Novel bispecific immunoprobe for rapid and sensitive detection of prostate-specific antigen.

Prostate-specific antigen (PSA) is one of the most useful tumor markers for the screening and follow-up of prostate cancer. Bispecific monoclonal antibodies (bsMAbs) are unique immunoprobes that incorporate two different binding sites in the same antibody molecule. This antibody designing can bring important advantages in the development of new immunoassays. We have developed a new hybrid hybridoma that secretes bsMAb anti-PSA x anti-horseradish peroxidase. This bsMAb has shown rapid kinetics and an excellent detection limit in a sandwich single-step assay with a total incubation time of 15 min and a 5-min substrate development. This assay in a manual format has a detection limit of 0.028 microgram/L. Comparison with the Hybritech Tandem-E PSA assay yielded a regression equation with slope = 0.433 [95% confidence interval (CI) = 0.415-0.451], intercept = 0.88 (CI = 0.45-1.31), and Sy/x = 1.83 micrograms/L (r = 0.98). This new immunoprobe can be used to develop a new generation of assays for clinical laboratories and can be adapted to screening devices for physicians' offices and even home diagnostics.