Dose sparing enabled by immunization with influenza vaccine using orally dissolving film.

Influenza vaccine delivered by orally dissolving film vaccine (ODFV) is a promising approach. In this study, we generated three ODFVs each comprising pulluan and trehalose with different doses of inactivated A/Puerto Rico/8/34, H1N1 virus (ODFV I, II, III) to evaluate their dose-sparing effect in mice. The ODFVs were placed on the tongues of mice to elicit immunization and after 3 immunizations at 4-week intervals, mice were challenged with a lethal dose of A/PR/8/34 to assess vaccine-induced protection. The 3 ODFVs containing 50, 250, or 750 μg of inactivated viruses elicited virus-specific antibody responses and virus neutralization in a dose-dependent manner. Dose-dependent antibody responses were also observed from the mucosal tissue samples, and also from antibody-secreting cells of the lungs and spleens. ODFV-induced cellular immunity, particularly germinal center B cells and T cells were also dose-dependent. Importantly, all 3 ODFVs evaluated in this study provided complete protection by strongly suppressing the pro-inflammatory cytokine production and lung virus titers. None of the immunized mice underwent noticeable weight loss nor succumbed to death, a phenomenon that was only observed in the infection challenge controls. These results indicated that the protection conferred by a low dose influenza vaccine formulated in ODF is comparable to that of a high-dose vaccine, thereby enabling vaccine dose sparing effect.