Cold stress equally enhances in vivo pro-inflammatory cytokine gene expression in chicken lines divergently selected for antibody responses

Leukocyte transcriptome from chickens infected with avian pathogenic Escherichia coli identifies pathways associated with resistance

Avian pathogenic Escherichia coli (APEC) causes colibacillosis, which is responsible for morbidity and mortality in chickens. Gene expression patterns have previously been demonstrated to differ between chicken populations that are resistant vs. susceptible to bacterial infection, but little is currently known about gene expression response to APEC. Increased understanding of gene expression patterns associated with resistance will facilitate genetic selection to increase resistance to APEC. Male broiler chicks were vaccinated at 2 weeks of age and challenged with APEC at 4 weeks of age. Peripheral blood leukocytes were collected at 1 and 5 day post-infection. Lesions on the liver, pericardium, and air sacs were used to assign a mild or severe pathology status to non-vaccinated, challenged chicks. Ten treatment groups were therefore generated with a priori factors of vaccination, challenge, day post-infection, and the a posteriori factor of pathology status. Global transcriptomic response was evaluated using the Agilent 44K chicken microarray. APEC infection resulted in more up-regulation than down-regulation of differentially expressed genes. Immune response and metabolic processes were enriched with differentially expressed genes. Although vaccination significantly reduced lesions in challenged bird, there was no detectable effect of vaccination on gene expression. This study investigated the transcriptomic differences in host responses associated with mild vs. severe pathology, in addition to the effects of vaccination and challenge, thus revealing genes and networks associated with response to APEC and providing a foundation for future studies on, and genetic selection for, genetic resistance to APEC.

Abundance of IFN-α and IFN-γ gene transcripts and absence of IL-2 transcripts in the blood of chickens vaccinated with live or inactivated NDV

As immune responses to live and inactivated vaccines might differ, temporal responses of broiler chickens to vaccination were examined on the basis of the abundance in the circulating blood of gene transcripts of IFN-α, IFN-γ and IL-2, critical cytokines for immune responses. Blood samples were collected 6, 12 and 24 hours, and 7 and 14 days following vaccination with either live or inactivated Newcastle disease virus, La Sota strain, at 14 days of age, and the abundance of transcripts for each cytokine was assayed by real-time RT-PCR. Physiological saline and vaccine emulsion without viral antigen were administered to control groups for live and inactivated vaccine groups, respectively. The abundance of IFN-γ transcripts was elevated during the early times following vaccination and had reached baseline by the seventh day but the abundance of IFN-α transcripts remained elevated. Transcripts for neither IFN gene were detected in the control birds. The abundance of transcripts for each IFN was not different between the two vaccinated groups at any time. Transcripts for IL-2 were detected only in spleens from chicken embryos that had been inoculated with the live virus. The results show that cells stimulated to produce IFN-α and IFN-γ enter the circulating blood but those stimulated to produce IL-2 do not, or in very low number, and the IFN responses to both vaccines are the same.

Characterization of the immunological response to Dermanyssus gallinae infestation in domestic fowl

Dermanyssus gallinae is a haematophagous ectoparasite of birds, which adversely affects both production and welfare of commercial poultry. Poultry in commercial production systems chronically exposed to D. gallinae do not appear to develop immunity to the mite. The objective of the current study was to determine the initial immune response of domestic fowl following exposure to D. gallinae. Two groups of birds (11 birds/group) had mite chambers secured to their backs. Controls received no mites, while infested birds received 200 unfed female D. gallinae on day 0 which were then removed on day 1 or 2. Spleen samples were collected on days -1, 1, 2 and 5. The expression of Th1 (IFNgamma, CXCLi2, IL6 and IL18), Th2 (IL4, IL10 and IL13) cytokines/chemokines normalized against a reference gene, GAPDH, were determined by semi-quantitative RT-PCR. Although there were no significant differences between treatments, numerical trends were observed. Th2 cytokine expression was not detected in any birds on any day. IL6, CXCLi2, IFNgamma and IL18 expression was increased on day 1 in the infested group, while on day 2 CXCLi2 and IFNgamma were lower and IL6 and IL18 levels were similar between treatments. The IL18 expression was similar between treatments on day 5, while IL6 and IFNgamma levels were increased and CXCLi2 expression was decreased in the infested group. Data suggest that D. gallinae feeding stimulates Th1 and pro-inflammatory cytokines/chemokines initially (day 1) followed by their subsequent down regulation. This study is the first report of the characterization of the immunological response of the domestic fowl to controlled numbers of D. gallinae.

Modulating effects of calcium on immune response of homoiothermal animal under thermoneutral conditions and during deep cooling

Preliminary ionophoretic administration of Ca(2+) ions into the skin prevents the inhibitory effects of deep cooling on some processes characterizing the immune response. Differently directed changes in some immune response parameters induced by exogenous calcium and deep cooling suggest that competitive interactions between calcium-dependent processes can serve as mechanisms of functional changes in various physiological systems during the formation of the systemic reaction of a homoiothermal organism to cold.

Understanding stress-induced immunosuppression: exploration of cytokine and chemokine gene profiles in chicken peripheral leukocytes

At present, the poultry meat and egg industry has gained a lot of ground, being viewed as a provider of a healthy alternative to red meat and other protein sources. If this trend is to be maintained, solutions must be found to improve resistance of chickens to disease, which often is weakened by stressful conditions. In poultry, stress-induced immunosuppression is manifested by failures in vaccination and increased morbidity and mortality of flocks. Currently, several modern cellular and molecular approaches are being used to explore the status of the immune system during stress and disease. It is likely that these new techniques will lead to the development of new strategies for preventing and controlling immunosuppression in poultry. Using quantitative reverse transcription-PCR assays, a broad spectrum of cytokine, chemokine, and their receptor genes can be quantified in birds and then be used as markers to assess the effects of stress on the immune system. Currently, we are investigating immune and endocrine interactions in the chicken, in particular the cells and molecules that are known to be involved in such interactions in mammals. We have evaluated the effects of corticosterone administration in drinking water on peripheral lymphocyte and heterophil cytokine and chemokine gene profiles. In particular, there seems to be effects on cytokine and chemokine mRNA expression levels in both lymphocytes and heterophils, especially expression of the proinflammatory cytokines interleukin (IL)-1beta, IL-6, and IL-18 and chemokines C-C motif, ligand 1 inflammatory (CCLi1); C-C motif, ligand 2 inflammatory (CCLi2); C-C motif, ligand 5 (CCL5); C-C motif, ligand 16 (CCL16); C-X-C motif ligand 1 inflammatory (CXCLi1); and C-X-C motif ligand 2 inflammatory (CXCLi2), which are initially upregulated and are potentially involved in modulating the adaptive immune response. A chronic treatment with corticosterone downregulates proinflammatory cytokines and chemokines, suggesting that the delayed effects of chronic stress can suppress the immune response. Messenger RNA expression levels of transforming growth factor-beta4 (TGF-beta4) are also upregulated in cortisosterone-treated birds. It appears that the balance between T-helper (Th) 1 and Th2/T regulatory cytokine production is altered in conditions associated with significant changes in plasma corticosterone concentration. Experiments are underway to decipher the cytokine and chemokine responses to vaccination and bacterial challenge on the background of stress-induced immunosuppression.

Cytokine and chemokine gene expression profiles in heterophils from chickens treated with corticosterone

In chickens, corticosterone is the end-product of stress. However, the nature of the immune response to elevated plasma corticosterone concentrations at the molecular level has not yet been characterised. We recently demonstrated that exposure to corticosterone in drinking water for 1 week significantly upregulates mRNA expression levels for the pro-inflammatory interleukins (IL)-1beta, IL-6, IL-18 and the pro-inflammatory chemokine CCLi2 in chicken lymphocytes, particularly 3 h after the treatment started. In the present study, we investigated cytokine and chemokine mRNA expression levels in circulating heterophils of chickens, and show that at 3 h post initial treatment with corticosterone in drinking water (20 mg/1L) the mRNA expression levels for IL-1beta, IL-6, IL-10, IL-12alpha and IL-18 are upregulated. The mRNA expression levels for IL-6, IL-10 and IL-18 correlate with plasma corticosterone concentration and total heterophil counts. Corticosterone downregulated the expression levels of all pro-inflammatory cytokines at 24 h and 1 week post-treatments. Repeated treatment with corticosterone upregulated mRNA expression levels of transforming growth factor-beta4 and the chemokine CCL16. These data indicate that cytokine and chemokine gene expression signatures in chicken heterophils can be altered during stress and therefore could be used as an indicator of stress.

The effect of adrenomedullin and cold stress on interleukin-6 levels in some rat tissues

Stress known to stimulate sympathetic activity, as well as the hypothalamic-pituitary-adrenal axis (HPA), produces a significant increase in adrenomedullin (AdM) levels, suggesting a regulatory or protective role for AdM in countering HPA activation that follows a variety of stressors. Stressors can modulate the secretion of proinflammatory cytokines. Interleukin (IL)-6 is a potent activator of the HPA and appears to play a pathogenic role in conditions related to stress. In the present study, we investigated the administration of AdM on IL-6 levels in cold exposed rats. Male Wistar rats were divided into four groups as control, adrenomedullin treatment, cold stress and cold stress+adrenomedullin-treated groups. In the adrenomedullin-treated group, animals received intraperitoneal (i.p.) injection of adrenomedullin (2000 ng/kg body weight) once a day for a week. For the cold stress exposure the rats were kept in separate cages at 10 degrees C for a week. Control group rats were kept in laboratory conditions. The concentration of IL-6 was determined using an enzyme-linked immunosorbent assay (ELISA) kit. When compared to control, IL-6 levels increased significantly in the cold stress- and adrenomedullin-treated groups (P<0.05). Administration of AdM in addition to cold stress decreased IL-6 levels in lung and liver, but increased in brain and heart when compared to control (P<0.05). The results suggest that cold stress may induce increase of rat proinflammatory cytokine IL-6 and adrenomedullin may play a regulatory or protective role for cold stress.

Immune responses of the domestic fowl to Dermanyssus gallinae under laboratory conditions

There appear to be few reports in the literature regarding the host-poultry red mite (Dermanyssus gallinae) immunological relationship, despite the negative impact D. gallinae can have on both bird welfare and egg production, as well as its potential to act as a reservoir of zoonotic infections. The current study investigated the effect of either continuous infestation (CI) for 22 days or repeated infestation (RI) for four 24-h periods 7 days apart with D. gallinae on humoral immunity (IgM and IgY) and Th1/Th2 cytokine mRNA expression in peripheral blood mononuclear cells (PBMC) compared to non-infested controls. Serum IgY levels and IgM concentration were significantly higher in CI than RI and control birds although Th1 and Th2 mRNA expression in PBMC did not differ significantly between groups. D. gallinae appeared to modify reproductive behaviour and progeny survival following successive feeding events. In the RI group, the proportion of eggs/mite was significantly higher (P < 0.05) after first infestation than later infestations while larval/nymphal mortality was significantly higher (P < 0.05) after the first two infestations than later infestations. These data suggest that D. gallinae might adopt a feeding strategy of minimal host interference while D. gallinae could determine host immune status via nymphal/larval survival rates. Further research is required to better understand the host immunomodulation or avoidance strategy of D. gallinae as well as whether the mite is able to determine host immunocompetence perhaps using progeny survival.

Effects of cold stress on the messenger ribonucleic acid levels of peroxisome proliferator-activated receptor-{gamma} in spleen, thymus, and bursa of Fabricius of chickens

This study was to investigate the expression trait of the peroxisome proliferator-activated receptor-gamma (PPAR-gamma) gene and the effect of cold stress on the mRNA levels of PPAR-gamma in spleen, thymus, and bursa of Fabricius of chickens. Eighty-four 1-d-old male chickens were randomly allocated to 12 groups (7 chickens per group). There was 1 control group and 5 treatment groups for acute cold stress and 3 control groups and 3 treatment groups for chronic cold stress. Chickens were maintained in our animal facility, kept under a 16L:8D cycle and temperature (30 +/- 2 degrees C), and given free access to standard chow and water. The cold stress was initiated when the birds were 15 d of age, with the duration of the acute cold stress being 1, 3, 6, 12, and 24 h, and the chronic cold stress was 5, 10, and 20 d, respectively. Cold stress temperature was 12 +/- 1 degrees C. Spleen, thymus, and bursa of Fabricius were collected for the assessment of the mRNA levels by real-time PCR after stress termination. The results showed that the PPAR-gamma gene is expressed in spleen, thymus, and bursa of Fabricius, and its expression level is different in different tissues and at different ages. Acute cold stress significantly decreased (P < 0.05) the mRNA levels of the PPAR-gamma gene of spleen and thymus in all treatment groups and significantly increased (P < 0.05) the mRNA levels of the PPAR-gamma gene of bursa of Fabricius in all treatment groups. Compared with the corresponding control groups, chronic cold stress resulted in a significant increase (P < 0.05) of the mRNA levels of the PPAR-gamma gene in spleen and a significant decrease (P < 0.05) of the mRNA levels of the PPAR-gamma gene in thymus and bursa of Fabricius. The results indicate that the PPAR-gamma gene is expressed in all 3 immune organs and has different expression traits. The magnitude and direction of change in PPAR-gamma gene expression differs with the type of cold stress applied and also varies by tissue.

Hypothermia augments NF-kappaB activity and the production of IL-12 and IFN-gamma

BACKGROUND

The differentiation of Th1 and Th2 is strictly regulated by humoral and cellular factors. The imbalance between Th1 and Th2 is considered to be the pathogenesis of allergic and autoimmune disorders. It is important to elucidate the effect of environmental factors, such as temperature, on the expression of cytokines of Th1 and Th2.

METHODS

We investigated the expression of IFN-gamma, IL-4, IL-5, IL-10 and IL-12 from LPS- or PHA-stimulated PBMCs at 30 degrees C or 37 degrees C using ELISA and Real-time PCR. We measured the change of NF-kappaB activity at 30 degrees C or 37 degrees C with LPS stimulation using the reporter gene assay.

RESULTS

IFN-gamma production from LPS-stimulated PBMCs at 30 degrees C was up-regulated compared with 37 degrees C. IL-5 and IL-10 production from PHA-stimulated PBMCs at 30 degrees C were down-regulated compared with 37 degrees C. This augmented IFN-gamma production was caused by the up-regulation of IL-12 production from CD14+ blood monocytes. Both IL-12 mRNA and IL12 protein at 30 degrees C were up-regulated compared with 37 degrees C. NF-kappaB, the key molecule for the expression of IL-12, was also augmented at 30 degrees C compared with 37 degrees C.

CONCLUSIONS

Hypothermia up-regulated the expression of IL-12 and IFN-gamma due to the augmented NF-kappaB activity. It is suggested that hypothermia modifies the pattern of cytokine gene expression.

Differential alterations in ultrastructural morphology of chicken heterophils and lymphocytes induced by corticosterone and lipopolysaccharide

Birds are continuously confronted by a large number of stressors, including pathogens. Despite their variety, all stressors induce an elevation in plasma corticosterone concentration, and consequently increase heterophil to leukocyte (H/L) ratio. In order to evaluate and differentiate effects of endocrine (non-bacterial) and bacterial stress on the proportions and ultrastructural characteristics of chicken leukocytes, a series of experiments were conducted with seven-week old chickens exposed either to dietary corticosterone or to intravenous (i.v.)-injected lipopolysaccharide (LPS). Samples were taken for haematological, endocrine, and electron microscopy examination. Administration of corticosterone and LPS significantly elevated plasma corticosterone concentrations and increased H/L ratios. Electron microscopy observations indicated changes in heterophil size, shape, and granulation, and lymphocyte cytoplasmic characteristics. Immature heterophils were observed in the peripheral blood, suggesting that corticosterone and LPS both stimulate an earlier release of heterophils from bone marrow and enhance their influx into blood circulation. The LPS induced a degenerative morphology and the destruction of lymphocytes, whereas corticosterone appeared to stimulate their redistribution rather than destruction. The results indicate that exposure to corticosterone or LPS similarly increase H/L ratios, but differentially alter the ultrastructure of heterophils and lymphocytes. Elucidation of the mechanisms that cause such changes may play an important role in distinguishing between a nonimmune and immune stress challenge at the molecular level.

The effect of compound nutrients on stress-induced changes in serum IL-2, IL-6 and TNF-alpha levels in rats

The effect of compound nutrients on serum concentrations of the cytokines, such as interleukin (IL)-2, tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-6 in immobilization and cold water-immersion stressed rat were investigated. Oral (gavage) administration of compound nutrients was found to attenuate the acute and chronic immobilization and cold water-immersion stress-induced increase in serum IL-6 level and decrease in IL-2 level. Compound nutrients exerted different effects on TNF-alpha level in two different models studied, with reduced serum TNF-alpha level in acute stress, while no significant effect in chronic stress. These results suggested that compound nutrients might be proposed as a possible candidate in the research or therapeutic modulation of stress-related disorders.

Influence of Hen Age on the Response of Turkey Poults to Cold Stress, Escherichia coli Challenge, and Treatment with a Yeast Extract Antibiotic Alternative

Two battery experiments were conducted to evaluate a commercial yeast extract feed supplement, Alphamune, in a cold stress-Escherichia coli challenge of 1-wk-old turkeys. Experiment 1 used 1-d-old male poults that were the progeny of 33-wk-old hens in their second week of lay. Experiment 2 used male poults of the same genetic line from 40-wk-old hens in their eighth week of lay. Poults were fed a standard unmedicated turkey starter diet or the same diet with either a low level (504 g/t) or a high level (1,008 g/t) of yeast extract. Challenged birds were exposed to intermittent cold stress during wk 1 to 3 and to a respiratory E. coli challenge at 1 wk of age. In both experiments, BW at wk 1 was increased by feeding yeast extract. In experiment 1, challenged, control-fed birds had decreased BW at wk 3 and feed conversion was protected by both levels of yeast extract supplementation. In experiment 2, challenge had no effect on control-fed birds; however, yeast extract decreased the BW of challenged birds. In experiment 1, total leukocyte numbers were decreased by challenge of control-fed birds only, and there was no effect of challenge on the heterophil/lymphocyte ratio. In experiment 2, total leukocyte numbers were decreased and the heterophil/lymphocyte ratio was increased in challenged, control-fed birds. Percentage mortality was not affected by challenge in experiment 1; however, in experiment 2, mortality was increased by challenge of control-fed birds and those fed the lower level of yeast extract. These results suggest that hen age should be considered when designing studies to evaluate antibiotic alternatives and in making decisions for incorporating such alternatives into production.

Temperature drops and the onset of severe avian influenza A H5N1 virus outbreaks

Global influenza surveillance is one of the most effective strategies for containing outbreaks and preparing for a possible pandemic influenza. Since the end of 2003, highly pathogenic avian influenza viruses (HPAI) H5N1 have caused many outbreaks in poultries and wild birds from East Asia and have spread to at least 48 countries. For such a fast and wide-spreading virulent pathogen, prediction based on changes of micro- and macro-environment has rarely been evaluated. In this study, we are developing a new climatic approach by investigating the conditions that occurred before the H5N1 avian influenza outbreaks for early predicting future HPAI outbreaks and preventing pandemic disasters. The results show a temperature drop shortly before these outbreaks in birds in each of the Eurasian regions stricken in 2005 and 2006. Dust storms, like those that struck near China's Lake Qinghai around May 4, 2005, exacerbated the spread of this HPAI H5N1 virus, causing the deaths of a record number of wild birds and triggering the subsequent spread of H5N1. Weather monitoring could play an important role in the early warning of outbreaks of this potentially dangerous virus.

Cytokines in reproductive remodeling of molting White Leghorn hens

The role of cytokines in regression of the ovary and oviduct during induced molting in chickens was investigated by evaluating the expressions of IL-1beta, IL-6, IFN-gamma, IL-2, TGF-beta2, MIP-1beta and IL-8 in the regressing ovary and oviduct by semi-quantitative RT-PCR. In addition, serum hormonal profiles (estrogen, progesterone and corticosterone), along with the gross regression and histological changes of the ovary and oviduct, were investigated. The correlation between expression of cytokines and hormonal changes during the induced molting was also studied. The expression of IL-6, IL-8, MIP-1beta and IFN-gamma mRNAs in the ovary, and IL-1beta, IL-6, IL-8, MIP-1beta, IFN-gamma and TGF-beta2 mRNAs in the oviduct, were up-regulated significantly during induced molting, suggesting their role in tissue regression. However, histological findings suggested no significant increase in immune cells in the regressing oviduct and ovary. Significant up-regulation of TGF-beta2 in the regressing oviduct might have suppressed leukocyte recruitment thereby preventing the inflammatory response and tissue damage. The down-regulation of estrogen and progesterone and up-regulation of corticosterone is well correlated with increased expression of cytokines. It appears that cytokines released during the process of induced molting may have a role in decreasing ovarian steroids and increasing the corticosterone levels in chicken. From this study, it may be concluded that cytokines play a major role in regression of the ovary and oviduct during induced molting in chickens.

Monoclonal antibodies against chicken interleukin-6

Monoclonal antibodies (mAb) were produced against a recombinant (r) chicken interleukin-6 (IL-6). Eight mAbs produced were tested for isotype; ability to inhibit recombinant forms of chicken (ch), human (h) and murine (m) IL-6; and recognition of rchIL-6 by Western immunoblotting. The mAb isotypes were represented by IgG1 (one), IgG2a (six) and IgG2b (one). In a mouse B9 hybridoma cell bioassay with rmIL-6, four mAbs effectively inhibited activity of rmIL-6. Further bioassays with the four mAbs at varying concentrations showed that two of these mAbs (1.20.7 and 1.26.4) were quite effective at inhibiting rmIL-6. Recombinant forms of ch, h and mIL-6 were all tested in a bioassay with the most potent inhibiting mAb (1.26.4), and this mAb was effective in inhibiting all three recombinant IL-6 proteins. Western immunoblotting revealed identification of the original IL-6 immunogen used for mAb production. Based upon inhibition of IL-6 activity in a standard bioassay and IL-6 recognition by Western immunoblotting, mAb 1.26.4 was judged the most useful antibody for future studies and applications.

Molecular immunophenotyping of lungs and spleens in naive and vaccinated chickens early after pulmonary avian influenza A (H9N2) virus infection

In a respiratory-infection-model with the avian influenza A H9N2 virus we studied lung and splenic immune reactions in chickens using a recently developed 5K chicken immuno-microarray. Groups of chickens were either mock-immunized (referred to as non-immune), vaccinated with inactivated viral antigen only (immune) or with viral antigen in a water-in-oil (W/O) immunopotentiator (immune potentiated). Three weeks after vaccination all animals were given a respiratory infection. Immune potentiated birds developed inhibitory antiviral antibodies, showed minimal lung histopathology and no detectable viral sequences, while non-immune animals showed microscopic immunopathology and detectable virus. Immune birds, receiving antigen in saline only, showed minimal microscopic histopathology, and intermediate levels of virus detection. These classical features in the different groups were mirrored by overlapping or specific mRNA gene expression profiles in lungs and spleen using microarray analysis. To our knowledge this is the first study demonstrating pneumonia-associated lung pathology of the low pathogenic avian influenza H9N2 virus. Our data provide insights into the molecular interaction of this virus with its natural host when naive or primed by vaccination.