Breast Could Be Best for Blocking HIV

New research suggests that an unidentified component of breast milk appears to kill HIV particles and HIV-infected cells, as well as to block transmission of the virus in mice with humanized immune systems.

Among babies born to HIV-positive mothers, about 15 percent who avoid infection during birth nevertheless contract HIV in early childhood. Because the virus can be present in breast milk, breast-feeding has been suspected as a transmission route. However, surprisingly few babies without HIV contract the virus through breast-feeding.

In the new study, Angela Wahl, of the University of North Carolina-Chapel Hill, and colleagues bred mice with human bone marrow, liver, and thymus tissues - all of which became infected if the mice were given an oral dose of HIV. The virus was not transmitted, however, when the animals were fed breast milk containing HIV.

"We have shown that milk has an intrinsic innate ability to kill HIV," said J. Victor Garcia, who supervised the research.

As to why some babies born to HIV-positive women who breast-feed do contract the virus, there is speculation that suckling on cracked nipples may expose the infant to HIV in the mother's blood.

Scientists next hope to identify the inhibitory component in breast milk, which possibly could be used to block other HIV infection routes, such as sexual transmission.

[PNU editor's note: The study, "Human Breast Milk and Antiretrovirals Dramatically Reduce Oral HIV-1 Transmission in BLT Humanized Mice," was published in PLoS Pathogens (2012;8(6):e1002732.]