Analysis of the size of DNA packaged by the human JC virus-like particle

Incorporation of Endosomolytic Peptides with Varying Disruption Mechanisms into EGFR-Targeted Protein Conjugates: The Effect on Intracellular Protein Delivery and EGFR Specificity in Breast Cancer Cells

Intracellular delivery of protein therapeutics remains a significant challenge limiting the majority of clinically available protein drugs to extracellular targets. Strategies to deliver proteins to subcellular compartments have traditionally relied on cell-penetrating peptides, which can drive enhanced internalization but exhibit unreliable activity and are rarely able to target specific cells, leading to off-target effects. Moreover, few design rules exist regarding the relative efficacy of various endosomal escape strategies in proteins. Accordingly, we developed a simple fusion modification approach to incorporate endosomolytic peptides onto epidermal growth factor receptor (EGFR)-targeted protein conjugates and performed a systematic comparison of the endosomal escape efficacy, mechanism of action, and capacity to maintain EGFR-targeting specificity of conjugates modified with four different endosomolytic sequences of varying modes of action (Aurein 1.2, GALA, HA2, and L17E). Use of the recently developed Gal8-YFP assay indicated that the fusion of each endosomolytic peptide led to enhanced endosomal disruption. Additionally, the incorporation of each endosomolytic peptide increased the half-life of the internalized protein and lowered lysosomal colocalization, further supporting the membrane-disruptive capacity. Despite this, only EGFR-targeted conjugates modified with Aurein 1.2 or GALA maintained EGFR specificity. These results thus demonstrated that the choice of endosomal escape moiety can substantially affect targeting capability, cytotoxicity, and bioactivity and provided important new insights into endosomolytic peptide selection for the design of targeted protein delivery systems.

Peptide-guided JC polyomavirus-like particles specifically target bladder cancer cells for gene therapy

The ultimate goal of gene delivery vectors is to establish specific and effective treatments for human diseases. We previously demonstrated that human JC polyomavirus (JCPyV) virus-like particles (VLPs) can package and deliver exogenous DNA into susceptible cells for gene expression. For tissue-specific targeting in this study, JCPyV VLPs were conjugated with a specific peptide for bladder cancer (SPB) that specifically binds to bladder cancer cells. The suicide gene thymidine kinase was packaged and delivered by SPB-conjugated VLPs (VLP-SPBs). Expression of the suicide gene was detected only in human bladder cancer cells and not in lung cancer or neuroblastoma cells susceptible to JCPyV VLP infection in vitro and in vivo, demonstrating the target specificity of VLP-SPBs. The gene transduction efficiency of VLP-SPBs was approximately 100 times greater than that of VLPs without the conjugated peptide. JCPyV VLPs can be specifically guided to target particular cell types when tagged with a ligand molecule that binds to a cell surface marker, thereby improving gene therapy.

Agmatine-grafted bioreducible poly(l-lysine) for gene delivery with low cytotoxicity and high efficiency

Bioreducible cationic polymers have gained considerable attention in gene delivery due to their low cytotoxicity and high efficiency. In the present work, we reported a cationic polymer, poly(disulfide-l-lysine)-g-agmatine (denoted as SSL-AG), and evaluated its ability to transfer pEGFP-ZNF580 plasmid (pZNF580) into human umbilical vein endothelial cells (HUVECs). This SSL-AG polymeric carrier efficiently condensed pZNF580 into positively charged particles (<200 nm) through electrostatic interaction. This carrier also exhibited excellent buffering capacity in the physiological environment, good pDNA protection against enzymatic degradation and rapid pDNA release in a highly reducing environment mainly because of the responsive cleavage of disulfide bonds in the polymer backbone. The hemolysis assay and in vitro cytotoxicity assay suggested that the SSL-AG carrier and corresponding gene complexes possessed both good hemocompatibility and great cell viability in HUVECs. The cellular uptake of the SSL-AG/Cy5-oligonucleotide group was 3.6 times that of the poly(l-lysine)/Cy5-oligonucleotide group, and its mean fluorescence intensity value was even higher than that of the PEI 25 kDa/Cy5-oligonucleotide group. Further, the intracellular trafficking results demonstrated that the SSL-AG/Cy5-oligonucleotide complexes exhibited a high nucleus co-localization rate (CLR) value (36.0 ± 2.8%, 3.4 times that of the poly (l-lysine)/Cy5-oligonucleotide group, 1.6 times that of the poly(disulfide-l-lysine)-g-butylenediamine/Cy5-oligonucleotide group) at 24 h, while the endo/lysosomal CLR value was relatively low. This suggested that SSL-AG successfully delivered plasmid into HUVECs with high cellular uptake, rapid endosomal escape and efficient nuclear accumulation owing to the structural advantages of the bioreducible and agmatine groups. In vitro transfection assay also verified the enhanced transfection efficiency in the SSL-AG/pZNF580 group. Furthermore, the results of CCK-8, cell migration and in vitro/vivo angiogenesis assays revealed that pZNF580 delivered by SSL-AG could effectively enhance the proliferation, migration and vascularization of HUVECs. In a word, the SSL-AG polymer has great potential as a safe and efficient gene carrier for gene therapy.

The 3Ds in virus-like particle based-vaccines: "Design, Delivery and Dynamics"

Vaccines need to be rationally designed in order be delivered to the immune system for maximizing induction of dynamic immune responses. Virus‐like particles (VLPs) are ideal platforms for such 3D vaccines, as they allow the display of complex and native antigens in a highly repetitive form on their surface and can easily reach lymphoid organs in intact form for optimal activation of B and T cells. Adjusting size and zeta potential may allow investigators to further fine‐tune delivery to lymphoid organs. An additional way to alter vaccine transfer to lymph nodes and spleen may be the formulation with micron‐sized adjuvants that creates a local depot and results in a slow release of antigen and adjuvant. Ideally, the adjuvant in addition stimulates the innate immune system. The dynamics of the immune response may be further enhanced by inclusion of Toll‐like receptor ligands, which many VLPs naturally package. Hence, considering the 3Ds in vaccine development may allow for enhancement of their attributes to tackle complex diseases, not usually amenable to conventional vaccine strategies.

Inhibition of human lung adenocarcinoma growth and metastasis by JC polyomavirus-like particles packaged with an SP-B promoter-driven CD59-specific shRNA

Lung cancer ranks first in both incidence and mortality and is a major health concern worldwide. Upon recognition of specific antigens on tumor cells, complement-dependent cytotoxicity (CDC) is activated, arresting cell growth or inducing apoptosis. However, by overexpressing CD59, a membrane complement regulatory protein (mCRP), lung cancer cells develop resistance to CDC. We previously showed that virus-like particles (VLPs) of human JC polyomavirus (JCPyV) could be used as a gene therapy vector to carry a suicide gene expression plasmid with a lung-specific promoter (SP-B (surfactant protein B)) for lung adenocarcinomas. Herein, we designed a CD59-specific short hairpin RNA (shRNA) expression plasmid driven by SP-B (pSPB-shCD59) to effectively and specifically inhibit CD59 overexpression in lung cancer cells. Treatment of lung cancer cells in vitro with JCPyV VLPs containing pSPB-shCD59 (pSPB-shCD59/VLPs) induces CDC and death of cancer cells. Mice that were subcutaneously injected with human lung cancer cells showed an 87% inhibition in tumor growth after tail vein injection of pSPB-shCD59/VLPs. Moreover, in a mouse model of lung cancer metastasis, a reduction in the lung weight by 39%, compared with the control group, was observed in mice treated with pSPB-shCD59/VLPs after tail vein injection of human lung cancer cells. Furthermore, tissue sectioning showed that the number and size of tumors produced was significantly reduced in the lungs of mice in the treatment group than those of the untreated group, indicating inhibition of metastasis by pSPB-shCD59/VLPs. Together, these results demonstrate the potential of pSPB-shCD59/VLPs as a therapeutic agent for CD59 overexpressed lung cancer.

The biomedical and bioengineering potential of protein nanocompartments

Protein nanocompartments (PNCs) are self-assembling biological nanocages that can be harnessed as platforms for a wide range of nanobiotechnology applications. The most widely studied examples of PNCs include virus-like particles, bacterial microcompartments, encapsulin nanocompartments, enzyme-derived nanocages (such as lumazine synthase and the E2 component of the pyruvate dehydrogenase complex), ferritins and ferritin homologues, small heat shock proteins, and vault ribonucleoproteins. Structural PNC shell proteins are stable, biocompatible, and tolerant of both interior and exterior chemical or genetic functionalization for use as vaccines, therapeutic delivery vehicles, medical imaging aids, bioreactors, biological control agents, emulsion stabilizers, or scaffolds for biomimetic materials synthesis. This review provides an overview of the recent biomedical and bioengineering advances achieved with PNCs with a particular focus on recombinant PNC derivatives.

Engineering protein nanocages as carriers for biomedical applications

Protein nanocages have been explored as potential carriers in biomedicine. Formed by the self-assembly of protein subunits, the caged structure has three surfaces that can be engineered: the interior, the exterior and the intersubunit. Therapeutic and diagnostic molecules have been loaded in the interior of nanocages, while their external surfaces have been engineered to enhance their biocompatibility and targeting abilities. Modifications of the intersubunit interactions have been shown to modulate the self-assembly profile with implications for tuning the molecular release. We review natural and synthetic protein nanocages that have been modified using chemical and genetic engineering techniques to impart non-natural functions that are responsive to the complex cellular microenvironment of malignant cells while delivering molecular cargos with improved efficiencies and minimal toxicity.

Gene Therapy for Human Lung Adenocarcinoma Using a Suicide Gene Driven by a Lung-Specific Promoter Delivered by JC Virus-Like Particles

Lung adenocarcinoma, the most commonly diagnosed type of lung cancer, has a poor prognosis even with combined surgery, chemotherapy, or molecular targeted therapies. Most patients are diagnosed with an in-operable advanced or metastatic disease, both pointing to the necessity of developing effective therapies for lung adenocarcinoma. Surfactant protein B (SP-B) has been found to be overexpressed in lung adenocarcinoma. In addition, it has also been demonstrated that human lung adenocarcinoma cells are susceptible to the JC polyomavirus (JCPyV) infection. Therefore, we designed that the JCPyV virus-like particle (VLP) packaged with an SP-B promoter-driven thymidine kinase suicide gene (pSPB-tk) for possible gene therapy of human lung adenocarcinoma. Plasmids expressing the GFP (pSPB-gfp) or thymidine kinase gene (pSPB-tk) under the control of the human SP-B promoter were constructed. The promoter's tissue specificity was tested by transfection of pSPB-gfp into A549, CH27, and H460 human lung carcinoma cells and non-lung cells. The JCPyV VLP's gene transfer efficiency and the selective cytotoxicity of pSPB-tk combined with ganciclovir (GCV) were tested in vitro and in a xenograft mouse model. In the current study, we found that SP-B promoter-driven GFP was specifically expressed in human lung adenocarcinoma (A549) and large cell carcinoma (H460) cells. JCPyV VLPs were able to deliver a GFP reporter gene into A549 cells for expression. Selective cytotoxicity was observed in A549 but not non-lung cells that were transfected with pSPB-tk or infected with pSPB-tk-carrying JCPyV VLPs. In mice injected with pSPB-tk-carrying JCPyV VLPs through the tail vein and treated with ganciclovir (GCV), a potent 80% inhibition of growth of human lung adenocarcinoma nodules resulted. The JCPyV VLPs combined with the use of SP-B promoter demonstrates effectiveness as a potential gene therapy against human lung adenocarcinoma.

Antigen delivery by virus-like particles for immunotherapeutic vaccination

Virus-like particles (VLPs) are an effective means of establishing both prophylactic and therapeutic immunity against their source virus or heterologous antigens. The particulate nature and repetitive structure of VLPs makes them ideal for stimulating potent immune responses. Epitopes delivered by VLPs can be presented on MHC-II for stimulation of a humoral immune response, or cross-presented onto MHC-I leading to cell-mediated immunity. VLPs as particulate subunit vaccine carriers are showing promise in preclinical and clinical trials for the treatment of many conditions including cancer, autoimmunity, allergies and addiction. Supporting the delivery of almost any form of antigenic material, VLPs are ideal candidate vectors for development of future vaccines.

Inhibition of human diffuse large B-cell lymphoma growth by JC polyomavirus-like particles delivering a suicide gene

Background

Diffuse large B-cell lymphoma (DLBCL) is one of the most common types of aggressive B-cell non-Hodgkin lymphoma. About one-third of patients are either refractory to the treatment or experience relapse afterwards, pointing to the necessity of developing other effective therapies for DLBCL. Human B-lymphocytes are susceptible to JC polyomavirus (JCPyV) infection, and JCPyV virus-like particles (VLPs) can effectively deliver exogenous genes to susceptible cells for expression, suggesting the feasibility of using JCPyV VLPs as gene therapy vectors for DLBCL.

Methods

The JCPyV VLPs packaged with a GFP reporter gene were used to infect human DLBCL cells for gene delivery assay. Furthermore, we packaged JCPyV VLPs with a suicide gene encoding thymidine kinase (TK) to inhibit the growth of DLBCL in vitro and in vivo.

Results

Here, we show that JCPyV VLPs effectively entered human germinal center B-cell-like (GCB-like) DLBCL and activated B-cell-like (ABC-like) DLBCL and expressed the packaged reporter gene in vitro. As measured by the MTT assay, treatment with tk-VLPs in combination with gancyclovir (GCV) reduced the viability of DLBCL cells by 60%. In the xenograft mouse model, injection of tk-VLPs through the tail vein in combination with GCV administration resulted in a potent 80% inhibition of DLBCL tumor nodule growth.

Conclusions

Our results demonstrate the effectiveness of JCPyV VLPs as gene therapy vectors for human DLBCL and provide a potential new strategy for the treatment of DLBCL.

Virus-Like Particles, a Versatile Subunit Vaccine Platform

Virus-like particles (VLPs) can be spontaneously formed after expression of self-polymerising viral capsid proteins. VLPs structurally resemble their native source virus, maintaining immunological relevance by retaining formation of immunogenic motifs with natural conformation. The absence of the virus genome renders VLPs safe for administration as a subunit vaccine. VLPs can target both arms of the immune response, with some VLPs initiating production of specific antibodies and others activating cytotoxic T cells. VLPs are also exceptionally versatile, conferring protection against the host virus or acting as a scaffold for antigenic molecules. In addition, VLP can support intraparticulate encapsulation for immunomodulation and gene delivery. VLP vaccines have been developed for prophylactic protection against infectious organisms, and therapeutic treatment of conditions such as Alzheimer’s disease, hypertension, and cancer. With an expanding list of vaccine candidates, VLP vaccines are a promising field with a wide range of applications.

Inhibition of BK virus replication in human kidney cells by BK virus large tumor antigen-specific shRNA delivered by JC virus-like particles

Polyomavirus-associated nephropathy (PVAN) due to lytic infection by the BK polyomavirus (BKPyV) remains an important cause of allograft dysfunction and graft loss in renal transplant recipients. PVAN is commonly treated by reducing the dosage of immunosuppressive drugs and adding adjuvant antiviral agents, but the outcomes have been less than satisfactory. The BKPyV early protein large tumor antigen (LT) is indispensable for viral genome replication and viral late protein expression. Therefore, suppressing LT expression may be a way to inhibit BKPyV replication without harming the host human kidney cells. Previous studies have shown that JC polyomavirus (JCPyV) virus-like particles (VLPs), which have tropism for the human kidney, can package and transfer exogenous genes into human kidney cells for expression. In this study, we constructed an expression plasmid for a BKPyV LT-specific shRNA (shLT) and used JCPyV VLPs as a delivery vehicle to transduce the shLT plasmid into BKPyV-infected human kidney cells. The expression of BKPyV early (LT) and late (VP1) proteins was examined after transduction by immunofluorescence microscopy and Western blotting. We found that transduction with the shLT plasmid decreased the proportions of BKPyV LT- and VP1-expressing cells by 73% and 82%, respectively, relative to control. The viral genomes were also decreased by 56%. These results point to the promising possibility of developing shLT-transducing JCPyV VLPs as a specific anti-BKPyV approach for PVAN treatment.

Pseudovirus mimics cell entry and trafficking of the human polyomavirus JCPyV

The normally asymptomatic human polyomavirus, JCPyV, is the causative agent of a rare but fatal demyelinating disease known as progressive multifocal leukoencephalopathy (PML). Individuals at risk for developing PML include those with AIDS, with other underlying immunosuppressive diseases, and in patients treated with immunomodulatory regimens. Drugs to prevent viral reactivation in the setting of immunosuppression or immunomodulation could be used to sustain lives. Development of such drugs has been impeded by the difficulty of growing and studying the virus. We sought to develop a more efficient method for screening drugs that inhibit viral infection. Pseudovirus models have been developed which may be of use in pharmaceutical research. The use of pseudoviruses as models for viral infection is dependent on them using similar pathways for infection as virus. We screened known inhibitors of viral entry for their ability to block pseudovirus infection. Here we show that the pseudovirus based on the human polyomavirus JCPyV recapitulates virus binding, entry and trafficking. This system can be used for high-throughput screening of antiviral drugs.

Production and biomedical applications of virus-like particles derived from polyomaviruses

Virus-like particles (VLPs), aggregates of capsid proteins devoid of viral genetic material, show great promise in the fields of vaccine development and gene therapy. These particles spontaneously self-assemble after heterologous expression of viral structural proteins. This review will focus on the use of virus-like particles derived from polyomavirus capsid proteins. Since their first recombinant production 27 years ago these particles have been investigated for a myriad of biomedical applications. These virus-like particles are safe, easy to produce, can be loaded with a broad range of diverse cargoes and can be tailored for specific delivery or epitope presentation. We will highlight the structural characteristics of polyomavirus-derived VLPs and give an overview of their applications in diagnostics, vaccine development and gene delivery.

Construction and characterization of virus-like particles: a review

Over the last three decades, virus-like particles (VLPs) have evolved to become a widely accepted technology, especially in the field of vaccinology. In fact, some VLP-based vaccines are currently used as commercial medical products, and other VLP-based products are at different stages of clinical study. Several remarkable advantages have been achieved in the development of VLPs as gene therapy tools and new nanomaterials. The analysis of published data reveals that at least 110 VLPs have been constructed from viruses belonging to 35 different families. This review therefore discusses the main principles in the cloning of viral structural genes, the relevant host systems and the purification procedures that have been developed. In addition, the methods that are used to characterize the structural integrity, stability, and components, including the encapsidated nucleic acids, of newly synthesized VLPs are analyzed. Moreover, some of the modifications that are required to construct VLP-based carriers of viral origin with defined properties are discussed, and examples are provided.