Type I IFN induces IL-10 production in an IL-27-independent manner and blocks responsiveness to IFN-gamma for production of IL-12 and bacterial killing in Mycobacterium tuberculosis-infected macrophages

Tuberculosis, caused by the intracellular bacterium Mycobacterium tuberculosis, currently causes ~1.4 million deaths per year, and it therefore remains a leading global health problem. The immune response during tuberculosis remains incompletely understood, particularly regarding immune factors that are harmful rather than protective to the host. Overproduction of the type I IFN family of cytokines is associated with exacerbated tuberculosis in both mouse models and in humans, although the mechanisms by which type I IFN promotes disease are not well understood. We have investigated the effect of type I IFN on M. tuberculosis-infected macrophages and found that production of host-protective cytokines such as TNF-a, IL-12, and IL-1ß is inhibited by exogenous type I IFN, whereas production of immunosuppressive IL-10 is promoted in an IL-27-independent manner. Furthermore, much of the ability of type I IFN to inhibit cytokine production was mediated by IL-10. Additionally, type I IFN compromised macrophage activation by the lymphoid immune response through severely disrupting responsiveness to IFN-?, including M. tuberculosis killing. These findings describe important mechanisms by which type I IFN inhibits the immune response during tuberculosis.This work was funded by Medical Research Council, U.K. Grant U117565642 and European Research Council Grant 294682-TB-PATH. M.S. and L.M.-T. were funded by the Fundacao para a Ciencia e Tecnologia, Portugal. M.S. is a Fundacao para a Ciencia e Tecnologia, Portugal investigator. L.M.T. was supported by Fundacao para a Ciencia e Tecnologia, Portugal Grant SFRH/BPD/77399/2011

Programmed death ligand 1 is over-expressed by neutrophils in the blood of patients with active tuberculosis

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), remains one of the world's largest infectious disease problems. Despite decades of intensive study, the immune response to Mtb is incompletely characterised, reflecting the extremely complex interaction between pathogen and host. Pathways that may alter the balance between host protection and pathogenesis are therefore of great interest. One pathway shown to play a role in the pathogenesis of chronic infections, including TB, is the programmed death-1 (PD-1) pathway. We show here that the expression of the programmed death ligand 1 (PD-L1), which interacts with PD-1, is increased in whole blood from active TB patients compared with whole blood from healthy controls or Mtb-exposed individuals, and that expression by neutrophils is largely responsible for this increase

Type I IFN inhibits alternative macrophage activation during mycobacterium tuberculosis infection and leads to enhanced protection in the absence of IFN-gamma signaling

Supplementary material: http://www.jimmunol.org/content/suppl/2016/11/12/jimmunol.1600584.DCSupplementalTuberculosis causes ∼1.5 million deaths every year, thus remaining a leading cause of death from infectious diseases in the world. A growing body of evidence demonstrates that type I IFN plays a detrimental role in tuberculosis pathogenesis, likely by interfering with IFN-γ–dependent immunity. In this article, we reveal a novel mechanism by which type I IFN may confer protection against Mycobacterium tuberculosis infection in the absence of IFN-γ signaling. We show that production of type I IFN by M. tuberculosis–infected macrophages induced NO synthase 2 and inhibited arginase 1 gene expression. In vivo, absence of both type I and type II IFN receptors led to strikingly increased levels of arginase 1 gene expression and protein activity in infected lungs, characteristic of alternatively activated macrophages. This correlated with increased lung bacterial burden and pathology and decreased survival compared with mice deficient in either receptor. Increased expression of other genes associated with alternatively activated macrophages, as well as increased expression of Th2-associated cytokines and decreased TNF expression, were also observed. Thus, in the absence of IFN-γ signaling, type I IFN suppressed the switching of macrophages from a more protective classically activated phenotype to a more permissive alternatively activated phenotype. Together, our data support a model in which suppression of alternative macrophage activation by type I IFN during M. tuberculosis infection, in the absence of IFN-γ signaling, contributes to host protection.This work was supported by the Fundação para a Ciência e Tecnologia, Portugal, cofunded by Programa Operacional Regional do Norte (ON.2 – O Novo Norte), Quadro de Referência Estratégico Nacional, through the Fundo Europeu de Desenvolvimento Regional (PTDC/SAU-MII/101977/2008 and PTDC/BIA-BCM/102776/2008); by the Francis Crick Institute, which receives its core funding from Cancer Research U.K. (FC001126), the U.K. Medical Research Council (FC001126), and the Wellcome Trust (FC001126); by the U.K. Medical Research Council (MR/U117565642/1); and by the European Research Council (294682-TB-PATH). This work was also supported by Research Grant 2015 from the European Society of Clinical Microbiology and Infectious Diseases (to M.S.). L.M.-T. was funded by the Fundação para a Ciência e Tecnologia (SFRH/BPD/77399/2011) and the European Research Council (294682-TB-PATH). The M.S. laboratory was financed by Fundo Europeu de Desenvolvimento Regional (FEDER) funds through the COMPETE 2020-Operacional Programme for Competitiveness and Internationalisation (POCI), Portugal 2020, and by Portuguese funds through Fundação para a Ciência e Tecnologia, Portugal, in the framework of the Institute for Research and Innovation in Health Sciences project (POCI-01-0145-FEDER-007274). M.S. is a Fundação para a Ciência e Tecnologia Associate Investigator. E.T. is a Fundação para a Ciência e Tecnologia Auxiliary Investigator

An interferon-inducible neutrophil-driven blood transcriptional signature in human tuberculosis

Tuberculosis (TB), caused by infection with Mycobacterium tuberculosis (M. tuberculosis), is a major cause of morbidity and mortality worldwide and efforts to control TB are hampered by difficulties with diagnosis, prevention and treatment 1,2. Most people infected with M. tuberculosis remain asymptomatic, termed latent TB, with a 10% lifetime risk of developing active TB disease, but current tests cannot identify which individuals will develop disease 3. The immune response to M. tuberculosis is complex and incompletely characterized, hindering development of new diagnostics, therapies and vaccines 4,5. We identified a whole blood 393 transcript signature for active TB in intermediate and high burden settings, correlating with radiological extent of disease and reverting to that of healthy controls following treatment. A subset of latent TB patients had signatures similar to those in active TB patients. We also identified a specific 86-transcript signature that discriminated active TB from other inflammatory and infectious diseases. Modular and pathway analysis revealed that the TB signature was dominated by a neutrophil-driven interferon (IFN)-inducible gene profile, consisting of both IFN-γ and Type I IFNαβ signalling. Comparison with transcriptional signatures in purified cells and flow cytometric analysis, suggest that this TB signature reflects both changes in cellular composition and altered gene expression. Although an IFN signature was also observed in whole blood of patients with Systemic Lupus Erythematosus (SLE), their complete modular signature differed from TB with increased abundance of plasma cell transcripts. Our studies demonstrate a hitherto under-appreciated role of Type I IFNαβ signalling in TB pathogenesis, which has implications for vaccine and therapeutic development. Our study also provides a broad range of transcriptional biomarkers with potential as diagnostic and prognostic tools to combat the TB epidemic

Systems Biology Approaches Reveal a Specific Interferon-Inducible Signature in HTLV-1 Associated Myelopathy

Human T-lymphotropic virus type 1 (HTLV-1) is a retrovirus that persists lifelong in the host. In ∼4% of infected people, HTLV-1 causes a chronic disabling neuroinflammatory disease known as HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The pathogenesis of HAM/TSP is unknown and treatment remains ineffective. We used gene expression microarrays followed by flow cytometric and functional assays to investigate global changes in blood transcriptional profiles of HTLV-1-infected and seronegative individuals. We found that perturbations of the p53 signaling pathway were a hallmark of HTLV-1 infection. In contrast, a subset of interferon (IFN)-stimulated genes was over-expressed in patients with HAM/TSP but not in asymptomatic HTLV-1 carriers or patients with the clinically similar disease multiple sclerosis. The IFN-inducible signature was present in all circulating leukocytes and its intensity correlated with the clinical severity of HAM/TSP. Leukocytes from patients with HAM/TSP were primed to respond strongly to stimulation with exogenous IFN. However, while type I IFN suppressed expression of the HTLV-1 structural protein Gag it failed to suppress the highly immunogenic viral transcriptional transactivator Tax. We conclude that over-expression of a subset of IFN-stimulated genes in chronic HTLV-1 infection does not constitute an efficient host response but instead contributes to the development of HAM/TSP

No requirement for TRAIL in intrathymic negative selection

The contribution of the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) pathway to intrathymic negative selection is a controversial subject with two studies suggesting a key role for TRAIL, while others demonstrated normal negative selection, in TRAIL- and TRAIL receptor-deficient mice. The basis of these discrepancies is unclear and may in part reflect differences in the negative selection models under investigation. Considering the importance of the negative selection process in the establishment of a competent immune system, it is essential that these discrepancies be fully resolved. In this study, we failed to identify a role for TRAIL in an acute model of peptide antigen-specific negative selection using a TCR transgenic system as well as antibody-mediated TCR/CD3 ligation in vitro and in vivo. Moreover, thymic dendritic cells, the main cellular mediators of negative selection in the thymus, did not constitutively express TRAIL, and TRAIL receptor (DR5) expression was negative or extremely low on thymocytes. Furthermore, in vitro thymocyte deletion was normal in C57BL/ 6 TRAIL gld mice, suggesting that TRAIL and FasL do not function cooperatively to induce negative selection. These results, combined with the fact that aged C57BL/6 TRAIL mice showed no signs of spontaneous autoimmunity, strongly indicate that intrathymic negative selection occurs normally in the absence of TRAIL signaling

Long-term retention of mature NK1.1+ NKT cells in the thymus

The NKT cell pool in the thymus contains immature (NK1.1) and mature (NK1.1) subsets that represent distinct linear stages of a linear developmental pathway. An unexplained paradox is why immature NK1.1 NKT cells are mainly exported to the periphery instead of the more mature and more abundant NK1.1 NKT cells. In this study we have determined that mature NK1.1 NKT cells are retained by the thymus to form an extremely long-lived resident population capable of rapid and prolonged production of IFN-γ and IL-4. The retention of mature NKT cells provides an explanation for why the periphery is mainly seeded by immature NK1.1 cells despite mature NK1.1 NKT cells being more abundant in the thymus. This is the first study to identify a mature T cell subset retained within the thymus and is additional evidence of the distinct developmental pathways of mainstream T cells and NKT cells

Peripheral NK1.1- NKT cells are mature and functionally distinct from their thymic counterparts

One interesting aspect of NKT cell development is that although they are thymus dependent, the pivotal transition from NK1.1 to NK1.1 can often take place after immature NK1.1 NKT cells are exported to the periphery. NK1.1 NKT cells in general are regarded as immature precursors of NK1.1 NKT cells, meaning that peripheral NK1.1 NKT cells are regarded as a transient, semimature population of recent thymic emigrant NKT cells. In this study, we report the unexpected finding that most NK1.1 NKT cells in the periphery of naive mice are actually part of a stable, mature and functionally distinct NKT cell population. Using adult thymectomy, we show that the size of the peripheral NK1.1 NKT cell pool is maintained independently of thymic export and is not the result of NK1.1 down-regulation by mature cells. We also demonstrate that most peripheral NK1.1 NKT cells are functionally distinct from their immature thymic counterparts, and from NK1.1 NKT cells in the periphery. We conclude that the vast majority of peripheral NK1.1 NKT cells are part of a previously unrecognized, mature NKT cell subset

TPL-2-ERK1/2 signaling promotes host resistance against intracellular bacterial infection by negative regulation of type I IFN production

Tuberculosis, caused by Mycobacterium tuberculosis, remains a leading cause of mortality and morbidity worldwide, causing ~1.4 million deaths per year. Key immune components for host protection during tuberculosis include the cytokines IL-12, IL-1, and TNF-a, as well as IFN-? and CD4(+) Th1 cells. However, immune factors determining whether individuals control infection or progress to active tuberculosis are incompletely understood. Excess amounts of type I IFN have been linked to exacerbated disease during tuberculosis in mouse models and to active disease in patients, suggesting tight regulation of this family of cytokines is critical to host resistance. In addition, the immunosuppressive cytokine IL-10 is known to inhibit the immune response to M. tuberculosis in murine models through the negative regulation of key proinflammatory cytokines and the subsequent Th1 response. We show in this study, using a combination of transcriptomic analysis, genetics, and pharmacological inhibitors, that the TPL-2-ERK1/2 signaling pathway is important in mediating host resistance to tuberculosis through negative regulation of type I IFN production. The TPL-2-ERK1/2 signaling pathway regulated production by macrophages of several cytokines important in the immune response to M. tuberculosis as well as regulating induction of a large number of additional genes, many in a type I IFN-dependent manner. In the absence of TPL-2 in vivo, excess type I IFN promoted IL-10 production and exacerbated disease. These findings describe an important regulatory mechanism for controlling tuberculosis and reveal mechanisms by which type I IFN may promote susceptibility to this important disease.This work was supported by Medical Research Council Grants U117584209 (to S. C. L.) and U117565642 (to A.O.G.) and European Research Council Grant 294682-TB-PATH (to A.O.G.). A.O.G. is supported by the Medical Research Council and National Heart and Lung Institute, Faculty of Medicine, Imperial College London. F. W. M. is supported by the Medical Research Council and European Research Council. J.E. is supported by the Medical Research Council