We took the surface spike S protein of transmissible gastroenteritis virus(TGEV)as the research object.Based on the Gram-positive enhancer matrix(GEM)-anchor protein(PA)display platform,two kinds of bacteria-like particles(BLPs)with surface-displayed TGEV DA and S1 were prepared using the insect cell-baculovirus expression system.The results showed that the lev-els of IL-4,IFN-γ,IgG,IgA,and sIgA induced by 50 μg BLP-DA were higher than those of the 25μg group.The levels of IL-4,IFN-γ,and sIgA induced by 50 μg BLP-S1 were higher than those of the 25 μg group,while the levels of IgG and IgA were lower than those of the 25 μg group.Under the same dose,when the dose was 25 μg,the levels of IFN-γ,IgG,IgA,and sIgA induced by BLP-S1 were higher than those of BLP-DA,while the level of IL-4 was lower than that of BLP-DA.When the dose was 50 μg,the level of IgG induced by BLP-DA was higher than that of BLP-S1,while the other indicators were lower than those of BLP-S1.Under different immunization routes,the levels of IgA and sIgA in the gavage group were higher than those in the intramuscular injec-tion group,and the levels of some cytokines were significantly higher in the gavage group than in the intramuscular injection group at specific time points,but there was no significant difference in the levels of IgG antibodies.In conclusion,the two types of TGEV BLPs constructed in this study both have good immunogenicity and can induce cellular and humoral immunity in mice.When the immunization doses are the same,the immunogenicity of BLP-S1 is better than that of BLP-DA.

We took the surface spike S protein of transmissible gastroenteritis virus(TGEV)as the research object.Based on the Gram-positive enhancer matrix(GEM)-anchor protein(PA)display platform,two kinds of bacteria-like particles(BLPs)with surface-displayed TGEV DA and S1 were prepared using the insect cell-baculovirus expression system.The results showed that the lev-els of IL-4,IFN-γ,IgG,IgA,and sIgA induced by 50 μg BLP-DA were higher than those of the 25μg group.The levels of IL-4,IFN-γ,and sIgA induced by 50 μg BLP-S1 were higher than those of the 25 μg group,while the levels of IgG and IgA were lower than those of the 25 μg group.Under the same dose,when the dose was 25 μg,the levels of IFN-γ,IgG,IgA,and sIgA induced by BLP-S1 were higher than those of BLP-DA,while the level of IL-4 was lower than that of BLP-DA.When the dose was 50 μg,the level of IgG induced by BLP-DA was higher than that of BLP-S1,while the other indicators were lower than those of BLP-S1.Under different immunization routes,the levels of IgA and sIgA in the gavage group were higher than those in the intramuscular injec-tion group,and the levels of some cytokines were significantly higher in the gavage group than in the intramuscular injection group at specific time points,but there was no significant difference in the levels of IgG antibodies.In conclusion,the two types of TGEV BLPs constructed in this study both have good immunogenicity and can induce cellular and humoral immunity in mice.When the immunization doses are the same,the immunogenicity of BLP-S1 is better than that of BLP-DA.

Infectious bronchitis in chickens is a serious threat to the global poultry industry.Despite the availability of commercial vaccines,the epidemic has not been effectively controlled.Therefore,the development of novel vaccines may provide new ways to prevent and control this disease.In this study,BLP-S1,a bacterium-like particle displaying the S1 subunit of infectious bronchitis virus on its surface,was constructed using the GEM-PA system.The immunoprotection results showed that BLP-S1 effectively induced the production of specific IgG and sIgA in commercial chickens and provided effective protection against a heterologous strain with a protection rate of up to 90％.This study demonstrated that BLP-S1 has good immunogenicity and immunoprotection,with the poten-tial to develop a novel vaccine against infectious bronchitis.