Intranasal vaccination with inactivated influenza viral antigens is an attractive and valid alternative to currently available influenza (flu) vaccines; many of which seem to need efficient and safe adjuvant, however. In this study, we examined whether hydroxypropyl-β-cyclodextrin (HP-β-CD), a widely used pharmaceutical excipient to improve solubility and drug delivery, can act as a mucosal adjuvant for intranasal flu vaccines. We found that intranasal immunization of mice with hemagglutinin split- as well as inactivated whole-virion influenza vaccine with HP-β-CD resulted in secretion of antigen-specific IgA and IgGs in the airway mucosa and the serum as well. As a result, both HP-β-CD adjuvanted-flu intranasal vaccine protected mice against lethal challenge with influenza virus, equivalent to those induced by experimental cholera toxin-adjuvanted ones. Of note, intranasal use of HP-β-CD as an adjuvant induced significantly lower antigen-specific IgE responses than that induced by aluminum salt adjuvant. These results suggest that HP-β-CD may be a potent mucosal adjuvant for seasonal and pandemic influenza vaccine.
