Fig 3.

Resistance of different tumor models to oncolytic viral therapy is mediated by localized immune suppression within the tumor. (A) Baseline levels of regulatory T-cells (T-reg) and Monocyte Derived Suppressor Cells (MDSC) in tumors prior to therapy. Syngeneic subcutaneous tumors were formed from different cell lines and mice sacrificed when tumors reached 100 to 200 mm³ and disaggregated. Flow cytometry was used to quantify the relative levels of T-reg (CD3⁺CD25⁺FoxP3⁺CD8⁻) and MDSC (CD11b⁺Gr-1⁺) in the tumors. (B) Effect of viral therapy on suppressive immune cell profile within the tumor. Tumor-bearing mice were treated with a single low dose (1×10⁷ PFU) intratumoral injection of WR.TK- and the levels of T-reg and MDSC in the tumors at different times after treatment were analyzed as in (A). (C) CD3⁺CD8⁺CD4⁻ T-cells were also quantified in the tumor as in (A) (*p<0.05). Error bars ±SEM. See also Figure S3 and S4.