Immunometabolic Regulation of CD8 T Cell Dynamics in Human Critical Illness and Sepsis
openNIGMS - National Institute of General Medical Sciences
PROJECT SUMMARY/ABSTRACT:
Critical illness syndromes, particularly sepsis, are a leading cause of morbidity and mortality worldwide
spanning all demographics. Sepsis arises from a dysregulated immune response to infection leading to
systemic end-organ injury. CD8 T cells, critical for pathogen defense, are profoundly impaired during sepsis,
exhibiting high rates of attrition, reduced cytokine production, and exhaustion-like phenotypes. Systemic
metabolic dysfunction, a hallmark of critical illness driven by hypoxemia, tissue hypoperfusion, and
inflammation, exacerbates immune cell dysfunction. However, the mechanisms linking metabolic stress to CD8
T cell failure in human critical illness with and without sepsis remain poorly understood. Our preliminary studies
reveal that effector CD8 T cells from critically ill and septic patients exhibit abnormal mitochondrial phenotypes,
including heightened glutamine metabolism that correlates with elevated exhaustion markers, impaired effector
function, and worse clinical outcomes. Using single-cell RNA sequencing, we further identified a distinct
effector CD8 T cell subset (CXCR4hi IL7Rlo) unique to critical illness, characterized by high levels of terminal
exhaustion markers TIM-3 and TOX, reduced cytotoxic features, and profound hypometabolism. Among the
most highly downregulated genes in this CXCR4hi IL7Rlo subset was phosphoglycerate mutase 1 (PGAM1), a
glycolytic enzyme that regulates both ATP production and biosynthesis. Accordingly, we hypothesize that
metabolic alterations in effector CD8 T cells drive their failure in human critical illness with and without sepsis.
Aim (1) will determine how glutamine metabolism modulates effector CD8 T cell fitness and function. Using
patient-derived CD8 T cells, we will employ advanced techniques, including high-dimensional spectral flow
cytometry, 13C-glutamine tracing, and pharmacologic manipulation of glutaminase activity. These will assess
how blocking glutaminolysis affects cytokine production, cytotoxicity, and exhaustion marker expression, and
directly trace glutamine usage for energy, biosynthesis, and antioxidant generation. Aim (2) will test the role of
PGAM1 as a metabolic switch controlling energy production and biosynthesis in effector CD8 T cells. We will
evaluate whether PGAM1 inhibition recapitulates the functional and metabolic impairments observed in
CXCR4hi IL7Rlo CD8 T effector cells, test whether rescuing glycolysis and biosynthetic pathways with pyruvate
and ribose-5-phosphate, respectively, can restore effector function in CXCR4hi IL7Rlo CD8 T cells, and
correlate CXCR4hi IL7Rlo CD8 T effector frequencies and phenotypes with clinical metrics in critical illness with
and without sepsis. These studies hold the promise of directly linking systemic metabolic dysfunction to CD8 T
cell immune failure in human critical illness and sepsis, providing key insights into immunometabolic regulation
and identifying new therapeutic targets. This award will provide essential training in translational
immunometabolism and human critical illness research, supported by mentorship and guidance from leading
investigators in these content areas, to develop the PI into a successful, independent physician-scientist.
Up to $186K
health research