Potent Neutralization of Influenza A Virus by a Single-Domain Antibody Blocking M2 Ion Channel Protein

Guowei Wei,Chang-You Chen,Haijiang Guo,Weixu Meng,Tao Peng,Weiqi Pan,Jinsong Liu,Ling Chen,Suryaprakash Sambhara

doi:10.1371/journal.pone.0028309

Abstract

Influenza A virus poses serious health threat to humans. Neutralizing antibodies against the highly conserved M2 ion channel is thought to offer broad protection against influenza A viruses. Here, we screened synthetic Camel single-domain antibody (VHH) libraries against native M2 ion channel protein. One of the isolated VHHs, M2-7A, specifically bound to M2-expressed cell membrane as well as influenza A virion, inhibited replication of both amantadine-sensitive and resistant influenza A viruses in vitro, and protected mice from a lethal influenza virus challenge. Moreover, M2-7A showed blocking activity for proton influx through M2 ion channel. These pieces of evidence collectively demonstrate for the first time that a neutralizing antibody against M2 with broad specificity is achievable, and M2-7A may have potential for cross protection against a number of variants and subtypes of influenza A viruses.

Highlights

As a serious public health threat, influenza A virus causes seasonal epidemics as well as occasional pandemics
After four rounds of panning, the selected VHH clones were tested for binding to matrix-2 protein (M2) protein expressed on the surface of Madin-Darby canine kidney (MDCK) cells infected with influenza A/Hong Kong/8/68 (H3N2)
The binding activity and specificity of the VHHs to M2 protein were confirmed by ELISA and the neutralizing activity for influenza A virus was examined by plaque inhibition assay

Summary

Introduction

As a serious public health threat, influenza A virus causes seasonal epidemics as well as occasional pandemics. The 1918 Spanish influenza pandemic infected close to 5% of the world’s population and caused a devastating effect [2]. Vaccines and anti-viral drugs are currently available to control influenza, their prophylactic and therapeutic effects remain incomplete. The time delay from monitoring the emergences of new viral strains to producing effective vaccines at an industrial scale limits our ability to provide immediate protection when a pandemic occurs [4]. Substantial amount of drug-resistant viruses emerged due to frequent use of these drugs. In humans, birds, and pigs, amantadine-resistant viruses constitute more than 90% of total [6,7,8]. There is a pressing need to develop effective prophylactic and therapeutic agents against infection of different variants and subtypes of influenza A viruses

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Conclusion