The function of interleukin 37 (formerly IL-1 family member 7) remains elusive. Expression of IL-37 in macrophages or epithelial cells imparted near complete suppression of pro-inflammatory cytokines, whereas the abundance of these cytokines increased with silencing of endogenous IL-37 in human blood cells. Anti-inflammatory cytokines remained unchanged under similar conditions. IL-37-transgenic mice were protected from lipopolysaccharide-induced shock, exhibiting markedly improved lung and kidney function and reduced liver damage. IL-37-transgenic mice had less circulating and tissue cytokines (72-95% lower) than wild-type mice and exhibited less dendritic cell activation. IL-37 interacted intracellularly with Smad3 and IL-37-expressing cells and transgenic mice exhibited less cytokine suppression when endogenous Smad3 was depleted. IL-37 thus emerges as a natural suppressor of innate inflammatory and immune responses.

Summary Understanding gut microbiota alterations associated with HIV-infection and factors that drive these alterations may help explain gut-linked diseases prevalent with HIV. 16S rRNA sequencing of feces from HIV infected individuals revealed that HIV infection is associated with highly characteristic gut community changes and antiretroviral therapy does not consistently restore the microbiota to an HIV-negative state. Despite the chronic gut inflammation characteristic of HIV infection, the associated microbiota showed limited similarity with other inflammatory states and instead showed increased, rather than decreased, diversity. Metaanalysis revealed that the microbiota of HIV-infected individuals in the US was most similar to a Prevotella-rich community composition typically observed in healthy individuals in agrarian cultures of Malawi and Venezuela and related to that of US individuals with carbohydrate-rich/ protein- and fat-poor diets. By evaluating innate and adaptive immune responses to lysates from bacteria that differ with HIV, we explore the functional drivers of these compositional differences.

A number of emerging molecules and pathways have been implicated in mediating the T-cell exhaustion characteristic of chronic viral infection. Not all dysfunctional T cells express PD-1, nor are they all rescued by blockade of the PD-1/PD-1 ligand pathway. In this study, we characterize the expression of T-cell immunoglobulin and mucin domain-containing protein 3 (Tim-3) in chronic hepatitis C infection. For the first time, we found that Tim-3 expression is increased on CD4 ؉ and CD8 ؉ T cells in chronic hepatitis C virus (HCV) infection. The proportion of dually PD-1/Tim-3-expressing cells is greatest in liver-resident T cells, significantly more so in HCV-specific than in cytomegalovirus-specific cytotoxic T lymphocytes. Tim-3 expression correlates with a dysfunctional and senescent phenotype (CD127 low CD57 high ), a central rather than effector memory profile (CD45RA negative CCR7 high ), and reduced Th1/Tc1 cytokine production. We also demonstrate the ability to enhance T-cell proliferation and gamma interferon production in response to HCV-specific antigens by blocking the Tim-3-Tim-3 ligand interaction. These findings have implications for the development of novel immunotherapeutic approaches to this common viral infection.Hepatitis C virus (HCV) is a major causative agent of chronic hepatitis, affecting approximately 200 million people throughout the world; the majority of individuals exposed to HCV become persistently infected (19). A broad array of functional impairments of virus-specific T cells from early to chronic stages of infection, including exhaustion (decreased antiviral cytokine production, cytotoxicity, and proliferative capacity) (8, 24) and arrested stages of differentiation (1, 13), is supported by considerable evidence. Recently, upregulation of programmed death 1 (PD-1) and downmodulation of CD127 (interleukin-7 [IL-7] receptor) have been linked to functional exhaustion of T cells in chronic HCV infection (5-7, 15, 21, 22). However, not all exhausted T cells express these phenotypic changes, and blockade of the PD-1/PD-L1 signaling pathway does not always reconstitute Th1/Tc1 cytokine production (4, 5), indicating that other molecules may contribute to the exhaustion typically associated with chronic viral infections (9). One such molecule is Tim-3 (T-cell immunoglobulin and mucin domain-containing molecule 3), a membrane protein initially identified on terminally differentiated Th1 but not Th2 cells in mice (9). A recent analysis of human immunodeficiency virus (HIV) infection demonstrates that Tim-3 is upregulated on both CD4 ϩ and CD8 ϩ T cells from patients with chronic infection relative to uninfected individuals and that virus-specific cells expressing high levels of Tim-3 secrete less IFN-␥ than do Tim-3-negative cells (10). In light of these findings, for the first time, this study assessed the expression of Tim-3 in chronic HCV infection. We found a higher frequency of Tim3-expressing CD4 ϩ and CD8 ϩ T cells in chronic HCV infection, with the highest on HCV-specific cytotoxic T...