A new Harvard study provides the most conclusive evidence yet that an HIV patient’s genetic charactersitics affect the rate at which the disease progresses.

Associate Professor of Medicine Marcus Altfeld and his team found that the structure of inherited immune system molecules, known as HLA Class I, partially determines HIV patients’ reaction to the virus.

“This means that some genetic factors have an important effect on HIV’s progression very early in infection,” Altfeld said. “What happens early in infection determines the rate at which the disease will progress as a whole.”

Altfeld conducted the cross-sectional study of 100 HIV patients at Massachusetts General Hospital over several years. The patients were followed from very early on in the progression of the disease, often from less than a week after diagnosis, according to Altfeld.

“We studied the HIV-specific immune responses and then tried to go a step further and understand the genetic factors that determine these immune responses,” Altfeld said.

He added that this study was important because previous studies of a similar nature had only involved three to 15 patients. As a result, he said, those studies’ conclusions were less definitive.

The results of the study also suggest that the development of HIV vaccines might have to take genetic differences into account.

Altfeld and his colleagues at Harvard Medical School plan to complete a study involving at least 500 subjects in the future to further explore the link between HLA Class I molecules and HIV’s progression.