Highly functional virus-specific cellular immune response in asymptomatic SARS-CoV-2 infection

J Exp Med. 2021 May 3;218(5):e20202617. doi: 10.1084/jem.20202617.


The efficacy of virus-specific T cells in clearing pathogens involves a fine balance between antiviral and inflammatory features. SARS-CoV-2-specific T cells in individuals who clear SARS-CoV-2 without symptoms could reveal nonpathological yet protective characteristics. We longitudinally studied SARS-CoV-2-specific T cells in a cohort of asymptomatic (n = 85) and symptomatic (n = 75) COVID-19 patients after seroconversion. We quantified T cells reactive to structural proteins (M, NP, and Spike) using ELISpot and cytokine secretion in whole blood. Frequencies of SARS-CoV-2-specific T cells were similar between asymptomatic and symptomatic individuals, but the former showed an increased IFN-γ and IL-2 production. This was associated with a proportional secretion of IL-10 and proinflammatory cytokines (IL-6, TNF-α, and IL-1β) only in asymptomatic infection, while a disproportionate secretion of inflammatory cytokines was triggered by SARS-CoV-2-specific T cell activation in symptomatic individuals. Thus, asymptomatic SARS-CoV-2-infected individuals are not characterized by weak antiviral immunity; on the contrary, they mount a highly functional virus-specific cellular immune response.

Publication types

  • Multicenter Study
  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Asymptomatic Infections*
  • COVID-19 / blood
  • COVID-19 / immunology*
  • Cytokines / blood
  • Cytokines / immunology*
  • Humans
  • Lymphocyte Activation*
  • Male
  • Middle Aged
  • SARS-CoV-2 / immunology*
  • SARS-CoV-2 / metabolism
  • T-Lymphocytes / immunology*
  • T-Lymphocytes / metabolism


  • Cytokines