Development of high-affinity single chain Fv against foot-and-mouth disease virus

• Antibody fragment (scFv) against serotype-O FMDV was successfully isolated.
• By FACS-based screening, the affinity of the isolated antibody could be further improved.
• The affinity-maturated antibody has also high binding affinity to whole FMDV with high selectivity.

Foot-and-mouth disease (FMD) is caused by the FMD virus (FMDV) and results in severe economic losses in livestock farming. For rapid FMD diagnostic and therapeutic purposes, an effective antibody against FMDV is needed. Here, we developed a high-affinity antibody against FMDV by FACS-based high throughput screening of a random library. With the FITC-conjugated VP1 epitope of FMDV and high-speed FACS sorting, we screened the synthetic antibody (scFv) library in which antibody variants are displayed in the periplasm of Escherichia coli. After three rounds of sorting, we isolated one antibody fragment (#138-scFv) against the VP1 epitope of FMDV. Next, to improve its affinity, a mutation library of #138-scFV was constructed by error-prone PCR and screened by FACS. After three rounds of sorting, we isolated one antibody (AM-32 scFv), which has a higher binding affinity (KD = 42.7 nM) than that of the original #138-scFv. We also confirmed that it specifically binds to whole inactivated FMDV.