3whe
From Proteopedia
A new conserved neutralizing epitope at the globular head of hemagglutinin in H3N2 influenza viruses
Structural highlights
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Function[T2HNI1_9INFA] Binds to sialic acid-containing receptors on the cell surface, bringing about the attachment of the virus particle to the cell. This attachment induces virion internalization of about two third of the virus particles through clathrin-dependent endocytosis and about one third through a clathrin- and caveolin-independent pathway. Plays a major role in the determination of host range restriction and virulence. Class I viral fusion protein. Responsible for penetration of the virus into the cell cytoplasm by mediating the fusion of the membrane of the endocytosed virus particle with the endosomal membrane. Low pH in endosomes induces an irreversible conformational change in HA2, releasing the fusion hydrophobic peptide. Several trimers are required to form a competent fusion pore (By similarity).[RuleBase:RU003324][SAAS:SAAS000149_004_327643] Publication Abstract from PubMedNeutralizing antibodies that target the hemagglutinin of influenza virus either inhibit binding of hemagglutinin to cellular receptors or prevent the low-pH-induced conformational change in hemagglutinin required for membrane fusion. In general, the former type of antibody binds to the globular head formed by HA1 and has narrow strain specificity, while the latter type binds to the stem mainly formed by HA2 and has broad strain specificity. In the present study, we analyzed the epitope and function of a broadly neutralizing human antibody against H3N2 viruses, F005-126. The crystal structure of F005-126 Fab in complex with hemagglutinin revealed that the antibody binds to the globular head, spans a cleft formed by two hemagglutinin monomers in a hemagglutinin trimer, and cross-links them. It recognizes two peptide portions (sites L and R) and a glycan linked to asparagine at residue 285 using three complementarity-determining regions and framework 3 in the heavy chain. Binding of the antibody to sites L (residues 171-173, 239 and 240) and R (residues 91, 92, 270-273, 284 and 285) is mediated mainly by van der Waals contacts with the main chains of the peptides in these sites and secondarily by hydrogen bonds with a few side chains of conserved sequences in HA1. Furthermore, the glycan recognized by F005-126 is conserved among H3N2 viruses. F005-126 has the ability to prevent low-pH-induced conformational changes in hemagglutinin. The newly identified conserved epitope including the glycan should be immunogenic in humans, and may induce production of broadly neutralizing antibodies against H3 viruses. IMPORTANCE: Antibodies play an important role in protection against influenza virus, and hemagglutinin is the major target for virus neutralizing Abs. It has long been believed that all effective neutralizing antibodies bind to the surrounding regions of the sialic acid-binding pocket and inhibit the binding of hemagglutinin to the cellular receptor. As mutations are readily introduced into such epitopes, this type of antibody shows narrow strain specificity. Recently, however, broadly neutralizing antibodies have been isolated. Most of these bind either to conserved sites in the stem region or to the sialic acid-binding pocket itself. In the present study, we identified a new neutralizing epitope in the head region recognized by a broadly neutralizing human antibody against H3N2. This epitope may be useful for design of vaccines. Conserved Neutralizing Epitope at Globular Head of Hemagglutinin in H3N2 Influenza Viruses.,Iba Y, Fujii Y, Ohshima N, Sumida T, Kubota-Koketsu R, Ikeda M, Wakiyama M, Shirouzu M, Okada J, Okuno Y, Kurosawa Y, Yokoyama S J Virol. 2014 Apr 9. PMID:24719430[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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