The known unknowns of T cell immunity to COVID-19

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Science Immunology  18 Nov 2020:
Vol. 5, Issue 53, eabe8063
DOI: 10.1126/sciimmunol.abe8063


  • Fig. 1 The unknowns about T cells in COVID-19 in relation to disease severity, memory formation, and vaccination.

    (A) Clinical and virological factors likely to be related to the development and function of antigen-specific T cell responses against SARS-CoV-2. The impact of factors including sex, age, chronic conditions affecting immune health, viral load dynamics, degree of lymphopenia, and risk of exposure to SARS-CoV-2, on the strength and efficacy of the early antiviral T cell response remains elusive. Furthermore, some individuals experience delayed viral clearance or other symptoms for an extended period (long COVID) despite viral clearance. (B) The broad clinical spectrum of acute COVID-19 includes asymptomatic, mild, severe, and fatal outcomes. Whether convalescent individuals will be protected against SARS-CoV-2 (re)infection and the longevity of this protection remain to be determined. RT-PCR, reverse transcription polymerase chain reaction. (C) Immunological and virological factors influence generation of SARS-CoV-2–specific T cells and may influence the clinical manifestations and quality of the induced T cell response in acute and convalescent patients with COVID-19. Here, the ability of the host to generate efficient T cell responses after SARS-CoV-2 infection is likely to be dependent on the epitopes targeted, antigen abundance, involvement of TRM at the site of infection, presence or absence of preexisting cross-reactive T cells, and host genetic factors such as HLA type and T cell receptor (TCR) repertoire. Furthermore, the level of inflammation and amount of proinflammatory cytokines are likely to be associated with T cell activation and exhaustion and subsequent T cell memory formation. CM, central memory; EM, effector memory. (D) The potential link between vaccine-induced T cell immunity and vaccination outcome remains to be determined. Ab, antibody.

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