Immunologic behavior of human cysteine-rich secretory protein 1 (hCRISP1) in primates: prospects for immunocontraception

Abstract

To evaluate the immunologic behavior of human cysteine-rich secretory protein 1 (hCRISP1), a human sperm epididymal protein involved in fertilization, to establish its immunocontraceptive potential. In vivo study in a nonhuman primate model. Animal care facility of an academic research center. Adult (6- to 15-year-old) male and female cynomolgus macaques (Macaca fascicularis) distributed into three groups. Animals received four injections (intramuscularly) of recombinant hCRISP1, recombinant monkey CRISP1 (mkCRISP1), or maltose-binding protein (MBP). Blood and semen samples were obtained before and after immunization. Anti-hCRISP1 and anti-mkCRISP1 levels in sera and seminal plasma were evaluated by enzyme-linked immunosorbent assay (ELISA). The specificity of the immune response was evaluated by Western blot and binding of the antibodies to sperm by immunofluorescence. Both hCRISP1 and mkCRISP1 raised an immune response that increased as a function of time and specifically recognized mkCRISP1 in sperm extracts. Sperm number, motility, and morphology were not affected by immunization. The presence of both specific antibodies in seminal plasma and a fluorescent labeling in sperm exposed only to second antibody indicated the ability of the anti-hCRISP1 antibodies both to enter into the male reproductive tract and to bind to the cells in vivo. These results support the potential involvement of anti-hCRISP1 antibodies in human immunoinfertility and hCRISP1 as a likely candidate for immunocontraception.