The S2 Subunit of QX-type Infectious Bronchitis Coronavirus Spike Protein Is an Essential Determinant of Neurotropism

The S2 Subunit of QX-type Infectious Bronchitis Coronavirus Spike Protein Is an Essential Determinant of Neurotropism

Jin-long Cheng, Ye Zhao, Gang Xu, Keran Zhang, Wenfeng Jia, Yali Sun, Jing Zhao, Jia Xue, Yanxin Hu, Guozhong Zhang

Some coronaviruses (CoVs) have an extra furin cleavage site (RRKR/S, furin-S2′ site) upstream of the fusion peptide in the spike protein, which plays roles in virion adsorption and fusion. Mutation of the S2′ site of QX genotype (QX-type) infectious bronchitis virus (IBV) spike protein (S) in a recombinant virus background results in higher pathogenicity, pronounced neural symptoms and neurotropism when compared with conditions in wild-type IBV (WT-IBV) infected chickens. In this study, we present evidence suggesting that recombinant IBV with a mutant S2′ site (furin-S2′ site) leads to higher mortality. Infection with mutant IBV induces severe encephalitis and breaks the blood−brain barrier. The results of a neutralization test and immunoprotection experiment show that an original serum and vaccine can still provide effective protection in vivo and in vitro. This is the first demonstration of IBV-induced neural symptoms in chickens with encephalitis and the furin-S2′ site as a determinant of neurotropism.

2019

coronavirus, infectious bronchitis virus, qx type, furin-s2′ site, encephalitis, neurotropism

DOI: 10.3390/v11100972

Viruses

MDPI AG

Microbiology

EN