Formulation and evaluation of a self-emulsifying emulsion as an effective adjuvant for inactivated foot-and-mouth disease vaccine in mice

Dechun Xuan¹Naiyan Sun²Zhi Li²Jianzhong Tang¹Yanyan Zhao¹Rong Fan¹Yafang Xu¹Haidong Wang³Cuiqin Huang⁴Jinqiu Zhang^1*Yuanyuan Xu²Jinfeng Miao²

• ¹Jiangsu Academy of Agricultural Sciences (JAAS), Nanjing, China
• ²Nanjing Agricultural University, Nanjing, China
• ³Shanxi Agricultural University, Jinzhong, China
• ⁴Longyan University, Longyan, China

Foot-and-mouth disease (FMD) is an acute and febrile infectious disease that spreads rapidly among cloven-hoofed animals. Vaccination is one of the most effective methods for controlling FMD. However, commercially available FMD vaccines often have limitations in terms of stability, safety and efficacy. In this study, a novel self-emulsifying oil-in-water (O/W) emulsion (SEEX2-17) was developed, characterized and evaluated as an adjuvant against the inactivated FMD vaccine in mice. The data revealed that SEEX2-17 was a homogeneous nanoemulsion with a small particle size (~25 nm) and excellent stability (for at least 2 months at 37 ℃). Toxicity evaluation of SEEX2-17 showed that it had good safety and tolerability in mice. Moreover, the SEEX2-17-adjuvanted inactivated FMD vaccine induced significantly higher titers of FMDV-specific IgG antibodies when administrated to mice subcutaneously, and prolonged the duration of high-titer antibodies than the commercial ISA206-adjuvanted vaccine or antigen alone, respectively, within 12 weeks after immunization (P < 0.05). Furthermore, the vaccine adjuvanted with SEEX2-17 elicited significantly higher levels of IgG1 and IgG2a antibodies, as well as higher concentrations of cytokines (IFN-γ, IL-2, IL-4 and IL-6) than the antigen alone, indicating that the SEEX2-17-adjuvanted vaccine stimulated vigorous and long-lasting humoral and cellular immunity in mice. Moreover, SEEX2-17 promoted the maturation and activation of dendritic cells (DCs) in the lymph nodes as well as the proliferation of lymphocytes in the spleen. Thus, SEEX2-17 could trigger enhanced immunity and provide a promising and easy-to-use adjuvant platform for inactivated FMD vaccines with favorable stability and safety.