Fig. 3

Production of effector memory T cells (T_EM) before and after intranasal boost immunization in Study 1. At 10 days post-2nd immunization (10 dp2i), spleen samples were collected and subjected to flow cytometry analysis to determine the percentages of CD44⁺CD62L⁻ T_EM cells, CD44⁺CD62L⁺ T_CM cells and CD44⁻ CD62L⁺ T_Naive cells in the CD3 (A–C), CD4 (D–F) and CD8 (G–I) subgroups. At 10 days post-3rd immunization (10 dp3i), lung samples were collected and subjected to flow cytometry analysis to determine the percentages of T_EM, T_CM and T_Naive cells in the CD4 (J–L) and CD8 (M–O) subgroups (n = 4, *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001, ns, not significant). Notably, Salmonella strain χ11802 harboring plasmids pYL180 and pYL230 was designated S180 and S230, respectively