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Hogwood, Catherine EM, Daniel G. Bracewell, and C. Mark Smales. "Measurement and control of host cell proteins (HCPs) in CHO cell bioprocesses." Current Opinion in Biotechnology 30 (December 2014): 153–60. http://dx.doi.org/10.1016/j.copbio.2014.06.017.
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Van Manen-Brush, Kathleen, Jacob Zeitler, John R. White, Paul Younge, Samantha Willis, and Marisa Jones. "Improving Chinese hamster ovary host cell protein ELISA using Ella®: an automated microfluidic platform." BioTechniques 69, no. 3 (September 2020): 186–92. http://dx.doi.org/10.2144/btn-2020-0074.
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Chinese hamster ovary (CHO) cells are a mammalian cell line used in the production of therapeutic proteins. Host cell proteins (HCPs) are process-related impurities that are derived from the host cell expression system. During biopharmaceutical drug development, removal of HCPs is required. Enzyme-linked immunosorbent assay (ELISA) is a common technique to quantitate HCPs, but is a labor-intensive process that takes up to 7 h. Ella® is an automated instrument that utilizes microfluidics and glass nanoreactors to quantitate HCPs in 75 min using similar ELISA reagents. The antibodies and antigens are captured on three distinct glass nanoreactors, resulting in sensitive reproducible data. Our results indicate that Ella quantitates CHO HCPs with precision, accuracy, sensitivity and trends comparable with our traditional CHO HCP ELISA.
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Gilgunn, Sarah, and Jonathan Bones. "Challenges to industrial mAb bioprocessing—removal of host cell proteins in CHO cell bioprocesses." Current Opinion in Chemical Engineering 22 (December 2018): 98–106. http://dx.doi.org/10.1016/j.coche.2018.08.001.
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Glinšek, Katja, Krištof Bozovičar, and Tomaž Bratkovič. "CRISPR Technologies in Chinese Hamster Ovary Cell Line Engineering." International Journal of Molecular Sciences 24, no. 9 (May 2, 2023): 8144. http://dx.doi.org/10.3390/ijms24098144.
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The Chinese hamster ovary (CHO) cell line is a well-established platform for the production of biopharmaceuticals due to its ability to express complex therapeutic proteins with human-like glycopatterns in high amounts. The advent of CRISPR technology has opened up new avenues for the engineering of CHO cell lines for improved protein production and enhanced product quality. This review summarizes recent advances in the application of CRISPR technology for CHO cell line engineering with a particular focus on glycosylation modulation, productivity enhancement, tackling adventitious agents, elimination of problematic host cell proteins, development of antibiotic-free selection systems, site-specific transgene integration, and CRISPR-mediated gene activation and repression. The review highlights the potential of CRISPR technology in CHO cell line genome editing and epigenetic engineering for the more efficient and cost-effective development of biopharmaceuticals while ensuring the safety and quality of the final product.
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Keysberg, Christoph, Oliver Hertel, Louise Schelletter, Tobias Busche, Chiara Sochart, Jörn Kalinowski, Raimund Hoffrogge, Kerstin Otte, and Thomas Noll. "Exploring the molecular content of CHO exosomes during bioprocessing." Applied Microbiology and Biotechnology 105, no. 9 (May 2021): 3673–89. http://dx.doi.org/10.1007/s00253-021-11309-8.
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Abstract In biopharmaceutical production, Chinese hamster ovary (CHO) cells derived from Cricetulus griseus remain the most commonly used host cell for recombinant protein production, especially antibodies. Over the last decade, in-depth multi-omics characterization of these CHO cells provided data for extensive cell line engineering and corresponding increases in productivity. However, exosomes, extracellular vesicles containing proteins and nucleic acids, are barely researched at all in CHO cells. Exosomes have been proven to be a ubiquitous mediator of intercellular communication and are proposed as new biopharmaceutical format for drug delivery, indicator reflecting host cell condition and anti-apoptotic factor in spent media. Here we provide a brief overview of different separation techniques and subsequently perform a proteome and regulatory, non-coding RNA analysis of exosomes, derived from lab-scale bioreactor cultivations of a CHO-K1 cell line, to lay out reference data for further research in the field. Applying bottom-up orbitrap shotgun proteomics and next-generation small RNA sequencing, we detected 1395 proteins, 144 micro RNA (miRNA), and 914 PIWI-interacting RNA (piRNA) species differentially across the phases of a batch cultivation process. The exosomal proteome and RNA data are compared with other extracellular fractions and cell lysate, yielding several significantly exosome-enriched species. Key points • First-time comprehensive protein and miRNA characterization of CHO exosomes. • Isolation protocol and time point of bioprocess strongly affect quality of extracellular vesicles. • CHO-derived exosomes also contain numerous piRNA species of yet unknown function.
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Alhuthali, Sakhr, and Cleo Kontoravdi. "Population balance modelling captures host cell protein dynamics in CHO cell cultures." PLOS ONE 17, no. 3 (March 23, 2022): e0265886. http://dx.doi.org/10.1371/journal.pone.0265886.
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Monoclonal antibodies (mAbs) have been extensively studied for their wide therapeutic and research applications. Increases in mAb titre has been achieved mainly by cell culture media/feed improvement and cell line engineering to increase cell density and specific mAb productivity. However, this improvement has shifted the bottleneck to downstream purification steps. The higher accumulation of the main cell-derived impurities, host cell proteins (HCPs), in the supernatant can negatively affect product integrity and immunogenicity in addition to increasing the cost of capture and polishing steps. Mathematical modelling of bioprocess dynamics is a valuable tool to improve industrial production at fast rate and low cost. Herein, a single stage volume-based population balance model (PBM) has been built to capture Chinese hamster ovary (CHO) cell behaviour in fed-batch bioreactors. Using cell volume as the internal variable, the model captures the dynamics of mAb and HCP accumulation extracellularly under physiological and mild hypothermic culture conditions. Model-based analysis and orthogonal measurements of lactate dehydrogenase activity and double-stranded DNA concentration in the supernatant show that a significant proportion of HCPs found in the extracellular matrix is secreted by viable cells. The PBM then served as a platform for generating operating strategies that optimise antibody titre and increase cost-efficiency while minimising impurity levels.
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Santoso, Adi. "PERKEMBANGAN TEKNOLOGI SEL MAMALIA CHINESE HAMSTER OVARY (CHO) UNTUK PRODUKSI OBAT BERBASIS PROTEIN." BERITA BIOLOGI 18, no. 2 (August 27, 2019): 125–33. http://dx.doi.org/10.14203/beritabiologi.v18i2.3705.
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Chinese hamsters ovary (CHO) and its derivative such as CHO-DXB11 cells, CHO-K1, CHO-DG44 and CHO-S are mammalian cells that are often used for production of therapeutic protein drugs. The CHO cells often used for protein production have several advantages including 1) host cells that are safe to use in drug production, 2) the level of production of proteins produced can be increased by amplifying genes using methotrexate (MTX), 3) having the capacity to make post-translation modificationsand 4) CHO cells can be adapted to grow in suspension. The high need for protein-based drugs triggers the development of basic knowledge and innovation in production of recombinant proteins. The impressive technological advances in CHO cell technology have made these cells can be used to produce proteins around 10 g/liter in order to meet the market demand. The first protein successfully produced using CHO mammalian cells was the therapeutic Tissue Plasminogen Activator (r-tPA, Activase) protein used for stroke patients. The presence of this drug is quickly followed by several other types of drugs. In this review, history of development of CHO cells, the contribution of CHO cells to basic research, progress of effective line cell screening and development technology are discussed.
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Romanova, Nadiya, Louise Schelletter, Raimund Hoffrogge, and Thomas Noll. "Hyperosmolality in CHO cell culture: effects on the proteome." Applied Microbiology and Biotechnology 106, no. 7 (March 21, 2022): 2569–86. http://dx.doi.org/10.1007/s00253-022-11861-x.
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AbstractChinese hamster ovary (CHO) cells are the most commonly used host cell lines for therapeutic protein production. Exposure of these cells to highly concentrated feed solution during fed-batch cultivation can lead to a non-physiological increase in osmolality (> 300 mOsm/kg) that affects cell physiology, morphology, and proteome. As addressed in previous studies (and indeed, as recently addressed in our research), hyperosmolalities of up to 545 mOsm/kg force cells to abort proliferation and gradually increase their volume—almost tripling it. At the same time, CHO cells also show a significant hyperosmolality-dependent increase in mitochondrial activity. To gain deeper insight into the molecular mechanisms that are involved in these processes, as detailed in this paper, we performed a comparative quantitative label-free proteome study of hyperosmolality-exposed CHO cells compared with control cells. Our analysis revealed differentially expressed key proteins that mediate mitochondrial activation, oxidative stress amelioration, and cell cycle progression. Our studies also demonstrate a previously unknown effect: the strong regulation of proteins can alter both cell membrane stiffness and permeability. For example, we observed that three types of septins (filamentous proteins that form diffusion barriers in the cell) became strongly up-regulated in response to hyperosmolality in the experimental setup. Overall, these new observations correlate well with recent CHO-based fluxome and transcriptome studies, and reveal additional unknown proteins involved in the response to hyperosmotic pressure by over-concentrated feed in mammalian cells.Key points• First-time comparative proteome analysis of CHO cells exposed to over-concentrated feed.• Discovery of membrane barrier-forming proteins up-regulation under hyperosmolality.• Description of mitochondrial and protein chaperones activation in treated cells.
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Lavoie, R., Alice di Fazio, R. Blackburn, Michael Goshe, Ruben Carbonell, and Stefano Menegatti. "Targeted Capture of Chinese Hamster Ovary Host Cell Proteins: Peptide Ligand Discovery." International Journal of Molecular Sciences 20, no. 7 (April 8, 2019): 1729. http://dx.doi.org/10.3390/ijms20071729.
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The growing integration of quality-by-design (QbD) concepts in biomanufacturing calls for a detailed and quantitative knowledge of the profile of impurities and their impact on the product safety and efficacy. Particularly valuable is the determination of the residual level of host cell proteins (HCPs) secreted, together with the product of interest, by the recombinant cells utilized for production. Though often referred to as a single impurity, HCPs comprise a variety of species with diverse abundance, size, function, and composition. The clearance of these impurities is a complex issue due to their cell line to cell line, product-to-product, and batch-to-batch variations. Improvements in HCP monitoring through proteomic-based methods have led to identification of a subset of “problematic” HCPs that are particularly challenging to remove, both at the product capture and product polishing steps, and compromise product stability and safety even at trace concentrations. This paper describes the development of synthetic peptide ligands capable of capturing a broad spectrum of Chinese hamster ovary (CHO) HCPs with a combination of peptide species that allow for advanced mixed-mode binding. Solid phase peptide libraries were screened for identification and characterization of peptides that capture CHO HCPs while showing minimal binding of human IgG, utilized here as a model product. Tetrameric and hexameric ligands featuring either multipolar or hydrophobic/positive amino acid compositions were found to be the most effective. Tetrameric multipolar ligands exhibited the highest targeted binding ratio (ratio of HCP clearance over IgG loss), more than double that of commercial mixed-mode and anion exchange resins utilized by industry for IgG polishing. All peptide resins tested showed preferential binding to HCPs compared to IgG, indicating potential uses in flow-through mode or weak-partitioning-mode chromatography.
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Vallis, Amy J., Viviane Finck-Barbançon, Timothy L. Yahr, and Dara W. Frank. "Biological Effects of Pseudomonas aeruginosa Type III-Secreted Proteins on CHO Cells." Infection and Immunity 67, no. 4 (April 1, 1999): 2040–44. http://dx.doi.org/10.1128/iai.67.4.2040-2044.1999.
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ABSTRACT A strain of Pseudomonas aeruginosa that fails to express known type III-secreted effector proteins was constructed as an expression host. Individual effectors were expressed intrans, and their biological effects on CHO cells were assessed in an acute cellular infection model. Intoxication with ExoS, ExoT, or ExoY resulted in alterations in cell morphology. As shown in previous genetic studies, ExoU expression was linked to acute cytotoxicity.
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Gehrke, Rainer, Michael Ecker, Stephan W. Aberle, Steven L. Allison, Franz X. Heinz, and Christian W. Mandl. "Incorporation of Tick-Borne Encephalitis Virus Replicons into Virus-Like Particles by a Packaging Cell Line." Journal of Virology 77, no. 16 (August 15, 2003): 8924–33. http://dx.doi.org/10.1128/jvi.77.16.8924-8933.2003.
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ABSTRACT RNA replicons derived from flavivirus genomes show considerable potential as gene transfer and immunization vectors. A convenient and efficient encapsidation system is an important prerequisite for the practical application of such vectors. In this work, tick-borne encephalitis (TBE) virus replicons and an appropriate packaging cell line were constructed and characterized. A stable CHO cell line constitutively expressing the two surface proteins prM/M and E (named CHO-ME cells) was generated and shown to efficiently export mature recombinant subviral particles (RSPs). When replicon NdΔME lacking the prM/M and E genes was introduced into CHO-ME cells, virus-like particles (VLPs) capable of initiating a single round of infection were released, yielding titers of up to 5 × 107/ml in the supernatant of these cells. Another replicon (NdΔCME) lacking the region encoding most of the capsid protein C in addition to proteins prM/M and E was not packaged by CHO-ME cells. As observed with other flavivirus replicons, both TBE virus replicons appeared to exert no cytopathic effect on their host cells. Sedimentation analysis revealed that the NdΔME-containing VLPs were physically distinct from RSPs and similar to infectious virions. VLPs could be repeatedly passaged in CHO-ME cells but maintained the property of being able to initiate only a single round of infection in other cells during these passages. CHO-ME cells can thus be used both as a source for mature TBE virus RSPs and as a safe and convenient replicon packaging cell line, providing the TBE virus surface proteins prM/M and E in trans.
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Liu, Xinrong, Ying Chen, Yiwei Zhao, Virginia Liu-Compton, Wesley Chen, Gillian Payne, and Alexandru C. Lazar. "Identification and characterization of co-purifying CHO host cell proteins in monoclonal antibody purification process." Journal of Pharmaceutical and Biomedical Analysis 174 (September 2019): 500–508. http://dx.doi.org/10.1016/j.jpba.2019.06.021.
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Larsen, Joachim Steen, Richard Torbjörn Gustav Karlsson, Weihua Tian, Morten Alder Schulz, Annemarie Matthes, Henrik Clausen, Bent Larsen Petersen, and Zhang Yang. "Engineering mammalian cells to produce plant-specific N-glycosylation on proteins." Glycobiology 30, no. 8 (February 10, 2020): 528–38. http://dx.doi.org/10.1093/glycob/cwaa009.
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Abstract Protein N-glycosylation is an essential and highly conserved posttranslational modification found in all eukaryotic cells. Yeast, plants and mammalian cells, however, produce N-glycans with distinct structural features. These species-specific features not only pose challenges in selecting host cells for production of recombinant therapeutics for human medical use but also provide opportunities to explore and utilize species-specific glycosylation in design of vaccines. Here, we used reverse cross-species engineering to stably introduce plant core α3fucose (α3Fuc) and β2xylose (β2Xyl) N-glycosylation epitopes in the mammalian Chinese hamster ovary (CHO) cell line. We used directed knockin of plant core fucosylation and xylosylation genes (AtFucTA/AtFucTB and AtXylT) and targeted knockout of endogenous genes for core fucosylation (fut8) and elongation (B4galt1), for establishing CHO cells with plant N-glycosylation capacities. The engineering was evaluated through coexpression of two human therapeutic N-glycoproteins, erythropoietin (EPO) and an immunoglobulin G (IgG) antibody. Full conversion to the plant-type α3Fuc/β2Xyl bi-antennary agalactosylated N-glycosylation (G0FX) was demonstrated for the IgG1 produced in CHO cells. These results demonstrate that N-glycosylation in mammalian cells is amenable for extensive cross-kingdom engineering and that engineered CHO cells may be used to produce glycoproteins with plant glycosylation.
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Chaussee, Michael S., Robert L. Cole, and Jos P. M. van Putten. "Streptococcal Erythrogenic Toxin B Abrogates Fibronectin-Dependent Internalization of Streptococcus pyogenes by Cultured Mammalian Cells." Infection and Immunity 68, no. 6 (June 1, 2000): 3226–32. http://dx.doi.org/10.1128/iai.68.6.3226-3232.2000.
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ABSTRACT Streptococcus pyogenes secretes several proteins that influence host-pathogen interactions. A tissue-culture model was used to study the influence of the secreted cysteine protease streptococcal erythrogenic toxin B (SPE B) on the interaction between S. pyogenes strain NZ131 (serotype M49) and mammalian cells. Inactivation of the speB gene enhanced fibronectin-dependent uptake of the pathogen by Chinese hamster ovary (CHO-K1) cells compared to that in the isogenic wild-type strain. Preincubation of the NZ131 speB mutant with purified SPE B protease significantly inhibited fibronectin-dependent uptake by both CHO-K1 and CHO-pgs745 cells. The effect was attributed to an abrogation of fibronectin binding to the surface of the bacteria that did not involve either the M49 protein or the streptococcal fibronectin-binding protein SfbI. In contrast, pretreatment of the NZ131 speB mutant with SPE B did not influence sulfated polysaccharide-mediated uptake by CHO-pgs745 cells. The results indicate that the SPE B protease specifically alters bacterial cell surface proteins and thereby influences pathogen uptake.
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Houeix, Benoit, and Michael T. Cairns. "Engineering of CHO cells for the production of vertebrate recombinant sialyltransferases." PeerJ 7 (February 11, 2019): e5788. http://dx.doi.org/10.7717/peerj.5788.
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Background Sialyltransferases (SIATs) are a family of enzymes that transfer sialic acid (Sia) to glycan chains on glycoproteins, glycolipids, and oligosaccharides. They play key roles in determining cell–cell and cell-matrix interactions and are important in neuronal development, immune regulation, protein stability and clearance. Most fully characterized SIATs are of mammalian origin and these have been used for in vitro and in vivo modification of glycans. Additional versatility could be achieved by the use of animal SIATs from other species that live in much more variable environments. Our aim was to generate a panel of stable CHO cell lines expressing a range of vertebrate SIATs with different physicochemical and functional properties. Methods The soluble forms of various animal ST6Gal and ST3Gal enzymes were stably expressed from a Gateway-modified secretion vector in CHO cells. The secreted proteins were IMAC-purified from serum-free media. Functionality of the protein was initially assessed by lectin binding to the host CHO cells. Activity of purified proteins was determined by a number of approaches that included a phosphate-linked sialyltransferase assay, HILIC-HPLC identification of sialyllactose products and enzyme-linked lectin assay (ELLA). Results A range of sialyltransferase from mammals, birds and fish were stably expressed in CHO Flp-In cells. The stable cell lines expressing ST6Gal1 modify the glycans on the surface of the CHO cells as detected by fluorescently labelled lectin microscopy. The catalytic domains, as isolated by Ni Sepharose from culture media, have enzymatic activities comparable to commercial enzymes. Sialyllactoses were identified by HILIC-HPLC on incubation of the enzymes from lactose or whey permeate. The enzymes also increased SNA-I labelling of asialofetuin when incubated in a plate format. Conclusion Stable cell lines are available that may provide options for the in vivo sialylation of glycoproteins. Proteins are active and should display a variety of biological and physicochemical properties based on the animal source of the enzyme.
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Addis, Maria Filippa, Paola Rappelli, and Pier Luigi Fiori. "Host and Tissue Specificity of Trichomonas vaginalis Is Not Mediated by Its Known Adhesion Proteins." Infection and Immunity 68, no. 7 (July 1, 2000): 4358–60. http://dx.doi.org/10.1128/iai.68.7.4358-4360.2000.
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ABSTRACT Adhesion of Trichomonas vaginalis is believed to be dependent on four adhesion proteins, which are thought to bind to vaginal epithelial cells in a specific manner with a ligand-receptor type of interaction. However, the specific receptors on the host cell have not yet been identified. In this work, the ability of the T. vaginalis adhesins to bind to cells of different histologic derivations and from different species has been studied. HeLa, CHO, and Vero cell lines; erythrocytes from different species; and a prokaryote without a cell wall, Mycoplasma hominis, were employed in order to investigate the cell specificity of the T. vaginalis adhesins. We observed that the T. vaginalisadhesins are able to bind to the different cell types to the same extent, suggesting that the host and tissue specificity of T. vaginalis adhesion should not be due to specificity of the parasite adhesins. Our results suggest that the data published to date on the subject are probably artifactual and that the experiments reported in the literature are not appropriate for identification of protozoan adhesins.
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Chen, T., R. J. Belland, J. Wilson, and J. Swanson. "Adherence of pilus- Opa+ gonococci to epithelial cells in vitro involves heparan sulfate." Journal of Experimental Medicine 182, no. 2 (August 1, 1995): 511–17. http://dx.doi.org/10.1084/jem.182.2.511.
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Neisseria gonorrhoeae attaches to host epithelial cells via pili and opacity-associated (Opa) outer membrane proteins. Pilus- gonococci (Gc) of strain MS11 adhere to both human and nonhuman cells, but only when particular Opa proteins are expressed; OpaA+ variants adhere best, OpaC+ variants are next best, and the seven other Opa+ variants adhere poorly or not at all. The adherence of OpaA+ Gc to Chinese hamster ovary (CHO) cells is inhibited by heparin or heparan sulfate (HS), but not by chondroitin sulfate. OpaA+ Gc do not adhere to CHO cells devoid of HS proteoglycans; low concentrations of heparin restore OpaA+ Gc adherence to these HS-deficient CHO cells and high concentrations inhibit it. 3H-heparin binding to whole Gc parallels their adherence abilities (OpaA+ > OpaC+ > OpaH+ > Opas B, D, E, F, G, I = Opa- = 0). Opa proteins separated by SDS-PAGE also bind 3H-heparin. These data suggest that adherence of pilus-, Opa+ Gc involves HS-proteoglycan of eukaryotic cells.
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Watarai, M., S. Funato, and C. Sasakawa. "Interaction of Ipa proteins of Shigella flexneri with alpha5beta1 integrin promotes entry of the bacteria into mammalian cells." Journal of Experimental Medicine 183, no. 3 (March 1, 1996): 991–99. http://dx.doi.org/10.1084/jem.183.3.991.
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Shigella is a genus of highly adapted bacterial pathogens that cause bacillary dysentery in humans. Bacteria reaching the colon invade intestinal epithelial cells by a process of bacterial-directed endocytosis mediated by the Ipa proteins: IpaB, IpaC, and IpaD of Shigella. The invasion of epithelial cells is thought to be a receptor-mediated phenomenon, although the cellular components of the host that interact with the Ipa proteins have not yet been identified. We report here that in a Shigella flexneri invasive system and Chinese hamster ovary (CHO) cell monolayers, the Ipa proteins were capable of interacting directly with alpha5beta1 integrin. The invasive capacity of S. flexneri for CHO cells increased as levels of alpha5beta1 integrin were elevated. When CHO cells were infected with S. flexneri, the tyrosine phosphorylation both of pp 125FAK, an integrin-regulated 125 K focal adhesion kinase, and of paxillin was stimulated. In contrast, an isogenic strain of S. flexneri that was defective in invasion owing to a mutation in its spa32 gene failed to induce such phosphorylation. Under in vitro and in vivo conditions, the released IpaB, IpaC, and IpaD proteins bound to alpha 5 beta 1 integrin in a manner different from that of soluble fibronectin but similar to that of the tissue form of fibronectin. At the site of attachment of S. flexneri to CHO cells, alpha5beta1 integrin converged with polymerization of actin. These data thus suggest that the capacity of Ipa proteins to interact with alpha5beta1 integrin may be an important Shigella factor in triggering the reorganization of actin cytoskeletons.
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Xu, Yanji, Peter M. Takvorian, Ann Cali, George Orr, and Louis M. Weiss. "Glycosylation of the Major Polar Tube Protein of Encephalitozoon hellem, a Microsporidian Parasite That Infects Humans." Infection and Immunity 72, no. 11 (November 2004): 6341–50. http://dx.doi.org/10.1128/iai.72.11.6341-6350.2004.
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ABSTRACT The microsporidia are ubiquitous, obligate intracellular eukaryotic spore-forming parasites infecting a wide range of invertebrates and vertebrates, including humans. The defining structure of microsporidia is the polar tube, which forms a hollow tube through which the sporoplasm is transferred to the host cell. Research on the molecular and cellular biology of the polar tube has resulted in the identification of three polar tube proteins: PTP1, PTP2, and PTP3. The major polar tube protein, PTP1, accounts for at least 70% of the mass of the polar tube. In the present study, PTP1 was found to be posttranslationally modified. Concanavalin A (ConA) bound to PTP1 and to the polar tube of several different microsporidia species. Analysis of the glycosylation of Encephalitozoon hellem PTP1 suggested that it is modified by O-linked mannosylation, and ConA binds to these O-linked mannose residues. Mannose pretreatment of RK13 host cells decreased their infection by E. hellem, consistent with an interaction between the mannosylation of PTP1 and some unknown host cell mannose-binding molecule. A CHO cell line (Lec1) that is unable to synthesize complex-type N-linked oligosaccharides had an increased susceptibility to E. hellem infection compared to wild-type CHO cells. These data suggest that the O-mannosylation of PTP1 may have functional significance for the ability of microsporidia to invade their host cells.
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Kaviani, Elina, Ahmad Hosseini, Elham Mahmoudi Maymand, Mani Ramzi, Abbas Ghaderi, and Amin Ramezani. "Triggering of lymphocytes by CD28, 4-1BB, and PD-1 checkpoints to enhance the immune response capacities." PLOS ONE 17, no. 12 (December 8, 2022): e0275777. http://dx.doi.org/10.1371/journal.pone.0275777.
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Tumor infiltrating lymphocytes (TILs) usually become exhausted and dysfunctional owing to chronic contact with tumor cells and overexpression of multiple inhibitor receptors. Activation of TILs by targeting the inhibitory and stimulatory checkpoints has emerged as one of the most promising immunotherapy prospectively. We investigated whether triggering of CD28, 4-1BB, and PD-1 checkpoints simultaneously or alone could enhance the immune response capacity of lymphocytes. In this regard, anti-PD-1, CD80-Fc, and 4-1BBL-Fc proteins were designed and produced in CHO-K1 cells as an expression host. Following confirmation of the Fc fusion proteins’ ability to bind to native targets expressed on engineered CHO-K1 cells (CHO-K1/hPD-1, CHO-K1/hCD28, CHO-K1/hCTLA4, and CHO-K1/h4-1BB), the effects of each protein, on its own and in various combinations, were assessed in vitro on T cell proliferation, cytotoxicity, and cytokines secretion using the Mixed lymphocyte reaction (MLR) assay, 7-AAD/CFSE cell-mediated cytotoxicity assay, and a LEGENDplex™ Human Th Cytokine Panel, respectively. MLR results demonstrated that T cell proliferation in the presence of the combinations of anti-PD-1/CD80-Fc, CD80-Fc/4-1BBL-Fc, and anti-PD-1/CD80-Fc/4-1BBL-Fc proteins was significantly higher than in the untreated condition (1.83-, 1.91-, and 2.02-fold respectively). Furthermore, anti-PD-1 (17%), 4-1BBL-Fc (19.2%), anti-PD-1/CD80-Fc (18.6%), anti-PD-1/4-1BBL-Fc (21%), CD80-Fc/4-1BBL-Fc (18.5%), and anti-PD-1/CD80-Fc/4-1BBL-Fc (17.3%) significantly enhanced cytotoxicity activity compared to untreated condition (7.8%). However, concerning the cytokine production, CD80-Fc and 4-1BBL-Fc alone or in combination significantly increased the secretion of IFN‐γ, TNF-α, and IL-2 compared with the untreated conditions. In conclusion, this research establishes that the various combinations of produced anti-PD-1, CD80-Fc, and 4-1BBL-Fc proteins can noticeably induce the immune response in vitro. Each of these combinations may be effective in killing or destroying cancer cells depending on the type and stage of cancer.
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ERGEN, Nuri, and Halil TÜFEKÇİ. "Mammalian cell lines used in bioprocessing." Journal of Experimental and Clinical Medicine 39, no. 3 (August 30, 2022): 884–92. http://dx.doi.org/10.52142/omujecm.39.3.55.
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A various number of expressions and host systems are used in biologics manufacturing. The most commonly preferred systems are based on bacteria, yeast, mammalian cells, insect cells, and transgenic animals. A wide range of molecules, including insulin, mAbs, vaccines, and recombinant proteins, are produced using different host systems. Because of several reasons impacting the product quality and yield, mammalian cells are utilized. Moreover, mammalian cells are generally used in virus-based vaccine manufacturing. Chinese Hamster Ovary (CHO) is the most widely used cell line for high yield stable recombinant protein production, while Human Embryonic Kidney (HEK) is favoured for transient transfection low yield protein manufacturing, viral-based vaccine and gene and cell therapy-related vector production. Other mammalian cell lines such as NSO, Sp2.0, Vero, MRC-5 and PerC.6 are also used in both recombinant protein and virus productions. Multiple modifications are carried out on industrial cell lines to make them more suitable for high yield and high-quality protein production. Thanks to these alterations, high productivity and quality levels are achieved in the biotechnology industry.
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Lin, Nan, Joaquina Mascarenhas, Natalie R. Sealover, Henry J. George, Jeanne Brooks, Kevin J. Kayser, Brian Gau, Isil Yasa, Parastoo Azadi, and Stephanie Archer-Hartmann. "Chinese hamster ovary (CHO) host cell engineering to increase sialylation of recombinant therapeutic proteins by modulating sialyltransferase expression." Biotechnology Progress 31, no. 2 (March 2015): 334–46. http://dx.doi.org/10.1002/btpr.2038.
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Baik, Jong Youn, Hye Jin Han, and Kelvin H. Lee. "DNA Double-Strand Breaks Affect Chromosomal Rearrangements during Methotrexate-Mediated Gene Amplification in Chinese Hamster Ovary Cells." Pharmaceutics 13, no. 3 (March 12, 2021): 376. http://dx.doi.org/10.3390/pharmaceutics13030376.
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Methotrexate (MTX)-mediated gene amplification has been widely used in Chinese hamster ovary (CHO) cells for the biomanufacturing of therapeutic proteins. Although many studies have reported chromosomal instability and extensive chromosomal rearrangements in MTX-mediated gene-amplified cells, which may be associated with cell line instability issues, the mechanisms of chromosomal rearrangement formation remain poorly understood. We tested the impact of DNA double-strand breaks (DSBs) on chromosomal rearrangements using bleomycin, a DSB-inducing reagent. Bleomycin-treated CHO-DUK cells, which are one of the host cell lines deficient in dihydrofolate reductase (Dhfr) activity, exhibited a substantial number of cells containing radial formations or non-radial formations with chromosomal rearrangements, suggesting that DSBs may be associated with chromosomal rearrangements. To confirm the causes of DSBs during gene amplification, we tested the effects of MTX treatment and the removal of nucleotide base precursors on DSB formation in Dhfr-deficient (i.e., CHO-DUK) and Dhfr-expressing (i.e., CHO-K1) cells. Immunocytochemistry demonstrated that MTX treatment did not induce DSBs per se, but a nucleotide shortage caused by the MTX-mediated inhibition of Dhfr activity resulted in DSBs. Our data suggest that a nucleotide shortage caused by MTX-mediated Dhfr inhibition in production cell lines is the primary cause of a marked increase in DSBs, resulting in extensive chromosomal rearrangements after gene amplification processes.
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Bailey‐Kellogg, Chris, Andres H. Gutiérrez, Leonard Moise, Frances Terry, William D. Martin, and Anne S. De Groot. "CHOPPI: A web tool for the analysis of immunogenicity risk from host cell proteins in CHO‐based protein production." Biotechnology and Bioengineering 111, no. 11 (July 14, 2014): 2170–82. http://dx.doi.org/10.1002/bit.25286.
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Naghneh, Ehsan, Es'hagh Pourmaleki, and Azam Rahimpour. "Evaluation of the Effects of Human Beta-Interferon Scaffold Attachment Region (IFN-SAR) on Expression of Vascular Endothelial Growth Factor-Fc (VEGF-Fc) Fusion Protein Expression in Chinese Hamster Ovary (CHO) Cells." Pharmaceutical Sciences 26, no. 4 (December 25, 2020): 393–98. http://dx.doi.org/10.34172/ps.2020.37.
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Background: Recombinant anti-vascular endothelial growth factor (VEGF) monoclonal antibodies and Fc-fusion proteins have been widely used for the effective treatment of retinal neovascular diseases. In this regard, VEGFR-Fc fusions, which act as strong VEGF inhibitors, have been approved for the treatment of age-related macular degeneration (AMD) and diabetic macular edema (DME). Production of monoclonal antibodies and Fc-fusion proteins relies on mammalian host systems such as Chinese hamster ovary (CHO) cells. Application of genomic regulatory elements including scaffold/matrix attachment regions (SAR/MARs) can profoundly affect recombinant protein expression in CHO cells. Methods: To construct the VEGFR-Fc expression vectors, the enhanced green fluorescent protein (EGFP) gene was replaced by the VEGFR-Fc coding sequence in pEGFP-SAR-puro and pEGFP-puro vectors. Recombinant plasmids were transfected to CHO-K1 cells using TurboFect transfection reagent. VEGFR-Fc expression was evaluated in transiently transfected cells as well as stable cell pools and clones using an enzyme-linked immunosorbent assay (ELISA). Results: IFN-SAR showed no significant effect on transient expression of VEGFR-Fc during 72 h of culture. However, a 2.2-fold enhancement in VEGFR-Fc fusion protein titer was observed in IFN-SAR containing stable cell pools. Further evaluation of the VEGFR-Fc expression level in single-cell clones also indicated that clones with the highest VEGFR-Fc expression belonged to the pools transfected with IFN-SAR construct. Conclusion: Our results indicate that the incorporation of IFN-SAR in expression vector can increase the expression of VEGFR-Fc in stable cell pools as well as single-cell clones. In contrast, transient expression of the fusion protein was not affected by IFN-SAR. More studies are needed to investigate the mechanism underlying this effect, including the analysis of mRNA expression and gene copy number in stable cell pools as well as clonal cells.
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Shin, Sung Wook, Dongwoo Kim, and Jae Seong Lee. "Controlling Ratios of Plasmid-Based Double Cut Donor and CRISPR/Cas9 Components to Enhance Targeted Integration of Transgenes in Chinese Hamster Ovary Cells." International Journal of Molecular Sciences 22, no. 5 (February 27, 2021): 2407. http://dx.doi.org/10.3390/ijms22052407.
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Chinese hamster ovary (CHO) cells are the most valuable expression host for the commercial production of biotherapeutics. Recent trends in recombinant CHO cell-line development have focused on the site-specific integration of transgenes encoding recombinant proteins over random integration. However, the low efficiency of homology-directed repair upon transfection of Cas9, single-guide RNA (sgRNA), and the donor template has limited its feasibility. Previously, we demonstrated that a double-cut donor (DCD) system enables highly efficient CRISPR/Cas9-mediated targeted integration (TI) in CHO cells. Here, we describe several CRISPR/Cas9 vector systems based on DCD templates using a promoter trap-based TI monitoring cell line. Among them, a multi-component (MC) system consisting of an sgRNA/DCD vector and Cas9 expression vector showed an approximate 1.5-fold increase in knock-in (KI) efficiency compared to the previous DCD system, when a systematically optimized relative ratio of sgRNA/DCD and Cas9 vector was applied. Our optimization efforts revealed that concurrently increasing sgRNA and DCD components relative to Cas9 correlated positively with KI efficiency at a single KI site. Furthermore, we explored component bottlenecks, such as effects of sgRNA components and applicability of the MC system on simultaneous double KI. Taken together, we improved the DCD vector design by tailoring plasmid constructs and relative component ratios, and this system can be widely used in the TI strategy of transgenes, particularly in CHO cell line development and engineering.
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Kumar, Praveen, Nidhi Ahuja, and Rakesh Bhatnagar. "Anthrax Edema Toxin Requires Influx of Calcium for Inducing Cyclic AMP Toxicity in Target Cells." Infection and Immunity 70, no. 9 (September 2002): 4997–5007. http://dx.doi.org/10.1128/iai.70.9.4997-5007.2002.
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ABSTRACT The anthrax edema toxin comprises two proteins: protective antigen and edema factor. Anthrax protective antigen binds to the receptors on the surface of target cells and facilitates the entry of edema factor into these target cells. Edema factor (EF) is an adenylate cyclase that catalyzes the synthesis of cyclic AMP (cAMP) in the cytosol of the host cells. In this study, we examined the requirement of extracellular calcium for anthrax edema toxin-induced toxicity in host cells. The cAMP response generated by edema toxin was analyzed in a variety of cells, including CHO, macrophage-like RAW264.7, human neutrophils, and human lymphocytes. Our investigations reveal that after EF reaches the cell cytosol, a rapid influx of calcium is triggered in the host cell that has a pivotal role in determining the cAMP response of the affected cells. Although the cAMP response generated by edema toxin in different cell types varied in intensity and in the time of initiation, the influx of calcium invariably preceded cAMP accumulation. Agents that blocked the uptake of calcium also inhibited edema toxin-induced accumulation of cAMP in the host cells. This is the first report that demonstrates that edema toxin induces accumulation of cAMP in lymphocytes. By accumulating cAMP, a potent inhibitor of immune cell function, edema toxin may actually be poisoning the immune system and thus facilitating the survival of the bacteria in the host.
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Klimstra, William B., Elizabeth M. Nangle, M. Shane Smith, Andrew D. Yurochko, and Kate D. Ryman. "DC-SIGN and L-SIGN Can Act as Attachment Receptors for Alphaviruses and Distinguish between Mosquito Cell- and Mammalian Cell-Derived Viruses." Journal of Virology 77, no. 22 (November 15, 2003): 12022–32. http://dx.doi.org/10.1128/jvi.77.22.12022-12032.2003.
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ABSTRACT C-type lectins such as DC-SIGN and L-SIGN, which bind mannose-enriched carbohydrate modifications of host and pathogen proteins, have been shown to bind glycoproteins of several viruses and facilitate either cis or trans infection. DC-SIGN and L-SIGN are expressed in several early targets of arbovirus infection, including dendritic cells (DCs) and cells of the reticuloendothelial system. In the present study, we show that DC-SIGN and L-SIGN can function as attachment receptors for Sindbis (SB) virus, an arbovirus of the Alphavirus genus. Human monocytic THP-1 cells stably transfected with DC-SIGN or L-SIGN were permissive for SB virus replication, while untransfected controls were essentially nonpermissive. The majority of control THP-1 cells were permissive when attachment and entry steps were eliminated through electroporation of virus transcripts. Infectivity for the DC-SIGN/L-SIGN-expressing cells was largely blocked by yeast mannan, EDTA, or a DC-SIGN/L-SIGN-specific monoclonal antibody. Infection of primary human DCs by SB virus was also dependent upon SIGN expression by similar criteria. Furthermore, production of virus particles in either C6/36 mosquito cells or CHO mammalian cells under conditions that limited complex carbohydrate content greatly increased SB virus binding to and infection of THP-1 cells expressing these lectins. C6/36-derived virus also was much more infectious for primary human DCs than CHO-derived virus. These results suggest that (i) lectin molecules such as DC-SIGN and L-SIGN may represent common attachment receptor molecules for arthropod-borne viruses, (ii) arbovirus particles produced in and delivered by arthropod vectors may preferentially target vertebrate host cells bearing these or similar lectin molecules, and (iii) a cell line has been identified that can productively replicate alphaviruses but is deficient in attachment receptors.
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Bhattacharya, Ilina, Tejabhiram Yadavalli, David Wu, and Deepak Shukla. "Plasma Membrane-Derived Liposomes Exhibit Robust Antiviral Activity against HSV-1." Viruses 14, no. 4 (April 12, 2022): 799. http://dx.doi.org/10.3390/v14040799.
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Plasma membranes host a plethora of proteins and glycans on their outer surface that are exploited by viruses to enter the cells. In this study, we have utilized this property to limit a viral infection using plasma membrane-derived vesicles. We show that plasma membrane-derived liposomes are prophylactically and therapeutically competent at preventing herpes simplex virus type-1 (HSV-1) infection. Plasma membrane liposomes derived from human corneal epithelial (HCE) cells, which are natural targets of HSV-1 infection, as well as Vero and Chinese hamster ovary (CHO) cells were used in this study. Our study clearly demonstrates that HCE and Vero-derived cellular liposomes, which express the viral entry-specific cell surface protein receptors, exhibit robust antiviral activity especially when compared to CHO-derived liposomes, which lack the relevant HSV-1 entry receptors. Further experimentation of the plasma membrane-derived liposomes with HSV type-2 (HSV-2) and pseudorabies virus yielded similar results, indicating strong potential for the employment of these liposomes to study viral entry mechanisms in a cell free-environment.
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Chang, Shu-Jung, Yu-Xun Chang, Roza Izmailyan, Yin-Liang Tang, and Wen Chang. "Vaccinia Virus A25 and A26 Proteins Are Fusion Suppressors for Mature Virions and Determine Strain-Specific Virus Entry Pathways into HeLa, CHO-K1, and L Cells." Journal of Virology 84, no. 17 (June 10, 2010): 8422–32. http://dx.doi.org/10.1128/jvi.00599-10.
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ABSTRACT Mature vaccinia virus enters cells through either fluid-phase endocytosis/macropinocytosis or plasma membrane fusion. This may explain the wide range of host cell susceptibilities to vaccinia virus entry; however, it is not known how vaccinia virus chooses between these two pathways and which viral envelope proteins determine such processes. By screening several recombinant viruses and different strains, we found that mature virions containing the vaccinia virus A25 and A26 proteins entered HeLa cells preferentially through a bafilomycin-sensitive entry pathway, whereas virions lacking these two proteins entered through a bafilomycin-resistant pathway. To investigate whether the A25 and A26 proteins contribute to entry pathway specificity, two mutant vaccinia viruses, WRΔA25L and WRΔA26L, were subsequently generated from the wild-type WR strain. In contrast to the WR strain, both the WRΔA25L and WRΔA26L viruses became resistant to bafilomycin, suggesting that the removal of the A25 and A26 proteins bypassed the low-pH endosomal requirement for mature virion entry. Indeed, WRΔA25L and WRΔA26L virus infections of HeLa, CHO-K1, and L cells immediately triggered cell-to-cell fusion at a neutral pH at 1 to 2 h postinfection (p.i.), providing direct evidence that viral fusion machinery is readily activated after the removal of the A25 and A26 proteins to allow virus entry through the plasma membrane. In summary, our data support a model that on vaccinia mature virions, the viral A25 and A26 proteins are low-pH-sensitive fusion suppressors whose inactivation during the endocytic route results in viral and cell membrane fusion. Our results also suggest that during virion morphogenesis, the incorporation of the A25 and A26 proteins into mature virions may help restrain viral fusion activity until the time of infections.
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DU, Xiaohan, Jiewei CAI, Jian-zhong ZHOU, Victoria L. STEVENS, and Martin G. LOW. "Tolerance of glycosylphosphatidylinositol (GPI)-specific phospholipase D overexpression by Chinese hamster ovary cell mutants with aberrant GPI biosynthesis." Biochemical Journal 361, no. 1 (December 17, 2001): 113–18. http://dx.doi.org/10.1042/bj3610113.
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Mammalian glycosylphosphatidylinositol (GPI)-specific phospholipase D (GPI-PLD) is capable of releasing GPI-anchored proteins by cleavage of the GPI moiety. A previous study indicated that overexpression of GPI-PLD in mouse RAW 264.7 monocytes/macrophages could be cytotoxic, since survivors of stable transfections had enzymic activity no higher than untransfected cells [Du and Low (2001) Infect. Immun. 69, 3214–3223]. We investigated this phenomenon by transfecting bovine GPI-PLD cDNA stably into Chinese hamster ovary (CHO) cells using a bi-cistronic expression system. The surviving transfectants showed an unchanged cellular level of GPI-PLD, supporting the cytotoxicity hypothesis. However, when using a CHO mutant defective in the second step of GPI biosynthesis as host, the expression level of GPI-PLD in stable transfectants was increased by 2.5-fold compared with untransfected or empty-vector-transfected cells. To identify the mechanism, we studied another CHO cell mutant (G9PLAP.D5), which seems to be defective at a later stage in GPI biosynthesis. In sharp contrast with wild-type cells, GPI-PLD activity in G9PLAP.D5 transfected with bovine GPI-PLD cDNA was 100-fold higher than untransfected or empty-vector-transfected cells. This was accompanied by a significant release of alkaline phosphatase into the medium and a decrease in membrane-associated alkaline phosphatase. Taken together, our results indicate that overexpression of GPI-PLD is lethal to wild-type cells, possibly by catalysing the overproduction of GPI-derived toxic substances. We propose that cells with abnormal GPI biosynthesis/processing can escape the toxic effect of these substances.
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Joucla, G., C. Le Sénéchal, M. Bégorre, B. Garbay, X. Santarelli, and C. Cabanne. "Cation exchange versus multimodal cation exchange resins for antibody capture from CHO supernatants: Identification of contaminating Host Cell Proteins by mass spectrometry." Journal of Chromatography B 942-943 (December 2013): 126–33. http://dx.doi.org/10.1016/j.jchromb.2013.10.033.
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Matthews, Alicia M., Thomas G. Biel, Uriel Ortega-Rodriguez, Vincent M. Falkowski, Xin Bush, Talia Faison, Hang Xie, Cyrus Agarabi, V. Ashutosh Rao, and Tongzhong Ju. "SARS-CoV-2 spike protein variant binding affinity to an angiotensin-converting enzyme 2 fusion glycoproteins." PLOS ONE 17, no. 12 (December 6, 2022): e0278294. http://dx.doi.org/10.1371/journal.pone.0278294.
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Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the causative agent of the Coronavirus disease 2019 (Covid-19) pandemic, continues to evolve and circulate globally. Current prophylactic and therapeutic countermeasures against Covid-19 infection include vaccines, small molecule drugs, and neutralizing monoclonal antibodies. SARS-CoV-2 infection is mainly mediated by the viral spike glycoprotein binding to angiotensin converting enzyme 2 (ACE2) on host cells for viral entry. As emerging mutations in the spike protein evade efficacy of spike-targeted countermeasures, a potential strategy to counter SARS-CoV-2 infection is to competitively block the spike protein from binding to the host ACE2 using a soluble recombinant fusion protein that contains a human ACE2 and an IgG1-Fc domain (ACE2-Fc). Here, we have established Chinese Hamster Ovary (CHO) cell lines that stably express ACE2-Fc proteins in which the ACE2 domain either has or has no catalytic activity. The fusion proteins were produced and purified to partially characterize physicochemical properties and spike protein binding. Our results demonstrate the ACE2-Fc fusion proteins are heavily N-glycosylated, sensitive to thermal stress, and actively bind to five spike protein variants (parental, alpha, beta, delta, and omicron) with different affinity. Our data demonstrates a proof-of-concept production strategy for ACE2-Fc fusion glycoproteins that can bind to different spike protein variants to support the manufacture of potential alternative countermeasures for emerging SARS-CoV-2 variants.
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Traustason, Bergthor, Matthew Cheeks, and Duygu Dikicioglu. "Computer-Aided Strategies for Determining the Amino Acid Composition of Medium for Chinese Hamster Ovary Cell-Based Biomanufacturing Platforms." International Journal of Molecular Sciences 20, no. 21 (November 2, 2019): 5464. http://dx.doi.org/10.3390/ijms20215464.
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Chinese hamster ovary (CHO) cells are used for the production of the majority of biopharmaceutical drugs, and thus have remained the standard industry host for the past three decades. The amino acid composition of the medium plays a key role in commercial scale biologics manufacturing, as amino acids constitute the building blocks of both endogenous and heterologous proteins, are involved in metabolic and non-metabolic pathways, and can act as main sources of nitrogen and carbon under certain conditions. As biomanufactured proteins become increasingly complex, the adoption of model-based approaches become ever more popular in complementing the challenging task of medium development. The extensively studied amino acid metabolism is exceptionally suitable for such model-driven analyses, and although still limited in practice, the development of these strategies is gaining attention, particularly in this domain. This paper provides a review of recent efforts. We first provide an overview of the widely adopted practice, and move on to describe the model-driven approaches employed for the improvement and optimization of the external amino acid supply in light of cellular amino acid demand. We conclude by proposing the likely prevalent direction the field is heading towards, providing a critical evaluation of the current state and the future challenges and considerations.
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Welke, Robert-William, Hannah Sabeth Sperber, Ronny Bergmann, Amit Koikkarah, Laura Menke, Christian Sieben, Detlev H. Krüger, Salvatore Chiantia, Andreas Herrmann, and Roland Schwarzer. "Characterization of Hantavirus N Protein Intracellular Dynamics and Localization." Viruses 14, no. 3 (February 23, 2022): 457. http://dx.doi.org/10.3390/v14030457.
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Hantaviruses are enveloped viruses that possess a tri-segmented, negative-sense RNA genome. The viral S-segment encodes the multifunctional nucleocapsid protein (N), which is involved in genome packaging, intracellular protein transport, immunoregulation, and several other crucial processes during hantavirus infection. In this study, we generated fluorescently tagged N protein constructs derived from Puumalavirus (PUUV), the dominant hantavirus species in Central, Northern, and Eastern Europe. We comprehensively characterized this protein in the rodent cell line CHO-K1, monitoring the dynamics of N protein complex formation and investigating co-localization with host proteins as well as the viral glycoproteins Gc and Gn. We observed formation of large, fibrillar PUUV N protein aggregates, rapidly coalescing from early punctate and spike-like assemblies. Moreover, we found significant spatial correlation of N with vimentin, actin, and P-bodies but not with microtubules. N constructs also co-localized with Gn and Gc albeit not as strongly as the glycoproteins associated with each other. Finally, we assessed oligomerization of N constructs, observing efficient and concentration-dependent multimerization, with complexes comprising more than 10 individual proteins.
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Sinegubova, Maria V., Nadezhda A. Orlova, Sergey V. Kovnir, Lutsia K. Dayanova, and Ivan I. Vorobiev. "High-level expression of the monomeric SARS-CoV-2 S protein RBD 320-537 in stably transfected CHO cells by the EEF1A1-based plasmid vector." PLOS ONE 16, no. 2 (February 2, 2021): e0242890. http://dx.doi.org/10.1371/journal.pone.0242890.
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The spike (S) protein is one of the three proteins forming the coronaviruses’ viral envelope. The S protein of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has a spatial structure similar to the S proteins of other mammalian coronaviruses, except for a unique receptor-binding domain (RBD), which is a significant inducer of host immune response. Recombinant SARS-CoV-2 RBD is widely used as a highly specific minimal antigen for serological tests. Correct exposure of antigenic determinants has a significant impact on the accuracy of such tests–the antigen has to be correctly folded, contain no potentially antigenic non-vertebrate glycans, and, preferably, should have a glycosylation pattern similar to the native S protein. Based on the previously developed p1.1 vector, containing the regulatory sequences of the Eukaryotic translation elongation factor 1 alpha gene (EEF1A1) from Chinese hamster, we created two expression constructs encoding SARS-CoV-2 RBD with C-terminal c-myc and polyhistidine tags. RBDv1 contained a native viral signal peptide, RBDv2 –human tPA signal peptide. We transfected a CHO DG44 cell line, selected stably transfected cells, and performed a few rounds of methotrexate-driven amplification of the genetic cassette in the genome. For the RBDv2 variant, a high-yield clonal producer cell line was obtained. We developed a simple purification scheme that consistently yielded up to 30 mg of RBD protein per liter of the simple shake flask cell culture. Purified proteins were analyzed by polyacrylamide gel electrophoresis in reducing and non-reducing conditions and gel filtration; for RBDv2 protein, the monomeric form content exceeded 90% for several series. Deglycosylation with PNGase F and mass spectrometry confirmed the presence of N-glycosylation. The antigen produced by the described technique is suitable for serological tests and subunit vaccine studies.
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Bestebroer, Jovanka, Miriam J. J. G. Poppelier, Laurien H. Ulfman, Peter J. Lenting, Cecile V. Denis, Kok P. M. van Kessel, Jos A. G. van Strijp, and Carla J. C. de Haas. "Staphylococcal superantigen-like 5 binds PSGL-1 and inhibits P-selectin–mediated neutrophil rolling." Blood 109, no. 7 (November 28, 2006): 2936–43. http://dx.doi.org/10.1182/blood-2006-06-015461.
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Abstract Staphylococcus aureus secretes several virulence factors interfering with host-cell functions. Staphylococcal superantigen-like (SSL) proteins are a family of 11 exotoxins with structural homology to superantigens but with generally unknown functions. Recently, we described that chemotaxis inhibitory protein of Staphylococcus aureus (CHIPS31-121), a potent inhibitor of C5a-induced responses, is structurally homologous to the C-terminal domain of SSL5. Here, we identify P-selectin glycoprotein ligand-1 (PSGL-1), involved in the initial rolling of neutrophils along the endothelium, as a target for SSL5. SSL5 specifically bound to Chinese hamster ovary cells stably expressing PSGL-1 (CHO–PSGL-1), which was dependent of sulfation and sialylation. Furthermore, SSL5 bound to PSGL-1/Ig fusion protein immobilized on a biosensor chip. SSL5 affected binding of soluble P-selectin/Fc chimera, the principle ligand of PSGL-1, to CHO–PSGL-1 cells and inhibited adhesion of neutrophils to immobilized P-selectin under static conditions. Under flow conditions SSL5 strongly decreased neutrophil rolling on immobilized P-selectin/Fc and activated human endothelial cells. In conclusion, SSL5 interferes with the interaction between PSGL-1 and P-selectin, suggesting that S aureus uses SSL5 to prevent neutrophil extravasation toward the site of infection. This makes SSL5 a potential lead for the development of new anti-inflammatory compounds for disorders characterized by excessive recruitment of leukocytes.
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Goulielmos, G., F. Gounari, S. Remington, S. Müller, M. Häner, U. Aebi, and S. D. Georgatos. "Filensin and phakinin form a novel type of beaded intermediate filaments and coassemble de novo in cultured cells." Journal of Cell Biology 132, no. 4 (February 15, 1996): 643–55. http://dx.doi.org/10.1083/jcb.132.4.643.
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The fiber cells of the eye lens possess a unique cytoskeletal system known as the "beaded-chain filaments" (BFs). BFs consist of filensin and phakinin, two recently characterized intermediate filament (IF) proteins. To examine the organization and the assembly of these heteropolymeric IFs, we have performed a series of in vitro polymerization studies and transfection experiments. Filaments assembled from purified filensin and phakinin exhibit the characteristic 19-21-nm periodicity seen in many types of IFs upon low angle rotary shadowing. However, quantitative mass-per-length (MPL) measurements indicate that filensin/phakinin filaments comprise two distinct and dissociable components: a core filament and a peripheral filament moiety. Consistent with a nonuniform organization, visualization of unfixed and unstained specimens by scanning transmission electron microscopy (STEM) reveals the the existence of a central filament which is decorated by regularly spaced 12-15-nm-diam beads. Our data suggest that the filamentous core is composed of phakinin, which exhibits a tendency to self-assemble into filament bundles, whereas the beads contain filensin/phakinin hetero-oligomers. Filensin and phakinin copolymerize and form filamentous structures when expressed transiently in cultured cells. Experiments in IF-free SW13 cells reveal that coassembly of the lens-specific proteins in vivo does not require a preexisting IF system. In epithelial MCF-7 cells de novo forming filaments appear to grow from distinct foci and organize as thick, fibrous laminae which line the plasma membrane and the nuclear envelope. However, filament assembly in CHO and SV40-transformed lens-epithelial cells (both of which are fibroblast-like) yields radial networks which codistribute with the endogenous vimentin IFs. These observations document that the filaments formed by lens-specific IF proteins are structurally distinct from ordinary cytoplasmic IFs. Furthermore, the results suggest that the spatial arrangement of filensin/phakinin filaments in vivo is subject to regulation by host-specific factors. These factors may involve cytoskeletal networks (e.g., vimentin IFs) and/or specific sites associated with the cellular membranes.
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Akhtar, Ayesha, Shivakumar Arumugam, and Shoaib Alam. "Evaluation of the Efficiency of Protein A Affinity Chromatography to Purify a Monoclonal Antibody for Cancer Treatment and its Purity Analysis." Current Chromatography 7, no. 2 (December 29, 2020): 121–33. http://dx.doi.org/10.2174/2213240607999201029204934.
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Background:: Protein A affinity chromatography is often employed as the most crucial purification step for monoclonal antibodies to achieve high yield with purity and throughput requirements. Introduction:: Protein A, also known as Staphylococcal protein A (SPA) is found in the cell wall of the bacteria staphylococcus aureus. It is one of the first discovered immunoglobulin binding molecules and has been extensively studied since the past few decades. The efficiency of Protein A affinity chromatography to purify a recombinant monoclonal antibody in a cell culture sample has been evaluated, which removes 99.0% of feed stream impurities. Materials and Method:: We have systematically evaluated the purification performance by using a battery of analytical methods SDS-PAGE (non-reduced and reduced sample), Cation Exchange Chromatography (CEX), Size-exclusion chromatography (SEC), and Reversed phased-Reduced Chromatography for a CHO-derived monoclonal antibody. Results and Discussion:: The analytical test was conducted to determine the impurity parameter, Host Cell Contaminating Proteins (HCP). It was evaluated to be 0.015ng/ml after the purification step; while initially, it was found to be 24.431ng/ml. Conclusion:: The tests showed a distinct decrease in the level of different impurities after the chromatography step. It can be concluded that Protein A chromatography is an efficient step in the purification of monoclonal antibodies.
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Lowenstein, D. H., D. A. Butler, D. Westaway, M. P. McKinley, S. J. DeArmond, and S. B. Prusiner. "Three hamster species with different scrapie incubation times and neuropathological features encode distinct prion proteins." Molecular and Cellular Biology 10, no. 3 (March 1990): 1153–63. http://dx.doi.org/10.1128/mcb.10.3.1153-1163.1990.
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Given the critical role of the prion protein (PrP) in the transmission and pathogenesis of experimental scrapie, we investigated the PrP gene and its protein products in three hamster species, Chinese (CHa), Armenian (AHa), and Syrian (SHa), each of which were found to have distinctive scrapie incubation times. Passaging studies demonstrated that the host species, and not the source of scrapie prions, determined the incubation time for each species, and histochemical studies of hamsters with clinical signs of scrapie revealed characteristic patterns of neuropathology. Northern (RNA) analysis showed the size of PrP mRNA from CHa, AHa, and SHa hamsters to be 2.5, 2.4, and 2.1 kilobases, respectively. Immunoblotting demonstrated that the PrP isoforms were of similar size (33 to 35 kilodaltons); however, the monoclonal antibody 13A5 raised against SHa PrP did not react with the CHa or AHa PrP molecules. Comparison of the three predicted amino acid sequences revealed that each is distinct. Furthermore, differences within the PrP open reading frame that uniquely distinguish the three hamster species are within a hydrophilic segment of 11 amino acids that includes polymorphisms linked to scrapie incubation times in inbred mice and an inherited prion disease of humans. Single polymorphisms in this region correlate with the presence or absence of amyloid plaques for a given hamster species or mouse inbred strain. Our findings demonstrate distinctive molecular, pathological, and clinical characteristics of scrapie in three related species and are consistent with the hypothesis that molecular properties of the host PrP play a pivotal role in determining the incubation time and neuropathological features of scrapie.
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Lemma, Solomon Mengistu, Cristiana Boi, and Ruben G. Carbonell. "Nonwoven Ion-Exchange Membranes with High Protein Binding Capacity for Bioseparations." Membranes 11, no. 3 (March 6, 2021): 181. http://dx.doi.org/10.3390/membranes11030181.
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This study presents the preparation and characterization of UV-grafted polybutylene terepthalate (PBT) ion exchange nonwoven membranes for chromatographic purification of biomolecules. The PBT nonwoven was functionalized with sulfonate and secondary amine for cation and anion exchange (CEX and AEX), respectively. The anion exchange membrane showed an equilibrium static binding capacity of 1300 mg BSA/g of membrane, while the cationic membranes achieved a maximum equilibrium binding capacity of over 700 mg hIgG/g of membrane. The CEX and AEX membranes resulted in dynamic binding capacities under flow conditions, with a residence time of 0.1 min, of 200 mg hIgG/mL of membrane and 55 mg BSA/mL of membrane, respectively. The selectivity of the PBT-CEX membranes was demonstrated by purifying antibodies and antibody fragments (hIgG and scFv) from CHO cell culture supernatants in a bind-an-elute mode. The purity of the eluted samples exceeded 97%, with good log removal values (LRV) for both host cell proteins (HCPs) and DNA. The PBT-AEX nonwoven membranes exhibited a DNA LRV of 2.6 from hIgG solutions in a flow-through mode with little loss of product. These results indicate that these membranes have significant potential for use in downstream purification of biologics.
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Beckett, Travis, Camilla Wang, Kei Kim, Valerie Odegard, Ken Mohler, and Catherine McMahan. "Small Modular ImmunoPharmaceutical (SMIPTM) Molecules Directed at the TCR Complex Block Acute Graft Versus Host Disease and Cause Minimal Cytokine Release In Vivo (145.30)." Journal of Immunology 184, no. 1_Supplement (April 1, 2010): 145.30. http://dx.doi.org/10.4049/jimmunol.184.supp.145.30.
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Abstract The T cell receptor complex (TCR) is a powerful therapeutic target for modulating autoimmunity and transplantation biology. A number of studies have shown that TCR/CD3-directed molecules are beneficial in mouse models of disease (e.g, acute graft vs host disease, aGVHD). However, both 145-2C11 (anti-CD3ϵ) and H57-597 (anti-TCRβ) are T cell mitogens and stimulate the activation of T cells and cytokine release in vitro and in vivo . In contrast to conventional antibodies, SMIP molecules are single chain binding proteins based on a scFv-CH2-CH3 format. Compared to their corresponding parent antibodies, SMIP molecules utilizing the 2C11 and H57 binding domains demonstrate a more robust down modulation of the TCR complex, enhanced efficacy in in vitro assays of T cell function, and significantly reduced levels of pro-inflammatory cytokines. Administration of these compounds in vivo results in significantly lower levels of cytokine release with no measurable changes in animal weight loss or adverse clinical symptoms despite dosage of 60 fold molar excess compared to the original full-length antibody. In addition, our SMIPs significantly abrogate donor cell engraftment in spleens of host animals in a parent into F1 model of aGVHD. These observations indicate that features in the SMIP format could generate novel anti-human CD3-directed therapeutics with greatly reduced levels of cytokine release in vivo.
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Ng, Wy Ching, Sarah L. Londrigan, Najla Nasr, Anthony L. Cunningham, Stuart Turville, Andrew G. Brooks, and Patrick C. Reading. "The C-type Lectin Langerin Functions as a Receptor for Attachment and Infectious Entry of Influenza A Virus." Journal of Virology 90, no. 1 (October 14, 2015): 206–21. http://dx.doi.org/10.1128/jvi.01447-15.
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ABSTRACTIt is well established that influenza A virus (IAV) attachment to and infection of epithelial cells is dependent on sialic acid (SIA) at the cell surface, although the specific receptors that mediate IAV entry have not been defined and multiple receptors may exist. Lec2 Chinese hamster ovary (CHO) cells are SIA deficient and resistant to IAV infection. Here we demonstrate that the expression of the C-type lectin receptor langerin in Lec2 cells (Lec2-Lg) rendered them permissive to IAV infection, as measured by replication of the viral genome, transcription of viral mRNA, and synthesis of viral proteins. Unlike SIA-dependent infection of parental CHO cells, IAV attachment and infection of Lec2-Lg cells was mediated via lectin-mediated recognition of mannose-rich glycans expressed by the viral hemagglutinin glycoprotein. Lec2 cells expressing endocytosis-defective langerin bound IAV efficiently but remained resistant to IAV infection, confirming that internalization via langerin was essential for infectious entry. Langerin-mediated infection of Lec2-Lg cells was pH and dynamin dependent, occurred via clathrin- and caveolin-mediated endocytic pathways, and utilized early (Rab5+) but not late (Rab7+) endosomes. This study is the first to demonstrate that langerin represents an authentic receptor that binds and internalizes IAV to facilitate infection. Moreover, it describes a unique experimental system to probe specific pathways and compartments involved in infectious entry following recognition of IAV by a single cell surface receptor.IMPORTANCEOn the surface of host cells, sialic acid (SIA) functions as the major attachment factor for influenza A viruses (IAV). However, few studies have identified specific transmembrane receptors that bind and internalize IAV to facilitate infection. Here we identify human langerin as a transmembrane glycoprotein that can act as an attachment factor and abone fideendocytic receptor for IAV infection. Expression of langerin by an SIA-deficient cell line resistant to IAV rendered cells permissive to infection. As langerin represented the sole receptor for IAV infection in this system, we have defined the pathways and compartments involved in infectious entry of IAV into cells following recognition by langerin.
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Peng, Tao, Manuel Ponce de Leon, Michael J. Novotny, Hongbin Jiang, John D. Lambris, Gary Dubin, Patricia G. Spear, Gary H. Cohen, and Roselyn J. Eisenberg. "Structural and Antigenic Analysis of a Truncated Form of the Herpes Simplex Virus Glycoprotein gH-gL Complex." Journal of Virology 72, no. 7 (July 1, 1998): 6092–103. http://dx.doi.org/10.1128/jvi.72.7.6092-6103.1998.
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ABSTRACT The herpes simplex virus (HSV) gH-gL complex is essential for virus infectivity and is a major antigen for the host immune system. The association of gH with gL is required for correct folding, cell surface trafficking, and membrane presentation of the complex. Previously, a mammalian cell line was constructed which produces a secreted form of gHt-gL complex lacking the transmembrane and cytoplasmic tail regions of gH. gHt-gL retains a conformation similar to that of its full-length counterpart in HSV-infected cells. Here, we examined the structural and antigenic properties of gHt-gL. We first determined its stoichiometry and carbohydrate composition. We found that the complex consists of one molecule each of gH and gL. The N-linked carbohydrate (N-CHO) site on gL and most of the N-CHO sites on gH are utilized, and both proteins also contain O-linked carbohydrate and sialic acid. These results suggest that the complex is processed to the mature form via the Golgi network prior to secretion. To determine the antigenically active sites of gH and gL, we mapped the epitopes of a panel of gH and gL monoclonal antibodies (MAbs), using a series of gH and gL C-terminal truncation variant proteins produced in transiently transfected mammalian cells. Sixteen gH MAbs (including H6 and 37S) reacted with the N-terminal portion of gH between amino acids 19 and 276. One of the gH MAbs, H12, reacted with the middle portion of gH (residues 476 to 678). Nine gL MAbs (including 8H4 and VIII 62) reacted with continuous epitopes within the C-terminal portion of gL, and this region was further mapped within amino acids 168 to 178 with overlapping synthetic peptides. Finally, plasmids expressing the gH and gL truncations were employed in cotransfection assays to define the minimal regions of both gH and gL required for complex formation and secretion. The first 323 amino acids of gH and the first 161 amino acids of gL can form a stable secreted hetero-oligomer with gL and gH792, respectively, while gH323-gL168 is the smallest secreted hetero-oligomer. The first 648 amino acids of gH are required for reactivity with MAbs LP11 and 53S, indicating that a complex of gH648-gL oligomerizes into the correct conformation. The data suggest that both antigenic activity and oligomeric structure require the amino-terminal portions of gH and gL.
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Huang, Zhiwei, Qingxuan Zhou, Pan Sun, Jing Yang, and Minliang Guo. "Two Agrobacterium tumefaciens CheW Proteins Are Incorporated into One Chemosensory Pathway with Different Efficiencies." Molecular Plant-Microbe Interactions® 31, no. 4 (April 2018): 460–70. http://dx.doi.org/10.1094/mpmi-10-17-0255-r.
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Agrobacterium tumefaciens is the agent that causes crown gall tumor disease on more than 140 species of dicotyledonous plants. Chemotaxis of A. tumefaciens toward the wound sites of the host plant is the first step to recognize the host. CheW is a coupling protein that bridges the histidine kinase CheA and the chemoreceptors to form the chemotaxis core signaling complex and plays a crucial role in the assembly and function of the large chemosensory array. Unlike all previously reported chemotaxis systems, A. tumefaciens has only one major che operon but two cheW homologs (atu2075 as cheW1 and atu2617 as cheW2) on unlinked loci. The in-frame deletion of either cheW gene significantly affects A. tumefaciens chemotaxis but does not abolish the chemotaxis, unless both cheW genes were deleted. The effect of cheW2 deletion on the chemotaxis is more severe than that of cheW1 deletion. Either CheW can interact with CheA and couple it to the cell poles. The promoter activity of cheW2 is always higher than that of cheW1 under all of the tested conditions. When two cheW genes were adjusted to the same expression level by using the identical promoter, the difference between the effects of two CheW proteins on the chemotaxis still existed. Therefore, we envision that both the different molecular ratio of two CheW proteins in cell and the different affinities of two CheW proteins with CheA and chemoreceptors result in the efficiency difference of two CheW proteins in functioning in the large chemosensory array.
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Wang, Fu-Zhang, Shaw M. Akula, Neelam Sharma-Walia, Ling Zeng, and Bala Chandran. "Human Herpesvirus 8 Envelope Glycoprotein B Mediates Cell Adhesion via Its RGD Sequence." Journal of Virology 77, no. 5 (March 1, 2003): 3131–47. http://dx.doi.org/10.1128/jvi.77.5.3131-3147.2003.
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ABSTRACT Human herpesvirus 8 (HHV-8) or Kaposi's sarcoma-associated herpesvirus, implicated in the pathogenesis of Kaposi's sarcoma, utilizes heparan sulfate-like molecules to bind the target cells via its envelope-associated glycoproteins gB and gpK8.1A. HHV-8-gB possesses the Arg-Gly-Asp (RGD) motif, the minimal peptide region of many proteins known to interact with subsets of host cell surface integrins. HHV-8 utilizes α3β1 integrin as one of the receptors for its entry into the target cells via its gB interaction and induces the activation of focal adhesion kinase (FAK) (S. M. Akula, N. P. Pramod, F.-Z. Wang, and B. Chandran, Cell 108:407-419, 2002). Since FAK activation is the first step in the outside-in signaling necessary for integrin-mediated cytoskeletal rearrangements, cell adhesions, motility, and proliferation, the ability of HHV-8-gB to mediate the target cell adhesion was examined. A truncated form of gB without the transmembrane and carboxyl domains (gBΔTM) and a gBΔTM mutant (gBΔTM-RGA) with a single amino acid mutation (RGD to RGA) were expressed in a baculovirus system and purified. Radiolabeled HHV-8-gBΔTM, gBΔTM-RGA, and ΔTMgpK8.1A proteins bound to the human foreskin fibroblasts (HFFs), human dermal microvascular endothelial (HMVEC-d) cells, human B (BJAB) cells, and Chinese hamster ovary (CHO-K1) cells with equal efficiency, which was blocked by preincubation of proteins with soluble heparin. Maxisorp plate-bound gBΔTM protein induced the adhesion of HFFs and HMVEC-d and monkey kidney epithelial (CV-1) cells in a dose-dependent manner. In contrast, the gBΔTM-RGA and ΔTMgpK8.1A proteins did not mediate adhesion. Adhesion mediated by gBΔTM was blocked by the preincubation of target cells with RGD-containing peptides or by the preincubation of plate-bound gBΔTM protein with rabbit antibodies against gB peptide containing the RGD sequence. In contrast, adhesion was not blocked by the preincubation of plate-bound gBΔTM protein with heparin, suggesting that the adhesion is mediated by the RGD amino acids of gB, which is independent of the heparin-binding domain of gB. Integrin-ligand interaction is dependent on divalent cations. Adhesion induced by the gBΔTM was blocked by EDTA, thus suggesting the role of integrins in the observed adhesions. Focal adhesion components such as FAK and paxillin were activated by the binding of gBΔTM protein to the target cells but not by gBΔTM-RGA protein binding. Inhibition of FAK phosphorylation by genistein blocked gBΔTM-induced FAK activation and cell adhesion. These findings suggest that HHV-8-gB could mediate cell adhesion via its RGD motif interaction with the cell surface integrin molecules and indicate the induction of cellular signaling pathways, which may play roles in the infection of target cells and in Kaposi's sarcoma pathogenesis.
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Slanina, Heiko, Sabrina Mündlein, Sabrina Hebling, and Alexandra Schubert-Unkmeir. "Role of Epidermal Growth Factor Receptor Signaling in the Interaction of Neisseria meningitidis with Endothelial Cells." Infection and Immunity 82, no. 3 (December 30, 2013): 1243–55. http://dx.doi.org/10.1128/iai.01346-13.
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ABSTRACTNeisseria meningitidis, the causative agent of meningitis and septicemia, attaches to and invades various cell types. Both steps induce and/or require tyrosine phosphorylation of host cell proteins. Here, we used a phospho array platform to identify active receptor tyrosine kinases (RTKs) and key signaling nodes inN. meningitidis-infected brain endothelial cells to decipher RTK-dependent signaling pathways necessary for bacterial uptake. We detected several activated RTKs, including the ErbB family receptors epidermal growth factor receptor (EGFR), ErbB2, and ErbB4. We found that pharmacological inhibition and genetic ablation of ErbB receptor tyrosine phosphorylation and expression resulted in decreased bacterial uptake and heterologous expression of EGFR, ErbB2, or ErbB4 in Chinese ovary hamster (CHO-K1) cells, which do not express of EGFR and ErbB4; the decrease caused a significant increase in meningococcal invasion. Activation of EGFR and ErbB4 was mediated by transactivation via the common ligand HB-EGF (heparin-binding EGF-like ligand), which was significantly elevated in infected cell culture supernatants. We furthermore determined thatN. meningitidisinduced phosphorylation of EGFR at Tyr845 independent of ligand binding, which required c-Src activation and was involved in mediating uptake ofN. meningitidisinto eukaryotic cells. Increased uptake was repressed by expression of EGFR Y845F, which harbored a point mutation in the kinase domain. In addition, activation of ErbB4 at its autophosphorylation site, Tyr1284, and phosphorylation of ErbB2 Thr686 were observed. Altogether, our results provide evidence that EGFR, ErbB2, and ErbB4 are activated in response toN. meningitidisinfection and shed new light on the role of ErbB signaling in meningococcal infection biology.
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Islam, Tuhidul, Amith D. Naik, Yasuhiro Hashimoto, Stefano Menegatti, and Ruben G. Carbonell. "Optimization of Sequence, Display, and Mode of Operation of IgG-Binding Peptide Ligands to Develop Robust, High-Capacity Affinity Adsorbents That Afford High IgG Product Quality." International Journal of Molecular Sciences 20, no. 1 (January 4, 2019): 161. http://dx.doi.org/10.3390/ijms20010161.
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This work presents the use of peptide ligand HWRGWV and its cognate sequences to develop affinity adsorbents that compete with Protein A in terms of binding capacity and quality of the eluted product. First, the peptide ligand was conjugated to crosslinked agarose resins (WorkBeads) at different densities and using different spacer arms. The optimization of ligand density and display resulted in values of static and dynamic binding capacity of 85 mg/mL and 65 mg/mL, respectively. A selected peptide-WorkBeads adsorbent was utilized for purifying Mabs from Chinese Hamster Ovary (CHO) cell culture supernatants. The peptide-WorkBeads adsorbent was found able to withstand sanitization with strong alkaline solutions (0.5 M NaOH). The purity of the eluted product was consistently higher than 95%, with logarithmic removal value (LRV) of 1.5 for host cell proteins (HCPs) and 4.0 for DNA. HCP clearance was significantly improved by adding a post-load washing step with either 0.1 M Tris HCl pH 9 or 1 M NaCl. The cognate peptide of HWRGWV, constructed by replacing arginine (R) with citrulline, further increased the HCP LRV to 2.15. The peptide-based adsorbent also showed a remarkable performance in terms of removal of Mab aggregates; unlike Protein A, in fact, HWRGWV was found to bind only monomeric IgG. Collectively, these results demonstrate the potential of peptide-based adsorbents as alternative to Protein A for the purification of therapeutic antibodies.
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Bozue, Joel, Krishna L. Moody, Christopher K. Cote, Bradley G. Stiles, Arthur M. Friedlander, Susan L. Welkos, and Martha L. Hale. "Bacillus anthracis Spores of the bclA Mutant Exhibit Increased Adherence to Epithelial Cells, Fibroblasts, and Endothelial Cells but Not to Macrophages." Infection and Immunity 75, no. 9 (July 2, 2007): 4498–505. http://dx.doi.org/10.1128/iai.00434-07.
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ABSTRACT Bacillus anthracis is the causative agent of anthrax, and the spore form of the bacterium represents the infectious particle introduced into a host. The spore is surrounded by an exosporium, a loose-fitting membrane composed of proteins and carbohydrates from which hair-like projections extend. These projections are composed mainly of BclA (Bacillus-collagen-like protein of B. anthracis). To date, exact roles of the exosporium structure and BclA protein remain undetermined. We examined differences in spore binding of wild-type Ames and a bclA mutant of B. anthracis to bronchial epithelial cells as well as to the following other epithelial cells: A549, CHO, and Caco-2 cells; the IMR-90 fibroblast line; and human umbilical vein vascular endothelium cells. The binding of wild-type Ames spores to bronchial epithelial cells appeared to be a dose-dependent, receptor-ligand-mediated event. There were similar findings for the bclA mutant, with an additional nonspecific binding component likely leading to significantly more adherence to all nonprofessional phagocytic cell types. In contrast, we detected no difference in adherence and uptake of spores by macrophages for either the wild-type Ames or the bclA mutant strain. These results suggest that one potential role of the BclA fibers may be to inhibit nonspecific interactions between B. anthracis spores with nonprofessional phagocytic cells and thus direct the spores towards uptake by macrophages during initiation of infection in mammals.
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Tanaka, Atsushi, Kiyomasa Oka, Keiji Tanaka, Atsushi Jinno, Sandra K. Ruscetti, and Kazushige Kai. "The Entire Nucleotide Sequence of Friend-Related and Paralysis-Inducing PVC-441 Murine Leukemia Virus (MuLV) and Its Comparison with Those of PVC-211 MuLV and Friend MuLV." Journal of Virology 72, no. 4 (April 1, 1998): 3423–26. http://dx.doi.org/10.1128/jvi.72.4.3423-3426.1998.
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ABSTRACT PVC-441 murine leukemia virus (MuLV) is a member of the PVC group of Friend MuLV (F-MuLV)-derived neuropathogenic retroviruses. In order to determine the molecular basis for the difference in neuropathogenicity between PVC-441 and the previously characterized PVC-211 MuLVs, the entire nucleotide sequence of PVC-441 MuLV was determined and compared with those of PVC-211 and F-MuLV. The results suggest that PVC-441 and PVC-211 MuLVs were formed as a result of random mutations of F-MuLV and developed differently. The distinct pathogenicities of PVC-441 and PVC-211 MuLVs were maintained in the viruses regenerated from their molecular clones, and the sequences responsible for the pathological differences observed can be localized to the env gene. The amino acid sequence of PVC-441 deduced from its nucleotide sequence revealed a number of differences from PVC-211, the most striking of which was a difference at position 129 of the SU proteins in the two viruses. Host range studies with a brain capillary endothelial cell line (RTEC-6) and Chinese hamster ovary cells (CHO-K1) revealed that PVC-441, like PVC-211, could infect these cells but its efficiency of infection was lower than that of PVC-211. These results may account for the difference in neuropathogenicity between PVC-441 and PVC-211.