Immune Effect of DNA Prime-Protein Boost Immune Strategy Based on H9N2 Avian Influenza Virus Matrix Protein 2

Influenza matrix protein 2(M2) is highly conserved in influenza A viruses.Considering the low immunogenicity of M2,DNA prime-protein boost immunization strategy was explored to improve the immune effect in our study.The M2 DNA plasmid and the sM2 protein(i.e.M2 protein without transmembrane domain expressed in E.coli) from avian influenza virus A/Chicken/Jiangsu/7/2002(H9N2) were prepared.The M2 DNA was intramuscularly injected into BALB/c mice by electroporation,and the sM2 protein was administered to mice by nasal dropping.The immunization interval was 3 weeks.Three weeks after the last immunization,the mice were challenged with lethal(5LD50) homologous virus.The effects of various immune strategies were evaluated by survival rate,body weight change,lung virus titer and the M2-specific IgG antibody levels in mice.The results showed that,compared with the unimmunized mice,M2 DNA prime + protein boost twice could provide complete protection for mice against lethal homologous virus challenge.