Figure 2. Engineered PLG vaccine in combination with blockade antibodies enhances intratumoral T effector cell activity.

(A) The total number of CD3⁺CD8⁺ T cells and (B) CD3⁺FoxP3⁺ T regulatory cells isolated from the B16 tumors of untreated mice (Control) and mice treated with PLG vaccines alone (Vax) or in combination with a antibodies to PD-1 (+PD-1) and CTLA-4 (+CTLA4). (C) The ratio of CD3⁺CD8⁺ T cells to CD3⁺FoxP3⁺ T regulatory cells isolated from the B16 tumors of untreated mice (Control) and mice treated with PLG vaccines alone (Vax) or in combination with antibodies to PD-1 (+PD-1) and CTLA-4 (+CTLA-4). (D) FACS plots representing tumor infiltrating leukocytes in tumors of untreated mice (Control) and mice treated with PLG vaccines alone (Vax) or in combination with antibodies to PD-1 (+PD-1) and CTLA-4 (+CTLA4). Single cell suspensions were prepared from tumors at day 18 and stained for activated cytotoxic T-cell markers, CD8 and CD107a. Numbers in FACS plots indicate the percentage of the cell population positive for both markers. (E) The numbers of CD8⁺, tumor-infiltrating T cells positive for either IFNγ or CD107a in blank matrices (Control), PLG vaccines alone or vaccines in combination with antibodies to PD-1 and CTLA-4. The antibody treatments were administered i.p. as described for vaccination experiments until tumor excision at day 18 for Tcell infiltration analysis. Vaccination was initiated 9 days after tumor challenge. All cellular staining was performed following MACS cell separation of total cells suspensions extracted from tumors. Values in A, B, C, and D (n=10) represent mean and standard deviation. * P<0.05 ** P<0.01 as compared to the vaccine alone (V vs V+P; V vs V+C) unless otherwise noted. This experiment was performed twice.