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Development of antisperm contraceptive vaccine for humans: why and how?


 A review of the obstacles in the way of producing anti-sperm contraception and progress to date is presented. While there are several lines of evidence pointing to the possibility of inducing immunity to sperm, in practice many roadblocks have appeared such as sperm antigens that cross react with other somatic antigens, effective sperm antigens that do not affect fertility, short acting immunity, and the problems of producing high titers in the local environment of the genital tract. Infertility of both men and women occurs in nature as a result of antisperm immunity. Conception can be obtained in these couples by immunosuppression. Data from human in vitro fertilization indicate that sperm antibodies can block fertilization. since whole sperm contain several antigens shared with other body tissues, a vaccine must be designed from purified antigens. After vaccines were developed from some antigens, such as HS-63, in vitro fertilization was blocked but not fertility in vivo. One antigen showing promise is FA-1 from human and mouse sperm, effective in reducing rabbit and human fertility. All the prototype vaccines have a short life time. Adjuvants and carriers are being tested to improve performance. The female genital tract is not rich in lymph tissue, but IgG and sigA antibodies do occur there, probably originating from gut-associated lymphoid tissue. Not only is a very high titer of antibodies needed to block fertilization in vivo, but local immunization is ineffective in inducing high titers. Probably combined local and systemic routes will be required.
