Increased expression of Interleukin-6 related to nephritis in chickens challenged with an Avian infectious bronchitis virus variant

Abstract

A Brazilian field isolate (IBV/Brazil/PR05) of avian infectious bronchitis virus (IBV), associated with development of nephritis in chickens, was previously genotyped as IBV variant after S1 gene sequencing. The aim of this study was to evaluate the levels of IL-6 in kidneys and trachea of birds vaccinated and challenged with IBV/Brazil/PR05 strain, correlating these results with scores of microscopic lesions, specific IBV antigen detection and viral load. The up-regulation of IL-6 and the increased levels of viral load on renal and tracheal samples were significantly correlated with scores of microscopic lesions. Reduced levels of viral load were detected in kidneys of birds previously vaccinated and challenged, compared to non-vaccinated challenged group, although markedly microscopic lesions were observed for both groups. The expression of IL-6, present both in the kidney and in the tracheas, was dependent on the load of the virus present in the tissue, and the development of lesions was related with IL-6 present in the tissues. These data suggest that variant IBV/Brazil/PR05 can induce the expression of proinflammatory cytokines in a manner correlated with viral load and increased IL-6 is involved in the tissue with the influx of inflammatory cells and subsequent nephritis. This may contribute with a model to the development of immunosuppressive agents of IL-6 to prevent acute inflammatory processes against infection with IBV and perhaps other coronaviruses, as well as contribute to the understanding of the immunopathogenesis of IBV nephropatogenic strains.

Early immune responses and development of pathogenesis of avian infectious bronchitis viruses with different virulence profiles

“…The scores of microscopic lesions in the kidney samples were determined as previously described [ 6 ]. The parameters evaluated included tubular degeneration and necrosis, and presence of inflammatory infiltrate, and the scores ranged from 0 to 3 according to the severity of lesions.…”

“…After replication at primary site in tracheal mucosa, viraemia and IBV secondary replication are also found in other respiratory tissues (nose, lungs and air sacs) and in many non-respiratory epithelial tissues (kidneys, testes, oviduct, and gastrointestinal tract). Nephritis is commonly observed, mainly in broilers, and depending on the pathotype of the IBV strain and on the bird age, it may cause high mortality, and microscopic lesions of degeneration and necrosis of the renal tubular cells and interstitial inflammatory cell infiltrate [ 3 , 4 , 5 , 6 ].…”

“…Levels 20 times higher of IL6 mRNA after IBV challenge were observed in an IBV-susceptible chicken line compared to the disease-resistant chicken line [ 22 ]. High level of IL6 gene expression were detected in renal samples of chickens challenged with a nephropathogenic IBV strain and it has been well correlated with viral load and influx of inflammatory cells in this organ [ 6 ].…”

Avian Infectious Bronchitis Virus: Immunogenicity Profiles and New Pathotypes in Brazil - Literature Review

“…Entretanto, a produção de algumas citocinas pró-inflamatórias varia dependendo da estirpe viral do VBI e da linhagem de aves infectadas (ASIF et al, 2007;FERNANDO et al, 2015, OKINO et al, 2017. Por conta disso, a superprodução de algumas citocinas, como IL6, IL1β e IFN, podem resultar em graves lesões patológicas locais, além de não ter efeito no sentido de reduzir a carga viral (ASIF et al, 2007, FERNANDO et al, 2015KAMEKA et al, 2014, OKINO et al, 2017.…”

Diagnostic Studies of Infectious Bronchitis Disease in Broilers using Pathological and Molecular Investigations in Kaliobeya Governorate, Egypt

“…In young chickens, the mortality rate is typically 25-30% but it can approach 80% depending on the virulence of the strain [1].Some strains of IBV cause acute nephritis and urolithiasis associated with the high mortality of infected chickens, more ever, the disease is a predisposing factor for secondary bacterial infection resulting in high mortality and morbidity rate [6]. Replication of IBV occurs primary in tracheal mucosa [7], after replication in tracheal mucosa, viraemia and secondary replication are found in other respiratory tissues as nose, lungs and air sacs and in non-respiratory tissues such as kidneys, gastrointestinal tract, oviduct, and testes [8]. Clinically, most birds infected with IBV showed depression, dullness, reduced feed consumption, ruffled feather, increase water consumption, huddle together under heat source, coughing, gasping, sneezing, tracheal rales, occulonasal discharge and mild swollen of sinus [9,10].…”