Cowpea Mosaic Virus Nanoparticles and Empty Virus-Like Particles Show Distinct but Overlapping Immunostimulatory Properties

Abstract

Cowpea mosaic virus (CPMV) is a plant virus that has been developed for multiple biomedical and nanotechnology applications, including immunotherapy. Two key platforms are available: virus nanoparticles (VNPs) based on the complete CMPV virion, including the genomic RNA, and virus-like nanoparticles (VLPs) based on the empty CPMV (eCPMV) virion. It is unclear whether these platforms differ in terms of immunotherapeutic potential. We therefore compared their physicochemical properties and immunomodulatory activities following in situ vaccination of an aggressive ovarian tumor mouse model (ID8-Defb29/Vegf-A). In physicochemical terms, CPMV and eCPMV were very similar, and both significantly increased the survival of tumor-bearing mice and showed promising antitumor efficacy. However, they demonstrated distinct yet overlapping immunostimulatory effects due to the presence of virus RNA in wild-type particles, indicating their suitability for different immunotherapeutic strategies. Specifically, we found that the formulations had similar effects on most secreted cytokines and immune cells, but the RNA-containing CPMV particles were uniquely able to boost populations of potent antigen-presenting cells, such as tumor-infiltrating neutrophils and activated dendritic cells. Our results will facilitate the development of CPMV and eCPMV as immunotherapeutic vaccine platforms with tailored responses. IMPORTANCE The engagement of antiviral effector responses caused by viral infection is essential when using viruses or virus-like particles (VLPs) as an immunotherapeutic agent. Here, we compare the chemophysical and immunostimulatory properties of wild-type cowpea mosaic virus (CPMV) (RNA containing) and eCPMV (RNA-free VLPs) produced from two expression systems (agrobacterium-based plant expression system and baculovirus-insect cell expression). CPMV and eCPMV could each be developed as novel adjuvants to overcome immunosuppression and thus promote tumor regression in ovarian cancer (and other tumor types). To our knowledge, this is the first study to define the immunotherapeutic differences between CPMV and eCPMV, which is essential for the further development of biomedical applications for plant viruses and the selection of rational combinations of immunomodulatory reagents.

The Antitumor Efficacy of CpG Oligonucleotides is Improved by Encapsulation in Plant Virus‐Like Particles

“…These are advantageous because plant viruses are noninfectious in mammals, easy and inexpensive to produce in large quantities by molecular farming in plants, highly immunogenic, rapidly taken up by immune cells (particularly antigen‐presenting cells), and some plant viruses can induce antitumor responses when introduced into the tumor microenvironment (TME) as an in situ vaccine. [ 28–32 ] Among the diverse applications of plant viruses in drug delivery, [ 33 ] Cowpea chlorotic mottle virus (CCMV) is mainly used as a gene delivery vector. [ 34,35 ] Its potential for the delivery of CpG‐ODNs and its use as an in situ vaccine have not been explored thus far.…”

Recent Advancements of Nanomedicine towards Antiangiogenic Therapy in Cancer

“…During prior decades, the understanding of viral-based nanotechnology has improved, simultaneous with development in their design and production [131,132]. Among various virus-based nanoparticles (VNPs), plant-derived VNPs are considered safe from a human health perspective because they are not pathogenic in mammals and proteinaceous plant VNPs have appeared as a key platform for engineering with multiple drugs, imaging molecules, and targeting ligands [133,134]. VNPs emanated in various sizes, shapes, and each virus species is highly symmetrical and monodisperse.…”

Recent Advances in the Use of Plant Virus-Like Particles as Vaccines

“…The analysis of several recent publications reveals the potential application of unmodified plant VLPs without any introduced antigens as cancer immunotherapy agents [71,72]. In one study, the authors compared differently prepared nanoparticles derived from CPMV as immunotherapeutic agents in a murine ovarian cancer model.…”

“…The enhanced immunomodulatory effect apparently is due to the presence of encapsidated ssRNA in native CPMV virions, which activates Toll-like receptors 7/8. Interestingly, the chosen recombinant host can also influence the immune-stimulating properties of produced plant VLPs [72].…”