New research may help explain why some patients with HIV experience neurological problems. Investigators have found that HIV weakens the blood-brain barrier -- a network of blood vessels that keeps potentially harmful chemicals and toxins out of the brain.

Standard antiretroviral treatments suppress the replication of HIV and slow its progression. However, recent studies reveal that 40 to 60 percent of patients on these therapies continue to experience mild to moderate neurological deficits such as memory loss and learning challenges.

In this new study, researchers found that HIV infection in a small number of supporting brain cells -- called astrocytes -- breaks down the blood-brain barrier, despite low to undetectable viral production. Normally, astrocytes help bolster the blood vessels comprising the barrier.

"Researchers have been stymied to explain why HIV-associated neurological complications persist, despite potent combination antiviral therapies that have dramatically improved health and survival," Igor Grant, an expert who studies HIV-associated neurocognitive impairment at the University of California, San Diego, was quoted as saying.

"This study provides a possible explanation indicating that minute numbers of infected astrocytes can trigger a cascade of signals that could open the brain to various toxic influences."

The investigators say these findings open up the possibility of developing new treatment approaches that block or modify the transmission of signals from the HIV-infected astrocytes.