Single-cell atlas of grass carp ( ) peripheral blood IgM B cells provides insights into B cell-mediated immune responses in teleost fish.

Teleost peripheral blood contains a remarkably high proportion of B cells, accounting for 15%-50% of circulating lymphocytes. However, their immune responses to bacterial infection are yet to be elucidated. In the present study, 10× Genomics single-cell RNA sequencing (scRNA-seq) was employed to characterize the transcriptomic landscape of peripheral blood IgM B cells in grass carp ( ) following challenge with , a major aquatic pathogen.

Identification and functional characterization of Cyprinus carpio cGAS reveals its pivotal role against viral infection.

Mammalian cyclic GMP-AMP synthetase (cGAS) exerts a pivotal role in innate immune response to viral infection by detecting viral DNA and activating the cGAS-STING pathway, which triggers type I interferon (IFN-I) production. Although cGAS has been widely investigated in mammals, its function in lower vertebrates, especially in teleost fish, remains poorly understood. Herein, a cGAS homolog (termed c-cGAS) in common carp was identified and functionally characterized to explore its involvement in immune activation and viral response.

Discovery of two IgM subclasses in Nile tilapia (Oreochromis niloticus) provides insights into IgM evolution in teleost fish.

Immunoglobulin M (IgM) is considered the most ancient and prevalent Ig in fish, which plays important roles in systemic and mucosal immunity. In the current study, two heavy chain genes of IgM (named Ighμ1 and Ighμ2) were cloned in Nile tilapia (Oreochromis niloticus), and the amino acid identity between the constant regions of the two IgM heavy chains were 82.58 %.

GCRV-II Triggers B and T Lymphocyte Apoptosis via Mitochondrial ROS Pathway.

Grass carp reovirus (GCRV), particularly the highly prevalent genotype II (GCRV-II), is known to infect peripheral blood leukocytes (PBLs) of grass carp. However, it is unclear whether GCRV-II can induce apoptosis in bystander lymphocytes within infected PBLs. Here, we have shown that GCRV-II infection induces apoptosis via the mitochondria-dependent caspase-3 pathway in infected PBLs.

Novel Antimicrobial Protein Fibroblast Growth Factor 8 Accelerates Skin Wound Healing via Directly Inhibiting Bacteria and Activating Glycolysis.

Repairing and preventing infections of skin wounds are crucial for the body health. Fibroblast growth factors (FGFs) have functions of repairing skin wounds, while antimicrobial peptides/proteins (AMPs) can prevent the infections of skin. Therefore, if FGFs can act like AMPs, they will have better application potential in promoting skin wound healing.

Cold-blooded vertebrates evolved regulatory B cells to participate in inflammatory diseases.

Background: Regulatory B cell (Breg), known for its immunosuppressive properties through the provision of IL-10, plays a critical role in the control of inflammatory diseases. Although Breg has been discovered for over two decades in mammals, its existence in non-mammalian vertebrates remains unclear. Here, we aimed to explore the differentiation mechanism and functional profiles of teleost CD25L Breg to gain insights into the origin and evolution of Breg.

Black carp STAT2 enhances IRF3-mediated antiviral signaling by regulating its ubiquitination and improving its nuclear translocation.

Interferon (IFN) regulatory factor 3 (IRF3) is a critical transcription factor involved in inducing IFN production. However, the regulatory mechanisms of piscine IRF3 remain inadequately explored. Here, we report that the signal transducer and activator of transcription 2 (STAT2) of black carp (Mylopharyngodon piceus) functions as a positive regulator in the black carp IRF3 (bcIRF3)-mediated IFN signaling pathway.

Genomic localization and immune response of IgT in grass carp (Ctenopharyngodon idellus).

Teleost fish have three types of immunoglobulins (Ig): IgM, IgD, and IgT, of which IgT is unique to teleost fish. Though grass carp (Ctenopharyngodon idella) is one of the most farmed freshwater fish species worldwide, the genomic localization of the heavy chain gene of IgT (IGHT) and the composition and usage of the heavy chain variable region (VH) genes remain unknown. In this study, tissue expression pattern analysis revealed that grass carp IgT is constitutively expressed in various tissues, with higher expression levels in the spleen, kidney, and skin.

The molecular adjuvant effect of the C-terminal peptide of complement C5a in a teleost fish.

The activation of the complement system can generate the component C5a, which has potent immunoregulatory activities, such as promoting phagocytosis, respiratory burst, and chemotaxis of leukocytes. Our previous study has shown that teleost C5a exhibits excellent molecular adjuvant function, however, the functional region and the underlying mechanism are still waiting for elucidation. Here, the sequence of grass carp C5a was determined through multiple sequence alignment.

Biochemical characterization and mucosal immune function of IgT in grass carp (Ctenopharyngodon idella).

Immunoglobulin T (IgT) is a teleost-specific immunoglobulin discovered to be specialized in mucosal immunity. For fish that live in water throughout their lives, eliciting a local mucosal immune response through immersion immunization is an important and highly suitable way for preventing fish diseases. However, due to the lack of corresponding antibodies against IgT, studies on its immune responses to pathogens and vaccines in commercial fish have largely been limited to rainbow trout.

Teleost IgM+ plasma-like cells: beyond antibody secretion.

Upon antigen encounter, B cells start a differentiation process toward antibody-secreting cells (ASCs), initially plasmablasts, and eventually long-lived plasma cells. All these ASCs specialize in secreting important amounts of antibodies and usually lose other functionalities of naïve B cells. This differentiation process is scarcely characterized in teleost fish, in which B cells have been shown to share many functional and phenotypic characteristics of mammalian B1 innate subsets.

Contribution of interleukins in the regulation of teleost fish immunity: A review from the perspective of regulating macrophages.

Interleukins (ILs) are potent secreted regulators of a wide range of cell types and cellular activities, particularly in the immune system. They are able to participate in intercellular communication in homeostasis and disease, thereby exerting immune functions. Macrophages serve as the innate immune cells of vertebrates and play a pivotal role in defending against and eliminating external pathogens.

Chinese yam polysaccharide induces the differentiation and natural antibody secretion of IgM B cells to prevent Aeromonas hydrophila infection in grass carp.

Chinese yam polysaccharide (CYP) is an effective immunostimulant, however, its efficacy in grass carp, an important commercial fish species in Asia, remains untested. Here, our study evaluated the immunostimulatory effects of CYP on IgM B cells in vitro and on humoral immunity and immune defense against Aeromonas hydrophila infection in vivo. In vitro stimulation experiments showed that CYP could induce the secretion of IgM antibodies, because it could stimulate the proliferation and differentiation of head kidney IgM B cells.

Crystal Structures of DNA-bound Fish IRF10 and IRF11 Reveal the Determinants of IFN Regulation.

IFN regulatory factors (IRFs) are transcription factors that mediate homeostatic mechanisms of host defense against pathogens. In addition to IRF1-9, which are conserved across vertebrates, teleost fishes have two other IRFs, IRF10 and IRF11. In zebrafish (Danio rerio), IRF10 represses the expression of IFNφ1 and IFNφ3, whereas IRF11 exerts the opposite effect.

Parabacteroides distasonis regulates the infectivity and pathogenicity of SVCV at different water temperatures.

Background: Spring viremia of carp virus (SVCV) infects a wide range of fish species and causes high mortality rates in aquaculture. This viral infection is characterized by seasonal outbreaks that are temperature-dependent. However, the specific mechanism behind temperature-dependent SVCV infectivity and pathogenicity remains unclear.

Phagocytic Plasma Cells in Teleost Fish Provide Insights into the Origin and Evolution of B Cells in Vertebrates.

Teleost IgM+ B cells can phagocytose, like mammalian B1 cells, and secrete Ag-specific IgM, like mammalian B2 cells. Therefore, teleost IgM+ B cells may have the functions of both mammalian B1 and B2 cells. To support this view, we initially found that grass carp (Ctenopharyngodon idella) IgM+ plasma cells (PCs) exhibit robust phagocytic ability, akin to IgM+ naive B cells.

Siah2- and LRSAM1-mediated K63-linked ubiquitination of snakehead vesiculovirus nucleoprotein facilitates viral replication.

Unlabelled: Nucleoprotein (N) is well known for its function in the encapsidation of the genomic RNAs of negative-strand RNA viruses, which leads to the formation of ribonucleoproteins that serve as templates for viral transcription and replication. However, the function of the N protein in other aspects during viral infection is far from clear. In this study, the N protein of snakehead vesiculovirus (SHVV), a kind of fish rhabdovirus, was proved to be ubiquitinated mainly via K63-linked ubiquitination.

Identification of ClpB, a molecular chaperone involved in the stress tolerance and virulence of Streptococcus agalactiae.

Bacterial ClpB is an ATP-dependent disaggregate that belongs to the Hsp100/Clp family and facilitates bacterial survival under hostile environmental conditions. Streptococcus agalactiae, which is regarded as the major bacterial pathogen of farmed Nile tilapia (Oreochromis niloticus), is known to cause high mortality and large economic losses. Here, we report a ClpB homologue of S.

Grass carp reovirus VP56 and VP35 induce formation of viral inclusion bodies for replication.

Viral inclusion bodies (VIBs) are subcellular structures required for efficient viral replication. How type II grass carp reovirus (GCRV-II), the mainly prevalent strain, forms VIBs is unknown. In this study, we found that GCRV-II infection induced punctate VIBs in grass carp ovary (GCO) cells and that non-structural protein 38 (NS38) functioned as a participant in VIB formation.

The Effects of the Al and Zr Contents on the Microstructure Evolution of Light-Weight AlNbTiVZr High Entropy Alloy.

To investigate the comprehensive effects of the Al and Zr element contents on the microstructure evolution of the AlNbTiVZr series light-weight refractory high entropy alloys (HEAs), five samples were studied. Samples with different compositions were designated AlNbTiVZr, AlNbTiVZr, AlNbTiVZr, AlNbTiVZr, and AlNbTiVZr. The results demonstrated that the actual density of the studied HEA samples ranged from 5.

Antimicrobial Protein LECT2-b Helps Maintain Gut Microbiota Homeostasis via Selectively Targeting Certain Pathogenic Bacteria.

Antimicrobial peptides/proteins (AMPs) constitute a critical component of gut immunity in animals, protecting the gut from pathogenic bacteria. However, the interactions between AMPs and gut microbiota remain elusive. In this study, we show that leukocyte-derived chemotaxin-2 (LECT2)-b, a recently discovered AMP, helps maintain gut homeostasis in grass carp (Ctenopharyngodon idella), one of the major farmed fish species globally, by directly regulating the gut microbiota.