Abstract
BackgroundEnterovirus 71 (EV71) is the etiologic agent of hand-foot-and-mouth disease (HFMD) in the Asia-Pacific region, Many strategies have been applied to develop EV71 vaccines but no vaccines are currently available. Mucosal immunization of the VP1, a major immunogenic capsid protein of EV71, may be an alternative way to prevent EV71 infection.ResultsIn this study, mucosal immunogenicity and protect function of recombinant VP1 protein (rVP1) in formulation with chitosan were tested and assessed in female ICR mouse model. The results showed that the oral immunization with rVP1 induced VP1-specific IgA antibodies in intestine, feces, vagina, and the respiratory tract and serum-specific IgG and neutralization antibodies in vaccinated mice. Splenocytes from rVP1-immunized mice induced high levels of Th1 (cytokine IFN-γ), Th2 (cytokine IL-4) and Th3 (cytokine TGF-β) type immune responses after stimulation. Moreover, rVP1-immunized mother mice conferred protection (survival rate up to 30%) on neonatal mice against a lethal challenge of 103 plaque-forming units (PFU) EV71.ConclusionsThese data indicated that oral immunization with rVP1 in formulation with chitosan was effective in inducing broad-spectrum immune responses and might be a promising subunit vaccine candidate for preventing EV71 infection.
Highlights
Enterovirus 71 (EV71) is the etiologic agent of hand-foot-and-mouth disease (HFMD) in the Asia-Pacific region, Many strategies have been applied to develop EV71 vaccines but no vaccines are currently available
The concentration of recombinant VP1 protein (rVP1) protein was adjusted to 2 mg/ml with BCA kit (Pierces, USA), in which the LPS level was detected below 1500 EU/mg with the kit mentioned above
The efficacy and protective functions of oral immunization with chitosan and recombinant EV71 VP1 formulations were analyzed and evaluated in ICR mouse model with lethal challenge of EV71, and the results presented that chitosan help EV71 rVP1 induced better VP1-specific IgA antibodies in intestine, feces, vagina, and respiratory tract, and systemic specific IgG and neutralization antibodies in humoral immune responses as well as the Th1 and Th2 cellular immune responses
Summary
Enterovirus 71 (EV71) is the etiologic agent of hand-foot-and-mouth disease (HFMD) in the Asia-Pacific region, Many strategies have been applied to develop EV71 vaccines but no vaccines are currently available. A wide range of strategies have been applied to develop EV71 vaccines, including attenuated live vaccine [3,4], inactivated vaccine [5,6], Virus-like particles (VLP) vaccine [7], VP1 subunit [6] or DNA vaccine [6,8], et al and their efficacy has been studied in animals or even clinical trials. To potentiate mucosal immune responses and protect antigens from the harsh environment of the alimentary canal, adjuvant is usually required. Previous studies showed that chitosan, as a potential use non-toxic delivery component, boosts both the humoral and cellular immune responses of the mucosal surface after co-administration with Helicobacter Pylori and influenza vaccines [10,11] and causes little irritability or antigenicity
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