Characterization and gene cloning of monoclonal antibody specific for the hepatitis B virus X protein

The hepatis B virus X protein (HBx) has been thought to be implicated in th e development of hepatocellular carcinoma. Although many functions of HBx h ave been reported, it is not clear which of HBx functions is important in h epatocellular carcinogenesis. To study HBx function, we produced a monoclon al anti-HBx Ab secreted by hybridoma cell clone H7 and mapped its epitope t o a region of HBx between amino acids 29 and 48 by Western blot with trunca ted forms of HBx and by enzyme-linked immunoadsorbent assay (ELISA) with sy nthetic HBx peptides. The variable regions of H7 anti-HBx Ab were cloned by polymerase chain reaction using the degenerate-primers and by the 5' rapid amplification-cDNA end method. The sequence analyses revealed that the var iable gene segments of the heavy and light chains are the members of mouse heavy chain variable gene 1 family and kappa light chain variable gene 2 fa mily, respectively. In addition, J(H)2 or J(kappa)4 gene segment at the end of the heavy-chain or light-chain variable region and DSP2.x gene segment in the CDR 3 of heavy chain were identified.