CD8A and COVID-19: The most dominant reactive T-cells, including CD4+, CD8+, CD4+CD154+CD137+, and CD154+CD137+, detected in mild and recovered COVID-19 patients were specific to SARS-CoV-2 structural proteins (SPs), including ORF3a, spike (S), membrane (M), and nucleocapsid (N) (41, 53, 66).