A LIVING microbicide reduces HIV-like infection in monkeys, and might one day provide women with long-lasting defence against the virus.

Dean Hamer of the National Institutes of Health in Bethesda, Maryland, and colleagues engineered naturally occurring vaginal bacteria to produce the anti-HIV protein cyanovirin-N.

They applied a gel containing the bacteria to the vaginas of rhesus macaques before infecting them by the same route with a hybrid of SIV and HIV. The engineered bacteria cut the infection rate by 63 per cent (Mucosal Immunology, DOI: 10.1038/mi.2011.30).

Human females have 10 times as much of the bacteria as female macaques, so the engineered bacteria could reduce infection rates even more dramatically, says Hamer. Clinical tests could begin in a few years after safety testing.