Influence of amino acids on hybridoma cell viability and antibody secretion

Development of optimal medium for production of commercially important monoclonal antibody 520C9 by hybridoma cell

Hybridoma HB-8696 produces monoclonal antibody (mAb) 520C9 (mouse IgG(1)), which recognizes breast cancer oncoprotein c-erbB2. The objective of this study was to optimize the medium recipe of HB 8696 cell for production of mAb 520C9. The optimization consisted of two steps: (1) screening of significant nutrients to make subsequent experiments more efficient with less runs and (2) locating their optimal concentrations. 29 variables including essential and non-essential amino acids, glucose, serum and 6 salts, namely NaCl, KCl, CaCl(2), NaH(2)PO(4), MgSO(4) and Na-pyruvate were chosen in screening phase. The Plackett-Burman method was used to screen the variables influencing mAb production. Seven factors namely glucose, serum, asparagine, threonine, serine, NaCl and NaH(2)PO(4) were identified to have a positive influencing role on mAb production with a confidence level >90 % (p < 0.1). Finally, Response surface methodology revealed the optimal level of the variables. The mAb production and average specific mAb production rate were enhanced by 111.05 and 105 %, respectively, compared to control medium.

The role of vitamins and amino acids on hybridoma growth and monoclonal antibody production

A balanced supplementation method was applied to develop a serum and protein- free medium supporting hybridoma cell batch culture. The aim was to improve systematically the initial formulation of the medium to prevent limitations due to unbalanced concentrations of vitamins and amino acids. In a first step, supplementation of the basal formulation with 13 amino acids, led to an increase of the specific IgA production rate from 0.60 to 1.07 pg cell(-1) h(-1). The specific growth rate remained unchanged, but the supplementation enabled maintenance of high cell viability during the stationary phase of batch cultures for some 70 h. Since IgA production was not growth- related, this resulted in an approximately4-fold increase in the final IgA concentration, from 26.6 to 100.2 mgl(-1). In a second step, the liposoluble vitamins E and K(3) were added to the medium formulation. Although this induced a slightly higher maximal cell concentration, it was followed by a sharp decline phase with the specific IgA production rate falling to 0.47 pg cell(-1) h(-1). However, by applying a second cycle of balanced supplementation with amino acids this decline phase could be reduced and a high cell viability maintained for over 300 h of culture. In this vitamin- and amino acid- supplemented medium, the specific IgA production rate reached a value of 1.10 pg cell(-1)h(-1) with a final IgA concentration of 129.8 mgl(-1). The latter represents an increase of approximately5-fold compared to the non- supplemented basal medium.

Monitoring glutamine in animal cell cultures using a chemiluminescence fiber optic biosensor

Together with flow injection analysis (FIA), a chemiluminescence (CL) fiber optic biosensor system has been developed for determining glutamine in animal cell cultures. Glutaminase (GAH) and glutamate oxidase (GLO) were onto separate porous aminopropyl glass beads via glutaraldehyde activation and packed to form an enzyme column. These two enzymes acted in sequence on glutamine to produce hydrogen peroxide, which was then reacted with luminol in the presence of ferricyanide to produce a light signal. An anion exchanger was introduced on-line to eliminate interfering endogenous glutamate in view of its negative charge at pH above 3.22 (isoelectric pH). Among several resins tested, the acetate form was most effective, and this type of ion exchanger also effectively adsorbed uric acid, acetaminophen, and aspartic acid.There was an excellent linear relationship between the CL response and standard glutamine concentration in the range 1 to 100 muM. A complete analysis could be performed in 2 min, including sampling and washing with a good reproducibility (+/- 4.4%). Both the bi-enzymic and ion exchange columns were useful for at least 500 analyses when the biosensor system was applied for the glutamine determination in murine hybridoma cell cultures and insect cell cultures. The values obtained compared well with those of HPLC, thus validating the applicability of the CL fiber optic system.

Process development for a recombinant Chinese hamster ovary (CHO) cell line utilizing a metal induced and amplified metallothionein expression system

The suspension Chinese Hamster Ovary cell line, 13-10-302, utilizing the metallothionein (MT) expression system producing recombinant human growth hormone (hGH) was studied in a serum-free and cadmium-free medium at different fermentation scales and modes of operation. Initial experiments were carried out to optimize the concentration of metal addition to induce the MT promoter. Subsequently, the cultivation of the 13-10-302 cell line was scaled up from spinner flasks into bioreactors, and the cultivation duration was extended with fed-batch and perfusion strategies utilizing 180 microM zinc to induce the promoter controlling expression of recombinant hGH. It was shown that a fed-batch process could increase the maximum cell numbers twofold, from 3.3 to 6.3 x 10(6) cell/mL, over those obtained in normal batch fermentations, and this coupled with extended fermentation times resulted in a fourfold increase in final hGH titer, from 135 +/- 15 to 670 +/- 70 mg/L at a specific productivity q(hGH) value of 12 pg cell(-1)d(-1). The addition of sodium butyrate increased the specific productivity of hGH in cells to a value of approximately 48 pg cell(-1)d(-1), resulting in a final hGH titer of over a gram per liter during fed-batch runs. A BioSep acoustic cell recycler was used to retain the cells in the bioreactor during perfusion operation. It was necessary to maintain the specific feeding rates (SFR) above a value of 0.2 vvd/(10(6) cell/mL) to maintain the viability and productivity of the 13-10-302 cells; under these conditions the viable cell number increased to over 10(7) cell/mL and resulted in a volumetric productivity of over 120 mg(hGH) L(-1)d(-1). Process development described in this work demonstrates cultivation at various scales and sustained high levels of productivity under cadmium free condition in a CHO cell line utilizing an inducible metallothionein expression system.

Bcl-xL expression interferes with the effects of L-glutamine supplementation on hybridoma cultures

While feeding protocols and ectopic expression of anti-apoptotic genes have been used to improve the viability of hybridoma cell lines, the effect of the expression levels of survival genes on the behavior of hybridomas following nutrient supplementation is unknown. In this study, we compared the behavior of the Sp2/0-Ag14 hybridoma (Bcl-xL(low)) and the P3x63-Ag8.653 myeloma (Bcl-xL(high)) following culture supplementation with the amino acid L-glutamine (L-Gln). Our data revealed that L-Gln addition substantially increased Sp2/0-Ag14 cell viability and total cell density, concomitant with a decrease in the rate of cell death. This effect was not seen when other amino acids or D-glucose (D-Glc) replaced L-Gln. The improvement in the culture behavior of Sp2/0-Ag14 cells was attributed to a reduction in the rate of accumulation of apoptotic cells. On the other hand, L-Gln supplementation had only a limited effect on the growth of the P3x63-Ag8.653 cells. Interestingly, Sp2/0-Ag14 cells over-expressing Bcl-xL showed a culture behavior upon L-Gln complementation that was similar to the P3x63-Ag8.653 myeloma. These results suggest that the anti-apoptotic gene expression profile of hybridoma cells can markedly impact on the beneficial effects afforded by nutrient supplementation.

Amino acids metabolism by VO 208 hybridoma cells: some aspects of the culture process and medium composition influence

In the present study an approach has been developed in order to examine the consequence of essential and non essential amino acid supplementation on VO208 hybridoma cells behaviour. The effect of amino acid enrichment has been studied taking into account the culture process, i.e., batch or continuous culture mode and the medium composition, i.e., a home made serum-free medium or a serum containing one. A group of 4 amino acids, i.e., Ser, Pro, Gly and Arg presented atypical evolution pattern of their extracellular concentration depending on the type of the medium and on the culture mode. Some amino acids were probably involved in the limitation of the cellular proliferation. Met was one of the amino acids that appears to may have been at limiting concentration in all cases. In continuous culture mode, an enrichment of amino acids resulted in a rapid improvement of the viable cell density in both media, with or without the presence of serum. For most amino acids, supplementation during continuous culture induced an increase of the amino acid uptake rate. A comparative analysis of amino acids utilisation, depending on the culture conditions studied in the present study, has been performed in order to propose an overall picture of amino acids metabolism by VO 208 Hybridoma cell line.

Hybridoma cell cultures continuously undergo apoptosis and reveal a novel 100 bp DNA fragment

This report represents an investigation into the nature of apoptosis in hybridoma cultures and its significance to their utilization in biotechnology. To this end DNA fragmentation and capillary electrophoresis of genomic DNA was studied during the culture of two hybridoma cell lines. This indicated that the phenomenon of apoptosis was always present even under normal culture conditions. Two DNA fragments not associated with the typical DNA fragmentation ladder were identified in the two hybridoma cultures: a previously unreported DNA fragment of about 100 bp and a large fragment which may correspond to one reported in the literature (Walker et al., 1993). The small fragment was identified as soon as the early exponential growth phase of culture, while the large fragment appeared only in the latter part of the growth curve when there was marked DNA fragmentation. In addition we present evidence that aurintricarboxylic acid, which inhibits apoptosis in neural cells, permits this process in hybridoma cells at levels below 100 microM. This unusual predisposition of hybridoma cultures to undergo apoptosis and their response to inhibitor of apoptosis may have important implications for approaches to the culture of hybridomas and their utilization for monoclonal production.

Laboratory scale production of monoclonal antibodies in a tumbling chamber

A simple device for laboratory scale production of monoclonal antibodies has been developed. Hybridomas were cultured in four individual dialysis tubes containing 40-50 ml medium with 10% foetal calf serum, surrounded by 1.5-2 litres supply medium without any serum supplement. Once placed on a roller the special design of the apparatus leads to an eccentric rotation, thus keeping the cells in a stable homogeneous suspension. The system is automatically gassed, and this makes long term cultivation possible. Several hybridomas were tested over a culture period of at least 3 weeks, with supply medium changes every 3-4 days. Cell densities of up to 2.5 x 10(7)/ml and antibody concentrations of 0.3-1.9 mg/ml after purification were obtained. Results with this in vitro system allow a complete renunciation of the established in vivo method. The so called 'tumbling chamber' apparatus is easy to handle and to sterilize, is economic and universally adaptable in any research laboratory.

HBs-MAb production in perfusion culture with selective ammonia removal system

Conventional serum-free perfusion cultures of hybridoma TO-405 cells using medium supplemented with additional amounts of glucose, glutamine, beta-mercaptoethanol and growth factors failed to yield cell densities and monoclonal antibody (MAb) concentrations which were significantly different from the results of unsupplemented perfusion cultures. Ammonia building-up to inhibitory concentrations in all the cultures was regarded as one of the primary reasons. When perfusion cultures and medium supplementation were done coupled to the ammonia removing system, the viable cell density grew to a maximum of 2.5 x 10(7) cells per ml at high percentage viability. This value is more than a 300% increase from that of conventional perfusion cultures and better compared to serum-supplemented cultures. The monoclonal antibody accumulated to a concentration as high as 26.3 x 10(5) mIU per ml. This is about 10-times when compared to that which can be achieved in ordinary perfusion cultures.

Growth and interferon-gamma production in batch culture of CHO cells

The relationship between growth and interferon-gamma (IFN-gamma) production in the recombinant cell line CHO 320 was studied by varying the foetal calf serum (FCS) concentration. The specific growth rate varied with the initial FCS concentration in a manner which could be well fitted by the Monod model. The Ks and mu max-values were found to be 0.771% (v/v) serum and 0.031 h-1 respectively. The average specific IFN-gamma production rates during the exponential phase increased with increasing FCS concentration. A good correlation between specific production rate and specific growth rate was found in all phases of the culture except the lag phase and it was clearly demonstrated that IFN-gamma production was growth associated. Specific glucose and glutamine utilisation rates were inversely related to specific growth rates.

A chemiluminescence fiber-optic biosensor system for the determination of glutamine in mammalian cell cultures

A chemiluminescence fiber-optic biosensor system has been developed for determining glutamine in hybridoma cell cultures producing monoclonal antibodies against viral surface antigens. Glutaminase and glutamate oxidase (GLO) were immobilized onto aminopropyl glass beads via glutaraldehyde activation separately and packed in a column. Two separate columns containing immobilized GLO and catalase were placed upstream to eliminate endogenous glutamate. In the presence of ferricyanide, luminol reacted with hydrogen peroxide released from the enzymatic reactions to produce a chemiluminescence (CL) light signal which was detected and quantitated with a fiber-optic system. In combination with flow injection analysis it was possible to process samples virtually identically, thus avoiding difficulties in reproducing the CL signal. There was an excellent linear relationship between the CL response and standard glutamine concentration in the range 10(-6) to 10(-3) M. A complete analysis could be performed in 2 min including sampling and washing. Each immobilized enzyme column was stable for at least 300 repeated analyses without any loss of activity. When the biosensor system was used for the determination of glutamine in spent mammalian cell cultures, the values obtained compared well with those of high-performance liquid chromatography, thus validating the applicability of the CL fiber-optic system.

Essential role of optimal protein synthesis in preventing the apoptotic death of cultured B cell hybridomas

The monoclonal antibody productivity of cell culture systems is strongly dependent on the maintenance of hybridoma cell viability. We report that partial (< 50%) and transient (3 h) inhibition of protein synthesis by cycloheximide or deprivation of an essential amino acid induces apoptosis (programmed cell death) in B cell hybridomas. This unusual mechanism of apoptosis induction is likely to play a significant role in limiting cell viability in batch and perfusion cultures of hybridomas and emphasizes the importance of constantly maintaining a near optimal rate of macromolecular synthesis by optimization of all culture parameters. Inhibition of apoptosis in hybridomas by cell engineering and other technologies should permit, in the near future, a significant increase in the antibody productivity of existing cell culture systems.

Role of metabolic waste products in the control of cell proliferation and antibody production by mouse hybridoma cells

In order to determine the factors limiting the proliferation and productivity of mouse hybridoma cells in batch/fed-batch cultures, we tested the influence of various environmental parameters on the growth of a model cell line VO 208. We observed that, among the major metabolic waste products, ammonium ions at concentrations superior to that present in the medium at the end of a batch culture do not exert a significant toxic effect on cell growth, whereas in contrast, lactic acid is cytotoxic at concentrations reached in cultures. Feeding of fructose instead of glucose during the stationary phase of the culture markedly prolongs the life span of the culture and enhances the antibody secretion accordingly. However, we failed to observe a satisfactory proliferation pattern in cultures grown in a glucose-free fructose-supplemented medium. We also noted that vitamin supply may be limiting in fed-batch cultures. It thus appears that thorough examination of the cell metabolic needs allows the designing of a culture regimen which significantly improves cell growth and secretion.

The enhancement of specific antibody production rate in glucose- and glutamine-controlled fed-batch culture

The concentration effects of certain amino acids (Asp, Ile, Leu, Lys, Met, Val, Phe and Gln which were highly consumed during cultivation), and glucose on cell growth and antibody productivity were investigated using dish culture. From these experiments, it was found that only glutamine enrichment enhanced the specific antibody production rate. The other amino acids described above did not affect either the specific growth rate or specific antibody production rate. Thus we investigated the quantitative effects of glutamine concentration in the range of 0.4-33.3 mmol.l-1 on kinetic parameters in fed-batch culture which kept both glucose and glutamine concentration constant. As a result the specific growth rate decreased with increase in glutamine concentration in the range larger than 20 mmol.l-1. The specific antibody production rate had a maximum value at about 25 mmol.l-1 glutamine concentration.

Purification of immunoglobulin production stimulation factor II alpha derived from Namalwa cells

An immunoglobulin production stimulating factor (IPSF) in human lymphoblastoid Namalwa cells was purified by the serial use of ammonium sulfate fractionation, hydrophobic interaction chromatography and gel filtration, and named IPSF-II alpha. IPSF-II alpha was estimated as a 112 KD protein composed of a 40 KD polypeptide and two 36 KD polypeptides. The 36 KD protein extracted from SDS-polyacrylamide gel showed IPSF activity, but not the 40 KD protein. The IPSF activity was reasonably stable in alkaline but unstable in acidic solution and heat-unstable. In a serum-free medium, IPSF-II alpha stimulated IgM production of human-human and mouse-mouse hybridomas 4-15 and 2-fold, respectively, although its growth stimulatory effect on hybridomas was negligible. The factor did not stimulate IgG production in either human or mouse hybridomas in the same serum-free medium. These results suggested that IPSF-II alpha was a new cellular factor for stimulating IgM productivity of hybridomas.

Selective removal of ammonia from animal cell culture broth

Serum-free perfusion cultures of hybridoma TO-405 cells were carried out in spinner flasks coupled with zeolite A-3 packed beads. Ammonia was selectively removed from the culture broth by passing cell free permeate from ceramic cross flow filtration, through the zeolite packed bed. Ammonia concentration in the culture broth was effectively maintained between 1 to 4 mmol/l which was below the inhibitory concentration for cell growth. Maximum cell density levels of 10(7) cells/ml as well as improved percentage cell viability higher than in serum-supplemented cultures were feasible in this system. The possible effects of shear stress, generated by variation of the flow rates of the broth through the ceramic filter module, on the growth of the hybridoma cells were investigated. Backwashing, by reversing the direction of the permeate, was found necessary to prolong the life of the filter. Variation of the flow rates of the broth through the ceramic module between 0.29 m/s to 0.59 m/s did not cause immediate cell damage but growth was repressed at the higher flow rate. This study also showed that glutamine appears to be one of the factors limiting the growth of the hybridoma cells.

Flow cytometric study of cultured mammalian cells

Flow cytometry provides a rapid, sensitive and accurate analytical means to monitor hybridoma cell cultures. The use of flow cytometry has enabled us to study the changes in DNA, RNA, protein, IgG, mitochondrial activity and cell size that take place during the growth cycle of batch culture. The temporal changes in the levels of these analytes and their heterogeneity have been related to the growth/death kinetics. The maximum proportion of S-cells was reached early in the growth phase while a population of low fluorescence cells with lower polidy than G1, dead cells and fragmented nuclei emerged during the death phase. Supplementation with amino acids during the exponential phase prolonged the growth cycle by enhancing cell proliferation. The fraction of S/G2 cells was much reduced by a reduction in serum concentration but was maintained during the prolonged non-proliferating "stationary" phase. The magnitude of Rhodamine 123 staining showed a consistent and general decrease during late exponential and decline phases. This trend was accompanied by an increase in the fraction of the Propidium Iodide-stained population which reflected the deteriorating metabolic and membrane integrity. Decrease in mean fluorescence intensity for DNA, RNA, protein and intracellular IgG was noted at the decline phase. Intracellular immunofluorescence was a more reliable indicator of antibody productivity than surface immunofluorescence.

Influence of inoculum age on hybridoma culture kinetics

To determine the influence of the inoculum age on the kinetics of hybridoma growth and metabolism, spinner flasks have been inoculated with cells previously propagated in T flasks for 43, 52, 62 and 71 hr respectively. Increasing the age of the inoculum is found to result in a longer lag phase, in a lower maximum specific growth rate and in a reduced maximal cell density. During the growth phase specific rates of glucose and glutamine uptake and of ammonia and lactate production are similar. However, with the older inoculum, much higher metabolic activities are observed during the lag phase. The production of antibodies is delayed with increasing inoculum age, but the final antibody concentrations are similar, which indicates a higher specific antibody production rate when inoculating with older cells.

Optimization of serum-free fermentation processes for antibody production

Serum free fermentation procedures of cell cultures have got a wide application in production of biochemicals. But, cells cultured in serum free media in general are more sensitive to changes in culture condition, especially to nutrient limitation. There are no substances from serum which can support the cells when conditions are changing. In this study special attention is directed to amino acid utilization of mouse hybridoma in batch, chemostat and perfusion fermentations. Detailed data are presented which show the considerable difference of amino acid consumption rates in different fermentation modes. Already, in batch mode there are differences of the two investigated mouse hybridoma cell lines, although they are derived from the same myeloma line. In chemostat running at a dilution rate representing maximal growth rate most of the consumption rates are significant higher than in batch. On the other hand, in perfusion mode the rates are lower than in batch. This indicates clearly the different conditions of the fermentation modes. Therefore, it is necessary to develop serum free processes under the desired production conditions. An accurate analysis of the process is strongly recommended.

Comparison of various methods for monitoring hybridoma cell proliferation

The design of a strategy for the control of large scale cultures of hybridoma cells requires the use of convenient indicators to monitor properly the evolution of the biomass. In order to select appropriate indicators, we have measured in parallel, in bulk cultures of mouse hybridoma cells, the evolution of several metabolic parameters together with those of cell density and viability. We observed that flow cytometry analysis gives an early indication of the proliferative capacity of the cell population. Determination of metabolic rates (i.e. glucose, glutamine, amino acid, consumption, lactic acid or ammonium production) adequately indicates the current metabolic status of the cells. Indeed, a sharp decrease in these metabolic rates occurs rapidly following nutrient deficiency. Finally, measurements of lactate dehydrogenase (LDH) and DNA fragments released into the culture supernatants accurately reflect the kinetics of cell death.

Mechanisms and kinetics of monoclonal antibody synthesis and secretion in synchronous and asynchronous hybridoma cell cultures

The kinetics of monoclonal antibody synthesis and secretion have been studied in synchronous and asynchronous mouse hybridoma cell cultures. Pulse-labelling of IgG followed by immunoprecipitation and quantitation of synthesized and secreted IgG in synchronous cultures show maximum production during G1/S phases. Secretion takes place through exocytotic release of vesicle contents. Pulse-chase experiments show that 71% of the synthesized IgG is secreted within 8 h of the pulsing period and only a further 4% is secreted by 22 h. Higher specific antibody production (QA) is obtained if (a) cells are arrested and then maintained in G1/S phases, (b) viability is decreased during the death phase of batch culture, (c) the dilution rate is decreased in continuous culture or (d) cells are subjected to hydrodynamically induced stress. The increase in QA in all these cases is mainly due to the passive release of the accumulated intracellular antibody. DNA and protein synthetic activity peak during the early exponential phase and decline rapidly during mid and late exponential and death phases. Metabolic activity however peaks up to 20 h after the peak in DNA synthesis, and declines similarly during the death phase. The data are consistent with the idea that slow growth and higher death rates increase QA and that Ig secretion is probably subject to complex intracellular control.

A continuous multistage roller reactor for animal cell culture: 1. Patterns of growth, production and catabolism of a murine hybridoma

A Tubular Liquid Film Reactor was designed as a model system to transfer a batch culture kinetic to a continuous cascade. Cell density, product formation and substrate consumption rates were followed during fermentation at two dilution rates. In spite of the high dilution rates effective in each segment by itself high cell densities of up to 10(7) cells/ml were achieved due to cell sedimentation. The model character of the reactor was taken to determine critical values of substrate concentrations that influence production rates and result in an adaptation of metabolism.