Regulatory CD4 T cells differentially modulate HIV-1 infection of polarized M1 and M2 macrophages (VIR9P.1156)

Macrophages are long-lived, widely distributed and relatively resistant to HIV-1 cytotoxicity. Effector macrophages are functionally polarized into M1 (pro-inflammatory) and M2 (anti-inflammatory) phenotypes. M1 macrophages suppress CCR5 (R5) HIV-1 replication, while M2 macrophages promote it. Recently, regulatory CD4 T cells (Tregs) were shown to inhibit HIV-1 infection of co-cultured CD4 T cells, but their effect on macrophage infection is unknown. Using an in vitro model of polarization, we generated M1 (GM-CSF+IFN-γ+LPS) and M2 (M-CSF+IL-4) macrophages with predicted phenotypes and infected them with R5 HIV-1 reporter viruses. We consistently found higher levels of HIV-1 (GFP and luciferase reporter viruses) infection of the M2 cells. Next, we co-cultured Tregs with HIV-1 infected polarized M1 and M2 MDM at a 1:1 ratio. Treg co-cultures yielded decreased HIV-1 infection of M1 but increased infection of M2 macrophages. Surprisingly, our results showed that Tregs mediate divergent effects on HIV-1 infection of M1 and M2 MDM depending on their polarization into a M1 or M2 phenotype. We are currently exploring whether Treg-mediated effects on HIV-1 infection of MDM are cytokine dependent and/or cell contact dependent using a transwell system and inhibitory cytokine antibodies. The research will provide increased knowledge of the role Tregs play in HIV-1, as well as a new understanding of how the M1 to M2 macrophage switch contributes to HIV-1/AIDS pathogenesis.