HIV in breast milk can be drug resistant

From Boston, at a conference on Retroviruses and Opportunistic Infections

A drug called nevirapine, sold as Viramune, can reduce the risk of mother-to-newborn transmission of HIV when taken by a woman at the onset of labor. Scientists now report that after taking nevirapine, the women often harbor a form of HIV with genetic mutations that make it resistant to the drug. Moreover, the mutant virus is more prevalent in the breast milk of infected women than in their blood.

The finding suggests that these women could be passing along resistant forms of the virus to their children during breast-feeding, says Esther Lee of Stanford University. HIV-infected mothers who choose to breastfeed have about a one-in-six chance of transmitting the virus to their babies via breast milk.

Lee and her colleagues analyzed blood and breast-milk samples from 20 nursing mothers in Zimbabwe who had received nevirapine when they went into labor. Thirteen of the women harbored nevirapine-resistant HIV in their breast milk, and eight of the women had these mutant viruses in their blood, Lee says. The samples were taken 2 and 8 weeks after birth.

Lee says that she and her colleagues expect to conduct a new study to determine how long the resistant HIV versions persist in the women.

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