On the basis of the reported association between hepatitis B vaccination(HBvacc) and autoimmune demyelinating complications such as multiple sclerosis(MS), we have looked for aminoacid similarities between the small hepatitisB virus surface antigen (SHBsAg), and the MS-autoantigens myelin basic protein(MBP) and myelin oligodendrocyte glycoprotein (MOG) that could serve as targetsof immunological cross-reactivity. The gene discussed is OMG; the disease is hepatitis B virus infection.