To date, our best tools for assessing the frequency and affinity of CD4+ T cells have been peptide:MHC (pMHC) tetramers or functional assays;neither of which effectively identify all of the responding cells to a particular antigen. This is in contrast to CD8+ T cells where these techniques prove more accurate. Generally, pMHC tetramers for class II antigens are difficult to produce and identify a small percentage of responding CD4+ T cells especially when antigen is derived from self proteins. The reason for this is that tetramer is based on affinity and if affinity is too low, then the tetramer is of limited use in assessing the response Functional responses also underestimate the number of antigen reactive CD4+ T cells. In the case of responses directed against myelin antigens for instance, the effector cytokine response is often determined using strong pharmacologic agents such as PMA and ionomycin, which hammer the T cell signaling cascade and may have little relevance to the cytokines being produced in response to antigen itself. To better assess the range of responding CD4+ T cells, we have begun to use micropipette based affinity assay. We report here a major advancement in assessment in the frequency and affinity of CD4+ T cells directed against myelin or viral antigens. Therefore for the first time, it is possible to track the range of affinities of a CD4+ T cells response during disease progression. Our preliminary findings have led to the following central hypothesis that the CD4+ T cell affinity profile directly impacts disease outcome and immune mediated tissue damage in the CNS.
Three specific aims are proposed to test this hypothesis focused on CD4+ T cells specific for self antigen myelin oligodendrocyte glycoprotein and pathogen associated lymphocytic choriomeningitis virus antigens.
Aim 1 - Identify the affinity of CD4+ T cells over the course of chronic autoimmune disease and viral infection.
Aim 2 - Define the connection between T cell affinity and effector phenotype.
Aim 3 - Establish the contribution of high versus low affinity T cells in response to antigens found in the CNS.

Public Health Relevance

CD4+ T cells play a major role in the pathogenesis of autoimmune responses such as multiple sclerosis (MS) and are critical for proper response to chronic viral infections. The overall goal of this grant is to define the range of T cell affinities for myelin and viral antigens in the central nervous system (CNS. The proposed studies apply a novel means for assessing the affinity if the responding T cell response in the murine EAE and LCMV models, but our results should be rapidly transferable to patients. Therefore, our findings are highly relevant to human health and will prove to be a valuable asset for assessing disease prognosis and for the development of effective treatments.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Research Project (R01)
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Special Emphasis Panel (ZRG1-BDCN-W (03))
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Utz, Ursula
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Emory University
Schools of Medicine
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Andargachew, Rakieb; Martinez, Ryan J; Kolawole, Elizabeth M et al. (2018) CD4 T Cell Affinity Diversity Is Equally Maintained during Acute and Chronic Infection. J Immunol 201:19-30
Blanchfield, Lori; Sabatino Jr, Joseph J; Lawrence, Laurel et al. (2017) NFM Cross-Reactivity to MOG Does Not Expand a Critical Threshold Level of High-Affinity T Cells Necessary for Onset of Demyelinating Disease. J Immunol 199:2680-2691
Bally, Alexander P R; Tang, Yan; Lee, Joshua T et al. (2017) Conserved Region C Functions To Regulate PD-1 Expression and Subsequent CD8 T Cell Memory. J Immunol 198:205-217
Shorter, Shayla K; Schnell, Frederick J; McMaster, Sean R et al. (2016) Viral Escape Mutant Epitope Maintains TCR Affinity for Antigen yet Curtails CD8 T Cell Responses. PLoS One 11:e0149582
Martinez, Ryan J; Andargachew, Rakieb; Martinez, Hunter A et al. (2016) Low-affinity CD4+ T cells are major responders in the primary immune response. Nat Commun 7:13848
Martinez, Ryan J; Neeld, Dennis K; Evavold, Brian D (2015) Identification of T cell clones without the need for sequencing. J Immunol Methods 424:28-31
Hood, Jennifer D; Zarnitsyna, Veronika I; Zhu, Cheng et al. (2015) Regulatory and T Effector Cells Have Overlapping Low to High Ranges in TCR Affinities for Self during Demyelinating Disease. J Immunol 195:4162-70
Frost, Elizabeth L; Kersh, Anna E; Evavold, Brian D et al. (2015) Cutting Edge: Resident Memory CD8 T Cells Express High-Affinity TCRs. J Immunol 195:3520-4
Martinez, Ryan J; Evavold, Brian D (2015) Lower Affinity T Cells are Critical Components and Active Participants of the Immune Response. Front Immunol 6:468
Hong, Jinsung; Persaud, Stephen P; Horvath, Stephen et al. (2015) Force-Regulated In Situ TCR-Peptide-Bound MHC Class II Kinetics Determine Functions of CD4+ T Cells. J Immunol 195:3557-64

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