Inhibition of in vitro gamete adhesion and in vivo fertility in mice by immunization with a synthetic peptide

Problem: To evaluate the contraceptive ability of a synthetic peptide in in vitro and in vivo fertility in the mouse. Method of study: A synthetic peptide segment: GELRERAPGQGTNG (SP) was used to immunize female B6CF1 (C57BL/6 × BALB/c) mice. A peptide with an amino acid sequence QQPLSIQQHERG (p2control) was used as control. Anti-SP and anti-p2control antisera were used to evaluate sperm function inhibition in vitro. Fertility of immunized mice was determined by microscopic evaluation of the number and state of preimplantation embryos (8-16 cell stage). Results: In the mouse, anti-SP antisera recognized surface antigens in the acrosome region of mature and capacitated sperm. Anti-SP antisera inhibited in vitro sperm binding to zona pellucida. In vivo, immune response against SP in Freund's adjuvant resulted in a significant increase (P < 0.01) in the number of dead embryos and eggs (a mean of 66%, in contrast with <25% in control mice). Fertility inhibition in vivo and in vitro was not observed when the p2control peptide was used in the immunizations. Conclusions: These results would suggest that the SP sequence is involved in gamete adhesion, and an antifertility vaccine against the SP peptide segment could be feasible. © 2006 Elsevier Inc. All rights reserved.