Innate Sensors Research Articles

Intratumoral STING agonist reverses immune evasion in PD-(L)1-refractory Merkel cell carcinoma: mechanistic insights from detailed biomarker analyses

BackgroundAntibodies blocking programmed death (PD)-1 or its ligand (PD-L1) have revolutionized cancer care, but many patients do not experience durable benefits. Novel treatments to stimulate antitumor immunity are needed in...

MRNA Vaccination: An Outlook on Innate Sensing and Adaptive Immune Responses.

Vaccination has led to significant dismantling of infectious diseases worldwide. Since the dawn of the SARS-CoV-2 pandemic, there has been increased popularity in the usage and study of the mRNA vaccine platform. Here, we highlight fundamental knowledge on mRNA vaccine pharmacology, followed by the immunity conferred by innate sensing and adaptive responses resulting from exposure to the mRNA vaccine construct and encapsulation materials. A better understanding of these immune mechanisms will shed light on further improvements in mRNA vaccine design, aiming to improve efficiency and optimize immune responses upon inoculation.

Heterozygous de novo dominant negative mutation of REXO2 results in interferonopathy

Mitochondrial RNA (mtRNA) in the cytosol can trigger the innate immune sensor MDA5, and autoinflammatory disease due to type I IFN. Here, we show that a dominant negative mutation in the gene encoding the mitochondrial exonuclease REXO2 may cause interferonopathy by triggering the MDA5 pathway. A patient characterized by this heterozygous de novo mutation (p.T132A) presented with persistent skin rash featuring hyperkeratosis, parakeratosis and acanthosis, with infiltration of lymphocytes and eosinophils around small blood vessels. In addition, circulating IgE levels and inflammatory cytokines, including IFNα, are found consistently elevated. Transcriptional analysis highlights a type I IFN gene signature in PBMC. Mechanistically, REXO2 (T132A) lacks the ability to cleave RNA and inhibits the activity of wild-type REXO2. This leads to an accumulation of mitochondrial dsRNA in the cytosol, which is recognized by MDA5, leading to the associated type I IFN gene signature. These results demonstrate that in the absence of appropriate regulation by REXO2, aberrant cellular nucleic acids may accumulate and continuously trigger innate sensors, resulting in an inborn error of immunity.

Innate Immune Sensing of Adeno-Associated Virus Vectors.

Adeno-associated virus (AAV) based viral vectors are widely used in human gene therapy and form the basis of approved treatments for several genetic diseases. Immune responses to vector and transgene products, however, substantially complicate these applications in clinical practice. The role of innate immune recognition of AAV vectors was initially unclear, given that inflammatory responses early after vector administration were typically mild in animal models. However, more recent research continues to identify innate immune pathways that are triggered by AAV vectors and that serve to provide activation signals for antigen-presenting cells and initiation of adaptive immune responses. Sensing of the AAV genome by the endosomal DNA receptor toll-like receptor 9 (TLR9) promotes early inflammatory response and interferon expression. Thus, activation of the TLR9>MyD88 pathway in plasmacytoid dendritic cells (pDCs) leads to the conditioning of antigen cross-presenting DCs through type I interferon (IFN-I) and ultimately CD8+ T cell activation. Alternatively, pDCs may also promote CD8+ T cell responses in a TLR9-independent manner by the production of IL-1 cytokines, thereby activating the IL-1R1>MyD88 signaling pathway. AAV can induce cytokine expression in monocyte-derived DCs, which in turn increases antibody formation. Binding of AAV capsid to complement components likely further elevates B cell activation. At high systemic vector doses in humans and in non-human primates, AAV vectors can trigger complement activation, with contributions by classical and alternative pathways, leading to severe toxicities. Finally, evidence for activation of TLR2 by the capsid and of additional innate receptors for nucleic acids has been presented. These observations show that AAV vectors can initiate several and likely redundant innate immune pathways resulting in an exaggerated adaptive immune response.

Endogenous innate sensor NLRP3 is a key component in peritoneal macrophage dynamics required for cestode establishment.

The NLRP3 receptor can assemble inflammasome platforms to trigger inflammatory responses; however, accumulating evidence suggests that it can also display anti-inflammatory properties. Here, we explored the role of nucleotide-binding oligomerization domain pyrin-containing protein 3 (NLRP3) in Taenia crassiceps experimental infection, which requires immune polarization into a Th2-type profile and peritoneal influx of suppressive macrophages for successful colonization. NLRP3 deficient mice (NLRP3-/-) were highly resistant against T. crassiceps, relative to wild-type (WT) mice. Resistance in NLRP3-/- mice was associated with a diminished IL-4 output, high levels of IL-15, growth factor for both innate and adaptive lymphocytes, and a dramatic decrease in peritoneum-infiltrating suppressive macrophages. Also, a transcriptional analysis on bone marrow-derived macrophages exposed to Taenia-secreted antigens and IL-4 revealed that NLRP3-/- macrophages express reduced transcripts of relm-α and PD-1 ligands, markers of alternative activation and suppressive ability, respectively. Finally, we found that the resistance displayed by NLRP3-/- mice is transferred through intestinal microbiota exchange, since WT mice co-housed with NLRP3-/- mice were significantly more resistant than WT animals preserving their native microbiota. Altogether, these data demonstrate that NLRP3 is a component of innate immunity required for T. crassiceps to establish, most likely contributing to macrophage recruitment, and controlling lymphocyte-stimulating cytokines such as IL-15.

HIV-1 with gag processing defects activates cGAS sensing.

Detection of viruses by host pattern recognition receptors induces the expression of type I interferon (IFN) and IFN-stimulated genes (ISGs), which suppress viral replication. Numerous studies have described HIV-1 as a poor activator of innate immunity in vitro. The exact role that the viral capsid plays in this immune evasion is not fully understood. To better understand the role of the HIV-1 capsid in sensing we tested the effect of making HIV-1 by co-expressing a truncated Gag that encodes the first 107 amino acids of capsid fused with luciferase or GFP, alongside wild type Gag-pol. We found that unlike wild type HIV-1, viral particles produced with a mixture of wild type and truncated Gag fused to luciferase or GFP induced a potent IFN response in THP-1 cells and macrophages. Innate immune activation by Gag-fusion HIV-1 was dependent on reverse transcription and DNA sensor cGAS, suggesting activation of an IFN response by viral DNA. Further investigation revealed incorporation of the Gag-luciferase/GFP fusion proteins into viral particles that correlated with subtle defects in wild type Gag cleavage and a diminished capacity to saturate restriction factor TRIM5α, likely due to aberrant particle formation. We propose that expression of the Gag fusion protein disturbs the correct cleavage and maturation of wild type Gag, yielding viral particles that are unable to effectively shield viral DNA from detection by innate sensors including cGAS. These data highlight the crucial role of capsid in innate evasion and support growing literature that disruption of Gag cleavage and capsid formation induces a viral DNA- and cGAS-dependent innate immune response. Together these data demonstrate a protective role for capsid and suggest that antiviral activity of capsid-targeting antivirals may benefit from enhanced innate and adaptive immunity in vivo.

Abstract 2680: Knockout on enhancer of zeste homolog 2 in triple-negative breast cancer model alters immune signaling and decreases tumor progression and lung metastasis

Abstract Triple-negative breast cancer (TNBC) is an aggressive and highly metastatic subtype of breast cancer. Lack of known targets, patient-to-patient variations of target antigens and resistance to immune checkpoint inhibitors make TNBC one of the most challenging cancers to treat. TNBC is enriched in tumor-infiltrating neutrophils (TINs). TINs are key contributors to pro-tumorigenic processes linked to “immunologically cold” tumors, in part by preventing recruitment of T-lymphocytes (TILs). Prior studies identified the Enhancer of zeste homolog 2 (EZH2) as a prominent methyltransferase expressed in primary and metastatic TNBC cells. EZH2 is an upstream regulator of the stimulator of interferon genes (STING), a critical innate sensor mediating anti-tumor responses that is inhibited in cold tumors. To date, EZH2/STING signaling in TINs is relatively unknown. Here, we hypothesized that EZH2 inhibition and subsequent STING activation could exert anti-tumor activity by modulating TINs. We derived EZH2-knockout (KO) and EZH2-overexpressed (OX) cell lines from the well-established 4T1 TNBC mouse cell line. We demonstrate a 10-fold decrease in lung metastasis and significant reduction of 4T1 EZH2 KO tumor growth compared to the parent 4T1 cell line. Concomitantly, the TIN:TIL ratio was significantly reduced in 4T1 EZH2 KO vs. control tumors. Overexpression of EZH2 in 4T1 TNBC cells did not affect the primary tumor growth or lung metastasis. A therapeutic study using the repeated injection of the STING agonist MSA-2 after tumor engraftment in vivo also demonstrated a decrease in lung metastasis and tumor growth in MSA-2 vs. vehicle injection with both 4T1 parent and EZH2 KO cell lines. Together, our findings suggest a key role for STING pathway modulation and TIN/TIL poise in primary TNBC progression and lung metastasis. Citation Format: Lenore Monterroza, Maria Parrilla, Sarah Samaranayake, Dormarie Rivera, Brian Dobosh, Periasamy Selvaraj, Rabindra M. Tirouvanziam. Knockout on enhancer of zeste homolog 2 in triple-negative breast cancer model alters immune signaling and decreases tumor progression and lung metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2680.

NFκB and NLRP3/NLRC4 inflammasomes regulate differentiation, activation and functional properties of monocytes in response to distinct SARS-CoV-2 proteins

Increased recruitment of transitional and non-classical monocytes in the lung during SARS-CoV-2 infection is associated with COVID-19 severity. However, whether specific innate sensors mediate the activation or differentiation of monocytes in response to different SARS-CoV-2 proteins remain poorly characterized. Here, we show that SARS-CoV-2 Spike 1 but not nucleoprotein induce differentiation of monocytes into transitional or non-classical subsets from both peripheral blood and COVID-19 bronchoalveolar lavage samples in a NFκB-dependent manner, but this process does not require inflammasome activation. However, NLRP3 and NLRC4 differentially regulated CD86 expression in monocytes in response to Spike 1 and Nucleoprotein, respectively. Moreover, monocytes exposed to Spike 1 induce significantly higher proportions of Th1 and Th17 CD4 + T cells. In contrast, monocytes exposed to Nucleoprotein reduce the degranulation of CD8 + T cells from severe COVID-19 patients. Our study provides insights in the differential impact of innate sensors in regulating monocytes in response to different SARS-CoV-2 proteins, which might be useful to better understand COVID-19 immunopathology and identify therapeutic targets.

Ethambutol and meropenem/clavulanate synergy promotes enhanced extracellular and intracellular killing of Mycobacterium tuberculosis.

Increasing evidence supports the repositioning of beta-lactams for tuberculosis (TB) therapy, but further research on their interaction with conventional anti-TB agents is still warranted. Moreover, the complex cell envelope of Mycobacterium tuberculosis (Mtb) may pose an additional obstacle to beta-lactam diffusion. In this context, we aimed to identify synergies between beta-lactams and anti-TB drugs ethambutol (EMB) and isoniazid (INH) by assessing antimicrobial effects, intracellular activity, and immune responses. Checkerboard assays with H37Rv and eight clinical isolates, including four drug-resistant strains, exposed that only treatments containing EMB and beta-lactams achieved synergistic effects. Meanwhile, the standard EMB and INH association failed to produce any synergy. In Mtb-infected THP-1 macrophages, combinations of EMB with increasing meropenem (MEM) concentrations consistently displayed superior killing activities over the individual antibiotics. Flow cytometry with BODIPY FL vancomycin, which binds directly to the peptidoglycan (PG), confirmed an increased exposure of this layer after co-treatment. This was reinforced by the high IL-1β secretion levels found in infected macrophages after incubation with MEM concentrations above 5 mg/L, indicating an exposure of the host innate response sensors to pathogen-associated molecular patterns in the PG. Our findings show that the proposed impaired access of beta-lactams to periplasmic transpeptidases is counteracted by concomitant administration with EMB. The efficiency of this combination may be attributed to the synchronized inhibition of arabinogalactan and PG synthesis, two key cell wall components. Given that beta-lactams exhibit a time-dependent bactericidal activity, a more effective pathogen recognition and killing prompted by this association may be highly beneficial to optimize TB regimens containing carbapenems.IMPORTANCEAddressing drug-resistant tuberculosis with existing therapies is challenging and the treatment success rate is lower when compared to drug-susceptible infection. This study demonstrates that pairing beta-lactams with ethambutol (EMB) significantly improves their efficacy against Mycobacterium tuberculosis (Mtb). The presence of EMB enhances beta-lactam access through the cell wall, which may translate into a prolonged contact between the drug and its targets at a concentration that effectively kills the pathogen. Importantly, we showed that the effects of the EMB and meropenem (MEM)/clavulanate combination were maintained intracellularly. These results are of high significance considering that the time above the minimum inhibitory concentration is the main determinant of beta-lactam efficacy. Moreover, a correlation was established between incubation with higher MEM concentrations during macrophage infection and increased IL-1β secretion. This finding unveils a previously overlooked aspect of carbapenem repurposing against tuberculosis, as certain Mtb strains suppress the secretion of this key pro-inflammatory cytokine to evade host surveillance.

Nuclear RPSA senses viral nucleic acids to promote the innate inflammatory response

Innate sensors initiate the production of type I interferons (IFN-I) and proinflammatory cytokines to protect host from viral infection. Several innate nuclear sensors that mainly induce IFN-I production have been identified. Whether there exist innate nuclear sensors that mainly induce proinflammatory cytokine production remains to be determined. By functional screening, we identify 40 S ribosomal protein SA (RPSA) as a nuclear protein that recognizes viral nucleic acids and predominantly promotes proinflammatory cytokine gene expression in antiviral innate immunity. Myeloid-specific Rpsa-deficient mice exhibit less innate inflammatory response against infection with Herpes simplex virus-1 (HSV-1) and Influenza A virus (IAV), the viruses replicating in nucleus. Mechanistically, nucleus-localized RPSA is phosphorylated at Tyr204 upon infection, then recruits ISWI complex catalytic subunit SMARCA5 to increase chromatin accessibility of NF-κB to target gene promotors without affecting innate signaling. Our results add mechanistic insights to an intra-nuclear way of initiating proinflammatory cytokine expression in antiviral innate defense.

EPCO-50. THE TRANSCRIPTIONAL LANDSCAPE OF KEY INNATE DNA SENSORS WITHIN PRIMARY BRAIN TUMORS

Abstract Primary brain tumors are notoriously resistant to immunotherapy. The efficacy of these treatments potentially requires normal expression of DNA innate sensors within both the immune and tumor compartments. Recently, we found that STING1, involved in the CGAS/STING pathway, is epigenetically silenced in the neoplastic cells of primary brain tumors. This silencing can be traced back to the normal brain. We and others have shown that rescue of STING1 expression can be modulated with epigenetic treatments. The mechanism by which DNA damage in cancer leads to an inflammatory response sheds light on the significance of other DNA sensors. We hypothesize that innate immune silencing within the tumor contributes to immunotherapy resistance and the addition of epigenetic treatments could increase efficacy. We evaluated the transcriptional landscape of DNA innate sensors within normal adult brain and in patient derived tumors including glioblastoma, pilocytic astrocytoma, and diffuse midline gliomas, H3K27M mutant. We found low expression of additional cytosolic DNA sensors including cGAS, AIM2, ZBP1 in normal neuronal as well as tumor cells. Since epigenetic silencing is modulated during normal development, we compared the transcriptional innate profiles from normal cortex brain development to primary brain cancers. DNA innate immune sensor expression correlates with pre-oligodendrocyte progenitor cells and oligodendrocyte progenitor cells. These results suggest the innate immune suppression of these key cytosolic DNA sensors is established early in fetal brain development and retained in the context of primary brain tumors. We are currently exploring the epigenetic profiles of fetal brain and brain tumors to determine how these innate immune expression patterns affect tumorigenesis and response to immunotherapy treatment.

Mitochondrial reactive oxygen species: double agents in Mycobacterium tuberculosis infection.

In addition to housing the major energy-producing pathways in cells, mitochondria are active players in innate immune responses. One critical way mitochondria fulfill this role is by releasing damage-associated molecular patterns (mtDAMPs) that are recognized by innate sensors to activate pathwaysincluding, but not limited to, cytokine expression, selective autophagy, and cell death. Mitochondrial reactive oxygen species (mtROS) is a multifunctional mtDAMP linked to pro- and antimicrobial immune outcomes. Formed as a by-product of energy generation, mtROS links mitochondrial metabolism with downstream innate immune responses. As a result, altered cellular metabolism can change mtROS levels and impact downstream antimicrobial responses in a variety of ways. MtROS has emerged as a particularly important mediator of pathogenesis during infection with Mycobacterium tuberculosis (Mtb), an intracellular bacterial pathogen that continues to pose a significant threat to global public health. Here, we will summarize how Mtb modulates mtROS levels in infected macrophages and how mtROS dictates Mtb infection outcomes by controlling inflammation, lipid peroxidation, and cell death. We propose that mtROS may serve as a biomarker to predict tuberculosis patient outcomes and/or a target for host-directed therapeutics.

An Outbred Calf Model for Determining Innate Immune Sensing and Evolutionary Trajectories of a Cell Culture-Adapted Bovine Foamy Virus Variant.

Bovine foamy virus (BFVbta) displays a very high degree of cell-associated replication which is unprecedented even among the other known foamy viruses. Interestingly, recent studies have shown that it can in fact adapt in vitro to high-titer (HT) cell-free transmission due to genetic changes acquired during repeated rounds of cell-free BFVbta passages in immortalized bovine MDBK cells. Molecular clones obtained from the HT BFVbta Riems cell-free variant (HT BFVbta Riems) have been thoroughly characterized in MDBK cell cultures However, during recent years, it has become increasingly clear that the source of the host cells used for virus growth and functional studies of virus replication and virus-cell interactions plays a paramount role. Established cell lines, mostly derived from tumors, but occasionally experimentally immortalized and transformed, frequently display aberrant features relating, for example. to growth, metabolism, and genetics. Even state-of-the-art organoid cultures of primary cells cannot replicate the conditions in an authentic host, especially those concerning cell diversity and the role of innate and adaptive immunity. Therefore, to determine the overall replication characteristics of the cloned wt and HT BFVbta Riems variant, we conducted a small-scale animal pilot study. The replication of the original wt BFVbta Riems isolate, as well as that of its HT variant, were analyzed. Both BFVbta variants established infection in calves, with proviruses in peripheral blood mononuclear cells and induced Gag-specific antibodies. In addition, a related pattern in the host innate immune reaction was detected in the peripheral blood leukocytes of the BFV-infected calves. Surprisingly, an analysis of the Gag sequence two weeks post-inoculation revealed that the HT BFVbta variant showed a very high level of genetic reversion to the wild type (parental BFVbta genotype).

TL-532, a novel specific Toll-like receptor 3 agonist rationally designed for targeting cancers: discovery process and biological characterization.

Toll-like receptor 3 (TLR3) is an innate immune receptor that recognizes double-stranded RNA (dsRNA) and induces inflammation in immune and normal cells to initiate anti-microbial responses. TLR3 acts also as a death receptor only in cancer cells but not in their normal counterparts, making it an attractive target for cancer therapies. To date, all of the TLR3-activating dsRNAs used at preclinical or clinical stages have major drawbacks such as structural heterogeneity, toxicity, and lack of specificity and/or efficacy. We conducted the discovery process of a new family of TLR3 agonists that are chemically manufactured on solid-phase support and perfectly defined in terms of sequence and size. A stepwise discovery process was performed leading to the identification of TL-532, a 70 base pair dsRNA that is potent without transfection reagent and is highly specific for TLR3 without activating other innate nucleic sensors such as RIG-I/MDA5, TLR7, TLR8, and TLR9. TL-532 induces inflammation in murine RAW264.7 myeloid macrophages, in human NCI-H292 lung cancer cells, and it promotes immunogenic apoptosis in tumor cells in vitro and ex vivo without toxicity towards normal primary cells. In conclusion, we identified a novel TLR3 agonist called TL-532 that has promising anticancer properties.

Mechanisms of Innate Immune Sensing of HTLV-1 and Viral Immune Evasion.

Human T lymphotropic virus-1 (HTLV-1) was the first identified oncoretrovirus, which infects and establishes a persistent infection in approximately 10-20 million people worldwide. Although only ~5% of infected individuals develop pathologies such as adult T-cell leukemia/lymphoma (ATLL) or a neuroinflammatory disorder termed HTLV-1-asssociated myelopathy/tropical spastic paraparesis (HAM/TSP), asymptomatic carriers are more susceptible to opportunistic infections. Furthermore, ATLL patients are severely immunosuppressed and prone to other malignancies and other infections. The HTLV-1 replication cycle provides ligands, mainly nucleic acids (RNA, RNA/DNA intermediates, ssDNA intermediates, and dsDNA), that are sensed by different pattern recognition receptors (PRRs) to trigger immune responses. However, the mechanisms of innate immune detection and immune responses to HTLV-1 infection are not well understood. In this review, we highlight the functional roles of different immune sensors in recognizing HTLV-1 infection in multiple cell types and the antiviral roles of host restriction factors in limiting persistent infection of HTLV-1. We also provide a comprehensive overview of intricate strategies employed by HTLV-1 to subvert the host innate immune response that may contribute to the development of HTLV-1-associated diseases. A more detailed understanding of HTLV-1-host pathogen interactions may inform novel strategies for HTLV-1 antivirals, vaccines, and treatments for ATLL or HAM/TSP.

Inhibition of cGAS aggravated the host inflammatory response to Aspergillus fumigatus

Backgroud: Aspergillus fumigatus (A. fumigatus) is a clinically important fungal pathogen. Invasive pulmonary aspergillosis (IPA) is the main fungal infection with increased morbidity and mortality in immunocompromised populations, although treatments are available. An innate DNA sensor known as cyclic GMP-AMP Synthase (cGAS) has recently been discovered that senses invading pathogens and has a significant impact on innate immunity. It can activate the cGAS-STING signaling pathway to stimulate downstream signals. But it is still unclear what role it plays in IPA’s pathogenesis.Methods: An investigation into the infection of A. fumigatus was conducted by inhibiting cGAS activity in vivo and in vitro using siRNA and RU.521(an inhibitor of cGAS).Results: We discovered that suppressing cGAS increased the host’s susceptibility to A. fumigatus and harmed those with infections by enhancing pulmonary tissue damage and edema, as well as decreasing fungal clearance. Furthermore, our findings show that inhibiting or silencing cGAS can exacerbate the inflammatory response in IPA mouse models and human bronchi epithelial cells (HBECs) treated with A. fumigatus by upregulating the production of inflammatory genes with non-type 1 interferon.Conclusion: Based on our analysis, we conclude that activating cGAS might increase host resistance to A. fumigatus, protect against pulmonary illnesses brought on by A. fumigatus and that exploring the cGAS-STING signaling pathway is beneficial not only for the immunological investigation of IPA but also may be a potential therapeutic objective.

Induction of STING/IL-29 signaling in human lung adenocarcinoma/tumor-associated neutrophil cocultures

Abstract LKB1-mutant lung adenocarcinoma (LUAD), is an intractable form of lung cancer. LKB1-mutant LUAD is poor in T-cells and does not respond to checkpoint inhibitor therapy, and instead is enriched in tumor-infiltrating neutrophils (TINs). STING is a key innate sensor mediating anti-tumor responses that is inhibited in LKB1-mutant LUAD. However, the status of STING signaling and if it can be induced in TINs to antagonize tumors is unknown. Here, we developed a novel human LKB1-mutant LUAD/TIN model to tackle this question. Based on prior work from our lab (Dobosh, STAR Protoc. 2021), we grew the H1944 LKB1-mutant LUAD line at air-liquid interface on Alvetex scaffolds (Reprocell), followed by the transmigration of human blood neutrophils. The effect of the STING agonist MSA-2 was assessed in the model by a 20-plex immune mediator assay(Mesoscale). We successfully manufactured a LKB1-mutant LUAD/TIN model from H1944 cells and human blood neutrophils. MSA-2 treatment resulted in significant increases in the STING-regulated mediators IL-6, IP-10 and MIP-1beta. Most strikingly, MSA-2 treatment induced IL-29 (type III interferon) levels by 27-fold, while neither type I nor type II interferons were induced. The model showcased here mimics LKB1-mutant LUAD/TIN interplay and shows responsiveness to STING agonist treatment through induction of type III (but not type I and II) interferon and other immune mediators. Since IL-29 receptor expression is limited to epithelial and myeloid cells (including neutrophils) and IL-29 is known to mediate immunomodulatory and anti-tumor responses, future work will address if and how the large IL-29 increase observed upon MSA-2 treatment affects LUAD proliferation and TIN activation in this context.

Pseudorabies Virus Infection Activates the TLR-NF-κB Axis and AIM2 Inflammasome To Enhance Inflammatory Responses in Mice.

Pseudorabies virus (PRV) infection activates inflammatory responses to release robust proinflammatory cytokines, which are critical for controlling viral infection and clearance of PRV. However, the innate sensors and inflammasomes involved in the production and secretion of proinflammatory cytokines during PRV infection remain poorly studied. In this study, we report that the transcription and expression levels of some proinflammatory cytokines, including interleukin 1β (IL-1β), IL-6, and tumor necrosis factor alpha (TNF-α), are upregulated in primary peritoneal macrophages and in mice during PRV infection. Mechanistically, Toll-like receptor 2 (TLR2), TLR3, TLR4, and TLR5 were induced by the PRV infection to enhance the transcription levels of pro-IL-1β, pro-IL-18, and gasdermin D (GSDMD). Additionally, we found that PRV infection and transfection of its genomic DNA triggered AIM2 inflammasome activation, apoptosis-related speckle-like protein (ASC) oligomerization, and caspase-1 activation to enhance the secretion of IL-1β and IL-18, which was mainly dependent on GSDMD, but not GSDME, in vitro and in vivo. Taken together, our findings reveal that the activation of the TLR2-TLR3-TRL4-TLR5-NF-κB axis and AIM2 inflammasome, as well as GSDMD, is required for proinflammatory cytokine release, which resists the PRV replication and plays a critical role in host defense against PRV infection. Our findings provide novel clues to prevent and control PRV infection. IMPORTANCE PRV can infect several mammals, including pigs, other livestock, rodents, and wild animals, causing huge economic losses. As an emerging and reemerging infectious disease, the emergence of PRV virulent isolates and increasing human PRV infection cases indicate that PRV is still a high risk to public health. It has been reported that PRV infection leads to robust release of proinflammatory cytokines through activating inflammatory responses. However, the innate sensor that activates IL-1β expression and the inflammasome involved in the maturation and secretion of proinflammatory cytokines during PRV infection remain poorly studied. In this study, our findings reveal that, in mice, activation of the TLR2-TLR3-TRL4-TLR5-NF-κB axis and AIM2 inflammasome, as well as GSDMD, is required for proinflammatory cytokine release during PRV infection, and it resists PRV replication and plays a critical role in host defense against PRV infection. Our findings provide novel clues to prevent and control PRV infection.

How the Innate Immune DNA Sensing cGAS-STING Pathway Is Involved in Apoptosis.

The cGAS-STING signaling axis can be activated by cytosolic DNA, including both non-self DNA and self DNA. This axis is used by the innate immune system to monitor invading pathogens and/or damage. Increasing evidence has suggested that the cGAS-STING pathway not only facilitates inflammatory responses and the production of type I interferons (IFN), but also activates other cellular processes, such as apoptosis. Recently, many studies have focused on analyzing the mechanisms of apoptosis induced by the cGAS-STING pathway and their consequences. This review gives a detailed account of the interplay between the cGAS-STING pathway and apoptosis. The cGAS-STING pathway can induce apoptosis through ER stress, NLRP3, NF-κB, IRF3, and IFN signals. Conversely, apoptosis can feed back to regulate the cGAS-STING pathway, suppressing it via the activation of caspases or promoting it via mitochondrial DNA (mtDNA) release. Apoptosis mediated by the cGAS-STING pathway plays crucial roles in balancing innate immune responses, resisting infections, and limiting tumor growth.

NLRC4-mediated activation of CD1c+ DC contributes to perpetuation of synovitis in rheumatoid arthritis.

The individual contribution of specific myeloid subsets such as CD1c+ conventional DC (cDC) to perpetuation of rheumatoid arthritis (RA) pathology remains unclear. In addition, the specific innate sensors driving pathogenic activation of CD1c+ cDC in patients with RA and their functional implications have not been characterized. Here, we assessed phenotypical, transcriptional, and functional characteristics of CD1c+ and CD141+ cDC and monocytes from the blood and synovial fluid of patients with RA. Increased levels of CCR2 and the IgG receptor CD64 on circulating CD1c+ cDC was associated with the presence of this DC subset in the synovial membrane in patients with RA. Moreover, synovial CD1c+ cDC are characterized by increased expression of proinflammatory cytokines and high abilities to induce pathogenic IFN-γ+IL-17+CD4+ T cells in vitro. Finally, we identified the crosstalk between Fcγ receptors and NLRC4 as a potential molecular mechanism mediating pathogenic activation, CD64 upregulation, and functional specialization of CD1c+ cDC in response to dsDNA-IgG in patients with RA.