Plant-Produced Viral Nanoparticles Decorated with Nanobodies Against HER2 Improve Retention and Recruitment of Immune Cells in Solid Tumors.

Potato virus X (PVX), a filamentous, positive-sense RNA plant virus, has been engineered into a molecular tool for diverse biotechnological applications, including cancer cell targeting. Here, we present the production and functional characterization of genetically-encoded PVX-derived nanoparticles decorated with nanobodies targeting two common receptors in human cancer cells, epidermal growth factor receptor (EGFR) and human epidermal growth factor 2 (HER2). We first generated a series of PVX-derived nanoparticles displaying distinct nanobodies against EGFR and HER2 in Nicotiana benthamiana plants. Self-assembly and structural integrity of the recombinant nanoparticles were confirmed by immunogold electron microscopy. We next characterized in vitro the cancer-cell binding capacity of the different recombinant viral nanoparticles (VNPs) by flow cytometry and confocal microscopy. Select VNPs were further assayed in a pilot in vivo study using tumor-bearing mice. Preliminary results showed that nanobody decoration can increase retention time and myeloid cell recruitment in the tumor microenvironment in HER2+ mouse tumor models in vivo. Nanobody-displaying PVX-derived nanoparticles may constitute a new plant-produced biotechnological product for cancer immunotherapy.