A pandemic influenza H1N1 live vaccine based on modified vaccinia Ankara is highly immunogenic and protects mice in active and passive immunizations.
BACKGROUND
The development of novel influenza vaccines inducing a broad immune response is an important objective. The aim of this study was to evaluate live vaccines which induce both strong humoral and cell-mediated immune responses against the novel human pandemic H1N1 influenza virus, and to show protection in a lethal animal challenge model.


RESULTS
For this purpose, the hemagglutinin (HA) and neuraminidase (NA) genes of the influenza A/California/07/2009 (H1N1) strain (CA/07) were inserted into the replication-deficient modified vaccinia Ankara (MVA) virus--a safe poxviral live vector--resulting in MVA-H1-Ca and MVA-N1-Ca vectors. These live vaccines, together with an inactivated whole virus vaccine, were assessed in a lung infection model using immune competent Balb/c mice, and in a lethal challenge model using severe combined immunodeficient (SCID) mice after passive serum transfer from immunized mice. Balb/c mice vaccinated with the MVA-H1-Ca virus or the inactivated vaccine were fully protected from lung infection after challenge with the influenza H1N1 wild-type strain, while the neuraminidase virus MVA-N1-Ca induced only partial protection. The live vaccines were already protective after a single dose and induced substantial amounts of neutralizing antibodies and of interferon-gamma-secreting (IFN-gamma) CD4- and CD8 T-cells in lungs and spleens. In the lungs, a rapid increase of HA-specific CD4- and CD8 T cells was observed in vaccinated mice shortly after challenge with influenza swine flu virus, which probably contributes to the strong inhibition of pulmonary viral replication observed. In addition, passive transfer of antisera raised in MVA-H1-Ca vaccinated immune-competent mice protected SCID mice from lethal challenge with the CA/07 wild-type virus.


CONCLUSIONS
The non-replicating MVA-based H1N1 live vaccines induce a broad protective immune response and are promising vaccine candidates for pandemic influenza.
Hessel
Annett
A
R&D Vaccines, Biomedical Research Center, Baxter BioScience, Orth/Donau, Austria.
Schwendinger
Michael
M
Fritz
Daniela
D
Coulibaly
Sogue
S
Holzer
Georg W
GW
Sabarth
Nicolas
N
Kistner
Otfried
O
Wodal
Walter
W
Kerschbaum
Astrid
A
Savidis-Dacho
Helga
H
Crowe
Brian A
BA
Kreil
Thomas R
TR
Barrett
P Noel
PN
Falkner
Falko G
FG
D000818:Animals; D000917:Antibody Formation / Q000276:immunology; D000918:Antibody Specificity / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D002460:Cell Line; D003429:Cross Reactions / Q000276:immunology; D004196:Disease Outbreaks; D005260:Female; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000276:immunology; D006801:Humans; D007116:Immunization, Passive / Q000379:methods*; D007121:Immunocompetence / Q000276:immunology; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000276:immunology*; D007251:Influenza, Human / Q000453:epidemiology* / Q000517:prevention & control*; D008168:Lung / Q000276:immunology; D051379:Mice; D009439:Neuraminidase / Q000276:immunology; D013154:Spleen / Q000276:immunology; D014611:Vaccination / Q000379:methods*; D014613:Vaccines, Attenuated / Q000276:immunology
C543345:H1N1 virus hemagglutinin; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D007252:Influenza Vaccines; D014613:Vaccines, Attenuated; D009439:Neuraminidase
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