Nasal vaccination with P6 outer membrane protein and α-galactosylceramide induces nontypeable Haemophilus influenzae-specific protective immunity associated with NKT cell activation and dendritic cell expansion in nasopharynx

The efficacy of α-galactosylceramide (α-GalCer) as a mucosal adjuvant was examined. Mice were immunized intranasally with nontypeable Haemophilus influenzae (NTHi) P6 protein and α-GalCer. P6-specific antibody responses in the form of P6-specific IgA in nasal washes and serum IgG titers were significantly elevated. Splenic CD4+ T cells expressed P6-specific Th1 and Th2 cytokine mRNA. In addition, NTHi was quantified in nasal washes following NTHi challenges, and the clearance of NTHi from the nasopharynx was also enhanced. These results indicate that α-GalCer might be an effective mucosal adjuvant.