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A genetic mutation could hold clues why some mothers infected with HIV transmit the virus to their babies and others don’t, according to researchers at the University of North Carolina at Chapel Hill.

Babies with mutations in a certain gene are less likely than others to become infected with HIV from their mothers before or during birth, the researchers found. The protection seen was only in infants of mothers with mild infections. No difference was found in infants of mothers with a high level of HIV infection.

“The more we know about how HIV is transmitted from one person to another, the better chance we have of preventing the spread,” said Steven Meshnick, Ph.D., UNC School of Public Health epidemiology professor and senior author of the study.

The results appeared Sept. 5, 2007, in PLoS One, an open access, online scientific journal from the Public Library of Science. The National Institutes of Health and UNC Center for AIDS Research funded the research.

Meshnick said the research team wondered why some mothers transmit HIV infections to their infants and others don’t. They suspected that variations in the CCR5 gene, which controls one of the entry pathways HIV exploits to enter human cells, had an impact on infection rates. The study was designed to discover whether the gene made a difference in rate of infection from mother to child.

The 4,000 women and their infants who participated in the study all live in Malawi, a densely populated country in southeastern Africa near Mozambique. Victor Mwapasa, Ph.D., lecturer at the University of Malawi College of Medicine, directed the clinical aspects of the study, enrolling women in the study and testing them and their infants for the virus. The infants were also tested for polymorphisms, or variations, in the CCR5 gene.

“We found that it didn’t make a difference if the mother’s viral load, the amount of infection, was really high,” Meshnick said. “But for mothers with a low level of virus, we found that babies with mutations associated with lower levels of CCR5 were better protected.”

Of the 4,000 women in the study, 29 percent were infected with HIV. “We’re taking about thousands of babies who are affected. Mother to child transmission of HIV in the US is down to 100 to 200 a year, but in Sub-Saharan Africa, about 700,000 babies a year are infected,” Meshnick said.

The CCR5 gene information might help researchers develop new therapies for treating HIV or possibly for developing an effective vaccine . “The better we understand what parameters are needed for transmission, the sooner we will be able to find ways to block infection,” he said.

“HIV has a tremendous effect on people in Malawi,” said Meshnick, explaining why the research was conducted there.

Co-authors include Bonnie R. Pedersen, a doctoral candidate in epidemiology at UNC School of Public Health, and Peter Zimmerman, Ph.D., associate professor in the Center for Global Health and Diseases at Case Western Reserve University in Cleveland, Ohio.

Note: Steven Meshnick can be reached at (919) 966-7414 or

School of Public Health contact: Ramona DuBose, (919) 966-7467 or

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