Abstract CB2 expression is upregulated in HIV-1 infected macrophages; CB2 agonists limits infection by inhibition of the HIV-1-LTR. Infiltrating monocytes and macrophages play a crucial role in the progression of HIV-1 infection in the CNS. Previous studies showed that activation of the CB2 can attenuate inflammatory responses and affect HIV-1 infectivity in T cells and microglia. Here, we report that CB2 agonists can also act as immunomodulators on HIV-1-infected macrophages. First, our findings indicated the presence of elevated levels of CB2 expression on monocytes/macrophages in perivascular cuffs of postmortem HIV-1 encephalitic cases. In vitro analysis by FACS of primary human monocytes revealed a step-wise increase in CB2 surface expression in monocytes, MDMs, and HIV-1-infected MDMs. We next tested the notion that up-regulation of CB2 may allow for the use of synthetic CB2 agonist to limit HIV-1 infection. Two commercially available CB2 agonists, JWH133 and GP1a, and a resorcinol-based CB2 agonist, O-1966, were evaluated. Results from measurements of HIV-1 RT activity in the culture media of 7 day-infected cells showed a significant decrease in RT activity when the CB2 agonist was present. Furthermore, CB2 activation also partially inhibited the expression of HIV-1 pol. CB2 agonists did not modulate surface expression of CXCR4 or CCR5 detected by FACS. We speculate that these findings indicate that prevention of viral entry is not a central mechanism for CB2-mediated suppression in viral replication. However, CB2 may affect the HIV-1 replication machinery. Results from a single-round infection with the pseudotyped virus revealed a marked decrease in HIV-1 LTR activation by the CB2 ligands. Together, these results indicate that CB2 may offer a means to limit HIV-1 infection in macrophages.