clipped from: news.bbc.co.uk   
HIV's double hit on brain cells
HIV can trigger learning and memory deficits by launching a double attack on the brain, research shows.
HIV
It was already known that a protein on the surface of the virus could kill off mature brain cells.
But the latest study shows it also prevents the production of replacements by crippling cells with the potential to step in and take their place.
"The HIV protein both causes brain injury and prevents its repair."
a protein called gp120, which is found on HIV's outer coating, can kill off brain cells by disrupting their internal chemistry.
It appears the same chemical disruption that kills cells is also responsible for blocking production of replacements.
"Antiretroviral drugs have lowered viral load so that HIV will not kill cells directly, but we don't know the consequences for brain functioning of a long-term low level of infection.