Antibacterial Immunity Research Articles

Characterization of interferon-stimulated gene 15 from Bostrychus sinensis: cloning, expression and functional analyses

In this study, the interferon-stimulated gene 15 (referred to as BsISG15) was sequenced and characterized in Bostrychus sinensis. BsISG15 encodes a 155-amino-acid protein weighing ∼17 kDa, featuring two conserved ubiquitin-like domains and an LRGG conjugation motif at the C-terminal. The real-time PCR assays revealed constitutive expression of the BsISG15 gene in all examined organs of healthy B. sinensis, with the peripheral blood showing the highest level of expression. The expression levels of the BsISG15 gene in the head kidney, liver, spleen, and peripheral blood of B. sinensis were significantly altered by both poly (I:C) stimulation and Vibrio parahaemolyticus infection. Western blot analyses showed that the expression of the BsISG15 protein was induced in both the liver and spleen of B. sinensis infected with either poly (I:C) or bacteria, with a concomitant increase in the levels of protein ISGylation, particularly evident in the bacterial-infected liver tissues. Besides, Western blot analyses have demonstrated that head kidney lymphocytes of B. sinensis are capable of secreting the free BsISG15 protein. The recombinant BsISG15 protein significantly increased the production of reactive oxygen species, synthesis of NO, and phagocytosis in macrophages from B. sinensis and also upregulated the expression of proinflammatory cytokine genes (IFNg, IL-1β, IL-6, and IL-8) in these cells. Knockdown of endogenous BsISG15 elevated the expression levels of proinflammatory cytokines IL-1β, IL-6, and IL-8, suggesting a negative regulation of BsISG15 on the inflammatory response in macrophages. The results indicate that BsISG15 plays a significant role in the innate antiviral and antibacterial immunity of B. sinensis.

JAK/STAT signaling pathway is involved in antibacterial immunity in the green peach aphid Myzus persicae (Sulzer)

The Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway within the innate immune system plays a crucial role in defending insects against bacterial, fungal, and viral pathogens. In this study, we identified and cloned five key genes of this signaling pathway in Myzus persicae: MpDome-1, MpDome-2, MpJak, MpStat92E-1, and MpStat92E-2. Our results illustrated that these genes were highly expressed in first, second and third-instar nymphs. Tissue-specific expression analysis revealed that the five genes were predominantly expressed in the gut. Upon bacterial challenge, particularly with Staphylococcus aureus, the expression levels of all five genes were significantly upregulated. Additionally, Escherichia coli infection significantly upregulated the expression levels of MpDome-1 and MpDome-2, while MpJak, MpStat92E-1 and MpStat92E-2 were weakly upregulated. Functional analysis through RNA interference-mediated knockdown of these target genes revealed a significant increase in mortality following infection with E. coli and S. aureus compared with the control group. These findings suggest that the JAK/STAT signaling pathway is crucial for immune defense against bacterial infections in M. persicae.

Characterization, expression and functional analysis of Hsp40 during LPS challenge in blood parrot Amphilophus citrinellus ×Vieja melanura

Heat shock protein 40 belonging to heat shock protein family plays an important role in the immune responses of organisms. In this study, the full length cDNA of Hsp40 was 2426 bp including a 1368 bp open reading frame (ORF) encoding 455 amino acids with a molecular weight of 49.16 kDa and a theoretical isoelectric point of 9.34 in blood parrot Vieja synspila ♀ × Amphilophus citrinellus ♂, an important ornamental fish in China. It had three conserved domains DnaJ, CRR and DnaJ_C. Phylogenetic analysis showed that the sequence of Hsp40 among species was conserved, and the blood parrot Hsp40 was closely related to Neolamprologus brichardi. Blood parrot Hsp40 mRNA could be detected in all of the tissues examined and mainly distributed in the cytoplasm. The expression of Hsp40 was upregulated during lipopolysaccharide (LPS) challenge. Upregulated Hsp40 inhibited the activity of nuclear factor κB (NF-κB) and activated protein 1 (AP-1) and reduced the ratio of Bax/Bcl-2 mRNA expression. This study provides a theoretical basis for further exploring the role of Hsp40 gene in the anti-bacterial immunity of blood parrot.

Plasma cell disorders supress mucosal anti-bacterial immunity: another dimension of immunoparesis in plasma cell neoplasms

Plasma cell disorders supress mucosal anti-bacterial immunity: another dimension of immunoparesis in plasma cell neoplasms

New Development of Edwarsiella Tarda Infection

Edwardsiella tarda is a pathogen in aquatic animals and as an opportunistic pathogen for humans. This bacteria is known to cause gastroenteritis and wound infections. There is evidence to suggest that these microorganisms can be a public health problem, as well as a threat to other animals such as pigs and cows. There is a cathepsin H (CsCatH) homology of C. semilaevis, in the healthy palm of the tongue, transcriptional expression of CsCatH was detected in nine different tissues. Knockdown of CsCatH and CsCatB significantly increased Edwardsiella tarda-induced replication and reduced Edwardsiella tarda-induced apoptosis. These findings reveal the importance of CsCatH and CsCatB in the anti-bacterial immunity of the tongue. Subsequent studies suggest that the flagellin secreted from Edwardsiella tarda may be a responsible factor for macrophage stimulation activity. The virulence factors of these bacteria are the secretion system type III, type VI and other proteins. Edwardsiella tarda can be identified and characterized by agglutination test methods, Enzyme-Linked Immunosorbent Assay (ELISA), and fluorescent antibody techniques, real-time PCR, loop mediated isothermal amplification (LAMP), and multiplex nested PCR.

A low-molecular-weight α-glucan from edible fungus Agaricus blazei Murrill activates macrophage TFEB-mediated antibacterial defense to combat implant-associated infection

Implant-associated infection (IAI) is a prevalent and potentially fatal complication of orthopaedic surgery. Boosting antibacterial immunity, particularly the macrophage-mediated response, presents a promising therapeutic approach for managing persistent infections. In this study, we successfully isolated and purified a homogeneous and neutral water-soluble polysaccharide, designated as AM-1, from the edible fungus Agaricus blazei Murrill. Structure analysis revealed that AM-1 (Mw = 3.87 kDa) was a low-molecular-weight glucan characterized by a primary chain of →4)-α-D-Glcp-(1 → and side chains that were linked at the O-6 and O-3 positions. In vivo assays showed that AM-1 effectively attenuated the progression of infection and mitigated infectious bone destruction in IAI mouse models. Mechanistically, AM-1 promotes intracellular autophagy-lysosomal biogenesis by inducing the nuclear translocation of transcription factor EB, finally enhancing the bactericidal capabilities and immune-modulatory functions of macrophages. These findings demonstrate that AM-1 significantly alleviates the progression of challenging IAIs as a presurgical immunoenhancer. Our research introduces a novel therapeutic strategy that employs natural polysaccharides to combat refractory infections.

Fish IL-26 collaborates with IL-10R2 and IL-20R1 to enhance gut mucosal barrier during the antibacterial innate immunity

IL-26 is a cytokine that is crucial for the maintenance and function of the gut mucosal barrier. IL-26 signaling pathway relies on a heterodimeric receptor complex, which is composed of two distinct subunits, IL-10R2 and IL-20R1. However, there are no reports on the antibacterial immunity of IL-26 and its receptors in fish. For this purpose, in this study we identified IL-26 and its receptors IL-10R2 and IL-20R1 in Carassius cuvieri × Carassius auratus red var. (named WR-IL-26, WR-IL10R2 and WR-IL20R1, respectively). Phylogenetic analysis confirmed the conservation of these genes, with shared structural motifs similar to those found in higher vertebrates. Upon exposure to Aeromonas hydrophila, a common fish pathogen, there was a significant upregulation of WR-IL-26, WR-IL10R2 and WR-IL20R1 in the gut, indicating a potential role in the immune response to infection. A co-immunoprecipitation assay revealed that WR-IL-26 formed complexes with WR-IL10R2 and WR-IL20R1. In vivo experiments demonstrated that administration of WR-IL-26 activated the JAK1-STAT3 signaling pathway and protected the gut mucosa barrier from A. hydrophila infection. Conversely, silencing WR-IL10R2 and WR-IL20R1 via RNA interference significantly attenuated the activation of WR-IL-26-mediated JAK1-STAT3 pathway. These results provided new insights into the role of IL-26 and its receptors in the gut mucosa barrier and could offer novel therapeutic strategies for managing bacterial infections in aquaculture.

Characterization of c-Jun N-terminal kinase (JNK) gene reveals involvement of immune defense against Vibrio splendidus infection in Apostichopus japonicus

The c-Jun N-terminal kinase (JNK) constitutes an evolutionarily conserved family of serine/threonine protein kinases, pivotal in regulating various physiological processes in vertebrates, encompassing apoptosis and antibacterial immunity. Nevertheless, the involvement of JNK in the innate immune response remains largely unexplored in pathogen-induced echinoderms. We isolated and characterized the JNK gene from Apostichopus japonicus (AjJNK) in our investigation. The full-length cDNA sequences of AjJNK spanned 1806 bp, comprising a 1299 bp open reading frame (ORF) encoding 432 amino acids, a 274 bp 5′-untranslated region (UTR), and a 233 bp 3′-UTR. Structural analysis revealed the presence of a classical S_TKc domain (37–335 amino acids) within AjJNK and contains several putative immune-related transcription factor-binding sites, including Elk-1, NF-κB, AP-1, and STAT5. Spatial expression analysis indicated ubiquitous expression of AjJNK across all examined tissues, with the highest expression noted in coelomocytes. The mRNA, protein, and phosphorylation levels of AjJNK were obviously induced in coelomocytes upon V. splendidus challenge and lipopolysaccharide stimulation. Immunofluorescence analysis demonstrated predominant cytoplasmic localization of AjJNK in coelomocytes with subsequent nuclear translocation following the V. splendidus challenge in vivo. Moreover, siRNA-mediated knockdown of AjJNK led to a significant increase in intracellular bacterial load, as well as elevated levels of Ajcaspase 3 and coelomocyte apoptosis post V. splendidus infection. Furthermore, the phosphorylation levels of AjJNK inhibited by its specific inhibitor SP600125 and also significantly suppressed the expression of Ajcaspase 3 and coelomocyte apoptosis during pathogen infection. Collectively, these data underscored the pivotal role of AjJNK in immune defense, specifically in the regulation of coelomocyte apoptosis in V. splendidus-challenged A. japonicus.

Itaconate uptake via SLC13A3 improves hepatic antibacterial innate immunity.

Itaconate is an immunoregulatory metabolite produced by the mitochondrial enzyme immune-responsive gene 1 (IRG1) in inflammatory macrophages. We recently identified an important mechanism by which itaconate is released from inflammatory macrophages. However, it remains unknown whether extracellular itaconate is taken up by non-myeloid cells to exert immunoregulatory functions. Here, we used a custom-designed CRISPR screen to identify the dicarboxylate transporter solute carrier family 13 member 3 (SLC13A3) as an itaconate importer and to characterize the role of SLC13A3 in itaconate-improved hepatic antibacterial innate immunity. Functionally, liver-specific deletion of Slc13a3 impairs hepatic antibacterial innate immunity invivo and invitro. Mechanistically, itaconate uptake via SLC13A3 induces transcription factor EB (TFEB)-dependent lysosomal biogenesis and subsequently improves antibacterial innate immunity in mouse hepatocytes. These findings identify SLC13A3 as a key itaconate importer in mouse hepatocytes and will aid in the development of potent itaconate-based antibacterial therapeutics.

Efficacy of zinc as an adjuvant therapy in acute pneumonia in children of age 2 months to 2 years: A randomized controlled trial

Background: Pneumonia is the most common Illness affecting infants and children globally. Childhood pneumonia has been identified as the major “forgotten killer of children” by UNICEF and the WHO. The WHO and United Nations Children’s Fund (UNICEF) in 2013, published the integrated Global Action Plan for Pneumonia and Diarrhoea (GAPPD) which outlined a framework for ending preventable child deaths due to diarrhoea and pneumonia by 2025. Zinc is a vital micro element that is essential for a variety of fundamental biological processes due to its function as a transition metal, cofactor, structural component, and signalling molecule. Zinc is also an essential component of antibacterial immunity. The impaired immunocompetence due to low zinc states enhances the establishment of a particular infection due to a reduction in the clearance of infectious agents. Recommend zinc nutritional intake is 10-20mg/day for children. It is estimated that 17-20% of the world’s population may be zinc deficient. Zinc deficiency is common among children in developing countries because of inadequate food intake, particularly from animal source and limited bioavailability from local diet. It has been proposed that zinc can be a real potential in the prevention of pneumonia morbidity and mortality. Objective: To study the effect of zinc supplementation as an adjuvant therapy on outcome of pneumonia. Method: We conducted a randomised controlled trial from march 2023 to february 2024. All children in the the age group of 2 months to 2 years, who presented with the features of pneumonia to the department of Paediatrics in Akash institute of medical sciences and research centre Devanhalli, Bangalore rural. Ethics consent was obtained from Institutional ethical committee. Demographic details such as name, age, gender along with clinical profile was taken. After admission, detailed history and physical and systemic examination were carried out and necessary data collected. Sample size being 50 cases, they were divided in two groups as case group (zinc group) and control group by stratified randomisation, 25 participants being in each group. Enrolled children were given standard treatment for pneumonia in the form of oxygen, intravenous fluids, bronchodilators, parenteral antibiotics. Enteral feeds were started once the child respiratory distress improved, oxygen saturations greater than 93%, baby was able to tolerate feed. Zinc group received 20 mg of elemental zinc per day as a single dose for 7 days. Result : Out of the total 50 cases, two groups were divided with 25 cases in zinc group and 25 cases in non-zinc group. In zinc group 6 cases (50%) took 24-48 hours for disappearance of symptoms, another 3 cases (26%) less than 24 hours, in 1 case time for disappearance of symptoms was 48-72 hours, another case which took 72-96 hours. The mean duration of time taken for disappearance of danger signs was 42.33 ± 13.89 hours. In the non-zinc group (36%) 5 cases took 24-48 hours for disappearance of danger signs, 3 cases (22%) which took 48-72 hours and 2 cases (14%) which took 96-120 hours, 2 more cases (14%) which took 120-144 hours. The mean duration of hospital stay in non-zinc group was 62.28 ± 10.84 hours which is comparatively more than that of zinc group. Conclusion: This study concluded that zinc supplementation shortens the time taken for resolution of respiratory distress and resolution of symptoms. However, it was not found to be of much help in improving oxygen saturation. It also did not show any significant decrease in time taken for disappearance of danger signs and duration of hospital stay.

A subpopulation of human bone marrow erythroid cells displays a myeloid gene expression signature similar to that of classic monocytes.

Erythroid cells, serving as progenitors and precursors to erythrocytes responsible for oxygen transport, were shown to exhibit an immunosuppressive and immunoregulatory phenotype. Previous investigations from our research group have revealed an antimicrobial gene expression profile within murine bone marrow erythroid cells which suggested a role for erythroid cells in innate immunity. In the present study, we focused on elucidating the characteristics of human bone marrow erythroid cells through comprehensive analyses, including NanoString gene expression profiling utilizing the Immune Response V2 panel, a BioPlex examination of chemokine and TGF-beta family proteins secretion, and analysis of publicly available single-cell RNA-seq data. Our findings demonstrate that an erythroid cell subpopulation manifests a myeloid-like gene expression signature comprised of antibacterial immunity and neutrophil chemotaxis genes which suggests an involvement of human erythroid cells in the innate immunity. Furthermore, we found that human erythroid cells secreted CCL22, CCL24, CXCL5, CXCL8, and MIF chemokines. The ability of human erythroid cells to express these chemokines might facilitate the restriction of immune cells in the bone marrow under normal conditions or contribute to the ability of erythroid cells to induce local immunosuppression by recruiting immune cells in their immediate vicinity in case of extramedullary hematopoiesis.

HLH-30/TFEB mediates sexual dimorphism in immunity in Caenorhabditis elegans

ABSTRACT Sexual dimorphism affects various biological functions, including immune responses. However, the mechanisms by which sex alters immunity remain largely unknown. Using Caenorhabditis elegans as a model species, we showed that males exhibit enhanced immunity against various pathogenic bacteria through the upregulation of HLH-30 (Helix Loop Helix 30/TFEB (transcription factor EB)), a transcription factor crucial for macroautophagy/autophagy. Compared with hermaphroditic C. elegans, males displayed increased activity of HLH-30/TFEB, which contributed to enhanced antibacterial immunity. atg-2 (AuTophaGy (yeast Atg homolog) 2) upregulated by HLH-30/TFEB mediated increased immunity in male C. elegans. Thus, the males appear to be equipped with enhanced HLH-30/TFEB-mediated autophagy, which increases pathogen resistance, and this may functionally prolong mate-searching ability with reduced risk of infection. Abbreviations: atg-2: AuTophaGy (yeast Atg homolog) 2; FUDR: 5-fluoro-2’-deoxyuridine; GSEA: gene set enrichment analysis; HLH-30: Helix Loop Helix 30; LC3: microtubule associated protein 1 light chain 3; NGM: nematode growth media; RNA-seq: RNA sequencing; SEM: standard error of the mean; TFEB: transcription factor EB; WT: wild-type

Antibiotic use attenuates response to immune checkpoint blockade in urothelial carcinoma via inhibiting CD74-MIF/COPA: revealing cross-talk between anti-bacterial immunity and anti-tumor immunity through a tumor marker prognostic study.

Immune checkpoint blockade (ICB) has emerged as a promising therapy for both resectable urothelial carcinoma (UC) patients preparing for radical surgery and unresectable UC patients, whereas the objective response rate of ICB remains unsatisfactory due to various factors. Antibiotic (ATB) use can influence intra-tumoral bacteria, which may further reduce ICB efficacy. The study aims to evaluate the effects of ATB use on prognosis and response in UC patients undergoing ICB, and explore potential molecular mechanisms of ATBs and intra-tumoral bacteria impacting UC immune microenvironment. Pooled analyses, synthesizing evidence from 12 studies and 3496 UC patients with ICB treatment, was conducted via a meta-analysis. In addition, single-cell RNA and single-cell microbiome data were analyzed based on eight UC samples and 63185 single cells. Bulk RNA sequencing and clinical data from a single-arm, multi-center, atezolizumab-treated, phase 2 trial, IMvigor210, were used for validation. The study is registered at PROSPERO (XXX) and at Research Registry (XXX). ATB use exhibited worse overall survival (HR=1.46, 95%CI=[1.20, 1.77], P<0.001, heterogeneity I²=51%) and lower objective response (OR=0.43, 95%CI=[0.27, 0.68], P<0.001, heterogeneity I²=0%) in UC patients receiving ICB. Single-cell transcriptome and single-cell microbiome analyses identified the presence of intra-tumoral bacteria was obviously related to elevated anti-bacterial immune functions; and anti-bacterial immunity was positively correlated to anti-tumor immunity in UC immune microenvironment. Intra-tumoral bacteria could up-regulate CD74-MIF/COPA signaling of immune cells and activation of CD74-MIF/COPA mediated the promotion of T cell anti-tumor function induced by anti-bacterial immune cells. UC patients with higher CD74-MIF/COPA signaling carried better overall survival (HR=1.60, 95%CI=[1.19, 2.15], P=0.002) in IMvigor210 immunotherapy cohort. ATB use reduces overall survival and objective response to ICB in UC patients. Anti-bacterial immune cell functions induced by intra-cellular bacteria in UC microenvironment might up-regulate the function of anti-tumor T immune cells via activating CD74-MIF/COPA, whereas ATB could inhibit the above process through killing intra-cellular bacteria and result in poorer clinical benefit of ICB. The use of ATB should be considered carefully during neoadjuvant immunotherapy period for resectable UC patients preparing for radical surgery and during immunotherapy period for unresectable UC patients.

The canonical antiviral protein oligoadenylate synthetase 1 elicits antibacterial functions by enhancing IRF1 translation

An important property of the host innate immune response during microbial infection is its ability to control the expression of antimicrobial effector proteins, but how this occurs post-transcriptionally is not well defined. Here, we describe a critical antibacterial role for the classic antiviral gene 2'-5'-oligoadenylate synthetase 1 (OAS1). Human OAS1 and its mouse ortholog, Oas1b, are induced by interferon-γ and protect against cytosolic bacterial pathogens such as Francisella novicida and Listeria monocytogenes invitro and invivo. Proteomic and transcriptomic analysis showed reduced IRF1 protein expression in OAS1-deficient cells. Mechanistically, OAS1 binds and localizes IRF1 mRNA to the rough endoplasmic reticulum (ER)-Golgi endomembranes, licensing effective translation of IRF1 mRNA without affecting its transcription or decay. OAS1-dependent translation of IRF1 leads to the enhanced expression of antibacterial effectors, such as GBPs, which restrict intracellular bacteria. These findings uncover a noncanonical function of OAS1 in antibacterial innate immunity.

Aconitate decarboxylase 1 (Acod1) suppresses inflammatory stimuli-induced immune responses in Japanese flounder (Paralichthys olivaceus)

Aconitate decarboxylase 1 (ACOD1, formerly termed as immunoresponsive gene 1) is an enzyme responsible for generation of anti-inflammatory metabolite itaconate through decarboxylation of cis-aconitate and plays a key role in inflammation regulation and anti-microbial host defense in mammals. However, the immune functions of Acod1 in fish remain largely undetermined. Here, we characterize a Acod1 homolog that is highly induced by LPS, poly(I:C) and extracellular ATP (eATP) challenges in the Japanese flounder Paralichthys olivaceus head kidney macrophages (HKMs). We find that Acod1 syntenic genes in P. olivaceus are similar with those in mammalian species and the deduced Japanese flounder ACOD1 protein shares similar protein domains and 3-D structures with its counterparts in mammals. We next show that itaconate derivatives dimethyl itaconate (DMI) and citraconate (Cit) can markedly down-regulate inflammatory stimuli, including LPS-, poly(I:C)- and eATP-induced inflammatory mediator nitric oxide (NO) production and gene expression of proinflammatory cytokines (IL-1β and TNF-α), chemokines (CXCL-8, CXCL-9 and CXCL-13), HMGB1 and inflammasome components (NLRP3, NLRC3, caspase1, ASC and GSDME), but up-regulate anti-inflammatory gene (IL-10 and SOCS1/3) expression in P. olivaceus HKMs. In addition, DMI and Cit treatment significantly inhibits Edwardsiella piscicida growth in P. olivaceus HKMs. Furthermore, knockdown of the endogenous Acod1 expression by siRNA silencing not only significantly increases LPS-, poly(I:C)- and eATP-induced proinflammatory gene expression but also decreases anti-inflammatory gene expression in the HKMs. In contrast, the LPS-, poly(I:C)- and eATP-indued proinflammatory gene expression and NO production are greatly attenuated in ACOD1 overexpressed Japanese flounder FG-9307 cells. Collectively, our studies demonstrate that the inducible fish Acod1 gene is a novel immune regulator in dampening inflammatory stimuli-induced immune responses and ACOD1-produced itaconate may play an essential role in anti-bacterial immunity in fish macrophages.

Selective autophagy receptor p62 promotes antibacterial and antiviral immunity in common carp (Cyprinus carpio)

Sequestosome 1 (SQSTM1/p62) is a selective autophagy adapter protein that participates in antiviral and bacterial immune responses and plays an important regulatory role in clearing the proteins to be degraded and maintaining intracellular protein homeostasis. In this study, two p62 genes were cloned from common carp (Cyprinus carpio), namely Ccp62-1 and Ccp62-2, and conducted bioinformatics analysis on them. The results showed that Ccp62s had the same structural domain (Phox and Bem1 domain, ZZ-type zinc finger domain, and ubiquitin-associated domain) as p62 from other species. Ccp62s were widely expressed in various tissues of fish, and highly expressed in immune organs such as gills, spleen, head kidney, etc. Subcellular localization study showed that they were mainly distributed in punctate aggregates in the cytoplasm. After stimulation with Aeromonas hydrophila and spring viraemia of carp virus (SVCV), the expression level of Ccp62s was generally up-regulated. Overexpression of Ccp62s in EPC cells could inhibit SVCV replication. Upon A. hydrophila challenge, the bacterial load in Ccp62s-overexpressing group was significantly reduced, the expression levels of pro-inflammatory cytokines and interferon factors were increased, and the survival rate of the fish was improved. These results indicated that Ccp62s were involved in the immune response of common carp to bacterial and viral infections.

LECT2 mediates antibacterial immune response induced by Nocardia seriolae infection in the northern snakehead

Leukocyte-derived chemotaxin-2 (LECT2) is a multifunctional immunoregulator that plays several pivotal roles in the host's defense against pathogens. This study aimed to elucidate the specific functions and mechanisms of LECT2 (CaLECT2) in the northern snakehead (Channa argus) during infections with pathogens such as Nocardia seriolae (N. seriolae). We identified CaLECT2 in the northern snakehead, demonstrating its participation in the immune response to N. seriolae infection. CaLECT2 contains an open reading frame (ORF) of 459 bp, encoding a peptide of 152 amino acids featuring a conserved peptidase M23 domain. The CaLECT2 protein shares 62%–84 % identities with proteins from various other fish species. Transcriptional expression analysis revealed that CaLECT2 was constitutively expressed in all examined tissues, with the highest expression observed in the liver. Following intraperitoneal infection with N. seriolae, CaLECT2 transcription increased in the spleen, trunk kidney, and liver. In vivo challenge experiments showed that injecting recombinant CaLECT2 (rCaLECT2) could protect the snakehead against N. seriolae infection by reducing bacterial load, enhancing serum antibacterial activity and antioxidant capacity, and minimizing tissue damage. Moreover, in vitro analysis indicated that rCaLECT2 significantly enhanced the migration, respiratory burst, and microbicidal activity of the head kidney-derived phagocytes. These findings provide new insights into the role of LECT2 in the antibacterial immunity of fish.

Cascade catalysis nanozyme for interfacial functionalization in combating implant infections associated with diabetes via sonodynamic therapy and adaptive immune activation

Innovative solutions are required for the intervention of implant associated infections (IAIs), especially for bone defect patients with chronic inflammatory diseases like diabetes mellitus (DM). The complex immune microenvironment of infections renders implants with direct antibacterial ability inadequate for the prolonged against of bacterial infections. Herein, a synergistic treatment strategy was presented that combined sonodynamic therapy (SDT) with adaptive immune modulation to treat IAIs in diabetes patients. A multifunctional coating was created on the surface of titanium (Ti) implants, consisting of manganese dioxide nanoflakes (MnO2 NFs) with cascade catalytic enzyme activity and a responsive degradable hydrogel containing a sonosensitizer. The reactive oxygen species (ROS) generated by glucose-hydrogen peroxide (H2O2) cascade catalysis and ultrasound (US) activation sonosensitizer helped kill bacteria and release bacterial antigens. Meanwhile, Mn2+ facilitated dendritic cells (DCs) maturation, enhancing antigen presentation to activate both cellular and humoral adaptive immunity against bacterial infections. This approach effectively eliminated bacteria in established diabetic IAIs model and activated systemic antibacterial immunity, providing long-term antibacterial protection. This study presents a non-antibiotic immunotherapeutic strategy for fighting IAIs in chronic diseases.

Blunt snout bream (Megalobrama amblycephala) circARHGEF15 enhances antibacterial immunity against Aeromonas hydrophila infection via ceRNA regulatory axis

Circular RNAs (circRNAs) can be used as therapeutic targets for various human diseases through competitive endogenous RNA (ceRNA). Earlier research in our laboratory has revealed that circRNAs could serve as ceRNA to sponge microRNAs (miRNAs) and regulate the innate immune response of blunt snout bream (Megalobrama amblycephala) after Aeromonas hydrophila infection, but the specific regulation is still uncertain. In this research, by means of overexpression/RNAi, qPCR, and luciferase assay etc., we discovered a circRNA termed circARHGEF15, which was upregulated following A. hydrophila challenge and positively regulated antibacterial immunity in the host. Moreover, we observed that miR-214 can restore the promotion of inflammatory factors due to circARHGEF15 overexpression. Further, our data indicated that circARHGEF15 may function as a ceRNA of miR-214 in the immune reaction generated by A. hydrophila, reduce the inhibition of miR-214 on hepcidin, and promote the expression of downstream proinflammatory factors such as il-1β, il-6, il-8, and tnf-α. In summary, the results of this study suggest that M. amblycephala circARHGEF15 acts a significant function in the modulation of antibacterial response to A. hydrophila infection, and lays the foundation for rapid diagnosis, effective control, and treatment of fish diseases from the perspective of circRNAs in the future.

The novel fish miRNA, Soc-miR-118, functions as a negative regulator in NF-κB–mediated inflammation by targeting IL-6 in teleost fish

Inflammation is initiated as a protective response of the organism to remove invading bacterial and initiate the healing process. Prolonged inflammation and excessive production of inflammatory cytokines lead to inflammatory disorders or autoimmune diseases. Thus, different layers of negative regulators are needed to achieve balances between protective immunity and inflammatory pathology. Accumulating evidences show that miRNAs act as significant and multifunctional regulators involved in regulating networks of host-pathogen interactions. However, the functions and mechanisms of miRNAs in directly targeting and regulating inflammatory cytokines remains largely unknown in lower vertebrates. In this study, we report a novel miRNA, Soc-miR-118, identified from Sciaenops ocellatus, which plays a negative role in antibacterial immunity by regulating Interleukin-6 (IL-6). Specifically, we found that Soc-miR-118 directly targets IL-6 and suppresses the production of inflammatory cytokines through the NF-κB signaling pathway, thereby avoiding excessive inflammatory response. Particularly, the mechanism by which Soc-miR-118 regulates IL-6 expression also exist in other fish, suggesting that the miRNA in fish has evolutionarily conserved regulatory systems. The collective results that Soc-miR-118 acts as a negative regulator involved in host antibacterial immunity through directly regulating inflammatory cytokines, will greatly enrich the intricate networks of host–pathogen interaction in lower vertebrates.