Abstract: Provided are an mRNA or an mRNA composition, and an mRNA vaccine comprising the mRNA or the mRNA composition. The mRNA or the mRNA composition comprises an mRNA sequence encoding an S protein of a novel coronavirus SARS-CoV-2 or a variant thereof, and an mRNA sequence encoding an RBD in the S protein or a variant thereof. Further provided are the applications of the mRNA or the mRNA composition, and the mRNA vaccine comprising the mRNA or the mRNA composition in preparation of a medication for preventing and/or treating a disease caused by a novel coronavirus SARS-CoV-2 infection.

Abstract: Provided are a protein antigen subjected to site-directed mutation and site-directed modification, and a method for site-directed mutation and site-directed modification of the protein antigen. The method comprises: site-directedly introducing an unnatural amino acid into a specific site of the protein antigen by genetic codon expansion technique; and performing site-directed modification with the protein antigen by the unnatural amino acid and a modifier, wherein the modifier is a receptor agonist such as tripalmitoyl-S-glyceryl cysteine and monophosphoryl lipid A. Further provided is use of the protein antigen subjected to site-directed mutation and site-directed modification, such as use as a vaccine.

Abstract: The present invention relates to a carrier protein with site-directed mutation and use thereof in preparation of a vaccine, wherein the carrier protein is selected from fusion proteins formed by one, two or more of diphtheria toxoid, a non-toxic mutant of diphtheria toxin, a bacterial outer membrane protein and a bacterially expressed protein, wherein an amino acid at at least one site on the carrier protein is mutated into an unnatural amino acid, and the unnatural amino acid contains an azido or alkynyl terminal group. In a mutual reaction process of the carrier protein with site-directed mutation of the present invention and a polysaccharide antigen, a covalent bond is formed, and meanwhile a formed conjugate is in a bead-string state, so that the carrier protein and the polysaccharide antigen can be effectively prevented from being excessively crosslinked.