T cells recognize pathogen-derived antigens and are crucial for fighting pathogens such as viruses and bacteria. In addition, T cells are able to recognize and attack certain types of tumors, in... Show moreT cells recognize pathogen-derived antigens and are crucial for fighting pathogens such as viruses and bacteria. In addition, T cells are able to recognize and attack certain types of tumors, in particular virally induced tumors. In this thesis we aimed 1) to obtain more insight into antigen-specific T cell responses and 2) to study how antigen-specific T cell responses can be improved. For the first aim we generated new tools that by enabling the visualization of antigen-specific CD4+ and CD8+ T cells allow the study of the dynamics of antigen-specific T cell responses in time throughout an ongoing immune response (chapter 2). In addition, we developed a novel technique that enables the study of family relationships between different T cell populations. This technique for instance allows us to determine whether two different types of effector T cell populations arise from the same or different pool(s) of na_ve T cells (chapter 5). For the second aim, we analyzed whether antigen-specific T cell responses can be manipulated by providing increased costimulation in the form of constitutive triggering of CD27 (chapter 3) or by generating CD4+ T cells that are modified by the introduction of MHC class I restricted TCRs (chapter 4). Show less
Adoptive transfer of T-cells that are ex vivo selected for tumor-specificity is an attractive treatment strategy for cancer. Epstein Barr virus (EBV)-associated malignancies are ideal candidates to... Show moreAdoptive transfer of T-cells that are ex vivo selected for tumor-specificity is an attractive treatment strategy for cancer. Epstein Barr virus (EBV)-associated malignancies are ideal candidates to develop this type of immunotherapy as EBV-specific T-cells can readily be selected and expanded from peripheral blood of EBV-seropositive individuals. The first part of thesis describes a phase 1 clinical study which demonstrates the feasibility and safety of this approach in patients with advanced stage EBV-positive nasopharyngeal carcinoma. Unfortunately only a small number of cancers express viral antigens that are easily recognized by the immune system. Therefore a strategy is required to generate large numbers of T-cells specific for antigens that normally elicit no or only a weak immune response. In the second part of this thesis a method is described of engrafting T-cells with the required specificity using retroviral transfer of T-cell receptors (TCRs). The TCRs were further modified to incorporate costimulation signals (CD28, OX40) that are essential to initiate and sustain an effective anti-tumor response but are often lacking on the target tumor cells. Finally, an inducible safety switch was developed that allows for the ablation of the infused T-cells in vivo in case of toxicity, which will facilitate the implementation of these novel immunotherapy approaches in clinical studies. Show less
