Vaccination with allergen-IL-18 fusion DNA protects against, and reverses established, airway hyperreactivity in a murine asthma model

Vaccination with naked DNA encoding a specific allergen has been shown prev iously to prevent, but not reverse, the development of allergen-induced air way hyperresponsiveness (AHR), To enhance the effectiveness of DNA vaccine therapies and make possible the treatment of established AHR, we developed a DNA vaccination plasmid containing OVA cDNA fused to IL-18 cDNA, Vaccinat ion of naive mice either with this fusion DNA construct or with an OVA cDNA -containing plasmid protected the mice from the subsequent induction of AHR , Protection from AHR correlated with increased IFN-gamma production and re duced OVA-specific IgE production, The protection appeared to be mediated b y IFN-gamma and CD8(+) cells because treatment of mice with neutralizing an ti-IFN-gamma mAb or with depleting anti-CD8 mAb abolished the protective ef fect. Moreover, vaccination of mice with preexisting AHR with the OVA-IL-18 fusion DNA, but not with the OVA cDNA plasmid, reversed established AHR, r educed allergen-specific IL-4, and increased allergen-specific IFN-gamma pr oduction. Thus, combining IL-18 cDNA with OVA cDNA resulted in a vaccine co nstruct that protected against the development of AHR, and that was unique among cDNA constructs in its capacity to reverse established AHR.