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Browsing by Subject "oncolytic virus"

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  • Juntunen, Maiju (2020)
    Cancer immunotherapy refers to therapy strategies that utilise the mechanisms of the immune system to treat cancer patients. The benefits of the approach include the possibility for specific targeting and utilisation of the host immune system. The treatment methods include cancer vaccines, oncolytic viruses (OVs), cell-based immunotherapies and antibodies. The interplay between the cancer and the immune system has been observed crucial for the progress of the cancer and the success of immunotherapies. An immune inflamed tumour microenvironment has been observed beneficial for the success of several therapy methods. Many immunotherapy methods rely on detecting tumour specific antigens that are used to guide the therapy agent to the target site. This strategy poses challenges when considering tumour immune evasion mechanisms, which can cause downregulation of target antigens, and heterogeneity of tumour cells and patients. OVs have the advantage of not requiring predetermined target structures to exert their effect to the tumour cells. They cause direct tumour cell lysis and induce immune responses, and may be modified to express additional genes, including immunostimulatory agents. However, virus-related immunosuppressive mechanisms and a rapid viral clearance may limit their effects. A Western Reserve (WR) Vaccinia virus (VACV) is a highly oncolytic virus strain but the virus has been observed to suppress the function of the cyclic guanosine monophosphate adenosine monophosphate synthase – stimulator of interferon genes (cGAS STING) innate immune pathway which has been shown to have a significant role in anti-tumour immune responses. The aim of this study was to create a WR VACV encoding a dominantly active (D A) STING and to determine whether the virus is capable of activating the cGAS STING pathway. The effects were compared to a corresponding virus vvdd tdTomato that does not have the STING encoding gene. The pathogenicity of viruses was controlled by a double deletion of the thymidine kinase and vaccinia growth factor genes which restricts the virus replication to tumour cells. Transgene fragments were cloned from template plasmids by polymerase chain reactions (PCRs) and joined together in a Gibson Assembly (GA) reaction to form a STING-P2A-eGFP gene insert. The insert was attached to a shuttle vector pSC65-tdTomato by restriction enzyme digestion, ligation and transformation in Escherichia coli. The correct transgene plasmid construct was verified by Sanger sequencing and PCRs. The transgene was inserted to a modified WR VACV vvdd-tdTomato-hDAI by a homologous recombination. The newly created VVdd STING-P2A-eGFP virus was purified by plaque purification. The STING protein expression was studied by an immunocytochemistry (ICC) assay. The immune signalling pathway activation was examined by testing nuclear factor kappa-light chain-enhancer of activated B cells (NF-κB) activation in RAW-Blue cells and dendritic cell activation and maturation in JAWS II cells. The cell viability after iinfection was studied with four cell lines; A549, B16-F10, HEK293 and MB49. The D-A STING expressing virus was produced successfully. The ICC experiment verified the capability of the VVdd STING-P2A eGFP to produce the STING protein in the infected cells. The preliminary findings indicate that the VVdd STING-P2A-eGFP virus activates the NF-κB signalling in the RAW-Blue cells and that the activation is dependent on the STING expression. The activation level is relative to the infection concentration at MOI range 0,001 to 0,1. The findings suggest that the VVdd-STING-eGFP virus can induce innate immune signalling via the STING pathway. The reference virus did not activate the signalling. The in vitro experiments also indicated that the STING virus may induce DC activation and maturation. We observed a trend of CD86 and CD40 expression upregulation on the JAWS II DCs. The effects to the cell viability were inconclusive. More studies should be conducted to verify the results. The effects of the virus should be studied in more advanced cancer models that take into account the complexity of the immune system. These preliminary results indicate the that the VVdd-STING-P2A-eGFP virus could stimulate the immune signalling through the STING pathway.
  • Honkasalo, Oona (2018)
    Cancer immunotherapies aim to target the immune defence mechanisms of the body specifically and efficiently against the tumour tissue. Cancer vaccines and oncolytic viruses are forms of active immunotherapies, which require patients having a properly functioning immune system. The vaccines are based on the administration of tumour antigens into the body to which the immune system reacts. However, often the response is not robust enough. The oncolytic viruses in turn kill the cancer cells which causes the release of antigens from the tumour tissue. Viruses usually elicit a strong immune response but sometimes it is targeted too much against the virus instead of the tumour. Oncolytic vaccine is a composition of an oncolytic virus and a cancer vaccine. Tumour antigens can be coded to the genome of the virus therefore, when the virus invades tumour cells they start to produce the antigens. Eventually the cancer cells are also destroyed due to viral replication. The antigens can be tumour-associated that is, they are expressed in healthy tissues too. Their usage is not always efficient which is why an interest towards utilizing tumour-specific antigens has been increased. Considering the expression of antigens, tumour tissue is very heterogenous and distinctive between patients. Hence, utilizing mutated patient unique neoantigens would enable the development of personalized tumour-specific oncolytic vaccines. Genetic modification of viruses is complicated thus, an easier way to insert the neoantigens to the virus has been invented. The developed oncolytic vaccine platform is called PeptiENV, and it is designed to use with enveloped viruses. The idea is to fuse tumour-specific antigens onto the envelope of the virus and eliminate the need of gene insertion. The aim of this study is to investigate in vivo the efficacy of PeptiENV in preventing tumour growth and eliciting a tumour-specific immune response. An object is also to observe survival times of the treated animals. Furthermore, the preservation of infectivity is studied in vitro. The research was executed with two potential oncolytic viruses, vaccinia virus (VACV) and herpes simplex virus type 1 (HSV-1). The PeptiENV complex was formed by using an artificial tumour antigen, ovalbumin epitope SIINFEKL, which was attached to the viral envelope with cell penetrating peptide (CPP) or cholesterol anchor. The preservation of infectivity was examined by measuring cell viability of PeptiENV infected cells. Animal experiments instead were performed with a mouse melanoma model created with B16-OVA cells, which express ovalbumin and therefore the antigen epitope SIINFEKL. PeptiENV was compared to control treatments which were virus, SIINFEKL peptide and complexation medium only. Treatments were administered as intratumoural injections. Tumour growth was followed by measuring the size of implanted tumours every other day. With flow cytometry, tumour-specific immune response was assessed by acquiring the relative amount of SIINFEKL-specific CD8+ T cells in the tumour tissue. Euthanizing dates were registered in order to observe the survival of the mice. According to the in vitro results, conjugation of peptides to the virus does not affect infectivity. In addition, the in vivo studies show that PeptiENV VACV CPP prevents tumour growth the most. Difference in tumour growth between PeptiENV VACV CPP and control treatments is significant. Mice injected with the same treatment also lived considerably longer than mice injected with virus, peptide or medium only. Also, PeptiENV HSV-1 hinders tumour growth distinctly more than virus only and slightly more than SIINFEKL only, but unfortunately it did not have an evident impact on the survival time. In both experiments, the PeptiENV treatment elicits the largest proportional amount of SIINFEKL-specific CD8+ T cells. In other words, PeptiENV engenders a tumour-specific immune response. In the PeptiENV VACV study the difference to control treatments is clearer than in the PeptiENV HSV-1 study. At present, the PeptiENV platforms performs better with VACV than HSV-1. With further investigations however, the results can be verified and improved. All in all, the results are encouraging. The PeptiENV platform shows great promise for being a part of personalized cancer immunotherapy developments in the future.