Type I interferon signaling attenuates regulatory T cell function in viral infection and in the tumor microenvironment. Type I interferon signaling attenuates regulatory T cell function in viral infection and in the tumor microenvironment

Regulatory T cells (Tregs) play a cardinal role in the immune system by suppressing detrimental autoimmune responses, but their role in acute/chronic infectious diseases and in the tumor microenvironment remains unclear. We recently demonstrated that IFN-a/b receptor (IFNAR) signaling promotes Treg function in autoimmunity. Here, we dissected the functional role of IFNAR-signaling in Tregs using Treg-specific IFNAR deficient (IFNARfl/flxFoxp3YFP-Cre) mice in acute LCMV Armstrong, chronic LCMV Clone-13 infection, and in a transplantable colon adenocarcinoma model. In both viral and tumor models, IFNARfl/flxFoxp3YFP-Cre mice Tregs expressed enhanced Treg associated activation antigens. The enhanced activated phenotype was also seen when we compared the transcriptomes of IFNARfl/flxFoxp3YFP-Cre mice Tregs with the wild type (WT) Tregs by RNA-Seq on day 5 Armstrong and day 25-post Clone-13 infection. LCMV-specific CD8+ T cells and tumor infiltrating lymphocytes from IFNARfl/flxFoxp3YFP-Cre mice produced less antiviral and antitumor IFN-g and TNF-a. In the chronic infection model, the numbers of antiviral effector and memory CD8+ T cells were decreased in IFNARfl/flxFoxp3YFP-Cre mice and the effector CD4+ and CD8+ T cells exhibited a phenotype compatible with enhanced exhaustion. IFNARfl/flxFoxp3YFP-Cre mice cleared Armstrong infection normally, but had higher viral titers in sera, kidneys and lungs during chronic infection, and a higher tumor burden than the WT controls. Thus, type I IFN signaling in Tregs is context-dependent, resulting in enhanced suppressor function in some models of autoimmunity, but decreased suppressor function in acute/chronic viral infection and in the tumor microenvironment. Overall design: mRNA from Treg cells from 4 WT and 4 IFNAR deficient mice were analyzed by RNA-seq using Illumina HiSeq 5 days post LCM Armstrong infection.