HLA-DRB1 and Epstein-Barr virus infection: An interaction between EBV infection and HLA genes associated with MS risk is suggested by the finding that HLA-DRB1*15 carriers with higher anti-EBNA-1 antibody titers have a markedly elevated risk of MS (102–104), which is increased further in the absence of the protective allele HLA-A*0201 (103).