Browsing by Subject "immunotherapy"

The human immune system can provide a powerful tool in developing therapies against various cancers. Even though the idea of an immune system actively searching for and disposing of potential mutated tumor cells is over a century old, only recent developments in various fields such as mass spectrometry, immuno-checkpoint blockade strategies and in silico modelling have enabled the realization of the full potential of recruiting immune system to fight cancer and the possibilities of personalized therapies. These therapeutic methods, including but not limited to oncolytic virus therapies, T-cell therapies and cancer vaccines, are based on the body’s ability to recognize mutated antigen peptides presented on the cell surface by MCH-receptors (also known as HLA-receptors in humans) and the disposal of the malignant cells by cytotoxic T-cells. Thus, the capability to map the individual HLA-presented peptidome and differentiate the immunogenic peptides is a foundation for this plethora of therapies and is in focus of ongoing research. This master thesis is a part of a project aiming to set up immunoaffinity-purification/MS based method in order to analyse the ligandome and determine T-cell recognized cancer associated antigens from tumor cells. Objectives of the work: 1. Characterizing tumor cell lines. 2. Immunological assay set up. 3. Collecting cell culture material for the ligandome affinity purification. 4. In silico prediction if the immunogenicity of selected peptides and assessing their source proteins. Methods used: 1. Cell culture. 2. FACS-analysis. 3. MTS-viability assay. 4. Immunological assays (ELISA, ELISPOT). 5. Immunological bioinformatics analysis tools (IEDB) and database search (UniPROT). Results: 1. Flow cytometric analysis provided essential information of the cell line HLA-1 expression. Additional information of PD-L1 expression can be used to evaluate cell line’s immune-evasion abilities. Preliminary MTS assay is used to determine linear range and optimal time frame for the PBMC/cancer cell co-culture killing assay. 2. Interferon γ cytokine secretion was determined by ELISPOT to assess PBMC response against known antigens in a preliminary experiment to approximate usable range for the following antigen specific PBMC assays. ELISA is used to confirm the presence of HLA-I receptors in the ligandome affinity purification eluates and to estimate the efficacy of purification. 3. Feasibility of in silico methods in the prediction of immunogenic peptides was explored. The experiments provided information that can be applied to the further development of the immune ligandome discovery project. In silico methods were successfully used to characterize previously identified HLA-restricted peptides and one previously identified immunogenic T-cell epitope. Even if the data acquired in silico can be considered only nominally verified at this stage, the results are encouraging.

During the past few decades, the explosion of discovery in cancer and immunological research has led to the increased understanding of the interactions between the immune system and tumors. These developments have provided vital information about the immune system’s role in cancer development. It is evidenced that the immunity system is capable to distinguish tumor cells from normal tissue by recognizing tumor antigens that are exclusively expressed on tumor cells or are presented in greater amounts on tumor cells than normal cells. Consequently, the immune cells start to attack tumors for protecting the host. The possibility to use the immune system as a weapon against cancer cells leaded to the promising innovation – cancer immunotherapy – which aims to activate the body’s own immune system and its components to mount antitumor immune responses for eliminating cancer cells. The antitumor efficacy and high safety profile of several immunotherapeutic strategies have already been demonstrated thereby resulting in their integration into clinical practice. However, most patients have not benefited from cancer immunotherapy as a single treatment. In this regard, new innovative methods are clearly needed to overcome the obstacles hindering the clinical success of this field. Therapeutic cancer vaccines are emerging as attractive immunotherapies currently being evaluated in both pre-clinical and clinical studies. The purpose of cancer vaccines is to eradicate tumor cells by eliciting antitumor CD8+ T cell responses against the injected tumor antigens. Due to the ability to specifically kill tumor cells and simultaneously trigger immune responses against tumor antigens via direct oncolysis and by encoding transferred tumor antigens, oncolytic viruses are of significant interest for being used as in situ cancer vaccines. Despite these unique properties, several factors such as tumor immunosuppression and immune tolerance to targeted tumor antigens resembling antigens of normal tissues hamper the use of oncolytic vaccines in clinic. Instead of focusing only on CD8+ T cells, it has been suggested that giving more attention to CD4+ T helper cells, which are required for priming and expansion of CD8+ T cell responses, could be the key to improve the efficacy of cancer vaccines. Researchers have also demonstrated that an ongoing antigen-specific CD4+ T cell response can lead to the bystander activation of surrounding T cells with unrelated antigen specificities. Based on this theory, the hypothesis of this study was to employ the pre-existing immunological CD4+ memory against infectious pathogens in generating bystander CD8+ immunity against solid tumors. In this study, mice transplanted with poorly immunogenic B16-OVA tumors were pre-immunized with the chosen vaccine to induce immunological CD4+ memory against an infectious pathogen. Tumors were then treated with already developed cancer vaccine, which was peptide-coated conditionally replicating adenovirus (PeptiCRAd) complex. PeptiCRAd was constructed by electrostatically coating adenovirus with both pathogen-derived and tumor-derived peptide. The intratumorally injected double-coated PeptiCRAd complex was assumed to activate peptide-specific T cells and thus, result in anti-pathogen CD4+ T cell recall responses and the following bystander activation of antitumor CD8+ T cells, which can then mount an effective immune response to destroy cancer cells. The efficacy of this treatment was observed in pre-immunized mice by measuring the growth of injected tumors. The experiment was repeated identically with non-immunized naïve mice to see the difference in the results. The immunological background of this treatment approach was investigated by analyzing mouse tissue samples with standard immunological techniques including ELISA, IFN-γ ELISPOT and flow cytometry. This study showed that long-term immunological memory against the pathogen was successfully accomplished and the strongest inhibition of tumor growth in pre-immunized mice was achieved with double-coated PeptiCRAd, whereas the antitumor efficacy was not seen in naïve mice. Additionally, a new ex vivo method to detect pathogen-specific CD4+ T cells from spleen was developed and the stimulation of cell-mediated immunity by this treatment was supported by finding the highest levels of pathogen-specific CD4+ Th1 cells from mice treated with double-coated PeptiCRAd. Some encouraging results concerning the beneficial immune cell composition of tumors and tumor draining lymph nodes were also obtained from other performed experiments. Though further immunological analyses are required for understanding the precise mechanisms of action behind the treatment, the increased immunogenicity and antitumor efficacy of double-coated PeptiCRAd can still be considered as a consequence of the bystander effect, which can possibly be utilized for developing improved strategies to win the fight against cancer.