Could a Pill Protect Like a Condom?
Defensins in humans appear to kill bacteria and viruses, immobilize sperm, and prevent fertilized eggs from implanting in the uterine wall. Since the DNA coding for Bin1b has similar genetic sequences in chimpanzees and even humans, discoveries in the rat might potentially apply to the human after considerable additional drug development and testing.
But the experts WebMD interviewed are skeptical about the claim that Bin1b may immobilize sperm simply because it is structurally similar to other defensins. "It would be like saying that because oranges are high in vitamin C and apples are also fruits, they must also be high in vitamin C," Scobey says.
One of the problems involved in using a protein such as Bin1b in pill form would be getting it into the epididymis in high enough quantities to be effective. "Without meaning to be facetious, these pills in all likelihood would have to be taken as suppositories rather than orally," Laing says.
Scobey's suggestions are "to focus research efforts on the properties of unique proteins that do act upon sperm and to discover ways in which these proteins can be exploited to affect male fertility."
Chances are this is a long way off. Latex condoms were first mass-produced around 1850 as a contraceptive and were promoted during World War II to keep the troops free of syphilis and other STDs. With the development of antibiotics and oral contraceptives, the condom fell out of favor -- at least until AIDS reared its ugly head.
"One could certainly call Bin1b 'nature's condom,' since it may very well act as a [contraceptive] in the epididymis," Roberts says. "We may be able to take advantage of this, and perhaps other, natural defense mechanisms to develop new and better [agents] to prevent infection of the reproductive tract."
Though researchers have developed male birth control pills, it will take at least three to four years of testing before any are available on the market. Condoms are often touted as the best defense against AIDS short of abstinence, and they prevent pregnancy without having the potentially dangerous side effects of drugs.