Development of a feline coronavirus spike protein-expressing mRNA vaccine and immune response in mice and cats

No effective vaccine exists against feline coronavirus infection. Coronavirus spike (S) protein is rich in antigen epitopes and can mediate the production of antibodies that infect the host. Therefore, we developed an S protein for the development of a messenger ribonucleic acid (mRNA) vaccine. In this study, we constructed in vitro transcription (IVT)-mRNAs with different untranslated regions (UTRs) (i.e., IVT-mRNA-n1, IVT-mRNA-n2, and IVT-mRNA-n3) and introduced enhanced green fluorescent protein into the S protein separately. The best IVT was selected. The lipid nanoparticle (LNP)-mRNA vaccine was assembled with cationic LNPs to evaluate the expression of the target gene in vitro and the immune response in mice and cats. The results revealed that the 5’ and 3’ UTRs patterns derived from human α-globulin were the best. The developed mRNA vaccine could induce cats to produce S protein-specific antibodies, and increase interferon (IFN)-γ, interleukin (IL)-4, and tumor necrosis factor (TNF)-α expression. The feline coronavirus (FCoV) mRNA vaccine developed in this study provided a basis for subsequent immunization of felines. In addition, the optimization of target genes, incorporation of UTR, and selection of delivery vectors in this study provided a basis for optimizing the FCoV mRNA vaccine platform.