Formulation of a potential antipregnancy vaccine based on the β-subunit of human chorionic gonadotropin (β-hCG)

Experiments were conducted in rabbits to determine the effect of adjuvant use on the antibody response following booster injections. The antigen used was in all cases the beta-subunit of human chorionic gonadotropin linked to tetanus toxoid (beta-hCG-TT). Adjuvants used were Al(OH)3, MDP analogs, and a streptococcus preparation, OK432. Primary vaccinations included Al(OH)3 adjuvant with or without supplementary adjuvants. In general, the greater the antibody response following primary vaccination, the greater the response following booster vaccination whether or not adjuvant was used in the booster. No increment in antibody titers was found by reason of including MDP analogs in booster vaccinations. OK432, in contrast, gave increased responses in booster injections which were in several cases statistically significant. The value of including Al(OH)3 in booster injections is not clear from the experimental data. In no case was the increment due to its inclusion large.