Development of an experimental inactivated vaccine from Vero cell adapted Enterovirus D68

Enterovirus D68 is an emerging respiratory disease pathogen causing multiple outbreaks worldwide. Enterovirus D68 strain US/KY/14-18953 was adapted to propagate in Vero cells resulting alteration of seven amino acids. The Vero cell adapted virus was inactivated with Formalin and immunized in mice. Formalin inactivated vaccine elicited high virus specific IgG antibody titer and neutralization titer. Avidity of the IgG antibodies elicited by two different doses of formalin inactivated vaccine is moderately high which got augmented by alum adjuvanted formulations. Formalin inactivated unadjuvanted vaccine elicited a balanced IgG1 type and IgG2a type antibody indicating a more balanced Th2/Th1 type immune response while alum formulated formalin inactivated antigen elicited significantly high IgG1 antibody in immunized sera and Th2 cytokines in mice splenocytes denoting Th2 type T cell immune response. Additionally, the formalin inactivated vaccine formulations has displayed excellent serum mediated invivo protective efficacy. These data suggested that formalin inactivated Enterovirus D68 is a promising vaccine candidate.