A novel linear B-cell epitope on S2 protein of transmissible gastroenteritis virus identified using a monoclonal antibody

Transmissible gastroenteritis virus (TGEV) is a devastating coronavirus that causes severe gastrointestinal symptoms and high mortality in piglets, resulting in substantial economic losses in the swine industry. The spike (S) protein, particularly its S2 subunit, plays a crucial role in virus-host membrane fusion and exhibits high conservation among TGEV strains. However, B-cell epitopes within the TGEV S2 protein remain largely uncharacterized. This study aimed to express and purify the TGEV S2 protein, generate monoclonal antibodies (mAbs) against it, and identify specific B-cell epitopes. We successfully expressed and purified the TGEV S2 protein using a prokaryotic expression system. Immunization of BALB/c mice with the purified S2 protein yielded mAb 12G8, characterized as an IgG2b isotype with a kappa light chain. The mAb 12G8 demonstrated specific reactivity against TGEV strains through multiple immunological assays. Epitope mapping identified 1109QGQALS1114 as the minimal B-cell specific epitope recognized by mAb 12G8, which exhibits high conservation across different TGEV strains. Three-dimensional structural modeling analysis localized this conserved epitope within the heptad repeat 1 domain of TGEV S2 protein. These findings advance the understanding of TGEV S2 protein antigenicity and provide valuable resources for developing improved diagnostic tools and therapeutic strategies against TGEV infection. The identification of a conserved B-cell epitope within the S2 protein establishes new avenues for targeted vaccine development and may contribute to more effective control measures against TGEV in the swine industry.