A novel approach to the generation of antibodies against phylogenetically preserved sperm antigens.

Conventional methods for immunization of laboratory animals against human spermatozoa proved not to be efficient enough to identify phylogenetically conserved sperm-specific antigens. A combination of vasectomy and subcutaneous administration of autologous testis homogenates was tested in 5 New-Zealand rabbits, and in 7 Long-Evans and 8 Spraque-Dawley rats in an attempt to induce an autoimmune response against such antigens. This experimental procedure resulted in a generation of sperm autoantibodies cross-reactive with human, rabbit and rat spermatozoa, as demonstrated by sperm-agglutination, ELISA and flow cytometry (FCM). No specific binding to human seminal plasma was detected by ELISA, indicating that intrinsic sperm membrane antigens rather than sperm-coating antigens were involved in establishing cross-reactivity with human spermatozoa. This suggestion was confirmed by the finding that rabbit autoantisera reacted more strongly against epididymal than against ejaculated human spermatozoa as shown by FCM. Humoral antispermatozoal response correlated well with impaired spermatogenesis in rabbits. The autoimmunized rats revealed severe alterations in reproductive tissues, including testicular and epididymal sperm granulomas; however, they showed a lower incidence of circulating antibodies. The results indicate that the established experimental model in rabbits can be further used to identify and characterize evolutionary preserved intrinsic sperm membrane autoantigens, which are desirable candidates for contraceptive vaccine development.