An object of the invention is to provide methods and compositions relating to a vaccine against prostate cancer which includes a non- human -primate PSA for administration to humans to provide an immune response against human PSA. More generally, an object of the invention is to provide methods and compositions relating to using a non-human primate xenogeneic antigen (e. g. protein) in a human, wherein, with respect to the non-human primate xenogeneic antigen that is used, there are relatively few interspecies differences between the non-human primate xenogeneic antigen and the human self antigen in order to induce an optimal immune response in the human to its native self antigen.