Immunization of livestock with DNA vaccines: current studies and future prospects.

Early studies using DNA immunization suggest the potential benefits of this form of immunization including: long-lived immunity, a broad spectrum of immune responses (both cell-mediated immunity and humoral responses) and the simultaneous induction of immunity to a variety of pathogens through the use of multivalent vaccines. Using marine and cow models, we studied methods to enhance and direct the immune response to polynucleotide vaccines. We demonstrated the ability to modulate the magnitude and direction of the immune response by co-administration of plasmid encoded cytokines and antigen. Also, we clearly demonstrated that the cellular components (cytosolic, membrane-anchored, or extracellular) to which the expressed antigen is delivered determines the types of immune responses induced. Since induction of immunity at mucosal surfaces (route of entry for many pathogens) is critical to prevent infection, various methods of delivering polynucleotide vaccines to animals including mucosal surfaces have been attempted and are described as future prospects for improving immune responses by DNA vaccination.