The ability of a vaccine linking beta hCG to a carrier to generate antibodies against hCG, its reversibility and safety was established by Phase I clinical trials conducted in India, Finland, Sweden, Chile and Brazil. Employing a hetero-species dimer (beta hCG-αoLH) linked to tetanus toxoid further improved the immunogenicity of the vaccine. Phase II clinical trials showed that anti-hCG titres above 50 ng/ml prevented pregnancy of sexually active fertile women without derangement of ovulation and menstrual regularity. On decline of antibodies, women conceived again to give birth to normal progeny. A genetically engineered vaccine consisting of beta hCG linked to B subunit of heat labile enterotoxin of E. coli has been made. It is expressed as DNA as well as protein. Priming with DNA followed by protein version of the vaccine generates very high titres against hCG in mice. Extensive toxicology studies in 2 species of rodents, and marmosets have shown complete safety of the vaccine. The vaccine is cleared for Clinical trials by the National Review committee on Genetic Manipulation and Drugs Controller General of India.
Immunization with the DNA form of the recombinant hCGβ-LTB vaccine twice at fortnightly interval followed by the proteinic form of the vaccine induces distinctly higher antibody response.
Introduction: There is continuing need for contraceptives. According to World Health Organization, 210 million pregnancies occur each year, out of which some 80 million are unintended. A vaccine offering privacy and periodic intake would be an attractive proposition. Areas covered: The article is a brief review of three vaccines developed against human chorionic gonadotropin (hCG) with progressively better attributes. Clinical trials have proven in more than one country the complete safety and reversibility of the anti-hCG vaccine(s) in women. Vaccination does not entail any disturbance in levels of reproductive tract hormones of the woman or any disturbance in menstrual regularity and bleeding profiles. Phase II clinical trials show the effective prevention of pregnancy in sexually active women of proven fertility. A recombinant vaccine amenable to industrial production has been developed; it induces substantially higher antibody titers in mice of four different genetic strains than those required to prevent pregnancy in women. Rigorous toxicology studies have been completed on this vaccine in rodents and marmosets. Expert opinion: This unique vaccine, requiring periodic intake and demonstrating no impairment of ovulation, hormonal profiles and menstrual regularity, is on the verge of final clinical trials under the aegis of the Indian Council of Medical Research and should be a valuable addition to the available contraceptives.
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