Th17 cells contribute to nontypeable Haemophilus influenzae-specific protective immunity induced by nasal vaccination with P6 outer membrane protein and α-galactosylceramide

Nasal vaccination is an effective therapeutic means of preventing upper respiratory infection. Recently, nasal vaccination with P6 outer membrane protein of nontypeable Haemophilus influenzae (NTHi) and alpha-galactosylceramide (alpha-GalCer) was reported to induce NTHi-specific protective immunity. The present study investigated the role of the Th17 cells induced by nasal vaccination. Mice were immunized with P6 and alpha-GalCer, and their P6-specific immune responses were examined. Cytokine-producing cells were analyzed by flow cytometry, and expression of cytokines in P6-specific CD4(+) T cells was determined by reverse transcription-polymerase chain reaction. Bacterial challenges were performed with live NTHi. To examine the role of Th17 cells, bacterial clearance was also evaluated after interleukin (IL)-17 neutralization. P6-specific nasal wash immunoglobulin (Ig) A and serum IgG were increased after immunization with P6 and alpha-GalCer. Specific IgA-producing cells increased markedly in the nasal passages (NPs) of the immunized mice. In addition to P6-specific Th1 and Th2 cells, IL-17-producing Th17 cells were induced in the NPs and spleen. Bacterial clearance was enhanced by nasal vaccination. Interestingly, impaired NTHi clearance was shown after IL-17 neutralization. These findings suggest that nasal vaccination with P6 and alpha-GalCer is an effective regimen for the induction of NTHi-specific protective immunity in the upper respiratory tract. In addition to antigen-specific secretory-IgA, specific Th17 cells induced by nasal vaccination contribute to protection against NTHi.