Transcriptional Innate Immune Response of the Developing Chicken Embryo to Newcastle Disease Virus Infection.

Megan A Schilling,Fulgence N Mpenda,Joram Buza,Meredith Cavanaugh,Susan J Lamont,Jessica Radzio-Basu,Sahar Memari,Melissa S Deist,Robab Katani,Vivek Kapur

doi:10.3389/fgene.2018.00061

Abstract

Traditional approaches to assess the immune response of chickens to infection are through animal trials, which are expensive, require enhanced biosecurity, compromise welfare, and are frequently influenced by confounding variables. Since the chicken embryo becomes immunocompetent prior to hatch, we here characterized the transcriptional response of selected innate immune genes to Newcastle disease virus (NDV) infection in chicken embryos at days 10, 14, and 18 of embryonic development. The results suggest that the innate immune response 72 h after challenge of 18-day chicken embryo is both consistent and robust. The expression of CCL5, Mx1, and TLR3 in lung tissues of NDV challenged chicken embryos from the outbred Kuroiler and Tanzanian local ecotype lines showed that their expression was several orders of magnitude higher in the Kuroiler than in the local ecotypes. Next, the expression patterns of three additional innate-immunity related genes, IL-8, IRF-1, and STAT1, were examined in the highly congenic Fayoumi (M5.1 and M15.2) and Leghorn (Ghs6 and Ghs13) sublines that differ only at the microchromosome bearing the major histocompatibility locus. The results show that the Ghs13 Leghorn subline had a consistently higher expression of all genes except IL-8 and expression seemed to be subline-dependent rather than breed-dependent, suggesting that the innate immune response of chicken embryos to NDV infection may be genetically controlled by the MHC-locus. Taken together, the results suggest that the chicken embryo may represent a promising model to studying the patterns and sources of variation of the avian innate immune response to infection with NDV and related pathogens.

Highlights

Newcastle disease virus (NDV) is one of the most important poultry pathogens worldwide, with over eighty countries in North and South America, Europe, Asia, and Africa reporting outbreaks each year (Diel et al, 2012)
Studies were performed to define the point during embryonic development when the chicken embryo is capable of producing a robust and consistent immune response to NDV, as well as to identify specific immune genes with the greatest differential expression post infection
The comparative transcriptional profile of Specific pathogen free (SPF) White Leghorn chicken embryos was determined using the Chicken Innate and Adaptive Immune Responses RT2 Profiler Array (QIAGEN Inc., Germantown, Marek’s Disease (MD), United States) as an initial screen to select for immune genes in the embryo that are differentially expressed during infection since studies have not been performed previously

Summary

Introduction

Newcastle disease virus (NDV) is one of the most important poultry pathogens worldwide, with over eighty countries in North and South America, Europe, Asia, and Africa reporting outbreaks each year (Diel et al, 2012). Backyard chickens are generally considered less susceptible to NDV and other infections than commercial chickens that are bred for high productivity. This reduced susceptibility is presumably due to their pre-sensitization with a higher frequency of natural exposure to pathogens in the scavenging environment, as well as through natural selection for hardiness to higher levels of pathogen exposure. Considerable variation in response to NDV infection has been noted both between and within ecotypes commonly found in backyard settings (Minga et al, 2004) Another breed of chickens hypothesized to be less susceptible to disease is the Kuroiler, a dual-purpose chicken, first bred for improving both meat and egg production of backyard poultry in India. The Kuroiler, which has multi-colored feathers to help with camouflage in the wild, and thrives in backyard or scavenging environments has recently been introduced in East Africa (including Tanzania) with reports suggesting that it can coexist with, and out-produce the local chickens in Uganda and Kenya (Dessie and Getachew, 2016)

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