The Antiviral Activity of the CXCR4 Antagonist AMD3100 Is Independent of the Cytokine-Induced CXCR4/HIV Coreceptor Expression Level

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Abstract
The chemokine receptor CXCR4 is the main coreceptor used by T-tropic X4 HIV-1 strains to infect its target T cells. It has been proven that the CXCR4 expression level in T cells is strongly up-regulated by interleukin (IL)-4, a Th2-type cytokine that is secreted preferentially in HIV-infected patients in a later stage of disease. This results in an enhancement of HIV-1 replication in CD4+ T-lymphocytes. We have now evaluated the potency of the CXCR4 antagonist AMD3100 in phytohemagglutinin (PHA)/IL-2- versus PHA/IL-4-activated T cells in order to determine whether the compound has comparable CXCR4-antagonistic and anti-HIV-1 effects under these different cytokine treatments. We analyzed the CXCR4 expression level and the dose-dependent inhibition of CXCR4 expression by AMD3100, by monitoring the binding of an anti-CXCR4 monoclonal antibody (clone 12G5). We also determined stromal cell-derived factor (SDF)-1-induced intracellular calcium signaling and HIV-1 replication in these cells in the absence and presence of AMD3100. The CXCR4 expression level in PHA/IL-4-stimulated cells was much higher than in PHA/IL-2-stimulated cells. However, the potency of the bicyclam AMD3100 to block anti-CXCR4 mAb binding, SDF-1-induced intracellular calcium signaling, and HIV-1 replication of the X4 NL4.3 strain and three primary isolates remained unchanged. Our data indicate that CXCR4 antagonists such as AMD3100 act independently of the HIV-1 coreceptor expression level. These compounds should therefore be useful in suppressing HIV-1 infection in all stages of the disease.