Researchers in Canada report discovery of unusual proteins in a small group of Kenyan sex workers that appear to be associated with resistance to infection with HIV, the virus that causes AIDS.

The discovery could lead to the improved design of vaccines and drugs to fight the deadly virus, which infects an estimated 40 million people worldwide, the scientists say in a new report.

In the new study, Adam Burgener and colleagues note that 140 of more than 2000 sex workers studied in Nairobi, Kenya, appear resistant to HIV infection. Although evidence suggests that certain biological factors in their vaginal fluid may play a role in resistance, the exact identity of these substances was unclear.

The scientists used a high-tech analytical method to compare differences among proteins in vaginal fluids from HIV-resistant women and those infected with the virus or susceptible to it. HIV-resistant women had proteins significantly different from other women. Vaginal fluids of the HIV-resistant women had higher levels of proteins with anti-viral and anti-inflammatory actions.

These proteins could be used as the basis for new medications to prevent infection, the scientists suggest.