SARS-COV-2 (L84I, N439K, D614G MUTANT) SPIKE GLYCOPROTEIN (S1)

SARS-CoV-2 (L84I, N439K, D614G mutant) spike glycoprotein (S1) is a recombinant antigen which contains the Spike protein amino acids 1-674 of subunit 1. This protein is manufactured in HEK293 mammalian cells to obtain more authentic post-translational modifications, compared to other expression systems. SARS-CoV-2, previously known as the 2019 Novel Coronavirus (2019-nCoV), causes the pandemic COVID-19 disease.

PRODUCT DETAILS – SARS-COV-2 (L84I, N439K, D614G MUTANT) SPIKE GLYCOPROTEIN (S1)

• SARS-CoV-2 L84I, N439K, D614G mutant spike subunit 1.
• Recombinant protein manufactured in HEK293 cells and purified from culture supernatant by Protein G chromatography.
• Contains Spike protein 1-674, C-terminally tagged with sheep Fc.
• Presented in Dulbecco’s phosphate buffered saline (DPBS) pH 7.4.

BACKGROUND

The D614G amino acid mutation in the SARS-CoV-2 Spike protein emerged early during the COVID-19 pandemic, quickly becoming the dominant circulating strain of the coronavirus. The transition from D614 to G614 occurred asynchronously in different regions throughout the world, beginning in Europe, followed by North America and Oceania and then Asia (Korber et al., 2020). Virus mutations may increase in frequency due to natural selection, random genetic drift, or features of recent epidemiology and as such it can be difficult to differentiate when a virus mutation becomes common through fitness or by chance (Korber et al., 2020). The mutation is located on the Spike protein, in the interface between the individual spike protomers, that stabilize its mature trimeric form on the virion surface through hydrogen bonding (not in the receptor-binding; RBD) (Grubaugh et al., 2020). The Spike D614G amino acid change is caused by an A-to-G nucleotide mutation at position 23,403 in the Wuhan reference strain. It is almost always accompanied by three other mutations: a C-to-T mutation in the 50 UTR (position 241 relative to the Wuhan reference sequence), a silent C-to-T mutation at position 3,037, and a C-to-T mutation at position 14,408 that results in an amino acid change in RNA dependent RNA polymerase (RdRp P323L). The haplotype comprising these 4 genetically linked mutations is now the globally dominant form (Korber et al., 2020).

The G614 variant grows to a higher titer as pseudotyped virions and in infected individuals may be associated with higher upper respiratory tract viral loads, but not with increased disease severity. Despite finding that clinical samples from G614 infections have higher levels of viral RNA, it’s still not clear if G614 is more infectious or transmissible than viruses containing D614. However, if it is the case that the mutation aids transmissibility, then the virus will be harder to control (Korber et al., 2020). The mutation has also been associated with increased sensitivity to neutralization of SARS-CoV-2 pseudoviruses in vitro and may stabilize a particular conformational state of the RBD (Weissman et al., 2020). Spike-pseudotyped lentivirus and intact SARS-CoV-2 virus in which the D614G mutation was introduced have been found to be up to 8-fold more effective at transducing cells than wild-type virus, in multiple cell lines, including human lung epithelial cells. Minimal differences in ACE2 receptor binding was observed between the Spike variants, but the G614 variant was more resistant to proteolytic cleavage in vitro and in human cells, suggesting a possible mechanism for the increased transduction (Daniloski et al., 2020; Huang et al., 2020).

REFERENCES

• Daniloski et al. (2020). The Spike D614G mutation increases SARS-CoV-2 infection of multiple human cell types. bioRxiv preprint.
• Grubaugh ND, Hanage WP, Rasmussen AL. Making Sense of Mutation: What D614G Means for the COVID-19 Pandemic Remains Unclear. Cell. 2020;182(4):794-795.
• Huang et al. (2020). The D614G mutation of SARS-CoV-2 spike protein enhances viral infectivity and decreases neutralization sensitivity to individual convalescent sera. bioRxiv preprint.
• Korber B, Fischer WM, Gnanakaran S, et al. Tracking Changes in SARS-CoV-2 Spike: Evidence that D614G Increases Infectivity of the COVID-19 Virus. Cell. 2020;182(4):812-827.e19.
• Weissman et al. (2020). D614G Spike Mutation Increases SARS CoV-2 Susceptibility to Neutralization. medRxiv preprint.