Gene Mutation That Protects Against Virtually Extinct Form of Malaria Makes Blacks More Susceptible to HIV, Study Says
A gene mutation that likely protected people living in sub-Saharan Africa from a form of malaria seldom found in the region now could make blacks more susceptible to HIV, according to a study published Wednesday in the journal Cell Host & Microbe, the New York Times reports. The researchers say if their results are confirmed by other research, important insights into HIV's biology could be gleaned (Wade, New York Times, 7/17). The researchers estimate that the gene mutation could account for about 11% of, or 2.7 million, HIV cases in sub-Saharan Africa (Russell, San Francisco Chronicle, 7/17).
According to the researchers, there are no immediate practical implications of the study's findings. However, the findings "in theory" could be used to develop a "susceptibility test" that can identify the mutation. In addition, HIV vaccine researchers could use the findings to tailor vaccine candidates to groups most likely to benefit from such vaccines, the Wall Street Journal reports (Naik, Wall Street Journal, 7/17).
For the study, researchers compared blood samples of 814 black U.S. military personnel who were HIV-negative with samples from 470 personnel who were HIV-positive. The researchers examined the samples for a protein known as the "Duffy antigen," which enables some malaria parasites to enter red blood cells (San Francisco Chronicle, 7/17). People with a genetic mutation that disables the Duffy antigen are protected against the Plasmodium vivax malaria parasite, a form of which was common in Africa thousands of years ago (Dunham, Reuters, 7/16).
About 90% of blacks living in Africa and 60% of U.S. blacks have a disabled Duffy antigen, according to the researchers. However, the Duffy antigen absorbs HIV, preventing the virus from entering white blood cells. Those with a disabled Duffy gene therefore are more susceptible to HIV, according to the study. The researchers found a 40% higher risk of HIV among the military personnel whose genes disabled the Duffy antigen (San Francisco Chronicle, 7/17).
In addition, the researchers found that HIV-positive people with a disabled Duffy antigen had a slower progression to AIDS and likely survived about two years longer than those without the variant (Wall Street Journal, 7/17). Although researchers are unsure why the absence of the antigen both increased susceptibility to HIV and slowed progression of the virus, it is possible that people without the antigen have lower levels of infection-fighting chemokines in their blood, which make infection more likely but limit damage to the body if infection occurs (Kaplan/Maugh, Los Angeles Times, 7/17).
Robin Weiss, a virologist at University College London and study co-author, said that the study "helps in part to explain why HIV is so prevalent in Africa," but added that additional research is needed among a larger group on the continent "to see if [the finding] really applies to Africa" (Wall Street Journal, 7/17).
Phill Wilson, chief executive of the Black AIDS Institute, said the study seems to confirm a theory that HIV risk is not connected solely to behavior. Wilson said that the behavior of black men who have sex with men "is no more risky" than among white MSM but vulnerability to HIV "is so much greater" among black MSM. Sunil Ahuja, lead study author from the South Texas Veterans Health Care System, said that social factors -- such as poverty, lack of access to health care and sexual behavior -- likely are more important indicators of a person's HIV risk than the gene mutation (Los Angeles Times, 7/17).
Cheryl Winkler, head of the Laboratory of Genomic Diversity at the National Cancer Institute, said she is "a little skeptical about" the study. Winkler added that the difference in HIV prevalence among participants who had the mutation and those who did not was barely statistically significant. The study researchers "don't have enough evidence," Winkler said, adding that the findings "definitely require[e] more study and replication of results before you can make these assumptions" (San Francisco Chronicle, 7/17).
The study is available online.