The porcine circovirus type 1 capsid gene promoter improves antigen expression and immunogenicity in a HIV-1 plasmid vaccine

• Main Authors: Burger Marieta, Palmer Kenneth E, Shephard Enid G, Tanzer Fiona L, Williamson Anna-Lise, Rybicki Edward P
• Format: Article
• Language: English
• Published: BMC 2011-02-01
• Series: Virology Journal
• Online Access: http://www.virologyj.com/content/8/1/51

<p>Abstract</p> <p>Background</p> <p>One of the promising avenues for development of vaccines against Human immunodeficiency virus type 1 (HIV-1) and other human pathogens is the use of plasmid-based DNA vaccines. However, relatively large doses of plasmid must be injected for a relatively weak response. We investigated whether genome elements from Porcine circovirus type 1 (PCV-1), an apathogenic small ssDNA-containing virus, had useful expression-enhancing properties that could allow dose-sparing in a plasmid vaccine.</p> <p>Results</p> <p>The linearised PCV-1 genome inserted 5' of the CMV promoter in the well-characterised HIV-1 plasmid vaccine pTHgrttnC increased expression of the polyantigen up to 2-fold, and elicited 3-fold higher CTL responses in mice at 10-fold lower doses than unmodified pTHgrttnC. The PCV-1 capsid gene promoter (Pcap) alone was equally effective. Enhancing activity was traced to a putative composite host transcription factor binding site and a "Conserved Late Element" transcription-enhancing sequence previously unidentified in circoviruses.</p> <p>Conclusions</p> <p>We identified a novel PCV-1 genome-derived enhancer sequence that significantly increased antigen expression from plasmids in <it>in vitro </it>assays, and improved immunogenicity in mice of the HIV-1 subtype C vaccine plasmid, pTHgrttnC. This should allow significant dose sparing of, or increased responses to, this and other plasmid-based vaccines. We also report investigations of the potential of other circovirus-derived sequences to be similarly used.</p>