PARIS - A common virus may help the AIDS virus to infect certain types of cells and wreak havoc on the immune system. The results, reported in tomorrow's issue of Science * require closer symbiotic relationship between HIV and its possible ally - Cytomegalovirus (CMV) -. Imagined before
CMV, a member of the herpesvirus family that infects 80% of adults and almost all HIV-infected homosexual men, has long been a prime suspect as a cofactor AIDS. A team led by Marc Alizon at the Cochin Institute in Paris, in collaboration with Michel Seman at the University of Paris, began probing whether HIV can use a protein called CMV US28 to enter into certain types of cells. The protein is expressed in cells experimentally infected with CMV. US28 had previously been shown to act as a reception point, or receptor, for the same immune system molecules called chemokines that bind to CCR5, a receptor used by HIV strains which dominates during the early stages of signaling infection.
In determining whether US28 could act as HIV accomplice, the French group has inserted the US28 gene in a human cell line that HIV normally do not infect. The group then sets Alizon those cells that express the protein US28 on their surfaces, various strains of HIV. In these and related experiments, the team found that Alizon US28 bearing cells were easily infected with HIV strains that normally use the CCR5 receptor on human chemokine, and a little less easily by strains that use another human receptor, CXCR4.
"the results are provocative and potentially important for HIV pathogenesis," says Philip Murphy, a chemokine receptor expert at the National Institute of Allergy and Infectious Diseases in Bethesda, Maryland. Adds David Posnett immunologist at Cornell University Medical College in New York who has studied CMV: "I wonder what it all means in real life."
Indeed, it is not yet clear if the French group results, which are limited to cell lines laboratory are relevant to people with HIV. "There is a total lack of information about when, where, and how many US28 is expressed in people infected with CMV," Murphy said. So experts continue to debate whether CMV is simply an opportunistic organism enjoying the immune suppression caused by HIV, or a partner in the destruction of the immune system.
* For details, Science Online Subscribers can create a link to the full report.
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