Optimization of A549 cell transfection efficiency with a plasmid encoding the N-protein of the SARS-COV-2 virus

To test new antiviral drugs aimed at degrading the nucleocapsid protein (N-protein) of the SARS-CoV-2 virus, it is desirable to have cells expressing the N-protein, for which it is necessary to find conditions for the maximum achievable efficiency of cell transfection with a plasmid encoding this protein. For transfection, polyplexes were used consisting of a plasmid encoding the N-protein fused with the mRuby3 fluorescent protein and polyethyleneimine (PEI)-polyethylene glycol (PEG)-TAT peptide block copolymers. The dependence of the transfection efficiency of human lung adenocarcinoma A549 cells on the PEG/PEI and N/P ratios (the ratio of nitrogen in PEI to phosphate in DNA) was studied. Significant positive correlations were shown between transfection efficiency determined by flow cytometry, the N/P ratio, and the proportion of polyplexes sized 40–54 nm. The data obtained can serve as a basis for creating an animal model of lung cells transiently expressing the N protein of the SARS-CoV-2 virus.