Infectious Bronchitis Virus Variants: Molecular Analysis and Pathogenicity Investigation

Abstract

Infectious bronchitis virus (IBV) variants constantly emerge and pose economic threats to poultry farms worldwide. Numerous studies on the molecular and pathogenic characterization of IBV variants have been performed between 2007 and 2017, which we have reviewed herein. We noted that viral genetic mutations and recombination events commonly gave rise to distinct IBV genotypes, serotypes and pathotypes. In addition to characterizing the S1 genes, full viral genomic sequencing, comprehensive antigenicity, and pathogenicity studies on emerging variants have advanced our understanding of IBV infections, which is valuable for developing countermeasures against IBV field outbreaks. This review of IBV variants provides practical value for understanding their phylogenetic relationships and epidemiology from both regional and worldwide viewpoints.

Keywords: antigenicity; genotypes; infectious bronchitis virus; pathogenicity; variants.

Figure 1

Phylogenetic analysis of the complete S1 gene of the IBV variants reviewed in this study and reference strains. The phylogenetic tree was constructed using MEGA version 6 by the neighbor-joining method (bootstrapping for 1000 replicates, bootstrap value >70%). CN: China; IT: Italy; KR: Korea; SE: Sweden; TW: Taiwan; US: United States.

Figure 2

Phylogenetic analysis of the full-length genome of the IBV variants reviewed in this study and reference strains. The strains with a symbol belong to the lineage with the same symbol when the S1 gene is analyzed. The phylogenetic tree was constructed using MEGA version 6 by the neighbor-joining method (bootstrapping for 1000 replicates, bootstrap value >70%). CN: China; IT: Italy; KR: Korea; SE: Sweden; TW: Taiwan; US: United States.