The production of human monoclonal anti-MMTV antibodies by in vitro immunization with anti-idiotypic antibodies.

We have previously reported the production of a series of human monoclonal antibodies reacting with mouse mammary tumor viral antigens as well as the human counterpart HuMTV antigen. Against two of these antibodies (B11 and 4.6/6), anti-idiotypic antibodies were generated, which appeared to be the internal image of viral antigen. Vaccination with the anti-idiotypic antibodies induced in mice humoral and cellular immunity against both MMTV and HuMTV. The current study describes a novel method to produce human anti-MMTV antibodies derived monoclonal antibodies. Normal peripheral blood lymphocytes (PBLs) were immunized in vitro in the presence of IL-2, with rabbit anti-B11 antibodies bound to silica beads. Following in vitro immunization, the lymphocytes were fused with the UC-792-6 human lymphoblastoid cell line. Four human hybridomas were found to secrete human monoclonal antibodies which bound to MMTV and HuMTV. Three of the secreted antibodies were of the IgG class and one of the IgM class. The specificity of binding was confirmed by direct and competitive ELISA assays and by radioimmunoprecipitation. Our study demonstrates the ability to generate human monoclonal anti-viral antibodies by in vitro immunization, employing "internal image" anti-idiotypic antibodies. The method can be used to generate human antibodies, especially against pathogenic agents or ill-defined antigens.