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The pathophysiology of allergic conjunctivitis (AC) is not fully explained by the traditional Th2-centric model. This study aimed to identify AC-associated candidate genes and delineate immune pathways, with a focus on cell-type-specific mechanisms that could contribute to disease heterogeneity. We employed an integrative multi-omics strategy, using three genomic analyses (FUSION, MAGMA, UTMOST) on human GWAS data to identify AC-associated candidate genes. These candidates were then investigated using single-cell RNA sequencing data from a mouse model of AC to map immune cell communication and signaling dynamics. Key pathways were validated in an independent ovalbumin-induced AC mouse model using clinical scoring, qRT-PCR and Western blot analysis. This approach identified nine high-confidence AC-associated candidate genes, including key components of the IL-1 and Toll-like receptor families. In the AC mouse model, the IL-18 receptor components and were selectively upregulated in NK and T cells from allergic versus control mice and correlated positively with interferon-γ ( ) expression. Cell-cell communication and pseudotime analyses indicated an allergic-state network characterized by enhanced NK cell-linked IFN-γ signaling to antigen-presenting cells and dynamic changes in NF-κB and JAK-STAT pathway activity. In the OVA-induced model, conjunctival IL-18, IL-18R1, IL-18RAP and phosphorylated NF-κB p65 were increased in AC versus controls and showed a stepwise rise across mild, moderate and severe clinical groups. Across human genetics, single-cell transcriptomics and validation, an IL-18 receptor/IFN-γ axis in NK and T cells emerges as a reproducible module associated with AC and its severity. These findings extend the immunopathological framework of AC beyond a purely Th2-driven process and nominate IL-18R-linked signaling as a candidate pathway for future mechanistic and therapeutic studies.

The inflammasome is a cytoplasmic multiprotein complex that promotes proinflammatory cytokine maturation in response to host- and pathogen-derived signals. Missense mutations in cryopyrin (NLRP3) result in a hyperactive inflammasome that drives overproduction of the proinflammatory cytokines IL-1β and IL-18, leading to the cryopyrin-associated periodic syndromes (CAPS) disease spectrum. Mouse lines harboring CAPS-associated mutations in Nlrp3 have elevated levels of IL-1β and IL-18 and closely mimic human disease. To examine the role of inflammasome-driven IL-18 in murine CAPS, we bred Nlrp3 mutations onto an Il18r-null background. Deletion of Il18r resulted in partial phenotypic rescue that abolished skin and visceral disease in young mice and normalized serum cytokines to a greater extent than breeding to Il1r-null mice. Significant systemic inflammation developed in aging Nlrp3 mutant Il18r-null mice, indicating that IL-1 and IL-18 drive pathology at different stages of the disease process. Ongoing inflammation in double-cytokine knockout CAPS mice implicated a role for caspase-1-mediated pyroptosis and confirmed that CAPS is inflammasome dependent. Our results have important implications for patients with CAPS and residual disease, emphasizing the need to explore other NLRP3-mediated pathways and the potential for inflammasome-targeted therapy.

Interleukin (IL)-18 is a proinflammatory cytokine that belongs to the IL-1 family and plays an important role in inflammation. The uncontrolled release of this cytokine is associated with severe chronic inflammatory disease. IL-18 forms a signalling complex with the IL-18 receptor α (Rα) and β (Rβ) chains at the plasma membrane, which induces multiple inflammatory cytokines. Here, we present a crystal structure of human IL-18 bound to the two receptor extracellular domains. Generally, the receptors’ recognition mode for IL-18 is similar to IL-1β; however, certain notable differences were observed. The architecture of the IL-18 receptor second domain (D2) is unique among the other IL-1R family members, which presumably distinguishes them from the IL-1 receptors that exhibit a more promiscuous ligand recognition mode. The structures and associated biochemical and cellular data should aid in developing novel drugs to neutralize IL-18 activity. IL-18 is a member of the IL-1 family of proinflammatory cytokines. Tsutsumi et al. present a crystal structure of IL-18 bound to the extracellular domains of its heterodimeric receptor, providing insight into how its unusual specificity may be targeted pharmacologically.

Achieving a cure is an urgent need for patients with advanced solid tumors. Here, we discover that oncolytic virus (OV) infection enhances IL-18 receptor expression but fails to increase IL-18 ligand expression. Therefore, we engineer armed oncolytic alphavirus M1 expressing wild-type IL-18 (wtIL-18) or a mutant variant (mutIL-18) that evades IL-18 binding protein (IL-18BP) while maintaining IL-18 receptor (IL-18R) binding. Intravenous administration of M1-mutIL-18 suppresses the growth of multiple advanced solid tumors in C57BL/6 and BALB/c mouse models and promotes long-term systemic immune memory. Mechanistically, armed M1-mutIL-18 enhances directed clonal expansion and differentiation of CD8 + T cells and sustains IFN-γ production. Thus, armed M1-mutIL-18 promotes dendritic cell (DC) activation, priming and activation of CD8 + T cells in lymphatic organs, and infiltration of IL-18R + CD8 + T cells in the tumor microenvironment, establishing a positive feedback loop. We further show that a PD-L1 inhibitor enhances the anti-tumor efficacy of mutIL-18 OVs. These results highlight the importance of the IL-18 pathway in oncolytic virus therapy and implicate reprogramming ligand-receptor interaction as an effective strategy for immunotherapy. Immunotherapy holds great potential, although strategies for durable responses against solid tumors are still needed. Here, the authors combine oncolytic virus (OV) engineering and reprogramming of the IL-18 pathway, showing that armed OVs expressing a decoy-resistant IL-18 elicit anti-tumor immunity and long-term immunological memory against multiple refractory tumors in mice.

Multisystem inflammatory syndrome in children is a post-infectious presentation SARS-CoV-2 associated with expansion of the T cell receptor Vβ21.3+ T-cell subgroup. Here we apply muti-single cell omics to compare the inflammatory process in children with acute respiratory COVID-19 and those presenting with non SARS-CoV-2 infections in children. Here we show that in Multi-Inflammatory Syndrome in Children (MIS-C), the natural killer cell and monocyte population demonstrate heightened CD95 (Fas) and Interleuking 18 receptor expression. Additionally, TCR Vβ21.3+ CD4+ T-cells exhibit skewed differentiation towards T helper 1, 17 and regulatory T cells, with increased expression of the co-stimulation receptors ICOS, CD28 and interleukin 18 receptor. We observe no functional evidence for NLRP3 inflammasome pathway overactivation, though MIS-C monocytes show elevated active caspase 8. This, coupled with raised IL18 mRNA expression in CD16- NK cells on single cell RNA sequencing analysis, suggests interleukin 18 and CD95 signalling may trigger activation of TCR Vβ21.3+ T-cells in MIS-C, driven by increased IL-18 production from activated monocytes and CD16- Natural Killer cells. Multi-Inflammatory Syndrome in Children (MIS-C) is a severe post-infectious presentation related to SARS-CoV-2 infection. Here authors used multi-omics approaches to characterise MIS-C cases and found increased CD95 and IL-18 signalling accompanying the expansion of TCR Vβ 21.3+ T cells.

Cytokine-mediated immunotherapy has rapidly emerged as an effective alternative approach for cancer treatment by modulating the anti-tumor response. Interleukin-18 (IL-18) is considered as a promising cancer therapeutic agent due to the ability of cytokines to inhibit cancer by enhancing natural killer (NK) cell and cytotoxic T cell responses. Since the activity of IL-18 is required for the specific binding to IL-18 receptors, the modification of binding residue at the protein interface is an attractive strategy for IL-18 activity enhancement. The aim of this study was to design and predict mutations increasing the activity of IL-18 through computational structure-based energy calculation and molecular dynamic simulations. Four candidate mutations, E6M, E6M+N111S+R131G, E6M+K129M+R131G, and E6M+N111S+K129M+R131G, could affect/facilitate the receptor binding and stability compared to the wild-type via electrostatic interaction. MD simulations demonstrated that the predicted mutation on IL-18 had no influence on the overall conformation stability, but increased flexibility in the β8–β9 hairpin loop. Furthermore, the dynamic behavior suggested that these candidates could be an alternative for the improvement of IL-18 biological activity, though the full simulation of the IL-18 complex remains necessary. In summary, this study offered a computer-aided design strategy which was of beneficial use in the design and development of IL-18 to increase its cytokine potency and efficiency.

Non-alcoholic fatty liver disease (NAFLD) is rising in prevalence, and a better pathophysiologic understanding of the transition to its inflammatory phenotype (NASH) is key to the development of effective therapies. To evaluate the contribution of the NLRP3 inflammasome and its downstream effectors IL-1 and IL-18 in this process, we applied the true-to-life “American lifestyle-induced obesity syndrome” (ALiOS) diet mouse model. Development of obesity, fatty liver and liver damage was investigated in mice fed for 24 weeks according to the ALiOS protocol. Lipidomic changes in mouse livers were compared to human NAFLD samples. Receptor knockout mice for IL-1 and IL-18 were used to dissect the impact of downstream signals of inflammasome activity on the development of NAFLD. The ALiOS diet induced obesity and liver steatosis. The lipidomic changes closely mimicked changes in human NAFLD. A pro-inflammatory gene expression pattern in liver tissue and increased serum liver transaminases indicated early liver damage in the absence of histological evidence of NASH. Mechanistically, Il-18r−/−- but not Il-1r−/− mice were protected from early liver damage, possibly due to silencing of the pro-inflammatory gene expression pattern. Our study identified NLRP3 activation and IL-18R-dependent signaling as potential modulators of early liver damage in NAFLD, preceding development of histologic NASH.

Support from human genetics increases the probability of success in drug development. However, few examples exist of successful genomically-driven drug repositioning. Given that a Mendelian form of severe enterocolitis is due to up-regulation of the interleukin-18 (IL18) signaling pathway, and pharmacologic inhibition of IL18 has been shown to reverse this enterocolitis, we undertook a Mendelian randomization study to test the causal effect of elevated IL18 levels on inflammatory bowel disease susceptibility (IBD) in 12,882 cases and 21,770 controls. Mendelian randomization is an established method to assess the role of biomarkers in disease etiology in a manner that minimizes confounding and prevents reverse causation. Using three SNPs that explained almost 7% of the variance in IL18 level, we found that each genetically predicted standard deviation increase in IL18 was associated with an increase in IBD susceptibility (odds ratio = 1.22, 95% CI = 1.11–1.34, P-value = 6 × 10 −5 ). This association was further validated in 25,042 IBD cases and 34,915 controls (odds ratio = 1.13, 95% CI = 1.05–1.20). Recently, an anti-IL18 monoclonal antibody, which decreased free IL18 levels, was found to be safe, yet ineffective in a phase II trial for type 2 diabetes. Taken together, these genomic findings implicated IBD as an alternative indication for anti-IL18 therapy, which should be tested in randomized controlled trials.

Cytokines and chemokines produced by tubular epithelial and infiltrating cells are critical to inflammation in renal ischemia–reperfusion injury. IL-37, a newly described IL-1 family member, inhibits IL-18-dependent pro-inflammatory cytokine production by its binding to IL-18 receptors and IL-18 binding protein. The potential role of IL-37 in renal ischemia–reperfusion injury is unknown. Here we found that exposure of tubular epithelial cells to exogenous IL-37 downregulated hypoxia and the IL-18-induced expression of TNFα, IL-6, and IL-1β. Importantly, human PT-2 tubular epithelial cells have inducible expression of IL-37. Moreover, pro-inflammatory cytokine expression was augmented in IL-37 mRNA-silenced tubular epithelial cells and inhibited by transfection with pCMV6-XL5-IL-37. In a mouse ischemic injury model, transgenic expression of human IL-37 inhibited kidney expression of TNFα, IL-6, and IL-1β and improved mononuclear cell infiltration, kidney injury, and function. Thus, human tubular epithelial cells express the IL-18 contra-regulatory protein IL-37 as an endogenous control mechanism to reduce inflammation. Augmenting kidney IL-37 may represent a novel strategy to suppress renal injury responses and promote kidney function after renal ischemic injury and transplantation.

In recent years, cytokine-mediated therapy has emerged as further advance alternative in cancer therapy. Interleukin-18 (IL-18) has exhibited interesting anti-cancer properties especially when combined with IL-12. We engineered IL-18 in order to improve its activity using single point mutagenesis. IL-18 mutants were constructed according to binding residues and polarity which we tried to increase polarity in M33Q and M60Q, enhanced cationicity in E6K, and flexibility in T63A. All IL-18 proteins were expressed in Pichia pastoris, purified, and then measured the activity by treating with the NK-92MI cell line to evaluate interferon-γ (IFN-γ) stimulation. The E6K and T63A mutant forms showed higher activity with respect to native proteins at the concentration of 200 ng mL-1 by inducing the expression of IFN-γ, about factors of 9 and 4, respectively. Meanwhile, M33Q and M60Q had no significant activity to induce IFN-γ. Interestingly, the combination of E6K and T63A mutations could synergize the induction activity of IL-18 to be 16 times at 200 ng mL-1. Furthermore, molecular dynamics studies have elucidated the effect due to mutation on conformation of the binding site of IL-18. The results turn out that E6K provides structural perseverance against mutation, while M33Q and M60Q promote vivid overall change in protein conformation, especially at the binding site. For T63A, mutation yields small difference in structure but clearly increases structural flexibility. However, a small structural change was observed when T63A was combined with E6K. Our research resulted in a novel version of IL-18 which could be a new key candidate for cytokine-mediated therapy.