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Fig. 3 | Journal of Biomedical Science

Fig. 3

From: A critical overview of current progress for COVID-19: development of vaccines, antiviralĀ drugs, and therapeutic antibodies

Fig. 3

Schematic representation of the structure of conventional mRNA and the structure and intracellular amplification of self-amplifying mRNA. A The design of IVT mRNA is based on the blueprint of eukaryotic mRNA, and it consists of a 5ā€™ cap, 5ā€™ and 3ā€™ untranslated regions (UTRs), an open reading frame (ORF) encoding antigen(s), and a 3ā€™ poly(A) tail. The IVT mRNA can be modified in one or multiple sites, e.g., by modification of the caps, the UTRs and the poly(A) tail, to modulate the duration and kinetic profile of protein expression. B Antigen expression in different types of mRNA vaccines. The immunogen is encoded by a non-replicating RNA flanked by 5ā€² and 3ā€² UTRs. Self-amplifying RNA encodes four nonstructural proteins and a sub-genomic promoter derived from the alphavirus genome. It encodes a replicase and amplifies vaccine-antigen transcripts. Trans-amplifying RNA uses two transcripts to enable self-amplification of replicase and the target antigen

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