Adenovirus Fibers as Ultra-Stable Vehicles for Intracellular Nanoparticle and Protein Delivery

Protein-based carriers are promising vehicles for the intracellular delivery of therapeutics. In this study, we designed and studied adenovirus protein fiber constructs with potential applications as carriers for the delivery of protein and nanoparticle cargoes. We used as a basic structural framework the fibrous shaft segment of the adenovirus fiber protein comprising of residues 61–392, connected to the fibritin foldon trimerization motif at the C-terminal end. A fourteen-amino-acid biotinylation sequence was inserted immediately after the N-terminal, His-tagged end of the construct in order to enable the attachment of a biotin moiety in vivo. We report herein that this His-tag biotinylated construct folds into thermally and protease-stable fibrous nanorods that can be internalized into cells and are not cytotoxic. Moreover, they can bind to proteins and nanoparticles through the biotin–streptavidin interaction and mediate their delivery to cells. We demonstrate that streptavidin-conjugated gold nanoparticles can be transported into NIH3T3 fibroblast and HeLa cancer cell lines. Furthermore, two streptavidin-conjugated model proteins, alkaline phosphatase and horseradish peroxidase can be delivered into the cell cytoplasm in their enzymatically active form. This work is aimed at establishing the proof-of-principle for the rational engineering of diverse functionalities onto the initial protein structural framework and the use of adenovirus fiber-based proteins as nanorods for the delivery of nanoparticles and model proteins. These constructs could constitute a stepping stone for the development of multifunctional and modular fibrous nanorod platforms that can be tailored to applications at the sequence level.

Development of a Broadly Applicable Cas12a-Linked Beam Unlocking Reaction for Sensitive and Specific Detection of Respiratory Pathogens Including SARS-CoV-2

The outbreak of novel coronavirus SARS-CoV-2 has caused a worldwide threat to public health. COVID-19 patients with SARS-CoV-2 infection can develop clinical symptoms that are often confused with the infections of other respiratory pathogens. Sensitive and specific detection of SARS-CoV-2 with the ability to discriminate from other viruses is urgently needed for COVID-19 diagnosis. Herein, we streamlined a highly efficient CRISPR-Cas12a-based nucleic acid detection platform, termed Cas12a-linked beam unlocking reaction (CALIBURN). We show that CALIBURN could detect SARS-CoV-2 and other coronaviruses and influenza viruses with little cross-reactivity. Importantly, CALIBURN allowed accurate diagnosis of clinical samples with extremely low viral loads, which is a major obstacle for the clinical applications of existing CRISPR diagnostic platforms. When tested on the specimens from SARS-CoV-2-positive and negative donors, CALIBURN exhibited 73.0% positive and 19.0% presumptive positive rates and 100% specificity. Moreover, unlike existing CRISPR detection methods that were mainly restricted to respiratory specimens, CALIBURN displayed consistent performance across both respiratory and nonrespiratory specimens, suggesting its broad specimen compatibility. Finally, using a mouse model of SARS-CoV-2 infection, we demonstrated that CALIBURN allowed detection of coexisting pathogens without cross-reactivity from a single tissue specimen. Our results suggest that CALIBURN can serve as a versatile platform for the diagnosis of COVID-19 and other respiratory infectious diseases.

Unraveling the mechanism of recognition of the 3' splice site of the adenovirus major late promoter intron by the alternative splicing factor PUF60

Pre-mRNA splicing is critical for achieving required amounts of a transcript at a given time and for regulating production of encoded protein. A given pre-mRNA may be spliced in many ways, or not at all, giving rise to multiple gene products. Numerous splicing factors are recruited to pre-mRNA splice sites to ensure proper splicing. One such factor, the 60 kDa poly(U)-binding splicing factor (PUF60), is recruited to sites that are not always spliced, but rather function as alternative splice sites. In this study, we characterized the interaction of PUF60 with a splice site from the adenovirus major late promoter (the AdML 3' splice site, AdML3’). We found that the PUF60–AdML3’ dissociation constants are in the micromolar range, with the binding affinity predominantly provided by PUF60’s two central RNA recognition motifs (RRMs). A 1.95 Å crystal structure of the two PUF60 RRMs in complex with AdML3’ revealed a dimeric organization placing two stretches of nucleic acid tracts in opposing directionalities, which can cause looping of nucleic acid and explain how PUF60 affects pre-mRNA geometry to effect splicing. Solution characterization of this complex by light-scattering and UV/Vis spectroscopy suggested a potential 2:1 (PUF60₂:AdML3’) stoichiometry, consistent with the crystal structure. This work defines the sequence specificity of the alternative splicing factor PUF60 at the pre-mRNA 3’ splice site. Our observations suggest that control of pre-mRNA directionality is important in the early stage of spliceosome assembly, and advance our understanding of the molecular mechanism by which alternative and constitutive splicing factors differentiate among 3’ splice sites.

Localized reconstruction in Scipion expedites the analysis of symmetry mismatches in cryo-EM data

Technological advances in transmission electron microscopes and detectors have turned cryogenic electron microscopy (cryo-EM) into an essential tool for structural biology. A commonly used cryo-EM data analysis method, single particle analysis, averages hundreds of thousands of low-dose images of individual macromolecular complexes to determine a density map of the complex. The presence of symmetry in the complex is beneficial since each projection image can be assigned to multiple views of the complex. However, data processing that applies symmetry can average out asymmetric features and consequently data analysis methods are required to resolve asymmetric structural features. Scipion is a cryo-EM image processing framework that integrates functions from different image processing packages as plugins. To extend its functionality for handling symmetry mismatches, we present here a Scipion plugin termed LocalRec implementing the localized reconstruction method. When tested on an adenovirus data set, the plugin enables resolving the symmetry-mismatched trimeric fibre bound to the five-fold vertices of the capsid. Furthermore, it improves the structure determination of the icosahedral capsid by dealing with the defocus gradient across the particle. LocalRec is expected to be widely applicable in a range of cryo-EM investigations of flexible and symmetry mismatched complexes.

Superhemophobic and Antivirofouling Coating for Mechanically Durable and Wash-Stable Medical Textiles

Medical textiles have a need for repellency to body fluids such as blood, urine, or sweat that may contain infectious vectors that contaminate surfaces and spread to other individuals. Similarly, viral repellency has yet to be demonstrated and long-term mechanical durability is a major challenge. In this work, we demonstrate a simple, durable, and scalable coating on nonwoven polypropylene textile that is both superhemophobic and antivirofouling. The treatment consists of polytetrafluoroethylene (PTFE) nanoparticles in a solvent thermally sintered to polypropylene (PP) microfibers, which creates a robust, low-surface-energy, multilayer, and multilength scale rough surface. The treated textiles demonstrate a static contact angle of 158.3 ± 2.6° and hysteresis of 4.7 ± 1.7° for fetal bovine serum and reduce serum protein adhesion by 89.7 ± 7.3% (0.99 log). The coated textiles reduce the attachment of adenovirus type 4 and 7a virions by 99.2 ± 0.2% and 97.6 ± 0.1% (2.10 and 1.62 log), respectively, compared to noncoated controls. The treated textiles provide these repellencies by maintaining a Cassie-Baxter state of wetting where the surface area in contact with liquids is reduced by an estimated 350 times (2.54 log) compared to control textiles. Moreover, the treated textiles exhibit unprecedented mechanical durability, maintaining their liquid, protein, and viral repellency after extensive and harsh abrasion and washing. The multilayer, multilength scale roughness provides for mechanical durability through self-similarity, and the samples have high-pressure stability with a breakthrough pressure of about 255 kPa. These properties highlight the potential of durable, repellent coatings for medical gowning, scrubs, or other hygiene textile applications.

Amphiphilic Polyphenylene Dendron Conjugates for Surface Remodeling of Adenovirus 5

Amphiphilic surface groups play an important role in many biological processes. The synthesis of amphiphilic polyphenylene dendrimer branches (dendrons), providing alternating hydrophilic and lipophilic surface groups and one reactive ethynyl group at the core is reported. The amphiphilic surface groups serve as biorecognition units that bind to the surface of adenovirus 5 (Ad5), which is a common vector in gene therapy. The Ad5/dendron complexes showed high gene transduction efficiencies in coxsackie-adenovirus receptor (CAR)-negative cells. Moreover, the dendrons offer incorporation of new functions at the dendron core by in situ post-modifications, even when bound to the Ad5 surface. Surfaces coated with these dendrons were analyzed for their blood-protein binding capacity, which is essential to predict their performance in the blood stream. A new platform for introducing bioactive groups to the Ad5 surface without chemically modifying the virus particles is provided.

MnCaCs-Biomineralized Oncolytic Virus for Bimodal Imaging-Guided and Synergistically Enhanced Anticancer Therapy

Oncolytic adenovirus (OA) is an ideal candidate for clinical anticancer treatment, because it can specifically replicate in tumor cells with high titer. However, its systemic administration is still hindered, because of severely compromised antitumor efficacy. Herein, an engineered OA was innovatively developed by enwrapping OA with calcium and manganese carbonates (MnCaCs) biomineral shell, which could protect the virus from removal of the host immune system and prolong its in vivo circulation. Upon accumulating in tumor sites, MnCaCs readily dissolved under the acidic microenvironment, releasing Mn²⁺ that could convert endogenous H₂O₂ into oxygen (O₂) and then enhance the duplication ability of OA, thus significantly increased the antitumor efficacy. Meanwhile, Mn²⁺ and the increased O₂ individually endowed the T1 modal magnetic resonance imaging (MRI) and photoacoustic imaging (PAI) feasibility, providing real-time monitoring information for the therapy. This versatile engineered OA demonstrated its promise for visible and efficient oncolytic virotherapy by systemic administration.

Genetically Engineered Cell Membrane Nanovesicles for Oncolytic Adenovirus Delivery: A Versatile Platform for Cancer Virotherapy

Currently, various oncolytic adenoviruses (OA) are being explored in both preclinical and clinical virotherapy. However, the pre-existing neutralizing antibodies (nAbs) and poor targeting delivery are major obstacles for systemically administered OA. Therefore, we designed bioengineered cell membrane nanovesicles (BCMNs) that harbor targeting ligands to achieve robust antiviral immune shielding and targeting capabilities for oncolytic virotherapy. We employed two distinct biomimetic synthetic approaches: the first is based on in vitro genetic membrane engineering to embed targeting ligands on the cell membrane, and the second is based on in vivo expression of CRISPR-engineered targeting ligands on red-blood-cell membranes. The results indicate that both bioengineering approaches preserve the infectivity and replication capacity of OA in the presence of nAbs, in vitro and in vivo. Notably, OA@BCMNs demonstrated a significant suppression of the induced innate and adaptive immune responses against OA. Enhanced targeting delivery, viral oncolysis, and survival benefits in multiple xenograft models were observed without overt toxicity. These findings reveal that OA@BCMNs may provide a clinical basis for improving oncolytic virotherapy by overcoming undesired antiviral immunity and enhancing cancer cell selectivity via biomimetic synthesis approaches.

Structural and functional annotation of hypothetical proteins of human adenovirus: prioritizing the novel drug targets

OBJECTIVE

Human adenoviruses are small double stranded DNA viruses that provoke vast array of human diseases. Next generation sequencing techniques increase genomic data of HAdV rapidly, which increase their serotypes. The complete genome sequence of human adenovirus shows that it contains large amount of proteins with unknown cellular or biochemical function, known as hypothetical proteins. Hence, it is indispensable to functionally and structurally annotate these proteins to get better understanding of the novel drug targets. The purpose was the characterization of 38 randomly retrieved hypothetical proteins through determination of their physiochemical properties, subcellular localization, function, structure and ligand binding sites using various sequence and structure based bioinformatics tools.

RESULTS

Function of six hypothetical proteins P03269, P03261, P03263, Q83127, Q1L4D7 and I6LEV1 were predicted confidently and then used further for structure analysis. We found that these proteins may act as DNA terminal protein, DNA polymerase, DNA binding protein, adenovirus E3 region protein CR1 and adenoviral protein L1. Functional and structural annotation leading to detection of binding sites by means of docking analysis can indicate potential target for therapeutics to defeat adenoviral infection.

A core viral protein binds host nucleosomes to sequester immune danger signals

Viral proteins mimic host protein structure and function to redirect cellular processes and subvert innate defenses. Small basic proteins compact and regulate both viral and cellular DNA genomes. Nucleosomes are the repeating units of cellular chromatin and play an important part in innate immune responses. Viral-encoded core basic proteins compact viral genomes, but their impact on host chromatin structure and function remains unexplored. Adenoviruses encode a highly basic protein called protein VII that resembles cellular histones. Although protein VII binds viral DNA and is incorporated with viral genomes into virus particles, it is unknown whether protein VII affects cellular chromatin. Here we show that protein VII alters cellular chromatin, leading us to hypothesize that this has an impact on antiviral responses during adenovirus infection in human cells. We find that protein VII forms complexes with nucleosomes and limits DNA accessibility. We identified post-translational modifications on protein VII that are responsible for chromatin localization. Furthermore, proteomic analysis demonstrated that protein VII is sufficient to alter the protein composition of host chromatin. We found that protein VII is necessary and sufficient for retention in the chromatin of members of the high-mobility-group protein B family (HMGB1, HMGB2 and HMGB3). HMGB1 is actively released in response to inflammatory stimuli and functions as a danger signal to activate immune responses. We showed that protein VII can directly bind HMGB1 in vitro and further demonstrated that protein VII expression in mouse lungs is sufficient to decrease inflammation-induced HMGB1 content and neutrophil recruitment in the bronchoalveolar lavage fluid. Together, our in vitro and in vivo results show that protein VII sequesters HMGB1 and can prevent its release. This study uncovers a viral strategy in which nucleosome binding is exploited to control extracellular immune signaling.

[THE APPLICATION OF DOT-TECHNIQUE FOR DETECTING ANTIGENS OF ADENOVIRUS IN CLINICAL SAMPLES]

The article substantiates possibility of application of point enzyme-linked immunosorbent assay (dot-technique) for detecting viral antigens in samples from patients. To diagnose adenovirus infection conjugate of virus-specific monoclonal antibodies and peroxidase of horse-radish were used The chromatographic rectification of conjugate from free peroxidase permits diminishing background coloring of nitrocellulose membrane and therefore to increase sensitivity. The application of direct conjugates on the basis of virus-specific monoclonal antibodies increases specifcity of dot-technique and significantly shortens time period of analysis. As in case of application of direct conjugates on the basis of polyclonal serum, samples from patients require preliminary processing with detergent for preventing non-specific reactions. The dot-technique demonstrates good coincidence with data of polymerase chain reaction and after clinical trials it can be used in diagnostic of human viral infections.

Quantitative nanoscale electrostatics of viruses

Electrostatics is one of the fundamental driving forces of the interaction between biomolecules in solution. In particular, the recognition events between viruses and host cells are dominated by both specific and non-specific interactions and the electric charge of viral particles determines the electrostatic force component of the latter. Here we probe the charge of individual viruses in liquid milieu by measuring the electrostatic force between a viral particle and the Atomic Force Microscope tip. The force spectroscopy data of co-adsorbed ϕ29 bacteriophage proheads and mature virions, adenovirus and minute virus of mice capsids is utilized for obtaining the corresponding density of charge for each virus. The systematic differences of the density of charge between the viral particles are consistent with the theoretical predictions obtained from X-ray structural data. Our results show that the density of charge is a distinguishing characteristic of each virus, depending crucially on the nature of the viral capsid and the presence/absence of the genetic material.

[Sample Preparation and Imaging of Single Adenovirus Particle Using Atomic Force Microscopy in Liquid]

Atomic force microscopy (AFM), as a sophisticated imaging tool with nanoscale resolution, is widely used in virus research and the application of functional viral particles. To investigate single viruses by AFM in a physiologically relevant environment (liquid), an appropriate surface treatment to properly adhere the viruses to the substrate is essential. Here we discuss hydrophobic treated glass coverslips as a suitable substrate for the adhesion of single adenovirus particle (Adenovirus type 5 F35, Ad5F35) when studied with AFM in liquid. From the high resolution AFM images, the orientation of the adhered virus particles can be distinguished. Furthermore, the particles exhibit the expected height of -90 nm. This illustrates that the viruses adhere to the substrate firmly without large deformations. Hence, the described method works well on (fragile) viruses. The described experimental approach can be widely used for AFM studies in liquid of virus structure and mechanics as well as for investigating the interaction of viruses with cellular receptors.

Structures of Adenovirus Incomplete Particles Clarify Capsid Architecture and Show Maturation Changes of Packaging Protein L1 52/55k

Adenovirus is one of the most complex icosahedral, nonenveloped viruses. Even after its structure was solved at near-atomic resolution by both cryo-electron microscopy and X-ray crystallography, the location of minor coat proteins is still a subject of debate. The elaborated capsid architecture is the product of a correspondingly complex assembly process, about which many aspects remain unknown. Genome encapsidation involves the concerted action of five virus proteins, and proteolytic processing by the virus protease is needed to prime the virion for sequential uncoating. Protein L1 52/55k is required for packaging, and multiple cleavages by the maturation protease facilitate its release from the nascent virion. Light-density particles are routinely produced in adenovirus infections and are thought to represent assembly intermediates. Here, we present the molecular and structural characterization of two different types of human adenovirus light particles produced by a mutant with delayed packaging. We show that these particles lack core polypeptide V but do not lack the density corresponding to this protein in the X-ray structure, thereby adding support to the adenovirus cryo-electron microscopy model. The two types of light particles present different degrees of proteolytic processing. Their structures provide the first glimpse of the organization of L1 52/55k protein inside the capsid shell and of how this organization changes upon partial maturation. Immature, full-length L1 52/55k is poised beneath the vertices to engage the virus genome. Upon proteolytic processing, L1 52/55k disengages from the capsid shell, facilitating genome release during uncoating.

IMPORTANCE

Adenoviruses have been extensively characterized as experimental systems in molecular biology, as human pathogens, and as therapeutic vectors. However, a clear picture of many aspects of their basic biology is still lacking. Two of these aspects are the location of minor coat proteins in the capsid and the molecular details of capsid assembly. Here, we provide evidence supporting one of the two current models for capsid architecture. We also show for the first time the location of the packaging protein L1 52/55k in particles lacking the virus genome and how this location changes during maturation. Our results contribute to clarifying standing questions in adenovirus capsid architecture and provide new details on the role of L1 52/55k protein in assembly.

Using a magnetic field to redirect an oncolytic adenovirus complexed with iron oxide augments gene therapy efficacy

Adenovirus (Ad) is a widely used vector for cancer gene therapy but its therapeutic efficacy is limited by low coxsackievirus and adenovirus receptor (CAR) expression in tumors and non-specifically targeted infection. Ad infectivity and specificity can be markedly improved by creating Ad-magnetic nanoparticles cluster complexes and directing their migration with an external magnetic field (MGF). We electrostatically complexed GFP-expressing, replication-incompetent Ad (dAd) with PEGylated and cross-linked iron oxide nanoparticles (PCION), generating dAd-PCION complexes. The dAd-PCION showed increased transduction efficiency, independent of CAR expression, in the absence or presence of an MGF. Cancer cell killing and intracellular oncolytic Ad (HmT)-PCION replication significantly increased with MGF exposure. Site-directed, magnetically-targeted delivery of the HmT-PCION elicited significantly greater therapeutic efficacy versus treatment with naked HmT or HmT-PCION without MGF in CAR-negative MCF7 tumors. Immunohistochemical tumor analysis showed increased oncolytic Ad replication in tumors following infection by HmT-PCION using an MGF. Whole-body bioluminescence imaging of tumor-bearing mice showed a 450-fold increased tumor-to-liver ratio for HmT-PCION with, versus without, MGF. These results demonstrate the feasibility and potential of external MGF-responsive PCION-coated oncolytic Ads as smart hybrid vectors for cancer gene therapy.

Biobased monoliths for adenovirus purification

Adenoviruses are important platforms for vaccine development and vectors for gene therapy, increasing the demand for high titers of purified viral preparations. Monoliths are macroporous supports regarded as ideal for the purification of macromolecular complexes, including viral particles. Although common monoliths are based on synthetic polymers as methacrylates, we explored the potential of biopolymers processed by clean technologies to produce monoliths for adenovirus purification. Such an approach enables the development of disposable and biodegradable matrices for bioprocessing. A total of 20 monoliths were produced from different biopolymers (chitosan, agarose, and dextran), employing two distinct temperatures during the freezing process (-20 °C and -80 °C). The morphological and physical properties of the structures were thoroughly characterized. The monoliths presenting higher robustness and permeability rates were further analyzed for the nonspecific binding of Adenovirus serotype 5 (Ad5) preparations. The matrices presenting lower nonspecific Ad5 binding were further functionalized with quaternary amine anion-exchange ligand glycidyltrimethylammonium chloride hydrochloride by two distinct methods, and their performance toward Ad5 purification was assessed. The monolith composed of chitosan and poly(vinyl) alcohol (50:50) prepared at -80 °C allowed 100% recovery of Ad5 particles bound to the support. This is the first report of the successful purification of adenovirus using monoliths obtained from biopolymers processed by clean technologies.

Safety profiles and antitumor efficacy of oncolytic adenovirus coated with bioreducible polymer in the treatment of a CAR negative tumor model

Adenovirus (Ad) vectors show promise as cancer gene therapy delivery vehicles, but immunogenic safety concerns and coxsackie and adenovirus receptor (CAR)-dependency have limited their use. Alternately, biocompatible and bioreducible nonviral vectors, including arginine-grafted cationic polymers, have been shown to deliver nucleic acids through a cell penetration peptide (CPP) and protein transduction domain (PTD) effect. We utilized the advantages of both viral and nonviral vectors to develop a hybrid gene delivery vehicle by coating Ad with mPEG-PEI-g-Arg-S-S-Arg-g-PEI-mPEG (Ad/PPSA). Characterization of Ad/PPSA particle size and zeta potential showed an overall size and cationic charge increase in a polymer concentration-dependent manner. Ad/PPSA also showed a marked transduction efficiency increase in both CAR-negative and -positive cells compared to naked Ad. Competition assays demonstrated that Ad/PPSA produced higher transgene expression levels than naked Ad and achieved CAR-independent transduction. Oncolytic Ad (DWP418)/PPSA was able to overcome the nonspecificity of polymer-only therapies by demonstrating cancer-specific killing effects. Furthermore, the DWP418/PPSA nanocomplex elicited a 2.24-fold greater antitumor efficacy than naked Ad in vivo. This was supported by immunohistochemical confirmation of Ad E1As accumulation in MCF7 xenografted tumors. Lastly, intravenous injection of DWP418/PPSA elicited less innate immune response compared to naked Ad, evaluated by interleukin-6 cytokine release into the serum. The increased antitumor effect and improved vector targeting to both CAR-negative and -positive cells make DWP418/PPSA a promising tool for cancer gene therapy.

Gene transfer to carcinoma of the breast with fiber-modified adenoviral vectors in a tissue slice model system

Successful adenoviral (Ad) vector-mediated strategies for breast cancer gene therapy and virotherapy have heretofore been hindered by low transduction efficiency. This has recently been understood to result from a relative paucity of expression of the primary adenovirus receptor, coxsackie-adenovirus-receptor (CAR), on primary tumor cells. To further investigate this issue, we evaluated the expression of CAR on breast cancer cell lines as well as primary breast cancer cells. With the exception of one patient sample, CAR expression was notably higher in the tumor cells from patients compared to CAR expression in the tumor cell lines. Furthermore, we explored CAR-independent targeting strategies to breast cancer tissue by exploring a panel of infectivity-enhanced Ad vectors, which contain CAR-independent targeting motifs for their utility in breast cancer gene therapy and virotherapy. These targeting motifs included Ad 3 knob (Ad5/3), canine Ad serotype 2 knob (Ad5CAV-2), RGD (Ad5.RGD), polylysine (Ad5.pK7), or both RGD and polylysine (Ad5.RGD.pK7), and were tested using the breast cancer tissue slice model, which is the most stringent substrate system available. Of all the tested tropism modified Ad vectors, Ad5/3 exhibited the highest transductional efficiency in breast cancer. These preclinical results suggest that Ad5/3 is the most useful modification to achieve higher clinical efficacy of breast cancer gene therapy and virotherapy.

Vascular gene transfer from metallic stent surfaces using adenoviral vectors tethered through hydrolysable cross-linkers

In-stent restenosis presents a major complication of stent-based revascularization procedures widely used to re-establish blood flow through critically narrowed segments of coronary and peripheral arteries. Endovascular stents capable of tunable release of genes with anti-restenotic activity may present an alternative strategy to presently used drug-eluting stents. In order to attain clinical translation, gene-eluting stents must exhibit predictable kinetics of stent-immobilized gene vector release and site-specific transduction of vasculature, while avoiding an excessive inflammatory response typically associated with the polymer coatings used for physical entrapment of the vector. This paper describes a detailed methodology for coatless tethering of adenoviral gene vectors to stents based on a reversible binding of the adenoviral particles to polyallylamine bisphosphonate (PABT)-modified stainless steel surface via hydrolysable cross-linkers (HC). A family of bifunctional (amine- and thiol-reactive) HC with an average t1/2 of the in-chain ester hydrolysis ranging between 5 and 50 days were used to link the vector with the stent. The vector immobilization procedure is typically carried out within 9 hr and consists of several steps: 1) incubation of the metal samples in an aqueous solution of PABT (4 hr); 2) deprotection of thiol groups installed in PABT with tris(2-carboxyethyl) phosphine (20 min); 3) expansion of thiol reactive capacity of the metal surface by reacting the samples with polyethyleneimine derivatized with pyridyldithio (PDT) groups (2 hr); 4) conversion of PDT groups to thiols with dithiothreitol (10 min); 5) modification of adenoviruses with HC (1 hr); 6) purification of modified adenoviral particles by size-exclusion column chromatography (15 min) and 7) immobilization of thiol-reactive adenoviral particles on the thiolated steel surface (1 hr). This technique has wide potential applicability beyond stents, by facilitating surface engineering of bioprosthetic devices to enhance their biocompatibility through the substrate-mediated gene delivery to the cells interfacing the implanted foreign material.

The targeted transduction of MMP-overexpressing tumor cells by ACPP-HPMA copolymer-coated adenovirus conjugates

We have designed and tested a new way to selectively deliver HPMA polymer-coated adenovirus type 5 (Ad5) particles into matrix metalloproteinase (MMP)-overexpressing tumor cells. An activatable cell penetrating peptide (ACPP) was designed and attached to the reactive 4-nitrophenoxy groups of HPMA polymers by the C-terminal amino acid (asparagine, N). ACPPs are activatable cell penetrating peptides (CPPs) with a linker between polycationic and polyanionic domains, and MMP-mediated cleavage releases the CPP portion and its attached cargo to enable cell entry. Our data indicate that the transport of these HPMA polymer conjugates by a single ACPP molecule to the cytoplasm occurs via a nonendocytotic and concentration-independent process. The uptake was observed to finish within 20 minutes by inverted fluorescence microscopy. In contrast, HPMA polymer-coated Ad5 without ACPPs was internalized solely by endocytosis. The optimal formulation was not affected by the presence of Ad5 neutralizing antibodies during transduction, and ACPP/polymer-coated Ad5 also retained high targeting capability to several MMP-overexpressing tumor cell types. For the first time, ACPP-mediated cytoplasmic delivery of polymer-bound Ad5 to MMP-overexpressing tumor cells was demonstrated. These findings are significant, as they demonstrate the use of a polymer-based system for the targeted delivery into MMP-overexpressing solid tumors and highlight how to overcome major cellular obstacles to achieve intracellular macromolecular delivery.

Multiplex and functional detection of antigen-specific human T cells by ITRA--indirect T cell recognition assay

The identification and functional characterization of pathogen-specific T cells plays a critical role in immunological research and diagnostics. In addition to the present standard technologies such as intracellular cytokine staining (ICS), enzyme-linked immunospot (ELISPOT) and peptide-major-histocompatibility-complex (MHC) multimer staining, we aimed to develop a multiplex detection assay, which provides fast in vitro functional data for both human CD4 and CD8 T cells with different antigen specificities in one sample. In this study, we have exploited the expression of CD83 on B cells to develop the cell array-based indirect T cell recognition assay (ITRA). In detail, B cells are pulsed with different pathogen peptide pools and fluorescently barcoded. Thereafter the B cells are pooled and co-cultured with autologous T cells. Subsequently each B cell population is analyzed via flow cytometry for CD83 expression, which indicates antigen-specific interaction with CD4 T cells. Moreover, we revealed donor dependent variations of cytotoxic activity of pathogen-specific CD4 T cells and CD8 T cells, evidenced by specific lysis of peptide-pulsed B cells. Taken together, ITRA is a novel antigen presenting cell (APC) array based method to analyze the presence and function of various antigen-specific T cells in one sample. It has the potential to be used in the future for epitope/antigen screening in research and for analysis of anti-tumor, anti-pathogen or autoimmune T cell responses in patient samples.

Proteome analysis of adenovirus using mass spectrometry

Analysis of proteins and their posttranslational modifications is important for understanding different biological events. For analysis of viral proteomes, an optimal protocol includes production of a highly purified virus that can be investigated with a high-resolving analytical method. In this Methods in Molecular Biology paper we describe a working strategy for how structural proteins in the Adenovirus particle can be studied using liquid chromatography-high-resolving mass spectrometry. This method provides information on the chemical composition of the virus particle. Further, knowledge about amino acids carrying modifications that could be essential for any part of the virus life cycle is collected. We describe in detail alternatives available for preparation of virus for proteome analysis as well as choice of mass spectrometric instrumentation suitable for this kind of analysis.

Therapeutic targeting of chitosan-PEG-folate-complexed oncolytic adenovirus for active and systemic cancer gene therapy

Adenovirus (Ad)-based cancer therapies have shown much promise. However, until now, Ad has only been delivered directly to primary tumors because the therapeutic efficacy of systemic delivery is limited by the immune response of the host, short blood circulation times, and non-specific liver uptake of Ad. In order to circumvent the issues regarding systemic delivery and to increase the safety and efficacy of Ad therapies, the surface of oncolytic Ad was coated with cationic polymer chitosan via ionic crosslinking (Ad/chitosan), after which polyethylene glycol (PEG) and/or folic acid (FA) was chemically conjugated onto the surface of Ad/chitosan, generating Ad/chitosan-FA, Ad/chitosan-PEG, and Ad/chitosan-PEG-FA nanocomplex. The FA-coordinated Ad nanocomplexes (Ad/chitosan-FA & Ad/chitosan-PEG-FA) elicited folate receptor (FR)-selective cancer cell killing efficacy. In vivo administration of Ad/chitosan-PEG or Ad/chitosan-PEG-FA into mice demonstrated that PEGylation greatly increased blood circulation time, resulting in 9.0-fold and 48.9-fold increases at 24h after injection compared with naked Ad, respectively. In addition, generation of Ad-specific neutralizing antibodies in mice treated with Ad/chitosan-PEG-FA was markedly decreased by 75.3% compared with naked Ad. The quantitative polymerase chain reaction assay results showed a 285.0-fold increase in tumor tissues and a 378-fold reduction of Ad/chitosan-PEG-FA in liver tissues compared with naked Ad. Bioluminescence imaging study further supported the enhanced tumor-to-liver ratio of Ad/chitosan-PEG-FA. Consequently, systemic delivery of Ad/chitosan-PEG-FA significantly inhibited the growth of FR-positive tumor, decreasing 52.8% compared to the naked Ad-treated group. Importantly, PEGylated oncolytic Ad nanocomplexes showed no elevation of both alanine transaminase and aspartate transaminase levels, demonstrating that systemically delivered Ad-related hepatic damage can be completely eliminated with PEG conjugation. In sum, these results demonstrate that conjugation of chitosan-PEG-FA to oncolytic Ad significantly improves antitumor efficacy and safety profiles, suggesting that Ad/chitosan-PEG-FA has potential as a therapeutic agent to target FR-positive cancer via systemic administration.

CryoEM visualization of an adenovirus capsid-incorporated HIV antigen

Adenoviral (Ad) vectors show promise as platforms for vaccine applications against infectious diseases including HIV. However, the requirements for eliciting protective neutralizing antibody and cellular immune responses against HIV remain a major challenge. In a novel approach to generate 2F5- and 4E10-like antibodies, we engineered an Ad vector with the HIV membrane proximal ectodomain region (MPER) epitope displayed on the hypervariable region 2 (HVR2) of the viral hexon capsid, instead of expressed as a transgene. The structure and flexibility of MPER epitopes, and the structural context of these epitopes within viral vectors, play important roles in the induced host immune responses. In this regard, understanding the critical factors for epitope presentation would facilitate optimization strategies for developing viral vaccine vectors. Therefore we undertook a cryoEM structural study of this Ad vector, which was previously shown to elicit MPER-specific humoral immune responses. A subnanometer resolution cryoEM structure was analyzed with guided molecular dynamics simulations. Due to the arrangement of hexons within the Ad capsid, there are twelve unique environments for the inserted peptide that lead to a variety of conformations for MPER, including individual α-helices, interacting α-helices, and partially extended forms. This finding is consistent with the known conformational flexibility of MPER. The presence of an extended form, or an induced extended form, is supported by interaction of this vector with the human HIV monoclonal antibody 2F5, which recognizes 14 extended amino acids within MPER. These results demonstrate that the Ad capsid influences epitope structure, flexibility and accessibility, all of which affect the host immune response. In summary, this cryoEM structural study provided a means to visualize an epitope presented on an engineered viral vector and suggested modifications for the next generation of Ad vectors with capsid-incorporated HIV epitopes.

Biomineralization-based virus shell-engineering: towards neutralization escape and tropism expansion

Biomineralization-based virus shell-engineering (BVSE) is a potential surface modification strategy to afford a biocompatible and biodegradable calcium phosphate (CaPi) shell onto single virus, allowing development of Trojan virus with enhanced infection, expanded tropism and neutralization escape, which open up the multiple applications of virus in biomedicines and materials.

Latest insights on adenovirus structure and assembly

Adenovirus (AdV) capsid organization is considerably complex, not only because of its large size (~950 Å) and triangulation number (pseudo T = 25), but also because it contains four types of minor proteins in specialized locations modulating the quasi-equivalent icosahedral interactions. Up until 2009, only its major components (hexon, penton, and fiber) had separately been described in atomic detail. Their relationships within the virion, and the location of minor coat proteins, were inferred from combining the known crystal structures with increasingly more detailed cryo-electron microscopy (cryoEM) maps. There was no structural information on assembly intermediates. Later on that year, two reports described the structural differences between the mature and immature adenoviral particle, starting to shed light on the different stages of viral assembly, and giving further insights into the roles of core and minor coat proteins during morphogenesis [1,2]. Finally, in 2010, two papers describing the atomic resolution structure of the complete virion appeared [3,4]. These reports represent a veritable tour de force for two structural biology techniques: X-ray crystallography and cryoEM, as this is the largest macromolecular complex solved at high resolution by either of them. In particular, the cryoEM analysis provided an unprecedented clear picture of the complex protein networks shaping the icosahedral shell. Here I review these latest developments in the field of AdV structural studies.

Targeted and armed oncolytic adenovirus via chemoselective modification

Oncolytic adenoviruses (Ads) are an emerging alternative therapy for cancer; however, clinical trial have not yet demonstrated sufficient efficacy. When oncolytic Ads are used in combination with taxoids a synergistic increase in both cytotoxicity and viral replication is observed. In order to generate a next generation oncolytic adenovirus, virion were physically conjugated to a highly potent taxoid, SB-T-1214, and a folate targeting motif. Conjugation was enabled via the metabolic incorporation of non-canonical monosaccharides (O-GlcNAz) and amino acids (homopropargylglycine), which served as sites for chemoselective modification.

Electrostatic force microscopy of self-assembled peptide structures

In this report electrostatic force microscopy (EFM) is used to study different peptide self-assembled structures such as tubes and particles. It is shown that not only geometrical information can be obtained using EFM, but also information about the composition of different structures. In particular we use EFM to investigate the structures of diphenylalanine peptide tubes, particles, and CSGAITIG peptide particles placed on pre-fabricated SiO(2) surfaces with a backgate. We show that the cavity in the peptide tubes could be due to the presence of water residues. Additionally we show that self-assembled amyloid peptides form spherical solid structures containing the same self-assembled peptide in its interior. In both cases transmission electron microscopy is used to verify these structures. Further, the limitations of the EFM technique are discussed, especially when the observed structures become small compared with the radius of the AFM tip used. Finally, an agreement between the detected signal and the structure of the hollow peptide tubes is demonstrated.

Cellular transduction gradients via vapor-deposited polymer coatings

Spatiotemporal control of gene delivery, particularly signaling gradients, via biomaterials poses significant challenges because of the lack of efficient delivery systems for therapeutic proteins and genes. This challenge was addressed by using chemical vapor deposition (CVD) polymerization in a counterflow set-up to deposit copolymers bearing two reactive chemical gradients. FTIR spectroscopy verified the formation of compositional gradients. Adenovirus expressing a reporter gene was biotinylated and immobilized using the VBABM method (virus-biotin-avidin-biotin-materials). Sandwich ELISA confirmed selective attachment of biotinylated adenovirus onto copolymer gradients. When cultured on the adenovirus gradients, human gingival fibroblasts exhibited asymmetric transduction with full confluency. Importantly, gradient transduction occurred in both lateral directions, thus enabling more advanced delivery studies that involve gradients of multiple therapeutic genes.

[Construction of the recombinant adenovirus expressing the CVB3 sVP1-C3d3 protein and study on its immunological effects in mice]

AIM

To construct recombinant adenovirus Ad/C3d3-sVP1 and investigate the immune effects against coxsackievirus infection in mouse.

METHODS

The recombinant adenovirus Ad/sVP1-C3d3 was constructed and packaged. BALB/c mouse were divided into four groups: Ad/sVP1-C3d3 group, Ad/VP1 group, Ad group and PBS group. The mice in each group were immunized by intramuscular injection. The titers of sera IgG and neutralizing antibody were detected by ELISA method and trace neutralization assay, respectively.The specific CTL cytotoxic activity was detected by CCK-8 assay. The mice in each group were challenged with lethal dose of coxsackievirus, the titers of the sera virus were titrated.

RESULTS

The recombinant adenovirus Ad/sVP1-C3d3 was successfully constructed. It's observed that the titers of CVB3 VP1 specific antibody and neutralizing antibody were much higher than those of the other three groups(P<0.01). CTL cytotoxicity activities was much higher than PBS and Ad group(P<0.01), but little higher than Ad/VP1 group(P<0.05).The titer of sera virus was lower than Ad and PBS groups after CVB3 challenged(P<0.05).

CONCLUSION

Both the celluar and humoral immune responses in mice could been significantly enhanced by Ad/sVP1-C3d3.

Phylogenetic analysis of fowl adenoviruses

The sequences of the L1 loop of the hexon protein from representative fowl adenovirus (FAdV) strains of the different European and American collections were determined and compared. This study highlighted the lack of consensus in the numbering of the individual serotypes between the American and the European classifications. An identification system is proposed based on restriction fragment length polymorphism of the hexonA/hexonB polymerase chain reaction product. In addition, new insights into the relationships among FAdV strains are presented and discussed on the basis of phylogenetic analysis of the L1 loops sequences. Six clusters of strains that are supported by high bootstrap values were identified. Three of them are clearly independent, forming groups A, B and C, whereas the three others are clustered in a single 'supergroup', denominated D. Interestingly, the Japanese strain TR22 that is presently classified as European type 5 (species B) could not be assigned to any of the aforementioned clusters and might therefore constitute the sole representative of a seventh cluster.

Chemoselective attachment of small molecule effector functionality to human adenoviruses facilitates gene delivery to cancer cells

We demonstrate here a novel two-step "click" labeling process in which adenoviral particles are first metabolically labeled during production with unnatural azido sugars. Subsequent chemoselective modification allows access to viruses decorated with a broad array of effector functionality. Adenoviruses modified with folate, a known cancer-targeting motif, demonstrated a marked increase in gene delivery to a murine cancer cell line.

Combination of adenovirus and cross-linked low molecular weight PEI improves efficiency of gene transduction

Recombinant adenovirus (Ad)-mediated gene therapy is an exciting novel strategy in cancer treatment. However, poor infection efficiency with coxsackievirus and adenovirus receptor (CAR) down-regulated cancer cell lines is one of the major challenges for its practical and extensive application. As an alternative method of viral gene delivery, a non-viral carrier using cationic materials could compensate for the limitation of adenovirus. In our study, adenovectors were complexed with a new synthetic polymer PEI-DEG-bis-NPC (PDN) based on polyethylenimine (PEI), and then the properties of the vehicle were characterized by measurement of size distribution, zeta potential and transmission electron microscopy (TEM). Enhancement of gene transduction by Ad/PDN complexes was observed in both CAR-overexpressing cell lines (A549) and CAR-lacking cell lines (MDCK, CHO, LLC), as a result of facilitating binding and cell uptake of adenoviral particles by the cationic component. Ad/PDN complexes also promoted the inhibition of tumor growth in vivo and prolonged the survival time of tumor-bearing mice. These data suggest that a combination of viral and non-viral gene delivery methods may offer a new approach to successful cancer gene therapy.

Antitumor effects of telomelysin in combination with paclitaxel or cisplatin on head and neck squamous cell carcinoma

Telomelysin (OBP-301) is a telomerase-specific replication-component adenovirus. Telomelysin has a human telomerase reverse transcriptase (hTERT) promoter element which efficiently kills human cancer cells, but not normal cells. The present study investigated the correlation between the antitumor effect of telomelysin and mRNA expression of hTERT and coxsackievirus and adenovirus receptor (CAR) in head and neck squamous cell carcinoma (HNSCC) in vitro and whether telomelysin enhances the antitumor effect of paclitaxel or cisplatin, in vivo using a HNSCC xenograft model. We also determined the optimal order for combining telomelysin treatment and chemotherapy as concurrent treatment, telomelysin treatment first and chemotherapy later, chemotherapy first and telomelysin treatment later for achieving the best anticancer effect. The mRNA expression of hTERT and CAR genes was examined by quantitative RT-PCR in 17 HNSCC cell lines. There was no significant correlation between the growth inhibition of telomelysin (ID50 for day 3, 5 and 7) in vitro and mRNA expression levels of hTERT and CAR. Regarding the correlation between CAR expression and telomelysin ID50 for day 3, all cell lines that showed a relative amount of CAR/beta-actin mRNA >0.4 had a low telomelysin ID50. This may indicate that CAR expression contributes to the efficacy of adenovirus infection and the antitumor activity of telomelysin in early stages of treatment. In our in vivo study, combining telomelysin and paclitaxel had an additive effect regardless of treatment order. On the other hand, combining telomelysin and cisplatin had additive effect only when cisplatin treatment preceded telomelysin treatment. These results suggest that paclitaxel is considered innocuous for replication of telomelysin, however cisplatin may influence replication of telomelysin.

Chemical modification with high molecular weight polyethylene glycol reduces transduction of hepatocytes and increases efficacy of intravenously delivered oncolytic adenovirus

Oncolytic adenoviruses are anticancer agents that replicate within tumors and spread to uninfected tumor cells, amplifying the anticancer effect of initial transduction. We tested whether coating the viral particle with polyethylene glycol (PEG) could reduce transduction of hepatocytes and hepatotoxicity after systemic (intravenous) administration of oncolytic adenovirus serotype 5 (Ad5). Conjugating Ad5 with high molecular weight 20-kDa PEG but not with 5-kDa PEG reduced hepatocyte transduction and hepatotoxicity after intravenous injection. PEGylation with 20-kDa PEG was as efficient at detargeting adenovirus from Kupffer cells and hepatocytes as virus predosing and warfarin. Bioluminescence imaging of virus distribution in two xenograft tumor models in nude mice demonstrated that PEGylation with 20-kDa PEG reduced liver infection 19- to 90-fold. Tumor transduction levels were similar for vectors PEGylated with 20-kDa PEG and unPEGylated vectors. Anticancer efficacy after a single intravenous injection was retained at the level of unmodified vector in large established prostate carcinoma xenografts, resulting in complete elimination of tumors in all animals and long-term tumor-free survival. Anticancer efficacy after a single intravenous injection was increased in large established hepatocellular carcinoma xenografts, resulting in significant prolongation of survival as compared with unmodified vector. The increase in efficacy was comparable to that obtained with predosing and warfarin pretreatment, significantly extending the median of survival. Shielding adenovirus with 20-kDa PEG may be a useful approach to improve the therapeutic window of oncolytic adenovirus after systemic delivery to primary and metastatic tumor sites.

A 49-kilodalton isoform of the adenovirus type 5 early region 1B 55-kilodalton protein is sufficient to support virus replication

The adenovirus type 5 (Ad5) early region 1B 55-kDa (E1B-55K) protein is a multifunctional regulator of cell-cycle-independent virus replication that participates in many processes required for maximal virus production. As part of a study of E1B-55K function, we generated the Ad5 mutant H5pm4133, carrying stop codons after the second and seventh codons of the E1B reading frame, thereby eliminating synthesis of the full-length 55K product and its smaller derivatives. Unexpectedly, phenotypic studies revealed that H5pm4133 fully exhibits the characteristics of wild-type (wt) Ad5 in all assays tested. Immunoblot analyses demonstrated that H5pm4133 and wt Ad5 produce very low levels of two distinct polypeptides in the 48- to 49-kDa range, which lack the amino-terminal region but contain segments from the central and carboxy-terminal part of the 55K protein. Genetic and biochemical studies with different Ad5 mutants show that at least one of these isoforms consists of two closely migrating polypeptides of 433 amino acid residues (433R) and 422R, which are produced by translation initiation at two downstream AUG codons of the 55K reading frame. Significantly, a virus mutant producing low levels of the 433R isoform alone replicated to levels comparable to those of wt Ad5, demonstrating that this polypeptide provides essentially all functions of E1B-55K required to promote maximal virus growth in human tumor cells. Altogether, these results extend previous findings that the wt Ad5 E1B region encodes a series of smaller isoforms of E1B-55K and demonstrate that very low levels of at least one of these novel proteins (E1B-433R) are sufficient for a productive infection.

Transduction of adenovirus vectors modified with cell-penetrating peptides

Adenovirus vectors (Advs) are widely used for basic and clinical research because of their high transduction efficiency. However, they are poorly transduced into cells lacking the primary adenovirus receptor, the coxsackievirus and adenovirus receptor (CAR). Here, we generated Adv conjugated with cell-penetrating peptides (CPPs), such as Tat, octaarginine (R8) or proline-rich (Pro) peptides, and compared the transduction properties of these constructs. We constructed the Advs conjugated to the CPPs (CPP-Adv) by chemical conjugation. The CPP-conjugated Advs created with optimal modification ratios led to gene expression 1-2log orders higher than unmodified Adv in CAR-negative cells. Tat-Adv and R8-Adv were taken up into the cells mainly through macropinocytosis, independently of the CAR. In addition, the cellular uptake of Tat-Adv was highly dependent on heparan sulfate on the cell surface, whereas that of R8-Adv was dependent on chondroitin sulfate B. These data suggest that the use of CPP-Advs with different cellular uptake pathways might create new methods for the delivery of Adv. The results obtained in this research encourage the use of CPP-peptide-modified Advs as an attractive tool for transducing cells and as useful platform vectors for gene therapy and basic research.

Cetuximab retargeting of adenovirus via the epidermal growth factor receptor for treatment of intraperitoneal ovarian cancer

Gene and virotherapy of ovarian cancer, using type 5 adenovirus (Ad5), has demonstrated good activity in preclinical animal studies, particularly after intraperitoneal administration of virus; however, success in clinical trials has been limited by poor infectivity of ovarian cancer cells and inflammatory responses to Ad5. We previously demonstrated that covalent modification of Ad5 with reactive copolymers on the basis of poly(hydroxypropylmethacrylamide) can shield the virus, offering protection from neutralizing antibodies and enabling retargeting to cancer-upregulated receptors with peptide ligands (basic fibroblast growth factor [bFGF] and murine epidermal growth factor [EGF]). These ligands may be less than ideal for clinical use, however, because they are potential mitogens. Accordingly, in this study we investigated the use of an anti-EGF receptor (EGFR) antibody, cetuximab, to retarget adenoviral transduction of EGFR-positives in vitro and in vivo. Cetuximab retargeting altered the physicochemical characteristics of Ad5, although it did not cause particle aggregation. Although cetuximab stimulated internalization of EGFR, similarly to EGF, it inhibited EGFR phosphorylation. Adenoviral transduction was inhibited after polymer coating, but was rescued in EGFR-positive cells (and not in EGFR-negative cells) by cetuximab retargeting. Cetuximab retargeting of wild-type adenovirus serotype 5 (Ad5WT) prolonged survival in an animal model of human ovarian cancer, similar to unmodified Ad5WT, but polymer coating ameliorated stimulation of adhesion formation. We conclude that polymer coating and covalent attachment of cetuximab successfully retargeted adenovirus to EGFR-positive cells, retained in vivo efficacy of an oncolytic adenovirus, and ameliorated side effects caused by unmodified adenovirus.

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.

Localization of the N-terminus of minor coat protein IIIa in the adenovirus capsid

Minor coat protein IIIa is conserved in all adenoviruses (Ads) and is required for correct viral assembly, but its precise function in capsid organization is unknown. The latest Ad capsid model proposes that IIIa is located underneath the vertex region. To obtain experimental evidence on the location of IIIa and to further define its role, we engineered the IIIa gene to encode heterologous N-terminal peptide extensions. Recombinant Ad variants with IIIa encoding six-histidine (6His) tag, 6His, and FLAG peptides, or with 6His linked to FLAG with a (Gly(4)Ser)(3) linker were rescued and analyzed for virus yield, capsid incorporation of heterologous peptides, and capsid stability. Longer extensions could not be rescued. Western blot analysis confirmed that the modified IIIa proteins were expressed in infected cells and incorporated into virions. In the Ad encoding the 6His-linker-FLAG-IIIa gene, the 6His tag was present in light particles, but not in mature virions. Immunoelectron microscopy of this virus showed that the FLAG epitope is not accessible to antibodies on the viral particles. Three-dimensional electron microscopy and difference mapping located the IIIa N-terminal extension beneath the vertex complex, wedged at the interface between the penton base and peripentonal hexons, therefore supporting the latest proposed model. The position of the IIIa N-terminus and its low tolerance for modification provide new clues for understanding the role of this minor coat protein in Ad capsid assembly and disassembly.

Passive tumour targeting of polymer-coated adenovirus for cancer gene therapy

Adenovirus provides many opportunities as a vector for delivery of cytotoxic genes to tumours. Polymer coating of adenovirus is known to increase its plasma circulation kinetics, affording the possibility of active and passive targeting to tumours. Here we show that polymer-coating adenovirus (pc-virus) abrogates its normal infectivity in vitro and also in liver following intravenous injection. The coated virus accumulates within solid subcutaneous AB22 mesothelioma tumours 40-times more than unmodified virus, and mediates higher levels of transgene expression within tumours. This is the first demonstration of passive tumour targeting of polymer-coated adenoviruses administered by intravenous injection, and also the first time pc-virus has been shown to be infectious following passive targeting to tumours in vivo. This technology provides an interesting option for delivery of therapeutic viruses to disseminated tumour masses by intravenous injection.

Effective induction of high-titer antibodies by viral vector vaccines

Protein-in-adjuvant vaccines have shown limited success against difficult diseases such as blood-stage malaria. Here we show that a recombinant adenovirus-poxvirus prime-boost immunization regime (known to induce strong T cell immunogenicity) can also induce very strong antigen-specific antibody responses, and we identify a simple complement-based adjuvant to further enhance immunogenicity. Antibodies induced against a blood-stage malaria antigen by this viral vector platform are highly effective against Plasmodium yoelii parasites in mice and against Plasmodium falciparum in vitro.

Creation of hybrid nanorods from sequences of natural trimeric fibrous proteins using the fibritin trimerization motif

Stable, artificial fibrous proteins that can be functionalized open new avenues in fields such as bionanomaterials design and fiber engineering. An important source of inspiration for the creation of such proteins are natural fibrous proteins such as collagen, elastin, insect silks, and fibers from phages and viruses. The fibrous parts of this last class of proteins usually adopt trimeric, beta-stranded structural folds and are appended to globular, receptor-binding domains. It has been recently shown that the globular domains are essential for correct folding and trimerization and can be successfully substituted by a very small (27-amino acid) trimerization motif from phage T4 fibritin. The hybrid proteins are correctly folded nanorods that can withstand extreme conditions. When the fibrous part derives from the adenovirus fiber shaft, different tissue-targeting specificities can be engineered into the hybrid proteins, which therefore can be used as gene therapy vectors. The integration of such stable nanorods in devices is also a big challenge in the field of biomechanical design. The fibritin foldon domain is a versatile trimerization motif and can be combined with a variety of fibrous motifs, such as coiled-coil, collagenous, and triple beta-stranded motifs, provided the appropriate linkers are used. The combination of different motifs within the same fibrous molecule to create stable rods with multiple functions can even be envisioned. We provide a comprehensive overview of the experimental procedures used for designing, creating, and characterizing hybrid fibrous nanorods using the fibritin trimerization motif.

Identification of CD46 binding sites within the adenovirus serotype 35 fiber knob

Species B human adenoviruses (Ads) are often associated with fatal illnesses in immunocompromised individuals. Recently, species B Ads, most of which use the ubiquitously expressed complement regulatory protein CD46 as a primary attachment receptor, have gained interest for use as gene therapy vectors. In this study, we focused on species B Ad serotype 35 (Ad35), whose trimeric fiber knob domain binds to three CD46 molecules with a KD (equilibrium dissociation constant) of 15.5 nM. To study the Ad35 knob-CD46 interaction, we generated an expression library of Ad35 knobs with random mutations and screened it for CD46 binding. We identified four critical residues (Phe242, Arg279, Ser282, and Glu302) which, when mutated, ablated Ad35 knob binding to CD46 without affecting knob trimerization. The functional importance of the identified residues was validated in surface plasmon resonance and competition binding studies. To model the Ad35 knob-CD46 interaction, we resolved the Ad35 knob structure at 2-A resolution by X-ray crystallography and overlaid it onto the existing structure for Ad11-CD46 interaction. According to our model, all identified Ad35 residues are in regions that interact with CD46, whereby one CD46 molecule binds between two knob monomers. This mode of interaction might have potential consequences for CD46 signaling and intracellular trafficking of Ad35. Our findings are also fundamental for better characterization of species B Ads and design of antiviral drugs, as well as for application of species B Ads as in vivo and in vitro gene transfer vectors.

Antitumour activity of cationic-liposome-conjugated adenovirus containing the CCL19 [chemokine (C-C motif) ligand 19] gene

CCL19 [chemokine (C-C motif) ligand 19; also known as MIP-3beta (macrophage inflammatory protein-3beta) or ELC (Epstein-Barr-virus-induced molecule 1 ligand chemokine)], one of the immunostimulatory cytokines, chemoattracts both DCs (dendritic cells) and T-lymphocytes. Adenoviral vector is one of the most used gene delivery vectors for cancer therapy because of its high gene-transfection efficiency. However, its wider application is limited, owing to immune responses that reduce transgene expression and decrease the efficacy of repeated administration. We constructed the recombinant replication deficient adenoviral vectors containing the CCL19 gene (Ad-CCL19) and combined them with PEG-PE [poly(ethylene glycol)-phosphatidylethanolamine]-modified cationic liposomes (Ad-CCL19/PEG-PE) for immunotherapy against murine fibrosarcoma. Although there were hardly any therapeutic differences between Ad-CCL19- and Ad-CCL19/PEG-PE-treated mice that were observed at the second administration, the final results demonstrated that Ad-CCL19/PEG-PE-treated mice survived much longer. The antitumour efficacy may be related to the high level of CCL19 after the final administration and lasting expression of IFN-gamma (interferon-gamma) and IL-12 (interleukin-12) in the Ad-CCL19/PEG-PE-treated group, which were measured by reverse-transcription PCR and ELISA. The results demonstrated that PEG-PE-cationic-liposome-conjugated adenovirus could prolong the expression of the therapeutic gene in vivo and may enhance the antitumour efficacy.

Adenoviral vectors for gene therapy

Vectors based on human adenovirus serotypes 2 (Ad2) and 5 (Ad5) of species C possess a number of features that have favored their widespread employment for gene delivery both in vitro and in vivo. However, the use of recombinant Ad2- and Ad5-based vectors for gene therapy also suffers from a number of disadvantages. These vectors possess the tropism of the parental viruses, which infect all cells that possess the appropriate surface receptors, precluding the targeting of specific cell types. Conversely, some cell types that represent important targets for gene transfer express only low levels of the cellular receptors, which lead to inefficient infection. Another major disadvantage of Ad2- and Ad5-based vectors in vivo is the elicitation of both an innate and an acquired immune response. Considerable attention has therefore been focused on strategies to overcome these limitations, thereby permitting the full potential of adenoviral vectors to be realized.

Modification of adenovirus gene transfer vectors with synthetic polymers: a scientific review and technical guide

The chemical modification of adenovirus (Ad) gene transfer vectors with synthetic polymers is a promising strategy for overcoming typical in vivo hurdles associated with Ad-mediated gene delivery. Polymer-modified Ad vectors induce significantly reduced innate immune responses, can evade pre-existing anti-Ad antibodies, allow for repeated vector delivery, and have been used for developing novel retargeting strategies. The most widely used polymers for covalent chemical capsid surface modification are poly-N-(2-hydroxypropyl)methacrylamide (poly-HPMA) and polyethylene glycol (PEG), and the latter is in wide clinical use for modifying protein biopharmaceuticals. In this review, we critically compare the properties of various polymers with respect to Ad vector shielding and retargeting, and identify areas for future research on polymer-modified viral vectors. We describe the potential technical pitfalls of polymer modification of Ad vectors and provide a technical guide for avoiding these while establishing polymer modification techniques in the laboratory.

Effective tumor targeted gene transfer using PEGylated adenovirus vector via systemic administration

Conjugation of polyethylene glycol to protein or particles (PEGylation) prolongs their plasma half-lives and promotes their accumulation in tumors due to enhanced permeability and retention (EPR) effect. Although PEGylation of adenovirus vectors (Ads) is an attractive strategy to improve the in vivo kinetics of conventional Ads, the EPR effect of PEGylated Ad (PEG-Ad) had not previously been reported. In this study, we prepared PEG-Ads with PEG at various modification ratios, injected them intravenously into tumor-bearing mice, and determined the blood kinetics, viral distribution, and gene expression patterns, respectively. In addition, we conducted a cancer therapeutic study of PEG-Ad encoding tumor necrosis factor (TNF)-alpha. The plasma half-life of PEG-Ad was longer than that of unmodified-Ad, and accumulation of PEG-Ad in tumor tissue increased as the PEG modification ratio increased. In particular, PEG-Ad with about 90% modification ratio showed higher (35 times) gene expression in tumor and lower (6%) in liver, compared with values for unmodified Ad. Moreover, PEG-Ad encoding TNF-alpha demonstrated not only stronger tumor-suppressive activity but also fewer hepatotoxic side effects compared with unmodified-Ad. PEGylation of Ad achieved tumor targeting through the EPR effect, and these attributes suggest that systemic injection of PEG-Ad has great potential as an anti-tumor treatment.