Recombinant Listeria promotes tumor rejection by CD8+ T cell-dependent remodeling of the tumor microenvironment.

Agents that remodel the tumor microenvironment (TME), prime functional tumor-specific T cells, and block inhibitory signaling pathways are essential components of effective immunotherapy. We are evaluating live-attenuated, double-deleted Listeria monocytogenes expressing tumor antigens (LADD-Ag) in the clinic. Here we show in numerous mouse models that while treatment with nonrecombinant LADD induced some changes in the TME, no antitumor efficacy was observed, even when combined with immune checkpoint blockade. In contrast, LADD-Ag promoted tumor rejection by priming tumor-specific KLRG1+PD1loCD62L- CD8+ T cells. These IFNγ-producing effector CD8+ T cells infiltrated the tumor and converted the tumor from an immunosuppressive to an inflamed microenvironment that was characterized by a decrease in regulatory T cells (Treg) levels, a proinflammatory cytokine milieu, and the shift of M2 macrophages to an inducible nitric oxide synthase (iNOS)+CD206- M1 phenotype. Remarkably, these LADD-Ag-induced tumor-specific T cells persisted for more than 2 months after primary tumor challenge and rapidly controlled secondary tumor challenge. Our results indicate that the striking antitumor efficacy observed in mice with LADD-based immunotherapy stems from TME remodeling which is a direct consequence of eliciting potent, systemic tumor-specific CD8+ T cells

31st Annual Meeting and Associated Programs of the Society for Immunotherapy of Cancer (SITC 2016) : part two

Background The immunological escape of tumors represents one of the main ob- stacles to the treatment of malignancies. The blockade of PD-1 or CTLA-4 receptors represented a milestone in the history of immunotherapy. However, immune checkpoint inhibitors seem to be effective in specific cohorts of patients. It has been proposed that their efficacy relies on the presence of an immunological response. Thus, we hypothesized that disruption of the PD-L1/PD-1 axis would synergize with our oncolytic vaccine platform PeptiCRAd. Methods We used murine B16OVA in vivo tumor models and flow cytometry analysis to investigate the immunological background. Results First, we found that high-burden B16OVA tumors were refractory to combination immunotherapy. However, with a more aggressive schedule, tumors with a lower burden were more susceptible to the combination of PeptiCRAd and PD-L1 blockade. The therapy signifi- cantly increased the median survival of mice (Fig. 7). Interestingly, the reduced growth of contralaterally injected B16F10 cells sug- gested the presence of a long lasting immunological memory also against non-targeted antigens. Concerning the functional state of tumor infiltrating lymphocytes (TILs), we found that all the immune therapies would enhance the percentage of activated (PD-1pos TIM- 3neg) T lymphocytes and reduce the amount of exhausted (PD-1pos TIM-3pos) cells compared to placebo. As expected, we found that PeptiCRAd monotherapy could increase the number of antigen spe- cific CD8+ T cells compared to other treatments. However, only the combination with PD-L1 blockade could significantly increase the ra- tio between activated and exhausted pentamer positive cells (p= 0.0058), suggesting that by disrupting the PD-1/PD-L1 axis we could decrease the amount of dysfunctional antigen specific T cells. We ob- served that the anatomical location deeply influenced the state of CD4+ and CD8+ T lymphocytes. In fact, TIM-3 expression was in- creased by 2 fold on TILs compared to splenic and lymphoid T cells. In the CD8+ compartment, the expression of PD-1 on the surface seemed to be restricted to the tumor micro-environment, while CD4 + T cells had a high expression of PD-1 also in lymphoid organs. Interestingly, we found that the levels of PD-1 were significantly higher on CD8+ T cells than on CD4+ T cells into the tumor micro- environment (p < 0.0001). Conclusions In conclusion, we demonstrated that the efficacy of immune check- point inhibitors might be strongly enhanced by their combination with cancer vaccines. PeptiCRAd was able to increase the number of antigen-specific T cells and PD-L1 blockade prevented their exhaus- tion, resulting in long-lasting immunological memory and increased median survival

The TLR4 Agonist Vaccine Adjuvant, GLA-SE, Requires Canonical and Atypical Mechanisms of Action for TH1 Induction.

The Toll-like receptor 4 agonist glucopyranosyl lipid adjuvant formulated in a stable emulsion (GLA-SE) promotes strong TH1 and balanced IgG1/IgG2 responses to protein vaccine antigens. This enhanced immunity is sufficient to provide protection against many diseases including tuberculosis and leishmaniasis. To better characterize the adjuvant action it is important to understand how the different cytokines and transcription factors contribute to the initiation of immunity. In the present study using T-bet-/- and IL-12-/- mice and a blocking anti-IFNαR1 monoclonal antibody, we define mechanisms of adjuvant activity of GLA-SE. In accordance with previous studies of TLR4 agonist based adjuvants, we found that TH1 induction via GLA-SE was completely dependent upon T-bet, a key transcription factor for IFNγ production and TH1 differentiation. Consistent with this, deficiency of IL-12, a cytokine canonical to TH1 induction, ablated TH1 induction via GLA-SE. Finally we demonstrate that the innate immune response to GLA-SE, including rapid IFNγ production by memory CD8+ T cells and NK cells, was contingent on type I interferon, a cytokine group whose association with TH1 induction is contextual, and that they contributed to the adjuvant activity of GLA-SE

Magnitude of Therapeutic STING Activation Determines CD8⁺ T Cell-Mediated Anti-tumor Immunity

STING pathway activation by intratumoral administration of cyclic dinucleotides (CDNs) results in stable tumor regression, yet the underlying innate and adaptive immune mechanisms are not fully established. ADU-S100, CDN under clinical evaluation, was used with an optimized dosing regimen to uncover key immune requirements for tumor regression. An immunogenic dose induces local expansion of tumor-specific CD8+ T cells, which are both necessary and sufficient for durable anti-tumor immunity and correlated with STING activation in hematopoietic but not tumor or stromal cells. Type I IFN, but not TNFα, drives optimal anti-tumor immune responses. The function of ADU-S100-induced CD8+ T cells was enhanced by combination with immune checkpoint modulators anti-PD-1 and anti-CTLA4. These results provide fundamental mechanistic insights into STING IT therapy

IFNα is produced early after GLA-SE immunization.

<p>B6 mice were immunized with saline or ID93+GLA-SE. Sera and draining inguinal LNs were collected0, 6, 24, or 48 hours later and analyzed for IFNα protein expression by ELISA. Data are shown as mean ± SEM and are the combined results of two independent experiments with similar results with 3 or 4 mice/group. Statistics by unpaired t test; *p≤0.05 compared to Saline group.</p

IFNαR1 signaling contributes to T_H1 skewing.

<p>B6 mice were treated with IFNαR1 antibody or its isotype and immunized with ID93+GLA-SE and responses were analyzed one week after prime. (A) ID93 stimulated splenocytes were analyzed for the production of CD154, IFNγ, TNF and IL-5 by CD4 T cells. (B) One week after prime CD4 T cells were isolated and stained with an I-A^b tetramer presenting the dominant epitope for Rv3619 and analyzed for T-bet induction. (C) Sera were collected one week after prime and serially diluted to assess levels of anti-ID93 IgG1 and IgG2c. Data are shown as mean ± SEM of N = 5 animal/group and are from one experiment representative of two experiments performed except for IL-5 and T-bet levels measurement which were only done once. Statistics by simple or multiple t test corrected for multiple comparisons using the Holm-Sidak method between IgG or cytokine groups; *p≤0.05</p