Mechanism of protection against influenza A virus by DNA vaccine encoding the hemagglutinin gene.
Influenza A virus with its two major antigenic surface proteins hemagglutinin (HA) and neuraminidase (NA) is a widely used model to study DNA immunizations in mice and other animals. Natural protection against influenza A virus infection is mediated by antibodies, which mostly are not protective against antigenic shift or drift variants of the original virus. Therefore, it would be a major task to induce a protective cellular immune response to more conserved proteins or epitopes. Injection of plasmid encoding a viral antigen is known to induce cellular as well as humoral immunity. In this study we investigate the mechanism of protection after intramuscular vaccination of C57Bl/6 mice with a DNA vaccine encoding HA of influenza A/PR/8/34. After a single injection, only a small percentage of mice survive the lethal challenge with homologous virus. The amount of protection can be doubled by applying a booster injection. Furthermore, by coinjection of plasmids encoding cytokines GM-CSF and IL-12, respectively, nearly all of the mice are protected. Mice with specific defects in the cellular immune response [perforin knockout (P-/-) mice] and in the humoral immune response [IgD/IgM knockout (muMT) mice], respectively, have been immunized with HA DNA with or without cytokine DNA. Protection could only be induced in P-/- mice, whereas muMT mice succumbed to the infection. Moreover, when muMT mice were infected with only 0.75 x50% lethal dose they died all the same, whereby mice that had been depleted of CD8+ T cells before infection showed an even greater progression of illness. Altogether these results demonstrate that antibodies mediate protection after immunization with plasmid coding for HA of influenza A virus, and that booster immunizations and coinjection of plasmids encoding GM-CSF or IL-12 can improve this protection.
Operschall
E
E
Institute of Medical Virology, University of Zurich, Switzerland.
Pavlovic
J
J
Nawrath
M
M
Mölling
K
K
D000818:Animals; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000235:genetics / Q000276:immunology; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics / Q000276:immunology*; D007114:Immunization; D007075:Immunoglobulin M / Q000235:genetics; D009980:Influenza A virus / Q000276:immunology*; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000276:immunology*; D018664:Interleukin-12 / Q000235:genetics / Q000276:immunology; D008562:Membrane Glycoproteins / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009976:Orthomyxoviridae Infections / Q000276:immunology / Q000517:prevention & control*; D054353:Perforin; D010957:Plasmids / Q000235:genetics; D052899:Pore Forming Cytotoxic Proteins; D019444:Vaccines, DNA / Q000008:administration & dosage / Q000276:immunology*
D019267:Hemagglutinin Glycoproteins, Influenza Virus; D007075:Immunoglobulin M; D007252:Influenza Vaccines; D008562:Membrane Glycoproteins; D052899:Pore Forming Cytotoxic Proteins; D019444:Vaccines, DNA; D054353:Perforin; D018664:Interleukin-12; D016178:Granulocyte-Macrophage Colony-Stimulating Factor