COVID-19(22) SARS-CoV-2(16) Treatment(6) Infection(6) viral replication(6) airway(6) Viral(6) Oxygenation(6) Host(4) viability(4) inhibited(4) Patient(4) had no(4) mechanisms(4) host defense(4) Trial(4) Activation(4) multiplicity(4) patient safety(4) Defense(4) cells(4) raise(4) Lung function(4) subjects(4) Placebo(4) Plaque assay(4) clinical trial(4) no effect(4) healthy subjects(4) USA-WA1/2020(4)