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  • Title: Immuno-contraception undergoing promising trials.
    Author: Koshy LM.
    Journal: Indian Med Trib; 1994 Aug 15; 2(13):7. PubMed ID: 12179186.
    Abstract:
    Immuno-contraception instructs the body to recognize a self-molecule as foreign, so that the body attacks the molecule, thereby effecting contraception. When researchers in India were developing a contraceptive vaccine, they considered 3 things: the targeted molecule should be crucial for reproduction, it should be transient in nature, and the antibodies against this molecule should not cross-react with other molecules in the body. They have developed a vaccine using beta-human chorionic gonadotropin (hCG). The pregnant woman's body produces beta-hCG. It sustains the corpus luteum for production of progesterone which induces changes in the uterus conducive to implantation of the zygote. Researchers have linked beta-hCG with a carrier molecule (tetanus toxoid or diphtheria) to induce an immune attack. They have successfully completed phase 2 efficacy trials. This vaccine also protects against tetanus or diphtheria. Animal studies show that it does not have any harmful side effects and is reversible. The phase 2 trials included women with 2 children cohabiting with fertile partners. Once the antibody titres surpassed the protective threshold, they discontinued contraceptive use and any avoided pregnancies would be attributed to the vaccine alone. The trials exceeded the norm of 750 protected menstrual cycles for the vaccine to be considered efficacious in April 1993. Researchers continued to monitor the women until their anti-beta-hCG titres reached a near-zero level. They are now ready to begin phase 3 trials. Logistical obstacles to overcome are a 2 month-lapse between 1st dose and sufficient titres to protect against pregnancy and multiple injections. Neem oil use may provide protection during the lag phase since it stimulates immune cells in the reproductive tract and has embryocidal and spermicidal effects. A single injection of biodegradable microcarrier systems releasing the vaccine may address the problem with multiple doses.
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