Repeated exposure to semen may lead some sex workers to become naturally resistant to HIV infection. Publishing their findings in the journal Mucosal Immunology, researchers analyzed a group of HIV-negative female sex workers in San Juan, Puerto Rico, who had been in the trade for at least three years and compared them with a group of women in the area who reported having low exposure to semen.

The researchers identified three means by which they believe the group of sex workers has evaded HIV. First, the women had lower rates of immune activation in the blood and mucosal tissues. The lack of activation makes it more difficult for the virus to establish an infection.

Second, the women had enhanced expression of the signaling protein interferon ε in their epithelial cells. Interferon ε helps protect the female reproductive tract from infections. The investigators found that that interferon ε levels were associated with the number of condomless sex acts, and that laboratory studies showed that semen could increase the protein’s expression.

Third, genes such as CD4 and Nucleoporin 153, which HIV depends upon to thrive, were found at lower levels in the sex workers.

To read a press release on the study, click here.

To read the study abstract, click here.