Localization of hepatitis B surface antigen epitopes present on variants and specifically recognised by anti-hepatitis B surface antigen monoclonal antibodies

Small hepatitis B surface antigen (HBsAg) is considered to be the best mark er for the diagnosis of Hepatitis B virus infection. However, HBsAg variant s with mutations within the "a" determinant may be poorly or not detected b y diagnostic assays. Three anti-HBsAg monoclonal antibodies (6H6B6, 27E7F10 , and 2G2G10), directed against conformational epitopes, were tested for th eir ability to detect the wild-type HBsAg as well as variant forms and thei r respective epitopes were localised on the HBsAg sequence by using the pha ge-displayed peptide library technology. Whereas 61-16136 did not detect mu tations T123N, S143L, D144A and G145R, 27E7F10 binding was affected by muta tions P120T and G145R. In contrast, 2G2G10 reacted strongly with all tested variants including variant with the G145R mutation. Part of the 6H6B6 epit ope was located in the major hydrophilic region (MHR) at residues 101 - 105 , the 27E7F10 epitope (residues 214-219) was located near the C-terminal en d of the antigen and the 2G2G10 epitope at residues 199-208, within the the oretical fourth transmembrane helix. The 2G2G10 epitope localisation brings information about the HBsAg structure and the validity of established topo logical models. Finally, 2G2G10 is a valuable tool for HBsAg variant detect ion that is used as capture phase in a new bioMerieux diagnostic assay, whi ch is currently in development. (C) 2001 Wiley-Liss, Inc.