Protection and antibody responses in different strains of mouse immunized with plasmid DNAs encoding influenza virus haemagglutinin, neuraminidase and nucleoprotein

Protection against influenza virus infection and antibody responses in mice vaccinated with plasmid DNAs encoding haemagglutinin (HA), neuraminidase (NA) and nucleoprotein (NP) were compared among BALB/c (H-2d), B10 (H-2b) and C3H (H-2k) mice. Mice were inoculated with each DNA construct twice, 3 weeks apart, at a dose of 1 microg per mouse by particle-mediated DNA transfer (gene gun) to the epidermis. They were challenged with a lethal dose of the homologous virus 7 days after the second vaccination. NA-DNA provided significant protection in all strains of mouse, whereas HA-DNA afforded significant protection only in BALB/c mice. The serum antibody titres against NA or HA molecules in BALB/c, C3H and B10 mice were high, intermediate and low, respectively. NP-DNA failed to provide protection in any strain of mouse, and elicited low titres of anti-NP antibodies. These results suggest that NA-DNA can be used as a vaccine component to provide effective protection against influenza virus infection in various strains of mouse.