In a breakthrough, which could eventually lead to a practical and cost effective new way to combat the HIV virus, scientists from the US National Cancer Institute have genetically modified bacteria living in the human body to produce chemicals that block HIV infection.
Most HIV transmission occurs on the surfaces of the gut and reproductive areas, which are normally coated with a layer of bacteria.
The researchers have successfully modified one of these bacteria - a form of E. coli - so that it began to secrete proteins that block HIV from infecting its target cells. When the modified bacteria were introduced in mice, they successfully colonized parts of the lower gut, and were also found in lower concentrations in the vagina.
The research findings appear in the journal Proceedings of the National Academy of Sciences.
Writing in the journal, the researchers said there was an urgent need for new ways to prevent the spread of HIV, especially in the developing world.
The researchers believe their approach has the potential to offer more lasting protection. Also, bacteria are simple and practical to manufacture, store, distribute and administer, and they are far less expensive than protein-based microbicides.
They also believe the method could be adapted to deliver bacteria secreting different proteins to different parts of the body.
Although primarily designed to prevent new HIV infections, they believe it could also be used, in combination with drug therapy, to treat people already carrying the virus.
Commenting on the new research, Dr Tim Farley, of the World Health Organization, said: "In principle a technique such as this which enhances the body's defenses against HIV sounds like a great idea.
"Clearly there are many steps to be completed in the development and clinical testing of the product, and there may be special safety concerns over unexpected side effects due to deliberately colonizing the gastrointestinal tract with genetically engineered bacteria."
Although the research tested on mice is still in early stage, the researchers hope it could eventually lead to a practical and cost effective new way to combat the virus.