An unknown component of breast milk kills HIV particles and virus-infected cells, as well as blocking HIV-transmission in mice with a human immune system, New Scientist reported.


Even if babies born to HIV-positive mothers avoid infection during birth, around 15 per cent contract HIV during early childhood. Since the virus can get into milk, breastfeeding was one possible suspect.

To investigate further, Angela Wahl at the University of North Carolina at Chapel Hill and her colleagues created mice with human bone marrow, liver and thymus tissues that all became infected with HIV if the mice were given an oral dose of the virus. However, if the rodents were fed breast milk contaminated with HIV, the virus wasn't transmitted.

Previous research had hinted at breast milk's antiviral properties, but it was unclear if they would prevent transmission of HIV. "We have shown that milk has an intrinsic innate ability to kill HIV," says J. Victor Garcia, who supervised the work.

The hunt is now on for the mysterious ingredient in breast milk that inhibits the virus. If it can be identified, it might even be used to prevent other forms of HIV transmission, such as sexual transmission.
 

Why do some breastfed babies born to HIV-positive mothers contract the virus, if breast milk doesn't transmit HIV? It's possible that suckling on cracked nipples may expose babies to virus in their mother's blood.