Structural characterization of a protective epitope spanning A(H1N1)pdm09 influenza virus neuraminidase monomers.

Hongquan Wan,James Stevens,Maryna C Eichelberger,Laura Couzens,Paul J Carney,Rebecca J Garten,Hua Yang,Lianlian Jiang,David A Shore,Julie Villanueva,Jin Gao

doi:10.1038/ncomms7114

Abstract

A(H1N1)pdm09 influenza A viruses predominated in the 2013–2014 USA influenza season, and although most of these viruses remain sensitive to Food and Drug Administration-approved neuraminidase (NA) inhibitors, alternative therapies are needed. Here we show that monoclonal antibody CD6, selected for binding to the NA of the prototypic A(H1N1)pdm09 virus, A/California/07/2009, protects mice against lethal virus challenge. The crystal structure of NA in complex with CD6 Fab reveals a unique epitope, where the heavy-chain complementarity determining regions (HCDRs) 1 and 2 bind one NA monomer, the light-chain CDR2 binds the neighbouring monomer, whereas HCDR3 interacts with both monomers. This 30-amino-acid epitope spans the lateral face of an NA dimer and is conserved among circulating A(H1N1)pdm09 viruses. These results suggest that the large, lateral CD6 epitope may be an effective target of antibodies selected for development as therapeutic agents against circulating H1N1 influenza viruses.

Highlights

A(H1N1)pdm[09] influenza A viruses predominated in the 2013–2014 USA influenza season, and most of these viruses remain sensitive to Food and Drug Administrationapproved neuraminidase (NA) inhibitors, alternative therapies are needed
The increased pH1N1 influenza activity and the emergence of oseltamivir-resistant pH1N1 viruses add urgency to the need for additional influenza antivirals. It would be advantageous for the new therapeutics to inhibit influenza virus through mechanisms distinct from oseltamivir and zanamivir, so that NA inhibitor-resistant viruses remain sensitive to the new drugs
Intravenous immunoglobulin[9,10,11] and influenza-specific monoclonal antibodies, those that bind to the conserved, stem region of the haemagglutinin (HA)[12,13,14], are being considered as alternative treatments. mAbs that inhibit the enzyme activity of NA have the potential to serve as therapeutic agents[15,16,17,18]

Summary

Introduction

A(H1N1)pdm[09] influenza A viruses predominated in the 2013–2014 USA influenza season, and most of these viruses remain sensitive to Food and Drug Administrationapproved neuraminidase (NA) inhibitors, alternative therapies are needed. Prophylactic treatment with mAbs specific for this antigenic site protected mice against lethal challenge with the homologous and heterologous N1-containing viruses, including pH1N1 These antibodies were less effective in inhibiting pH1N1 virus than the homologous virus[15]. We report the characterization of one of these mAbs, CD6, which is effective in inhibiting pH1N1 virus in both in vitro and in vivo studies, with a focus on the crystallographic analysis of the CA/09 NA in complex with CD6 Fab. Our study reveals a unique epitope bridging neighbouring NA monomers, with a large number of contacts between antibody and antigen. Our study reveals a unique epitope bridging neighbouring NA monomers, with a large number of contacts between antibody and antigen This epitope is conserved among circulating pH1N1 viruses, representing an attractive target for the development of novel therapeutics against influenza

Methods

Results

Conclusion