Figure 1.

Schematic diagram of SARS-CoV-2: (A) SARS-CoV-2 is a positive-sense, single-stranded enveloped RNA.

Notes: The lipid envelope (E) is studded with several spike (S) glycoproteins giving the virus a crown-like appearance. The membrane (M) glycoprotein is the most abundant structural protein and spans the envelope. (B) The 5′ end of the SARS-CoV-2 genome consists of open reading frame (ORF)1a/b that encodes a polyprotein, which is post-translationally cleaved into 16 non-structural proteins (nsp1–16), including RNA-dependent RNA polymerase (RdRp). The 3′ terminus of the viral genome contains ORFs encoding the four main structural proteins, spike (S), envelope (E), membrane (M), and nucleocapsid (N), as well as nine putative accessory factors. Figure created with BioRender.com. Figure adapted from Wang N, Shang J, Jiang S, Du L. Subunit vaccines against emerging pathogenic human coronaviruses. Front Microbiol. 2020;11:298.³⁰ Creative Commons Attribution License (CC-BY 4.0; https://creativecommons.org/licenses/by/4.0/legalcode).