Inovio Pharmaceuticals Inc (INO)

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HOW DO NUCLEIC ACID VACCINES TRIGGER IMMUNITY?

In the case of DNA vaccines, a piece of DNA encoding the antigen is first inserted into a bacterial plasmid. This is a circular piece of DNA used by a bacterium to store and share genes which may benefit its survival – a bit like a computer flash drive. Plasmids can replicate independently of the main chromosomal DNA and provide a simple tool for transferring genes between cells. Because of this, they are already widely used within the field of genetic engineering.

DNA plasmids carrying the antigen are usually injected into the muscle, but a key challenge is getting them to cross into people’s cells. This is an essential step, because the machinery which enables the antigen to be translated into protein is located inside cells. Various technologies are being developed to aid this process - such as electroporation, where short pulses of electric current are used to create temporary pores in patients’ cell membranes; a ‘gene gun’ which uses helium to propel DNA into skin cells; and encapsulating the DNA in nanoparticles which are designed to fuse with the cell membrane.

RNA vaccines encode the antigen of interest in messenger RNA (mRNA) or self-amplifying RNA (saRNA) – molecular templates used by cellular factories to produce proteins. Because of its transitory nature, there is zero risk of it integrating with our own genetic material. The RNA can be injected by itself, encapsulated within nanoparticles (as Pfizer’s mRNA-based Covid vaccine is), or driven into cells using some of the same techniques being developed for DNA vaccines.

Once the DNA or RNA is inside the cell and it starts producing antigens, these are then displayed on its surface, where they can be detected by the immune system, triggering a response. This response includes killer T cells, which seek out and destroy infected cells, as well as antibody-producing B cells and helper T cells which support antibody production.
https://www.gavi.org/vaccineswork/what-are-nucleic-acid-vaccines-and-how-could-they-be-used-against-covid-19