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Galectins are a family of β -galactoside-binding lectins that play key roles in the invertebrate innate immunity system, but no galectin genes have been identified in the mud crab (Scylla paramamosain) so far. The present study is the first to clone a galectin gene (SpGal) from S. paramamosain , by the rapid amplification of cDNA ends technique based on expressed sequence tags. The full-length cDNA of SpGal was 3142 bp. Its open reading frame encoded a polypeptide of 280 amino acids containing a GLECT/Gal-bind lectin domain and a potential N-glycosylation site. The deduced amino acid sequence and multi-domain organization of SpGal were highly similar to those of invertebrate galectins, and phylogenetic analysis showed that SpGal was closely related to galectin isolated from Portunus trituberculatus. The mRNA transcripts of SpGal were found to be constitutively expressed in a wide range of tissues, with its expression level being higher in the hepatopancreas, gill, and hemocytes. The mRNA expression level of SpGal increased rapidly after the crabs were stimulated by Vibrio alginolyticus , and the maximum expression appeared at 6 h after the challenge. The lipopolysaccharide-binding ability of SpGal was dependent on its concentration, and it also exhibited agglutination activity with three Gram-negative (Aeromonas hydrophila , Chryseobacterium indologenes and Vibrio alginolyticus) and three Gram-positive (Bacillus aquimaris , Staphylococcus aureus and Micrococcus lysodeik) bacterial strains. In addition, hemagglutination activity with rabbit erythrocytes was observed in the absence of d -galactose. These results indicate that SpGal in S. paramamosain acts as a pattern recognition receptor to recognize a broad spectrum of microbes. The findings together indicate that SpGal plays an important role in the innate immune mechanisms of S. paramamosain against pathogenic infection. • A novel galectin in Scylla paramamosain (SpGal) was identified and characterized. • SpGal showed high sequence similarity to other crustacean galectins. • SpGal exhibited high hemagglutination activity and LPS-binding ability. • SpGal exhibited broad-spectrum bacterial agglutination activity. • SpGal may play an important role in innate immunity in S. paramamosain. [ABSTRACT FROM AUTHOR]

mRNA vaccine platforms present numerous advantages, such as versatility, rapid production, and induction of cellular and humoral responses. Moreover, mRNAs have inherent adjuvant properties due to their complex interaction with pattern recognition receptors (PRRs). This recognition can be either beneficial in activating antigen-presenting cells (APCs) or detrimental by indirectly blocking mRNA translation. To decipher this Janus effect, we describe the different innate response mechanisms triggered by mRNA molecules and how each element from the 5 ′ cap to the poly-A tail interferes with innate/adaptive immune responses. Then, we emphasize the importance of some critical steps such as production, purification, and formulation as key events to further improve the quality of immune responses and balance innate and adaptive immunity. mRNA-based vaccines enable the well-controlled design of on-demand transcript sequences and could be adapted to any pandemic crisis. In vitro -transcribed (IVT) mRNA used for formulation and subsequent administration has to be highly homogeneous with no DNA, dsRNA, or 5′ triphosphate transcripts in order to avoid any overstimulation of innate immunity. During the formulation process, mRNA–cargo interactions could unmask sequences leading to unexpected side effects. The intricate mechanisms of RNA sensing by PRRs, accounts for the unpredictability of in vitro assays. To date, there is no animal model for mRNA vaccines that matches perfectly human immune responses, underlying the importance of clinical trials. Moreover, innate immune activation by mRNA molecules is dependent on the route of administration and the species, hampering the interpretation of in vitro or preclinical data. [ABSTRACT FROM AUTHOR]

Background & Aims: Acute‐on‐chronic liver failure (ACLF) is characterized by acute decompensation of cirrhosis (AD), organ failure(s) and high risk of short‐term mortality with bacterial infection frequently as precipitating event. Innate immune pattern recognition receptors and members of the lectin pathway of complement activation are crucial to the innate immune response to pathogens. The aim of this study was to investigate whether single nucleotide polymorphisms (SNPs) of innate immune components are associated with the occurrence of bacterial infections or mortality in patients with cirrhosis hospitalized for AD or ACLF. Methods: Twenty‐one innate immunity SNPs with known functional implications were genotyped in 826 AD/ACLF patients included in the CANONIC study. Associations between baseline characteristics of the patients, the occurrence of bacterial infections and survival rate at 90 days of follow‐up in relation to the innate immunity genetic variants were analysed. Results: The NOD2‐G908R genetic variant was associated with mortality (HR 2.25, P =.004) independently of age and MELD Score. This association was also found in a predefined subgroup analysis in patients with bacterial infections (HR 2.78, P <.001) along with MBL_Yx (HR 1.72, P =.008) and MASP2_371 (HR 1.67, P =.012) genetic variants. None of the analysed SNPs were significantly associated with the occurrence of acute bacterial infections or spontaneous bacterial peritonitis in particular. Conclusions: Innate immune system‐specific NOD2‐G908R, MBL_Yx and MASP2_371 genetic variants were independently associated with increased risk of short‐term mortality in AD/ACLF patients with bacterial infection. [ABSTRACT FROM AUTHOR]

The aim of this study was to explore this relationship in the first year following severe exacerbation in our previously cited cohort of school-aged children.[7] We also compared asthma characteristics recorded at baseline and asthma outcomes at 1 year. At 1-year visit, patients were classified into three groups according to asthma outcomes: (a) good responders: no exacerbation during follow-up and well-controlled asthma according to GINA guidelines; (b) partial responders: no more than one severe exacerbation during follow-up and/or partly controlled asthma; (c) poor responders: >=2 severe exacerbations during follow-up and/or uncontrolled asthma. We also observed that control and lung function evaluated 8 weeks after an asthma exacerbation might be predictive of future asthma outcomes. The influence of asthma control on the severity of virus-induced asthma exacerbations. [Extracted from the article]

Pattern recognition receptors (PRRs) are a class of immune sensors that play a critical role in detecting and responding to several conserved patterns of microorganisms. As such, they play a major role in the maintenance of immune homeostasis and anti-microbial defense. Fundamental knowledge pertaining to the discovery of PRR functions and their ligands continue to advance the understanding of immune system and disease resistance, which led to the rational design and/or application of various PRR ligands as vaccine adjuvants. In addition, the conserved nature of many PRRs throughout the animal kingdom has enabled the utilization of the comparative genomics approach in PRR identification and the study of evolution, structural features, and functions in many animal species including avian. In the present review, we focused on PRR sensing and signaling functions in the avian species, domestic chicken, mallard, and domestic goose. In addition to summarizing recent advances in the understanding of avian PRR functions, the present review utilized a comparative biology approach to identify additional PRRs, whose functions have been well studied in mammalians but await functional characterization in avian. [ABSTRACT FROM AUTHOR]

Plant pattern recognition receptors (PRRs) perceive pathogen‐associated molecular patterns (PAMPs) to activate immune responses. Medium‐chain 3‐hydroxy fatty acids (mc‐3‐OH‐FAs), which are widely present in Gram‐negative bacteria, were recently shown to be novel PAMPs in Arabidopsis thaliana. The Arabidopsis PRR LIPOOLIGOSACCHARIDE‐SPECIFIC REDUCED ELICITATION (LORE) is a G‐type lectin receptor‐like kinase that recognizes mc‐3‐OH‐FAs and subsequently mounts an immune response; however, the mechanisms underlying LORE activation and downstream signaling are unexplored. Here, we report that one of the mc‐3‐OH‐FAs, 3‐OH‐C10:0, induces phosphorylation of LORE at tyrosine residue 600 (Y600). Phosphorylated LORE subsequently trans‐phosphorylates the receptor‐like cytoplasmic kinase PBL34 and its close paralogs, PBL35 and PBL36, and therefore activates plant immunity. Phosphorylation of LORE Y600 is required for downstream phosphorylation of PBL34, PBL35, and PBL36. However, the Pseudomonas syringae effector HopAO1 targets LORE, dephosphorylating the tyrosine‐phosphorylated Y600 and therefore suppressing the immune response. These observations uncover the mechanism by which LORE mediates signaling in response to 3‐OH‐C10:0 in Arabidopsis. Synopsis: The Arabidopsis lectin receptor‐like kinase LORE serves as pattern‐recognition receptor for bacterial fatty acid metabolites. Here, LORE‐mediated activation of plant immune responses is shown to be mediated by LORE auto‐phosphorylation and activation of novel receptor‐like cytoplasmic kinases. LORE exhibits tyrosine kinase activity.Bacterial fatty acid metabolite 3‐OH‐C10:0 activates LORE via its phosphorylation on Tyr600.LORE phosphorylates receptor‐like cytoplasmic kinases PBL34/PBL35/PBL36 to activate immune responses.Bacterial pathogen P. syringae inhibits LORE via the secreted tyrosine phosphatase HopAO1. [ABSTRACT FROM AUTHOR]

Background: Horseshoe crabs are ancient marine arthropods with a long evolutionary history extending back approximately 450 million years, which may benefit from their innate immune systems. However, the genetic mechanisms underlying their abilities of distinguishing and defending against invading microbes are still unclear. Results: Here, we describe the 2.06 Gbp genome assembly of Tachypleus tridentatus with 24,222 predicted protein-coding genes. Comparative genomics shows that T. tridentatus and the Atlantic horseshoe crab Limulus polyphemus have the most orthologues shared among two species, including genes involved in the immune-related JAK-STAT signalling pathway. Divergence time dating results show that the last common ancestor of Asian horseshoe crabs (including T. tridentatus and C. rotundicauda) and L. polyphemus appeared approximately 130 Mya (121–141), and the split of the two Asian horseshoe crabs was dated to approximately 63 Mya (57–69). Hox gene analysis suggests two clusters in both horseshoe crab assemblies. Surprisingly, selective analysis of immune-related gene families revealed the high expansion of conserved pattern recognition receptors. Genes involved in the IMD and JAK-STAT signal transduction pathways also exhibited a certain degree of expansion in both genomes. Intact coagulation cascade-related genes were present in the T. tridentatus genome with a higher number of coagulation factor genes. Moreover, most reported antibacterial peptides have been identified in T. tridentatus with their potentially effective antimicrobial sites. Conclusions: The draft genome of T. tridentatus would provide important evidence for further clarifying the taxonomy and evolutionary relationship of Chelicerata. The expansion of conserved immune signalling pathway genes, coagulation factors and intact antimicrobial peptides in T. tridentatus constitutes its robust and effective innate immunity for self-defence in marine environments with an enormous number of invading pathogens and may affect the quality of the adaptive properties with regard to complicated marine environments. [ABSTRACT FROM AUTHOR]

"Functional cure" is being pursued as the ultimate endpoint of antiviral treatment in chronic hepatitis B (CHB), which is characterized by loss of HBsAg whether or not anti-HBs antibodies are present. "Functional cure" can be achieved in <10% of CHB patients with currently available therapeutic agents. The dysfunction of specific immune responses to hepatitis B virus (HBV) is considered the major cause of persistent HBV infection. Thus, modulating the host immune system to strengthen specific cellular immune reactions might help eliminate HBV. Strategies are needed to restore/enhance innate immunity and induce HBV-specific adaptive immune responses in a coordinated way. Immune and resident cells express pattern recognition receptors like TLRs and RIG I/MDA5, which play important roles in the induction of innate immunity through sensing of pathogen-associated molecular patterns (PAMPs) and bridging to adaptive immunity for pathogen-specific immune control. TLR/RIG I agonists activate innate immune responses and suppress HBV replication in vitro and in vivo , and are being investigated in clinical trials. On the other hand, HBV-specific immune responses could be induced by therapeutic vaccines, including protein (HBsAg/preS and HBcAg), DNA, and viral vector-based vaccines. More than 50 clinical trials have been performed to assess therapeutic vaccines in CHB treatment, some of which display potential effects. Most recently, using genetic editing technology to generate CAR-T or TCR-T, HBV-specific T cells have been produced to efficiently clear HBV. This review summarizes the progress in basic and clinical research investigating immunomodulatory strategies for curing chronic HBV infection, and critically discusses the rather disappointing results of current clinical trials and future strategies. [ABSTRACT FROM AUTHOR]

The host immune system is engaged in a constant battle with microorganisms, with the immediate detection of pathogenic invasion and subsequent signalling acting as crucial deterrents against the establishment of a successful infection. For this purpose, cells are equipped with a variety of sensors called pattern recognition receptors (PRR), which rapidly detect intruders leading to the expression of antiviral type I interferons (IFN). Type I IFN are crucial cytokines which exert their biological effects through the induction of hundreds of IFN-stimulated genes (ISGs). The expression profile of these ISGs varies depending on the virus. For a small subset of ISGs, their anti- or even proviral effects have been revealed, however, the vast majority are uncharacterised. The spotlight is now on herpesviruses, with their large coding capacity and long co-evolution with their hosts, as a key to understanding the impact of ISGs during viral infection. Studies are emerging which have identified multiple herpesviral antagonists specifically targeting ISGs, hinting at the significant role these proteins must play in host defence against viral infection, with the promise of more to come. In this review, we will discuss the current knowledge of the complex interplay between ISGs and human herpesviruses: the antiviral role of selected ISGs during herpesviral infections, how herpesviruses antagonise these ISGs and, in some cases, even exploit them to benefit viral infection. [ABSTRACT FROM AUTHOR]

Pattern recognition receptors (PRRs) are crucial for responses to infections and tissue damage; however, their role in autoimmunity is less clear. Herein we demonstrate that 2 C-type lectin receptors (CLRs) Mcl and Mincle play an important role in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). Congenic rats expressing lower levels of Mcl and Mincle on myeloid cells exhibited a drastic reduction in EAE incidence. In vivo silencing of Mcl and Mincle or blockade of their endogenous ligand SAP130 revealed that these receptors' expression in the central nervous system is crucial for T cell recruitment and reactivation into a pathogenic Th17/GM-CSF phenotype. Consistent with this, we uncovered MCL- and MINCLE-expressing cells in brain lesions of MS patients and we further found an upregulation of the MCL/MINCLE signaling pathway and an increased response following MCL/MINCLE stimulation in peripheral blood mononuclear cells from MS patients. Together, these data support a role for CLRs in autoimmunity and implicate the MCL/MINCLE pathway as a potential therapeutic target in MS. [ABSTRACT FROM AUTHOR]

Understanding the molecular drivers and feedback loops of osteoarthritis (OA) may provide future therapeutic strategies to modulate the disease progression. The current paradigm of OA is evolving from a purely mechanical disease caused by cartilage wear toward a complex biological response connecting biomechanics, inflammation, and the immune system. The view of OA as a chronic wound highlights the role inflammation plays and also the body's attempts to repair an ongoing injury. Inflammatory signals, including cytokines such as interleukin‐1 and tissue necrosis factor α, surface‐expressed pattern recognition receptors such as toll‐like receptors 2 and 4, complement factors such as C5, as well as pathogen‐associated molecular patterns and damage‐associated molecular patterns drive the enzymatic cascade that degrades cartilage matrix in OA. Considering the joint as an entire organ, interactions between the cells that reside in the synovium including macrophages and other immune cells, appear to drive enzymatic activity in cartilage, which, in turn, feeds signals back to the synovium that continues stimulating degradation in a feed‐forward loop. This review will explore the potential roles of immune cells such as macrophages and T cells in the synovium in both stimulating and modulating the inflammatory response in OA. © 2019 Orthopedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:253‐257, 2020 [ABSTRACT FROM AUTHOR]

Mammalian retinoic acid-inducible gene I (RIG-I)-like receptors detect viral double-stranded RNA (dsRNA) and 5'-triphosphorylated RNA to activate the transcription of interferon genes and promote antiviral defense. The Caenorhabditis elegans RIG-I-like receptor DRH-1 promotes defense through antiviral RNA interference (RNAi), but less is known about its role in regulating transcription. Here, we describe a role for DRH-1 in directing a transcriptional response in C. elegans called the intracellular pathogen response (IPR), which is associated with increased pathogen resistance. The IPR includes a set of genes induced by diverse stimuli, including intracellular infection and proteotoxic stress. Previous work suggested that the proteotoxic stress caused by intracellular infections might be the common trigger of the IPR, but here, we demonstrate that different stimuli act through distinct pathways. Specifically, we demonstrate that DRH-1/RIG-I is required for inducing the IPR in response to Orsay virus infection but not in response to other triggers like microsporidian infection or proteotoxic stress. Furthermore, DRH-1 appears to be acting independently of its known role in RNAi. Interestingly, expression of the replication-competent Orsay virus RNA1 segment alone is sufficient to induce most of the IPR genes in a manner dependent on RNA-dependent RNA polymerase activity and on DRH-1. Altogether, these results suggest that DRH-1 is a pattern recognition receptor that detects viral replication products to activate the IPR stress/immune program in C. elegans. [ABSTRACT FROM AUTHOR]

Interleukin-1 receptor associated kinase (IRAK1) is one of the crucial signal transduction mediators in TLR/IL-1R signaling pathways in host immune system. To investigate about it in rohu (Labeo rohita), one of the economically important freshwater fish species in the Indian subcontinent, we cloned, characterized and analyzed its expression following bacterial infection and pathogens associated molecular patterns (PAMPs) stimulation. The full-length cDNA of rohu IRAK1 (LrIRAK1) consisted of 2765 nucleotide (nt) having an ORF of 2115 nt encoding a polypeptide of 704 amino acids (aa) with a molecular mass of 70.4 kDa. Structurally, LrIRAK1 consisted of twenty-nine helix, twelve strands and forty one coils making one N-terminal death domain (19–94 aa) and a central serine threonine kinase catalytic domain (or kinase domain) (188-489aa). In addition to these two prominent domains, LrIRAK1 also contained highly conserved amino acids viz., lysine 215 and aspartic acid 314 and threonine 185, 361 which were reported to be important for kinase and phosphorylation activity respectively in other animals. Similar to higher vertebrates, LrIRAK1 also consisted of CDK1 (cyclin-dependent kinase1) at 338–352 aa; NEK2 (NIMA-related kinase 2) at 47–61 aa; NEK6 (NIMA-related kinase 6) at 581–595 aa and AMPK (AMP- activated protein kinase) motif at 518–538 aa. Phylogenetically, LrIRAK1 is closely related to cave fish, common carp exhibiting high similarity (~95%) and identity (~90%). In the uninfected fish, the LrIRAK1 expression was highest in liver (~11.5 fold) and lowest in blood. In response to Aeromonas hydrophila, Edwardsiella tarda and Bacillus subtilis infection and various TLR and NLR-ligands stimulation, the expression of LrIRAK1 was markedly enhanced at various time points in almost all the tested tissues. These results together suggest the key role of LrIRAK1 in pattern recognition receptors (PRRs)-mediated host defense against pathogenic insults. • The full- length cDNA of LrIRAK1 consisted of 2765 bp, with an ORF of 2115 bp encoding 704 aa polypeptide. • LrIRAK1 protein comprised of 29 helix, 12 strands and 41 coils. • Phylogenetically LrIRAK1 was related to cave fish and common carp. • In TLR and NLR-ligands stimulation, LrIRAK1 was induced both in-vitro and in-vivo. • In A.hydrophila, E. tarda and B. subtilis infection, LrIRAK1 gene expression was significantly induced in various organs. [ABSTRACT FROM AUTHOR]

Subclinical endometritis (SE) is one cause of repeat breeder syndrome (RBS). When endometrial cells come into contact with antigens during inflammatory events like endometritis, they act like innate immune system cells. Ovsynch-based therapies stimulate the innate immune system, which is how they may be able to cure SE and then RBS. This study aimed to assess the effects of presynch-10 and ovsynch applications on mRNA expressions of some endometrial Toll- and Nod-like receptors (TLRs and NLRs) in cows with RBS. A total of 40 repeat breeder cows were used in the study. The presynch-10 and ovsynch protocols were used in group 1 (G1, n=20), and no protocol was used in group 2 (G2, n=20). Endometrial samples were collected before and after the synchronization protocols in G1. In G2, samples were collected, and after waiting time up to the duration of synchronization protocol in G1, samples were taken again. The expression profiles of the genes being investigated were examined using RT-qPCR. NLRC4, NALP3 and TLR4 were basically expressed in all of the samples while NOD2 expression was completely undetectable. There was a statistical difference when NOD1 and TLR2 expressions in the second samples were compared between G1 and G2 (P<0.05). It was concluded that presynch-10 and ovsynch administration in cows may have a positively effect on the innate immune response and so be effective in the treatment of SE. [ABSTRACT FROM AUTHOR]

The mechanisms involved in the induction of allergic sensitization by pollen are not fully understood. Within the last few decades, findings from epidemiological and experimental studies support the notion that allergic sensitization is not only dependent on the genetics of the host and environmental factors, but also on intrinsic features of the allergenic source itself. In this review, we summarize the current concepts and newest advances in research focusing on the initial mechanisms inducing pollen sensitization. Pollen allergens are embedded in a complex and heterogeneous matrix composed of a myriad of bioactive molecules that are co‐delivered during the allergic sensitization. Surprisingly, several purified allergens were shown to lack inherent sensitizing potential. Thus, growing evidence supports an essential role of pollen‐derived components co‐delivered with the allergens in the initiation of allergic sensitization. The pollen matrix, which is composed by intrinsic molecules (e.g. proteins, metabolites, lipids, carbohydrates) and extrinsic compounds (e.g. viruses, particles from air pollutants, pollen‐linked microbiome), provide a specific context for the allergen and has been proposed as a determinant of Th2 polarization. In addition, the involvement of various pattern recognition receptors (PRRs), secreted alarmins, innate immune cells, and the dependency of DCs in driving pollen‐induced Th2 inflammatory processes suggest that allergic sensitization to pollen most likely results from particular combinations of pollen‐specific signals rather than from a common determinant of allergenicity. The exact identification and characterization of such pollen‐derived Th2‐polarizing molecules should provide mechanistic insights into Th2 polarization and pave the way for novel preventive and therapeutic strategies against pollen allergies. [ABSTRACT FROM AUTHOR]

Pattern Recognition Receptors (PRRs) detect evidence of infection and tissue damage. The activation of these receptors and their downstream signal transduction pathways initiate a protective immune response. These signaling pathways are influenced by their spatial context, and precise subcellular positioning of proteins and protein complexes in these pathways is essential for effective immune responses in vivo. This organization is not limited to transmembrane proteins that reside in specific organelles, but also to proteins that engage membrane lipid head groups for proper positioning. In this review, we focus on the role of cell membranes and protein–lipid interactions in innate immune signal transduction and how their mechanisms of localization regulate the immune response. We will discuss how lipids spatially regulate the sensing of damage or infection, mediate effector activity, and serve as messengers of cell death and tissue damage. [ABSTRACT FROM AUTHOR]

Innate immunity represents the human immune system’s first line of defense against a pathogenic intruder and is initiated by the recognition of conserved molecular structures known as pathogen-associated molecular patterns (PAMPs) by specialized cellular sensors, called pattern recognition receptors (PRRs). Human immunodeficiency virus type 1 (HIV-1) is a unique human RNA virus that causes acquired immunodeficiency syndrome (AIDS) in infected individuals. During the replication cycle, HIV-1 undergoes reverse transcription of its RNA genome and integrates the resulting DNA into the human genome. Subsequently, transcription of the integrated provirus results in production of new virions and spreading infection of the virus. Throughout the viral replication cycle, numerous nucleic acid derived PAMPs can be recognized by a diverse set of innate immune sensors in infected cells. However, HIV-1 has evolved effcient strategies to evade or counteract this immune surveillance and the downstream responses. Understanding the molecular underpinnings of the concerted actions of the innate immune system, as well as the corresponding viral evasion mechanisms during infection, is critical to understanding HIV-1 transmission and pathogenesis, and may provide important guidance for the design of appropriate adjuvant and vaccine strategies. Here, we summarize current knowledge of the molecular basis for sensing HIV-1 in human cells, including CD4+ T cells, dendritic cells, and macrophages. Furthermore, we discuss the underlying mechanisms by which innate sensing is regulated, and describe the strategies developed by HIV-1 to evade sensing and immune responses. [ABSTRACT FROM AUTHOR]

Background: Germline‐encoded innate immune pattern recognition receptors (PRR) are expressed at epithelial surfaces and modulate epithelial defenses. Evidence suggests that stimulation of the Toll‐like receptor (TLR) family of PRR may regulate epithelial barrier integrity by upregulating tight junction (TJ) complex protein expression, but it is not known whether this mechanism is utilized in esophageal epithelial cells. TJ complex proteins maintain intact barrier function and are dysregulated in atopic disorders including eosinophilic esophagitis. Methods: Pattern recognition receptors expression was assessed in EoE and control primary esophageal epithelial cells, demonstrating robust expression of TLR2 and TLR3. The three‐dimensional air‐liquid interface culture (ALI) model was used to test whether TLR2 or TLR3 stimulation alters epithelial barrier function using an in vitro model of human epithelium. Transepithelial electrical resistance (TEER) and FITC‐Dextran permeability were evaluated to assess membrane permeability. ALI cultures were evaluated by histology, immunohistochemistry, Western blotting, and chromatin immunoprecipitation (ChIP). Results: TLR3 stimulation did not change TEER in the ALI model. TLR2 stimulation increased TEER (1.28‐ to 1.31‐fold) and decreased paracellular permeability to FITC‐Dextran, and this effect was abolished by treatment with anti‐TLR2 blocking antibody. TJ complex proteins claudin‐1 and zonula occludens‐1 were upregulated following TLR2 stimulation, and ChIP assay demonstrated altered histone 4 acetyl binding at the TJP1 enhancer and CLDN1 enhancer and promoter following zymosan treatment, implying the occurrence of durable chromatin changes. Conclusions: Our findings implicate the TLR2 pathway as a potential regulator of esophageal epithelial barrier function and suggest that downstream chromatin modifications are associated with this effect. [ABSTRACT FROM AUTHOR]

Avian Tembusu virus (TMUV) is a newly emerging avian pathogenic flavivirus in China and Southeast Asia with features of rapid spread, an expanding host range, and cross-species transmission. The mechanisms of its infection and pathogenesis remain largely unclear. Here, we investigated the tropism of this arbovirus in peripheral blood mononuclear cells of specific-pathogen-free (SPF) ducks and SPF chickens and identified monocytes/macrophages as the key targets of TMUV infection. In vivo studies in SPF ducks and SPF chickens with monocyte/macrophage clearance demonstrated that the infection of monocytes/macrophages was crucial for viral replication, transmission, and pathogenesis. Further genome-wide transcriptome analyses of TMUV-infected chicken macrophages revealed that host antiviral innate immune barriers were the major targets of TMUV in macrophages. Despite the activation of major pattern recognition receptor signaling, the inductions of alpha interferon (IFN-γ) and IFN-δ were blocked by TMUV infection on transcription and translation levels, respectively. Meanwhile, TMUV inhibited host redox responses by repressing the transcription of genes encoding NADPH oxidase subunits and promoting Nrf2-mediated antioxidant responses. The recovery of either of the abovementioned innate immune barriers was sufficient to suppress TMUV infection. Collectively, we identify an essential step of TMUV infection and reveal extensive subversion of host antiviral innate immune responses. [ABSTRACT FROM AUTHOR]

Latrophilin is a member of adhesion GPCRs involved in various physiological pro1cesses. The extracellular fragment of Tribolium castaneum Latrophilin (TcLph) contains a galactose-binding lectin (GBL) domain. However, the biological function of GBL domain remains mysterious. Here, we initially studied the role of TcLph in recognizing pathogens through its GBL domain and then triggering immune defense in invertebrates. Results showed that GBL domain was highly conserved, and its predicted 3D structure was similar to rhamnose-binding lectin domain of mouse Latrophilin-1 with a unique α/β fold and two long loops. Molecular docking and ELISA results revealed the GBL domain can bind to D-galactose, L-rhamnose, lipopolysaccharide and peptidoglycan. The recombinant extracellular segment of TcLph and the recombinant GBL exhibited strong agglutinating and binding activities to all tested bacteria in a Ca2+-dependent manner. Moreover, TcLph was markedly induced after infection by Escherichia coli or Staphylococcus aureus , while its silencing exacerbated bacterial loads and larvae mortality. TcLph -deficient larvae significantly decreased the transcription levels of antimicrobial peptides and prophenoloxidase activating system-related genes, leading to a significant reduction in phenoloxidase activity. It indicated that TcLph functioned as a pattern recognition receptor in pathogen recognition and activated immune responses to eliminate invasive microbes, suggesting a potential target for insecticides. [ABSTRACT FROM AUTHOR]

Galectins, as members of lectin families, exhibit a high affinity for β-galactosides and play diverse roles in biological processes. They function as pattern recognition receptors (PRRs) with important roles in immune defense. In this study, galectin-1, designated as SpGal-1, was identified and characterized from silver pomfret (Pampus argenteus). The SpGal-1 comprises an open reading frame (ORF) spanning 396 base pairs (bp) and encodes a deduced amino acid (aa) sequence containing a single carbohydrate recognition domain (CRD). Sublocalization analysis revealed that SpGal-1 was mainly expressed in the cytoplasm. The mRNA transcripts of SpGal-1 were ubiquitously detected in various tissues, with a higher expression level in the intestine. In addition, when exposed to Photobacterium damselae subsp. damselae (PDD) infection, both the liver and head kidney exhibited significantly increased SpGal-1 mRNA expression. The recombinant protein of SpGal-1 (named as rSpGal-1) demonstrated hemagglutination against red blood cells (RBCs) from Larimichthys crocea and P. argenteus in a Ca2+ or β-Mercaptoethanol (β-ME)-independent manner. Notably, rSpGal-1 could bind with various pathogen-associated molecular patterns (PAMPs) including D-galactose, D-mannose, lipopolysaccharide (LPS), and peptidoglycan (PGN), with highest affinity to PGN. Moreover, rSpGal-1 effectively interacted with an array of bacterial types encompassing Gram-positive bacteria (Staphylococcus aureus and Nocardia seriolae) and Gram-negative bacteria (PDD and Escherichia coli, among others), with the most robust binding affinity towards PDD. Collectively, these findings highlight that SpGal-1 is a crucial PRR with involvement in the host immune defense of silver pomfret. • Galectin-1, designated as SpGal-1, was identified and characterized from Pampus argenteus. • The rSpGal-1 demonstrated hemagglutination against RBCs from Larimichthys crocea and P. argenteus. • The rSpGal-1 could bind with various pathogen-associated molecular patterns (PAMPs) and an array of bacterial types. [ABSTRACT FROM AUTHOR]

Laboratory of Genetics and Physiology 2 (LGP2), along with Retinoic Acid Induced Gene-I (RIG-I) and Melanoma Differentiation Associated Gene 5, are members of the retinoic acid-inducible gene-I-like receptors (RLRs) in pattern recognition receptors, playing an important role in the host's innate immunity. Due to lacking a caspase activation and recruitment domain, LGP2 is controversially regarded as a positive or negative regulator in the antiviral response. This study aimed to explore how duck LGP2 (duLGP2) participates in duck innate immunity and its role in countering the duck Tembusu virus (DTMUV). In duck embryo fibroblast cells, the overexpression of duLGP2 significantly reduced the cell's antiviral capacity by inhibiting type I interferon (IFN) production and the expression of downstream IFN-stimulated genes. Conversely, duLGP2 knockdown had the opposite effect. For the first time, we introduced the LGP2 gene fragment into duck embryos using a lentiviral vector to ensure persistent expression and generated gene-edited ducks with LGP2 overexpression. We demonstrated that duLGP2 facilitates DTMUV replication in both in vitro and in vivo experiments, leading to robust inflammatory and antiviral responses. Interestingly, the repressive effects of duLGP2 on type I IFN production were only observed in the early stage of DTMUV infection, with type I IFN responses becoming enhanced as the viral load increased. These results indicate that duLGP2 acts as a negative regulator during the resting state and early stages of DTMUV infection. This study provides a theoretical basis for further research on duck RLRs and developing new anti-DTMUV drugs or vaccine adjuvants. • The role of duLGP2 was determined in vitro and in vivo. • Lentivirus vector is used to construct duLGP2 overexpression gene editing duck. • DuLGP2 participates in duck innate immunity and plays a negative role. • DuLGP2 promotes DTMUV replication and enhances inflammatory response. [ABSTRACT FROM AUTHOR]

[Display omitted] Inflammation is a first responder against injury and infection and is also critical for the regeneration and repair of tissue after injury. The role of professional immune cells in tissue healing is well characterized. Professional immune cells respond to pathogens with humoral and cytotoxic responses; remove cellular debris through efferocytosis; secrete angiogenic cytokines and growth factors to repair the microvasculature and parenchyma. However, non-immune cells are also capable of responding to damage or pathogens. Non-immune somatic cells express pattern recognition receptors (PRRs) to detect pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs). The PRRs activation leads to the release of inflammatory cytokines required for tissue defense and repair. Notably, the activation of PRRs also triggers epigenetic changes that promote DNA accessibility and cellular plasticity. Thus, non-immune cells directly respond to the local inflammatory cues and can undergo phenotypic modifications or even cell lineage transitions to facilitate tissue regeneration. This review will focus on the novel role of cell-autonomous inflammatory signaling in mediating cell plasticity, a process which is termed transflammation. We will discuss the regulation of this process by changes in the functions and expression levels of epigenetic modifiers, as well as metabolic and ROS/RNS-mediated epigenetic modulation of DNA accessibility during cell fate transition. We will highlight the recent technological developments in detecting cell plasticity and potential therapeutic applications of transflammation in tissue regeneration. [ABSTRACT FROM AUTHOR]

C-type lectins (CTLs), a superfamily of Ca2+-dependent carbohydrate-recognition proteins, serve as pattern recognition receptors (PRRs) in the immune response of many species. However, little is currently known about the CTLs of the commercially and ecologically important bivalve species, blood clam (Tegillarca granosa). In this study, a CTL (designated as Tg CTL-1) with a single carbohydrate-recognition domain (CRD) containing unique QPN/WDD motifs was identified in the blood clam through transcriptome and whole-genome searching. Multiple alignment and phylogenetic analysis strongly suggested that Tg CTL-1 was a new member of the CTL superfamily. Expression analysis demonstrated that TgCTL-1 was highly expressed in the hemocytes and visceral mass of the clam under normal condition. In addition, the expression of TgCTL-1 was shown to be significantly up-regulated upon pathogen challenge. Moreover, the recombinant Tg CTL-1 (r Tg CTL-1) displayed agglutinating and binding activities against both the gram-positive and gram-negative bacteria tested in a Ca2+-dependent manner. Furthermore, it was found that the in vitro phagocytic activity of hemocytes was significantly enhanced by r Tg CTL-1. In general, our results showed that Tg CTL-1 was an inducible acute-phase secretory protein, playing crucial roles in recognizing, agglutinating, and binding to pathogenic bacteria as well as modulating phagocytic activity of hemocytes in the innate immune defense of blood clam. • A novel C-type lectin, TgCTL-1 , was identified in blood clam, T. granosa. • TgCTL- 1 has a single carbohydrate-recognition domain (CRD) containing QPN/WDD motifs. • Expression of TgCTL-1 was rapidly and markedly up-regulated upon pathogen challenge. • The r Tg CTL-1 exhibited binding and agglutinating activities in a Ca+-dependent manner. • r Tg CTL-1 was shown to promote phagocytic activity of hemocytes especially with Ca2+. [ABSTRACT FROM AUTHOR]

The immune system is composed of two subsystems—the innate immune system and the adaptive immune system. The innate immune system is the first to respond to pathogens and does not retain memory of previous responses. Innate immune responses are evolutionarily older than adaptive responses and elements of innate immunity can be found in all multicellular organisms. If a pathogen persists, the adaptive immune system will engage the pathogen with specificity and memory. Several components of the adaptive system including immunoglobulins (Igs), T cell receptors (TCR), and major histocompatibility complex (MHC), are assumed to have arisen in the first jawed vertebrates—the Gnathostomata. This review will discuss and compare components of both the innate and adaptive immune systems in Gnathostomes, particularly in Chondrichthyes (cartilaginous fish) and in Osteichthyes [bony fish: the Actinopterygii (ray-finned fish) and the Sarcopterygii (lobe-finned fish)]. While many elements of both the innate and adaptive immune systems are conserved within these species and with higher level vertebrates, some elements have marked differences. Components of the innate immune system covered here include physical barriers, such as the skin and gastrointestinal tract, cellular components, such as pattern recognition receptors and immune cells including macrophages and neutrophils, and humoral components, such as the complement system. Components of the adaptive system covered include the fundamental cells and molecules of adaptive immunity: B lymphocytes (B cells), T lymphocytes (T cells), immunoglobulins (Igs), and major histocompatibility complex (MHC). Comparative studies in fish such as those discussed here are essential for developing a comprehensive understanding of the evolution of the immune system. [ABSTRACT FROM AUTHOR]

C-type lectins (CTLs) have characteristic carbohydrate recognition domains (CRDs) and play important roles in the immune system. In the present study, a new CTL, Sp CTL5, was identified from the hepatopancreas of the mud crab Scylla paramamosain. The open reading frame of Sp CTL5 comprised 762 bp, encoding a polypeptide of 253 amino acids with a putative signaling peptide of 20 amino acids. The predicted Sp CTL5 protein contained a single CRD. Sp CTL5 transcripts were distributed in all examined tissues, with the highest level being detected in the hepatopancreas. Upon challenging with Vibrio alginolyticus , the mRNA levels of Sp CTL5 in the hepatopancreas were up-regulated. The recombinant protein of Sp CTL5 could agglutinate three Gram-positive bacteria and three Gram-negative bacteria in the presence of Ca2+. Furthermore, hemagglutination analysis showed that the recombinant protein of Sp CTL5 can agglutinate rabbit erythrocytes. This study indicated that Sp CTL5 acts as a pattern recognition receptor for the innate immune response which protects S. paramamosain from bacterial infection. Moreover, these findings also provide information to further our understanding of the innate immunology of invertebrates. • Sp CTL5 might be involved in the innate immune response. • Sp CTL5 can agglutinate Gram-positive and Gram-negative bacteria. • Sp CTL5 acts as a pattern recognition receptor with Ca2+ dependently. [ABSTRACT FROM AUTHOR]

In a context of a sustainable viticulture, the implementation of innovative eco-friendly strategies, such as elicitor-triggered immunity, requires a deep knowledge of the molecular mechanisms underlying grapevine defense activation, from pathogen perception to resistance induction. During plant-pathogen interaction, the first step of plant defense activation is ensured by the recognition of microbe-associated molecular patterns, which are elicitors directly derived from pathogenic or beneficial microbes. Vitis vinifera , like other plants, can perceive elicitors of different nature, including proteins, amphiphilic glycolipid, and lipopeptide molecules as well as polysaccharides, thanks to their cognate pattern recognition receptors, the discovery of which recently began in this plant species. Furthermore, damage-associated molecular patterns are another class of elicitors perceived by V. vinifera as an invader's hallmark. They are mainly polysaccharides derived from the plant cell wall and are generally released through the activity of cell wall–degrading enzymes secreted by microbes. Elicitor perception and subsequent activation of grapevine immunity end in some cases in efficient grapevine resistance against pathogens. Using complementary approaches, several molecular markers have been identified as hallmarks of this induced resistance stage. This review thus focuses on the recognition of elicitors by Vitis vinifera describing the molecular mechanisms triggered from the elicitor perception to the activation of immune responses. Finally, we discuss the fact that the link between elicitation and induced resistance is not so obvious and that the formulation of resistance inducers remains a key step before their application in vineyards. [ABSTRACT FROM AUTHOR]

Toll-like receptors (TLRs) play an important role in the activation of innate immune response in animals. In this study, we identified a TLR from the oriental river prawn, Macrobrachium nipponense (MnToll1) and investigated its functions in immunity. The MnToll1 protein shares similar structural characteristics with other known Toll family proteins. MnToll1 transcripts are broadly distributed in all of the examined tissues, and its expression level was significantly up-regulated by bacterial challenge. RNAi-mediated knockdown of MnToll1 significantly impaired the survivability of Vibrio -challenged prawns. RNAi experiments also revealed that the expression of several antimicrobial peptide genes were regulated by MnToll1. Moreover, we found the extracellular region of MnToll1 could directly bind to bacteria and bacterial glycoconjugates. These findings suggest that MnToll1 function as a pattern recognition receptor to recognize invading pathogen and initiate downstream gene expression, to participate in antibacterial defense of M. nipponense. • RNAi-mediated knockdown of MnToll1 significantly impaired the survivability of Vibrio -challenged prawns. • The expression of several antimicrobial peptide genes were regulated by MnToll1. • The extracellular region of MnToll1 could directly bind to bacteria and bacterial glycoconjugates. [ABSTRACT FROM AUTHOR]

In invertebrates, both fibrinogen-related proteins (FREPs) and C-type lectins are acknowledged to act as pattern recognition receptors (PRRs) to participate particularly in an innate immunity. Hereby, a unique C-type lectin designated as FmLFd was isolated from the hemocytes of Fenneropenaeus merguiensis. FmLFd contained one open reading frame which encoding a peptide of 312 amino acid residues and a signal peptide of 18 amino acids. The primary sequence of FmLFd was composed of a fibrinogen-like domain (Fd) with a Ca2+-binding site and possessing specificity to bind N-acetyl glucosamine (GlcNAc). The FmLFd transcripts were detected mainly in hemocytes of healthy shrimp. The expression of FmLFd was significantly up-regulated upon challenge shrimp with Vibrio parahaemolyticus and Vibrio harveyi which more potent than by white spot syndrome virus (WSSV). The knocking down shrimp with FmLFd double-stranded RNA caused dramatical gene down-regulation. The gene silencing with co-injection of pathogens resulted in reduction of the shrimp survival rate. Recombinant protein of FmLFd (rFmLFd) could agglutinate and bind directly to both Gram-negative and Gram-positive bacteria in a Ca2+-dependent manner and showed the sugar specificity to GlcNAc and bacterial saccharides; peptidoglycan (PGN), lipopolysaccharide (LPS) and lipoteichoic acid (LTA). Recombinant protein of Fd domain (rFd) displayed the lower activity and specificity only to PGN. The binding between recombinant proteins of FmLFd and its domain confirming by ELISA demonstrated that both rFmLFd and rFd could bind to PGN, LPS and LTA with the highest affinity respected to PGN including a less extent of rFd. Besides, rFmLFd but not rFd could bind to WSSV proteins with the highest binding affinity to capsid VP15 and decreasing in order to envelope VP28 and tegument VP39A, respectively. It was presumed that entire molecule of FmLFd exhibited the antimicrobial ability by inhibiting the growth of pathogenic V. parahaemolyticus and this action was not affected by GlcNAc. Otherwise, FmLFd, a lectin containing fibrinogen-like domain, was firstly reported to be capable of promoting encapsulation by hemocytes. Altogether, we concluded that FmLFd belonged to a FREP family indentified by the existence of a conserved fibrinogen-like domain with possessing an ability to bind GlcNAc. It was a new C-type lectin existed in F. merguiensis and might presumably act as a kind of PRRs to participate in the shrimp immune defense towards bacterial and viral pathogens. • FmLFd expression is extremely up-regulated upon Vibrio parahaemolyticus challenge. • Gene silencing by dsRNA inhibits severely FmLFd transcription and raises mortality. • rFmLFd has activities of agglutination, direct binding and antibacterial ability. • rFmLFd but not its domain displays firstly to promote encapsulation by hemocytes. • FmLFd containing fibrinogen-like domain serves as PRR against pathogens. [ABSTRACT FROM AUTHOR]

The innate immune defense of mammalian hosts relies on its capacity to detect invading pathogens and then directly eliminate them or help guide adaptive immune responses. Recognition of microbial DNA and RNA by pattern recognition receptors (PRRs) is central to the detection of pathogens by initiating cytokine-mediated innate immunity. In contrast, disturbance of this pathogen surveillance system can result in aberrant innate immune activation, leading to proinflammatory or autoimmune diseases. Among the many important PRRs are proteins of the retinoic acid-inducible gene-I (RIG-I)-like receptor (RLR) family as well as cyclic GMP-AMP synthase (cGAS), which detect viral RNA and DNA, respectively, within the host cell. Intriguingly, recent evidence has shown that "unmasked," misprocessed, or mislocalized host-derived RNA or DNA molecules can also be recognized by RLRs or cGAS, thereby triggering antiviral host defenses or causing inflammation. Here, we review recent advances of endogenous nucleic acid recognition by RLRs and cGAS during viral infection and systemic proinflammatory/autoimmune disorders. [ABSTRACT FROM AUTHOR]

• CD14 works as a multi-talented receptor to relay context dependent signals that regulate the inflammation outcome. • To define CDs activities in different context, in this review, we summarize recent progresses toward the molecular definition of the multiple roles exerted by CD14 and advancements in its basic biology. Human monocyte differentiation antigen CD14 is a pattern recognition receptor (PRR) that enhances innate immune responses. CD14 was first identified as a marker of monocytes to signal intracellular responses upon bacterial encounters. Given the absence of an intracellular tail, CD14 was doubted to have the signaling capacities. Later CD14 was confirmed as the TLR co-receptor for the detection of pathogen-associated molecular patterns. However, CD14 has been revealed as a multi-talented receptor. In last decade, CD14 was identified to activate NFAT to regulate the life cycle of myeloid cells in a TLR4-independent manner and to transport inflammatory lipids to induce phagocyte hyperactivation. And its influences on multiple related diseases have been further considered. In this review, we summarize advancements in the basic biology of the CD14 including its structure, binding ligands, signaling pathways, and its roles in the pathogenesis of inflammation, atherosclerosis, tumor and metabolic diseases. We also discuss the therapeutic potential of targeting the CD14 in related diseases. [ABSTRACT FROM AUTHOR]

Amyloid formation contributes to the development of progressive metabolic and neurodegenerative diseases, while also serving functional roles in host defense. Emerging evidence suggests that as amyloidogenic peptides populate distinct aggregation states, they interact with different combinations of pattern recognition receptors (PRRs) to direct the phenotype and function of tissue-resident and infiltrating innate immune cells. We review recent evidence of innate immunomodulation by distinct forms of amyloidogenic peptides produced by mammals (humans, non-human primates), bacteria, and fungi, as well as the corresponding cell-surface and intracellular PRRs in these interactions, in human and mouse models. Our emerging understanding of peptide aggregate-innate immune cell interactions, and the factors regulating the balance between amyloid function and pathogenicity, might aid the development of anti-amyloid and immunomodulating therapies. Amyloidogenic peptides of both bacterial and mammalian origin transition through multiple aggregation states with distinct effects on mononuclear phagocyte function, commonly mediated by TLR2 and NLRP3. Promising therapeutic agents target such macrophage/peptide interactions. Disease-associated amyloidogenic peptides may act as antimicrobial peptides. Soluble oligomers bind microbial cell walls, protofibrils limit adhesion to host cells, and fibrils wall off invading pathogens. Infectious or sterile inflammatory stimuli may partially drive amyloidosis, a hypothesis supported by cross-seeding of endogenous amyloid formation by products of innate immune cell activation: apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) specks and neutrophil extracellular traps (NETs). Cross-seeding can also occur between amyloids in different tissues, such as the gut and brain, and across species. Manipulation of microbial amyloids might be a potential therapeutic approach to treat amyloid and inflammatory diseases. [ABSTRACT FROM AUTHOR]

Background. There is evidence that suggests variation in gene encoding pattern recognition receptors, the essential components of innate immunity, might be associated with atopic diseases. However, results have been inconclusive. Objectives. The aim of the study was to determine the individual associations and possible interactive effects of the CD14 (cluster of differentiation 14), TLR4 (toll-like receptor 4) and TLR2 (toll-like receptor 2) polymorphisms on allergic diseases. Material and methods. The CD14 C-159T, TLR4 +896A/G and TLR2 A-16934T polymorphisms were identified in 115 children aged from 6 to 17 years. All subjects were selected using a detailed questionnaire which included questions on symptoms and each one underwent skin prick testing. All single-nucleotide polymorphisms (SNPs) were determined using real-time polymerase chain reaction (PCR) assays. Results. There was no statistically significant correlation between the 3 polymorphisms (CD14 C-159T, TLR4 +896A/G and TLR2/-16934A/T) and either asthma, allergic rhinitis or atopy. We observed that children who were heterozygous or homozygous for both the CD14/-159T and TLR2/-16934A alleles had a 4-fold lower risk for asthma than children who were carriers of the T allele of CD14 but non-carriers of the A allele of TLR2, and an almost 3-fold lower risk for asthma when compared to all other groups. Concerning allergic rhinitis, a similar trend was observed. In addition, the presence of at least 1 A allele in the TLR2/-16934 polymorphism reduced the risk for asthma and allergic rhinitis, but only in children who were homozygous for the common A allele in the TLR4 +896 polymorphism. Conclusions. Our study supports the idea that the CD14, TLR2 and TLR4 polymorphisms may not be directly involved in the development of atopic diseases. However, our results suggest that their impact on the risk of asthma and allergic rhinitis might be modulated by gene-gene interactions. [ABSTRACT FROM AUTHOR]

Tolls/Toll-like receptors (TLRs) play a key role in innate immunity by detecting the invading microbes and subsequently activating downstream signaling cascades. In this study, two new molluscan Toll members (designed as HcToll6 and HcToll7) were identified from triangle-shell pearl mussel (Hyriopsis cumingii). The obtained HcToll6 full-length cDNA was 3207 bp consisting of a 2223 bp open reading frame (ORF) that encoded a peptide of 740 amino acids. HcToll7 cDNA is a 3216 bp molecule that contains an ORF of 2139 bp encoding a protein of 712 amino acids. The deduced HcToll6 and HcToll7 proteins share two common structures: extracellular leucine-rich repeat (LRR) domains and intracellular Toll/interleukin-1 receptor (TIR) domain. Quantitative real-time PCR results showed that HcToll6 and HcToll7 were mainly expressed in the hepatopancreas and the gills, and they responded rapidly to bacterial stimulation. RNA interference by dsRNA results revealed that HcToll6 and HcToll7 RNAi strongly decreased the expression of lysozyme (HcLyso) and defensin (HcDef) in the gills of RNAi-treated mussels with Vibrio parahaemolyticus challenge. As a pattern recognition receptor, the prokaryotic expressed the recombinant LRR domains of HcToll6 and HcToll7 (rHcToll6-LRR and rHcToll7-LRR) could bind to Gram-positive and Gram-negative bacteria and had a strong tendency to recognize lipopolysaccharide (LPS) and peptidoglycan (PNG). rHcToll6-LRR and rHcToll7-LRR exhibited a significant in vitro bactericidal activity against V. parahaemolyticus and Staphylococcus aureus. These findings provide useful information to characterize Tolls in mussels. [ABSTRACT FROM AUTHOR]

C-type lectins (CTLs) are pattern recognition receptors (PRRs) that are important in invertebrate innate immunity for the recognition and elimination of pathogens. Although they were reported in many shrimp, C-type lectins subfamily contain a large number of members with different functions that need to research in deep. In this present study, a new type of CTL, PmCL1 with 861 bp long full-length cDNA, that encodes a protein with 164-amino acid from a 495-bp open reading frame, was isolated and characterized from tiger shrimp (Penaeus monodon). The mRNA transcript of PmCL1 showed the highest expression in the hepatopancreas, whereas it was barely detected in the ovary. After the shrimp were stimulated by Vibrio harveyi and Vibrio anguillarum , PmCL1 expression in the hepatopancreas and gill was significantly upregulated. A carbohydrate-binding assay revealed the specificity of PmCL1 for pathogen-associated molecular patterns (PAMPs) that included peptidoglycan (PGN) and lipopolysaccharide (LPS), and saccharides that included d -glucose, galactosamine, α-lactose, treholose, and d -mannose. Recombinant PmCL1 agglutinated gram-positive (Staphylococcus aureus) and gram-negative bacteria (V. harveyi , V. anguillarum , Vibrio alginolyticus , Vibrio parahemolyticus , Vibrio vulnificus , and Aeromonas hydrophila) in the presence of calcium ions and enhanced the efficiency of clearing the invading bacteria. Collectively, our results suggested that PmCL1 might play an important role as a pattern recognition receptor (PRR) in the immune response towards pathogen infections, as well as the response towards ammonia nitrogen stress. • A PmCL1 gene belongs to the C-type lectin subfamilies and was up-regulated by gram-positive and gram-negative bacteria. • Ammonia-N stress significantly influenced the mRNA levels of PmCL1 in the tissues. • RPmCL1 had specificity to various carbohydrates and PAMPs. • RPmCL1 could induce agglutination of bacteria in the presence of calcium ion. • RPmCL1 could enhance the efficiency of clearing the invading bacteria in vivo. [ABSTRACT FROM AUTHOR]

The innate immune system-based recognition of the pathogens or their PAMPs initiates the pro-inflammatory immune response required for the maintenance of the homeostasis. The dysregulation of this innate immune response causes several diseases including sepsis, cancer and autoimmunity. However, pattern recognition receptors (PRRs) including toll-like receptors (TLRs), complement receptors (CRs) and NLRs of inflammasomes regulate both these processes of recognition of pathogens/PAMPs and their clearance. These three major components of the innate immune arm were studied independently/separately for a long time. Various studies have now shown that they work in close association and their crosstalk is required for the pathogen clearance via regulating the process of phagocytosis and mounting the controlled but potent immune response. The loss or inhibition of any of the three components affects the other in a positive/negative manner that can affect the immune process required for efficient host defense. The present review is designed to provide the current information on their evolution like the requirement of TLRs and inflammasomes for pathogen recognition even in the presence of complements system and their interaction during various immunological processes including phagocytosis, autophagy and inflammatory immune response. [ABSTRACT FROM AUTHOR]

TLRs are a class of pattern recognition receptors (PRRs) that detect invading microbes by recognizing pathogen‐associated molecular patterns (PAMPs). Upon PAMP engagement, TLRs activate a signaling cascade that leads to the production of inflammatory mediators. The localization of TLRs, either on the plasma membrane or in the endolysosomal compartment, has been considered to be a fundamental aspect to determine to which ligands the receptors bind, and which transduction pathways are induced. However, new observations have challenged this view by identifying complex trafficking events that occur upon TLR‐ligand binding. These findings have highlighted the central role that endocytosis and receptor trafficking play in the regulation of the innate immune response. Here, we review the TLR4 and TLR9 transduction pathways and the importance of their different subcellular localization during the inflammatory response. Finally, we discuss the implications of TLR9 subcellular localization in autoimmunity. [ABSTRACT FROM AUTHOR]

Earthworms are not endowed with adaptive immunity and they are rely on the tools of innate immunity. Cells of the innate immune system utilize pattern recognition receptors, such as Toll-like receptors, to detect the pathogen-associated molecular patterns (PAMPs). The first earthworm TLR was isolated from Eisenia andrei earthworms (Ea TLR), which belongs to the single cysteine cluster TLR (sccTLR). Here, we identified a new multiple cysteine cluster TLR (mccTLR) in E. andrei earthworms. Phylogenetic DNA analysis revealed that it has no variability within one earthworm as well as in the population. By screening of the tissue expression profile, the TLR was expressed primarily in earthworm seminal vesicles and receptacles suggesting a connection to sperm cells. Seminal vesicles are often heavily infected by gregarine parasites. As a sign of immune response, a strong melanization reaction is visible around parasites. Stimulation experiments with profilin from related parasite Toxoplasma gondii , led to the upregulation of mcc Ea TLR in the earthworm seminal vesicles. Also, profilin activated prophenoloxidase cascade, the efficient mechanism of innate immunity. However, its involvement in the NF-κB signaling was not proven. Further, we provide evidence that the antibiotics metronidazole and griseofulvin destroyed the developing spermatocytes. The observed decrease in the mcc Ea TLR mRNA levels after the antibiotic treatment of parasites is caused by the decline of sperm cells numbers rather than by diminution of the parasites. Since earthworms with extensively reduced parasite load had a similar amount of mcc Ea TLR mRNA, presumably, earthworm sperm cells have a certain level of mcc Ea TLR expressed as a standard, which can be augmented by particular antigenic stimulation. Also, mcc Ea TLR was expressed mainly in the early stages of earthworm development and presumably is primarily involved in early embryonic development. Expression of mcc Ea TLR in seminal vesicles correlates with the expression of endothelial monocyte-activation polypeptide II. High-throughput sequencing of gregarine DNA from seminal vesicles of individual earthworms resulted in great diversity of the observed genotypes. Phylogenetically, all observed OTUs belong to the clade of earthworm gregarines suggesting host specificity. Overall, mcc Ea TLR is supposed to play a function role in early embryonic development and potentially it participates in immune response against parasites. [ABSTRACT FROM AUTHOR]

Abstract Peptidoglycan recognition proteins (PGRPs) are members of an important class of pattern recognition receptors in insects that can specifically recognize peptidoglycan (PGN) in bacterial cell walls and participate in immune regulation and bacterial clearance. Although the role of PGRPs in regulating the innate immune response in Drosophila melanogaster has been studied, little is known regarding PGRPs in Lepidoptera species. In this study, five short (S)-type Bombyx mori PGRPs (BmPGRPs) were cloned, expressed, and evaluated for their function in innate immunity. B. mori larvae that were injected with the gram-positive bacterium Bacillus megaterium or the gram-negative bacterium Escherichia coli exhibited a rapid and significant upregulation in S-type BmPGRP expression. The results showed that the five evaluated BmPGRPs have significant agglutination activity toward E. coli and B. megaterium and more notable amidase activity toward meso -diaminopimelic acid peptidoglycan (DAP-PGN). Furthermore, only in the presence of BmPGRP-S5 did B. mori larval hemocytes exhibit significant phagocytosis against E. coli and B. megaterium. Graphical abstract Image 109941 Peptidoglycan recognition proteins (PGRPs), as a very important class of pattern recognition receptors, can specifically recognize peptidoglycan (PGN) in the bacterial cell wall and participate in insect immune regulation. The function of PGRPs in Drosophila has been studied. In this study, five short (S)-type BmPGRPs in Bombyx mori were cloned and expressed. The five S-type BmPGRPs have significant agglutination effects on E. coli and B. megaterium but have more obvious amidase activity on me-so-diaminopimelic acid peptidoglycan (DAP-PGN). Only in the presence of BmPGRP-S5 did the hemocytes of the B. mori larvae have significant phagocytosis effects against E. coli and B. megaterium. Highlights • There are five S-type BmPGRPs in silkworm and could be rapidly up-regulated expression by E. coli and B. megaterium. • The five S-type BmPGRPs have significant agglutination effects on E. coli and B. megaterium but have more obvious amidase activity on DAP-PGN. • Only in the presence of BmPGRP-S5 did the hemocytes of the B. mori larvae have significant phagocytosis effects against E. coli and B. megaterium. [ABSTRACT FROM AUTHOR]

Purpose: NOD1 and NOD2 (nucleotide-binding oligomerization domain)—receptors are intracellular receptors and belong to the family of pattern recognition receptors being present in both human and murine renal tubular cells. Besides, NOD1 has been proved to promote apoptosis, upon its overexpression. Hence, we aimed to investigate NOD1 and NOD2 expression in human clear cell renal cell carcinoma (ccRCC). Methods: Tumor and corresponding adjacent healthy tissues from 41 patients with histopathological diagnosis of ccRCC as well as primary isolated renal tubular epithelial cells (TECs) and tumor tissue from a murine xenograft model using CAKI-1 ccRCC cells were analyzed. Results: NOD1 and NOD2 mRNA was constitutively expressed in both tumor and adjacent healthy renal tissue, with NOD1 being significantly lower and in contrast NOD2 significantly higher expressed in tumor tissue compared to healthy tissues. Immunohistochemically, NOD1 was located not only in the cytoplasm, but also in the nucleus in ccRCC tissue whereas NOD2 was solely localized in the cytoplasm in both human ccRCC as well as in the healthy tubular system. Focusing on the vasculature, NOD2 displayed broader expression than NOD1. In primary TECs as well as CAKI-1 cells NOD1 and NOD2 was constitutively expressed and increasable upon LPS stimulation. In the mouse xenograft model, human NOD1 mRNA was significantly higher expressed compared to NOD2. In contrast hereto, we observed a shift towards lower mouse NOD1 compared to NOD2 mRNA expression. Conclusion: In view of reduced apoptosis-associated NOD1 expression in ccRCC tissue opposed to higher expression of NOD2 in tumor vasculature, inducibility of NOD expression in TECs as well as the detected shift of NOD1 and NOD2 expression in the mouse xenograft model, modulation of NOD receptors might, therefore, provide a molecular therapeutic approach in ccRCC. [ABSTRACT FROM AUTHOR]

Pattern-recognition receptors (PRRs), which are single transmembrane proteins belonging to the receptor-like kinase (RLK) and receptor-like protein (RLP) super families, sense microbe- and host-derived molecular patterns to activate immune responses in plants. PRRs associate with co-receptors, scaffold proteins and receptor-like cytoplasmic kinases (RLCKs) to form immune receptor complexes at the cell surface, allowing activation of cellular responses upon perception of extracellular ligands. Recent advances have uncovered new mechanisms by which these immune receptor complexes are regulated at the levels of composition, stability and activity. It has become clear that RLCKs are central components directly linking PRRs to multiple downstream signalling modules. Furthermore, new studies have provided important insights into the regulation of reactive oxygen species, mitogenactivated protein (MAP) kinase cascades and heterotrimeric G proteins, which has not only deepened our understanding of immunity, but also expanded our view of transmembrane signalling in general [ABSTRACT FROM AUTHOR]

Abstract. Leucine-rich repeat (LRR)-only proteins are involved in innate immune responses through mediating protein-ligand or protein-protein interactions, yet the exact roles of most LRR-only proteins in invertebrates are not well documented. In the present study, a novel LRR-only protein (designated Cf LRRop-7) was identified in Zhikong scallop Chlamys farreri. The full-length cDNA sequence of Cf LRRop-7 was 1463 bp and contained an open reading frame of 1086 bp, which encoded a protein of 361 amino acids. Five LRR motifs with a conserved signature sequence LxxLxLxxNxL were identified in the predicted protein sequence. The expression of Cf LRRop-7 was particularly high in hemocytes. The expression of Cf LRRop-7 was relatively high in oocytes and embryos during the ontogenesis of scallops. Cf LRRop-7 expression changed in hemocytes in response to stimulation with different microbes, including Vibrio splendidus , Staphylococcus aureus and Pichia pastoris. Cf LRRop-7 recognized five kinds of ligands/agonists. Cf LRRop-7 recombinant protein inhibited bacterial proliferation in hemolymph and induced lysozyme activity in serum. After knocking down Cf LRRop-7, the mRNA expression of selected antimicrobial peptides was reduced. All these results indicated that Cf LRRop-7 might be a potential pattern recognition receptor that recognizes various pathogen associated molecular patterns, and regulates antibacterial immunity in scallops. Highlights • A novel LRR-only protein (Cf LRRop-7) was identified in scallop Chlamys farreri. • Cf LRRop-7 exhibited recognition capacity to various PAMPs. • Cf LRRop-7 inhibits the bacterial proliferation by regulating expression of antimicrobial peptides. [ABSTRACT FROM AUTHOR]

Abstract Lipopolysaccharide (LPS) is a well-known pathogen-associated molecular pattern (PAMP) produced by gram-negative bacteria. Previous studies showed that a key metabolic intermediate in LPS biosynthesis, d - glycero -β- d - manno -heptose 1,7-bisphosphate (HBP), could activate the NF-κB pathway and trigger the innate immune responses. However, it was unclear whether HBP could be a novel PAMP and its pattern recognition receptor (PRR) is not fully understood. Very recently, the Shao group reported that another key metabolic intermediate in LPS biosynthesis, ADP-heptose, could be transported into mammalian cells and bind with ALPK1 (alpha-kinase 1), which leads to a series of strong immune responses. These findings broaden our understanding on bacterial metabolites as a new type of PAMP and these small molecules hold great potential to be applied in the development of novel immune modulators. This minireview focuses on the roles of ADP-heptose related metabolites in innate immunity. Graphical abstract Image 1 Highlights • The recent research on the biosynthesis of ADP-heptose is reviewed. • The discovery of ADP-heptose as a novel pathogen-associated molecular pattern (PAMP) is reviewed. • The new roles of ADP-heptose in enteropathogen infection are reviewed. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Neutrophils uptake Leishmania promastigotes and tolerate amastigote differentiation. • During early infection, parasites do not seem to signal through neutrophil PRRs. • Visceral and cutaneous species of Leishmania activate neutrophil oxidative burst. • The extracellular activity of neutrophil enzymes is dependent on parasite species. • Neutrophils emit NETs against cutaneous and visceral species of Leishmania. Abstract Neutrophils are short-lived phagocytic cells equipped with several receptors for pathogen recognition and phagocytosis and have intracellular and extracellular effector mechanisms that can inactivate pathogens. Leishmaniases are diseases caused by different species of Leishmania that mainly afflicts poorer populations of tropical and subtropical regions and immunocompromised individuals. Thus, the present study aims to investigate the effector response of murine neutrophils to species of Leishmania causing American cutaneous leishmaniasis and zoonotic visceral leishmaniasis by evaluating pattern recognition receptors (PRR) and intracellular and extracellular effector microbicide activity. When exposed to Leishmania parasites, mouse neutrophils produced superoxide, released enzymes in the extracellular space and generated neutrophil extracellular traps, although PRR gene expression is negatively regulated. L. infantum , L. guyanensis , and L. shawi inhibited enzymatic activity, whereas L. amazonensis reduced the emission of extracellular structures. These findings indicate that although neutrophils trigger several microbicide mechanisms, Leishmania parasites can manipulate extracellular effector mechanisms. The present study also provides evidence that neutrophils can internalize parasites by coiling phagocytosis. [ABSTRACT FROM AUTHOR]

In the current concept of bacterial infections, pathogen-associated molecular patterns (PAMPs) derived from pathogens and damage-associated molecular patterns (DAMPs) released from damaged/necrotic host cells are crucial factors in induction of innate immune responses. However, the implication of DAMPs in apical and marginal periodontitis is unknown. Serum amyloid A (SAA) is a DAMP that is involved in the development of various chronic inflammatory diseases, such as rheumatoid arthritis. In the present study, we tested whether SAA is involved in the pathogenesis of periapical lesions, using human periapical surgical specimens and mice deficient in SAA and Toll-like receptors (TLR). SAA1/2 was locally expressed in human periapical lesions at the mRNA and protein levels. The level of SAA protein appeared to be positively associated with the inflammatory status of the lesions. In the development of mouse periapical inflammation, SAA1.1/2.1 was elevated locally and systemically in wild-type (WT) mice. Although SAA1.1/2.1 double-knockout and SAA3 knockout mice had redundant attenuation of the extent of periapical lesions, these animals showed strikingly improved inflammatory cell infiltration versus WT. Recombinant human SAA1 (rhSAA1) directly induced chemotaxis of WT neutrophils in a dose-dependent manner in vitro. In addition, rhSAA1 stimulation significantly prolonged the survival of WT neutrophils as compared with nonstimulated neutrophils. Furthermore, rhSAA1 activated the NF-κB pathway and subsequent IL-1α production in macrophages in a dose-dependent manner. However, TLR2/TLR4 double deficiency substantially diminished these SAA-mediated proinflammatory responses. Taken together, the SAA-TLR axis plays an important role in the chronicity of periapical inflammation via induction of inflammatory cell infiltration and prolonged cell survival. The interactions of PAMPs and DAMPs require further investigation in dental/oral inflammation. [ABSTRACT FROM AUTHOR]

Abstract Galactoside-binding lectin (galectin) is a type of pathogen recognition molecule that occupies an important position in the invertebrate innate immunity system. Our previous study has identified a galectin gene in mollusk Solen grandis (SgGal-1) and illustrated its potential roles in innate immunity. By the functional study using recombinant protein and specific antibody, here, we confirmed the pivotal roles of SgGal-1 in immune defense of S. grandis. SgGal-1 protein was expressed in many tested tissues including gill, mantle, hepatopancreas and gonad, except hemocytes and muscle. The recombinant SgGal-1 (rSgGal-1) bound PGN and β-glucan instead of LPS in vitro , and it further caused significant agglutination of five different microbes, suggesting SgGal-1 served as a pattern recognition receptor (PRR) involved in immune defense of mollusk. Furthermore, SgGal-1 recruited hemocytes to encapsulate, which was blocked by anti-rSgGal-1 serum. In the meantime, rSgGal-1 as well as promoted the phagocytosis of hemocytes against Escherichia coli in vitro. All these results suggested that SgGal-1 in S. grandis not only acted as a PRR recognizing microbes but also directly participated in the process of immune opsonization to protect the host from pathogenic infection. Highlights • Galactoside-binding lectin is a multifunctional protein in Solen grandis. • SgGal-1 is distributed in many different tissues. • SgGal-1 serves as a PRR to bind PGN and glucan. • SgGal-1 involves in the anti-microbial response through agglutination. • SgGal-1 acts as an opsonin mediating encapsulation and phagocytosis of hemocytes. [ABSTRACT FROM AUTHOR]

Abstract The interplay between human cytomegalovirus (HCMV) and the innate immune response is a critical process that has attracted the attention of many research groups. The emerging scenario is that the immune response of an HCMV-infected host is mediated by a plethora of viral DNA sensors acting as pattern recognition receptors (PRRs), which are capable of inhibiting indirectly viral infection through the activation of two distinct downstream signaling cascades. The first one triggers the production of cytokines, chemokines and interferons (IFNs), while the second one leads to inflammasome complex formation, which in turn promotes the maturation and secretion of pro-inflammatory cytokines such as interleukin-1β (IL-1β). An additional first line of defense against HCMV is represented by a multiplicity of constitutively expressed restriction factors that inhibit viral replication by directly interfering with the activity of essential viral/cellular genes. Here, we take a closer look at some of the most representative intrinsic restriction factors involved in HCMV infection (e.g. IFI16, ND10 complex, viperin and APOBEC3) and review our current understanding of the mechanisms that HCMV has evolved to counteract both IFN and inflammasome responses. Highlights • Recent advances in the innate immune response against HCMV. • HCMV DNA sensing mechanisms. • Impact of interferon and inflammasome pathways on HCMV infection. • Host restriction factors hijacking HCMV replication and counteracting measures. [ABSTRACT FROM AUTHOR]

Insects and mammals share evolutionary conserved innate immune responses to maintain intestinal homeostasis. We investigated whether the larvae of the greater wax moth Galleria mellonella may be used as an experimental organism to distinguish between symbiotic Bacteroides vulgatus and pathobiotic Escherichia coli , which are mammalian intestinal commensals. Oral application of the symbiont or pathobiont to G. mellonella resulted in clearly distinguishable innate immune responses that could be verified by analyzing similar innate immune components in mice in vivo and in vitro. The differential innate immune responses were initiated by the recognition of bacterial components via pattern recognition receptors. The pathobiont detection resulted in increased expression of reactive oxygen and nitrogen species related genes as well as antimicrobial peptide gene expression. In contrast, the treatment/application with symbiotic bacteria led to weakened immune responses in both mammalian and insect models. As symbionts and pathobionts play a crucial role in development of inflammatory bowel diseases, we hence suggest G. mellonella as a future replacement organism in inflammatory bowel disease research. [ABSTRACT FROM AUTHOR]

C-type lectins are a member of pattern recognition receptors (PRRs) that can interact with pathogen-associated molecular patterns of invading microorganisms by using their conserved motifs in carbohydrate recognition domain (CRD). The binding can trigger various immune responses in both direct and indirect mechanisms. Hereby, an ultimate C-type lectin with dual CRDs each of which containing a different motif was identified from hepatopancreas of Fenneropenaeus merguiensis (mentioned as FmLC6). The full-length cDNA of FmLC6 consisted of 1148 bp comprising one 1005 bp open reading frame (ORF) encoding a signal peptide and a mature protein of 317 residues. FmLC6 was composed of two CRDs with a highly conserved QPD (Gln-Pro-Asp) motif and one variant EPQ (Glu-Pro-Gln) motif for illustrating the carbohydrate binding affinity. The transcription of FmLC6 was detected only in hepatopancreas of normal shrimp. After injection with pathogens or immunostimulants, the expression of FmLC6 was significantly up-regulated and reached the highest level at 12 h post-injection except with lipoteichoic acid challenge. The FmLC6 expression was severely suppressed by knockdown based-silencing. This gene silencing with co-injection by Vibrio parahaemolyticus caused increasing in cumulative mortality and reduction of the median lethal time. Purified recombinant proteins of an entire ORF and two individual CRDs of FmLC6 produced in Escherichia coli could induce a broad spectrum of microbial agglutination with calcium dependence. The agglutination induced by rFmLC6, rCRD1 and rCRD2 was suppressed by galactose plus mannose, galactose and mannose, respectively which this event was confirmed by the inhibition of hemagglutination. All three recombinant proteins possessed ability to inhibit the bacterial growth with a dose-response. Purified rFmLC6 could bind directly to white spot syndrome virus particles and also its recombinant proteins including VP15, VP39A and VP28 with different affinity. Altogether, these results indicate that FmLC6 acts as a PRR to recognize invading microorganisms and leads to mediating the immune response to cooperation in pathogenic elimination via the binding, agglutination and antimicrobial activity. [ABSTRACT FROM AUTHOR]