Sperm-Hunting Antibodies Used In A Potential New Contraceptive

An early foray into this idea was recently published in the journal Science Translational Medicine. A team of biomedical scientists from a variety of institutions across the US engineered sperm-binding antibodies that were based on a natural antibody against human sperm.

Some people can naturally create antibodies against sperm cells whereby the immune system mistakenly identifies sperm as a foreign invader in the body and attacks it. It’s very rare and can lead to a bunch of complications, but for the purposes of this experiment, they provided the ideal blueprint. The researchers obtained these anti-sperm antibodies from the reproductive tract of a number of women who experience infertility and engineered them by fusing on different numbers of additional antigen-binding fragments. 

They found the potency and sperm-binding abilities of the anti-sperm antibodies had increased by at least 10-fold by adding these additional antigen-binding fragments. Testing the antibodies out on the vagina of a sheep, they were found to reduce the number of mobile sperm by more than 99.9 percent compared to control groups.

Hormone-based birth control, like “the pill,” is widely used and very effective, but they bring on an array of undesirable side-effects, including nausea, bloating, mood changes, migraines, and blood clotting. As many pointed out, the risk of a severe blood clot is substantially higher among people taking the pill than any of the vaccines against COVID-19.

The researchers point out a number of limitations with the work. For one, the study didn't directly demonstrate whether the method could prevent pregnancies. This latest research is still very much in its early days — given the big hold up over the development of a male contraceptive pill, you shouldn't expect this kind of technology on the shelves any time soon — but the team hopes they can pave the way towards a new alternative to conventional contraceptives. The study authors write: “Although tests in humans are needed, these [engineered antibodies] may offer women another alternative to hormonal contraception.”

This team isn’t the only group looking towards antibody-based contraceptives. Just last month, another team of US scientists demonstrated a novel contraceptive method that used antibodies to essentially make sperm clump up, rendering it useless. This was only demonstrated in a lab and, once against, the research is only in its infancy, but it appears interesting things could be on the horizon.