Design of a Universal Influenza A Vaccine Candidate Based on M2e.FliC; Immunoinformatics Analysis, Protein Modeling, and Its Expression in Escherichia coli

Background: Due to the rapid accumulation of mutations in influenza virus and the unpredictability of new influenza, the current influenza vaccines require an almost yearly reformulation. The extracellular domain of matrix protein 2 (M2e) of influenza A viruses is conserved and is an attractive alternative approach to be used as a vaccine with a broad cross- protection. Objectives: In this study, a vector containing three repeats of M2e gene of influenza A virus fused with molecular adjuvant of FliC was constructed. Methods: In silico analysis of 3M2e.FliC chimeric polypeptide was performed based on 3M2e.FliC sequence, virtual fusion construc- tion translation, linear epitope prediction of 3M2e.FliC, 3M2e.FliC modeling, and validation score consideration through immunoin- formatics approaches. Expression of 3M2e.FliC was carried out in two strains of Escherichia coli (BL21 [DE3] and ER2566). The fidelity of expression in both hosts was analyzed through a time course of sampling by SDS-PAGE and confirmed by western blotting. Results: The immunoinformatics results indicated that M2e and FliC epitopes were at the surface of protein, which would be acces- sible for the immune system. The expression results demonstrated that the 3M2e.FliC construct was expressed well in both strains of E. coli, although the efficiency of expression in ER2566 strain was higher than that of BL21 (DE3) strain. Conclusions: The 3M2e.Flic protein as a recombinant antigen may be considered as a universal influenza vaccine candidate after its evaluation and assessment in animal models.