Identification of effective constituents of influenza vaccine by immunization with plasmid DNAs encoding viral proteins.

The use of plasmid DNA encoding influenza viral proteins to vaccinate animals constitutes a promising approach to the development of effective subunit vaccines. This review describes the results obtained by the immunization of mice with such plasmid DNAs. (i) Both hemagglutinin (HA)- and neuraminidase (NA)-expressing DNAs for the surface glycoproteins from A/PR/8/34 (H1N1) or B/Ibaraki/2/85 virus can provide the most effective protection against influenza A-type or B-type virus infection among the various viral protein-expressing DNAs tested in BALB/c mice. (ii) A mixture of plasmid DNAs encoding HA and NA can provide more effective protection against virus challenge than plasmid DNA encoding HA or NA alone in BALB/c mice. (iii) NA-DNA can provide protection against infection not only by homologous virus but also by drift viruses. (iv) HA-DNA from A/PR/8/34 (H1N1) virus provides significant protection only in BALB/c (H-2(b)) mice, whereas HA-DNA from B/Ibaraki/2/85 virus affords significant protection in BALB/c, B10 (H-2(d)), and C3H (H-2(k)) mice. NA-DNA from both A-type and B-type viruses provides significant protection in the three strains of mice. These results suggest that both HA and NA molecules should be used as vaccine components to provide effective protection against influenza A-type and B-type virus infection in genetically heterogeneous humans.