Monoclonal antibody and B-cell epitope mapping of the VP7 protein in bluetongue virus

Bluetongue virus (BTV) VP7 is a group-specific protein that is highly conserved in different serotypes. In this study, BALB/c mice were immunized with purified recombinant BTV-1 VP7 protein expressed in E. coli. Then six monoclonal antibodies (mAbs), 2A7, 2B2, 2B3, 2D3, 2D7, and 2H2, against the BTV-1 VP7 protein were produced using hybridoma technology. The reactivity of the mAbs was identified using western blotting, enzyme-linked immunosorbent assay, and immunofluorescence assay. A series of truncated peptides derived from VP7 expressed as glutathione S-transferase fusion proteins were mapped with mAbs by western blotting. The results indicated that 2A7 recognized the epitope ⁷¹SAAGINVGPI⁸⁰, 2B3 recognized ¹¹⁰ARVTGETSTWG¹²⁰, 2B2 and 2D3 recognized ¹²⁵PYGFFLETEET¹³⁵, and 2D7 and 2H2 recognized ³³²VNPMPGPLTRA³⁴². Amino acid sequence analysis showed that these four epitopes were conserved in 24 typical BTV serotypes. Cross-reaction results showed that mAb 2A7 could recognize the recombinant VP7 protein of BTV-1, African horse sickness virus serotype 1 (AHSV-1), and epidemic hemorrhagic disease virus serotype 1 (EHDV-1). The mAbs 2B2, 2B3, and 2D3 could recognize the recombinant VP7 protein of BTV-1 and EHDV-1, and the mAbs 2D7 and 2H2 specifically recognized the BTV-1 VP7 protein. These specific mAbs and identified B-cell epitopes provided key insights into the structure and function of VP7, while facilitating the development of BTV diagnostics and the design of epitope-based vaccines.