# Two novel conserved linear B-cell epitopes identified in the S2 subunit of the infectious bronchitis virus spike protein

## TL;DR

Researchers identified two new immune targets in a key protein of a chicken virus, which could help improve diagnostics and understanding of the virus.

## Contribution

Discovery of two novel conserved B-cell epitopes in the S2 subunit of IBV spike protein.

## Key findings

- Two novel linear B-cell epitopes, 1040KWWND1044 and 1046KHELPDF1052, were identified in the S2 subunit of IBV.
- The epitope 1046KHELPDF1052 is highly conserved across different IBV genotypes.
- Both epitopes are located in the heptad repeat 2 region and are surface-exposed, making them potential immunological targets.

## Abstract

•Four monoclonal antibodies against S2 subunit of IBV spike protein were prepared.•Two novel epitopes of 1040KWWND1044 and 1046KHELPDF1052 were identified.•The epitope 1046KHELPDF1052 is highly conserved among different IBV genotypes.•Both epitopes are located within the heptad repeat 2 region and are surface-exposed.

Four monoclonal antibodies against S2 subunit of IBV spike protein were prepared.

Two novel epitopes of 1040KWWND1044 and 1046KHELPDF1052 were identified.

The epitope 1046KHELPDF1052 is highly conserved among different IBV genotypes.

Both epitopes are located within the heptad repeat 2 region and are surface-exposed.

Infectious bronchitis (IB), caused by the infectious bronchitis virus (IBV), is a contagious respiratory disease of chickens that poses a serious threat to the poultry industry worldwide. In this study, four monoclonal antibodies (mAbs) targeting the heptad repeat 2 (HR2) region of the spike protein S2 subunit were generated through mouse immunization, hybridoma cell fusion, and clonal purification. Western blot and indirect immunofluorescence assays confirmed that all four mAbs specifically recognized IBV. Epitope identification revealed two novel linear B-cell epitopes: 1040KWWND1044, recognized by mAbs 6A6 and 6E2; and 1046KHELPDF1052, recognized by mAbs 6A1 and 6A9, which are conserved among different IBV lineages. Furthermore, both epitopes are exposed on the surface of the spike protein, suggesting their potential as immunologically relevant targets. This study contributes to further elucidating the structure and function of the IBV S2 subunit and provide assistance for the development of IBV diagnostic technology.