Drugs that fight genital
herpes also significantly reduce levels of human immunodeficiency
virus (HIV) in patients infected with both viruses, a new study
finds. Most HIV-positive patients also carry the herpes simplex
virus, so anti-herpes drugs might help to restrict the spread
of HIV.
The study, published in the New England Journal of Medicine
this week1, highlights the importance of testing HIV patients
for
genital herpes — an infection that causes periodic genital
ulcers but can lurk silently in the body for years.
Nicolas Nagot
of the London School of Hygiene and Tropical Medicine in the
United Kingdom and his colleagues conducted
a clinical trial of 136 African women infected with both HIV-1
and the most common form of herpes simplex virus. Half the
patients were given valacyclovir, a common herpes treatment;
the other half received a placebo.
Women taking the drug had 70% lower levels of HIV in their
plasma, and 50% lower levels of the virus in their genitals
compared with those who received the placebo. Longer treatments
could produce even better results, says Nagot, because HIV
loads declined steadily through to the end of the three-month
study.
Stopping the spread
An important next step is to see how this reduction affects
transmission or progression of the disease. Studies involving
other HIV treatments have shown that similar reductions in
viral load reduce transmission and slow progression.
"HIV transmission is highly related to the quantity
of virus in the genitals," says Nagot. "So we're
pretty sure this treatment is going to reduce transmission."
Researchers aren't sure how HIV and the herpes simplex virus
interact. Some think that herpes infection causes the immune
cells in which HIV hides to multiply, giving HIV more living
room. Other evidence suggests that the herpes virus somehow
promotes HIV replication.
Other sexually transmitted infections, such as gonorrhoea
and chlamydia, are also correlated with higher amounts of
HIV in patients.
Missing the obvious
Faced with the challenge of managing HIV infection, doctors
and patients sometimes overlook herpes, says virologist Lawrence
Corey of the Fred Hutchinson Cancer Research Center in Seattle,
Washington. "Herpes simplex virus leads to very few
hospitalizations, and therefore the perception of it as a
serious opportunistic infection in HIV-infected people is
low."
But, he points out that Nagot's study shows a reduction
in HIV viral load similar to that achieved by using the anti-HIV
drug zidovudine.
Corey is working to evaluate the effect of anti-herpes drugs
on HIV transmission in 3,000 couples in which one partner
has the virus. The study has already enrolled 2,700 couples,
he says.
Previous work with small numbers of patients had suggested
that reducing herpes simplex virus also reduced HIV levels.
But the larger study is a crucial step forward, says virologist
Timothy Schacker of the University of Minnesota in Minneapolis.
Schacker hopes that the treatment will provide a quick route
to reducing transmission of the virus. "It's really
important to get people thinking about other strategies that
are relatively simple and inexpensive to reduce transmission
rates," says Schacker. "We're not going to have
a vaccine anytime soon, so anything we can do is important." |
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