3.3 Intratracheal immunization with S1-SF-10 induces S1-specific antibody secreting cells in spleen and lungs
S1-SF-10-IT resulted in marked induction of both S-IgA and IgG in BALF (Figure 2B, D). To determine the antibody producing sites, we analyzed S1-specific IgG and IgA ASCs. For this purpose, lymphocytes were harvested from the spleen and lungs of triple-vaccinated mice with 10 μg of S1-IM, S1-AS03-IM and S1-SF-10-IT at two weeks after the last immunization, and the S1-specific IgG and IgA ASCs were detected by ELISPOT assay (Figure 3). Only a few S1-specific IgG ASCs were detected in the spleen of S1-IM group, and S1-specific IgA in the spleen, IgG and IgA in the lungs were even below the detection limits. Although the number of S1-specific IgG ASCs in the spleen of the S1-AS03-IM group was higher than approximately 2-fold of that of S1-SF-10-IT group (Figure 3A), their number was lower in the lungs of mice immunized with S1-AS03-IM at approximately 1/15-fold of that found in S1-SF-10-IT group (Figure 3C). In addition, S1-specific IgA ASCs in the both spleen and lung were detected in S1-SF-10-IT group, but hardly S1-AS03-IM group (Figure 3B, C).