ABSTRACT
DNA vaccination using plasmid encoding the hemagglutinin (HA) gene of influenza A/PR/8/34 virus to induce long-lasting protective immunity against respiratory infection was evaluated in this study. Using liposomes as carriers, the efficacy of DNA vaccines was determined using a lethal influenza infection model in mice. Mice immunized intranasally or intramuscularly with liposome-encapsulated pCI plasmid encoding HA (pCI-HA10) were completely protected against an intranasal 5 LD(50) influenza virus challenge. Mice immunized with liposome-encapsulated pCI-HA10, but not naked pCI-HA10, by intranasal administration were found to produce high titers of serum IgA. These results suggest DNA vaccines encapsulated in liposomes are efficacious in inducing complete protective immunity against respiratory influenza virus infection.
