Oxidative and nitrosative responses of the chicken macrophage cell line MQ-NCSU to experimentalSalmonellainfection

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.

Antibacterial activity of ZnO quantum dots and its protective effects of chicks infected withSalmonella pullorum

In light of emerging antibiotic resistance, synthesis of active, environmental friendly antimicrobial alternatives becomes increasingly necessary. In this study, ZnO quantum dots (ZnO QDs) were developed by the sol-gel method and characterized. The antibacterial activities of ZnO QDs againstEscherichia coli(E. coli),Staphylococcus aureus(S. aureus) andSalmonella Pullorum(S. Pullorum) were systematically investigated. Moreover, the protective effects of ZnO QDs on Salmonella-caused pullorosis in chicks were also explored. The results indicated that the size range of ZnO QDs was 3-6 nm. Antibacterial results showed that ZnO QDs treatment inhibited the growth ofE. coli,S. aureus, andS. Pullorumin the rate of 87.06 ± 0.98%, 94.75 ± 2.28%, and 85.55 ± 1.15%, respectively. Its excellent antibacterial property was manifested with the minimum inhibitory concentration of 0.7812, 0.0976, and 0.1953 mg ml^-1, which may be attributed to the production of reactive oxygen species, the dissolution of Zn²⁺ions, and the loss of cell integrity. Furthermore, in thein vivotest, the ZnO QDs effectively reduced the mortality of chicks infected withS. Pullorumvia regulating the balance of the intestinal flora, protecting liver and intestine, and modulating the balance of antioxidation systems. This study reveals that ZnO QDs exerts remarkably antibacterial activityin vitroand anti-pullorosis effect in chicks.

Biomimetic hydroxyapatite nanocrystals are an active carrier for Salmonella bacteriophages

PURPOSE

The use of bacteriophages represents a valid alternative to conventional antimicrobial treatments, overcoming the widespread bacterial antibiotic resistance phenomenon. In this work, we evaluated whether biomimetic hydroxyapatite (HA) nanocrystals are able to enhance some properties of bacteriophages. The final goal of this study was to demonstrate that biomimetic HA nanocrystals can be used for bacteriophage delivery in the context of bacterial infections, and contribute - at the same time - to enhance some of the biological properties of the same bacteriophages such as stability, preservation, antimicrobial activity, and so on.

MATERIALS AND METHODS

Phage isolation and characterization were carried out by using Mitomycin C and following double-layer agar technique. The biomimetic HA water suspension was synthesized in order to obtain nanocrystals with plate-like morphology and nanometric dimensions. The interaction of phages with the HA was investigated by dynamic light scattering and Zeta potential analyses. The cytotoxicity and intracellular killing activities of the phage-HA complex were evaluated in human hepatocellular carcinoma HepG2 cells. The bacterial inhibition capacity of the complex was assessed on chicken minced meat samples infected with Salmonella Rissen.

RESULTS

Our data highlighted that the biomimetic HA nanocrystal-bacteriophage complex was more stable and more effective than phages alone in all tested experimental conditions.

CONCLUSION

Our results evidenced the important contribution of biomimetic HA nanocrystals: they act as an excellent carrier for bacteriophage delivery and enhance its biological characteristics. This study confirmed the significant role of the mineral HA when it is complexed with biological entities like bacteriophages, as it has been shown for molecules such as lactoferrin.

Virulence of Salmonella enterica serovar Pullorum isolates compared using cell-based and chicken embryo infection models

To reveal differences in virulence among strains of Salmonella enterica serovar Pullorum (S. Pullorum), we used 2 cell-based infection models and a chicken embryo infection model in this study. S. Pullorum strain S06004 was used to infect 4 different avian cell lines (HD-11, DF-1, LMH, DT-40), and the results showed that the infection of S06004 in both LMH and HD-11 cells was more stable than in DF-1 and DT-40 cells. Therefore, the HD-11 and LMH cell lines were used as the appropriate macrophage and epithelial cell models, respectively, to study the infection of S. Pullorum. Fifty strains isolated during the years 1962 to 2010 were then analyzed to compare their infection rates in HD-11 and LMH cells. The result showed that the infection rates of most strains were very similar to that of S06004, except for S9876 which displayed the highest infection rate among these strains. Based on the cell infection results, 10 strains were selected to be used in the chicken embryo infection model. Sixteen-day-old SPF chicken embryos were infected with the pathogen at a dose of 103 CFU/100 μL via allantoic cavity inoculation. The strains C79-13, 7101, and S06013 caused death of more than 80% embryos, whereas S09C12 and 6703 resulted less than 20% death. Thus, this study established cell-based infection models to screen S. Pullorum strains in vitro, and a chick embryo model to evaluate their in vivo virulence.

Avian pathogenic Escherichia coli-induced activation of chicken macrophage HD11 cells

Avian pathogenic Escherichia coli (APEC) can cause severe respiratory diseases in poultry. The initial interaction between APEC and chicken macrophages has not been characterized well and it is unclear how effective chicken macrophages are in neutralizing APEC. Therefore, the effect of APEC on activation of chicken macrophage HD11 cells was studied. Firstly, the effect of temperature (37 vs 41 °C) on phagocytosis of APEC by HD11 cells was determined. The results showed that APEC was more susceptible to being phagocytosed by HD11 cells at 41 °C than 37 °C. Subsequently, the capacity of HD11 cells to kill APEC was shown. In addition, HD11 cells produced nitric oxide (NO) at 18 h post-infection and a strong increase in the mRNA expression of IL-8, IL-6, IL-1β and IL-10 was detected, while IFN-β gene expression remained unaffected. Finally, it was shown that the response of HD11 was partially dependent on viability of APEC since stimulation of HD11 cells with heat-killed APEC resulted in a reduced expression level of these cytokines. In conclusion, APEC induces an effector response in chicken macrophages by enhanced NO production and cytokines gene expression.

Salmonella enterica in the Chicken: How it has Helped Our Understanding of Immunology in a Non-Biomedical Model Species

Salmonella infection of the chicken is important both as a source of foodborne human salmonellosis and as a source of disease in the chicken itself. Vaccination and other control strategies require an understanding of the immune response and as such have been important in understanding both mucosal immunity and more generally the response to bacterial infection. In this review, we discuss the contribution the study of avian salmonellosis has made to understanding innate immunity including the function of phagocytic cells, pattern recognition receptors, and defensins. The mucosal response to Salmonella infection and its regulation and the contribution this makes in protection against infection and persistence within the gut and future directions in better understanding the role of TH17 and Tregs in this response. Finally, we discuss the role of the immune system and its modulation in persistent infection and infection of the reproductive tract. We also outline key areas of research required to fully understand the interaction between the chicken immune system and Salmonella and how infection is maintained in the absence of substantive gastrointestinal disease.

Cytokines Expression and Nitric Oxide Production under Induced Infection to Salmonella Typhimurium in Chicken Lines Divergently Selected for Cutaneous Hypersensitivity

In the present study, the impact of Salmonella Typhimurium on cell-mediated immunity (CMI) was investigated in 5 week-old immuno divergent broiler lines selected for the high and low response to phytohemagglutinin-P. The immune response was assessed in peripheral-blood mononuclear cells (PBMCs) induced with Salmonella Typhimurium at different time intervals (0 h, 0.5 h, 2 h, 4 h, 6 h, 12 h and 24 h). The differential mRNA expression patterns of IFN-γ, IL-2 and iNOS were evaluated by quantitative real time PCR. In-vitro production of nitric oxide (NO) was also estimated in the culture supernatant and correlated with iNOS mRNA expression. Present study showed higher production of NO in the high cell-mediated line (HCMI) as compared to the low cell-mediated line (LCMI) upon stimulation with Salmonella Typhimurium. Correspondingly, higher mRNA expression of iNOS and IFN-γ were observed in high response birds (HCMI); but IL-2 was down regulated in this line compared to the low response birds (LCMI). Significantly (p<0.05) higher expression of iNOS, IFN-γ and higher production of NO in high line indicated that the selection for PHA-P response might be employed for increasing the immune competence against Salmonella Typhimurium in chicken flocks.

Influence of bacteriophage P22 on the inflammatory mediator gene expression in chicken macrophage HD11 cells infected with Salmonella Typhimurium

This study was designed to evaluate the effects of bacteriophage on the intracellular survival and immune mediator gene expression in chicken macrophage-like HD11 cells. The invasive ability and intracellular survival of Salmonella Typhimurium (ST(P22-) ) and lysogenic S. Typhimurium (ST(P22+) ) in HD11 cells were evaluated at 37 °C for 24 h postinfection (hpi). The expression of inflammatory mediator genes was determined in ST(P22-) - and ST(P22+) -infected HD11 cells treated with and without bacteriophage P22 at 1 and 24 hpi using quantitative RT-PCR. The ability of ST(P22-) and ST(P22+) to invade HD11 cells was significantly decreased by bacteriophage P22 at 1 hpi. The numbers of intracellular ST(P22-) and ST(P22+) were significantly decreased from 2.39 to 1.62 CFU cm(-2) and from 3.40 to 1.72 CFU cm(-2) in HD11 cells treated with bacteriophage P22, respectively, at 24 hpi. The enhanced expression of inflammatory mediators was observed in ST(P22-) - and ST(P22+) -infected HD11 cells treated with and without bacteriophage P22. These results suggest that the application of bacteriophage could be an effective way to control the intracellular infection.

Immunity to bacterial infection in the chicken

Bacterial infections remain important to the poultry industry both in terms of animal and public health, the latter due to the importance of poultry as a source of foodborne bacterial zoonoses such as Salmonella and Campylobacter. As such, much focus of research to the immune response to bacterial infection has been to Salmonella. In this review we will focus on how research on avian salmonellosis has developed our understanding of immunity to bacteria in the chicken from understanding the role of TLRs in recognition of bacterial pathogens, through the role of heterophils, macrophages and γδ lymphocytes in innate immunity and activation of adaptive responses to the role of cellular and humoral immunity in immune clearance and protection. What is known of the immune response to other bacterial infections and in particular infections that have emerged recently as major problems in poultry production including Campylobacter jejuni, Avian Pathogenic Escherichia coli, Ornithobacterium rhinotracheale and Clostridium perfringens are discussed.

Nitric oxide as a biomarker of intracellular Salmonella viability and identification of the bacteriostatic activity of protein kinase A inhibitor H-89

Salmonella enterica serovar Enteritidis is one of the most prevalent Salmonella serovars in poultry and is often associated with human salmonellosis. S. Enteritidis is known to suppress nitric oxide (NO) production in infected chicken macrophage HD11 cells, while dead S. Enteritidis stimulates a high level of NO production, suggesting a bacterial inhibitory effect on NO production. Based on these observations, the present study was conducted to evaluate whether NO production in S. Enteritidis-infected HD11 cells can be used as a biomarker to identify molecules that kill intracellular Salmonella. Since Salmonella are known to manipulate the host cell kinase network to facilitate intracellular survival, we screened a group of pharmaceutical inhibitors of various kinases to test our hypothesis. A protein kinase A inhibitor, H-89, was found to reverse the suppression of NO production in S. Enteritidis-infected HD11 cells. Production of NO in S. Enteritidis-infected HD11 cells increased significantly following treatment with H-89 at or above 20 µM. Inversely, the number of viable intracellular Salmonella decreased significantly in cells treated with H-89 at or above 30 µM. Furthermore, the growth rate of S. Enteritidis in culture was significantly inhibited by H-89 at concentrations from 20 to 100 µM. Our results demonstrate that NO-based screening using S. Enteritidis-infected HD11 cells is a viable tool to identify chemicals with anti-intracellular Salmonella activity. Using this method, we have shown H-89 has bacteriostatic activity against Salmonella, independent of host cell protein kinase A or Akt1 activity.

A comparative study on invasion, survival, modulation of oxidative burst, and nitric oxide responses of macrophages (HD11), and systemic infection in chickens by prevalent poultry Salmonella serovars

Poultry is a major reservoir for foodborne Salmonella serovars. Salmonella Typhimurium, Salmonella Enteritidis, Salmonella Heidelberg, Salmonella Kentucky, and Salmonella Senftenberg are the most prevalent serovars in U.S. poultry. Information concerning the interactions between different Salmonella species and host cells in poultry is lacking. In the present study, the above mentioned Salmonella serovars were examined for invasion, intracellular survival, and their ability to modulate oxidative burst and nitric oxide (NO) responses in chicken macrophage HD11 cells. All Salmonella serovars demonstrated similar capacity to invade HD11 cells. At 24 h post-infection, a 36-43% reduction of intracellular bacteria, in log(10)(CFU), was observed for Salmonella Typhimurium, Salmonella Heidelberg, Salmonella Kentucky, and Salmonella Senftenberg, whereas a significantly lower reduction (16%) was observed for Salmonella Enteritidis, indicating its higher resistance to the killing by HD11 cells. Production of NO was completely diminished in HD11 cells infected with Salmonella Typhimurium and Salmonella Enteritidis, but remained intact when infected with Salmonella Heidelberg, Salmonella Kentucky, and Salmonella Senftenberg. Phorbol myristate acetate-stimulated oxidative burst in HD11 cells was greatly impaired after infection by each of the five serovars. When newly hatched chickens were challenged orally, a high rate (86-98%) of systemic infection (Salmonella positive in liver/spleen) was observed in birds challenged with Salmonella Typhimurium, Salmonella Enteritidis, Salmonella Heidelberg, and Salmonella Kentucky, while only 14% of the birds were Salmonella Senftenberg positive. However, there was no direct correlation between systemic infection and in vitro differential intracellular survival and modulation of NO response among the tested serovars.

Effects of fructooligosaccharide-inulin on Salmonella-killing and inflammatory gene expression in chicken macrophages

Salmonella Enteritidis (SE) is one of the leading causes of food-borne salmonellosis, and macrophages play an essential role in eliminating this pathogen. Among the interventions to improve Salmonella clearance in chickens are the use of prebiotics and direct fed microbials (DFM) in animal feed as they have immunomodulatory effects. Therefore, we tested the influence of a prebiotic fructooligosaccharide (FOS)-inulin on the ability of the chicken macrophage HD11 cell line to phagocytose and kill SE, and express selected inflammatory cytokines and chemokines in an in vitro model. There were significantly fewer viable intracellular SE in HD11 cells treated with FOS-inulin than the untreated cells. However, SE phagocytosis, nitric oxide expression or production were not influenced by the prebiotic treatment. Among the inflammatory markers tested, IL-1β expression was significantly lower in HD11 cells treated with FOS-inulin. These results suggest that FOS-inulin has the ability to modulate the innate immune system as shown by the enhanced killing of SE and decreased inflammasome activation.

Heterogeneity of persistence of Salmonella enterica serotype Senftenberg strains could explain the emergence of this serotype in poultry flocks

Salmonella enterica serotype Senftenberg (S. Senftenberg) has recently become more frequent in poultry flocks. Moreover some strains have been implicated in severe clinical cases. To explain the causes of this emergence in farm animals, 134 S. Senftenberg isolates from hatcheries, poultry farms and human clinical cases were analyzed. Persistent and non-persistent strains were identified in chicks. The non-persistent strains disappeared from ceca a few weeks post inoculation. This lack of persistence could be related to the disappearance of this serotype from poultry farms in the past. In contrast, persistent S. Senftenberg strains induced an intestinal asymptomatic carrier state in chicks similar to S. Enteritidis, but a weaker systemic infection than S. Enteritidis in chicks and mice. An in vitro analysis showed that the low infectivity of S. Senftenberg is in part related to its low capacity to invade enterocytes and thus to translocate the intestinal barrier. The higher capacity of persistent than non-persistent strains to colonize and persist in the ceca of chickens could explain the increased persistence of S. Senftenberg in poultry flocks. This trait might thus present a human health risk as these bacteria could be present in animals before slaughter and during food processing.

Salmonella Enteritidis strains from poultry exhibit differential responses to acid stress, oxidative stress, and survival in the egg albumen

Salmonella Enteritidis is the major foodborne pathogen that is primarily transmitted by contaminated chicken meat and eggs. We recently demonstrated that Salmonella Enteritidis strains from poultry differ in their ability to invade human intestinal cells and cause disease in orally challenged mice. Here we hypothesized that the differential virulence of Salmonella Enteritidis strains is due to the differential fitness in the adverse environments that may be encountered during infection in the host. The responses of a panel of six Salmonella Enteritidis strains to acid stress, oxidative stress, survival in egg albumen, and the ability to cause infection in chickens were analyzed. This analysis allowed classification of strains into two categories, stress-sensitive and stress-resistant, with the former showing significantly (p<0.05) reduced survival in acidic (gastric phase of infection) and oxidative (intestinal and systemic phase of infection) stress. Stress-sensitive strains also showed impaired intestinal colonization and systemic dissemination in orally inoculated chickens and failed to survive/grow in egg albumen. Comparative genomic hybridization microarray analysis revealed no differences at the discriminatory level of the whole gene content between stress-sensitive and stress-resistant strains. However, sequencing of rpoS, a stress-regulatory gene, revealed that one of the three stress-sensitive strains carried an insertion mutation in the rpoS resulting in truncation of σ(S). Finding that one of the stress-sensitive strains carried an easily identifiable small polymorphism within a stress-response gene suggests that the other strains may also have small polymorphisms elsewhere in the genome, which likely impact regulation of stress or virulence associated genes in some manner.

β 1-4 mannobiose enhances Salmonella-killing activity and activates innate immune responses in chicken macrophages

Salmonella spp. is one of the major causes of food-borne illness in humans, and Salmonella enteritidis (SE) infection in commercial poultry is a world-wide problem. Here we have investigated the in vitro immune-modulating effects of β 1-4 mannobiose (MNB), which was previously found to prevent SE infection in vivo in chickens, using chicken macrophage (MQ-MCSU) cells. Treatment of MQ-NCSU cells with MNB dose-dependently increased both phagocytic activity and Salmonella-killing activity of macrophages, with the highest reduction in SE viability observed at a concentration of 40 μg/ml at 48 h post-infection. Likewise, both hydrogen peroxide (H(2)O(2)) and nitric oxide (NO) production were increased in a dose-dependent manner by MNB. Gene expression analysis of MNB-treated macrophages revealed significant increases in the expression of iNOS, NOX-1, IFN-γ, NRAMP1, and LITAF, genes critical for host defense and antimicrobial activity, when compared to untreated cells. This data confirms that MNB possesses potent innate immune-modulating activities and can up-regulate antibacterial defenses in chicken macrophages.

Effects of methyltestosterone on immunity against Salmonella Pullorum in dwarf chicks

This study was conducted to determine effects of methyltestosterone on innate immunity and adaptive immunity against Salmonella Pullorum in dwarf chicks. In vivo experiment, comparisons of pathological sections, viable counts of bacteria, specific antibody levels, and subsets of T lymphocytes were set forth between chicks with or without 10(-7) M methyltestosterone treatment (2 d of age through 21 d of age) and challenged with 5 x 10(8) virulent Salmonella Pullorum (7 d of age), and in vitro experiment, phagocytic and killing abilities, reactive oxygen intermediate production, and reactive nitrogen intermediate production of monocytes-macrophages treated with high (10(-8) M/10(6) cell) or physiological (10(-14) M/10(6) cell) concentration of methyltestosterone were examined after Salmonella Pullorum infection. The results showed that (1) in vivo, administration of methyltestosterone enhanced susceptibility to Salmonella Pullorum infection and depressed cellular immunity against Salmonella Pullorum, whereas it had no effect on humoral immunity in dwarf chicks; (2) in vitro, at high concentration, methyltestosterone reduced (P < 0.05) monocytes-macrophages mediated reactive oxygen intermediate-dependent killing of Salmonella Pullorum, whereas low concentration of methyltestosterone enhanced (P < 0.05) reactive oxygen intermediate-dependent killing of Salmonella Pullorum in male dwarf chicks but not in females; and (3) although challenged with Salmonella Pullorum, phagocytic ability and monocytes-macrophages mediated reactive nitrogen intermediate-dependent killing were not affected by methyltestosterone in vitro. The results indicated that methyltestosterone affected the immune response to Salmonella Pullorum in dwarf chicks by changing monocytes-macrophages mediated reactive oxygen intermediate-dependent killing and cellular immunity, and the effects were dose-dependent; furthermore, the former 2 pathways played important roles in preventing Salmonella Pullorum infection in dwarf chicks, although the mechanism needs further study.

Effect of long chain fatty acids on Salmonella killing, superoxide and nitric oxide production by chicken macrophages

The objective of this study was to investigate the effect of uptake of different commonly consumed long chain fatty acids on superoxide (O(2)(-)), nitric oxide (NO) production, and ability to kill Salmonella enterica serotype typhimurium (S. typhimurium) by chicken macrophages (HD11 cells). All the fatty acids were taken up by HD11 cells with stearic acid uptake higher than polyunsaturated fatty acids. Uptake of green fluorescent protein-labeled bacteria and the viability of HD11 cells (measured by flow cytometry) was not affected by any of the fatty acids tested. Bacterial clearance (measured by the plating of sorted viable infected cells) was significantly higher with n-3 fatty acids alpha-linolenic acid (ALA) and docosahexanoic acid (DHA). However, stearic acid (SA) and the n-6 fatty acid, arachidonic acid (ARA) did not influence S. typhimurium killing by HD11 cells. The improved S. typhimurium clearance by ALA and DHA was not associated with increased NO or O(2)(-) production by HD11 cells. These results suggest a role for n-3 polyunsaturated fatty acids in Salmonella clearance by chicken macrophages however in vivo studies are essential to confirm their efficacy in controlling Salmonella infection in chickens and contamination in shell eggs.

Reduced nitric oxide production and iNOS mRNA expression in IFN-gamma-stimulated chicken macrophages transfected with iNOS siRNAs

Utilizing RNA interference technology with siRNA in the HD11 macrophage cell line, we determined how the inhibition or knock-down of the iNOS (inducible nitric oxide synthase) gene affected IFN-gamma-induced macrophage production of nitric oxide (NO) and mRNA expression of genes involved in this biological pathway in the chicken. Chicken macrophages produce NO when stimulated with recombinant chicken IFN-gamma, however, when transfected with iNOS siRNAs, the production of NO is significantly decreased. We observed a 14-28% reduction in NO production by IFN-gamma-stimulated HD11 cells at 48h after initial siRNA transfection compared to non-transfected IFN-gamma-stimulated macrophages. Significant knock-down of iNOS mRNA expression (15 to 50-fold lower) was observed for each of four iNOS siRNAs, when compared to non-transfected IFN-gamma-stimulated macrophages and to those treated with a negative control siRNA. The IFN-gamma-stimulated chicken macrophages transfected with iNOS siRNAs did not show altered levels of mRNA expression for genes involved in IFN-gamma signaling and iNOS pathways (IL-1beta, IL-6, IFN-gamma, TGF-beta4, or SOCS-3) suggesting that the observed decrease in NO production is a direct result of siRNA mediated knock-down of iNOS, rather than IFN-gamma-induced changes in the other genes tested.

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.

Changes in Tissue Nitrite Concentration in the Crop of the Turkey Poult in Response to Salmonella Typhimurium Challenge

The present study examines whether Salmonella typhimurium colonization of the crop of young turkeys influences nitrite concentration in the component tissues of the crop. Nitric oxide (NO) is the principal compound in biological samples that is converted into nitrites and NO is known to be a component of the early host response to infection. Challenge with S. typhimurium increased the concentration of nitrite in the crop wall of 3-wk-old turkey poults. The magnitude of the response was reduced at 8 h and absent at 48 h after challenge. As would be expected, S. typhimurium concentrations in the crop were markedly increased following challenge, and were nondetectable in control poults.