Women and HIV Transmission

HIV scientists and researchers were once under the notion that women had an almost protective barrier against the virus in their vaginal tracts. They believed that the virus could not penetrate the lining of the vaginal tissue during a normal sexual encounter. However, years of this theory went down the drain when new research emerged from a group of researchers at Northwestern University’s Feinberg School of Medicine. This new research has evidenced that the virus has the ability to access a healthy woman’s vaginal tissue and go through to the point where it can attack the immune cells.

Thomas Hope, the lead researcher of the team states, “This is an unexpected and important result. We have a new understanding of how HIV can invade the female vaginal tract. Until now, science has really had no idea about the details of how sexual transmission of HIV actually works. The mechanism was all very murky.” Hope and his fellow researchers determined that the vaginal tissue has a distinct vulnerability to HIV. This location is where the vaginal tract sheds skin cells and then replaces them; it is at this site that the cells are more loosely bound than at other sites. According to data recently released by the CDC (Centers for Disease Control), women account for over one-quarter of new cases of HIV in the United States and over half of new cases of HIV worldwide. Hope and his colleagues feel that their study along with other relevant studies may help in the quest to develop a vaccine and/or microbicides against HIV. He states, “We urgently need new prevention strategies or therapeutics to block the entry of HIV through a woman’s genital skin.” Even though contraceptives like condoms are extremely effective at preventing a transmission of the virus, “people don’t always use them for cultural and other reasons,” he adds.

Using animals as models and utilizing tissue garnered from a hysterectomy, researchers studied how the virus was able to penetrate the tissue. They made the virus easy to spot with photo-activated fluorescent tags as it made its way though the lining of the vaginal tract. In only four hours, the virus quickly made its way through the lining approximately 50 microns underneath the actual skin. This is comparable to the width of one single strand of human hair. At this stage under the skin is where immune cells can be attacked by HIV. Using these models, the research team was able to see where a woman’s most vulnerable spot was, in terms of being attacked by HIV. “As pieces of the skin flake off, that’s the loose point in the system where the virus can get in.”

Scientists had previously believed that the weak point was a singular layer of cells that lined the cervix. Earlier studies, however, had shown this was not the case. In one study in Africa where woman were given diaphragms to protect the cervix, there was no reduction in the transmission rates of HIV. Another group of scientists had also previously felt that HIV could only be transmitted to a woman during intercourse if that woman had an open lesion (i.e. a lesion attributed to a herpes outbreak). Hope states, “A big mistake in this field is the idea that transmission only takes place one way. Our perspective is the viruses can infect people in more than one way. We say one of those ways that needs to be in the equation is that the virus can be transmitted directly through the skin.”