Purification of cell culture-derived influenza A virus via continuous anion exchange chromatography on monoliths

Quality by design for mRNA platform purification based on continuous oligo-dT chromatography

Oligo-deoxythymidine (oligo-dT) ligand-based affinity chromatography is a robust method for purifying mRNA drug substances within the manufacturing process of mRNA-based products, including vaccines and therapeutics. However, the conventional batch mode of operation for oligo-dT chromatography has certain drawbacks that reduce the productivity of this process. Here, we report a new continuous oligo-dT chromatography process for the purification of in vitro transcribed mRNA, which reduces losses, improves the efficiency of oligo-dT resin use, and intensifies the chromatography process. Furthermore, the quality by design (QbD) framework was used to establish a design space for the newly developed method. The optimization of process parameters (PPs), including salt type, salt concentration, load flow rate and mRNA load concentration both in batch and the continuous mode, achieved a greater than 90% yield (mRNA recovery) along with greater than 95% mRNA integrity and greater than 99% purity. The productivity of continuous chromatography was estimated to be 5.75-fold higher, and the operating cost was estimated 15% lower, when compared with batch chromatography. Moreover, the QbD framework was further used to map the relationship between critical quality attributes and key performance indicators as a function of critical process parameters and critical material attributes.

Advances in preparation of acellular human dermis for tissue banking and transplantation

Non-healing wounds cost the National Health Service over £5.6 billion annually in wound management. Skin allografts are used to treat non-healing wounds, ulcers and burns, offering the best protection against infection. In order to allow host cells to repopulate and to avoid immunogenicity, cell components are removed through decellularisation. Decellularisation of human dermis has so far been performed in NHS Blood and Transplant using a combination of two enzymes (RNase T1 and the recombinant human DNase Pulmozyme)®. This study aims at validating a new method to remove DNA from donated dermis via the use of a single enzyme, Benzonase, known for its effectiveness of DNA digestion. Skin samples were decellularised by removing the epidermis, lysing of dermal cells, removal of cellular fragments by a detergent wash and removal of nucleic acids by a nuclease incubation with either Benzonase or Pulmozyme + RNase T1. DNA quantification with PicoGreen, as well as histology on wax-embedded biopsies, stained with DAPI and haemotoxylin and eosin, were performed. In vitro toxicity test on human osteosarcoma immortalised cells and skin fibroblasts, and biomechanical (tensile) testing, were also performed. The effectiveness of DNA digestion with the new methodology was comparable to previous procedure. Mean DNA removal percentage following decellularisation with Pulmozyme + RNase was 99.9% (3.83 ng/mg). Mean DNA removal percentage with Benzonase was 99.8% (9.97 ng/mg). Histology staining showed complete decellularisation following either method. Benzonase was proven to be non-toxic to both cell lines used, and a one-way Anova test showed no significant difference in neither stress nor strain between acellular dermal matrix decellularised with either Benzonase or Pulmozyme + RNase T1. Benzonase was able to effectively decellularise dermis after prior removal of epidermis. It performed just as well as the combination of Pulmozyme + RNase T1, but represents significant advantages in terms of cost effectiveness, procurement and storage; Benzonase has been successfully used in the decellularisation of other tissues, thus would be better for Tissue Banking use. Switching to this combined DNase/RNase can have far-reaching consequences in the production of acellular human dermal matrix by NHSBT and in the treatment of patients requiring it.

Vaccine process technology-A decade of progress

In the past decade, new approaches to the discovery and development of vaccines have transformed the field. Advances during the COVID-19 pandemic allowed the production of billions of vaccine doses per year using novel platforms such as messenger RNA and viral vectors. Improvements in the analytical toolbox, equipment, and bioprocess technology have made it possible to achieve both unprecedented speed in vaccine development and scale of vaccine manufacturing. Macromolecular structure-function characterization technologies, combined with improved modeling and data analysis, enable quantitative evaluation of vaccine formulations at single-particle resolution and guided design of vaccine drug substances and drug products. These advances play a major role in precise assessment of critical quality attributes of vaccines delivered by newer platforms. Innovations in label-free and immunoassay technologies aid in the characterization of antigenic sites and the development of robust in vitro potency assays. These methods, along with molecular techniques such as next-generation sequencing, will accelerate characterization and release of vaccines delivered by all platforms. Process analytical technologies for real-time monitoring and optimization of process steps enable the implementation of quality-by-design principles and faster release of vaccine products. In the next decade, the field of vaccine discovery and development will continue to advance, bringing together new technologies, methods, and platforms to improve human health.

Toward microfluidic continuous-flow and intelligent downstream processing of biopharmaceuticals

Biopharmaceuticals have emerged as powerful therapeutic agents, revolutionizing the treatment landscape for various diseases, including cancer, infectious diseases, autoimmune and genetic disorders. These biotherapeutics pave the way for precision medicine with their unique and targeted capabilities. The production of high-quality biologics entails intricate manufacturing processes, including cell culture, fermentation, purification, and formulation, necessitating specialized facilities and expertise. These complex processes are subject to rigorous regulatory oversight to evaluate the safety, efficacy, and quality of biotherapeutics prior to clinical approval. Consequently, these drugs undergo extensive purification unit operations to achieve high purity by effectively removing impurities and contaminants. The field of personalized precision medicine necessitates the development of novel and highly efficient technologies. Microfluidic technology addresses unmet needs by enabling precise and compact separation, allowing rapid, integrated and continuous purification modules. Moreover, the integration of intelligent biomanufacturing systems with miniaturized devices presents an opportunity to significantly enhance the robustness of complex downstream processing of biopharmaceuticals, with the benefits of automation and advanced control. This allows seamless data exchange, real-time monitoring, and synchronization of purification steps, leading to improved process efficiency, data management, and decision-making. Integrating autonomous systems into biopharmaceutical purification ensures adherence to regulatory standards, such as good manufacturing practice (GMP), positioning the industry to effectively address emerging market demands for personalized precision nano-medicines. This perspective review will emphasize on the significance, challenges, and prospects associated with the adoption of continuous, integrated, and intelligent methodologies in small-scale downstream processing for various types of biologics. By utilizing microfluidic technology and intelligent systems, purification processes can be enhanced for increased efficiency, cost-effectiveness, and regulatory compliance, shaping the future of biopharmaceutical production and enabling the development of personalized and targeted therapies.

A Single-Step Method for Harvesting Influenza Viral Particles from MDCK Cell Culture Supernatant with High Yield and Effective Impurity Removal

Influenza vaccines, which are recommended by the World Health Organization (WHO), are the most effective preventive measure against influenza virus infection. Madin-Darby canine kidney (MDCK) cell culture is an emerging technology used to produce influenza vaccines. One challenge when purifying influenza vaccines using this cell culture system is to efficiently remove impurities, especially host cell double-stranded DNA (dsDNA) and host cell proteins (HCPs), for safety assurance. In this study, we optimized ion-exchange chromatography methods to harvest influenza viruses from an MDCK cell culture broth, the first step in influenza vaccine purification. Bind/elute was chosen as the mode of operation for simplicity. The anion-exchange Q chromatography method was able to efficiently remove dsDNA and HCPs, but the recovery rate for influenza viruses was low. However, the cation-exchange SP process was able to simultaneously achieve high dsDNA and HCP removal and high influenza virus recovery. For the SP process to work, the clarified cell culture broth needed to be diluted to reduce its ionic strength, and the optimal dilution rate was determined to be 1:2 with purified water. The SP process yielded a virus recovery rate exceeding 90%, as measured using a hemagglutination units (HAUs) assay, with removal efficiencies over 97% for HCPs and over 99% for dsDNA. Furthermore, the general applicability of the SP chromatography method was demonstrated with seven strains of influenza viruses recommended for seasonal influenza vaccine production, including H1N1, H3N2, B (Victoria), and B (Yamagata) strains, indicating that the SP process could be utilized as a platform process. The SP process developed in this study showed four advantages: (1) simple operation, (2) a high recovery rate for influenza viruses, (3) a high removal rate for major impurities, and (4) general applicability.

Enhanced Downstream Processing for a Cell-Based Avian Influenza (H5N1) Vaccine

H5N1 highly pathogenic avian influenza virus (HPAIV) infections pose a significant threat to human health, with a mortality rate of around 50%. Limited global approval of H5N1 HPAIV vaccines, excluding China, prompted the need to address safety concerns related to MDCK cell tumorigenicity. Our objective was to improve vaccine safety by minimizing residual DNA and host cell protein (HCP). We developed a downstream processing method for the cell-based H5N1 HPAIV vaccine, employing CaptoTM Core 700, a multimodal resin, for polishing. Hydrophobic-interaction chromatography (HIC) with polypropylene glycol as a functional group facilitated the reversible binding of virus particles for capture. Following the two-step chromatographic process, virus recovery reached 68.16%. Additionally, HCP and DNA levels were reduced to 2112.60 ng/mL and 6.4 ng/mL, respectively. Western blot, high-performance liquid chromatography (HPLC), and transmission electron microscopy (TEM) confirmed the presence of the required antigen with a spherical shape and appropriate particle size. Overall, our presented two-step downstream process demonstrates potential as an efficient and cost-effective platform technology for cell-based influenza (H5N1 HPAIV) vaccines.

Improved adeno-associated virus empty and full capsid separation using weak partitioning multi-column AEX chromatography

Recombinant adeno-associated virus (rAAV) empty and full capsid separation has been a topic of interest in the rAAV gene therapy community for many years and the anion exchange chromatography (AEX) step has undergone various process optimizations to improve rAAV empty capsid separation, including AEX stationary phase, mobile phase, and process parameters. Here, we present a new AEX method that employs both weak partitioning chromatography (WPC) and multi-column chromatography (MCC) to achieve improved full rAAV percentage in the AEX pool. The WPC technology allows empty rAAV to be displaced by full rAAV during loading, while the MCC technology enables parallel column processing which further increases AEX step productivity. Our results show that, compared to baseline AEX batch chromatography, the AEX-WPC-MCC method demonstrated improvements in both AEX pool full rAAV percentage (∼ 20% increase) and rAAV genome recovery (∼ 20% increase). As a result, the productivity (full capsid generated per liter of AEX column per hour of processing time) of the AEX step increased by ∼34-fold from the baseline AEX batch run to the AEX-WPC-MCC run. It is foreseeable that this AEX-WPC-MCC method could find applications in large-scale rAAV manufacturing processes to improve AEX yield and reduce the cost of goods of rAAV manufacturing.

Purification of a recombinant oncolytic virus from clarified cell culture media by anion exchange monolith chromatography

The use of viral vectors for vaccine, gene therapy, and oncolytic virotherapy applications has received increased attention in recent years. Large-scale purification of viral vector-based biotherapeutics still presents a significant technical challenge. Chromatography is the primary tool for the purification of biomolecules in the biotechnology industry; however, the majority of chromatography resins currently available have been designed for the purification of proteins. In contrast, convective interaction media monoliths are chromatographic supports that have been designed and successfully utilized for the purification of large biomolecules, including viruses, viruslike particles, and plasmids. We present a case study on the development of a purification method for recombinant Newcastle disease virus directly from clarified cell culture media using strong anion exchange monolith technology (CIMmultus QA, BIA Separations). Resin screening studies showed at least 10 times higher dynamic binding capacity of CIMmultus QA compared to traditional anion exchange chromatography resins. Design of experiments was used to demonstrate a robust operating window for the purification of recombinant virus directly from clarified cell culture without any further pH or conductivity adjustment of the load material. The capture step was successfully scaled up from 1 mL CIMmultus QA columns to the 8 L column scale and achieved a greater than 30-fold reduction in process volume. Compared to the load material, total host cell proteins were reduced by more than 76%, and residual host cell DNA by more than 57% in the elution pool, respectively. Direct loading of clarified cell culture onto a high-capacity monolith stationary phase makes convective flow chromatography an attractive alternative to centrifugation or TFF-based virus purification procedures.

Current challenges and recent advances on the path towards continuous biomanufacturing

Continuous biopharmaceutical manufacturing is currently a field of intense research due to its potential to make the entire production process more optimal for the modern, ever-evolving biopharmaceutical market. Compared to traditional batch manufacturing, continuous bioprocessing is more efficient, adjustable, and sustainable and has reduced capital costs. However, despite its clear advantages, continuous bioprocessing is yet to be widely adopted in commercial manufacturing. This article provides an overview of the technological roadblocks for extensive adoptions and points out the recent advances that could help overcome them. In total, three key areas for improvement are identified: Quality by Design (QbD) implementation, integration of upstream and downstream technologies, and data and knowledge management. First, the challenges to QbD implementation are explored. Specifically, process control, process analytical technology (PAT), critical process parameter (CPP) identification, and mathematical models for bioprocess control and design are recognized as crucial for successful QbD realizations. Next, the difficulties of end-to-end process integration are examined, with a particular emphasis on downstream processing. Finally, the problem of data and knowledge management and its potential solutions are outlined where ontologies and data standards are pointed out as key drivers of progress.

Simple, Fast and Convenient Magnetic Bead-Based Sample Preparation for Detecting Viruses via Raman-Spectroscopy

We introduce a magnetic bead-based sample preparation scheme for enabling the Raman spectroscopic differentiation of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2)-positive and -negative samples. The beads were functionalized with the angiotensin-converting enzyme 2 (ACE2) receptor protein, which is used as a recognition element to selectively enrich SARS-CoV-2 on the surface of the magnetic beads. The subsequent Raman measurements directly enable discriminating SARS-CoV-2-positive and -negative samples. The proposed approach is also applicable for other virus species when the specific recognition element is exchanged. A series of Raman spectra were measured on three types of samples, namely SARS-CoV-2, Influenza A H1N1 virus and a negative control. For each sample type, eight independent replicates were considered. All of the spectra are dominated by the magnetic bead substrate and no obvious differences between the sample types are apparent. In order to address the subtle differences in the spectra, we calculated different correlation coefficients, namely the Pearson coefficient and the Normalized cross correlation coefficient. By comparing the correlation with the negative control, differentiating between SARS-CoV-2 and Influenza A virus is possible. This study provides a first step towards the detection and potential classification of different viruses with the use of conventional Raman spectroscopy.

SARS-CoV-2 Production, Purification Methods and UV Inactivation for Proteomics and Structural Studies

Severe acute respiratory syndrome coronavirus-2 is the causative agent of COVID-19. During the pandemic of 2019–2022, at least 500 million have been infected and over 6.3 million people have died from COVID-19. The virus is pleomorphic, and due to its pathogenicity is often handled in very restrictive biosafety containments laboratories. We developed two effective and rapid purification methods followed by UV inactivation that allow easy downstream handling of the virus. We monitored the purification through titering, sequencing, mass spectrometry and electron cryogenic microscopy. Although pelleting through a sucrose cushion, followed by gentle resuspension overnight gave the best particle recovery, infectivity decreased, and the purity was significantly worse than if using the size exclusion resin Capto Core. Capto Core can be used in batch mode, and was seven times faster than the pelleting method, obviating the need for ultracentrifugation in the containment laboratory, but resulting in a dilute virus. UV inactivation was readily optimized to allow handling of the inactivated samples under standard operating conditions. When containment laboratory space is limited, we recommend the use of Capto Core for purification and UV for inactivation as a simple, rapid workflow prior, for instance, to electron cryogenic microscopy or cell activation experiments.

Continuous Affinity Purification of Adeno-Associated Virus Using Periodic Counter-Current Chromatography

Replacing batch unit operations of biopharmaceuticals by continuous manufacturing is a maturing concept, with periodic counter-current chromatography (PCC) favoured to replace batch chromatography. Continuous affinity capture of adeno-associated virus (AAV) using PCC has the potential to cope with the high doses required for AAV therapies thanks to its inherent high throughput. The implementation of continuous AAV affinity capture using a four-column PCC process is described herein. First, elution buffer screening was used to optimize virus recovery. Second, breakthrough curves were generated and described using a mechanistic model, which was later used to characterize the loading zone of the PCC. The experimental runs achieved a stable cyclic steady state yielding virus recoveries in line with the optimized batch process (>82%), with almost a three-fold improvement in productivity. The PCC affinity capture process developed here can bolster further improvements to process economics and manufacturing footprint, thereby contributing to the integrated continuous manufacturing concept.

Stabilizing vaccines via drying: Quality by design considerations

Pandemics and epidemics are continually challenging human beings' health and imposing major stresses on the societies particularly over the last few decades, when their frequency has increased significantly. Protecting humans from multiple diseases is best achieved through vaccination. However, vaccines thermal instability has always been a hurdle in their widespread application, especially in less developed countries. Furthermore, insufficient vaccine processing capacity is also a major challenge for global vaccination programs. Continuous drying of vaccine formulations is one of the potential solutions to these challenges. This review highlights the challenges on implementing the continuous drying techniques for drying vaccines. The conventional drying methods, emerging technologies and their adaptation by biopharmaceutical industry are investigated considering the patented technologies for drying of vaccines. Moreover, the current progress in applying Quality by Design (QbD) in each of the drying techniques considering the critical quality attributes (CQAs), critical process parameters (CPPs) are comprehensively reviewed. An expert advice is presented on the required actions to be taken within the biopharmaceutical industry to move towards continuous stabilization of vaccines in the realm of QbD.

Quantification methods for viruses and virus-like particles applied in biopharmaceutical production processes

INTRODUCTION

Effective cell-based production processes of virus particles are the foundation for the global availability of classical vaccines, gene therapeutic vectors, and viral oncolytic treatments. Their production is subject to regulatory standards ensuring the safety and efficacy of the pharmaceutical product. Process analytics must be fast and reliable to provide an efficient process development and a robust process control during production. Additionally, for the product release, the drug compound and the contaminants must be quantified by assays specified by regulatory authorities.

AREAS COVERED

This review summarizes analytical methods suitable for the quantification of viruses or virus-like particles. The different techniques are grouped by the analytical question that may be addressed. Accordingly, methods focus on the infectivity of the drug component on the one hand, and on particle counting and the quantification of viral elements on the other hand. The different techniques are compared regarding their advantages, drawbacks, required assay time, and sample throughput.

EXPERT OPINION

Among the technologies summarized, a tendency toward fast methods, allowing a high throughput and a wide applicability, can be foreseen. Driving forces for this progress are miniaturization and automation, and the continuous enhancement of process-relevant databases for a successful future process control.

Understanding the interaction of proteins to ion exchange chromatographic supports: A surface energetics approach

Ion exchange chromatography is one of the most widely used chromatographic technique for the separation and purification of important biological molecules. Due to its wide applicability in separation processes, a targeted approach is required to suggest the effective binding conditions during ion exchange chromatography. A surface energetics approach was used to study the interaction of proteins to different types of ion exchange chromatographic beads. The basic parameters used in this approach are derived from the contact angle, streaming potential, and zeta potential values. The interaction of few model proteins to different anionic and cationic exchanger, with different backbone chemistry, that is, agarose and methacrylate, was performed. Generally, under binding conditions, it was observed that proteins having negative surface charges showed strong to lose interaction (20 kT for Hannilase to 0.5 kT for IgG) with different anionic exchangers (having different positive surface charges). On the contrary, anionic exchangers showed almost no interaction (0-0.1 kT) with the positively charged proteins. An inverse behavior was observed for the interaction of proteins to cationic exchangers. The outcome from these theoretical calculations can predict the binding behavior of different proteins under real ion exchange chromatographic conditions. This will ultimately propose a better bioprocess design for protein separation.

Downstream processing for influenza vaccines and candidates: An update

Seasonal and pandemic influenza outbreaks present severe health and economic burdens. To overcome limitations on influenza vaccines' availability and effectiveness, researchers chase universal vaccines providing broad, long-lasting protection against multiple influenza subtypes, and including pandemic ones. Novel influenza vaccine designs are under development, in clinical trials, or reaching the market, namely inactivated, or live-attenuated virus, virus-like particles, or recombinant antigens, searching for improved effectiveness; all these bring downstream processing (DSP) new challenges. Having to deal with new influenza strains, including pandemics, requires shorter development time, driving the development of faster bioprocesses. To cope with better upstream processes, new regulatory demands for quality and safety, and cost reduction requirements, new unit operations and integrated processes are increasing DSP efficiency for novel vaccine formats. This review covers recent advances in DSP strategies of different influenza vaccine formats. Focus is given to the improvements on relevant state-of-the-art unit operations, from harvest and clarification to purification steps, ending with sterile filtration and formulation. The development of more efficient unit operations to cope with biophysical properties of the new candidates is discussed: emphasis is given to the design of new stationary phases, 3D printing approaches, and continuous processing tools, such as continuous chromatography. The impact of the production platforms and vaccine designs on the downstream operations for the different influenza vaccine formats approved for this season are highlighted.

Oncolytic virus purification with periodic counter-current chromatography

Virus-based biologicals are one of the most promising biopharmaceuticals of the 21st century medicine and play a significant role in the development of innovative therapeutic, prophylactic, and clinical applications. Oncolytic virus manufacturing scale can range from 5 L in research and development up to 50 L for clinical studies and reach hundreds of liters for commercial scale. The inherent productivity and high integration potential of periodic counter-current chromatography (PCC) offer a transversal solution to decrease equipment footprint and the reduction of several non-value-added unit operations. We report on the design of an efficient PCC process applied to the intermediate purification of oncolytic adenovirus. The developed ion-exchange chromatographic purification method was carried out using a four-column setup for three different scenarios: (i) variation in the feedstock, (ii) potential use of a post-load washing step to improve virus recovery, and (iii) stability during extended operation. Obtained virus recoveries (57%-86%) and impurity reductions (>80% DNA, and >70% total protein) match or overcome batch purification. Regarding process stability and automation, our results show that not only the dynamic control strategy used is able to suppress perturbations in the sample inlet but also allows for unattended operation in the case of ion exchange capture.

Performance of agarose and gigaporous chromatographic media as function of pore-to-adsorbate size ratio over wide span from ovalbumin to virus like particles

Two commercially available agarose ion exchange media, DEAE-Capto and DEAE-Sepharose FF (DEAE-FF), and two gigaporous media DEAE -AP-120 nm and DEAE-AP-280 nm were evaluated for their applicability in adsorption of five proteins with large span of radius ranges from 2.9 nm to 14.1 nm, which include ovalbumin, bovine serum albumin (BSA), haptoglobin, thyroglobulin and hepatitis B surface antigen (HBsAg) virus like particle. The average pore radius of the four media was determined to be 6.9 nm, 18.5 nm, 59.4 nm and 139.3 nm, respectively, which was obtained by log normal distribution for DEAE-Capto and DEAE-FF and by bimodal Gaussian distribution for the two DEAE-AP media. The performance of these four media including phase ratio, static and dynamic binding capacity, and transport properties for the adsorption of these five model proteins as function of pore-to-adsorbate size ratio were investigated and compared. The best ratio of pore-to-adsorbate size was found dependent on the protein size. For protein with radius from 2.9 nm (ovalbumin) to 5.4 nm (BSA), the agarose media was superior to gigaporous media. Both the static and dynamic adsorption capacities reduced with the increase of pore size, and the highest values were obtained at the smallest pore-to-adsorbate size of about 2 times in this study, although the highest accessible surface area was obtained at pore-to-adsorbate size ratio about 16 to 20. For proteins with radius of 5.4 nm or larger than that, their adsorption capacities decreased firstly and then increased with the increase of ratio of pore-to-adsorbate size, and the highest values were obtained on the gigaporous media DEAE-AP-280 nm, which could provide faster diffusivity and larger accessible surface area. However, protein with radius of 14.1 nm (HBsAg) had much lower capacities compared to other proteins at the same pore-to-adsorbate size ratio, implying large protein needs greater pore-to-adsorbate size ratio to achieve a satisfactory capacity. For all the five tested proteins, the DEAE-Capto media having the smallest pore radius and branched dextran chains, was found superior to DEAE-FF in terms of both higher adsorption capacities and uptake kinetics, which suggested that the "chain delivery effect" took place on proteins over large size span from ovalbumin to HBsAg, though the effect on the larger proteins was much less significant than that on the smaller ones. Results from the present work provided more information on how do the relationships of pore size of chromatography media and adsorbate size interactively affect the chromatography behaviors, thus will provide general guidance for selection of suitable adsorbent for biologics of a given size.

Advances in Lentivirus Purification

Lentiviral vectors (LVs) have been increasingly used as a tool for gene and cell therapies since they can stably integrate the genome in dividing and nondividing cells. LV production and purification processes have evolved substantially over the last decades. However, the increasing demands for higher quantities with more restrictive purity requirements are stimulating the development of novel materials and strategies to supply the market with LV in a cost-effective manner. A detailed review of each downstream process unit operation is performed, limitations, strengths, and potential outcomes being covered. Currently, the majority of large-scale LV manufacturing processes are still based on adherent cell culture, although it is known that the industry is migrating fast to suspension cultures. Regarding the purification strategy, it consists of batch chromatography and membrane technology. Nevertheless, new solutions are being created to improve the current production schemes and expand its clinical use.

Construction of polymer monolithic columns in polypropylene ink-pen tubes for separation of proteins by cation-exchange chromatography

We describe the synthesis of polymer monoliths inside polypropylene tubes from ink pens. These tubes are cheap, chemically stable, and resistant to pressure. UV-initiated grafting with 5 wt% benzophenone in methanol for 20 min activated the internal surface, thus enabling the covalent binding of ethylene glycol dimethacrylate, also via photografting. The pendant vinyl groups attached a poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) monolith prepared via photopolymerization. These tubes measured 100-110 mm long, with 2 mm of internal diameter. The parent monoliths were functionalized with Na₂ SO₃ or iminodiacetate to produce strong and weak cation exchangers, respectively. The columns exhibited permeabilities varying from 2.7 to 3.3 × 10^-13  m² , which enabled the separation of proteins at 500 µL/min and back pressures <2.8 MPa. Neither structure collapse nor monolith detachment occurred at flow rates as high as 2.0 mL/min, which produced back pressures between 6.9 and 9.0 MPa. The retention times of ovalbumin, ribonuclease A, cytochrome C, and lysozyme in salt gradient at pH 7.0 followed the order of increasing isoelectric points, confirming the cation exchange mechanism. Separation and determination of lysozyme in egg white proved the applicability of the columns to the analysis of complex samples.

Polysaccharide-based chromatographic adsorbents for virus purification and viral clearance

Viruses still pose a significant threat to human and animal health worldwide. In the fight against viral infections, high-purity viral stocks are needed for manufacture of safer vaccines. It is also a priority to ensure the viral safety of biopharmaceuticals such as blood products. Chromatography techniques are widely implemented at both academic and industrial levels in the purification of viral particles, whole viruses and virus-like particles to remove viral contaminants from biopharmaceutical products. This paper focuses on polysaccharide adsorbents, particulate resins and membrane adsorbers, used in virus purification/removal chromatography processes. Different chromatographic modes are surveyed, with particular attention to ion exchange and affinity/pseudo-affinity adsorbents among which commercially available agarose-based resins (Sepharose®) and cellulose-based membrane adsorbers (Sartobind®) occupy a dominant position. Mainly built on the development of new ligands coupled to conventional agarose/cellulose matrices, the development perspectives of polysaccharide-based chromatography media in this antiviral area are stressed in the conclusive part.

Capture and purification of Human Immunodeficiency Virus-1 virus-like particles: Convective media vs porous beads

Downstream processing (DSP) of large bionanoparticles is still a challenge. The present study aims to systematically compare some of the most commonly used DSP strategies for capture and purification of enveloped viruses and virus-like particles (eVLPs) by using the same staring material and analytical tools. As a model, Human Immunodeficiency Virus-1 (HIV-1) gag VLPs produced in CHO cells were used. Four different DSP strategies were tested. An anion-exchange monolith and a membrane adsorber, for direct capture and purification of eVLPs, and a polymer-grafted anion-exchange resin and a heparin-affinity resin for eVLP purification after a first flow-through step to remove small impurities. All tested strategies were suitable for capture and purification of eVLPs. The performance of the different strategies was evaluated regarding its binding capacity, ability to separate different particle populations and product purity. The highest binding capacity regarding total particles was obtained using the anion exchange membrane adsorber (5.3 × 10¹² part/mL membrane), however this method did not allow the separation of different particle populations. Despite having a lower binding capacity (1.5 × 10¹¹ part/mL column) and requiring a pre-processing step with flow-through chromatography, Heparin-affinity chromatography showed the best performance regarding separation of different particle populations, allowing not only the separation of HIV-1 gag VLPs from host cell derived bionanoparticles but also from chromatin. This work additionally shows the importance of thorough sample characterization combining several biochemical and biophysical methods in eVLP DSP.

Continuous Chromatography Purification of Virus-Based Biopharmaceuticals: A Shortcut Design Method

Novel biopharmaceutical products, such as vaccines and viral vectors, play a significant role in the development of innovative therapeutic, prophylactic, and clinical applications. However, several challenges are posed when manufacturing these products. The diversity of cell lines and the different physical and chemical properties of these biologicals require the use of different production and processing technologies. Alternative purification strategies that can improve the purification yield, such as continuous chromatography, are regarded nowadays as enabling technologies to overcome some of the bottlenecks in biomanufacturing. This chapter offers a shortcut approach to implement a semi-continuous chromatography purification of hepatitis C virus-like particles produced in insect cells with recombinant baculovirus. Although the purification is based on ion exchange chromatography, the present methodology can be extended to other types of chromatography.

Current challenges in biotherapeutic particles manufacturing

Introduction: The development of novel complex biotherapeutics led to new challenges in biopharmaceutical industry. The potential of these particles has been demonstrated by the approval of several products, in the different fields of gene therapy, oncolytic therapy, and tumor vaccines. However, their manufacturing still presents challenges related to the high dosages and purity required.Areas covered: The main challenges that biopharmaceutical industry faces today and the most recent developments in the manufacturing of different biotherapeutic particles are reported here. Several unit operations and downstream trains to purify virus, virus-like particles and extracellular vesicles are described. Innovations on the different purification steps are also highlighted with an eye on the implementation of continuous and integrated processes.Expert opinion: Manufacturing platforms that consist of a low number of unit operations, with higher-yielding processes and reduced costs will be highly appreciated by the industry. The pipeline of complex therapeutic particles is expanding and there is a clear need for advanced tools and manufacturing capacity. The use of single-use technologies, as well as continuous integrated operations, are gaining ground in the biopharmaceutical industry and should be supported by more accurate and faster analytical methods.

Application of benzonase in preparation of decellularized lamellar porcine corneal stroma for lamellar keratoplasty

This study was to develop anovel and efficient method using endonuclease (benzonase) to preparedecellularized lamellar porcine corneal stroma (DLPCS). The DLPCS was preparedfrom native lamellar porcine corneal stroma (NLPCS) and was treated with 1000 U/ml benzonase for 5hours. We conducted the following measurements and animal transplantation tocompare DLPCS and NLPCS. The residual DNA was decreased significantly from 367.13 ± 19.96 ng/mg to 15.41 ± 0.65 ng/mg after treatment of benzonase by the detection of fluorescentnucleic acid stain. The residual benzonase was also less than detection limit.There was no significant difference in light transmittance of DLPCS comparedwith NLPCS. The extracts of DLPCS did not inhibit cell proliferation of human cornealepithelial cells, mouse fibroblast (L‐929) and African green monkey kidney cell(Vero cell). The DLPCS was transplanted into the corneas of rabbit by lamellarkeratoplasty. There was no corneal melting and graft rejection been observedwithin 12 months. The images demonstrated that the repairment of corneal nervesand keratocytes of DLPCS were in indentical shape and reflection compared withnormal cornea, and no obvious inflammatory cells were observed postoperation, byin vivo confocal microscopy. We provided novel evidence that the application ofbenzonase may improve the quality of DLPCS.