Science

A gel that can prevent HIV transmissions: The Tenofovir Story…

Every two years, the International AIDS Society holds a conference at which leaders in the field of HIV/AIDS prevention and treatment gather together to discuss the newest developments.

This year, one of the stars of the conference in Vienna was Tenofovir gel. Tenofovir gel is a microbicide, a substance that prevents the sexual transmission of HIV to women when applied directly to the vagina. Tenofovir belongs to a group of antiretroviral drugs that are most commonly administered in an oral tablet form, usually used in the treatment of HIV. It works by preventing the activity of an enzyme found in HIV, which ordinarily allows the virus to replicate and spread throughout the bloodstream. What the research scientists at Gilead Sciences have done is use the active ingredient of the oral Tenofovir drug to create a topical gel.

The gel has been under testing in a three year long clinical trial undertaken by the Centre for the AIDS Program of Research in South Africa (CAPRISA). The study, which took place in the rural and urban areas of South Africa, found that the gel significantly reduced the acquisition of HIV in women by 39%. Adherence to the gel also made a difference in prevention, with women with high gel adherence (>80%) having 54% acquisition reduction, and intermediate (50 – 80%) and low (<50%) adherers having a reduction in HIV acquisition by 38% and 28% respectively. These results, which have been eagerly awaited for the past three years, are causing a buzz in the scientific world. They are the highest ever disease prevention figures reported for any microbicide, and thus establish Tenofovir gel as the first microbicide with the proven capability to prevent HIV transmission to women.

The clinical trial named CAPRISA 004 ran from May 2007 to March 2010 and involved 988 South African women from urban and rural regions, aged 18 to 40. The study randomly assigned the women to two groups: one group using the Tenofovir gel, and a control group using a placebo gel. All women were provided with a single use, gel-filled applicator to be utilized 12 hours prior to sexual intercourse and 12 hours post. During the three year period, they were tested for HIV every month. As well as this, they received free condoms, extensive risk-reduction counselling and pregnancy tests. The contraception and counselling ensured that the women had the tools for practicing safe sex at their disposal. Also, as the gel had not yet been tested on pregnant women, the pregnancy tests were necessary to remove any pregnant women from the study, safeguarding the mother and the child from any potential side-effects.

The study is of great importance, seeing as we are facing a global health crisis where women are being disproportionately affected by HIV/AIDS. The Joint United Nations Programme on HIV and AIDS (UNAIDS) has stated that of the 39.5 million individuals suffering from HIV/AIDS, over 50% are women. In Africa, specifically in sub-Saharan countries such as South Africa, young women bear the greatest burden of this disease. Women in these regions account for 59% of all cases of HIV, and of all infected individuals aged 15 to 24, women make up 76%. Additionally, 70 to 90% of cases of HIV in women are due to heterosexual sex, and women are twice as likely to acquire the virus during it.

Women are in a more vulnerable position when it comes to HIV acquisition not only for biological, but also cultural reasons. In some regions of Africa, young women frequently engage in sex with older HIV-positive men, often unwillingly. Also, although condom use does prevent HIV acquisition, the social position of women in these areas sometimes makes it difficult for them to negotiate condom use with their male partners. These alarming facts and statistics highlight the urgent need for a method that successfully prevents the infection of women. So what does this gel mean for the future of HIV and women at high risk of obtaining it?

Well, for many of these women, this gel could be the light at the end of a bleak tunnel. Not only could it make a massive difference to their lives, but it would also fill a huge gap in the prevention of HIV worldwide. At the moment, as results are only limited to a single study, the gel has not yet been mass produced or globally distributed. However, if it were to become mass manufactured and widely distributed, the effects it could have would be astounding. Experts are suggesting that this gel could help alter the course of the HIV pandemic. Calculations predict that it could prevent a staggering 1.3 million infections and 100,000 worldwide HIV related deaths of women per year for the next two decades. Here is hoping the gel does live up to these great expectations and becomes the catalyst for change in the prevention of HIV infections to women all over the world.

Sheila Mburu

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