EPITOPE MAPPING OF PROSTATE-SPECIFIC ANTIGEN WITH MONOCLONAL-ANTIBODIES

Prostate-specific antigen (PSA) is a widely used marker for screening and monitoring prostate cancer, We identified and characterized the ep itopes of two anti-PSA monoclonal antibodies (mAbs) designated B80 and B87. The epitopes were initially mapped as nonoverlapping by developi ng a sandwich immunoassay to measure PSA with the two anti-PSA mAbs, T he two antibodies do not cross-react with homologous pancreatic kallik rein, but recognize epitopes unique to PSA, B80 and B87 can recognize both free and complexed PSA. and hence measure total PSA. Epitope scan ning and bacteriophage peptide library affinity selection procedures w ere used to identify and locate an epitope on PSA, A possible epitope for B80 was identified as being located on or near PSA amino acid resi dues 50-58 (-GRH-SLFHP-), The epitope for B87 was likely on an exposed nonlinear conformational determinant, unique to PSA, and not masked b y the binding of B80 or alpha(1)-antichymotrypsin.