Enhanced neutralizing antibody response induced by inactivated enterovirus 71 in cynomolgus monkeys

Abstract

Enterovirus 71 (EV71) is a major etiological agent of various public health issues, particularly in the Asia-Pacific region. EV71 causes hand-foot-and-mouth disease (HFMD) and is associated with serious neurological disorders in young children. A formalin-inactivated EV71 candidate vaccine (KCDC-HFMDV1-EV71) based on the C4 subgenotype was previously developed and confirmed to be a potential candidate vaccine for prevention of EV71 infection in mice. In this study, an inactivated EV71 vaccine was used for analysis of long-term immunogenicity and efficacy in cynomolgus monkeys, a common nonhuman primate model. The vaccine was immunized three times at 0, 4, and 8 weeks with either 20-μg doses of EV71 candidate vaccine formulated with aluminum hydroxide gel adjuvant or phosphate-buffered saline as a control. The group immunized with the inactivated EV71 showed significantly increased EV71-specific antibody and serum neutralizing antibody titers at 3 weeks after vaccination and maintained these elevated titers until the end of the experiment (54 weeks after vaccination). The sera from vaccinated cynomolgus monkeys showed a crossreactive neutralizing antibody response to the heterologous subtype of EV71 (B1-4, C1, and C2). These findings suggest that the inactivated EV71 candidate vaccine may be a potential vaccine candidate and valuable tool for the control of HFMD.

Fig 1. EV71-specific IgG responses induced by the inactivated EV71 vaccine.

Cynomolgus monkeys were vaccinated with inactivated EV71 vaccine (EV71) or PBS (mock) as a control. Serology, including EV71-specific total IgG (A) and IgG subclass (B) responses, was assessed by ELISA. ***P < 0.001 using Two-way ANOVA with Bonferroni post-hoc test compared with the control group (mock).

Fig 2. EV71-specific SN antibody titers against homologous and heterologous strains after EV71 vaccination.

Cynomolgus monkeys were vaccinated with inactivated EV71 vaccine (EV71) or PBS (mock) as a control. The levels of serum neutralizing antibodies against EV71 were measured using the vaccine strain (A) and nine heterologous strains belonging to different subgenotypes (B). ***P < 0.001 using Two-way ANOVA with Bonferroni post-hoc test.

Fig 3. EV71-specific cell-mediated immune responses induced by the inactivated EV71 vaccine.

Cynomolgus monkeys were vaccinated with inactivated EV71 vaccine (EV71) or PBS (mock) as a control. PBMCs from monkeys were isolated and stimulated with EV71 vaccine. The supernatants of cultured PBMCs were harvested at 24 h after stimulation and analyzed for cytokines using a multiplex system.