Role of Toll-Like Receptor 9 in Epstein-Barr Virus DNA-Triggered IL-17 production in BALB-c mice -

Abstract

Background: The Epstein-Barr virus (EBV) is a DNA virus that establishes latent infections that often reactivats. Previous studies demonstrated a relation between EBV and autoimmune diseases such as rheumatoid arthritis, multiple sclerosis and systemic lupus erythematosus. A previous study conducted at the Department of Experimental Pathology, Immunology and Microbiology demonstrated a relation between injecting EBV DNA and increased production of IL-17 in mice. IL-17 is a proinflammatory cytokine associated with various autoimmune diseases. On the other hand, reports investigating interaction of EBV with Toll-like receptors (TLRs) showed that EBV DNA is possibly recognized by TLR9.Therefore, the study at hand focused on the role of TLR9 on the enhancement of IL-17 production caused by EBV DNA in BALB-c mouse peripheral blood mononuclear cells (PBMCs) in culture as well as in BALB-c mice in vivo. Methods (Ex vivo): Blood was collected from 11 BALB-c mice and PBMCs were separated using Ficoll-isopaque. Mouse PBMCs were then cultured for 24 hours with EBV DNA, EBV DNA and the TLR9 inhibitor ODN 2088, TLR9 inhibitor alone or with Staphyloccocus epidermidis DNA used as a non-viral DNA control. Untreated cells were included as well. Subsequently, the level of IL-17 was assessed in culture supernatants with an enzyme-linked immunosorbent assay (ELISA). Methods (In vivo): To assess the role of TLR9 in the enhancement of IL-17 caused by EBV DNA in vivo, 45 female BALB-c mice were used. Mice were divided into 5 groups each containing 9 mice. Mouse groups were injected with EBV DNA, EBV DNA and the TLR9 inhibitor, TLR9 inhibitor alone or with S. epidermidis DNA. A group that was injected with sterile distilled water was assessed as well. Three mice were sacrificed per group on days 3, 6, and 9 post-injection. Blood was collected by cardiac puncture and pooled per group per time point. Serum was then collected to assess IL-17 levels by ELISA. Results: Mouse PBMCs treated with EBV DNA displayed increased levels of IL-17;