Two novel neutralizing antigenic epitopes of the s1 subunit protein of a QX-like avian infectious bronchitis virus strain Sczy3 as revealed using a phage display peptide library

Abstract

The spike (S) protein of the infectious bronchitis virus (IBV) plays a central role in the pathogenicity, the immune antibody production, serotype and the tissue tropism. In this study, we generate 11 monoclonal antibodies (mAbs) against S1 subunit of IBV Sczy3 strain, and two mAbs 1D5 and 6A12 were positive in indirect ELISA against both His-S1 protein and the purified whole viral antigen. MAb 6A12 and 1D5 could recognized by other 10 IBV strains (IBVs) from five different genotypes, except that 1D5 had a relatively low reaction with two of the 10 tested IBVs. End-point neutralizing assay performed in chicken embro kidney (CEK) cells revealed that the neutralization titer of 6A12 and 1D5 against Sczy3 reached 1:44.7 and 1:40.6, respectively. After screening a phage display peptide library and peptide scanning, we identified two linear B-cell epitopes that were recognized by the mAbs 1D5 and 6A12, which corresponded to the amino acid sequences (87)PPQGMAW(93) and (412)IQTRTEP(418), respectively, in the IBV S1 subunit. Sequences comparison revealed that epitope (412)IQTRTEP(418) was conserved among IBVs, while the epitope (87)PPQGMAW(93) was relatively variable among IBVs. The novel mAbs and the epitopes identified will be useful for developing diagnostic assays for IBV infections.

Phylogenetic and antigenic analysis of avian infectious bronchitis virus in southwestern China, 2012–2016

“…This phenomenon may be explained by the existence of common VN epitopes present in different IBV genes. For example, in cK/CH/SCDY/141030 and Sczy3, two common VN epitopes (87PPQGMAW93 and 412IQTRTEP418) (Zou et al, 2015) were observed in the S1 genes of both strains. Although the five VN epitopes in the HVRs were quite different between strains cK/CH/SCDY/141030 and H120, other common VN epitopes may be located in the S2 and N proteins of these two strains, as there are reports that the S2 and N proteins may induce neutralizing reactions (Ignjatovic and Sapats, 2005;Koch et al, 1990).…”

Antigenic and Pathogenic Characteristics of QX-Type Avian Infectious Bronchitis Virus Strains Isolated in Southwestern China

“…IB is an economically important, highly contagious, acute, upper-respiratory tract disease of chickens and other fowl, caused by the avian coronavirus IBV [31,32]. Although multiple genotypes of IBV have continuously been detected, e.g., QX-type, TW-type, and TC07-2, QX-type IBV is still the prevalent genotype in China [12,15,33]. Therefore, it is important to understand the antigenicity and pathogenicity of QX-type IBV field isolates for the prevention and control of IB.…”

Peptides with 16R in S2 protein showed broad reactions with sera against different types of infectious bronchitis viruses

“…IBV is a typical coronavirus that is constantly recombining and mutating its antigenicity, leading to the presence of multiple serotypes and genotypes of IBV strains and causing major challenges in disease prevention and control (Cavanagh, 2007). As an important antigenic protein, S1 has been used in vaccine development (Hodgson et al, 2004;Wickramasinghe et al, 2014;Zou et al, 2015). Notably, S2 protein also can induce protective immune responses (Eldemery et al, 2017;Ignjatovic and Sapats, 2005).…”