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

Flagellin, a monomeric subunit of bacterial flagella, is one of many pathogen-associated molecular pattern (PAMP) proteins that are recognized by two germline-encoded receptors, TLR5 and NLRC4/NAIP5, on a number of innate and adaptive immune cells. Flagellin has been frequently used as a molecular fusion adjuvant in recent decades [11] [12] [13] [14] , and both receptors are thought to be involved in its adjuvant activity. Flagellin has also been used as a fusion partner to enhance the solubility of many hard-to-express proteins [15] . However, the conjugation effect of flagellin varies depending on the target antigen or the direction of its conjugation [13, 16] . Therefore, the conjugation of flagellin to different terminals (the N-or C-terminus) of S0 could influence both solubility and immunogenicity.