A prevalence of neurological symptoms, cardiopulmonary complications and acute mortality caused by Enterovirus 71 (EV71) infection has been increased since its discovery. Due to the important role of airway in defending early EV71 invasion, intranasal vaccines has been suggested to provide protective immunity. However, the lack of effective nasal adjuvants has been the major obstacle to the development of intranasal vaccines. In this study, we examined the potential immuno-inducibility and protective efficiency of zymosan as a nasal adjuvant in an inactivated EV71 intranasal vaccine, which is a fungal glucan with β-1, 3-linkage that interacts with the highly expressed innate receptors in respiratory epithelial cells and dendritic cells including Toll-like receptor (TLR) 2/6 heterodimer, dectin-1 and dectin-2. At the cellular level, we showed that maturation of bone-marrow derived dendritic cells (BMDC) was promoted after treatment with zymosan by inducing IL-10, IL-12 p40 and IL-12 p70 production. In Balb/c mice, we found that three times of immunization with inactivated EV71 plus zymosan led to enhanced antigen-specific immune responses, including the IgG titer in sera, the IgA titer in nasal wash, the proliferative activity and IL-17 production from the restimulated splenocytes, but without affecting the weight of mice. Furthermore, we confirmed the serum antibodies of zymosan-adjuvanted mice to have neutralizing and cross-neutralizing ability in human Rhabdomyosarcoma (RD) cells. Taken together, our data suggested that zymosan could be used as potential adjuvants in an inactivated EV71intransal vaccine.
Key words: Adjuvant, Enterovirus 71, Intranasal vaccine, Zymosan.