Laboratory studies of mouth tissue suggest that unprotected
oral sex does have the potential to transmit HIV, but one expert
said it is still less risky than other routes of transmission.
Dr. Xuan Liu of Charles R. Drew University of Medicine and
Science 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 keratinocytes that line the mouth's surface, and
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
"HIV is able to get into [keratinocytes], but it reproduces
less than it would in blood cells... because saliva contains an HIV
inhibitor," said Liu.
Researchers found that keratinocytes have two receptors that
bind to HIV. However, when the team used inhibitors to block HIV
from attaching to those receptors, they noticed that they did not
completely block transmission, suggesting that the cells may have
lower 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.
Dr. Jeffrey Laurence, senior scientific consultant for
programs at the American Foundation for AIDS Research and
director of AIDS Virus Research at Cornell's Weill College of
Medicine, said that keratinocytes lack two of the most common
receptors for HIV transmission -- CD4 and the CCR5 co-receptor. An
effective vaccine would likely have to block these two primary
receptors, which are found in cells that line the vagina and
Laurence believes the findings indicate there is "no reason
for altering safer sex guidelines that have been talked about for
over 15 years." Laurence said, "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."
Back to other CDC news for March 28, 2003
This article was provided by CDC National Prevention Information Network.
It is a part of the publication CDC HIV/Hepatitis/STD/TB Prevention News Update.