non-viral control DNA. Three mice were sacrificed per group on days 3, 6, and 9 post-injection, then RNA was extracted from mouse spleens per group per time point to assess the transcriptional levels of Th17 markers (IL-17A, IL-21 and RORγT) in addition to regulatory T-cell markers (FOXP3 and CTLA4) by real-time reverse transcriptase PCR. Results: Normalized to transcriptional levels in mice that received a sterile water injection and assessed on day 3 post injection, the transcriptional levels of RORγT, IL-17 and IL-21 increased with the highest levels being 524 (p=0.0094), 512 (p=0.0006) and 1462 folds (p=0.0077) respectively on day 6 post-injection with EBV DNA. These results indicate that EBV DNA induces Th17 lymphocyte activity which subsequently leads to the production