Prevent Disease.com - Study Looks at How HIV May Spread Through Oral Sex



		Study Looks at How HIV May Spread Through Oral Sex Excerpt By Michael Broom, Reuters Health Laboratory studies of mouth tissue suggest that unprotected oral sex does have the potential to transmit HIV, but an expert said it is still less risky than other routes of transmission. The results of this study help researchers understand how HIV is transmitted and suggest that even oral tissue that is intact -- without any tears or sores -- can become infected with HIV under the right circumstances. Dr. Xuan Liu, of Charles R. Drew University of Medicine and Science in Los Angeles, California and colleagues at the University of California, Los Angeles obtained oral tissue samples from over 50 healthy, HIV-negative patients and exposed the tissue to three different types of HIV. They found that two of the types could infect and reproduce within cells called keratinocytes that line the surface of the mouth, and that these cells can then transfer the infection to adjacent white blood cells. However, the level of infection in the mouth cells was much lower than that seen in white blood cells -- approximately one-fourth to one-eighth lower. The findings were published in the March issue of the Journal of Virology. "HIV is able to get into (keratinocytes), but it reproduces less than it would in blood cells ... because saliva contains an HIV inhibitor," Liu told Reuters Health. Under certain circumstances, Liu said, keratinocytes are able to release the virus to blood cells, which proliferate much faster than keratinocytes. Thus, the transfer of the infection from keratinocytes to white blood cells may provide a "foothold" for HIV in the body. In the study, the researchers examined three receptors found on cells that HIV uses to latch onto and infect cells. The receptors they looked at did not include CD4, a receptor found on white blood cells that is the most common target of HIV. They found that keratinocytes have two receptors that bind to HIV. However, when the research team used inhibitors to block HIV from attaching to these receptors, they noticed that they did not completely block transmission, suggesting that the cells may have low levels of other receptors used by the virus. Further research is necessary to determine if the laboratory results mimic what actually happens in a living patient, Liu said. It also remains to be seen how applicable the current study is to a potential treatment. Dr. Jeffrey Laurence, senior scientific consultant for programs at the American Foundation for AIDS Research (AmFAR) and director of AIDS Virus Research at Cornell's Weill College of Medicine, told Reuters Health that keratinocytes still lack two of the most important receptors for HIV transmission -- CD4 and the CCR5 co-receptor. An effective vaccine would probably have to block these two primary receptors, which are also found in cells that line the vagina and rectum. Laurence believes the findings indicate there is "no reason for altering safer sex guidelines that have been talked about for over 15 years." "No exchange of infected bodily fluids is absolutely safe, but kissing has been shown to be of no risk, and oral sex is of much lower risk than the other traditional factors known to spread HIV." SOURCE: Journal of Virology 2003;77:3470-3476. Reference Source 89 For more information on how to prevent other diseases, use PreventDisease.com's "Quick Prevention Resources".