Formulation of FMD vaccine in Naloxone/Alum mixture: A potency study

Background Current Foot-and-Mouth disease (FMD) vaccines are commonly formulated in the alum adjuvant. Several studies showed that this form of vaccine, although able to control the infection, lacks the ability to eradicate the infection completely. Objectives In this study, the FMD vaccine was formulated in a naloxone/alum mixture as an adjuvant, and its potency was compared with the alum-formulated vaccine. Methods Experimental Balb/c mice were immunized with a commercial vaccine or naloxone/alum-based vaccine two times, subcutaneously at two-week intervals. Lymphocyte proliferation was assessed using BrdU, and IL-4, IFN-γ, and TNF-α cytokines, specific total IgG as well as IgG1/IgG2a were evaluated by ELISA. In addition, the gene expression profiles of IL-12, IL-17, and IFN-γ cytokines were determined by real-time PCR. Results Results showed that mice immunized with the FMD vaccine formulated with the naloxone/alum mixture exhibited a tiny increase in the production of IFN-γ and TNF-α cytokines compared to the routine vaccine. However, mice immunized with the FMD vaccine formulated with the naloxone/alum mixture revealed a significant increase in the expression of IL-12, IL-17, and IFN-γ cytokines compared to those immunized with the routine vaccine. In addition, the novel formulation led to increased production of specific total IgG in comparison with the routine vaccine. Conclusions Our findings suggest that naloxone formulated in the FMD vaccine could improve cellular and humoral immune responses. However, the effect of this formulation on the efficacy of vaccine is remained to be clarified in future studies.