Matrix 2
protein ectodomain (M2e) is considered a promising candidate for a broadly protective
influenza vaccine. M2e-based
vaccines against
human influenza A provide only partial protection against
avian influenza viruses because of differences in the M2e sequences. In this work, we evaluated the possibility of obtaining equal protection and immune response by using
recombinant protein on the basis of
flagellin as a carrier of the M2e
peptides of human and
avian influenza A viruses.
Recombinant protein was generated by the fusion of two tandem copies of consensus M2e sequence from
human influenza A and two copies of M2e from avian A/H5N1 viruses to
flagellin (Flg-2M2eh2M2ek). Intranasal immunisation of Balb/c mice with
recombinant protein significantly elicited anti-M2e
IgG in serum,
IgG and
sIgA in BAL.
Antibodies induced by the fusion
protein Flg-2M2eh2M2ek bound efficiently to synthetic
peptides corresponding to the human consensus M2e sequence as well as to the M2e sequence of A/Chicken/Kurgan/05/05 RG (H5N1) and recognised native M2e
epitopes exposed on the surface of the MDCK cells infected with A/PR/8/34 (H1N1) and A/Chicken/Kurgan/05/05 RG (H5N1) to an equal degree. Immunisation led to both anti-M2e
IgG1 and
IgG2a response with
IgG1 prevalence. We observed a significant intracellular production of
IL-4, but not IFN-γ, by CD4+ T-cells in spleen of mice following immunisation with Flg-2M2eh2M2ek. Immunisation with the Flg-2M2eh2M2ek fusion
protein provided similar protection from lethal challenge with
human influenza A viruses (H1N1, H3N2) and
avian influenza virus (H5N1). Immunised mice experienced significantly less
weight loss and decreased lung viral titres compared to control mice. The data obtained show the potential for the development of an M2e-flagellin candidate
influenza vaccine with broad spectrum protection against influenza A viruses of various origins.