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).