The professor in the department of neurology with McGovern Medical School at UTHealth Houston discussed outcomes of a recent study exploring the specificity of T cells in the spinal fluid of patients diagnosed with multiple sclerosis.
Previous research has provided evidence of the association between multiple sclerosis (MS) and Epstein–Barr virus (EBV) infection, a common herpesvirus that impacts over 90% of the population worldwide.1 Researchers in the field originally hypothesized this connection because of an increase in MS risk observed in post-infectious mononucleosis and elevated antibodies specific to EBV antigens. In 2022, a longitudinal study showed a 30-fold increase in MS following EBV infection whereas those uninfected showed minimal risk.2 Recent research of this association has aimed to understand the underlying mechanisms, offering potential avenues for the development of targeted MS treatments.
A recent study published in the Proceedings of the National Academy of Sciences revealed a significant presence of T-cells specifically targeting EBV-infected cells in the cerebrospinal fluid (CSF) of patients at the initial stages of MS.3 Led by senior author J. William Lindsey, MD, a professor in the department of neurology at McGovern Medical School, UTHealth Houston, investigators examined blood and CSF samples from 8 patients undergoing MS diagnosis. Employing various stimuli on the patients' blood cells, Lindsey, who also serves as the Opal C. Rankin professor in neurology, and colleagues, utilized RNA sequencing for T-cell receptors to observe the specific responses of CSF T-cells to these stimuli.
In a new iteration of NeuroVoices, Lindsey sat down to dive deeper into the comparison between the abundance of T cells specific for EBV-infected cells in the spinal fluid of patients with MS and T cells directed at other infections. During the conversation, he shared valuable insights regarding the study's implications for understanding the potential role of T cells in the autoimmune response of MS, particularly those directed at EBV. Lindsey also touched upon the forthcoming stages of the research, emphasizing the exploration of B lymphocytes and the detailed examination of T cell activities in the spinal fluid of patients affected by MS.
J. William Lindsey, MD: Our primary objective in this study was to elucidate the specificity of cells in the spinal fluid of patients with MS. One of the challenges in MS research lies in identifying a target for the autoimmune attack, despite the widespread assumption that MS is an autoimmune disease. While substantial evidence supports this notion, recent findings have also linked MS to EBV, adding complexity to our understanding. Our focus was to determine the specificity of cells in the spinal fluid of patients with MS, as we have struggled to identify a target in the brain for the autoimmune response, which differs from other autoimmune diseases where the target is known.
To accomplish this, we utilized spinal fluid samples obtained from patients with MS undergoing lumbar punctures for diagnostic purposes. These individuals had not yet undergone any treatment and were in the early stages of the disease, experiencing their first episode of symptoms. Our approach involved extracting cells from the spinal fluid and sequencing the T cell receptors, specifically focusing on the CDR3 sequence – a short part of the receptor known for its specificity. Simultaneously, we collected blood samples and stimulated them with various antigens, including the EBV, EBV-infected lymphoblastoid cell lines, varicella virus (chickenpox), influenza, and candida. Flow cytometry was employed to sort out the responding T cells for each antigen, and their T cell receptors were sequenced to determine specificity.
Surprisingly, our findings revealed that a significant proportion of the T cells in the spinal fluid were specific for EBV-infected cells. Our sequencing analysis considered the abundance of T cell receptor sequences, with a particular focus on the most abundant 1% of sequences. This subset of T cells was deemed crucial, as we hypothesized that these cells were either specifically recruited from the blood and retained in the spinal fluid or recruited into the spinal fluid and underwent division and proliferation, potentially playing a role in the disease process. Remarkably, almost half (47%) of the most abundant T cell receptors were specific to EBV-infected cells.
It's worth noting that previous studies have identified T cells specific for EBV-infected cells in the spinal fluid of patients with MS. However, our work distinguishes itself by breaking down specificity by abundance, a feature not commonly explored because of varied methodologies in previous studies. Additionally, our study provides comparative insights into the presence of T cells specific for other infections, such as flu and candida, in the spinal fluid, highlighting the elevated presence of EBV-specific T cells.
Moving forward, our study prompts the crucial question of the functional role of these EBV -specific T cells in the spinal fluid. Our next steps involve employing single-cell sequencing to capture not only the T cell receptor but also other RNAs expressed by these cells. This will provide insights into the cellular activities, including whether these T cells are actively killing other cells, participating in broader immune responses, or exhibiting regulatory or exhausted behaviors. Furthermore, we acknowledge the need to explore B lymphocytes, another crucial component of the immune system, and determine whether they exhibit similar specificity for EBV-infected cells in the spinal fluid. These ongoing investigations aim to unravel the functional significance of the observed T cell specificity and contribute to a comprehensive understanding of the immune response in MS.
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