[Genetic, immunological, and pharmacological strategies to generate improved oncolytic viruses]

Tutorial: design, production and testing of oncolytic viruses for cancer immunotherapy

Oncolytic viruses (OVs) represent a novel class of cancer immunotherapy agents that preferentially infect and kill cancer cells and promote protective antitumor immunity. Furthermore, OVs can be used in combination with established or upcoming immunotherapeutic agents, especially immune checkpoint inhibitors, to efficiently target a wide range of malignancies. The development of OV-based therapy involves three major steps before clinical evaluation: design, production and preclinical testing. OVs can be designed as natural or engineered strains and subsequently selected for their ability to kill a broad spectrum of cancer cells rather than normal, healthy cells. OV selection is further influenced by multiple factors, such as the availability of a specific viral platform, cancer cell permissivity, the need for genetic engineering to render the virus non-pathogenic and/or more effective and logistical considerations around the use of OVs within the laboratory or clinical setting. Selected OVs are then produced and tested for their anticancer potential by using syngeneic, xenograft or humanized preclinical models wherein immunocompromised and immunocompetent setups are used to elucidate their direct oncolytic ability as well as indirect immunotherapeutic potential in vivo. Finally, OVs demonstrating the desired anticancer potential progress toward translation in patients with cancer. This tutorial provides guidelines for the design, production and preclinical testing of OVs, emphasizing considerations specific to OV technology that determine their clinical utility as cancer immunotherapy agents.

[Autophagy modulation by viruses: An important role in tumor progression]

Autophagy is an important process for cellular homeostasis at critical steps of development or in response to environmental stress. In the context of cancers, autophagy has a significant impact on tumor occurrence and tumor cell growth. On the one hand, autophagy limits the transformation of precancerous cells into cancer cells at an early stage. However, on the other hand, it promotes cell survival, cell proliferation, metastasis and resistance to anti-tumor therapies in more advanced tumors. Autophagy can be induced by a variety of extracellular and intracellular stimulus. Viral infections have often been associated with a modulation of autophagy, with variable impacts on viral replication and on the survival of infected cells depending on the model studied. In a tumor context, the modulation of autophagy induced by the viral infection of tumor cells seems to have a significant impact on tumor progression. The aim of this review article is to present recent findings regarding the consequences of autophagy disturbance by viral infections on tumor behavior.

[Antitumoral microorganisms: The Swiss army knife of immunotherapy]

Research on viruses, bacteria and protozoa-based immunotherapy has been on the rise for several years. The antitumoral efficacy of these microorganisms relies on three main mechanisms: Destruction of tumor cells, stimulation of the immune response and reprogramming of the tumor microenvironment. In order to optimize their immunotherapeutic action, these microorganisms can be genetically engineered to enhance their tumor-targeting efficacy or to vectorize immunostimulating molecules and/or antibodies. To this aim, molecular engineering allows the design of new antibody formats optimizing their functions. From whole antibodies to tandem single-chain variable fragments, various antibody formats can be vectorized by microorganisms to target receptors such as immune checkpoints or recruit immune effector cells within the tumor. Such possibilities broaden the arsenal of immunotherapeutic cancer treatment. This review focuses on these innovations and their advantages for immunotherapy.

Exploiting tumor epigenetics to improve oncolytic virotherapy

Oncolytic viruses (OVs) comprise a versatile and multi-mechanistic therapeutic platform in the growing arsenal of anticancer biologics. These replicating therapeutics find favorable conditions in the tumor niche, characterized among others by increased metabolism, reduced anti-tumor/antiviral immunity, and disorganized vasculature. Through a self-amplification that is dependent on multiple cancer-specific defects, these agents exhibit remarkable tumor selectivity. With several OVs completing or entering Phase III clinical evaluation, their therapeutic potential as well as the challenges ahead are increasingly clear. One key hurdle is tumor heterogeneity, which results in variations in the ability of tumors to support productive infection by OVs and to induce adaptive anti-tumor immunity. To this end, mounting evidence suggests tumor epigenetics may play a key role. This review will focus on the epigenetic landscape of tumors and how it relates to OV infection. Therapeutic strategies aiming to exploit the epigenetic identity of tumors in order to improve OV therapy are also discussed.

[Vesicular stomatitis virus in the fight against cancer]

Cancer is a complex disease that affects more and more people around the world. Unfortunately, existing treatments are only partially efficient and often induce major side effects. Thus, the use of viruses to selectively kill cancer cells is a new promising therapeutic approach. Recently, VSV has been used in oncolytic virotherapy because of its capacity to preferentially infect most human tumor cells. However, despite the availability of good oncolytic VSV mutants, the large variability of tumor cell types and the multiple ways in which they can evade viral infection suggests that therapeutic combinations of various viruses will be necessary to efficiently treat most cancers. A better understanding of the infection mechanisms and immune system recruitment by oncolytic viruses will be of great value for the development of safe and efficient strategies for cancer treatment.