Developing a protocol for a preventive oral health exam for elderly people (EDePAM) using E-Delphi methodology.

The aim of this study was to develop a Preventive Oral Health Exam for Elderly People (EDePAM), using the e-Delphi technique, to diagnose oral health problems in people 65 or older. The e-Delphi technique was used with experts in multiple stages, and in a final workshop, where an agreement on an examination protocol was reached for diagnosing dental caries, oral mucosa lesions, periodontal diseases, and masticatory function disorders. Quantitative analyses of all the rounds of the e-Delphi method were conducted. It was agreed that the International Caries Detection and Assessment System (ICDAS) should be used together with a modified version of the Nyvad criteria to detect and assess caries lesions. It was also agreed that an assessment was needed of the different factors involved in determining caries risk, namely socioeconomic level, access to fluoride, level of dependence/functionality, salivary flow, history of head and neck cancer treatment, use of medications that decrease salivary flow, diet, use of removable dental prostheses, exposure of root surfaces, and caries history. Furthermore, patients would be required to undergo an examination of the oral mucosa, where any existing lesion should be described in terms of its clinical appearance, location, and risk potential. It was also agreed that an assessment of masticatory function should be performed using the Leake index, together with chewing-gum combined with a color scale to categorize masticatory performance. The number of pairs of occluding antagonist teeth was considered as the best predictor of masticatory function. The 2018 classification by the American Academy of Periodontology (AAP) / European Federation of Periodontology (EFP) was accepted as the standard to assess periodontal status, and it was agreed that this assessment should include an evaluation of clinical attachment loss and bleeding on probing. The novel EDePAM was considered as appropriate for conducting a functional assessment of oral health by providing a comprehensive diagnosis of oral diseases.

Developing a protocol for a preventive oral health exam for elderly people (EDePAM) using E-Delphi methodology

Abstract The aim of this study was to develop a Preventive Oral Health Exam for Elderly People (EDePAM), using the e-Delphi technique, to diagnose oral health problems in people 65 or older. The e-Delphi technique was used with experts in multiple stages, and in a final workshop, where an agreement on an examination protocol was reached for diagnosing dental caries, oral mucosa lesions, periodontal diseases, and masticatory function disorders. Quantitative analyses of all the rounds of the e-Delphi method were conducted. It was agreed that the International Caries Detection and Assessment System (ICDAS) should be used together with a modified version of the Nyvad criteria to detect and assess caries lesions. It was also agreed that an assessment was needed of the different factors involved in determining caries risk, namely socioeconomic level, access to fluoride, level of dependence/functionality, salivary flow, history of head and neck cancer treatment, use of medications that decrease salivary flow, diet, use of removable dental prostheses, exposure of root surfaces, and caries history. Furthermore, patients would be required to undergo an examination of the oral mucosa, where any existing lesion should be described in terms of its clinical appearance, location, and risk potential. It was also agreed that an assessment of masticatory function should be performed using the Leake index, together with chewing-gum combined with a color scale to categorize masticatory performance. The number of pairs of occluding antagonist teeth was considered as the best predictor of masticatory function. The 2018 classification by the American Academy of Periodontology (AAP) / European Federation of Periodontology (EFP) was accepted as the standard to assess periodontal status, and it was agreed that this assessment should include an evaluation of clinical attachment loss and bleeding on probing. The novel EDePAM was considered as appropriate for conducting a functional assessment of oral health by providing a comprehensive diagnosis of oral diseases.

Coronavirus Awareness and Mental Health: Clinical Symptoms and Attitudes Toward Seeking Professional Psychological Help.

The current study analyzed the relationship between Coronavirus (COVID-19) Awareness, mental health, and willingness to seek professional psychological help. This was made through a quantitative approach, using online questionnaires to collect data from 855 subjects. The questionnaires included the Brief Symptom Inventory (BSI-53) to measure mental health indicators, the Attitudes Toward Seeking Professional Psychological Help Scale-Short Form, and the Coronavirus Awareness Scale-10 (CAS-10). An Exploratory Factor Analysis suggests that three factors underlie the CAS-10: Coronavirus Concern, Exaggerated Perception, and Immunity Perception. Results indicate a significant positive correlation between Coronavirus Concern and both general anxiety and phobic anxiety symptoms. Immunity Perception is positively related to paranoid ideation and psychotic symptoms. A Mediation Analysis determined that Coronavirus Concern has a significant positive direct effect on Openness to Seeking Psychological Treatment (OSPT), while Exaggerated Perception and Immunity Perception scores have significant direct negative effects on the Value and Need in Seeking Treatment (VNST) scores. Indirectly, the relationship between Coronavirus Concern and OPST is significantly mediated by anxiety symptoms. Similar results were found for the VNST subscale. There is a negative significant effect of Immunity Perception over OSPT mediated by Paranoid Ideation. However, the overall model only achieved small r 2 coefficients for the OSPT (0.060) and VNST (0.095) scores. Comparisons in Coronavirus Awareness between sex, age, and the presence of children and older adults at home were also made. These results are discussed regarding their practical implications for mental health providers and policymakers.

Cell spheroids as a versatile research platform: formation mechanisms, high throughput production, characterization and applications.

Three-dimensional (3D) cell culture has tremendous advantages to closely mimic thein vivoarchitecture and microenvironment of healthy tissue and organs, as well as of solid tumors. Spheroids are currently the most attractive 3D model to produce uniform reproducible cell structures as well as a potential basis for engineering large tissues and complex organs. In this review we discuss, from an engineering perspective, processes to obtain uniform 3D cell spheroids, comparing dynamic and static cultures and considering aspects such as mass transfer and shear stress. In addition, computational and mathematical modeling of complex cell spheroid systems are discussed. The non-cell-adhesive hydrogel-based method and dynamic cell culture in bioreactors are focused in detail and the myriad of developed spheroid characterization techniques is presented. The main bottlenecks and weaknesses are discussed, especially regarding the analysis of morphological parameters, cell quantification and viability, gene expression profiles, metabolic behavior and high-content analysis. Finally, a vast set of applications of spheroids as tools forin vitrostudy model systems is examined, including drug screening, tissue formation, pathologies development, tissue engineering and biofabrication, 3D bioprinting and microfluidics, together with their use in high-throughput platforms.

Periodontal Treatment Protocol for Decompensated Diabetes Patients.

Background: Decompensated diabetes is associated with a higher prevalence and severity of periodontitis and poorer response to periodontal therapy. It is conceivable that periodontal therapy may cause systemic and local complications in this type of patients. The aim of the present study was to identify and describe the best available evidence for the treatment of periodontitis in decompensated diabetics. Material and methods: An expert committee including participants from different areas gathered to discuss and develop a treatment guideline under the guidance of the Cochrane Associate Center, Faculty of Dentistry, University of Chile. In total, four research questions were prepared. The questions prepared related to decompensated diabetic patients (glycated hemoglobin >8) were, (1) Does the exposure to periodontal treatment increase the risk of infectious or systemic complications? (2) Does the antibiotic treatment or prophylaxis, compared to not giving it, reduce infectious complications? (3) Does the exposure to periodontal treatment, compared to no treatment, reduce the glycated hemoglobin levels (HbA1c)? Last question was related to diabetic patients, (4) Does the exposure to a higher level of HbA1c, compared to stable levels, increase the risk of infectious complications? Based on these questions, a search strategy was developed using MEDLINE and EPISTEMONIKOS. Only systematic reviews were considered. Results: For question 1, the search yielded 12 records in EPISTEMONIKOS and 23 in MEDLINE. None of these studies addressed the question. For question 2, the search yielded 58 records in EPISTEMONIKOS and 11 in MEDLINE. None of these studies addressed the question. For question 3, the search yielded 16 records in EPISTEMONIKOS and 11 in MEDLINE. Thirteen addressed the question. For question 4, the search yielded 7 records in EPISTEMONIKOS and 9 in MEDLINE. One addressed the question. Conclusions: In decompensated diabetic patients, there is lack of scientific information about risk of infectious or systemic complications as a result of periodontal treatment and about the impact of antibiotic treatment or prophylaxis on reduction if infectious complications. A defined HbA1c threshold for dental and periodontal treatment in diabetic patients has yet to be determined. Finally, periodontal treatment does have an impact on HbA1c levels.

DROSOPHILA S2 cell culture in a WAVE Bioreactor: potential for scaling up the production of the recombinant rabies virus glycoprotein.

The transmembrane rabies virus glycoprotein (RVGP) is the main antigen of vaccine formulations used around the world to prevent rabies, the most lethal preventable infectious disease known. The objective of this work was to evaluate the potential of a bioreactor using wave-induced agitation in the initial steps of scaling up the rRVGP production process by a Drosophila melanogaster S2 cell line to produce rRVGP in sufficient quantities for immunization and characterization studies. Taking advantage of some remarkable features recognized in Drosophila S2 cells for scaling the culture process, a robust recombinant lineage (S2MtRVGPH-His) engineered by our group for the expression of rRVGP using a copper-inducible promoter was used in the bioreactor cultures. The WAVE Bioreactor was chosen because it represents an innovative approach to the cultivation of animal cells using single-use technology. For that purpose, we firstly established a procedure for culturing the S2MtRVGPH-His lineage in 100 mL Schott flasks. Using an inoculum of 5 × 105 cells/mL in culture medium (Sf900-III) induced with solution of CuSO4 (0.7 mM) and a convenient pH range (6.2-7.0), optimal parameter values such as time of induction (72 h) and temperature (28 °C) to increase rRVGP production could be defined. This procedure was reproduced in culture experiments conducted in a WAVE Bioreactor™ 2/10 using a 2 L Cellbag. The results in Schott flasks and in WAVE Bioreactor™ were very similar, yielding a maximum titer of rRVGP above of 1 mg.L-1. The immunization study showed that the rRVGP produced in the bioreactor was of high immunogenic quality.

Drosophila S2 cell culture in a wave bioreactor: potential for scaling up the production of the recombinant rabies virus glycoprotein

The transmembrane rabies virus glycoprotein (RVGP) is the main antigen of vaccine formulations used around the world to prevent rabies, the most lethal preventable infectious disease known. The objective of this work was to evaluate the potential of a bioreactor using wave-induced agitation in the initial steps of scaling up the rRVGP production process by a Drosophila melanogaster S2 cell line to produce rRVGP in sufficient quantities for immunization and characterization studies. Taking advantage of some remarkable features recognized in Drosophila S2 cells for scaling the culture process, a robust recombinant lineage (S2MtRVGPH-His) engineered by our group for the expression of rRVGP using a copper-inducible promoter was used in the bioreactor cultures. The WAVE Bioreactor was chosen because it represents an innovative approach to the cultivation of animal cells using single-use technology. For that purpose, we firstly established a procedure for culturing the S2MtRVGPH-His lineage in 100 mL Schott flasks. Using an inoculum of 5 x 10(5) cells/mL in culture medium (Sf900-III) induced with solution of CuSO4 (0.7 mM) and a convenient pH range (6.2-7.0), optimal parameter values such as time of induction (72 h) and temperature (28 degrees C) to increase rRVGP production could be defined. This procedure was reproduced in culture experiments conducted in a WAVE Bioreactor (TM) 2/10 using a 2 L Cellbag. The results in Schott flasks and inWAVE Bioreactor (TM) were very similar, yielding a maximum titer of rRVGP above of 1 mg.L-1. The immunization study showed that the rRVGP produced in the bioreactor was of high immunogenic quality.

DROSOPHILA S2 cell culture in a WAVE Bioreactor: potential for scaling up the production of the recombinant rabies virus glycoprotein

The transmembrane rabies virus glycoprotein (RVGP) is the main antigen of vaccine formulations used around the world to prevent rabies, the most lethal preventable infectious disease known. The objective of this work was to evaluate the potential of a bioreactor using wave-induced agitation in the initial steps of scaling up the rRVGP production process by a Drosophila melanogaster S2 cell line to produce rRVGP in sufficient quantities for immunization and characterization studies. Taking advantage of some remarkable features recognized in Drosophila S2 cells for scaling the culture process, a robust recombinant lineage (S2MtRVGPH-His) engineered by our group for the expression of rRVGP using a copper-inducible promoter was used in the bioreactor cultures. The WAVE Bioreactor was chosen because it represents an innovative approach to the cultivation of animal cells using single-use technology. For that purpose, we firstly established a procedure for culturing the S2MtRVGPH-His lineage in 100 mL Schott flasks. Using an inoculum of 5 x 10(5) cells/mL in culture medium (Sf900-III) induced with solution of CuSO4 (0.7 mM) and a convenient pH range (6.2-7.0), optimal parameter values such as time of induction (72 h) and temperature (28 degrees C) to increase rRVGP production could be defined. This procedure was reproduced in culture experiments conducted in a WAVE Bioreactor (TM) 2/10 using a 2 L Cellbag. The results in Schott flasks and inWAVE Bioreactor (TM) were very similar, yielding a maximum titer of rRVGP above of 1 mg.L-1. The immunization study showed that the rRVGP produced in the bioreactor was of high immunogenic quality.

Log law of the wall revisited in Taylor-Couette flows at intermediate Reynolds numbers.

We provide Reynolds averaged azimuthal velocity profiles, measured in a Taylor-Couette system in turbulent flow, at medium Reynolds (7800 < Re < 18000) number with particle image velocimetry technique. We find that in the wall regions, close to the inner and outer cylinders, the azimuthal velocity profile reveals a significant deviation from classical logarithmic law. In order to propose a new law of the wall, the profile of turbulent mixing length was estimated from data processing; it was shown to behave nonlinearly with the radial wall distance. Based on this turbulent mixing length expression, a law of the wall was proposed for the Reynolds averaged azimuthal velocity, derived from momentum balance and validated by comparison to different data. In addition, the profile of viscous dissipation rate was investigated and compared to the global power needed to maintain the inner cylinder in rotation.

Transient expression of rabies virus glycoprotein (RVGP) in Drosophila melanogaster Schneider 2 (S2) cells.

The transient transfection process has been developed to allow rapid production of recombinant proteins. In this paper, we describe the transient expression of recombinant rabies virus glycoprotein (RVGP) in Drosophila melanogaster Schneider 2 (S2) cells. Different cell transfection reagents were evaluated, together with the effects of different cell cultivation procedures on RVGP expression. Yields of RVGP in the range 50-90ng/10(7) cells were obtained in multi-well plate transfection experiments, where it was observed that RVGP expression was linked to the DNA concentration. RVGP expression was 1.3 times higher using 10µg rather than 5µg of DNA. Inhibition of RVGP expression was observed at higher concentrations of DNA, with DNA concentrations above 15µg decreasing RVGP expression 1.5-fold for cells transfected with polyethylenimine (PEI) and 1.6-fold for cells transfected with cationic lipid. The results of shake flask transfection indicated that S2 cells were more effectively transfected in suspension than under static conditions. RVGP yields of 182.2ng/10(7) cells (PEI), 201ng/10(7) cells (calcium phosphate), and 215ng/10(7) cells (cationic lipid) were obtained for S2 cell suspension cultures. The highest volumetric RVGP concentration (309ng/mL) was found for cells transfected with cationic lipid. This value was 1.21 and 1.16 times higher, respectively, than for cells transfected with PEI (253.4ng/mL) and calcium phosphate (237.2ng/mL). There was little effect of transfection on the kinetics of cell growth, with growth rates of 1.12 and 1.19d(-1) for transfected and control cells, respectively. In spinner flasks, the expression of RVGP was 150 and 138ng/10(7) cells for transfection using PEI and calcium phosphate, respectively. A comparison of the different transfection reagents (calcium phosphate, cationic lipid, and cationic polymer) showed no significant differences in RVGP expression when shake flasks were used. Overall, the data indicated that transient expression in D. melanogaster S2 cells is a practical way of synthesizing RVGP for use in structural and functional studies.

Growth and functional harvesting of human mesenchymal stromal cells cultured on a microcarrier-based system.

Human mesenchymal stromal cells (hMSCs) cells are attractive for applications in tissue engineering and cell therapy. Because of the low availability of hMSCs in tissues and the high doses of hMSCs necessary for infusion, scalable and cost-effective technologies for in vitro cell expansion are needed to produce MSCs while maintaining their functional, immunophenotypic and cytogenetic characteristics. Microcarrier-based culture systems are a good alternative to traditional systems for hMSC expansion. The aim of the present study was to develop a scalable bioprocess for the expansion of human bone marrow mesenchymal stromal cells (hBM-MSCs) on microcarriers to optimize growth and functional harvesting. In general, the results obtained demonstrated the feasibility of expanding hBM-MSCs using microcarrier technology. The maximum cell concentration (n = 5) was ~4.82 ± 1.18 × 10(5) cell mL(-1) at day 7, representing a 3.9-fold increase relative to the amount of inoculated cells. At the end of culture, 87.2% of the cells could be harvested (viability = 95%). Cell metabolism analysis revealed that there was no depletion of important nutrients such as glucose and glutamine during culture, and neither lactate nor ammonia byproducts were formed at inhibitory concentrations. The cells that were recovered after the expansion retained their immunophenotypic and functional characteristics. These results represent an important step toward the implementation of a GMP-compliant large-scale production system for hMSCs for cellular therapy.

Effect of hypothermic temperatures on production of rabies virus glycoprotein by recombinant Drosophila melanogaster S2 cells cultured in suspension.

Aiming at maximizing the production of transmembrane rabies virus glycoprotein (rRVGP), the influence of hypothermic temperature on a recombinant Drosophila melanogaster S2 cell culture in Sf-900II medium was investigated. Cell growth and rRVGP production were assessed at 4 culture temperatures in Schott flasks: 16, 20, 24 and 28 °C. The maximum specific growth rates µ(max) were, respectively: 0.009, 0.019, 0.038 and 0.035 h(-1), while the maximum rRVGP levels C(max)(rRVGP) were: 0.075, 2.973, 0.480 and 1.404 mg L(-1). The best production temperature (20 °C) was then tested in a bioreactor with control of pH and dissolved oxygen in batch and fed-batch modes. In the batch culture, µ(max) and C(max)(rRVGP) were 0.060 h(-1) and 0.149 mg L(-1) at 28 °C and 0.026 h(-1) and 0.354 mg L(-1) at 20 °C, respectively. One batch-culture experiment was carried out with adaptation of the cells by the temperature falling in steps from 20 °C to 16 °C, so that µ(max) fell from 0.023 to 0.013 h(-1), while C(max)(rRVGP) was improved to 0.567 mg L(-1). In the fed-batch mode at 20 °C, µ(max) was 0.025 h(-1) and C(max)(rRVGP) was 1.155 mg L(-1). Taken together, these results indicate that the best strategy for optimized rRVGP production is the culture at hypothermic temperature of 20 °C, when µ(max) is kept low and with feeding of limitant aminoacids.

Drosophila melanogaster S2 cells for expression of heterologous genes: From gene cloning to bioprocess development.

In the present review we discuss strategies that have been used for heterologous gene expression in Drosophila melanogaster Schneider 2 (S2) cells using plasmid vectors. Since the growth of S2 cells is not dependent on anchorage to solid substrates, these cells can be easily cultured in suspension in large volumes. The factors that most affect the growth and gene expression of S2 cells, namely cell line, cell passage, inoculum concentration, culture medium, temperature, dissolved oxygen concentration, pH, hydrodynamic forces and toxic metabolites, are discussed by comparison with other insect and mammalian cells. Gene expression, cell metabolism, culture medium formulation and parameters involved in cellular respiration are particularly emphasized. The experience of the authors with the successful expression of a biologically functional protein, the rabies virus glycoprotein (RVGP), by recombinant S2 cells is presented in the topics covered.

Recombinant rabies virus glycoprotein synthesis in bioreactor by transfected Drosophila melanogaster S2 cells carrying a constitutive or an inducible promoter.

S2 cell populations (S2AcRVGP2K and S2MtRVGP-Hy) were selected after transfection of gene expression vectors carrying the cDNA encoding the rabies virus glycoprotein (RVGP) gene under the control of the constitutive (actin) or inductive (metallothionein) promoters. These cell populations were cultivated in a 1L bioreactor mimicking a large scale bioprocess. Cell cultures were carried out at 90 rpm and monitored/controlled for temperature (28 degrees C) and dissolved oxygen (10 or 50% air saturation). Cell growth attained approximately 1.5-3 x 10(7)cells/mL after 3-4 days of cultivation. The constitutive synthesis of RVGP in S2AcRVGP2K cells led to values of 0.76 microg/10(7) cells at day 4 of culture. The RVGP synthesis in S2MtRVGP-Hy cell fraction increased upon CuSO(4) induction attaining specific productivities of 1.5-2 microg/10(7) cells at days 4-5. RVGP values in supernatant as a result of cell lysis were always very low (<0.2 microg/mL) indicating good integrity of cells in culture. Overall the RVGP productivity was of 1.5-3mg/L. Our data showed an important influence of dissolved oxygen on RVGP synthesis allowing a higher and sustained productivity by S2MtRVGP-Hy cells when cultivated with a DO of 10% air saturation. The RVGP productivity in bioreactors shown here mirrors those previously observed for T-flasks and shaker bottles and allow the preparation of the large RVGP quantities required for studies of structure and function.

Nomenclature and guideline to express the amount of a membrane protein synthesized in animal cells in view of bioprocess optimization and production monitoring.

Studies of a bioprocess optimization and monitoring for protein synthesis in animal cells face a challenge on how to express in quantitative terms the system performance. It is possible to have a panel of calculated variables that fits more or less appropriately the intended goal. Each mathematical expression approach translates different quantitative aspects. We can basically separate them into two categories: those used for the evaluation of cell physiology in terms of product synthesis, which can be for bioprocess improvement or optimization, and those used for production unit sizing and for bioprocess operation. With these perspectives and based on our own data of kinetic S2 cells growth and metabolism, as well as on their synthesis of the transmembrane recombinant rabies virus glycoprotein, here indicated as P, we show and discuss the main characteristics of calculated variables and their recommended use. Mainly applied to a bioprocess improvement/optimization and that mainly used for operation definition and to design the production unit, we expect these definitions/recommendations would improve the quality of data produced in this field and lead to more standardized procedures. In turn, it would allow a better and easier comprehension of scientific and technological communications for specialized readers.

Bioreactor culture of recombinant Drosophila melanogaster S2 cells: characterization of metabolic features related to cell growth and production of the rabies virus glycoprotein.

Although several reports have been published on recombinant protein expression using Drosophila cells, information on their metabolism and growth in vitro is relatively scarce. In the present study, we have analyzed the growth and metabolism of transfected S2 cells (S2AcRVGP) in bioreactor cultures with serum-free medium Sf900 II, to evaluate its potential for mass production of a rabies virus glycoprotein (RVGP). Cells were cultured in a 3 l-stirred-tank bioreactor at 28 degrees C with pH controlled at 6.2 and dissolved oxygen at 50% air saturation. The cells attained a specific growth rate and maximum cell density as high as 0.084 h(-1) and 2.3 x 10(7 )cell ml(-1), respectively. The main substrates consumed during this rapid growth phase were glucose, glutamine and proline. An atypical accumulation of ammonia and alanine was observed in the culture medium, up to 62 mM and 47 mM, respectively, but lactate was produced in low levels. After exhaustion of glutamine and proline as energy sources, alanine was consumed and production of ammonia increased. The production of recombinant RVGP reached concentrations as high as 178 mug l(-1). Premature exhaustion of glutamine, serine and cysteine could be related to degradation of the recombinant glycoprotein. In general, the results demonstrated that S2AcRVGP can be considered an effective vehicle for large-scale recombinant glycoprotein expression and that several critical factors of the bioprocess could be optimized to increase the quality and productivity of the RVGP.

Enhanced production of recombinant rabies virus glycoprotein (rRVGP) by Drosophila melanogaster S2 cells through control of culture conditions.

Culture conditions that affect product quality are important to the successful operation and optimization of recombinant protein production. The objective of this study was to optimize culture conditions for growth of recombinant Drosophila melanogaster S2 cells (S2AcRVGP) in order to enhance the production of rRVGP. The addition of DMSO and glycerol to the medium and growth at a reduced temperature (22 degrees C) were the culture condition variations selected to be tested. Experimental cultures were first performed in serum-free Sf900 II medium in 250 ml Schott flasks. The most promising conditions identified in these experiments were also tested on a higher scale in a 3l bioreactor. In the Schott flasks experiments, all the changes in culture conditions resulted in an increase of rRVGP production. The protein concentration was 3.6-fold higher with addition of 1% DMSO and 1% glycerol and 9.3-fold higher when the cells were cultured at 22 degrees C instead of the standard 28 degrees C. The maximum concentration of rRVGP reached was 591 mug l(-1). In bioreactor experiments, with control of pH at 6.20 and DO at 50%, the reduced culture temperature (22 degrees C) was the strategy that promoted the highest glycoprotein production, 928 mug l(-1).

Characterization of growth and metabolism of Drosophila melanogaster cells transfected with the rabies-virus glycoprotein gene.

In the present study, the growth and key metabolic features of a gene-transfected Drosophila melanogaster (fruitfly) S2 (Schneider 2) cell population (S2AcRVGP cells), cultured in Sf900-II medium, have been evaluated to provide substantial support for the development of a bioprocess to produce RVGP (rabies-virus glycoprotein). Experimental cultures were grown both in a 100 ml Schott flask incubated in a shaker at 28 degrees C and 100 rev./min and in a 3 litre stirred-tank bioreactor at 28 degrees C, with increasing agitation. In small-scale culture, S2AcRVGP cells reached a maximum cell concentration of 1.13 x 10(7) cell/ml, presented a mu(max) (maximum specific growth rate) of 0.037 h(-1) and the growth was limited by oxygen deprivation. An early and remarkably long stationary phase was observed under hypoxia. Cell cultures grown in the bioreactor without oxygen limitation exhibited a maximum cell concentration of 2.2 x 10(7) cells/ml and mu(max) values as high as 0.048 h(-1). The main substrate consumed in order to reach such a high growth rate was the amino acid proline, which seems to play an important role as a source of metabolic energy in the culture of S2AcRVGP cells. Under conditions of hypoxia, the cells were able to survive for 15 h without apparent damage, recovering their previous metabolic activity.

Enhanced production of recombinant rabies virus glycoprotein (rRVGP) by Drosophila melanogaster S2 cells through control of culture conditions

Abstract Culture conditions that affect product quality are important to the successful operation and optimization of recombinant protein production. The objective of this study was to optimize culture conditions for growth of recombinant Drosophila melanogaster S2 cells (S2AcRVGP) in order to enhance the production of rRVGP. The addition of DMSO and glycerol to the medium and growth at a reduced temperature (22 °C) were the culture condition variations selected to be tested. Experimental cultures were first performed in serum-free Sf900 II medium in 250 ml Schott flasks. The most promising conditions identified in these experiments were also tested on a higher scale in a 3l bioreactor. In the Schott flasks experiments, all the changes in culture conditions resulted in an increase of rRVGP production. The protein concentration was 3.6-fold higher with addition of 1% DMSO and 1% glycerol and 9.3-fold higher when the cells were cultured at 22 °C instead of the standard 28 °C. The maximum concentration of rRVGP reached was 591 ìg l−1. In bioreactor experiments, with control of pH at 6.20 and DO at 50%, the reduced culture temperature (22 °C) was the strategy that promoted the highest glycoprotein production, 928 ìg l−1. Keywords Drosophila melanogaster S2 cells - Dimethyl sulfoxide - Glycerol - Rabies virus glycoprotein - Recombinant protein production - Reduced temperature cultivation

Bioreactor culture of recombinant Drosophila melanogaster S2 cells: characterization of metabolic features related to cell growth and production of the rabies virus glycoprotein

Although several reports have been published on recombinant protein expression using Drosophila cells, information on their metabolism and growth in vitro is relatively scarce. In the present study, we have analyzed the growth and metabolism of transfected S2 cells (S2AcRVGP) in bioreactor cultures with serum-free medium Sf900 II, to evaluate its potential for mass production of a rabies virus glycoprotein (RVGP). Cells were cultured in a 3 l-stirred-tank bioreactor at 28 ‹C with pH controlled at 6.2 and dissolved oxygen at 50% air saturation. The cells attained a specific growth rate and maximum cell density as high as 0.084 h−1 and 2.3 ~ 107 cell ml−1, respectively. The main substrates consumed during this rapid growth phase were glucose, glutamine and proline. An atypical accumulation of ammonia and alanine was observed in the culture medium, up to 62 mM and 47 mM, respectively, but lactate was produced in low levels. After exhaustion of glutamine and proline as energy sources, alanine was consumed and production of ammonia increased. The production of recombinant RVGP reached concentrations as high as 178 ƒÊg l−1. Premature exhaustion of glutamine, serine and cysteine could be related to degradation of the recombinant glycoprotein. In general, the results demonstrated that S2AcRVGP can be considered an effective vehicle for large-scale recombinant glycoprotein expression and that several critical factors of the bioprocess could be optimized to increase the quality and productivity of the RVGP.