M2 specific candidates isolation using bio-panning.

(A) Three rounds of bio-panning were performed with positive samples, in which M2 antigens were displayed on the yeast cell surfaces (M2::YSD), and negative samples (EBY100). Numerous phagemid colonies were randomly selected and the binding affinity measured for both positive and negative samples in each bio-panning round using Phage ELISA. Data are expressed as means ± SD. (B) Ten candidates with the highest binding affinity to M2::YSD were chosen using Phage ELISA from random phagemid colonies. (C) The 10 candidates, scFv and single-domain VL forms, were detected using PCR with specific primers (scFv at 900 bp and VL at 400 bp).