Abstract

Avian infectious bronchitis, a highly contagious disease caused by avian infectious bronchitis virus (IBV), is of considerable economic importance to the poultry industry. New IBV TW-like strains have increasingly emerged in China in recent years; hence, evaluating their pathogenicity and developing a specific vaccine to guard against their potential threat to the poultry industry is important. Here, we examined the pathogenicity of a TW-like IBV strain (GD), and evaluated the protective efficacy of the QX-like strain (JS) against GD in challenge infections in chickens. The results revealed that strain-GD-infected birds experienced severe respiratory signs, renal lesions, and 30–40% mortality. The GD virus had extensive tissue tropism, especially in the trachea, lungs, kidneys, and bursa of Fabricius, and was continuously shed via the respiratory tract and cloaca. The QX-like IBV strain JS is able to completely protect chickens from challenge with the TW-like IBV GD field strain, with no clinical signs or gross lesions, decreased tissue replication rates, lower ciliostasis score, and reduced virus shedding. These findings indicate that IBV GD is highly virulent, and that QX-like JS may serve as an effective vaccine against the threat posed by IBV TW-like viruses.

Highlights

  • Infectious bronchitis (IB) is an acute, highly contagious respiratory, and urogenital disease caused by infections bronchitis virus (IBV)

  • Existing vaccines for IB no longer provide protection and they tend to be ineffective against the epidemic infectious bronchitis virus (IBV) strains when new variant IBV isolates emerge or when new serotypes appear (Sun et al, 2011)

  • Our results suggest that TW-like IBV GD is highly virulent, and that QX-like JS may provide effective vaccine protection against TW-like IBV viruses

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Summary

INTRODUCTION

Infectious bronchitis (IB) is an acute, highly contagious respiratory, and urogenital disease caused by infections bronchitis virus (IBV). Pathogenicity and Protection of a TW-like IBV of the inaccuracy of the coronavirus RNA-dependent RNA polymerase and high frequency of homologous RNA recombination, the emergence of new variant strains, genotypes, and serotypes of IBV is continuously reported (Cavanagh et al, 1986). Existing vaccines for IB no longer provide protection and they tend to be ineffective against the epidemic IBV strains when new variant IBV isolates emerge or when new serotypes appear (Sun et al, 2011). Screening new live-attenuated vaccine strains based on new isolates is necessary to protect chickens against the common epidemic IBV strains. A predominant IBV type, QX-like IBV, has been circulating in China since 1998 when the first variant of this type was reported (Wang et al, 1998; Zhao et al, 2014). Our results suggest that TW-like IBV GD is highly virulent, and that QX-like JS may provide effective vaccine protection against TW-like IBV viruses

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