J Vet Sci.  2019 Nov;20(6):e70. 10.4142/jvs.2019.20.e70.

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

  • 1Department of Agricultural Biotechnology and Research Institute of Agriculture and Life Science, Seoul National University, Seoul 08826, Korea.
  • 2Institute of Green-Bio Science & Technology, Seoul National University Graduate School of International Agricultural Technology, Pyeongchang 25354, Korea. kangsk01@snu.ac.kr


Porcine epidemic diarrhea (PED) is a highly contagious enteric swine disease. The large economic impact of PED on the swine industry worldwide has made the development of an effective PED vaccine a necessity. S0, a truncated region of the porcine epidemic diarrhea virus (PEDV) spike protein, has been suggested as a candidate antigen for PED subunit vaccines; however, poor solubility problems when the protein is expressed in Escherichia coli, and the inherent problems of subunit vaccines, such as low immunogenicity, remain. Flagellin has been widely used as a fusion partner to enhance the immunogenicity and solubility of many difficult-to-express proteins; however, the conjugation effect of flagellin varies depending on the target antigen or the position of the fusion placement. Here, we conjugated flagellin, Vibrio vulnificus FlaB, to the N- and C-termini of S0 and evaluated the ability of the fusion to enhance the solubility and immunogenicity of S0. Flagellin conjugation in the presence of the trigger factor chaperone tig greatly improved the solubility of the fusion protein (up to 99%) regardless of its conjugation position. Of importance, flagellin conjugated to the N-terminus of S0 significantly enhanced S0-specific humoral immune responses compared to other recombinant antigens in Balb/c mice. The mechanism of this phenomenon was investigated through in vitro and in vivo studies. These findings provide important information for the development of a novel PED vaccine and flagellin-based immunotherapeutics.


Porcine epidemic diarrhea; subunit vaccine; flagellin; fusion adjuvant; solubility

MeSH Terms

Escherichia coli
Immunity, Humoral*
In Vitro Techniques
Porcine epidemic diarrhea virus*
Swine Diseases
Vaccines, Subunit
Vibrio vulnificus*
Vaccines, Subunit
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