Augmentation of immune responses to hepatitis E virus ORF2 DNA vaccination by codelivery of cytokine genes.

DNA vaccines encoding a viral structural protein have been shown to induce antiviral immune responses and provide protection against subsequent viral challenge. In the present study we show that DNA immunization with a plasmid expressing the hepatitis E virus ORF2 structural protein (pcDNA-ORF2) induced low levels of long-lasting antibody responses in the murine model. The use of plasmids expressing interleukin-2 (IL-2) and granulocyte-macrophage colony-stimulating-factor (GM-CSF) in conjunction with pcDNA-ORF2 enhanced the antibody responses generated by pORF-2. We further show that the immune responses generated by plasmid pcDNA-ORF2 can be boosted with virus-like particles composed of the ORF2 protein expressed through a baculovirus expression system.