People of African descent may progress more slowly to AIDS according to two studies presented at the 16th Conference on Retroviruses and Opportunistic Infections (CROI) in Montreal and reported by aidsmap.

Activists and scientists once feared that people of African descent may have faster HIV disease progression than Caucasians. Research in the United States and Africa, however, has since indicated that when Africans and African Americans have ready access to comprehensive HIV care and necessary social services, they do not progress more quickly. And now, reports suggest that people of African descent may actually have slower disease progression.

The first report, an analysis of data from the Swiss Cohort Study, examined the medical records of nearly 600 patients in Europe, of whom roughly 20 percent were of African descent. More than 60 percent were women. Presented by Viktor Müller, PhD, from Eötvös Loránd University in Budapest and his colleagues, data from the Swiss study found that people of African descent not on treatment lost CD4 cells over time at roughly half the rate as people of European descent. This was true regardless of a person’s starting viral load or HIV subtype.

These results are even more striking when paired with the results of a second study presented by John Phair, MD, from Northwestern University in Chicago. Phair and his colleagues looked at data from the Multicenter AIDS Cohort Study (MACS) in the United States. They compared 55 people who had very slow HIV progression, called long-term nonprogressors (LTNP), with 179 people estimated to progress at the average rate—an AIDS diagnosis within 12 years of initial infection with HIV—called expected progressors (EP). Phair’s group found that overall, African Americans were generally more likely to progress more slowly than Caucasians.

Researchers associated with both studies hypothesized that over many generations, people of African descent have developed genetic mutations from being constantly exposed to tropical diseases, and that this may result in a better response to HIV. In the MACS, African Americans were also more likely to have been infected with, and cleared, hepatitis B virus (HBV) infection, indicating that whatever genetic benefit they have against HIV may also be beneficial against HBV.