Figure 4.

Expansion of Intratumoral CD103⁺ DCs by Local Delivery of the FL Cytokine Enhances the Efficacy of Oncolytic Virotherapy Treatment

(A) Graphical timeline of the treatment scheme in ID8-T tumor-bearing mice. C57BL/6 mice were injected i.p. with 3 × 10⁵ ID8-T cells. Treatment with OVV or OVV-CXCR4-A (10⁸ PFU delivered i.p.) was initiated 10 days later. To expand CD103⁺ DCs, FL was injected i.p. at 5 μg/injection for 4 consecutive days, beginning on day 8 after virotherapy treatment. Percentages of CD11b⁺ and CD103⁺ DCs in peritoneal washes of OVV- or OVV-CXCR4-A-treated, ID8-T-bearing mice (n = 3–5 mice/group) after i.p. delivered FL were analyzed 2 days later, whereas percentages of CD8⁺ TILs were assessed on day 32 by flow cytometry. (B and C) Relative proportions (left panel) and representative flow cytometry plots (right panel) of intratumoral CD11b⁺ and CD103⁺ DCs within MHCII⁺F4/80^loCD24^hi populations of myeloid cells infiltrating the peritoneal cavities of ID8-T tumor-bearing mice after OVV and FL treatment (B) as well as OVV-CXCR4-A and FL treatment (C). Results are presented as mean ± SD of four experiments. *p < 0.05, **p < 0.01. (D) FL-mobilized CD103⁺ DCs exhibited increased phagocytosis of tumor cell debris. CD45⁺ leukocytes isolated from peritoneal cavities of ID8-T tumor-bearing mice 2 days after treatment with OVV or OVV-CXCR4-A alone or in combination with FL were cultured with OVV-treated and CellTracker-labeled ID8-T cancer cells. After overnight incubation, the capture of tumor-associated fluorescent debris by CD103⁺ DCs was analyzed by flow cytometry. Percentages of phagocytosis of virally treated tumor cell debris by CD103⁺ DCs are presented as mean ± SD of 3 experiments. *p < 0.05. (E) Progression of ID8-T tumor growth in mice (n = 5 mice/group) treated with OVV or OVV-CXCR4-A delivered alone or in combination with the FL cytokine was monitored by bioluminescence. Data points represent mean ± SD. *p < 0.05.