New Male Contraceptive

American Scientist

November 16, 2004 - Vol. 2 , No. 46

Shot Makes Monkeys Momentarily Infertile

An experimental vaccine given to male macaque monkeys temporarily sapped their fertility, pushing the potential for a new contraceptive for men a step closer to reality, according to new research written up in the journal Science. The novel treatment, dubbed “immunocontraception,” worked like this: Every three weeks, researchers injected nine monkeys with a protein called Eppin, which is involved in the production of sperm. In immunological response, seven of those monkeys created antibodies, which then attacked the Eppin and rendered the monkeys sterile. Five of the sterile monkeys regained their ability to conceive once the immunizations stopped.

Turning that success in monkeys into a new contraceptive for men, and improving its efficacy, will take lots of further research, time and money, said lead researcher Michael O’Rand, a cell and developmental biologist at the University of North Carolina at Chapel Hill. To get there, O’Rand and his colleagues will need a clearer understanding of the mechanics at work. Their best guess: “We think the immunocontraception works by preventing the sperm from freeing itself from the seminal fluid to make its way to the uterus and oviducts to fertilize the egg,” O’Rand told Associated Press.

Right now, the list of male contraceptives stops after condoms and vasectomies. So a good amount of research has gone toward developing hormone-based contraceptives, and those actually may be closer to reality. Previous attempts at a vaccine that shackles sperm have gone a bit too far. But the effects here were reversible. Researchers believe that’s because Eppin, which serves as a coating for sperm, literally caps the process of sperm production. Because Eppin is so late to the male reproductive party, the antibodies don’t damage the male testes.

Susan Benoff, a former president of the Society for Male Reproduction, pointed out to USA Today that for immunocontraception to catch on someday, some psychological hurdles will have to be overcome. Not only might men be reluctant to give up their fertility for a time, said Benoff, but women would have to make a leap of faith. "If you are the woman," said Benoff, "you are the one who’s going to be pushing out the 8-pound bowling ball, so you really have to trust that he’s going to do what he says he’s going to do."

(Source: American Scientist)