Mapping of antigenic determinants on a SAT2 foot-and-mouth disease virus using chicken single-chain antibody fragments

摘要

Recombinant single-chain variable fragments (scFvs) of antibodies make it possible to localize antigenicand immunogenic determinants, identify protective epitopes and can be exploited for the design ofimproved diagnostic tests and vaccines. A neutralizing epitope, as well as other potential antigenic sites ofa SAT2 foot-and-mouth disease virus (FMDV) were identified using phage-displayed scFvs. Three uniqueZIM/7/83-specific scFvs, designated scFv1, scFv2 and scFv3, were isolated. Further characterization ofthese scFvs revealed that only scFv2 was capable of neutralizing the ZIM/7/83 virus and was used togenerate neutralization-resistant virus variants. Sequence analysis of the P1 region of virus escapingneutralization revealed a residue change from His to Arg at position 159 of the VP1 protein. Residue159 is not only surface exposed but is also located at the C-terminal base of the G–H loop, a knownimmunogenic region of FMDV. A synthetic peptide, of which the sequence corresponded to the predictedantigenic site of the VP1 G–H loop of ZIM/7/83, inhibited binding of scFv2 to ZIM/7/83 in a concentrationdependentmanner. This region can therefore be considered in the design of SAT2 vaccine seed virusesfor the regional control of FMD in Africa.