Abstract:
Porcine epidemic diarrhea virus can infect pigs at different ages and cause porcine epidemic diarrhea, leading to heavy economic losses to the pig industry around the world. There is currently no effective treatment for porcine epidemic diarrhea, and vaccination seems to be its key preventive approach. In order to develop an effective porcine epidemic diarrhea virus subunit vaccine, a tandem epitope subunit (EC) was assembled from the COE region (E1), S1D region (E2), and C-terminal region (E3) of spike protein, and the M3 region (E4) of membrane protein, and a baculovirus expression system was constructed for the production of subunit vaccine EC. The reported candidate subunits COE and S1 were used as positive controls. Three target proteins of EC, COE and S1 were produced by baculovirus expression vector systems in insect cell line Sf9, and purified with a nickel affinity chromatography column, respectively. The immunogenicity of the different subunit vaccines was evaluated on BALB/c mouse. The results showed that the EC, COE and S1 gene sequences were successfully inserted into the baculovirus genome. All the three proteins could be expressed and secreted into culture supernatant. Compared with the subunit vaccines of COE and S1, subunit vaccine EC could stimulate mouse to produce larger amount of specific immunoglobulin G, interferon-γ and tumor necrosis factor-α than controls. The above results indicate that each subunit vaccine can stimulate the humoral and cellular immunity of mouse, and the immunogenicity of subunit vaccine EC is much stronger.