Prokaryotic Expression and Immunogenicity Analysis of VP1 Structural Protein from Type O Foot-and-Mouth Disease Virus

Purpose To construct the recombinant plasmid pET-28a-His-VP1 for expressing the VP1 protein of type O foot-and-mouth disease virus (FMDV). The expressed VP1 protein was purified and used to immunize mice to analyze its immunogenicity, aiming to provide theoretical and experimental insights for the development of FMDV subunit vaccine.

Methods Expression conditions for VP1 protein were optimized by adjusting isopropyl-β-D-thiogalactopyranoside (IPTG) concentration, induction temperature, and induction time. Serum antibody titers and subtypes were determined by indirect ELISA. A serum neutralization test was performed using BHK-21 cells to assess protective efficacy, and mRNA expression levels of cytokines were quantified by qPCR.

Results Maximal VP1 protein expression was achieved by induction with 0.8 mol/L IPTG at 37 ℃ for 10 h. Immunization with the VP1 protein triggered a strong humoral immune response, with an antibody titer reaching 1∶409600, and induced a mixed Th1/Th2 immune response, as indicated by the presence of IgG2a, IgG2b, and IgG1 subtypes. VP1 immunoserum exhibited good neutralizing activity, which could effectively inhibited viral adsorption. Additionally, VP1 immunization significantly upregulated the mRNA expression of IL-6 and TNF-α.

Conclusion The recombinant VP1 fusion protein is successfully expressed in Escherichia coli with high immunogenicity, offering a promising candidate antigen for FMDV subunit vaccine design.