CC-CKR-5: Second Coreceptor for HIV

To completely enter and infect cells, the AIDS virus must use two types of receptors located on the surface of the cell it is attacking. The receptor required for attachment of HIV to the cell surface is called CD4. A second coreceptor allows HIV to fuse with the cell, enter it, and begin replicating. Scientists recently discovered a cell-surface protein called fusin which acts as the coreceptor for HIV strains that infect T cells, an infection that might occur late in the stages of AIDS. Now, scientists have found another protein, called CC-CKR-5, and this one acts as the coreceptor for strains of HIV that are active during the early phases of AIDS, a time which may be more critical to the development of the disease.

The fact that HIV uses different kinds of coreceptors during different stages of infection may explain why the human immune system eventually succumbs to HIV. By switching receptors, HIV may be able to circumvent processes that would otherwise block HIV, such as the binding of chemokines to coreceptors. Further research will focus on the possibility of blocking CC-CKR-5 to treat AIDS and on looking for defects in the structures of these receptors in individuals that are infected with HIV but have not developed AIDS.

Source: "A Second Coreceptor for HIV in Early Stages of Infection," by Michael Balter, Science, June 21, 1996.

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