Particle formation by a conserved domain of the herpes simplex virus protein VP22 facilitating protein and nucleic acid delivery

VP22, a structural protein of herpes simplex virus, exhibits unusual traffi cking properties which we proposed might be exploited in gene and protein d elivery applications. To pursue the use of the protein itself for cargo del ivery into cells, we developed an expression system for the C-terminal half of VP22, residues 159-301 (VP22.C1), and purified the protein in high yiel ds. Addition of short oligonucleotides (ODNs) induced the assembly of novel particles, which were regular spheres with a size range of 0.3 to 1.0 mum in diameter, incorporating both protein and ODN. Following the particles in living cells using fluorescently tagged ODNs, we show that they enter effi ciently within 2-4 h, and reside stably in the cell cytoplasm for up to sev eral days. Remarkably, however, light activation induced particle disruptio n and release of the protein and ODN to the nucleus and cytoplasm within se conds, a process that we have captured by time lapse microscopy. In additio n to delivering antisense ODNs, ribozymes, and RNA/DNA hybrids, the VP22.C1 protein could also be modified to include peptides or proteins. These part icles have the potential for delivery of a wide range of therapeutic agents in gene therapy and vaccine development.