Dialysis cultures with immobilized hybridoma cells for effective production of monoclonal antibodies

An industrial scale reactor concept for continuous cultivation of immobilized animal cells (e.g. hybridoma cells) in a radial-flow fixed bed is presented, where low molecular weight metabolites are removed via dialysis membrane and high molecular products (e.g. monoclonal antibodies) are enriched. In a new nutrient-split feeding strategy concentrated medium is fed directly to the fixed bed unit, whereas a buffer solution is used as dialysis fluid. This feeding strategy was investigated in a laboratory scale reactor with hybridoma cells for production of monoclonal antibodies. A steady state monoclonal antibody concentration of 478 mg l^-1 was reached, appr. 15 times more compared to the concentration reached in chemostat cultures with suspended cells. Glucose and glutamine were used up to 98%. The experiments were described successfully with a kinetic model for immobilized growing cells. Conclusions were drawn for scale-up and design of the large scale system.Abbreviations: c_Glc – glucose concentration, mmol l^-1; c_Gln – glutamine concentration, mmol l^-1; c_Amm – ammonia concentration, mmol l^-1; c_Lac – lactate concentration, mmol l^-1; c_MAb – MAb concentration, mg l^-1; D – dilution rate, d^-1; D_i – dilution rate in the inner chamber of the membrane dialysis reactor, d^-1; D₀ – dilution rate in the outer chamber of the membrane dialysis reactor, d^-1; q*_FB,Glc – volume specific glucose uptake rate related to the fixed bed volume, mmol l_FB ^-1 h^-1; q*_FB,Gln – volume specific glutamine uptake rate related to the fixed bed volume, mmol l_FB ^-1 h^-1.     

Improving an on-line feeding strategy for fed-batch cultures of hybridoma cells by dialysis and `Nutrient-Split'-feeding

The concept of the feeding strategy was to minimise the formation of inhibiting metabolites and to increase the yield of monoclonal antibodies in fed-batch cultures of hybridoma cells by a balanced supply of substrates. A process control system based on fieldbus technology was used for monitoring and control. External program routines were implemented to control dissolved oxygen (DO) and to calculate the oxygen uptake rate (OUR) and cumulative oxygen consumption (COC) simultaneously. A concentrated feed solution was supplied according to the off-line estimated stoichiometric ratio between oxygen and glucose consumption (GC). Feeding was initiated automatically when the OUR decreased due to substrate limitation. The antibody concentration increased three-fold compared to the conventional batch culture by applying this strategy. But it was not possible to avoid inhibition by ammonia during the fed-batch phase. This was accomplished by the use of a dialysis membrane. Dialysis fed-batch cultures were performed in a membrane dialysis reactor with a `nutrient-split' feeding strategy, where concentrated medium is fed to the cells and toxic metabolites are removed into a buffer solution. This resulted in a ten-fold increase of the antibody concentration compared to the batch. Amino acid concentrations were analysed to identify limiting conditions during the cultivation and to analyse the performance of the nutrient supply in the fed-batch and dialysis fed-batch.     

A serum substitute for fed-batch culturing of hybridoma cells

We developed a substitute for serum to produce fed-batch cultures of hybridoma cells in serum-free medium and confirmed that the cells could be successfully cultivated this way. Our substitute consisted of 12 components. The specific production rates of lactate and ammonia, which are harmful byproducts from the cells, were significantly reduced compared with a conventional serum-containing batch culture. This reduction led to a higher cell concentration and a longer production lifetime. As a result, the final concentration of monoclonal antibody was 400 mg/L, or five times greater than that in the conventional serum-containing batch culture. The developed substitute is expected to enable fed-batch cultivation in a serum-free condition.     

Effects of ammonia and lactate on hybridoma growth, metabolism, and antibody production

The influence of ammonia and lactate on cell growth, metabolic, and antibody production rates was investigated for murine hybridoma cell line 163.4G5.3 during batch culture. The specific growth rate was reduced by one-half in the presence of an initial ammonia concentration of 4 mM. Increasing ammonia levels accelerated glucose and glutamine consumption, decreased ammonia yield from glutamine, and increased alanine yield from glutamine. Although the amount of antibody produced decreased with increasing ammonia concentration, the specific antibody productivity remained relatively constant around a value of 0.22 pg/cell-h. The specific growth rate was reduced by one-half at an initial lactate concentration of 55 mM. Although specific glucose and glutamine uptake rates were increased at high lacatate concentration, they showed a decrease after making corrections for medium osmolarity. The yield coefficient of lactate from glucose decreased at high lactate concentrations. A similar decrease was observed for the ammonia yield coefficient from glutamine. At elevated lactate concentrations, specific antibody productivities increased, possibly due to the increase in medium osmolarity. The specific oxygen uptake rate was insensitive to ammonia and lactate concentrations. Addition of ammonia and lactate increased the calculated metabolic energy production of the cells. At high ammonia and lactate, the contribution of glycolysis to total energy production increased. Decreasing external pH and increasing ammonia concentrations caused cytoplasmic acidification. Effect of lactate on intracellular pH was insignificant, whereas increasing osmolarity caused cytoplasmic alkalinization.     

Fed-batch cultivation of recombinant escherichia coli JM103 and production of the fusion protein SPA::EcoRI in a 60-L working volume airlift tower loop reactor

SPA::EcoRI fusion protein was produced by Escherichia coli JM103 carrying the multicopy expression plasmid pMTC48, the multicopy repressor plasmid pRK248, and the multicopy protection plasmid pEcoR4 in a 60-L working volume airlift tower loop reactor on M9 minimal medium with glucose. Cell mass concentration, total cell count, number of colony-forming units, specific growth rate, yield coefficient, and metabolite (acetate, pyruvate, succinate, lactate, ethanol) concentrations were monitored during the growth phase and gene expression. Gene expression was induced by temperature shift or chemically by isopropyl-thiogalactosidase in the airlift tower loop reactor (ALTR) at constant cultivation time and in a small stirred tank reactor at different cultivation times. During induction, the cultivation medium was supplemented with concentrated Luria-Bertani (LB) medium. The intracellular enzyme activity was evaluated as a function of the time after the start of the induction. It was found that the reduction of the glucose concentration and increase of the dissolved oxygen concentration reduced the acetate produced and increased the intracellular enzyme activity. (c) 1993 John Wiley & Sons, Inc.     

Analysis of the ammonia metabolism of rat primary hepatocytes and a human hepatocyte cell line Huh 7

Ammonia metabolism of ratprimary hepatocytes and a human hepatocyte cell line,Huh 7, at different concentrations of glutamine,glucose and ammonia was examined. During theincubation of the primary hepatocyte cells, glutamineand ammonia concentrations decreased, that of ureaincreased, and that of glucose remained the same. Inthe case of Huh 7 cells, glucose was consumed rapidly,the concentration of ammonia increased and that of urearemained the same. The major energy sources amongmedium components were glutamine for the primary cellsand glucose for Huh 7 cells, although the primaryhepatocytes may utilize intracellular glycogen asenergy source. As the glutamine concentration in theincubation medium increased, the specific rates of notonly glutamine consumption, but also ammonia productionby the primary cells and Huh 7 cells increased. Besides, specific urea production rate by the primarycells increased then. Increase of glucoseconcentration had no effect on glutamine and ammoniametabolism by both cells, although it increased glucoseconsumption by Huh 7 cells. The incubation of theprimary cells with higher ammonia concentrationincreased all specific rates of glutamine consumption,ammonia consumption and urea production. An increasein the ammonia concentration to 5 mM changed theammonia metabolism from production to consumption andincreased the specific glucose consumption rate. Consequently, increases in the glutamine and ammoniaconcentrations were revealed to have negative andpositive effects, respectively, on decreasing ammoniaconcentration by both of rat primary hepatocytes andHuh 7 cells.     

Applications of improved stoichiometric model in medium design and fed-batch cultivation of animal cells in bioreactor

In our previous work (Xie and Wang, 1994a), a simplified stoichiometric model on energy metabolism for animal cell cultivation was developed. Fed-batch experiments were performed in T-flasks using this model in supplemental medium design (Xie and Wang, 1994b). In this work, the major pathways of glucose and glutamine metabolism were incorporated into the stoichiometric model. Fed-batch culture was conducted in a 2-liter bioreactor with appropriate process control strategies. Nutrient concentrations, especially glucose and glutamine, were maintained at constant but low levels through the automated feeding of a supplemental medium formulated using the improved stoichiometric model. The formation of toxic byproducts, such as ammonia and lactate (Hassellet al., 1991), was greatly reduced. The specific lactate production rate was decreased by 62-fold compared with batch culture in bioreactor and by 8-fold compared to fed-batch culture in T-flask using the previous stoichiometric model. Ammonia formation was also decreased compared with both the batch and fed-batch cultures. Most importantly, the monoclonal antibody concentration reached 900 mg l^?1, an increase of 17- and 1.6-fold compared with the batch and fed-batch cultures respectively.     

Fed-batch cultivation of animal cells using different medium design concepts and feeding strategies

In animal cell cultivation, cell density and product concentration are often low due to the accumulation of toxic end-products such as ammonia and lactate and/or the depletion of essential nutrients. A hybridoma cell line (CRL-1606) was cultivated in T-flasks using a newly devised medium feeding strategy. The goals were to decrease ammonia and lactate formation by the design of an initial medium which would provide a starting environment to achieve optimal cell growth. This was followed by using a stoichiometric equation governing animal cell growth and then designing a supplemental medium for feeding strategy used to control the nutritional environment. The relationship between the stoichiometric demands for glutamine and nonessential amino acids was also studied. Through stoichiometric feeding, nutrient concentrations were controlled reasonably well. Consequently, the specific production rate of lactate was decreased by fourfold compared with conventional fed-batch culture and by 26-fold compared with conventional batch culture. The specific production rate of ammonia was decreased by tenfold compared with conventional fed-batch culture and by 50-fold compared with conventional batch culture. Most importantly, total cell density and monoclonal antibody concentration were increased by five- and tenfold respectively, compared with conventional batch culture. (c) 1994 John Wiley & Sons, Inc.     

Influence of lactate, ammonia, and osmotic stress on adherent and suspension BHK cells.

Adherent and suspension Baby Hamster Kidney (BHK) 21c13 cells were cultivated in a 2.5-1 stirred-tank reactor with indirect aeration. Cell concentration and viability as well as glucose, lactate, ammonia, and protein concentrations in the medium and intracellular and extracellular activities of the intracellular enzymes were determined off-line. The concentrations of glucose, lactate, ammonia, and the activity of lactate dehydrogenase in the culture medium were monitored on-line. The cell/cell fragment size distribution was determined by laser flow cytometer off-line. In several runs, the size distributions were ascertained on-line by a laser flow cytometer. The influence of lactate, ammonia, and osmotic pressure on the viability and biological parameters of the suspension cells was evaluated. In Roux flasks, lactate and ammonia had considerable influence on the cell properties; in stirred tank reactors, these influences were negligible up to 9.5 g l-1 lactate and 150 mg l-1 NH+4 ion concentrations. The influence of high osmolarity on the biological parameters of the cells was much less in the stirred-tank than in the Roux flasks. The adhesion of adherent cells on a surface was impeded neither by the lactate (up to 6 g l-1) nor by the ammonia concentration (up to 150 mg l-1). However, with increasing osmolarity, the fraction of the cells adhered to a surface reduced to below 5% (at 680 mOsmol l-1).     

Design and performance of a trickle-bed bioreactor with immobilized hybridoma cells

A trickle-bed system employing inert matrices of vermiculite or polyurethane foam packed in the downcomer section of a split-flow air-lift reactor has been developed for hybridoma culture to enhance antibody productivity. This quiescent condition favoured occlusion and allowed the cells to achieve densities twelve fold greater (12.8×10⁶ cells/ml reactor for polyurethane foam) than in free cell suspension. The reactor was operated in a cyclic batch mode whereby defined volumes of medium were periodically withdrawn and replaced with equal volumes of fresh medium. The pH of the medium was used as the indicator of the feeding schedule. Glucose, lactate and ammonia concentrations reached a stationary value after 5 days. With vermiculite packing, a monoclonal antibody (MAb) concentration of 2.4 mg/l was achieved after 12 days. The MAb concentration declined then increased to a value of 1.8 mg/l. In the polyurethane foam average monoclonal antibody (MAb) concentrations reached a stationary value of 1.1 mg/l in the first 20 days and increased to a new stationary state value of 2.1 mg/l for the remainder of the production. MAb productivity in the trickle-bed reactor was 0.3 mg/l·d (polyurethane foam) and 0.18 mg/l.d (vermiculite) in comparison to 0.12 mg/l·d for free cell suspension. This trickle-bed system seems to be an attractive way of increasing MAb productivity in culture.     

Multi-rate nonlinear state and parameter estimation in a bioreactor

This paper concerns real-time, multi-rate, nonlinear state and parameter estimation in a pilot-scale biochemical reactor in which cultivation of mouse-mouse hybridoma cells takes place. A multi-rate estimator is designed and implemented to estimate specific growth rate and concentrations of viable cells, total cells, glucose, glutamine, and monoclonal antibodies (MAb) in the reactor. These are estimated from frequent measurement (inferred values) of oxygen uptake rate (OUR) and infrequent and delayed measurements of the concentrations of viable cells, total cells, glucose, glutamine, and MAb. The infrequent measurements are available every 2 to 17 h with a time delay of 0.08 to 2.00 h, and OUR is inferred from dissolved oxygen concentration measurements that are available very 0.17 h. For each of the process variables, its infrequent measurement data and the profile of its estimate are presented to show the performance of the multi-rate estimator.     

Biological responses of hybridoma cells to hydrodynamic shear in an agitated bioreactor.

Effects of long-term hydrodynamic shear on hybridoma cells were investigated in a 250-ml continuous stirred-tank reactor (CSTR). Cells grown at steady state were subjected to step changes in agitation rates. Cell viability, glucose consumption, and monoclonal antibody (MAb) production were determined at high agitation rates and compared with the control (100 rev min-1). Impeller tip speeds higher than 40 cm s-1 caused a significant drop in cell concentration and respiration activity, and increased lactate dehydrogenase (LDH) release to the culture medium. Also, high agitation speeds caused a decrease in MAb concentration and an increase in specific glucose consumption rate. The effects of dilution rate and serum concentration on the sensitivity of hybridoma cells to hydrodynamic shear were determined. Serum was found to protect the cells against shear damage and had a significant positive effect on hybridoma growth and MAb production. Shear damage on cells in CSTR was approximated to first-order kinetics. The death rate constant increased sharply at impeller tip speeds above 40 cm s-1.     

Glucose uptake rate as a tool to estimate hybridoma growth in a packed bed bioreactor

The immobilisation of cells in a perfusion culture allows to obtain a high cell concentration and an efficient removal of the catabolites without cell loss. A disadvantage of this system is that the cell density cannot be directly monitored. The cellular metabolism is just followed by online measurements of pH and dissolved oxygen (DO) and off-line determinations of residual metabolites. In this article, we report a high cell density achieved by the cultivation of a hybridoma in a bubble-column bioreactor filled with hollow glass cylinders. The parameters monitored during the cultivation were pH, temperature, DO, glucose, lactate and monoclonal antibody. The glucose uptake rate was used to estimate the cell concentration along the time. The maximum cell concentration calculated for the considered cultivation time was 2.7?×?10⁷ cell?·?ml^?1. The glucose concentration in the media decreased stepwise twice, causing a decrease on the specific growth rate, while maintaining high antibody productivity levels. Maximum monoclonal antibody productivity was 503?μg?·?l^?1?·?day^?1 and specific productivity, considering calculated cell density, was 0.019?ng?·?cell^?1?·?day^?1.     

Growth characterizations of a human monocytic leukemia cell line in a serum-free medium

A clone, AH-01S, derived from a human monocytic leukemia cell line, THP-1, grew rapidly in a serum-free medium containing insulin, transferrin, ethanolamine, and sodium selenite. In batch culture using the serum-free medium, the AH-01S cells proliferated at a specific growth rate (μ) of 0.30 to 0.50 (1/day) from a cell concentration of 1 × 10⁴ cells/ml to 1.6 × 10⁶ cells/ml, an increase of 160 times. A higher cell concentration of 0.45 × 10⁷ cells/ml (cell volume ratio was 0.5%) was obtained in spinner flask culture using the serum-free medium. A mean specific growth rate 0.50 (1/day) was also observed in a culture in a fully instrumented cell culture fermentor. However, μ decreased drastically after the cell concentration reached 1.5 × 10⁶ cells/ml. Analyses of medium composition during cultivation revealed that under lower cell concentration, l-glutamine was the main carbon source while glucose was converted to lactate almost stoichiometrically, and that the production of lactate from glucose decreased at higher cell concentrations. To obtain cultures of 1 × 10⁹ cells, 1,200 to 1,300 mg of a carbon source (glucose) and 400 to 500 of amino acids were consumed during high cell concentration cultivation of the AH-01S cells in the serum-free medium.     

Ammonia inhibition of hybridomas propagated in batch, fed-batch, and continuous culture

The nature and temporal development of ammonia inhbition were investigated in batch, fed-batch, and continuous cultures. Significant inhibition was observed when cells were inoculated in serum-containing or chemically defined medium containing more than 2 mM of ammonia. In contrast, no inhibition was observed at greater than 10 mM when the ammonia concentration was gradually increased over the span of a batch culture by feeding ammonium chloride. Strong growth inhibition was observed after each of five step changes (2.8 --> 3.7 --> 4.0 --> 4.9 --> 7.7 --> 13.5 mM) in continuous culture. Following a period of adaptation at each higher value, the viable cell density stabilized at a new lower value. The lowering in viable cell density was caused by an increase in specific death rate and a decreased cell yield on glucose, glutamine, and oxygen. Increased ammonia concentration had little or no effect on the steady-state specific growth kinetics or specific antibody productivity. (c) 1994 John Wiley & Sons, Inc.     

表达抗-CD25单克隆抗体的GS-NS0骨髓瘤细胞无血清培养及代谢特性

抗-CD25单克隆抗体作为免疫抑制剂拥有广阔的市场前景和巨大的经济价值。本实验以表达抗?CD25单克隆抗体的GS-NS0细胞为研究对象,开发了支持其大规模培养和抗体表达的无血清低蛋白培养基,批培养最大活细胞密度和最大抗体浓度分别达3×106cells/mL和300mg/L以上,比商业无血清培养基(Excell 620+0.2% primatone)分别提高了100%和46%。通过批培养实验,研究了细胞的生长、葡萄糖和氨基酸代谢、以及产物表达特点,并揭示了批培养过程中初始葡萄糖浓度对GS-NS0细胞生长与代谢的影响规律。为优化GS-NS0细胞培养过程和抗CD25单抗成功迈向产业化提供了重要的科学依据。     

Hybridoma growth and productivity: effects of conditioned medium and of inoculum size

Apart from gas concentrations, temperature, and pH, generally only the initial conditions can be manipulated in batch culture. Inoculum size and initial conditioned medium concentration represent two important considerations for optimal batch production. Two hybridoma cell lines were used to assess the impact of these initial conditions on population growth and monoclonal antibody productivity in suspension batch culture. Varying initial cell concentration over the range of 1.0 × 105 cells mL-1 to 3.0 × 105 cells mL-1 did not affect maximum product titre or maximum volumetric cell-hours attained. Initial percent of conditioned medium up to 40 percent strongly impacted on population growth and productivity, with initial levels of 30 to 40% conditioned medium reducing or eliminating lag phase and increasing average viable cell density. However, specific productivity and product titre declined with increasing initial percent conditioned medium, even on a per volume of fresh medium basis. Glutamine and glucose depletion or ammonia toxicity could cause depressed product titres when conditioned medium is used. Glutamine and glucose levels can easily be replenished in conditioned medium at minimal cost, and ammonia can be removed. Specific productivity was higher during cyclic batch operating mode than during batch operating mode. This may be because cyclic batch operating mode results in an incidental volume of conditioned medium at the beginning of each cycle. A two stage, cyclic-batch/batch operating mode can be employed to fully utilize medium and maximize product titre.     

Production of alkaline serine protease subtilisin Carlsberg by Bacillus licheniformis on complex medium in a stirred tank reactor

Bacillus licheniformis (DSM 641) was cultivated on complex medium in batch and fed-batch operations in a 20-l working volume stirred tank reactor. The medium composition (maltose, glucose, sucrose, fructose, ammonia, phosphate) and O₂ and CO₂ in the off-gas were monitored on-line; pH, pO₂, turbidity, culture fluorescence were monitored in situ; optical density, concentrations of sugars, amino acids, phosphate, proteins, DNA, protease activity and total solids content were monitored off-line. Problems of on-line sampling, cell concentration monitoring, and culture fluorescence measurements and the influence of medium components on the enzyme productivity are discussed. Close relationships between variations of pH, pO₂, O₂ transfer rate and CO₂ production rate on the one hand and cell mass and fluorescence intensity on the other were demonstrated in batch and in fed-batch cultures. Using suitable cultivation conditions, alkaline protease with high volume activity [15300 units (U)/ml] and specific activity (510 U/mg) was produced. By replacing the complex medium with a semisynthetic one, the volumetric activity was reduced by a factor of ten (to 1650 U/ml), but the specific productivity by a factor of only two (to 210 U/ml). Correspondence to: K. Schügerl     

Substitution of glutamine by pyruvate to reduce ammonia formation and growth inhibition of mammalian cells

In mammalian cell culture technology glutamine is required for biomass synthesis and as a major energy source together with glucose. Different pathways for glutamine metabolism are possible, resulting in different energy output and ammonia release. The accumulation of ammonia in the medium can limit cell growth and product formation. Therefore, numerous ideas to reduce ammonia concentration in cultivation broths have been developed. Here we present new aspects on the energy metabolism of mammalian cells. The replacement of glutamine (2 mM) by pyruvate (10 mM) supported cell growth without adaptation for at least 19 passages without reduction in growth rate of different adherent commercial cell lines (MDCK, BHK21, CHO-K1) in serum-containing and serum-free media. The changes in metabolism of MDCK cells due to pyruvate uptake instead of glutamine were investigated in detail (on the amino acid level) for an influenza vaccine production process in large-scale microcarrier culture. In addition, metabolite profiles from variations of this new medium formulation (1-10 mM pyruvate) were compared for MDCK cell growth in roller bottles. Even at very low levels of pyruvate (1 mM) MDCK cells grew to confluency without glutamine and accumulation of ammonia. Also glucose uptake was reduced, which resulted in lower lactate production. However, pyruvate and glutamine were both metabolized when present together. Amino acid profiles from the cell growth phase for pyruvate medium showed a reduced uptake of serine, cysteine, and methionine, an increased uptake of leucine and isoleucine and a higher release of glycine compared to glutamine medium. After virus infection completely different profiles were found for essential and nonessential amino acids.     

Metabolism of hybridoma cells and antibody secretion at high cell densities in dialysis tubing.

The experimental setup, consisting of a bundle of dialysis tubing 2.5 mm in diameter [10-15 kD cutoff, mean pore size 25 A, 20 microns (dry) and 40 microns (wet) wall thickness] inserted into a 1-l glass bioreactor supplied with oxygen and pH electrodes, a porous gas distributor, a sampling tube, and a holder for the eight pieces of dialysis tubing, was developed to investigate the properties and the microenvironment of hybridoma cells enclosed in the tubing during their batch cultivation. The concentrations of low-molecular-weight medium components were the same inside and outside the tubing, and it was possible to control the microenvironment of the cells in the tubing easily. The cell damage caused by mechanical stress was less in the dialysis tubing than in stirred spinner flasks. The influence of the initial cell density in the range from 4 X 10(5) to 1 X 10(8) cells ml-1 and the cultivation time were evaluated according to the total and viable cell concentrations and the cell/cell fragment size distributions. Furthermore, the cell membrane properties, glucose consumption rate, lactate, ammonia and lipid storage material, and the monoclonal antibody production rates as well as intracellular enzyme activities in the culture medium were measured and compared to those in reference cultures in spinner flasks with the same inoculum at low initial cell densities. In dialysis tubing in a concentration range of 5 X 10(6) to 10(8) cells ml-1, the total and viable concentrations of cells remained the same during cultivation.(ABSTRACT TRUNCATED AT 250 WORDS)