Intestinal bacteria may cause HIV to infect brain

A brain section of a mouse infected with HIV following exposure to LPS

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Tuesday, 19, Aug 2008 12:00

Scientists have found that intestinal bacteria may cause the HIV virus to infect patients' brains.

In up to 20 per cent of people infected with HIV, the virus manages to escape from the bloodstream and enter the brain, leading to dementia and other cognitive disorders.

Researchers at the Albert Einstein College of Medicine at Yeshiva University have now uncovered strong evidence that a component of the cell walls of intestinal bacteria lipopolysaccharide (LPS) – present in high levels in the blood of HIV patients – helps the virus penetrate the usually-impregnable blood brain barrier (BBB).

The new findings, published in the Journal of Virology, could lead to scientists discovering ways of preventing HIV from entering the brain.

"These results demonstrate very dramatically that HIV infection of cells associated with the BBB, in conjunction with LPS exposure, contributes to BBB breakdown," Dr Harris Goldstein, director of the Einstein-Montefiore Medical Centre for Aids Research and senior author of the study, said.

"So when HIV infection occurs, we seem to have a 1-2-3 combination of punches working in concert to facilitate entry of HIV-infected monocytes into the BBB-protected brain: HIV infection of monocytes increases their capacity to cross even an intact BBB; HIV infection in the gut releases LPS into the bloodstream allowing it to erode the BBB; and HIV infection of the cells of the BBB makes them more sensitive to the deleterious effects of LPS."

"Ideally, we would promptly start newly diagnosed HIV-infected patients on a treatment to reinforce their BBB's so that HIV can't penetrate it - and perhaps we could even strengthen the BBB's of people who've been infected for quite a while.

"But before we can prevent the tragedy of HIV-associated dementia, we need to better understand the mechanism by which these molecular and cellular 'punches' interact to undermine the BBB."