Antifertility effects of porcine zona pellucida-3 immunization using permissible adjuvants in female bonnet monkeys (Macaca radiata): reversibility, effect on follicular development and hormonal profiles

Abstract

Female bonnet monkeys Macaca radiata (n=8, four per group) were immunized with purified 55 kDa glycoprotein from porcine zona pellucida (ZP3) and ZP3 conjugated to the β subunit of human chorionic gonadotrophin (β hCG) using adjuvants permissible for human use (alum, muramyl dipeptide and sodium phthalyl derivative of lipopolysaccharide). The animals were monitored for anti-ZP3 antibody titres, biweekly progesterone concentrations, menstrual cyclicity and status of fertility. All the animals generated a good anti-ZP3 antibody response, continued to have ovulatory cycles, remained infertile in the presence of high anti-ZP3 antibody titres and showed no disturbance in cyclicity (except summer amenorrhoea). Examinations by laparoscope showed normal ovaries with developing follicles or corpora lutea on the surface. Fifty per cent of the animals conceived after a decline in antibody titres. Ovaries of animals that failed to regain fertility were examined for changes in morphology at times when anti-ZP3 antibody titres in the circulation were low and following a booster when titres were high. None of the ovaries showed any sign of inflammation or lymphocytic infiltration. Follicles at different stages of development were seen in all of the ovaries. No significant reduction in the number of follicles, except in one monkey (MRA 178), was observed. There was no increase in the numbers of atretic or degenerating follicles. The results showed that ZP3 immunization with permissible adjuvants could be used for immunocontraception without obvious ovarian changes.