Increase of hybridoma productivity using an original dialysis culture system

Hybridoma cell growth and monoclonal antibody production were investigated with a laboratory-made system in which cells were grown in dialysis tubing (MW cut-off 25 kD). The dialysis system contained 10 ml of cell suspension and was immersed in 200 ml of culture medium which when replaced or was at 4-day intervals. With this system, monoclonal antibody concentrations similar to those observed in ascites (concentrations in the order of one gramme per liter) were obtained. With no medium replacement, the antibody production was 3.3 g/l and the cell productivity 3.2×10^–8 g of IgM produced per cell in one minute. With medium replacement the antibody production was higher, 4.4 g/l but the cell productivity was lower, 1.49×10^–8 g per cell in one minute. Cells cultivated in non-optimized conditions were better producers than cells growing in a good environment.Abbreviations FCS fetal calf serum - Ig immunoglobulin - MAb monoclonal antibody - MW molecular weight - MWCO molecular weight cut off - RM replaced medium - NRM non replaced medium     

Effects of high cell density on growth-associated monoclonal antibody production by hybridoma T0405 cells immobilized in macroporous cellulose carriers

Relationship between monoclonal antibody (MAb) productivity and growth rate, and effects of high cell density on MAb production of hybridoma T0405 cells immobilized in macroporous cellulose carriers were investigated in continuous and batch cultures. The results showing, that the specific MAb production rate increased with increasing specific growth rate in both suspended and immobilized continuous cultures indicate a positively growth-associated relationship between MAb productivity and growth rate. Moreover, the specific production rate was higher in the immobilized cell culture than that in suspended one at all dilution rates. In order to clarify these phenomena, MAb mRNA expression and cell cycle distribution were investigated in batch cultures with immobilized cells and suspended cells. RT-PCR was used for observation of MAb mRNA expression and a two-color bromode-oxyuridine (BrdU)/propidium iodide (PI) flow cytometry method for determination of cell cycle distribution. The results revealed that MAb mRNA expression reached the peak during the exponential growth phase, suggest a positively growth-associated MAb production. And the immobilized cells continued the MAb mRNA expression until dead phase, which was longer than that in suspended cells. The cell cycle distribution patterns were observed almost the same for both immobilized and suspended cells. Such results may imply that a high cell density state has positive influence on the mRNA expression and on growth-associated MAb productivity of T0405 cells.     

The production of monoclonal antibody in growth-arrested hybridomas cultivated in suspension and immobilized modes.

The effects of the microenvironment and the nature of the limiting nutrient on culture viability and overall MAb productivity were explored using a hybridoma cell line which characteristically produces MAb in the stationary phase. A direct comparison was made of the changes in the metabolic profiles of suspension and PEG-alginate immobilized (0.8 mm beads) batch cultures upon entry into the stationary phase. The shifts in glucose, glutamine, and amino acid metabolism upon entry into the stationary phase were similar for both microenvironments. While the utilization of most nutrients in the stationary phase decreased to below 20% of that in the growth phase, antibody production was not dramatically affected. The immobilized culture did exhibit a 1.5-fold increase in the specific antibody rate over the suspension culture in both the growth and stationary phases. The role of limiting nutrient on MAb production and cell viability was assessed by artificially depleting a specific nutrient to 1% of its control concentration. An exponentially growing population of HB121 cells exposed to these various depletions responded with dramatically different viability profiles and MAb production kinetics. All depletions resulted in growth-arrested cultures and nongrowth-associated MAb production. Depletions in energy sources (glucose, glutamine) or essential amino acids (isoleucine) resulted in either poor viability or low antibody productivity. A phosphate or serum depletion maintained antibody production over at least a six day period with each resulting in a 3-fold higher antibody production rate than in growing batch cultures. These results were translated to a high-density perfusion culture of immobilized cells in the growth-arrested state with continued MAb expression for 20 days at a specific rate equal to that observed in the phosphate- and serum-depleted batch cultures.     

High density culture of hybridoma cells in a dual hollow fiber bioreactor

Summary Hybridoma cells were cultured for two months in the dual hollow fiber bioreactor (DHFBR) which had been successfully used for high cell density cultures of various microbial cells. In batch suspension culture the concentration of monoclonal antibody (Mab) against human Chorionic Gonadotropin (hCG) and the cell density of Alps 25-3 hybridoma cells were obtained in 30 μg/mL and 2.35×10⁶ cells/mL, respectively. The continuous culture with DHFBR produced Mab of 100–130 μg/mL for 30 days and the estimated cell density in the extracapillary space of DHFBR was 1.87×10⁸ cells/mL based on the antibody production rate. The productivity of Mab was 205 mg/day per litre of the total reactor volume while that of the batch suspension culture was only 10 mg/L day.     

Long-term Continuous Production of Monoclonal Antibody by Hybridoma Cells Immobilized in a Fibrous-Bed Bioreactor

The kinetics and long-term stability of continuous production of monoclonal antibody IgG2b by hybridoma HD-24 cells immobilized in a fibrous-bed bioreactor (FBB) were studied for a period of ～8 months. The cells were immobilized in the fibrous bed by surface attachment of cells and entrapment of large cell clumps in the void space of the fibrous matrix. A high viable cell density of 1.01 × 10⁸/ml was attained in the bioreactor, which was about 63 times higher than those in conventional T-flask and spinner flask cultures. The continuous FBB produced IgG at a concentration of ～0.5 g/l, with reactor productivity of ～7 mg/h·l, which was about 23 times higher than those from conventional T-flask and spinner flask cultures. The IgG concentration can be further increased to ～0.67 g/l by using higher feed (glucose and glutamine) concentrations and running the reactor at a recycle batch or fed-batch mode. The long-term performance of this bioreactor was also evaluated. For a period of 36 days monitored, the MAb produced in the continuous well-mixed bioreactor at 50 h retention time (0.02/h dilution rate) was maintained at a steady concentration level of ～0.3 g/l with less than 8% drift. At the end of the study, it was found that ～25% of the cells were strongly attached to the fiber surfaces and the other ～75% entrapped or weakly immobilized in the fibrous matrix. The strongly attached cells had a high viability of ～90%, compared to ～75% for cells weakly immobilized and only ～1.4% for freely suspended cells, suggesting that the fibrous matrix preferentially retained and protected the viable (productive) cells. The FBB thus was able to maintain its long-term productivity because nonviable and dead cells were continuously washed off from the fibrous matrix. The high MAb concentration and production rate and excellent stability for continuous long-term production obtained in this study compare favorably to other bioreactor studies reported in the literature. The reactor performance can be further improved by providing better pH and aeration controls at higher feed concentrations. The FBB is easy to operate and scale-up, and thus can be used economically for industrial production of MAb.     

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.     

Production of monoclonal antibody using free-suspended and immobilized hybridoma cells: Effect of serum

The effect of serum on cell growth and monoclonal antibody (MAb) productivity was studied in a repeated fedbatch mode using both free-suspended and immobilized S3H5/gamma2bA2 hybridoma cells. In the suspension culture, serum influenced the cell growth rate but not the specific MAb productivity. The average specific growth rate of the suspension culture in medium containing 10% serum was approximately 0.99 +/- 0.12 day(-1) (+/-standard deviation), while that in medium containing 1% serum was approximately 0.73 +/- 0.12 day(-1). The specific MAb productivity was almost constant at 3.69 +/- 0.57 mug/10(6) cells/day irrespective of serum concentration reached a maximum at ca. 1.8 x 10(6) cells/mL of medium in 10% serum medium, and the cell concentration was gradually reduced to 1%. The specific MAb productivity of the immobilized cells was more than three times higher than that of the free-suspended cells. The amount of serum in the medium did not influence the specific MAb production rate of the immobilized cells. The maintenance of high cell concentration and the enhanced specific MAb productivity of the immobilized cell culture resulted in a higher volumetric MAb productivity. In addition, MAb yield in the immobilized cell culture with medium containing 1% serum was 2.2 mg/mL of serum, which was approximately three times higher than that in the suspension culture.     

High Yield of Human Monoclonal Antibody Produced by Stably Transfected Drosophila Schneider 2 Cells in Perfusion Culture Using Wave Bioreactor

Since it was first introduced in late 1990s Wave bioreactor has been used for protein production by mammalian and insect cell lines. However, using Wave bioreactor to produce human monoclonal antibody by stable Drosophila Schneider 2 (S2) cell transfectants has not been reported before. In this study, S2 cells were co-transfected with an inducible vector expressing human monoclonal antibody heavy and light chains, respectively, specific for hemagglutinin (HA) of H5N1 influenza virus. Stable S2 transfectant clone was selected by limiting dilution assay. Stable S2 transfectant clone that produce the highest amount of human monoclonal antibody was inoculated into two 2-l disposable cellbags, where cell growth and antibody production were compared between batch and perfusion cultures using Wave bioreactor. Here, we report that maximum viable cell density reached 1.06?×?10(7) cells/ml in batch culture; whereas 1.04?×?10(8)?cells/ml was achieved in perfusion culture. The maximum volumetric antibody productivity in batch culture was 52?mg/l/day; while perfusion culture yielded 1,437?mg/l/day. As a result, the total antibody production was 201?mg in batch culture and 8,212?mg in perfusion culture. The antibody produced by both cultures displays full neutralizing activity. Thus, our results provide strong support for using Wave bioreactor in perfusion culture for a large-scale production of human monoclonal antibody by stable S2 cell transfectants.     

A comparison of oxygenation methods fro high-density perfusion culture of animal cells

A perfusion culture system was developed to investigate the oxygenation of high-density hybridoma cell cultures. The culture system was composed of a stirred-tank bioreactor and an external microfiltration hollow fiber cartridge for medium perfusion. Cell growth and antibody production were examined with large bubble ( approximately 5 mm in diameter), micron-sized bubble ( approximately 80 mum in diameter), and silicone tubing oxygenation techniques. Comparable cell growth and monoclonal antibody (MAb) production were found for both the micron-sized and large oxygenation methods, provided that large bubbles were enriched with pure oxygen. Relatively low cell growth and MAb production were attained with the bubble-free silicone tubing oxygenation. It is concluded that direct bubble oxygenation can be applied successfully in high-density animal cell cultures, provided that the culture medium is supplemented with Pluronic F-68. The accumulation of ammonia in the culture medium rather than oxygen limitation was found to be one of the possible problems that eventually inhibited cell growth. This and the fouling of the filtration cartridge during long-term cultivation were found to be more problematic than simple bubble oxygenation of high-density cell culture. The micron-sized bubble oxygenation method is highly recommended for high-density animal cell cultures, provided that Pluronic F-68 is supplemented into the culture medium. (c) 1993 John Wiley & Sons, Inc.     

Production of immunoglobulin A in different reactor configurations

A murine hybridoma line (Zac3), secreting an IgA monoclonal antibody, was cultivated in different systems: a BALB/c mouse, a T-flask, a stirred-tank bioreactor and a hollow fiber reactor. These systems were characterized in terms of cell metabolism and performances for IgA production. Cultures in T-flask and batch bioreactor were found to be glutamine-limited. Ammonia and lactate were produced in significant amounts. IgA productivity was found to be constant and growth associated. Final IgA concentration was similar in both systems. In fed-batch cultures, supplemented with glutamine and glucose, maximum viable cell concentration was increased by 60% and final IgA concentration by 155%. The hollow fiber reactor was able to produce very large amounts of IgA at very high concentrations, similar to the value found in ascites fluid. The productivity ofZac3 is similar to the values reported for IgG-producing cell lines.     

Large-scale production of monoclonal antibodies in defined serum-free media in airlift bioreactors

Forty- and ninety-liter airlift bioreactors have been used successfully to grow hybridoma cell lines in chemically defined serum-free media. In the airlift bioreactor, hybridoma cell growth and monoclonal antibody productivity are comparable to that obtained by conventional cell culture. At sparging rates of 0.60-1.20 vvh (volume of sparged gas per bioreactor volume per hour), the airlift bioreactor achieves rapid mixing and adequate oxygen mass transfer. Foaming is minimal and inconsequential for serum-free media and media supplemented with 5%-10% fetal bovine serum. The use of serum-free medium facilitates monoclonal antibody purification and enhances the purity of the final MAb product.     

Optimization of monoclonal antibody production: combined effects of potassium acetate and perfusion in a stirred tank bioreactor

To increase the yield of monoclonal antibody in a hybridoma culture, it is important to optimize the combination of several factors including cell density, antibody productivity per cell, and the duration of the culture. Potassium acetate enhances the production of antibodies by cells but sometimes depresses cell density. The production of anti-(human B-type red blood cell surface antigen) antibody by Cp9B hybridoma was studied. In batch cultures, potassium acetate inhibited Cp9B cells growth and decreased the maximal cell density but the productivity of antibody per cell was increased. The balance of the two effects resulted in a slight decline of antibody production. In a stirred tank bioreactor, the inhibitory effect of potassium acetate on cell density was overcome by applying the perfusion technique with the attachment of a cell-recycling apparatus to the bioreactor. In such a reactor, potassium acetate at 1 g l^-1 did not cause a decrease in the cell density, and the antibody concentration in the culture supernatant was increased from 28 μg ml^-1 to 38 μg ml^-1. Potassium acetate also suppressed the consumption of glucose and the accumulation of lactate in batch cultures, but the glucose and lactate levels were kept stable by applying the perfusion technique in the stirred tank bioreactor. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of culture conditions on monoclonal antibody production from genetically modified tobacco suspension cultures

Oxygen supply and inoculum age were found to affect the production of the heavy chain monoclonal antibody (HC MAb) from genetically modified tobacco suspension cultures. The increase of oxygen supply increased both cell growth and HC MAb production. Furthermore, the increased aeration and mixing improved the production of HC MAb based on the unit amount of cells or total soluble proteins. This indicated that the increased aeration improved the production and secretion of HC MAb more than other cell components. HC MAb production and cell growth also improved when batch cultures were inoculated with actively dividing cells (5-day old) rather than the fullygrown cells (7- or 10-day old cells) that are commonly used for subcultures. The addition of glutamine to the medium also improved cell growth and HC MAb production.     

Effect of endogenous proteins on growth and antibody productivity in hybridoma batch cultures

It has been shown that some B-cell hybridomas secrete autocrine factorsin vitro which can influence cell metabolic processes. Rather than screen specifically for suspected cytokines, that may or may not affect our cell line, we have examined the lumped effects of intracellular and secreted factors on cell proliferation and monoclonal productivity in hybridoma batch cultures. Firstly, supplements of total soluble intracellular proteins combined with other intracellular metabolites were found to both decrease the specific growth rate and increase the antibody production rate at higher concentrations in batch culture. This is an important consideration in high cell density cultures, such as perfusion systems, where a reduction of growth by the presence of intracellular factors may be compensated by an increase in MAb production. In addition, flow cytometry data revealed that the average cell cycle G₁ phase fraction was unaffected by the variation in the maximum specific growth rates during the exponential growth phase, caused by the addition of intracellular factors; this suggests that higher MAb productivity at lower growth rates are not a result of cell arrest in the G₁ phase. Secondly, secreted extracellular proteins larger than 10,000 Daltons, which were concentrated from spent culture supernatant, were shown to have no significant effect on growth and specific MAb productivity when supplemented to batch culture at levels twice that encountered late in normal batch culture. This indicates that endogenous secreted cytokines, if at all present, do not play a major autocrine role for this cell line.Abbreviations FBS fetal bovine serum - MAb monoclonal antibody - MWCO molecular weight cut off - SDS-PAGE sodium dodecyl-sulphate-polyacrylamide gel electrophoresis - k _d exponential phase death rate, h^–1 - q _MAb exponential phase specific monoclonal antibody productivity, pg/(cell·h) - t time, h - X _d dead cell density, cells/mL - X _v viable cell density, cells/mL - specific growth rate, h^–1 - _{max app} apparent maximum specific growth rate, h^–1 - _max maximum specific growth rate, h^–1 _max = _{max app + Kd}      

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)     

Effect of specific growth rates on productivity in continuous open and partial cell retention animal cell bioreactors.

A clonal derivative of a transfectant of the SP2/0 myeloma cell line producing a chimeric monoclonal antibody was cultivated in both continuous open and continuous partially-closed bioreactors. Using an open system for the determination of kinetic parameters, we showed that the production of this chimeric mAb was growth associated. As such, the volumetric productivity increased linearly with increasing dilution rate up to the maximum dilution rate. Three continuous cultivations employing partial cell retention were conducted. In agreement with mathematical predictions, the product titer and volumetric productivity were independent of the degree of cell retention when the total dilution was held constant. When cells were maintained at a low specific growth rate, the product titer was independent of dilution rate and the volumetric productivity increased with increasing dilution rate, again in agreement with mathematical predictions. Since the partially-closed bioreactor could be operated at dilution rates in excess of the maximum specific cellular growth rate, volumetric productivities were greater than those achievable in the open bioreactor. However, when cells were maintained at a high specific growth rate, cell accumulation was limited and product titers decreased at high dilution rates. Therefore, the volumetric productivity in this latter case did not increase at higher dilution rates.     

A novel continuous centrifugal bioreactor for high-density cultivation of mammalian and microbial cells

A continuous centrifugal bioreactor (CCBR), developed to study the growth and productivity of dense suspensions cultures, has been applied to both fermentation and mammalian cell cultivation processes. With this approach, high-density nonflocculent cultures are maintained in a tapered fluidized bed by balancing the drag forces on the cells due to following substrate with the centrifugal forces. The Sysyem was first used to produce ethanol by fermentation with Saccharomyces cerevisiae; then with H21A1 mouse hybridoma cells secreting monoclonal antibody (MoAb), lgM. Results of this research show the feasibility of using the CCBR for both production of secreted products and as a research tool for studying cell metabolism and production kinetics. Media recycle may be used to modify the behavior of the system form a plug flow apparatus to a continuous stirred reactor (CSTR).     

Changes in monoclonal antibody productivity of recombinant BHK cells immobilized in collagen gel particles

Animal cell perfusion high density culture is often adopted for the production of biologicals in industry. In high density culture sometimes the productivity of biologicals has been found to be enhanced. Especially in immobilized animal cell culture, significant increase in the productivity has been reported. We have found that the specific monoclonal antibody (MAb) productivity of an immobilized hybridoma cell is enhanced more than double. Several examples of enhancing productivities have been also shown by collagen immobilized cells. Immobilized cells involve some different points from non-immobilized cells in high density culture: In immobilized culture, some cells are contacted together, resulting in locally much higher cell concentration more than 10⁸ cells/ml. Information originating from a cell can be easily transduced to the others in immobilized culture because the distance between cells is much nearer. Here we have performed collagen gel immobilized culture of recombinant BHK cells which produce a human IgG monoclonal antibody in a protein-free medium for more than three months. In this high density culture a stabilized monoclonal antibody production was found with around 8 times higher specific monoclonal antibody productivity compared with that in a batch serum containing culture. No higher MAb productivity was observed using a conditioned medium which was obtained from the high density culture, indicating that no components secreted from the immobilized cells work for enhancing monoclonal antibody production. The MAb productivity by the non-immobilized cells obtained by dissolving collagen using a collagenase gradually decreased and returned to the original level in the batch culture using a fresh medium. This suggests that the direct contact of the cells or a very close distance between the cells has something to do with the enhancement of the MAb productivity, and the higher productivity is kept for a while in each cell after they are drawn apart.     

A new process for the continuous production of succinic acid from glucose at high yield, titer, and productivity

A novel three stages continuous fermentation process for the bioproduction of succinic acid at high concentration, productivity and yield using A. succiniciproducens was developed. This process combined an integrated membrane-bioreactor-electrodialysis system. An energetic characterization of A. succiniciproducens during anaerobic cultured in a cell recycle bioreactor was done first. The very low value of Y(ATP) obtained suggests that an ATP dependent mechanism of succinate export is present in A. succiniciproducens. Under the best culture conditions, biomass concentration and succinate volumetric productivity reach values of 42 g/L and 14.8 g/L.h. These values are respectively 28 and 20 times higher compared to batch cultures done in our laboratory. To limit end-products inhibition on growth, a mono-polar electrodialysis pilot was secondly coupled to the cell recycle bioreactor. This system allowed to continuously remove succinate and acetate from the permeate and recycle an organic acids depleted solution in the reactor. The integrated membrane-bioreactor-electrodialysis process produced a five times concentrated succinate solution (83 g/L) compared to the cell recycle reactor system, at a high average succinate yield of 1.35 mol/mol and a slightly lower volumetric productivity of 10.4 g/L.h. The process combined maximal production yield to high productivity and titer and could be economically viable for the development of a biological route for succinic acid production.     

Expression of a human anti-rabies virus monoclonal antibody in tobacco cell culture

A Nicotiana tabacum cv. Xanthi cell culture was initiated from a transgenic plant expressing a human anti-rabies virus monoclonal antibody. Within 3 months, plant cell suspension cultures were established and recombinant protein expression was examined. The antibody was stably produced during culture growth. ELISA, protein G purification, Western blotting, and neutralization assay confirmed that the antibody was fully processed, with association of light and heavy-chains, and that it was able to bind and neutralize rabies virus. Quantification of antibody production in plant cell suspension culture revealed 30 microg/g of cell dry weight for the highest-producing culture (0.5 mg/L), 3 times higher than from the original transgenic plant. The same production level was observed 3 months after cell culture initiation. Plant cell suspension cultures were successfully grown in a new disposable plastic bioreactor, with a growth rate and production level similar to that of cultures in Erlenmeyer flasks.