Fed-batch process development using metabolically efficient CHO cells

The development and application of fed-batch strategies have greatly contributed to the improvement of the productivity of cell culture processes. However, in such processes, lactate and ammonia accumulation in the culture medium over time can have detrimental impacts on cell growth and product quality. Continuous cell lines typically exhibit an inefficient metabolism whereby most of the pyruvate derived from glucose is diverted to lactate and only a small percentage is incorporated into the TCA cycle. Thus, further process improvements can be expected by combining the application of rational fed-batch strategies with targeted metabolic engineering of cells to reduce waste metabolite accumulation. We have previously reported the establishment of a PYC2-expressing CHO cell line that exhibits a significantly altered lactate metabolism compared to its parental cell line; the ensuing reduction in waste metabolite accumulation is associated with a prolonged exponential growth phase, leading to significant increases in both maximum cell density and product titer in batch culture. In this work, we demonstrate further process enhancements by cultivating the PYC2-expressing cells in fed-batch mode. Unlike the parental cell line, even under high nutrient levels, the engineered cells maintained their highly efficient metabolism characterized by low lactate\glucose and ammonia\glutamine molar ratios. This effectively alleviates the need to control substrates at low levels to avoid waste accumulation, a strategy which can negatively impact product quality. And unlike nutrient substitutions which are often accompanied by cell growth reduction, the decrease in lactate accumulation is associated with an increased in maximum cell density translating into a net gain (20%) in final volumetric productivity. To further characterize the process, isotopic tracer studies were conducted to analyze the fate of the main nutrients and various product characterizations were performed to assess the impact of this cellular engineering approach on antibody qualit

Impact de la modification du métabolisme primaire des cellules CHO sur leur productivité

Les approches thérapeutiques à base d’anticorps monoclonaux font partie des avenues les plus encourageantes pour le traitement de nombreux cancers. Les cellules ovariennes de hamster chinois (CHO) demeurent la plateforme d’expression d’anticorps la plus couramment utilisée dans l’industrie et est actuellement la plus efficace pour la production à grande échelle. Ces cellules sont capables de produire des anticorps présentant un patron de glycosylation très proche du profil humain et d’atteindre des niveaux de production généralement plus élevés que ceux obtenus avec les autres lignées cellulaires continues existantes. Ces dernières années, les progrès accomplis dans le développement de procédés en cuvée alimentée (fed-batch) ont permis d’augmenter significativement les rendements de production. Néanmoins, les performances des procédés de culture demeurent limitées par les caractéristiques métaboliques des cellules utilisées. Celles-ci présentent en effet une glycolyse et une glutaminolyse dérégulées associées à une forte production de métabolites toxiques tels que le lactate et les ions ammonium. Seule une fraction minime du pyruvate issu de la métabolisation du glucose est incorporée dans le cycle des acides tricarboxyliques (ATC), ce qui explique en partie le métabolisme peu efficace des cellules CHO. Une des enzymes responsables de la connexion entre la glycolyse et le cycle des ATC est la pyruvate carboxylase qui catalyse la conversion du pyruvate en oxaloacétate. Dans les cellules CHO, seulement 5 à 10 % du pyruvate est métabolisé par cette enzyme. Ce projet de recherche s’appuie sur l’hypothèse selon laquelle contrer la déficience de l’activité de la pyruvate carboxylase dans les cellules CHO pourrait pallier en partie au phénomène de dérégulation de la glycolyse, ce qui permettrait d’améliorer la productivité d’anticorps des cellules tout en maintenant une glycosylation adéquate du produit final. Au cours de ces travaux, une lignée cellulaire exprimant de façon stable l’enzyme pyruvate carboxylase de levure, au niveau cytosolique (PYC2) a été générée. Cultivées en mode cuvée alimentée, ces cellules ont montré une croissance et une production d’anticorps améliorées par rapport à la lignée parentale non modifiée. L’analyse des flux métaboliques par marquage isotopique a permis de caractériser en détail le métabolisme de ces cellules. Des différences majeures dans la distribution des flux métaboliques intracellulaires notamment au niveau des flux associés à la lactate déshydrogénase et au cycle de Krebs ont été mises en évidence. L’analyse de la glycosylation a révélé pour sa part, que l’augmentation de la production d’anticorps associée à la modification du métabolisme n’avait pas altéré significativement la qualité du produit final. De façon générale, ce projet de recherche semble corroborer l’existence d’un lien entre la productivité d’anticorps et le métabolisme cellulaire. La caractérisation du métabolisme des cellules CHO et plus précisément du métabolisme du lactate participe à améliorer notre compréhension du métabolisme des cellules CHO et pourrait permettre une amélioration plus rationnelle des fonctions cellulaires d’une part, et des conditions de culture d’autre part.Antibody-based therapy is a promising approach for cancer treatment. Chinese hamster ovary (CHO) cells represents the most common and efficient antibody expression platform for large scale production. Their abilities to perform human-like glycosylation and produce high antibody titer make them the most suitable system compared to other continuous cell lines. In the past few years, advances in fed-batch process development led to significantly increase production yields. Nevertheless, the metabolic features of continuous cell lines constitute a hurdle to the improvement of process performances. Continuous cell lines typically exhibit a deregulated glycolysis and glutaminolysis causing the accumulation of toxic metabolites such as lactate and ammonia. Thus, only a small percentage of pyruvate, derived from glucose, is incorporated into the tricarboxylic acids (TCA) cycle explaining at least, in part the inefficient CHO cell metabolism. The mitochondrial pyruvate carboxylase, which catalyzes the conversion of pyruvate into oxaloacetate, is one of the key enzymes at the junction of the glycolysis and the TCA cycle. In CHO cells, only 5-10 % of the pyruvate pool is metabolized via this pathway. In this project, we hypothesized that counteracting the pyruvate carboxylase deficiency in CHO cells could alleviate in part, the deregulated glycolysis and consequently improve antibody production yield while maintaining satisfactory antibody glycosylation. In this work, a recombinant CHO cell line producing an antibody was further genetically modified with the insertion of a cytoplasmic yeast pyruvate carboxylase (PYC2) gene. Cultivated in fed-batch mode, PYC2 cells exhibited enhanced cell growth and antibody production yield compared to the parental cell line. Metabolic flux analysis using isotopic tracer led to a detailed characterisation of both cell line metabolism. The metabolic flux distribution obtained highlighted major differences in lactate and TCA fluxes. Comparative glycosylation analysis revealed that the metabolism alteration associated with the increase in antibody production did not significantly alter the product quality. This work seems to corroborate the presumed existence of a link between metabolism and antibody productivity. The cell metabolism characterization and more precisely, lactate production contribute to gain knowledge in CHO cell metabolism and led to rationally improve cellular functions and culture conditions

Short-Term Sensorimotor Deprivation Impacts Feedforward and Feedback Processes of Motor Control

International audienceSensory loss involves irreversible behavioral and neural changes. Paradigms of short-term limb immobilization mimic deprivation of proprioceptive inputs and motor commands, which occur after the loss of limb use. While several studies have shown that short-term immobilization induced motor control impairments, the origin of such modifications is an open question. A Fitts' pointing task was conducted, and kinematic analyses were performed to assess whether the feedforward and/or feedback processes of motor control were impacted. The Fitts' pointing task specifically required dealing with spatial and temporal aspects (speed-accuracy trade-off) to be as fast and as accurate as possible. Forty trials were performed on two consecutive days by Control and Immobilized participants who wore a splint on the right arm during this 24 h period. The immobilization modified the motor control in a way that the full spatiotemporal structure of the pointing movements differed: A global slowdown appeared. The acceleration and deceleration phases were both longer, suggesting that immobilization impacted both the early impulse phase based on sensorimotor expectations and the later online correction phase based on feedback use. First, the feedforward control may have been less efficient, probably because the internal model of the immobilized limb would have been incorrectly updated relative to internal and environmental constraints. Second, immobilized participants may have taken more time to correct their movements and precisely reach the target, as the processing of proprioceptive feedback might have been altered

Simplifying and optimising the management of uncomplicated acute malnutrition in children aged 6–59 months in the Democratic Republic of the Congo (OptiMA-DRC): a non-inferiority, randomised controlled trial

BACKGROUND: Global access to acute malnutrition treatment is low. Different programmes using different nutritional products manage cases of severe acute malnutrition and moderate acute malnutrition separately. We aimed to assess whether integrating severe acute malnutrition and moderate acute malnutrition treatment into one programme, using a single nutritional product and reducing the dose as the child improves, could achieve similar or higher individual efficacy, increase coverage, and minimise costs compared with the current programmes. METHODS: We conducted an open-label, non-inferiority, randomised controlled trial in the Democratic Republic of the Congo. Acutely malnourished children aged 6-59 months with a mid-upper-arm circumference (MUAC) of less than 125 mm or oedema were randomly assigned (1:1), using specially developed software and random blocks (size was kept confidential), to either the current standard strategy (one programme for severe acute malnutrition using ready-to-use therapeutic food [RUTF] at an increasing dose as weight increased, another for moderate acute malnutrition using a fixed dose of ready-to-use supplementary food [RUSF]) or the OptiMA strategy (a single programme for both severe acute malnutrition and moderate acute malnutrition using RUTF at a decreasing dose as MUAC and weight increased). The primary endpoint was a favourable outcome at 6 months, defined as being alive, not acutely malnourished as per the definition applied at inclusion, and with no further episodes of acute malnutrition throughout the 6-month observation period; the endpoint was analysed in the intention-to-treat (all children) and per-protocol populations (participants who had a minimum prescription of 4 weeks' RUTF, received at least 90% of the total amount of RUTF they were supposed to receive as per the protocol, or were prescribed RUSF rations for a minimum of 4 weeks [ie, minimum of 28 RUSF sachets], and had a maximum interval of 6 weeks between any two visits in the 6-month follow-up). The non-inferiority analysis (margin 10%) was to be followed by a superiority analysis (margin 0%) if non-inferiority was concluded. This trial is registered at ClinicalTrials.gov, NCT03751475, and is now closed. FINDINGS: Between July 22 and Dec 6, 2019, 912 children were randomly assigned; after 16 were excluded, 896 were analysed (446 in the standard group and 450 in the OptiMA group). In the intention-to-treat analysis, 282 (63%) of 446 children in the standard group and 325 (72%) of 450 children in the OptiMA group had a favourable outcome (difference -9.0%, 95% CI -15.9 to -2.0). In the per protocol analysis, 161 (61%) of 264 children in the standard group and 291 (74%) of 392 children in the OptiMA group had a favourable outcome (-13.2%, -21.6 to -4.9). INTERPRETATION: In this non-inferiority trial treating children with MUAC of less than 125 mm or oedema, decreasing RUTF dose according to MUAC and weight increase proved to be a superior strategy to the standard protocol in the Democratic Republic of the Congo. These results demonstrate the safety and benefits of an approach that could substantially increase access to treatment for millions of children with acute malnutrition in sub-Saharan Africa. FUNDING: Innocent Foundation and European Civil Protection and Humanitarian Aid Operations. TRANSLATION: For the French translation of the abstract see Supplementary Materials section

Homéostasie des acides gras des membranes myocardiques au cours de l’insuffisance cardiaque chez le rat

National audienc

MALDI-TOF mass spectrometry identification of filamentous fungi in the clinical laboratory.

Pôle MERS F. DalleInternational audienceThis study aimed to validate the effectiveness of a standardised procedure for the MALDI-TOF mass spectrometry (MS)-based identification on a large sample of filamentous fungi routinely identified in university hospitals' laboratories. Non-dermatophyte filamentous fungi prospectively isolated in the routine activity of five teaching hospitals in France were first identified by conventional methods in each laboratory and then by MS in one centre. DNA sequence-based identification resolved discrepancies between both methods. In this study, of the 625 analysed filamentous fungi of 58 species, 501 (80%) and 556 (89%) were correctly identified by conventional methods and MS respectively. Compared with the conventional method, MS dramatically enhanced the performance of the identification of the non-Aspergillus filamentous fungi with a 31-61% increase in correct identification rate. In conclusion, this study on a large sample of clinical filamentous fungi taxa demonstrates that species identification is significantly improved by MS compared with the conventional method. The main limitation is that MS identification is possible only if the species is included in the reference spectra library. Nevertheless, for the routine clinical laboratory, MS provides the means to attain markedly accurate results in filamentous fungi identification, which was previously restricted to only a few reference laboratories

Membrane chromatography-based downstream processing for cell-culture produced influenza vaccines

New influenza strains are constantly emerging, causing seasonal epidemics and raising concerns to the risk of a new global pandemic. Since vaccination is an effective method to prevent the spread of the disease and reduce its severity, the development of robust bioprocesses for producing pandemic influenza vaccines is exceptionally important. Herein, a membrane chromatography-based downstream processing platform with a demonstrated industrial application potential was established. Cell culture-derived influenza virus H1N1/A/PR/8/34 was harvested from benchtop bioreactor cultures. For the clarification of the cell culture broth, a depth filtration was selected as an alternative to centrifugation. After inactivation, an anion exchange chromatography membrane was used for viral capture and further processing. Additionally, two pandemic influenza virus strains, the H7N9 subtype of the A/Anhui/1/2013 and H3N2/A/Hong Kong/8/64, were successfully processed through similar downstream process steps establishing optimized process parameters. Overall, 41.3–62.5% viral recovery was achieved, with the removal of 86.3–96.5% host cell DNA and 95.5–99.7% of proteins. The proposed membrane chromatography purification is a scalable and generic method for the processing of different influenza strains and is a promising alternative to the current industrial purification of influenza vaccines based on ultracentrifugation methodologies