Enhancement of mucosal immune responses to the influenza virus HA protein by alternative approaches to DNA immunization

DNA immunization provides many advantages as an approach to prevent infecti ous diseases. However, although previous studies using this approach have d emonstrated immune responses in serum, they were not successful in inducing significant levels of antibodies in secretions. In this study, plasmid DNA s expressing the influenza virus hemagglutinin glycoprotein have been evalu ated for their ability to induce antibody responses in serum and saliva whe n used alone or along with either liposomes or bioadhesive polymers as muco sal delivery vehicles. Significant levels of virus-specific Ig in serum as well as secretory IgA in saliva were detected in mice following mucosal DNA immunization. These antibodies were found to block the infectivity of the virus using a plaque reduction assay. Our findings thus indicate that mucos al DNA immunization with specific delivery systems can elicit virus-specifi c antibody responses in serum as well as IgA responses at mucosal surfaces.