CpG-ODN-induced nitric oxide production is mediated through clathrin-dependent endocytosis, endosomal maturation, and activation of PKC, MEK1/2 and p38 MAPK, and NF-kappaB pathways in avian macrophage cells (HD11)

Compartmentalization proteomics revealed endolysosomal protein network changes in a goat model of atrial fibrillation

Endolysosomes (EL) are known for their role in regulating both intracellular trafficking and proteostasis. EL facilitate the elimination of damaged membranes, protein aggregates, membranous organelles and play an important role in calcium signaling. The specific role of EL in cardiac atrial fibrillation (AF) is not well understood. We isolated atrial EL organelles from AF goat biopsies and conducted a comprehensive integrated omics analysis to study the EL-specific proteins and pathways. We also performed electron tomography, protein and enzyme assays on these biopsies. Our results revealed the upregulation of the AMPK pathway and the expression of EL-specific proteins that were not found in whole tissue lysates, including GAA, DYNLRB1, CLTB, SIRT3, CCT2, and muscle-specific HSPB2. We also observed structural anomalies, such as autophagic-vacuole formation, irregularly shaped mitochondria, and glycogen deposition. Our results provide molecular information suggesting EL play a role in AF disease process over extended time frames.

pH-sensitive cationic nanoparticles for endosomal cell-free DNA scavenging against acute inflammation

Cell-free DNA (cfDNA) released from dead cells could be a player in some autoimmune disorders by activating Toll-like receptor 9 (TLR9) and inducing proinflammatory cytokines. Cationic nanoparticles (cNPs) address cfDNA clearance, yet challenges persist, including toxicity, low specificity and ineffectiveness against endocytosed cfDNA. This study introduced pH-sensitive cNPs, reducing off-target effects and binding cfDNA at inflammatory sites. This unique approach inhibits the TLR9 pathway, offering a novel strategy for inflammation modulation. Synthesized cNPs, with distinct cationic moieties, exhibit varied pKa values, enhancing cfDNA binding. Comprehensive studies elucidate the mechanism, demonstrating minimal extracellular binding, enhanced endosomal DNA binding, and optimal tumor necrosis factor-α suppression. In a traumatic brain injury mice model, pH-sensitive cNPs effectively suppress inflammatory cytokines, highlighting their potential in acute inflammation regulation.

Screening of Optimal CpG-Oligodeoxynucleotide for Anti-Inflammatory Responses in the Avian Macrophage Cell Line HD11

CpG-oligodeoxynucleotides (.

CpG-ODNs

) have been shown to possess immunostimulatory features in both mammals and birds. However, compared to their proinflammatory effects, little is known about the anti-inflammatory responses triggered by CpG-ODN in avian cells. Hence, in this study, the anti-inflammatory response in the chicken macrophage cell line HD11 was characterized under stimulation with five types of CpG-ODNs: CpG-A₁₅₈₅, CpG-A_D35, CpG-B₁₅₅₅, CpG-B_K3, and CpG-C₂₃₉₅. Single-stimulus of CpG-B₁₅₅₅, CpG-B_K3, or CpG-C₂₃₉₅ induced interleukin (IL)-10 expression without causing cell injury. The effects of pretreatment with CpG-ODNs before subsequent lipopolysaccharide stimulation were also evaluated. Interestingly, pretreatment with only CpG-C₂₃₉₅ resulted in high expression levels of IL-10 mRNA in the presence of lipopolysaccharide. Finally, gene expression analysis of inflammation-related cytokines and receptors revealed that pre-treatment with CpG-C₂₃₉₅ significantly reduced the mRNA expression of tumor necrosis factor-α, IL-1β, IL-6, and Toll-like receptor 4. Overall, these results shed light on the anti-inflammatory responses triggered by CpG-C₂₃₉₅ stimulation through a comparative analysis of five types of CpG-ODNs in chicken macrophages. These results also offer insights into the use of CpG-ODNs to suppress the expression of proinflammatory cytokines, which may be valuable in the prevention of avian infectious diseases in the poultry industry.

The Chicken Embryo Model: A Novel and Relevant Model for Immune-Based Studies

Dysregulation of the immune system is associated with many pathologies, including cardiovascular diseases, diabetes, and cancer. To date, the most commonly used models in biomedical research are rodents, and despite the various advantages they offer, their use also raises numerous drawbacks. Recently, another in vivo model, the chicken embryo and its chorioallantoic membrane, has re-emerged for various applications. This model has many benefits compared to other classical models, as it is cost-effective, time-efficient, and easier to use. In this review, we explain how the chicken embryo can be used as a model for immune-based studies, as it gradually develops an embryonic immune system, yet which is functionally similar to humans'. We mainly aim to describe the avian immune system, highlighting the differences and similarities with the human immune system, including the repertoire of lymphoid tissues, immune cells, and other key features. We also describe the general in ovo immune ontogeny. In conclusion, we expect that this review will help future studies better tailor their use of the chicken embryo model for testing specific experimental hypotheses or performing preclinical testing.

The Interplay between Salmonella and Intestinal Innate Immune Cells in Chickens

Salmonellosis is a common infection in poultry, which results in huge economic losses in the poultry industry. At the same time, Salmonella infections are a threat to public health, since contaminated poultry products can lead to zoonotic infections. Antibiotics as feed additives have proven to be an effective prophylactic option to control Salmonella infections, but due to resistance issues in humans and animals, the use of antimicrobials in food animals has been banned in Europe. Hence, there is an urgent need to look for alternative strategies that can protect poultry against Salmonella infections. One such alternative could be to strengthen the innate immune system in young chickens in order to prevent early life infections. This can be achieved by administration of immune modulating molecules that target innate immune cells, for example via feed, or by in-ovo applications. We aimed to review the innate immune system in the chicken intestine; the main site of Salmonella entrance, and its responsiveness to Salmonella infection. Identifying the most important players in the innate immune response in the intestine is a first step in designing targeted approaches for immune modulation.

Can the exposure system adopted influence the results of the atrazine toxicity in hepatic tissue of fish?

The widespread use of atrazine, a herbicide used to control weeds, has contributed to the increased contamination of aquatic environments. To assess the toxicological effects of a xenobiotic on a nontarget organism in the laboratory, different models of toxicological exposure systems have been widely used. Therefore, the aim of this study was to evaluate and compare the action of sublethal concentrations of atrazine on the hepatic histology of Oreochromis niloticus, considering two models of exposure: static (where atrazine was only added once) and semi-static (where atrazine was periodically renewed). Fish were exposed to a concentration of 2 ppm atrazine for 15 days, which was verified by high-performance liquid chromatography. The livers were stained with hematoxylin and eosin and histopathological data were collected. In addition, they were submitted to immunohistochemistry for inducible nitric oxide synthase (iNOS). A maximum variation of 45% (static) and 12.5% (semi-static) was observed between the observed and nominal atrazine concentration. Nuclear and cytoplasmic changes were observed in both experimental models. Hepatocytes from the livers of the static system showed a degenerative appearance, while in the semi-static system, intense cytoplasmic vacuolization and necrosis were observed. iNOS positive cells were identified only in macrophages in the hepatocytes of fish in the semi-static system. These results directly showed how the choice of exposure system can influence the results of toxicological tests. However, future analysis investigating the by-products and nitrogen products should be carried out since the histopathological findings revealed the possibility of these compounds serving as secondary contamination routes.

The immunostimulator Victrio activates chicken toll-like receptor 21

The immunostimulator Victrio consists of bacterial plasmid DNA encased in cationic liposomes and protects embryonated chicken eggs and newly hatched chickens against Escherichia coli induced mortality. It is demonstrated that Victrio specifically and potently activates recombinant chicken toll-like receptor 21 (TLR21) in a nuclear factor kappa B reporter gene assay. This TLR21 stimulatory activity is dependent on the presence of nonmethylated CpG and requires liposomal formulation of the DNA, as naked plasmid DNA proves to be inactive. Nitric oxide production is induced by Victrio in HD11 chicken macrophages that express TLR21 naturally, supporting the proposal that chicken TLR21 is a component of the molecular mode of action of Victrio.

Targeting Delivery of Oligodeoxynucleotides to Macrophages by Mannosylated Cationic Albumin for Immune Stimulation in Cancer Treatment

To efficiently deliver CpG oligodeoxynucleotides (ODNs) to macrophages for the reversal of cancer-induced immunosuppression, nanoparticles ODN@MCBSA with mannosylated cationic albumin (MCBSA) as a macrophage targeting vector were constructed. Compared with ODN@CBSA with cationic albumin (CBSA) as a vector, ODN@MCBSA exhibited significantly improved cellular uptake mediated by mannose moieties, resulting in significantly enhanced secretion of proflammatory cytokines including IL-12, IL-6, TNF-α, and iNOS. The modulation of macrophages toward the favorable M1 phenotype was confirmed by the upregulated CD80 expression after being treated by ODN delivery systems. In addition to immune cells, the effects of the ODN delivery system on cancerous HeLa cells were also investigated. The results showed that ODN@MCBSA did not affect the overall tumor cell viability. However, enhanced NF-κB, p-Akt, PIK3R3, Fas, and FasL, as well as upregulated caspases were observed in tumor cells, implying the pleiotropic effects on tumor cells. Our study provides a more in-depth understanding on the immunotherapeutic effects of CpG ODNs and highlights the importance of macrophage targeting delivery to minimize the effects on tumor cells. These results indicate that MCBSA could serve as a promising delivery vector of CpG ODNs to macrophages for cancer immunotherapy.

Glycyrrhizic acid activates chicken macrophages and enhances their Salmonella-killing capacity in vitro

Objective: Salmonella enterica remains a major cause of food-borne disease in humans, and Salmonella Typhimurium (ST) contamination of poultry products is a worldwide problem. Since macrophages play an essential role in controlling Salmonella infection, the aim of this study was to evaluate the effect of glycyrrhizic acid (GA) on immune function of chicken HD11 macrophages. Methods: Chicken HD11 macrophages were treated with GA (0, 12.5, 25, 50, 100, 200, 400, or 800 μg/ml) and lipopolysaccharide (LPS, 500 ng/ml) for 3, 6, 12, 24, or 48 h. Evaluated responses included phagocytosis, bacteria-killing, gene expression of cell surface molecules (cluster of differentiation 40 (CD40), CD80, CD83, and CD197) and antimicrobial effectors (inducible nitric oxide synthase (iNOS), NADPH oxidase-1 (NOX-1), interferon-γ (IFN-γ), LPS-induced tumor necrosis factor (TNF)-α factor (LITAF), interleukin-6 (IL-6), and IL-10), and production of nitric oxide (NO) and hydrogen peroxide (H₂O₂). Results: GA increased the internalization of both fluorescein isothiocyanate (FITC)-dextran and ST by HD11 cells and markedly decreased the intracellular survival of ST. We found that the messenger RNA (mRNA) expression of cell surface molecules (CD40, CD80, CD83, and CD197) and cytokines (IFN-γ, IL-6, and IL-10) of HD11 cells was up-regulated following GA exposure. The expression of iNOS and NOX-1 was induced by GA and thereby the productions of NO and H₂O₂ in HD11 cells were enhanced. Notably, it was verified that nuclear factor-κB (NF-κB) and c-Jun N-terminal kinase (JNK) pathways were responsible for GA-induced synthesis of NO and IFN-γ gene expression. Conclusions: Taken together, these results suggested that GA exhibits a potent immune regulatory effect to activate chicken macrophages and enhances Salmonella-killing capacity.

Synthetic CpG-ODN rapidly enriches immune compartments in neonatal chicks to induce protective immunity against bacterial infections

Oligodeoxynucleotides containing CpG motifs (CpG-ODN) induce innate immunity against bacterial infections. Despite recent advances, how CpG-ODN alone protects against bacterial infections remained elusive. Here, we report for the first time, to our knowledge, that CpG-ODN orchestrates anti-microbial protective immunity by inducing a rapid enrichment of various immune compartments in chickens. In this study, eighteen-day-old embryonated eggs were injected with either 50 µg of CpG-ODN or saline (~n = 90 per group). In the first experiment, four days after CpG-ODN treatment, chicks were challenged subcutaneously with a virulent strain of Escherichia coli (E. coli) and mortality was monitored for 8 days. We found significant protection, and reduced clinical scores in CpG-ODN treated chicks. To gain insights into mechanisms of protection induced by CpG-ODN, first we investigated cytokine expression kinetics elicited by CpG-ODN. The spleen and lung were collected from embryos or chicks (n = 3-4 per group) at 10 time points post-CpG-ODN inoculation. Multiplex gene analysis (interleukin (IL)-1, IL-4, IL-6, IL-10, IL-18, interferon (IFN)-γ, IFN-α, and lipopolysaccharide induced tumor necrosis factor (LITAF), revealed a significantly higher expression of pro-inflammatory cytokines following CpG-ODN treatment compared to the saline controls. In our study, LITAF stands out in the cytokine profiles of spleen and lungs, underscoring its role in CpG-ODN-induced protection. The third experiment was designed to examine the effects of CpG-ODN on immune cell populations in spleen, lungs, and thymus. Flow cytometry analysis was conducted at 24, 48 and 72 hrs (thymus only collected at 72 hr) after CpG-ODN administration to examine the changes in CD4⁺ and CD8⁺ T-cell subsets, monocyte/macrophage cell populations and their expression of maturation markers (CD40 and CD86). Flow cytometry data indicated a significant enrichment of macrophages, CD4⁺ and CD8⁺ T-cell subsets in both spleen and lungs of CpG-ODN treated embryos and chicks. Macrophages in spleen and lungs showed an upregulation of CD40 but not CD86, whereas thymocytes revealed significantly high CD4 and CD8 expression. Overall, the present study has demonstrated that CpG-ODN provides protection in neonatal chicks against E. coli infection not only by eliciting cytokine responses and stimulating immune cells but also through enriching immunological niches in spleen and lungs.

The role of type I interferons (IFNs) in the regulation of chicken macrophage inflammatory response to bacterial challenge

Mammalian type I interferons (IFNα/β) are known to modulate inflammatory processes in addition to their antiviral properties. Indeed, virus-induced type I interferons regulate the mammalian phagocyte immune response to bacteria during superinfections. However, it remains unresolved whether type I IFNs similarly impact the chicken macrophage immune response. We first evidenced that IFNα and IFNβ act differently in terms of gene expression stimulation and activation of intracellular signaling pathways in chicken macrophages. Next, we showed that priming of chicken macrophages with IFNα increased bacteria uptake, boosted bacterial-induced ROS/NO production and led to an increased transcriptional expression or production of NOS2/NO, IL1B/IL-1β and notably IFNB/IFNβ. Neutralization of IFNβ during bacterial challenge limited IFNα-induced augmentation of the pro-inflammatory response. In conclusion, we demonstrated that type I IFNs differently regulate chicken macrophage functions and drive a pro-inflammatory response to bacterial challenge. These findings shed light on the diverse functions of type I IFNs in chicken macrophages.

Identification of new CpG oligodeoxynucleotide motifs that induce expression of interleukin-1β and nitric oxide in avian macrophages

Unmethylated CpG motifs are known to stimulate mammalian toll-like receptor-9 expressing cells such as macrophages. However, the magnitude of immune-stimulation by CpG-motif can be sequence- and host-specific, implying the importance of identifying new immune-stimulatory motifs. This study aimed to determine the frequency distribution of 256 unique hexamers CpG-motifs in the Salmonella genome and to characterize their immune-stimulatory activity in avian host. We synthesized 256 CpG oligodeoxynucleotides (CpG-ODNs) each containing triplicates of a unique hexamer CpG-motif and tested their ability to induce expression of pro-inflammatory cytokine IL-1β in avian macrophages using q-RT PCR in four rounds of screening assays. CpG-ODNs that induced significantly higher IL-1β expression were also subjected to Griess assay to determine their ability to induce nitric oxide (NO) production in avian macrophages. This analysis resulted in identification of 7 CpG-ODNs that consistently induced IL-1β expression and NO production in avian macrophages at a level similar to the expression achieved using commercially available PTO-CpG-ODN 2007 and LPS derived from Salmonella. To the best of our knowledge, this is the first report showing comprehensive screening of all possible unique CpG hexamer (n=256) motifs for their ability to induce IL-1β expression and NO production in avian macrophages. We also show that the newly identified CpG-motifs with high immune-stimulatory activity are widely distributed in Salmonella genome. The CpG-ODNs identified in this study may serve as promising immunoprophylactics to potentiate innate responses in chickens against Salmonella and other infectious agents.

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.

Mechanisms involved in glucocorticoid induction of pituitary GH expression during embryonic development

Glucocorticoid hormones are involved in functional differentiation of GH-producing somatotrophs. Glucocorticoid treatment prematurely induces GH expression in mammals and birds in a process requiring protein synthesis and Rat sarcoma (Ras) signaling. The objective of this study was to investigate mechanisms through which glucocorticoids initiate GH expression during embryogenesis, taking advantage of the unique properties of chicken embryos as a developmental model. We determined that stimulation of GH expression occurred through transcriptional activation of GH, rather than enhancement of mRNA stability, and this process requires histone deacetylase activity. Through pharmacological inhibition, we identified the ERK1/2 pathway as a likely downstream Ras effector necessary for glucocorticoid stimulation of GH. However, we also found that chronic activation of ERK1/2 activity with a constitutively active mutant or stimulatory ligand reduced initiation of GH expression by glucocorticoid treatment. Corticosterone treatment of cultured embryonic pituitary cells increased ERK1/2 activity in an apparent cyclical manner, with a rapid increase within 5 minutes, followed by a reduction to near-basal levels at 3 hours, and a subsequent increase again at 6 hours. Therefore, we conclude that ERK1/2 signaling must be strictly controlled for maximal glucocorticoid induction of GH to occur. These results are the first in any species to demonstrate that Ras- and ERK1/2-mediated transcriptional events requiring histone deacetylase activity are involved in glucocorticoid induction of pituitary GH during embryonic development. This report increases our understanding of the molecular mechanisms underlying glucocorticoid recruitment of somatotrophs during embryogenesis and should provide insight into glucocorticoid-induced developmental changes in other tissues and cell types.

Development of a subunit vaccine containing recombinant Riemerella anatipestifer outer membrane protein A and CpG ODN adjuvant

Riemerella anatipestifer, a Gram-negative bacillus, causes septicemia that can result in high mortality for ducklings. In this study, we evaluated the immune response and protective efficacy provided by a subunit vaccine containing recombinant outer membrane protein A (rOmpA) and plasmid constructs containing CpG oligodeoxynucleotides (ODN). Results showed that CpG ODN enhanced both humoral and cell-mediated immunity elicited by rOmpA as early as two weeks after primary immunization. When compared to ducks immunized with rOmpA, ducks immunized with rOmpA+CpG ODN showed higher levels (p<0.05) of antibody titer, T cell proliferation, and percentages of CD4(+) and CD8(+) T cell in peripheral blood mononuclear cells (PBMCs). The relative fold inductions of mRNA expression of Th1-type (IFN-γ and IL-12), and Th2-type (IL-6) cytokines in PBMCs isolated from ducks immunized with rOmpA+CpG ODN were significantly higher than those of the rOmpA group. Homologous challenge result showed that the rOmpA+CpG ODN vaccine reduced the pathological score by 90% in comparison with the saline control. In conclusion, our study found that CpG ODN can enhance both humoral and cellular immunity elicited by a rOmpA vaccine. The rOmpA+CpG ODN vaccine can be further developed as a subunit vaccine against R. anatipestifer.

A flagellated motile Salmonella Gallinarum mutant (SG Fla+) elicits a pro-inflammatory response from avian epithelial cells and macrophages and is less virulent to chickens

Salmonella enterica subspecies enterica serovar Gallinarum biovar Gallinarum (SG) is a non-flagellated bacterium which causes fowl typhoid, a systemic disease associated with high mortality in birds. It has been suggested that the absence of flagella in SG is advantageous in the early stages of systemic infection through absence of TLR-5 activation. In order to investigate this hypothesis in more detail a flagellated and motile SG mutant (SG Fla(+)) was constructed. The presence of flagella increased invasiveness for chicken kidney cells (CKC) while its presence did not alter survival in HD11 macrophages. SG Fla(+) induced higher levels of CXCLi2, IL-6 and iNOS mRNA expression in CKC than the SG parent strain. The expression of genes responsible for immune response mediators in infected HD11 macrophages were not related to the presence of flagella. Mortality rates were lower in birds challenged with SG Fla(+) when compared with the SG parent. SG Fla(+) was recovered from caecal contents which showed pathological changes suggestive of inflammation and suggested increased colonization ability.

A critical role for MAPK signalling pathways in the transcriptional regulation of toll like receptors

Toll-like Receptors (TLR) are phylogenetically conserved transmembrane proteins responsible for detection of pathogens and activation of immune responses in diverse animal species. The stimulation of TLR by pathogen-derived molecules leads to the production of pro-inflammatory mediators including cytokines and nitric oxide. Although TLR-induced events are critical for immune induction, uncontrolled inflammation can be life threatening and regulation is a critical feature of TLR biology. We used an avian macrophage cell line (HD11) to determine the relationship between TLR agonist-induced activation of inflammatory responses and the transcriptional regulation of TLR. Exposure of macrophages to specific TLR agonists induced upregulation of cytokine and nitric oxide pathways that were inhibited by blocking various components of the TLR signalling pathways. TLR activation also led to changes in the levels of mRNA encoding the TLR responsible for recognising the inducing agonist (cognate regulation) and cross-regulation of other TLR (non-cognate regulation). Interestingly, in most cases, regulation of TLR mRNA was independent of NFκB activity but dependent on one or more of the MAPK pathway components. Moreover, the relative importance of ERK, JNK and p38 was dependent upon both the stimulating agonist and the target TLR. These results provide a framework for understanding the complex pathways involved in transcriptional regulation of TLR, immune induction and inflammation. Manipulation of these pathways during vaccination or management of acute inflammatory disease may lead to improved clinical outcome or enhanced vaccine efficacy.

Gene Expression Analysis of Toll-Like Receptor Pathways in Heterophils from Genetic Chicken Lines that Differ in Their Susceptibility to Salmonella enteritidis

Previously conducted studies using two chicken lines (A and B) show that line A birds have increased resistance to a number of bacterial and protozoan challenges and that heterophils isolated from line A birds are functionally more responsive. Furthermore, when stimulated with Toll-like receptor (TLR) agonists, heterophils from line A expressed a totally different cytokine and chemokine mRNA expression pattern than heterophils from line B. A large-scale gene expression profile using an Agilent 44K microarray on heterophils isolated from line A and line B also revealed significantly differential expression in many immune-related genes following Salmonella enteritidis (SE) stimulation, which included genes involved in the TLR pathway. Therefore, we hypothesize the differences between the lines result from distinctive TLR pathway signaling cascades that mediate heterophil function and, thus, innate immune responsiveness to SE. Using quantitative RT-PCR on mRNA from heterophils isolated from control and SE-stimulated heterophils of each line, we profiled the expression of all chicken homologous genes identified in a reference TLR pathway. Several differentially expressed genes found were involved in the TLR-induced My88-dependent pathway, showing higher gene expression in line A than line B heterophils following SE stimulation. These genes included the TLR genes TLR4, TLR15, TLR21, MD-2, the adaptor proteins Toll-interleukin 1 receptor domain-containing adaptor protein (TIRAP), Tumor necrosis factor-receptor associated factor 3 (TRAF3), the IκB kinases transforming growth factor-β-activating kinase 1 (TAK1), IKKε and IKKα, the transcription factors NFkB2 and interferon regulatory factor 7, phosphatidylinositol-3 kinase (PI-3K), and the mitogen-activated protein kinase p38. These results indicate that higher expression of TLR signaling activation of both MyD88-dependent and TRIF-dependent pathways are more beneficial to avian heterophil-mediated innate immunity and a complicated regulation of downstream adaptors is involved in stronger induction of a TLR-mediated innate response in the resistant line A. These findings identify new targets for genetic selection of chickens to increase resistance to bacterial infections.

Single-stranded DNA oligonucleotides inhibit TLR3-mediated responses in human monocyte-derived dendritic cells and in vivo in cynomolgus macaques

TLR3 is a key receptor for recognition of double-stranded RNA and initiation of immune responses against viral infections. However, hyperactive responses can have adverse effects, such as virus-induced asthma. Strategies to prevent TLR3-mediated pathology are therefore desired. We investigated the effect of single-stranded DNA oligonucleotides (ssDNA-ODNs) on TLR3 activation. Human monocyte-derived dendritic cells up-regulate maturation markers and secrete proinflammatory cytokines on treatment with the synthetic TLR3 ligand polyinosine-polycytidylic acid (poly I:C). These events were inhibited in cultures with ssDNA-ODNs. Poly I:C activation of nonhematopoietic cells was also inhibited by ssDNA-ODNs. The uptake of poly I:C into cells was reduced in the presence of ssDNA-ODNs, preventing TLR3 engagement from occurring. To confirm this inhibition in vivo, we administered ssDNA-ODNs and poly I:C, alone or in combination, via the intranasal route in cynomolgus macaques. Proinflammatory cytokines were detected in nasal secretions in the poly I:C group, while the levels were reduced in the groups receiving ssDNA-ODNs or both substances. Our results demonstrate that TLR3-triggered immune activation can be modulated by ssDNA-ODNs and provide evidence of dampening proinflammatory cytokine release in the airways of cynomolgus macaques. These findings may open novel perspectives for clinical strategies to prevent or treat inflammatory conditions exacerbated by TLR3 signaling.

Co-stimulation with TLR3 and TLR21 ligands synergistically up-regulates Th1-cytokine IFN-γ and regulatory cytokine IL-10 expression in chicken monocytes

Toll-like receptors (TLRs) are pattern recognition receptors of the innate immune system for various conserved pathogen-associated molecular motifs. Chicken TLR3 and TLR21 (avian equivalent to mammalian TLR9) recognize poly I:C (double-stranded RNA) and CpG-ODN (a CpG-motif containing oligodeoxydinucleotide), respectively. Interaction between TLR3 and TLR21 agonists poly I:C and CpG-ODN has been reported to synergize in expression of proinflammatory cytokines and chemokines and the production of nitric oxide in chicken monocytes. However, the interaction between poly I:C and CpG-ODN on the expression of interferons (IFNs) and Th1/Th2 cytokines remains unknown. The objective of the present study was to investigate the effect of the interaction between poly I:C and CpG-ODN on the mRNA expression levels of IFN-α and IFN-β, Th1 cytokines IFN-γ and IL-12, Th2 cytokine IL-4, and regulatory IL-10 in chicken monocytes. When stimulated with either agonist alone, CpG-ODN significantly up-regulated the expression of INF-γ, IL-10, and IL-12p40, but not IFN-α and IFN-β; whereas poly I:C induced the expression of INF-γ, IFN-α, IFN-β, and IL-10; but not IL-12p40. However, stimulation with a combinatory CpG-ODN and poly I:C further synergistically increased the expression of IFN-γ and IL-10 mRNA. Our results provide strong evidence supporting the critical role of TLR3 and TLR21 in avian innate immunity against both viral and bacterial infections; and the synergistic interaction between the TLR3 and TLR21 pathways produces a stronger Th1-biased immune response in chicken monocytes. Our result also suggest a potential use of poly I:C and CpG-ODN together as a more efficient adjuvant for poultry vaccine development.

Immune dynamics following infection of avian macrophages and epithelial cells with typhoidal and non-typhoidal Salmonella enterica serovars; bacterial invasion and persistence, nitric oxide and oxygen production, differential host gene expression, NF-κB signalling and cell cytotoxicity

Poultry-derived food is a common source of infection of human with the non-host-adapted salmonellae while fowl typhoid and pullorum disease are serious diseases in poultry. Development of novel immune-based control strategies against Salmonella infection necessitates a better understanding of the host-pathogen interactions at the cellular level. Intestinal epithelial cells are the first line of defence against enteric infections and the role of macrophages is crucial in Salmonella infection and pathogenesis. While gene expression following Salmonella infection has been investigated, a comparison between different serovars has not been, as yet, extensively studied in poultry. In this study, chicken macrophage-like cells (HD11) and chick kidney epithelial cells (CKC) were used to study and compare the immune responses and mechanisms that develop after infection with different Salmonella serotypes. Salmonella serovars Typhimurium, Enteritidis, Hadar and Infantis showed a greater level of invasion and/or uptake characters when compared with S. Pullorum or S. Gallinarum. Nitrate and reactive oxygen species were greater in Salmonella-infected HD11 cells with the expression of iNOS and nuclear factor-κB by chicken macrophages infected with both systemic and broad host range serovars. HD11 cells revealed higher mRNA gene expression for CXCLi2, IL-6 and iNOS genes in response to S. Enteritidis infection when compared to S. Pullorum-infected cells. S. Typhimurium- and S. Hadar-infected HD11 showed higher gene expression for CXCLi2 versus S. Pullorum-infected cells. Higher mRNA gene expression levels of pro-inflammatory cytokine IL-6, chemokines CXCLi1 and CXCLi2 and iNOS genes were detected in S. Typhimurium- and S. Enteritidis-infected CKC followed by S. Hadar and S. Infantis while no significant changes were observed in S. Pullorum or S. Gallinarum-infected CKC.

Regulation of nitric oxide production in snail (Lymnaea stagnalis) defence cells: a role for PKC and ERK signalling pathways

BACKGROUND INFORMATION

Nitric oxide (NO) is an important molecule in innate immune responses. In molluscs NO is produced by mobile defence cells called haemocytes; however, the molecular mechanisms that regulate NO production in these cells is poorly understood. The present study focused on the role of cell signalling pathways in NO production by primary haemocytes from the snail Lymnaea stagnalis.

RESULTS

When haemocytes were challenged with PMA (10 microM) or the beta-1,3-glucan laminarin (10 mg/ml), an 8-fold and 4-fold increase in NO production were observed after 60 min respectively. Moreover, the NOS (NO synthase) inhibitors L-NAME (N(G)-nitro-L-arginine methyl ester) and L-NMMA (N(G)-monomethyl-L-arginine) were found to block laminarin- and PMA-induced NO synthesis. Treatment of haemocytes with PMA or laminarin also increased the phosphorylation (activation) status of PKC (protein kinase C). When haemocytes were preincubated with PKC inhibitors (calphostin C or GF109203X) or inhibitors of the ERK (extracellular-signal-regulated kinase) pathway (PD98059 or U0126) prior to challenge, significant reductions in PKC and ERK phosphorylation and NO production were observed following exposure to laminarin or PMA. The greatest effect on NO production was seen with GF109203X and U0126, with PMA-induced NO production inhibited by 94% and 87% and laminarin-induced NO production by 50% and 91% respectively.

CONCLUSIONS

These data suggest that ERK and PKC comprise part of the signalling machinery that regulates NOS activation and subsequent production of NO in molluscan haemocytes. To our knowledge, this is the first report that shows a role for these signalling proteins in the generation of NO in invertebrate defence cells.

A novel pathway responsible for lipopolysaccharide-induced translational regulation of TNF-α and IL-6 expression involves protein kinase C and fascin

Fascin, as a substrate of protein kinase C (PKC), is a well-known cytoskeletal regulatory protein required for cell migration, invasion, and adhesion in normal and cancer cells. In an effort to identify the role of fascin in PKC-mediated cellular signaling, its expression was suppressed by stable transfection of specific short hairpin RNAs (shRNAs) in mouse monocytic leukemia RAW264.7 cells. Suppression of fascin expression resulted in impaired cellular migration and invasion through extracellular matrix proteins. Unexpectedly, the specific shRNA transfectants exhibited a marked reduction in LPS-induced expression of TNF-α and IL-6 by blocking the translation of their mRNAs. Transient transfection assay using a luciferase expression construct containing the 3' untranslated region of TNF-α or IL-6 mRNA revealed a significant reduction in both LPS- and PMA- (the direct activator of PKC) induced reporter activity in cells transfected with fascin-specific shRNA, indicating that fascin-mediated translational regulation targeted 3' untranslated region. Furthermore, LPS-induced translational activation of reporter expression was blocked by a pharmacological inhibitor of PKC, and the dominant-negative form of PKCα attenuated LPS-induced translational activation. The same type of regulation was also observed in the human monocytic leukemia cell line THP-1 and in mouse peritoneal macrophages. These data demonstrate the involvement of fascin in the PKC-mediated translational regulation of TNF-α and IL-6 expression during the LPS response.

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.

BAFF and APRIL induce inflammatory activation of THP-1 cells through interaction with their conventional receptors and activation of MAPK and NF-κB

BACKGROUND

BAFF and APRIL, as closely related members of the TNF superfamily, are important regulators of B-cell survival. They share two receptors, TACI and BCMA, and BAFF can stimulate an additional receptor, BAFF-R. Although these molecules have been under intense investigation in order to identify their role in immune reactions, the effect of BAFF and APRIL on macrophage function has not been tested.

METHODS

The human macrophage-like cell line THP-1, which expresses BAFF/APRIL and all three of their receptors, was stimulated with recombinant human BAFF or APRIL or monoclonal antibodies against the receptors and the resulting cellular responses were investigated. Treatment of the cells with these agents induced the expression of pro-inflammatory mediators such as matrix metalloproteinase (MMP)-9 and IL-8. Suppression of the expression of these receptors using specific siRNAs resulted in the blocking of the response, confirming that these responses require specific interaction between BAFF/APRIL and their receptors. Inhibitors of MAPK and NF-κB blocked the expression of IL-8. Furthermore, inhibitors of MAPK blocked the BAFF-induced specific DNA binding activity of NF-κB.

CONCLUSION

These data indicate that BAFF and APRIL can induce inflammatory activation of THP-1 cells through the activation of MAPK, which leads to the subsequent activation of NF-κB.

CpG oligodeoxynucleotides containing GACGTT motifs enhance the immune responses elicited by a goose parvovirus vaccine in ducks

Recombinant parvovirus VP2 (rVP2) was formulated with different types of adjuvant, including aluminum adjuvant and CpG oligodeoxynucleotides (ODNs), and the immunological responses after vaccination in ducks were examined. In comparison with the control group, production of rVP2-specific antibodies, expression of cytokines in peripheral blood mononuclear cells (PBMC) stimulated by rVP2, and percentage of CD4(+)/CD8(+) cells in PBMC were significantly increased in ducks immunized with rVP2 formulated with CpG ODNs containing 3 copies of GACGTT motif. CpG ODNs with GACGTT motifs might be used to improve the efficacy of vaccines for ducks.

Adjuvant effect of liposome in chicken result from induction of nitric oxide

Intranasal delivery of liposome-encapsulated inactivated Newcastle Disease virus (NDV) is known to be an effective vaccine for inducing immunity in the respiratory tract from our previous reports. Four-week-old specific pathogen-free chickens were intranasally immunized with NDV entrapped in phosphatidylcholine-liposomes (PC-Lip). The mucosal levels of anti-NDV s-immunoglobulin A (IgA), serum IgG, a high hemagglutination inhibition titer (1:640), and the high survival rate with the PC-Lip vaccine were comparable to those of our previous report. The immune mechanisms of the PC-Lip adjuvant were determined by in vitro cellular experiments using the NO production of chicken spleen macrophages. The most important finding of this study was proving that macrophages were stimulated by PC-Lip via the extracellular regulated kinase (ERK) 1/2 and nuclear factor (NF)-κB activation pathways. This finding may be useful for developing potent mucosal vaccine delivery systems in the future.

Modulation of chicken macrophage effector function by T(H)1/T(H)2 cytokines

Regulation of macrophage activity by T(H)1/2 cytokines is important to maintain the balance of immunity to provide adequate protective immunity while avoiding excessive inflammation. IFN-γ and IL-4 are the hallmark T(H)1 and T(H)2 cytokines, respectively. In avian species, information concerning regulation of macrophage activity by T(H)1/2 cytokines is limited. Here, we investigated the regulatory function of chicken T(H)1 cytokines IFN-γ, IL-18 and T(H)2 cytokines IL-4, IL-10 on the HD11 macrophage cell line. Chicken IFN-γ stimulated nitric oxide (NO) synthesis in HD11 cells and primed the cells to produce significantly greater amounts of NO when exposed to microbial agonists, lipopolysaccharide, lipoteichoic acid, peptidoglycan, CpG-ODN, and poly I:C. In contrast, chicken IL-4 exhibited bi-directional immune regulatory activity: it activated macrophage NO synthesis in the absence of inflammatory agonists, but inhibited NO production by macrophages in response to microbial agonists. Both IFN-γ and IL-4, however, enhanced oxidative burst activity of the HD11 cells when exposed to Salmonella enteritidis. IL-18 and IL-10 did not affect NO production nor oxidative burst in HD11 cells. Phagocytosis and bacterial killing by the HD11 cells were not affected by the treatments of these cytokines. Infection of HD11 cells with S.enteritidis was shown to completely abolish NO production regardless of IFN-γ treatment. This study has demonstrated that IFN-γ and IL-4 are important T(H)1 and T(H)2 cytokines that regulate macrophage function in chickens.

Role of Hsp90 in CpG ODN mediated immunostimulation in avian macrophages

In mammals, CpG mediated immune activation is initiated through toll-like receptor (TLR) 9 and Hsp90 via activation of MAPK/ERK and PI3K/AKT pathways. However, in the absence of TLR9 ortholog in chicken genome, the role of Hsp90 and kinase (MAPK/ERK and PI3K/AKT) pathways in initiating CpG ODN(2007) induced immune activation in chicken is not clear. Using electrophoretic mobility shift assay (EMSA) and selective inhibitors of signal transduction pathways, we determined the role of these pathways in the production of Th1 cytokines/chemokines and nitric oxide (NO) in CpG ODN(2007) treated avian macrophage cells. Hsp90alpha but not Hsp90beta is bound to CpG ODN(2007). Inhibition of Hsp90 with geldanamycin resulted in the inactivation of MAPK/ERK and PI3K/AKT pathways leading to significantly reduced levels of IFN-gamma, IL-6 and NO mRNAs in CpG ODN(2007) stimulated cells. Moreover, inhibition of ERK1/2 and PI3/AKT kinase pathways with PD985009 and LY294002, respectively, suppresses the phosphorylation of ERK2 and AKT leading to the production of decreased amounts of IFN-gamma, IL-6 and NO mRNAs in CpG ODN(2007) stimulated cells. Our results demonstrate that binding of CpG ODN(2007) to Hsp90 induces activation of ERK2 and AKT phosphorylation leading to the production of high levels of IFN-gamma, IL-6, MIP-3alpha and nitric oxide (NO). In contrast to mammals, our results suggest that Hsp90alpha but not Hsp90beta binds with the CpG ODN(2007) and may play a major role in CpG ODN(2007) induced immunoactivation in avian macrophage cells. To our knowledge, this is the first report evaluating the involvement of Hsp90 and kinase (MAPK/ERK and PI3K/AKT) pathways in CpG mediated immunostimulation in avian macrophage cells.

CpG oligodeoxynucleotide and double-stranded RNA synergize to enhance nitric oxide production and mRNA expression of inducible nitric oxide synthase, pro-inflammatory cytokines and chemokines in chicken monocytes

Toll-like receptors (TLRs) recognize microbial components and initiate the innate immune responses that control microbial infections. The interaction between ligands of TLR3 and TLR9, poly I:C (an analog of viral double-stranded RNA) and CpG-ODN (a CpG-motif containing oligodeoxydinucleotide) on the inflammatory immune responses, including the production of nitric oxide (NO) and the expression of inducible NO synthase (iNOS), pro-inflammatory cytokines interleukin (IL)-1β and IL-6, and chemokines IL-8 and macrophage inflammatory protein (MIP)-1β, were investigated in chicken monocytes. The NO production was significantly higher when stimulated with a combination of CpG-ODN and poly I:C than with either CpG-ODN or poly I:C alone. Similarly, a significant synergistic effect by CpG-ODN and poly I:C was observed in the up-regulation of iNOS and IL-8 mRNA after 2 h and persisted up to 24 h. Although the combinatory treatment of CpG-ODN and poly I:C enhanced the expression of IL-1β, IL-6, and MIP-1β(3 after 2 h stimulation, the synergism in the up-regulation of IL-1β and IL-6 mRNA was observed after 8-h and 24-h stimulation, respectively, whereas there was no synergistic effect on MIP-1β. Our results demonstrate that CpG-ODN synergizes with poly I:C to induce pro-inflammatory immune response in chicken monocytes.

Involvement of TLR21 in baculovirus-induced interleukin-12 gene expression in avian macrophage-like cell line HD11

Our previous work showed that baculovirus (Antheraea pernyi nuclear polyhedrosis virus [ApNPV]) induced a strong innate immunity and protected chicken from a lethal challenge of bronchitis virus. The purpose of present study was to determine the chicken Toll-like receptors (TLRs) used by BV-infected immune cells to induce this immune response. We first investigated the expression of the Toll-like receptor (TLR) genes in resting and BV-infected HD11 (chicken macrophage-like cell line) and DT40 (chicken B cell-like cell line) cells. Expressions of TLRs were detected in both cell types. After BV stimulation, TLR21 was the only upregulated TLR in HD11 cells, and all the TLRs were down-regulated in DT40 cells. Since TLR activation generally leads to cytokine induction, we then determined the expression of IL-12 in the two cell lines following treatment with BV or oligodeoxynucleotides (ODN) containing CpG dinucleotides (CpG-ODN). BV and CpG-ODN treatment induced the expression of IL-12 in HD11 but not in DT40 cells. HD11 cells transfected with siRNA specific for TLR21 significantly diminished BV- and CpG-ODN-induced IL-12 expression. Therefore, BV and CpG-ODN stimulated IL-12 expression involved TLR21 signaling and chicken TLR21 may have similar functions to the mammalian TLR9.

Chicken TLR21 acts as a functional homologue to mammalian TLR9 in the recognition of CpG oligodeoxynucleotides

Similar to mammalian species, chickens show marked immunological responses to CpG oligodeoxynucleotides (ODNs) both in vivo and in vitro. In mammals, the receptor for ODNs has been demonstrated to be TLR9; however, an orthologue to mammalian TLR9 is absent in the chicken genome. In this study, chicken TLRs 7, 15 and 21 were expressed in mammalian HEK-293T cells; expression of TLR21 but not TLR7 or 15 resulted in marked NF-kappaB activation upon stimulation with exogenous ODN. This activation was not observed when cells were stimulated by TLR agonists other than ODNs. In addition, responsiveness of the ectopically expressed TLR21 demonstrated similar kinetics of activation as reported for mammalian TLR9 and was dependent on the nucleotide sequence of the ODN. The same ODN specificity was observed for chicken HD11 macrophage when ODN mediated activation was monitored by up-regulation of IL1, IL6 and iNOS transcripts. Furthermore, when TLR21, but not TLR15, was partially silenced in HD11 cells by RNA interference, ODN mediated responses were reduced. TLR21-mediated NF-kappaB activation in HEK-293T cells was inhibited by bafilomycin A suggesting that endosomal maturation is required for TLR21 activation and observations by confocal microscopy and digestion with endoglycosidase H suggest TLR21 localizes to the endoplasmic reticulum (ER) of resting cells. Expression of TLR21 transcripts was found in all chicken tissues examined but was significantly less in the lung and small intestine of newly hatched birds. Two of the leucine rich repeat regions (LRRs) of TLR21 showed homology with a LRR conserved within mammalian TLR9 and implicated in ligand binding. We hypothesize that avian TLR21 plays a similar role to that of mammalian TLR9 and enables recognition of microbial DNA as a danger signal resulting in downstream innate and adaptive immune responses.

Synthetic methylated CpG ODNs are potent in vivo adjuvants when delivered in liposomal nanoparticles

Although it is well documented that the immunological activity of cytosine-guanine (CpG) motifs is abrogated by 5' methylation of the cytosine residue, encapsulation within stabilized lipid nanoparticles endows these methylated cytosine-guanine- (mCpG-) containing oligonucleotides (ODNs) with potent immunostimulatory activity in murine animal models. Surprisingly, not only do liposomal nanoparticulate (LN) mCpG ODN possess immunostimulatory activity, their potency is found to be equivalent and often greater than the equivalent unmethylated form, as judged by a number of ex vivo innate and adaptive immune parameters and anti-tumor efficacy in murine models. Preliminary data indicate that both methylated and unmethylated CpG ODN act through a common receptor signaling pathway, specifically via toll-like receptor (TLR) 9, based on observations of up-regulated TLR9 expression, induction of nitric oxide and dependence on endosomal maturation. This is confirmed in TLR9 knockout animals which show no immunostimulatory activity following treatment with LN-mCpG ODN. These data, therefore, indicate that the mCpG DNA is fully competent to interact with TLR9 to initiate potent immune responses. Furthermore, this work implicates an as yet unidentified mechanism upstream of TLR9 which regulates the relative activities of free methylated versus unmethylated CpG ODN that is effectively bypassed by particulate delivery of CpG ODN.

The in vitro and in ovo responses of chickens to TLR9 subfamily ligands

Although Toll-like receptors (TLRs) have been well characterised in mammals, less work has been carried out in non-mammalian species, such as chickens. In this study the response of chicken cells to the TLR9 subfamily of ligands was characterised in vitro and in ovo. It was found that even though chickens appear to have only one functional receptor to represent the TLR9 subfamily, stimulation of chicken splenocytes with TLR7 and TLR9 ligands induced proinflammatory cytokine production and cell proliferation, similar to that observed when the homologous mammalian receptors are stimulated. Furthermore, we demonstrated that the in ovo administration of these TLR ligands elicits a response, such as cytokine production, that can be detected post-hatch. The current knowledge of the action of TLR ligands in mammals, in conjunction with their immunomodulating ability shown in this study, draws attention to their potential use as therapeutic agents for the poultry industry.

Phosphorothioate oligodeoxyribonucleotides induce in vitro proliferation of chicken B-cells

The study aimed to evaluate short synthetic oligodeoxyribonucleotides (ODN) as inducers of proliferation of chicken peripheral blood mononuclear cells (PBMC) and to identify the proliferating cells. A panel of different ODN; with phosphodiester and/or phosphorothioate backbone, with and without CpG-motifs, was therefore assessed for in vitro induction of proliferation. Six complete phosphorothioate ODN induced proliferation of PBMC while the complete phosphodiester or chimeric phosphodiester/phosphorohiate ODN did not. Moreover, CpG-motifs were not essential for induction of proliferation as responses to CpG-ODN were similar to those of their GpC controls. Two stimulatory phosphorothioate ODN were also used in phosphodiester form. In this comparison, only the phosphorothioate ODN were active despite the identical nucleotide sequences of their phosphodiester counterparts. In order to deliver DNA to the cytoplasm and decrease degradation of ODN by nucleases, stimulating as well as inactive ODN were treated with lipofectin prior to induction. However, proliferative responses were not influenced by lipofectin treatment and in analogy, none of the inactive ODN induced proliferation after lipofectin treatment. Among PBMC, ODN-responding cells were identified as predominantly Bu-1, immunoglobulin and major histocompatibility complex class II expressing cells, while CD3 expressing cells were not responding. Using magnetic cell separation of Bu-1 expressing cells prior to culture it was found that Bu-1 depleted cells did not proliferate upon ODN stimulation while the Bu-1 enriched cells were able to proliferate upon this stimulus. Taken together, among ODN in the present panel, only phosphorothioate ODN induced proliferation of PBMC. Responses were induced regardless of the presence of CpG-motifs and were not influenced by addition of lipofectin. Amid the chicken PBMC, predominantly cells of a B-cell phenotype proliferated in response to ODN stimulation and they were able to respond to this stimulus without the presence of other cell types.

Protection of neonatal broiler chicks against Salmonella Typhimurium septicemia by DNA containing CpG motifs

Oligodeoxynucleotides (ODN) containing cytosine-phosphodiester-guanine (CpG-ODN) motifs have been shown to stimulate the innate immune system against a variety of bacterial and protozoan infections in a variety of vertebrate species. The objective of this study was to investigate the immunostimulatory effect of CpG-ODN in neonatal broilers against Salmonella Typhimurium septicemia. Day-old broiler chicks, or embryonated eggs that had been incubated for 18 days, received 50 microg of CpG-ODN, 50 microg of non-CpG-ODN, or saline. Four days after exposure to CpG-ODN or day 2 posthatch, 1 x 10(6) or 1 x 10(7) colony-forming units (cfu) of a virulent isolate of Salmonella Typhimurium was inoculated by the subcutaneous route in the neck. Clinical signs, pathology, bacterial isolations from the air sacs, and mortality were observed for 10 days following challenge with Salmonella Typhimurium. The survival rate of birds in groups receiving either non-CpG-ODN or saline following Salmonella Typhimurium infection was 40%-45%. In contrast, birds receiving CpG-ODN had significantly higher survival rate of 80%-85% (P < 0.0001). Bacterial loads and pathology were low in groups treated with CpG-ODN compared to the groups receiving saline or non-CpG-ODN. Colony-forming units of Salmonella Typhimurium in the peripheral blood were significantly lower in birds treated with CpG-ODN compared to the group that received saline. This is the first time that CpG-ODN has been demonstrated to have an immunoprotective effect against an intracellular bacterial infection in neonatal broiler chickens following in ovo delivery.

In ovo treatment with CpG oligodeoxynucleotides decreases colonization of Salmonella enteriditis in broiler chickens

Induction of the innate immune response in newly hatched chickens is important for limiting infections with bacteria, such as Salmonella enterica serovar Enteriditis (SE). CpG oligodeoxynucleotides (CpG-ODN) can stimulate the innate immune response of young chickens. Therefore, we examined the effectiveness of CpG-ODN administered in ovo on intestinal colonization by SE and the ability to modulate the function of heterophils in young chickens. Heterophils were isolated from 2-day-old chickens and were stimulated with heat-killed SE (HK-SE) or PMA for oxidative burst and HK-SE or live SE for degranulation assays. CpG-ODN treatment had no effect on heterophil oxidative burst when stimulated with HK-SE or PMA. However, HK-SE and live SE increased degranulation (P<0.01) in heterophils from CpG-ODN-treated birds compared to PBS-treated controls. In a second experiment, chickens were orally infected with SE on day 10 post-hatch and cecal contents were collected 6 days later for assessment of SE intestinal colonization. CpG-ODN treatment reduced SE colonization by greater than 10-fold (P<0.001) compared to PBS-injected control birds. Overall, we show for the first time that CpG-ODN given in ovo stimulates innate immune responsiveness of chicken heterophils and increases resistance of young chickens to SE colonization.

Flagellin and lipopolysaccharide up-regulation of IL-6 and CXCLi2 gene expression in chicken heterophils is mediated by ERK1/2-dependent activation of AP-1 and NF-κB signaling pathways

The Toll-like receptor agonists, flagellin (FLG) and lipopolysaccharide (LPS), stimulate chicken heterophils to induce the expression and secretion of pro-inflammatory cytokines by a mechanism involving the triggering of differential MEK-ERK signaling cascades. However, the translocation and activation of transcription factors potentially involved in the control of cytokine gene expression remains unknown. Herein, we examined the effects of FLG and LPS on the activation of the transcription factors NF-κB and AP-1 and their role in regulating heterophil activation leading to cytokine gene expression. Treatment of heterophils with either FLG or LPS induced a significant increase in DNA binding by the NF-κB family members p50, c-Rel, and RelB. Likewise, FLG and LPS induced a significant increase in DNA binding by the AP-1 family members c-Jun and JunD. The activation of both NF-κB and AP-1 was inhibited following treatment of heterophils with specific inhibitors of ERK1/2 (U0126 and PD098059), NF-κB (Bay 11-7086 and the cell-permeable NF-κB peptide, SN50), and AP-1 (Tanshinone IIA). Likewise, the up-regulation of gene expression of the pro-inflammatory cytokine, IL-6, and the inflammatory chemokine, CXCLi2, were inhibited when heterophils were treated with the same specific inhibitors. Taken together these data demonstrate that FLG and LPS stimulate the up-regulation of expression of IL-6 and CXCLi2 through an ERK1/2-dependent activation of both NF-κB and AP-1.

Cruzipain and SP600125 induce p38 activation, alter NO/arginase balance and favor the survival of Trypanosoma cruzi in macrophages

Cruzipain (Cz), an antigen of Trypanosoma cruzi, mediates the activation of arginase involving p38 MAPK. In this work, it was studied whether the phosphorylation of MAPKs into macrophages (Mvarphi) could be induced by Cz and/or by the parasite. We found that Cz induced activation of p38, while the parasite produced phosphorylation of JNK and p44/p42. MAPK phosphorylation changed and JNK activation was blocked when Mvarphi were pre-incubated with Cz, before coming into contact with T. cruzi. We investigated the role of JNK inhibitor SP600125 on T. cruzi infection, since it also induces p38 phosphorylation. Thus, J774 cells were pre-treated with SP600125 and then infected with T. cruzi. This set of cells showed a decrease in nitric oxide (NO) production and an increase in arginase I expression. Another group of J774 cells was pre-treated with SP600125 and incubated with Cz before being infected with T. cruzi. This second group showed a greater reduction in NO production. These results can be correlated with the parasitic growth since the ex vivo treatment with SP600125 on adherent spleen cells (ASC) of BALB/c infected mice also increased the parasitic growth. Therefore, Cz and SP600125 favor the T. cruzi survival in Mvarphi by changing the iNOS/arginase balance.

Differential induction of nitric oxide, degranulation, and oxidative burst activities in response to microbial agonist stimulations in monocytes and heterophils from young commercial turkeys

The toll-like receptors (TLRs) recognize microbial pathogens and pathogen-associated molecular patterns and trigger inflammatory immune responses to control the infection. Here, we examined functional innate immune responses to Salmonella enteritidis (SE, live or formalin-killed) and various TLR agonists including lipoteichoic acid (LTA) and peptidoglycan (PGN) from Staphylococcus aureus and synthetic lipoprotein Pam3CSK4 (PAM), poly I:C (synthetic double-stranded RNA analog), lipopolysaccharide (LPS) from S. enteritidis, flagellin (FGN) from S. typhimurium, loxoribine (LOX) and R837 (synthetic anti-viral compounds), and CpG oligodeoxydinucleotide (CpG ODN)by measuring antimicrobial activities including oxidative burst and degranulation in heterophils and nitric oxide production in peripheral blood monocytes. Our results demonstrate differential nitric oxide responses to TLR agonists in turkey monocytes. LTA and CpG ODN were the most potent stimuli for nitric oxide induction followed by PAM, poly I:C, and LPS, whereas FGN, PGN, LOX, R837, and control ODN stimulated little or no nitric oxide production. Live SE stimulated significantly less NO production than formalin-killed SE (FKSE). Although FKSE induced significant degranulation and oxidative burst, most TLR agonists stimulate little oxidative burst and degranulation responses in turkey heterophils.

Phospholipase C, phosphatidylinositol 3-kinase, and intracellular [Ca(2+)] mediate the activation of chicken HD11 macrophage cells by CpG oligodeoxynucleotide

The activation of phospholipases is one of the earliest key events in receptor-mediated cellular responses to a number of extracellular signaling molecules. Oligodeoxynucleotides containing CpG motifs (CpG ODN) mimic microbial DNA and are immunostimulatory to most vertebrate species. In the present study, we used the production of nitric oxide (NO) as an indicator to evaluate the involvement of the signaling cascades of phospholipases and phosphatidylinositol 3-kinase (PI3K) in the activation of chicken HD11 macrophage cells by CpG ODN. Using selective inhibitors, we have identified the involvement of phosphatidylinositol (PI)-phospholipase C (PI-PLC), but not phosphatidylcholine (PC)-phospholipase C (PC-PLC) and PC-phospholipase D (PC-PLD), in CpG ODN-induced NO production in HD11 cells. Preincubation with PI-PLC selective inhibitors (U-73122) completely abrogated CpG ODN-induced NO production in HD11 cells, whereas PC-PLC inhibitor (D609) and PC-PLD inhibitor (n-butanol) had no inhibitory effects. Additionally, inhibition of PI3K and protein kinase C (PKC) with selective inhibitors and chelation of intracellular [Ca(2+)] also significantly attenuated NO production in CpG ODN-activated HD11 cells. Our results demonstrate that PI-PLC, PI3 K, PKC, and intracellular [Ca(2+)] are important components of the CpG ODN-induced signaling pathway that leads to the production of NO in avian macrophage cells.

Avian genomics and the innate immune response to viruses

Viral diseases pose a significant threat to the poultry industry. However, there is currently a lack of antivirals and suitable vaccine adjuvants available to the poultry industry to combat this problem. The innate immune system is now recognised to be essential in the response to viral infection. However, in contrast to mammals, the innate immune response in chickens is relatively uncharacterised. The release of the full chicken genome sequence has accelerated the identification of genes involved in the immune response. The characterisation of these genes, including Toll-like receptors and cytokines has led to the identification of potential alternate antivirals and adjuvants.

In vivo priming heterophil innate immune functions and increasing resistance to Salmonella enteritidis infection in neonatal chickens by immune stimulatory CpG oligodeoxynucleotides

Oligodeoxynucleotides (ODN) containing CpG dinucleotides (CpG-ODN) mimic bacterial DNA and stimulate the innate immune system of vertebrates. Here, we investigated the effects of intraperitoneal (ip) administered CpG-ODN on the innate immune functions of chicken heterophils. Our results demonstrated CpG-ODN-dependent priming of chicken heterophil degranulation and oxidative burst. Heterophils from chickens treated with CpG-ODN exhibited significantly higher (p<0.05) degranulation activity compared to PBS and control ODN (ODN containing no CpG motif) treated groups when stimulated with opsonized Salmonella enterica serovar enteritidis. Similarly, oxidative burst activity, which generates bactericidal reactive oxygen species, was significantly higher (p<0.05) in heterophils from the CpG-ODN treated group than from PBS and control ODN groups when stimulated with formalin-killed S. enteritidis. The priming effects of CpG-ODN on heterophil immune functions continued at least 4 days post-treatment. In the infection study, newly hatched chickens were treated with CpG-ODN, control ODN or PBS for 24h then challenged with oral inoculation of S. enteritidis. A significant reduction (p<0.05) in colonization by S. enteritidis was observed in chickens treated with CpG-ODN. Our study provides evidence that immunostimulatory CpG-ODN potentiates the innate immune responses of heterophils and enhances resistance to infectious pathogens in neonatal chickens.

Synergy of CpG oligodeoxynucleotide and double-stranded RNA (poly I:C) on nitric oxide induction in chicken peripheral blood monocytes

Toll-like receptors (TLRs) recognize microbial components and initiate the innate immune responses that control microbial infections. We have investigated the innate immune response of chicken monocytes to ligands of TLR3 and TLR9, poly I:C (an analog of viral double-stranded RNA) and CpG-ODN (a CpG-motif containing oligodeoxydinucleotide) by measuring the induction of nitric oxide (NO) synthesis in chicken monocytes. Our results show that poly I:C and CpG-ODN synergized the induction of NO. When stimulated separately, CpG-ODN induced significant NO production in the chicken monocytes; whereas, poly I:C stimulated very little NO production. In combination, CpG-ODN and poly I:C induced significantly higher level of NO in chicken monocytes than either agonist alone. The addition of poly I:C prior to or simultaneously with CpG-ODN was required for the synergy. No synergistic effects on NO production were observed when monocytes were stimulated with combinations of CpG-ODN or poly I:C with other TLR agonists. Unlike chicken monocytes, cells of a chicken macrophage cell line, HD11, were readily stimulated to produce NO by both CpG-ODN and poly I:C with no synergism on NO induction when HD11 cells were stimulated by a combination of CpG-ODN and poly I:C. Using a pharmacological inhibitor, we also demonstrated that double-stranded RNA-dependent protein kinase (PKR) is indispensable for stimulation of NO production by CpG-ODN alone or in combination with poly I:C in both chicken peripheral blood monocytes and HD11 macrophage cells. Our results show that a combination of bacterial DNA and dsRNA induces an enhanced inflammatory immune response that has both antiviral and antibacterial activity in primary chicken monocytes.