The investigators found that the DARC variation, not race, explained the differences in WBC counts in African Americans with HIV. Among those who were leukopenic, only those with the DARC variation experienced a significant survival benefit. Additionally, this survival advantage became increasingly pronounced in those with progressively lower WBC counts, suggesting that the interaction between DARC and WBC counts was the primary influence on slowing HIV disease progression in African Americans.

"The results of this collaborative study highlight the importance of accounting for other factors, such as the white blood cell count, to uncover the full effects of genetic variations that may influence HIV disease course," said Capt. Gregory Martin, MD, United States Navy, program director for the Infectious Diseases Clinical Research Program (IDCRP) and an expert on infectious diseases who was not involved with the study.

"White blood cells are intricately linked to inflammation, and inflammation is known to fuel HIV disease progression. Thus, future studies will need to decipher whether the interaction between the DARC variant and low white blood cell counts results in a reduced inflammatory state," said Vincent Marconi, MD, of the IDCRP.

The U.S. Centers for Disease Control estimates that about 1 million people in the United States are living with HIV or AIDS, and that about 60,000 individuals are infected with HIV each year.

The study represents a collaboration between investigators at the IDCRP at the Uniformed Services University of the Health Sciences, Bethesda, MD, the VA, and the University of Texas Health Science Center at San Antonio. The study was funded by the National Institutes of Health and the VA.

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