ANTIGEN RECOGNITION CHARACTERISTICS AND COMPARATIVE PERFORMANCE IN IMMUNOAFFINITY PURIFICATION OF 2 MONOCLONAL-ANTIBODIES SPECIFIC FOR THE HEPATITIS-B VIRUS SURFACE-ANTIGEN

In this paper we describe the antigen recognition characteristics, var iable region base and amino acid sequence, and performance as immunoaf finity chromatography ligands of two MAb specific to the a determinant of the HBsAg, derived from the same fusion. We show that the epitope recognized by CB-Hep.0 (IgM) is probably associated to an intrachain d isulfide bond in the antigen. On the other hand, CB-Hep.1 (IgG2b) reco gnizes a heat-resistant non-conformation dependent antigenic determina nt on HBsAg. PCR-cloning and sequencing of the variable regions of the se two MAb indicated that both heavy chain variable regions were origi nated from the usage of the same germinal V and J genes. However, the outstanding differences in the size of the VH CDR3, and the absolute d ifference in the light chain sequences, suggest that the hybridomas we re originated from different precursor B lymphocytes. With respect to their use as immunoaffinity chromatography ligands for the purificatio n of a recombinant HBsAg, we found that the IgM immunogel exhibited in creased performance with respect to amount of eluted antigen, and fina l recovery. This difference in overall performance could be attributed to a series of factors: the higher valence number of IgM, a dissimila r distribution of IgM and IgG in the activated gel particles, and diff erences in antigen recognition between both MAb. Our results suggest t hat IgM antibodies may be useful in immunopurification, particularly i f the antigen is structurally complex and has a high density of repeat ing epitopes. (C) 1997 Elsevier Science B.V.