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The COVID-19 pandemic highlights the opportunity for mRNA vaccines and their nanotechnology carriers to make an impact as a countermeasure to infectious disease. As alternative to the synthetic lipid nanoparticles or mammalian viruses, we developed a tobacco mosaic virus (TMV)-based mRNA vaccine delivery platform. Specifically, purified coat protein from TMV was used to package a self-amplifying Nodamura replicon expressing the receptor binding domain (RBD) from the Omicron strain of SARS-CoV-2. The replicon construct contains the origin of assembly sequence from the tobacco mosaic virus (TMV) for encapsulation and mRNA stabilization. The nanoparticle vaccine was obtained through in vitro assembly using purified TMV coat proteins and in vitro transcribed mRNA cassettes. Cell assays confirmed delivery of self-amplifying mRNA vaccine, amplification of the transgene and expression of the target protein, RBD, in mammalian cells. Immunization of mice yielded RBDspecific IgG antibodies that demonstrated neutralization of SARS-CoV-2 using an in vitro neutralization assay. The TMV platform nanotechnology does not require ultralow freezers for storage or distribution; and the in vitro assembly method provide ‘plug-and-play’ to adapt the vaccine formulation rapidly as new strains or diseases emerge. Finally, opportunity exists to produce and self-assemble the vaccine candidate in plants through molecular farming techniques, which may allow production in the region-for the region and could make a contribution to less resourced areas of the world. 

Abstract Delivery of agrochemicals into soil presents a challenge, as the active ingredients are often hydrophobic and do not possess adequate soil mobility to reach their target pest. Previously, plant virus nanoparticles have been shown to penetrate soil and deliver agrochemicals for the treatment of plant parasitic nematodes. For example, tobacco mild green mosaic virus (TMGMV) can be functionalized with agrochemicals through bioconjugation, infusion at the coat protein interface, or encapsulation through thermal shapeshifting (rod-to-sphere). There continues to be a need to expand approaches for agrochemical display and delivery with a need for plug-and-play technology to be applicable for multiple nanoparticle platforms and agrochemicals. Toward this goal, we turned toward a bio-specific coupling strategy making use of the biotin-(strept)avidin system. Herein, we conjugated TMGMV with either avidin or biotin using azide-alkyne cycloaddition. The avidin/biotin-functionalized TMGMV nanoparticles were then characterized by gel electrophoresis and electron microscopy to confirm cargo loading and the nanoparticle’s structural integrity. Soil column assays confirmed that soil mobility was maintained upon chemical modification. Ivermectin modified with biotin or streptavidin linkers was then introduced to the TMGMV-avidin/biotin nanoparticles and binding propensity and loading were validated by QCM-D and a competitive ELISA. Finally, the ivermectin-loaded TMGMV nanoparticles were used to treatC. elegansin a gel burrowing assay, demonstrating that either pesticide loading strategy resulted in active TMGMV nanoparticle formulation that significantly reduced the mobility of nematodes, even after passing through soil. In stark contrast, free ivermectin only exhibited efficacy when applied directly to nematodes; the free pesticide was lost in the soil column—highlighting the need for a delivery system. The presented approach provides a facile plug-and-play approach for pesticide loading onto TMGMV nanoparticles. In particular, biotinylated TMGMV with streptavidin-conjugated ivermectin served as the most effective formulation. Importantly this method does not require heat, which contrasts our previous method of thermal reshaping that requires sample and pesticide exposure to temperatures > 96 °C. We envision the bio-specific loading strategy could be extended to other protein or inorganic nanoparticles to advance soil treatment strategies. 

Plant virus-like particles (VLPs) are biocompatible, non-infectious nanomaterials with promising applications as immunotherapeutics and vaccines. However, slow-release VLP formulations are needed to achieve long-term efficacy without repeated administration. VLP hydrogels allow the encapsulation and sustained delivery of VLPs, but the particles must covalently bind the hydrogel polymers to avoid premature loss. This has been achieved so far by in situ VLP polymerization, which requires high viral concentrations (5–10 mg/mL, 0.5–1 wt%) to form stable hybrid VLP–hydrogel networks and this complicates scalability and clinical translation. Here, we developed a novel swell-and-click method that led to successful VLP scaffold formation regardless of the viral load used. As a result, VLP-functionalized hydrogels were fabricated with viral concentrations as low as 0.1–1 mg/mL (0.01–0.1 % wt%) without compromising the scaffold stability on the process. The hydrogels incorporate VLPs during swelling, followed by copper-free click chemistry reactions that bind the particles covalently to the polymer. The swell-and-click method also resulted in more than a two-fold enhancement in VLP uptake into the hydrogels and it provides a means of combined burst release and prolonged sustained release, desired traits for cancer immunotherapy treatment. The present work introduces a novel methodology for the design of VLP-based hydrogels, which could facilitate the scalability of the fabrication process and move a significant step forward towards clinical translation of long-term VLP vaccination in cancer disease. 

The dramatic effectiveness of recent mRNA (mRNA)-based COVID vaccines delivered in lipid nanoparticles has highlighted the promise of mRNA therapeutics in general. In this report, we extend our earlier work on self-amplifying mRNAs delivered in spherical in vitro reconstituted virus-like particles(VLPs), and on drug delivery using cylindrical virus particles. In particular, we carry out separate in vitro assemblies of a self-amplifying mRNA gene in two different virus-like particles: one spherical, formed with the capsid protein of cowpea chloroticmottle virus (CCMV), and the other cylindrical, formed from the capsid protein of tobacco mosaic virus (TMV). The mRNA gene is rendered self-amplifying by genetically fusing it to the RNA-dependent RNA polymerase (RdRp) of Nodamura virus, and the relative efficacies of cell uptake and downstream protein expression resulting from their CCMV- and TMV-packaged forms are compared directly. This comparison is carried out by their transfections into cells in culture: expressions of two self-amplifying genes, enhanced yellow fluorescent protein (EYFP) and Renilla luciferase (Luc), packaged alternately in CCMV and TMV VLPs, are quantified by fluorescence and chemiluminescence levels, respectively, and relative numbers of the delivered mRNAs are measured by quantitative real-time PCR. The cellular uptake of both forms of these VLPs is further confirmed by confocal microscopy of transfected cells. Finally, VLP-mediated delivery of the self-amplifying- mRNA in mice following footpad injection is shown by in vivo fluorescence imaging to result in robust expression of EYFP in the draining lymph nodes, suggesting the potential of these plant virus-like particles as a promising mRNA gene and vaccine delivery modality. These results establish that both CCMV and TMV VLPs can deliver their in vitro packaged mRNA genes to immune cells and that their self-amplifying forms significantly enhance in situ expression. Choice of one VLP (CCMV or TMV) over the other will depend on which geometry of nucleocapsid is self-assembled more efficiently for a given length and sequence of RNA, and suggests that these plant VLP gene delivery systems will prove useful in a wide variety of medical applications, both preventive and therapeutic. 

Grafting-from ROMP-derived polynorbornene-basedUOconjugates retain bioactivity, improves stability, and evades anti-PEG recognition and could be a potential PEG alternative. 

In this work, we introduce a 3D-printable virus-like particle (VLP)-enhanced cross-linked biopolymer system. 

Abstract Chemical pesticide delivery is a fundamental aspect of agriculture. However, the extensive use of pesticides severely endangers the ecosystem because they accumulate on crops, in soil, as well as in drinking and groundwater. New frontiers in nano-engineering have opened the door for precision agriculture. We introduced Tobacco mild green mosaic virus (TMGMV) as a viable delivery platform with a high aspect ratio and favorable soil mobility. In this work, we assess the use of TMGMV as a chemical nanocarrier for agriculturally relevant cargo. While plant viruses are usually portrayed as rigid/solid structures, these are “dynamic materials,” and they “breathe” in solution in response to careful adjustment of pH or bathing media [e.g., addition of solvent such as dimethyl sulfoxide (DMSO)]. Through this process, coat proteins (CPs) partially dissociate leading to swelling of the nucleoprotein complexes—allowing for the infusion of active ingredients (AI), such as pesticides [e.g., fluopyram (FLP), clothianidin (CTD), rifampicin (RIF), and ivermectin (IVM)] into the macromolecular structure. We developed a “breathing” method that facilitates inter-coat protein cargo loading, resulting in up to  ~ 1000 AIs per virion. This is of significance since in the agricultural setting, there is a need to develop nanoparticle delivery strategies where the AI is not chemically altered, consequently avoiding the need for regulatory and registration processes of new compounds. This work highlights the potential of TMGMV as a pesticide nanocarrier in precision farming applications; the developed methods likely would be applicable to other protein-based nanoparticle systems.