3.4 Effect of route of vaccine administration on induction of Th cytokine secreting cells in spleen and lungs
We reported previously that mucosal immunization of HAv-SF-10, induces antigen-responsive Th1, Th2, and Th17 cytokines in the spleen.19 To analyze the T cell associated immunities against SARS-CoV-2 induced by S1-SF-10-IT, we measured S1-responsive Th CSCs in the spleen and lungs. Mice received triple vaccinations with S1-IM, S1-AS03-IM and S1-SF-10-IT, and the splenocytes and lung lymphocytes of these mice were isolated at two weeks after the last vaccination, followed by incubation with or without S1 for 24 h. The S1-responsive Th1 (IFN-γ), Th2 (IL-4) and Th17 (IL-17A) CSCs were detected by ELISPOT assay (Figure 4). The levels of S1-responsive IFN-γ CSCs induced by S1-AS03-IM and S1-SF-10-IT in the spleen were comparable and higher than those induced by S1-IM. In comparison, S1-responsive IFN-γ CSCs in lungs were only detected in the S1-SF-10-IT group. Further analysis showed that the highest levels of S1-responsive IL-4 CSCs in the spleen were found in the S1-AS03-IM group while those in the S1-SF-10-IT group were slightly lower than those of the S1-IM group. With regard to the lungs, similar levels of S1-responsive IL-4 CSCs were detected in the S1-IM, S1-AS03-IM and S1-SF-10-IT groups. The level of S1-responsive IL-17A CSCs in the spleen of the S1-SF-10-IT group was the highest among the vaccination groups and the S1-responsive IL-17A CSCs in the lungs were detected only in the S1-SF-10-IT group.