An alternative gateway for the AIDS virus to enter the nervoussystem is suggested by the specific binding of the viral coatprotein gp120 to the brain glycolipid galactosyl ceramide(GalCer), according to a report in the latest issue of theProceedings of the National Academy of Sciences.

The viral protein gp120 allows the virus to enter immune cellsthrough their CD4 molecules. But neural cells in the brain thatdo not have CD4 on their surfaces nevertheless are ofteninfected. Scientists from the University of Pennsylvaniamedical center in Philadelphia found that recombinant gp120specifically binds to GalCer and does not bind to other brainlipids. The sugar-lipid linkage of galactose to ceramideappears crucial to the gp120 interaction.

This research team previously found that antibodies to GalCerblock entry of HIV in cultured cells of neural origin.

GalCer, an important component of the fatty sheath calledmyelin that wraps around the conducting fibers of nerve cells,is crucial to the signalling between nerve cells. Many bacteriaand their toxins can use brain glycolipids as entry points, theresearchers noted. The demyelinating neurologic disordersoften seen with HIV infection may be explained by the bindingof gp120 to GalCer, they concluded.

-- Roberta Friedman, PhD. Special to BioWorld

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