We have created a new mRNA vaccine that can completely prevent swine fever
Background and Challenges
Traditional swine fever (CSF) vaccines utilize the E2 glycoprotein, but rapid viral mutations lead to decreased efficacy of existing vaccines and insufficient induction of cell-mediated immunity. Specifically, the E2 envelope protein of CSFV plays a crucial role in binding to host cell surface receptors and initiating infection. Modifying this region is challenging, and failure to do so hinders the ability to respond to new variants. Current commercial E2-based subunit vaccines have a slow immune response, limiting their ability to control rapidly spreading viruses in large-scale farms. The emergence of rapidly evolving CSFV 2.1c strains in China poses a significant risk of billions of dollars in losses to the global swine industry. Therefore, there is an urgent need for a next-generation vaccine platform that can induce faster and stronger immunity.
Research Methods and Key Findings
Leveraging the advantages of nucleic acid-based vaccines, we designed three mRNA-lipid nanoparticle (LNP) vaccines encoding modified E2 proteins. The first is a standard E2-expressing mRNA-LNP, the second is an XCL1-E2-mRNA-LNP that targets XCR1-expressing dendritic cells (DCs) by attaching XCL1 (chemokine ligand 1) to the N-terminus of E2, and the third is a Ub-E2-mRNA-LNP that fuses ubiquitin (Ub) to E2, promoting rapid proteasomal degradation and presentation via the MHC I pathway. All mRNAs were stabilized with modified nucleosides, such as N1-methyl-pseudouridine, to minimize innate immune recognition, and LNPs were formulated with a mixture of PEG-lipid and ionizable lipid to enhance intracellular delivery. Following immunization in rabbits and piglets, Ub-E2-mRNA-LNP significantly increased antigen-specific CD8+ T cells and IFN-γ secretion, and neutralizing antibody titers were more than three times higher compared to existing subunit vaccines. Importantly, this vaccine demonstrated 100% survival in a challenge study with the highly virulent CSFV Shimen strain, confirming complete protection.
Immune Effects and Protective Outcomes
The protection conferred by Ub-E2-mRNA-LNP is not solely explained by antibodies; the ubiquitin tag promotes rapid degradation of the E2 protein by intracellular proteasomes, leading to the generation of peptides that bind to MHC I molecules and are presented to CD8+ T cells. This process is known as cross-presentation and enables effective cell-mediated immunity early in viral infection, leading to the direct elimination of infected cells. Furthermore, compared to the DC-targeting XCL1-E2-mRNA-LNP, Ub-E2-mRNA-LNP further enhanced the Th1-biased response of CD4+ T cells, promoting IL-2 and TNF-α secretion, which also contributed to the formation of long-term memory B cells. In rabbit studies, no CSFV RNA was detected in the spleen after vaccination, and in pigs, there was no fever or clinical signs, demonstrating its potential for application in the field. This multi-faceted activation of immune pathways is the key mechanism that enables complete protection.
Future Implications or Prospects
This study demonstrates that combining ubiquitin tags with the mRNA-LNP platform to rapidly degrade and present antigens can induce superior cell-mediated immunity compared to traditional subunit vaccines. In the future, this technology can be used to rapidly design customized vaccines for other livestock diseases, such as African swine fever (ASF) or avian influenza. Furthermore, ubiquitin-based antigen design can also be applied to the development of human cancer antigen vaccines or viral disease vaccines, potentially accelerating the development of next-generation vaccines. We are currently collaborating with domestic and international regulatory agencies to verify safety and large-scale production processes, and commercialization will reduce annual losses to the global swine industry by billions of dollars. Ultimately, this innovative approach, which combines mRNA and protein degradation mechanisms, is likely to become a new standard in vaccine science.
Classical swine fever (CSF), caused by classical swine fever virus (CSFV), continues to threaten the global swine industry. Current E2-based subunit vaccines are limited by their slow adaptation to emerging viral strains and insufficient cell-mediated immunity. To address these challenges, we developed mRNA-lipid nanoparticle (LNP) vaccines encoding modified forms of the CSFV E2 glycoprotein. In this study, we constructed three novel mRNA-LNP vaccines encoding engineered E2 proteins: E2-mRNA-LNP, XCL1-E2-mRNA-LNP containing the X-C motif chemokine ligand 1 (XCL1) to target dendritic cells, and Ub-E2-mRNA-LNP containing ubiquitin (Ub) to enhance antigen presentation through Ub-mediated degradation. These vaccines were evaluated in rabbits and piglets. Following challenge with the live attenuated CSFV C-strain, rabbits immunized with XCL1-E2-mRNA-LNP or Ub-E2-mRNA-LNP exhibited neither fever nor detectable viral RNA in the spleens. Notably, immunization with Ub-E2-mRNA-LNP conferred complete protection against challenge with the highly virulent CSFV Shimen strain in piglets, outperforming the E2-based subunit vaccine, the unmodified E2-mRNA-LNP, and XCL1-E2-mRNA-LNP. Further analysis revealed that Ub-E2-mRNA-LNP elicited more potent antibody and cell-mediated immune responses. Our study demonstrates that Ub-E2-mRNA-LNP is a promising vaccine candidate for CSF prevention. IMPORTANCECSF remains a major threat to the global swine industry. Recently, a moderately virulent subgenotype CSFV 2.1c strain was isolated and reported in China. Given that the mRNA platform enables rapid vaccine development to address emerging pathogens, we constructed three nucleoside-modified mRNA-LNP vaccines expressing engineered E2 glycoproteins of CSFV, including E2-mRNA-LNP, XCL1-E2-mRNA-LNP (targeting dendritic cells), and Ub-E2-mRNA-LNP (enhancing proteasomal degradation). Evaluated in rabbits, XCL1-E2- and Ub-E2-mRNA-LNPs conferred strong protection against CSFV C-strain challenge, with no
The real problem this research aims to solve is the more than $2 billion annual loss to the global swine industry caused by swine fever (CSF) and the rapid viral mutations that render existing vaccines ineffective. Previously, E2 protein-based subunit vaccines have been limited by their inability to induce sufficient immune responses and their difficulty in rapidly responding to variant viruses, hindering their application in the field. We have overcome these limitations by combining ubiquitin tags with mRNA-LNP to promote proteasomal degradation and MHC I cross-presentation, achieving a breakthrough in inducing potent cell-mediated immunity. This will enable swine farmers to prevent outbreaks and reduce annual losses by billions of dollars, and it will shorten vaccine development time from weeks to months, enabling rapid response. In the future, this platform can be applied to other livestock diseases and human mRNA vaccines, revolutionizing global vaccine development paradigms.