Chimerization of Antitumor Antibodies via Homologous Recombination Conversion Vectors

Homologous recombination vectors were designed to convert murine hybridoma cell lines expressing IgG3, IgG1, or IgG2a heavy chains into chimeric human IgG1 producers. These conversion vectors included homology both upstream and downstream of the target sequences and consistently resulted in a higher frequency of successful gene targeting than an insertion vector bearing a single region of homology. A human K light chain conversion vector was also constructed and used to complete chimerization of the anticarcinoma hybridoma cell line BR96. The resulting cell line expressed antigen-specific chimeric antibody at comparable levels to those found in the murine parental cell line. Southern blots confirm that recombination occurred within the upstream and downstream regions of homology for both vectors, resulting in the loss of murine constant region sequences.