Pathogenic characteristics of a QX-like infectious bronchitis virus strain SD in chickens exposed at different ages and protective efficacy of combining live homologous and heterologous vaccination

Abstract

Continued reports of infections with infectious bronchitis virus (IBV) variants have occurred since its first isolation in the 1930s. Currently, QX-like IBVs are the predominant circulating genotype around the world. Here, the pathogenicity of QX-like IBV strain SD was characterized in chickens at different ages of exposure to the virus, and the protection efficacy of available vaccine combinations against IBV was evaluated. The results revealed that QX-like IBV strain SD was severely pathogenic in chickens, causing respiratory, urinary and reproductive infections, irrespective of age, based on clinical observations, viral distribution in tissues and a ciliostasis study. Severe respiratory signs, tracheal cilia injury, nephritis and abnormal development of the oviduct and ovarian follicles were evident throughout the experiment. A challenge experiment demonstrated that the homologous QX vaccine showed superior protection efficacy compared with other available vaccines, confirming the importance of IBV vaccine seed homology against the circulating IBV strains. Our findings aid an understanding of the pathogenicity of QX-like IBVs that may help to further control the infection.

Characterization of the Protective Efficacy Against QX Strain of a Recombinant Infectious Bronchitis Virus With H120 Backbone and QX Spike Gene

“…This recombinant virus is more adaptive to chicken embryos, with a higher ELD 50 and EID 50 than the parental H120 or donor QX strain. Although rH120-QX(S) still exhibits pathogenicity in chicken embryos, it is nonpathogenic in SPF chicken, comparable to the parental H120 strain, whereas the lethality of the donor strain QX is up to 60%, similar to the previously described (Shao et al, 2020). Thus, the QX S protein does not confer virulence to rH120-QX(S).…”

Unveiling the Hidden Regulators: The Impact of lncRNAs on Zoonoses

“…Belonging to the Orthocoronavirinae subfamily, coronaviruses encompass four genera: α coronavirus, β coronavirus, γ coronavirus, and δ coronavirus. These single-stranded positive-sense RNA viruses were first identified in cases of infectious bronchitis in chickens [ 153 , 154 ]. Throughout millennia of evolution, coronaviruses have continually crossed species boundaries, causing profound infections in a diverse range of species, including humans, mammals, and birds [ 155 ].…”

Key Aspects of Coronavirus Avian Infectious Bronchitis Virus

“…IBV infections in young chickens are common between the ages of 1 to 30 days and can cause reproductive tract defects [ 84 , 85 , 86 ]. The infected chickens develop cystic oviducts, leading to false layer syndrome with distinctly low peak egg production [ 86 , 87 , 88 , 89 ]. Infection with IBV in laying hens can negatively influence egg production with poor-quality eggs [ 90 , 91 , 92 ].…”