CD4 ⁺ T cell lymphopenia and dysfunction in severe COVID-19 disease is autocrine TNF-α/TNFRI-dependent

Lymphopenia is common in severe COVID-19 disease, yet the mechanisms are poorly understood. 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 to recovered, mild disease (p<0.0001). In severe disease, immunodominant CD4 ⁺ T cell responses to Spike-1(S1) produced increased in vitro TNF-α, but impaired proliferation and increased susceptibility to activation-induced cell death (AICD). CD4 ⁺ TNF-α ⁺ T cell responses inversely correlated with absolute CD4 ⁺ counts from severe COVID-19 patients (n=76; R=-0.744, P<0.0001). TNF-α blockade including infliximab or anti-TNFRI antibodies strikingly rescued S1-specific CD4 ⁺ proliferation and abrogated S1-AICD in severe COVID-19 patients (P<0.001). Single-cell RNAseq demonstrated downregulation of Type-1 cytokines and NFκB signaling in S1-stimulated CD4 ⁺ cells with infliximab treatment. Lung CD4 ⁺ T cells in severe COVID-19 were reduced and produced higher TNF-α versus PBMC. Together, our findings show COVID-19-associated CD4 ⁺ lymphopenia and dysfunction is autocrine TNF-α/TNFRI-dependent and therapies targeting TNF-α may be beneficial in severe COVID-19.