Hepatitis B antigen subtypes-history, significance and immunogenicity.

Initial work showed that all hepatitis B surface antigens (HBs Ag) were identical. Subsequent, additional studies revealed that hepatitis B surface antigens have a group reactive determinant, a, plus additional specificities which are not universally present on all antigens. Four well-defindd subtypes of HBs Ag exist (HBs Ag/adw, HBs Ag/ayw, HBs Ag/adr, HBs Ag/ayr) but additional subtypes will be forthcoming as newly described determinants are confirmed. The subtype specificities are determined by the hepatitis B virus and not the host. Subtypes of HBs Ag are already of great use in the epidemiology of hepatitis B virus infections; yet they may have additional significance. Current work on HBs Ag subtypes is limited by the ability to find or produce antibodies to other than the a or group reactive determinant. The other determinants appear to be less immunogenic than a.