Oral vaccination with influenza hemagglutinin combined with human pulmonary surfactant-mimicking synthetic adjuvant SF-10 induces efficient local and systemic immunity compared with nasal and subcutaneous vaccination and provides protective immunity in mice.

We reported previously that a synthetic mucosal adjuvant SF-10, which mimics human pulmonary surfactant, delivers antigen to mucosal dendritic cells in the nasal cavity and promotes induction of humoral and cellular immunity. The aim of the present study was to determine the effects of oral administration of antigen combined with SF-10 (antigen-SF-10) on systemic and local immunity. Oral administration of ovalbumin, a model antigen, combined with SF-10 enhanced ovalbumin uptake into intestinal antigen presenting MHC IICD11c cells and their CD11bCD103 and CD11bCD103 subtype dendritic cells, which are the major antigen presenting subsets of the intestinal tract, more efficiently compared to without SF-10. Oral vaccination with influenza hemagglutinin vaccine (HAv)-SF-10 induced HAv-specific IgA and IgG in the serum, and HAv-specific secretory IgA and IgG in bronchoalveolar lavage fluid, nasal washes, gastric extracts and fecal material; their levels were significantly higher than those induced by subcutaneous HAv or intranasal HAv and HAv-SF-10 vaccinations. Enzyme-linked immunospot assay showed high numbers of HAv-specific IgA and IgG antibody secreting cells in the gastrointestinal and respiratory mucosal lymphoid tissues after oral vaccination with HAv-SF-10, but no or very low induction following oral vaccination with HAv alone. Oral vaccination with HAv-SF-10 provided protective immunity against severe influenza A virus infection, which was significantly higher than that induced by HAv combined with cholera toxin. Oral vaccination with HAv-SF-10 was associated with unique cytokine production patterns in the spleen after HAv stimulation; including marked induction of HAv-responsive Th17 cytokines (e.g., IL-17A and IL-22), high induction of Th1 cytokines (e.g., IL-2 and IFN-γ) and moderate induction of Th2 cytokines (e.g., IL-4 and IL-5). These results indicate that oral vaccination with HAv-SF-10 induces more efficient systemic and local immunity than nasal or subcutaneous vaccination with characteristically high levels of secretory HAv-specific IgA in various mucosal organs and protective immunity.