THURSDAY, Nov. 11, 2004 (HealthDayNews) -- A vaccine against a sperm-related protein made male monkeys temporarily infertile, an approach that might lead to a contraceptive for men, researchers report.
But there are a lot of questions to be answered and many tests to be done before such a contraceptive becomes a reality, said Michael G. O'Rand, a professor of cell biology at the University of North Carolina at Chapel Hill. He is leader of the group reporting the finding in the Nov. 12 issue of Science.
While women have the pill, men now are limited to using condoms or having a vasectomy for contraception. The search for a male pill has been going on for years, mainly aiming at interfering with the male sex hormones. O'Rand's group is trying an alternative approach called immunocontraception, which tries to have the immune system attack sperm and render them incapable of fertilization.
The vaccine they used in the trial is aimed at a protein designated Eppin, which is found in the epididymis, the network of tubes through which sperm passes.
Seven of nine macaque monkeys injected with the vaccine developed immune responses against their sperm strong enough to make them infertile, the journal report said, and five of the seven recovered fertility when immunization stopped.
The next step after the monkey trial is uncertain, O'Rand said, because "it depends on whether we can secure some funding." His hope is that a pharmaceutical company will provide the money needed for safety tests and other trials needed before a human study is conceivable.
"People are aware of the possibilities, but how interested they are I don't know," O'Rand said.
But the need is there, according to O'Rand. "Women have many alternatives," he said. "Men have almost none, particularly in developing countries."
There are a lot of questions to be answered, agreed Susan Benoff, director of the fertility research laboratory at North Shore-Long Island Jewish Hospital in Manhasset, N.Y., and past president of the Society for Male Reproduction and Urology.
The vaccine failed in two of the nine monkeys, an unacceptably high rate, and two of the monkeys failed to recover fertility, Benoff noted. "I don't know that any man who is not considering a vasectomy would be willing to do something that would not be reversible," she said.
Also, the method would have to be shown completely effective in its attack against sperm, Benoff said. "It takes only one motile sperm to initiate a pregnancy," she said.
This is not the first attempt at immunocontraception, Benoff said. "People have tried to make anti-sperm antibodies for years," she said. "I don't see anything to suggest that this is any better than previous efforts."
Still, she said she doesn't rule out the possibility that O'Rand and his colleagues could succeed. "Maybe if they can answer some of my questions, this could be developed," Benoff said. "But a lot more information is required."
An overview of male contraceptive research can be found at the Population Council.