Nasal administration of recombinant Neospora caninum secreting IL-15/IL-15Rα inhibits metastatic melanoma development in lung.

BACKGROUND: Metastases are the leading cause of mortality in many cancer types and lungs are one of the most common sites of metastasis alongside the liver, brain, and bones. In melanoma, 85% of late-stage patients harbor lung metastases. A local administration could enhance the targeting of metastases while limiting the systemic cytotoxicity. Therefore, intranasal administration of immunotherapeutic agents seems to be a promising approach to preferentially target lung metastases and decrease their burden on cancer mortality. From observations that certain microorganisms induce an acute infection of the tumor microenvironment leading to a local reactivating immune response, microbial-mediated immunotherapy is a next-generation field of investigation in which immunotherapies are engineered to overcome immune surveillance and escape from microenvironmental cancer defenses. METHODS: The goal of our study is to evaluate the potential of the intranasal administration of Neospora caninum in a syngeneic C57BL6 mouse model of B16F10 melanoma lung metastases. It also compares the antitumoral properties of a wild-type N. caninum versus N. caninum secreting human interleukin (IL)-15 fused to the sushi domain of the IL-15 receptor α chain, a potent activator of cellular immune responses. RESULTS: The treatment of murine lung metastases by intranasal administration of an N. caninum engineered to secrete human IL-15 impairs lung metastases from further progression with only 0,08% of lung surface harboring metastases versus 4,4% in wild-type N. caninum treated mice and 36% in untreated mice. The control of tumor development is associated with a strong increase in numbers, within the lung, of natural killer cells, CD8+ T cells and macrophages, up to twofold, fivefold and sixfold, respectively. Analysis of expression levels of CD86 and CD206 on macrophages surface revealed a polarization of these macrophages towards an antitumoral M1 phenotype. CONCLUSION: Administration of IL-15/IL-15Rα-secreting N. caninum through intranasal administration, a non-invasive route, lend further support to N. caninum-demonstrated clear potential as an effective and safe immunotherapeutic approach for the treatment of metastatic solid cancers, whose existing therapeutic options are scarce. Combination of this armed protozoa with an intranasal route could reinforce the existing therapeutic arsenal against cancer and narrow the spectrum of incurable cancers.

[Antitumoral microorganisms: The Swiss army knife of immunotherapy]. / Micro-organismes anti-cancéreux et armement - Le couteau suisse de l'immunothérapie.

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.

TITLE: Micro-organismes anti-cancéreux et armement - Le couteau suisse de l'immunothérapie. ABSTRACT: Depuis plusieurs années, la recherche sur les micro-organismes pour une utilisation à des fins d'immunothérapie antitumorale est en plein essor. L'efficacité antitumorale de ces micro-organismes repose sur trois mécanismes principaux : la destruction des cellules tumorales, la stimulation du système immunitaire et la reprogrammation du microenvironnement tumoral. Afin d'optimiser leur action immunothérapeutique, ces micro-organismes peuvent être génétiquement modifiés pour les rendre capables de vectoriser des molécules immunostimulantes ou des anticorps. Par ingénierie moléculaire, il est désormais possible de diversifier les formats et fonctions de ces anticorps afin d'inhiber les points de contrôle immunitaire ou encore de recruter les cellules immunitaires effectrices au site de la tumeur. Cette Synthèse s'intéresse particulièrement à ces innovations et à leurs avantages en immunothérapie.

Neospora caninum: a new class of biopharmaceuticals in the therapeutic arsenal against cancer.

BACKGROUND: Microorganisms that can be used for their lytic activity against tumor cells as well as inducing or reactivating antitumor immune responses are a relevant part of the available immunotherapy strategies. Viruses, bacteria and even protozoa have been largely explored with success as effective human antitumor agents. To date, only one oncolytic virus-T-VEC-has been approved by the US Food and Drug Administration for use in biological cancer therapy in clinical trials. The goal of our study is to evaluate the potential of a livestock pathogen, the protozoan Neospora caninum, non-pathogenic in humans, as an effective and safe antitumorous agent. METHODS/RESULTS: We demonstrated that the treatment of murine thymoma EG7 by subcutaneous injection of N. caninum tachyzoites either in or remotely from the tumor strongly inhibits tumor development, and often causes their complete eradication. Analysis of immune responses showed that N. caninum had the ability to 1) lyze infected cancer cells, 2) reactivate the immunosuppressed immune cells and 3) activate the systemic immune system by generating a protective antitumor response dependent on natural killer cells, CD8-T cells and associated with a strong interferon (IFN)-γ secretion in the tumor microenvironment. Most importantly, we observed a total clearance of the injected agent in the treated animals: N. caninum exhibited strong anticancer effects without persisting in the organism of treated mice. We also established in vitro and an in vivo non-obese diabetic/severe combined immunodeficiency mouse model that N. caninum infected and induced a strong regression of human Merkel cell carcinoma. Finally, we engineered a N. caninum strain to secrete human interleukin (IL)-15, associated with the alpha-subunit of the IL-15 receptor thus strengthening the immuno-stimulatory properties of N. caninum. Indeed, this NC1-IL15hRec strain induced both proliferation of and IFN-γ secretion by human peripheral blood mononuclear cells, as well as improved efficacy in vivo in the EG7 tumor model. CONCLUSION: These results highlight N. caninum as a potential, extremely effective and non-toxic anticancer agent, capable of being engineered to either express at its surface or to secrete biodrugs. Our work has identified the broad clinical possibilities of using N. caninum as an oncolytic protozoan in human medicine.