E2-based mRNA vaccine encapsulated in lipid nanoparticles protects pigs against classical swine fever virus

Classical swine fever (CSF), caused by the classical swine fever virus (CSFV), remains a significant threat to the global pig industry. Recent advances in mRNA vaccines offered a promising platform for combating CSFV. In this study, we designed and evaluated three lipid nanoparticle (LNP)-encapsulated mRNA vaccine candidates encoding the ectodomain of E2 glycoprotein (E2_EX), E2_EX fused with the transmembrane (TM) region of the PEDV S protein (E2tm), and E2_EX fused with the TM region of the influenza virus HA protein (E2tm-HA). Among these, the E2tm mRNA vaccine induced the most robust antibody responses in pigs. Immunization of piglets with the E2tm mRNA vaccine showed that its immunogenicity was not impaired by maternal antibodies. Comparative analysis of pseudouridine (Ψ)-modified ( Ψ E2tm) and unmodified (E2tm) mRNA vaccines revealed that E2tm induced significantly higher antibodies titers than Ψ E2tm. All vaccinated pigs survived the CSFV challenge, with the 150 µg E2tm dose providing optimal protection, effectively suppressing viremia and preventing viral dissemination to tissues while also resulting in undetectable viral RNA in swab samples. Our findings provide a promising novel mRNA vaccine that could be used as an alternative vaccination strategy against CSFV infection. IMPORTANCE Classical swine fever virus (CSFV) remains a significant threat to the global pig industry. While live attenuated and subunit vaccines are currently in use, there is an urgent need for more effective and safer vaccination strategies. Here, we present a novel mRNA vaccine encoding the CSFV E2 glycoprotein, which provides protective immunity against the CSFV challenge in pigs. Our findings underscore the promising efficacy of this mRNA-based vaccine platform and offer an alternative strategy for CSFV prevention and control.