Three studies examining uninfected wives of HIV-positive men in England and Thailand found that some women seem to be able to naturally ward off HIV infection, Newsday reports. The studies, all carried out independently, indicated that an as-yet-unidentified protein is protecting these women, who have engaged in unprotected sex with their HIV-positive husbands for several years. Researchers found elevated levels of CD8 white blood cells in the HIV-resistant women in all three studies. One study also found a soluble suppresive factor in test subjects blood, mostly likely produced by macrophages, that was shown to inhibit viral growth in a laboratory setting. The same two-pronged immune system defense of elevated CD8 cells and macrophage suppresive factor has already been identified in nonconverting prostitutes in Kenya and Thailand. Researchers hope to isolate the protective protein, analyze it, and determine whether it might offer clues for effective HIV treatment or vaccination.