IDENTIFICATION OF RAT PROSTATIC STEROID-BINDING PROTEIN AS A TARGET ANTIGEN OF EXPERIMENTAL AUTOIMMUNE PROSTATITIS - IMPLICATIONS FOR PROSTATE-CANCER THERAPY

The long term goal of this study is to develop autoimmune prostatitis as a therapy for prostate cancer, An immune attack capable of destroyi ng normal prostate epithelial cells should also destroy malignant pros tate tissue and provide therapeutic benefit in cancer patients, The cu rrent study was initiated to identify antigenic targets for experiment al autoimmune prostatitis on the assumption that such proteins might a lso be suitable targets for immunotherapy of prostate cancer, Male Lew is rats were immunized with syngeneic prostate homogenates, and the im mune sera were used to screen prostate proteins for immunoreactivity b y Western blot analysis, The dominant protein recognized by the immune sera was purified by ion exchange chromatography and reverse phase HP LC, Microsequence analysis of two polypeptide components of this immun odominant protein demonstrated N-terminal sequences identical with two of the three component chains of rat prostatic steroid-binding protei n (PSBP). T cell responses to PSBP were also detected in rats immunize d with prostate homogenate. Immunizing male rats with purified PSBP in duced vigorous Ab and T cell responses, Significant prostate inflammat ion was observed in some rats immunized with PSBP. Adoptive transfer o f T cells immune to PSBP induced rapid and severe destructive autoimmu ne prostatitis. These results demonstrate that PSBP is a major target Ag of experimental autoimmune prostatitis in a rat model and may serve as a target Ag for Vaccine and T cell therapy against prostate cancer .