Oncolytic Viruses (OVs) are often attenuated to increase their safety profile, however this can lead to reduced efficacy in heterogeneous malignancies and result in resistance to OV therapy. Our group utilizes small molecule enhancers of OV therapy termed viral sensitizers. These small molecules have been shown to enhance the replication and spread of oncolytic rhabdovirus VSVΔ51 in vitro and prolong survival in tumour-bearing mice. In this study, we evaluate the ef-fect of these viral sensitizers on the innate antiviral response in order to identify the mechanism of action responsible for their viral-sensitizing properties. Our previous data suggest that VSe1 and its structural analogues affect the type I IFN antiviral response and have the potential to af-fect cellular redox homeostasis. We hypothesized that VSe1 and its structural analogues potenti-ate VSV∆51 activity by inhibiting the type I IFN response via redox-mediated dysregulation. In this study, we demonstrate that the viral sensitizers inhibit the nuclear translocation and transcrip-tional activity of NFκB, which in turn dampens the expression of antiviral cytokines IFN-, TNFα and IL-6. We also provide evidence supporting the possibility that the NFκB inhibition may be a result of the formation of ROS intermediates by the viral sensitizers, which leads to re-duced nuclear translocation of NFκB subunits, thereby preventing NFκB-mediated cytokine production. Overall, this work contributes to the identification of the mechanism of action of our viral sensitizers and highlights the finding that oncolytic VSV infection can be enhanced through redox-mediated modulation of the innate antiviral response.

Oncolytic viruses (OV) are an emerging class of anticancer bio-therapeutics that induce antitumor immunity through selective replication in cancer cells. However, the efficacy of OVs as single agents remains limited. We postulate that resistance to oncolytic virotherapy results in part from the failure of tumor cells to be sufficiently infected. In this study, we provide evidence that in the context of sarcoma, a highly heterogeneous malignancy, the infection of tumors by different oncolytic viruses varies greatly. Similarly, for a given oncolytic virus, productive infection of tumors across patient samples varies by many orders of magnitude. To overcome this issue, we hypothesize that the infection of resistant tumors can be achieved through the use of selected small molecules. Here, we have identified two novel drug classes with the ability to improve the efficacy of OV therapy: fumaric and maleic acid esters (FMAEs) and vanadium compounds. FMAEs are enhancing infection of cancer cells by several oncolytic viruses in cancer cell lines and human tumor biopsies. The ability of FMAEs to enhance viral spread is due to their ability to inhibit type I IFN production and response, which is associated with their ability to block nuclear translocation of transcription factor NF-κB. Vanadium-based phosphatase inhibitors enhance OV infection of RNA viruses in vitro and ex vivo, in resistant cancer cell lines. Mechanistically, this involves subverting the antiviral type I IFN response towards a death-inducing and proinflammatory type II IFN response, leading to improved OV spread, increased bystander killing of cancer cells, and enhanced anti-tumor immune-stimulation. Both FMAEs and vanadium compounds improve therapeutic outcomes of OV treatment in syngeneic tumor models, leading to durable responses, even in models otherwise refractory to OV and drug alone. Overall, we showcased novel avenues for the development of improved immunotherapy strategies.

Replicating viruses for the treatment of cancer have a number of advantages over traditional therapeutic modalities. They are highly targeted, self-amplifying, and have the added potential to act as both gene-therapy delivery vehicles and oncolytic agents. ORFV, (Parapoxvirus ovis, or Orf virus) is the prototypic species of the Parapoxvirus genus, causing a benign disease in its natural ungulate host. ORFV possesses a number of unique properties that make it an ideal viral backbone for the development of a cancer therapeutic: it is safe in humans, has the ability to cause repeat infections even in the presence of antibody, and it induces a potent Th-1 dominated immune response. Here I show for the first time that live replicating ORFV induces an anti-tumour immune response in multiple syngeneic mouse models of cancer that is mediated largely by the potent activation of both cytokine-secreting, and tumouricidal natural killer (NK) cells. I have also highlighted the clinical potential of the virus by demonstration of human cancer cell oncolysis including efficacy in an A549 xenograft model of cancer. The mechanism of ORFV-mediated activation of NK cells has been explored, where I have demonstrated activation via direct ex vivo infection of NK cells. I have also highlighted ORFV-mediated activation of dendritic cells (DCs), both in vivo and by direct infection ex vivo. An in vivo DC depletion study demonstrated an indirect mechanism for ORFV NK cell activation, where in the absence of DCs, NK cell activation was diminished, as was the ability of ORFV to clear lung metastases. The ORFV innate immune stimulatory profile has been harnessed for therapeutic application in an experimental surgery model of cancer, where ORFV therapy at the time of surgery reduces the number of cancer metastases. These data highlight the clinical potential of a live, immune stimulating Parapoxvirus therapeutic.

Glioblastoma is the most common primary brain tumour in adults. Despite the aggressive standard of care currently used, median patient survival following treatment is only 14 months. Innovative treatment options are needed for these patients. Recently, oncolytic viruses have emerged as promising immunotherapies for the treatment of solid tumours. Preliminary work in our lab has demonstrated that Farmington virus, a novel brain-safe oncolytic rhabdovirus, can be engineered to encode a tumour-associated antigen (TAA) to prime and boost antigen-specific adaptive immune responses. Since other rhabdoviruses share this boosting capacity, a heterologous rhabdovirus prime/boost regimen can be designed to combine two powerful oncolytics and a robust anti-TAA adaptive immune response. We evaluated Farmington’s ability to vaccinate against a self- glioblastoma antigen and two foreign glioblastoma-associated antigens. Farmington was able to vaccinate against the foreign antigens, leading to efficacy in prophylactic and therapeutic glioblastoma models. Additionally, treatment with heterologous rhabdoviruses demonstrated efficacy in an aggressive murine mammary carcinoma model. Herein, we demonstrate promising preliminary results for a novel glioblastoma therapeutic approach. Le glioblastome est la tumeur primaire la plus fréquente chez l’adulte. La survie moyenne des patients n’excède pas 14 mois malgré une prise en charge thérapeutique agressive. Par conséquent, la mise au point de traitements innovants et efficaces est une nécessité pour ces patients. Des avancées récentes ont mise en évidence l’intérêt des virus oncolytiques dans le traitement des tumeurs solides. Des travaux préliminaires réalisés au sein de notre laboratoire ont, en effet, démontré que le virus Farmington pouvait être modifié afin d’exprimer un antigène associé aux tumeurs (AAT), pour initier et potentialiser une réponse immunitaire adaptative spécifique. D’autres rhabdovirus possèdent des capacités de potentialisation immunitaire similaires et peuvent être utilisés en association avec le virus Farmington modifié pour amorcer et amplifier la réponse immunitaire oncolytique de l’hôte. Le but de ce projet était d’évaluer le potentiel du virus Farmington comme vaccin contre des antigènes tumoraux d’origine endogène ou exogène associés au glioblastome. Nos résultats ont montré que le virus Farmington a la capacité d’induire une réponse immunitaire prophylactique et thérapeutique contre les antigènes tumoraux exogènes dans des modèles de glioblastome. De plus, l’utilisation de rhabdovirus hétérologues s’est aussi révélée efficace pour le traitement de carcinome mammaire agressif chez la souris. Cette étude préliminaire apporte des résultats prometteurs pour le développement de nouvelles approches thérapeutiques efficaces dans le traitement du glioblastome.

No description available.

Cancer is the leading cause of death in Canada and one of the leading causes of death worldwide. Conventional cancer therapies such as chemotherapy often include severe side effects that can decrease the quality of life of patients undergoing treatment. Immunotherapy is designed to harness the host immune response and enhance its ability to seek out and kill cancer cells. Immunotherapy has gained traction in the past decade due to its improved safety and efficacy over conventional cancer therapies. However, there is room for improvement as most patients fail to respond to immunotherapy. The work described in this dissertation involves the development of therapeutic combination platforms that are designed to improve upon immunotherapy outcomes. Murine tumor models were used to develop a better understanding of biological processes associated with therapeutic efficacy. These findings can be used for the development of therapeutic strategies that can further improve the efficacy of cancer immunotherapy. / Cancer immunotherapy has demonstrated immense promise in the past decade. Immune checkpoint therapy has shown unprecedented responses in many cancers; however most patients fail to respond to checkpoint therapy. This highlights the need to develop a better understanding of factors in the tumor microenvironment that can influence therapeutic outcomes. In this body of work, we have utilized oncolytic viruses (OVs) to enhance immunogenicity in the tumor and study the cellular mechanisms that enable a therapeutic response. We utilize a combination of OVs and low dose chemotherapy to further sensitize murine models of mismatch repair-deficient colorectal cancer to checkpoint therapy. Using a Clariom S transcriptome assay we found that the combination induced gene signatures associated with the recruitment and activation of myeloid subsets. When we assessed tumor infiltrates, we found that the combination induced the chemoattraction of several myeloid subsets, including type I conventional DCs (cDC1s) which are known for their role in antigen presentation. Using Batf3-/- mice, we demonstrated that the therapeutic efficacy of our combination platform was dependent on the presence of cDC1s. In this dissertation, we also studied the role of OV-induced type I IFN (IFNI) in enabling or suppressing antitumor immunity. We found that OVs induced the upregulation of PD-L1 in an IFN-I-dependent manner in cancer cells and circulating immune cells. Inhibition of IFN-I signaling using an anti-IFNAR monoclonal antibody partially prevented OV-induced upregulation of PD-L1. Furthermore, the combination of OV and v | P a g e IFNAR blockade enhanced the effector functions of tumor-specific T cells and led to better tumor control compared to OV monotherapy. Altogether, these findings demonstrate that OVs can be an effective agent for enhancing immunogenicity in the tumor and promoting the infiltration of inflammatory myeloid subsets. By combining OVs with checkpoint or IFNAR inhibitors, we prevent the onset of immunosuppression and enable a favorable therapeutic response. / Thesis / Doctor of Philosophy (Medical Science)

No description available.

The adoptive transfer of cancer-specific T-cells has demonstrated success as a novel treatment strategy in some hematological malignancies but this approach has not yet achieved widespread curative potential in the majority of tumors. To circumvent many of the limitations currently facing adoptive cell therapies, our lab has recently developed a combination therapy involving the in vivo boosting of adoptively transferred tumor-specific memory T-cells with an oncolytic viral vaccine. While this represents a demonstrably powerful approach in preclinical models of cancer it is limited by its targeting of a single antigen. Therapeutic resistance is a common concern when targeting a single antigen or pathway and an ideal therapy would include built-in mechanisms to address the heterogeneity and mutability that is inherent to cancer. Thus the focus of this research involved the development of a strategy to target therapeutic resistance in the context of the adoptive cell transfer with oncolytic viral boost regimen. In order to address the single antigen limitations, the engineering of tumor-specific T-cells with a targeting capacity for a second antigen is described. In addition to their endogenous tumor target it is shown that these cells have specificity for and can kill cells expressing ligands for the natural killer group 2 member D receptor which are commonly upregulated on both cancer cells and components of the tumor microenvironment. Indeed it is demonstrated in an in vivo model of relapse that T-cells capable of targeting both antigens produce more consistent and prolonged remissions than those with only their endogenous targeting capacity. Furthermore pharmacological strategies for the enhancement of engineered T cell survival and efficacy are also described. Finally the early development of a chimeric tumor model to further characterize the potential of dual-specific T-cells to address tumor heterogeneity is presented. / Thesis / Master of Science (MSc)

Intratumoral injection of oncolytic viruses provides a direct means of tumor cell elimination for inoperable tumors. Unfortunately, oncolytic vectors based on human adenovirus (HAdV) typically do not spread efficiently throughout the tumor mass, reducing the efficacy of treatment. In this thesis, I explore the efficacy of conditionally replicating HAdV vectors expressing either the p14 Fusion Associated Small Transmembrane (FAST) protein (CRAdFAST) or p14 FAST protein in combination with the adenovirus death protein (CRAdFAST-ADP). The p14 FAST protein mediates cell-cell fusion, which may enhance spread of the virus-mediated, tumor cell-killing effect, while ADP aids in cell lysis and HAdV spread at late times in infection. I first explored the efficacy of CRAdFAST in the 4T1 immune competent mouse model of cancer. Treatment with CRAdFAST resulted in enhanced cell death compared to vector lacking the p14 FAST gene in vitro, but did not reduce the tumor growth rate in vivo. The 4T1 model was significantly resistant to HAdV infection and propagation, so I next explored CRAdFAST efficacy in human A549 cell culture and a xenograft mouse model of cancer. In the human A549 lung adenocarcinoma model of cancer, CRAdFAST showed significantly improved oncolytic efficacy in vitro and in vivo. In an A549 xenograft tumor model in vivo, CRAdFAST induced tumor cell fusion which led to the formation of large acellular regions within the tumor, and significantly reduced the tumor growth rate compared to control vector. Finally, to assess the use of a newly constructed CRAdFAST vector co-expressing the adenovirus death protein (ADP), a new model was explored comprised of CMT-64.6 mouse lung carcinoma cells which are syngeneic with Balb/C mice. This model was significantly more sensitive to HAdV infection and CRAdFAST induced fusion than the 4T1 cell line. In this model, expression of ADP and p14 FAST from a CRAdFAST-like vector (CRAdFAST-ADP) resulted in significant oncolytic synergy in vitro but not in vivo. My results indicate that expression of p14 FAST protein, and potentially ADP, from an oncolytic HAdV can improve vector efficacy for the treatment of cancer, but improved in vivo models will be required to analyze the full preclinical potential of these oncolytic HAdV vectors.

Oncolytic virotherapy is emerging as a new treatment option for cancer patients. At present, there are relatively few oncolytic virus clinical trials that are underway or have been conducted, however one virus that shows promise in pre-clinical models is Vesicular Stomatitis Virus (VSV). VSV is a naturally occurring oncolytic rhabdovirus that has the ability to preferentially replicate in and kill malignant versus normal cells. VSV also has a low seroprevalence, minimal associated morbidity and mortality in humans, and simple non-integrating genome that can be genetically manipulated, making it an optimal oncolytic vector. Currently, many labs are using a variety of different strategies including inserting trans genes that can modulate the innate and adaptive immune response. VSV can also be retargeted by altering its surface glycoprotein (G) or be made replication incompetent by deleting the G protein. Currently, our lab has engineered a series of new recombinant VSVs, incorporating either the murine p53 (mp53), IPS-1, or TRIF transgene. mp53, IPS-1 and TRIF were incorporated into the normal VSV-XN2 genome and mp53 was also incorporated into the mutated VSV-ΔM vector generating VSV-mp53, VSV-IPS-1, VSV-TRIF and VSV-ΔM-mp53. Our data using these new viruses indicate that these viruses preferentially replicate in and kill transformed versus non-transformed cells and efficiently express the transgene. However, despite the ability for VSV-IPS-1 and VSV-TRIF to induce a robust type 1 IFN response, VSV-ΔM-mp53 was the only construct that had reduced toxicity and elicited an increased anti-tumor response against a syngeneic metastatic mammary tumor model. VSV- ΔM-mp53 treatment lead to a reduction in IL-6 and IP-10 production, an increase in tumor specific CD8+ T cells, and immunologic memory against the tumor. Collectively these studies highlight the necessity for additional VSV construct development and the generation of new clinically relevant treatment schema.