Final Report Summary - MITOCHONDRIA (Unraveling and targeting mitochondrial biogenesis in CD8+ T cells to improve memory formation and vaccine efficacy) The main objectives of this proposal were the following: 1) Determine the role of PGC-1 in mitochondrial metabolism during CD8+ memory T cell (TM) development.2) Investigate whether agents that promote mitochondrial biogenesis (MB) enhance vaccine efficacy. Most of objective 1 and part of objective 2 have been successfully addressed. Due to an infection in the animal unit I have not been able to use any mice for about a year. The required mouse strain for objective 1 (PGC-1a/b deficient in T cells) was lost for even a longer time, and was only acquired again in January of this year. For the same reason, the in vivo experiments planned for objective 2 have only partially been performed. To address objective 1, I have performed metabolic analyses of PGC1a and PGC1b deficient T cells and compared those to control T cells. I also analyzed the functional properties of these cells and their ability to form memory cells in vivo. Specifically my data indicate that both PGC-1a and PGC-1b are not essential for mitochondrial metabolism and memory formation of CD8 T cells. However, to exclude the possibility that these proteins can take over each other’s function, I need to do the experiments using the double PGC-1ab T cell deficient mice. These experiments are still ongoing.To address objective 2, I have tested several drugs that have been described to enhance mitochondrial biogenesis in other cell types. Especially using one of these drugs in vitro yielded interesting data. We found that this drug increased mitochondrial biogenesis, and OXPHOS, most strikingly in effector T cells rather than memory T cells. Importantly, this drug also increased cytokine production by T cells, and thus improved effector function. I am currently testing whether these effects of the drug are PGC1a and/or PGC1b dependent, and setting up in vivo experiments.Since I did not have mice available for a long time, but was still interested in the role of mitochondrial metabolism in T cell function, I focussed on a related project using human T cells. Thus, as a valuable addition to the described objectives, human T cells were metabolically characterized, both derived from healthy controls and from leukaemia patients that are known to have dysfunctional T cells. This allowed for the comprehensive comparison of the metabolic properties of functional and dysfunctional human T cells. Preliminary data from this work have been used in an approved grant (Netherlands Organisation for Scientific Research), and I am the daily supervisor of three PhD students that were hired on this project.We found that there are metabolic defects in chronic lymphocytic leukemia (CLL)-derived CD8 T cells that could explain their dysfunction. Specifically, in response to stimulation, CLL T cells became less activated, and showed decreased glucose uptake and glycolysis. I have shown previously that mitochondrial metabolism contributes to the ability of T cells to rapidly induce glycolysis upon stimulation. Indeed I found that resting CLL-derived CD8 T cells have impaired mitochondrial function. This was indicated by increased mitochondrial membrane potential, -ROS production and basal respiration, while levels of PGC1a and the anti-oxidant super oxide dismutase 2, and the spare respiratory capacity was reduced in CLL CD8 T cells. Taken together, these data indicate that the metabolic fitness of CD8 T cells is impaired in CLL. Boosting T cell metabolism in CLL might therefore improve emerging immunotherapies such as chimeric antigen receptor (CAR)-T cell therapy. Currently CAR T cells from CLL patients are being analyzed on a metabolic level. I am senior author on the submitted manuscript.Most of these findings have not been published yet, but will be in the coming year. In the scientific community there is currently a great interest in understanding how immune cell function is controlled by metabolic pathways, including in the field of (cancer) immunotherapy. As such it is likely that these findings will contribute to metabolism-based approaches used in therapeutic settings. Therefore, I am convinced that the novel insights obtained from this project will be published in well-respected international peer-reviewed journals, and will have high international scientific impact.
