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

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.