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==Dissecting human monoclonal antibody responses from mRNA and protein-based booster vaccinations against XBB1.5 SARS-CoV-2==
<StructureSection load='9cci' size='340' side='right'caption='[[9cci]], [[Resolution|resolution]] 2.65&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[9cci]] is a 3 chain structure with sequence from [https://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] and [https://en.wikipedia.org/wiki/Severe_acute_respiratory_syndrome_coronavirus_2 Severe acute respiratory syndrome coronavirus 2]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=9CCI OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=9CCI FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">Electron Microscopy, [[Resolution|Resolution]] 2.65&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=NAG:N-ACETYL-D-GLUCOSAMINE'>NAG</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=9cci FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=9cci OCA], [https://pdbe.org/9cci PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=9cci RCSB], [https://www.ebi.ac.uk/pdbsum/9cci PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=9cci ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/SPIKE_SARS2 SPIKE_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]<ref>PMID:32075877</ref> <ref>PMID:32142651</ref> <ref>PMID:32155444</ref>   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]
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== Publication Abstract from PubMed ==
The emergence of highly contagious and immune-evasive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants has required reformulation of coronavirus disease 2019 (COVID-19) vaccines to target those new variants specifically. While previous infections and booster vaccinations can enhance variant neutralization, it is unclear whether the monovalent version, administered using either mRNA or protein-based vaccine platforms, can elicit de novo B-cell responses specific for Omicron XBB.1.5 variants. Here, we dissected the genetic antibody repertoire of 603 individual plasmablasts derived from five individuals who received a monovalent XBB.1.5 vaccination either with mRNA (Moderna or Pfizer/BioNtech) or adjuvanted protein (Novavax). From these sequences, we expressed 100 human monoclonal antibodies and determined binding, affinity and protective potential against several SARS-CoV-2 variants, including JN.1. We then select two vaccine-induced XBB.1.5 mAbs, M2 and M39. M2 mAb was a de novo, antibody, i.e., specific for XBB.1.5 but not ancestral SARS-CoV-2. M39 bound and neutralized both XBB.1.5 and JN.1 strains. Our high-resolution cryo-electron microscopy (EM) structures of M2 and M39 in complex with the XBB.1.5 spike glycoprotein defined the epitopes engaged and revealed the molecular determinants for the mAbs' specificity. These data show, at the molecular level, that monovalent, variant-specific vaccines can elicit functional antibodies, and shed light on potential functional and genetic differences of mAbs induced by vaccinations with different vaccine platforms.\.

Dissecting human monoclonal antibody responses from mRNA- and protein-based XBB.1.5 COVID-19 monovalent vaccines.,Fantin RF, Clark JJ, Cohn H, Jaiswal D, Bozarth B, Civljak A, Rao V, Lobo I, Nardulli JR, Srivastava K, Yong J, Andreata-Santos R, Bushfield K, Lee ES, Singh G, Kleinstein SH, Krammer F, Simon V, Bajic G, Coelho CH bioRxiv [Preprint]. 2024 Jul 16:2024.07.15.602781. doi: , 10.1101/2024.07.15.602781. PMID:39071292<ref>PMID:39071292</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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<div class="pdbe-citations 9cci" style="background-color:#fffaf0;"></div>
== References ==
<references/>
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</StructureSection>
[[Category: Homo sapiens]]
[[Category: Large Structures]]
[[Category: Severe acute respiratory syndrome coronavirus 2]]
[[Category: Bajic G]]
[[Category: Jaiswal D]]