Intranasal Immunization with Nasal Immuno-Inducible Sequence-Fused Antigens Elicits Antigen-Specific Antibody Production

Intranasal immunization is one of the most effective methods for eliciting lung mucosal immunity. Multiple intranasal immunization with bacterial polypeptide, termed as a modified PnxIIIA (MP3) protein, is known to elicit production of a specific antibody in mice. In this study, a nasal immuno-inducible sequence (NAIS) was designed to remove the antigenicity of the MP3 protein that can induce mucosal immunity by intranasal immunization, and was examined to induce antigen-specific antibodies against the fused bacterial thioredoxin (Trx) as a model antigen. A NAIS was modified and generated to remove a large number of predicted MHC (Major Histocompatibility Complex)-I and MHC-II binding sites in parent protein PnxIIIA and MP3 in order to reduce the number of antigen epitope sites. For comparative analysis, full-length NAIS291, NAIS230, and NAIS61 fused with Trx and 6× His tag and Trx-fused 6× His tag were used as antigen variants for the intranasal immunization of BALB/c mice every two weeks for three immunizations. Anti-Trx antibody titers in serum and bronchoalveolar lavage fluid (BALF) IgA obtained from NAIS291-fused Trx-immunized mice were significantly higher than those from Trx-immunized mice. The antibody titers against NAIS alone were significantly lower than those against Trx alone in the serum IgG, serum IgA, and BALF IgA. These results indicate that the NAIS contributes to antibody elicitation of the fused antigen as an immunostimulant in intranasal vaccination vaccines. The results indicate that the NAIS and target inactivated antigen fusions can be applied to intranasal vaccine systems.