People normally have two copies of the gene, but investigators have found that about 1 percent of the white population has a large deletion, or missing DNA segment, in both of their CC-CKR-5 genes.
and his colleagues have found that those with the deletion in only one CC-CKR-5 gene enjoy no protection from HIV infection.
O'Brien notes that about 20 percent of white people appear to harbor the deletion in at least one CC-CKR-5 gene.
In test-tube studies, chemokines that bind to CC-CKR-5
seem to prevent some HIV strains from infecting cells.
The defects occur in a gene for an immune cell protein known as CC-CKR-5.
The discovery also strengthens the hypothesis that drugs which interfere with the interaction between HIV and CC-CKR-5 can safely slow the spread of the virus in infected individuals.
Now, in a discovery that offers an explanation for why some people exposed to the virus remain uninfected, several research groups report that the HIV most commonly found in people actually infects via CC-CKR-5, a different protein on the surface of immune cells.
The HIV that requires CC-CKR-5 "is the kind of virus transmitted during sex.