Fig. 3.

A, DNA vaccine induction of humoral and cellular mucosal immune response. 1 transfection of epithelial cell 2 expression of S1 protein, 3 secretion of S1 protein, 4 S1 protein taken up by M cells, 5 transported to immune cells with 6 uptake by dendritic cells and MHC II antigen presentation to T-cells with subsequent draining into lymph node stimulating humoral response. 8. MHC 1 presentation stimulated cytotoxic lymphocyte response. B, DNA vaccine treatment with secreted S1 spike protein acting as a competitive antagonist by interfering with the coronavirus binding to ACE2 receptors. 1 transfected cell 2.expression of S1 protein, 3 secretion of the S1 protein, and 4 ACE2 receptor blockade by S1 protein preventing SARS-CoV-2 from binding to ACE2 receptor (Reproduced with permission from ref [28] Copyright 2020 John Wiley and Sons).