Chicken single-chain antibody fragments directed against recombinant VP7 of bluetongue virus

VP7, the major structural core protein of bluetongue virus, is conserved among the 24 bluetongue virus serotypes. The gene encoding VP7 of serotype 4 was expressed in Escherichia coli. A semi-synthetic chicken antibody library was screened with the resulting protein. Six single-chain antibody fragments (scFvs) were isolated. Immune sera blocked the binding of four of the six scFvs in enzyme-linked immunosorbent assays. These scFvs recognised recombinant VP7 coated directly onto a plastic surface. Their behaviour therefore differs from that of scFv F10 which was selected earlier on directly immobilised bluetongue virus and which binds to VP7 only when it is captured by an immobilised immunoglobulin directed against bluetongue virus.