Fig. 5. Long-term immune-memory effects.

(A) Schematic illustration of bacteria-based PTT therapy to inhibit cancer relapse. (B) Tumor growth curves of rechallenged tumors inoculated 40 days after elimination of their first tumors (eight mice per group). Data are presented as the mean ± SEM. (C) Morbidity-free survival of different groups of mice with rechallenged CT26 tumors after various treatments indicated to eliminate their primary tumors (10 mice per group). Bacteria-based PTT, even in the absence of anti–CTLA-4 blockade, could trigger strong enough immune responses to reject rechallenged tumor. (D) Quantification of proportions of CD8⁺ effector memory T cells (T_EM) gated on CD3⁺ cells in the spleen analyzed at day 40 right before rechallenging mice with secondary tumors. (E) Cytokine levels, including TNF-α and IFN-γ, in sera from mice isolated at day 47. Data are presented as the mean ± SD. Statistical analysis was performed using the Student’s two-tailed t test (***P < 0.001, **P < 0.01, and *P < 0.05). (F) Schematic illustration of bacteria-based photothermal immunotherapy to inhibit the growth of primary tumors, abscopal metastatic tumors, and rechallenged tumors.