Figure 7. Commensal bacteria epitope cross-reactivity mediates an antitumor response.

(A) Jackson mice (n = 5 SVY ACT; n = 4 no treatment) were injected with 2 × 10⁶ B16.SIY cells subcutaneously on day 0. CD8⁺ T cells were harvested from spleens of independent Jackson mice and stimulated with K^bSVY/anti-CD28 nanoparticles. On day 8, 1.3 × 10⁵ of the resultant K^bSVY-specific CD8⁺ T cells were injected intravenously into the tumor-bearing mice. Tumor growth curves show SVY ACT treatment significantly delayed tumor growth as compared with no treatment. P value = 0.0136, measured by 2-way ANOVA with Bonferroni’s post hoc test for multiple comparisons. Additionally, K^bSVY ACT significantly increased survival compared with the no treatment group. Significance was measured by the log-rank test. P value = 0.0015. (B) Jackson mice were injected with 2 × 10⁶ B16.SIY cells subcutaneously on day 0 and treated on day 8 with 1.3 × 10⁵ K^bSVY-specific CD8⁺ T cells via intravenous injection. Tumors were harvested on day 24 and analyzed by flow cytometry for GFP expression. Orange and blue indicate SVY T cell–treated mice and red indicates untreated mice. (C). Jackson mice (n = 3 SIY ACT, and n = 3 no treatment) were injected with 2 × 10⁶ B16.SIY cells subcutaneously on day 0. CD8⁺ T cells were harvested from spleens of independent Jackson mice and stimulated with K^bSIY/anti-CD28 nanoparticles. On day 8, 1.3 × 10⁵ of the resultant SIY-reactive T cells were injected intravenously into tumor-bearing mice. Tumor growth curves show SIY ACT treatment significantly delayed tumor growth as compared with no treatment. Significance was measured by 2-way ANOVA with Bonferroni’s post hoc test for multiple comparisons (P < 0.001). ACT also significantly extended survival. Significance was measured by the log-rank test. P value = 0.024. N = 3/group.