Immunogenicity Of Multi-epitope Vaccines Based On Staphylococcus Aureus FnBPA And Streptococcus Dysgalactiae GapC_1-150

Staphylococcus aureus and streptococcus are important pathogens of dairy cow mastitis.Antibiotics have been unable to effectively prevent S.aureus and streptococcus.Vaccination has become an effective measure to prevent S.aureus and Streptococcus infections.Studies have shown that both cellular and humoral immune responses play important roles during S.aureus and streptococcus infections.Therefore,it is necessary to study a multi-epitope vaccine that can prevent both S.aureus and streptococcus and induce cellular and humoral immune responses.Staphylococcus aureus Fn BPA and Streptococcus Gap C are highly conserved and have good immune protection.In this experiment,a multi-epitope vaccine containing CD4+ T-cell epitopes and B-cell epitopes of Fn BPA and Gap C1-150 was constructed and the immunogenicity was studied.We constructed epitope-vaccines FTB2,FB1B2 and FTB1B2 with a T cell epitope(Fn BPA488-505,abbreviated as FT)and two B cell epitopes(Fn BPA352-364,abbreviated as FB1,and Fn BPA763-772,abbreviated as FB2),which were identified in Fn BPA of S.aureus,in tandem by GSGSGS linker.BALB/c mice were immunized to evaluate the effect of the vaccines.The results showed that the levels of cytokines induced by FTB1B2 were significantly higher than those of other epitope vaccines,but lower than Fn BPA;the levels of induced Ig G were significantly higher than those of other epitope vaccines except for FB1B2 and Fn BPA.The number of bacterial colonies in organs of FTB1B2 immunized mice was significantly lower than that of other epitope vaccines,but higher than that of Fn BPA immunized mice.It is shown that the multi-epitope vaccine FTB1B2 can induce a strong cellular and humoral immune response and effectively inhibit the colonization of S.aureus.We constructed epitope-vaccines GTB1,GB1B2 and GTB1B2 with a T cell epitope(Gap C63-77,abbreviated as GT)and two B cell epitopes(Gap C30-36,abbreviated as GB1,and Gap C97-103,abbreviated as GB2),which were identified in Gap C1-150 of S.dysgalactiae,in tandem by GSGSGS linker.BALB/c mice were immunized to evaluate the effect of the vaccines.The results showed that the levels of cytokines and Ig G induced by GTB1B2 were lower than those of Gap C1-150,but significantly higher than those of other epitope vaccine immunized groups.Moreover,the colonization number of S.dysgalactiae in the organs of mice immunizedin the GTB1B2 group was higher than that in the Gap C1-150 immunized group.It is shown that the T-cell epitope and B-cell epitope in the epitope-vaccine jointly resist bacterial attack,and the multi-epitope vaccine GTB1B2 could induce stronger cellular and humoral immune responses and inhibit the colonization of S.dysgalactiae.Based on these studies,we constructed epitope-vaccine FG with FTB1B2 and GTB1B2,and constructed epitope-vaccine FGT with FT and GT.The effect of the vaccines was evaluated by immunizing BALB/c.The results show that FT,GT,and FGT could only induce cellular immune responses,and could not significantly inhibit colonization of S.aureus or S.dysgalactiae.The cellular and humoral immune responses induced by FG were significantly higher than those of GT,FGT and GST,but significantly worse than those of FTB1B2 and GTB1B2;The bacterial colonization numbers in the organs of the mice immunized with FG were lower than those of the mice immunized with FT,GT and FGT,but higher than those of the mice immunized with FTB1B2 and GTB1B2.The above results indicated that the T-cell epitope and B-cell epitope in the epitope vaccine jointly resisted S.aureus and streptococcus infection.The above results indicated that the T-cell epitope and B-cell epitope in the epitope vaccine jointly resisted S.aureus and streptococcus infection.The FG epitope-vaccine constructed in this experiment could induce an ideal immune response and inhibit colonization of S.aureus and S.dysgalactiae in the organs of challenged mice.