Author ORCID Identifier

https://orcid.org/0000-0002-8704-377X

Date of Award

2024

Document Type

Thesis (Ph.D.)

Department or Program

Microbiology and Immunology

First Advisor

Edward J. Usherwood

Abstract

CD8+ T cells are crucial immune cells that control viruses and cancers due to their high antigen specificity and proliferative capacity. Consequently, CD8+ T cells are being extensively explored in adoptive T cell therapy for cancer, autoimmune diseases, and infections in clinical and pre-clinical studies. Given that T cells rely on nutrient microenvironments and employ various nutrient processing pathways, metabolic intervention presents a promising strategy to enhance CD8+ T cell function and differentiation.

Pyruvate dehydrogenase (PDH) serves as a critical bifurcation point in the metabolic pathway, determining whether glucose-derived pyruvate undergoes mitochondrial oxidative phosphorylation (OXPHOS) or cytosolic lactate fermentation. While studies have highlighted the role of PDH inactivation by pyruvate dehydrogenase kinase 1 (PDK1) in effector T cell differentiation, the contrasting role of pyruvate dehydrogenase phosphatase 1 (PDP1) and their impact on CD8+ T cell immune responses to various antigenic challenges in vivo remains poorly understood. In this study, I retrovirally transduced mouse CD8+ T cells with PDK1 or PDP1 and analyzed their metabolic profiles using Seahorse assays, RNA-sequencing transcriptomics, and metabolomics with 13C and 13C15N carbon/nitrogen-tracing experiments. I also assessed in vivo CD8+ T cell effector and memory responses against murine gammaherpesvirus 68 (MHV-68), Listeria monocytogenes, B16 melanoma, and B cell lymphoma.

My findings revealed that enforced expression of PDK1 and PDP1 both enhanced glycolysis and OXPHOS metabolism in vitro, accompanied by increased expression of mitochondrial metabolism pathway genes. This was attributed to differences in fuel source utilization: PDK1 expression promoted glutamine-derived TCA cycle anaplerosis, whereas PDP1 expression led to citrate accumulation and fatty acid-derived TCA cycle intermediates. These engineered CD8+ T cells exhibited improved responses to MHV-68 infection, with increased population size and larger memory-recall responses. However, this enhanced CD8+ T cell response was not observed in bacterial infections and cancer. Specifically, in the B cell lymphoma challenge, the engineered cells produced smaller effector populations in the tumor, resulting in larger tumors and poor survival.

Overall, this study suggests that PDK1 and PDP1 both enhance CD8+ T cell metabolic capacity, and the nature of the antigen significantly influences the efficacy of metabolic engineering of CD8+ T cells.

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