Novel chimeric proteins mimicking SARS-CoV-2 spike epitopes with broad inhibitory activity. Cano Muñoz, Mario Polo Megías, Daniel Gavira Gallardo, José Antonio Rodríguez López, María J. Conejero Lara, Francisco COVID-19 Fusion inhibitor Vaccine SARS-CoV-2 spike (S) protein mediates virus attachment to the cells and fusion between viral and cell membranes. Membrane fusion is driven by mutual interaction between the highly conserved heptad-repeat regions 1 and 2 (HR1 and HR2) of the S2 subunit of the spike. For this reason, these S2 regions are interesting therapeutic targets for COVID-19. Although HR1 and HR2 have been described as transiently exposed during the fusion process, no significant antibody responses against these S2 regions have been reported. Here we designed chimeric proteins that imitate highly stable HR1 helical trimers and strongly bind to HR2. The proteins have broad inhibitory activity against WT B.1 and BA.1 viruses. Sera from COVID-19 convalescent donors showed significant levels of reactive antibodies (IgG and IgA) against the HR1 mimetic proteins, whereas these antibody responses were absent in sera from uninfected donors. Moreover, both inhibitory activity and antigenicity of the proteins correlate positively with their structural stability but not with the number of amino acid changes in their HR1 sequences, indicating a conformational and conserved nature of the involved epitopes. Our results reveal previously undetected spike epitopes that may guide the design of new robust COVID-19 vaccines and therapies. 2022-11-07T08:26:38Z 2022-11-07T08:26:38Z 2022-12-01 journal article Published version: Mario Cano-Muñoz... [et al.]. Novel chimeric proteins mimicking SARS-CoV-2 spike epitopes with broad inhibitory activity, International Journal of Biological Macromolecules, Volume 222, Part B, 2022, Pages 2467-2478, ISSN 0141-8130, [https://doi.org/10.1016/j.ijbiomac.2022.10.031] https://hdl.handle.net/10481/77788 10.1016/j.ijbiomac.2022.10.031 eng info:eu-repo/grantAgreement/EC/H2020/681032 http://creativecommons.org/licenses/by-nc-nd/4.0/ open access Attribution-NonCommercial-NoDerivatives 4.0 Internacional Elsevier