Bacteria in yogurt have been modified to deliver a drug that blocks HIV infection.
In their natural state, the bacteria (Lactococcus lactis) produce lactic acid and are used to make cheese and yogurt. It is not harmful to humans.
Research based at Brown Medical School in Rhode Island altered the genetics of the bacteria so they generate cyanovirin, a drug that has prevented HIV infection in monkeys and human cells, according to a report at firstname.lastname@example.org.
Cyanovirin binds to sugar molecules that are attached to the HIV virus, blocking a receptor used by HIV to infect cells.
"It's basically passive immunization," said Sean Hanniffy, a member of the research team from the Institute of Food Research in Norwich, UK.
Cyanovirin could be put into gels that women would apply to the vagina before sex. Or, an oral dose might provide long-term protection, the researchers speculate. They note that there could be public resistance to the whole idea of genetic modification.
The work has only been proved in a lab setting, however. Human trials could begin in 2007.