While the virus that leads to AIDS has long been recognized to be “sloppy” in its replication, changing over time into divergent strains, a National Institutes of Health-funded study recently found the virus that a person transmits tends to continue to look like the virus that originally infected that person. The study, significant for the light it sheds on how the virus behaves, and for how that, in turn, can steer biomedical prevention efforts, was made possible by a long-running collaborative project in Uganda, involving thousands of participants since the early 1990s.
For the study, scientists looked at samples collected from hundreds of HIV-positive heterosexuals over eight years from the Rakai Health Sciences Program, an ongoing collaboration between Ugandan and U.S.-based researchers in the country’s Rakai district. They found that the virus varied more within individuals over time than it did across the population. In 22 of 31 couples — about 70 percent — between whom transmission of HIV had occurred, the viruses in those newly infected more closely resembled the virus in samples collected from their already HIV-positive partners early in those partners’ own infections, than in samples collected from those partners later, at the time of transmission. The tendency for original infecting strains to be the strain eventually transmitted indicated they had an “evolutionary advantage” over strains that appeared later in infection, scientists said.
While a vaccine will need to effective against a diverse array of HIV strains, the findings suggest that vaccine design should target those transmitted strains, which many are doing, said Andrew Redd, a National Institutes of Health staff scientist who led the study with senior investigator Dr. Thomas Quinn.
While the NIH researchers began working with the Rakai cohort about five years ago for this study, the information gathered was the culmination of nearly two decades of work, by hundreds of Ugandans, as well as Johns Hopkins researchers, and about 40,000 people from about 50 villages in the Rakai district of Uganda who have contributed to the study, Redd said. This study, and others, he said, continue to fulfill the long term goals of their project of helping scientists to better understand the virus and its dynamics.
The next step, Redd added, will be to seek to identify characteristics of the transmitted strains that gives them an advantage in transmission.