Browsing by Subject "Beak and feather disease virus"

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    Open Access
    The porcine circovirus type 1 capsid gene promoter improves antigen expression and immunogenicity in a HIV-1 plasmid vaccine
    (BioMed Central Ltd, 2011) Tanzer, Fiona; Shephard, Enid; Palmer, Kenneth; Burger, Marieta; Williamson, Anna-Lise; Rybicki, Edward
    BACKGROUND: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. RESULTS: 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. CONCLUSIONS: We identified a novel PCV-1 genome-derived enhancer sequence that significantly increased antigen expression from plasmids in in vitro 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.
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    Open Access
    Recombinant expression of beak and feather disease virus capsid protein and assembly of virus-like particles in Nicotiana benthamiana
    (BioMed Central, 2017-09-11) Regnard, Guy L; Rybicki, Edward P; Hitzeroth, Inga I
    Background: Beak and feather disease virus (BFDV) is an important disease causing agent affecting psittacines. BFDV is highly infectious and can present as acute, chronic or subclinical disease. The virus causes immunodeficiency and is often associated with secondary infections. No commercial vaccine is available and yields of recombinant BFDV capsid protein (CP) expressed in insect cells and bacteria are yet to be seen as commercially viable, although both systems produced BFDV CP that could successfully assemble into virus-like particles (VLPs). Plants as expression systems are increasingly becoming favourable for the production of region-specific and niche market products. The aim of this study was to investigate the formation and potential for purification of BFDV VLPs in Nicotiana benthamiana. Methods: The BFDV CP was transiently expressed in N. benthamiana using an Agrobacterium-mediated system and plant expression vectors that included a bean yellow dwarf virus (BeYDV)-based replicating DNA vector. Plant-produced BFDV CP was detected using immunoblotting. VLPs were purified using sucrose cushion and CsCl density gradient centrifugation and visualised using transmission electron microscopy. Results: In this study we demonstrate that the BFDV CP can be successfully expressed in N. benthamiana, albeit at relatively low yield. Using a purification strategy based on centrifugation we demonstrated that the expressed CP can self-assemble into VLPs that can be detected using electron microscopy. These plant-produced BFDV VLPs resemble those produced in established recombinant expression systems and infectious virions. It is possible that the VLPs are spontaneously incorporating amplicon DNA produced from the replicating BeYDV plant vector. Conclusions: This is the first report of plant-made full-length BFDV CP assembling into VLPs. The putative pseudovirions could be used to further the efficacy of vaccines against BFDV.