SARS-CoV-2 variant Alpha has a spike-dependent replication advantage over the ancestral B.1 strain in human cells with low ACE2 expression
Fig 5
VOC Alpha spike protein shows decreased proteolytic processing.
(A) Spike processing in lysates of HEK293T cells expressing empty vector or SARS-CoV-2 spike-HA encoding individual or all VOC Alpha-corresponding mutations was quantified by immunoblotting (upper panel). At least 4 independent biological replicates (using independent lentivirus particle preparations) were performed. Shown is 1 representative immunoblot (bottom panel) out of 4. (B) Protein in lysed lentiviral particles pseudotyped with SARS-CoV-2 spike-HA was quantified by immunoblotting (upper panel). Shown is 1 representative immunoblot (bottom panel) out of 4. (C) Vero E6 cells were infected with SARS-CoV-2 (MOI 5). Cells and virus-containing supernatants were harvested at 48 hours postinfection and processed for detection of spike and nucleocapsid by immunoblotting. Processing of spike in cell lysates (left panel) and spike incorporation in concentrated virion preparations (middle panel) was quantified. One representative blot out of 2 is shown (right panel). Black and white arrowheads indicate the bands of the uncleaved spike-HA precursor and of the cleaved S2-HA subunit, respectively. Statistical significance was calculated by a 2-tailed, paired Student t test. kDa, kilodalton; MOI, multiplicity of infection; SARS-CoV-2, Severe Acute Respiratory Syndrome Coronavirus 2; UI, uninfected; VOC, variant of concern. See S1 Data.