BioEd Online

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."