Advances in contraceptive vaccine research.

Researchers are developing vaccines to control fertility by inducing antibody and/or cell-mediated immune response against either a hormone or an antigen associated with gametes. Seven experimental vaccines have reached the clinical testing stage. The beta-human chorionic gonadotropin (hCG) vaccine delivered with the tetanus toxoid vaccine is reversible and causes only minimal side effects. It causes a large variability of antibody response and women with low titres tend to conceive. An improved version of this vaccine uses the beta-hCG linked with the alpha-subunit of another species (heterospecies dimer [HSD]). It is more immunogenic and produces antibodies with improved bioneutralization capacity. It produces antibodies in women at higher titres than does the beta-hCG-TT vaccine. It does not affect menstrual regularity number of bleeding days or amount of bleeding. Before it can move to phase III trials there should be a companion compatible approach to prevent pregnancy during the primary immunization period 1 administration of the multiple doses at 1 contact point and a live recombinant vector. A recombinant vaccine stopped metastasis of lung tumors in all 3 patients in a clinic in Mexico. The vaccine with 37-amino acid carboxyl terminal peptide of beta-hCG linked to diphtheria toxoid as carrier has undergone phase I clinical trials causing no serious side effects. Two luteinizing hormone releasing hormone (LHRH) vaccines are undergoing clinical trials and have caused high antibody titres and much atrophy of the prostate and impairment of testicular functions of spermatogenesis and testosterone production in animals. One LHRH vaccine is being used in clinical trials to treat prostate cancer. The follicle stimulating hormone vaccine has caused oligospermia and reduced fertilizing capacity of the sperm in monkeys. Injection of BCG in the epididymis of mammals causes azoospermia. Injection of a small amount of Praneem in the vas deferens stops spermatogenesis without changing testosterone.