Serotype shift of a 793/B genotype infectious bronchitis coronavirus by natural recombination

Abstract

An infectious bronchitis coronavirus, designated as ck/CH/LHLJ/140906, was isolated from an infectious bronchitis virus (IBV) strain H120-vaccinated chicken flock, which presented with a suspected infectious bronchitis virus (IBV) infection. A phylogenetic analysis based on the S1 gene clustered ck/CH/LHLJ/140906 with the 793/B group; however, a pairwise comparison showed that the 5' terminal of the S1 gene (containing hypervariable regions I and II) had high sequence identity with the H120 strain, while the 3' terminal sequence was very similar to that of IBV 4/91 strain. A SimPlot analysis of the complete genomic sequence, which was confirmed by a phylogenetic analysis and nucleotide similarities using the corresponding gene fragments, suggested that isolate ck/CH/LHLJ/140906 emerged from multiple recombination events between parental IBV strains 4/91 and H120. Although the isolate ck/CH/LHLJ/140906 had slightly higher S1 amino acid sequence identity to strain 4/91 (88.2%) than to strain H120 (86%), the serotype of the virus was more closely related to that of the H120 strain (32% antigenic relatedness) than to the 4/91 strain (15% antigenic relatedness). Whereas, vaccination of specific pathogen-free chickens with the 4/91 vaccine provided better protection against challenge with ck/CH/LHLJ/140906 than did vaccination with the H120 strain according to the result of virus re-isolation. As the spike protein, especially in the hypervariable regions of the S1 domain, of IBVs contains viral neutralizing epitopes, the results of this study showed that recombination of the S1 domain resulted in the emergence of a new serotype.

A novel low virulent respiratory infectious bronchitis virus originating from the recombination of QX, TW and 4/91 genotype strains in China

“…The 4/91 vaccine strain, the donor of the N gene and 3'UTR to JX17 strain, has been widely used in the global poultry industry. Recent studies revealed that the 4/91 strain has become an important gene donor to variants in genetic evolution of IBV in China (Han et al, 2011;Zhang et al, 2015). Moreover, the typical strain TW2575/98 of TW genotype, the donor of the S1 gene to JX17 strain, were isolated frequently in past few years (Feng et al, 2017).…”

“…IBV strains isolated in Taiwan were divided into TW-I and TW-II genotypes, both of which were grouped into GI-7, with the former isolated frequently in mainland China commonly exhibiting nephrogenic, and the later isolated in Taiwan before 1990s usually presenting with respiratory symptoms (Wang and Huang, 2000;Wang and Tsai, 1996). Another widely prevalent genotype in China, the 793/ B (4/91) type (GI-13), which first emerged in Europe in 1991 and quickly spread around the world (Cook et al, 1996), is easy to recombine with other strains in China (Liu et al, 2013;Zhang et al, T 2015).…”

“…SAIBK variant, presenting as nephrogenic, was proved to be the recombinant virus of YX10 strain (GI-19), YN strain (GI-19) and Mass-type strain (GI-1) (Yang and Ma, 2013). Coincidentally, variants such as ck/CH/LZJ/ 111113, originating from ck/CH/LDL/09/022 (GI-19) and 4/91(GI-13), and ck/CH/LHLJ/140906, which presented as a new serotype, originating from 4/91 (GI-13) and H120 (GI-1), were isolated in China (Liu et al, 2013;Zhang et al, 2015). In recent years, the recombinant strains of QX and 4/91 genotype emerged.…”

Altered pathogenicity of a tl/CH/LDT3/03 genotype infectious bronchitis coronavirus due to natural recombination in the 5′- 17 kb region of the genome

“…In the course of our continuous surveillance of IBV in China, several natural recombinant IBV strains have been isolated and identified. These IBV strains were shown to have originated from recombination events between field and vaccine strains, different types of vaccine strains, or different types of field strains (Liu et al, 2013a,b;Liu et al, 2014;Zhang et al, 2015). Some of the recombinant strains were shown to have undergone multiple recombination events (Liu et al, 2013b;Liu et al, 2014;Zhang et al, 2015).…”

Serotype, antigenicity, and pathogenicity of a naturally recombinant TW I genotype infectious bronchitis coronavirus in China

“…Thus far, two major groups of classification systems, including functional tests that examine the biological functions of a virus (immunotypes, protectotypes, and serotypes) and non-functional tests that assess the viral genome (genotypes), are commonly used for IBV typing (de Wit, 2000). For a specific IBV strain, although evidence from some studies suggests that there is a high correlation between the genotype and serotype, other studies have presented conflicting data (de Wit, 2000;Zhang et al, 2015;Chen et al, 2015), which may lead to contradictory results. The disadvantages of each system are that they only analyze one or several characteristics of a virus strain.…”