Effect of activation of A2a receptors on CCR5-mediated HIV-1 viral infection. (A) FACS analysis revealed a decrease in the CCR5 level on activated human monocytes after pretreatment with RANTES for 30 minutes at 37°C. (B) FACS analysis revealed a decrease in the CCR5 level on activated human monocytes after pretreatment with CGS21680 (2 μM) for 30 minutes at 37°C. Pretreatment with cAMPs, Rp-isomer (PKAI) at 100 μM reversed the inhibitory effects by CGS21680. (C) Homologous competition binding analysis, using ¹²⁵ I-labeled RANTES, on the binding affinity (K_d) and binding sites (Bmax) on human monocytes. (D) Treatment with CGS21680 (2 μM) decreased RANTES binding affinity by 5-fold and RANTES binding sites by 39% (2-way ANOVA analysis of panel C versus panel D yield P < .001). (E) Effect of pretreatment with CGS21680 on the susceptibility of monocytes to R5 HIV-1. Monocytes were pretreated with either CGS21680 (CGS), the adenosine receptor antagonist ZM241385 (ZM), or both (ZM/CGS) at concentrations from 1 to 100 μM, and after 1 hour, the monocytes were exposed to HIV-1 strain JRFL. Cells were washed after 1 hour and returned to culture for 48 hours, and the supernatants were collected. The HIV p24 level in the supernatants was determined by ELISA. Data are representative of 6 experiments.