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Thursday, July 17, 2008

Gene Variation May Increase Vulnerability to H.I.V

Interesting possible important possible fact reported in The NY Times

The genetic variation has been studied in U.S. Air Force personnel whose H.I.V. infections have been followed for 25 years. African-Americans who carry it were 50 percent more likely to acquire H.I.V. than African-Americans who do not carry the variation, although their disease progressed more slowly, say researchers led by Sunil K. Ahuja, director of the Veterans Administration HIV/AIDS Center, San Antonio, , and Matthew J. Dolan of the Uniformed Services University in Bethesda, Md.

The genetic variation, called a SNP (“snip”), involves a change in a single unit of DNA. This particular snip has a far-reaching consequence, that of preventing red blood cells from inserting a certain protein on their surface. The protein is called a receptor because it receives signals from a hormone known as CCL5, which is part of the immune system’s regulatory system.

Dr. Weiss said the red blood cell receptor was similar to another receptor, CCR5, which occurs on the surface of the white blood cells that are H.I.V.’s major target. A few percent of Europeans have a mutation that prevents the CCR5 receptor from being displayed on the surface of white blood cells, and they are protected against H.I.V.

It is somewhat puzzling that absence of the two receptors has the opposite effect — vulnerability to H.I.V. when the red cell receptor is missing, protection when the white cell receptor is withdrawn.

NICHOLAS WADE goes on to warn that the statistical result is very preliminary and might not amount to anything.

My guess of a possible explanation is that the red blood cell CCL5 receptor binds HIV and causes them to infect the red cell where they can't reproduce, because HIV incorporates a reverse transcript of its genome in host cell chromosomes and red blood cells do not contain chromosomes.

If so, this could potentially be exploited. HIV infection of other cells could be reduced with a bifunctional antibody to a red blood cell surface protein (you know as in blood types) and to HIV.

Maybe maybe it would be possible to make an antigen which combines part of an HIV surface protein and a blood surface protein and which then induces a magic antibody which makes HIV infect red blood cells instead of white blood cells.

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