Recombinant M2e-HA2 fusion protein induced immunity responses against intranasally administered H9N2 influenza virus

Influenza is a highly contagious respiratory tract disease and is considered a serious community health problem. Influenza viruses possess multiple conserved epitopes which are used for designing universal vaccines. To this aim, the gene coding for N-terminal part of M2e (SLLTEVET) and HA2 (GLFGAIAGF), was synthesized, linked by a (Gly4Ser)₄ peptide linker, and cloned into pGS-21a vector. Afterwards, the construct was transferred into E. coli BL21 (DE3) cells to produce the designed antigenic protein called M2e-HA2. Immunization of mice with these peptides significantly induced humoral immune responses against the influenza virus. Three weeks after the last booster, mice were inoculated intranasally with 1 × 10⁶ EID₅₀ of H9N2 virus. The results indicated that the recombinant M2e-HA2 fusion protein could protect mice against H9N2 virus.