The Effects Of New Class Of Adjuvants On FMDV DNA Vaccination

Foot-and-mouth disease (FMD) is a highly contagious viral disease of cloven-hoofed animals, including cattles, pigs and sheep. Current FMD vaccines are mainly based on inactivated virus, although effective, but outbreaks of FMD have been directly associated with incomplete inactivation of virus, and even some time contribution to the escape of virus from vaccine manufacturing facilities. In addition, this traditional type of vaccine is often formulated with oil as adjuvant. Despite their efficacy in generating humoral immune responses, the oil formulation have generally proved ineffective in inducing cellular immune responses that are most relevant to antiviral protection. Another drawback of the oil formulations is that their use often results in undesirable side effects such as granulomas and cysts. These adverse reactions are caused by several factors including impure components of the oil adjuvant. Alternative adjuvants or regimens have been investigated to develop more safe and effective FMD vaccines. DNA vaccination is useful for generating immune responses, particularly the cell-mediated immune response, in a wide variety of species. However, DNA vaccination generally induces only relatively weak responses, particularly in large animals and human. Although, various approaches have been developed recently in order to improve its efficacy or immunopotency, limited success has been achieved in a practical term. We have recently tested several chemicals for their usefulness as adjuvants in facilitating DNA vaccination. To study the immune effects of adjuvant on FMDV DNA vaccine, the recombinent plasmid pcD-VP1 was injected mixed with different adjuvants. The different MHC class-restricted mice, Kunming White (outbred), Balb/C (H-2Dd) and C57B/6 (H-2Db), were immunized with pcD-VP1 mixed 1% LMS, control group without LMS. The specific antibody titer IgG of VP1 was detected by indirect ELISA and the level of cellular immunity was tested by MTS and DTH, and the cytokine also be tested by RT-PCR. The experimental results showed that not only the level of the cellular response but also the humoral response can be enhanced due to LMS in the experimental group. Based on above results, several more improved and potent adjuvant formulations were tested in the regards to argument the cellular and humoral responses without compromising long-term immunity. To that end, the mice were injected with the FMDV DNA vaccine, pcD-VP1, mixed different formulations, and the LMS as a control. The results indicated the adjuvant containing the squalane showed good immune responses and long duration have been achieved for the levels of antibody response and cytolytic T cell activity.