Construction of vitamin E-based oil-in-water nano-emulsion adjuvant enhances immunogenicity of inactivated pseudorabies virus vaccine.

Despite being a common way to prevent infection with the pseudorabies virus (PRV), inactivated vaccines are less effective because of their poor immunogenicity. Adjuvants, as an important component of vaccines, can greatly boost and alter the immune response. In this study, a newly oil-in-water nano-emulsion adjuvant OEBB containing 20 % vitamin E, 30 % Tween-80, and 50 % 1,3-propylene didecanoate was easily prepared with a good thermal stability and biosafety. Combining an inactivated PRV (10 TCID50/20 μL) with OEBB, the inactivated OEBB/PRV nano-vaccine with the effective particle diameter of 194.01 ± 59.54 nm was formulated. It displayed a good temperature stability and maintained the particle size within 28 days. Then, the OEBB/PRV nano-vaccine was evaluated for its safety and immunization effect using mice and piglets. The results showed that the OEBB/PRV nano-vaccine significantly increased model animals' antibody and cytokines. The neutralizing antibody was higher than PRV alone but there was no significantly difference from commercial adjuvant ISA201. Moreover, the challenge protection rate can reach 80 %, which was obviously superior to that of ISA201 (70 %). Safety tests found no hemolytic side effects, no symptoms of PRV or significant toxic reactions, and no damage to organs. The OEBB could enhance the activation of antigen-presenting cells in the local injection skin to deliver the PRV antigen to nearby lymph nodes. This led to increase CD3 population and promote differentiation to CD4 and CD8, which ultimately induced humoral and cellular immunity. The as-prepared OEBB in this study is an effective adjuvant for PRV inactivated vaccine.