Reduction of fertility in female rabbits and mice actively immunized with a germ cell antigen (GA-1) from the rabbit.

Female rabbits and mice were actively immunized against germ cell antigen (GA-1) of 63 kDa molecular mass isolated from rabbit sperm and testis. There was a significant (P less than 0.05) reduction of fertility in rabbits actively immunized with GA-1 as compared to controls, as seen by the percentage of 9-day implants/corpora lutea ratio (GA-1, 36.3%; controls, 85.7%). In mice, there was again a significant (P less than 0.01) reduction in fertility as seen by mean 7-9 day implants +/- S.D. per mated mouse actively immunized with GA-1 whether through the intraperitoneal route (GA-1, 1.2 +/- 1.6; controls, 8.0 +/- 3.4) or through the subcutaneous/intramuscular route (GA-1, 3.8 +/- 3.4; controls, 10.1 +/- 3.9). The antisera from these actively immunized animals were negative for sperm agglutinating and immobilizing antibodies. In the Western blot enzyme-immunobinding procedure, the antisera showed specific binding to a single protein of 63 kDa. The incidence of fertilization of eggs recovered from rabbits inseminated with anti-GA-1 antibodies-treated sperm was not significantly different from control rabbits. The percentage of fertilized eggs obtained from rabbits inseminated with anti-GA-1 antibodies-treated sperm that reached the blastocyst stage upon in vitro incubation, however, was significantly less than that for embryos obtained from rabbits inseminated with control serum-treated sperm. Incubation of normal fertilized eggs in vitro with the antibodies did not affect development. Neither antiserum nor immune uterine fluid reacted with 4-day blastocysts in the indirect immunofluorescence technique. It is concluded that active immunization with GA-1 results in post-fertilization reduction of fertility in rabbits and mice by inhibiting early embryonic development.