Innate and adaptive effects of inflammasomes on T cell responses

Construction and validation of programmed cell death-based molecular clusters for prognostic and therapeutic significance of clear cell renal cell carcinoma

As the dominant histological subtype of kidney cancer, clear cell renal cell carcinoma (ccRCC) poorly responds to conventional chemotherapy and radiotherapy. Although novel immunotherapies such as immune checkpoint inhibitors could have a durable effect in treating ccRCC patients, the limited availability of dependable biomarkers has restricted their application in clinic. In the study of carcinogenesis and cancer therapies, there has been a recent emphasis on researching programmed cell death (PCD). In the current study, we discovered the enriched and prognostic PCD in ccRCC utilizing gene set enrichment analysis (GSEA) and investigate the functional status of ccRCC patients with different PCD risks. Then, genes related to PCD that had prognostic value in ccRCC were identified for the conduction of non-negative matrix factorization to cluster ccRCC patients. Next, the tumor microenvironment, immunogenicity, and therapeutic response in different molecular clusters were analyzed. Among PCD, apoptosis and pyroptosis were enriched in ccRCC and correlated with prognosis. Patients with high PCD levels were related to poor prognosis and a rich but suppressive immune microenvironment. PCD-based molecular clusters were identified to differentiate the clinical status and prognosis of ccRCC. Moreover, the molecular cluster with high PCD levels may correlate with high immunogenicity and a favorable therapeutic response to ccRCC. Furthermore, a simplified PCD-based gene classifier was established to facilitate clinical application and used transcriptome sequencing data from clinical ccRCC samples to validate the applicability of the gene classifier. We thoroughly extended the understanding of PCD in ccRCC and constructed a PCD-based gene classifier for differentiation of the prognosis and therapeutic efficacy in ccRCC.

NLRP3 Inflammasome Contributes to Host Defense Against Talaromyces marneffei Infection

Talaromyce marneffei is an important thermally dimorphic pathogen causing disseminated mycoses in immunocompromised individuals in southeast Asia. Previous studies have suggested that NLRP3 inflammasome plays a critical role in antifungal immunity. However, the mechanism underlying the role of NLRP3 inflammasome activation in host defense against T. marneffei remains unclear. We show that T. marneffei yeasts but not conidia induce potent IL-1β production. The IL-1β response to T. marneffei yeasts is differently regulated in different cell types; T. marneffei yeasts alone are able to induce IL-1β production in human PBMCs and monocytes, whereas LPS priming is essential for IL-1β response to yeasts. We also find that Dectin-1/Syk signaling pathway mediates pro-IL-1β production, and NLRP3-ASC-caspase-1 inflammasome is assembled to trigger the processing of pro-IL-1β into IL-1β. In vivo, mice deficient in NLRP3 or caspase-1 exhibit higher mortality rate and fungal load compared to wild-type mice after systemic T. marneffei infection, which correlates with the diminished recruitment of CD4 T cells into granulomas in knockout mice. Thus, our study first demonstrates that NLRP3 inflammasome contributes to host defense against T. marneffei infection.

Interleukin-1 Links Autoimmune and Autoinflammatory Pathophysiology in Mixed-Pattern Psoriasis

Autoinflammatory and autoimmune diseases are characterized by an oversensitive immune system with loss of the physiological endogenous regulation, involving multifactorial self-reactive pathological mechanisms of mono- or polygenic nature. Failure in regulatory mechanisms triggers a complex network of dynamic relationships between innate and adaptive immunity, leading to coexistent autoinflammatory and autoimmune processes. Sustained exposure to a trigger or a genetic alteration at the level of the receptors of the natural immune system may lead to abnormal activation of the innate immune system, adaptive system activation, loss of self-tolerance, and systemic inflammation. The IL-1 family members critically activate and regulate innate and adaptive immune responses' diversity and plasticity in autoimmune and/or autoinflammatory conditions. The IL-23/IL-17 axis is key in the communication between innate immunity (IL-23-producing myeloid cells) and adaptive immunity (Th17- and IL-17-expressing CD8+ T cells). In psoriasis, these cytokines are decisive to the different clinical presentations, whether as plaque psoriasis (psoriasis vulgaris), generalized pustular psoriasis (pustular psoriasis), or mixed forms. These forms reflect a gradient between autoimmune pathophysiology with predominant adaptive immune response and autoinflammatory pathophysiology with predominant innate immune response.

A Network Pharmacology Approach to Identify Potential Molecular Targets for Cannabidiol's Anti-Inflammatory Activity

Introduction: Published preclinical and clinical studies support the anti-inflammatory activity of CBD, but the molecular targets (e.g., genes and proteins) that are involved in its mechanisms of action remain unclear. Herein, a network-based pharmacology analysis was performed to aid in the identification of potential molecular targets for CBD's anti-inflammatory activity. Materials and Methods: Target genes and proteins were obtained from several online databases, including Swiss target prediction, Online Mendelian Inheritance in Man, and the DrugBank database. A compound-target-disease network was constructed with Cytoscape tool, and a network of protein-protein interactions was established with the Search Tool for the Retrieval of Interacting Genes/Proteins database. Lead proteins identified from the compound-target-disease network were further studied for their interactions with CBD by computational docking. In addition, biological pathways involved in CBD's anti-inflammatory activity were identified with the Gene Ontology enrichment and the Kyoto Encyclopedia of Genes and Genomes analysis. Results: A panel of proteins, including cellular tumor antigen p53, NF-kappa-B essential modulator, tumor necrosis factor (TNF) receptor, transcription factor p65, NF-kappa-B p105, NF-kappa-B inhibitor alpha, inhibitor of nuclear factor kappa-B kinase subunit alpha, and epidermal growth factor receptor, were identified as lead targets involved in CBD's anti-inflammatory activity. This finding was further supported by molecular docking, which showed interactions between the lead proteins and CBD. In addition, several signaling pathways, including TNF, toll-like receptor, mitogen-activated protein kinases, nuclear factor kappa-light-chain-enhancer of activated B cells, and nucleotide-binding oligomerization domain-like receptors, were identified as key regulators in the mediation of CBD's anti-inflammatory activity. Conclusion: A network-based pharmacology analysis identified potential molecular targets and signaling pathways for CBD's anti-inflammatory activity. Findings from this study add to the growing body of data supporting the utilization of CBD as a promising anti-inflammatory natural product.

Suppression of Inflammasome Activation by IRF8 and IRF4 in cDCs Is Critical for T Cell Priming

Inflammasome activation leads to pyroptotic cell death, thereby eliminating the replicative niche of virulent pathogens. Although inflammasome-associated cytokines IL-1β and IL-18 have an established role in T cell function, whether inflammasome activation in dendritic cells (DCs) is critical for T cell priming is not clear. Here, we find that conventional DCs (cDCs) suppress inflammasome activation to prevent pyroptotic cell death, thus preserving their ability to prime both CD4 and CD8 T cells. Transcription factors IRF8 and IRF4, in cDC1s and cDC2s, respectively, mediate suppression of inflammasome activation by limiting the expression of inflammasome-associated genes. Overexpression of IRF4 or IRF8 inhibits inflammasome activation in macrophages, while reduced expression of IRF8 leads to aberrant inflammasome activation in cDC1s and hampers their ability to prime CD8 T cells. Thus, activation of inflammasome in DCs is detrimental to adaptive immunity, and our results reveal that cDCs use IRF4 and IRF8 to suppress this response.

The role of inflammasome activation in eliciting adaptive immune responses against pathogens is poorly understood. McDaniel et al. demonstrate that conventional dendritic cells use IRF4 and IRF8 to suppress the transcription of inflammasome-associated machinery. This resulting suppression of inflammasome activation allows DCs to prime T cell responses against virulent pathogens.

Inflammasomes and adaptive immune responses

A fundamental concept in immunology is that the innate immune system initiates or instructs downstream adaptive immune responses. Inflammasomes are central players in innate immunity to pathogens, but how inflammasomes shape adaptive immunity is complex and relatively poorly understood. Here we highlight recent work on the interplay between inflammasomes and adaptive immunity. We address how inflammasome-dependent release of cytokines and antigen activates, shapes or even inhibits adaptive immune responses. We consider how distinct tissue or cellular contexts may alter the effects of inflammasome activation on adaptive immunity and how this contributes to beneficial or detrimental outcomes in infectious diseases, cancer and autoimmunity. We aspire to provide a framework for thinking about inflammasomes and their connection to the adaptive immune response.

Primary Immunodeficiency and Thrombocytopenia

Primary immunodeficiency (PID) or Inborn errors of immunity (IEI) refers to a heterogeneous group of disorders characterized by immune system impairment. Although patients with IEI manifest highly variable symptoms, the most common clinical manifestations are recurrent infections, autoimmunity and malignancies. Some patients present hematological abnormality including thrombocytopenia due to different pathogenic mechanisms. This review focuses on primary and secondary thrombocytopenia as a complication, which can occur in IEI. Based on the International Union of Immunological Societies phenotypic classification for IEI, the several innate and adaptive immunodeficiency disorders can lead to thrombocytopenia. This review, for the first time, describes manifestation, mechanism and therapeutic modalities for thrombocytopenia in different classes of IEI.

Enhanced production of pro-inflammatory cytokines and chemokines in Ethiopian cutaneous leishmaniasis upon exposure to Leishmania aethiopica

The clinical course and outcome of cutaneous leishmaniasis (CL) vary due to the infecting Leishmania species and host genetic makeup that result in different immune responses against the parasites. The host immune response to Leishmania aethiopica (L.aethiopica), the causative agent of CL in Ethiopia, is poorly understood. To contribute to the understanding of the protective immune response in CL due to L.aethiopica, we characterized the cytokine response to L. aethiopica in patients with the localized form of CL (LCL) and age-and sex-matched apparently healthy controls. By applying a whole blood based in vitro culture we found enhanced release of TNF, IL-6, MCP-1 or CCL2, IP-10 or CXCL10, MIP-1β or CCL4 and IL-8 or CXCL8- but not of IL-10CL patients in response to L. aethiopica compared to the controls. No difference was observed between LCL cases and controls in the secretion of these cytokines and chemokines in whole blood cultures treated with the TLR-ligands LPS, MALP-2 or polyI: C. The observed increased secretion of the pro-inflammatory cytokines/chemokines reflects an enhanced response against the parasites by LCL patients as compared to healthy controls rather than a generally enhanced ability of blood leukocytes from LCL patients to respond to microbial constituents. Our findings suggest that the enhanced production of pro-inflammatory cytokines/chemokines is associated with localized cutaneous leishmaniasis caused by L.aethiopica.

Impact of Heat-Killed Lactobacillus casei Strain IMAU60214 on the Immune Function of Macrophages in Malnourished Children

Malnutrition is commonly associated with immunological deregulation, increasing the risk of infectious illness and death. The objective of this work was to determine the in vitro effects of heat-killed Lactobacillus casei IMAU60214 on monocyte-derived macrophages (MDMs) from well-nourished healthy children, well-nourished infected children and malnourished infected children, which was evaluated by an oxygen-dependent microbicidal mechanism assay of luminol-increase chemiluminescence and the secretion of tumor necrosis factor (TNF-α), interleukin (IL-1β), IL-6 and IL-10, as well as phagocytosis using zymosan and as its antibacterial activity against Salmonella typhimurium, Escherichia coli and Staphylococcus aureus. We found that reactive oxygen species (ROS), secretion cytokines (TNFα, IL-1β, IL-6 and IL-10 levels), phagocytosis and bactericidal capacity increased in all groups after pre-treatment with heat-killed L. casei IMAU60214 at a ratio of 500:1 (bacteria:MDM) over 24 h compared with MDM cells without pre-treatment. The results could indicate that heat-killed L. casei IMAU60214 is a potential candidate for regulating the immune function of macrophages.

Cellular Stress and General Pathological Processes

From the viewpoint of the general pathology, most of the human diseases are associated with a limited number of pathogenic processes such as inflammation, tumor growth, thrombosis, necrosis, fibrosis, atrophy, pathological hypertrophy, dysplasia and metaplasia. The phenomenon of chronic low-grade inflammation could be attributed to non-classical forms of inflammation, which include many neurodegenerative processes, pathological variants of insulin resistance, atherosclerosis, and other manifestations of the endothelial dysfunction. Individual and universal manifestations of cellular stress could be considered as a basic element of all these pathologies, which has both physiological and pathophysiological significance. The review examines the causes, main phenomena, developmental directions and outcomes of cellular stress using a phylogenetically conservative set of genes and their activation pathways, as well as tissue stress and its role in inflammatory and para-inflammatory processes. The main ways towards the realization of cellular stress and its functional blocks were outlined. The main stages of tissue stress and the classification of its typical manifestations, as well as its participation in the development of the classical and non-classical variants of the inflammatory process, were also described. The mechanisms of cellular and tissue stress are structured into the complex systems, which include networks that enable the exchange of information with multidirectional signaling pathways which together make these systems internally contradictory, and the result of their effects is often unpredictable. However, the possible solutions require new theoretical and methodological approaches, one of which includes the transition to integral criteria, which plausibly reflect the holistic image of these processes.

Inflammasome in HIV infection: Lights and shadows

The importance of inflammasome, and related cytokines IL-1ß and IL-18, in host defense against pathogens is well documented, however, at the same time, dysregulation of inflammasome has been associated to multifactorial diseases characterized by chronic inflammation (i.e.: metabolic disorders, cardiovascular diseases, neurodegenerative diseases, autoimmunity, cancer). Inflammasome activation has been described in response to HIV-1 and possibly contributes to the resistance against virus establishment, however, on the other hand, when viral infection becomes chronic, independently from antiretroviral therapy, the increase constitutive activation of inflammasome has been eventually associated to a worse prognosis, raising the question about the role played by inflammasome and/or some specific receptors in this context. Due to the chance to imply targeted therapies that inhibit inflammasome activation and/or cytokines release, it will be important to define the impact of the complex in the pathogenesis of HIV. The purpose of this review is to depict the double-faced inflammasome role in HIV-1 infection, trying to unveil whether besides its role in first line defense against the virus, it exerts a harmful effect during the chronic phase of infection.

Impact of neonatal malnutrition on expression TLR-9, NF-kB and cytokines of macrophages infected in vitro with methicillin resistant Staphylococcus aureus

Early nutritional aggressions promote epigenetic adjustments that culminate in the loss of phenotype plasticity (with permanent long-term modifications). Maternal diet and inadequate neonatal nutrition can result in fetal programming that presents susceptibility to infections in adult life. Thus, it becomes essential to verify the impacts of neonatal malnutrition (even following nutritional replacement) on the immunological response to methicillin resistant Staphylococcus aureus (MRSA) infections. Male rats were divided into two distinct groups: Nourished and Malnourished. After isolation of mononuclear cells, four systems were established: negative control, positive control and two testing systems, (MSSA and MRSA). Tests were performed to analyze expression of TLR-9, NF-kB, IL-1β, IL-18 and IL-33. For statistical analysis, we used the Student t and ANOVA tests p < 0.05. Even after nutritional replacement, malnutrition in the neonatal period compromised the animals' weight gains p < 0.05. There was a reduction in the expression of the immunological response in the positive control, however deregulation was observed in the gene expression of MRSA-infected macrophages, with a reduction in TLR-9 expression, and overexpression in NF-kB and cytokines p < 0.05. Puppies inflicted with protein-calorie malnutrition were compromised; (long-term) body growth and immune response. In the infectious scenario, immune collapse is reflected in inflammatory response exacerbation with a likely histolytic character. Immune disabling (resulting from gene expression deregulation) causes susceptibility to infections due to ineffective recognition, intense pro-inflammatory mediation, and cell death. It is suggested that neonatal malnutrition can program susceptibility to multiresistant bacterial infections, and generally favors a triggering of more intense confrontations with fatal outcomes.

Therapeutic HIV-1 vaccine: time for immunomodulation and combinatorial strategies

PURPOSE OF REVIEW

The purpose is to recall some of the key immunological elements that are at the crossroad and need to be combined for developing a potent therapeutic HIV-1 vaccine.

RECENT FINDINGS

Therapeutic vaccines and cytokines have been commonly used to enhance and/or recall preexisting HIV-1 specific cell-mediated immune responses aiming to suppress virus replication. While the vaccine is important to stimulate HIV-1 specific T-cell responses, the cytokine may support the expansion of the stimulated virus-specific T cells. Moreover, the current success of immune checkpoint blockers in cancer therapy render them very attractive to use in HIV-1 infected individuals, with the objective to preserve the function of HIV-specific T cells from exhaustion and target directly HIV-1 cell reservoir. More recently, the development of passive immunotherapy using broad neutralizing HIV antibodies (bNAbs) and their potential capacity to elicit innate or adaptive HIV-cellular responses, beyond their neutralizing activity, offers a new opportunity to improve the efficiency of therapeutic vaccine. These major advances provide the scientific basis for developing potent combinatorial interventions in HIV-1 infected patients.

SUMMARY

Major advances in our immunological understanding resulting from basic science and clinical trials studies have paved the way and established a solid platform to jump over the stumbling blocks that prevent the field from developing a therapeutic HIV-1 vaccine. It is time for immuno-modulation and combinatorial strategies towards HIV-1 eradication.

Osteopontin in the host response to Leishmania amazonensis

BACKGROUND

Leishmania (L.) spp are intracellular eukaryotic parasites responsible for cutaneous or visceral leishmaniasis, replicating predominantly in macrophages (MF). In C57BL/6 mice virulence with L. amazonensis has been associated with inhibition of Th1 immune responses and an uncontrolled lesion development, whereas DBA/2 mice control any lesion. Parasitic clearance by the MFs requires the activation of proper immune responses. One of the immune related genes expressed in immune cells including MF, codes for osteopontin (OPN). OPN is a secreted glycoprotein, acting as an immune regulator. Its implication in promoting Th1 immunity in response to infectious microorganisms and its known protective effect against viral and bacterial infections via activation of the immune response, render OPN a molecule of interest in the study of the host response to L. amazonensis.

RESULTS

We examined the host response to L. amazonensis of opn mutant and wild type C57BL/6 mice. Bone marrow derived MFs were infected with the parasites in vitro, and opn mutant and wild type mice were inoculated in vivo by intradermal injection in the ears. The DBA/2 strain known to control L. amazonensis infection was also used for comparison. Our data indicate that the parasites increased opn gene expression and OPN protein while parasitic proliferation was contained in the presence of OPN. In the presence of parasites the expression of inflammation-related transcripts was inhibited. Interleukin-1-beta (IL-1β), and transcripts of the NLR-family (NLRC4, NLRP3) were down regulated after L. amazonensis infection. In the absence of OPN, the inhibition by the parasites of IL-1β transcripts was less efficient and a pyroptosis-like cell phenotype was detected in vitro, suggesting a central role of OPN in the host-response to L. amazonensis. Similarly, in vivo, in the absence of OPN, while the clinical inflammatory phenotype is more severe, an increase of these transcripts was observed.

CONCLUSIONS

L. amazonensis infection induces opn gene expression and protein, which in turn participates in shaping the host response to the parasites, seemingly by decreasing the activation of inflammation. OPN, further evaluated as a target for Leishmaniasis control represents an additional interest in improving vaccination strategies against the parasites.

The inflammasome as a target for pain therapy

The interleukin-1 family of cytokines are potent inducers of inflammation and pain. Proteolytic activation of this family of cytokines is under the control of several innate immune receptors that coordinate to form large multiprotein signalling platforms, termed inflammasomes. Recent evidence suggests that a wide range of inflammatory diseases, cancers, and metabolic and autoimmune disorders, in which pain is a common complaint, may be coordinated by inflammasomes. Activation of inflammasomes results in cleavage of caspase-1, which subsequently induces downstream initiation of several potent pro-inflammatory cascades. Therefore, it has been proposed that targeting inflammasome activity may be a novel and effective therapeutic strategy for these pain-related diseases. The purpose of this narrative review article is to provide the reader with an overview of the activation and regulation of inflammasomes and to investigate the potential therapeutic role of inflammasome inhibition in the treatment of diseases characterized by pain, including the following: complex regional pain syndrome, gout, rheumatoid arthritis, inflammatory pain, neuropathic pain, chronic prostatitis, chronic pelvic pain syndrome, and fibromyalgia. We conclude that the role of the inflammasome in pain-associated diseases is likely to be inflammasome subtype and disease specific. The currently available evidence suggests that disease-specific targeting of the assembly and activity of the inflammasome complex may be a novel therapeutic opportunity for the treatment of refractory pain in many settings.

NLRP3 Inflammasome Participates in Host Response to Neospora caninum Infection

Neospora caninum is an intracellular protozoan parasite closely related to Toxoplasma gondii that mainly infects canids as the definitive host and cattle as the intermediate host, resulting in abortion in cattle and leading to financial losses worldwide. Commercial vaccines or drugs are not available for the prevention and treatment of bovine neosporosis. Knowledge about the hallmarks of the immune response to this infection could form the basis of important prevention strategies. The innate immune system first responds to invading parasite and subsequently initiates the appropriate adaptive immune response against this parasite. Upon infection, activation of host pattern-recognition receptors expressed by immune cells triggers the innate immune response. Toll-like receptors, NOD-like receptors, and C-type lectin receptors play key roles in recognizing protozoan parasite. Therefore, we aimed to explore the role of the NLRP3 inflammasome during the acute period of N. caninum infection. In vitro results showed that N. caninum infection of murine bone marrow-derived macrophages activated the NLRP3 inflammasome, accompanied by the release of IL-1β and IL-18, cleavage of caspase-1, and induction of cell death. K⁺ efflux induced by N. caninum infection participated in the activation of the inflammasome. Infection of mice deficient in NLRP3, ASC, and caspase-1/11 resulted in decreased production of IL-18 and reduced IFN-γ in serum. Elevated numbers of monocytes/macrophages and neutrophils were found at the initial infection site, but they failed to limit N. caninum replication. These findings suggest that the NLRP3 inflammasome is involved in the host response to N. caninum infection at the acute stage and plays an important role in limiting parasite growth, and it may enhance Th1 response by inducing production of IFN-γ. These findings may help devise protocols for controlling neosporosis.

The intra- and extracellular functions of ASC specks

Inflammasomes are the central signaling hubs of the inflammatory response. They process cytosolic evidence of infection, cell damage, or metabolic disturbances, and elicit a pro-inflammatory response mediated by members of the interleukin-1 family of cytokines and pyroptotoic cell death. On the molecular level, this is accomplished by the sensor-nucleated recruitment and oligomerization of the adapter protein ASC. Once a tunable threshold is reached, cooperative assembly of ASC into linear filaments and their condensation into macromolecular ASC specks promotes an all-or-none response. These structures are highly regulated and provide a unique signaling platform or compartment to control the activity of caspase-1 and likely other effectors. Emerging evidence indicates that ASC specks are also released from inflammasome-activated cells and accumulate in inflamed tissues, where they can continue to mature cytokines or be internalized by surrounding cells to further nucleate ASC specks in their cytosol. Little is known about the mechanisms governing ASC speck release, uptake, and endosomal escape, as well as its contribution to inflammation and disease. Here, we describe the different outcomes of inflammasome activation and discuss the potential function of extracellular ASC specks. We highlight gaps in our understanding of this central process of inflammation, which may have direct consequences on the modulation of host responses and chronic inflammation.

Redox Signaling, Neuroinflammation, and Neurodegeneration

Production of pro-inflammatory and anti-inflammatory cytokines is part of the defense system that mostly microglia and macrophages display to induce normal signaling to counteract the deleterious actions of invading pathogens in the brain. Also, redox activity in the central nervous system (CNS) constitutes an integral part of the metabolic processes needed by cells to exert their normal molecular and biochemical functions. Under normal conditions, the formation of reactive oxygen and nitrogen species, and the following oxidative activity encounter a healthy balance with immunological responses to preserve cell functions in the brain. However, under different pathological conditions, inflammatory responses recruit pro-oxidant signals and vice versa. The aim of this article is to review the basic concepts about the triggering of inflammatory and oxidative responses in the CNS. Recent Advances: Diverse concurrent toxic pathways are described to provide a solid mechanistic scope for considering intervention at the experimental and clinical levels that are aimed at diminishing the harmful actions of these two contributing factors to nerve cell damage. Critical Issues and Future Directions: The main conclusion supports the existence of a narrow cross-talk between pro-inflammatory and oxidative signals that can lead to neuronal damage and subsequent neurodegeneration. Further investigation about critical pathways crosslinking oxidative stress and inflammation will strength our knowlegde on this topic. Antioxid. Redox Signal. 28, 1626-1651.

NLRP3 Inflammasome and Caspase-1/11 Pathway Orchestrate Different Outcomes in the Host Protection Against Trypanosoma cruzi Acute Infection

Infection with protozoan parasite Trypanosoma cruzi results in activation of nucleotide-binding domain and leucine-rich repeat containing receptors (NLRs). NLR activation leads to inflammasome formation, the activation of caspase-1, and the subsequent cleavage of IL-1β and IL-18. Considering that inflammasome activation and IL-1β induction by macrophages are key players for an appropriate T cell response, we investigated the relevance of NLR pyrin domain-containing 3 (NLRP3) and caspase-1/11 to elucidate their roles in the induction of different T cell phenotypes and the relationship with parasite load and hepatic inflammation during T. cruzi-Tulahuen strain acute infection. We demonstrated that infected nlrp3-/- and C57BL/6 wild type (WT) mice exhibited similar parasitemia and survival, although the parasite load was higher in the livers of nlrp3-/- mice than in those of WT mice. Increased levels of transaminases and pro-inflammatory cytokines were found in the plasma of WT and nlrp3-/- mice indicating that NLRP3 is dispensable to control the parasitemia but it is required for a better clearance of parasites in the liver. Importantly, we have found that NLRP3 and caspase-1/11-deficient mice differentially modulate T helper (Th1, Th2, and Th17) and cytotoxic T lymphocyte phenotypes. Strikingly, caspase-1/11-/- mice showed the most dramatic reduction in the number of IFN-γ- and IL-17-producing CD4+ and CD8+ T cells associated with higher parasitemia and lower survival. Additionally, caspase-1/11-/- mice demonstrated significantly reduced liver inflammation with the lowest alanine aminotransferase (ALT) levels but the highest hepatic parasitic load. These results unequivocally demonstrate that caspase-1/11 pathway plays an important role in the induction of liver adaptive immunity against this parasite infection as well as in hepatic inflammation.

Priming and Activation of Inflammasome by Canarypox Virus Vector ALVAC via the cGAS/IFI16-STING-Type I IFN Pathway and AIM2 Sensor

Viral vectors derived from different virus families, including poxvirus (canarypox virus vector ALVAC) and adenovirus (human Ad5 vector), have been widely used in vaccine development for a range of human diseases including HIV/AIDS. Less is known about the mechanisms underlying the host innate response to these vectors. Increasing evidence from clinical vaccine trials testing different viral vectors has suggested the importance of understanding basic elements of host-viral vector interactions. In this study, we investigated the innate interactions of APCs with two commonly used HIV vaccine vectors, ALVAC and Ad5, and identified AIM2 as an innate sensor for ALVAC, triggering strong inflammasome activation in both human and mouse APCs. Microarray and comprehensive gene-knockout analyses (CRISPR/Cas9) identified that ALVAC stimulated the cGAS/IFI16-STING-type I IFN pathway to prime AIM2, which was functionally required for ALVAC-induced inflammasome activation. We also provided evidence that, in contrast to ALVAC, the Ad5 vector itself was unable to induce inflammasome activation, which was related to its inability to stimulate the STING-type I IFN pathway and to provide inflammasome-priming signals. In preconditioned APCs, the Ad5 vector could stimulate inflammasome activation through an AIM2-independent mechanism. Therefore, our study identifies the AIM2 inflammasome and cGAS/IFI16-STING-type I IFN pathway as a novel mechanism for host innate immunity to the ALVAC vaccine vector.

NOD-Like Receptor P3 Inflammasome Controls Protective Th1/Th17 Immunity against Pulmonary Paracoccidioidomycosis

The NOD-like receptor P3 (NLRP3) inflammasome is an intracellular multimeric complex that triggers the activation of inflammatory caspases and the maturation of IL-1β and IL-18, important cytokines for the innate immune response against pathogens. The functional NLRP3 inflammasome complex consists of NLRP3, the adaptor protein apoptosis-associated speck-like protein, and caspase-1. Various molecular mechanisms were associated with NLRP3 activation including the presence of extracellular ATP, recognized by the cell surface P2X7 receptor (P2X7R). Several pattern recognition receptors on innate immune cells recognize Paracoccidioides brasiliensis components resulting in diverse responses that influence adaptive immunity and disease outcome. However, the role of NLRP3 inflammasome was scantily investigated in pulmonary paracoccidioidomycosis (PCM), leading us to use an intratracheal (i.t.) model of infection to study the influence of this receptor in anti-fungal immunity and severity of infection. For in vivo studies, C57BL/6 mice deficient for several NLRP3 inflammasome components (Nlrp3^−/−, Casp1/11^−/−, Asc^−/−) as well as deficient for ATP receptor (P2x7r^−/−) were infected via i.t. with P. brasiliensis and several parameters of immunity and disease severity analyzed at the acute and chronic periods of infection. Pulmonary PCM was more severe in Nlrp3^−/−, Casp1/11^−/−, Asc^−/−, and P2x7r^−/− mice as demonstrated by the increased fungal burdens, mortality rates and tissue pathology developed. The more severe disease developed by NLRP3, ASC, and Caspase-1/11 deficient mice was associated with decreased production of IL-1β and IL-18 and reduced inflammatory reactions mediated by PMN leukocytes and activated CD4⁺ and CD8⁺ T cells. The decreased T cell immunity was concomitant with increased expansion of CD4⁺CD25⁺Foxp3 regulatory T (Treg) cells. Characterization of intracellular cytokines showed a persistent reduction of CD4⁺ and CD8⁺ T cells expressing IFN-γ and IL-17 whereas those producing IL-4 and TGF-β appeared in increased frequencies. Histopathological studies showed that all deficient mouse strains developed more severe lesions containing elevated numbers of budding yeast cells resulting in increased mortality rates. Altogether, these findings led us to conclude that the activation of the NLRP3 inflammasome has a crucial role in the immunoprotection against pulmonary PCM by promoting the expansion of Th1/Th17 immunity and reducing the suppressive control mediated by Treg cells.

OM-85 is an immunomodulator of interferon-β production and inflammasome activity

The inflammasome–IL-1 axis and type I interferons (IFNs) have been shown to exert protective effects upon respiratory tract infections. Conversely, IL-1 has also been implicated in inflammatory airway pathologies such as asthma and chronic obstructive pulmonary disease (COPD). OM-85 is a bacterial extract with proved efficacy against COPD and recurrent respiratory tract infections, a cause of co-morbidity in asthmatic patients. We therefore asked whether OM-85 affects the above-mentioned innate immune pathways. Here we show that OM-85 induced interferon-β through the Toll-like receptor adaptors Trif and MyD88 in bone marrow-derived dendritic cells. Moreover, it exerted a dual role on IL-1 production; on the one hand, it upregulated proIL-1β and proIL-1α levels in a MyD88-dependent manner without activating the inflammasome. On the other hand, it repressed IL-1β secretion induced by alum, a well-known NLRP3 activator. In vivo, OM-85 diminished the recruitment of inflammatory cells in response to peritoneal alum challenge. Our findings therefore suggest that OM-85 favors a protective primed state, while dampening inflammasome activation in specific conditions. Taken together, these data bring new insights into the mechanisms of OM-85 action on innate immune pathways and suggest potential explanations for its efficacy in the treatment of virus-induced airway diseases.

Increased expression of NLRP3 inflammasome components and interleukin-18 in patients with bullous pemphigoid

BACKGROUND

Bullous pemphigoid (BP) is the most common blistering autoimmune disease severely affecting older people. The complex interplay between innate and adaptive immunity is critical in the development of BP. Inflammasomes, which lead to cleavage-induced maturation of pro-inflammatory cytokines, have been shown to participate in a variety of autoimmune diseases. However, the role of inflammasomes in BP has not been delineated.

OBJECTIVE

The present work aimed to investigate whether inflammasomes are involved in the pathogenesis and progression of BP.

METHODS

Expressions of inflammasome components at the messenger RNA (mRNA) and protein levels in peripheral blood mononuclear cells (PBMCs) from patients with BP and from healthy controls were investigated by quantitative real-time PCR (qRT-PCR) and western blot, respectively. ELISA was employed to evaluate interleukin (IL)-1β, IL-18, lactate dehydrogenase (LDH), and high-mobility group-1 (HMGB1) levels in the serum and blister fluid of patients with BP. Immunohistochemical staining was used to detect IL-18 expression in the skin lesion of patients with BP.

RESULTS

The mRNA levels of NLRP3 inflammasome components (NLRP3, pro-caspase-1, and pro-IL-18) in PBMCs were significantly up-regulated in BP patients compared with those in healthy controls, and were positively correlated with the autoantibody titers for BP180-NC16A. Western Blot analysis showed that the baseline expressions of NLRP3 inflammasome components were increased in PBMCs of BP patients compared with healthy controls, and we failed to observe the mature IL-1β and IL-18. Further analysis showed that IL-18 was elevated in serum, blister fluid and lesional skin from patients with BP, and the serum IL-18 level was positively correlated with the titers of anti-BP180-NC16A autoantibody in BP patient. Most importantly, we found that mRNA expressions of the NLRP3-caspase-1-IL-18 axis components and the serum IL-18 level in BP patients decreased dramatically after effective treatment, which indicated that the up-regulation of NLRP3 inflammasome was responsible, at least to a great degree, for the enhanced IL-18 level in BP patients.

CONCLUSIONS

This study demonstrates that the expression of the NLRP3-caspase-1-IL-18 axis is highly expressed in the PBMCs of patients with BP, and correlated with disease activity, suggesting its involvement in the pathogenesis and progression of BP.

In vivo imaging of inflammasome activation reveals a subcapsular macrophage burst response that mobilizes innate and adaptive immunity

The inflammasome is activated in response to a variety of pathogens and has an important role in shaping adaptive immunity, yet the spatiotemporal orchestration of inflammasome activation in vivo and the mechanisms by which it promotes an effective immune response are not fully understood. Using an in vivo reporter to visualize inflammasome assembly, we establish the distribution, kinetics and propagation of the inflammasome response to a local viral infection. We show that modified vaccinia Ankara virus induces inflammasome activation in subcapsular sinus (SCS) macrophages, which is immediately followed by cell death and release of extracellular ASC specks. This transient inflammasome signaling in the lymph node generates a robust influx of inflammatory cells and mobilizes T cells from the circulation to increase the magnitude of T cell responses. We propose that after infection, SCS macrophages deliver a burst response of inflammasome activity and cell death that translates into the broadening of T cell responses, identifying an important aspect of inflammasome-driven vaccination strategies.

Inflammasome priming is similar for francisella species that differentially induce inflammasome activation

Inflammasome activation is a two-step process where step one, priming, prepares the inflammasome for its subsequent activation, by step two. Classically step one can be induced by LPS priming followed by step two, high dose ATP. Furthermore, when IL-18 processing is used as the inflammasome readout, priming occurs before new protein synthesis. In this context, how intracellular pathogens such as Francisella activate the inflammasome is incompletely understood, particularly regarding the relative importance of priming versus activation steps. To better understand these events we compared Francisella strains that differ in virulence and ability to induce inflammasome activation for their relative effects on step one vs. step two. When using the rapid priming model, i.e., 30 min priming by live or heat killed Francisella strains (step 1), followed by ATP (step 2), we found no difference in IL-18 release, p20 caspase-1 release and ASC oligomerization between Francisella strains (F. novicida, F. holarctica -LVS and F. tularensis Schu S4). This priming is fast, independent of bacteria viability, internalization and phagosome escape, but requires TLR2-mediated ERK phosphorylation. In contrast to their efficient priming capacity, Francisella strains LVS and Schu S4 were impaired in inflammasome triggering compared to F. novicida. Thus, observed differences in inflammasome activation by F. novicida, LVS and Schu S4 depend not on differences in priming but rather on their propensity to trigger the primed inflammasome.

Nicotinamide Riboside Ameliorates Hepatic Metaflammation by Modulating NLRP3 Inflammasome in a Rodent Model of Type 2 Diabetes

Low-grade chronic inflammation (metaflammation) is a major contributing factor for the onset and development of metabolic diseases, such as type 2 diabetes, obesity, and cardiovascular disease. Nicotinamide riboside (NR), which is present in milk and beer, is a functional vitamin B3 having advantageous effects on metabolic regulation. However, the anti-inflammatory capacity of NR is unknown. This study evaluated whether NR modulates hepatic nucleotide binding and oligomerization domain-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome. Male, 8-week-old KK/HlJ mice were allocated to the control or NR group. NR (100 mg/kg/day) or vehicle (phosphate-buffered saline) was administrated by an osmotic pump for 7 days. Glucose control, lipid profiles, NLRP3 inflammasome, and inflammation markers were analyzed, and structural and histological analyses were conducted. NR treatment did not affect body weight gain, food intake, and liver function. Glucose control based on the oral glucose tolerance test and levels of serum insulin and adiponectin was improved by NR treatment. Among tested lipid profiles, NR lowered the total cholesterol concentration in the liver. Histological and structural analysis by hematoxylin and eosin staining and transmission electron microscopy, respectively, showed that NR rescued the disrupted cellular integrity of the mitochondria and nucleus in the livers of obese and diabetic KK mice. In addition, NR treatment significantly improved hepatic proinflammatory markers, including tumor necrosis factor-alpha, interleukin (IL)-6, and IL-1. These ameliorations were accompanied by significant shifts of NLRP3 inflammasome components (NLRP3, ASC, and caspase1). These results demonstrate that NR attenuates hepatic metaflammation by modulating the NLRP3 inflammasome.

Glycans as Vaccine Antigens and Adjuvants: Immunological Considerations

Carbohydrates can be found on the cell surface of nearly every cell ranging from bacteria to fungi right up to mammalian cells. Carbohydrates and their interactions with carbohydrate-binding proteins play crucial roles in multiple biological processes including immunity, homeostasis, cellular communication, cell migration, and the regulation of serum glycoprotein levels. In the last decades, the interest in exploiting the biological activity of glycans as vaccine components has considerably increased. On the one hand, carbohydrates display epitopes to generate protective antibodies against pathogen-derived cell wall structures and on the other hand, glycans have the potential to stimulate the immune system; thus they can act as potent vaccine adjuvants.An effective vaccine consists of two major components, the vaccine antigen and an adjuvant. The vaccine antigen is an original or modified part of the pathogen that causes the disease. The immune response triggered by vaccination should induce antigen-specific plasma cells secreting protective antibodies as well as the development of memory T and B cells. Carbohydrate structures on pathogens represent an important class of antigens that can activate B cells to produce protective anti-carbohydrate antibodies in adults. A major breakthrough in vaccine development was the design of conjugate vaccines that evoke protective antibody responses against encapsulated bacteria strains such as Haemophilus influenzae, Streptococcus pneumoniae, or Neisseria meningitidis in adults, but also in young children. The first part of this chapter focuses on immune responses triggered by carbohydrate-based vaccines. The second part of the chapter discusses the immunological mechanisms of carbohydrate-based adjuvants to increase the immunogenicity of vaccines.

Inflammasome activation is critical to the protective immune response during chemically induced squamous cell carcinoma

Chronic inflammation affects most stages of tumorigenesis, including initiation, promotion, malignant differentiation, invasion and metastasis. Inflammasomes have been described as involved with persistent inflammation and are known to exert both pro and antitumour effects. We evaluated the influence of apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) and caspase (CASP)-1 in the antitumor immune response using a multistage model of squamous cell carcinoma (SCC) development. Absence of ASC and CASP-1 resulted in an earlier incidence and increased number of papilloma. Loss of inflammassome function in mice resulted in decreased presence of natural killer (NK), dendritic (DC), CD4⁺, CD8⁺ and CD45RB⁺ T cells in the tumor lesions as well as in lymph nodes (LN) compared with WT mice. Increased percentage of CD4⁺CD25⁺Foxp3⁺ T cells was associated with association with inflammasome loss of function. Moreover, significant differences were also found with neutrophils and macrophage infiltrating the lesions. Myeloperoxidase (MPO), but not elastase (ELA), activity oscillated among the groups during the SCC development. Levels of proinflammatory cytokines IL-1β, IL-18, Tumor Necrosis Factor (TNF)-α and Interferon (IFN)-γ were decreased in the tumor microenvironment in the absence of inflammasome proteins. These observations suggest a link between inflammasome function and SCC tumorigenesis, indicating an important role for inflammasome activation in the control of SCC development.

Scaling of immune responses against intracellular bacterial infection

Macrophages detect bacterial infection through pattern recognition receptors (PRRs) localized at the cell surface, in intracellular vesicles or in the cytosol. Discrimination of viable and virulent bacteria from non-virulent bacteria (dead or viable) is necessary to appropriately scale the anti-bacterial immune response. Such scaling of anti-bacterial immunity is necessary to control the infection, but also to avoid immunopathology or bacterial persistence. PRR-mediated detection of bacterial constituents in the cytosol rather than at the cell surface along with cytosolic recognition of secreted bacterial nucleic acids indicates viability and virulence of infecting bacteria. The effector responses triggered by activation of cytosolic PRRs, in particular the RIG-I-induced simultaneous rapid type I IFN induction and inflammasome activation, are crucial for timely control of bacterial infection by innate and adaptive immunity. The knowledge on the PRRs and the effector responses relevant for control of infection with intracellular bacteria will help to develop strategies to overcome chronic infection.

Near-term anti-CD25 monoclonal antibody administration protects murine liver from ischemia-reperfusion injury due to reduced numbers of CD4+ T cells

BACKGROUND

CD4(+) T cell is acknowledged as a key factor in the initiation phase of liver ischemia reperfusion injury. The purpose of current study is to demonstrate the effect of antecedent near-term anti-CD25 monoclonal antibody treatment on IR-induced liver injury by modulation of CD4(+) T cells.

METHODS

70% liver warm IR was induced in male C57BL/6 mice after anti-CD25 mAb or non-specific IgG administration. Liver function, histological damage, in vitro Proliferation, FACS, cytokine production, and immunofluorescence were assessed to evaluate the impact of antecedent near-term PC61 treatment on IR-induced liver injury.

RESULTS

After 70% liver ischemia, mice preconditioned with PC61 displayed significantly preserved liver function as characterized by less histological damage and reduced serum enzymes level. Mechanistic studies revealed that the protection effect of anti-CD25 mAb was associated with ameliorated intrahepatic inflammatory milieu and reduced CD4(+) T lymphocytes as manifested by the decrease of proinflammatory cytokine production (less expression of TNF-α, IFN-γ, IL-2, and IL-6) and the lower CD4/CD8 proportion.

CONCLUSIONS

Our results provide first line of evidence indicating that near-term treatment with anti-CD25 monoclonal antibody might provide protection for livers against IR-induced injury by reducing CD4(+) T cells, but not influencing functional Treg population. Therefore, our results demonstrate a potential function of anti-CD25 monoclonal antibody which was neglected in the past, and may be helpful in various clinical conditions, particularly in liver and kidney transplantations.

The Role of Non-Cognate T Cell Stimulation during Intracellular Bacterial Infection

Intra-macrophage bacterial infections cause significant morbidity and mortality in both the developed and developing world. Protective host immune responses to these infections initially requires the activation and expansion of pathogen-specific CD4 Th1 cells within lymphoid tissues and subsequent relocation of these effector cells to sites of infection. After entering infected tissues, the elicitation of Th1 bactericidal activity can be triggered by cognate or non-cognate signals that are delivered by locally infected antigen-presenting cells and innate cells. However, the contribution of non-cognate stimulation to the resolution of bacterial infection remains poorly understood, especially in the context of a Th1 response. Here, we review the current data on Th1 cell activation and expansion in mouse models of Salmonella and Chlamydia infection and discuss the potential role of non-cognate Th1 cell stimulation in these disease models. Greater understanding of this pathway of T cell activation may lead to the design of therapeutics or vaccines to combat intra-macrophage pathogens.

Caspase-1-like regulation of the proPO-system and role of ppA and caspase-1-like cleaved peptides from proPO in innate immunity

Invertebrates rely on innate immunity to respond to the entry of foreign microorganisms. One of the important innate immune responses in arthropods is the activation of prophenoloxidase (proPO) by a proteolytic cascade finalized by the proPO-activating enzyme (ppA), which leads to melanization and the elimination of pathogens. Proteolytic cascades play a crucial role in innate immune reactions because they can be triggered more quickly than immune responses that require altered gene expression. Caspases are intracellular proteases involved in tightly regulated limited proteolysis of downstream processes and are also involved in inflammatory responses to infections for example by activation of interleukin 1ß. Here we show for the first time a link between caspase cleavage of proPO and release of this protein and the biological function of these fragments in response to bacterial infection in crayfish. Different fragments from the cleavage of proPO were studied to determine their roles in bacterial clearance and antimicrobial activity. These fragments include proPO-ppA, the N-terminal part of proPO cleaved by ppA, and proPO-casp1 and proPO-casp2, the fragments from the N-terminus after cleavage by caspase-1. The recombinant proteins corresponding to all three of these peptide fragments exhibited bacterial clearance activity in vivo, and proPO-ppA had antimicrobial activity, as evidenced by a drastic decrease in the number of Escherichia coli in vitro. The bacteria incubated with the proPO-ppA fragment were agglutinated and their cell morphology was altered. Our findings show an evolutionary conserved role for caspase cleavage in inflammation, and for the first time show a link between caspase induced inflammation and melanization. Further we give a more detailed understanding of how the proPO system is regulated in time and place and a role for the peptide generated by activation of proPO as well as for the peptides resulting from Caspase 1 proteolysis.

Melanization is an important reaction in most multicellular organisms, both animals and plants. The initiation steps of this reaction in invertebrates are catalyzed by the prophenoloxidase (proPO) activating system a proteolytic enzyme cascade, which primary function is to recognize cell wall products from microorganisms and respond by activation of the system and generation of immune effector molecules. This cascade requires careful regulation to achieve spatial and temporal control to avoid dangerous side effects. We here show that a Caspase1-like enzyme can inactivate proPO when ppA is not activating the proPO to avoid deleterious effects and further we show for the first time that the N-terminal peptide from ppA cleavage of proPO (activation of proPO) has an important biological function as also the Caspase1 cleaved fragments. Our results also show that Caspase 1-induced inflammatory response is evolutionarily conserved and is linked to melanization.

Adaptive immunity, inflammation, and cardiovascular complications in type 1 and type 2 diabetes mellitus

Diabetes mellitus (DM) is a pandemics that affects more than 170 million people worldwide, associated with increased mortality and morbidity due to coronary artery disease (CAD). In type 1 (T1) DM, the main pathogenic mechanism seems to be the destruction of pancreatic β -cells mediated by autoreactive T-cells resulting in chronic insulitis, while in type 2 (T2) DM primary insulin resistance, rather than defective insulin production due to β -cell destruction, seems to be the triggering alteration. In our study, we investigated the role of systemic inflammation and T-cell subsets in T1- and T2DM and the possible mechanisms underlying the increased cardiovascular risk associated with these diseases.