Engineering in vitro-assembled beak and feather disease virus-like particles loaded with biomolecules

Beak and feather disease virus (BFDV) is a member of the Circoviridae family and causes psittacine beak and feather diseases (PBFD) in birds. Abnormal feathers, brittle claws and beaks, and susceptibility to secondary infections are typical sympotoms of the BFDV-infected birds. The BFDV virion possesses a single-stranded DNA genome encapsidated within a 17-22 nm non-enveloped icosahedral virions. This study evaluated the loading capacity of BFDV virus-like particles (VLPs) with different biomolecules, such as DNA, RNA, and proteins. The reassembled BFDV (ReBFDV) VLPs successfully encapsidated plasmids, small interfering RNA (siRNA), the BFDV genome, and fluorophore-coupled transferrin but not the fluorophore-coupled streptavidin. However, streptavidin conjugated with the biotinylated oligomers, which served as the nuclear factor, could be loaded into the reassembled VLPs. Using urea disruption assays, the stability of ReBFDV packing biomolecules was shown to be comparable with that of the native BFDV virions. The presence of fluorophore-coupled proteins and siRNA and the expressed proteins from plasmids inside the cells, as determined by the immunofluorescence assay, indicated the successful delivery of cargoes by the ReBFDV VLPs. An attenuation of immunogenicity and nitric oxide release was found when the cells were infected with the ReBFDV VLPs coated with polyethylene glycol.