HLA DR2b-binding peptides from human endogenous retrovirus envelope, Epstein-Barr virus and brain proteins in the context of molecular mimicry in multiple sclerosis

The aetiology of multiple sclerosis (MS) is as yet poorly understood. Multiple mechanisms in different disease stages are responsible for immunopathology in MS. HLA Class II DR2b (DRB1*1501 β, DRA1*0101 α) is the strongest genetic risk factor for MS. Remnants of ancient retroviruses in the human genome, termed human endogenous retroviruses (HERV), and Epstein-Barr virus (EBV) infection are also associated with MS. In silico analyses of human endogenous retroviral envelope (HERV env) proteins and three myelin proteins that are principal targets of an autoimmune response in MS showed sequence similarities between potential TH epitopes within pairs of viral and myelin peptides predicted to bind HLA DR2b. This led to the proposal that such molecular mimicry may potentially trigger MS. HLA DR2b binding characteristics of previously identified peptides from the three myelin proteins and HERV env proteins as well as additional in silico predicted peptides from other encephalitogenic brain proteins and EBV proteins were studied to further investigate molecular mimicry. Peptides containing potential TH epitopes from the myelin oligodendrocyte glycoprotein and HERV env previously predicted to bind HLA DR2b as well as other pertinent potential HLA DR2b-restricted TH epitopes were confirmed to bind HLA DR2b molecules. Molecular modelling of HLA DR2b in complex with high affinity peptides derived from MOG and HERV env proteins showed that their binding could occur in a similar manner to a HLA DR2b-binding peptide containing a known TH epitope. A structurally related pair of peptides predicted to bind HLA DR2b from the EBV protein EBNA1 and β synuclein, a brain protein implicated in MS, were also shown to similarly bind HLA DR2b. The findings justify investigating CD4+ T cell responses to the identified peptides.