Extracellular vesicles selective capture by peptide-functionalized hollow fiber membranes

Recently, membrane devices and processes have been applied for the separation and concentration of subcellular components such as extracellular vesicles (EVs), which play a diagnostic and therapeutic role in many pathological conditions. However, the separation and isolation of specific EV populations from other components found in biological fluids is still challenging. Here, we developed a peptide-functionalized hollow fiber (HF) membrane module to achieve the separation and enrichment of highly pure EVs derived from the culture media of human cardiac progenitor cells. The strategy is based on the functionalization of PSf HF membrane module with BPt, a peptide sequence able to bind nanovesicles characterized by highly curved membranes. HF membranes were modified by a nanometric coating with a copoly azide polymer to limit non-specific interactions and to enable the conjugation with peptide ligand by click chemistry reaction. The BPt-functionalized module was integrated into a TFF process to facilitate the design, rationalization, and optimization of EV isolation. This integration combined size-based transport of species with specific membrane sensing ligands. The TFF integrated BPt-functionalized membrane module demonstrated the ability to selectively capture EVs with diameter < 200 nm into the lumen of fibers while effectively removing contaminants such as albumin. The captured and released EVs contain the common markers including CD63, CD81, CD9 and syntenin-1. Moreover, they maintained a round shape morphology and structural integrity highlighting that this approach enables EVs concentration and purification with low shear stress. Additionally, it achieved the removal of contaminants such as albumin with high reliability and reproducibility, reaching a removal of 93%.

Analytical figures of merit of a dual-wavelength absorbance approach for real-time broad protein content monitoring for biomanufacturing

Real-time in-line broad protein content monitoring in biomanufacturing downstream unit operations enables the ability to optimize and afford consistent protein recovery. Protein determination from 2 to 400 mg/mL is demonstrated herein via real-time dual-wavelength LED photometric sensor configured at 280 and 310 nm. The figures of merit of this approach include measurement accuracy within the common acceptance criteria of 100 % ± 5 with negligible bias across the linear dynamic ranges. This work expands the utility of an LED based photometric sensor for biopharmaceutical process analytical technology (PAT) applications. It is also congruent with process digitalization and automation industry 4.0 concepts underpinned by Quality by Design (QbD) principles.

Effects of ultra-filtration purification of infectious bursal disease virus on immune responses and cytokine activation in specific pathogen free chickens

Purification is an important step in the production of viral vaccines that strongly affects product recovery and subsequent immune responses. The present study was carried out with the aim of improving the purification of infectious bursal disease virus (IBDV) by the tangential flow filtration (TFF) method. Then, the effect of the purified virus on the induction of immune responses against IBDV in specific pathogen free (SPF) chickens was investigated. The IBD07IR strain was propagated in embryonated SPF eggs. The virus was purified using a 100 kDa cassette. The quality of the recovered viruses was evaluated by titration. A total number of 60 SPF chickens were randomly divided into three groups (n = 20) and received the concentrated viral antigen, commercial live IBDV vaccine and phosphate-buffered saline at the age of 3 weeks by eye drop method. The bursa of Fabricius was examined histopathologically for possible changes. Sera were collected at 1-week intervals from day 0 until the end of 6 weeks after vaccination. The IBDV-specific antibody levels, induction of cell-mediated immunity and mRNA expression levels of cytokines were evaluated. The results showed that despite a relative raise in virus titer from 7.66 to 8.17 embryo infectious dose (EID)50 mL-1 following purification, both the purified IBDV and commercial vaccine are able to induce strong immune responses against the virus. Within a context of egg-based IBDV vaccine production, a single-step TFF can be applied for the relatively purification. This platform requires a further study in the selection of multiple membranes to optimize the operating conditions and final product.

Analysis of distribution, collection, and confirmation of capacity dependency of small extracellular vesicles toward a therapy for liver cirrhosis

BACKGROUND

The progression of liver fibrosis leads to portal hypertension and liver dysfunction. However, no antifibrotic agents have been approved for cirrhosis to date, making them an unmet medical need. Small extracellular vesicles (sEVs) of mesenchymal stem cells (MSCs) are among these candidate agents. In this study, we investigated the effects of sEVs of MSCs, analyzed their distribution in the liver post-administration, whether their effect was dose-dependent, and whether it was possible to collect a large number of sEVs.

METHODS

sEVs expressing tdTomato were generated, and their uptake into constituent liver cells was observed in vitro, as well as their sites of uptake and cells in the liver using a mouse model of liver cirrhosis. The efficiency of sEV collection using tangential flow filtration (TFF) and changes in the therapeutic effects of sEVs in a volume-dependent manner were examined.

RESULTS

The sEVs of MSCs accumulated mostly in macrophages in damaged areas of the liver. In addition, the therapeutic effect of sEVs was not necessarily dose-dependent, and it reached a plateau when the dosage exceeded a certain level. Furthermore, although ultracentrifugation was commonly used to collect sEVs for research purposes, we verified that TFF could be used for efficient sEV collection and that their effectiveness is not reduced.

CONCLUSION

In this study, we identified some unknown aspects regarding the dynamics, collection, and capacity dependence of sEVs. Our results provide important fundamentals for the development of therapies using sEVs and hold potential implications for the therapeutic applications of sEV-based therapies for liver cirrhosis.

Presence of an ultra-small microbiome in fermented cabbages

Background

Ultramicrobacteria (UMB), also known as ultra-small bacteria, are tiny bacteria with a size less than 0.1 µm³. They have a high surface-to-volume ratio and are found in various ecosystems, including the human body. UMB can be classified into two types: one formed through cell contraction and the other that maintains a small size. The ultra-small microbiome (USM), which may contain UMB, includes all bacteria less than 0.2 µm in size and is difficult to detect with current methods. However, it poses a potential threat to food hygiene, as it can pass through sterilization filters and exist in a viable but non-culturable (VBNC) state. The data on the USM of foods is limited. Some bacteria, including pathogenic species, are capable of forming UMB under harsh conditions, making it difficult to detect them through conventional culture techniques.

Methods

The study described above focused on exploring the diversity of USM in fermented cabbage samples from three different countries (South Korea, China, and Germany). The samples of fermented cabbage (kimchi, suancai, and sauerkraut) were purchased and stored in chilled conditions at approximately 4 °C until filtration. The filtration process involved two steps of tangential flow filtration (TFF) using TFF cartridges with different pore sizes (0.2 µm and 100 kDa) to separate normal size bacteria (NM) and USM. The USM and NM isolated via TFF were stored in a refrigerator at 4 °C until DNA extraction. The extracted DNA was then amplified using PCR and the full-length 16S rRNA gene was sequenced using single-molecule-real-time (SMRT) sequencing. The transmission electron microscope (TEM) was used to confirm the presence of microorganisms in the USM of fermented cabbage samples.

Results

To the best of our knowledge, this is the first study to identify the differences between USM and NM in fermented cabbages. Although the size of the USM (average 2,171,621 bp) was smaller than that of the NM (average 15,727,282 bp), diversity in USM (average H' = 1.32) was not lower than that in NM (average H' = 1.22). In addition, some members in USM probably underwent cell shrinkage due to unfavorable environments, while others maintained their size. Major pathogens were not detected in the USM in fermented cabbages. Nevertheless, several potentially suspicious strains (genera Cellulomonas and Ralstonia) were detected. Our method can be used to screen food materials for the presence of USM undetectable via conventional methods. USM and NM were efficiently separated using tangential flow filtration and analyzed via single-molecule real-time sequencing. The USM of fermented vegetables exhibited differences in size, diversity, and composition compared with the conventional microbiome. This study could provide new insights into the ultra-small ecosystem in fermented foods, including fermented cabbages.

A practical guide to separate and concentrate ALNs and femtoplankton entities

The development of new technologies of microscopy, flow cytometry and genomics has allowed a profound reconsideration of the diversity and ecological role of femtoplankton entities (i.e., viruses, vesicles, aster like nanoparticles -ALNs-). Among these, the discovery of ALNs, raise serious questions about their exact nature and their biological and environmental roles. The elaboration of a practical guide for the concentration and separation of femtoplankton entities, including ALNs, is necessary for a better understanding of their diversity, ontogeny, and ecology. Here, we propose a step-by-step procedure for the enrichment and isolation of femtoplankton entities and prokaryotes. The established protocol couples tangential flow filtration to differential centrifugation, leading to differentiate enriched samples (with different target entity contents), usable as a matrix for sorting by flow cytometry. All entities were identified, characterized and counted by transmission electron microscopy and flow cytometry. The procedure allows an efficient detection, concentration and separation of femtoplankton entities (up to purity rate of 92, 67, 81 and 85% for virus like particles, vesicles, prokaryotes and ALNs, respectively), and different morphotypes of ALNs into different fractions (up to 51, 72, 52, 40 and 79% of total ALNs for 20-, 11-, budding 11-, 5-10- and 4-armed ALNs, respectively).

Large-scale Isolation of Exosomes Derived from NK Cells for Anti-tumor Therapy

Exosomes are lipid bilayer-enclosed vesicles, actively secreted by cells, containing proteins, lipids, nucleic acids, and other substances with multiple biological functions after entering target cells. Exosomes derived from NK cells have been shown to have certain anti-tumor effects and potential applications as chemotherapy drug carriers. These developments have resulted in high demand for exosomes. Although there has been large-scale industrial preparation of exosomes, they are only for generally engineered cells such as HEK 293T. The large-scale preparation of specific cellular exosomes is still a major problem in laboratory studies. Therefore, in this study, we used tangential flow filtration (TFF) to concentrate the culture supernatants isolated from NK cells and isolated NK cell-derived exosomes (NK-Exo) by ultracentrifugation. Through a series of characterization and functional verification of NK-Exo, the characterization, phenotype, and anti-tumor activity of NK-Exo were verified. Our study provides a considerably time- and labor-saving protocol for the isolation of NK-Exo.

Assessment of anti-inflammatory bioactivity of extracellular vesicles is susceptible to error via media component contamination

Extracellular vesicles (EVs) are widely implicated as novel diagnostic and therapeutic modalities for a wide range of diseases. Thus, optimization of EV biomanufacturing is of high interest. In the course of developing parameters for a human embryonic kidney cells (HEK293T) EV production platform, we examined the combinatorial effects of cell culture conditions (i.e., static versus dynamic) and isolation techniques (i.e., ultracentrifugation versus tangential flow filtration versus size-exclusion chromatography) on functional characteristics of HEK293T EVs, including anti-inflammatory bioactivity using a well-established lipopolysaccharide-stimulated mouse macrophage model. We unexpectedly found that, depending on culture condition and isolation strategy, HEK293T EVs appeared to significantly suppress the secretion of pro-inflammatory cytokines (i.e., interleukin-6, RANTES [regulated upon activation, normal T cell expressed and secreted]) in the stimulated mouse macrophages. Further examination revealed that these results were most likely due to non-EV fetal bovine serum components in HEK293T EV preparations. Thus, future research assessing the anti-inflammatory effects of EVs should be designed to account for this phenomenon.

Producing vesicle-free cell culture additive for human cells extracellular vesicles manufacturing

A new paradigm has emerged recently, which consists in shifting from cell therapy to a more flexible acellular "extracellular vesicle (EV) therapy" approach, thereby opening a new and promising field in nanomedicine. Important technical limitations have still to be addressed for the large-scale production of clinical-grade EV. Cells are cultured in media supplemented with human platelet lysate (hPL) (xenogenic-free) or GMP-grade fetal calf serum (FCS). However, these additives contain high amounts of EV that cannot be separated from cell-secreted -EV. Therefore, cells are generally maintained in additive-free medium during the EV secretion phase, however this can substantially limit their survival. In the present work, we developed a method to prepare vesicle-free hPL (EV-free hPL) or vesicle-free FCS (EV-free FCS) using tangential flow filtration (TFF). We show a very efficient EV depletion (>98%) for both pure hPL and FCS, with a highly conserved protein content. Culture medium containing our EV-free additives supported the survival of human bone marrow MSC (BM-MSC). MSC could survive at least 216 h, their conditioned medium being collected and changed every 72 h. Both the cell survival and the cumulative EV production were substantially higher than in the starving conditions classically used for EV production. In EV-free hPL containing medium, we show that purified EV kept their morphologic and molecular characteristics throughout the production. Finally, we tested our additives with 3 other cell types, human primary Endothelial Colony Forming Cells (ECFC) and two non-adherent human cell lines, Jurkat and THP-1. We confirmed that both EV-free hPL and FCS were able to maintain cell survival and EV production for at least 216 h. Our method provides therefore a new option to help producing large amounts of EV from virtually any mammalian cells, particularly those that do not tolerate starvation. This method can apply to any animal serum for research and development purpose. Moreover, EV-free hPL is clinical-grade compatible and allows preparing xenobiotic-free media for massive therapeutic EV production in both 2D (cell plates) and 3D (bioreactor) setting.

Effect of the Tubing Material Used in Peristaltic Pumping in Tangential Flow Filtration Processes of Biopharmaceutics on Particle Formation and Flux

Tangential flow filtration (TFF) is a central step in manufacturing of biopharmaceutics. Membrane clogging leads to decreased permeate flux, longer process time and potentially complete failure of the process. The effect of peristaltic pumping with tubings made of three different materials on protein particle formation during TFF was monitored via micro flow imaging, turbidity and photo documentation. At low protein concentrations, pumping with a membrane pump resulted in a stable flux with low protein particle concentration. Using a peristaltic pump led to markedly higher protein particle formation dependent on tubing type. With increasing protein particle formation propensity of the tubing, the permeate flux rate became lower and the process took longer. The protein particles formed in the pump were captured in the cassette and accumulated on the membrane leading to blocking. Using tubing with a hydrophilic copolymer modification counteracted membrane clogging and flux decrease by reducing protein particle formation. In ultrafiltration mode the permeate flux decrease was governed by the viscosity increase rather than by the protein aggregation; but using modified tubing is still beneficial due to a lower particle burden of the product. In summary, using tubing material for peristaltic pumping in TFF processes which leads a less protein particle formation, especially tubing material with hydrophilic modification, is highly beneficial for membrane flux and particle burden of the product.

A scalable, integrated downstream process for production of a recombinant measles virus-vectored vaccine

Purification of very large and complex, enveloped viruses, such as measles virus is very challenging, it must be performed in a closed system because the final product cannot be sterile filtered and often loss of virus titer and poor product purity has been observed. We developed a purification process where the clarified and endonuclease treated culture supernatant is loaded on a restricted access chromatography medium where small impurities are bound and the virus is collected in the flow-through, which is then concentrated, and buffer exchanged by ultra/diafiltration. Up to 98.5% of host cell proteins could be captured by direct loading of clarified and endonuclease treated cell culture supernatant. Reproducible process performance and scalability of the chromatography step were demonstrated from small to pilot scale, including loading volumes from 50 mL up to 9 L. A 10-fold virus concentration was achieved by the ultrafiltration using a 100 kDa flat-sheet membrane. The order of individual process steps had a large impact on the virus infectivity and total process yields. The developed process maintained virus infectivity and is twice as fast as the traditional process train, where concentration is performed before loading on the chromatography column. Capturing impurities by the restricted access medium makes it a platform purification process with a high flexibility, which can be easily and quickly adapted to other vectors based on the measles virus vector platform.

Comprehensive Phytotoxicity Assessment Protocol for Engineered Nanomaterials

In order for nanotechnology to be sustainably applied in agriculture, emphasis should be on comprehensive assessment of multiple endpoints, including biouptake and localization of engineered nanomaterials (ENMs), potential effects on food nutrient quality, oxidative stress responses, and crop yield, before ENMs are routinely applied in consumer and agronomic products. This chapter succinctly outlines a protocol for conducting nanophytotoxicity studies focusing on nanoparticle purification and characterization, arbuscular mycorrhizal fungi (AMF)/symbiont inoculation, biouptake and translocation/localization, varied endpoints of oxidative stress responses, and crop yield.

Adaptive perfusion: An in vitro release test (IVRT) for complex drug products

In this work, adaptive perfusion, a pressure-driven separation method based on the principle of tangential flow filtration (TFF) was developed for investigating the rate and extent of drug release from drug products containing particulates, such as emulsions, suspensions, liposomes, drug-protein complexes. The TFF filters were pre-conditioned with unique conditioning solutions and processes to improve the fiber reproducibility and robustness. The adaptive perfusion method achieved size-based separation of the particulates with simultaneous analysis of the released drug as well as remaining drug. By contrast to conventional dialysis methods, the adaptive perfusion method can be used to measure the rate and extent of the drug release from drug solution, drug loaded micelles and nanoemulsions via adjustment of the filter molecular weight cutoff, feed flow rate or back-pressure. Notably, the adaptive perfusion method provided discriminatory drug release profiles for drug in solution, in micelles, and in small, medium, and large globule size nanoemulsions. The drug release profile obtained using adaptive perfusion method was found significantly faster (e.g., minutes rather than hours) and higher (e.g., >60%) than the release obtained using dialysis method. The IVRT method presented here is free from the constraints of rate-limiting factors, such as diffusion through dialysis membrane, and has potential to be extended further to examine the impact of manufacturing process on drug distribution and release characteristics of other challenging complex drug products.

Recent Progress in Harvest and Recovery Techniques of Mammalian and Algae Cells for Industries

In our modern world, biotechnology products play important roles not only in our health and culture, but also various industries such as food, agriculture, sewage treatment, biofuels, nutraceuticals, and pharmaceuticals. Rapid technological advances in biotechnology over the last few decades have allowed industrial integration of mammalian cells (like the Chinese hamster ovary cells) and algae cells in pharmaceutical and biofuel industries to produce commercial products and valuable biomolecules. However, the cost of cell harvest and recovery can become expensive depending on the harvesting technique, degree of purification, and intended use of the end-products. This has led to numerous research in exploring and developing efficient harvesting techniques. Therefore, in this review, the popular harvesting techniques and their recent applications will be discussed.

Integrated effects of Ulva prolifera bloom and decay on nutrients inventory and cycling in marginal sea of China

Ulva prolifera blooms occur annually in the Yellow Sea. Most studies focus on how U. prolifera blooming is influenced by nitrogen chemical forms and concentrations, while little concern goes to how U. prolifera bloom-decay cycle would impact local seawater nutrients structure. Therefore, we use ¹⁵N-labeled NO₃ tracers and transcriptome analysis to determine N uptake, metabolism, and interconversion during U. prolifera growth and decay, so that we can quantify the conversions rate and fluxes of different nitrogen chemical forms. U. prolifera absorbes 17.37 μmol g^-1·d^-1 NO₃-N during growth. NO₃-N predominates (73.75-92.15%) in the dissolved inorganic nitrogen (DIN) in U. prolifera. During decay, NH₄-N accountes for 60.87-92.13% of the in-cell DIN. The decomposing U. prolifera releases considerable amounts of NH₄-N and dissolved organic nitrogen (DON) (63.8-98.2% < 1 kDa fraction and 1.8-36.2% is > 1 kDa fraction) into the ambient environment. The high DON release rate (59.57 μmol g^-1 d^-1) indicates active DON biosynthesis in U. prolifera. The isotope ¹⁵NO₃-N tracer showes that 73.6% of the ¹⁵NO₃-N is transformed to DON. The <1 kDa and the >1 kDa fractions account for 67.46-90.86% and 9.14-32.54% of the DON, respectively. The high efficiency of U. prolifera in utilizing NO₃-N is explained by the responsive nitrate/nitrite transporter in cell membrane, and the DON biosynthesized capability is attributed to the up-regulated glutamine synthetase. Our study highlights the unique role of U. prolifera as a "Nitrogen-Pump" in converting nitrogen chemical forms during its bloom-decay cycle and quantifies its impacts on local N-nutrients inventory.

Comparison of Strategies in Development and Manufacturing of Low Viscosity, Ultra-High Concentration Formulation for IgG1 Antibody

Monoclonal antibodies requiring higher doses for exerting therapeutic effect but having lower stability, are administered as dilute infusions, or as two (low concentration) injections both resulting in reduced patient compliance. Present research summarizes impact of manufacturing conditions on ultra-high concentration (≥150 mg/mL) IgG1 formulation, which can be administered as one subcutaneous injection. IgG1 was concentrated to ~200 mg/mL using tangential flow filtration (TFF). Alternatively, spray dried (SPD) and spray freeze dried (SFD) IgG1, was reconstituted in 30%v/v propylene glycol to form ultra-high concentration (~200 mg/mL) injectable formulation. Reconstituted, SPD and SFD IgG1 formulations, increased viscosity beyond an acceptable range for subcutaneous injections (<20 cP). Formulations developed by reconstitution of SPD IgG1, demonstrated increase in high and low molecular weight impurities, at accelerated and stressed conditions. Whereas, the stability data suggested reconstituted SFD IgG1 was comparable to control IgG1 formulation concentrated by TFF. Also, formulation of IgG1 diafiltered with proline using TFF, reduce viscosity from ~21.9 cP to ~11 cP at 25 °C and had better stability. Thus, conventional TFF technique stands to be one of the preferred methods for manufacturing of ultra-high concentration IgG1 formulations. Additionally, SFD could be an alternative method for long term storage of IgG1 in a dry powder state.

Exosomes as drug delivery vehicle and contributor of resistance to anticancer drugs

Exosomes are small membranous vesicles implicated in intercellular signalling. Through their uncanny ability to carry and deliver donor cellular cargo (biomolecules) to target cells, they exert a profound effect on the regular functioning of healthy cells and play a significant role in pathogenesis and progression of several diseases, including cancer. The composition and number of endogenously circulating exosomes frequently vary, which is often reflective of the pathophysiological status of the cell. Applicability of exosomes derived from normal cells as a drug carrier with or without modifying their intraluminal and surface components are generally tested. Conversely, exosomes also are reported to contribute to resistance towards several anti-cancer therapies. Therefore, it is necessary to carefully evaluate the role of exosomes in cancer progression, resistance and the potential use of exosomes as a delivery vehicle of cancer therapeutics. In this review, we summarize the recent advancements in the exploitation of exosomes as a drug delivery vehicle. We also discuss the role of exosomes in conferring resistance to anti-cancer therapeutics. While this review is focused on cancer, the exosome-based drug delivery and resistance is also applicable to other human diseases.

Increased cell numbers improve marine biodegradation tests for persistence assessment

Currently available OECD biodegradation screening tests (BSTs) are not particularly suited for persistence screening. Their duration can be much less than international half-life thresholds for persistence and they are variable and stringent, therefore prone to false negatives. The present study extended test durations beyond 28 days and increased biomass concentrations for marine BSTs to better represent the microbial diversity inherent in the sampled environment. For this so-called environmentally relevant BST (erBST) marine cell concentrations were nominally increased 100-fold by tangential flow filtration. The marine erBST was validated against a standard BST using five ¹⁴C labeled reference compounds with a range of biodegradation potentials (aniline, 4-fluorophenol, 4-nitrophenol, 4-chloroaniline and pentachlorophenol) in a modified OECD 301B test. A full mass balance was collated to follow chemical fate in the tests. The erBST was more accurate and less variable than the comparator BST in assigning the reference compounds to their expected biodegradation classifications (non-persistent or potentially persistent). According to the REACH non-persistence criterion of ≥60% biodegradation over 60 days, the erBST correctly classified 60% of chemical replicates according to their expected biodegradation classification and had a coefficient of variation of 21% between replicates. In contrast, the BST correctly assessed 40% of reference chemicals in regards to their expected biodegradation classification with a coefficient of variation of 36%. All non-persistent chemicals showed increased degradation in the erBST, except for 4-chloroaniline, which did not degrade in either BST or erBST. Both tests showed no false positive results, correctly classifying the negative control pentachlorophenol as potentially persistent. Next, it is recommended to further validate the marine erBST in an inter-laboratory study incorporating different seawater sources to fully assess its variability and reliability.

Phase I/II Manufacture of Lentiviral Vectors Under GMP in an Academic Setting

In clinical gene transfer applications, lentiviral vectors (LV) have rapidly become the primary means to achieve permanent and stable expression of a gene of interest or alteration of gene expression in target cells. This status can be attributed primarily to the ability of the LV to (1) transduce dividing as well as quiescent cells, (2) restrict or expand tropism through envelope pseudo-typing, and (3) regulate gene expression within different cell lineages through internal promoter selection. Recent progress in viral vector design such as the elimination of unnecessary viral elements, split packaging, and self-inactivating vectors has established a significant safety profile for these vectors. The level of GMP compliance required for the manufacture of LV is dependent upon their intended use, stage of drug product development, and country where the vector will be used as the different regulatory authorities who oversee the clinical usage of such products may have different requirements. As such, successful GMP manufacture of LV requires a combination of diverse factors including: regulatory expertise, compliant facilities, validated and calibrated equipments, starting materials of the highest quality, trained production personnel, scientifically robust production processes, and a quality by design approach. More importantly, oversight throughout manufacturing by an independent Quality Assurance Unit who has the authority to reject or approve the materials is required. We describe here the GMP manufacture of LV at our facility using a four plasmid system where 293T cells from an approved Master Cell Bank (MCB) are transiently transfected using polyethylenimine (PEI). Following transfection, the media is changed and Benzonase added to digest residual plasmid DNA. Two harvests of crude supernatant are collected and then clarified by filtration. The clarified supernatant is purified and concentrated by anion exchange chromatography and tangential flow filtration. The final product is then diafiltered directly into the sponsor defined final formulation buffer and aseptically filled.

Benchmarking protocols for the metagenomic analysis of stream biofilm viromes

Viruses drive microbial diversity, function and evolution and influence important biogeochemical cycles in aquatic ecosystems. Despite their relevance, we currently lack an understanding of their potential impacts on stream biofilm structure and function. This is surprising given the critical role of biofilms for stream ecosystem processes. Currently, the study of viruses in stream biofilms is hindered by the lack of an optimized protocol for their extraction, concentration and purification. Here, we evaluate a range of methods to separate viral particles from stream biofilms, and to concentrate and purify them prior to DNA extraction and metagenome sequencing. Based on epifluorescence microscopy counts of viral-like particles (VLP) and DNA yields, we optimize a protocol including treatment with tetrasodium pyrophosphate and ultra-sonication to disintegrate biofilms, tangential-flow filtration to extract and concentrate VLP, followed by ultracentrifugation in a sucrose density gradient to isolate VLP from the biofilm slurry. Viromes derived from biofilms sampled from three different streams were dominated by Siphoviridae, Myoviridae and Podoviridae and provide first insights into the viral diversity of stream biofilms. Our protocol optimization provides an important step towards a better understanding of the ecological role of viruses in stream biofilms.

The effect of culture salinity on the harvesting of microalgae biomass using pilot-scale tangential-flow-filter membrane

In this study, the effect of culture salinity (4-6% NaCl) on the harvesting of two microalgal strains (i.e., Picochlorum sp., and Tetraselmis sp.) was investigated using pilot-scale TFF membranes. The cultures of these two strains were collected from their respective continuous cultivation in 2, 25,000 L raceway ponds. For both strains, an increase in culture salinity aggravated the membrane fouling and hence negatively influenced the permeate flux rate, biomass concentrating factor, and energy requirement in biomass harvesting. For the TFF membranes, an increase in 1% NaCl salinity, the volume of processed permeate reduced by 30-44 %, the energy consumption per unit volume of permeate increased by 3-63%, and the biomass concentrating factor reduced by 47-61%.

A novel method to purify adenovirus based on increasing salt concentrations in buffer

With the rapid development of gene therapy, gene-based medicine with adenovirus as vectors has become a new method for disease treatment. However, there are still enormous challenges in the large-scale production of adenoviruses for clinical use. Recent reports show that ion-exchange chromatography (IEC) is an effective tool for the isolation and purification of adenovirus. However, during the separation and purification, host cell protein and DNA, as well as serum from the culture medium, can non-specifically occupy numerous binding sites of the chromatography packings, thereby reducing the binding between the adenovirus and packing media. We here report a novel method for highly efficient purification of adenoviruses by increasing the salt concentrations of the samples to be ultrafiltrated by tangential flow filtration, the diafiltration buffer, and the samples for IEC purification. This method could significantly remove a large amount of serum proteins and host cell proteins, increase the amount of sample loaded on the IEC column, and improve the binding of the adenovirus samples to the packing media. A purity of > 95% could be obtained after one chromatography operation, and the number of purification steps and the amount of used packing media were reduced. The method is simple, economical, and efficient, and has excellent applications.

Spontaneously released Neisseria meningitidis outer membrane vesicles as vaccine platform: production and purification

Outer membrane vesicles (OMVs) are nanoparticles produced by Gram-negative bacteria that can be used as vaccines. The application of OMVs as vaccine component can be expanded by expressing heterologous antigens on OMVs, creating an OMV-based antigen presenting platform. This study aims to develop a production process for such OMV-based vaccines and studies a production method based on meningococcal OMVs that express heterologous antigens on their surface. As a proof of concept, the Borrelia burgdorferi antigens OspA and OspC were expressed on Neisseria meningitidis OMVs to create a concept anti-Lyme disease vaccine. Production of OMVs released in the culture supernatant was induced by high dissolved oxygen concentrations and purification was based on scalable unit operations. A crude recovery of 90 mg OMV protein could be obtained per liter culture. Expressing heterologous antigens on the OMVs did result in minor reduction of bacterial growth, while OMV production remained constant. The antigen expression did not alter the OMV characteristics. This study shows that production of well characterized OMVs containing heterologous antigens is possible with high yields by combining high oxygen concentrations with an optimized purification process. It is concluded that heterologous OMVs show potential as a vaccine platform.

High-Efficiency Lentiviral Gene Modification of Primary Murine Bone-Marrow Mesenchymal Stem Cells

Lentiviral vectors are the method of choice for stable gene modification of a variety of cell types. However, the efficiency with which they transduce target cells varies significantly, in particular their typically poor capacity to transduce primary stem cells. Here we describe the isolation and enrichment of murine bone-marrow mesenchymal stem cells (MSCs) via fluorescence-activated cell sorting (FACS); the cloning, production, and concentration of high-titer second generation lentiviral vectors via combined tangential flow filtration (TFF) and ultracentrifugation; and the subsequent high-efficiency gene modification of MSCs into insulin-producing cells via overexpression of the furin-cleavable human insulin (INS-FUR) gene.

Manufacturing of Proteins and Antibodies: Chapter Downstream Processing Technologies

Cell harvesting is the separation or retention of cells and cellular debris from the supernatant containing the target molecule Selection of harvest method strongly depends on the type of cells, mode of bioreactor operation, process scale, and characteristics of the product and cell culture fluid. Most traditional harvesting methods use some form of filtration, centrifugation, or a combination of both for cell separation and/or retention. Filtration methods include normal flow depth filtration and tangential flow microfiltration. The ability to scale down predictably the selected harvest method helps to ensure successful production and is critical for conducting small-scale characterization studies for confirming parameter targets and ranges. In this chapter we describe centrifugation and depth filtration harvesting methods, share strategies for harvest optimization, present recent developments in centrifugation scale-down models, and review alternative harvesting technologies.

A Scalable Lentiviral Vector Production and Purification Method Using Mustang Q Chromatography and Tangential Flow Filtration

Lentiviral vectors have rapidly become a favorite tool for research and clinical gene transfer applications which seek to permanently introduce alterations in the genome. This status can be attributed primarily to their ability to transduce dividing as well as quiescent cells. When coupled with internal promotor selection to drive expression in one cell type but not another, the ease with which the vectors can be pseudotyped to either restrict or expand tropism offers unique opportunities previously unavailable to the researcher to manipulate the genome. Although LV can be produced from stable packaging cell lines and/or in suspension culture, by and far, most LV vectors are produced using adherent 293 T cells grown in plasticware and production plasmids transiently transfected with either PEI or Calcium Phosphate. The media is usually changed and un-concentrated vector supernatant collected between 24 and 48 h post-transfection. The supernatant may then be purified by Mustang Q chromatography, concentrated by Tangential Flow Filtration, and finally diafiltered into the final formulation buffer of choice. Here we describe a pilot scale method for the manufacture of a Lentiviral vector that purifies and concentrates approximately 6 L of un-concentrated LV supernatant to approximately 150 mL. Typical titers for most vector constructs range between 1 × 10⁸ and 1 × 10⁹ infectious particles per mL. This method may be performed reiteratively to increase total volume or can be further scaled up to increase yield.

Multimodal Production of Adeno-Associated Virus

Adeno-associated virus (AAV) is an increasingly popular tool in the research laboratory, and use of this viral vector clinically is occurring at an accelerated pace. Nevertheless, despite its popularity, AAV is a relatively cumbersome virus to produce; however, significant efforts have been invested to develop, optimize, and simplify methodology that allows the generation of high-quality AAV with significantly increased production yields. Here we describe multiple modalities for production and purification of AAV particles produced in HEK293 cell cultures using an iodixanol density gradient. We include two methods adapted for harvesting virus from the culture media: tangential flow filtration (TFF) and polyethylene glycol precipitation (PEGylation). Moreover, we also describe the protocol for anion exchange chromatography, which can be used after the iodixanol gradient as an additional purification step. Last, we provide various protocols for determining virus titer.

Tangential Flow Filtration with or Without Subsequent Bind-Elute Size Exclusion Chromatography for Purification of Extracellular Vesicles

Extracellular vesicles (EVs) have gained increased attention over the last decade due to their potential as biomarkers and therapeutic entities. However, the characterization and development of EV research has been hampered by the lack of sufficiently effective purification methods. Several concerns have been raised toward the gold standard purification method ultracentrifugation, such as operator-dependent yields, crushing and aggregation of vesicles, poor scalability, and relative lack of purity. Here, we describe, in details, the use of an alternative purification technique: tangential flow filtration with or without subsequent bind-elute size exclusion chromatography that we have previously shown to be reproducible and scalable for purification of EVs.

Simplified purification approach of urinary neutrophil gelatinase-associated lipocalin by tangential flow filtration and ion exchange chromatography

This investigation reports a simplified approach for the purification of urinary siderocalin known as neutrophil gelatinase-associated lipocalin (NGAL). Urinary NGAL was purified by tangential flow filtration and ion exchange chromatography. Isolated NGAL was analyzed by SDS-PAGE, immunoblotting and mass spectrometry (MS). The relative molecular mass of NGAL is 23674Da. Peptide mass fingerprinting of the purified NGAL yielded peptides that partially matched with known sequence of P80188 (NGAL_HUMAN). The tryptic digestion profile of isolated NGAL infers that it may be unique and additive molecule in the dictionary of urinary proteins. This is the first report of purification and validation of urinary NGAL from large volume sample by using tangential flow filtration and peptide sequencing respectively. This cost-effective and simplified approach to purification of NGAL, together with the easy availability of urine sample makes the large-scale production of NGAL possible, allowing exploration of various bioclinical as well as biodiagnostic applications.

Integrated economic and experimental framework for screening of primary recovery technologies for high cell density CHO cultures

Increases in mammalian cell culture titres and densities have placed significant demands on primary recovery operation performance. This article presents a methodology which aims to screen rapidly and evaluate primary recovery technologies for their scope for technically feasible and cost‐effective operation in the context of high cell density mammalian cell cultures. It was applied to assess the performance of current (centrifugation and depth filtration options) and alternative (tangential flow filtration (TFF)) primary recovery strategies. Cell culture test materials (CCTM) were generated to simulate the most demanding cell culture conditions selected as a screening challenge for the technologies. The performance of these technology options was assessed using lab scale and ultra scale‐down (USD) mimics requiring 25–110mL volumes for centrifugation and depth filtration and TFF screening experiments respectively. A centrifugation and depth filtration combination as well as both of the alternative technologies met the performance selection criteria. A detailed process economics evaluation was carried out at three scales of manufacturing (2,000L, 10,000L, 20,000L), where alternative primary recovery options were shown to potentially provide a more cost‐effective primary recovery process in the future. This assessment process and the study results can aid technology selection to identify the most effective option for a specific scenario.

Hemagglutinin and neuraminidase containing virus-like particles produced in HEK-293 suspension culture: An effective influenza vaccine candidate

Virus-like particles (VLPs) constitute a promising alternative as influenza vaccine. They are non-replicative particles that mimic the morphology of native viruses which make them more immunogenic than classical subunit vaccines. In this study, we propose HEK-293 cells in suspension culture in serum-free medium as an efficient platform to produce large quantities of VLPs. For this purpose, a stable cell line expressing the main influenza viral antigens hemagglutinin (HA) and neuraminidase (NA) (subtype H1N1) under the regulation of a cumate inducible promoter was developed (293HA-NA cells). The production of VLPs was evaluated by transient transfection of plasmids encoding human immunodeficiency virus (HIV) Gag or M1 influenza matrix protein. To facilitate the monitoring of VLPs production, Gag was fused to the green fluorescence protein (GFP). The transient transfection of the gag containing plasmid in 293HA-NA cells increased the release of HA and NA seven times more than its counterpart transfected with the M1 encoding plasmid. Consequently, the production of HA-NA containing VLPs using Gag as scaffold was evaluated in a 3-L controlled stirred tank bioreactor. The VLPs secreted in the culture medium were recovered by ultracentrifugation on a sucrose cushion and ultrafiltered by tangential flow filtration. Transmission electron micrographs of final sample revealed the presence of particles with the average typical size (150-200nm) and morphology of HIV-1 immature particles. The concentration of the influenza glycoproteins on the Gag-VLPs was estimated by single radial immunodiffusion and hemagglutination assay for HA and by Dot-Blot for HA and NA. More significantly, intranasal immunization of mice with influenza Gag-VLPs induced strong antigen-specific mucosal and systemic antibody responses and provided full protection against a lethal intranasal challenge with the homologous virus strain. These data suggest that, with further optimization and characterization the process could support mass production of safer and better-controlled VLPs-based influenza vaccine candidate.

A scale-down cross-flow filtration technology for biopharmaceuticals and the associated theory

Use of microfiltration (MF) and ultrafiltration (UF) in cross-flow mode has been intensifying in downstream processing for expensive biopharmaceuticals. A scale-down cross-flow module with ring channel was constructed for reducing costs and increasing throughput. Commensurate with its validation, a new scale down (or scale up) theoretical framework has been further developed to 3 operational parities: (1) ratio of initial sample volume to membrane area, (2) shear force adjacent to membrane surface, and (3) initial permeate flux. By keeping identical initial physicochemical properties, we show that these 3 operational parities are equivalent to 2 further time-dependent theoretical parities for flux and transmission respectively. Importantly, transmission sensitively reflects membrane conditions for partially transmissible molecules or particles. Computational fluid dynamics simulation was conducted to confirm nearly identical shear forces for the mini and its reference filters. Permeate fluxes in suspension containing Escherichia coli phage T7, a monoclonal antibody (MAb) or other proteins, and transmission (with phage T7) were measured. For application demonstration, diafiltration and concentration modes were applied to the MAb, and separation mode to a mixture of bovine serum albumin and lysozyme. In conclusion, the developed scale-down filter has been shown to behave identically or similarly to its reference filter.

Purification of diverse hemoglobins by metal salt precipitation

Although donated blood is the preferred material for transfusion, its limited availability and stringent storage requirements have motivated the development of blood substitutes. The giant extracellular hemoglobin (aka erythrocruorin) of the earthworm Lumbricus terrestris (LtEc) has shown promise as a blood substitute, but an efficient purification method for LtEc must be developed to meet the potential large demand for blood substitutes. In this work, an optimized purification process that uses divalent and trivalent metal salts to selectively precipitate human, earthworm, and bloodworm hemoglobin (HbA, LtEc, and GdHb, respectively) from crude solutions was developed. Although several metal ions were able to selectively precipitate LtEc, Zn(2+) and Ni(2+) provided the lowest heme oxidation and highest overall yield of LtEc. In contrast, Zn(2+) was the only metal ion that completely precipitated HbA and GdHb. Polyacrylamide gel electrophoresis (PAGE) analysis shows that metal precipitation removes several impurities to provide highly pure hemoglobin samples. Heme oxidation levels were relatively low for Zn(2+)-purified HbA and LtEc (2.4±1.3% and 5.3±2.1%, respectively), but slightly higher for Ni(2+)-purified LtEc (8.4±1.2%). The oxygen affinity and cooperativity of the precipitated samples are also identical to samples purified with tangential flow filtration (TFF) alone, indicating the metal precipitation does not significantly affect the function of the hemoglobins. Overall, these results show that hemoglobins from several different species can be highly purified using a combination of metal (Zn(2+)) precipitation and tangential flow filtration.

Tangential flow ultrafiltration for detection of white spot syndrome virus (WSSV) in shrimp pond water

Water represents the most important component in the white spot syndrome virus (WSSV) transmission pathway in aquaculture, yet there is very little information. Detection of viruses in water is a challenge, since their counts will often be too low to be detected by available methods such as polymerase chain reaction (PCR). In order to overcome this difficulty, viruses in water have to be concentrated from large volumes of water prior to detection. In this study, a total of 19 water samples from aquaculture ecosystem comprising 3 creeks, 10 shrimp culture ponds, 3 shrimp broodstock tanks and 2 larval rearing tanks of shrimp hatcheries and a sample from a hatchery effluent treatment tank were subjected to concentration of viruses by ultrafiltration (UF) using tangential flow filtration (TFF). Twenty to 100l of water from these sources was concentrated to a final volume of 100mL (200-1000 fold). The efficiency of recovery of WSSV by TFF ranged from 7.5 to 89.61%. WSSV could be successfully detected by PCR in the viral concentrates obtained from water samples of three shrimp culture ponds, one each of the shrimp broodstock tank, larval rearing tank, and the shrimp hatchery effluent treatment tank with WSSV copy numbers ranging from 6 to 157mL(-1) by quantitative real time PCR. The ultrafiltration virus concentration technique enables efficient detection of shrimp viral pathogens in water from aquaculture facilities. It could be used as an important tool to understand the efficacy of biosecurity protocols adopted in the aquaculture facility and to carry out epidemiological investigations of aquatic viral pathogens.

Efficient purification and concentration of viruses from a large body of high turbidity seawater

Marine viruses are the most abundant entities in the ocean and play crucial roles in the marine ecological system. However, understanding of viral diversity on large scale depends on efficient and reliable viral purification and concentration techniques. Here, we report on developing an efficient method to purify and concentrate viruses from large body of high turbidity seawater. The developed method characterizes with high viral recovery efficiency, high concentration factor, high viral particle densities and high-throughput, and is reliable for viral concentration from high turbidity seawater. Recovered viral particles were used directly for subsequent analysis by epifluorescence microscopy, transmission electron microscopy and metagenomic sequencing. Three points are essential for this method:•

The sampled seawater (>150 L) was initially divided into two parts, water fraction and settled matter fraction, after natural sedimentation.

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Both viruses in the water fraction concentrated by tangential flow filtration (TFF) and viruses isolated from the settled matter fraction were considered as the whole viral community in high turbidity seawater.

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The viral concentrates were re-concentrated by using centrifugal filter device in order to obtain high density of viral particles.

Detecting Virus-Like Particles from the Umgeni River, South Africa

It is important to consider viruses in water quality because of their incidence as causal agents for diarrhoeal disease, and due to their characteristics, which allow them to survive in changing environmental conditions indefinitely. This study assessed the viral quality of the Umgeni River in South Africa seasonally. A two-step tangential flow filtration process was setup to remove the bacteria and to concentrate the virus populations from large volume water samples. The concentrated water samples contained up to 659 and 550 pfu/mL of somatic and F-RNA coliphages, respectively. Several virus families including Adenoviridae, Herpesviridae, Orthomyxoviridae, Picornaviridae, Poxviridae and Reoviridae were found in the river based on the morphologies examined under transmission electron microscopy. All concentrated water samples produced substantial cytopathic effects on the Vero, HEK 293, Hela and A549 cell lines. These results indicate the potential of viruses in the water samples especially from the lower catchment areas of the Umgeni River to infect human hosts throughout the year. The present study highlights the importance of routine environmental surveillance of human enteric viruses in water sources. This can contribute to a better understanding of the actual burden of disease on those who might be using the water directly without treatment.

Use of hollow fiber tangential flow filtration for the recovery and concentration of HIV virus-like particles produced in insect cells

Attenuated viruses, inactivated viruses and virus like particles (VLPs) are known to be efficient vaccines partially due to their particulate structure. A potential HIV vaccine candidate engineered as a VLP (HIV gag-VLP) and produced in insect cells is currently under preclinical trials demanding large amounts. Due to their extreme fragility and sensitivity to shear forces the recovery and concentration of these extracellular enveloped particles of approximately 120 nm in size is challenging. The current bench scale gradient ultracentrifugation and precipitation methods have been found unsuitable for larger scale processes. In this study a two-step tangential flow filtration (TFF) process using hollow fibers was developed for the clarification and concentration of HIV gag-VLPs. The first step is microfiltration for cell removal and the second step is ultrafiltration for concentrating the HIV gag-VLPs. The chosen parameters for the microfiltration step were hollow fiber membranes of 0.45 μm cut off 5000 s(-1) shear force and a flux of 10 LMH. The chosen parameters for the ultrafiltration step were a 500 kDa cut off membrane, 6000 s(-1) shear force and a trans-membrane pressure (TMP) of 1.25 bar. The utilization of these parameters provided with concentrated HIV-gag VLPs from 2L of starting cell suspension within 6h of processing time. These downstream processing conditions are extremely valuable for the further large-scale purification process development for HIV gag-VLPs and other particulate bioproducts.