Figure 1.

In vivo genetic complementation assay to assess the expression of a full-length feline immunodeficiency virus (FIV) Pr50^Gag protein, both with and without His₆-tag, resulting in the release of virus-like particles (VLPs) that can package FIV sub-genomic RNA. (A) Schematic representation of the FIV genome, FIV full-length eukaryotic Gag expression plasmids with His₆-tag (AD2) and without His₆-tag (AD3), and the FIV sub-genomic transfer vector, MB87 [36] serving as a source of packageable RNA. (B) Graphical representation of the design of the genetic complementation assay. Following co-transfection of the transfer vector MB87 with either of the Gag-expression vectors (AD2 and AD3) in 293T cells should result in production of VLPs containing MB87-specific RNA due to the presence of the packaging signal (Ψ) on the vector. (C-upper panel) RT-PCR amplification of MB87, an FIV-based transfer vector RNA, packaged by VLPs from His₆-tag (+) and His₆-tag (−) Gag clones from a representative experiment. (C-lower panel) The relative packaging efficiency (RPE) of the FIV-based transfer vector (MB87) RNA by VLPs produced by Gag expression plasmids either with His₆-tag (AD2) or without His₆-tag (AD3), as measured by quantitative real time RT-PCR (qRT-PCR) conducted in triplicates.