Although many individuals infected with the hepatitis C virus (HCV) are naturally able to control levels of the virus with their immune systems, those who also become infected with HIV, the virus that causes AIDS, may lose that ability. In a report in the December issue of PLOS Medicine, a group of researchers from the Partners AIDS Research Center at Massachusetts General Hospital (PARC-MGH) report one of the first studies of how HIV infection impacts immune system functions involved with HCV control. Their findings suggest that beginning antiretroviral therapy earlier than is generally recommended may help preserve HCV control in patients infected with both viruses.
"The global burden on health of chronic viral infections is immense, and HCV and HIV are chief among culprit viruses," says Arthur Kim, MD, of PARC-MGH, co-first author of the PLOS Medicine report. "Due to shared routes of transmission, infection with both viruses is common. Unfortunately, HCV behaves as an opportunistic infection in the presence of HIV and is becoming a leading cause of illness and death in persons with HIV."
In order to examine immune system factors associated with spontaneous control of HCV and how that control is altered by HIV infection, the researchers enrolled four groups of participants: 60 were infected with both viruses, and half of those had low HCV levels upon entering the study. The other two groups of 17 participants were infected with HCV only, with one group successfully controlling viral levels. Spontaneous HCV control is known to rely on the activity of CD4 helper T cells specifically targeted against the virus, and destruction of CD4 cells by HIV underlies the immune deficiency that characterizes AIDS. Therefore the researchers measured participants' T cell response to HCV at the outset of the study and at two- to six-month intervals during the study period.