EXPRESSION OF PROSTATE-SPECIFIC ANTIGEN ON THE SURFACE OF A FILAMENTOUS PHAGE

We have constructed two phagemid vectors containing the gene coding fo r human Prostate Specific Antigen (PSA) translationally fused to a pel B signal sequence and minor coat protein III of phage fd leading to ph age particles that carry PSA on their tips. Phages were characterized by Western blotting and by panning, using biotinylated monoclonal anti -PSA antibodies immobilized onto streptavidin-coated microtitration we lls. Binding of PSA-phages was 10(2)- to 5x10(3)-fold more effective t han that of wildtype phages. Trypsin treatment of the phage abolished the specific binding. Competitive panning with different concentration s of added purified PSA demonstrated that binding was PSA specific. Fi nally, Western-blot analysis confirmed that full-length and shorter de gradation products of the fusion between PSA and protein III were visi ble as probed with anti-PSA antibody. (C) Academic Press, Inc.