Transcriptional cytokine responses associated with pathological outcomes in chickens experimentally infected with pigeon variant of avian avulavirus type 1

Abstract

Background: Newcastle disease (ND) caused by virulent avian avulavirus 1 (AAvV-1) within the family paramyxoviridae, affects variety of avian species around the globe as well as responsible for significant economic losses in the poultry industry.Methods: Transcriptional response of selected cytokines associated with pathological outcomes were studied on chickens after experimental infection with three virulent isolates of pigeon variant avian avulavirus type 1 (PAvV-1). The specific pathogen free (SPF) chickens were used in the study, after virus inoculation via the intranasal route virus, observed daily for clinical symptoms. On day 3 of post infection, the experiment was terminated and then anatomopathogical and histopathological changes, virus load and transcriptional cytokine response were determined in the spleen.Results: For the study, four cytokines were chosen: interferons (IFN-β, IFN-γ) and interleukins (IL-2, IL-6). The increased transcriptional levels of cytokine expression were associated with viral gene expression and marked lesions. The increase in the mRNA levels of IL-6 was most significant in chickens with clinical symptoms. The combined up-regulations of IFN-γ and IL-6 mRNA expression were detected simultaneously with infiltration of macrophages in the histopathology analysis. The RNA expression of IL-2 and slight up-regulation of IFN-β were only in chickens infected with isolate closely related to poultry isolates in the phylogenetic study.Conclusions: The difference in the mRNA expression levels of cytokines may help to elucidate mechanisms of immune responses in birds infected with different virulent strains of avian avulavirus type 1.