Birth control pills are a particularly effective contraceptive that millions of women use all over the world. The pills are based on hormones that stop the ovulation process, and their use is often accompanied by unpleasant side effects that prevent women from using them. There are also women who cannot use hormone.based contraceptives for medical reasons. Therefore there is a great need to develop other effective contraceptives, which do not use hormones.
It turns out that nature has already created such contraceptives, and can be found in some women and men who suffer from infertility. Their immune system produces antibodies against sperm cells, and these capture the sperm on their way to the egg and do not allow them to fertilize it. These antibodies may be found in both female vaginal fluid and male semen. Such a condition is called immune infertility, and as of today the reasons for it are not entirely clear.
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BResearch, Published in the journal Science Translational Medicine, researchers at the University of North Carolina used this phenomenon to engineer sperm.capturing antibodies as a non.hormonal contraceptive. To do this, they took familiar antibodies that had previously been identified in healthy women who had suffered from immune infertility, and engineered new antibodies from them that had a stronger ability to bind to sperm cells.
A normal antibody has two “arms” that can bind to their target – usually some protein from an unwanted factor such as a bacterium or virus. In contrast, the artificial antibodies created by the researchers had between six and ten such arms, which may give them an improved ability to inhibit sperm cells. Indeed, when the new antibodies were put into a test tube with sperm cells, they were eight times more efficient at binding and stopping the sperm than the original antibody.
Reduces sperm by more than 99%
To test the effectiveness of the antibodies in a more realistic environment, the researchers added the antibodies to the test tubes with women’s vaginal fluid and monitored the ability of the sperm to progress within it. It was found that all new types of antibodies inhibited sperm cell movement more successfully than control antibody that did not bind to sperm cells.
In the latest experiment, the researchers used sheep to test the activity of antibodies in a living body. They used a test similar to the one performed on humans for fertility testing, called PCT. As part of this test, a sample is taken from the woman’s cervix shortly after having sex, and sperm cells are found in it in motion.
The researchers first injected into the reproductive system of engineered antibody sheep, normal antibodies of the type on which they based the new ones, or a solution that did not contain antibodies. They were then injected with human sperm and collected two minutes later to test their motility. The engineered antibodies were able to reduce sperm cell movement by 97 percent, and the best antibody reduced it by more than 99 percent. All engineered antibodies were much more effective than the original antibody.
The findings of the study show that antibodies can ostensibly be used as non.hormonal means of contraception. The antibodies engineered by the researchers are very specific for a protein that exists only in sperm cells and the male reproductive system, and should therefore be very safe for use in a woman’s body. Although the researchers did not examine the likelihood of developing pregnancy despite the treatment, the link between sperm motility and fertility has been known for many years, so it makes sense to focus on the development of a new contraceptive. According to the authors of the article, in the end it is possible that the administration of the antibodies will be done by a ring that will be inserted into the vagina and release antibodies in a controlled manner.
There is still a long way to go before antibodies can be used as a safe and effective contraceptive against pregnancy. However, the study presents a promising demonstration of topical and temporary contraceptive treatment, which does not include intervention in a woman’s natural hormonal process.