COVID-19(6) SARS-CoV-2(5) Cancer(5) natural killer(4) immunized mice(4) therapy(4) evaluated(4) anti-SARS-CoV-2(4) Cytotoxic T cells(4) vaccine candidate(4) Therapies(4) natural killer T cells(4) complex(4) coronavirus(4) Cell(4) multifunctional(4) Antigen(4) Effectiveness(4) T-cell(4) Evidence(4) acute respiratory syndrome(4) Efficacy(4) cytotoxic(4) adaptive(4) applied(4) immunization(4) memory T cells(4) murine model(4) single dose(4) CTLs(4)