title: Naturally occurring antibodies in humans can neutralize a variety of influenza virus strains, including H3, H1, H2, and H5.
abstract: Influenza A viruses are classified into 16 subtypes according to the serotypes of hemagglutinin (HA). It is generally thought that neutralizing antibodies (Abs) are not broadly cross-reactive among HA subtypes. We examined the repertoire of neutralizing Abs against influenza viruses in humans. B lymphocytes were collected from donors by apheresis, and Ab libraries were constructed by using phage-display technology. Anti-HA clones were isolated by screening with H3N2 viruses. Their binding activity was examined, and four kinds of Abs showing broad strain specificity were identified from one donor. Two of the Abs, F045-092 and F026-427, were extensively analyzed. They neutralized not only H3N2 but also H1N1, H2N2, and H5N1 viruses, although the activities were largely varied. Flow cytometry suggested that they have the ability to bind to HA and HA1 artificially expressed on the cell surface. They show hemagglutination inhibition activity and do not compete with C179, an Ab thought to bind to the stalk region. F045-092 competes with Abs that recognize sites A and B for binding to HA. Furthermore, the serine at residue 136 in site A could be a part of the epitope. Thus, it is likely that F045-092 and F026-427 bind to a conserved epitope in the head region formed by HA1. Interestingly, while the V(H)1-69 gene can encode MAbs against the HA stem that are group 1 specific, F045-092 and its relatives that recognize the head region also use V(H)1-69. The possible epitope recognized by these clones is discussed.
authors.affiliation: Division of Antibody Project, Institute for Comprehensive Medical Science, Fujita Health University, Toyoake, Aichi 470-1192, Japan.
authors.forename: Nobuko
authors.initials: N
authors.lastname: Ohshima
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Iba
authors.forename: Ritsuko
authors.initials: R
authors.lastname: Kubota-Koketsu
authors.forename: Yoshizo
authors.initials: Y
authors.lastname: Asano
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Okuno
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Kurosawa
mesh_terms: D057134:Antibodies, Neutralizing / Q000276:immunology*; D000914:Antibodies, Viral / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology; D003429:Cross Reactions; D000939:Epitopes / Q000276:immunology; D006385:Hemagglutination Inhibition Tests; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000276:immunology / Q000378:metabolism; D006801:Humans; D009980:Influenza A virus / Q000276:immunology*; D008969:Molecular Sequence Data; D009500:Neutralization Tests; D019151:Peptide Library; D011485:Protein Binding; D017422:Sequence Analysis, DNA
chemical_list: D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D000939:Epitopes; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D019151:Peptide Library