Promising microbicide ‘a step forward’ for HIV research

The microbicide was found to be 39 per cent effective in reducing transmission Copyright: Flickr/World Bank Photo Collection

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[OUDTSHOORN] The first vaginal microbicide gel that significantly reduces a woman’s risk of HIV infection has provided renewed hope for the HIV/AIDS community following the disappointment of earlier trials.

Researchers from the Centre for the AIDS Programme of Research in South Africa (CAPRISA) reported the results of the CAPRISA 004 trial at the XVIII International AIDS Conference in Vienna, Austria this week. Their work was published in Science.

The double-blind, randomized controlled trial was conducted in KwaZulu-Natal with participants considered to be at high risk of infection. Some 445 women received the microbicide containing tenofovir, which prevents HIV from growing inside human cells, while 444 women received a placebo.

The microbicide was found to be 39 per cent effective in reducing transmission. Thirty-three per cent is considered a statistically significant result.

It can prevent infection if used up to 12 hours before having sex, and soon after. Unlike other gels, which have failed, tenofovir is not active on the skin’s surface. It is absorbed by the target cells, where HIV is also heading, and stops infection there.

In a teleconference with the researchers, husband-and-wife team Salim Abdool Karim and Quarraisha Abdool Karim said the success rate could have been higher — up to 54 per cent — with better compliance, which tended to decline during the 18 months of using the gel.

Quarraisha Karim, an AIDS researcher in South Africa and an associate professor of epidemiology at Columbia University, said women at the clinic where she worked in rural KwaZulu-Natal repeatedly asked for a product they could use to stop infection.

"Until now I haven’t been able to offer anything," she said. "Today that changes because, from being able to tell women for years that I have nothing, I can now offer one per cent tenofovir gel."

 Tenofovir gel appears to have a dual affect, also protecting against herpes simplex virus-2.

"Since women with genital herpes are much more likely to become infected with HIV, the additional protection of tenofovir gel against herpes creates a second mechanism whereby the gel may have a bigger impact in preventing HIV," said Salim Karim, the director of CAPRISA and a pro vice-chancellor (research) at the University of KwaZulu-Natal.

Marcus Low, a researcher for the South African AIDS activist organisation, the Treatment Action Campaign, told SciDev.Net: "It certainly is a step forward, since this is the first time a gel has been shown to provide any protection against HIV infection. However, there is still a lot of research to be done before we’ll know if the gel is really safe and effective, and if it is a realistic candidate for rolling out."

Gita Ramjee, director of the South African Medical Research Council’s HIV Prevention Unit, said another research trial — VOICE (Vaginal and Oral Interventions to Control the Epidemic) currently underway in Malawi, Uganda, South Africa and Zimbabwe, "will build on the CAPRISA 004 outcome".

The CAPRISA 004 research was funded by the South African Technology Innovation Agency, the Department of Science and Technology, and the US Agency for International Development.