Chaperna-assisted self-assembly of foot and mouth disease virus-like particles and nanoparticles

Abstract Foot-and-mouth disease virus (FMDV) is a highly contagious pathogen affecting cloven-hoofed livestock worldwide, necessitating the development of safe and effective vaccines. While conventional inactivated vaccines require biosafety level 3 (BSL-3) facilities, bacterially produced recombinant subunit vaccines would offer a safer and cost-effective alternative. However, expression and assembly of soluble structural proteins of FMDV in Escherichia coli in an immunologically relevant conformation has remained a significant challenge. In this study, we successfully expressed FMDV virus-like particles (VLPs) and pentameric VP1 constructs in E. coli using a novel RNA-assisted chaperone (chaperna) system. While direct expression of VP0, VP1, VP3, and Labile Toxin B subunit (LTB)-FMDV VP1 resulted in insoluble aggregates, fusion with tRNA interacting domain (tRID) significantly enhanced solubility and expression yields. Structural characterization by size exclusion chromatography (SEC) and transmission electron microscopy (TEM) confirmed the assemblage into VLPs and pentameric sub-virion nanoparticles (NPs). In a competitive ELISA using sera from immunized mice, both the VLP and FMDV VP1 pentamer groups showed percentage inhibition values above the assay cut-off, supporting preservation of antigenicity. These findings demonstrate that chaperna enables efficient folding and assembly of structurally intact FMDV antigens as subunit vaccine candidates in E. coli. This approach offers a bio-safe and scalable platform for vaccine development, particularly for serotypes like Asia1, and highlights the potential of chaperna strategies in microbial production of recombinant FMDV vaccines. Graphical abstract Key points • RNA-interacting domain fusion enables soluble expression of VP0/VP1/VP3 in E. coli • Individual VP capsid proteins self-assemble into VLPs and FMDV VP1 pentamers • This platform enables a low-cost bacterial production for FMDV subunit antigens