Protein transduction into human cells by adenovirus dodecahedron using WW domains as universal adaptors

Overcoming biological barriers by virus-like drug particles for drug delivery

Virus-like particles (VLPs) have natural structural antigens similar to those found in viruses, making them valuable in vaccine immunization. Furthermore, VLPs have demonstrated significant potential in drug delivery, and emerged as promising vectors for transporting chemical drug, genetic drug, peptide/protein, and even nanoparticle drug. With virus-like permeability and strong retention, they can effectively target specific organs, tissues or cells, facilitating efficient intracellular drug release. Further modifications allow VLPs to transfer across various physiological barriers, thus acting the purpose of efficient drug delivery and accurate therapy. This article provides an overview of VLPs, covering their structural classifications, deliverable drugs, potential physiological barriers in drug delivery, strategies for overcoming these barriers, and future prospects.

Evaluation of the human type 3 adenoviral dodecahedron as a vector to target acute myeloid leukemia

Intensive systemic chemotherapy is the gold standard of acute myeloid leukemia (AML) treatment and is associated with considerable off-target toxicities. Safer and targeted delivery systems are thus urgently needed. In this study, we evaluated a virus-like particle derived from the human type 3 adenovirus, called the adenoviral dodecahedron (Dd) to target AML cells. The vectorization of leukemic cells was proved very effective at nanomolar concentrations in a time- and dose-dependent manner, without vector toxicity. The internalization involved clathrin-mediated energy-dependent endocytosis and strongly correlated with the expression of αVβ3 integrin. The treatment of healthy donor peripheral blood mononuclear cells showed a preferential targeting of monocytes compared to lymphocytes and granulocytes. Similarly, monocytes but also AML blasts were the best-vectorized populations in patients while acute lymphoid leukemia blasts were less efficiently targeted. Importantly, AML leukemic stem cells (LSCs) could be addressed. Finally, Dd reached peripheral monocytes and bone marrow hematopoietic stem and progenitor cells following intravenous injection in mice, without excessive spreading in other organs. These findings reveal Dd as a promising myeloid vector especially for therapeutic purposes in AML blasts, LSCs, and progenitor cells.

The Adenovirus Dodecahedron: Beyond the Platonic Story

Many geometric forms are found in nature, some of them adhering to mathematical laws or amazing aesthetic rules. One of the best-known examples in microbiology is the icosahedral shape of certain viruses with 20 triangular facets and 12 edges. What is less known, however, is that a complementary object displaying 12 faces and 20 edges called a 'dodecahedron' can be produced in huge amounts during certain adenovirus replication cycles. The decahedron was first described more than 50 years ago in the human adenovirus (HAdV3) viral cycle. Later on, the expression of this recombinant scaffold, combined with improvements in cryo-electron microscopy, made it possible to decipher the structural determinants underlying their architecture. Recently, this particle, which mimics viral entry, was used to fish the long elusive adenovirus receptor, desmoglein-2, which serves as a cellular docking for some adenovirus serotypes. This breakthrough enabled the understanding of the physiological role played by the dodecahedral particles, showing that icosahedral and dodecahedral particles live more than a simple platonic story. All these points are developed in this review, and the potential use of the dodecahedron in therapeutic development is discussed.

HER3-targeted protein chimera forms endosomolytic capsomeres and self-assembles into stealth nucleocapsids for systemic tumor homing of RNA interference in vivo

RNA interference represents a potent intervention for cancer treatment but requires a robust delivery agent for transporting gene-modulating molecules, such as small interfering RNAs (siRNAs). Although numerous molecular approaches for siRNA delivery are adequate in vitro, delivery to therapeutic targets in vivo is limited by payload integrity, cell targeting, efficient cell uptake, and membrane penetration. We constructed nonviral biomaterials to transport small nucleic acids to cell targets, including tumor cells, on the basis of the self-assembling and cell-penetrating activities of the adenovirus capsid penton base. Our recombinant penton base chimera contains polypeptide domains designed for noncovalent assembly with anionic molecules and tumor homing. Here, structural modeling, molecular dynamics simulations, and functional assays suggest that it forms pentameric units resembling viral capsomeres that assemble into larger capsid-like structures when combined with siRNA cargo. Pentamerization forms a barrel lined with charged residues mediating pH-responsive dissociation and exposing masked domains, providing insight on the endosomolytic mechanism. The therapeutic impact was examined on tumors expressing high levels of HER3/ErbB3 that are resistant to clinical inhibitors. Our findings suggest that our construct may utilize ligand mimicry to avoid host attack and target the siRNA to HER3+ tumors by forming multivalent capsid-like structures.

The Use of Adenovirus Dodecahedron in the Delivery of an Enzymatic Activity in the Cell

Penton-dodecahedron (Pt-Dd) derived from adenovirus type 3 is a symmetric complex of pentameric penton base plus fiber which can be produced in the baculovirus system at a high concentration. The size of Pt-Dd is smaller than the virus, but this virus-like particle (VLP) has the major proteins recognized by specific receptors on the surface of almost all types of cell. In this study, by direct observation with fluorescence microscopy on a fixed and living cell, the intracellular trafficking and localization of Pt-Dd labeled with fluorescence dyes in the cytoplasm of HeLa Tub-GFP showed a rapid internalization characteristic. Subsequently, the linkage of horseradish peroxidase (HRP) with Pt-Dd as the vector demonstrated an efficient system to deliver this enzyme into the cell without interfering its enzymatic activity as shown by biochemical and cellular experiments. These results were supported by additional studies using Bs-Dd or free form of the HRP used as the control. Overall, this study strengthens the potential role of Pt-Dd as an alternative vector for delivering therapeutic agents.

Adenovirus Dodecahedron, a VLP, Can be Purified by Size Exclusion Chromatography Instead of Time-Consuming Sucrose Density Gradient Centrifugation

Adenoviral dodecahedron (Dd) is a virus-like particle composed of twelve pentameric penton base (Pb) proteins, responsible for adenovirus cell penetration. It is generated spontaneously in the baculovirus system upon expression of the Pb gene of adenovirus serotype 3. This particle shows remarkable cell penetration ability with 2,00,000-3,00,000 Dd internalized into one cell in culture, conceivably delivering several millions of foreign cargo molecules to the target cell. We have used it in the past for delivery of small drugs as well as a vaccination platform, in which Dd serves as a particulate vaccine delivery system. Since development of new biomedicals depends strongly on the cost of their expression and purification, we attempted, albeit unsuccessfully, to obtain Dd expression in bacteria. We therefore retained its expression in the baculovirus/insect cells system but introduced significant improvements in the protocols for Dd expression and purification, leading to considerable savings in time and improved yield.

Virus-like particle-mediated intracellular delivery of mRNA cap analog with in vivo activity against hepatocellular carcinoma

Adenovirus dodecahedron (Dd), a nanoparticulate proteinaceous biodegradable virus-like particle (VLP), was used as a vector for delivery of an oncogene inhibitor to hepatocellular carcinoma (HCC) rat orthotopic model. Initiation factor eIF4E is an oncogene with elevated expression in human cancers. Cell-impermeant eIF4E inhibitor, cap structure analog (cap) and anti-cancer antibiotic doxorubicin (Dox) were delivered as Dd conjugates. Dd-cap and Dd-dox inhibited cancer cell culture proliferation up to 50 and 84%, respectively, while with free Dox similar results could be obtained only at a 5 times higher concentration. In animal HCC model the combination treatment of Dd-cap/Dd-dox caused 40% inhibition of tumor growth. Importantly, the level of two pro-oncogenes, eIF4E and c-myc, was significantly diminished in tumor sections of treated rats. Attachment to Dd, a virus-like particle, permitted the first demonstration of cap analog intracellular delivery and resulted in improved doxorubicin delivery leading to statistically significant inhibition of HCC tumor growth.

Molecular basis of the binding of YAP transcriptional regulator to the ErbB4 receptor tyrosine kinase

The newly discovered transactivation function of ErbB4 receptor tyrosine kinase is believed to be mediated by virtue of the ability of its proteolytically-cleaved intracellular domain (ICD) to physically associate with YAP2 transcriptional regulator. In an effort to unearth the molecular basis of YAP2-ErbB4 interaction, we have conducted a detailed biophysical analysis of the binding of WW domains of YAP2 to PPXY motifs located within the ICD of ErbB4. Our data show that the WW1 domain of YAP2 binds to PPXY motifs within the ICD in a differential manner and that this behavior is by and large replicated by the WW2 domain. Remarkably, while both WW domains absolutely require the integrity of the PPXY consensus sequence, non-consensus residues within and flanking this motif do not appear to be critical for binding. In spite of this shared mode of binding, the WW domains of YAP2 display distinct conformational dynamics in complex with PPXY motifs derived from ErbB4. Collectively, our study lends new insights into the molecular basis of a key protein-protein interaction involved in a diverse array of cellular processes.

Use of dodecahedron "VLPs" as an alternative to the whole adenovirus

During human adenovirus type 3 (Ad3) infection, an excess of penton base and fiber proteins are produced. These form dodecahedral particles composed of 12 pentamers of penton base and 12 trimers of fiber protein. Beside this "natural" expression, the adenovirus dodecahedron can be expressed in the heterologous baculovirus system in two forms: a fiber-devoid dodecahedron made only of 12 penton bases (called base-dodecahedron: Bs-Dd) and the fiber-containing dodecahedron (called penton dodecahedron: Pt-Dd). These particles partly mimic the adenoviral cellular entry pathway but are devoid of genetic information making them an unusual tool for basic research or applications. We report here how these particles are expressed and purified, the labeling method for trafficking studies as well as their use in molecular interaction studies. The potential of these particles for biotechnological applications is under evaluation, making their study a "niche" along side traditional adenoviral vectors.

Self-adjuvanting influenza candidate vaccine presenting epitopes for cell-mediated immunity on a proteinaceous multivalent nanoplatform

We exploit the features of a virus-like particle, adenoviral dodecahedron (Ad Dd), for engineering a multivalent vaccination platform carrying influenza epitopes for cell-mediated immunity. The delivery platform, Ad Dd, is a proteinaceous, polyvalent, and biodegradable nanoparticle endowed with remarkable endocytosis activity that can be engineered to carry 60 copies of a peptide. Influenza M1 is the most abundant influenza internal protein with the conserved primary structure. Two different M1 immunodominant epitopes were separately inserted in Dd external positions without destroying the particles' dodecahedric structure. Both kinds of DdFluM1 obtained through expression in baculovirus system were properly presented by human dendritic cells triggering efficient activation of antigen-specific T cells responses. Importantly, the candidate vaccine was able to induce cellular immunity in vivo in chickens. These results warrant further investigation of Dd as a platform for candidate vaccine, able to stimulate cellular immune responses.

Towards a novel influenza vaccine: engineering of hemagglutinin on a platform of adenovirus dodecahedron

Background

The production process for the current influenza vaccine takes about 6 months and its antigenic composition must be modified annually. In the attempt towards developing influenza vaccine production that would be faster, safer and cheaper we engineered an influenza vaccine in which multiple copies of hemagglutinin (HA) would be delivered by a vector, adenovirus dodecahedron (Ad Dd). Dd is a virus-like particle, formed by assembly of twelve copies of pentameric penton base (Pb) proteins responsible for virus penetration. In order to attach HA to the vector, an adaptor containing WW domains was used. The WW domain is a linear peptide fragment identified as a partner of proline-proline-x-tyrosine (PPxY) motif present at the N-terminal extremity of the Pb protein, which is a building block of Dd. That tandem of three WW domains in fusion with the protein of interest enables interaction with Dd and efficient translocation to the cytoplasm of cells in culture.

Results

Since HA is an oligomeric protein with complicated processing, we prepared six different constructs of HA (A/swan/Poland/467/2006(H5N1)) in fusion with the WW adaptor. Herein we report baculovirus expression and functional analysis of six HA-WW variants. The best behaving variant was successfully delivered into human cells in vitro.

Conclusions

Engineering of a soluble complex of HA with Dd, a virus-like particle that serves as a vector, an adjuvant and as a multivalent presentation platform, is an important step toward a novel influenza vaccine.

Development of adenovirus capsid proteins for targeted therapeutic delivery

The outer shell of the adenovirus capsid comprises three major types of protein (hexon, penton base and fiber) that perform the majority of functions facilitating the early stages of adenovirus infection. These stages include initial cell-surface binding followed by receptor-mediated endocytosis, endosomal penetration and cytosolic entry, and intracellular trafficking toward the nucleus. Numerous studies have shown that the penton base contributes to several of these steps and have supported the development of this protein into a delivery agent for therapeutic molecules. Studies revealing that the fiber and hexon bear unexpected properties of cell entry and/or nuclear homing have supported the development of these capsid proteins, as well into potential delivery vehicles. This review summarizes the findings to date of the protein-cell activities of these capsid proteins in the absence of the whole virus and their potential for therapeutic application with regard to the delivery of foreign molecules.

Functional characterisation of the WW minimal domain for delivering therapeutic proteins by adenovirus dodecahedron

Protein transduction offers a great therapeutic potential by efficient delivery of biologically active cargo into cells. The Adenovirus Dd (Dodecahedron) has recently been shown to deliver proteins fused to the tandem WW_2-3-4 structural domains from the E3 ubiquitin ligase Nedd4. In this study, we conclusively show that Dd is able to efficiently deliver cargo inside living cells, which mainly localize in fast moving endocytic vesicles, supporting active transport along the cytoskeleton. We further improve this delivery system by expressing a panel of 13 WW-GFP mutant forms to characterize their binding properties towards Dd. We identified the domain WW₃ and its mutant form WW₃_10_13 to be sufficient for optimal binding to Dd. We greatly minimise the interacting WW modules from 20 to 6 kDa without compromising its efficient delivery by Dd. Using these minimal WW domains fused to the tumor suppressor p53 protein, we show efficient cellular uptake and distribution into cancer cells, leading to specific induction of apoptosis in these cells. Taken together, these findings represent a step further towards the development of a Dd-based delivery system for future therapeutic application.

The structural basis for the integrity of adenovirus Ad3 dodecahedron

During the viral life cycle adenoviruses produce excess capsid proteins. Human adenovirus serotype 3 (Ad3) synthesizes predominantly an excess of free pentons, the complexes of pentameric penton base and trimeric fiber proteins, which are responsible for virus penetration. In infected cells Ad3 pentons spontaneously assemble into dodecahedral virus-like nano-particles containing twelve pentons. They also form in insect cells during expression in the baculovirus system. Similarly, in the absence of fiber protein dodecahedric particles built of 12 penton base pentamers can be produced. Both kinds of dodecahedra show remarkable efficiency of intracellular penetration and can be engineered to deliver several millions of foreign cargo molecules to a single target cell. For this reason, they are of great interest as a delivery vector. In order to successfully manipulate this potential vector for drug and/or gene delivery, an understanding of the molecular basis of vector assembly and integrity is critical. Crystallographic data in conjunction with site-directed mutagenesis and biochemical analysis provide a model for the molecular determinants of dodecamer particle assembly and the requirements for stability. The 3.8 Å crystal structure of Ad3 penton base dodecamer (Dd) shows that the dodecahedric structure is stabilized by strand-swapping between neighboring penton base molecules. Such N-terminal strand-swapping does not occur for Dd of Ad2, a serotype which does not form Dd under physiological conditions. This unique stabilization of the Ad3 dodecamer is controlled by residues 59-61 located at the site of strand switching, the residues involved in putative salt bridges between pentamers and by the disordered N-terminus (residues 1-47), as confirmed by site directed mutagenesis and biochemical analysis of mutant and wild type protein. We also provide evidence that the distal N-terminal residues are externally exposed and available for attaching cargo.

Impact of human adenovirus type 3 dodecahedron on host cells and its potential role in viral infection

During human adenovirus type 3 (Ad3) infection, an excess of penton base and fiber proteins are produced which form dodecahedral particles composed of 12 pentamers of penton base and 12 trimers of fiber protein. No biological functions have yet been ascribed to Ad3 dodecahedra. Here, we show that dodecahedra compete with Ad3 virions for binding to the cell surface and trigger cell remodeling, giving new insights into possible biological functions of dodecahedra in the Ad3 infectious cycle.

Generation and biological properties of a recombinant dodecahedron containing the short fiber protein of the human adenovirus 41

OBJECTIVE

In order to gain further insight into the function of the enteric adenovirus short fiber (SF), we have constructed a recombinant dodecahedron containing the SF protein of HAdV-41 and the HAdV-3 penton base.

METHODS

Recombinant baculoviruses expressing the HAdV-41 SF protein and HAdV-3 penton base were cloned and amplified in Sf9 insect cells. Recombinant dodecahedra were expressed by coinfection of High Five™ cells with both baculoviruses, 72 h post-infection. Cell lysate was centrifuged on sucrose density gradient and the purified recombinant dodecahedra were recovered.

RESULTS

Analysis by negative staining electron microscopy demonstrated that chimeric dodecahedra made of the HAdV-3 penton base and decorated with the HAdV-41 SF were successfully generated. Next, recombinant dodecahedra were digested with pepsin and analyzed by Western blot. A 'site-specific' proteolysis of the HAdV-41 SF was observed, while the HAdV-3 penton base core was completely digested.

CONCLUSION

These results show that, in vitro, the HAdV-41 SF likely undergoes proteolysis in the gastrointestinal tract, its natural environment, which may facilitate the recognition of receptors in intestinal cells. The results obtained in the present study may be the basis for the development of gene therapy vectors towards the intestinal epithelium, as well as orally administered vaccine vectors, but also for the HAdV-41 SF partner identification.

The adenovirus type 3 dodecahedron's RGD loop comprises an HSPG binding site that influences integrin binding

Human type 3 adenovirus dodecahedron (a virus like particle made of twelve penton bases) features the ability to enter cells through Heparan Sulphate Proteoglycans (HSPGs) and integrins interaction and is used as a versatile vector to deliver DNA or proteins. Cryo-EM reconstruction of the pseudoviral particle with Heparan Sulphate (HS) oligosaccharide shows an extradensity on the RGD loop. A set of mutants was designed to study the respective roles of the RGD sequence (RGE mutant) and of a basic sequence located just downstream. Results showed that the RGE mutant binding to the HS deficient CHO-2241 cells was abolished and unexpectedly, mutation of the basic sequence (KQKR to AQAS) dramatically decreased integrin recognition by the viral pseudoparticle. This basic sequence is thus involved in integrin docking, showing a close interplay between HSPGs and integrin receptors.

In vivo delivery of antigens by adenovirus dodecahedron induces cellular and humoral immune responses to elicit antitumor immunity

Cancer vaccines based on virus-like particles (VLPs) vectors may offer many advantages over other antigen-delivery systems and represent an alternative to the ex vivo cell therapy approach. In this study, we describe the use of penton-dodecahedron (Pt-Dd) VLPs from human adenovirus type 3 (Ad3) as cancer vaccine vehicle for specific antigens, based on its unique cellular internalization properties. WW domains from the ubiquitin ligase Nedd4 serve as an adapter to bind the antigen to Pt-Dd. By engineering fusion partners of WW with the model antigen ovalbumin (OVA), Pt-Dd can efficiently deliver WW-OVA in vitro and the Pt-Dd/WW complex can be readily internalized by dendritic cells (DCs). Immunization with WW-OVA/Pt-Dd results in 90% protection against B16-OVA melanoma implantation in syngeneic mice. This high level of protection correlates with the development of OVA-specific CD8(+) T cells. Moreover, vaccination with WW-OVA Pt-Dd induces robust humoral responses in mice as shown by the high levels of anti-OVA antibodies (Abs) detected in serum. Importantly, treatment of mice bearing B16-OVA tumors with WW-OVA/Pt-Dd results in complete tumor regression in 100% of cases. Thus, our data supports a dual role of Pt-Dd as antigen-delivery vector and natural adjuvant, able to generate integrated cellular and humoral responses of broad immunogenic complexity to elicit specific antitumor immunity. Antigen delivery by Pt-Dd vector is a promising novel strategy for development of cancer vaccines with important clinical applications.

Adenovirus dodecahedron, as a drug delivery vector

Background

Bleomycin (BLM) is an anticancer antibiotic used in many cancer regimens. Its utility is limited by systemic toxicity and dose-dependent pneumonitis able to progress to lung fibrosis. The latter can affect up to nearly 50% of the total patient population, out of which 3% will die. We propose to improve BLM delivery by tethering it to an efficient delivery vector. Adenovirus (Ad) dodecahedron base (DB) is a particulate vector composed of 12 copies of a pentameric viral protein responsible for virus penetration. The vector efficiently penetrates the plasma membrane, is liberated in the cytoplasm and has a propensity to concentrate around the nucleus; up to 300000 particles can be observed in one cell in vitro.

Principal Findings

Dodecahedron (Dd) structure is preserved at up to about 50°C at pH 7–8 and during dialysis, freezing and drying in the speed-vac in the presence of 150 mM ammonium sulfate, as well as during lyophilization in the presence of cryoprotectants. The vector is also stable in human serum for 2 h at 37°C. We prepared a Dd-BLM conjugate which upon penetration induced death of transformed cells. Similarly to free bleomycin, Dd-BLM caused dsDNA breaks. Significantly, effective cytotoxic concentration of BLM delivered with Dd was 100 times lower than that of free bleomycin.

Conclusions/Significance

Stability studies show that Dds can be conveniently stored and transported, and can potentially be used for therapeutic purposes under various climates. Successful BLM delivery by Ad Dds demonstrates that the use of virus like particle (VLP) results in significantly improved drug bioavailability. These experiments open new vistas for delivery of non-permeant labile drugs.

Three-dimensional structure of canine adenovirus serotype 2 capsid

There are more than 100 known adenovirus (AdV) serotypes, including 50 human serotypes. Because AdV-induced disease is relatively species specific, vectors derived from nonhuman serotypes may have wider clinical potential based, in part, on the lack of ubiquitous memory immunity. Whereas a few of the human serotype capsids have been studied at the structural level, none of the nonhuman serotypes has been analyzed. The basis laid by the analysis of human AdV (hAdV) has allowed us to determine and compare the three-dimensional structure of the capsid of canine serotype 2 (CAV-2) to that of hAdV serotype 5 (hAdV-5). We show that CAV-2 capsid has a smoother structure than the human serotypes. Many of the external loops found in the hAdV-5 penton base and the hexon, against which the antibody response is directed, are shorter or absent in CAV-2. On the other hand, the CAV-2 fiber appears to be more complex, with two bends in the shaft. An interesting difference between the human and canine viruses is that the C-terminal part of protein IX is in a different position, making an antenna sticking out of the CAV-2 capsid. The comparison between the two viruses allows the identification of sites that should be easy to modify on the CAV-2 capsid for altering tissue tropism or other biological activities.

Adenovirus dodecahedron cell attachment and entry are mediated by heparan sulfate and integrins and vary along the cell cycle

The adenovirus penton base is a strategic protein involved in the virus internalisation pathway through interaction between its RGD sequences and integrin. In some human adenovirus serotypes, this pentameric protein features the ability of interacting together by twelve, leading to the formation of a symmetric nanoparticle called dodecahedron (Dd). This non-infectious adenovirus-like particle exhibiting sixty RGD sequences interacts with integrin but also with heparan sulfate proteoglycans (HSPGs) expressed at the cell surface. In this study, we discriminate the respective importance of HSPGs and integrin on human adenovirus serotype 3 dodecahedron attachment and entry. Using different cell lines and a specific integrin inhibitor, we have determined that HSPGs are mainly responsible for particle attachment to the cell surface, favouring a strictly required interaction with integrin that triggers internalisation. No other receptors are involved in Dd entry and integrins on their own can mediate the particle entry in HSPGs-deficient cells. Moreover, integrin recognition by Dd is highly susceptible to cations and particularly to manganese that enhances particle binding by 4- to 7-fold compared to calcium. Interestingly, investigations on Dd receptors along the cell cycle revealed an enhanced particle targeting to mitotic cells and a loss of internalisation at this stage. This phenomenon observed with both HeLa- and HSPGs-deficient cells, depends on integrin remodelling during mitosis. This provides new clues for the use of this adenovirus nanoparticle as a delivery vector and sheds light on the integrin and HSPGs relationship in both resting and dividing cells.

Development of the dodecahedral penton particle from adenovirus 3 for therapeutic application

The subviral dodecahedral particle of adenovirus 3, which assembles spontaneously in insect cells expressing the viral penton base protein, shows promise as a vector for drug delivery. Its ability to gain cell entry has been demonstrated and recent structural analysis has outlined details of the interfaces between penton bases and the importance of proteolysis of the penton base N terminus for assembly, providing a basis for understanding particle assembly and stability. Here, work in manipulating the assembly status of the dodecahedron by changing buffer conditions and subsequent success in passively encapsidating a marker molecule is described. This represents an important stage towards development of the dodecahedral particle for use as a delivery vehicle capable of targeting therapeutic molecules to specific cell types.