The clinical application of murine monoclonal antibodies has been hindered by their immunogenicity, pharmacokinetics and limited biologic activity. This project will characterize (both in vitro and in vivo) chimeric mouse human monoclonal antibodies made up of the variable region of 17-1A (mouse monoclonal antibody to colon cancer) and each of the human IgG subclass constant regions. These chimeric antibodies will be isolated and purified by immunoaffinity columns and be analyzed as regards quantitation of antibody binding to tumor cells, epitope specificity and binding affinity as compared to native murine 17-1A. Each subclass will be carefully analyzed in regard to its ability to interact with human complement (C) including C' mediated tumor cell lysis, C' 3 activation on the tumor cell surface and aggregate-induced C' consumption. Each subclass will be further analyzed in regard to Fc receptor interaction including mediation of leukocyte ADCC, competitive inhibition of standard ADCC reactions and non-specific mediating of Fc receptor binding. In nude mice, the antibodies will be tested for their ability to image colon cancer implants and to prevent tumor growth using a Winne assay system. In man, the chi- meric antibodies will be characterized as regard the pharmacokinetics of varying doses, pharmacokinetics of repetitive doses, characterization of the immune response to chimeric antibody administration and characterization of anti-idiotype and anti-anti- idiotype response. These observations may be extended to other chimeric antibodies as they are developed. These studies should provide vital laboratory information for the successful implementation of chimeric antibodies in human studies. They will also shed light on basic questions relevant to human immunoglobulin subclass function.
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