Science / Medicine : ‘Free’ HIV Found in Brain Cells

AIDS patients suffering from brain inflammation and dementia have high levels of “free” virus in their brain tissue, California researchers reported last week in Nature.

The human immunodeficiency virus, which causes AIDS, can either be incorporated into the genetic material of an infected human cell or remain free inside the cell. A team led by Irvin Chen of UCLA found in autopsies that the brains of patients with AIDS-related encephalitis, an inflammation associated with dementia, consistently contained high levels of free HIV--ranging from six to 80 times the amount of virus integrated into genetic material. But AIDS patients who were not afflicted with HIV-linked encephalitis at the time of their deaths did not show high levels of free virus.

Given the high levels of free virus, researchers speculated that replication of HIV in the brain may differ from that elsewhere in the body. Chen said it is not known if the high levels of free virus are directly responsible for the brain inflammation. But he noted that high proportions of free virus have been linked to greater cell death in an AIDS-like viral disease affecting cats.

In the test tube, free HIV is generally associated with high rates of viral multiplication and re-infection, marked by release of viral-made proteins called antigens. But the UCLA and UC San Diego team found no correlation between viral antigens and levels of free virus in the brain, which they said may indicate that free virus can exist in an inactive state.