interleukin-8 and Influenza-in-Birds

The chicken upper respiratory tract is the portal of entry for respiratory pathogens including avian influenza virus (AIV). There is a paucity of information about the role of airway epithelial cells in the induction of antiviral responses in the chicken trachea. A better understanding of the role of these cells in the initiation of innate responses may improve prophylactic or therapeutic strategies for control of viral infections. The present study aimed to characterize antiviral innate responses in chicken tracheal epithelial cells (cTECs) induced by TLR ligands. The results demonstrated that stimulation of cTECs with TLR ligands induced antiviral responses, and subsequently reduced the replication of AIV in cTECs. Additionally, stimulated cTECs were able to influence the function of other cells such as macrophages. Overall, these results provided evidence that cTECs mount antiviral responses after stimulation with TLR ligands through IRF7 and NF-κB signaling pathways, leading to activation of other cells, such as macrophages.

Topics: Animals; Avian Proteins; Chickens; Epithelial Cells; Immunity, Innate; Influenza A virus; Influenza in Birds; Interferon Regulatory Factors; Interleukin-1beta; Interleukin-8; Ligands; Macrophages; Poly I-C; Poultry Diseases; Toll-Like Receptor 3; Toll-Like Receptor 4; Trachea

Interleukins are reported to be valuable immunostimulants in enhancing the immune efficiency of conventional vaccines. In this study, the effect of expression of interleukin 8 (IL-8) on the immune response of ducks to avian influenza vaccine was investigated. The results showed that the serum antibody titer, lymphocyte transformation efficiency and serum interferon gamma (IFN-γ) level of ducks injected with avian influenza vaccine along with a plasmid expressing duck IL-8 were higher than those of ducks injected with conventional immunostimulant Astragalus polysaccharide (APS) or empty plasmid. Therefore, the duck IL-8 may be used as a good immunostimulant to enhance the immune efficiency of avian influenza vaccine in ducks.

Topics: Animals; Antibodies, Viral; Ducks; Influenza A Virus, H5N1 Subtype; Influenza in Birds; Influenza Vaccines; Interleukin-8; Poultry Diseases

Our previous studies have illustrated three strains of duck-origin H5N1 highly pathogenic avian influenza viruses (HPAIVs) had varying levels of pathogenicity in ducks (Sun et al., 2011). However, the host immune response of ducks infected with those of H5N1 HPAIVs was unclear. Here, we compared viral distribution and mRNA expression of immune-related genes in ducks following infection with the two HPAIV (A/Duck/Guangdong/212/2004, DK212 and A/Duck/Guangdong/383/2008, DK383). DK383 could replicate in the tested tissue of ducks (brain, spleen, lungs, cloacal bursa, kidney, and pancreas) more rapid and efficiently than DK212 at 1 and 2 days post-inoculation. Quantitative real-time PCR analysis showed that the expression levels of TLR3, IL-6, IL-8, and MHC class II in brains were higher than those of respective genes in lungs during the early stage of post infection. Furthermore, the expression levels of IL-6 and IL-8 in the brain of ducks following infection with DK383 were remarkably higher than those of ducks infected with DK212, respectively. Our results suggest that the shift in the H5N1 HPAIVs to increased virulence in ducks may be associated with efficient and rapid replication of the virus, accompanied by early destruction of host immune responses. These data are helpful to understand the underlying mechanism of the different outcome of H5N1 HPAIVs infection in ducks.

Topics: Animals; Ducks; Influenza A Virus, H5N1 Subtype; Influenza in Birds; Interleukin-6; Interleukin-8; Lung; Poultry Diseases; Real-Time Polymerase Chain Reaction; Spleen; Virulence

Avian influenza viruses (AIV) pose a threat towards the health of both poultry and humans. To interrupt the transmission of the virus, novel prophylactic strategies must be considered which may reduce the shedding of AIV. One potential is the prophylactic use of Toll-like receptor (TLR) ligands. Many cells of the immune system express TLRs, and cellular responses to TLR stimulation include activation and the production of cytokines. TLR ligands have been employed as prophylactic treatments to enhance host resistance to pathogens both in mammals and chickens. Therefore, the present study was conducted to determine whether TLR ligands may be used prophylactically in chickens to enhance host immunity to AIV. Chickens received intramuscular injections of either low or high doses of the TLR ligands poly I:C, lipopolysaccharide (LPS) and CpG ODN. Twenty-four hours post-treatment, chickens were infected with the low pathogenic avian influenza virus H4N6, and both oropharyngeal and cloacal virus shedding were assessed on days 4 and 7 post-infection. To identify potential correlates of immunity, spleen and lungs were collected on days 2, 4 and 7 post-infection for RNA extraction. The results suggested that all of the TLR ligand treatments induced a significant reduction in virus shedding, with the TLR3 ligand poly I:C conferring the greatest AIV immunity compared to control birds, followed by CpG ODN and LPS. Furthermore, transcriptional analysis of gene expression in the spleen and lungs suggest IFN-α and IL-8 as correlates of immunity conferred by poly I:C, and IFN-γ for CpG ODN and LPS. In conclusion, TLR ligands, have the ability to enhance host immunity against AIV, and future studies should consider exploring the combinatory effects of poly I:C and CpG ODN prophylaxis in conjunction with AIV vaccination.

Topics: Animals; Chickens; Influenza A virus; Influenza in Birds; Interferon-alpha; Interferon-gamma; Interleukin-8; Ligands; Lipopolysaccharides; Lung; Oligodeoxyribonucleotides; Poly I-C; Spleen; Toll-Like Receptor 3; Virus Shedding

This study analysed the immune response in the intestinal tract of ducks infected with low-pathogenic avian influenza viruses compared with ducks treated orally with R848, a synthetic Toll-like receptor 7 (TLR7) agonist. Influenza virus infection induced a type I interferon (IFN)-dependent immune response characterized by the expression of Mx transcripts in the ileum at levels that were proportional to viral load. Mx transcripts were detected in differentiated enterocytes from influenza virus-infected ducks. By contrast, in R848-treated ducks, Mx transcripts were detected solely in intraepithelial round cells of haematopoietic origin. An increase was detected in the number of intraepithelial TLR7-positive cells and intraepithelial IFN-α-producing cells in influenza virus-infected ducks, albeit to a lower level than in R848-treated ducks. IFN-γ expression was also upregulated in the intestine of influenza virus-infected and R848-treated ducks. Finally, interleukin (IL)-1β and IL-8 transcripts were expressed at high levels in R848-treated ducks but were not increased in influenza virus-infected ducks. These findings suggest that a type I IFN-mediated immune response in enterocytes and the activation of IFN-γ-secreting cells contribute to the control of influenza virus replication in the duck intestine.

Topics: Animals; Ducks; Enterocytes; Ileum; Imidazoles; Immunohistochemistry; Influenza A Virus, H7N1 Subtype; Influenza in Birds; Interferon-alpha; Interferon-gamma; Interleukin-1beta; Interleukin-8; Microscopy; Toll-Like Receptor 7

Highly pathogenic avian influenza virus (HPAIV) of the H5N1 subtype has been reported to infect pigeons asymptomatically or induce mild symptoms. However, host immune responses of pigeons inoculated with HPAIVs have not been well documented. To assess host responses of pigeons against HPAIV infection, we compared lethality, viral distribution and mRNA expression of immune related genes of pigeons infected with two HPAIVs (A/Pigeon/Thailand/VSMU-7-NPT/2004; Pigeon04 and A/Tree sparrow/Ratchaburi/VSMU-16-RBR/2005; T.sparrow05) isolated from wild birds in Thailand. The survival experiment showed that 25% of pigeons died within 2 weeks after the inoculation of two HPAIVs or medium only, suggesting that these viruses did not cause lethal infection in pigeons. Pigeon04 replicated in the lungs more efficiently than T.sparrow05 and spread to multiple extrapulmonary organs such as the brain, spleen, liver, kidney and rectum on days 2, 5 and 9 post infection. No severe lesion was observed in the lungs infected with Pigeon04 as well as T.sparrow05 throughout the collection periods. Encephalitis was occasionally observed in Pigeon04- or T.sparrow05-infected brain, the severity, however was mostly mild. To analyze the expression of immune-related genes in the infected pigeons, we established a quantitative real-time PCR analysis for 14 genes of pigeons. On day 2 post infection, Pigeon04 induced mRNA expression of Mx1, PKR and OAS to a greater extent than T.sparrow05 in the lungs, however their expressions were not up-regulated concomitantly on day 5 post infection when the peak viral replication was observed. Expressions of TLR3, IFNα, IL6, IL8 and CCL5 in the lungs following infection with the two HPAIVs were low. In sum, Pigeon04 exhibited efficient replication in the lungs compared to T.sparrow05, but did not induce excessive host cytokine expressions. Our study has provided the first insight into host immune responses of pigeons against HPAIV infection.

Topics: Animals; Chemokine CCL5; Columbidae; Cytokines; Influenza A Virus, H5N1 Subtype; Influenza in Birds; Interferon-alpha; Interleukin-6; Interleukin-8; Lung; Real-Time Polymerase Chain Reaction; Toll-Like Receptor 3