Multiple Sclerosis (MS), a neuronal demyelination disease of the central nervous system, is the most common neurological disease in young adults worldwide, with an unknown cause. It affects over 23,000 people in Australia, and despite effective immune-based treatments, clinical deterioration and disability still occur. Epstein-Barr Virus (EBV), a human herpesvirus, which infects early in life and remains dormant within immune cells, is common in the unaffected population but almost universal in MS patients. Studies have found that MS patients maintain elevated EBV-specific antibody levels, most notably against latent Epstein-Barr Nuclear Antigen-1 (EBNA-1) proteins. The aims of this research were to investigate the significance of EBV immune responses, including those targeting the novel epitope EBNA-1(398-413), previously associated with MS risk in disease-discordant identical twins, and to understand the relationship between EBV-specific serological responses and genetic risk factors in an established MS cohort (n=426) and healthy controls (n=186). This study also investigated the influence of arginine modification (citrullination) on EBNA-1(398-413)-specific antibody responses, as well as the role of EBNA-1-specific IgG subclass bias. Novel in-house assays were compared with commercial ELISAs for EBV viral capsid antigen (VCA) and EBNA-1. MS patients had significantly higher antibodies against all EBV targets. Inclusion of EBNA-1(398-413)-specific antibody levels further discriminated cases and controls in risk analysis, in addition to genetic risk factors. Citrullinated and IgG1-specific EBNA-1 antibody levels were also elevated in MS cases compared to controls, although they did not improve case-control classification in combined statistical models. EBNA-1(398-413)-specific IgG from acute patients showed different protein reactivity from whole serum, as well as differences between progressive MS serum and healthy control plasma. This project contributes to the importance of EBV in the pathogenesis of the complex disease MS, and has identified novel and statistically powerful relationships between environmental and genetic MS risk factors
