In silico identification of components of the Toll-like receptor (TLR) signaling pathway in clustered chicken expressed sequence tags (ESTs)

Citrus pectins impact the function of chicken macrophages

The restrictions on excessive use of antimicrobials in the poultry industry have led to the search for alternative strategies including nutritional interventions to enhance gut health with the ultimate aim to prevent gut infections. Pectins as prebiotics have shown beneficial effects on gut health in humans and mice by improving the gut barrier function, altering the gut microbiota, and by modulating the gut immune response. However, little is known about immunomodulatory properties of pectins in chickens. The present in vitro study assessed the effect of three pectins (SPE6, SPE7, SPE8) differing in methyl esterification, on responsiveness of the chicken macrophage cell line HD11 cells and primary monocyte derived macrophage from the blood, through interaction with chicken TLRs. All three pectins increased gene expression of iNOS and IL10 in chicken macrophages. Differences in immunomodulatory activity between the three pectins were observed in other assays. The low methoxyl pectin (SPE8) interacted with TLR4 leading to the production of NO, but also to increased phagocytosis of E. coli, while high methoxyl pectins SPE6 and SPE7 did not activate TLR4. All three pectins were able to attenuate PAM3CSK4 induced activation of chicken macrophages as measured by decreased NO production and phagocytosis. Additional studies using ITC and flow cytometry suggest that the inhibiting properties of pectins (SPE6, SPE7) on macrophages are due to pectins occupying TLR2 and blocking PAM3CSK4 to activate chicken macrophages, whereas SPE8 actually binds to the TLR2 ligand and that way attenuates the PAM3CSK4 induced activation. Based on these immunomodulatory properties observed in this study, these pectins may in the future be suitable as feed additive for the treatment and prevention of inflammatory disorders in poultry.

Effects of Eimeria maxima infection doses on growth performance and gut health in dual-infection model of necrotic enteritis in broiler chickens

The objective of this study was to investigate the effects of the different doses of Eimeria maxima (EM) oocysts on growth performance and intestinal health in broiler chickens challenged with a dual infection model of necrotic enteritis (NE) using EM and NetB+ Clostridium perfringens (CP). A total of 432 fourteen-d-old male Cobb 500 broiler chickens were divided into 6 groups with 6 replicates each. The six different groups were as follows: Control, non-challenged; T0+, challenged with CP at 1 × 109 colony forming unit; T5K+, T0+ + 5,000 EM oocysts; T10K+, T0+ + 10,000 EM oocysts; T20K+; T0+ + 20,000 EM oocysts; and T40K+; T0+ + 40,000 EM oocysts. The challenge groups were orally inoculated with EM strain 41A on d 14, followed by NetB+ CP strain Del-1 on 4 days post inoculation (dpi). Increasing EM oocysts decreased d 21 body weight, body weight gain, feed intake (linear and quadratic, p < 0.001), and feed efficiency (linear, p < 0.001) from 0 to 7 dpi. Increasing EM oocysts increased jejunal NE lesion score and intestinal permeability on 5, 6, and 7 dpi (linear, p < 0.05). On 7 dpi, increasing the infection doses of EM oocysts increased jejunal CP colony counts (linear, p < 0.05) and increased fecal EM oocyst output (linear and quadratic, p < 0.001). Furthermore, increasing the infection doses of EM oocysts decreased the villus height to crypt depth ratios and the goblet cell counts (linear, p < 0.05) on 6 dpi. Increasing EM oocysts downregulated the expression of MUC2, B0AT, B0,+AT, PepT1, GLUT2, AvBD3 and 9, LEAP2, and TLR4, while upregulating CLDN1, CATHL3, IL-1β, IFN-γ, TNFSF15, TNF-α, IL-10, and Gam56 and 82 on 6 dpi (linear, p < 0.05). Additionally, increasing EM oocysts decreased Pielou's evenness and Shannon's entropy (linear, p < 0.01). In conclusion, increasing the infection doses of EM significantly aggravated the severity of NE and exerted negative impact on intestinal health from 5 to 7 dpi.

The effect of delayed feeding post-hatch on caeca development in broiler chickens

1. Broiler chicks are frequently deprived of food up to 72 h due to uneven hatching rates, management procedures and transportation to farms. Little is known about the effect of delayed feeding due to extended hatching times on the early neonatal development of the caeca. Therefore, the objective of this study was to investigate the developmental changes and effects of a 48-h delay in feed access immediately post-hatch (PH) on the caeca.2. After hatch, birds (Ross 708) were randomly divided into two treatment groups (n = 6 battery pen/treatment). One group (early fed; EF) received feed and water immediately after hatch, while the second group (late fed; LF) had access to water but had delayed access to feed for 48 h. Contents averaging across all regions of the caeca were collected for mRNA expression as well as for histological analysis at -48, 0, 4 h PH and then at 1, 2, 3, 4, 6, 8, 10, 12 and 14 days PH.3. Expression of MCT-1 (a nutrient transporter), Cox7A2 (related to mitochondrial function) IgA, pIgR, and ChIL-8 (immune function) genes was affected by delayed access to feed that was dependent by the time PH. Expression of immune and gut barrier function-related genes (LEAP2 and MUC2, respectively) was increased in LF group. There was no effect of feed delay on expression of genes related to mitochondrial functions in the caeca, although developmental changes were observed (ATP5F1B, Cox4|1). Caecal mucus and muscle thickness were affected by delayed access to feed during caeca development.4. The data suggested a limited effect of delayed feed access PH on the developmental changes in caecal functions. However, the caeca seemed to be relatively resistant to delayed access to feed early PH, with only a few genes affected.

Evaluation of antioxidant capacity and immunomodulatory effects of yeast hydrolysates for hepatocytes of blunt snout bream (Megalobrama amblycephala)

An in-vitro study was carried out to examine the effects of yeast hydrolysate (YH) on antioxidant capacity and innate immunity of blunt snout bream (Megalobrama amblycephala) hepatocytes. Fish primary hepatocytes were seeded at a density of 3 × 10⁵ cells mL^-1 in 6-well tissue culture plates and treated with two different media including: 1) DMEM/F12 medium (control), and 2) YH medium [DMEM/F12 + 0.1 g L^-1 YH]. After incubation for 24 h, the culture medium and primary hepatocytes were collected for subsequent analyses. The results showed no significant (P > 0.05) effect of YH on aspartate aminotransferase (AST), alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) activities and urea nitrogen (UN) concentration in the conditioned medium. However, significantly (P < 0.05) higher ALT and AST activities were found in YH treated hepatocytes compared to control. Moreover, YH supplementation led to significant enhancement of superoxide dismutase (SOD), catalase (CAT), alternative complement pathway (ACH50) and glutathione peroxidase (GPX) activities and reduction of malondialdehyde (MDA) concentration in the conditioned medium. Furthermore, YH application upregulated the expression of SOD, CAT and NOX2 genes and downregulated mRNA levels of Keap1, Nrf2 and Bach1 in hepatocytes. Also, markedly higher lysozyme activity and albumin concentration were found in the conditioned medium of YH group compared to the control. Additionally, expression of immune-related genes such as antimicrobial peptides 1 (Leap 1) and Leap 2 were significantly upregulated by YH application. Down-regulated expression of NADPH oxidase-2 (NOX2), Kelch-like-ECH-associated protein 1 (Keap1), NF-E2-related factor 2 (Nrf2) and BTB and CNC homolog 1 (Bach1) were observed in YH treated hepatocytes. To conclude, YH supplementation improved antioxidant capacity and innate immunity of blunt snout bream hepatocytes.

Induction of Chicken Host Defense Peptides within Disease-Resistant and -Susceptible Lines

Host defense peptides (HDPs) are multifunctional immune molecules that respond to bacterial and viral pathogens. In the present study, bone marrow-derived cells (BMCs) and chicken embryonic fibroblasts (CEFs) were cultured from a Leghorn line (Ghs6) and Fayoumi line (M15.2), which are inbred chicken lines relatively susceptible and resistant to various diseases, respectively. The cells were treated by lipopolysaccharide (LPS) or polyinosinic-polycytidylic acid (poly(I:C)) and, subsequently, mRNA expression of 20 chicken HDPs was analyzed before and after the stimulation. At homeostasis, many genes differed between the chicken lines, with the Fayoumi line having significantly higher expression (p < 0.05) than the Leghorn line: AvBD1, 2, 3, 4, 6, and 7 in BMCs; CATH1, CATH3, and GNLY in CEFs; and AvDB5, 8, 9, 10, 11, 12, 13 in both BMCs and CEFs. After LPS treatment, the expression of AvBD1, 2, 3, 4, 5, 9, 12, CATH1, and CATHB1 was significantly upregulated in BMCs, but no genes changed expression in CEFs. After poly(I:C) treatment, AvBD2, 11, 12, 13, CATHB1 and LEAP2 increased in both cell types; CATH2 only increased in BMCs; and AvBD3, 6, 9, 14, CATH1, CATH3, and GNLY only increased in CEFs. In addition, AvBD7, AvBD14, CATH1, CATH2, GNLY, and LEAP2 showed line-specific expression dependent upon cell type (BMC and CEF) and stimulant (LPS and poly(I:C)). The characterization of mRNA expression patterns of chicken HDPs in the present study suggests that their functions may be associated with multiple types of disease resistance in chickens.

Effects of lysine and methionine in a low crude protein diet on the growth performance and gene expression of immunity genes in broilers

Globally, the poultry industry is 1 of the most advanced livestock industries. Feed contributes to the biggest proportion (65-70%) of the production cost. Most feed ingredients in Malaysia are imported, which contributes to the high food bill annually, and alternative feed formulation may help decrease the cost of poultry feed. Feed formulation are improved to efficiently meet the dietary requirements of the broilers and 1 of the ways is by reducing the level of crude protein in the diet while supplementing essential amino acids. In this study, the effects of methionine and lysine, which are the 2 most limiting amino acids in the chicken diet, were supplemented in a low crude protein diet, and its effects on the growth and expression of immunity genes such as MUC2, SLC, GAL6, and LEAP-2 were studied. A total of 300 Cobb500 broilers were tested with 10 different dietary treatments. Experimental treatment diets consist of high, standard, and low levels of methionine and lysine in the diet with reduced crude protein. The control group consists of diet with standard levels of lysine, methionine, and crude protein as recommended for Cobb500 broilers. Ribonucleic acid was extracted from the jejunum, spleen, and liver for gene expression analysis which was performed with real-time polymerase chain reaction using SYBR Green chemistry. Results of the growth performance at 6 wk showed improved feed conversion ratio when lysine was increased by 0.2% in a low crude protein diet at 1.96 ± 0.11. Gene expression of MUC2 gene in the jejunum showed a significant increase across all experimental diets with the treatment with higher lysine in low crude protein diet with the highest increase of 3.8 times as compared with the control diet. The other genes expressed in the spleen and liver were mostly downregulated. It was concluded that supplementation of high lysine with standard methionine in a low crude protein diet performed better in terms of lowest feed conversion ratio and high upregulation of MUC2 gene.

Evaluation of antioxidant capacity and immunomodulatory effects of cottonseed meal protein hydrolysate and its derivative peptides for hepatocytes of blunt snout bream (Megalobrama amblycephala)

Two in vitro trials were conducted to identify a peptide with antioxidant activity and immunoenhancement from cottonseed meal protein hydrolysate (CPH) for fish. Primary hepatocytes of Megalobrama amblycephala were treated with CPH. In experiment 1, CPH significantly increased aspartate aminotransferase (GOT), alanine aminotransferase (GPT), total superoxide dismutase (t-SOD), catalase (CAT), and lysozyme activities, as well as up-regulated SOD, CAT, antimicrobial peptides 1 (Leap 1) and Leap 2 mRNA levels (p < 0.05). However, CPH significantly down-regulated the expression of NADPH oxidase-2 (NOX2), Kelch-like-ECH-associated protein 1 (Keap1), NF-E2-related factor 2 (Nrf2) and BTB and CNC homolog 1 (Bach1) mRNA (p < 0.05) in fish hepatocytes. Experiment 2 showed that the molecular mass of CPH was distributed mainly in the 700-1024 Da range. Peptide 1 (P1) and P2 significantly decreased GOT and GPT activities in conditioned medium (p < 0.05); however, P4 and P6 did not affect GOT and GPT activities (p > 0.05). Furthermore, P4 significantly increased hepatocyte GOT, GPT, t-SOD, CAT levels and lysozyme activities (p < 0.05), up-regulated SOD, CAT, Leap1 and Leap2 mRNA expression levels, and down-regulated the expression of Nrf2 and NOX2 mRNA (p < 0.05) in fish hepatocytes. The above results indicated that CPH and P4 enhanced hepatocyte metabolism, as well as improved antioxidant capacities and innate immunity of blunt snout bream hepatocytes.

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

Objective

This study was conducted to identify duck liver-expressed antimicrobial peptide 2 (LEAP-2) and demonstrate its antimicrobial activity against various pathogens.

Methods

Tissue samples were collected from 6 to 8-week-old Pekin ducks (Anas platyrhynchos domesticus), total RNA was extracted, and cDNA was synthesized. To confirm the duck LEAP-2 transcript expression levels, quantitative real-time polymerase chain reaction was conducted. Two kinds of peptides (a linear peptide and a disulfide-type peptide) were synthesized to compare the antimicrobial activity. Then, antimicrobial activity assay and fluorescence microscopic analysis were conducted to demonstrate duck LEAP-2 bactericidal activity.

Results

The duck LEAP-2 peptide sequence showed high identity with those of other avian species (>85%), as well as more than 55% of identity with mammalian sequences. LEAP-2 mRNA was highly expressed in the liver with duodenum next, and then followed by lung, spleen, bursa and jejunum and was the lowest in the muscle. Both of LEAP-2 peptides efficiently killed bacteria, although the disulfide-type LEAP-2 showed more powerful bactericidal activity. Also, gram-positive bacteria was more susceptible to duck LEAP-2 than gram-negative bacteria. Using microscopy, we confirmed that LEAP-2 peptides could kill bacteria by disrupting the bacterial cell envelope.

Conclusion

Duck LEAP-2 showed its antimicrobial activity against both gram-positive and gram-negative bacteria. Disulfide bonds were important for the powerful killing effect by disrupting the bacterial cell envelope. Therefore, duck LEAP-2 can be used for effective antibiotics alternatives.

Toll-like receptor (TLR)4 signalling induces myeloid differentiation primary response gene (MYD) 88 independent pathway in avian species leading to type I interferon production and antiviral response

Engagement of toll-like receptor (TLR)4 ligand, lipopolysaccharide (LPS) with TLR4 in mammals activates two downstream intracellular signaling routes; the myeloid differentiation primary response gene (MyD)88 dependent and independent pathways. However, existence of the later pathway leading to production of type I interferons (IFNs) in avian species has been debated due to conflicting observations. The objective of our study was to investigate whether LPS induces type I IFN production in chicken macrophages leading to antiviral response attributable to type I IFN. We found that LPS elicits type I IFN response dominated by IFN-β production. We also found that reduction in infectious laryngotracheitis virus (ILTV) replication by LPS-mediated antiviral response is attributable to type I IFNs in addition to nitric oxide (NO). Our findings imply that LPS elicits both MyD88 dependent and independent pathways in chicken macrophages consequently eliciting anti-ILTV response attributable to production of both type I IFNs and NO.

Identification of Biomarkers for Footpad Dermatitis Development and Wound Healing

Footpad dermatitis (FPD) is a type of skin inflammation that causes necrotic lesions on the plantar surface of the footpads in commercial poultry, with significant animal welfare, and economic implications. To identify biomarkers for FPD development and wound healing, a battery cage trial was conducted in which a paper sheet was put on the bottom of cages to hold feces to induce FPD of broilers. Day-of-hatch Ross 308 male broiler chicks were fed a corn–soybean meal diet and assigned to 3 treatments with 8 cages per treatment and 11 birds per cage. Cages without paper sheets were used as a negative control (NEG). Cages with paper sheets during the entire growth period (d 0–30) were used as a positive control (POS) to continually induce FPD. Cages with paper sheets during d 0–13 and without paper sheets during d 14–30 were used to examine the dynamic of FPD development and lesion wound healing (LWH). Footpad lesions were scored to grade (G) 1–5 with no lesion in G1 and most severe lesion in G5. Covering with paper sheets in POS and LWH induced 99% incidence of G3 footpads on d 13. Removing paper sheets from LWH healed footpad lesions by d 30. One representative bird, with lesions most close to pen average lesion score, was chosen to collect footpad skin samples for biomarker analysis. Total collagen protein and mRNA levels of tenascin X (TNX), type I α1 collagen (COL1A1), type III α1 collagen (COL3A1), tissue inhibitor of metalloproteinase 3 (TIMP3), and integrin α1 (ITGA1) mRNA levels were decreased (P < 0.05), while mRNA levels of tenascin C (TNC), tumor necrosis factor (TNF) α, Toll-like receptor (TLR) 4 and vascular endothelial growth factor (VEGF), IL-1β, and the ratio of MMP2 to all TIMP were increased (P < 0.03) in G3 footpads in POS and LWH compared to G1 footpads in NEG on d 14. These parameters continued to worsen with development of more severe lesions in POS. After paper sheets were removed (i.e., LWH), levels of these parameters gradually or rapidly returned to levels measured in NEG. Regression analysis indicated significant quadratic changes of these parameters to footpad lesion scores. In summary, these biomarkers were interrelated with dynamic changes of footpad lesion scores, suggesting they may be used as potential biomarkers for footpad lesion development and wound healing process.

Host Avian Beta-Defensin and Toll-Like Receptor Responses of Pigeons following Infection with Pigeon Paramyxovirus Type 1

The high morbidity and mortality in pigeons caused by pigeon paramyxovirus type 1 (PPMV-1) highlights the need for new insights into the host immune response and novel treatment approaches. Host defense peptides (HDPs) are key components of the innate immune system. In this study, three novel avian β-defensins (AvBDs 2, 7, and 10) were characterized in pigeons and shown to possess direct antiviral activity against PPMV-1 in vitro. In addition, we evaluated the mRNA expression of these AvBDs and other immune-related genes in tissues of 2-month-old infected pigeons at 3 and 7 days postinfection. We observed that the expression of AvBD2 in the cecal tonsil, lungs, and proventriculus, as well as the expression of AvBD10 in the spleen, lungs, proventriculus, and kidneys, was upregulated in infected pigeons. Similarly, the expression of both Toll-like receptor 3 (TLR3) and TLR7 was increased in the spleen, trachea, and proventriculus, while TLR15 expression was increased only in the lungs of infected pigeons. In addition, inducible nitric oxide synthase (iNOS) expression was upregulated in the spleen, the bursa of Fabricius, the trachea, and the proventriculus of infected pigeons. Furthermore, we observed a high correlation between the expression of AvBD2 and the expression of either TLR7 or TLR15, as well as between AvBD10 expression and either TLR3 or TLR7 expression in respective tissues. The results suggest that PPMV-1 infection can induce innate host responses characterized by the activation of TLRs, particularly TLR3 and TLR7, AvBDs (2 and 10), and iNOS in pigeons.

In ovo delivery of CpG DNA reduces avian infectious laryngotracheitis virus induced mortality and morbidity

Endosomal toll-like receptor-21 and -9 sense CpG DNA activating production of pro-inflammatory mediators with antimicrobial effects. Here, we investigated the induction of antiviral response of in ovo delivered CpG DNA against infectious laryngotracheitis virus (ILTV) infection. We found that in ovo delivered CpG DNA significantly reduces ILTV infection pre-hatch correlating with the expression of IL-1β and increase of macrophages in lungs. As assessed in vitro, CpG DNA stimulated avian macrophages could be a potential source of IL-1β and other pro-inflammatory mediators. Since we also found that in ovo CpG DNA delivery maintains increased macrophages in the lungs post-hatch, we infected the chickens on the day of hatch with ILTV. We found that in ovo delivered CpG DNA significantly reduces mortality and morbidity resulting from ILTV infection encountered post-hatch. Thus, CpG DNA can be a candidate innate immune stimulant worthy of further investigation for the control of ILTV infection in chickens.

Characterisation of Toll-like receptors 4, 5 and 7 and their genetic variation in the grey partridge

Toll-like receptors (TLRs) are a cornerstone of vertebrate innate immunity. In this study, we identified orthologues of TLR4, TLR5 and TLR7 (representing both bacterial- and viral-sensing TLRs) in the grey partridge (Perdix perdix), a European Galliform game bird species. The phylogeny of all three TLR genes follows the known phylogeny of Galloanserae birds, placing grey partridge TLRs (PePeTLRs) in close proximity to their turkey and pheasant orthologues. The predicted proteins encoded by the PePeTLR genes were 843, 862-863 and 1,047 amino acids long, respectively, and clearly showed all TLR structural features. To verify functionality in these genes we mapped their tissue-expression profiles, revealing generally high PePeTLR4 and PePeTLR5 expression in the thymus and absence of PePeTLR4 and PePeTLR7 expression in the brain. Using 454 next-generation sequencing, we then assessed genetic variation within these genes for a wild grey partridge population in the Czech Republic, EU. We identified 11 nucleotide substitutions in PePeTLR4, eight in PePeTLR5 and six in PePeTLR7, resulting in four, four and three amino acid replacements, respectively. Given their locations and chemical features, most of these non-synonymous substitutions probably have a minor functional impact. As the intraspecific genetic variation of the three TLR genes was low, we assume that either negative selection or a bottleneck may have reduced TLR population variability in this species.

Toll-like receptor 2 ligand, lipoteichoic acid is inhibitory against infectious laryngotracheitis virus infection in vitro and in vivo

Lipoteichoic acid (LTA) is one of the pathogen associated molecular patterns (PAMPs) that activates toll-like receptor (TLR)2-cluster of differentiation (CD)14 signalling pathway. This recognition elicits antiviral responses that have been recorded against viruses of mammals although such responses have not been characterized adequately against avian viruses. In this investigation, we characterized the LTA induced antiviral responses against infectious laryntotracheitis virus (ILTV) infection in vitro and in vivo. We found that LTA is capable of up regulating mRNA expression of innate proteins in macrophages such as MyD88, iNOS and IL-1β and reduces the ILTV plaques in vitro. Similarly, we found that LTA treatment of embryonic day 18 (ED18) eggs can lead to the antiviral response against pre-hatch ILTV infection in vivo and is associated with expansion of macrophage populations and expression of IL-1β and MyD88 in the lung. The data highlight that LTA can be a potential innate immune stimulant that can be used against ILTV infection in chickens.

Characterization, evolution and functional analysis of the liver-expressed antimicrobial peptide 2 (LEAP-2) gene in miiuy croaker

As an evolutionarily older defense strategy, the innate immune is the dominant immune system and provides a first line of antimicrobial host defense in teleost. Liver-expressed antimicrobial peptide-2 (LEAP-2) is a critical molecule of the innate immune system and plays a very important role in resistance against bacterial infections. We reported comprehensive analysis and characterization of LEAP-2 gene from miiuy croaker (Miichthys miiuy) in here. The complete cDNA of miiuy croaker LEAP-2 consists 2360 bp, including a 5' terminal untranslated region (UTR) of 170 bp, an open reading frame (ORF) of 312 bp, and a 3'-UTR of 1878 bp. Interestingly, two polyadenylation signals (AATTAAA) which may involve the stability, translation efficiency, or localization of an mRNA in a tissue were found in 3'-UTR. Genomic DNA of miiuy croaker LEAP-2 includes three exons and two introns, which is similar to LEAP-2 genes in other mammals and fish. The deduced 103 amino acids consist of signal peptide, prodomain and mature peptide. Four highly conserved cysteine residues involved two disulfide bridges in mature peptide. Real-time PCR results showed that LEAP-2 was ubiquitously expressed in all tissues and the expression level was highest in liver. Significantly, the expression levels were increased after infection with Vibrio anguillarum in liver and spleen. The antimicrobial activity analysis result of LEAP-2 in vitro indicated that LEAP-2 of miiuy croaker was effective in controlling Aeromonas hydrophila. In addition, we performed evolutionary analysis in order to estimate the selective constraints on the LEAP-2 gene. The result indicated that no positive selection exists in LEAP-2 gene sequences, which may be on account of irreplaceable function constrains. Meanwhile, we compared the structure of LEAP-2 with that of another Liver-expressed antimicrobial peptide (LEAP-1, also named HAMP), and found the LEAP-2 from miiuy croaker comprises of α-helix, β-sheet, and β-turn while the LEAP-1 of miiuy croaker only contains β-sheet.

Protein evolution of Toll-like receptors 4, 5 and 7 within Galloanserae birds

BACKGROUND

Toll-like receptors (TLR) are essential activators of the innate part of the vertebrate immune system. In this study, we analysed the interspecific variability of three TLR (bacterial-sensing TLR4 and TLR5 and viral-sensing TLR7) within the Galloanserae bird clade, investigated their phylogeny, assessed their structural conservation and estimated site-specific selection pressures.

RESULTS

Physiochemical properties varied according to the TLR analysed, mainly with regards to the surface electrostatic potential distribution. The predicted ligand-binding features (mainly in TLR4 and TLR5) differed between the avian proteins and their fish and mammalian counterparts, but also varied within the Galloanserae birds. We identified 20 positively selected sites in the three TLR, among which several are topologically close to ligand-binding sites reported for mammalian and fish TLR. We described 26, 28 and 25 evolutionarily non-conservative sites in TLR4, TLR5 and TLR7, respectively. Thirteen of these sites in TLR4, and ten in TLR5 were located in functionally relevant regions. The variability appears to be functionally more conserved for viral-sensing TLR7 than for the bacterial-sensing TLR. Amino-acid positions 268, 270, 343, 383, 444 and 471 in TLR4 and 180, 183, 209, 216, 264, 342 and 379 in TLR5 are key candidates for further functional research.

CONCLUSIONS

Host-pathogen co-evolution has a major effect on the features of host immune receptors. Our results suggest that avian and mammalian TLR may be differentially adapted to pathogen-derived ligand recognition. We have detected signatures of positive selection even within the Galloanserae lineage. To our knowledge, this is the first study to depict evolutionary pressures on Galloanserae TLR and to estimate the validity of current knowledge on TLR function (based on mammalian and chicken models) for non-model species of this clade.

Early immune responses in rainbow trout liver upon viral hemorrhagic septicemia virus (VHSV) infection

Among the essential metabolic functions of the liver, in mammals, a role as mediator of systemic and local innate immunity has also been reported. Although the presence of an important leukocyte population in mammalian liver is well documented, the characterization of leukocyte populations in the teleost liver has been only scarcely addressed. In the current work, we have confirmed the presence of IgM⁺, IgD⁺, IgT⁺, CD8α⁺, CD3⁺ cells, and cells expressing major histocompatibility complex (MHC-II) in rainbow trout (Oncorhynchus mykiss) liver by flow cytometry and/or immunohistochemistry analysis. Additionally, the effect of viral hemorrhagic septicemia virus (VHSV) on the liver immune response was assessed. First, we studied the effect of viral intraperitoneal injection on the transcription of a wide selection of immune genes at days 1, 2 and 5 post-infection. These included a group of leukocyte markers genes, pattern recognition receptors (PRRs), chemokines, chemokine receptor genes, and other genes involved in the early immune response and in acute phase reaction. Our results indicate that T lymphocytes play a key role in the initial response to VHSV in the liver, since CD3, CD8, CD4, perforin, Mx and interferon (IFN) transcription levels were up-regulated in response to VHSV. Consequently, flow cytometry analysis of CD8α⁺ cells in liver and spleen at day 5 post-infection revealed a decrease in the number of CD8α⁺ cells in the spleen and an increased population in the liver. No differences were found however in the percentages of B lymphocyte (IgM⁺ or IgD⁺) populations. In addition, a strong up-regulation in the transcription levels of several PRRs and chemokines was observed from the second day of infection, indicating an important role of these factors in the response of the liver to viral infections.

Molecular characterization of LEAP-2 cDNA in common carp (Cyprinus carpio L.) and the differential expression upon a Vibrio anguillarum stimulus; indications for a significant immune role in skin

LEAP-2 is a cysteine-rich cationic antimicrobial peptide (AMP) playing an important role in host innate immune system. LEAP-2 genes have been identified from higher vertebrates and several fish species. Here we report the cloning and identification of two LEAP-2 cDNA sequences from the liver of common carp (Cyprinus carpio L.). The LEAP-2A cDNA was 1325 bp long and contained an ORF of 279 bp encoding a protein of 92 amino acids. The LEAP-2B cDNA was 608 bp long and contained an ORF of 276 bp encoding a protein of 91 amino acids. Both LEAP-2 proteins consisted of 41 amino acid residues and shared four cysteines at the conserved positions in the predicted mature peptides, highly similar to LEAP-2 of other species. Sequence alignment showed that LEAP-2 amino acid sequences were well conserved in different species, and the phylogenetic relation of LEAP-2 was coincident with evolution of biological species. Expression analysis data revealed that LEAP-2A and LEAP-2B mRNAs were expressed in a wide range of common carp tissues including liver, spleen, head kidney, skin, gills, hindgut and foregut. When injected intraperitoneally with Vibrio anguillarum, the expression level of common carp LEAP-2A was quickly up-regulated in liver, spleen, head kidney, skin, gills, foregut and hindgut, however, the expression level of LEAP-2B was similarly up-regulated in spleen, skin, gills and hindgut but not in liver, head kidney and foregut. Our results showed that the LEAP-2A had a markedly high constitutive expression in skin, and the LEAP-2A and the LEAP-2B had a significantly high up-regulated expression after stimulus in skin. This differential expression of LEAP-2 in common carp suggests that it may play a key role in immune responses against invading pathogens and both LEAP-2 molecules may be involved in mucosal immunity.

Avian host defense peptides

Host defense peptides (HDPs) are important effector molecules of the innate immune system of vertebrates. These antimicrobial peptides are also present in invertebrates, plants and fungi. HDPs display broad-spectrum antimicrobial activities and fulfill an important role in the first line of defense of many organisms. It is becoming increasingly clear that in the animal kingdom the functions of HDPs are not confined to direct antimicrobial actions. Research in mammals has indicated that HDPs have many immunomodulatory functions and are also involved in other physiological processes ranging from development to wound healing. During the past five years our knowledge about avian HDPs has increased considerably. This review addresses our current knowledge on the evolution, regulation and biological functions of HDPs of birds.

Unique features of chicken Toll-like receptors

Toll-like receptors (TLRs) are a major class of innate immune pattern recognition receptors that have a key role in immune homeostasis and the defense against infections. The research explosion that followed the discovery of TLRs more than a decade ago has boosted fundamental knowledge on the function of the immune system and the resistance against disease, providing a rational for clinical modulation of the immune response. In addition, the conserved nature of the ancient TLR system throughout the animal kingdom has enabled a comparative biology approach to understand the evolution, structural architecture, and function of TLRs. In the present review we focus on TLR biology in the avian species, and, especially, on the unique functional properties of the chicken TLR repertoire.

Induction of Toll-like receptor 4 signaling in avian macrophages inhibits infectious laryngotracheitis virus replication in a nitric oxide dependent way

LPS is one of the pathogen associated molecular patterns that activates Toll-like receptor 4 (TLR4) signaling pathway eliciting antiviral host responses in mammals although information on such responses in avian species is scarce. Our objectives were to characterize the LPS induced innate responses particularly the expression of LPS receptors (TLR4, CD14) in avian macrophages and observe whether TLR4 mediated induction of NO can elicit antiviral response against infectious laryngotracheitis virus (ILTV) replication. We found that LPS was capable of inducing the expression of TLR4, CD14 and NO production but not the type 1 interferons in an avian macrophage cell line, MQ-NCSU. We also showed that TLR4 mediated NO production can lead to antiviral response against ILTV replication when MQ-NCSU cells were treated with LPS and the resultant supernatant was then transferred to ILTV replicating cells to assess antiviral activity. Antiviral activity of NO was blocked by a selective inhibitor, S-methylisothiourea sulfate that inhibits inducible NO synthase. This observation confirms that the antiviral activity is positively correlated with NO production. The data show that LPS can be a potential innate immune stimulant that can be used against ILTV infection in chickens that require further evaluation in vivo.

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.

In silico analysis of candidate genes associated with humoral innate immune response in chicken

Background

Production and function of natural antibodies (NAbs) constitutes an important mechanism of the humoral innate immunity in vertebrates. The level of NAbs in chicken is heritable and the genetic background has been partly investigated. However, to date the genetic determination of humoral innate immune response in avian species has not been fully described. The goal of this study was to propose a new set of candidate genes with a potential effect on the NAb phenotype for further SNP association study.

Methods

In silico analysis of positional and functional candidate genes covered 14 QTL regions associated with LPS, LTA & KLH NAbs and located on six chromosomes: GGA5, GGA6, GGA9, GGA14, GGA18 and GGAZ. The function of the genes was subsequently determined based on the NCBI, KEGG, Gene Ontology and InnateDB databases.

Results

As a result, the core panel of 38 genes participating in metabolic pathways of innate immune response was proposed. Most of them were assigned to chromosomes: GGA14, GGA5, GGA6 and GGAZ (13, 9, 8 and 5 genes, respectively). These candidate genes encode proteins predicted to play a role in (i) proliferation, differentiation and function of B lymphocytes; (ii) TLR signalling pathway, and (iii) MAP signalling cascade.

Conclusions

Proposed set of candidate genes is recommended to be included in the follow-up studies to model genetic networks of innate humoral immune response in chicken.

Human and chicken TLR pathways: manual curation and computer-based orthology analysis

The innate immune responses mediated by Toll-like receptors (TLR) provide an evolutionarily well-conserved first line of defense against microbial pathogens. In the Reactome Knowledgebase we previously integrated annotations of human TLR molecular functions with those of over 4000 other human proteins involved in processes such as adaptive immunity, DNA replication, signaling, and intermediary metabolism, and have linked these annotations to external resources, including PubMed, UniProt, EntrezGene, Ensembl, and the Gene Ontology to generate a resource suitable for data mining, pathway analysis, and other systems biology approaches. We have now used a combination of manual expert curation and computer-based orthology analysis to generate a set of annotations for TLR molecular function in the chicken (Gallus gallus). Mammalian and avian lineages diverged approximately 300 million years ago, and the avian TLR repertoire consists of both orthologs and distinct new genes. The work described here centers on the molecular biology of TLR3, the host receptor that mediates responses to viral and other doubled-stranded polynucleotides, as a paradigm for our approach to integrated manual and computationally based annotation and data analysis. It tests the quality of computationally generated annotations projected from human onto other species and supports a systems biology approach to analysis of virus-activated signaling pathways and identification of clinically useful antiviral measures.

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.

Inhibition of NF-kB 1 (NF-kBp50) by RNA interference in chicken macrophage HD11 cell line challenged with Salmonellaenteritidis

The NF-kB pathway plays an important role in regulating the immunity response in animals. In this study, small interfering RNAs (siRNA) were used to specifically inhibit NF-kB 1 expression and to elucidate the role of NF-kB in the signal transduction pathway of the Salmonella challenge in the chicken HD11 cell line. The cells were transfected with either NF-kB 1 siRNA, glyceraldehyde 3-phosphate dehydrogenase siRNA (positive control) or the negative control siRNA for 24 h, followed by Salmonella enteritidis (SE) challenge or non-challenge for 1 h and 4 h. Eight candidate genes related to the signal pathway of SE challenge were selected to examine the effect of NF-kB 1 inhibition on their expressions by mRNA quantification. The results showed that, with a 36% inhibition of NF-kB 1 expression, gene expression of both Toll-like receptor (TLR) 4 and interleukin (IL)-6 was consistently and significantly increased at both 1 h and 4 h following SE challenge, whereas the gene expression of MyD88 and IL-1β was increased at 1 h and 4 h, respectively. These findings suggest a likely inhibitory regulation by NF-kB 1, and could lay the foundation for studying the gene network of the innate immune response of SE infection in chickens.

The avian Toll-Like receptor pathway--subtle differences amidst general conformity

The Toll-Like receptor (TLR) pathway plays a core role in innate immunity and is maintained with remarkable consistency across all vertebrate species. Amidst this background of overall conservation, subtle differences in the components that make up this pathway may have important implications for species-specific defense against key pathogens. Here we employ a homology-based comparative method to characterize the TLR pathway in the recently sequenced chicken and zebra finch genomes, which represent two distantly related bird species. The key features of the TLR pathway are conserved in birds and mammals, although some clear differences exist. The TLR receptors show a pattern of gene duplication and gene loss in both avian species when compared to mammals. In particular, we observe avian specific duplication of both TLR1 and TLR2 as well and a recent duplication of the TLR7 gene in the zebra finch lineage. Both positive selection and gene conversion shape the evolution of the avian specific TLR2 genes. In addition, there are notable differences in the zebra finch repertoire of antimicrobial peptides (AMPs) when compared to those of the chicken. Bioinformatic analysis reveals no evidence of cathelicidins in the zebra finch genome but does identify a cluster of 12 novel defensins which map to the avian beta-defensin locus on chromosome 3. These findings contribute to the characterization of the differing immune response systems that have evolved in individual vertebrate species in response to their microbiological environment.

Molecular cloning and expression analysis of the liver-expressed antimicrobial peptide 2 (LEAP-2) gene in grass carp

Liver-expressed antimicrobial peptide 2 (LEAP-2) is a novel antimicrobial peptide (AMP) recently found in vertebrates, and exhibits distinct amino acid sequence, secondary structure and expression pattern from other peptides. In this study, the LEAP-2 gene and its full-length cDNA were cloned from grass carp. Grass carp LEAP-2 gene consists of two introns and three exons. The translated product contains 92 amino acids, including a 26 amino acids signal peptide and a mature peptide of 41 amino acids. Grass carp LEAP-2 gene was expressed in a wide range of tissues except blood, with the highest level of transcripts found in liver. Upon induction by Aeromonas hydrophila, its expression was significantly up-regulated in liver, gill, skin, muscle, spleen, blood, head kidney, heart and intestine, but down-regulated in trunk kidney and brain. The transcript level was high in embryos at the 16-cell stage but declined gradually afterwards, suggesting that LEAP-2 transcripts in early embryos might be maternal. Mature peptides obtained by in vitro expression displayed selective antimicrobial activities. These results together further our understanding of the physiological function of LEAP-2 in vertebrates.

Molecular cloning and expression analysis of chickenMyD88andTRIFgenes

Toll-like receptors (TLRs) trigger the innate immune system by responding to specific components of microorganisms. MyD88 and TRIF are Toll/interleukin (IL)-1 (TIR)-domain containing adapters, which play essential roles in TLR-mediated signalling via the MyD88-dependant and -independent pathways, respectively. Genes encoding several TLRs have been identified in the chicken genome, however, elements of their signalling pathways have not been well characterized. Here we describe the cloning of chicken MyD88 and TRIF orthologs, and examine the spatial and temporal expression of these genes. The chicken MyD88 cDNA was shown to have an open reading frame (ORF) of 1104 bp, encoding a predicted protein sequence of 368 aa, 8 aa short of a previously published coding sequence due to a premature stop codon. MyD88 gene expression was detected in each tissue tested except in muscle. The chicken TRIF cDNA possessed an ORF of 2205 bp, encoding a predicted protein sequence of 735 aa, which shared 37.3% similarity and 28.9% identity to human TRIF protein sequence. TRIF was ubiquitously expressed in all tissues.

Toll-like receptor signaling in hen ovarian granulosa cells is dependent on stage of follicle maturation

The recent identification of toll-like receptor (TLR) signaling within ovarian granulosa cells has broad implications for ovarian physiology. Functions of TLRs within granulosa cells of the laying hen are of particular interest due to the method of transovarian transmission of Salmonella enteritidis, which results in egg contamination. This study utilized hen granulosa cells to evaluate the expression and function of Gallus TLR-signaling at distinct stages of follicular maturity. Data presented herein demonstrate the presence of TLR2, TLR4, and TLR15 mRNAs in undifferentiated granulosa cells from prehierarchal follicles and differentiated granulosa cells from preovulatory follicles, together with mRNAs encoding adaptor proteins and signaling components required for TLR signaling gene. Treatment with lipopolysaccharide (LPS) or LH, in vitro, led to the differential regulation of TLRs based on the stage of follicle maturation, with the largest (F1) follicle granulosa cells having the most rapid response. Furthermore, treatment with LPS resulted in attenuation of agonist-induced progesterone synthesis in undifferentiated, but not differentiated, granulosa cells. Additionally, undifferentiated granulosa cells were significantly more sensitive to LPS-induced apoptosis than differentiated granulosa cells from the F1 follicle. Together, these data provide evidence for a complete and functional TLR signaling pathway in hen granulosa cells, with effects on steroidogenesis and cell viability dependent upon stage of maturation. These differences may reflect the susceptibility of granulosa cells at early stages of maturation to undergo apoptosis in response to select pathogenic stimuli, thus attenuating transovarian transmission, whereas granulosa cells from preovulatory follicles are comparably resistant to LPS-mediated apoptosis.

Identification of the first Toll-like receptor gene in passerine birds: TLR4 orthologue in zebra finch (Taeniopygia guttata)

Toll-like receptors (TLRs) are the basic components of the vertebrate pathogen recognition system. Despite uniform general structure, remarkable variability in domain composition can be found in individual TLRs among species. Knowledge of interspecific differences is of particular importance to our understanding of selective pressures on TLRs. Currently, most TLRs are characterized only in a limited number of model species, including domestic chicken as a universal avian model. Here, we describe structure and expression pattern of TLR4 in zebra finch, a widely used passerine model species. The tgTlr4 gene consists of three exons (204, 167 and 3033-3043 bp) that are transcribed into messenger RNA with a relatively long 3'-untranslated region (788 bp). Predicted protein is composed of 842 amino acids (aas) forming extracellular domain with nine leucine-rich repeat (LRR) motives flanked at the carboxy-terminal end by leucine-rich repeat carboxy-terminal domain, transmembrane domain and cytoplasmic toll/interleukin-1 receptor domain. The overall structure is similar to other known TLR4 molecules with 32%-49% aa identity to various mammals and 74% to chicken. Although the position of most of the domains in zebra finch TLR4 resembles their position in chicken, there is one extra LRR at the aa position 207-229 in tgTLR4 and one LRR known in chTLR4 is missing. The gene is highly expressed in the bone marrow and in the spleen, intermediately in the gut and low expression was found in the liver and lungs. For the first time in birds, expression of tgTLR4 in peritoneal macrophages was found to be enhanced by the Escherichia coli lipopolysaccharide treatment.

Genetic lines differ in Toll-like receptor gene expression in spleens of chicks inoculated with Salmonella enterica serovar Enteritidis

Toll-like receptors (TLR) recognize evolutionarily conserved molecular motifs (pathogen-associated molecular patterns) of infectious microbes and initiate innate immune response upon activation with relevant pathogens. This study investigated the acute effect of Salmonella Enteritidis challenge on TLR mRNA expression in cecum and spleen of birds from 3 distinct genetic lines. Chicks from broiler, Leghorn, and Fayoumi lines were inoculated or mock-inoculated with Salmonella Enteritidis. The mRNA expression levels of TLR2, TLR4, and TLR5 genes were assessed by quantitative reverse transcription-PCR of cecum and spleen tissue harvested at 2 or 18 h postinoculation (PI). There were no significant genetic line effects on TLR mRNA expression in spleen or cecum of mock-infected birds, or in the cecum of infected birds. Genetic line effect was significant (P < 0.05) on TLR mRNA expression in the spleen of Salmonella Enteritidis-infected birds. The Fayoumi line had higher TLR2 and TLR4 expression than Leghorn, higher TLR2 mRNA expression than broiler, and the broiler line had higher TLR5 expression than Leghorn and Fayoumi. In Salmonella Enteritidis-infected birds, the TLR2 expression in both cecum and spleen and TLR4 expression in spleen were significantly higher at 18 h PI than 2 h PI. The results demonstrate a significant genetic line effect on TLR expression in the spleen of Salmonella Enteritidis-infected birds, which may partly explain genetic variability in immune response to Salmonella Enteritidis.

Evaluation of combining several statistical methods with a flexible cutoff for identifying differentially expressed genes in pairwise comparison of EST sets

The detection of differentially expressed genes from EST data is of importance for the discovery of potential biological or pharmaceutical targets, especially when studying biological processes in less characterized organisms and where large-scale microarrays are not an option. We present a comparison of five different statistical methods for identifying up-regulated genes through pairwise comparison of EST sets, where one of the sets is generated from a treatment and the other one serves as a control. In addition, we specifically address situations where the sets are relatively small (~2,000–10,000 ESTs) and may differ in size. The methods were tested on both simulated and experimentally derived data, and compared to a collection of cold stress induced genes identified by microarrays. We found that combining the method proposed by Audic and Claverie with Fisher’s exact test and a method based on calculating the difference in relative frequency was the best combination for maximizing the detection of up-regulated genes. We also introduced the use of a flexible cutoff, which takes the size of the EST sets into consideration. This could be considered as an alternative to a static cutoff. Finally, the detected genes showed a low overlap with those identified by microarrays, which indicates, as in previous studies, low overall concordance between the two platforms.

Toll-like receptor gene expression in cecum and spleen of advanced intercross line chicks infected with Salmonella enterica serovar Enteritidis

Understanding the changes in host gene expression that occur with bacterial infection will help to elucidate the basis of molecular genetic control of disease resistance. The effect of infecting chicks with Salmonella enterica serovar Enteritidis on the RNA expression level of Toll-like receptor (TLR) genes, and the correlation between TLR RNA expression level and bacterial burden in the cecum and spleen of young birds was studied. Chicks from two advanced intercross lines were either infected or mock infected with S. enteritidis at 1 day of age. The RNA expression levels of TLR2, TLR4 and TLR5 genes were assessed by quantitative reverse transcriptase-PCR (qRT-PCR) in cecum and spleen tissues harvested at one week post-infection. Infected chicks had significant upregulation of TLR2 RNA expression in spleen, TLR4 RNA expression in both cecum and spleen, and downregulation of TLR5 RNA expression in cecum. Bacterial burden of S. enteritidis in infected birds was not correlated with TLR RNA expression level. Infecting chicks with S. enteritidis caused an increase in TLR2, TLR4 and TLR5 RNA expression level in spleen in males but not in females. The effect of sex on response to S. enteritidis infection suggests a role for TLR signaling pathways in sex-based modulation of immune response to pathogens. High correlation between TLR2 and TLR4 mRNA expression level in cecum of S. enteritidis infected birds suggests coordinated regulation or simultaneous stimulation of these genes by S. enteritidis. In conclusion, this study clearly showed that young chicks respond to S. enteritidis infection by upregulating TLR2, TLR4 RNA expression. The downregulation of TLR5 RNA expression was observed in cecum by S. enteritidis infection, which might be beneficial to protect host cells from overstimulation by bacterial flagellin.

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.

Functional genomics of the chicken--a model organism

Since the sequencing of the genome and the development of high-throughput tools for the exploration of functional elements of the genome, the chicken has reached model organism status. Functional genomics focuses on understanding the function and regulation of genes and gene products on a global or genome-wide scale. Systems biology attempts to integrate functional information derived from multiple high-content data sets into a holistic view of all biological processes within a cell or organism. Generation of a large collection ( approximately 600K) of chicken expressed sequence tags, representing most tissues and developmental stages, has enabled the construction of high-density microarrays for transcriptional profiling. Comprehensive analysis of this large expressed sequence tag collection and a set of approximately 20K full-length cDNA sequences indicate that the transcriptome of the chicken represents approximately 20,000 genes. Furthermore, comparative analyses of these sequences have facilitated functional annotation of the genome and the creation of several bioinformatic resources for the chicken. Recently, about 20 papers have been published on transcriptional profiling with DNA microarrays in chicken tissues under various conditions. Proteomics is another powerful high-throughput tool currently used for examining the dynamics of protein expression in chicken tissues and fluids. Computational analyses of the chicken genome are providing new insight into the evolution of gene families in birds and other organisms. Abundant functional genomic resources now support large-scale analyses in the chicken and will facilitate identification of transcriptional mechanisms, gene networks, and metabolic or regulatory pathways that will ultimately determine the phenotype of the bird. New technologies such as marker-assisted selection, transgenics, and RNA interference offer the opportunity to modify the phenotype of the chicken to fit defined production goals. This review focuses on functional genomics in the chicken and provides a road map for large-scale exploration of the chicken genome.

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.

Avian genomics in the 21st century

The chicken has long been an important model organism for developmental biology, as well as a major source of protein with billions of birds used in meat and egg production each year. Chicken genomics has been transformed in recent years, with the characterisation of large EST collections and most recently with the assembly of the chicken genome sequence. As the first livestock genome to be fully sequenced it leads the way for others to follow--with zebra finch later this year. The genome sequence and the availability of three million genetic polymorphisms are expected to aid the identification of genes that control traits of importance in poultry. As the first bird genome to be sequenced it is a model for the remaining 9,600 species thought to exist today. Many of the features of avian biology and organisation of the chicken genome make it an ideal model organism for phylogenetics and embryology, along with applications in agriculture and medicine. The availability of new tools such as whole-genome gene expression arrays and SNP panels, coupled with information resources on the genes and proteins are likely to enhance this position.

Isolation and characterization of antimicrobial proteins and peptide from chicken liver

Endogenous antimicrobial peptides and proteins are crucial components of the innate immune system and play an essential role in the defense against infection. Antimicrobial activity was detected in the acid extract of livers harvested from healthy adult White Leghorn hens, Gallus gallus. Two antimicrobial proteins and one antimicrobial polypeptide were isolated from the liver extract by cation-exchange and gel filtration chromatography, followed by two-step reverse-phase high-performance liquid chromatography (RP-HPLC). These antimicrobial components were identified as histones H2A and H2B.V, and histone H2B C-terminal fragment using peptide mass fingerprinting and partial sequencing by tandem nanoelectrospray mass spectrometry. The proteins and the peptide identified in the present study, which exhibited antimicrobial activity against both Gram-positive and Gram-negative bacteria, were thermostable and showed salt-resistant activity. The antimicrobial properties of histones and histone fragment in chicken provide further evidence that histones, in addition to their role in nucleosome formation, may play an important role in innate host defense against intracellular or extracellular microbe invasion in a wide range of animal species.

The Central Leucine-Rich Repeat Region of Chicken TLR16 Dictates Unique Ligand Specificity and Species-Specific Interaction with TLR2

The ligand specificity of human TLR (hTLR) 2 is determined through the formation of functional heterodimers with either hTLR1 or hTLR6. The chicken carries two TLR (chTLR) 2 isoforms, type 1 and type 2 (chTLR2t1 and chTLR2t2), and one putative TLR1/6/10 homologue (chTLR16) of unknown function. In this study, we report that transfection of HeLa cells with the various chicken receptors yields potent NF-kappaB activation for the receptor combination of chTLR2t2 and chTLR16 only. The sensitivity of this complex was strongly enhanced by human CD14. The functional chTLR16/chTLR2t2 complex responded toward both the hTLR2/6-specific diacylated peptide S-(2,3-bispalmitoyloxypropyl)-Cys-Gly-Asp-Pro-Lys-His-Pro-Lys-Ser-Phe (FSL-1) and the hTLR2/1 specific triacylated peptide tripalmitoyl-S-(bis(palmitoyloxy)propyl)-Cys-Ser-(Lys)(3)-Lys (Pam(3)CSK(4)), indicating that chTLR16 covers the functions of both mammalian TLR1 and TLR6. Dissection of the species specificity of TLR2 and its coreceptors showed functional chTLR16 complex formation with chTLR2t2 but not hTLR2. Conversely, chTLR2t2 did not function in combination with hTLR1 or hTLR6. The use of constructed chimeric receptors in which the defined domains of chTLR16 and hTLR1 or hTLR6 had been exchanged revealed that the transfer of leucine-rich repeats (LRR) 6-16 of chTLR16 into hTLR6 was sufficient to confer dual ligand specificity to the human receptor and to establish species-specific interaction with chTLR2t2. Collectively, our data indicate that diversification of the central LRR region of the TLR2 coreceptors during evolution has put constraints on both their ligand specificity and their ability to form functional complexes with TLR2.

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.

Induction of a novel chicken Toll-like receptor following Salmonella enterica serovar Typhimurium infection

Toll-like receptors (TLRs) are a group of highly conserved molecules that initiate the innate immune response to pathogens by recognizing structural motifs expressed by microbes. We have identified a novel TLR, TLR15, by bioinformatic analysis of the chicken genome, which is distinct from any known vertebrate TLR and thus appears to be avian specific. The gene for TLR15 was sequenced and is found on chromosome 3, and it has archetypal TIR and transmembrane domains and a distinctive arrangement of extracellular leucine-rich regions. mRNA for TLR15 was detected in the spleen, bursa, and bone marrow of healthy chickens, suggesting a role for this novel receptor in constitutive host defense. Following in vivo Salmonella enterica serovar Typhimurium infection, quantitative real-time PCR demonstrated significant upregulation of TLR15 in the cecum of infected chickens. Interestingly, similar induction of TLR2 expression following infection was also observed. In vitro studies revealed TLR15 upregulation in chicken embryonic fibroblasts stimulated with heat-killed S. enterica serovar Typhimurium. Collectively, these results suggest a role for the TLR in avian defense against bacterial infection. We hypothesize that TLR15 may represent an avian-specific TLR that has been either retained in chicken and lost in other taxa or gained in the chicken.

Bioinformatic and expression analysis of novel porcine β-defensins

Beta-defensins are a major group of mammalian antimicrobial peptides. Although more than 30 beta-defensins have been identified in humans, only one porcine beta-defensin has been reported. In this article we report the identification and initial characterization of 11 novel porcine beta-defensins (pBD). Using bioinformatic approaches, we screened 287,821 porcine expressed sequence tags for similarity of their predicted peptides to known human beta-defensins and identified full-length or partial sequences for the 11 novel pBDs. Similar to the previously identified pBD1, all of these peptides have a consensus beta-defensin motif. A differential expression pattern for these newly identified genes was found. For example, unlike most beta-defensins, pBD2 and pBD3 were expressed in bone marrow and in other lymphoid tissues including thymus, spleen, lymph nodes, duodenum, and liver. Including pBD2 and pBD3, six porcine beta-defensins were expressed in lung and skin. Several newly identified porcine beta-defensins, including pBD123, pBD125, and pBD129, were expressed in male reproductive tissues, including lobuli testis and some segments of the epididymis. Phylogenetic analysis indicates that in most cases the evolutionary relationship between individual porcine beta-defensins and their human orthologs is closer than the relationship among beta-defensins in the same species. These findings establish the existence of multiple porcine beta-defensins and suggest that the pig may be an ideal model for the characterization of beta-defensin diversity and function.