Local Innate Responses to TLR Ligands in the Chicken Trachea.

Neda Barjesteh,Tamiru Alkie,Éva Nagy,Douglas Hodgins,Shayan Sharif

doi:10.3390/v8070207

Abstract

The chicken upper respiratory tract is the portal of entry for respiratory pathogens, such as avian influenza virus (AIV). The presence of microorganisms is sensed by pathogen recognition receptors (such as Toll-like receptors (TLRs)) of the innate immune defenses. Innate responses are essential for subsequent induction of potent adaptive immune responses, but little information is available about innate antiviral responses of the chicken trachea. We hypothesized that TLR ligands induce innate antiviral responses in the chicken trachea. Tracheal organ cultures (TOC) were used to investigate localized innate responses to TLR ligands. Expression of candidate genes, which play a role in antiviral responses, was quantified. To confirm the antiviral responses of stimulated TOC, chicken macrophages were treated with supernatants from stimulated TOC, prior to infection with AIV. The results demonstrated that TLR ligands induced the expression of pro-inflammatory cytokines, type I interferons and interferon stimulated genes in the chicken trachea. In conclusion, TLR ligands induce functional antiviral responses in the chicken trachea, which may act against some pathogens, such as AIV.

Highlights

Avian influenza virus (AIV), which belongs to the family of Orthomyxoviridae, is an enveloped virus with a negative sense, single-stranded and segmented RNA [1]
Treatment of Tracheal organ cultures (TOC) with low dose or high dose of Pam3CSK4 or LPS significantly up-regulated the expression of inducible nitric oxide synthase at 3, 8, and 18 h post-treatment
Tracheal organ culture has been used for culturing viruses, such as avian infectious bronchitis organ culture hasvirus beenpathogenesis used for culturing such has as avian infectiousofbronchitis virusTracheal

Summary

Introduction

Avian influenza virus (AIV), which belongs to the family of Orthomyxoviridae, is an enveloped virus with a negative sense, single-stranded and segmented RNA [1]. Following infection of the respiratory tract with AIV, the host must produce appropriate immune responses in a short period of time to limit viral replication and eliminate the virus. Innate responses provide the first line of defense against influenza virus at mucosal surfaces aiming to block the entry of the virus and viral replication. When the virus passes the preliminary barriers, the airway epithelial cells are the primary target for the virus. Pathogenicity of AIV in chickens is initiated by the same phenomenon as mentioned above, by infecting the tracheal cells by influenza virus [2,3]. Chemoattractants produced by the trachea recruit other cells of the immune system, such as macrophages and lymphocytes, toward the trachea to limit spread of the virus [4,5,6,8]. Airway epithelial cells are of prime importance in host responses against

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