Views: 0 Author: Site Editor Publish Time: 2023-05-15 Origin: Site
The goal of vaccines is to stimulate the adaptive immune system to produce antibodies that are precisely directed against specific pathogens.The markers on the pathogens that the antibodies target are called antigens.Traditional vaccines stimulate antibody responses by injecting the antigen, attenuated (weakened) virus, inactivated (killed) virus, or a recombinant antigen-encoding viral vector (a harmless carrier virus with an antigen transgene).These antigens and viruses are prepared and grown in vitro.In contrast, mRNA vaccines introduce short-lived synthetic fragments of the viral RNA sequence into vaccinated individuals.These mRNA fragments are taken up by dendritic cells through phagocytosis.Dendritic cells use their internal machinery (ribosomes) to read mRNA and produce viral antigens encoded by the mRNA.Within days of introduction, the body degrades the mRNA fragments.Although nonimmune cells may also take up vaccine mRNA, produce antigen, and display antigen on their surface, dendritic cells more readily take up mRNA globules.mRNA fragments are translated in the cytoplasm, do not affect the body's genomic DNA, and are located solely in the nucleus.
Once the host cells produce the viral antigens, normal adaptive immune system processes take place.Antigens are broken down by the proteasome.MHC class I and class II molecules then attach to the antigen and transport it to the cell membrane, "activating" the dendritic cell.Once activated, dendritic cells migrate to lymph nodes where they present antigens to T and B cells.This triggers the production of antibodies specific to the antigen and ultimately immunity.
Compared with traditional vaccines, mRNA vaccines have special advantages.Because mRNA vaccines are not constructed from live pathogens (or even inactivated ones), they are non-infectious.In contrast, traditional vaccines require the production of pathogens, which, if produced in large quantities, could increase the risk of localized virus outbreaks in production facilities.Another biological advantage of mRNA vaccines is that since the antigens are produced intracellularly, they can stimulate both cellular and humoral immunity.mRNA vaccines have the manufacturing advantage of being rapidly designed. Moderna designed its mRNA-1273 vaccine against COVID-19 in 2 days.They can also be manufactured faster and cheaper in a more standardized manner (with lower error rates in production), which can improve responsiveness to severe outbreaks.The Pfizer-BioNTech vaccine initially took 110 days to produce (Pfizer began optimizing the production process to just 60 days), which is much faster than traditional flu and polio vaccines.Within this larger time frame, the actual production time was only about 22 days: two weeks for molecular cloning of DNA plasmids and DNA purification, four days for DNA-to-RNA transcription and mRNA purification, four days for Used to encapsulate mRNA in lipid nanoparticles, then fill and finish.Most of the time required for each production run is allocated to strict quality control at each stage.
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