Finding a partner for fusin at last.

Earlier this year, researchers identified a protein on the surface of immune cells that allows HIV, the AIDS virus, to infect the cells (SN: 5/11/96, p.293). The protein, called fusin, turned out to be the portal for only some strains of HIV, mainly those found in the late stages of AIDS. But what role does fusin play in an uninfected person?

Fusin binds to a molecule called stromal-cell-derived factor 1, or SDF-1, two research groups now report. That well-known molecule is a chemokine, a compound released at a site of infection to attract immune cells. The discovery of fusin's role is described in the Aug. 29 Nature by a group led by Estelle Oberlin of the Pasteur Institute in Paris and another group led by Conrad C. Bleul of the Dana-Farber Cancer Institute in Boston.

The result isn't surprising, considering that another molecule which HIV uses to infect cells binds to other chemokines. This immune cell surface protein, CC-CKR-5, is commandeered by the most common strains of HIV (SN: 6/22/96, p.390). In test-tube studies, chemokines that bind to CC-CKR-5 seem to prevent some HIV strains from infecting cells. In similar studies, investigators have now shown that SDF-1 can block the HIV strains that depend on fusin.