The Shot That Could Replace the Pill

Harnessing the immune system to create a sure-fire birth control. 

By Kathy A. Svitil|Sunday, June 27, 2004

In as little as a decade, foolproof contraception could be as effortless as an annual flu shot, predicts Peter Sutovsky, a reproductive biologist at the University of Missouri at Columbia. He has been developing a method of birth control that uses a woman’s own immune system to block fertilization.

After a sperm binds with an egg, a cap on the head of the sperm bursts open and releases a burst of proteasomes, enzymes that eat away at the egg’s jellylike coating so that sperm can wriggle inside (right). Sutovsky proposes blocking the process by injecting a woman with snippets of protein that resemble the building blocks of proteasomes. In response, the woman’s body would churn out antibodies that disable the real proteasomes. Without the action of the proteasomes, the sperm could not enter the egg, so conception would become impossible. The immune system would need about 30 days to ramp up this response, but afterward it could be maintained with yearly booster shots. Skipping the booster would allow the immune response to weaken, so a woman could become fertile again in about a year.

Other researchers are working on related contraceptives that zero in on the proteins that allow sperm to bind to the egg. “But because so many molecules are involved in the process, knocking out one will only reduce fertility, not bring it down to zero,” Sutovsky says. His experiments on sperm and eggs from pigs and cows seem more promising: “When you block proteasomes, you prevent fertilization 100 percent of the time.” He is testing the procedure on animals and has started a biotech company, AndroLogika, to commercialize the technique. “The antibodies would not affect any other process in the body,” Sutovsky says. “Honestly, we don’t see any major drawbacks.”

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