Open AccessThe Receptor-Binding Domain of Influenza Virus Hemagglutinin Produced in Escherichia coli Folds into Its Native, Immunogenic Structure
Author(s) -
Rebecca M. DuBois,
José Manuel AguilarYáñez,
Gonzalo I MendozaOchoa,
Yuriana OropezaAlmazán,
Stacey SchultzCherry,
Mario Moisés Álvarez,
Stephen W. White,
Charles J. Russell
Publication year - 2011
Publication title -
journal of virology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.617
H-Index - 292
eISSN - 1070-6321
pISSN - 0022-538X
DOI - 10.1128/jvi.01412-10
Subject(s) - biology , hemagglutinin (influenza) , virology , escherichia coli , virus , influenza a virus , microbiology and biotechnology , genetics , gene
The hemagglutinin (HA) surface glycoprotein promotes influenza virus entry and is the key protective antigen in natural immunity and vaccines. The HA protein is a trimeric envelope glycoprotein consisting of a globular receptor-binding domain (HA-RBD) that is inserted into a membrane fusion-mediating stalk domain. Similar to other class I viral fusion proteins, the fusogenic stalk domain spontaneously refolds into its postfusion conformation when expressed in isolation, consistent with this domain being trapped in a metastable conformation. Using X-ray crystallography, we show that the influenza virus HA-RBD refolds spontaneously into its native, immunogenic structure even when expressed in an unglycosylated form inEscherichia coli . In the 2.10-Å structure of the HA-RBD, the receptor-binding pocket is intact and its conformational epitopes are preserved. Recombinant HA-RBD is immunogenic and protective in ferrets, and the protein also binds with specificity to sera from influenza virus-infected humans. Overall, the data provide a structural basis for the rapid production of influenza vaccines inE. coli . From an evolutionary standpoint, the ability of the HA-RBD to refold spontaneously into its native conformation suggests that influenza virus acquired this domain as an insertion into an ancestral membrane-fusion domain. The insertion of independently folding domains into fusogenic stalk domains may be a common feature of class I viral fusion proteins.