Oral vancomycin treatment enhances the direct and abscopal antitumor effects of hypofractionated RT in preclinical melanoma and lung/cervical tumor models. Given the role of the gut microbiota in modulating immune cells that are also known to be involved in the response to RT, we examined whether the microbiota-regulated systemic immune response contributes to the RT-mediated anticancer immune response. The effects of oral vancomycin treatment are localized and impact the gut microbiota directly without any known systemic effects (21-23). Vancomycin (mostly targeting gram-positive bacteria) or a neomycin/metronidazole (Neo/Met) regimen (mostly targeting gram-negative bacteria

SummaryViral infections frequently induce acute and chronic inflammatory diseases, yet the contribution of the innate immune response to a detrimental host response remains poorly understood. In virus-infected cells, double-stranded RNA (dsRNA) is generated as an intermediate during viral replication. Cell necrosis (and the release of endogenous dsRNA) is a common event during both sterile and infectious inflammatory processes. The discovery of Toll-like receptor 3 (TLR3) as an interferon-inducing dsRNA sensor led to the assumption that TLR3 was the master sentinel against viral infections. This simplistic view has been challenged by the discovery of at least three members of the DExd/H-box helicase cytosolic sensors of dsRNA that share with TLR3 the Toll-interleukin-1 receptor (TIR) -adapter molecule TIR domaincontaining adaptor protein interferon-b (TRIF) for downstream type I interferon signalling. Data are conflicting on the role of TLR3 in protective immunity against viruses in the mouse model. Varying susceptibility to infection and disease outcomes have been reported in TLR3-immunodeficient mice. Surprisingly, the susceptibility to develop herpes simplex virus-1 encephalitis in humans with inborn defects of the TLR3 pathway varies, and TLR3-deficient humans do not show increased susceptibility to other viral infections. Therefore, a current challenge is to understand the protective versus pathogenic contribution of TLR3 in viral infections. We review recent advances in the identification of TLR3-signalling pathways, endogenous and virus-induced negative regulators of the TLR3 cascade, and discuss the protective versus pathogenic role of TLR3 in viral pathogenesis.

DNA-based vaccination is a promising approach to cancer immunotherapy. DNA-based vaccines specific for tumor-associated antigens (TAAs) are indeed relatively simple to produce, cost-efficient and well tolerated. However, the clinical efficacy of DNA-based vaccines for cancer therapy is considerably limited by central and peripheral tolerance. During the past decade, considerable efforts have been devoted to the development and characterization of novel DNA-based vaccines that would circumvent this obstacle. In this setting, particular attention has been dedicated to the route of administration, expression of modified TAAs, co-expression of immunostimulatory molecules, and co-delivery of immune checkpoint blockers. Here, we review preclinical and clinical progress on DNA-based vaccines for cancer therapy.

Despite their differential cell tropisms, HIV-1 and HCV dramatically influence disease progression in coinfected patients. Macrophages are important target cells of HIV-1. We hypothesized that secreted HCV core protein might modulate HIV-1 replication. We demonstrate that HCV core significantly enhances HIV-1 replication in human macrophages by upregulating TNF-α and IL-6 via TLR2-, JNK-, and MEK1/2-dependent pathways. Furthermore, we show that TNF-α and IL-6 secreted from HCV core-treated macrophages reactivates monocytic U1 cells latently infected with HIV-1. Our studies reveal a previously unrecognized role of HCV core by enhancing HIV-1 infection in macrophages.

BackgroundTumor endothelial marker 1 (TEM1) is a protein expressed in the tumor-associated endothelium and/or stroma of various types of cancer. We previously demonstrated that immunization with a plasmid-DNA vaccine targeting TEM1 reduced tumor progression in three murine cancer models. Radiation therapy (RT) is an established cancer modality used in more than 50% of patients with solid tumors. RT can induce tumor-associated vasculature injury, triggering immunogenic cell death and inhibition of the irradiated tumor and distant non-irradiated tumor growth (abscopal effect). Combination treatment of RT with TEM1 immunotherapy may complement and augment established immune checkpoint blockade.MethodsMice bearing bilateral subcutaneous CT26 colorectal or TC1 lung tumors were treated with a novel heterologous TEM1-based vaccine, in combination with RT, and anti-programmed death-ligand 1 (PD-L1) antibody or combinations of these therapies, tumor growth of irradiated and abscopal tumors was subsequently assessed. Analysis of tumor blood perfusion was evaluated by CD31 staining and Doppler ultrasound imaging. Immunophenotyping of peripheral and tumor-infiltrating immune cells as well as functional analysis was analyzed by flow cytometry, ELISpot assay and adoptive cell transfer (ACT) experiments.ResultsWe demonstrate that addition of RT to heterologous TEM1 vaccination reduces progression of CT26 and TC1 irradiated and abscopal distant tumors as compared with either single treatment. Mechanistically, RT increased major histocompatibility complex class I molecule (MHCI) expression on endothelial cells and improved immune recognition of the endothelium by anti-TEM1 T cells with subsequent severe vascular damage as measured by reduced microvascular density and tumor blood perfusion. Heterologous TEM1 vaccine and RT combination therapy boosted tumor-associated antigen (TAA) cross-priming (ie, anti-gp70) and augmented programmed cell death protein 1 (PD-1)/PD-L1 signaling within CT26 tumor. Blocking the PD-1/PD-L1 axis in combination with dual therapy further increased the antitumor effect and gp70-specific immune responses. ACT experiments show that anti-gp70 T cells are required for the antitumor effects of the combination therapy.ConclusionOur findings describe novel cooperative mechanisms between heterologous TEM1 vaccination and RT, highlighting the pivotal role that TAA cross-priming plays for an effective antitumor strategy. Furthermore, we provide rationale for using heterologous TEM1 vaccination and RT as an add-on to immune checkpoint blockade as triple combination therapy into early-phase clinical trials.

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Parkin is an E3 ubiquitin ligase that plays a key role in the development of Parkinson’s disease. Parkin defects also occur in numerous cancers, and a growing body of evidence indicates that Parkin functions as a tumor suppressor that impedes a number of cellular processes involved in tumorigenesis. Here, we generated murine and human models that closely mimic the advanced-stage tumors where Parkin deficiencies are found to provide deeper insights into the tumor suppressive functions of Parkin. Loss of Parkin expression led to aggressive tumor growth that was associated with poor tumor antigen presentation and limited antitumor CD8+ T cell infiltration and activation. The effect of Parkin deficiency on tumor growth was lost following depletion of CD8+ T cells. In line with previous findings, Parkin deficiency was linked with mitochondria-associated metabolic stress, PTEN degradation, and enhanced AKT activation. Increased AKT signaling led to dysregulation of antigen presentation, and treatment with the AKT inhibitor MK2206-HCl restored antigen presentation in Parkin-deficient tumors. Analysis of data from clear cell renal cell carcinoma patients indicated that Parkin expression was downregulated in tumors and that low expression correlated with reduced overall survival. Furthermore, low Parkin expression correlated with reduced patient response to immunotherapy. Overall, these results identify a role for Parkin deficiency in promoting tumor immune evasion that may explain the poor prognosis associated with loss of Parkin across multiple types of cancer.

Somatic mitochondria DNA (mtDNA) abnormalities have been identified in various types of human cancers. Previously, we generated tumor protective immunity under prophylactic and therapeutic approaches employing a murine kidney tumor model system and dendritic cell (DC)-based vaccination containing RENCA-derived mitochondria enriched lysates. Our results shown that tumor-associated mitochondria antigens (TAMAs) are targetable antigens for cancer immunotherapy (PMID: 26378078). Preliminary data also revealed increased endogenous PD-L1 mRNA expression levels in RENCA tumors of treated mice versus healthy kidney tissue. To investigate the impact of PD1/PD-L1 axis antagonism, Balb/C mice were challenged with RENCA cells at day 0 followed by TAMA-vaccination at day 3 and concurrent administration of anti-PD1 (aPD1) 5 times every 3 days. Interestingly, the aPD1-TAMA treatment resulted in reduced tumor growth, greater T CD4+ and T CD8+ cell infiltration, and lower intratumoral-MDSC as compared to the TAMA vaccine alone. In addition, we observed higher T cell activation from the aPD1-TAMA group upon co-culture with bone marrow-derived dendritic cells exposed to RENCA mitochondria lysate, suggesting that the inhibition of PD1 also enhanced the immunogenicity of the TAMA vaccine. Further analysis of the tumor environment revealed that the PD1-PD-L1 axis antagonism correlated with an increment of intratumoral CTLA4 expression and recruitment of T regulatory (Treg) cells. We introduced a third arm of treatment including a CTLA4 antagonist antibody in combination with aPD1 and TAMA vaccine in vivo. Strikingly, the tumor progression was greatly impacted causing tumor rejection in the majority of tumor-bearing animals, sustained tumor volume reduction in the others, a decrease in Treg cell recruitment, and concomitant increment of T CD8+ cell infiltration and activation. Altogether, the combination of check point inhibitors in vivo significantly improved the efficacy of the TAMA immunotherapy by remodeling the tumor microenvironment, reducing the immunosuppressive potential, and facilitating the infiltration of effector T cells into the tumor. Citation Format: Renzo F. Perales-Linares, Stefano Pierini, Mireia Uribe, Sergei Pustylnikov, Francesca Costabile, Silvia Beghi, Andrea Facciabene. Anti-PD1 and -CTLA-4 combination in vivo enhances DC-based tumor-associated mitochondria antigen immunotherapy efficacy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3218.