Antiretroviral treatment may provide protection against HIV transmission during breast-feeding

Women who take combination AIDS drugs not only have benefits for their own health but also may pass along high levels of the medication through breast-feeding, potentially protecting their infants from HIV infection, suggests research being presented at the 42nd Annual Meeting of the Infectious Diseases Society of America (IDSA).

• Babies born to HIV-positive women may be able to avoid being infected by receiving their mothers' AIDS drugs through breast-feeding, a new study suggests.
• Up to one in eight babies born to HIV-positive women are infected through breast-feeding.
• This strategy may help prevent transmission of the virus in developing countries where breast-feeding often is the best option for preventing other infectious diseases among infants.

"It's a really surprising finding and could potentially mean a two-for-one situation," said Roger Shapiro, MD, research associate for the Harvard School of Public Health and instructor at Harvard Medical School, Boston.

As many as one in eight babies born to women with HIV/AIDS acquire the virus during breast-feeding. Because of that risk, HIV-positive women in industrialized nations are advised to formula-feed their infants, rather than nurse them. In developing countries with limited access to infant formula and clean water, breast-feeding often is the most feasible option. Researchers are searching for ways to decrease transmission of the virus during breast-feeding.

"Although studies are ongoing, it is believed that putting uninfected babies on antiretroviral medication may prevent them from acquiring the virus from their infected mothers while they are breast-feeding," said Dr. Shapiro. "Our study suggests that putting mothers on antiretrovirals could provide infants with high enough levels of these medications through breast-feeding, so that the infants may not have to take any medication separately."

He noted, however, that exposure to AIDS medications - known as antiretroviral therapy - through breast milk alone may pose a risk for infants who have already acquired HIV in utero or during birth. In these babies, resistant mutations of the virus may develop from exposure to drug levels that are lower than those needed for treatment, and may potentially compromise future treatment with the drugs.

Using antiretroviral therapy to prevent transmission of the virus is standard practice in a number of situations. Women who are HIV-positive are advised to take antiretroviral therapy while pregnant and during childbirth to prevent transmission of the virus to the baby. The babies then typically receive daily doses of an antiretroviral drug such as zidovudine (AZT) for up to a month, sometimes in combination with a single dose at birth of another drug known as nevirapine, said Dr. Shapiro. In the developing world, researchers are now taking the next step and studying the possibility of preventing transmission of HIV during breast-feeding by giving antiretrovirals to babies that are breast-feeding.

Conducted in Botswana, the Harvard School of Public Health study included 20 HIV-positive mothers with full-blown AIDS who for their own health were placed on a combination regimen of three antiretrovirals: nevirapine, lamivudine and AZT. All of the infants also received one dose of nevirapine at birth and oral AZT during the course of breast-feeding.

Researchers measured drug levels in the breast milk as well as in the blood of mothers and infants either 2 or 5 months after birth. The tests showed high levels of all three drugs in the breast milk. The blood tests showed the infants may have achieved high enough levels of nevirapine (and possibly lamivudine and AZT) through breast-feeding to provide protection against becoming HIV-infected from breast-feeding.

In addition to the risk of developing resistance mutations among infants who are already HIV-infected, another potential downside is that babies might develop toxicities to these antiretrovirals. Toxicities to these agents include lowered blood counts, liver problems, or allergic reactions, said Dr. Shapiro.

"It is generally believed that maternal antiretroviral therapy will decrease the chances of HIV transmission to breast-feeding infants by lowering the levels of virus in the blood and breast milk of mothers," said Dr. Shapiro. "This study supports the possibility that maternal antiretroviral therapy may also decrease HIV transmission from breast-feeding by providing the drugs directly to the infants."

Co-authors of a paper based on the topic being presented by Dr. Shapiro at IDSA are Diane Holland, Edmund Capparelli, Shahin Lockman, Ibou Thior, Carolyn Wester, Lisa Stevens, Trevor Peter, Max Essex, James Connor and Mark Mirochnick.

IDSA is an organization of physicians, scientists and other health care professionals dedicated to promoting human health through excellence in infectious diseases research, education, prevention and patient care. Housed within IDSA is the HIV Medicine Association (HIVMA), which represents more than 2,600 physicians, scientists and other health professionals dedicated to the field of HIV/AIDS. IDSA, which has 7,500 members, was founded in 1963 and is headquartered in Alexandria, Va.