A. Each photo depicts a western blot using the primary antibody indicated below it (Myc, 2B2, 1A9, 4B12, or 1G10). Empty vector-transfected 293FT cell products are on the lanes labelled as ‘Vec’, while products of 293FT cells expressing Myc-tagged SARS-CoV-2 S protein fragment (aa 1048–1206; SARS-CoV-2 numbering) or Myc-tagged HBcAg are on the lanes respectively labelled ‘S’ or ‘HBcAg’. Primary antibodies were labelled with horseradish peroxidase-conjugated secondary antibodies. A ladder indicative of the molecular weights in kD of the proteins relative to their vertical position on the blots, is indicated on the left of the panel.