Effect of pH and ionic strength on the physical stability of adenovirus type 5

Lyophilization as an effective tool to develop AAV8 gene therapy products for refrigerated storage

Recombinant adeno-associated virus (rAAV) has emerged as the leading gene delivery platform for treatment of monogenic disorders. Currently, for clinical and commercial products, rAAVs are typically formulated and stored below -65 °C as frozen liquid. Their long-term storage is often far from ideal because it may result in shorter drug product (DP) shelf-life compared to recombinant protein-based biologics, and also presents challenges for supply chain and inventory management. Consequently, there is great interest in developing robust lyophilized AAV DPs that are stable at 2 to 8 °C. In this study, we evaluated formulation excipients required for stable lyophilized AAV8 products including buffers, salts, cryoprotectants/lyoprotectants, surfactants, and bulking agents, and optimized the concentrations and ratios between the excipients. This led to the identification of the lead formulation that demonstrated short-term in-solution stability at 25 °C and, upon lyophilization, sufficient long-term stability at 2 to 8 °C. Our study demonstrated that, in the presence of 110 mM salts, mannitol can serve as an effective bulking agent with the appropriate formulation and lyophilization process design, and the sucrose to mannitol ratio is critical to maintain the stability and cake appearance of the lyophilized AAV8 DP. Thorough characterization of the effect of formulation components on the properties and quality of the lyophilized DP led to an optimized AAV8 lyophilized DP. This approach could be applied to streamline the future development of lyophilized AAV gene therapy products with various target transgenes and capsid serotypes.

Study of Oncolytic Virus Preservation and Formulation

In recent years, oncolytic viruses (OVs) have emerged as an effective means of treating cancer. OVs have multiple oncotherapeutic functions including specifically infecting and lysing tumor cells, initiating immune cell death, attacking and destroying tumor angiogenesis and triggering a broad bystander effect. Oncolytic viruses have been used in clinical trials and clinical treatment as drugs for cancer therapy, and as a result, oncolytic viruses are required to have long-term storage stability for clinical use. In the clinical application of oncolytic viruses, formulation design plays a decisive role in the stability of the virus. Therefore, this paper reviews the degradation factors and their degradation mechanisms (pH, thermal stress, freeze-thaw damage, surface adsorption, oxidation, etc.) faced by oncolytic viruses during storage, and it discusses how to rationally add excipients for the degradation mechanisms to achieve the purpose of maintaining the long-term stability of oncolytic viral activity. Finally, the formulation strategies for the long-term formulation stability of oncolytic viruses are discussed in terms of buffers, permeation agents, cryoprotectants, surfactants, free radical scavengers, and bulking agent based on virus degradation mechanisms.

Incubation Temperature and Period During Denarase Treatment and Microfiltration Affect the Yield of Recombinant Adenoviral Vectors During Downstream Processing

Adenoviral vectors (AV) are commonly used as vaccine and gene therapy vehicles because of their ease of construction, ability to grow to high titers in the large-scale production process, and safety for human applications. However, the efficiency rate of downstream processes for adenoviral vectors still varies greatly. In the current study, we aimed to investigate the effect of the downstream treatment protocol and microfiltration of the harvested upstream material on viral vector yield. We compared the performance of the repeated freeze-thaw (RFT) and the Tween-20 detergent lysis (DLT) methods. In addition, the effects of the cell lysis method, incubation temperature, and time on viral yield were investigated. The samples were incubated at either room temperature or 37 °C for 1-, 2-, and 4-h periods. Samples were filtered with PES and SFCA membrane. Virus yield and infectivity were assayed by qPCR and immuno-titration. In conclusion, our results suggest that 2-h incubation gives the best results when incubated at 37 °C for denarase activity when Tween-20 is used for virus recovery. If the room temperature is preferred, 4-h incubation could be preferred. A phase 1 clinical trial (NCT05526183, January 21, 2022) was started with the recombinant adenovirus used in the study.

Disinfection efficacy and mechanism of olanexidine gluconate against norovirus

BACKGROUND

The purpose of this study was to evaluate the virucidal activity of a new olanexidine-containing formulation for hand hygiene (olanexidine gluconate hand rub; OLG-HR) against non-enveloped viruses and to understand its mechanism of action.

METHODS

The virucidal activities of OLG-HR against two strains of caliciviruses and three adenovirus serotypes were evaluated through suspension tests. Also, virus-like particles were used to predict the effect of olanexidine gluconate on virus particle structure.

RESULTS

The results of suspension tests under conditions with and without interfering substances (1.5% BSA) indicated that OLG-HR had a broad-spectrum effect against non-enveloped viruses, and the virucidal effect was unaffected by organic contaminants. Furthermore, olanexidine inhibited the binding ability of virus-like particles to the binding receptor of human norovirus and increased the aggregation of virus-like particles in a dose-dependent manner. Transmission electron microscopy showed that the morphology of the virus-like particles was affected by exposure to olanexidine, indicating that the protein-denaturing effect of olanexidine gluconate caused the loss of receptor-binding capability of the viral capsid protein.

CONCLUSIONS

This study suggests that olanexidine gluconate is a potential biological and environmental disinfectant against norovirus and adenovirus.

Quantification of infectious Human mastadenovirus in environmental matrices using PMAxx-qPCR

Molecular methodologies providing data on viral concentration and infectivity have been successfully used in environmental virology, supporting quantitative risk assessment studies. The present study aimed to assess human mastadenovirus (HAdV) intact particles using a derivative of propidium monoazide associated with qPCR (PMAxx-qPCR) in aquatic matrices. Initially, different concentrations of PMAxx were evaluated to establish an optimal protocol for treating different naturally contaminated matrices, using 10 min incubation in the dark at 200 rpm at room temperature and 15 min of photoactivation in the PMA-Lite™ LED photolysis device. There was no significant reduction in the quantification of infectious HAdV with increasing concentration of PMAxx used (20 μM, 50 μM, and 100 μM), except for sewage samples. In this matrix, a reduction of 5.01 log of genomic copies (GC)/L was observed from the concentration of 50 μM and revealed 100% HAdV particles with damaged capsids. On the other hand, the mean reduction of 0.51 log in stool samples using the same concentration mentioned above demonstrated 83% of damaged particles eliminated in the stool. Following, 50 μM PMAxx-qPCR protocol revealed a log reduction of 0.91, 0.67, and 1.05 in other samples of raw sewage, brackish, and seawater where HAdV concentration reached 1.47 × 10⁴, 6.81 × 10², and 2.33 × 10² GC/L, respectively. Fifty micrometers of PMAxx protocol helped screen intact viruses from different matrices, including sea and brackish water.

Acidification induces condensation of the adenovirus core

The adenovirus (AdV) icosahedral capsid encloses a nucleoprotein core formed by the dsDNA genome bound to numerous copies of virus-encoded, positively charged proteins. For an efficient delivery of its genome, AdV must undergo a cascade of dismantling events from the plasma membrane to the nuclear pore. Throughout this uncoating process, the virion moves across potentially disruptive environments whose influence in particle stability is poorly understood. In this work we analyze the effect of acidic conditions on AdV particles by exploring their mechanical properties, genome accessibility and capsid disruption. Our results show that under short term acidification the AdV virion becomes softer and its genome less accessible to an intercalating dye, even in the presence of capsid openings. The AFM tip penetrates deeper in virions at neutral pH, and mechanical properties of genome-less particles are not altered upon acidification. Altogether, these results indicate that the main effect of acidification is the compaction of the nucleoproteic core, revealing a previously unknown role for chemical cues in AdV uncoating. STATEMENT OF SIGNIFICANCE: Studying the behavior of virus particles under changing environmental conditions is key to understand cell entry and propagation. One such change is the acidification undergone in certain cell compartments, which is thought to play a role in the programmed uncoating of virus genomes. Mild acidification in the early endosome has been proposed as a trigger signal for human AdV uncoating. However, the actual effect of low pH in AdV stability and entry is not well defined. Understanding the consequences of acidification in AdV structure and stability is also relevant to define storage conditions for therapeutic vectors, or design AdV variants resistant to intestinal conditions for oral administration of vaccines.

Manufacturing Challenges and Rational Formulation Development for AAV Viral Vectors

Adeno-associated virus (AAV) has emerged as a leading platform for gene delivery for treating various diseases due to its excellent safety profile and efficient transduction to various target tissues. However, the large-scale production and long-term storage of viral vectors is not efficient resulting in lower yields, moderate purity, and shorter shelf-life compared to recombinant protein therapeutics. This review provides a comprehensive analysis of upstream, downstream and formulation unit operation challenges encountered during AAV vector manufacturing, and discusses how desired product quality attributes can be maintained throughout product shelf-life by understanding the degradation mechanisms and formulation strategies. The mechanisms of various physical and chemical instabilities that the viral vector may encounter during its production and shelf-life because of various stressed conditions such as thermal, shear, freeze-thaw, and light exposure are highlighted. The role of buffer, pH, excipients, and impurities on the stability of viral vectors is also discussed. As such, the aim of this review is to outline the tools and a potential roadmap for improving the quality of AAV-based drug products by stressing the need for a mechanistic understanding of the involved processes.

The Effect of Residual Triton X-100 on Structural Stability and Infection Activity of Adenovirus Particles

To ensure the high purity and biological activity of the adenovirus vector to be used for clinical applications, a stable and linearly scalable preparation method is highly imperative. During the adenovirus-harvesting process, the Triton X-100-based lysis method possesses the advantages of higher efficiency as well as easier linearization and amplification. Most Triton X-100 can be removed from the adenovirus sample by chromatographic purification. However, there is no report that a small amount of residual Triton X-100, present in adenovirus sample, can affect the particle integrity, infectivity, and structure of adenoviruses. Here, we found that although residual Triton X-100 affected the short-term stability, purity, infectivity, and structure of adenoviruses at 37°C, it did not hamper these properties of adenoviruses at 4°C. This study suggests that although the Triton X-100-based lysis method is a simple, efficient, and easy-to-scale process for lysing host cells to release the adenovirus, the storage conditions of adenovirus products must be taken into consideration.

Live vaccine preserved at room temperature: Preparation and characterization of a freeze-dried classical swine fever virus vaccine

The heat-stable live-attenuated classical swine fever virus (CSFV) vaccine is an urgent need in many countries of Asia, Europe and Latin America. In this study, the thermostability of lyophilized live-attenuated CSFV vaccine formulations were investigated using accelerated stability at 37 °C for 10 days. The freeze-dried heat-stable formulation ST16, containing excipient combinations of trehalose, glycine, thiourea and phosphate buffer shows the superior thermostability. Moreover, the lyophilized vaccine with formula ST16 kept loss of viral activity less than 0.5 log₁₀ during 24 months at storage temperatures of 2-8 °C. In thermal study, ST16 stabilized the vaccine within 1.0 log₁₀ loss after storage at up to 25 °C for 6 months and room temperature for 7 months. Even under the harshest storage conditions of 37 °C for 25 days and 45 °C for 2 weeks, the virus titer dropped less than 1.0 log₁₀ using ST16. Besides, it is notable that ST16 excluded gelatin and exogenous proteins, which might cause allergic reactions, thus avoiding immune side effects. The vaccine formulated ST16 proved to be safe and effective when immunized to piglets in vivo. The characteristics of dried vaccines were analyzed by X-ray powder diffraction, residual water measurements, differential scanning calorimetry and it was found that vaccine antigen were preserved in an amorphous matrix with high glass transition temperature above 60 °C and low residual water content below 2%, which made the vaccine more stable during storage.

Tumour vasculature: Friend or foe of oncolytic viruses?

In the past two decades there have been substantial advances in understanding the anti-cancer mechanisms of oncolytic viruses (OVs). OVs can mediate their effects directly, by preferentially infecting and killing tumour cells. Additionally, OVs can indirectly generate anti-tumour immune responses. These differing mechanisms have led to a paradoxical divergence in strategies employed to further increase the potency of oncolytic virotherapies. On one hand, the tumour neovasculature is seen as a vital lifeline to the survival of the tumour, leading some to use OVs to target the tumour vasculature in hopes to starve cancers. Therapeutics causing vascular collapse can potentiate tumour hypoxia, nutrient restriction and pro-inflammatory cytokine release, which has shown promise in oncological studies. On the other hand, the same vasculature plays an important role for the dissemination of OVs, trafficking of effector cells and other therapeutics, which has prompted researchers to find ways of normalizing the vasculature to enhance infiltration of leukocytes and delivery of therapeutic agents. This article describes the recent developments of therapies aimed to shut down versus normalize tumour vasculature in order to inform researchers striving to optimize OV-based therapies.

Effect of Shear Stresses on Adenovirus Activity and Aggregation during Atomization To Produce Thermally Stable Vaccines by Spray Drying

Considering the substantive potential benefits of thermally stable dry powder vaccines to public health, causes for inactivation of their sensitive viral vectors during preparation require intensive study. The focus of this work was atomization of suspensions containing encapsulating excipients and a human type 5 adenovirus, involving a detailed investigation of shear stresses in the nozzle of a spray dryer. Samples were sprayed at 25 °C into falcon tubes and immediately evaluated for viral activity by in vitro testing, minimizing the confounding of thermal effects on the deactivation of the virus, although interfacial stresses could not be decoupled from shear stresses. Despite the expectations of only virus deactivation with ever-increasing shear stresses in the spray nozzle, some conditions were found to show better activity than the positive control, leading to investigations of viral aggregation. It was found that the adenovirus experienced minor aggregation when mixed with the excipient solutions, which was reversed by subjecting samples to moderate shear conditions in the spray nozzle. At very high shear rates, the activity diminished again because of damage to the viral capsid fibers, which also led to the production of new aggregates after atomization. Despite these findings, activity losses caused by shear were small compared to the overall spray drying process loss. However, formulation composition, solution viscosity, and process conditions should be considered carefully for optimization because of their impact on aggregation. This is the first known report comparing shear, aggregation, and biological activity loss during the atomization step of spray drying viral vaccines.

Stabilization and formulation of a recombinant Human Cytomegalovirus vector for use as a candidate HIV-1 vaccine

Live attenuated viral vaccine/vector candidates are inherently unstable and infectivity titer losses can readily occur without defining appropriate formulations, storage conditions and clinical handling practices. During initial process development of a candidate vaccine against HIV-1 using a recombinant Human Cytomegalovirus vector (rHCMV-1), large vector titer losses were observed after storage at 4 °C and after undergoing freeze-thaw. Thus, the goal of this work was to develop candidate frozen liquid formulations of rHCMV-1 with improved freeze-thaw and short-term liquid stability for potential use in early clinical trials. To this end, a virus stability screening protocol was developed including use of a rapid, in vitro cell-based immunofluorescence focus assay to quantitate viral titers. A library of ∼50 pharmaceutical excipients (from various known classes of additives) were evaluated for their effect on vector stability after freeze-thaw cycling or incubation at 4 °C for several days. Certain additives including sugars and polymers (e.g., trehalose, sucrose, sorbitol, hydrolyzed gelatin, dextran 40) as well as removal of NaCl (lower ionic strength) protected rHCMV-1 against freeze-thaw mediated losses in viral titers. Optimized solution conditions (e.g., solution pH, buffers and sugar type) slowed the rate of rHCMV-1 titer losses in the liquid state at 4 °C. After evaluating various excipient combinations, three new candidate formulations were designed and rHCMV-1 stability was benchmarked against both the currently-used and a previously reported formulation. The new candidate formulations were significantly more stable in terms of reducing rHCMV-1 titer losses after 5 freeze-thaw cycles or incubation at 4 °C for 30 days. This case study highlights the utility of semi-empirical design of frozen liquid formulations of a live viral vaccine candidate, where protection against infectivity titer losses due to freeze-thaw and short-term liquid storage are sufficient to enable more rapid initiation of early clinical trials.

Systemic delivery and SPECT/CT in vivo imaging of 125I-labelled oncolytic adenoviral mutants in models of pancreatic cancer

Early phase clinical trials have demonstrated good therapeutic index for oncolytic adenoviruses in patients with solid tumours when administered intratumorally, resulting in local tumour elimination. Entrapment and binding of adenovirus to erythrocytes, blood factors, and neutralising antibodies have prevented efficient systemic delivery and targeting of distant lesions in the clinic. We previously generated the novel replication-selective Ad-3∆-A20T to improve tumour targeting by increasing the viral dose at distant sites. Here, we developed a protocol to directly radiolabel the virus for rapid and sensitive detection by single-photon emitted computed tomography (SPECT/CT) providing a convenient method for determining biodistribution following intravenous administration in murine models. Longitudinal whole-body scans, demonstrated efficient viral uptake in pancreatic Suit-2 and Panc04.03 xenografts with trace amounts of ¹²⁵I-Ad-3∆-A20T up to 48 h after tail vein delivery. Hepatic and splenic radioactivity decreased over time. Analysis of tissues harvested at the end of the study, confirmed potency and selectivity of mutant viruses. Ad-3∆-A20T-treated animals showed higher viral genome copy numbers and E1A gene expression in tumors than in liver and spleen compared to Ad5wt. Our direct radiolabeling approach, allows for immediate screening of novel oncolytic adenoviruses and selection of optimal viral genome alterations to generate improved mutants.

Factors determining phage stability/activity: challenges in practical phage application

Introduction: Phages consist of nucleic acids and proteins that may lose their activity under different physico-chemical conditions. The production process of phage formulations may decrease phage infectivity. Ingredients present in the preparation may influence phage particles, although preparation and storage conditions may also cause variations in phage titer. Significant factors are the manner of phage application, the patient's immune system status, the type of medication being taken, and diet. Areas covered: We discuss factors determining phage activity and stability, which is relevant for the preparation and application of phage formulations with the highest therapeutic efficacy. Our article should be helpful for more insightful implementation of clinical trials, which could pave the way for successful phage therapy. Expert opinion: The number of naturally occurring phages is practically unlimited and phages vary in their susceptibility to external factors. Modern methods offer engineering techniques which should lead to enhanced precision in phage delivery and anti-bacterial activity. Recent data suggesting that phages may also be used in treating nonbacterial infections as well as anti-inflammatory and immunomodulatory agents add further weight to such studies. It may be anticipated that different phage activities could have varying susceptibility to factors determining their actions.

Effect of cold atmospheric plasma (CAP) on human adenoviruses is adenovirus type-dependent

More than 70 human adenovirus types were identified divided into 7 different species (A-G). Diseases caused by human adenoviruses are type-dependent and can range from mild to severe respiratory infections, gastrointestinal infections or eye infections such as epidemic keratoconjunctivitis. Unfortunately there is no specific anti-adenovirus therapy available. Here we addressed the question whether treatment with cold atmospheric plasma (CAP) for anti-adenoviral therapy such as virus-mediated ulcerations may be feasible. CAP has already been explored for the treatment of dermatological diseases such as chronic wounds. To investigate whether CAP is an effective antiviral tool, purified human adenovirus types derived from different human adenovirus species (HAdV -4, -5, -20, -35, -37, -50) tagged with luciferase were treated with defined dosages of plasma. The CAP treatment was varied by incrementally increasing the time span of CAP treatment. After CAP treatment, the virus containing solution was added to eukaryotic cells and the viral load was determined by measurement of luciferase expression levels. Through the plasma treatment the adenovirus driven luciferase expression directly correlating with adenovirus transduction efficiencies could be reduced for HAdV-5 and HAdV-37. Plasma treatment had no influence on adenovirus derived luciferase expression levels for HAdV-4 and HAdV-50 and it even had a positive effect on luciferase expression levels for HAdV-20 and HAdV-35. These results suggest that CAP has a type dependent effect on adenoviruses and that infectivity can be even increased for certain adenovirus types. Further studies should address the mechanisms behind this phenomenon. In summary we demonstrate that CAP may represent an interesting option for antiviral treatment in a virus type dependent manner.

Comparison of internal process control viruses for detection of food and waterborne viruses

Enteric viruses are pathogens associated with food- and waterborne outbreaks. The recovery of viruses from food or water samples is affected by the procedures applied to detect and concentrate them. The incorporation of an internal process control virus to the analyses allows monitoring the performance of the methodology. The aim of this study was to produce a recombinant adenovirus (rAdV) and apply it together with bacteriophage PP7 as process controls. The rAdV carries a DNA construction in its genome to differentiate it from wild-type adenovirus by qPCR. The stability of both control viruses was evaluated at different pH conditions. The rAdV was stable at pH 3, 7, and 10 for 18 h. PP7 infectious particles were stable at pH 7 and showed a 2.14 log reduction at pH 10 and total decay at pH 3 after 18 h. Three virus concentration methods were evaluated: hollow-fiber tap water ultrafiltration, wastewater ultracentrifugation, and elution-PEG precipitation from lettuce. Total and infectious viruses were quantified and their recoveries were calculated. Virus recovery for rAdV and PP7 by ultrafiltration showed a wide range (2.10-84.42 and 13.54-84.62%, respectively), whereas that by ultracentrifugation was 5.05-13.71 and 6.98-13.27%, respectively. The performance of ultracentrifugation to concentrate norovirus and enteroviruses present in sewage was not significantly different to the recovery of control viruses. For detection of viruses from lettuce, genomic copies of PP7 were significantly more highly recovered than adenovirus (14.74-18.82 and 0.00-3.44%, respectively). The recovery of infectious virus particles was significantly affected during sewage ultracentrifugation and concentration from lettuce. The simultaneous use of virus controls with dissimilar characteristics and behaviors might resemble different enteric viruses.

Identification of Excipients for Stabilizing Fiberless Adenovirus as Biopharmaceuticals

Reducing the promiscuous tropism of native adenovirus by using fiberless adenovirus is advantageous toward its use as a gene therapy vector or vaccine component. The removal of the fiber protein on native adenovirus abrogates several undesirable interactions; however, this approach decreases the particle's physical stability. To create stable fiberless adenovirus for pharmaceutical use, the effects of temperature and pH on the particle's stability profile must be addressed. Our results indicate that the stability of fiberless adenovirus is increased when it is stored in mildly acidic conditions around pH 6. The stability of fiberless adenovirus can be further enhanced by using excipients. Excipient screening results indicate that the nonionic surfactant Pluronic F-68 and the amino acid glycine are potential stabilizers because of their ability to increase the thermal transition temperature of the virus particle and promote retention of biological activity after exposure to prolonged thermal stress. Our data indicate that the instability of fiberless adenovirus can be ameliorated by storing the virus in the appropriate environment, and it should be possible to further optimize the virus so that it can be used as a biopharmaceutical.

Ionic strength effects on the photodegradation reactions of riboflavin in aqueous solution

A study of the effect of ionic strength on the photodegradation reactions (photoreduction and photoaddition) of riboflavin (RF) in phosphate buffer (pH7.0) has been carried out using a specific multicomponent spectrometric method. It has been found that the rates of photodegradation reactions of RF are dependent upon the ionic strength of the solutions at different buffer concentrations. The apparent first-order rate constants (kobs) for the photodegradation of riboflavin at ionic strengths of 0.1-0.5 (0.5M phosphate) lie in the range of 7.35-30.32 × 10(-3) min(-1). Under these conditions, the rate constants for the formation of the major products, lumichrome (LC) by photoreduction pathway, and cyclodehydroriboflavin (CDRF) by photoaddition pathway, are in the range of 3.80-16.03 and 1.70-6.07 × 10(-3) min(-1), respectively. A linear relationship has been observed between log kobs and √μ/1+√μ. A similar plot of log k/ko against √μ yields a straight line with a value of ~+1 for ZAZB showing the involvement of a charged species in the rate determining step. NaCl appears to promote the photodegradation reactions of RF probably by an excited state interaction. The implications of ionic strength on RF photodegradation by different pathways and flavin-protein interactions have been discussed.

Behaviour and recovery of human adenovirus from tropical sediment under simulated conditions

This study assessed the contributions of pH and organic matter (OM) on the recovery of infectious human adenovirus 5 (HAdV-5) and genome copies (GCs) in waters that were artificially contaminated with tropical soil. The use of a mathematical equation was proposed based on the flocculation index of clay to assess the recovery of total GCs in these controlled assays. The results suggest that solids in the water reduced the viral genome copy loads per millilitre (GC · mL(-1)) and viral infectivity. OM did not influence the GC · mL(-1) recovery rate (p > 0.05) but led to a 99% (2 log10) reduction in plaque-forming unit counts per millilitre (PFU/mL), which indicates that infectivity and gene integrity were non-related parameters. Our findings also suggest that acidic pH levels hinder viral inactivation and that clay is the main factor responsible for the interactions of HAdV-5 with soil. These findings may be useful for future eco-epidemiological investigations and studies of viral inactivation or even as parameters for future research into water quality analysis and water treatment.

The effect of fiber truncations on the stability of adenovirus type 5

While fiberless adenovirus has the potential for use as a vaccine or gene delivery vector, some groups have observed instability issues associated with the modified virus. To investigate the effect of fiber modification on adenovirus stability, we produced mutant adenovirus particles that contained the tail and a portion of the shaft domain without the knob. The shaft domain was either completely removed (i.e., fiberless) or truncated to 7-, 14-, or 21-repeats. The mutants were evaluated by biophysical characterization techniques to determine their relative stabilities based on temperature-induced changes to the secondary, tertiary, and quaternary structures of the virus and its constituent proteins. Data acquired using circular dichroism, intrinsic/extrinsic fluorescence, and static/dynamic light scattering were compiled into a comprehensive empirical phase diagram, which showed that native adenovirus was the most stable followed by fiberless adenovirus and then the mutants with truncated fiber protein. In summary, the individual biophysical measurements and the empirical phase diagram showed that providing several repeats of shaft protein negatively impacted the structural stability of the virus more so than completely removing the fiber protein.

Scalable production of adenovirus vectors

Recombinant adenoviruses (AdV) are highly efficient at gene transfer for a broad spectrum of cell types and species. They became one of the vectors of choice for gene delivery and expression of foreign proteins in gene therapy and vaccination purposes. To meet the need of significant amounts of adenoviral vectors for preclinical and possibly clinical uses, scalable and reproducible production processes are required.In this chapter, we review processes used for scalable production of two types of first generation (E1-deleted) adenoviral vectors (Human and Canine) using stirred tank bioreactors. The production of adenovirus vectors using either suspension (HEK 293) or anchorage-dependent cells (MDCK-E1) are described to exemplify scalable production processes with different cell-culture types. The downstream processes will be covered in the next chapter.

pH shift assembly of adenoviral serotype 5 capsid protein nanosystems for enhanced delivery of nanoparticles, proteins and nucleic acids

Empty adenovirus serotype 5 (Ad5) capsids devoid of viral genome were developed as a novel delivery system for nanoparticles, proteins, and nucleic acids. Ad5 capsids of 110 nm diameter undergo an increase in particle size to 1637 nm in 1mM acetic acid at pH4.0 and then shrink to 60 nm, following pH reversal to 7.4. These pH shifts induced reversible changes in capsid zeta potential and secondary structure and irreversible changes in tertiary structure of capsid proteins. Using pH shift dependent changes in capsid size and structure, 20 nm fluorescent nanoparticles, FITC-BSA, and Alexa Fluor® 488 conjugated siRNA were encapsulated with high efficiency in Ad5 capsids, as confirmed by electron microscopy and/or flow cytometry. HEK cell uptake with capsid delivery system was 7.8-, 7.4-, and 2.9-fold greater for nanoparticles, FITC-BSA, and Alexa-siRNA, respectively, when compared to plain solutes. Physical mixtures of capsids and fluorescent solutes exhibited less capsid associated fluorescence intensity and cell uptake. Further, unlike physical mixture, pH shift assembled Ad5 capsids protected siRNA from RNase degradation. Ad5 capsids before and after pH shift exhibited endolysosomal escape. Thus, empty Ad5 capsids can encapsulate a variety of solutes based on pH shift assembly, resulting in enhanced cellular delivery.

The role of capsid maturation on adenovirus priming for sequential uncoating

Adenovirus assembly concludes with proteolytic processing of several capsid and core proteins. Immature virions containing precursor proteins lack infectivity because they cannot properly uncoat, becoming trapped in early endosomes. Structural studies have shown that precursors increase the network of interactions maintaining virion integrity. Using different biophysical techniques to analyze capsid disruption in vitro, we show that immature virions are more stable than the mature ones under a variety of stress conditions and that maturation primes adenovirus for highly cooperative DNA release. Cryoelectron tomography reveals that under mildly acidic conditions mimicking the early endosome, mature virions release pentons and peripheral core contents. At higher stress levels, both mature and immature capsids crack open. The virus core is completely released from cracked capsids in mature virions, but it remains connected to shell fragments in the immature particle. The extra stability of immature adenovirus does not equate with greater rigidity, because in nanoindentation assays immature virions exhibit greater elasticity than the mature particles. Our results have implications for the role of proteolytic maturation in adenovirus assembly and uncoating. Precursor proteins favor assembly by establishing stable interactions with the appropriate curvature and preventing premature ejection of contents by tightly sealing the capsid vertices. Upon maturation, core organization is looser, particularly at the periphery, and interactions preserving capsid curvature are weakened. The capsid becomes brittle, and pentons are more easily released. Based on these results, we hypothesize that changes in core compaction during maturation may increase capsid internal pressure to trigger proper uncoating of adenovirus.

Altering adenoviral tropism via click modification with ErbB specific ligands

Methods for targeting oncolytic viruses can increase efficacy and accelerate development. Genetic engineering, the predominant method for changing vector tropism, is limited in scope and often represents the bottleneck for vector development. Metabolic incorporation of an unnatural azido sugar, O-GlcNAz, at a specific site on the adenoviral surface allows chemoselective attachment of affibodies for Her2 or EGF receptors. Modification with these high-affinity, high-selectivity proteins is straightforward and readily generalizable, demonstrates minimal impact on virus physiology, and affords significant increases in gene delivery to cancer cells. As a result, this method has significant potential to increase the efficacy of next-generation viral vectors.

Advances in vaccines against neglected tropical diseases: enhancing physical stability of a recombinant hookworm vaccine through biophysical and formulation studies

A bivalent recombinant vaccine for human hookworm disease is under development. One of the lead candidate antigens in the vaccine is a glutathione S-transferase cloned from the hookworm Necator americanus (Na-GST-1) which is expressed in the yeast Pichia pastoris. Based on preliminary studies demonstrating that the recombinant protein was not stable in an acetate buffer at pH 6, we undertook an extensive stability analysis of the molecule. To improve and optimize stability we complemented traditional methods employed for macromolecule and vaccine stabilization with biophysical techniques that were incorporated into a systematic process based on an eigenvector approach. Large data sets, obtained from a variety of experimental methods were used to establish a color map ("empirical phase diagram") of the physical stability of the vaccine antigen over a wide range of temperature and pH. The resulting map defined "apparent phase boundaries" that were used to develop high throughput screening assays. These assays were then employed to identify excipients that stabilized the antigen against physical degradation that could otherwise result in losses of physicochemical integrity, immunogenicity, and potency of the vaccine. Based on these evaluations, the recombinant Na-GST-1 antigen was reformulated and ultimately produced under Good Manufacturing Practices and with an acceptable stability profile.

Coated microneedle arrays for transcutaneous delivery of live virus vaccines

Vaccines are sensitive biologics that require continuous refrigerated storage to maintain their viability. The vast majority of vaccines are also administered using needles and syringes. The need for cold chain storage and the significant logistics surrounding needle-and-syringe vaccination is constraining the success of immunization programs. Recombinant live viral vectors are a promising platform for the development of vaccines against a number of infectious diseases, however these viruses must retain infectivity to be effective. Microneedles offer an effective and painless method for delivery of vaccines directly into skin that in the future could provide solutions to current vaccination issues. Here we investigated methods of coating live recombinant adenovirus and modified vaccinia virus Ankara (MVA) vectors onto solid microneedle arrays. An effective spray-coating method, using conventional pharmaceutical processes, was developed, in tandem with suitable sugar-based formulations, which produces arrays with a unique coating of viable virus in a dry form around the shaft of each microneedle on the array. Administration of live virus-coated microneedle arrays successfully resulted in virus delivery, transcutaneous infection and induced an antibody or CD8(+) T cell response in mice that was comparable to that obtained by needle-and-syringe intradermal immunization. To our knowledge, this is the first report of successful vaccination with recombinant live viral vectored vaccines coated on microneedle delivery devices.

Multidimensional methods for the formulation of biopharmaceuticals and vaccines

Determining and preserving the higher order structural integrity and conformational stability of proteins, plasmid DNA, and macromolecular complexes such as viruses, virus-like particles, and adjuvanted antigens are often a significant barrier to the successful stabilization and formulation of biopharmaceutical drugs and vaccines. These properties typically must be investigated with multiple lower resolution experimental methods because each technique monitors only a narrow aspect of the overall conformational state of a macromolecular system. This review describes the use of empirical phase diagrams (EPDs) to combine large amounts of data from multiple high-throughput instruments and construct a map of a target macromolecule's physical state as a function of temperature, solvent conditions, and other stress variables. We present a tutorial on the mathematical methodology, an overview of some of the experimental methods typically used, and examples of some of the previous major formulation applications. We also explore novel applications of EPDs including potential new mathematical approaches as well as possible new biopharmaceutical applications such as analytical comparability, chemical stability, and protein dynamics.

Protein-excipient interactions: mechanisms and biophysical characterization applied to protein formulation development

The purpose of this review is to demonstrate the critical importance of understanding protein-excipient interactions as a key step in the rational design of formulations to stabilize and deliver protein-based therapeutic drugs and vaccines. Biophysical methods used to examine various molecular interactions between solutes and protein molecules are discussed with an emphasis on applications to pharmaceutical excipients in terms of their effects on protein stability. Key mechanisms of protein-excipient interactions such as electrostatic and cation-pi interactions, preferential hydration, dispersive forces, and hydrogen bonding are presented in the context of different physical states of the formulation such as frozen liquids, solutions, gels, freeze-dried solids and interfacial phenomenon. An overview of the different classes of pharmaceutical excipients used to formulate and stabilize protein therapeutic drugs is also presented along with the rationale for use in different dosage forms including practical pharmaceutical considerations. The utility of high throughput analytical methodologies to examine protein-excipient interactions is presented in terms of expanding formulation design space and accelerating experimental timelines.

Magnetic nanoparticles for targeted vascular delivery

Magnetic targeting has shown promise to improve the efficacy and safety of different classes of therapeutic agents by enabling their active guidance to the site of disease and minimizing dissemination to nontarget tissues. However, its translation into clinic has proven difficult because of inherent limitations of traditional approaches inapplicable for deep tissue targeting in human subjects and a need for developing well-characterized and fully biocompatible magnetic carrier formulations. A novel magnetic targeting scheme based on the magnetizing effect of deep-penetrating uniform fields is presented as an example of a strategy providing a potentially clinically viable solution for preventing injury-triggered reobstruction of stented blood vessels (in-stent restenosis). The design of optimized magnetic carrier formulations and experimental results showing the feasibility of uniform field-controlled targeting for site-specific vascular delivery of small-molecule pharmaceuticals, biotherapeutics, and cells are discussed in the context of antirestenotic therapy. The versatility of this approach applicable to different classes of therapeutic agents exerting their antirestenotic effects through distinct mechanisms prompts exploring the utility of uniform field-mediated magnetic stent targeting for combination therapies with enhanced efficiencies and improved safety profiles. Additional improvements in terms of site specificity and protracted carrier retention at the site of injury may be expected from the development and use of magnetic carriers exhibiting affinity for arterial wall-specific antigens.

Vaccines with aluminum-containing adjuvants: optimizing vaccine efficacy and thermal stability

Aluminum-containing adjuvants have been used to enhance the immune response against killed, inactivated, and subunit antigens for more than seven decades. Nevertheless, we are only beginning to gain important insight as to what may be some very fundamental parameters for optimizing their use. For example, there is evidence that the conventional approach of maximizing antigen binding (amount and/or strength) may not result in an optimal immune response. Adsorption of antigen onto the adjuvant has recently been suggested to decrease the thermal stability of some antigens; however, whether adsorption-induced alterations to the structure and/or stability of the antigen have consequences for the elicited immune response is unclear. Finally, the thermal stability of vaccines with aluminum-containing adjuvants is not robust. Optimizing the stability of these vaccines requires an understanding of the freeze sensitivity of the adjuvant, freeze and heat sensitivity of the antigen in the presence of the adjuvant, and perhaps most important, how (or whether) various approaches to formulation can be used to address these instabilities. This review attempts to summarize recent findings regarding issues that may dictate the success of vaccines with aluminum-containing adjuvants.

Arginine as a synergistic virucidal agent

Development of effective and environmentally friendly disinfectants, or virucidal agents, should help prevent the spread of infectious diseases through human contact with contaminated surfaces. These agents may also be used, if non-toxic to cells and tissues, as chemotherapeutic agents against infectious diseases. We have shown that arginine has a synergistic effect with a variety of virucidal conditions, namely acidic pH and high temperature, on virus inactivation. All of these treatments are effective, however, at the expense of toxicity. The ability of arginine to lower the effective threshold of these parameters may reduce the occurrence of potential toxic side effects. While it is clear that arginine can be safely used, the mechanism of its virus inactivation has not yet been elucidated. Here we examine the damages that viruses suffer from various physical and chemical stresses and their relations to virus inactivation and aggregation. Based on the relationship between the stress-induced structural damages and the infectivity of a virus, we will propose several plausible mechanisms describing the effects of arginine on virus inactivation using the current knowledge of aqueous arginine solution properties.

Polymer-functionalized nanoparticles: from stealth viruses to biocompatible quantum dots

In this article, we focus on nanoparticles that have been functionalized by polymers. We draw our examples from nanoparticle systems that have found biomedical and therapeutic applications. Our aim is to highlight the physical principles that might explain why these systems have been found to be successful in biomedical applications and to highlight other physical properties that might lead to new applications. We consider viruses, gold nanoparticles, magnetic nanoparticles and quantum dots, focussing attention on the ways in which functionalization by polymers has been used to alter the physical characteristics of the particular nanoparticle to improve its function as a possible therapy. In the case of viral vectors, polymer functionalization tunes the biocompatibility, suppressing the binding of antibodies and conferring the nanoparticle with stealth properties. By contrast, the inorganic nanoparticles comprise materials in a form that is not normally encountered in the human body, and polymer functionalization is necessary to ensure biocompatibility.

Adenovirus

Of the 53 different human adenovirus (HAdV) serotypes belonging to species A-G, a significant number are associated with acute respiratory, gastrointestinal and ocular infections. Replication-defective HAdV-5-based vectors also continue to play a significant role in gene transfer trials and in vaccine delivery efforts in the clinic. Although significant progress has been made from studies of AdV biology, we still have an incomplete understanding of AdV's structure as well as its multifactorial interactions with the host. Continuing efforts to improve knowledge in these areas, as discussed in this chapter, will be crucial for revealing the mechanisms of AdV pathogenesis and for allowing optimal use of AdV vectors for biomedical applications.

Structure and uncoating of immature adenovirus

Maturation via proteolytic processing is a common trait in the viral world and is often accompanied by large conformational changes and rearrangements in the capsid. The adenovirus protease has been shown to play a dual role in the viral infectious cycle: (a) in maturation, as viral assembly starts with precursors to several of the structural proteins but ends with proteolytically processed versions in the mature virion, and (b) in entry, because protease-impaired viruses have difficulties in endosome escape and uncoating. Indeed, viruses that have not undergone proteolytic processing are not infectious. We studied the three-dimensional structure of immature adenovirus particles as represented by the adenovirus type 2 thermosensitive mutant ts1 grown under non-permissive conditions and compared it with the mature capsid. Our three-dimensional electron microscopy maps at subnanometer resolution indicate that adenovirus maturation does not involve large-scale conformational changes in the capsid. Difference maps reveal the locations of unprocessed peptides pIIIa and pVI and help define their role in capsid assembly and maturation. An intriguing difference appears in the core, indicating a more compact organization and increased stability of the immature cores. We have further investigated these properties by in vitro disassembly assays. Fluorescence and electron microscopy experiments reveal differences in the stability and uncoating of immature viruses, both at the capsid and core levels, as well as disassembly intermediates not previously imaged.

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.

Adenoviruses: update on structure and function

Adenoviruses have been studied intensively for over 50 years as models of virus-cell interactions and latterly as gene vectors. With the advent of more sophisticated structural analysis techniques the disposition of most of the 13 structural proteins have been defined to a reasonable level. This review seeks to describe the functional properties of these proteins and shows that they all have a part to play in deciding the outcome of an infection and act at every level of the virus's path through the host cell. They are primarily involved in the induction of the different arms of the immune system and a better understanding of their overall properties should lead to more effective ways of combating virus infections.

Spectroscopic methods for the physical characterization and formulation of nonviral gene delivery systems

Currently, with the exception of naked DNA formulations, most pharmaceutical preparations of plasmid DNA employ some type of polycationic delivery vector such as synthetic cationic polymers and lipids to enhance delivery. A number of biophysical techniques are readily available for the structural characterization of plasmid DNA within synthetic gene delivery complexes. Here we present applications of ultraviolet (UV) absorption, circular dichroism (CD), infrared (IR), and fluorescence spectroscopies as well as dynamic light scattering to the structural analysis of the oligonucleotide component of nonviral gene delivery vectors. We also illustrate this approach for the investigation of the formulation of lipoplex and polyplex-based gene delivery systems. To summarize such data, we show how the macromolecular complexes can be represented as vectors in a highly dimensional space in which the components of the vector consist of normalized values of experimental parameters measured as a function of different solution conditions such as pH and ionic strength.

A Biophysical Characterization of the Peptide Drug Pramlintide (AC137) Using Empirical Phase Diagrams

AC137 (pramlintide) is a 37-residue peptide analogue of the hormone amylin. Pramlintide has been studied as an adjunct antihyperglycemic treatment for patients with type 2 or type 1 diabetes who use insulin. This study took an empirical phase diagram (EPD) approach to obtain information about the structural stability of this peptide by compiling thermal perturbation data acquired from multiple spectroscopic methods, including high-resolution second-derivative UV absorbance spectroscopy, optical density, fluorescence, and circular dichroism. This approach enabled us to accomplish two major goals: (1) characterize the structure and physical stability of AC137 and (2) assess the application of EPDs to a small peptide. Results obtained at low concentration of AC137 revealed a peptide with ill-defined structure and insensitivity to pH. Use of isotope exchange NMR confirmed this lack of structure. At the current formulation of pH 4, AC137 exhibited stability at concentrations of 1.8 to 8.8 mg/mL. High concentrations of the peptide showed a tendency to aggregate at pH 6-7.5. Construction of EPDs under the various experimental conditions examined manifested color changes that correlated well with the raw data. The utility and limitations of the EPD approach when applied to weakly structured peptides are discussed.

Purification and concentration of bacteriophage T4 using monolithic chromatographic supports

Phages are gaining importance due to their wide usage. In this work strong anion exchange monolithic chromatographic column was used for single step phage purification. Most of the proteins and DNA were removed and recovery of approximately 70% of infective virus was reproducibly achieved. 30 ml of phage sample was purified in around 10 min.

The challenge of drying method selection for protein pharmaceuticals: product quality implications

Numerous drying methods are used to dry solutions of proteins in the laboratory and/or in pharmaceutical manufacturing. In this review article, we will discuss many of these drying methods. We will briefly introduce and compare the unit operations involved in the drying methods to give an insight on thermal history, and the different stresses that a drying method can present to an active ingredient, particularly for protein molecules. We will review and compare some important physico-chemical properties of the dried powder that result from using different drying methods such as specific surface area, molecular dynamics, secondary structure (for protein molecules), and composition heterogeneity. We will discuss some factors that might lead to differences in the physico-chemical properties of different powders of the same formulation prepared by different techniques. We will examine through a literature review how differences in some of these properties can affect storage stability. Also, we will review process modifications of the basic drying methods and how these modifications might impact physico-chemical properties, in-process stability and/or storage stability of the dried powders.

High yield purification of functional baculovirus vectors by size exclusion chromatography

Recombinant baculoviruses carrying mammalian expression cassettes or "BacMam" are promising gene delivery vehicles shown to transduce mammalian cells efficiently both in vitro and in vivo. These viruses are vectors of choice because they are non-pathogenic; able to accommodate large foreign DNA inserts and can be produced at high titers. Hence, the demand for pure and functional baculovirus vectors for gene delivery experiments is anticipated in the future. The main goal of this work is to develop a simple and efficient process to purify recombinant baculovirus derived from Autographa californica multiple nucleopolyhedrovirus from a culture supernatant by size exclusion chromatography. The final yields obtained for total and infectious particles were 1.39 x 10(11) and 1.02 x 10(10) and recoveries of 25% and 24%, respectively. The virus was purified from the majority of the protein contaminants as shown by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Negative stain electron microscopy demonstrated that >95% of the purified virus was intact particles with shape like rod and average diameter and length of 60 and 266 nm, respectively. Transduction of 293 human embryonic kidney cells by a purified GFP-expressing BacMam at a multiplicity of transduction of 200 resulted in 36% positive cell population.