23.9.09 da "www.news.com.au"
September 23, 2009
AUSTRALIAN scientists have identified another key "reservoir" for HIV - in the brain - posing a new challenge in the search for a way to eradicate the virus from the body.
Conventional antiretroviral drugs have become so effective at suppressing the virus inside an infected person's body that there is a prospect of getting rid of it altogether.
This effort is seen as a more promising field of research than working to create a HIV vaccine, but it hinges on perfecting techniques to kill off infected cells in the known reservoirs for HIV in the body.
Melbourne-based Dr Melissa Churchill said HIV was known to hide out in a the thymus and lymph tissues, the gut, spleen, testes, bone marrow and - according to her latest research - in astrocyte cells in the brain.
"The astrocytes are basically the support cells - they mop up toxins released from other cells and maintain a really nice environment for the neurons to function,'' Dr Churchill said of the vital role played by these cells for cognition.
"Previously, people weren't sure if we have to actually consider it as a genuine viral reservoir, but it is.''
Dr Churchill, from the Burnett Institute, teamed up with researchers at Monash University, St Vincent's Hospital in Sydney and John Hopkins University in Baltimore, USA, for the work.
They used latest in high-powered microscopes to examine brain tissue from HIV-positive people to gauge the presence of the virus in these astrocyte cells.
Dr Churchill said it had been thought the virus had about a "one per cent'' presence, but the research showed it was up to 19 per cent and "very significant''.
It's a discovery that poses several new challenges for scientists now progressing the work of finding ways to eradicate HIV from the body.
"One of the issues of the brain as a reservoir is that it's quite inaccessible to the immune system and to anti-retrovirals,'' Dr Churchill said.
Then there is the potential for brain damage.
"The cells that make up the other reservoirs, they can be regenerated - they are blood cells, things like that - but if you kill astrocytes, especially at this level, they don't regenerate.
"You lose the function that they normally carry out ... so you end up with a poorer (brain functioning) environment.''
It is thought these infected and underperforming cells are also the cause of HIV-associated dementia, which commonly occurs in the later phases of HIV infection.
It can also strike much earlier. HIV is the world's leading cause of dementia in people aged under 40.