SARS-CoV-2(9) coronavirus(7) the SARS-CoV-2(7) virus(6) plasmids(5) caused(5) mice(5) Particle(5) target(5) virion(5) Vaccine(5) variants(4) Transmission(4) Spike protein(4) acute respiratory syndrome(4) mucosa(3) Macrophage(3) Pathogenesis(3) in vitro(3) IgA level(3) immune cells(3) distribution(3) Evidence(3) coronavirus disease(3) viral antigens(3) feature(3) peptide(3) elicit(3) death(3) respiratory tract(3)