Infectious bursal disease virus infection induces macrophage activation via p38 MAPK and NF-κB pathways

CircMYO1B/miR-155 pathway is a common mechanism of stress-induced immunosuppression affecting immune response to three vaccines in chicken

Stress-induced immunosuppression (SIIS) can weaken the immune response effect of poultry vaccination, and bring huge hidden dangers and economic losses to the poultry industry. However, the detailed molecular mechanisms are still not fully understood. Unveiling the common mechanism of SIIS affecting the immune response to different vaccines is critical for detecting and minimizing the losses caused by SIIS. This study used glucocorticoid dexamethasone (Dex) to simulate SIIS, and three classic avian vaccines (including avian influenza virus (AIV), Newcastle disease virus (NDV), and infectious bursal disease virus (IBDV)) were used to induce immune responses in chicken. Quantitative real-time PCR (qRT-PCR) revealed the expression characteristics and functions of circMYO1B and miR-155 in the processes of SIIS affecting the immune response to the aforementioned avian vaccines, as well as their targeted regulatory relationship. Subsequent bioinformatics analysis predicted FOS, one of the potential target genes of miR-155. The results showed that circMYO1B/miR-155 pathway served as a key common mechanism by which SIIS affected the immune response to the three vaccines. Both heart and proventriculus appeared to be the crucial tissues for this process, with five days post immunization (dpi) emerging as the primary time of interest. Moreover, mitogen-activated protein kinase (MAPK) signaling system played a key role in modulating the immune response subsequent to SIIS administration. Our findings provide new insights into the immune function of competitive endogenous RNA (ceRNA), which have important function in the detection and treatment of SIIS affecting vaccine immunity.

Interaction between chicken TRIM25 and MDA5 and their role in mediated antiviral activity against IBDV infection

Infectious Bursal Disease Virus (IBDV) is the causative agent of an immunosuppressive disease that affects domestic chickens (Gallus gallus) severely affecting poultry industry worldwide. IBDV infection is characterized by a rapid depletion of the bursal B cell population by apoptosis and the atrophy of this chief lymphoid organ. Previous results from our laboratory have shown that exposure of infected cells to type I IFN leads to an exacerbated apoptosis, indicating an important role of IFN in IBDV pathogenesis. It has been described that recognition of the dsRNA IBDV genome by MDA5, the only known cytoplasmic pattern recognition receptor for viral RNA in chickens, leads to type I IFN production. Here, we confirm that TRIM25, an E3 ubiquitin ligase that leads to RIG-I activation in mammalian cells, significantly contributes to positively regulate MDA5-mediated activation of the IFN-inducing pathway in chicken DF-1 cells. Ectopic expression of chTRIM25 together with chMDA5 or a deletion mutant version exclusively harboring the CARD domains (chMDA5 2CARD) enhances IFN-β and NF-ĸB promoter activation. Using co-immunoprecipitation assays, we show that chMDA5 interacts with chTRIM25 through the CARD domains. Moreover, chTRIM25 co-localizes with both chMDA5 and chMDA5 2CARD, but not with chMDA5 mutant proteins partially or totally lacking these domains. On the other hand, ablation of endogenous chTRIM25 expression reduces chMDA5-induced IFN-β and NF-ĸB promoter activation. Interestingly, ectopic expression of either wild-type chTRIM25, or a mutant version (chTRIM25 C59S/C62S) lacking the E3 ubiquitin ligase activity, restores the co-stimulatory effect of chMDA5 in chTRIM25 knockout cells, suggesting that the E3-ubiquitin ligase activity of chTRIM25 is not required for its downstream IFN-β and NF-ĸB activating function. Also, IBDV-induced expression of IFN-β, Mx and OAS genes was reduced in chTRIM25 knockout as compared to wild-type cells, hence contributing to the enhancement of IBDV replication. Enhanced permissiveness to replication of other viruses, such as avian reovirus, Newcastle disease virus and vesicular stomatitis virus was also observed in chTRIM25 knockout cells. Additionally, chTRIM25 knockout also results in reduced MAVS-induced IFN-β promoter stimulation. Nonetheless, similarly to its mammalian counterpart, chTRIM25 overexpression in wild-type DF-1 cells causes the degradation of ectopically expressed chMAVS.

Infectious bursal disease virus replication is inhibited by avain T cell chemoattractant chemokine CCL19

Chemokine CCL19, together with its receptor CCR7, is one of the most important factors recruiting immune cells into target organ during virus infection. Our previous study has shown that CCL19 played a vital role in the process of T cell trafficking into bursae during bursal disease virus (IBDV) infection. In this study, we hypothesized that CCL19 could exert direct influences on IBDV replication other than recruiting immune cells. A eukaryotic expression vector of pEGFP-N1/CCL19 was successfully constructed and identified by PCR, double enzymes digestion, and sequencing. Different concentrations of pEGFP-N1/CCL19 plasmids were transfected into DF1 cells and CCL19 protein was highly expressed. Then, DF1 cells were infected with IBDV B87 strain post-transfection. Based on PCR and Western blot results, CCL19 could obviously decrease the gene levels of VP1 and VP2 and the protein levels of VP2 and VP3. When CCL19 was knocked down, the gene levels of VP1 and VP2 were significantly upregulated. Moreover, indirect immunostaining revealed that the IBDV content was largely decreased after CCL19 overexpression. Additionally, CCL19 inhibitory effects might rely on activation of the JNK signal pathway. Taken together, chemokine CCL19 directly blocks IBDV replication in DF1 cells, indicating that CCL19 could play crucial functions other than recruiting T cells during the pathogenesis of IBDV.

Infectious bursal disease virus' interferences with host immune cells: What do we know?

AbstractInfectious bursal disease virus (IBDV) induces one of the most important immunosuppressive diseases in chickens leading to high economic losses due increased mortality and condemnation rates, secondary infections and the need for antibiotic treatment. Over 400 publications have been listed in PubMed.gov in the last five years pointing out the research interest in this disease and the development of improved preventive measures. While B cells are the main target cells of the virus, also other immune and non-immune cell populations are affected leading a multifaceted impact on the normally well orchestrated immune system in IBDV-infected birds. Recent studies clearly revealed the contribution of innate immune cells as well as T cells to a cytokine storm and subsequent death of affected birds in the acute phase of the disease. Transcriptomics identified differential regulation of immune related genes between different chicken genotypes as well as virus strains, which may be associated with a variable disease outcome. The recent availability of primary B cell culture systems allowed a closer look into virus-host interactions during IBDV-infection. The new emerging field of research with transgenic chickens will open up new opportunities to understand the impact of IBDV on the host also under in vivo conditions, which will help to understand the complex virus-host interactions further.

Comparative trachea transcriptome analysis in SPF broiler chickens infected with avian infectious bronchitis and avian influenza viruses

Infectious bronchitis virus (IBV) and avian influenza virus (AIV) are two major respiratory infections in chickens. The coinfection of these viruses can cause significant financial losses and severe complications in the poultry industry across the world. To examine transcriptome profile changes during the early stages of infection, differential transcriptional profiles in tracheal tissue of three infected groups (i.e., IBV, AIV, and coinfected) were compared with the control group. Specific-pathogen-free chickens were challenged with Iranian variant-2-like IBV (IS/1494), UT-Barin isolates of H9N2 (A/chicken/Mashhad/UT-Barin/2017), and IBV-AIV coinfection; then, RNA was extracted from tracheal tissue. The Illumina RNA-sequencing (RNA-seq) technique was employed to investigate changes in the Transcriptome. Up- and downregulated differentially expressed genes (DEGs) were detected in the trachea transcriptome of all groups. The Kyoto Encyclopedia of Genes and Genomes pathway and Gene Ontology databases were examined to identify possible relationships between DEGs. In the experimental groups, upregulated genes were higher compared to downregulated genes. A more severe immune response was observed in the coinfected group; further, cytokine-cytokine receptor interaction, RIG-I-like receptor signaling, Toll-like receptor signaling, NOD-like receptor signaling, Janus kinase/signal transducer, and activator of transcription, and apoptotic pathways were important upregulated genes in this group. The findings of this paper may give a better understanding of transcriptome changes in the trachea during the early stages of infection with these viruses.

Effect of Lycium barbarum polysaccharides on cell signal transduction pathways

Lycium barbarum polysaccharide (LBP), is a major active ingredient Lycium barbarum (LB), which exhibits several beneficial effects through NF-κB, PI3K-Akt-mTOR, p38-MAPK, Wnt-β-catenin, PI3K-Akt-GSK-3β, and MyD88 signal pathway, including anti-oxidation, and anti-aging, hypolipidemic and hypoglycemic, radiation, anti-tumor, and neuroprotection. Today, many researching papers are published on the LBP in physiology and pathology; however, the review of the LBP taking part in the signal transduction pathway in physiology and pathology is rear searched. Therefore, this research topic is a collection of reviews and original research articles that focus on the methods of the LBP extraction and its effects on the signal transduction pathway. The aim of this study is to provide theoretical evidence for in-depth analysis of the mechanisms of LBP in clinical clinical research studies.

Hulless barley and β-glucanase affect ileal digesta soluble beta-glucan molecular weight and digestive tract characteristics of coccidiosis-vaccinated broilers

Exogenous β-glucanase (BGase) in barley-based feed has been shown to reduce digesta viscosity in chickens, and thereby improve performance. Less well studied is the potential for BGase to convert barley β-glucan into low molecular weight carbohydrates, which might influence digestive tract function and enteric disease. Coccidiosis-vaccinated broiler chickens were fed graded levels of hulless barley (HB) and BGase to determine their effects on β-glucan depolymerization and digestive tract characteristics. Broilers were fed high β-glucan HB (0%, 30% and 60% replacing wheat) and BGase (0%, 0.01% and 0.1%) in a 3 × 3 factorial arrangement. A total of 5,346 broilers were raised in litter floor pens and vaccinated for coccidiosis on d 5. Each treatment was assigned to 1 pen in each of 9 rooms. The significance level was set at P ≤ 0.05. At both 11 and 33 d of broiler ages, peak molecular weight of β-glucan in ileal digesta decreased with increasing BGase for 30% and 60% HB. The maximum molecular weight for the smallest 10% β-glucan molecules (MW-10%) decreased with BGase at both ages for 30% and 60% HB; for birds fed 0% HB, only 0.1% BGase decreased MW-10%. The 0.1% BGase increased caecal short chain fatty acids (SCFA) compared to the 0.01% BGase at d 11 only for the 60% HB. Ileal pH increased with increasing HB and BGase at d 11 and 33. Caecal pH was lower for 0.1% BGase than 0% BGase for 60% HB at d 11. Relative mRNA expression of interleukin 6 (IL-6) and IL-8 in the ileum increased with 0.1% BGase at d 11 and 33, respectively, whereas expression of ileal mucin 2 (MUC2) decreased with 0.1% BGase at d 33. In the caeca, interactions between HB and BGase were significant for monocarboxylate transporter 1 (MCT1) and mucin 5AC (MUC5 AC) on d 11, but no treatment effects were found at d 33. In conclusion, BGase depolymerized high molecular weight β-glucan in HB in a dose-dependent manner. Hulless barley and BGase did not increase SCFA concentrations (except for 60% HB with 0.1% BGase at d 11) and caused minor effects on digestive tract histomorphological measurements and relative mRNA gene expression.

Redox Homeostasis in Poultry: Regulatory Roles of NF-κB

Redox biology is a very quickly developing area of modern biological sciences, and roles of redox homeostasis in health and disease have recently received tremendous attention. There are a range of redox pairs in the cells/tissues responsible for redox homeostasis maintenance/regulation. In general, all redox elements are interconnected and regulated by various means, including antioxidant and vitagene networks. The redox status is responsible for maintenance of cell signaling and cell stress adaptation. Physiological roles of redox homeostasis maintenance in avian species, including poultry, have received limited attention and are poorly characterized. However, for the last 5 years, this topic attracted much attention, and a range of publications covered some related aspects. In fact, transcription factor Nrf2 was shown to be a master regulator of antioxidant defenses via activation of various vitagenes and other protective molecules to maintain redox homeostasis in cells/tissues. It was shown that Nrf2 is closely related to another transcription factor, namely, NF-κB, responsible for control of inflammation; however, its roles in poultry have not yet been characterized. Therefore, the aim of this review is to describe a current view on NF-κB functioning in poultry with a specific emphasis to its nutritional modulation under various stress conditions. In particular, on the one hand, it has been shown that, in many stress conditions in poultry, NF-κB activation can lead to increased synthesis of proinflammatory cytokines leading to systemic inflammation. On the other hand, there are a range of nutrients/supplements that can downregulate NF-κB and decrease the negative consequences of stress-related disturbances in redox homeostasis. In general, vitagene-NF-κB interactions in relation to redox balance homeostasis, immunity, and gut health in poultry production await further research.

Determination of antiviral action of long non-coding RNA loc107051710 during infectious bursal disease virus infection due to enhancement of interferon production

The functions and profiles of lncRNAs during infectious bursal disease virus (IBDV) infection have not been determined, yet. The objectives of this study were to determine the antiviral action of loc107051710 lncRNA during IBDV infection by investigating the relationship between loc107051710 and IRF8, Type I IFN, STATs, and ISGs. DF-1 cells were either left untreated as non-infected controls (n = 1) or infected with IBDV (n = 3). RNA sequencing was applied for analysis of mRNAs and lncRNAs expression. Differentially expressed genes were verified by RT-qPCR. Then identification, of 230 significantly different expressed genes (182 mRNAs and 48 lncRNA) by pairwise comparison of the infected and control groups, was carried out. The functions of differentially expressed lncRNAs were investigated by selection of lncRNAs and mRNAs significantly enriched in the aforementioned biological processes and signaling pathways for construction of lncRNA-mRNA co-expression networks. The techniques of gene ontology and Kyoto Encyclopedia of Genes and Genomes pathways were applied. It was suggested that these differentially expressed genes were involved in the interaction between the host and IBDV. Loc107051710 was found to have potential antiviral effects. RT-qPCR and western blot were applied and revealed that loc107051710 was required for induction of IRF8, type I IFN, STAT, and ISG expression, and its knockdown promoted IBDV replication. By fluorescence in situ hybridization, it was found that loc107051710 was translocated from the nucleus to the cytoplasm after infection with IBDV. Overall, loc107051710 promoted the production of IFN-α and IFN-β by regulating IRF8, thereby promoting the antiviral activity of ISGs.

Host CARD11 Inhibits Newcastle Disease Virus Replication by Suppressing Viral Polymerase Activity in Neurons

Host factors play multiple essential roles in the replication and pathogenesis of mammalian neurotropic viruses. However, the cellular proteins of the central nervous system (CNS) involved in avian neurotropic virus infection have not been completely elucidated. Here, we employed a gene microarray to identify caspase recruitment domain-containing protein 11 (CARD11), a lymphoma-associated scaffold protein presenting brain-specific upregulated expression in a virulent neurotropic Newcastle disease virus (NDV)-infected natural host. Chicken primary neuronal cells infected with NDV appeared slightly syncytial and died quickly. CARD11 overexpression inhibited viral replication and delayed cytopathic effects; conversely, depletion of CARD11 enhanced viral replication and cytopathic effects in chicken primary neuronal cells. The inhibition of viral replication by CARD11 could not be blocked with CARD11-Bcl10-MALT1 (CBM) signalosome and NF-κB signaling inhibitors. CARD11 was found to interact directly with the viral phosphoprotein (P) through its CC1 domain and the X domain of P; this X domain also mediated the interaction between P and the viral large polymerase protein (L). The CARD11 CC1 domain and L competitively bound to P via the X domain that hindered the P-L interaction of the viral ribonucleoprotein (RNP) complex, resulting in a reduction of viral polymerase activity in a minigenome assay and inhibition of viral replication. Animal experiments further revealed that CARD11 contributed to viral replication inhibition and neuropathology in infected chicken brains. Taken together, our findings identify CARD11 as a brain-specific antiviral factor of NDV infection in avian species.IMPORTANCE Newcastle disease virus (NDV) substantially impacts the poultry industry worldwide and causes viral encephalitis and neurological disorders leading to brain damage, paralysis, and death. The mechanism of interaction between this neurotropic virus and the avian central nervous system (CNS) is largely unknown. Here, we report that host protein CARD11 presented brain-specific upregulated expression that inhibited NDV replication, which was not due to CARD11-Bcl10-MALT1 (CBM) complex-triggered activation of its downstream signaling pathways. The inhibitory mechanism of viral replication is through the CARD11 CC1 domain, and the viral large polymerase protein (L) competitively interacts with the X domain of the viral phosphoprotein (P), which hampers the P-L interaction, suppressing the viral polymerase activity and viral replication. An in vivo study indicated that CARD11 alleviated neuropathological lesions and reduced viral replication in chicken brains. These results provide insight into the interaction between NDV infection and the host defense in the CNS and a potential antiviral target for viral neural diseases.

AVIAN INNATE IMMUNITY WITH AN EMPHASIS ON CHICKEN MELANOMA DIFFERENTIATION-ASSOCIATED GENE 5 (MDA5)

Avian species have immune system to fight invading pathogens. The immune system comprises innate and adaptive immunity. Innate immunity relies on pattern recognition receptors to sense particular molecules present in pathogens, i.e. pathogen-associated molecular patterns (PAMPs), or danger signals in the environment, i.e. danger-associated molecular patterns (DAMPs). Cytoplasmic retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs) and nucleotide-binding oligomerization domain-like receptors (NLRs) are the sensors recognizing cytoplasmic PAMP and/or DAMP. Among common avian species, chickens do not have RIG-I whereas ducks and finches do. Therefore, the other RLR member, melanoma differentiation-associated gene 5 (MDA5), is believed to play an important role to recognize intracellular pathogens in chickens. Chicken MDA5 has been identified and its function determined. Chicken MDA5 maintains the same domain architecture compared with MDA5 analogs in other animal species. The expression of chicken MDA5 was upregulated when a synthetic double-stranded RNA (dsRNA), polyriboinosinic:polyribocytidylic acids (poly(I:C)), was transfected into chicken cells, whereas that did not change when cells were incubated with poly(I:C). The enhanced expression of chicken MDA5 in chicken cells upregulated the expression of chicken interferon-[Formula: see text] (IFN-[Formula: see text]). The infection of dsRNA infectious bursal disease virus (IBDV) in non-immune cells triggered the activation of chicken MDA5 signaling pathway, leading to the production of IFN-[Formula: see text] and subsequent response of IFN-stimulated genes. Furthermore, in immune cells like macrophages, chicken MDA5 participated in sensing the infection of IBDV by activating downstream antiviral genes and molecules and modulating adaptive immunity.

On the contrary, one of cytoplasmic NLR member, NLR family pyrin domain containing 3 (NLRP3), was cloned and functionally characterized in chicken cells. Chicken NLRP3 conserved the same domain architecture compared with NLRP3 analogs in other animal species. Chicken NLRP3 was highly expressed in kidney, bursa of Fabricius and spleen. The production of mature chicken interleukin 1 [Formula: see text] (IL-1[Formula: see text] in chicken macrophages was stimulated by lipopolysaccharide (LPS) treatment followed by short ATP exposure.

In summary, chicken MDA5 was a cytoplasmic dsRNA sensor that mediated the production of type I IFN upon ligand engagement, whereas NLRP3 sensed danger signals, such as ATP, in the cytoplasm and cleaved pro-IL-1[Formula: see text] to produce mature IL-1[Formula: see text]. Chicken MDA5 was not only involved in the activation of innate immune responses in non-immune and immune cells, but it also participated in modulating adaptive immunity in immune cells. Chicken NLRP3 participated in the production of mature chicken IL-1[Formula: see text] upon ligand engagement.

Molecular Characterization of Two Mitogen-Activated Protein Kinases: p38 MAP Kinase and Ribosomal S6 Kinase From Bombyx mori (Lepidoptera: Bombycidae), and Insight Into Their Roles in Response to BmNPV Infection

Proteins p38 map kinase and ribosomal S6 kinase (S6K) as members of mitogen-activated protein kinases (MAPKs) play important roles against pathogens. In this study, Bmp38 and BmS6K were identified as differentially expressed proteins from iTRAQ database. Bmp38 and BmS6K were expressed, and recombinant proteins were purified. The bioinformatics analysis showed that both proteins have serine/threonine-protein kinases, catalytic domain (S_TKc) with 360 and 753 amino acids, respectively. The real-time quantitative polymerase chain reaction (RT-qPCR) results suggest that Bmp38 and BmS6K had high expression in the midgut and hemolymph. The comparative expression level of Bmp38 and BmS6K in BC9 was upregulated than in P50 in the midgut after Bombyx mori nucleopolyhedrovirus (BmNPV) infection. Western bolt results showed a positive correlation between RT-qPCR and iTRAQ data for Bmp38, but BmS6K data showed partial correlation with iTRAQ. Injection of anti-Bmp38 and anti-BmS6K serum suggested that Bmp38 may be involved against BmNPV infection, whereas BmS6K may require phosphorylation modification to inhibit BmNPV infection. Taken together, our results suggest that Bmp38 and BmS6k might play an important role in innate immunity of silkworm against BmNPV.

Molecular characterization of p38 MAPK from blunt snout bream (Megalobrama amblycephala) and its expression after ammonia stress, and lipopolysaccharide and bacterial challenge

p38 mitogen-activated protein kinase (MAPK) is an important protein which plays a key role in regulating the innate immunity, so exploring its molecular characterization is helpful in understanding the resistance against microbial infections in cultured fish. Here, a full-length cDNA of p38 MAPK was cloned from liver of blunt snout bream (Megalobrama amblycephala) which covered 2419 bp with an open reading frame of 1086 bp encoding 361 amino acids. p38 MAPK contained the characteristic structures of Thr-Gly-Tyr (TGY) motif and substrate binding site Ala-Thr-Arg-Trp (ATRW), which are conserved in MAPK family. To investigate p38 MAPK functions, two in vivo experiments were carried out to examine its expression following ammonia exposure and bacterial challenge. Also, an in vitro experiment was conducted to assess the role of p38 MAPK in inflammation of primary hepatocytes induced by lipopolysaccharide (LPS). The results showed the ubiquitous expression of p38 MAPK in all the tested tissues with varying levels. p38 MAPK mRNA expression was significantly up-regulated by ammonia stress and Aeromonas hydrophila challenge, and altered in a time-dependent manner. Moreover, the results indicated that the inflammatory response induced by LPS in hepatocytes is p38 MAPK dependent as knockdown of p38 MAPK using siRNA technology depressed the expression of IL-1β and IL-6. The findings in this study showed that p38 MAPK has anti-stress property, and plays key role in protection against bacterial infection and inflammation in blunt snout bream.

Tanshinol upregulates the expression of aquaporin 5 in lung tissue of rats with sepsis

Aquaporin 5 (AQP-5) is a water channel protein that is closely associated with non-small cell lung cancer tissues. The present study aimed to investigate the mechanism of tanshinol treatment on AQP-5 in the lung tissue of rats with sepsis. Animals in a rat sepsis model were randomly divided into six groups including blank control (ctrl), sham operation (SO), model (sepsis), low dose tanshinol (5 mg/kg/day; Tan-L), moderate dose tanshinol (10 mg/kg/day; Tan-M) and high dose tanshinol (20 mg/kg/day; Tan-H) groups. After 7 days of administration, the expression level of AQP-5 mRNA was detected by reverse transcription-quantitative polymerase chain reaction. The levels of interleukin-6 (IL-6) and tumor necrosis factor α (TNF-α) were measured by ELISA. Hematoxylin and eosin staining was used for histopathological observation. The expression levels of AQP-5, P38 and phosphorylated (P)-P38 protein in lung tissues were detected by western blot analysis. The expression levels of AQP-5 in the sepsis group were significantly decreased compared with those in ctrl and SO groups (P<0.01), while the levels of TNF-α, IL-6 and p-P38 were significantly increased in sepsis group compared with those in ctrl and SO groups (P<0.01). Following tanshinol intervention, the expression levels of AQP-5 were significantly increased, while the levels of TNF-α, IL-6 and p-P38 were decreased compared with those in sepsis group. Tanshinol may upregulate the expression of AQP-5 by inhibiting the inflammatory cytokines and phosphorylation of P38, therefore protecting the lung tissue of rats with sepsis.

Exacerbated Apoptosis of Cells Infected with Infectious Bursal Disease Virus upon Exposure to Interferon Alpha

Infectious bursal disease virus (IBDV) belongs to the Birnaviridae family and is the etiological agent of a highly contagious and immunosuppressive disease (IBD) that affects domestic chickens (Gallus gallus). IBD or Gumboro disease leads to high rates of morbidity and mortality of infected animals and is responsible for major economic losses to the poultry industry worldwide. IBD is characterized by a massive loss of IgM-bearing B lymphocytes and the destruction of the bursa of Fabricius. The molecular bases of IBDV pathogenicity are still poorly understood; nonetheless, an exacerbated cytokine immune response and B cell depletion due to apoptosis are considered main factors that contribute to the severity of the disease. Here we have studied the role of type I interferon (IFN) in IBDV infection. While IFN pretreatment confers protection against subsequent IBDV infection, the addition of IFN to infected cell cultures early after infection drives massive apoptotic cell death. Downregulation of double-stranded RNA (dsRNA)-dependent protein kinase (PKR), tumor necrosis factor alpha (TNF-α), or nuclear factor κB (NF-κB) expression drastically reduces the extent of apoptosis, indicating that they are critical proteins in the apoptotic response induced by IBDV upon treatment with IFN-α. Our results indicate that IBDV genomic dsRNA is a major viral factor that contributes to the triggering of apoptosis. These findings provide novel insights into the potential mechanisms of IBDV-induced immunosuppression and pathogenesis in chickens.IMPORTANCE IBDV infection represents an important threat to the poultry industry worldwide. IBDV-infected chickens develop severe immunosuppression, which renders them highly susceptible to secondary infections and unresponsive to vaccination against other pathogens. The early dysregulation of the innate immune response led by IBDV infection and the exacerbated apoptosis of B cells have been proposed as the main factors that contribute to virus-induced immunopathogenesis. Our work contributes for the first time to elucidating a potential mechanism driving the apoptotic death of IBDV-infected cells upon exposure to type I IFN. We provide solid evidence about the critical importance of PKR, TNF-α, and NF-κB in this phenomenon. The described mechanism could facilitate the early clearance of infected cells, thereby aiding in the amelioration of IBDV-induced pathogenesis, but it could also contribute to B cell depletion and immunosuppression. The balance between these two opposing effects might be dramatically affected by the genetic backgrounds of both the host and the infecting virus strain.

Nitric oxide induced by Indian ginseng root extract inhibits Infectious Bursal Disease virus in chicken embryo fibroblasts in vitro

Infectious Bursal Disease is a severe viral disease of chicken responsible for serious economic losses to poultry farmers. The causative agent, Infectious Bursal Disease virus, is inhibited by nitric oxide. Root extract of the Indian ginseng, Withania somnifera, inhibits Infectious Bursal Disease virus in vitro. Also, Withania somnifera root extract is known to induce nitric oxide production in vitro. Therefore, the present study was undertaken to determine if the inhibitory activity of Withania somnifera against Infectious Bursal Disease virus was based on the production of nitric oxide. We show that besides other mechanisms, the inhibition of Infectious Bursal Disease virus by Withania somnifera involves the production of nitric oxide. Our results also highlight the paradoxical role of nitric oxide in the pathogenesis of Infectious Bursal Disease.

Bursal transcriptome profiling of different inbred chicken lines reveals key differentially expressed genes at 3 days post-infection with very virulent infectious bursal disease virus

Infectious bursal disease is a highly contagious disease in the poultry industry and causes immunosuppression in chickens. Genome-wide regulations of immune response genes of inbred chickens with different genetic backgrounds, following very virulent infectious bursal disease virus (vvIBDV) infection are poorly characterized. Therefore, this study aims to analyse the bursal tissue transcriptome of six inbred chicken lines 6, 7, 15, N, O and P following infection with vvIBDV strain UK661 using strand-specific next-generation sequencing, by highlighting important genes and pathways involved in the infected chicken during peak infection at 3 days post-infection. All infected chickens succumbed to the infection without major variations among the different lines. However, based on the viral loads and bursal lesion scoring, lines P and 6 can be considered as the most susceptible lines, while lines 15 and N were regarded as the least affected lines. Transcriptome profiling of the bursa identified 4588 genes to be differentially expressed, with 2985 upregulated and 1642 downregulated genes, in which these genes were commonly or uniquely detected in all or several infected lines. Genes that were upregulated are primarily pro-inflammatory cytokines, chemokines and IFN-related. Various genes that are associated with B-cell functions and genes related to apoptosis were downregulated, together with the genes involved in p53 signalling. In conclusion, bursal transcriptome profiles of different inbred lines showed differential expressions of pro-inflammatory cytokines and chemokines, Th1 cytokines, JAK-STAT signalling genes, MAPK signalling genes, and their related pathways following vvIBDV infection.

Lipopolysaccharide induced Interleukin-6 production is mediated through activation of ERK 1/2, p38 MAPK, MEK, and NFκB in chicken thrombocytes

Thrombocytes express Toll-like receptor 4 and apparently use both mitogen-activated protein kinase (MAPK) and nuclear factor kappa-light-chain-enhancer of activated B cells (NFKB) pathways for nuclear signaling. However, it is not well known if the same enzyme systems found in mammalian cells are fully functional in chickens. Therefore, kinase inhibitors were used with thrombocytes to block kinases in lipopolysaccharide (LPS) stimulated cells to determine if interleukin (IL)-6 expression and production would be diminished. Results demonstrated that extracellular-signal-regulated kinase (ERK)1/2 and p38 MAPK pathways influence gene expression of IL-6 through treatment with either ERK or p38 MAPK inhibitor. In addition, thrombocyte lysates from cells treated with ERK, p38, mitogen-activated protein kinase kinase (MEK)1/2 and inhibitor of nuclear factor kappa-B kinase (IKK) inhibitor showed different levels of the phosphorylated form of ERK1/2, p38 and NFκB. Furthermore, IL-6 gene expression and production were significantly upregulated in LPS stimulated thrombocytes relative to all inhibitor-treated cells.

Characterization of Chicken Splenic-Derived Dendritic Cells Following Vaccine and Very Virulent Strains of Infectious Bursal Disease Virus Infection

Studies have shown that infectious bursal disease virus (IBDV) infects lymphoid cells, mainly B cells and macrophages. This study was aimed to examine the involvement of chicken splenic-derived dendritic cells (ch-sDCs) in specific-pathogen-free chickens following inoculation with IBDV vaccine strain (D78) and a very virulent (vv) strain (UPM0081). Following IBDV infection, enriched activated ch-sDCs were collected by using the negative selection method and were examined based on morphology and immunophenotyping to confirm the isolation method for dendritic cells (DCs). The presence of IBDV on enriched activated ch-sDCs was analyzed based on the immunofluorescence antibody test (IFAT), flow cytometry, and quantitative real-time PCR (RT-qPCR) while the mRNAs of several cytokines were detected using RT-qPCR. The isolated ch-sDCs resembled typical DC morphologies found in mammals by having a veiled shape and they grew in clusters. Meanwhile, the expression of DC maturation markers, namely CD86 and MHCII, were increased at day 2 and day 3 following vvIBDV and vaccine strain inoculation, respectively, ranging from 10% to 40% compared to the control at 2.55% (P < 0.05). At day 3 postinfection, IBDV VP3 proteins colocalized with CD86 were readily detected via IFAT and flow cytometry in both vaccine and vvIBDV strains. In addition, enriched activated ch-sDCs were also detected as positive based on the VP4 gene by RT-qPCR; however, a higher viral load was detected on vvIBDV compared to the vaccine group. Infection with vaccine and vvIBDV strains induced the enriched activated ch-sDCs to produce proinflammatory cytokines and Th1-like cytokines from day 3 onward; however, the expressions were higher in the vvIBDV group (P < 0.05). These data collectively suggest that enriched activated ch-sDCs were permissive to IBDV infection and produced a strong inflammatory and Th1-like cytokine response following vvIBDV infection as compared to the vaccine strain.

Transcriptional profiles in bursal B-lymphoid DT40 cells infected with very virulent infectious bursal disease virus

Background

Infectious bursal disease virus (IBDV) causes a highly contagious, immunosuppressive disease in chickens. The virus mainly infects immature B lymphocytes in the bursa of Fabricius (BF). Chicken B cell line DT40, an avian leukosis virus-induced B cell line, supports very virulent IBDV (vvIBDV) infection in vitro and thereby serves as a good model for investigating the infection and pathogenesis of this virus. However, a transcriptome-wide understanding of the interaction between vvIBDV and B cells has not yet been achieved. This study aimed to employ time-course DNA microarrays to investigate gene expression patterns in DT40 cells after infection with vvIBDV strain LX.

Results

DT40 cells infected with vvIBDV exhibited alterations in the expression of many important host genes involved in signal transduction pathways, including MAPK signaling, PI3K/mTOR signaling, cell death and survival, BCR signaling, and antigen presentation. The changes in cellular mRNA levels identified by microarray analysis were confirmed for 8 selected genes using real-time reverse transcription-PCR. The upregulation of inflammatory cytokines and Toll-like receptors (TLRs) in the bursa of vvIBDV-infected chickens might involve excessive activation of the innate immune and inflammatory responses and contribute to tissue damage.

Conclusions

The present study is the first to provide a comprehensive differential transcriptional profile of cultured DT40 cells in response to vvIBDV infection and further extends our understanding of the molecular mechanisms underlying vvIBDV infection and pathogenesis.

Infectious bursal disease virus in poultry: current status and future prospects

Infectious bursal disease virus (IBDV) affects immature B lymphocytes of the bursa of Fabricius and may cause significant immunosuppression. It continues to be a leading cause of economic losses in the poultry industry. IBDV, having a segmented double-stranded RNA genome, is prone to genetic variation. Therefore, IBDV isolates with different genotypic and phenotypic diversity exist. Understanding these features of the virus and the mechanisms of protective immunity elicited thereof is necessary for developing vaccines with improved efficacy. In this review, we highlighted the pattern of virus evolution and new developments in prophylactic strategies, mainly the development of new generation vaccines, which will continue to be of interest for research as well as field application in the future.

Role of chicken melanoma differentiation-associated gene 5 in induction and activation of innate and adaptive immune responses to infectious bursal disease virus in cultured macrophages

The objective of the present study was to determine if chicken melanoma-differentiation-associated gene 5 (MDA5) senses infectious bursal disease virus infection to induce innate immunity that bridges to adaptive immunity. During IBDV infection in HD11 cells, IBDV titers and RNA loads increased up to 3.4 × 10(7) plaque-forming units (PFU)/mL and 1114 ng/µL, respectively, at 24 hours postinfection (hpi). IBDV infection in HD11 cells induced significantly upregulated (p < 0.05) expression levels of chicken MDA5 (59-fold), interferon-β (IFN-β) (693-fold), dsRNA-dependent protein kinase (PKR) (4-fold), 2', 5'-oligoadenylate synthetase (OAS) (286-fold), myxovirus resistance gene (Mx) (22-fold), interleukin-1β (IL-1β) (5-fold), IL-6 (146-fold), IL-8 (4-fold), IL-10 (4-fold), inducible nitric oxide synthase (iNOS) (15-fold), and major histocompatibility complex class I (MHC class I) (4-fold). Nitric oxide production in the culture supernatants increased significantly (p < 0.05) up to 6.5 μM at 24 hpi. The expressed chMDA5 and IBDV-derived dsRNA were localized in the cytoplasm of HD11 cells during IBDV infection. ChMDA5-knockdown HD11 cells had significantly higher (p < 0.05) IBDV RNA loads at 24 hpi and significantly lower (p < 0.05) nitric oxide production and expression levels of chicken MDA5, IFN-β, PKR, OAS, Mx, IL-1β, IL-6, IL-8, IL-12(p40), IL-18, IL-10, iNOS, MHC class I and CD86 at 24 hpi. In addition, chMDA5 overexpression in HD11 cells resulted in significantly reduced (p < 0.05) IBDV titers and RNA loads and significantly increased (p < 0.05) nitric oxide production at 16 and 24 hpi. It also resulted in significantly higher (p < 0.05) expression levels of chicken MDA5, IFN-β, PKR, OAS, Mx, IL-1β, IL-6, IL-8, IL-12(p40), IL-10 and iNOS at 2 hpi. In conclusion, the results indicate that chMDA5 senses IBDV infection in chicken macrophages, and this is associated with IBDV-induced expression of IFN-β and initiation of an innate immune response that in turn activates the adaptive immune response and limits IBDV replication.

Differential Expression Profile of Chicken Embryo Fibroblast DF-1 Cells Infected with Cell-Adapted Infectious Bursal Disease Virus

RNA-Seq was used to unveil the transcriptional profile of DF-1 cells at the early stage of caIBDV infection. Total RNAs were extracted from virus-infected cells at 0, 6 and 12 hpi. RNA-Seq datasets of respective samples mapped to 56.5–57.6% of isoforms in the reference genome Galgal4.73. At 6 hpi, 23 isoforms underwent an elevated expression, while 128 isoforms were up-regulated and 5 were down-regulated at 12 hpi in the virus-infected group. Besides, 10 isoforms were exclusively expressed in the virus-infected cells. Though no significant change was detected in cytokine and interferon expression levels at the first 12 hours of infection, modulations of the upstream regulators were observed. In addition to the reported regulatory factors including EIF2AK2, MX, OAS*A, GBP7 and IFIT, IBDV infection also triggered a IFIT5-IRF1/3-RSAD5 pathway in the DF-1 cells which potentially restricted the viral replication cycle in the early infection stage. Over-expression of LIPA and CH25H, together with the suppression of STARD4, LSS and AACS genes implied a modulation of membrane fluidity and lipid raft arrangement in the infected cells. Alternative splicing of the EFR3 homolog A gene was also through to be involved in the lipid membrane regulation, and these cumulative responses projected an inhibition of viral endocytosis. Recognition of viral RNA genomes and intermediates was presumably enhanced by the elevated levels of IFIH1, DHX58 and TRIM25 genes which possess properties on detecting viral dsRNA. On the other hand, the caIBDV arrested the host's apoptotic process by inducing the expression of apoptosis inhibitors including NFKBIA/Z, TNFAIP2/3 and ITA at the first 12 hours of infection. In conclusion, the differential expression landscape demonstrated with RNA-Seq provides a comprehensive picture on the molecular interactions between host cells and virus at the early stage of infection.

Differential modulation of immune response and cytokine profiles in the bursae and spleen of chickens infected with very virulent infectious bursal disease virus

Background

Very virulent infectious bursal disease virus (vvIBDV) induces immunosuppression and inflammation in young birds, which subsequently leads to high mortality. In addition, infectious bursal disease (IBD) is one of the leading causes of vaccine failure on farms. Therefore, understanding the immunopathogenesis of IBDV in both the spleen and the bursae could help effective vaccine development. However, previous studies only profiled the differential expression of a limited number of cytokines, in either the spleen or the bursae of Fabricius of IBDV-infected chickens. Thus, this study aims to evaluate the in vitro and in vivo immunoregulatory effects of vvIBDV infection on macrophage-like cells, spleen and bursae of Fabricius.

Results

The viral load was increased during the progression of the in vitro infection in the HD11 macrophage cell line and in vivo, but no significant difference was observed between the spleen and the bursae tissue. vvIBDV infection induced the expression of pro-inflammatory and Th1 cytokines, and chemokines from HD11 cells in a time- and dosage-dependent manner. Furthermore, alterations in the lymphocyte populations, cytokine and chemokine expression, were observed in the vvIBDV-infected spleens and bursae. A drastic rise was detected in numbers of macrophages and pro-inflammatory cytokine expression in the spleen, as early as 2 days post-infection (dpi). On 4 dpi, macrophage and T lymphocyte infiltration, associated with the peak expression of pro-inflammatory cytokines in the bursae tissues of infected chickens were observed. The majority of the significantly regulated pro-inflammatory cytokines and chemokines, in vvIBDV-infected spleens and bursae, were also detected in vvIBDV-infected HD11 cells. This cellular infiltration subsequently resulted in a sharp rise in nitric oxide (NO) and lipid peroxidation levels.

Conclusion

This study suggests that macrophage may play an important role in regulating the early expression of pro-inflammatory cytokines, first in the spleen and then in the bursae, the latter tissue undergoing macrophage infiltration at 4 dpi.

Micro RNA expression profiles in peripheral blood cells of rats that were experimentally infected with Trypanosoma congolense and different Trypanosoma brucei subspecies

To identify miRNAs whose expression are differentially regulated during trypanosome infections a microarray targeting more than 600 rat miRNA was used to analyze the miRNA expression profiles between uninfected rats and animals infected by Trypanosoma congolense and Trypanosoma brucei s.l. The potential targets of dysregulated miRNAs as well as their biological pathways and functions were predicted using several bioinformatics software tools. Irrespective of the infecting trypanosome species, eight miRNAs (seven up- and one down-regulated) were dysregulated during infections. Moreover, other miRNAs were differentially regulated in rats infected by specific trypanosome species. Functional analyses of differentially regulated miRNAs indicated their involvement in diverse biological processes. Among these, transcription repressor activity, gene expression control as well as protein transporter activity were predominant. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis of dysregulated miRNAs revealed their involvement in several biological pathways and disease conditions. This suggests possible modulation of such pathways following trypanosome infection; for example, the MAPK signaling pathway which is known to play vital roles in apoptosis, innate immune response and response to viral infections was highly affected. Axon guidance was equally highly impacted and may indicate a cross reactivity between pathogen proteins and guidance molecules representing one pathological mechanism as it has been observed with influenza HA. Furthermore, Ingenuity pathway analyses of dysregulated miRNAs and potential targets indicated strong association with inflammatory responses, cell death and survival as well as infectious diseases. The data generated here provide valuable information to understand the regulatory function of miRNAs during trypanosome infections. They improved our knowledge on host-parasite cross-talks and provide a framework for investigations to understand the development of trypanosomes in their hosts as well as the differences in the clinical and pathological evolutions of the disease.

Dietary L-arginine modulates immunosuppression in broilers inoculated with an intermediate strain of infectious bursa disease virus

BACKGROUND

The effects of dietary l-arginine (Arg) on immunosuppression following infectious bursal disease virus (IBDV) inoculation in broiler chickens were evaluated. The design of this study was a 5 × 2 factorial arrangement (n = 5) with five Arg concentrations (starter: 9.9, 13.9, 17.6, 21.3 and 25.3 g kg(-1) ; grower-finisher: 9.5, 13.5, 17.1, 20.1 and 23.6 g kg(-1) ) with or without IBDV inoculation (IBDV or saline inoculation at 14 days). Chickens were sampled at 2, 4 and 6 days post-inoculation (DPI) and 42 days of age.

RESULTS

The IBDV inoculation decreased (P = 0.05) CD3(+) , CD4(+) , and CD8(+) T cell counts at 2 days post-inoculation (DPI) and monocyte counts at 6 DPI; and reduced (P < 0.05) bursal interleukin-1β (IL-1β) mRNA expression at 2 DPI and serum IL-6 concentration at 4 DPI. Increasing Arg concentration increased (P < 0.05) CD4(+) and CD8(+) T cell counts at 2 DPI, linearly increased (P = 0.05) CD3(+) T cell counts in IBDV-inoculated groups and monocyte counts in control groups at 4 DPI; increased (P < 0.05) serum IL-6 concentration in IBDV-inoculated groups at 2 DPI; and increased (P < 0.05) serum anti-IBDV antibody titres at 42 days of age.

CONCLUSION

Varying concentrations of Arg supplementation attenuated IBDV inoculation induced immunosuppression via modulating circulating T cell sub-populations.

Analysis of the early immune response to infection by infectious bursal disease virus in chickens differing in their resistance to the disease

Chicken whole-genome gene expression arrays were used to analyze the host response to infection by infectious bursal disease virus (IBDV). Spleen and bursal tissue were examined from control and infected birds at 2, 3, and 4 days postinfection from two lines that differ in their resistance to IBDV infection. The host response was evaluated over this period, and differences between susceptible and resistant chicken lines were examined. Antiviral genes, including IFNA, IFNG, MX1, IFITM1, IFITM3, and IFITM5, were upregulated in response to infection. Evaluation of this gene expression data allowed us to predict several genes as candidates for involvement in resistance to IBDV.

IMPORTANCE Infectious bursal disease (IBD) is of economic importance to the poultry industry and thus is also important for food security. Vaccines are available, but field strains of the virus are of increasing virulence. There is thus an urgent need to explore new control solutions, one of which would be to breed birds with greater resistance to IBD. This goal is perhaps uniquely achievable with poultry, of all farm animal species, since the genetics of 85% of the 60 billion chickens produced worldwide each year is under the control of essentially two breeding companies. In a comprehensive study, we attempt here to identify global transcriptomic differences in the target organ of the virus between chicken lines that differ in resistance and to predict candidate resistance genes.

PRAK interacts with DJ-1 and prevents oxidative stress-induced cell death

As a core member of p38 MAPK signal transduction pathway, p38 regulated/activated kinase (PRAK) is activated by cellular stresses. However, the function of PRAK and its downstream interacting partner remain undefined. Using a yeast two-hybrid system, we identified DJ-1 as a potential PRAK interacting protein. We further verified that DJ-1 bound to PRAK in vitro and in vivo and colocalized with PRAK in the nuclei of NIH3T3 cells. Furthermore, following H₂O₂ stimulation the majority of endogenous DJ-1 in PRAK^+/+ cells still remained in the nucleus, whereas most DJ-1 in PRAK^−/− cells translocated from the nucleus into the cytoplasm, indicating that PRAK is essential for DJ-1 to localize in the nucleus. In addition, PRAK-associated phosphorylation of DJ-1 was observed in vitro and in vivo of H₂O₂-challenged PRAK^+/+ cells. Cytoplasmic translocation of DJ-1 in H₂O₂-treated PRAK^−/− cells lost its ability to sequester Daxx, a death protein, in the nucleus, and as a result, Daxx gained access to the cytoplasm and triggered cell death. These data highlight that DJ-1 is the downstream interacting target for PRAK, and in response to oxidative stress PRAK may exert a cytoprotective effect by facilitating DJ-1 to sequester Daxx in the nucleus, thus preventing cell death.

Avian Immunosuppressive Diseases and Immunoevasion

Subclinical immunosuppression in chickens is an important but often underestimated factor in the subsequent development of clinical disease. Immunosuppression can be caused by pathogens such as chicken infectious anemia virus, infectious bursal disease virus, reovirus, and some retroviruses (e.g., reticuloendotheliosis virus). Mycotoxins and stress, often caused by poor management practices, can also cause immunosuppression. The effects on the innate and acquired immune responses and the mechanisms by which mycotoxins, stress and infectious agents cause immunosuppression are discussed. Immunoevasion is a common ploy by which viruses neutralize or evade immune responses. DNA viruses such as herpesvirus and poxvirus have multiple genes, some of them host-derived, which interfere with effective innate or acquired immune responses. RNA viruses may escape acquired humoral and cellular immune responses by mutations in protective antigenic epitopes (e.g., avian influenza viruses), while accessory non-structural proteins or multi-functional structural proteins interfere with the interferon system (e.g., Newcastle disease virus).

Effects of reticuloendotheliosis virus infection on cytokine production in SPF chickens

Infection with reticuloendotheliosis virus (REV), a gammaretrovirus in the Retroviridae family, can result in immunosuppression and subsequent increased susceptibility to secondary infections. The effects of REV infection on expression of mRNA for cytokine genes in chickens have not been completely elucidated. In this study, using multiplex branched DNA (bDNA) technology, we identified molecular mediators that participated in the regulation of the immune response during REV infection in chickens. Cytokine and chemokine mRNA expression levels were evaluated in the peripheral blood mononuclear cells (PBMCs). Expression levels of interleukin (IL)-4, IL-10, IL-13 and tumor necrosis factor (TNF)-α were significantly up-regulated while interferon (IFN)-α, IFN-β, IFN-γ, IL-1β, IL-2, IL-3, IL-15, IL-17F, IL-18 and colony-stimulating factor (CSF)-1 were markedly decreased in PBMCs at all stages of infection. Compared with controls, REV infected chickens showed greater expression levels of IL-8 in PBMCs 21 and 28 days post infection. In addition, REV regulates host immunity as a suppressor of T cell proliferative responses. The results in this study will help us to understand the host immune response to virus pathogens.

Infectious Bursal Disease: a complex host-pathogen interaction

Infectious Bursal Disease (IBD) is caused by a small, non-enveloped virus, highly resistant in the outside environment. Infectious Bursal Disease Virus (IBDV) targets the chicken's immune system in a very comprehensive and complex manner by destroying B lymphocytes, attracting T cells and activating macrophages. As an RNA virus, IBDV has a high mutation rate and may thus give rise to viruses with a modified antigenicity or increased virulence, as emphasized during the last decades. The molecular basis of pathogenicity and the exact cause of clinical disease and death are still poorly understood, as it is not clearly related to the severity of the lesions and the extent of the bursal damage. Recent works however, pointed out the role of an exacerbated innate immune response during the early stage of the infection with upregulated production of promediators that will induce a cytokine storm. In the case of IBDV, immunosuppression is both a direct consequence of the infection of specific target immune cells and an indirect consequence of the interactions occurring in the immune network of the host. Recovery from disease or subclinical infection will be followed by immunosuppression with more serious consequences if the strain is very virulent and infection occurs early in life. Although the immunosuppression caused by IBDV is principally directed towards B-lymphocytes, an effect on cell-mediated immunity (CMI) has also been demonstrated therefore increasing the impact of IBDV on the immunocompetence of the chicken. In addition to its zootechnical impact and its role in the development of secondary infections, it may affect the immune response of the chicken to subsequent vaccinations, essential in all types of intensive farming. Recent progress in the field of avian immunology has allowed a better knowledge of the immunological mechanisms involved in the disease but also should give improved tools for the measurement of immunosuppression in the field situation. Although satisfactory protection may be provided by the induction of high neutralizing antibody titres, interference from parental antibodies with vaccination has become the most important obstacle in the establishment of control programs. In this context, recombinant HVT and immune complex vaccines show promising results.

MicroRNA expression profile in different tissues of BALB/c mice in the early phase of Schistosoma japonicum infection

Schistosomiasis remains an important global public health problem that affects 200 million people in 76 countries. The molecular mechanisms of host-parasite interaction are complex, and in schistosome infection regulation of microRNA (miRNA) and the host micro-environment may be involved. In this study, an miRNA microarray was applied to investigate differences in miRNA expression in different tissues of mice before and 10 days post infection. In total, 220 miRNAs were detected in different tissues of the BALB/c mice before and after infection, including 8 miRNAs in liver, 8 in spleen and 28 in the lungs with up-regulated expression, and 3 miRNAs in liver, 5 in spleen and 28 in the lungs with down-regulated expression in mice 10 days post infection with schistosomes. The functions of these differentially expressed miRNAs are related mainly to the immune response, nutrient metabolism, cell differentiation, apoptosis, and signal pathways. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of the differentially expressed miRNAs revealed that many important biological pathways are triggered by schistosome infection in BALB/c mice, such as the MAPK signaling pathway, insulin signaling pathway, Toll-like receptor signaling pathway and TGF-β signaling pathway.The results reveal that miRNAs may be an important regulator of schistosome-host interaction in the early phase of Schistosoma japonicum infection. The data presented here provide valuable information to increase understanding of the regulatory function of the miRNAs in the host micro-environment, as well as the mechanism of host-parasite interactions. This may be helpful in the search for potential new drugs, and for biomarkers of early S. japonicum infection applicable in the future control of schistosomiasis.

Protocatechuic acid, a new active substance against the challenge of avian infectious bursal disease virus

The present study aims to investigate the potential antiviral activity of protocatechuic acid (PCA) and its mechanism against infectious bursal disease virus (IBDV) infection. In the curative test, dosages of PCA of 40, 20, and 10 mg/kg, the survival rate was 90, 90, and 60%, respectively, and the BW gain was 36.63, 31.85, and 51.8%, respectively. The survival rate for the Astragalus polysaccharide (ASP) group was significantly lower than those of the birds treated with 20 mg/kg or 40 mg/kg of PCA. The bursa indeces of chickens in 40 mg/kg, 20 mg/kg, and ASP groups were significantly higher than that of the infection group, whereas a significant increase of the spleen index was found in birds with 20 mg/kg PCA in comparison with other challenged groups. The birds treated with 20 mg/kg or 40 mg/kg of 3,4-dihydroxybenzoic acid also showed slightly higher levels of IBDV clearance in the bursa of Fabricius. Furthermore, the chickens treated with 20 mg/kg of PCA induced a significant lymphocyte proliferation and a significant increase in the CD4+/CD8+ ratio in comparison with the ASP chickens. These results imply that chickens treated with 20 mg/kg of PCA for 5 d could effectively induce active nonspecific immune responses against the IBDV infection.

Characterization of p38 MAPKs from orange-spotted grouper, Epinephelus coioides involved in SGIV infection

p38 mitogen-activated protein kinases (MAPKs) are broadly expressed signaling molecules that involves in the regulation of cellular responsible for various extracellular stimuli. In this study, three p38 MAPK genes (Ec-p38a, p38b and p38β) were cloned from grouper, Epinephelus coioides and their characteristics were investigated in vitro. Although Ec-p38a, p38b and p38β showed high homologies to other fish p38a MPAK, p38b MAPK and p38β MAPK, respectively, they all contained the conserved structures of Thr-Gly-Tyr (TGY) motif and substrate binding site Ala-Thr-Arg-Trp (ATRW). Phylogenetic analysis indicated that Ec-p38a, p38b and p38β are more closely related to those from fish than mammals. The tissue distribution patterns of Ec-p38a, p38b and p38β were different, and Ec-p38β was up-regulated most obviously in head kidney after Singapore grouper iridovirus (SGIV) infection. Overexpression of Ec-p38β in FHM cells delayed the occurrence of CPE induced by SGIV infection. Further analysis indicated that overexpression of Ec-p38β inhibited viral gene transcription and protein synthesis, as well as SGIV induced typical apoptosis in fish cells. Taken together, our data indicated that Ec-p38β played a crucial role in regulating apoptosis and virus replication during iridovirus infection.

Bacterial toll-like receptor agonists induce sequential NF-κB-mediated leukotriene B4 and prostaglandin E2 production in chicken heterophils

Studies of the response of the primary avian polymorphonuclear leukocyte, the heterophil, to microbe associated molecular patterns (MAMPs) through toll-like receptors (TLR) has concentrated on the activation of the respiratory burst, release of intracellular granules, and the induction of cytokine and chemokine expression. Virtually no studies have been described on the role of lipid mediators, leukotrienes and prostaglandins, as effectors of the avian inflammatory response. We have previously shown that flagellin (FLG), the bacterial lipoprotein mimic palmitoly-3-cysteine-serine-lysine-4 (PAM), and unmethylated CpG motifs of bacteria DNA (CpG) are all potent activators of the avian innate immune system. In the present studies, we hypothesized that FLG, PAM, and CpG are also capable of eliciting the production of these lipid mediators of inflammation by avian heterophils. Compared to non-stimulated control heterophils, all three TLR agonists were potent inducers (3-5-fold increase) of a rapid production (30 min) of leukotriene B(4) (LTB(4)) followed by a later release (60-120 min) of prostaglandin (PGE(2)) by the heterophils. LTB(4) and PGE(2) production were derived from lipoxygenase-5 (5-LO) and cyclooxygenase-2 (COX-2) enzymatic activities, respectively, as the selective 5-LO (caffeic acid) and COX-2 (NS-398) inhibitors eliminated LTB(4) and PGE(2) production from the MAMP-stimulated heterophils. These results demonstrate that both the lipoxygenase and cycloxygenase pathways are operational in avian heterophils in response to bacterial MAMPs. Treatment of heterophils with either FLG, PAM, or CpG also induced a significant increase in DNA binding by NF-κB family members' p50, c-Rel, and RelB. Additionally, the production of LTB(4) and PGE(2) were inhibited following treatment of heterophils with the specific pharmacologic inhibitor of NF-κB (Bay 11-7086), thus suggesting that TLR pathway activation of NF-κB controls LTB(4) and PGE(2) production. This the first report of the production of lipid mediators of inflammation by avian heterophils in response to PAMPs. Since FLG, lipoproteins, and bacterial CpG DNA are abundant during bacterial infections, these data support their role in the inflammatory response mediated by avian heterophils.

Infectious bursal disease virus-induced activation of JNK signaling pathway is required for virus replication and correlates with virus-induced apoptosis

The Jun NH2-terminal kinase (JNK) which serves as an important component of cellular signal transduction pathways has been shown to regulate many viral infections. The present study demonstrated for the first time that infectious bursal disease virus (IBDV), the causative agent of a highly contagious disease in chickens, can activate JNK1/2 pathway in IBDV-infected cells dependent upon viral replication. IBDV-induced JNK1/2 activation causes its downstream target c-Jun phosphorylation, which kinetically paralleled JNK1/2 activation. Investigations into the mechanism of JNK1/2 regulation revealed that inhibition of JNK1/2 activation leads to reduced viral progeny release, which is associated with decreased viral transcription and lower virus protein expression, and thereby limiting apoptotic cell death as evidenced by blockage of Bax activation, cytochrome c release, and caspase activation. These data suggest that the JNK pathway plays an important role in the IBDV replication and contributes to virus-mediated changes in host cells.

Aquatic birnavirus-induced ER stress-mediated death signaling contribute to downregulation of Bcl-2 family proteins in salmon embryo cells

Aquatic birnavirus induces mitochondria-mediated cell death, but whether connects to endoplasmic reticulum (ER) stress is still unknown. In this present, we characterized that IPNV infection triggers ER stress-mediated cell death via PKR/eIF2α phosphorylation signaling for regulating the Bcl-2 family protein expression in fish cells. The IPNV infection can induce ER stress as follows: (1) ER stress sensor ATF6 cleavaged; (2) ER stress marker GRP78 upregulation, and (3) PERK/eIF2α phosphorylation. Then, the IPNV-induced ER stress signals can induce the CHOP expression at early (6 h p.i.) and middle replication (12 h p.i.) stages. Moreover, IPNV-induced CHOP upregulation dramatically correlates to apparently downregulate the Bcl-2 family proteins, Bcl-2, Mcl-1 and Bcl-xL at middle replication stage (12 h p.i.) and produces mitochondria membrane potential (MMP) loss and cell death. Furthermore, with GRP78 synthesis inhibitor momitoxin (VT) and PKR inhibitor 2-aminopurine (2-AP) treatment for blocking GRP78 expression and eIF2α phosphorylation, PKR/PERK may involve in eIF2α phosphorylation/CHOP upregulation pathway that enhances the downstream regulators Bcl-2 family proteins expression and increased cell survival. Taken together, our results suggest that IPNV infection activates PKR/PERK/eIF2α ER stress signals for regulating downstream molecules CHOP upregulation and Bcl-2 family downregulation that led to induce mitochondria-mediated cell death in fish cells, which may provide new insight into RNA virus pathogenesis and disease.

Differential modulation of cytokine, chemokine and Toll like receptor expression in chickens infected with classical and variant infectious bursal disease virus

Infectious bursal disease (IBD) is an important immunosuppressive disease of chickens. The causative agent, infectious bursal disease virus (IBDV), consists of two serotypes, 1 and 2. Serotype 1 consists of classic IBDV (cIBDV) and variant IBDV (vIBDV). Both of these strains vary in antigenicity and pathogenesis. The goal of this study was to compare the immunopathogenesis of cIBDV and vIBDV. Three-week-old specific pathogen free chickens were inoculated intraocularly with standard challenge strain (STC) (cIBDV) and a variant strain Indiana (IN) (vIBDV). The cIBDV produced more pronounced bursal damage, inflammatory response and infiltration of T cells as compared to vIBDV. There were significant differences in the expression of innate (IFN-α and IFN-β), proinflammatory cytokine and mediator (IL-6 and iNOS) in cIBDV- and vIBDV-infected bursas. The expression of chemokines genes, IL-8 and MIP-α was also higher in cIBDV-infected chickens during the early phase of infection. The expression of Toll like receptor 3 (TLR3) was downregulated at post inoculation days (PIDs) 3, 5, and 7 in the bursas of vIBDV-infected chickens whereas TLR3 was upregulated at PIDs 3 and 5 in cIBDV-infected bursas. In vIBDV-infected bursa, TLR7 expression was downregulated at PIDs 3 and 5 and upregulated at PID 7. However, TLR7 was upregulated at PIDs 3 and 7 in cIBDV-infected bursas. The expression of MyD88 was downregulated whereas TRIF gene expression was upregulated in cIBDV- and vIBDV-infected bursa. These findings demonstrate the critical differences in bursal lesions, infiltration of T cells, expression of cytokines, chemokines and TLRs in the bursa of cIBDV-and vIBDV-infected chickens.

Activation of cytokine expression occurs through the TNFα/NF-κB-mediated pathway in birnavirus-infected cells

The infectious pancreatic necrosis virus (IPNV) belongs to the Birnaviridae family of viruses and causes acute contagious diseases in a number of economically important freshwater and marine fish. In this study, we infected zebrafish embryonic cells (ZF4) with IPNV and analyzed the gene expression patterns of normal and infected cells using quantitative real-time PCR. We identified a number of immune response genes, including ifna, ifng, mx, irf1, irf2, irf4, tnfa, tnfb, il-1b, il-15, il-26, ccl4 and mmp family genes, that are induced after viral infection. Transcriptional regulators, including cebpb, junb, nfkb and stat1, stat4 and stat5, were also upregulated in IPNV-infected cells. In addition, we used Pathway Studio software to identify TNFα as having the greatest downstream influence among these altered genes. Treating virus-infected cells with an siRNA targeting TNFα inhibited NF-κB expression. To further interrupt the TNFα/NF-κB-mediated pathway, the expression levels of cytokines and metalloproteinases were inhibited in IPNV-infected cells. These data suggest that, during IPNV infection, the expression of cytokines and metalloproteinases might be initiated through the TNFα/NF-κB-mediated pathway. The modulation of TNFα/NF-κB-related mechanisms may provide a therapeutic strategy for inhibiting viral infection in teleosts.

Protection against avian metapneumovirus subtype C in turkeys immunized via the respiratory tract with inactivated virus

Avian metapneumovirus subtype C (aMPV/C) causes a severe upper respiratory tract (URT) infection in turkeys. Turkeys were inoculated oculonasally with inactivated aMPV/C adjuvanted with synthetic double-stranded RNA polyriboinosinic polyribocytidylic acid (Poly IC). Immunized turkeys had elevated numbers of mucosal IgA+ cells in the URT and increased levels of virus-specific IgG and IgA in the lachrymal fluid and IgG in the serum. After 7 or 21 days post immunization, turkeys were challenged oculonasally with pathogenic aMPV/C. Immunized groups were protected against respiratory lesions induced by the challenge virus. Further, the viral copy number of the challenge virus in the URT were significantly lower in the immunized turkeys than in the unimmunized turkeys (P<0.05). These results showed that inactivated aMPV/C administered by the respiratory route induced protective immunity against pathogenic virus challenge.

Characterization of host responses against a recombinant fowlpox virus-vectored vaccine expressing the hemagglutinin antigen of an avian influenza virus

There currently are commercial fowlpox virus (FPV)-vectored vaccines for use in chickens, including TROVAC-AIV H5, which expresses the hemagglutinin (HA) antigen of an avian influenza virus and can confer immunity against avian influenza in chickens. Despite the use of recombinant FPV (rFPV) for vaccine delivery, very little is known about the immune responses generated by these viruses in chickens. The present study was designed to investigate host responses to rFPV in vivo and in vitro. In cultured cells infected with TROVAC-AIV H5, there was an early increase in the expression of type I interferons (IFN), Toll-like receptors 3 and 7 (TLR3 and TLR7, respectively), TRIF, and MyD88, which was followed by a decrease in the expression of these genes at later time points. There also was an increase in the expression of interleukin-1beta (IL-1beta), IL-8, and beta-defensin genes at early time points postinfection. In chickens immunized with TROVAC-AIV H5, there was higher expression of IFN-gamma and IL-10 at day 5 postvaccination in spleen of vaccinated birds than in that of control birds. We further investigated the ability of the vaccine to induce immune responses against the HA antigen and discovered that there was a cell-mediated response elicited in vaccinated chickens against this antigen. The findings of this study demonstrate that FPV-vectored vaccines can elicit a repertoire of responses marked by the early expression of TLRs, type I interferons, and proinflammatory cytokines, as well as cytokines associated with adaptive immune responses. This study provides a platform for designing future generations of rFPV-vectored vaccines.

Molecular characterization and expression profiles in response to bacterial infection of Chinese soft-shelled turtle interleukin-8 (IL-8), the first reptilian chemokine gene

In this study, an IL-8 homologue has been cloned and identified from a reptile, Chinese soft-shelled turtle for the first time. The full-length cDNA of turtle IL-8 was 1188bp and contained a 312bp open reading frame (ORF) coding for a protein of 104 amino acids. The chemokine CXC domain, which contained Glu-Leu-Arg (ELR) motif and four cysteine residues, was well conserved in turtle IL-8. The 4924bp genomic DNA of turtle IL-8 contained four exons and three introns. Phylogenetic analysis showed that the amino acid sequence of turtle IL-8 clustered together with birds. RT-PCR analysis showed that turtle IL-8 mRNA was constitutively expressed liver, spleen, kidney, heart, blood and intestine tissues of control turtles. Real-time quantitative PCR analysis further indicated that the turtle IL-8 mRNA expression was apparent in various tissues at 8h and up-regulated significantly during 8h-7d after Aeromonas hydrophila infection. The present studies will help us to understand the evolution of IL-8 molecule and the inflammatory response mechanism in reptiles.

Structural and functional homology among chicken, duck, goose, turkey and pigeon interleukin-8 proteins

Interleukin (IL)-8-encoding regions of five avian species were cloned, sequenced and characterized. Each IL-8-encoding region is 312 nucleotides long and encodes IL-8 which is 103 amino acids. Pairwise sequence analysis showed that sequence identities of IL-8-encoding regions ranged from 87% to 100%. The IL-8 protein identities varied from 84% to 100%. Phylogenetic analysis indicated that IL-8-encoding regions and encoded proteins of chicken, duck, goose and turkey clustered together and evolved into a distinct phylogenetic lineage from that of pigeon which evolved into a second lineage. The results from binding reactivities of antiserum against each recombinant IL-8 (rIL-8) protein to homologous or heterologous rIL-8 proteins, chemotactic activities of each rIL-8 protein or reduction levels of the chemotactic activity of rIL-8 protein which was pretreated with homologous or heterlogous antiserum have suggested that all five IL-8 proteins were functionally active, and shared structural and functional identity with each other.

Thrombocytes respond to lipopolysaccharide through Toll-like receptor-4, and MAP kinase and NF-κB pathways leading to expression of interleukin-6 and cyclooxygenase-2 with production of prostaglandin E2

Chicken thrombocytes are equivalent in hemostatic function to mammalian platelets. Platelets are enucleated components of mammalian blood, while thrombocytes are nucleated blood leukocytes of chickens. Platelets and thrombocytes share characteristics that contribute to innate immunity. Experiments were conducted to determine if thrombocytes could respond in vitro to lipopolysaccharide (LPS) of Salmonella minnesota through Toll-like receptor-4 (TLR4). The aim was to activate the signal pathways leading to expression of interleukin-6 (IL-6) and inducible cyclooxygenase (COX-2) and to production of prostaglandin E2 (PGE2). Chicken thrombocytes were found to express TLR4, and LPS-induced an increase in thrombocyte mRNA expression of IL-6 and COX-2 with release of PGE2 into culture media. An increase of COX-2 and PGE2 due to LPS stimulation was inhibited by MEK1 inhibitor PD98059, but IL-6 expression was unaffected by PD98059. The IKK-2 inhibitor BMS345541 inhibited IL-6 and COX-2 with reduction of PGE2 concentrations. Therefore, the MAP kinase (MAPK) pathway activates expression of COX-2 and ultimately PGE2 production, but this pathway has little or no influence on IL-6 expression in thrombocytes. The NF-kappaB pathway also influences COX-2 expression and PGE2 production, and it is a primary activation signaling cascade for IL-6 gene expression in chicken thrombocytes. Thrombocytes represent a major component of the innate immune system of chickens in response to LPS and possibly other microbial products.