Montanide ISA™ 201 adjuvanted FMD vaccine induces improved immune responses and protection in cattle.

Despite significant advancements in modern vaccinology, inactivated whole virus vaccines for foot-and-mouth disease (FMD) remain the mainstay for prophylactic and emergency uses. Many efforts are currently devoted to improve the immune responses and protective efficacy of these vaccines. Adjuvants, which are often used to potentiate immune responses, provide an excellent mean to improve the efficacy of FMD vaccines. This study aimed to evaluate three oil adjuvants namely: Montanide ISA-201, ISA-206 (SEPPIC, France) and GAHOL (an in-house developed oil-adjuvant) for adjuvant potential in inactivated FMD vaccine. Groups of cattle (n=6) were immunized once intramuscularly with monovalent FMDV 'O' vaccine formulated in these adjuvants, and humoral (serum neutralizing antibody, IgG1 and IgG2) and cellular (lymphoproliferation) responses were measured. Montanide ISA-201 adjuvanted vaccine induced earlier and higher neutralizing antibody responses as compared to the two other adjuvants. All the adjuvants induced mainly serum IgG1 isotype antibody responses against FMDV. However, Montanide ISA-201 induced relatively higher IgG2 responses than the other two adjuvants. Lymphoproliferative responses to recall FMDV antigen were relatively higher with Montanide ISA-201, although not always statistically significant. On homologous FMDV challenge at 30 days post-vaccination, 100% (6/6) of the cattle immunized with Montanide-201 adjuvanted vaccine were protected, which was superior to those immunized with ISA-206 (66.6%, 4/6) or GAHOL adjuvanted vaccine (50%, 3/6). Virus replication following challenge infection, as determined by presence of the viral genome in oropharynx and non-structural protein serology, was lowest with Montanide ISA-201 adjuvant. Collectively, these results indicate that the Montanide ISA-201 adjuvanted FMD vaccine induces enhanced immune responses and protective efficacy in cattle.