MOLECULAR CHARACTERIZATION AND STRUCTURAL MODELING OF IMMUNOGLOBULIN VARIABLE REGIONS FROM MURINE MONOCLONAL-ANTIBODIES SPECIFIC FOR HEPATITIS-B VIRUS SURFACE-ANTIGEN

We have characterized structurally the V regions of a set of murine mo noclonal antibodies designated A1.2, A3.1, and A2.1, which recognize a group-specific epitope associated with hepatitis B virus surface anti gen (HBsAg). The selection of these antibodies for this characterizati on was based on data which indicated that A1.2 and A3.1 recognize an o verlapping epitope, while A2.1 recognizes a different group-specific e pitope, on the HBsAg molecule. In addition, a conformation-dependent c ross reactive Id is expressed on both A1.2 and A3.1, but not on A2.1. We have determined the primary sequence structures of these three mono clonal antibodies to HBsAg (anti-HBs), and have aligned them to evalua te V region sequence homology and identify potential regions of struct ural homology which provide a basis for the HBsAg epitope recognition and the cross reactive Id. Both A1.2 and A3.1 express V(H) regions whi ch are highly homologous to the V(H)NP gene family (V186-2), both use members of the DSP2 D region gene family and utilize the J(H)2 and J(H )1 J gene segments, respectively. Alternatively, A2.1 is related to th e V(H) J558 gene family and expresses a fusion of the DFL16.1 and DQ52 D gene regions in conjunction with the J(H)1 gene segment. Each of th ese three monoclonal anti-HBs utilize light chains from the V(kappa)21 and the J(kappa)4 gene families. Primary amino acid sequence data wer e employed to construct computer generated models of the A 1.2, A3.1, and A2.1 V regions to determine potential antigen combining site struc tures and the basis for the expression of the cross reactive Id. These results are discussed in terms of potential interaction sites with HB sAg and V region sites involved in Id expression.