A Synthetic Peptide Comprising Heterodimeric Epitopes of M Protein Elicits Mice Protective Immunity against H5N1 Influenza a Virus

Abstract

Background: The high degree of conservation of the M2 protein of influenza A virus and its cross-reactive immunity that decreased the severity of diseases caused by influenza virus in animal models make it a prime candidate for a universal influenza vaccine. Studies showed that recombinant HA, NA and M2 proteins were poorly immunogenic and required multiple doses or the inclusion of adjuvant for improved immunogenicity and efficacy. Methods: A synthetic peptide PEP-M2 comprising heterodimeric epitopes was employed to immunize mice in the presence or absence of a 'K' type CpG ODN adjuvant. Results: Mice vaccinated with PEP-M2 peptide elicited strong IgG ELISA antibody titers to this peptide and increased protection (with survival rates raised from 25% to 60%) for mice challenged by lethal influenza A virus (NIBRG-14, 1000TCID50). The CpG ODN, used as an adjuvant for PEP-M2, elicited significantly higher antibody titers in mice. Further, PEP-M2 plus CpG ODN promoted in immunized mice higher survival rate (83.3%) and slower weight loss than PEP-M2 alone in lethal challenge assay. Conclusions: Results from this study revealed that peptide comprising heterodimeric epitopes of M Protein could elicit in mice protective immunity against influenza A virus in the presence of CpG ODN adjuvant.