Production and formulation of adenovirus vectors

Uncertainty quantification for gene delivery methods: A roadmap for pDNA manufacturing from phase I clinical trials to commercialization

The fast-growing interest in cell and gene therapy (C>) products has led to a growing demand for the production of plasmid DNA (pDNA) and viral vectors for clinical and commercial use. Manufacturers, regulators, and suppliers need to develop strategies for establishing robust and agile supply chains in the otherwise empirical field of C>. A model-based methodology that has great potential to support the wider adoption of C> is presented, by ensuring efficient timelines, scalability, and cost-effectiveness in the production of key raw materials. Specifically, key process and economic parameters are identified for (1) the production of pDNA for the forward-looking scenario of non-viral-based Chimeric Antigen Receptor (CAR) T-cell therapies from clinical (200 doses) to commercial (40,000 doses) scale and (2) the commercial (40,000 doses) production of pDNA and lentiviral vectors for the current state-of-the-art viral vector-based CAR T-cell therapies. By applying a systematic global sensitivity analysis, we quantify uncertainty in the manufacturing process and apportion it to key process and economic parameters, highlighting cost drivers and limitations that steer decision-making. The results underline the cost-efficiency and operational flexibility of non-viral-based therapies in the overall C> supply chain, as well as the importance of economies-of-scale in the production of pDNA.

Bioprocessing and the Production of Antiviral Biologics in the Prevention and Treatment of Viral Infectious Disease

Emerging, re-emerging and zoonotic viral pathogens represent a serious threat to human health, resulting in morbidity, mortality and potentially economic instability at a global scale. Certainly, the recent emergence of the novel SARS-CoV-2 virus (and its variants) highlighted the impact of such pathogens, with the pandemic creating unprecedented and continued demands for the accelerated production of antiviral therapeutics. With limited effective small molecule therapies available for metaphylaxis, vaccination programs have been the mainstay against virulent viral species. Traditional vaccines remain highly effective at providing high antibody titres, but are, however, slow to manufacture in times of emergency. The limitations of traditional vaccine modalities may be overcome by novel strategies, as outlined herein. To prevent future disease outbreaks, paradigm shift changes in manufacturing and distribution are necessary to advance the production of vaccines, monoclonal antibodies, cytokines and other antiviral therapies. Accelerated paths for antivirals have been made possible due to advances in bioprocessing, leading to the production of novel antiviral agents. This review outlines the role of bioprocessing in the production of biologics and advances in mitigating viral infectious disease. In an era of emerging viral diseases and the proliferation of antimicrobial resistance, this review provides insight into a significant method of antiviral agent production which is key to protecting public health.

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.

Optimization of an adenovirus-vectored zoster vaccine production process with chemically defined medium and a perfusion system

OBJECTIVES

Cells grown in chemically defined medium are sensitive to shear force, potentially resulting in decreased cell growth. We optimized the perfusion process for HEK293 cell-based recombinant adenovirus-vectored zoster vaccine (Ad-HER) production with chemically defined medium.

METHODS

We first studied the pseudo-continuous strategies in shake flasks as a mimic of the bioreactor equipped with perfusion systems. Using design of experiment (DoE) in shake flasks, we obtained the regression models between Ad-HER titer/virus input-output ratio and three production process parameters: time of infection (TOI), multiplicity of infection (MOI), and virus production pH (pH). We then confirmed the effect of Pluronic F68 (PF-68) at 3.0 g/L on HEK293 cell growth and Ad-HER production in shake flasks and a 2 L benchtop bioreactor.

RESULTS

The optimized process was scale-up to a 2 L benchtop bioreactor with the PATFP perfusion system, which yielded cell density of 7.4 × 10⁶ cells/mL and Ad-HER titer of 9.8 × 10⁹ IFU/mL at 2 dpi, comparable to the bioreactor with a ATF2 system.

CONCLUSION

This optimization strategy could be used to develop a robust process with stable cell culture performance and adenovirus titer. Increasing PF-68 concentration in chemically defined medium could protect cells from shear stress generated by perfusion system.

Preparation and identification of a single domain antibody specific for adenovirus vectors and its application to the immunoaffinity purification of adenoviruses

Adenovirus belongs to the family of Adenoviridae. As a vaccine carrier, it has high safety and stimulates the body to produce cellular immunity and humoral immunity. This study prepared an adenoviral vector-specific single-domain antibody for use in adenovirus identification and purification. We successfully constructed a single domain antibody phage display library with a capacity of 1.8 × 10⁹ by immunizing and cloning the VHH gene from Bactrian camel. After the second round of biopanning, clones specific for adenovirus were screened using phage ELISA. Twenty-two positive clones were obtained, and two clones with the highest binding affinity from ELISA were selected and named sdAb 5 and sdAb 31 for further application. The recombinant single-domain antibody was solublely expressed in E. coli and specifically bound to adenoviruses rAd26, ChAd63 and HAd5 in ELISA and live cell immunofluorescence assays. We established an effective method for immunoaffinity purification of adenovirus by immobilizing the single domain antibody to Sepharose beads, and it may be used to selectively capture adenoviruses from cell culture medium. The preparation of the adenovirus-specific single-domain antibody lays a foundation for the one-step immunoaffinity purification and identification of adenoviruses.

Adenoviral vectors for cardiovascular gene therapy applications: a clinical and industry perspective

Abstract

Despite the development of novel pharmacological treatments, cardiovascular disease morbidity and mortality remain high indicating an unmet clinical need. Viral gene therapy enables targeted delivery of therapeutic transgenes and represents an attractive platform for tackling acquired and inherited cardiovascular diseases in the future. Current cardiovascular gene therapy trials in humans mainly focus on improving cardiac angiogenesis and function. Encouragingly, local delivery of therapeutic transgenes utilising first-generation human adenovirus serotype (HAd)-5 is safe in the short term and has shown some efficacy in drug refractory angina pectoris and heart failure with reduced ejection fraction. Despite this success, systemic delivery of therapeutic HAd-5 vectors targeting cardiovascular tissues and internal organs is limited by negligible gene transfer to target cells, elimination by the immune system, liver sequestration, off-target effects, and episomal degradation. To circumvent these barriers, cardiovascular gene therapy research has focused on determining the safety and efficacy of rare alternative serotypes and/or genetically engineered adenoviral capsid protein-modified vectors following local or systemic delivery. Pre-clinical studies have identified several vectors including HAd-11, HAd-35, and HAd-20–42-42 as promising platforms for local and systemic targeting of vascular endothelial and smooth muscle cells. In the past, clinical gene therapy trials were often restricted by limited scale-up capabilities of gene therapy medicinal products (GTMPs) and lack of regulatory guidance. However, significant improvement of industrial GTMP scale-up and purification, development of novel producer cell lines, and issuing of GTMP regulatory guidance by national regulatory health agencies have addressed many of these challenges, creating a more robust framework for future adenoviral-based cardiovascular gene therapy. In addition, this has enabled the mass roll out of adenovirus vector-based COVID-19 vaccines.

Key messages

First-generation HAd-5 vectors are widely used in cardiovascular gene therapy.

HAd-5-based gene therapy was shown to lead to cardiac angiogenesis and improved function.

Novel HAd vectors may represent promising transgene carriers for systemic delivery.

Novel methods allow industrial scale-up of rare/genetically altered Ad serotypes.

National regulatory health agencies have issued guidance on GMP for GTMPs.

Sixteen capillary electrophoresis applications for viral vaccine analysis

A broad range of CE applications from our organization is reviewed to give a flavor of the use of CE within the field of vaccine analyses. Applicability of CE for viral vaccine characterization, and release and stability testing of seasonal influenza virosomal vaccines, universal subunit influenza vaccines, Sabin inactivated polio vaccines (sIPV), and adenovirus vector vaccines were demonstrated. Diverse CZE, CE-SDS, CGE, and cIEF methods were developed, validated, and applied for virus, protein, posttranslational modifications, DNA, and excipient concentration determinations, as well as for the integrity and composition verifications, and identity testing (e.g., CZE for intact virus particles, CE-SDS application for hemagglutinin quantification and influenza strain identification, chloride or bromide determination in process samples). Results were supported by other methods such as RP-HPLC, dynamic light scattering (DLS), and zeta potential measurements. Overall, 16 CE methods are presented that were developed and applied, comprising six adenovirus methods, five viral protein methods, and methods for antibodies determination of glycans, host cell-DNA, excipient chloride, and process impurity bromide. These methods were applied to support in-process control, release, stability, process- and product characterization and development, and critical reagent testing. Thirteen methods were validated. Intact virus particles were analyzed at concentrations as low as 0.8 pmol/L. Overall, CE took viral vaccine testing beyond what was previously possible, improved process and product understanding, and, in total, safety, efficacy, and quality.

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.

Introducing Genes into Mammalian Cells: Viral Vectors

Over the years, many different viral vector systems have been developed to take advantage of the specific biological properties and tropisms of a large number of mammalian viruses. As a result, researchers wanting to introduce and/or express genes in mammalian cells have many options, as discussed here.

Interference chromatography: a novel approach to optimizing chromatographic selectivity and separation performance for virus purification

Background

Oncolytic viruses are playing an increasingly important role in cancer immunotherapy applications. Given the preclinical and clinical efficacy of these virus-based therapeutics, there is a need for fast, simple, and inexpensive downstream processing methodologies to purify biologically active viral agents that meet the increasingly higher safety standards stipulated by regulatory authorities like the Food and Drug Administration and the European Agency for the Evaluation of Medicinal Products. However, the production of virus materials for clinical dosing of oncolytic virotherapies is currently limited—in quantity, quality, and timeliness—by current purification technologies. Adsorption of virus particles to solid phases provides a convenient and practical choice for large-scale fractionation and recovery of viruses from cell and media contaminants. Indeed, chromatography has been deemed the most promising technology for large-scale purification of viruses for biomedical applications. The implementation of new chromatography media has improved process performance, but low yields and long processing times required to reach the desired purity are still limiting.

Results

Here we report the development of an interference chromatography-based process for purifying high titer, clinical grade oncolytic Newcastle disease virus using NatriFlo® HD-Q membrane technology. This novel approach to optimizing chromatographic performance utilizes differences in molecular bonding interactions to achieve high purity in a single ion exchange step.

Conclusions

When used in conjunction with membrane chromatography, this high yield method based on interference chromatography has the potential to deliver efficient, scalable processes to enable viable production of oncolytic virotherapies.

Clinical-Grade Oncolytic Adenovirus Purification Using Polysorbate 20 as an Alternative for Cell Lysis

Introduction:

Oncolytic virus therapy is currently considered as a promising therapeutic ap-proach for cancer treatment. Adenovirus is well-known and extensively characterized as an oncolytic agent. The increasing number of clinical trials using this virus generates the demand for the development of a well-established purification approach. Triton X-100 is commonly used in cell lysis buffer prepara-tions. The addition of this surfactant in the list of substances with the very high concern of the Registra-tion, Evaluation, Authorization and Restriction of Chemicals (REACH) regulation promoted the research for effective alternatives.

Methods:

In this work, a purification strategy for oncolytic adenovirus compatible with phase I clinical trials, using an approved surfactant – Polysorbate 20 was developed. The proposed downstream train, composed by clarification, concentration using tangential flow filtration, intermediate purification with anion exchange chromatography, followed by a second concentration and a final polishing step was evaluated for both Triton X-100 and Polysorbate 20 processes. The impact of cell lysis with Polysorb-ate20 and Triton X-100 for each downstream step was evaluated in terms of product recovery and impu-rities removal. Overall, 61 ± 4% of infectious viral particles were recovered. Depletion of host cell pro-teins and ds-DNA was 99.9% and 97.1%, respectively.

Results & Conclusion:

The results indicated that Polysorbate 20 can be used as a replacement for Triton X-100 during cell lysis with no impact on product recovery, potency, and purity. Moreover, the devel-oped process is scalable and able to provide a highly purified product to be used in phase I and II clinical trials.

Ultra scale-down approaches to study the centrifugal harvest for viral vaccine production

Large scale continuous cell-line cultures promise greater reproducibility and efficacy for the production of influenza vaccines, and adenovirus for gene therapy. This paper seeks to use an existing validated ultra scale-down tool, which is designed to mimic the commercial scale process environment using only milliliters of material, to provide some initial insight into the performance of the harvest step for these processes. The performance of industrial scale centrifugation and subsequent downstream process units is significantly affected by shear. The properties of these cells, in particular their shear sensitivity, may be changed considerably by production of a viral product, but literature on this is limited to date. In addition, the scale-down tool used here has not previously been applied to the clarification of virus production processes. The results indicate that virus infected cells do not actually show any increase in sensitivity to shear, and may indeed become less shear sensitive, in a similar manner to that previously observed in old or dead cell cultures. Clarification may be most significantly dependent on the virus release mechanism, with the budding influenza virus producing a much greater decrease in clarification than the lytic, non-enveloped adenovirus. A good match was also demonstrated to the industrial scale performance in terms of clarification, protein release, and impurity profile.

Engineered HSV vector achieves safe long-term transgene expression in the central nervous system

Previously we reported a new series of highly defective herpes simplex virus type 1 (HSV-1) vectors that were functionally devoid of all viral immediately early (IE) genes, resulting in virtual absence of viral gene expression. Nevertheless, a reporter gene cassette inserted into the vector flanked by boundary elements from the viral latency locus showed high, persistent reporter gene activity in non-neuronal cells while an independent expression cassette inserted into a deleted ICP4 locus remained almost silent. In contrast to non-neuronal cells, we show here that the ICP4 locus cassette permitted robust reporter gene expression in a diversity of neurons following stereotactic injection of different rat brain regions; transgene expression in the hippocampus lasted up to 6 months and was essentially restricted to neurons. No evidence of neuronal cell toxicity or induction of inflammatory cell infiltrates was observed. An independent reporter gene cassette located in an intergenic region remained silent, indicating that the transgene promoter and/or insertion site are critical for sustained expression. These findings suggest the suitability of this vector for therapeutic intervention into diseases of the central nervous system that require the expression of large and/or multiple therapeutic transgenes.

Standard free droplet digital polymerase chain reaction as a new tool for the quality control of high-capacity adenoviral vectors in small-scale preparations

High-capacity adenoviral vectors (HCAdVs) are promising tools for gene therapy as well as for genetic engineering. However, one limitation of the HCAdV vector system is the complex, time-consuming, and labor-intensive production process and the following quality control procedure. Since HCAdVs are deleted for all viral coding sequences, a helper virus (HV) is needed in the production process to provide the sequences for all viral proteins in trans. For the purification procedure of HCAdV, cesium chloride density gradient centrifugation is usually performed followed by buffer exchange using dialysis or comparable methods. However, performing these steps is technically difficult, potentially error-prone, and not scalable. Here, we establish a new protocol for small-scale production of HCAdV based on commercially available adenovirus purification systems and a standard method for the quality control of final HCAdV preparations. For titration of final vector preparations, we established a droplet digital polymerase chain reaction (ddPCR) that uses a standard free-end-point PCR in small droplets of defined volume. By using different probes, this method is capable of detecting and quantifying HCAdV and HV in one reaction independent of reference material, rendering this method attractive for accurately comparing viral titers between different laboratories. In summary, we demonstrate that it is possible to produce HCAdV in a small scale of sufficient quality and quantity to perform experiments in cell culture, and we established a reliable protocol for vector titration based on ddPCR. Our method significantly reduces time and required equipment to perform HCAdV production. In the future the ddPCR technology could be advantageous for titration of other viral vectors commonly used in gene therapy.

Impact of adenovirus life cycle progression on the generation of canine helper-dependent vectors

Helper-dependent adenovirus vectors (HDVs) are safe and efficient tools for gene transfer with high cloning capacity. However, the multiple amplification steps needed to produce HDVs hamper a robust production process and in turn the availability of high-quality vectors. To understand the factors behind the low productivity, we analyzed the progression of HDV life cycle. Canine adenovirus (Ad) type 2 vectors, holding attractive features to overcome immunogenic concerns and treat neurobiological disorders, were the focus of this work. When compared with E1-deleted (ΔE1) vectors, we found a faster helper genome replication during HDV production. This was consistent with an upregulation of the Ad polymerase and pre-terminal protein and led to higher and earlier expression of structural proteins. Although genome packaging occurred similarly to ΔE1 vectors, more immature capsids were obtained during HDV production, which led to a ~4-fold increase in physical-to-infectious particles ratio. The higher viral protein content in HDV-producing cells was also consistent with an increased activation of autophagy and cell death, in which earlier cell death compromised volumetric productivity. The increased empty capsids and earlier cell death found in HDV production may partially contribute to the lower vector infectivity. However, an HDV-specific factor responsible for a defective maturation process should be also involved to fully explain the low infectious titers. This study showed how a deregulated Ad cycle progression affected cell line homeostasis and HDV propagation, highlighting the impact of vector genome design on virus-cell interaction.

Adenovirus type 4 and 7 vaccination or adenovirus type 4 respiratory infection elicits minimal cross-reactive antibody responses to nonhuman adenovirus vaccine vectors

Antivector immunity may limit the immunogenicity of adenovirus vector vaccines. We tested sera from individuals immunized with adenovirus type 4 and 7 (Ad4 and Ad7, respectively) vaccine or naturally infected with Ad4 for their ability to neutralize a panel of E1-deleted human and chimpanzee adenoviruses (ChAd). Small statistically significant increases in titers to ChAd63, ChAd3, human Ad35, and human Ad5 were observed. Neutralizing antibodies elicited by Ad4 infection or immunization results in a small amount of adenovirus cross-reactivity.

Oncolytic adenoviruses: design, generation, and experimental procedures

Oncolytic adenoviruses are designed to take advantage of the virus' native ability to replicate in cancer cells to induce oncolysis. Subsequently, the released viral progeny spread and kill the neighboring cancer cells. These characteristics, together with the ability of adenovirus to infect a broad spectrum of cells, its well understood replication machinery, and relative ease of manufacture have led to the intensive use of adenovirus as an anticancer agent. This unit describes cloning strategies, procedures to turn the intended design into virus, and quality analyses of resultant adenoviral vectors. Most of these procedures were optimized especially for oncolytic adenoviral vectors.

Downstream processing of cell culture-derived virus particles

Manufacturing of cell culture-derived virus particles for vaccination and gene therapy is a rapidly growing field in the biopharmaceutical industry. The process involves a number of complex tasks and unit operations ranging from selection of host cells and virus strains for the cultivation in bioreactors to the purification and formulation of the final product. For the majority of cell culture-derived products, efforts focused on maximization of bioreactor yields, whereas design and optimization of downstream processes were often neglected. Owing to this biased focus, downstream procedures today often constitute a bottleneck in various manufacturing processes and account for the majority of the overall production costs. For efficient production methods, particularly in sight of constantly increasing economic pressure within human healthcare systems, highly productive downstream schemes have to be developed. Here, we discuss unit operations and downstream trains to purify virus particles for use as vaccines and vectors for gene therapy.

Production of adenovirus vectors and their use as a delivery system for influenza vaccines

IMPORTANCE OF THE FIELD

With the emergence of highly pathogenic avian influenza H5N1 viruses that have crossed species barriers and are responsible for lethal infections in humans in many countries, there is an urgent need for the development of effective vaccines which can be produced in large quantities at a short notice and confer broad protection against these H5N1 variants. In order to meet the potential global vaccine demand in a pandemic scenario, new vaccine-production strategies must be explored in addition to the currently used egg-based technology for seasonal influenza.

AREAS COVERED IN THIS REVIEW

Adenovirus (Ad) based influenza vaccines represent an attractive alternative/supplement to the currently licensed egg-based influenza vaccines. Ad-based vaccines are relatively inexpensive to manufacture, and their production process does not require either chicken eggs or labor-intensive and time-consuming processes necessitating enhanced biosafety facilities. Most importantly, in a pandemic situation, this vaccine strategy could offer a stockpiling option to reduce the response time before a strain-matched vaccine could be developed.

WHAT THE READER WILL GAIN

This review discusses Ad-vector technology and the current progress in the development of Ad-based influenza vaccines.

TAKE HOME MESSAGE

Ad vector-based influenza vaccines for pandemic preparedness are under development to meet global vaccine demand.

Influence of method of systemic administration of adenovirus on virus-mediated toxicity: focus on mortality, virus distribution, and drug metabolism

INTRODUCTION

Doses of 2 x 10(12) virus particles/kilogram (vp/kg) and higher of recombinant human adenovirus serotype 5 (HAdV-5) given via the tail vein induce significant toxicity and mortality in the rat. This was not observed when doses of 5.7 x 10(12) vp/kg were given through a surgically implanted jugular catheter. Here we assess how the manner by which HAdV-5 is introduced into the systemic circulation affects biodistribution, transgene expression, toxicity and mortality 0.25, 1, and 4 days after treatment in the rat. Animals were given 5.7 x 10(12) vp/kg of HAdV-5 expressing beta-galactosidase or saline through a jugular catheter or by direct tail vein injection.

RESULTS

All animals survived after jugular vein dosing. Tail vein injection of HAdV-5 increased the mortality rate to 42% (p< or =0.01). All deaths occurred within 4 h. Animals dosed through the jugular vein had significantly higher levels of transgene expression in the liver and spleen and significantly more viral genomes in these tissues and kidney and lung within the first 24 h of viral infection compared to those dosed by tail vein injection (p< or =0.01). There was no significant difference between the groups thereafter. Samples from animals that died contained even higher levels of viral genomes and serum transaminases were elevated on average by a factor of 4 at the time of death. There was no significant difference between the two dosing methods with respect to changes in hepatic cytochrome P450 expression and activity throughout the study.

CONCLUSION

These findings suggest that the method of systemic administration should be carefully considered when assessing toxicity data and other parameters at early time points after virus administration in the rat and possibly other animal models.