HIV can cause dementia in aging HIV patients

A study reported this week at the International Conference on Alzheimer's Disease in Philadelphia suggests that aging HIV patients may face risks of developing chronic dementia, regardless of whether they are on successful highly active antiretroviral therapy regimens, the Oakland Tribune reports. The dementia is not related to the cognitive problems that are common in patients with advanced AIDS, say researchers at the University of California, San Francisco. They report that a human protein--called amyloid beta protein--that can damage brain cells is commonly produced at a higher level in people as they age, but that a naturally occurring enzyme, neprilysin, works to break down the protein and prevent cellular damage. A key protein in HIV, called Tat, was discovered to block the effects of neprilysin, allowing amyloid beta to accumulate. High levels of the protein in the body can result in slow memory loss and can be exacerbated by other genetic factors. The longer a patient has HIV, the more amyloid beta accumulates, regardless of age and whether the patients are taking antiretroviral medications. A laboratory study found that a synthetic version of HIV's Tat protein boosted amyloid beta levels 125% in brain cells. Autopsies of 14 HIV-positive people also showed heightened levels of the protein in brain cells. The researchers say they suspect many HIV patients will show signs of slow memory loss as they age, and they recommend studies using treatments for Alzheimer's patients, including the drugs Aricept and Cognex, to see if the medications can help slow the development of HIV-related dementia.