Research showing that Herpes Simplex Virus-2 (HSV-2 or genital herpes) is a major risk factor for the acquisition of HIV infection is adding urgency to calls for hastening the development of effective vaccines and treatment for this incurable sexually transmitted disease.

Results of a retrospective cohort study of 2,732 HIV-negative patients at STD clinics in Pune, India, in 1993-2000 seem to confirm that HSV-2 is a major independent risk factor of HIV infection.

The study suggests that recent HSV-2 infection, which causes genital ulcers, is independently associated with a 3.64-fold increased risk of primary HIV-infection. Most significant, perhaps, this supports the hypothesis that mucosal infection from acute HSV-2 may be a key biological mechanism that facilitates HIV acquisition.

“HSV-2 appears to be the ‘silent friend’ of HIV,” said Steven Reynolds, the principal author of the data and researcher at Johns Hopkins University’s Division of Infectious Diseases, at the beginning of his presentation on Monday.

“Our findings suggest that the development of a vaccine against HSV-2 should a key part of strategies for preventing the transmission of HIV,” Reynolds said. He added that an effective vaccine would be particularly useful as young people are overrepresented among those exposed to this form of herpes, and could be effectively targeted for prophylaxis.

Another major study involved 20,000 adults in 18 rural communities in Uganda in 1994-2000. At baseline, nearly 30% of this cohort were infected with HSV-2. Presenter Dr Anatoli Kamali, of the Medical Research Programme on AIDS, in Entebbe, said the findings indicate a strong association between HIV infection and HSV-2 incidence and the need for anti-HSV-2 therapy in STI syndrome management to reduce HIV transmission.

HSV-2 is often neglected. Research on a vaccine began in the 1930s but has failed to produce useful results, as Dr Anne Buvé of the Institute of Tropical Medicine in Antwerp, Belgium, noted in a presentation at XII ICASA conference in Ouagadougou in December.

Better suppressive therapy may be in the pipeline, however. According to comments by Dr Helene Gayle, Director of the Gates Foundation, at Tuesday’s plenary, planning is nearing completion for a United States National Institutes of Health-sponsored HIV Prevention Trial Network Phase III trial that will examine whether acyclovir treatment for HSV-2 helps protect HSV-positive individuals from HIV transmission.

The randomized, double blind placebo-control trial will enroll 2,000 individuals from Peru, Zambia, Zimbabwe and the United States.

AIDS 2002 Conference News produced by Health & Development Networks/Key Correspondent Team