Fig. 2: Adjuvanticity and physical properties of pharmaceutical base materials.

A Mice were intranasally administered saline (SA), split influenza vaccine (SV) alone, or SV with either pharmaceutical base materials (final 50% v/v) or existing adjuvants in a single dose. Three weeks post-administration, bronchoalveolar lavage fluid (BALF) was collected, and vaccine antigen-specific IgA antibody levels were measured by ELISA. The red column indicates pharmaceutical base materials that exhibited a marked increase in the mean IgA antibody titer. B Viscosity of pharmaceutical base materials diluted to 50% v/v in PBS. The red column indicates pharmaceutical base materials that exhibited a marked increase in the mean IgA antibody titer. C pH of pharmaceutical base materials diluted to 50% v/v in PBS. The red column indicates pharmaceutical base materials that exhibited a marked increase in the mean IgA antibody titer. D Correlation between viscosity and IgA antibody levels in BALF. The red dots represent pharmaceutical base materials that demonstrated a marked increase in the mean IgA antibody titer. Each dot represents data from an individual animal (n = 4) from two independent experiments. A Bar graphs indicate mean values and error bars represent the SEM of data from two independent experiments. B and C indicate the average value of two independent measurements. *p < 0.05, **p < 0.01, and ***p < 0.001 by Dunnett’s multiple comparison test following the Kruskal–Wallis test.