Effect of W/O/W adjuvant added with two immunopotentiator on inactivated foot-and-mouth disease vaccine
To enhance the immune efficacy of the inactivated foot-and-mouth disease vaccine,this study incorporated immunopotentiators into the water-in-oil-in-water(W/O/W)adjuvant formulation.Two types of immunopotentiators,natural compound vitamin E(VE)and synthetic derivative imiquimod(IMQ-Chol)were used.The basic formulation was mixed with the inactivated foot-and-mouth disease virus,along with three different doses(low,medium,high)of each immunopotentiator,to prepare various adjuvants.The appearance and physicochemical properties of each vaccine were determined,including stability,viscosity,particle size,and polydispersity index(PDI).The safety of the immunopotentiator was evaluated through mouse body weight,routine blood test,blood biochemistry,and histological changes.Furthermore,the impact of the immunopotentiator on vaccine immune efficacy was assessed by examining specific antibodies,antibody subtypes,cytokine levels in mouse sera,and differentiation of mouse splenic T lymphocytes.The results showed that the prepared vaccines were milky white W/O/W emul-sions with no phase separation after 9 weeks at 37 ℃.The viscosity remained below 16 cp,and the parti-cle size ranged from 270 nm to 370 nm,with the PDI between 0.34 and 0.42.None of the immunopotentiators affected mouse body weight(P＞0.05),and routine blood test,blood biochemistry and histological sections indicated that both immunopotentiators had good biological safety.Compared to the basic formula group,the groups immunized with VE or IMQ-Chol showed significantly higher level of specific antibody(P＜0.01).Notably,the group with high-dose VE and low-dose IMQ-Chol significantly increased the spe-cific antibody level(P＜0.001),as well as the secretion levels of Th1-related molecules(IgG2a,IFN-γ,IL-12)and Th2-related molecules(IgG1,IL-4,IL-6)(P＜0.05).The proportions of CD3+CD4+T cells in these two groups were 75.2％and 77.3％,which were higher than the 69.6％in the basic formulation group,and the CD4+/CD8+ratio was higher as well(P＜0.05).The above results indicated that both VE and IMQ-Chol did not impact the physicochemical properties of the vaccine,maintained good safety,and the addition of high-dose VE or low-dose IMQ-Chol could enhance the immune efficacy of the inactivated foot-and-mouth disease vaccine.
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