Porcine deltacoronavirus (PDCoV) is a global epidemic enteropathogenic coronavirus that mainly infects piglets, and causes huge losses to the pig industry. However, there are still no commercial
vaccines available for PDCoV prevention and controlment. Receptor-binding domain (RBD) is located at the S1 subunit of PDCoV and is the major target for developing viral inhibitor and
vaccine. In this study, the characteristics of the RBD were analyzed by bioinformatic tools, and
codon optimization was performed to efficiently express the PDCoV-RBD
protein in the insect baculovirus expression system. The purified PDCoV-RBD
protein was obtained and fully emulsified with CPG2395 adjuvant, aqueous adjuvant and Al(
OH)3 adjuvant, respectively, to develop
vaccines. The humoral and cellular immune responses were assessed on mice. The results showed that both the RBD/CPG2395 and RBD/aqueous adjuvant could induce stronger immune responses in mice than that of RBD/Al(
OH)3. In addition, the PDCoV challenge
infection was conducted and the RBD/CPG2395 could provide better protection against PDCoV in mice. Our study showed that the RBD
protein has good antigenicity and can be used as a protective
antigen, which provided a basis for the development of the PDCoV
vaccine.