The T-cell response to SARS-CoV-2: kinetic and quantitative aspects and the case for their protective role

Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2), the etiological agent of Coronavirus Diseases 2019 (COVID-19), triggers an adaptive immunity in the infected host that results in the production of virus-specific antibodies and T cells. Although kinetic and quantitative aspects of antibodies have been analyzed in large patient cohorts, similar information about SARS-CoV-2-specific T cells are scarce. We summarize the available knowledge of quantitative and temporal features of the SARS-CoV-2 T-cell response in this review. Currently, most of the data are derived only from the analysis of the circulatory compartment. Despite this limitation, early appearance, multi-specificity and functionality of SARS-CoV-2-specific T cells are associated with accelerated viral clearance and with protection from severe COVID-19.