Fig. 2
Effect of the EV-A71 + EV-D68 bivalent vaccine on EV-D68- and EV-A71-specific IgG and IgA and neutralization titres against infection by different enteroviruses in immunized mice. Mice were intranasally immunized with PBS, formalin-inactivated EV-A71 (2.5 μg/mouse), formalin-inactivated EV-D68 (2.5 μg/mouse), and combined formalin-inactivated EV-A71 (2.5 μg/mouse) and EV-D68 (2.5 μg/mouse) thrice at 3-week intervals. a Three-dose immunization schedules. b The levels of EV-D68-specific IgA and IgG and c EV-A71-specific IgA and IgG in the saliva, nasal wash, BALF, and feces of mice after the third immunization were measured using ELISA. d The levels of EV-D68-specific IgG and IgA and e EV-A71-specific IgG and IgA in the sera of mice after the third intranasal immunization were measured using ELISA. Sera were serially diluted (23–212), mixed with f EV-D68 and g EV-A71 virus, and used to infect RD cells. After 4 d, the the highest dilution that resulted in the virus producing no cytopathic effect was considered to be the neutralization titre. All data are expressed as the mean ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001