Competition ELISA of 40 PF sera was carried out to see if the binding against standard Dsg1 ELISA plates of PF sera was blocked by adding anti-Dsg1scFv mAbs. 3–30/3h (shown in orange), 3–97/1c, 3–94/O18O8 (shown in green) and 1–18/L12 (shown in blue) were used as competitors. When >20% inhibition was considered as significant (shown in broken line), the bindings were blocked by pathogenic 3–30/3h mAb in 29 PF sera. 3–97/1c and 3–94/O18O8, which recognized the precursor form, blocked the binding in 10 PF sera.