Comprehensive genome­wide analysis of the chicken heat shock protein family: identification, genomic organization, and expression profiles in indigenous chicken with highly pathogenic avian influenza infection.

BACKGROUND: Heat shock proteins (HSPs) function as molecular chaperones with critical roles in chicken embryogenesis, immune response to infectious diseases, and response to various environmental stresses. However, little is known on HSP genes in chicken. In this study, to understand the roles of chicken HSPs, we performed genome-wide identification, expression, and functional analyses of the HSP family genes in chicken. RESULTS: A total of 76 HSP genes were identified in the chicken genome, which were further classified into eight distinct groups (I-VIII) based on phylogenetic tree analysis. The gene-structure analysis revealed that the members of each clade had the same or similar exon-intron structures. Chromosome mapping suggested that HSP genes were widely dispersed across the chicken genome, except in chromosomes 16, 18, 22, 25, 26, and 28-32, which lacked chicken HSP genes. On the other hand, the interactions among chicken HSPs were limited, indicating that the remaining functions of HSPs could be investigated in chicken. Moreover, KEGG pathway analysis showed that the HSP gene family was involved in the regulation of heat stress, apoptotic, intracellular signaling, and immune response pathways. Finally, RNA sequencing data revealed that, of the 76 chicken HSP genes, 46 were differentially expressed at 21 different growth stages in chicken embryos, and 72 were differentially expressed on post-infection day 3 in two indigenous Ri chicken lines infected with highly pathogenic avian influenza. CONCLUSIONS: This study provides significant insights into the potential functions of HSPs in chicken, including the regulation of apoptosis, heat stress, chaperone activity, intracellular signaling, and immune response to infectious diseases.

Chicken miR-148a-3p regulates immune responses against AIV by targeting the MAPK signalling pathway and IFN-γ.

MicroRNAs are involved in the immune systems of host animals and play essential roles in several immune-related pathways. In the current study, we investigated the systemic biological function of the chicken miRNA gga-miR-148a-3p on immune responses in chicken lines resistant and susceptible to HPAIV-H5N1. We found that gga-miR-148a expression in the lung tissue of H5N1-resistant chickens was significantly downregulated during HPAIV-H5N1 infection. Overexpression of gga-miR-148a and a reporter construct with wild type or mutant IFN-γ, MAPK11, and TGF-ß2 3' untranslated region (3' UTR)-luciferase in chicken fibroblasts showed that gga-miR-148a acted as a direct translational repressor of IFN-γ, MAPK11, and TGF-ß2 by targeting their 3' UTRs. Furthermore, miR-148a directly and negatively influenced the expression of signalling molecules related to the MAPK signalling pathway, including MAPK11, TGF-ß2, and Jun, and regulated antiviral responses through interferon-stimulated genes and MHC class I and class II genes by targeting IFN-γ. Downstream of the MAPK signalling pathway, several proinflammatory cytokines such as IL-1ß, IFN-γ, IL-6, TNF-α, IFN-ß, and interferon-stimulated genes were downregulated by the overexpression of gga-miR-148a. Our data suggest that gga-miR-148a-3p is an important regulator of the MAPK signalling pathway and antiviral response. These findings improve our understanding of the biological functions of gga-miR-148a-3p, the mechanisms underlying the MAPK signalling pathway, and the antiviral response to HPAIV-H5N1 infection in chickens as well as the role of gga-miR-148a-3p in improving the overall performance of chicken immune responses for breeding disease-resistant chickens.

Exosomal miRNA profiling from H5N1 avian influenza virus-infected chickens.

Exosomes are membrane vesicles containing proteins, lipids, DNA, mRNA, and micro RNA (miRNA). Exosomal miRNA from donor cells can regulate the gene expression of recipient cells. Here, Ri chickens were divided into resistant (Mx/A; BF2/B21) and susceptible (Mx/G; BF2/B13) trait by genotyping of Mx and BF2 genes. Then, Ri chickens were infected with H5N1, a highly pathogenic avian influenza virus (HPAIV). Exosomes were purified from blood serum of resistant chickens for small RNA sequencing. Sequencing data were analysed using FastQCv0.11.7, Cutadapt 1.16, miRBase v21, non-coding RNA database, RNAcentral 10.0, and miRDeep2. Differentially expressed miRNAs were determined using statistical methods, including fold-change, exactTest using edgeR, and hierarchical clustering. Target genes were predicted using miRDB. Gene ontology analysis was performed using gProfiler. Twenty miRNAs showed significantly different expression patterns between resistant control and infected chickens. Nine miRNAs were up-regulated and 11 miRNAs were down-regulated in the infected chickens compared with that in the control chickens. In target gene analysis, various immune-related genes, such as cytokines, chemokines, and signalling molecules, were detected. In particular, mitogen-activated protein kinase (MAPK) pathway molecules were highly controlled by differentially expressed miRNAs. The result of qRT-PCR for miRNAs was identical with sequencing data and miRNA expression level was higher in resistant than susceptible chickens. This study will help to better understand the host immune response, particularly exosomal miRNA expression against HPAIV H5N1 and could help to determine biomarkers for disease resistance.

MicroRNA gga-miR-200a-3p modulates immune response via MAPK signaling pathway in chicken afflicted with necrotic enteritis.

MicroRNAs (miRNAs) are small non-coding RNAs that contribute to host immune response as post-transcriptional regulation. The current study investigated the biological role of the chicken (Gallus gallus) microRNA-200a-3p (gga-miR-200a-3p), using 2 necrotic enteritis (NE) afflicted genetically disparate chicken lines, 6.3 and 7.2, as well as the mechanisms underlying the fundamental signaling pathways in chicken. The expression of gga-miR-200a-3p in the intestinal mucosal layer of NE-induced chickens, was found to be upregulated during NE infection in the disease-susceptible chicken line 7.2. To validate the target genes, we performed an overexpression analysis of gga-miR-200a-3p using chemically synthesized oligonucleotides identical to gga-miR-200a-3p, reporter gene analysis including luciferase reporter assay, and a dual fluorescence reporter assay in cultured HD11 chicken macrophage cell lines. Gga-miR-200a-3p was observed to be a direct transcriptional repressor of ZAK, MAP2K4, and TGFß2 that are involved in mitogen-activated protein kinase (MAPK) pathway by targeting the 3'-UTR of their transcripts. Besides, gga-miR-200a-3p may indirectly affect the expression of protein kinases including p38 and ERK1/2 at both transcriptional and translational levels, suggesting that this miRNA may function as an important regulator of the MAPK signaling pathway. Proinflammatory cytokines consisting of IL-1ß, IFN-γ, IL-12p40, IL-17A, and LITAF belonging to Th1 and Th17-type cytokines, were upregulated upon gga-miR-200a-3p overexpression. These findings have enhanced our knowledge of the immune function of gga-miR-200a-3p mediating the chicken immune response via regulation of the MAPK signaling pathway and indicate that this miRNA may serve as an important biomarker of diseases in domestic animals.

Identification of duck liver-expressed antimicrobial peptide 2 and characterization of its bactericidal activity.

OBJECTIVE: This study was conducted to identify duck liver-expressed antimicrobial peptide 2 (LEAP-2) and demonstrate its antimicrobial activity against various pathogens. METHODS: Tissue samples were collected from 6 to 8-week-old Pekin ducks (Anas platyrhynchos domesticus), total RNA was extracted, and cDNA was synthesized. To confirm the duck LEAP-2 transcript expression levels, quantitative real-time polymerase chain reaction was conducted. Two kinds of peptides (a linear peptide and a disulfide-type peptide) were synthesized to compare the antimicrobial activity. Then, antimicrobial activity assay and fluorescence microscopic analysis were conducted to demonstrate duck LEAP-2 bactericidal activity. RESULTS: The duck LEAP-2 peptide sequence showed high identity with those of other avian species (>85%), as well as more than 55% of identity with mammalian sequences. LEAP-2 mRNA was highly expressed in the liver with duodenum next, and then followed by lung, spleen, bursa and jejunum and was the lowest in the muscle. Both of LEAP-2 peptides efficiently killed bacteria, although the disulfide-type LEAP-2 showed more powerful bactericidal activity. Also, gram-positive bacteria was more susceptible to duck LEAP-2 than gram-negative bacteria. Using microscopy, we confirmed that LEAP-2 peptides could kill bacteria by disrupting the bacterial cell envelope. CONCLUSION: Duck LEAP-2 showed its antimicrobial activity against both gram-positive and gram-negative bacteria. Disulfide bonds were important for the powerful killing effect by disrupting the bacterial cell envelope. Therefore, duck LEAP-2 can be used for effective antibiotics alternatives.

Chicken novel leukocyte immunoglobulin-like receptor subfamilies B1 and B3 are transcriptional regulators of major histocompatibility complex class I genes and signaling pathways.

OBJECTIVE: The inhibitory leukocyte immunoglobulin-like receptors (LILRBs) play an important role in innate immunity. The present study represents the first description of the cloning and structural and functional analysis of LILRB1 and LILRB3 isolated from two genetically disparate chicken lines. METHODS: Chicken LILRB1-3 genes were identified by bioinformatics approach. Expression studies were performed by transfection, quantitative polymerase chain reaction. Signal transduction was analyzed by western blots, immunoprecipitation and flow cytometric. Cytokine levels were determined by enzyme-linked immunosorbent assay. RESULTS: Amino acid homology and phylogenetic analyses showed that the homologies of LILRB1 and LILRB3 in the chicken line 6.3 to those proteins in the chicken line 7.2 ranged between 97%-99%, while homologies between chicken and mammal proteins ranged between 13%-19%, and 13%-69%, respectively. Our findings indicate that LILRB1 and LILRB3 subdivided into two groups based on the immunoreceptor tyrosine-based inhibitory motifs (ITIM) present in the transmembrane domain. Chicken line 6.3 has two ITIM motifs of the sequence LxYxxL and SxYxxV while line 7.2 has two ITIM motifs of the sequences LxYxxL and LxYxxV. These motifs bind to SHP-2 (protein tyrosine phosphatase, non-receptor type 11) that plays a regulatory role in immune functions. Moreover, our data indicate that LILRB1 and LILRB3 associated with and activated major histocompatibility complex (MHC) class I and ß2-microglobulin and induced the expression of transporters associated with antigen processing, which are essential for MHC class I antigen presentation. This suggests that LILRB1 and LILRB3 are transcriptional regulators, modulating the expression of components in the MHC class I pathway and thereby regulating immune responses. Furthermore, LILRB1 and LILRB3 activated Janus kinase2/tyrosine kinase 2 (JAK2/TYK2); signal transducer and activator of transcription1/3 (STAT1/3), and suppressor of cytokine signaling 1 genes expressed in Macrophage (HD11) cells, which induced Th1, Th2, and Th17 cytokines. CONCLUSION: These data indicate that LILRB1 and LILRB3 are innate immune receptors associated with SHP-2, MHC class I, ß2-microglobulin, and they activate the Janus kinase/signal transducer and activator of transcription signaling pathway. Thus, our study provides novel insights into the regulation of immunity and immunopathology.

Interleukin-34 Regulates Th1 and Th17 Cytokine Production by Activating Multiple Signaling Pathways through CSF-1R in Chicken Cell Lines.

Interleukin-34 (IL-34) is a newly recognized cytokine with functions similar to macrophage colony-stimulating factor 1. It is expressed in macrophages and fibroblasts, where it induces cytokine production; however, the mechanism of chicken IL-34 (chIL-34) signaling has not been identified to date. The aim of this study was to analyze the signal transduction pathways and specific biological functions associated with chIL-34 in chicken macrophage (HD11) and fibroblast (OU2) cell lines. We found that IL-34 is a functional ligand for the colony-stimulating factor receptor (CSF-1R) in chicken cell lines. Treatment with chIL-34 increased the expression of Th1 and Th17 cytokines through phosphorylation of tyrosine and serine residues in Janus kinase (JAK) 2, tyrosine kinase 2 (TYK2), signal transducer and activator of transcription (STAT) 1, STAT3, and Src homology 2-containing tyrosine phosphatase 2 (SHP-2), which also led to phosphorylation of NF-κB1, p-mitogen-activated protein kinase kinase kinase 7 (TAK1), MyD88, suppressor of cytokine signaling 1 (SOCS1), and extracellular signal-regulated kinase 1 and 2 (ERK1/2). Taken together, these results suggest that chIL-34 functions by binding to CSF-1R and activating the JAK/STAT, nuclear factor κ B (NF-κB), and mitogen-activated protein kinase signaling pathways; these signaling events regulate cytokine expression and suggest roles for chIL-34 in innate and adaptive immunity.

Leukocyte Immunoglobulin-Like Receptors A2 and A6 are Expressed in Avian Macrophages and Modulate Cytokine Production by Activating Multiple Signaling Pathways.

The activating leukocyte immunoglobulin-like receptors (LILRAs) play an important role in innate immunity. However, most of the LILRA members have not been characterized in avian species including chickens. The present study is the first attempt at cloning, structural analysis and functional characterization of two LILRAs (LILRA2 and LILRA6) in chickens. Multiple sequence alignments and construction of a phylogenetic tree of chicken LILRA2 and LILRA6 with mammalian proteins revealed high conservation between chicken LILRA2 and LILRA6 and a close relationship between the chicken and mammalian proteins. The mRNA expression of LILRA2 and LILRA6 was high in chicken HD11 macrophages and the small intestine compared to that in several other tissues and cells tested. To examine the function of LILRA2 and LILRA6 in chicken immunity, LILRA2 and LILRA6 were transfected into HD11 cells. Our findings indicated that LILRA2 and LILRA6 are associated with the phosphorylation of Src kinases and SHP2, which play a regulatory role in immune functions. Moreover, LILRA6 associated with and activated MHC class I, ß2-microglobulin and induced the expression of transporters associated with antigen processing but LILRA2 did not. Furthermore, both LILRA2 and LILRA6 activated JAK-STAT, NF-κB, PI3K/AKT and ERK1/2 MAPK signaling pathways and induced Th1-, Th2- and Th17-type cytokines and Toll-like receptors. Collectively, this study indicates that LILRA2 and LILRA6 are essential for macrophage-mediated immune responses and they have the potential to complement the innate and adaptive immune system against pathogens.

Expression and regulation of avian beta-defensin 8 protein in immune tissues and cell lines of chickens.

OBJECTIVE: Defensins are a large family of antimicrobial peptides and components of the innate immune system that invoke an immediate immune response against harmful pathogens. Defensins are classified into alpha-, beta-, and theta-defensins. Avian species only possess beta-defensins (AvBDs), and approximately 14 AvBDs (AvBD1-AvBD14) have been identified in chickens to date. Although substantial information is available on the conservation and phylogenetics, limited information is available on the expression and regulation of AvBD8 in chicken immune tissues and cells. METHODS: We examined AvBD8 protein expression in immune tissues of White Leghorn chickens (WL) by immunohistochemistry and quantitative reverse transcription-polymerase chain reaction (RT-qPCR). In addition, we examined AvBD8 expression in chicken T-, B-, macrophage-, and fibroblast-cell lines and its regulation in these cells after lipopolysaccharide (LPS) treatment by immunocytochemistry and RT-qPCR. RESULTS: Our results showed that chicken AvBD8 protein was strongly expressed in the WL intestine and in macrophages. AvBD8 gene expression was highly upregulated in macrophages treated with different LPS concentrations compared with that in T- and B-cell lines in a time-independent manner. Moreover, chicken AvBD8 strongly interacted with other AvBDs and with other antimicrobial peptides as determined by bioinformatics. CONCLUSION: Our study provides the expression and regulation of chicken AvBD8 protein in immune tissues and cells, which play crucial role in the innate immunity.

Distribution and differential expression of microRNAs in the intestinal mucosal layer of necrotic enteritis induced Fayoumi chickens.

OBJECTIVE: Despite an increasing number of investigations into the pathophysiology of necrotic enteritis (NE) disease, etiology of NE-associated diseases, and gene expression profiling of NE-affected tissues, the microRNA (miRNA) profiles of NE-affected poultry have been poorly studied. The aim of this study was to induce NE disease in the genetically disparate Fayoumi chicken lines, and to perform non-coding RNA sequencing in the intestinal mucosal layer. METHODS: NE disease was induced in the Fayoumi chicken lines (M5.1 and M15.2), and non-coding RNA sequencing was performed in the intestinal mucosal layer of both NE-affected and uninfected chickens to examine the differential expression of miRNAs. Next, quantitative real-time polymerase chain reaction (real-time qPCR) was performed to further examine four miRNAs that showed the highest fold differences. Finally, bioinformatics analyses were performed to examine the four miRNAs target genes involvement in the signaling pathways, and to examine their interaction. RESULTS: According to non-coding RNA sequencing, total 50 upregulated miRNAs and 26 downregulated miRNAs were detected in the NE-induced M5.1 chickens. While 32 upregulated miRNAs and 11 downregulated miRNAs were detected in the NE-induced M15.2 chickens. Results of real-time qPCR analysis on the four miRNAs (gga-miR-9-5p, gga-miR-20b-5p, gga-miR-196-5p, and gga-let-7d) were mostly correlated with the results of RNAseq. Overall, gga-miR-20b-5p was significantly downregulated in the NE-induced M5.1 chickens and this was associated with the upregulation of its top-ranking target gene, mitogen-activated protein kinase, kinase 2. Further bioinformatics analyses revealed that 45 of the gene targets of gga-miR-20b-5p were involved in signal transduction and immune system-related pathways, and 35 of these targets were predicted to interact with each other. CONCLUSION: Our study is a novel report of miRNA expression in Fayoumi chickens, and could be very useful in understanding the role of differentially expressed miRNAs in a NE disease model.

The novel chicken interleukin 26 protein is overexpressed in T cells and induces proinflammatory cytokines.

In the present study, we describe the cloning and functional characterization of chicken interleukin 26 (ChIL-26). ChIL-26, a member of the IL-10 cytokine family, induces the production of proinflammatory cytokines by T cells. The ChIL-26 cDNA encodes an 82-amino-acid protein whose amino acid sequence has 22.63, 46.31 and 43.15% homology with human IL-26, pig IL-26 and canary IL-26, respectively. ChIL-26 signals through a heterodimeric receptor complex composed of the IL-20R1 and IL-10R2 chains, which are expressed primarily in the CU91 T cell line as well as CD4(+) and CD8(+) T cells. Recombinant ChIL-26 protein induced Th1 cytokines (IL-16 and IFN-γ), Th2 cytokines (IL-4, IL-6 and IL-10), Th17 cytokines (IL-17A, IL-17D, and IL-17F), and chemokine transcripts (mainly CCL3, CCL4, CCL5, CCL20 and CXCL13) in the CU91 T cell line and in CD4(+) and CD8(+) T cells, however IL-18 was not expressed in the CU91 T cell line. Taken together, the data demonstrates that T cells express the functional ChIL-26 receptor complex and that ChIL-26 modulates T cell proliferation and proinflammatory gene expression. To the best of our knowledge, this is the first report of cloned ChIL-26. We evaluated its functional roles, particularly in the pathogenic costimulation of T cells, which may be significantly associated with the induction of cytokines.

Effects of dietary vitamin E on fertility functions in poultry species.

Vitamin E is found in high quantities in vegetable oils. Although vitamin E has multiple functions in humans and animals, its key function is protecting cells from oxidative damage. Since its discovery, several studies have demonstrated that vitamin E deficiency causes impaired fertility in humans and lab animals. However, the effects of vitamin E deficiency or of its supplementation on the fertility of farm animals, particularly on poultry, are less well studied. Therefore, a comprehensive review of the effects of dietary vitamin E on the fertility of poultry species is needed in order to understand the beneficial role of vitamin E in the maintenance of sperm and egg qualities. Based on the observations reviewed here, we found that a moderate amount of vitamin E in poultry diet significantly protects semen/sperm qualities in male birds and egg qualities in female birds via decreasing the lipid peroxidation in semen/sperms and eggs. This review provides an overall understanding of the effects of dietary vitamin E on fertility functions in poultry species.

RNA-seq Profiles of Immune Related Genes in the Spleen of Necrotic Enteritis-afflicted Chicken Lines.

The study aimed to compare the necrotic enteritis (NE)-induced transcriptome differences between the spleens of Marek's disease resistant chicken line 6.3 and susceptible line 7.2 co-infected with Eimeria maxima/Clostridium perfringens using RNA-Seq. Total RNA from the spleens of two chicken lines were used to make libraries, generating 42,736,296 and 42,617,720 usable reads, which were assembled into groups of 29,897 and 29,833 mRNA genes, respectively. The transcriptome changes were investigated using the differentially expressed genes (DEGs) package, which indicated 3,255, 2,468 and 2,234 DEGs of line 6.3, line 7.2, and comparison between two lines, respectively (fold change ≥2, p<0.01). The transcription levels of 14 genes identified were further examined using qRT-PCR. The results of qRT-PCR were consistent with the RNA-seq data. All of the DEGs were analysed using gene ontology terms, the Kyoto Encyclopedia of Genes and Genomes (KEGG) database and the DEGs in each term were found to be more highly expressed in line 6.3 than in line 7.2. RNA-seq analysis indicated 139 immune related genes, 44 CD molecular genes and 150 cytokines genes which were differentially expressed among chicken lines 6.3 and 7.2 (fold change ≥2, p<0.01). Novel mRNA analysis indicated 15,518 novel genes, for which the expression was shown to be higher in line 6.3 than in line 7.2 including some immune-related targets. These findings will help to understand host-pathogen interaction in the spleen and elucidate the mechanism of host genetic control of NE, and provide basis for future studies that can lead to the development of marker-based selection of highly disease-resistant chickens.

Differential regulation of microRNA transcriptome in chicken lines resistant and susceptible to necrotic enteritis disease.

Necrotic enteritis (NE) is a re-emerging disease as a result of increased restriction on the use of antibiotics in poultry. However, the molecular mechanisms underlying the pathogenesis of NE are unclear. Small RNA transcriptome analysis was performed using spleen and intestinal intraepithelial lymphocytes (IEL) from 2 inbred chicken lines selected for resistance or susceptibility to Marek's disease (MD) in an experimentally induced model of avian NE to investigate whether microRNA (miRNA) control the expression of genes associated with host response to pathogen challenge. Unique miRNA represented only 0.02 to 0.04% of the total number of sequences obtained, of which 544 were unambiguously identified. Hierarchical clustering revealed that most of miRNA in IEL were highly expressed in the MD-susceptible line 7.2 compared with MD-resistant line 6.3. Reduced CXCL14 gene expression was correlated with differential expression of several unique miRNA in MD-resistant chickens, whereas TGFßR2 gene expression was correlated with altered gga-miR-216 miRNA levels in MD-susceptible animals. In conclusion, miRNA profiling and deep sequencing of small RNA in experimental models of infectious diseases may be useful for further understanding of host-pathogen interactions, and for providing insights into genetic markers of disease resistance.

Unveiling the immunomodulatory role of soluble chicken fractalkine: Insights from functional characterization and pathway activation analyses.

This study describes the first successful cloning and functional characterization of chicken CX3CL1, a chemokine involved in immune cell migration and inflammatory responses. Evolutionary analyses revealed its close relation to CX3CL1 from other avian species, particularly duck, turkey, and quail. Structurally, chicken CX3CL1 includes a signal peptide and a chemokine interleukin-8-like domain characterized by unique alpha-helices and disulfide bonds. Additionally, we produced and purified recombinant CX3CL1 protein and assessed its endotoxin levels. Chemotaxis assays revealed that CX3CL1 significantly enhances the migration of HD11 macrophages and CU91 T cells. Furthermore, recombinant CX3CL1 induced the expression of pro-inflammatory cytokines (TNF-α, IFN-ß, IFN-γ, IL-6, and CCL20) in a time-dependent manner, while exerting differential effects on anti-inflammatory cytokines (IL-4, IL-10). Conversely, transfection with siCX3CL1 or siCX3CR1 led to the downregulation of these responses. We also observed activation of the MAPK, NF-κB, and JAK/STAT pathways, evidenced by increased phosphorylation of key signaling molecules. These findings underscore the crucial role of chicken CX3CL1 in regulating immune responses, cell migration, and the activation of key signaling pathways. This study provides valuable insights into the immunomodulatory functions of soluble CX3CL1, highlighting its potential as a therapeutic target for inflammatory conditions and enhancing our understanding of immune cell dynamics.

In vitro analysis of antiviral immune response against avian influenza virus in chicken tracheal epithelial cells.

OBJECTIVE: Avian influenza virus (AIV) infections first affect the respiratory tract of chickens. The epithelial cells activate the host immune system, which leads to the induction of immune-related genes and the production of antiviral molecules against external environmental pathogens. In this study, we used chicken tracheal epithelial cells (TECs) in vitro model to investigate the immune response of the chicken respiratory tract against avian respiratory virus infections. METHODS: Eighteen-day-old embryonic chicken eggs were used to culture the primary chicken TECs. Reverse transcription-polymerase chain reaction (RT-PCR) and immunocytochemistry (ICC) analysis of epithelial cell-specific gene makers were performed to confirm the characteristics, morphology, and growth pattern of primary cultured chicken TECs. Moreover, to investigate the cellular immune response to AIV infection or polyinosinic-polycytidylic acid (poly [I:C]) treatment, the TECs were infected with the H5N1 virus or poly (I:C). Then, immune responses were validated by RT-qPCR and western blotting. RESULTS: The TECs exhibited polygonal morphology and formed colony-type cell clusters. The RT-qPCR results showed that H5N1 infection induced a significant expression of antiviral genes in TECs. We found that TECs treated with poly (I:C) and exposed to AIV infection-mediated activation of signaling pathways, leading to the production of antiviral molecules (e.g., pro-inflammatory cytokines and chemokines), were damaged due to the loss of junction proteins. We observed the activation of the nuclear factor kappa B and mitogen-activated protein kinase (MAPK) pathways, which are involved in inflammatory response by modulating the release of pro-inflammatory cytokines and chemokines in TECs treated with poly (I:C) and pathway inhibitors. Furthermore, our findings indicated that poly (I:C) treatment compromises the epithelial cell barrier by affecting junction proteins in the cell membrane. CONCLUSION: Our study highlights the utility of in vitro TEC models for unraveling the mechanisms of viral infection and understanding host immune responses in the chicken respiratory tract.

Relative disease susceptibility and clostridial toxin antibody responses in three commercial broiler lines coinfected with Clostridium perfringens and Eimeria maxima using an experimental model of necrotic enteritis.

Necrotic enteritis is an enteric disease of poultry resulting from infection by Clostridium perfringens with coinfection by Eimeria spp. constituting a major risk factor for disease pathogenesis. This study compared three commercial broiler chicken lines using an experimental model of necrotic enteritis. Day-old male Cobb, Ross, and Hubbard broilers were orally infected with viable C. perfringens and E. maxima and fed a high-protein diet to promote the development of experimental disease. Body weight loss, intestinal lesions, and serum antibody levels against alpha-toxin and necrotic enteritis B-like (NetB) toxin were measured as parameters of disease susceptibility and host immune response. Cobb chickens exhibited increased body weight loss compared with Ross and Hubbard breeds and greater gut lesion severity compared with Ross chickens. NetB antibody levels were greater in Cobb chickens compared with the Ross or Hubbard groups. These results suggest that Cobb chickens may be more susceptible to necrotic enteritis in the field compared with the Ross and Hubbard lines.

Exosome-mediated delivery of gga-miR-20a-5p regulates immune response of chicken macrophages by targeting IFNGR2, MAPK1, MAP3K5, and MAP3K14.

OBJECTIVE: This study aims to evaluate the target genes of gga-miR-20a-5p and the regulated immune responses in the chicken macrophage cell line, HD11, by the exosome-mediated delivery of miR-20a-5p. METHODS: Exosomes were purified from the chicken macrophage cell line HD11. Then, mimic gga-miR-20p or negative control miRNA were internalized into HD11 exosomes. HD11 cells were transfected with gga-miR-20a-5p or negative control miRNA containing exosomes. After 44 h of transfection, cells were incubated with or without 5 µg/mL poly(I:C) for 4 h. Then, expression of target genes and cytokines was evaluated by quantitative real-time polymerase chain reaction. RESULTS: Using a luciferase reporter assay, we identified that gga-miR-20a-5p directly targeted interferon gamma receptor 2 (IFNGR2), mitogen-activated protein kinase 1 (MAPK1), mitogen-activated protein kinase kinase kinase 5 (MAP3K5), and mitogen-activated protein kinase kinase kinase 14 (MAP3K14). Moreover, the exosome-mediated delivery of gga-miR-20a-5p successfully repressed the expression of IFNGR2, MAPK1, MAP3K5, and MAP3K14 in HD11 cells. The expressions of interferon-stimulated genes (MX dynamin like GTPase 1 [MX1], eukaryotic translation initiation factor 2A [EIF2A], and oligoadenylate synthase-like [OASL]) and proinflammatory cytokines (interferon-gamma [IFNG], interleukin-1 beta [IL1B], and tumor necrosis factor-alpha [TNFA]) were also downregulated by exosomal miR-20a-5p. In addition, the proliferation of HD11 cells was increased by exosomal miR-20a-5p. CONCLUSION: The exosome-mediated delivery of gga-miR-20a-5p regulated immune responses by controlling the MAPK and apoptotic signaling pathways. Furthermore, we expected that exosomal miR-20a-5p could maintain immune homeostasis against highly pathogenic avian influenza virus H5N1 infection by regulating the expression of proinflammatory cytokines and cell death.

Chicken miR-26a-5p modulates MDA5 during highly pathogenic avian influenza virus infection.

MicroRNAs play crucial roles in immune-related pathways in host animals. In this study, we aimed to investigate the systemic biological function of gga-miR-26a-5p, a chicken miRNA, in the immune responses to HPAIV H5N1 infection in the Vietnamese Ri chicken line. Our results showed a significant downregulation in gga-miR-26a expression in the lung tissue of Ri chickens during HPAIV H5N1 infection. Overexpression of gga-miR-26a and the reporter construct, either containing the wildtype or mutant melanoma differentiation-associated protein 5 (MDA5) 3' untranslated region (3' UTR)-luciferase, into a chicken fibroblast cell line, revealed that gga-miR-26a can act as a direct translational repressor of MDA5 by targeting the 3' UTRs. Additionally, miR-26a negatively regulated the expression of the signaling molecules related to the MDA5 signaling pathway, including MDA5, mitochondrial antiviral-signaling (MAVS), interferon regulatory factor 7 (IRF7), p38 mitogen-activated protein kinases, and nuclear factor-kappa B (NF-κB). Moreover, downstream of the IRF7 and NF-κB signaling pathway, the proinflammatory cytokines such as IL-1ß, IFN-γ, IFN-α, IFN-ß, and the interferon-stimulated gene (Mx1) were, likewise, downregulated by the overexpression of gga-miR-26a. These findings suggest that gga-miR-26a-5p serves as an important regulator in the MDA5 signaling pathway and antiviral response. Overall, our results contribute to an improved understanding of the biological functions of gga-miR-26a-5p, alongside the mechanisms underlying the MDA5 signaling pathway, and the antiviral response to HPAIV-H5N1 infection in chickens.

Analysis of miRNA expression in the trachea of Ri chicken infected with the highly pathogenic avian influenza H5N1 virus.

BACKGROUND: Highly pathogenic avian influenza virus (HPAIV) is considered a global threat to both human health and the poultry industry. MicroRNAs (miRNA) can modulate the immune system by affecting gene expression patterns in HPAIV-infected chickens. OBJECTIVES: To gain further insights into the role of miRNAs in immune responses against H5N1 infection, as well as the development of strategies for breeding disease-resistant chickens, we characterized miRNA expression patterns in tracheal tissues from H5N1-infected Ri chickens. METHODS: miRNAs expression was analyzed from two H5N1-infected Ri chicken lines using small RNA sequencing. The target genes of differentially expressed (DE) miRNAs were predicted using miRDB. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis were then conducted. Furthermore, using quantitative real-time polymerase chain reaction, we validated the expression levels of DE miRNAs (miR-22-3p, miR-146b-3p, miR-27b-3p, miR-128-3p, miR-2188-5p, miR-451, miR-205a, miR-203a, miR-21-3p, and miR-200a-3p) from all comparisons and their immune-related target genes. RESULTS: A total of 53 miRNAs were significantly expressed in the infection samples of the resistant compared to the susceptible line. Network analyses between the DE miRNAs and target genes revealed that DE miRNAs may regulate the expression of target genes involved in the transforming growth factor-beta, mitogen-activated protein kinase, and Toll-like receptor signaling pathways, all of which are related to influenza A virus progression. CONCLUSIONS: Collectively, our results provided novel insights into the miRNA expression patterns of tracheal tissues from H5N1-infected Ri chickens. More importantly, our findings offer insights into the relationship between miRNA and immune-related target genes and the role of miRNA in HPAIV infections in chickens.