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Three RBD-down state of SARS-CoV-2 D614G spike in complex with the SP1-77 neutralizing antibody Fab fragment
Structural highlights
FunctionSPIKE_SARS2 attaches the virion to the cell membrane by interacting with host receptor, initiating the infection (By similarity). Binding to human ACE2 receptor and internalization of the virus into the endosomes of the host cell induces conformational changes in the Spike glycoprotein (PubMed:32142651, PubMed:32075877, PubMed:32155444). Uses also human TMPRSS2 for priming in human lung cells which is an essential step for viral entry (PubMed:32142651). Proteolysis by cathepsin CTSL may unmask the fusion peptide of S2 and activate membranes fusion within endosomes.[HAMAP-Rule:MF_04099][1] [2] [3] mediates fusion of the virion and cellular membranes by acting as a class I viral fusion protein. Under the current model, the protein has at least three conformational states: pre-fusion native state, pre-hairpin intermediate state, and post-fusion hairpin state. During viral and target cell membrane fusion, the coiled coil regions (heptad repeats) assume a trimer-of-hairpins structure, positioning the fusion peptide in close proximity to the C-terminal region of the ectodomain. The formation of this structure appears to drive apposition and subsequent fusion of viral and target cell membranes.[HAMAP-Rule:MF_04099] Acts as a viral fusion peptide which is unmasked following S2 cleavage occurring upon virus endocytosis.[HAMAP-Rule:MF_04099] Publication Abstract from PubMedSARS-CoV-2 Omicron subvariants have generated a worldwide health crisis due to resistance to most approved SARS-CoV-2 neutralizing antibodies and evasion of vaccination-induced antibodies. To manage Omicron subvariants and prepare for new ones, additional means of isolating broad and potent humanized SARS-CoV-2 neutralizing antibodies are desirable. Here, we describe a mouse model in which the primary B cell receptor (BCR) repertoire is generated solely through V(D)J recombination of a human V(H)1-2 heavy chain (HC) and, substantially, a human Vkappa1-33 light chain (LC). Thus, primary humanized BCR repertoire diversity in these mice derives from immensely diverse HC and LC antigen-contact CDR3 sequences generated by nontemplated junctional modifications during V(D)J recombination. Immunizing this mouse model with SARS-CoV-2 (Wuhan-Hu-1) spike protein immunogens elicited several V(H)1-2/Vkappa1-33-based neutralizing antibodies that bound RBD in a different mode from each other and from those of many prior patient-derived V(H)1-2-based neutralizing antibodies. Of these, SP1-77 potently and broadly neutralized all SARS-CoV-2 variants through BA.5. Cryo-EM studies revealed that SP1-77 bound RBD away from the receptor-binding motif via a CDR3-dominated recognition mode. Lattice light-sheet microscopy-based studies showed that SP1-77 did not block ACE2-mediated viral attachment or endocytosis but rather blocked viral-host membrane fusion. The broad and potent SP1-77 neutralization activity and nontraditional mechanism of action suggest that it might have therapeutic potential. Likewise, the SP1-77 binding epitope may inform vaccine strategies. Last, the type of humanized mouse models that we have described may contribute to identifying therapeutic antibodies against future SARS-CoV-2 variants and other pathogens. An antibody from single human V(H)-rearranging mouse neutralizes all SARS-CoV-2 variants through BA.5 by inhibiting membrane fusion.,Luo S, Zhang J, Kreutzberger AJB, Eaton A, Edwards RJ, Jing C, Dai HQ, Sempowski GD, Cronin K, Parks R, Ye AY, Mansouri K, Barr M, Pishesha N, Williams AC, Vieira Francisco L, Saminathan A, Peng H, Batra H, Bellusci L, Khurana S, Alam SM, Montefiori DC, Saunders KO, Tian M, Ploegh H, Kirchhausen T, Chen B, Haynes BF, Alt FW Sci Immunol. 2022 Oct 28;7(76):eadd5446. doi: 10.1126/sciimmunol.add5446. Epub , 2022 Aug 11. PMID:35951767[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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