High levels of SARS-CoV-2–specific T cells with restricted functionality in severe courses of COVID-19
David Schub, Verena Klemis, Sophie Schneitler, Janine Mihm, Philipp M. Lepper, Heinrike Wilkens, Robert Bals, Hermann Eichler, Barbara C. Gärtner, Sören L. Becker, Urban Sester, Martina Sester, Tina Schmidt
David Schub, Verena Klemis, Sophie Schneitler, Janine Mihm, Philipp M. Lepper, Heinrike Wilkens, Robert Bals, Hermann Eichler, Barbara C. Gärtner, Sören L. Becker, Urban Sester, Martina Sester, Tina Schmidt
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Clinical Research and Public Health COVID-19

High levels of SARS-CoV-2–specific T cells with restricted functionality in severe courses of COVID-19

Abstract

BACKGROUND Patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) differ in the severity of disease. We hypothesized that characteristics of SARS-CoV-2–specific immunity correlate with disease severity.METHODS In this study, SARS-CoV-2–specific T cells and antibodies were characterized in uninfected controls and patients with different coronavirus disease 2019 (COVID-19) disease severity. SARS-CoV-2–specific T cells were flow cytometrically quantified after stimulation with SARS-CoV-2 peptide pools and analyzed for expression of cytokines (IFN-γ, IL-2, and TNF-α) and markers for activation, proliferation, and functional anergy. SARS-CoV-2–specific IgG and IgA antibodies were quantified using ELISA. Moreover, global characteristics of lymphocyte subpopulations were compared between patient groups and uninfected controls.RESULTS Despite severe lymphopenia affecting all major lymphocyte subpopulations, patients with severe disease mounted significantly higher levels of SARS-CoV-2–specific T cells as compared with convalescent individuals. SARS-CoV-2–specific CD4+ T cells dominated over CD8+ T cells and closely correlated with the number of plasmablasts and SARS-CoV-2–specific IgA and IgG levels. Unlike in convalescent patients, SARS-CoV-2–specific T cells in patients with severe disease showed marked alterations in phenotypical and functional properties, which also extended to CD4+ and CD8+ T cells in general.CONCLUSION Given the strong induction of specific immunity to control viral replication in patients with severe disease, the functionally altered characteristics may result from the need for contraction of specific and general immunity to counteract excessive immunopathology in the lung.FUNDING The study was supported by institutional funds to MS and in part by grants of Saarland University, the State of Saarland, and the Rolf M. Schwiete Stiftung.

Authors

David Schub, Verena Klemis, Sophie Schneitler, Janine Mihm, Philipp M. Lepper, Heinrike Wilkens, Robert Bals, Hermann Eichler, Barbara C. Gärtner, Sören L. Becker, Urban Sester, Martina Sester, Tina Schmidt

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Figure 3

Altered cytokine profiles and characteristics of SARS-CoV-2–specific T cells in patients with a severe course of COVID-19.

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Altered cytokine profiles and characteristics of SARS-CoV-2–specific T c...
Expression patterns of SARS-CoV-2–specific T cells were determined from combined T cells reacting to the individual peptide pools for each individual. (A) SARS-CoV-2–specific and SEB-reactive CD4+ T cells were divided into 7 subpopulations according to their expression of the cytokines IFN-γ, IL-2, and TNF-α. Distribution of these subgroups was compared between ICU patients and convalescent patients. To ensure robust statistical analysis, cytokine profiling was restricted to CD4+ T cells and to all samples with at least 35 measurable CD69+IFN-γ+ cells (all ICU patients and 20 convalescent patients). (B) CTLA-4 expression of SARS-CoV-2–specific and SEB-reactive CD4+ and CD8+ T cells was compared between ICU patients and convalescent patients. Analysis was restricted to individuals with sufficient SARS-CoV-2–specific immunity, i.e., where the total number of measurable CD69+IFN-γ+ cells reached at least 20 cells (n = 13 and 3 ICU patients and 17 and 18 convalescent patients for CD4+ and CD8+ T cells, respectively). (C) In a subgroup of 10 patient samples (5 ICU patients and 5 convalescent patients), where a larger sample volume for in vitro stimulations was available, expression of PD-1, Ki67, and granzyme B of SARS-CoV-2–specific and SEB-reactive CD4+ and CD8+ T cells was analyzed. Overlaid contour plots (built using BD FACSDiva 8) of samples from a 31-year-old convalescent patient stimulated with SARS-CoV-2 antigens are shown in the upper panel. PD-1 MFI was analyzed from all stimulatory reactions with at least 20 CD69+IFN-γ+ cells (n = 8 and 4 for CD4+ and CD8+ T cells, respectively). Analysis of intranuclear presence of Ki67 (%Ki67+) and expression of granzyme B (%granzyme B+) was restricted to samples with at least 20 specific CD4+ (n = 8 for SARS-CoV-2 and n = 7 for SEB) or CD8+ T cells (n = 4), respectively. ICU patients are depicted by dark symbols and convalescent patients by light symbols. Bar charts in A represent mean and SD, and differences between the 2 groups were assessed using unpaired 2-tailed t test. Bars in B and C represent medians with IQRs. Differences between the groups were calculated using Mann-Whitney U test. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. MFI, median fluorescence intensity.