Molecular Cloning of an Immunoglobulin Gene Encoding the Kappa Chain of a Monoclonal Antibody Specific for the pre-S2 Antigen of Hepatitis B Virus

We have cloned an immunoglobulin (Ig) gene which encodes the kappa (κ) chain of a murine monoclonal antibody (mAb) (γ2b, κ) specific for the pre-S2 surface antigen of HBV from H8 hybridoma cell line. Southern analysis of H8 chromosomal DNA revealed that about 6-kb BamHI fragment carries a rearranged Vκ and Cκ gene. The BamHI fragments were subcloned into pUC18 to construct a partial genomic library, which was then screened with variable region of κ chain-specific cDNA coding for the H8 mAb as a probe. Two positive clones (pMKG-S2) were isolated and characterized to be identical by the analysis of restriction maps. The nucleotide sequence analysis of the clone showed that the gene contains a functionally rearranged Vκ gene and the transcriptional elements required for B cell-specific expression. The Vκ gene fused with human Cκ gene and then expressed in murine myeloma cells directed the synthesis of the chain mRNA, suggesting that the immunoglobulin gene is functional.