Scientists at Dartmouth Medical School have uncovered a key mechanism in mother-to-child transmission of HIV-1 virus through breast-feeding. The research was conducted by graduate student Magdalena Lyimo under faculty supervisors Ruth Connor and Alexandra Howell, both research professors of microbiology and immunology at DMS. The paper, titled “Innate Factors in Human Breast Milk Inhibit Cell-Free HIV-1 but Not Cell-Associated HIV-1 Infection of CD4+ Cells,” was published in the Journal of Acquired Immune Deficiency Syndromes on April 2.
Past research has shown that the HIV-1 virus is present in two forms in the breast milk of HIV-positive women. These two forms are the cell-free form, which consists of the virion itself, and the cell-associated form, which refers to the virus after it has infected a CD4+ T lymphocyte cell, Connor said in an interview with the Dartmouth Undergraduate Journal of Science.
Lyimo’s research demonstrated that immune factors in human breast milk taken from healthy women inhibited infection due to cell-free HIV-1 virus in vitro, but they did not appear to reduce infection due to cell-associated HIV-1. The authors reported in their paper that breast milk might play a protective role against cell-free HIV-1 transmission, but not against cell-associated HIV-1 transmission from mother to infant.
These findings are novel, as they present the first demonstrated inhibitory mechanism involved in breast-feeding HIV transmission, Lyimo said in an interview with the DUJS. While past epidemiological studies have proven inconclusive, her research shows that innate factors in breast milk are effective at blocking an early stage of the viral life cycle of cell-free HIV-1.
Lyimo’s work may have implications for improved drug treatment of HIV-1 in breastfeeding mothers, according to Connor. Current antiretroviral drugs effectively decrease the levels of cell-free virus in breast milk, but have little effect on the amount of cell-associated virus, she said. According to Connor, Lyimo’s research stands to provide insight into how to target infected CD4+ cells in the future by increasing knowledge of the mechanisms involved in mother-to-child transmission.
“Reading the literature, there really isn’t much that’s known about what’s going on with mother-to-child transmission through breast milk,” Lyimo explained.
Lyimo, who is originally from Tanzania, explained that her personal experience of working in a hospital in a developing country, where HIV/AIDS is highly prevalent, contributed to her decision to pursue this area of research.
“Breast milk transmission of HIV is something I thought was very interesting. It’s something that’s going on back home,” she said.
The research team’s next step will be to investigate whether or not HIV-positive breast milk collected from infected women in Tanzania can mimic normal breast-milk’s ability to differentially inhibit HIV-1 infection, according to Lyimo. The experiment will determine whether HIV-specific immune factors found in the breast milk of infected women confer a similar or modulated protective function, she explained.
“Breast milk is beneficial,” Lyimo said, referring to its role in passing immune factors from mother to infant. “We’re trying to add a better understanding of what’s going on so that we can preserve the goodness of breast feeding but at the same time reduce transmission of HIV, especially in settings where women really don’t have the option of not breastfeeding.”