Fifth of HIV patients vulnerable to brain damage

Washington, Aug 19 : A fifth of HIV patients are particularly vulnerable to brain damage like dementia and other disorders when the lethal virus manages to slip out of the bloodstream and cross into the brain.

Scientists at Albert Einstein College of Medicine have found strong evidence that a component of cell walls of intestinal bacteria - a chemical present in the blood of HIV-infected people, helps the virus penetrate the blood brain barrier (BBB).

The findings could lead to strategies for preventing HIV from entering the brain and causing serious complications.

"Previous research has suggested that it's not individual HIV viruses that get into the brain but rather HIV-infected immune cells known as monocytes," said Harris Goldstein, director of the Einstein-Montefiore Medical Centre for AIDS Research and co-author of the study.

"Using an animal model, we wanted to find out first of all whether being infected with HIV enables monocytes to do what they don't usually do - escape from blood vessels and enter brain tissue."

"Results demonstrated very clearly that being infected with HIV somehow gives monocytes the capacity to cross an intact BBB," said Goldstein.

"But we also suspected that something else was making it easier for HIV-infected monocytes to breach the defences protecting the brain from infection."

In 2006, scientists at the National Institutes of Health had reported that HIV infection breaks down barriers in the intestine that normally prevent intestinal bacteria from entering the bloodstream.

The blood of HIV-infected people was found to contain markedly elevated levels of lipopolysaccharide (LPS), a component of certain bacteria that are normally confined to the intestine but leak out due to HIV infection.

To test this hypothesis, his team injected control mice with very low doses of LPS that were comparable to the levels in the bloodstream of HIV-infected individuals and would only minimally weaken their BBB's.

"Clearly, HIV-infected monocytes... benefit from the LPS that is present in high amounts in the blood of HIV-infected people," said Goldstein.

"So when HIV-infected monocytes are 'knocking on the door' of the BBB and starting to crack it open, the LPS facilitates their entry by making the BBB more permeable, apparently by weakening blood vessel structure."

These findings were published in the August issue of the Journal of Virology.

--IANS