The effects of the pandemic following the emergence of a new SARS-CoV-2 coronavirus in China in 2019 are visible in the strain on health care systems, global economy and geopolitics, and changing socio-economic conditions. The development of effective vaccines is therefore crucial. DNA vaccines are a successful immunisation method due to their ease of preparation, cost-effectiveness, long-term durability and specific immune response against the desired antigen and are also suitable for the development of SARS-CoV-2 vaccines. Gene electrotransfer is an efficient method for introducing plasmid DNA into cells or tissues, and in our study we used it to introduce commercially available plasmids with sequences for SARS-CoV-2 antigens, namely the spike protein (S protein) and the nucleocapsid (N protein). The study was performed in vitro on the murine myoblast cell line C2C12, as model cells for muscle tissue. Both plasmid genes were expressed at the mRNA level, but only the N protein was detected at the protein level, both in the cell medium and in the cell lysate. Gene electroporation of both plasmid vectors together lead to the expression of both antigens at the mRNA level to the same extent as after gene electroporation of the individual plasmid DNA. At the protein level, we were only able to demonstrate the N protein after gene transfer of both plasmid vectors at the same time. The results of our study form a good basis for further in vivo studies in mouse models to demonstrate the effectiveness of introducing plasmid DNA with a transcript for SARS-CoV-2 antigens into muscle tissue and to monitor the specific immune response.
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