Encephalitogenic stem-like T cells in MS and its disease models

About This Grant

Despite currently available therapeutic approaches, multiple sclerosis (MS) remains an incurable disease. Studies in MS patients and corresponding animal models show that encephalitogenic T effector cells (TEFF) promote key autoimmune responses during MS pathogenesis. Within the central nervous system (CNS) of MS patients, these autoimmune T cells infiltrate the brain and then circulate back into the peripheral immune system, where they are maintained and reactivated, making such T cells a feasible diagnostic and therapeutic target. The mechanisms responsible for the maintenance of the encephalitogenic TEFF repertoire remain unclear. Stem- like T cells (TSTEM) that continue to differentiate into TEFF were proposed to contribute to the onset and exacerbation of human MS and its animal models. However, gaps in knowledge about the molecular characteristics of these encephalitogenic T cells and technical limitations severely hamper such advances. To overcome these limitations, we have developed a novel, state-of-the-art analytical tool, Seqtometry (sequencing- to-measurement), for analyzing single-cell sequencing data. As presented in this proposal, we performed an in- depth transcriptomic analysis of encephalitogenic T cells from the CNS and peripheral blood of MS patients and successfully identified MS-linked TSTEM, which were conspicuously absent in healthy or MS-free controls. We confirmed our findings using T cells specific for myelin oligodendrocyte glycoprotein (MOG), a relevant neuronal antigen, in an animal model of MS. Our most recent studies identified CD4+ T cells programmed for differentiation into TEFF with specific transcriptomic signature profiles corresponding to the MS-linked TSTEM, highlighting the conservation of encephalitogenic TSTEM. Based on these significant findings, we hypothesize that key transcriptomic characteristics that are conserved in T cells from MS patients and relevant animal models can foretell the early disease process and offer insights into the molecular mechanisms that govern the encephalitogenic differentiation of autoimmune T cells. Our further studies revealed in encephalitogenic TSTEM specific molecular mechanisms dependent on the homeodomain-only protein (Hopx) that governs effector differentiation of these cells. We additionally hypothesize that intrinsic mechanisms of Hopx in TSTEM orchestrate key pro-encephalitogenic functions. We will test our hypotheses in three aims: In Aim 1, we will determine the trajectories of encephalitogenic differentiation, In Aim 2, we will reveal the molecular mechanisms orchestrating fate and functions of TSTEM and clarify functions of Hopx, In Aim 3, we will determine the molecular characteristics of MS-linked TSTEM. Overall, the expected results of this research would provide us with key insights into molecular mechanisms underlying differentiation of encephalitogenic T cells, also helping to usher us into developing new MS diagnostic tools.