Natural Protein in Breast Milk May Decrease HIV Transmission

A protein naturally found in breast milk that’s responsible for fetal development and wound healing could also have neutralizing effects against HIV-1, according to a recent study.

Genevieve G. Fouda of the Human Vaccine Institute and co-authors found that the breast milk of HIV-1 positive women with increased levels of the protein Tenascin (TNC) was less likely to transmit HIV-1 to infants than breast milk that was absent or deficient of TNC. The presence of the protein may explain why many infants who are exposed to HIV-1 through breast milk do not contract the virus, the authors said.

While TNC’s developmental properties are fairly known, its antimicrobial characteristics are not well established, the researchers wrote. TNC neutralizes and prevents the transmission of HIV-1 by binding to “the HIV-1 Envelope protein at a site that is induced upon engagement of its primary receptor, CD4, and is blocked by V3 loop- (19B and F39F) and chemokine coreceptor binding site-directed (17B) monoclonal antibodies,” the investigators said.

“It is likely that TNC is acting in concert with other anti-HIV factors in breast milk,” co-author Sallie Permar, MD, PhD, added in a statement.

The researchers said that other methods, such as antiretroviral prophlyaxis that is used to decrease HIV-1 transmission, have had partial success in developing regions due to being “limited by access, adherence, toxicities, and resistance of maternal HIV-1 strains.” However, the presence of TNC in breast milk may explain why the transmission rate isn’t higher. The authors found that when antiretroviral prophlyaxis isn’t used, “greater than 90% of infants exposed to HIV-1 via breastfeeding remain uninfected, despite daily mucosal exposure to the virus for up to 2 years.”

As an alternative to antiretroviral prophlyaxis, the TNC protein “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.