3.1 Intratracheal administration of S1-SF-10 vaccine induces S1-specific humoral immunities in sera and respiratory mucosal fluid.
To analyze SF-10 adjuvanticity against S1 antigen, mice were immunized twice with 10 μg of intramuscular and intratracheal S1, and 1 and 10 μg of intratracheal S1-SF-10 vaccine. At 2 weeks after the last immunization, the S1-specific IgG in serum and S-IgA in BALF were measured by ELISA (Figure 1). S1-IM and -IT antigen induced very low levels of S1-specific IgG in serum. In contrast, S1-SF-10-IT vaccine induced noticeable levels of S1-specific IgG in serum at over 100-fold higher than S1 antigen alone (Figure 1A).
On the other hand, S1-specific S-IgA induction in BALF was detected in the 1 and 10 μg of S1-SF-10-IT group, but none of the S1-IT and -IM antigen groups (Figure 1B). These results indicate that SF-10-IT had immunostimulatory effects as mucosal adjuvant for SARS-CoV-2 vaccine.