Anti-sperm and anti-ovum vaccines: the selection of candidate antigens and the outcome of preclinical studies.

A clear conceptual basis for anti-sperm and other modes of immunological birth control exists in spite of the limited basic research done on surface antigens of sperm or egg. In the normal physiological condition, the immune system does not respond to sperm, egg or fetus. Compared with anti-egg or anti-fetus immunocontraception, an anti-sperm vaccine has two theoretical advantages. First it would work in both males and females; second, it would not raise problems of autoimmunity in the female if a sperm-specific protein is used. However, for the development of such contraceptive vaccines the following scientific questions need to be resolved: (1) what surface protein to use as an antigen; (2) what adjuvant to use in humans for an anti-fertility vaccine; (3) how to maintain a high titre; (4) how the contraceptive effect will be terminated; and (5) what are the potential side-effects.