A new research has identified a substance present in breast milk that neutralizes HIV and may protect babies from acquiring HIV from their infected mothers.

Researchers at Duke Medicine have for the first time identified the protein, called Tenascin-C or TNC, which had previously been recognized as playing a role in wound healing, but had not been known to have antimicrobial properties.

The researchers describe how the TNC protein in breast milk binds to and neutralizes the HIV virus, potentially 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 percent are receiving the prevention drugs, particularly in countries with few resources. So there is still a need for alternative strategies to prevent mother-to-child transmission, which is why this work is important," senior author Sallie Permar, assistant professor of pediatrics, immunology and molecular genetics and microbiology at Duke said.

Permar and colleagues focused on breast milk, which has long been recognized as having some protective quality that inhibits mother-to-child transmission despite multiple daily exposures over months and even years of nursing.

The Duke team screened mature milk samples from uninfected women for neutralizing activity against a panel of HIV strains, confirming that all of the detectable HIV-neutralization activity was contained in the high molecular weight portion. Using a multi-step protein separation process, the researchers narrowed the detectable HIV-neutralization activity to a single protein, and identified it as TNC.

Permar said that TNC is a component of the extracellular matrix that is integral to how tissues hold themselves together. This is a protein involved during wound healing, playing a role in tissue repair. It is also known to be important in fetal development, but its reason for being a component of breast milk or its antiviral properties had never been described.

Permar said TNC would also appear to 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 is published in the journal Proceedings of the National Academy of Sciences.