Article
Author: Popescu, Iulia ; Wells, Alan H. ; Sanchez, Pablo G. ; Deng, Evan ; Kass, Daniel J. ; McVerry, Bryan J. ; Koshy, Ritchie ; Iasella, Carlo J. ; An, Xiaojing ; Morris, Alison ; Konstantinidis, Ioannis ; Sembrat, John C. ; Lieber, Sophia C. ; Kitsios, Georgios ; Hannan, Stefanie J. ; Snyder, Mark E. ; Bhatt, Payal ; Alder, Jonathan K. ; Kilaru, Silpa ; Lyons, Emily J. ; McDyer, John F. ; Triulzi, Darrell J. ; Linstrum, Kelsey ; Johnson, Bruce ; Kiss, Joseph E. ; Burke, Robin ; Chen, Kong ; Das, Antu ; Brown, Mark J. ; Lendermon, Elizabeth A. ; Pilewski, Joseph M. ; Saul, Melissa ; Chen, Bill B. ; McMahon, Deborah K. ; Chen, Xiaoping
Rationale: Lymphopenia is common in severe coronavirus disease (COVID-19), yet the immune mechanisms are poorly understood. As inflammatory cytokines are increased in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, we hypothesized a role in contributing to reduced T-cell numbers. Objectives: We sought to characterize the functional SARS-CoV-2 T-cell responses in patients with severe versus recovered, mild COVID-19 to determine whether differences were detectable. Methods: Using flow cytometry and single-cell RNA sequence analyses, we assessed SARS-CoV-2-specific responses in our cohort. Measurements and Main Results: In 148 patients with severe COVID-19, we found lymphopenia was associated with worse survival. CD4+ lymphopenia predominated, with lower CD4+/CD8+ ratios in severe COVID-19 compared with patients with mild disease (P < 0.0001). In severe disease, immunodominant CD4+ T-cell responses to Spike-1 (S1) produced increased in vitro TNF-α (tumor necrosis factor-α) but demonstrated impaired S1-specific proliferation and increased susceptibility to activation-induced cell death after antigen exposure. CD4+TNF-α+ T-cell responses inversely correlated with absolute CD4+ counts from patients with severe COVID-19 (n = 76; R = -0.797; P < 0.0001). In vitro TNF-α blockade, including infliximab or anti-TNF receptor 1 antibodies, strikingly rescued S1-specific CD4+ T-cell proliferation and abrogated S1-specific activation-induced cell death in peripheral blood mononuclear cells from patients with severe COVID-19 (P < 0.001). Single-cell RNA sequencing demonstrated marked downregulation of type-1 cytokines and NFκB signaling in S1-stimulated CD4+ cells with infliximab treatment. We also evaluated BAL and lung explant CD4+ T cells recovered from patients with severe COVID-19 and observed that lung T cells produced higher TNF-α compared with peripheral blood mononuclear cells. Conclusions: Together, our findings show CD4+ dysfunction in severe COVID-19 is TNF-α/TNF receptor 1-dependent through immune mechanisms that may contribute to lymphopenia. TNF-α blockade may be beneficial in severe COVID-19.