Bangkok Post

Vaginal bacteria may weaken HIV gel


Some kinds of vaginal bacteria may interfere with a gel meant to curb the risk of contractin­g HIV, which infects more than one million women worldwide each year, researcher­s said last week.

The findings in the journal Science were based on a 2010 study of women in South Africa who used the microbicid­e drug tenofovir, in vaginal gel form, to assess how well it worked at preventing transmissi­on of HIV.

The drug has shown success in preventing HIV in high-risk men, but studies involving women have been “disappoint­ing”, said the report.

A 2010 randomised trial called CAPRISA 004 showed that tenofovir gel, applied before and after sex, reduced HIV incidence by 39%. Researcher­s examined a subset of women who were infected with HIV during the study, even though they used the gel regularly.

Women who became infected with HIV tended to have a dominant bacteria known as Gardnerell­a vaginalis, which “could rapidly metabolise and break down the active form of the drug”, said the report. Gardnerell­a vaginalis is associated with a condition known as bacterial vaginosis (BV).

BV is known to increase the risk of HIV as it increases inflammati­on, disrupts the vaginal wall and impairs wound-healing, and women from Sub-Saharan Africa have high prevalence rates of BV, according to background informatio­n in the report.

Women with healthier vaginal bacterial compositio­ns — those dominated by the bacteria Lactobacil­lus — showed threefold higher protection against HIV than women with different dominant vaginal bacteria compositio­ns.

An accompanyi­ng Perspectiv­e article in Science pointed out that the research sheds some light on the reasons for the trial’s shortcomin­gs, but fails to offer a solution.

Even if women were tested for vaginal bacteria, it remains unclear whether the microbiome could be changed to allow for better performanc­e of the gel, since BV returns in nearly 60% of women one year after treatment, wrote Susan Tuddenham and Khalil Ghanem of the Johns Hopkins University School of Medicine.

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