A. Shini

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)-1β, 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-1β, IL-6, IL-10, IL-12α 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-β4 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 potential for probiotics to prevent reproductive tract lesions in free-range laying hens

A study was undertaken to investigate the ability of two commercial probiotics applied in free-range laying hens (from 18 to 22 weeks of age) in reducing the occurrence of reproductive tract pathologies, and improving hen health and performance. In all, 630 17-week-old brown layers were transferred to a freshly cleaned free-range laying facility, and randomly divided into three groups, with three replicates of 70 birds each. Both probiotics were administered in the drinking water (Groups 1 and 2) on a daily basis for 4 weeks, while Group 3 was left untreated. At 38 weeks of age, the results demonstrated that treatment with either probiotic significantly reduced the occurrence of reproductive tract pathologies (control vs probiotics, 33% vs 22% and 11%; P < 0.01), mortalities (control vs probiotics; 3.8% vs 1.5 and 1.9%; P < 0.01), and increased the performance of hens, for another 20 weeks post-treatments (hen day production for control vs probiotics 75% vs 90% and 94%; P < 0.01). Birds treated with probiotics maintained their bodyweight and egg weights at standard ranges, while untreated birds did not perform at this level. Although we were unable to show any effect on cloacal bacterial colonisation, the results of the present study provided some initial evidence that reproductive pathologies that often cause drops in egg production and sudden deaths of birds, can be reduced if free range hens are treated with a commercial probiotic before or during the onset of lay. The use of a probiotic benefits the health and performance status of hens, resulting in better hen welfare and significant economic gains to egg producers.

Oestrogen-treated chickens: An avian model to study inflammatory and immune characteristics of non-alcoholic fatty liver diseases of humans

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