Practice question

Messenger RNA vaccines represent nucleic acid platform delivering synthetic mRNA encoding pathogen antigen directly to host cytoplasm where host ribosomal machinery translates it transiently. Manufacturing involves in vitro transcription using T7 RNA polymerase from linearized plasmid DNA template encoding spike protein, incorporation of modified nucleoside N1 methylpseudouridine replacing uridine reducing TLR7 mediated inflammation and increasing translation half-life, addition of 5' cap 7-methylguanosine via vaccinia capping enzyme and 2'O-methylation, and 3' polyadenine tail 100 nt for stability. mRNA encapsulated in lipid nanoparticles LNP composed of ionizable lipid ALC-0315 or SM-102 protonated at low pH encapsulating RNA, helper lipid DSPC forming bilayer, cholesterol fluidity, and PEGylated lipid reducing aggregation and prolonging circulation. Upon intramuscular injection LNPs fuse with cell membrane or endocytosed, ionizable lipid becomes cationic at endosomal low pH disrupting endosome releasing mRNA to cytosol. Ribosomes translate antigen protein undergoing post translational modifications, secreted or membrane anchored, processed for MHC I and II presentation inducing neutralizing IgG and CD4 Th1 and CD8 cytotoxic memory. mRNA degraded within days by RNases no integration risk enabling rapid design.