Reduction of fertility in female baboons immunized with lactate dehydrogenase C4

Immunization of female rabbits and mice with the sperm-specific isozyme of lactate dehydrogenase, LDH-C4, significantly reduced their fertility. Similar studies have been extended to nonhuman primates. Two female baboons, immunized with human LDH-C4, produced low antibody titers. These titers were markedly enhanced by booster injections of murine LDH-C4. An additional seven female baboons responded with relatively high antibody titers after receiving murine LDH-C4 as both priming and booster dosages. All nine females received injections of murine LDH-C4 at varying times determined by serum titer levels during fertility studies. These antisera reacted with human, mouse, and baboon LDH-C4. In a series of breeding experiments, 22 of 30 matings, or 73%, were infertile as compared with 28% in control matings. This contraceptive effect of the vaccine containing LDH-C4 was related to antibody titer and was reversible. Normal pregnancies ensued in animals in which the titer declined after termination of booster injections of vaccine.