The invention provides a prostate specific antigen oligo-epitope peptide (PSA-OP) that is useful as an immunogen in the prevention or treatment of prostatic cancer and in the inhibition of prostatic cancer cells and in the establishment and characterization of PSA-specific cytotoxic T-cell lines. In particular, the invention provides methods for eliciting an immune response against PSA comprising administering (i) a priming inoculation of a first recombinant virus encoding PSA-OP and (ii) one or more boosting inoculations of a second recombinant virus encoding PSA-OP, wherein the first and second recombinant viruses are from a different genus.
