Abstract
BackgroundThe extracellular domain of matrix protein 2 (M2e) of influenza A virus is a promising target for the development of a universal vaccine against influenza because M2e sequences are highly conserved among human influenza A strains. However, native M2e is poorly immunogenic, but its immunogenicity can be increased by delivery in combination with adjuvants or carrier particles. It was previously shown that fusion of M2e to bacterial flagellin, the ligand for Toll-like receptor (TLR) 5 and powerful mucosal adjuvant, significantly increases the immunogenicity and protective capacity of M2e.ResultsIn this study, we report for the first time the transient expression in plants of a recombinant protein Flg-4M comprising flagellin of Salmonella typhimurium fused to four tandem copies of the M2e peptide. The chimeric construct was expressed in Nicotiana benthamiana plants using either the self-replicating potato virus X (PVX) based vector, pA7248AMV-GFP, or the cowpea mosaic virus (CPMV)-derived expression vector, pEAQ-HT. The highest expression level up to 30 % of total soluble protein (about 1 mg/g of fresh leaf tissue) was achieved with the PVX-based expression system. Intranasal immunization of mice with purified Flg-4M protein induced high levels of M2e-specific serum antibodies and provided protection against lethal challenge with influenza virus.ConclusionsThis study confirms the usefulness of flagellin as a carrier of M2e and its relevance for the production of M2e-based candidate influenza vaccines in plants.Electronic supplementary materialThe online version of this article (doi:10.1186/s12896-015-0164-6) contains supplementary material, which is available to authorized users.
Highlights
The extracellular domain of matrix protein 2 (M2e) of influenza A virus is a promising target for the development of a universal vaccine against influenza because M2e sequences are highly conserved among human influenza A strains
Viral vectors for expression of the hybrid protein consisting of flagellin linked to four copies of influenza M2e peptide in N. benthamiana plants The highly conserved extracellular domain of the influenza virus M2 protein, M2e, is a promising target for the development of recombinant “universal” vaccines against influenza [5]
In order to make a broader range candidate vaccine, a hybrid protein flagellin of Salmonella typhimurium (Flg)-4M containing two copies of human consensus M2e sequence and two copies of the M2e peptide of avian influenza virus strain A/Chicken/Kurgan/05/2005 fused to the C-terminus of S. typhimurium FljB was designed
Summary
The extracellular domain of matrix protein 2 (M2e) of influenza A virus is a promising target for the development of a universal vaccine against influenza because M2e sequences are highly conserved among human influenza A strains. It was previously shown that fusion of M2e to bacterial flagellin, the ligand for Toll-like receptor (TLR) 5 and powerful mucosal adjuvant, significantly increases the immunogenicity and protective capacity of M2e. It has been previously shown that genetically fusing an antigen of interest to bacterial flagellin, the ligand for TLR5, significantly increases the immunogenicity and protective capacity of the antigen [12, 13]. The ability of flagellin to be both the platform and the adjuvant for different vaccines was demonstrated in various models of infection including influenza [13,14,15,16,17,18,19]
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