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In China, Procambarus clarkii has grown to be one of the most important cultivated crustacean species due to its excellent resistance ability against viral and bacterial infection. However, this broad-spectrum mechanism of disease resistance is less well known. In this study, a new LGBP known as Pc LGBP was cloned and described. Its full-length cDNA is 1200 bp with an open reading frame (ORF) of 1086 bp, encoding a 361 amino acid polypeptide. The transcripts of Pc LGBP were widely dispersed in P. clarkii tissues, with particularly elevated expression levels in hemocytes. Furthermore, Aeromonas hydrophila and white spot syndrome virus (WSSV) challenge dramatically increased its mRNA expression in hemocytes and gills. The purified recombinant Pc LGBP protein could bind to different kinds of pathogenic microorganisms, demonstrating a broad-spectrum pathogen recognition ability. Besides, Pc LGBP knockdown by RNA interference and r Pc LGBP injection experiments confirmed that the protein could apparently accelerate the bacterial clearance and inhibit the WSSV proliferation in vivo , thus increase the survival rate of A. hydrophila or WSSV infected P. clarkii. Further studies revealed that silencing of Pc LGBP resulted in inactivation of prophenoloxidase (proPO) system, decreased the expression levels of Toll/IMD pathway components, as well as some antimicrobial peptides (AMPs). Taken together, Pc LGBP may protect P. clarkii from diverse invading pathogens through activating the proPO system, NF-κB pathway and the expression of AMPs. These findings would contribute to the exploration of the crustacean immunity regulatory mechanisms and hold potential for the disease resistance breeding of P. clarkii. • A novel member of LGBP family named Pc LGBP was identified in Procambarus clarkii. • Pc LGBP was involved in both anti-bacterial and anti-viral immune response. • Pc LGBP exhibited broad-spectrum resistance ability in vivo. • Pc LGBP participate in the activation of the proPO system and NF-κB pathway. [ABSTRACT FROM AUTHOR]

At the end of December 2019, the COVID-19 pandemic began in Wuhan of China. COVID-19 affects different people with a wide spectrum of clinical manifestations, ranging from asymptomatic with recovery without hospitalization up to a severe acute respiratory syndrome (SARS). The innate and adaptive immunity appears responsible for the defense against the virus and recovery from the disease. The innate immune system, as the first line of defense, is essential for the detection of virus and subsequent activation of acquired immunity. The innate immune response is carried out by sentinel cells such as monocytes/macrophages and dendritic cells and by receptors known as pattern recognition receptors (PRR). These receptors can recognize various components of the virus, which lead to intracellular signaling and subsequently the synthesis of various cytokines. These cytokines then recruit other immune cells, activate adaptive immune responses, and inhibit viral spreading. The most common receptors include Toll-like receptors, C-type lectin receptors, and RIG-I like receptors. This review describes the current knowledge about the interplay between innate immune responses and SARS-CoV-2 with a focus on the innate immune cells and the role of their receptors in viral RNA recognition, as well as their mechanisms for recognizing SARS-CoV-2. [ABSTRACT FROM AUTHOR]

C-type lectins (CTL) are a large group of pattern-recognition proteins and to play important roles in glycoprotein metabolism, multicellular integration, and immunity. Based on their overall domain structure, they can be classified as different groups that possess different physiological functions. A typical C-type lectin (named as Om Lec1) was identified from the fish, Onychostoma macrolepis , an important cultured fish in China. Open reading frame of Om Lec1 contains a 570 bp, encoding a protein of 189 amino acids that includes a signal peptide and a single carbohydrate-recognition domain. The phylogenetic analysis showed that Om Lec1 could be grouped with C-type lectin from other fish. Om Lec1 was expressed in all the tissues in our study, and the expression level was highest in liver. And its relative expression levels were significantly upregulated following infection with Aeromonas hydrophila. The recombinant Om Lec1 protein (r Om Lec1) could agglutinate some Gram-negative bacteria and Gram-positive bacteria in vitro in the presence of Ca2+, showing a typical Ca2+-dependent carbohydrate-binding protein. Furthermore, r Om Lec1 purified from E. coli BL21 (DE3), strongly bound to LPS and PGN, as well as all tested bacteria in a Ca2+-dependent manner. These results indicate that Om Lec1 plays a central role in the innate immune response and as a pattern recognition receptor that recognizes diverse pathogens among O. macrolepis. • A typical C-type lectin with a EPN/WND motif (Om Lec1) was identified and characterized from Onychostoma macrolepis. • The expression levels of Om Lec1 gene were significantly up-regulated after pathogen challenge. • Recombinant Om Lec1 can agglutinates various bacteria in vitro in the presence of Ca2+. • Recombinant Om Lec1 could bind some saccharides such as d -mannose, LPS and PGN. [ABSTRACT FROM AUTHOR]

The migratory plant‐parasitic nematode Bursaphelenchus xylophilus is the causal agent of pine wilt disease, which causes serious damage to pine forests in China. Plant immunity plays an important role in plant resistance to multiple pathogens. Activation of the plant immune system is generally determined by immune receptors, including plant pattern recognition receptors, which mediate pattern recognition. However, little is known about molecular pattern recognition in the interaction between pines and B. xylophilus. Based on the B. xylophilus transcriptome at the early stages of infection and Agrobacterium tumefaciens‐mediated transient expression and infiltration of recombinant proteins produced by Pichia pastoris in many plant species, a novel molecular pattern (BxCDP1) was characterized in B. xylophilus. We found that BxCDP1 was highly up‐regulated at the early infection stages of B. xylophilus, and was similar to a protein in Pararhizobium haloflavum. BxCDP1 triggered cell death in Nicotiana benthamiana when secreted into the apoplast, and this effect was dependent on brassinosteroid‐insensitive 1‐associated kinase 1, but independent of suppressor of BIR1‐1. BxCDP1 also exhibited cell death‐inducing activity in pine, Arabidopsis, tomato, pepper, and lettuce. BxCDP1 triggered reactive oxygen species production and the expression of PAMP‐triggered immunity marker genes (NbAcre31, NbPTI5, and NbCyp71D20) in N. benthamiana. It also induced the expression of pathogenesis‐related genes (PtPR‐3, PtPR‐4, and PtPR‐5) in Pinus thunbergii. These results suggest that as a new B. xylophilus molecular pattern, BxCDP1 can not only be recognized by many plant species, but also triggers innate immunity in N. benthamiana and defence responses of P. thunbergii. [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]

The innate immune system is the first line of defense protecting the hosts against invading pathogens. Mud crab (Scylla paramamosain) is widely distributed in China and Indo-west Pacific countries, which develops a very complicated innate immune system against pathogen invasions. Innate immunity involves the humoral and cellular responses that are linked to the pattern recognition receptors (PRRs). PRRs initially recognize the infection and trigger the activation of signaling cascades, leading to transcriptional regulation of inflammatory mediators that function in pathogenic control and clearance. In mud crab S. paramamosain , the Toll/Toll-like receptors, lipopolysaccharide and β-1,3-glucan binding proteins, C-type lectins, scavenger receptors, and down syndrome cell adhesion molecules have been identified as receptor families responsible for the recognition of bacteria, fungi, and viruses, and are important components in the innate immune system. In this review, we summarize the literature on the current knowledge and the roles of PRRs in the immune defenses of mud crab, which in an effort to provide much information for further researches. • Five pattern recognition receptors (PRRs) have been reported in mud crab. • Different PRRs target to different ligands in the innate immunity. • PRRs activate the intracellular signaling cascades and subsequently respond to the infections. [ABSTRACT FROM AUTHOR]