Researchers found some of the sex workers in Kenya produced the same 15 proteins that seemed to give them immunity to HIV.

"This group looked at the vaginal fluid of the women and said 'Well, they have something in the vaginal fluid that perhaps protects them against the virus,'" said Dr. Jay Levy, an AIDS researcher at UCSF.

For years, Dr. Levy's team has looked at women here in the U.S. with a specific white cell, which also protects them from the most common HIV virus.

Canadian and Kenyan scientists have followed 3,000 sex workers in Kenya for at least three years. For this study, they only focused on 39 women and found 10 were resistant to HIV.

The study was published in the Journal of Proteome Research.

Because it was such a small study, researchers would like to see more sex workers participate in a larger study to give more validity to these findings.

"We have 15 to 20 new HIV infections in San Francisco every week, and over 7,000 infections globally every day and so we desperately need to identify new safe and effective prevention strategies," said Jonathan Fuchs M.D. with the San Francisco Department of Health.

Dr. Levy says the African study could help develop new methods to protect women.

"This would be a similar approach to what we call a microbicide -- something that kills germs," said Dr. Levy.

A microbicide is a gel or cream used by women to protect against sexually transmitted diseases. The study could also lead to other research that would replicate the high levels of these proteins in others.