Contraceptive responses of female hamsters immunized with recombinant sperm protein P26h.

BACKGROUND: A number of antigens have been characterized and proposed as potential candidates for immunocontraception. P26h, a 26-kDa hamster sperm protein located on the acrosomal cap, is known to be involved in sperm-zona pellucida interactions. Furthermore, in vivo fertilization can be blocked by active immunization of male hamsters against P26h or maltose-binding protein recombinant P26h (MBP-P26h). OBJECTIVE: The aim of this study was to investigate the immune response and reproductive function of female hamsters immunized against MBP-P26h. RESULTS: Active immunization against MBP-P26h resulted in anti-P26h circulating antibodies, with enzyme-linked immunosorbent assay (ELISA) titers showing interindividual variability. The antibodies produced by the animals immunized against MBP-P26h reacted with the native P26h protein in ELISA, in Western blot analysis and in immunostaining performed on cauda epididymal spermatozoa. Mating of immunized female hamsters resulted in a significant decrease in the number of viable fetuses only in females with high titers of anti-P26h circulating antibodies. DISCUSSION: This result is in agreement with the sperm-zona pellucida binding assay's results. Indeed, sera collected from immunized animals, and not from control animals, significantly blocked sperm-zona pellucida binding in vitro. Histological studies showed that active immunization did not cause any pathology in the reproductive tissues. CONCLUSION: These findings suggest that P26h is a potential candidate for the development of a contraceptive vaccine in both males and females.

P26h and dicarbonyl/L-xylulose reductase are two distinct proteins present in the hamster epididymis.

We have previously identified a 34 kDa protein (P34H) on the human sperm surface covering the acrosome. Using the hamster, we have also described a sperm protein, P26h, which is acquired by spermatozoa during epididymal transit. Both P34H and P26h belong to the carbonyl reductase family. Using molecular tools derived from P34H, we searched in the hamster epididymis for another protein related to the human sperm protein. Cloning and sequencing of P31h cDNA revealed 100% homology with the kidney DCXR (Dicarbonyl/L-Xylulose reductase). Northern Blot experiments revealed a single mRNA that was more expressed in the caput than in the corpus and cauda segment of adult epididymides. In situ hybridization was performed on sexually mature hamsters showing that the mRNA was localized in the principal cells throughout the epididymis. Using an anti-P34H antibody we have identified a P34H related protein named P31h (for 31 kDa). This protein showed 2D-electrophoretic behavior different from P26h and was detectable all along the epididymis (caput, corpus, and cauda) by Western Blot analysis. Immunohistochemistry techniques showed that P31h was localized in the perinuclear region of the principal cells of the epididymal epithelium within the three sections, both in sexually mature and immature animals. Results are discussed with regards to the potential function of DCXR in the epididymis.