Inactivates Human Plasmacytoid Dendritic Cells by Functional Mimicry of IL-10.

Plasmacytoid dendritic cells (pDCs) are the major producers of IFN-α, an antiviral cytokine involved in immunomodulation and control of HIV type 1 replication, whereas is a life-threatening opportunistic infection in AIDS patients. During infection with HIV type 1, human pDCs decrease in circulation and remaining pDC produce lower amounts of IFN-α in response to viral stimulation. In this study, we investigated the impact of coinfection with on the innate virus-directed responses of human pDCs. Using intracellular flow cytometry and fluorescence microscopy, we determined that invaded but did not induce IFN-α or TNF-α in human pDC. However, inhibited IFN-α and TNF-α produced in response to HSV and HIV, thus functionally inactivating pDC. IFN-α production was inhibited only in cells infected by , which inhibited neither uptake of GFP-HSV nor localization of TLR9 in CD71 endosomes, directing us to investigate downstream events. Using imaging flow cytometry, we found that both and IL-10 inhibited virus-induced nuclear translocation, but not phosphorylation, of IFN response factor 7. Blockade of IFN response factor 7 nuclear translocation and inhibition of the IFN-α response was partially reversed by a deficiency in the -derived ROP16 kinase, known to directly phosphorylate STAT3, a critical mediator of IL-10's anti-inflammatory effects. Taken together, our results indicate that suppresses pDC activation by mimicking IL-10's regulatory effects through an ROP16 kinase-dependent mechanism. Our findings further imply a convergent mechanism of inhibition of TLR signaling by and IL-10 and suggest potential negative consequences of HIV/ coinfection.