Immunogenicity of oncolytic vaccinia viruses JX-GFP and TG6002 in a human melanoma in vitro model: studying immunogenic cell death, dendritic cell maturation and interaction with cytotoxic T lymphocytes

Abstract

Oncolytic virotherapy is an emerging immunotherapeutic modality for cancer treatment. Oncolytic viruses with genetic modifications can further enhance the oncolytic effects on tumor cells and stimulate antitumor immunity. The oncolytic vaccinia viruses JX-594-GFP+/hGM-CSF (JX-GFP) and TG6002 are genetically modified by secreting granulocyte-macrophage colony-stimulating factor (GM-CSF) or transforming 5-fluorocytosine (5-FC) into 5-fluorouracil (5-FU). We compared their properties to kill tumor cells and induce an immunogenic type of cell death in a human melanoma cell model using SK29-MEL melanoma cells. Their influence on human immune cells, specifically regarding the activation of dendritic cells (DCs) and the interaction with the autologous cytotoxic T lymphocyte (CTL) clone, was investigated. Melanoma cells were infected with either JX-GFP or TG6002 alone or in combination with 5-FC and 5-FU. The influence of viral infection on cell viability followed a time- and multiplicity of infection dependent manner. Combination of virus treatment with 5-FU resulted in stronger reduction of cell viability. TG6002 in combination with 5-FC did not significantly strengthen the reduction of cell viability in this setting. Expression of calreticulin and high mobility group 1 protein (HMGB1), markers of immunogenic cell death (ICD), could be detected after viral infection. Accordingly, DC maturation was noted after viral oncolysis. DCs presented stronger expression of activation and maturation markers. The autologous CTL clone IVSB expressed the activation marker CD69, but viral treatment failed to enhance cytotoxicity marker. In summary, vaccinia viruses JX-GFP and TG6002 lyse melanoma cells and induce additional immunostimulatory effects to promote antitumor immune response. Further investigation in vivo is needed to consolidate the data.

In vitro PUVA treatment triggers calreticulin exposition and HMGB1 release by dying T lymphocytes in GVHD: New insights in extracorporeal photopheresis

“…This cannot be explained by ATP degradation by ectonucleotidases such as CD73 or CD39 43 since we did not detect any adenosine diphosphate or adenosine monophosphate in ivPUVA-treated cells supernatants (not shown). In hypericin-based PDT, CRT exposure and HMGB1 release were accompanied with ATP secretion by dying cells 40 ; on the contrary, ATP secretion was not detected in the oncolytic virus-induced cell death model, 38 despite dendritic cell maturation being induced in both instances. Since ivPUVA-treatment of T cells induced CRT expression at the surface of dying cells, we asked whether APC could phagocytize ivPUVA-treated T cells.…”

“…CRT exposure was detected at the surface of early apoptotic cells following ivPUVA treatment in several models (primary T cells, alloreactive activated T cells from GVHD patients or in vitro-generated alloreactive T cells, and CTCL cells). CRT expression by human cells in the context of ICD has been reported on a melanoma cell line following infection with oncolytic vaccinia viruses, 38 and on a bladder carcinoma cell line following hypericin-based PDT. 39,40 CRT exposure at the surface of human acute myeloid leukemia blasts has also been correlated to enhanced autologous T cell responses, 41 independently of chemotherapy treatment.…”

Immunotherapy of Esophageal Cancer: Current Status, Many Trials and Innovative Strategies

“…They cause an increase of T-cell numbers and activity. In combination with anti-CTLA-4 and/or anti-PD-L1 agents, they are capable of strengthening the anti-tumor response [33][34][35]. Talimogene laherparepvec (or T-Vec), a second-generation oncolytic herpes simplex virus type 1 armed with granulocyte-macrophage colony-stimulating factor, has been the first oncolytic virus with positive results and approval in melanoma patients [36].…”

Outlook: Immunotherapy in Gastrointestinal Carcinoma - Innovative Strategies

“…Oncol Res Treat 2018;41:313-315 315 to redirect and reboost the human immune system by release of additionaly new tumor antigens [10,21,22]. T-VEC, a double mutated HSV-1 virus, releasing GM-CSF, was well tolerated by patients with breast, head/neck, and gastrointestinal cancers [23].…”