Download MendeleyNeutralization of SARS-CoV-2 by IgM-14 via engagement of two distinct spike epitopes.
Wang, Y., Hu, Y., Ku, Z., Yeung, J., Zou, J., Woodson, M., Prokhorov, N.S., Knyazhanskaya, E.S., Zhao, H., Sherman, M.B., An, Z., Carroll, S.F., Shi, P.Y., Leiman, P.G., Xie, X.(2026) PLoS Pathog 22: e1014071-e1014071
- PubMed: 41880376 Search on PubMedSearch on PubMed Central
- DOI: https://doi.org/10.1371/journal.ppat.1014071
- Primary Citation Related Structures:
9YNR, 9YNX, 9YOK, 9YPB, 9YPR - PubMed Abstract:
Engineered immunoglobulin M (IgM) antibodies typically exhibit superior neutralization potency and avidity compared to their parental IgG counterparts, primarily due to multivalent binding to repeated epitopes on a targeting antigen. In this study, we characterize the neutralization breadth and mechanism of action of IgM-14, a previously reported intranasally deliverable antibody targeting SARS-CoV-2. IgM-14 demonstrates remarkably potent antiviral activity against all pre-Omicron variants but significantly reduced efficacy against Omicron BA.1, and complete loss of activity against the later subvariant JN.1. Resistance selection identified two key mutations in the receptor-binding domain (RBD), G476D and F486P, which disrupt IgM-14 binding and confer strong resistance. Cryo-electron microscopy analysis uncovered two distinct Fab-RBD interfaces: a primary interface overlapping the angiotensin-converting enzyme 2 (ACE2)-binding region, and a unique secondary interface formed only when the RBD adopts the ACE2-inaccessible "down" conformation, involving a neighboring spike protomer. Site-directed mutagenesis and structural modeling revealed a critical role of this secondary site in IgM-14-mediated neutralization. Unlike IgG-14, structural modeling suggested that IgM-14 can simultaneously engage both interfaces in diverse modes, indicating a noncanonical avidity mechanism. Collectively, these findings highlight the structural and functional uniqueness of IgM-14 and offer valuable insights into the rational design of next-generation spike-targeted antibody therapeutics with enhanced breadth and potency.
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America.
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