Enhancement of antigen-specific humoral immune responses and protein solubility through conjugation of bacterial flagellin, Vibrio vulnificus FlaB, to the N-terminus of porcine epidemic diarrhea virus surface protein antigen S0

Oh, Seo-ho; Kim Cho, Young-Saeng; Lee, Ho-Bin; Lee, Sang-Mok; Kim, Whee-Soo; Hong, Liang; Cho, Chong-Su; Choi, Yun-Jaie; Kang, Sang-Kee

The truncated S0 region (25-229 amino acid) of the PEDV spike protein, which contains neutralizing epitopes and supports cross-protection among non-S-Indel PEDV strains [10] , was chosen as the target antigen. Bacterial flagellin from Vibrio vulnificus, FlaB, was used as a fusion adjuvant candidate. FlaB was fused to the C-or N-terminus of S0 to generate S0-F and F-S0, respectively ( Fig. 2A) . Nucleotide sequences encoding each recombinant protein (S0, S0-F, F-S0 and F) were inserted into the pET-28a(+) expression vector, which supports hexahistidine tags (6His-tags) that flank the N-and C-terminus of the target protein to enhance purification efficiency. The BamHI and NheI restriction enzyme sites were used to generate S0-F and F-S0 in which each sequence of S0 and F were linked by two amino acids (Gly-Ser or Ser-Ser, respectively). All genetic codons were optimized to facilitate expression in E. coli.