LONG-TERM ANTINUCLEOPROTEIN CELLULAR AND HUMORAL IMMUNITY IS INDUCED BY INTRAMUSCULAR INJECTION OF PLASMID DNA CONTAINING NP GENE

Cytolytic T-lymphocyte-mediated killing is thought to be an important effector mechanism in controlling viral infections. Recently, we repor ted that intramuscular injection of plasmid DNA containing the nucleop rotein (NP) gene of the influenza virus resulted in generating nucleop rotein-specific cytolytic T cells and antibodies. Gene-injected mice w ere subsequently protected from a lethal challenge with live influenza virus. Here we show that a single intramuscular injection of a small dose of nucleoprotein plasmid DNA generates nucleoprotein-specific cel lular and humoral immune responses that last 1 year. The cellular resp onse is associated with the CD8+ subpopulation of T cells. Thus, plasm id DNA injections can be used to induce long-lasting immune responses against the viral gene product without an exposure to live virus itsel f.