Accessory receptors for HIV

Different isolates of HIV-1 have varying tropisms for CD4 positive cells:

• during the early stages of infection HIV is predominatly macrophage-tropic (M-tropic)
• during later stages of infection HIV isolates are T-cell tropic (T-tropic)

CD8 positive cells can inhibit the replication of HIV by two means:

• cell-mediated cytolysis of infected cells
• secretion of soluble factors

Three soluble factors have been found which specifically inhibit M-tropic HIV replication:

• RANTES
• MIP-1 alpha
• MIP-1 beta

These three inhibitory factors bind to a chemokine receptor called CCR-5. Subsequent work has shown that CCR-5 on macrophages is the co-receptor, along with CD4, for M-tropic HIV infection.

One soluble factor has been found which specifically inhibits T-tropic HIV replication:

• SDF-1

SDF-1 binds to a chemokine receptor called CXCR-4. CXCR-4 (also called fusin) on T-cells is the co-receptor, along with CD4, for T-tropic HIV infection.