Glycolytic metabolism of pathogenic T cells enables early detection of GvHD by 13C-MRI
Graft-versus-host disease (GvHD) is a prominent barrier to allogeneic hematopoietic stem cell transplantation (HSCT). Definitive diagnosis of GvHD is invasive and biopsies of involved tissues pose a high risk of bleeding and infection. Our previous studies in a chronic GvHD mouse model demonstrated that alloreactive CD4+ T cells are distributed to target organs ahead of overt symptoms, meanwhile CD4+ T cell activation is tied to increased glycolysis. Thus, we hypothesized that metabolic imaging of glycolysis would allow non-invasive detection of insipient GvHD in target organs infiltrated by glycolytic effector memory CD4+ T cells. We metabolically characterized CD4+ T cell subsets on day 14 post-transplant before the onset of chronic GvHD in a pre-clinical mouse model and performed 13C hyperpolarized magnetic resonance imaging (MRI) to quantify glycolytic activity in the liver of mice over the course of the disease. Intracellular metabolic screening and ex vivo metabolic profiling of CD4+ T cell subsets at day 14 confirmed that activated CD4+ T cells were highly glycolytic. Concurrently, hyperpolarized 13C-pyruvate MRI of the liver showed high conversion of pyruvate to lactate, indicative of increased glycolytic activity, that distinguished allogeneic from syngeneic HSCT recipients prior to the development of overt chronic GvHD. Furthermore, single cell sequencing of T cells in patients undergoing allogeneic HSCT indicated that similar metabolic changes may play a role in acute GvHD, providing a rationale for testing this imaging approach in the clinical post-HSCT setting. Our imaging approach is amenable to clinical translation and may allow early, non-invasive diagnosis of GvHD.