Characterization of neutralizing anti-pre-S1 and anti-pre-S2 (HBV) monoclonal antibodies and their fragments

Single-chain Fv fragments (scFv) were generated from two murine monoclonal antibodies directed to the neutralizing epitopes of the pre-Si and pre-SZ r egion of hepatitis B virus, respectively, using different assembly cloning strategies. The scFv fragments were solubly expressed in E, coli. Dissociat ion constants were in the nanomolar range for all forms (whole IgG antibodi es, Fab fragment and scFv fragments), The epitopes of both antibodies were mapped using solid phase peptide synthesis on continuous cellulose membrane s and turned out to be linear determinants. The minimal epitope for the ant i-pre-S2 antibody 1F6 was identified to be DPRVRGLYF (amino acid 133-141 of the pre-S region). For the anti-pre-Si antibody MA 18/7 the minimal epitop e proved to be the hexamer LDPAFR (amino acid 30-35 of the pre-S region), C omplete substitutional analyses as well as truncation experiments revealed key residues for these antibody-antigen interactions. On the basis of those results we used computer-assisted modeling techniques to suggest models fo r both antibody-peptide interactions providing insight into the structural basis of these molecular recognitions. (C) 1999 Elsevier Science Ltd. All r ights reserved.