Development of region-specific antisera and immunoassay for human prostate-specific antigen (PSA) with use of purposely designed synthetic peptides

Prostate-specific antigen (PSA) immunoassay is now widely used in the clinical management of prostate cancer. However, the diversity of molecular forms of the protein caused the results of PSA immunoassay variable depending on specificity of the antibody used. The current study provided an efficient method for production of anti-PSA antisera strictly specific for the expected region of the molecule using purposely designed synthetic peptides. The synthetic peptides included PSA (42-92), (53-92), (50-70), (76-92), (174-184) and (199-210). Immunization of the peptides in rabbits afforded seventeen kinds of antisera. Binding activity to native PSA and immunohistochemistry with human prostate proved nine of them, three anti-PSA (42-92), two anti-PSA (53-92) and four anti-PSA (50-70) antisera, to be useful for further experiment. None of antisera against PSA (76-92) and (174-184) showed binding activity with native PSA and immunostaining in human prostate. Using anti-PSA (53-92) antisera with synthetic PSA (42-92) peptide as antigen and biotinyl-Gly-Gly-PSA (42-92) as labeled antigen, a novel type of PSA specific enzyme immunoassay system was successfully developed. The assay system is well defined in terms of region specificity, which is highly advantageous for its clinical use. In addition, the strict region-specificity will make the assay system useful as an analytical tool for characterization of the PSA molecule in blood. Attempts for production of PSA antisera specific to other regions of PSA molecule along this line is now in progress.