Fig. 5

Gene-based vaccine candidates for SARS-CoV-2 including viral vector vaccines (non-replicating and replicating) and nucleic acid vaccines (DNA and RNA with a lipid coat). Viral vector vaccines enter the nucleus after IM injection. mRNA coated with lipids reaches the cytoplasm through endocytosis after IM injection. Eventually, mRNA translation in the cytoplasm leads to antigen expression. DNA-containing vaccines injected as IM + EP or ID + EP lead to gene transcription by entering the nucleus (EP involves the application of electrical pulses, generating pores in skin cells to enhance cellular uptake of genetic material), and translation in the cytoplasm. The produced antigens can be uptaken and presented by APCs, activating B cells, CD4+ T cells, CD8+ T cells and leading to the induction of humoral response with the production of neutralizing antibodies that can bind to the spike proteins on SARS-CoV-2 virus, preventing SARS-CoV2 infection, and/or the T-cell mediated destruction of infected cells. The magnification indicates a three-dimensional 3D rendering of SARS-CoV-2 that showcases the key spike protein mutations on each of the SARS-CoV-2 variants of concern: B.1.1.7, B.1.351, P.1, B.1.526, B.1.427 and B.1.429. IM intramuscular, ID intradermal, EP electroporation, APC antigen-presenting cell, NAbs neutralizing antibodies