Electric pulses increase the immunogenicity of an influenza DNA vaccine injected intramuscularly in the mouse.

Vaccination by intramuscular injection of naked DNA is very efficient in the mouse, but immunogenicity of DNA vaccines needs to be improved in man. The aim of our study was to determine in BALB/c mice if suitable electric pulses delivered to the muscle after DNA injection--a procedure called electrotransfer--could improve the immunogenicity of suboptimal doses of a DNA vaccine expressing the influenza hemagglutinin protein. The results show a significant enhancement of the cellular and antibody responses following electrotransfer for the 1- and 10-microg DNA doses, respectively, but no effect on a lower dose. At the 10-microg dose, the IgG and hemagglutination inhibition mean titres were increased 25-fold and the inter-individual variability was markedly reduced.