The promise (成功前景) of mRNA vaccines is changing how we think about COVID-19 immunization. The most traditional methods of vaccine development introduce the body to either an inactivated or weakened form of a virus or to one of its viral proteins. The immune system responds by producing antibodies that recognize particular proteins of the virus. Those antibodies could fight future infections as long as the virus doesn’t evolve. mRNA vaccines take a novel (新穎的) approach that has never been licensed for human use. Their development is faster as it bypasses the more laborious (艱巨的) tasks of inactivating viruses or isolating proteins.
The vaccine contains snippets (片斷) of viral mRNA, a molecule with instructions for making proteins. Scientists pack the mRNA inside a slippery pod made of lipids, so it can slide into the cells.
Phospholipids, arranged in a bilayer, make up the basic fabric of the plasma membrane. (www.khanacademy.org)
Once inside the cells, the mRNA finds the ribosomes. They are the machinery for building all proteins in the body.
Ribosome, particle that is present in large numbers in all living cells and serves as the site of protein synthesis...Ribosomes are made up of ribosomal proteins and ribosomal RNA (rRNA)...Ribosomal molecules of messenger RNA (mRNA) determine the order of transfer RNA (tRNA) molecules that are bound to nucleotide triplets (codons). The order of tRNA molecules ultimately determines the amino acid sequence of a protein. (www.britannica.com)
https://www.genome.gov/sites/default/files/tg/en/illustration/transfer_rna_adv.jpg
Ribosomes start making SARS-CoV-2 spike proteins based on the viral mRNA. Spike proteins coat the surface of the virus and are harmless on their own. They are considered a good vaccine target which is also called an antigen.
The coronavirus spike protein is a multifunctional molecular machine that mediates coronavirus entry into host cells. (www.ncbi.nlm.nih.gov)
An immune cell perceives (把…看作) the spike proteins as if the body had been infected. It kicks off a sequence of events that results in the creation of antibodies and other defenses.
(Paragraphs with bold text: https://www.nationalgeographic.com/science/2020/05/moderna-coronavirus-vaccine-how-it-works-cvd/)
