Cui, J.; Yuan, F.; Qin, J.; Jeon, J. H.; Yun, D. S.; Wang, T.; Xu, R.; Cao, H.; Chen, J.

Viral capsid proteins are widely explored for subunit vaccine development but are often hampered by their complexity of production and low immunogenicity. Here, we report a simple approach to overcome these challenges by combining mRNA vaccine technology with protein engineering. Using African swine fever virus (ASFV) capsid proteins P72 and penton as models, we engineered them into membrane-bound and secreted forms, and compared their immunogenicity to the native intracellular form in mice and pigs through mRNA vaccination. The membrane-bound and secreted P72 and penton folded into their native multimeric structure independent of viral chaperone, therefore preserving their conformational epitopes. The membrane-bound P72 and penton also elicited significantly stronger antibody and T cell responses than their secreted or intracellular counterparts. Our study provides a simple approach to enhance folding, multimeric structure formation, and immunogenicity of viral capsid proteins for ASFV subunit vaccine development and immunogenicity of intracellular proteins in general.