Breast milk protein may protect babies from HIV

Scientists have for the first time identified a protein in breast milk that neutralises HIV and may protect babies from acquiring the virus from their infected mothers.
The protein, called Tenascin-C or TNC, had previously been recognised as playing a role in wound healing, but had not been known to have antimicrobial properties. The discovery could lead to potential new HIV-prevention strategies.
Researchers at Duke University Medical Center found the TNC protein in breast milk binds to and neutralises the HIV virus, protecting exposed infants who might otherwise become infected from repeated exposures to the virus.
"Even though we have antiretroviral drugs that can work to prevent mother-to-child transmission, not every pregnant woman is being tested for HIV, and less than 60 per cent are receiving the prevention drugs, particularly in countries with few resources," said senior study author Sallie Permar, assistant professor of pediatrics, immunology and molecular genetics and microbiology at Duke.

"So there is still a need for alternative strategies to prevent mother-to-child transmission, which is why this work is important," Permar said.
In their study, the Duke team screened mature milk samples from uninfected women for neutralising activity against a panel of HIV strains, confirming that all of the detectable HIV-neutralisation activity was contained in the high molecular weight portion.

Using a multi-step protein separation process, the researchers narrowed the detectable HIV-neutralisation activity to a single protein, and identified it as TNC.
"TNC is a component of the extracellular matrix that is integral to how tissues hold themselves together," Permar said, noting that co-author Harold Erickson, professor of cell biology at Duke, was among the first to identify and describe TNC in the 1980s.

Researchers found the protein is uniquely effective in capturing virus particles and neutralises the virus, specifically binding to the HIV envelope.
"It's likely that TNC is acting in concert with other anti-HIV factors in breast milk, and further research should explore this," Permar said.
"But given TNC's broad-spectrum HIV-1-binding and neutralising activity, it could be developed as an HIV-prevention therapy, given orally to infants prior to breastfeeding, similar to the way oral rehydration salts are routinely administered to infants in developing regions," Permar said.
Permar said TNC would also be inherently safe, since it is a naturally occurring component of breast milk, and it may avoid the problem of HIV resistance to antiretroviral regimens that complicate maternal/infant applications.

The study was published in the journal Proceedings of the National Academy of Sciences.