title: The mucosal and systemic immune responses elicited by a chitosan-adjuvanted intranasal influenza H5N1 vaccine.
abstract: BACKGROUND
  Development of influenza vaccines that induce mucosal immunity has been highlighted by the World Health Organisation as a priority (Vaccine 2005;23:1529). Dose-sparing strategies and an efficient mass-vaccination regime will be paramount to reduce the morbidity and mortality of a future H5N1 pandemic.
  
  
  OBJECTIVE
  This study has investigated the immune response and the dose-sparing potential of a chitosan-adjuvanted intranasal H5N1 (RG-14) subunit (SU) vaccine in a mouse model.
  
  
  METHODS
  Groups of mice were intranasally immunised once or twice with a chitosan (5 mg/ml)-adjuvanted SU vaccine [7·5, 15 or 30 μg haemagglutinin (HA)] or with a non-adjuvanted SU vaccine (30 μg HA). For comparison, another group of mice were intranasally immunised with a whole H5N1 (RG-14) virus (WV) vaccine (15 μg HA), and the control group consisted of unimmunised mice.
  
  
  RESULTS
  The chitosan-adjuvanted SU vaccine induced an immune response superior to that of the non-adjuvanted SU vaccine. Compared with the non-adjuvanted SU group, the chitosan-adjuvanted SU vaccine elicited higher numbers of influenza-specific antibody-secreting cells (ASCs), higher concentrations of local and systemic antibodies and correspondingly an improved haemagglutination inhibition (HI) and single radial haemolysis (SRH) response against both the homologous vaccine strain and drifted H5 strains. We measured a mixed T-helper 1/T-helper 2 cytokine response in the chitosan-adjuvanted SU groups, and these groups had an increased percentage of virus-specific CD4(+) T cells producing two Thelper 1 (Th1) cytokines simultaneously compared with the non-adjuvanted SU group. Overall, the WV vaccine induced higher antibody concentrations in sera and an HI and SRH response similar to that of the chitosan-adjuvanted SU vaccine. Furthermore, the WV vaccine formulation showed a stronger bias towards a T-helper 1 profile than the SU vaccine and elicited the highest frequencies of CD4(+) Th1 cells simultaneously secreting three different cytokines (INFγ(+) , IL2(+) and INFα(+) ). As expected, two immunisations gave a better immune response than one in all groups. The control group had very low or not detectable results in the performed immunoassays.
  
  
  CONCLUSIONS
  The cross-clade serum reactivity, improved B- and T-cell responses and dose-sparing potential of chitosan show that a chitosan-adjuvanted intranasal influenza vaccine is a promising candidate vaccine for further preclinical development.
authors.affiliation: Influenza Centre, The Gade Institute, University of Bergen, Bergen, Norway. signe.svindland@gades.uib.no
authors.forename: Signe C
authors.initials: SC
authors.lastname: Svindland
authors.forename: Åsne
authors.initials: Å
authors.lastname: Jul-Larsen
authors.forename: Rishi
authors.initials: R
authors.lastname: Pathirana
authors.forename: Solveig
authors.initials: S
authors.lastname: Andersen
authors.forename: Abdullah
authors.initials: A
authors.lastname: Madhun
authors.forename: Emanuele
authors.initials: E
authors.lastname: Montomoli
authors.forename: Inderjit
authors.initials: I
authors.lastname: Jabbal-Gill
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Cox
mesh_terms: D000276:Adjuvants, Immunologic / Q000008:administration & dosage*; D000284:Administration, Oral; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D048271:Chitosan / Q000008:administration & dosage*; D016207:Cytokines / Q000378:metabolism; D005260:Female; D006385:Hemagglutination Inhibition Tests; D053124:Influenza A Virus, H5N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000276:immunology*; D016131:Lymphocyte Subsets / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D014611:Vaccination / Q000379:methods
chemical_list: D000276:Adjuvants, Immunologic; D000914:Antibodies, Viral; D016207:Cytokines; D007252:Influenza Vaccines; D048271:Chitosan