Oncolytic Orf virus licenses NK cells via cDC1 to activate innate and adaptive antitumor mechanisms and extends survival in a murine model of late-stage ovarian cancer.

BACKGROUND: Novel therapies are needed to improve outcomes for women diagnosed with ovarian cancer. Oncolytic viruses are multifunctional immunotherapeutic biologics that preferentially infect cancer cells and stimulate inflammation with the potential to generate antitumor immunity. Herein we describe Parapoxvirus ovis (Orf virus (OrfV)), an oncolytic poxvirus, as a viral immunotherapy for ovarian cancer. METHODS: The immunotherapeutic potential of OrfV was tested in the ID8 orthotopic mouse model of end-stage epithelial ovarian carcinoma. Immune cell profiling, impact on secondary lesion development and survival were evaluated in OrfV-treated mice as well as in Batf3 knockout, mice depleted of specific immune cell subsets and in mice where the primary tumor was removed. Finally, we interrogated gene expression datasets from primary human ovarian tumors from the International Cancer Genome Consortium database to determine whether the interplay we observed between natural killer (NK) cells, classical type 1 dendritic cells (cDC1s) and T cells exists and influences outcomes in human ovarian cancer. RESULTS: OrfV was an effective monotherapy in a murine model of advanced-stage epithelial ovarian cancer. OrfV intervention relied on NK cells, which when depleted abrogated antitumor CD8+ T-cell responses. OrfV therapy was shown to require cDC1s in experiments with BATF3 knockout mice, which do not have mature cDC1s. Furthermore, cDC1s governed antitumor NK and T-cell responses to mediate antitumor efficacy following OrfV. Primary tumor removal, a common treatment option in human patients, was effectively combined with OrfV for optimal therapeutic outcome. Analysis of human RNA sequencing datasets revealed that cDC1s correlate with NK cells in human ovarian cancer and that intratumoral NK cells correlate positively with survival. CONCLUSIONS: The data herein support the translational potential of OrfV as an NK stimulating immunotherapeutic for the treatment of advanced-stage ovarian cancer.

Quantifying Antibody Responses Induced by Antigen-Agnostic Immunotherapies.

As the development and clinical application of cancer immunotherapies continue to expand, so does the need for novel methods to dissect their mechanisms of action. Antibodies are important effector molecules in cancer therapies due to their potential to bind directly to surface-expressed antigens and facilitate Fc receptor-mediated uptake of antigens by antigen-presenting cells. Quantifying antibodies that are specific for defined antigens is straightforward. However, we describe herein a preclinical method to evaluate tumor-associated and virus-specific antibody responses to antigen-agnostic immunotherapies. This method uses autologous tumor cells as reservoirs of bulk tumor antigens, which can be bound by antibodies from the serum or plasma of tumor-bearing mice. These antibodies can then be detected and quantified using isotype-specific secondary antibodies conjugated to a fluorochrome. Alternatively, virus-infected cells can be used as a source of viral antigens. This method will enable researchers to assess antibody responses following immunotherapies without requiring pre-defined antigens. Alternatively, total virus-specific antibody responses could be studied as an alternative to more limited virus-neutralizing antibody assays. Therefore, this method can facilitate studying the role of humoral responses in the context of immunotherapies, including those that rely on the use of viral vectors.

Myeloid Cells during Viral Infections and Inflammation.

Myeloid cells represent a diverse range of innate leukocytes that are crucial for mounting successful immune responses against viruses. These cells are responsible for detecting pathogen-associated molecular patterns, thereby initiating a signaling cascade that results in the production of cytokines such as interferons to mitigate infections. The aim of this review is to outline recent advances in our knowledge of the roles that neutrophils and inflammatory monocytes play in initiating and coordinating host responses against viral infections. A focus is placed on myeloid cell development, trafficking and antiviral mechanisms. Although known for promoting inflammation, there is a growing body of literature which demonstrates that myeloid cells can also play critical regulatory or immunosuppressive roles, especially following the elimination of viruses. Additionally, the ability of myeloid cells to control other innate and adaptive leukocytes during viral infections situates these cells as key, yet under-appreciated mediators of pathogenic inflammation that can sometimes trigger cytokine storms. The information presented here should assist researchers in integrating myeloid cell biology into the design of novel and more effective virus-targeted therapies.