HUMAN IgM ANTI-SARS-COV-2 SPIKE (S1) ANTIBODY (CR3022)

Human IgM anti SARS-CoV-2 Spike antibody (CR3022) is a recombinant monoclonal antibody that recognizes the SARS-CoV and SARS-CoV-2 Spike glycoprotein, the causative agent of COVID-19. The antibody binds to both SARS-CoV and SARS-CoV-2 with high affinity at amino acids 318-510 (RBD, Receptor Binding Domain) in the S1 subunit of the Spike protein.

PRODUCT DETAILS – HUMAN IgM ANTI-SARS-COV-2 SPIKE (S1) ANTIBODY (CR3022)

• Anti SARS-CoV-2 Spike IgM antibody binds the amino acids 318-510 in the S1 domain of the SARS-CoV Spike protein as well as SARS-CoV-2 (COVID-19) Spike protein.
• Isotype – Human IgM, Kappa. Reformatted using the variable domain sequences of the original Human IgG1 format.
• The original monoclonal antibody was generated by collecting peripheral blood lymphocytes of a patient exposed to the SARS-CoV.
• Affinity purified using a recombinant lectin column.
• Suitable for use in ELISA, NTRL, SPR, Crystallography.

BACKGROUND

Human coronaviruses are the major cause of upper respiratory tract illness. They are positive-stranded RNA viruses, and contain the largest viral RNA genomes known to date (27-31 kb). SARS (severe acute respiratory syndrome) and COVID-19 are both caused by human coronaviruses, SARS-CoV and SARS-CoV-2, respectively. The genome of SARS-CoV-2 shares 82% nucleotide identity with human SARS-CoV and 89% with bat SARS-like-CoVZXC21 (Lu et al., 2020; Zhao et al., 2020). However, it displays lower pathogenicity and higher human to human transmissibility (Li et al., 2020). The coronavirus genome encodes four structural proteins: the spike (S) protein, nucleocapsid (N) protein, membrane (M) protein, and the envelope (E) protein. Cell entry is the first step in cross-species transmission and SARS-CoV-2 is likely to infect lung type II alveolar cells, which may explain the severe alveolar damage observed after infection (Zhao et al., 2020). Both SARS-CoV and SARS-CoV-2 uses the spike (S) protein to gain entry into host cells and it has been shown that the spike binds the entry receptor angiotensin-converting enzyme 2 (ACE2) on infected cells. It is predicted that SARS-CoV-2 recognizes human ACE2 more efficiently than SARS -CoV (Wan et al., 2020). Therefore, the S protein is considered a key target for vaccine development (Li et al, 2020).

This recombinant antibody binds to both SARS-CoV and SARS-CoV-2 (COVID-19) with high affinity; 86% of the epitope residues are conserved between SARS-CoV and SARS-CoV-2 (Tian et al., 2020; Yuan et al., 2020). The binding site is amino acids 318-510 (RBD, Receptor Binding Domain) in the S1 subunit of the Spike protein (Yuan et al., 2020). The antibody also binds to P462L-substituted S318–510 fragments of the SARS spike protein (Joyce et al. 2020). The crystal structure of this antibody has been resolved in complex with the RBD of the SARS-CoV-2 spike protein. The spike binding epitope is only accessible in the “open” conformation of the spike protein. The epitope can only be accessed by the antibody when at least two RBD on the trimeric spike protein are in the “up” conformation and slightly rotated (Joyce et al. 2020; Yuan et al., 2020). Antibody was originally isolated from a convalescent SARS patient, and is a neutralizing antibody that targets the receptor-binding domain (RBD) of SARS-CoV (ter Meulen, 2006). It did not neutralize SARS-CoV-2 in an in vitro assay, although it may show neutralisation in combination with other antibodies (Yuan et al., 2020). It has been shown to work synergistically in combination with antibodies that target the ACE2 binding site on the SARS-CoV RBD and reduce viral escape capacity. This antibody does not compete with ACE2 for binding to RBD, unlike most other known SARS RBD-targeted antibodies (ter Meulen, 2006). The epitope of this antibody does not overlap with the SARS-CoV-2 ACE2 binding site (Tian et al., 2020).

REFERENCES

• Joyce GM, et al. (2020). A Cryptic Site of Vulnerability on the Receptor Binding Domain of the SARS-CoV-2 Spike Glycoprotein. BioRxiv.
• Li Q, Guan X, Wu P, et al. (2020). Early Transmission Dynamics in Wuhan, China, of Novel Coronavirus-Infected Pneumonia. N Engl J Med. 2020;382(13):1199–1207.
• Li H, Zhou Y, Zhang M, Wang H, Zhao Q, Liu J. (2020). Updated approaches against SARS-CoV-2. Antimicrob Agents Chemother. 2020;AAC.00483-20.
• Lu, R., Zhao, X., Li, J., Niu, P., Yang, B., Wu, H., Wang, W., Song, H., Huang, B., Zhu, N., et al. (2020). Genomic characterisation and epidemiology of 2019 novel coronavirus: implications for virus origins and receptor binding. Lancet 395, 565–574.
• ter Meulen J, van den Brink EN, Poon LL, et al. (2006). Human monoclonal antibody combination against SARS coronavirus: synergy and coverage of escape mutants. PLoS Med. 2006;3(7):e237.
• Tian X, Li C, Huang A, et al. (2020). Potent binding of 2019 novel coronavirus spike protein by a SARS coronavirus-specific human monoclonal antibody. Emerg Microbes Infect. 2020;9(1):382–385.
• Wan Y, Shang J, Graham R, Baric RS, Li F. Receptor Recognition by the Novel Coronavirus from Wuhan: an Analysis Based on Decade-Long Structural Studies of SARS Coronavirus. J Virol. 2020;94(7):e00127-20.
• Yuan M, Wu NC, Zhu X, et al. (2020). A highly conserved cryptic epitope in the receptor-binding domains of SARS-CoV-2 and SARS-CoV. Science. 2020;eabb7269.
• Zhao et al. (2020). Single -cell RNA 2expression profiling of ACE2, the putative receptor of Wuhan 2019 -nCov. BioRxiv.
• Zhou P, Yang XL, Wang XG, et al. A pneumonia outbreak associated with a new coronavirus of probable bat origin. Nature. 2020;579(7798):270–273.