Yoghurt could help fend off HIV

YOGURT may soon be enlisted in the battle against AIDS. Lactobacillus, a harmless bacterium that helps turn milk into yogurt, has been engineered to make HIV-fighting microbicides. Eating yogurt containing these bacteria could provide a way for women to fend off HIV if no other means are available.

As well as appearing in yogurt, lactobacillus naturally inhabits the human vagina. It survives passage through the gut and can easily traverse the short distance from the anus and colonise the vagina. Once there, the bioengineered bacteria would churn out compounds that inhibit transmission of HIV, thus helping prevent infection.

Researchers have in the past tried to insert genes for the microbicide cyanovirin-N into a separate ring of DNA. However, this could easily slip out of one bacterium and into another, posing a possible environmental or health risk. Now Peter Lee at Stanford University in California and his colleagues have inserted the cyanovirin-N gene into the bacterium's main chromosome, where it is much more stable. In tests in mice, the integrated gene produced the microbicide at concentrations sufficient to inhibit HIV replication (Antimicrobial Agents and Chemotherapy, vol 50, p 3250).

"It's a milestone," says Jim Turpin, senior programme manager for microbicides at the US National Institutes of Health. The advantage of this approach over microbicidal gels is that the bacteria last several days longer.