FRIDAY, July 25 (HealthDay News) -- A new study challenges the long-held belief that the hepatitis C virus (HCV) impairs the immune system's ability to restore itself after HIV patients are treated with highly active antiretroviral therapy (HAART).

From 50 percent to 90 percent of HIV-infected drug users are also infected with HCV. Intravenous drug use is the main cause of both types of infection.

Researchers at Wake Forest University Baptist Medical Center focused on levels of CD4 cells -- the immune cells that are attacked by HIV -- and whether CD4 cells can rebuild after HAART is used to suppress HIV infection. For the study, the researchers analyzed the medical records of 322 patients.

"We've been observing that in some patients that are co-infected with hepatitis C, we were treating their HIV with HAART but didn't always get very good restoration of CD4," lead researcher Dr. Marina Nunez, an assistant professor of infectious diseases, said in a Wake Forest news release. "Some studies have suggested it was because of the hepatitis C. This study says it's not the presence of active hepatitis C replication."

She said impaired immune restoration seen in some HIV/HCV-infected patients after HAART may be due to a number of other causes, such as genetic factors involved in immune system regulation, confounding factors associated with HCV acquisition, or other unknown factors.

"Research efforts should pursue the role of those other factors in the immune restoration," Nunez said.

"From a clinical standpoint, although these findings will not alter the clinical management of HIV-HCV-co-infected patients, they make clear that even after successful treatment of the HCV infection, some patients may not get an adequate CD4 recovery under HIV treatment," she said.

The study was published in the July issue of AIDS Research and Human Retroviruses.

More information

The U.S. National Institute of Allergy and Infectious Diseases has more about HIV treatment.