Pilot production of u-PA with porous microcarrier cell culture

Biomanufacturing Recombinantly Expressed Cripto-1 Protein in Anchorage-Dependent Mammalian Cells Growing in Suspension Bioreactors within a Three-Dimensional Hydrogel Microcarrier

Biotherapeutic soluble proteins that are recombinantly expressed in mammalian cells can pose a challenge when biomanufacturing in three-dimensional (3D) suspension culture systems. Herein, we tested a 3D hydrogel microcarrier for a suspension culture of HEK293 cells overexpressing recombinant Cripto-1 protein. Cripto-1 is an extracellular protein that is involved in developmental processes and has recently been reported to have therapeutic effects in alleviating muscle injury and diseases by regulating muscle regeneration through satellite cell progression toward the myogenic lineage. Cripto-overexpressing HEK293 cell lines were cultured in microcarriers made from poly (ethylene glycol)-fibrinogen (PF) hydrogels, which provided the 3D substrate for cell growth and protein production in stirred bioreactors. The PF microcarriers were designed with sufficient strength to resist hydrodynamic deterioration and biodegradation associated with suspension culture in stirred bioreactors for up to 21 days. The yield of purified Cripto-1 obtained using the 3D PF microcarriers was significantly higher than that obtained with a two-dimensional (2D) culture system. The bioactivity of the 3D-produced Cripto-1 was equivalent to commercially available Cripto-1 in terms of an ELISA binding assay, a muscle cell proliferation assay, and a myogenic differentiation assay. Taken together, these data indicate that 3D microcarriers made from PF can be combined with mammalian cell expression systems to improve the biomanufacturing of protein-based therapeutics for muscle injuries.

Cell encapsulation utilizing PEG-fibrinogen hydrogel supports viability and enhances productivity under stress conditions

Recent advances in the bioengineering field have introduced new opportunities enabling cell encapsulation in three-dimensional (3D) structures using either various natural or synthetic materials. However, such hydrogel scaffolds have not been fully biocompatible for cell cultivation due to the lack of physical stability or bioactivity. Here, we utilized a uniquely fabricated semi-synthetic 3D polyethylene glycol-fibrinogen (PEG-Fb) hydrogel scaffold, which exhibits both high stability and high bioactivity, to encapsulate HEK293 cells for the production of human recombinant acetylcholine esterase (AChE). To examine the beneficial bioactive effect of the PEG-Fb scaffold over 2D surfaces, an experimental system was established to compare the viability, proliferation and AChE secretion of encapsulated cells versus non-encapsulated surface-adherent cells in serum starvation. Our results show that the transfer of surface-adherent HEK293 cells from fully enriched medium with 10% FCS to 0.2% FCS resulted in an eightfold reduction in cell number and a fourfold reduction in AChE production. In contrast, the encapsulated cells were highly viable and about twofold more efficient in AChE production. In addition, they had round morphology with a twofold larger cell diameter, supporting the observation of increased AChE production. These results suggest a role of the PEG-Fb scaffold in providing a supportive microenvironment in reduced serum conditions that enhances encapsulated cell functions, opening new directions to study the implementation of this platform in large-scale pharmaceutical protein production.

Synergistic inhibitory effects of an engineered antibody-like molecule ATF-Fc and trastuzumab on tumor growth and invasion in a human breast cancer xenograft mouse model

The overexpression of the oncogene human epidermal growth factor receptor 2 (HER-2) has been associated with decreased disease-free survival and is a marker of poor prognosis of invasive breast cancer. Although the high efficacy of trastuzumab, a drug that targets the HER-2 oncogene, has been widely recognized, the efficiency of the treatment remains at ~30%. Therefore, novel effective treatments are required for patients with recurrent metastatic breast cancer. The present study aimed to investigate the effects of an engineered antibody-like molecule administered alone or in combination with trastuzumab on the tumor growth and metastasis of HER-2-positive breast cancer. Another aim was to investigate novel cancer therapies for HER-2-positive breast cancer. The engineered antibody-like molecule consists of the amino-terminal fragment (ATF) of human urokinase-type plasminogen (uPA) and is conjugated with the Fc fragment of human immunoglobulin G1 (ATF-Fc). The anti-cancer effect of ATF-Fc (alone and in combination with trastuzumab) on tumor cells and in a nude mouse tumor model was evaluated by detecting the expression of uPA, urokinase plasminogen activator receptor (uPAR) and HER-2. In vitro experiments demonstrated that specifically blocking the uPA-uPAR and HER-2 signaling pathways may effectively promote the apoptosis of breast cancer cells. Additionally, ATF-Fc-induced cell death in HER-2-positive breast cancer cells was observed in vivo. When ATF-Fc was administered in combination with trastuzumab, cell death was increased and breast cancer metastasis was reduced. The novel engineered antibody-like molecule ATF-Fc was able to inhibit HER-2-positive breast cancer cell growth and metastasis by interfering with uPA and its receptor (uPA-uPAR) system. Additionally, the antibody-like molecule exhibits a synergistic inhibitory effect when administered in combination with trastuzumab.

Approaches to optimizing animal cell culture process: substrate metabolism regulation and protein expression improvement

Some high value proteins and vaccines for medical and veterinary applications by animal cell culture have an increasing market in China. In order to meet the demands of large-scale productions of proteins and vaccines, animal cell culture technology has been widely developed. In general, an animal cell culture process can be divided into two stages in a batch culture. In cell growth stage a high specific growth rate is expected to achieve a high cell density. In production stage a high specific production rate is stressed for the expression and secretion of qualified protein or replication of virus. It is always critical to maintain high cell viability in fed-batch and perfusion cultures. More concern has been focused on two points by the researchers in China. First, the cell metabolism of substrates is analyzed and the accumulation of toxic by-products is decreased through regulating cell metabolism in the culture process. Second, some important factors effecting protein expression are understood at the molecular level and the production ability of protein is improved. In pace with the rapid development of large-scale cell culture for the production of vaccines, antibodies and other recombinant proteins in China, the medium design and process optimization based on cell metabolism regulation and protein expression improvement will play an important role. The chapter outlines the main advances in metabolic regulation of cell and expression improvement of protein in animal cell culture in recent years.

Evaluation of solid and porous microcarriers for cell growth and production of recombinant proteins

Microcarrier technology opened new perspectives for anchorage-dependent cell culture, by providing increased surface areas for cell adhesion and proliferation, and therefore improving both cell and product yields obtained in these cultures. The establishment of a successful microcarrier culture depends on many factors, such as the type of microcarrier, the cells, and the culture conditions. In this chapter, the basic steps required for the evaluation and optimization of a microcarrier culture for the purpose of production of recombinant proteins are described, for both solid and porous microcarriers.

The impact of microcarrier culture optimization on the glycosylation profile of a monoclonal antibody

Microcarriers are widely used for the large-scale culture of attachment-dependent cells with increased cell densities and, ultimately, higher product yield. In these processes, the specific culture conditions can affect the quality of the product, which is closely related to its glycosylation pattern. Furthermore, the lack of studies in the area reinforces the need to better understand the effects of microcarrier culture in product glycosylation. Consequently, in this work, the glycosylation profile of a monoclonal antibody (mAb) produced by adherent CHO-K1 cells grown in Cytodex 3 was evaluated under different conditions, and compared to that obtained of typical adherent cultures. It was found that microcarrier cultures result in a glycosylation profile with different characteristics from T-flask cultures, with a general increase in galactosylation and decrease in fucosylation levels, both with a potentially positive impact on mAb activity. Sialylation also varied but without a general tendency. This study then showed that the specific culture conditions used in microcarrier culture influence the mAb glycan profile, and each functional element (galactose, core fucose, sialic acid) is independently affected by these conditions. In particular, great reductions of fucosylation (from 79 to 55%) were obtained when using half volume at inoculation, and notable decreases in sialylation (from 23 to 2%) and glycoform heterogeneity (from 20 to 11 glycoforms) were observed for shake flask culture, potentially associated with the improved cell densities achieved in these culture vessels.

New developments in lentiviral vector design, production and purification

INTRODUCTION

Lentiviruses are a very potent class of viral vectors for which there is presently a rapidly growing interest for a number of gene therapy. However, their construction, production and purification need to be performed according to state-of-the-art techniques in order to obtain sufficient quantities of high purity material of any usefulness and safety.

AREAS COVERED

The recent advances in the field of recombinant lentivirus vector design, production and purification will be reviewed with an eye toward its utilization for gene therapy. Such a review should be helpful for the potential user of this technology.

EXPERT OPINION

The principal hurdles toward the use of recombinant lentivirus as a gene therapy vector are the low titer at which it is produced as well as the difficulty to purify it at an acceptable level without degrading it. The recent advances in the bioproduction of this vector suggest these issues are about to be resolved, making the retrovirus gene therapy a mature technology.

Effect of low culture temperature on urokinase production in hollow fiber reactor

The effect of culture temperature on urokinase production by HT-1080 cell line was studied in batch culture and hollow fiber reactor. Small-scale t-flask experiments revealed that urokinase production could be enhanced and media utilization could be reduced by lowering the culture temperature in production phase. Urokinase production was scaled up using a hollow fiber perfusion reactor system. Temperature of culture was maintained at the physiological 37 °C during growth phase that extended up to 12 days in hollow fiber bioreactor. Subsequently, in the production phase, culture temperature was lowered to 34 °C. Decrease in culture temperature resulted in a significant increase in urokinase production. Proteolytic degradation and inhibition was also minimized. The medium utilization rate was decreased at lower temperature, and hence, a higher economy of production could be obtained.

Polymerase chain reaction and real-time PCR for diagnosing of Leishmania infantum chagasi in dogs

The importance of dogs as a reservoir for Leishmania infantumchagasi in urban environments has stimulated numerous studies assessing diagnostic techniques. When performed properly, such procedures are an important step in preventing leishmaniasis in humans. Molecular methods have become prominent for this purpose. The aim of the present study was to determine the performance of the polymerase chain reaction (PCR) and real-time PCR (qPCR) for diagnosing of canine visceral leishmaniasis (CVL) using different biological samples. For this, 35 dogs from an area endemic for CVL were used. Bone marrow aspirate and lymph node and spleen fragments from these dogs were used for the molecular diagnosis. In the present study, qPCR was able to detect a greater number of positive animals than seen with PCR. Among the different biological samples used, there was no significant difference in L. infantumchagasi DNA detection between PCR and qPCR. However, considering that lymph nodes are easy to acquire, these can be considered to be the best samples for making molecular diagnoses of L. infantum chagasi infection.

Preparation and characterization of chitosan porous microcarriers for hepatocyte culture

BACKGROUND

The bioartificial liver (BAL) is considered a possible alternative method for treating liver failure. The core of the BAL system is culturing liver cells in vitro with high density and activity. Microcarrier culture is a mode of high-density culture. We set out to prepare a novel porous microcarrier to improve the activity of liver cells in vitro.

METHODS

Chitosan was used to prepare a novel porous spherical microcarrier with interconnected structure. The chitosan porous microcarriers (CPMs) were modified with gelatin to improve their biocompatibility. CPMs were co-cultured with liver cells, HL-7702 (L-02), to evaluate their effect on cell culture.

RESULTS

The average size of the CPMs was about 400 μm in diameter and their apertures were less than 30 μm. The pores of the microcarrier were interconnected. After fixation by sodium tripolyphosphate, the structure of the first freeze-dried CPMs was stable. To further improve the biocompatibility, the surface of CPMs was modified with gelatin through chemical crosslinking (GM-CPMs). Comparing the proliferation curves of L-02 cells cultured on simple CPMs, GM-CPMs and tissue culture polystyrene (TCPS, a mode of planar cell culture), the proliferation rates were similar in the first 5 days and the cells proliferated until day 8 in culture with microcarriers. The OD value of liver cells cultured on GM-CPMs was 1.97-fold higher than that on TCPS culture at day 8. Levels of urea and albumin in supernatants of cells cultured on GM-CPMs increased steadily for 8 days, and were clearly higher than those of cells cultured on TCPS (P<0.05).

CONCLUSIONS

The novel CPMs were promising microcarriers for hepatocyte culture and the GM-CPM seemed better. Porous microcarrier culture was beneficial for hepatocyte function and activity.

Detachment factors for enhanced carrier to carrier transfer of CHO cell lines on macroporous microcarriers

In this publication different detachment factors were tested for enhancing carrier to carrier transfer for scale-up of macroporous microcarrier based bioprocesses. Two Chinese hamster ovary cell lines, CHO-K1 and a genetically engineered CHO-K1 derived cell line (CHO-MPS), producing recombinant human Arylsulfatase B, were examined. The cells were grown on Cytoline 1microcarriers (Amersham Biosciences, Uppsala, Sweden) in protein-free and chemically defined medium respectively. Fully colonised microcarriers were used at passage ratios of approximately 1:10 for carrier to carrier transfer experiments. To accelerate the colonisation of the non-colonised, freshly added microcarriers the detachment reagents trypsin, papain, Accutasetrade mark (PAA, Linz, Austria), heparin and dextransulphate were used. Both cell lines showed good results with trypsin, Accutase and dextransulphate (Amersham Biosciences, Uppsala, Sweden), while papain failed to enhance carrier to carrier transfer in comparison to the non-treated reference. The maximum growth rate of cells on microcarriers with 2% dextransulphate in the medium was 0.25 +/- 0.02d(-1) and 0.27 +/- 0.03d(-1) for the CHO-MPS and CHO-K1, respectively. TheCHO-K1 grew best after detachment with trypsin (mu = 0.36 +/- 0.03d(-1)). This indicates, that one of the key parameters for carrier to carrier transfer is the uniform distribution of cells on the individual carriers during the initial phase. When this distribution can be improved, growth rate increases, resulting in a faster and more stable process.

External modulation of HT-1080 human fibrosarcoma cells improves urokinase production

Urokinase was produced in a hollow fiber reactor using HT-1080 human fibrosarcoma cells. External modulation comprised replenishing of the medium in the extracapillary space, reducing the serum concentration in the extracapillary space from 10% to 2% and increasing flow rate of the circulating medium in the intracapillary space from 20 to 80 mL/min, each according to a specific protocol. More than sixfold increase was observed in the cumulative urokinase production for two and three medium replenishing modulations of the extracapillary space. After 15 days of continuous operation, the highest cumulative urokinase obtained was 1.63 x 10(6) PU/mL. SDS-PAGE and zymogram study established that the urokinase obtained was in the high molecular weight range of 54 kDa. The effect of external modulation on cumulative urokinase production was visualized as trajectories with respect to the ratio of lactic acid production rate (LPR) to the glucose uptake rate (GUR). The collective external modulation data showed two separate physiological regions in the cumulative urokinase vs. LPR/GUR plane. The HT-1080 cells exhibited two distinct morphologies in these regions that may be related to acidosis and metastasis. These regions also correspond to low and high urokinase productivity.

The effects of microcarrier culture on recombinant CHO cells under biphasic hypothermic culture conditions

A Chinese hamster ovary (CHO) cell line, producing recombinant secreted human placental alkaline phosphatase (SEAP) was investigated under three different culture conditions (suspension cells, cells attached to Cytodex 3 and Cytopore 1 microcarriers) in a biphasic culture mode using a temperature shift to mild hypothermic conditions (33 degrees C) in a fed-batch bioreactor. The cell viability in both the suspension and the Cytodex 3 cultures was maintained for significantly longer periods under hypothermic conditions than in the single-temperature cultures, leading to higher integrated viable cell densities. For all culture conditions, the specific productivity of SEAP increased after the temperature reduction; the specific productivities of the microcarrier cultures increased approximately threefold while the specific productivity of the suspension culture increased nearly eightfold. The glucose and glutamine consumption rates and lactate and ammonia production rates were significantly lowered after the temperature reduction, as were the yields of lactate from glucose. However, the yield of ammonia from glutamine increased in response to the temperature shift.

Three-dimensional culture for monoclonal antibody production by hybridoma cells immobilized in macroporous gel particles

Cell proliferation and long-term production of monoclonal antibody IgG(2b) by M2139 hybridoma cells immobilized in macroporous gel particles (MGPs) in packed-bed reactor were studied for a period of 60 days. The MGPs were made of supermacroporous gels produced in frozen conditions from crosslinked polyacrylamide and modified with gelatin which were housed in special plastic carriers (7 x 9 mm(2)). Cells were trapped in the interior part of MGPs by attaching to the void space of the gel matrix as three-dimensional (3D) cultivation using gelatin as a substrate layer. Optimizing productivity by hybridoma cell relies on understanding regulation of antibody production. In this study, the behavior of M2139 cells in two-dimensional cultures on multiwell plate surfaces was also investigated. The effect of three different medium such as basal medium Dulbecco's modified Eagle's medium (D-MEM) containing L-glutamine or L-glutamine + 2 mM alpha-ketoglutarate or L-alanyl-glutamine (GlutaMAXtrade mark) was studied prior to its use in 3D cultivation. The kinetics of cell growth in basal medium containing L-glutamine + alpha-ketoglutarate was similar to cells grown on GlutaMAX containing medium, whereas D-MEM containing L-glutamine showed lower productivity. With the maximal viable cell density (6.85 x 10(6) cells mL(-1)) and highest specific mAb production rate (3.9 mug mL(-1) 10(-4) viable cell day(-1)), D-MEM-GlutaMAX was further selected for 3D cultivation. Cells in MGPs were able to grow and secrete antibody for 30 days in packed-bed batch reactor, before a fresh medium reservoir was replaced. After being supplied with fresh medium, cells again showed continuous growth for another 30 days with mAb production efficiency of 50%. These results demonstrate that MGPs can be used efficiently as supporting carrier for long-term monoclonal antibody production.

Cell Attachment to Microcarriers Affects Growth, Metabolic Activity, and Culture Productivity in Bioreactor Culture

It is not well understood how changes from suspension to microcarrier cultures affect cell growth, metabolism, and yield of recombinant proteins. To investigate the effects of culture conditions on cell characteristics, fed-batch bioreactor cultures were performed under different culture conditions (suspension cultures, cultures attached to Cytodex 3 and Cytopore 1 microcarriers) using two different Chinese hamster ovary cell lines producing either secreted human placental alkaline phosphatase (TR2-255) or tissue plasminogen activator (CHO 1-15-500). In controlled, agitated bioreactors, suspension cultures reached cell densities and product titers higher than those in microcarrier cultures, in contrast to the results in static flask cultures. Growth and metabolic activities showed similar trends in suspension and microcarrier culture regardless of cell line. However, the responses of the specific productivities to the different culture conditions differed significantly between the cell lines.

Antitumor activities of TEM8-Fc: an engineered antibody-like molecule targeting tumor endothelial marker 8

Tumor endothelial marker 8 (TEM8) was discovered as a cell membrane protein that is predominantly expressed in tumor endothelium and identified as a receptor for anthrax toxin. We developed an antibody-like molecule that consists of the protective antigen (PA)-binding domain of human TEM8 linked to the Fc portion of human immunoglobulin G1 (TEM8-Fc). This engineered protein bound to PA in a divalent cation-dependent manner and efficiently protected J774A.1 macrophage-like cells against anthrax toxin challenge in a dose-dependent manner. TEM8-Fc suppressed the growth and metastasis of xenograft human tumors in athymic nude mice (control versus 10 mg/kg TEM8-Fc, mean tumor weight: LS-180, 1.72 versus 0.16 g, difference = 1.56 g, 95% confidence interval [CI] = 0.96 to 2.16 g; P<.001; MCF-7, 1.12 versus 0.08 g, difference = 1.04 g, 95% CI = 0.77 to 1.31 g; P<.001; HepG2, 1.28 versus 0.35 g, difference = 0.93 g, 95% CI = 0.60 to 1.25 g; P<.001). Furthermore, TEM8 interacted with the M2 isoenzyme of pyruvate kinase (M2-PK), which has an important role in tumor growth and metastasis. TEM8-Fc is a novel therapeutic antibody-like agent in the management of solid tumors that may act by trapping M2-PK.

Biopharmaceuticals in China

The biopharmaceutical industry, whose products are produced mainly by recombinant DNA technology, antibody technologies and cytotechnology, is the most important sector in industrial biotechnology, and is one of the most rapidly growing high-tech industries. The global market for biopharmaceuticals had been growing at annual growth rates of 15-33% over the last 8 years, and sales exceeded 55 billion dollars in 2005. This review presents an overview of the Chinese biopharmaceutical industry, listing the global top-selling biopharmaceuticals in 2005, and briefly describes the major biotech drugs approved by the Chinese State Food and Drug Administration, such as recombinant cytokines, therapeutic antibodies, recombinant vaccines, and gene therapy products.

Synthesis, regulation and production of urokinase using mammalian cell culture: a comprehensive review

Urokinase, a serine protease, catalyzes the conversion of plasminogen to plasmin, which is responsible for dissolution of clots in blood vessels. It is an important drug for treatment of thromboembolic disease. Production of urokinase by mammalian cell culture has the following important steps: synthesis, regulation and secretion. Production and accumulation of this product in a bioreactor is a real challenge for biochemical engineers. Considerable information at molecular level needs to be understood for production of urokinase in order to correlate different parameters, which in turn can maximize the productivity. This information will be highlighted in this review. Moreover, urokinase production is a product-inhibited process. Therefore, in situ urokinase separation strategy is required to operate a bioreactor at its maximum urokinase formation rate. Integrated urokinase production and isolation processes developed recently will also be discussed briefly in this review.

Industrial choices for protein production by large-scale cell culture

Traditional barriers to large-scale mammalian culture have now been addressed, with the standard stirred-tank reactor emerging as industry's technology of choice. The issues of adapting cells to suspension culture, shear sensitivity and oxygen supply have been largely resolved. But for many low-volume and specialty applications, such as the production of viral vaccines and gene therapies, reactor technology remains diversified, with reactor types ranging from roller bottles to stacked plates and hollow fibers.