PP7 virus-like particle as a functional peptide carrying platform

Virus-like particles (VLPs) have attracted attention as therapeutic platforms for the delivery of peptide-based motifs for immunology, cell targeting, and drug delivery. The functional peptide sequences of interest are covalently attached to the VLP surface by either genetic fusion or bioconjugation techniques. Here, we report our initial exploration of the Leviviridae PP7 bacteriophage capsid as a platform for the genetically-programmed display of multiple peptide sequences of therapeutic and targeting interest. These peptides include short and long sequences that bind cell-surface EGF or transferrin receptors, as well as examples of other functional (Z-domain) and antigenic (OVA) peptides. The PP7 structure is far more tolerant than the closely related Q VLP to self-assembly of C- or N-terminally extended capsid proteins. Some of these constructs were able to form stable and homogeneous particles entirely from such proteins, thereby displaying exactly 180 copies of the functional peptide on the VLP surface, a property not shared by other Leviviridae-based platforms. Preliminary exploration of the chemical reactivity of the PP7 particle also shows it to be highly tolerant toward standard bioconjugation techniques. PP7 is therefore an excellent candidate for elaboration into useful diagnostic and therapeutic agents