COVID-19(10) caused(10) supplementary material(9) antibody(9) SARS-CoV-2(8) Receptor binding domain(7) Cell(7) expressed(7) therapeutic(7) epitope(6) N-terminal(6) protease(6) Protein(6) the SARS-CoV-2(6) Escherichia coli (6) Spike protein(6) Amino acid(6) Neutralizing(5) Vaccine(5) Protective(4) E. coli(4) regions(4) linker(4) antigenic protein(4) expression of SARS-CoV-2(4) Escherichia coli(4) CBM9(4) intestinal(4) tested(4) C-terminal(4)