Production of Plant-Based Recombinant Vaccine Against Porcine Deltacoronavirus in the Form of Bacteria-Like Particles Using Lactococcus lactis

Porcine deltacoronavirus (PDCoV) is an enteropathogenic swine coronavirus that causes severe diarrheal disease in suckling piglets and young pigs, leading to death. Transfer of maternal neutralizing antibodies from sows to piglets is critical to protecting piglets from PDCoV. Therefore, highly immunogenic antigens are required for the development of effective vaccine. Here, we produced plant-based recombinant protein vaccine against PDCoV in the form of bacteria-like particles (BLPs) using Lactococcus lactis to enhance the antigenicity. The S1 domain of spike protein from KNU16-07 strain was used as an antigen. The antigen was fused with lysine motifs (LysM) and coiled domains of coronin 1 (ccCor1) for L. lactis surface display. This fusion strategy facilitated the separation of the expressed proteins and increased antigenicity. The recombinant proteins were expressed in Nicotiana benthamiana and purified as BLPs. To determine whether PDCoV S1-coated BLPs could be immunized in the absence of adjuvants, plasma samples were obtained from mice injected with antigen. In conclusion, the PDCoV S1 domain generated from N. benthamiana excellently produced antibodies as a potential antigen and can be considered as an effective vaccine for passive immunization of piglets against PDCoV.