title: Prokaryote-expressed M2e protein improves H9N2 influenza vaccine efficacy and protection against lethal influenza A virus in mice.
abstract: BACKGROUND
  Influenza vaccines are prepared annually based on global epidemiological surveillance data. However, since there is no method by which to predict the influenza strain that will cause the next pandemic, the demand to develop new vaccination strategies with broad cross-reactivity against influenza viruses are clearly important. The ectodomain of the influenza M2 protein (M2e) is an attractive target for developing a vaccine with broad cross-reactivity. For these reasons, we investigated the efficacy of an inactivated H9N2 virus vaccine (a-H9N2) mixed with M2e (1xM2e or 4xM2e) proteins expressed in Escherichia coli, which contains the consensus of sequence the extracellular domain of matrix 2 (M2e) of A/chicken/Vietnam/27262/09 (H5N1) avian influenza virus, and investigated its humoral immune response and cross-protection against influenza A viruses.
  
  
  RESULTS
  Mice were intramuscularly immunized with a-H9N2, 1xM2e alone, 4xM2e alone, a-H9N2/1xM2e, or a-H9N2/4xM2e. Three weeks post-vaccination, mice were challenged with lethal homologous (A/ chicken /Korea/ma163/04, H9N2) or heterosubtypic virus (A/Philippines/2/82, H3N2 and A/aquatic bird/Korea/maW81/05, H5N2). Our studies demonstrate that the survival of mice immunized with a-H9N2/1xM2e or with a-H9N2/4xM2e (100% survival) was significantly higher than that of mouse-adapted H9N2 virus-infected mice vaccinated with 1xM2e alone or with 4xM2e alone (0% survival). We also evaluated the protective efficacy of the M2e + vaccine against infection with mouse-adapted H5N2 influenza virus. Protection from death in the control group (0% survival) was similar to that of the 1×M2e alone and 4xM2e alone-vaccinated groups (0% survival). Only 40% of mice vaccinated with vaccine alone survived challenge with H5N2, while the a-H9N2/1×M2e and a-H9N2/4×M2e groups showed 80% and 100% survival following mouse-adapted H5N2 challenge, respectively. We also examined cross-protection against human H3N2 virus and found that the a-H9N2/1×M2e group displayed partial cross-protection against H3N2 (40% survival), whereas vaccine alone, 1×M2e alone, 4×M2e alone, or H9N2/1×M2e groups showed incomplete protection (0% survival) in response to challenge with a lethal dose of human H3N2 virus.
  
  
  CONCLUSIONS
  Taken together, these results suggest that prokaryote-expressed M2e protein improved inactivated H9N2 virus vaccine efficacy and achieved cross-protection against lethal influenza A virus infection in mice.
authors.affiliation: Microbiology Department, College of Medicine and Medical Research Institute, Chungbuk National University, 12 Gaeshin-Dong Heungduk-Ku, Cheongju 361-763, Republic of Korea.
authors.forename: Eun-Ha
authors.initials: EH
authors.lastname: Kim
authors.forename: Jun-Han
authors.initials: JH
authors.lastname: Lee
authors.forename: Philippe Noriel Q
authors.initials: PN
authors.lastname: Pascua
authors.forename: Min-Suk
authors.initials: MS
authors.lastname: Song
authors.forename: Yun-Hee
authors.initials: YH
authors.lastname: Baek
authors.forename: Hyeok-Il
authors.initials: HI
authors.lastname: Kwon
authors.forename: Su-Jin
authors.initials: SJ
authors.lastname: Park
authors.forename: Gyo-Jin
authors.initials: GJ
authors.lastname: Lim
authors.forename: Arun
authors.initials: A
authors.lastname: Decano
authors.forename: Mohammed Ye
authors.initials: MY
authors.lastname: Chowdhury
authors.forename: Su-Kyung
authors.initials: SK
authors.lastname: Seo
authors.forename: Man Ki
authors.initials: MK
authors.lastname: Song
authors.forename: Chul-Joong
authors.initials: CJ
authors.lastname: Kim
authors.forename: Young-Ki
authors.initials: YK
authors.lastname: Choi
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D056738:Cross Protection; D003429:Cross Reactions; D005260:Female; D053124:Influenza A Virus, H5N1 Subtype / Q000276:immunology; D053127:Influenza A Virus, H9N2 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000276:immunology*; D007273:Injections, Intramuscular; D051379:Mice; D008807:Mice, Inbred BALB C; D016019:Survival Analysis; D014611:Vaccination / Q000379:methods; D014614:Vaccines, Synthetic / Q000008:administration & dosage / Q000276:immunology; D014763:Viral Matrix Proteins / Q000276:immunology*; D000086082:Viroporin Proteins
chemical_list: D000914:Antibodies, Viral; D007252:Influenza Vaccines; D014614:Vaccines, Synthetic; D014763:Viral Matrix Proteins; C488937:M2 protein, Influenza A virus; D000086082:Viroporin Proteins
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