70 results on '"I. Bally"'
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2. Identifying vigour controlling rootstocks for mango
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C. Wright, I. Bally, R. Kolala, A. Mizani, P. T. Ibell, and C. Maddox
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Canopy ,Horticulture ,Breeding program ,Tropical trees ,Sowing ,Mangifera ,Cultivar ,Orchard ,Biology ,Rootstock - Abstract
Vigour reduction in many tree crops is an essential element of highly productive, high density systems that is often achieved through rootstocks. Mangoes are large vigorous tropical trees that are traditionally grown at low density as suitable vigour reducing technologies are not commercially available. The aim of this work was to identify rootstock cultivars for mango that reduced scion vigour while maintaining or boosting yields. Ninety rootstocks are being evaluated for their ability to reduce vigour in two Australian mango scion cultivars from the National Mango Breeding Program (NMBP); ‘NMBP-1243’ and ‘NMBP-4069’. The evaluated rootstocks were sourced from a wide genetic range within Mangifera indica and related Mangifera spp. from the Australian National Mango Gene Bank and the Australian Mango Breeding Program. Rootstock-scion combinations were field planted at Walkamin, Queensland, Australia over three years, from May 2014 in randomised incomplete blocks. Tree height, canopy depth, canopy length (along the row), canopy width (across the row), rootstock trunk diameter (10 cm above the ground and 10 cm below the graft point) and scion diameter (10 cm above the graft) were measured every six months as indicators of tree growth and vigour. This is a report on the progress of 29 rootstocks from the May 2014 planting. There was a significant (p
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- 2018
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3. The effects of alternative training and planting systems on light relations in mango (Mangifera indica) orchards in Far North Queensland
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J. D. Wilkie, I. Bally, C. Wright, R. Kolala, and P. T. Ibell
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0106 biological sciences ,Canopy ,Crop yield ,Biennial bearing ,Sowing ,04 agricultural and veterinary sciences ,Horticulture ,01 natural sciences ,Agronomy ,040103 agronomy & agriculture ,0401 agriculture, forestry, and fisheries ,Habit (biology) ,Mangifera ,Interception ,Orchard ,010606 plant biology & botany ,Mathematics - Abstract
Part of a project to transform subtropical/tropical tree productivity in Queensland is a study of light relations in mango (Mangifera indica) orchards in Far North Queensland. A study of the baseline relationship between light interception, canopy volume and yield in ‘Kensington Pride’ trees found that as canopy volume increased, light interception reached a maximum between 61 and 68%. The relationship between light interception and tree yield (t ha-1) varied over two years highlighting the biennial bearing habit of mango. An associated ongoing study is looking at the effects on light interception, canopy volume and yield for three mango cultivars, resulting from various planting density and tree training systems. The planting systems being studied include three planting densities: low density (208 trees ha-1, 8×6 m), medium density (450 tree ha-1, 6×4 m) and high density (1250 trees ha-1, 4×2 m) and two training systems (conventional and single leader) in three commercial mango cultivars (‘Keitt, CalypsoTM’ and ‘NMBP 1243’). The first year’s results have indicated that density and cultivar had significant effects on light interception in 1.5-year-old trees. ‘Keitt’ canopies had higher light interception than ‘CalypsoTM’ or ‘NMBP1243’, while high density plantings intercepted significantly more light. Training system also increased light interception from 1.38% in the low-density conventional planting to 9.5% in the single leader, high-density planting although this increase was not significant. There were also significant positive relationships between light interception and canopy volume (m3 ha-1). When both experiments are considered the results suggest the total light interception in 1.5-year-old, high-density trees (9.2%) was similar to the total light interception of 4-year-old trees (11.0%) in the baseline study. These results highlight the benefits of high density plantings in increasing total orchard light interception earlier than in conventional low-density mango orchards. In the future, the relationships between yield, canopy volume, light interception and training systems will be further examined in the planting systems experiment. © 2018 International Society for Horticultural Science.
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- 2018
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4. Synthesis ofN-[1-13C]caproyl-N′-phenylthiourea
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Catalina Mihaela Barna, C. Postolache, Alexandru T. Balaban, Corina Anca Simion, Ileana Chirtoc, Calin Deleanu, and I. Bally
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Chemistry ,Organic Chemistry ,chemistry.chemical_element ,Barium ,Manganese ,Biochemistry ,Chloride ,Analytical Chemistry ,Phenacemide ,chemistry.chemical_compound ,Drug Discovery ,medicine ,Organic chemistry ,Carbonate ,Radiology, Nuclear Medicine and imaging ,Barium carbonate ,Spectroscopy ,medicine.drug - Abstract
An optimal synthesis of N-[1-13C]caproyl-N′-phenylthiourea with isotopic enrichment 82% is described, starting from barium [13C]carbonate, using five synthetic steps. Yields were 95% relative to caproyl chloride and 46% relative to barium carbonate. Oxidation of the title compound with manganese dioxide yields the corresponding ureide. Structural similarities with anticonvulsants such as phenacemide make N-caproyl-N′-phenylthiourea an interesting model compound. Copyright © 2004 John Wiley & Sons, Ltd.
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- 2004
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5. Effect of nitrogen on the skin colour and other quality attributes of ripe ‘Kensington Pride’ mango (Mangifera indicaL.) fruit
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R. J. Holmes, Robyn McConchie, H. Nguyen, B. Stubbings, P. Hofman, and I. Bally
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Production area ,Tropics ,chemistry.chemical_element ,Horticulture ,Biology ,Skin colour ,Nitrogen ,chemistry ,Botany ,Genetics ,Mangifera ,Orchard ,Panicle ,Green colour - Abstract
Near-ripe ‘Kensington Pride’ mango (Mangifera indica L.) fruit with green skin colour generally return lower wholesale and retail prices. Pre-harvest management, especially nitrogen (N) nutrition, appears to be a major causal factor. To obtain an understanding of the extent of the problem in the Burdekin district (dry tropics; the major production area in Australia), green mature ‘Kensington Pride’ mango fruit were harvested from ten orchards and ripened at 20 ± 0.5 O C. Of these orchards, 70% produced fruit with more than 25% of the skin surface area green when ripe. The following year, the effect of N application on skin colour and other quality attributes was investigated on three orchards, one with a high green (HG) skin problem and two with a low green (LG) skin problem. N was applied at pre-flowering and at panicle emergence at the rate of 0,75,150,300 g per tree (soil applied) or 50 g per tree as foliar N for the HG orchard, and 0,150,300,450 g per tree (soil applied) or 50 g per tree (foliar) for the LG orchards. In all orchards the proportion of green colour on the ripe fruit was significantly (P
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- 2004
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6. Baculovirus-mediated expression of truncated modular fragments from the catalytic region of human complement serine protease C1s. Evidence for the involvement of both complement control protein modules in the recognition of the C4 protein substrate
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V, Rossi, I, Bally, N M, Thielens, A F, Esser, and G J, Arlaud
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Complement C1s ,Complement C4 ,Spodoptera ,Catalysis ,Peptide Fragments ,Recombinant Proteins ,Substrate Specificity ,Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization ,Animals ,Humans ,Electrophoresis, Polyacrylamide Gel ,Cloning, Molecular ,Baculoviridae ,Chromatography, Liquid - Abstract
C1s is the modular serine protease responsible for cleavage of C4 and C2, the protein substrates of the first component of complement. Its catalytic region (gamma-B) comprises two complement control protein (CCP) modules, a short activation peptide (ap), and a serine protease domain (SP). A baculovirus-mediated expression system was used to produce recombinant truncated fragments from this region, deleted either from the first CCP module (CCP2-ap-SP) or from both CCP modules (ap-SP). The aglycosylated fragment CCP2-ap-SPag was also expressed by using tunicamycin. The fragments were produced at yields of 0.6-3 mg/liter of culture, isolated, and characterized chemically and then tested functionally by comparison with intact C1s and its proteolytic gamma-B fragment. All recombinant fragments were expressed in a proenzyme form and cleaved by C1r to generate active enzymes expressing esterolytic activity and reactivity toward C1 inhibitor comparable to those of intact C1s. Likewise, the activated fragments gamma-B, CCP2-ap-SP, and ap-SP retained C1s ability to cleave C2 in the fluid phase. In contrast, whereas fragment gamma-B cleaved C4 as efficiently as C1s, the C4-cleaving activity of CCP2-ap-SP was greatly reduced (about 70-fold) and that of ap-SP was abolished. It is concluded that C4 cleavage involves substrate recognition sites located in both CCP modules of C1s, whereas C2 cleavage is affected mainly by the serine protease domain. Evidence is also provided that the carbohydrate moiety linked to the second CCP module of C1s has no significant effect on catalytic activity.
- Published
- 1998
7. X-ray structure of the catalytic domain of human complement protease C1s: a trypsin-like domain modulated by aCCPmodule handle
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J.C. Fontecilla, V. Rossi, Gérard J. Arlaud, Christine Gaboriaud, and I. Bally
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Crystallography ,Protease ,Structural Biology ,Chemistry ,medicine.medical_treatment ,medicine ,Protein engineering ,Trypsin ,medicine.drug ,Catalysis ,Enzyme catalysis ,Domain (software engineering) ,Complement (complexity) - Published
- 2000
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8. Functional topology of the catalytic region of human C1s: Insights into the molecular determinants of C1s specificity
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Gérard J. Arlaud, V. Rossi, Nicole M. Thielens, and I. Bally
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Pharmacology ,Chemistry ,Topology ,Topology (chemistry) - Published
- 2000
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9. X-ray structure of the human C1s catalytic domain: A protease with a CCP module handle
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V. Rossi, J.C. Fontecilla, Gérard J. Arlaud, C. Gaboriaud, and I. Bally
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Pharmacology ,Crystallography ,Protease ,Materials science ,medicine.medical_treatment ,Structure (category theory) ,medicine ,X-ray ,Domain (software engineering) ,Catalysis - Published
- 2000
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10. Molecular structure and tautomerism of the 1,3,2-benzodioxaarsole ether of tropolone
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Vladimir I. Minkin, I. Bally, V. P. Metlushenko, Alexandru T. Balaban, N. G. Furmanova, and L. P. Olekhnovich
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Chemistry ,Organic Chemistry ,Ether ,Activation energy ,Biochemistry ,Tautomer ,Tropolone ,symbols.namesake ,Crystallography ,chemistry.chemical_compound ,Trigonal bipyramidal molecular geometry ,Computational chemistry ,Intramolecular force ,Drug Discovery ,symbols ,Molecule ,Van der Waals radius - Abstract
The molecular structure of 2′-tropolonyl-1,3,2-benzodioxaarsole (A) was determined by X-ray analysis substantiating the previous structure assignment as II, and refining it. The molecular structure evidences three short O-As bonds and a longer fourth O-As bond, which however is much shorter than the sum of Van der Waals radii. The incipient intramolecular coordination between the CO oxygen and the As atom requires an unusual configuration (distorted trigonal bipyramid) around the As atom, leading to a conformation which is similar to the structure of the transition state for Berry pseudorotations. This explains the 13C NM R spectra of II which indicates a rapid reversible migration of the 1,3,2-benzodioxaarsole moiety from one tropolone oxygen to another. Since the 13C NMR spectra show no broadening at − 70°, the upper limit for the free energy of activation is Δ−≠ < 6.5kcal/mole.
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- 1981
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11. Dipole moments of boron chelates with tropolone and 1,3-diketone derivatives
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A.I. Usachev, V.I. Minkin, I. Bally, and Alexandru T. Balaban
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Diketone ,Dibenzoylmethane ,Acetylacetone ,Organic Chemistry ,chemistry.chemical_element ,Diphenylborinic acid ,Photochemistry ,Biochemistry ,Tropolone ,chemistry.chemical_compound ,Dipole ,chemistry ,Drug Discovery ,Polymer chemistry ,Chelation ,Boron - Abstract
Dipole moments were determined for the chelates 2-6 of benzodioxaborole or diphenylborinic acid with tropolone derivatives or with 1,3-diketones (acetylacetone, dibenzoylmethane). Correlations with the structure were attempted.
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- 1977
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12. Synthesis of14C-labelled isotope-isomeric alkanes. I n-heptane-1-14C and -2-14C
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Maria Biltz, I. Bally, Elieabeta Ciornei, Eugenia Gǎrd, and Alexandru T. Balaban
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Heptane ,Isotope ,Chemistry ,Organic Chemistry ,General Medicine ,Grignard reagent ,Biochemistry ,Chloride ,Analytical Chemistry ,chemistry.chemical_compound ,Bromide ,Drug Discovery ,medicine ,Organic chemistry ,Radiology, Nuclear Medicine and imaging ,Spectroscopy ,medicine.drug - Abstract
The synthesis of n-heptane-1-14C is described. starting from 14CH3I via (14CH3) 2Cd and caproyl chloride; for obtaining n-heptane-2-14C, n-pentyl bromide is converted into the Grignard reagent, carbonated with 14CO2, and the resulted coproic acid is converted into its chloride and treated with dimethyloadmium. In both cases the labelled n-heptan-2-one is finally reduced to labelled n-heptane by the Kishner-Wolff method.
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- 1975
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13. Preparation of 2-(p-biphenylyl)-5-aryloxazoles by friedel-crafts reaction of azlactones with aromatics
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Alexandru T. Balaban, Ludmila Bîrlădeanu, Ecaterina Ciorănescu, P.T. Frangopol, Maria Băcescu, and I. Bally
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chemistry.chemical_compound ,Absorption spectroscopy ,chemistry ,Aryl ,Organic Chemistry ,Drug Discovery ,Uv absorption ,Photochemistry ,Biochemistry ,Friedel–Crafts reaction ,Spectral line - Abstract
By means of the AlCl 3 -catalysed reaction between p -phenylhippuric acid azlactone and aromatic hydrocarbons, p -phenylbenzoylaminomethyl aryl ketones were obtained in high yields; these ketones were subsequently dehydrated to 2-( p -biphenylyl)-5-aryloxazoles. By comparing the UV absorption spectra of 2,5-diaryloxazoles with those of p -diarylbenzenes correlations are established and an explanation for the six spectral types is provided.
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- 1963
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14. Sur la corrélation entre l’activité du catalyseur de plateformage et certaines propriétés physiques
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I. V. Nicolescu, Al. Popescu, I. Bally, A. Papia, and C. Fordea
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Biochemistry - Abstract
Par l’etude roentgenographique d’un catalyseur de plate-formage actif et thermiquement desactive, ainsi que par l’etude de la conductivite electrique et de l’energie d’activation de la conductivite electrique, on a obtenu les resultats suivants :— On a montre que l’alumine active utilisee comme support est l’alumine eta et non pas l’alumine gamma.— La diminution de l’activite catalytique, par calcination ou par regeneration a hautes temperatures, est le resultat d’une diminution de degre de dispersion du platine, ainsi que d’une deformation a l’echelle atomique du reseau cristallin du platine, avec un deplacement carre moyen des atomes, d’environ 0,45 A.— La conductivite electrique specifique du catalyseur actif dans l’air et dans l’hydrogene, dans l’intervalle de temperature de 429-500 °C, est superieure a celle du catalyseur desactive thermiquement.— L’energie d’activation de la conductivite electrique est plus petite pour le catalyseur actif par rapport au catalyseur desactive.Ces resultats indiquent l’existence d’une correlation entre certaines proprietes physiques du catalyseur etudie et son activite catalytique, clans le processus de plateformage.
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- 1960
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15. Electronic absorption spectra of spiroborates and of 1,3,2-dioxaborinium salts
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Alexandru T. Balaban, C.N. Renţea, M. Paraschiv, A. Barabás, I. Bally, and A. Arsene
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Absorption spectroscopy ,Chemistry ,Stereochemistry ,General Engineering ,Physical chemistry ,Spectral line - Abstract
The preparation and spectra of tropophenylene spiroborates (III), 1,3-diketonato-benzodioxaborole (XVII), 1,3-diketonato-diphenylborine (XVIII), bis-1,3-diketonato-boronium salts (XIX) and 1,3,2-benzodioxaborinium salts (XX) are discussed. Interconversions between the last three classes of compounds are reviewed.
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- 1967
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16. Preparation and spectra of para-substituted 2,5-diphenyloxazoles
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Alexandru T. Balaban, I. Bally, M. Mocanu, Zeno Simon, L. Bîrlǎdeanu, and P.T. Frangopol
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Absorption spectroscopy ,Organic Chemistry ,Hippuric acid ,Anisole ,Biochemistry ,Medicinal chemistry ,Acceptor ,Toluene ,chemistry.chemical_compound ,chemistry ,Drug Discovery ,Bathochromic shift ,Nitro ,Organic chemistry ,Benzene - Abstract
2,5 Diaryloxazoles, with the 2-, and 5-aryl groups, substituted in the para position by halo, methyl, methoxy or nitro groups were obtained by the Friedel-Crafts reaction of p -substituted hippuric acid azlactones with benzene, or the hippuric acid azlactone with halobenzenes, toluene, and anisole, followed by treatment with phosphorus oxychloride. Grignard and Ullmann reactions of p -halo-substituted 2,5-diaryloxazoles are described. Absorption spectra of these compounds are discussed and the pronounced bathochromic effect of coupled donor and acceptor groups in both para positions is accounted for by a simple MO treatment.
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- 1963
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17. Proton magnetic resonance spectra of chelated boronium and beryllium bis-(1,3-diketonates)
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A. Trestianu, H. Niculescu-Majewska, I. Bally, Alexandru T. Balaban, and A. Barabás
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Silicon ,Dibenzoylmethane ,Acetylacetone ,Organic Chemistry ,Inorganic chemistry ,chemistry.chemical_element ,Biochemistry ,Spectral line ,NMR spectra database ,Metal ,Crystallography ,chemistry.chemical_compound ,chemistry ,visual_art ,Drug Discovery ,visual_art.visual_art_medium ,Chelation ,Beryllium - Abstract
PMR spectra of chelated 2-(β-diketonato)-1,3,2-benzodioxaboroles (I), β-diketonato-diphenyl-borinates (II), 1,3,2-dioxaborinium salts (III), bis-(β-diketonato)-boronium salts (IV) and beryllium β-diketonates (V) are described and discussed. The β-diketones employed were acetylacetone (a), benzoylacetone (b), dibenzoylmethane (c), 3-methylacetylacetone (d) and 3-phenylacetylacetone (e). Peaks due to methyl or methine protons are deshielded additively by phenyl groups, and correlations are made with electronic and geometric factors. The absence of ring current in chelates I, II, IV and V and the similarity of their NMR spectra with those of silicon or metal 1,3-diketone chelates makes it probable that there is no ring current in the latter compounds.
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- 1968
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18. Isotopic exchange of active methyl hydrogens. II. Deuteration of diphenylmethylpyrylium and methyltropylium salts
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I. Bally, A. Arsene, Eugenia Gǎrd, A. Vasilescu, and Alexandru T. Balaban
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Organic Chemistry ,Oxide ,General Medicine ,Biochemistry ,Analytical Chemistry ,chemistry.chemical_compound ,Acetic acid ,chemistry ,Deuterium ,Group (periodic table) ,Drug Discovery ,Organic chemistry ,Radiology, Nuclear Medicine and imaging ,Spectroscopy - Abstract
Methyl groups of 2, 6-diphenyl-4-methylpyrylium, 2, 4-diphenyl-6-methylpyrylium and methyltropylium salts were deuterated with deuterim oxide and/or acetic acid. The dedeuteration rated of the two diphenylmethylpyrylium salts are contrary to expectations, the 4-methyl group reacting faster than the 2-methyl groups at 50° in acetic acid.
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- 1965
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19. 1,3,2-Dioxaborinium (boroxaropyrylium) salts and their decomposition to bis - 1,3-diketonato-boronium salts
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E. Romas, Alexandru T. Balaban, A. Barabás, M. Paraschiv, I. Bally, and A. Arsene
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Chemistry ,Organic Chemistry ,Drug Discovery ,Polymer chemistry ,Biochemistry ,Decomposition - Published
- 1965
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20. Heterocyclic organoboron compounds—XVI
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E. Ciornei, Alexandru T. Balaban, I. Bally, and A. Vasilescu
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NMR spectra database ,Organoboron compounds ,Chemistry ,Organic Chemistry ,Drug Discovery ,Organic chemistry ,Chelation ,Diphenylborinic acid ,Biochemistry - Abstract
The reaction of β-aminoenones 4 with diphenylborinic acid or 2-alkoxy-1,3,2-benzodioxaborole affords chelated compounds whose UV, IR and NMR spectra are discussed.
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- 1973
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21. ChemInform Abstract: SYNTHESIS OF CARBON-14-LABELED ISOTOPE-ISOMERIC ALKANES. III. THE 1-, 2-, AND D 7-CARBON-14-LABELED N-TETRADECANES
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N. Negoita, I. Bally, Alexandru T. Balaban, and E. Gard
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Isotope ,Chemistry ,Radiochemistry ,Carbon-14 ,General Medicine - Published
- 1979
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22. ChemInform Abstract: HETEROCYCLIC ORGANOBORON COMPOUNDS PART 16, CHELATED COMPOUNDS WITH ALPHA,BETA-UNSATURATED BETA-AMINOKETONES
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E. Ciornei, I. Bally, A. Vasilescu, and Alexandru T. Balaban
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Organoboron compounds ,Stereochemistry ,Chemistry ,Alpha (ethology) ,Chelation ,General Medicine ,Beta (finance) - Published
- 1974
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23. ChemInform Abstract: HETEROCYCLISCHE ORGANO-BORVERBINDUNGEN 14. MITT. BOR-CHELATE MIT BIS-(1,3-DIKETONEN)
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I. Bally and A. T. Balaban
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Chemistry ,General Medicine ,Medicinal chemistry - Published
- 1971
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24. ChemInform Abstract: HETEROCYCLISCHE ORGANO-BORVERBINDUNGEN 12. MITT. 2,4,6-TRISUBSTITUIERTE 1,3,2-DIOXABORINIUMSALZE
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Alexandru T. Balaban, E. Romas, M. Paraschiv, A. Arsene, A. Barabás, I. Bally, and M. Roman
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Chemistry ,General Medicine ,Medicinal chemistry - Published
- 1970
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25. Anti-SARS-CoV-2 serology based on ancestral RBD antigens does not correlate with the presence of neutralizing antibodies against Omicron variants.
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Dépéry L, Bally I, Amen A, Némoz B, Buisson M, Grossi L, Truffot A, Germi R, Guilligay D, Veloso M, Vilotitch A, Epaulard O, Morand P, Weissenhorn W, Poignard P, and Lupo J
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- Humans, Neutralization Tests, Male, Female, COVID-19 Serological Testing methods, Middle Aged, Immunoglobulin G blood, Immunoglobulin G immunology, Adult, Antigens, Viral immunology, Aged, Enzyme-Linked Immunosorbent Assay methods, Antibodies, Neutralizing immunology, Antibodies, Neutralizing blood, SARS-CoV-2 immunology, SARS-CoV-2 genetics, Antibodies, Viral blood, Antibodies, Viral immunology, COVID-19 immunology, COVID-19 diagnosis, COVID-19 virology, Spike Glycoprotein, Coronavirus immunology
- Abstract
Neutralizing antibody titers and binding antibody levels are considered correlates of protection against severe SARS-CoV-2 infection. The clinical utility of serology should be reevaluated in light of the emergence of escape variants, as commercial antibody-binding assays have not been adapted to the virus' antigenic evolution. We compared anti-SARS-CoV-2 antibody titers in four quantitative serological tests based on variable ancestral spike antigens (three in-house ELISAs and the prototype VIDAS SARS-CoV-2 IgG QUANT assay) and neutralization assays against the pseudotyped Wuhan, BA.2, BA.4/5, BQ.1.1, and XBB.1.1 viruses in a cohort of 100 patients infected in 2020 or during the Omicron waves. Binding antibody levels correlated well with neutralizing antibody titers for Wuhan, BA.2, and BA.4/5, but the association decreased for BQ.1.1 and XBB.1 (for the VIDAS assay, Spearman's correlation was 0.82 [95% CI 0.74-0.88] and 0.61 [0.46-0.72] for BA.2 and XBB.1, respectively). In 15% of patients with no neutralizing antibodies against XBB.1, the VIDAS assay still yielded binding antibody levels ranging from 74 to 7,652 binding antibody units/mL. Using an adjusted threshold based on receiver operating characteristic (ROC) curve analysis, the specificity of neutralizing antibody detection increased from 0.15 (95% CI 0.02-0.45) and 0.17 (0.04-0.41) to 0.92 (0.64-1.00) and 0.83 (0.59-0.96) against BQ.1.1 and XBB.1, respectively. Serological tests based on receptor-binding domain antigens from the ancestral virus fail to predict neutralizing activity against the latest circulating Omicron variants. Adapting serological tests may improve their clinical utility in immunocompromised patients., Importance: Anti-SARS-CoV-2 serology was developed in 2020 in response to the COVID-19 pandemic to diagnose SARS-CoV-2 infection and monitor an individual's immunity following natural infection or vaccination. Given the relationship between neutralizing antibody titers and protection against severe infection, many studies have evaluated the correlation between serology tests and neutralization assays in the pre-Omicron era. An important potential clinical use of serology, which explores binding antibodies, is estimating an individual's level of protection against new infection, particularly in immunosuppressed individuals and those at risk of severe COVID. However, in the Omicron era, as new viruses evade the immunity induced by previous infections and vaccination, the correlation between binding antibody levels determined by serological assays developed from ancestral antigens and neutralizing antibody titers against new viruses should be re-examined in order to determine whether these assays should be optimized by adapting antigens to the circulating SARS-CoV-2 strains., Competing Interests: The virology laboratory (CHU Grenoble Alpes) received grants from bioMérieux to carry out the study.
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- 2025
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26. Target-agnostic identification of human antibodies to Plasmodium falciparum sexual forms reveals cross stage recognition of glutamate-rich repeats.
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Amen A, Yoo R, Fabra-García A, Bolscher J, Stone WJR, Bally I, Dergan-Dylon S, Kucharska I, de Jong RM, de Bruijni M, Bousema T, Richter King C, MacGill RS, Sauerwein RW, Julien JP, Poignard P, and Jore MM
- Abstract
Circulating sexual stages of Plasmodium falciparum (Pf) can be transmitted from humans to mosquitoes, thereby furthering the spread of malaria in the population. It is well established that antibodies (Abs) can efficiently block parasite transmission. In search for naturally acquired Ab targets on sexual stages, we established an efficient method for target-agnostic single B cell activation followed by high-throughput selection of human monoclonal antibodies (mAbs) reactive to sexual stages of Pf in the form of gamete and gametocyte extract. We isolated mAbs reactive against a range of Pf proteins including well-established targets Pfs48/45 and Pfs230. One mAb, B1E11K, was cross-reactive to various proteins containing glutamate-rich repetitive elements expressed at different stages of the parasite life cycle. A crystal structure of two B1E11K Fab domains in complex with its main antigen, RESA, expressed on asexual blood stages, showed binding of B1E11K to a repeating epitope motif in a head-to-head conformation engaging in affinity-matured homotypic interactions. Thus, this mode of recognition of Pf proteins, previously described only for PfCSP, extends to other repeats expressed across various stages. The findings augment our understanding of immune-pathogen interactions to repeating elements of the Plasmodium parasite proteome and underscore the potential of the novel mAb identification method used to provide new insights into the natural humoral immune response against Pf ., Impact Statement: A naturally acquired human monoclonal antibody recognizes proteins expressed at different stages of the Plasmodium falciparum lifecycle through affinity-matured homotypic interactions with glutamate-rich repeats.
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- 2024
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27. Revisiting the interaction between complement lectin pathway protease MASP-2 and SARS-CoV-2 nucleoprotein.
- Author
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Bally I, Drumont G, Rossi V, Guseva S, Botova M, Reiser JB, Thépaut M, Dergan Dylon S, Dumestre-Pérard C, Gaboriaud C, Fieschi F, Blackledge M, Poignard P, and Thielens NM
- Subjects
- Humans, Protein Binding, Coronavirus Nucleocapsid Proteins immunology, Coronavirus Nucleocapsid Proteins metabolism, Complement Activation immunology, Mannose-Binding Lectin metabolism, Mannose-Binding Lectin immunology, Phosphoproteins, Mannose-Binding Protein-Associated Serine Proteases metabolism, Mannose-Binding Protein-Associated Serine Proteases immunology, SARS-CoV-2 immunology, Complement Pathway, Mannose-Binding Lectin immunology, COVID-19 immunology, COVID-19 virology
- Abstract
Complement activation is considered to contribute to the pathogenesis of severe SARS-CoV-2 infection, mainly by generating potent immune effector mechanisms including a strong inflammatory response. Involvement of the lectin complement pathway, a major actor of the innate immune anti-viral defense, has been reported previously. It is initiated by recognition of the viral surface Spike glycoprotein by mannose-binding lectin (MBL), which induces activation of the MBL-associated protease MASP-2 and triggers the proteolytic complement cascade. A role for the viral nucleoprotein (N) has also been reported, through binding to MASP-2, leading to protease overactivation and potentiation of the lectin pathway. In the present study, we reinvestigated the interactions of the SARS-CoV-2 N protein, produced either in bacteria or secreted by mammalian cells, with full-length MASP-2 or its catalytic domain, in either active or proenzyme form. We could not confirm the interaction of the N protein with the catalytic domain of MASP-2 but observed N protein binding to proenzyme MASP-2. We did not find a role of the N protein in MBL-mediated activation of the lectin pathway. Finally, we showed that incubation of the N protein with MASP-2 results in proteolysis of the viral protein, an observation that requires further investigation to understand a potential functional significance in infected patients., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Bally, Drumont, Rossi, Guseva, Botova, Reiser, Thépaut, Dergan Dylon, Dumestre-Pérard, Gaboriaud, Fieschi, Blackledge, Poignard and Thielens.)
- Published
- 2024
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28. Tixagevimab-cilgavimab (AZD7442) for the treatment of patients hospitalized with COVID-19 (DisCoVeRy): A phase 3, randomized, double-blind, placebo-controlled trial.
- Author
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Hites M, Massonnaud CR, Lapique EL, Belhadi D, Jamard S, Goehringer F, Danion F, Reignier J, de Castro N, Garot D, Lacombe K, Tolsma V, Faure E, Malvy D, Staub T, Courjon J, Cazenave-Roblot F, Dyrhol Riise AM, Leturnier P, Martin-Blondel G, Roger C, Akinosoglou K, Moing VL, Piroth L, Sellier P, Lescure X, Trøseid M, Clevenbergh P, Dalgard O, Gallien S, Gousseff M, Loubet P, Vardon-Bounes F, Visée C, Belkhir L, Botelho-Nevers É, Cabié A, Kotanidou A, Lanternier F, Rouveix-Nordon E, Silva S, Thiery G, Poignard P, Carcelain G, Diallo A, Mercier N, Terzic V, Bouscambert-Duchamp M, Gaymard A, Trabaud MA, Destras G, Josset L, Billard N, Han TH, Guedj J, Couffin-Cadiergues S, Dechanet A, Delmas C, Esperou H, Fougerou-Leurent C, Mestre SL, Métois A, Noret M, Bally I, Dergan-Dylon S, Tubiana S, Kalif O, Bergaud N, Leveau B, Eustace J, Greil R, Hajdu E, Halanova M, Paiva JA, Piekarska A, Rodriguez Baño J, Tonby K, Trojánek M, Tsiodras S, Unal S, Burdet C, Costagliola D, Yazdanpanah Y, Peiffer-Smadja N, Mentré F, and Ader F
- Subjects
- Humans, Antibodies, Monoclonal, Drug Combinations, Randomized Controlled Trials as Topic, Clinical Trials, Phase III as Topic, Antibodies, Neutralizing, COVID-19
- Abstract
Competing Interests: Declaration of Competing Interest M.H. reports grants from The Belgian Center for Knowledge (KCE), the Fonds Erasme-COVID-Université Libre de Bruxelles and the EU-Horizon program, for the submitted work; and has received support for attending meetings from Pfizer; support for participation on an advisory board for therapeutics on COVID-19; and support for leadership for the Belgian guidelines on therapeutics for COVID-19 and acting as a treasurer for the Belgian Society of Clinical Microbiology and Infectious Diseases. R.G. reports consulting fees from Celgene, Novartis, Roche, Bristol Myers Squibb, Takeda, Abbvie, AstraZeneca, Janssen, Merck Sharp & Dohme, Merck, Gilead, and Daiichi Sankvo; lecture fees from Celgene, Roche, Merck, Takeda, AstraZeneca, Novartis, Amgen, Bristol Myers Squibb, Merck Sharp & Dohme, Sandoz, Abbvie, Gilead, and Daiichi Sankvo; support for attending meetings from Roche, Amgen, Janssen, AstraZeneca, Novartis, Merck Sharp & Dohme, Celgene, Gilead, Bristol Myers Squibb, Abbvie, and Daiichi Sankvo; participation in a Data Safety and Monitoring Board for Celgene, Novartis, Roche, Bristol Myers Squibb, Takeda, Abbvie, AstraZeneca, Janssen, Merck Sharp & Dohme, Merck, Gilead, and Daiichi Sankyo; research grants from Celgene, Roche, Merck, Takeda, AstraZeneca, Novartis, Amgen, Bristol Myers Squibb, Merck Sharp & Dohme, Sandoz, Abbvie, Gilead, and Daiichi Sankyo. J.-A.P. reports consulting fees from Pfizer, Merck Sharp & Dohme, and Janssen-Cilag; lecture fees from Pfizer; and support for attending meetings from Pfizer. D.C. reports grants and lecture fees from Janssen and lecture fees from Gilead, outside the submitted work. C.B. reports participation in a Data Safety and Monitoring Board for 4Living Biotech; and consulting fees from Da Volterra and Mylan Pharmaceuticals, outside the submitted work. F.M. reports grants and consulting fees from Da Volterra, grants from Sanofi, and consulting fees from Ipsen, outside the submitted work. All other authors declare no competing interests.
- Published
- 2024
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29. Promoter insertion leads to polyembryony in mango - a case of convergent evolution with citrus.
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Yadav CB, Rozen A, Eshed R, Ish-Shalom M, Faigenboim A, Dillon N, Bally I, Webb M, Kuhn D, Ophir R, Cohen Y, and Sherman A
- Abstract
Sexual reproduction in plants is the main pathway for creating new genetic combinations in modern agriculture. In heterozygous plants, after the identification of a plant with desired traits, vegetative propagation (cloning) is the primary path to create genetically uniform plants. Another natural plant mechanism that creates genetically uniform plants (clones) is apomixis. In fruit crops like citrus and mango, sporophytic apomixis results in polyembryony, where seeds contain multiple embryos, one of which is sexually originated and the others are vegetative clones of the parent mother tree. Utilizing the mango genome and genetic analysis of a diverse germplasm collection, we identified MiRWP as the gene that causes polyembryony in mango. There is a strong correlation between a specific insertion in the gene's promoter region and altered expression in flowers and developing fruitlets, inducing multiple embryos. The MiRWP gene is an ortholog of CitRWP that causes polyembryony in citrus. Based on the data, we speculate that promoter insertion events, which occurred independently in citrus and mango, induced nucellar embryogenesis. The results suggest convergent evolution of polyembryony in the two species. Further work is required to demonstrate the utility of these genes (mango and citrus) in other biological systems as a tool for the clonal production of other crops., Competing Interests: None declared., (© The Author(s) 2023. Published by Oxford University Press on behalf of Nanjing Agricultural University.)
- Published
- 2023
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30. HMGB1 cleavage by complement C1s and its potent anti-inflammatory product.
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Lorvellec M, Chouquet A, Koch J, Bally I, Signor L, Vigne J, Dalonneau F, Thielens NM, Rabilloud T, Dalzon B, Rossi V, and Gaboriaud C
- Subjects
- Humans, Complement C4 metabolism, Lipopolysaccharides, Anti-Inflammatory Agents, Complement C1s, HMGB1 Protein
- Abstract
Complement C1s association with the pathogenesis of several diseases cannot be simply explained only by considering its main role in activating the classical complement pathway. This suggests that non-canonical functions are to be deciphered for this protease. Here the focus is on C1s cleavage of HMGB1 as an auxiliary target. HMGB1 is a chromatin non-histone nuclear protein, which exerts in fact multiple functions depending on its location and its post-translational modifications. In the extracellular compartment, HMGB1 can amplify immune and inflammatory responses to danger associated molecular patterns, in health and disease. Among possible regulatory mechanisms, proteolytic processing could be highly relevant for HMGB1 functional modulation. The unique properties of HMGB1 cleavage by C1s are analyzed in details. For example, C1s cannot cleave the HMGB1 A-box fragment, which has been described in the literature as an inhibitor/antagonist of HMGB1. By mass spectrometry, C1s cleavage was experimentally identified to occur after lysine on position 65, 128 and 172 in HMGB1. Compared to previously identified C1s cleavage sites, the ones identified here are uncommon, and their analysis suggests that local conformational changes are required before cleavage at certain positions. This is in line with the observation that HMGB1 cleavage by C1s is far slower when compared to human neutrophil elastase. Recombinant expression of cleavage fragments and site-directed mutagenesis were used to confirm these results and to explore how the output of C1s cleavage on HMGB1 is finely modulated by the molecular environment. Furthermore, knowing the antagonist effect of the isolated recombinant A-box subdomain in several pathophysiological contexts, we wondered if C1s cleavage could generate natural antagonist fragments. As a functional readout, IL-6 secretion following moderate LPS activation of RAW264.7 macrophage was investigated, using LPS alone or in complex with HMGB1 or some recombinant fragments. This study revealed that a N-terminal fragment released by C1s cleavage bears stronger antagonist properties as compared to the A-box, which was not expected. We discuss how this fragment could provide a potent brake for the inflammatory process, opening the way to dampen inflammation., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Lorvellec, Chouquet, Koch, Bally, Signor, Vigne, Dalonneau, Thielens, Rabilloud, Dalzon, Rossi and Gaboriaud.)
- Published
- 2023
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31. Biophysical Characterization of the Oligomeric States of Recombinant Immunoglobulins Type-M and Their C1q-Binding Kinetics by Biolayer Interferometry.
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Chouquet A, Pinto AJ, Hennicke J, Ling WL, Bally I, Schwaigerlehner L, Thielens NM, Kunert R, and Reiser JB
- Abstract
Immunoglobulins type-M (IgMs) are one of the first antibody classes mobilized during immune responses against pathogens and tumor cells. Binding to specific target antigens enables the interaction with the C1 complex which strongly activates the classical complement pathway. This biological function is the basis for the huge therapeutic potential of IgMs. But, due to their high oligomeric complexity, in vitro production, biochemical characterization, and biophysical characterization are challenging. In this study, we present recombinant production of two IgM models (IgM617 and IgM012) in pentameric and hexameric states and the evaluation of their polymer distribution using different biophysical methods (analytical ultracentrifugation, size exclusion chromatography coupled to multi-angle laser light scattering, mass photometry, and transmission electron microscopy). Each IgM construct is defined by a specific expression and purification pattern with different sample quality. Nevertheless, both purified IgMs were able to activate complement in a C1q-dependent manner. More importantly, BioLayer Interferometry (BLI) was used for characterizing the kinetics of C1q binding to recombinant IgMs. We show that recombinant IgMs possess similar C1q-binding properties as IgMs purified from human plasma., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Chouquet, Pinto, Hennicke, Ling, Bally, Schwaigerlehner, Thielens, Kunert and Reiser.)
- Published
- 2022
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32. Elicitation of potent SARS-CoV-2 neutralizing antibody responses through immunization with a versatile adenovirus-inspired multimerization platform.
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Chevillard C, Amen A, Besson S, Hannani D, Bally I, Dettling V, Gout E, Moreau CJ, Buisson M, Gallet S, Fenel D, Vassal-Stermann E, Schoehn G, Poignard P, Dagher MC, and Fender P
- Subjects
- Adenoviridae genetics, Animals, Antibodies, Neutralizing, Antibodies, Viral, COVID-19 Vaccines, Cryoelectron Microscopy, Humans, Mice, Vaccination, COVID-19 prevention & control, SARS-CoV-2
- Abstract
Virus-like particles (VLPs) are highly suited platforms for protein-based vaccines. In the present work, we adapted a previously designed non-infectious adenovirus-inspired 60-mer dodecahedric VLP (ADDomer) to display a multimeric array of large antigens through a SpyTag/SpyCatcher system. To validate the platform as a potential COVID-19 vaccine approach, we decorated the newly designed VLP with the glycosylated receptor binding domain (RBD) of SARS-CoV-2. Cryoelectron microscopy structure revealed that up to 60 copies of this antigenic domain could be bound on a single ADDomer particle, with the symmetrical arrangements of a dodecahedron. Mouse immunization with the RBD decorated VLPs already showed a significant specific humoral response following prime vaccination, greatly reinforced by a single boost. Neutralization assays with SARS-CoV-2 spike pseudo-typed virus demonstrated the elicitation of strong neutralization titers, superior to those of COVID-19 convalescent patients. Notably, the presence of pre-existing immunity against the adenoviral-derived particles did not hamper the immune response against the antigen displayed on its surface. This plug and play vaccine platform represents a promising new highly versatile tool to combat emergent pathogens., Competing Interests: Declaration of interests We declare no competing interests., (Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.)
- Published
- 2022
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33. Immunization with synthetic SARS-CoV-2 S glycoprotein virus-like particles protects macaques from infection.
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Sulbaran G, Maisonnasse P, Amen A, Effantin G, Guilligay D, Dereuddre-Bosquet N, Burger JA, Poniman M, Grobben M, Buisson M, Dergan Dylon S, Naninck T, Lemaître J, Gros W, Gallouët AS, Marlin R, Bouillier C, Contreras V, Relouzat F, Fenel D, Thepaut M, Bally I, Thielens N, Fieschi F, Schoehn G, van der Werf S, van Gils MJ, Sanders RW, Poignard P, Le Grand R, and Weissenhorn W
- Subjects
- Animals, Antibodies, Neutralizing immunology, Antibodies, Viral immunology, COVID-19 epidemiology, COVID-19 immunology, COVID-19 virology, COVID-19 Vaccines immunology, Chlorocebus aethiops, Disease Models, Animal, HEK293 Cells, Humans, Immunoglobulin A immunology, Immunoglobulin G immunology, Liposomes, Macaca fascicularis, Male, Pandemics prevention & control, Th1 Cells immunology, Treatment Outcome, Vaccines, Virus-Like Particle immunology, Vero Cells, COVID-19 prevention & control, COVID-19 Vaccines administration & dosage, SARS-CoV-2 immunology, Spike Glycoprotein, Coronavirus immunology, Vaccination methods, Vaccines, Virus-Like Particle administration & dosage
- Abstract
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has caused an ongoing global health crisis. Here, we present as a vaccine candidate synthetic SARS-CoV-2 spike (S) glycoprotein-coated lipid vesicles that resemble virus-like particles. Soluble S glycoprotein trimer stabilization by formaldehyde cross-linking introduces two major inter-protomer cross-links that keep all receptor-binding domains in the "down" conformation. Immunization of cynomolgus macaques with S coated onto lipid vesicles (S-LVs) induces high antibody titers with potent neutralizing activity against the vaccine strain, Alpha, Beta, and Gamma variants as well as T helper (Th)1 CD4
+ -biased T cell responses. Although anti-receptor-binding domain (RBD)-specific antibody responses are initially predominant, the third immunization boosts significant non-RBD antibody titers. Challenging vaccinated animals with SARS-CoV-2 shows a complete protection through sterilizing immunity, which correlates with the presence of nasopharyngeal anti-S immunoglobulin G (IgG) and IgA titers. Thus, the S-LV approach is an efficient and safe vaccine candidate based on a proven classical approach for further development and clinical testing., Competing Interests: The authors declare no competing interests., (© 2022 The Authors.)- Published
- 2022
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34. Lipid bilayer degradation induced by SARS-CoV-2 spike protein as revealed by neutron reflectometry.
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Luchini A, Micciulla S, Corucci G, Batchu KC, Santamaria A, Laux V, Darwish T, Russell RA, Thepaut M, Bally I, Fieschi F, and Fragneto G
- Subjects
- Angiotensin-Converting Enzyme 2 chemistry, Angiotensin-Converting Enzyme 2 metabolism, Binding Sites, COVID-19 metabolism, COVID-19 physiopathology, Cell Line, Humans, Membrane Fusion physiology, Neutron Diffraction methods, Protein Binding, Protein Domains, Spike Glycoprotein, Coronavirus chemistry, Virus Internalization, COVID-19 virology, Lipid Bilayers metabolism, SARS-CoV-2 metabolism, Spike Glycoprotein, Coronavirus metabolism
- Abstract
SARS-CoV-2 spike proteins are responsible for the membrane fusion event, which allows the virus to enter the host cell and cause infection. This process starts with the binding of the spike extramembrane domain to the angiotensin-converting enzyme 2 (ACE2), a membrane receptor highly abundant in the lungs. In this study, the extramembrane domain of SARS-CoV-2 Spike (sSpike) was injected on model membranes formed by supported lipid bilayers in presence and absence of the soluble part of receptor ACE2 (sACE2), and the structural features were studied at sub-nanometer level by neutron reflection. In all cases the presence of the protein produced a remarkable degradation of the lipid bilayer. Indeed, both for membranes from synthetic and natural lipids, a significant reduction of the surface coverage was observed. Quartz crystal microbalance measurements showed that lipid extraction starts immediately after sSpike protein injection. All measurements indicate that the presence of proteins induces the removal of membrane lipids, both in the presence and in the absence of ACE2, suggesting that sSpike molecules strongly associate with lipids, and strip them away from the bilayer, via a non-specific interaction. A cooperative effect of sACE2 and sSpike on lipid extraction was also observed., (© 2021. The Author(s).)
- Published
- 2021
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35. DC/L-SIGN recognition of spike glycoprotein promotes SARS-CoV-2 trans-infection and can be inhibited by a glycomimetic antagonist.
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Thépaut M, Luczkowiak J, Vivès C, Labiod N, Bally I, Lasala F, Grimoire Y, Fenel D, Sattin S, Thielens N, Schoehn G, Bernardi A, Delgado R, and Fieschi F
- Subjects
- Animals, Antigens, CD metabolism, COVID-19 prevention & control, Cell Adhesion Molecules metabolism, Cell Line, Chlorocebus aethiops, Humans, Jurkat Cells, Lung metabolism, Mannose-Binding Lectins metabolism, Mannosides pharmacology, Protein Binding drug effects, Receptors, Cell Surface metabolism, Respiratory Mucosa metabolism, Vero Cells, COVID-19 transmission, Lectins, C-Type metabolism, SARS-CoV-2 metabolism, Spike Glycoprotein, Coronavirus metabolism
- Abstract
The efficient spread of SARS-CoV-2 resulted in a unique pandemic in modern history. Despite early identification of ACE2 as the receptor for viral spike protein, much remains to be understood about the molecular events behind viral dissemination. We evaluated the contribution of C-type lectin receptors (CLRS) of antigen-presenting cells, widely present in respiratory mucosa and lung tissue. DC-SIGN, L-SIGN, Langerin and MGL bind to diverse glycans of the spike using multiple interaction areas. Using pseudovirus and cells derived from monocytes or T-lymphocytes, we demonstrate that while virus capture by the CLRs examined does not allow direct cell infection, DC/L-SIGN, among these receptors, promote virus transfer to permissive ACE2+ Vero E6 cells. A glycomimetic compound designed against DC-SIGN, enable inhibition of this process. These data have been then confirmed using authentic SARS-CoV-2 virus and human respiratory cell lines. Thus, we described a mechanism potentiating viral spreading of infection., Competing Interests: The authors have declared that no competing interests exist.
- Published
- 2021
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36. Molecular Basis of Complement C1q Collagen-Like Region Interaction with the Immunoglobulin-Like Receptor LAIR-1.
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Fouët G, Bally I, Chouquet A, Reiser JB, Thielens NM, Gaboriaud C, and Rossi V
- Subjects
- Binding Sites, Complement C1q genetics, Humans, Immune Tolerance, Mutation, Protein Binding, Receptors, Immunologic genetics, Collagen metabolism, Complement C1q metabolism, Receptors, Immunologic metabolism
- Abstract
The immune system homeostasis relies on a tight equilibrium of interconnected stimulatory and inhibitory signals. Disruption of this balance is characteristic of autoimmune diseases such as systemic lupus erythematosus (SLE). Aside from activating the classical complement pathway and enhancing pathogens and apoptotic cells phagocytosis, C1q has been recently shown to play an important role in immune modulation and tolerance by interacting with several inhibitory and stimulatory immune receptors. Due to its functional organization into collagen-like (CLR) and globular (GR) regions and its multimeric nature, C1q is able to interact simultaneously with several of these receptors and locally congregate pro- and anti-inflammatory signals, thus modulating the immune response. Leukocyte associated immunoglobulin-like (Ig-like) receptor 1 (LAIR-1), a ubiquitous collagen receptor expressed in many immune cell types, has been reported to interact with the CLR of C1q. In this study, we provide new insights into the molecular and structural determinants underlying C1q/LAIR-1 interaction. Recombinant LAIR-1 extracellular Ig-like domain was produced and tested for its interaction with C1q. A molecular dissection of C1q combined with competition assays reveals that LAIR-1 interacts with C1q's CLR through a binding site close but different from the one of its associated C1r2s2 proteases tetramer. On the other side, we identified LAIR-1 residues involved in C1q interaction by site-directed mutational analysis. All together, these results lead to propose a possible model for C1q interaction with LAIR-1 and will contribute to the fundamental understanding of C1q-mediated immune tolerance.
- Published
- 2021
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37. Functional recombinant human complement C1q with different affinity tags.
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Bally I, Ancelet S, Reiser JB, Rossi V, Gaboriaud C, and Thielens NM
- Subjects
- Amino Acid Sequence, Complement Activation, Complement C1q genetics, Complement C1q metabolism, HEK293 Cells, Humans, Immunoassay methods, Protein Multimerization, Recombinant Proteins genetics, Recombinant Proteins isolation & purification, Recombinant Proteins metabolism, Transfection, Complement C1q isolation & purification, Molecular Probes genetics
- Abstract
Complement C1q is a multifunctional protein able to sense pathogens and immune molecules such as immunoglobulins and pentraxins, and to trigger the classical complement pathway through activation of its two associated proteases, C1r and C1s. C1q is a multimeric protein composed of three homologous yet distinct polypeptide chains A, B, and C, each composed of an N-terminal collagen-like sequence and a C-terminal globular gC1q module, that assemble into six heterotrimeric (A-B-C) subunits. This hexameric structure exhibits the characteristic shape of a bouquet of flowers, comprising six collagen-like triple helices, each terminating in a trimeric C-terminal globular head. We have produced previously functional recombinant full-length C1q in stably transfected HEK 293-F cells, with a FLAG tag inserted at the C-terminal end of C1qC chain. We report here the generation of additional recombinant C1q proteins, with a FLAG tag fused to the C-terminus of C1qA or C1qB chains, or to the N-terminus of the C1qC chain. Two other variants harboring a Myc or a 6-His tag at the C-terminal end of C1qC were also produced. We show that all C1q variants, except for the His-tagged protein, can be produced at comparable yields and are able to bind with similar affinities to either IgM, a ligand of the globular regions, or to the C1r
2 -C1s2 tetramer, and to trigger IgM-mediated serum complement activation. These new recombinant C1q variants provide additional tools to investigate the multiple functions of C1q., (Copyright © 2021 Elsevier B.V. All rights reserved.)- Published
- 2021
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38. Headless C1q: a new molecular tool to decipher its collagen-like functions.
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Fouët G, Bally I, Signor L, Häußermann K, Thielens NM, Rossi V, and Gaboriaud C
- Subjects
- Amino Acid Sequence, Collagen chemistry, Collagen genetics, Collagen metabolism, Complement Activation genetics, Complement C1q genetics, Complement C1q metabolism, Humans, Ligands, Mass Spectrometry, Microscopy, Electron, Mutation, Missense, Photometry, Protein Binding, Recombinant Proteins metabolism, Recombinant Proteins ultrastructure, Surface Plasmon Resonance, Complement C1q chemistry, Protein Domains, Protein Multimerization, Recombinant Proteins chemistry
- Abstract
Complement component C1q, a soluble defense collagen, is the recognition protein of the classical complement pathway. C1q is able to recognize and interact with multiple targets and, via the subsequent activation of its cognate serine proteases C1r and C1s, initiates the complement cascade. C1q is made up of six ABC heterotrimers each containing two different functional regions, an N-terminal collagen-like region (CLR) and a C-terminal globular region (GR). These heterotrimers assemble via their N-terminal regions, resulting in the characteristic 'bouquet-like' shape of C1q with an N-terminal bundle of collagen fibers with six diverging stems each exhibiting a C-terminal globular head. The GRs are responsible for the versatile recognition of multiple C1q targets, whereas the CLRs trigger immune response through interacting with several cellular or soluble partners. We report here the generation of the first recombinant form of human C1q without its recognition globular heads. The noncollagenous domain 2 (nc2) of type IX collagen has been substituted for the C1q GR in order to control the correct registering of the collagen triple helices of C1q chains A, B, and C. The resulting CLR_nc2 recombinant protein produced in stably transfected EXPI293 mammalian cells was correctly assembled and folded, as demonstrated by mass spectrometry, mass photometry, and electron microscopy experiments. Its interaction properties were investigated using surface plasmon resonance analysis with known CLR ligands: the tetramer of C1r and C1s dimers and MBL-associated protein MAp44. Comparison with the interaction properties of native serum-derived C1q and CLR revealed that recombinant CLR_nc2 retains C1q CLR functional properties., (The FEBS Journal (2020) © 2020 Federation of European Biochemical Societies.)
- Published
- 2021
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39. Complement C1q Interacts With LRP1 Clusters II and IV Through a Site Close but Different From the Binding Site of Its C1r and C1s-Associated Proteases.
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Fouët G, Gout E, Wicker-Planquart C, Bally I, De Nardis C, Dedieu S, Chouquet A, Gaboriaud C, Thielens NM, Kleman JP, and Rossi V
- Subjects
- Animals, Apoptosis physiology, Binding Sites physiology, CHO Cells, Cell Line, Cell Membrane metabolism, Cricetulus, HEK293 Cells, Humans, Ligands, Protein Domains physiology, Complement C1q metabolism, Complement C1r metabolism, Complement C1s metabolism, Low Density Lipoprotein Receptor-Related Protein-1 metabolism, Peptide Hydrolases metabolism
- Abstract
LRP1 is a large endocytic modular receptor that plays a crucial role in the scavenging of apoptotic material through binding to pattern-recognition molecules. It is a membrane anchored receptor of the LDL receptor family with 4 extracellular clusters of ligand binding modules called cysteine rich complement-type repeats that are involved in the interaction of LRP1 with its numerous ligands. Complement C1q was shown to interact with LRP1 and to be implicated in the phagocytosis of apoptotic cells. The present work aimed at exploring how these two large molecules interact at the molecular level using a dissection strategy. For that purpose, recombinant LRP1 clusters II, III and IV were produced in mammalian HEK293F cells and their binding properties were investigated. Clusters II and IV were found to interact specifically and efficiently with C1q with K
Ds in the nanomolar range. The use of truncated C1q fragments and recombinant mutated C1q allowed to localize more precisely the binding site for LRP1 on the collagen-like regions of C1q (CLRs), nearby the site that is implicated in the interaction with the cognate protease tetramer C1r2s2. This site could be a common anchorage for other ligands of C1q CLRs such as sulfated proteoglycans and Complement receptor type 1. The use of a cellular model, consisting in CHO LRP1-null cells transfected with full-length LRP1 or a cluster IV minireceptor (mini IV) confirmed that mini IV interacts with C1q at the cell membrane as well as full-length LRP1. Further cellular interaction studies finally highlighted that mini IV can endorse the full-length LRP1 binding efficiency for apoptotic cells and that C1q has no impact on this interaction., (Copyright © 2020 Fouët, Gout, Wicker-Planquart, Bally, De Nardis, Dedieu, Chouquet, Gaboriaud, Thielens, Kleman and Rossi.)- Published
- 2020
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40. Molecular and Cellular Interactions of Scavenger Receptor SR-F1 With Complement C1q Provide Insights Into Its Role in the Clearance of Apoptotic Cells.
- Author
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Wicker-Planquart C, Dufour S, Tacnet-Delorme P, Bally I, Delneste Y, Frachet P, Housset D, and Thielens NM
- Subjects
- Calreticulin immunology, Cell Communication immunology, Complement C1q metabolism, Humans, Scavenger Receptors, Class F metabolism, THP-1 Cells, Apoptosis immunology, Complement C1q immunology, Macrophages immunology, Phagocytosis immunology, Scavenger Receptors, Class F immunology
- Abstract
The scavenger receptor SR-F1 binds to and mediates the internalization of a wide range of ligands, and is involved in several immunological processes. We produced recombinant SR-F1 ectodomain and fragments deleted from the last 2 or 5 C-terminal epidermal growth factor-like modules and investigated their role in the binding of acetylated low density lipoprotein (AcLDL), complement C1q, and calreticulin (CRT). C1q measured affinity was in the 100 nM range and C1q interaction occurs via its collagen-like region. We identified two different binding regions on SR-F1: the N-terminal moiety interacts with C1q and CRT whereas the C-terminal moiety binds AcLDL. The role of SR-F1 N-linked glycans was also tested by mutating each of the three glycosylated asparagines. The three mutants retained binding activities for both AcLDL and C1q. A stable THP-1 cell line overexpressing SR-F1 was generated and C1q was shown to bind more strongly to the surface of SR-F1 overexpressing macrophages, with C1q/SR-F1 colocalization observed in some membrane areas. We also observed a higher level of CRT internalization for THP-1 SR-F1 cells. Increasing SR-F1 negatively modulated the uptake of apoptotic cells. Indeed, THP-1 cells overexpressing SR-F1 displayed a lower phagocytic capacity as compared with mock-transfected cells, which could be partially restored by addition of C1q in the extracellular milieu. Our data shed some light on the role of SR-F1 in efferocytosis, through its capacity to bind C1q and CRT, two proteins involved in this process., (Copyright © 2020 Wicker-Planquart, Dufour, Tacnet-Delorme, Bally, Delneste, Frachet, Housset and Thielens.)
- Published
- 2020
- Full Text
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41. Transient pentameric IgM fulfill biological function-Effect of expression host and transfection on IgM properties.
- Author
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Hennicke J, Schwaigerlehner L, Grünwald-Gruber C, Bally I, Ling WL, Thielens N, Reiser JB, and Kunert R
- Subjects
- Animals, CHO Cells, Complement Activation, Complement C1q chemistry, Complement C1q metabolism, Cricetinae, Cricetulus, Glycosylation, HEK293 Cells, Humans, Immunoglobulin M chemistry, Immunoglobulin M genetics, Microscopy, Electron, Transmission, Oligosaccharides chemistry, Plasmids genetics, Plasmids metabolism, Transfection, Immunoglobulin M metabolism
- Abstract
Recombinant production of IgM antibodies poses a special challenge due to the complex structure of the proteins and their not yet fully elucidated interactions with the immune effector proteins, especially the complement system. In this study, we present transient expression of IgM antibodies (IgM617, IgM012 and IgM012_GL) in HEK cells and compared it to the well-established stable expression system in CHO cells. The presented workflow investigates quality attributes including productivity, polymer distribution, glycosylation, antibody structure and activation of the classical complement pathway. The HEK293E transient expression system is able to generate comparable amounts and polymer distribution as IgM stably produced in CHO. Although the glycan profile generated by HEK293E cells contained a lower degree of sialylation and a higher portion of oligomannose structures, the potency to activate the complement cascade was maintained. Electron microscopy also confirmed the structural integrity of IgM pentamers produced in HEK293E cells, since the conventional star-shaped structure is observed. From our studies, we conclude that the transient expression system provides an attractive alternative for rapid, efficient and high-throughput production of complex IgM antibodies with slightly altered post-translational modifications, but comparable structure and function., Competing Interests: The authors have declared that no competing interests exist.
- Published
- 2020
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42. Recombinant C1q variants modulate macrophage responses but do not activate the classical complement pathway.
- Author
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Espericueta V, Manughian-Peter AO, Bally I, Thielens NM, and Fraser DA
- Subjects
- Humans, Recombinant Proteins chemistry, Recombinant Proteins metabolism, Complement C1q chemistry, Complement C1q immunology, Complement Pathway, Classical immunology, Macrophages immunology, Phagocytosis immunology
- Abstract
Complement protein C1q plays a dual role in a number of inflammatory diseases such as atherosclerosis. While in later stages classical complement pathway activation by C1q exacerbates disease progression, C1q also plays a beneficial role in early disease. Independent of its role in complement activation, we and others have identified a number of potentially beneficial interactions of C1q with phagocytes in vitro, including triggering phagocytosis of cellular and molecular debris and polarizing macrophages toward an anti-inflammatory phenotype. These interactions may also be important in preventing autoimmunity. Here, we characterize variants of recombinant human C1q (rC1q) which no longer initiate complement activation, through mutation of the C1r
2 C1s2 interaction site. For insight into the structural location of the site of C1q that is important for interaction with phagocytes, we investigated the effect of these mutations on phagocytosis and macrophage inflammatory polarization, as compared to wild-type C1q. Phagocytosis of antibody coated sheep erythrocytes and oxidized LDL was measured in human monocytes and monocyte-derived macrophages (HMDM) respectively that had interacted with rC1q wild-type or variants. Secreted levels of cytokines were also measured in C1q stimulated HMDM. All variants of C1q increased phagocytosis in HMDM compared to controls, similar to native or wild-type rC1q. In addition, levels of certain pro-inflammatory cytokines and chemokines secreted by HMDM were modulated in cells that interacted with C1q variants, similar to wild-type rC1q and native C1q. This includes downregulation of IL-1α, IL-1β, TNFα, MIP-1α, and IL-12p40 by native and rC1q in both resting and M1-polarized HMDM. This suggests that the site responsible for C1q interaction with phagocytes is independent of the C1r2 C1s2 interaction site. Further studies with these classical pathway-null variants of C1q should provide greater understanding of the complement-independent role of C1q, and allow for potential therapeutic exploitation., (Copyright © 2019 Elsevier Ltd. All rights reserved.)- Published
- 2020
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43. Two Different Missense C1S Mutations, Associated to Periodontal Ehlers-Danlos Syndrome, Lead to Identical Molecular Outcomes.
- Author
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Bally I, Dalonneau F, Chouquet A, Gröbner R, Amberger A, Kapferer-Seebacher I, Stoiber H, Zschocke J, Thielens NM, Rossi V, and Gaboriaud C
- Subjects
- Amino Acid Substitution, HEK293 Cells, Humans, Protein Folding, Complement C1r genetics, Complement C1r immunology, Complement C1s genetics, Complement C1s immunology, Ehlers-Danlos Syndrome genetics, Ehlers-Danlos Syndrome immunology, Ehlers-Danlos Syndrome pathology, Mutation, Missense, Periodontal Diseases genetics, Periodontal Diseases immunology, Periodontal Diseases pathology
- Abstract
Ehlers-Danlos syndromes (EDS) are clinically and genetically heterogeneous disorders characterized by soft connective tissue alteration like joint hypermobility and skin hyper-extensibility. We previously identified heterozygous missense mutations in the C1R and C1S genes, coding for the complement C1 proteases, in patients affected by periodontal EDS, a specific EDS subtype hallmarked by early severe periodontitis leading to premature loss of teeth and connective tissue alterations. Up to now, there is no clear molecular link relating the nominal role of the C1r and C1s proteases, which is to activate the classical complement pathway, to these heterogeneous symptoms of periodontal EDS syndrome. We aim therefore to elucidate the functional effect of these mutations, at the molecular and enzymatic levels. To explore the molecular consequences, a set of cell transfection experiments, recombinant protein purification, mass spectroscopy and N-terminal analyses have been performed. Focusing on the results obtained on two different C1S variants, namely p.Val316del and p.Cys294Arg, we show that HEK293-F cells stably transfected with the corresponding C1s variant plasmids, unexpectedly, do not secrete the full-length mutated C1s, but only a truncated Fg40 fragment of 40 kDa, produced at very low levels. Detailed analyses of the Fg40 fragments purified for the two C1s variants show that they are identical, which was also unexpected. This suggests that local misfolding of the CCP1 module containing the patient mutation exposes a novel cleavage site, between Lys353 and Cys354, which is not normally accessible. The mutation-induced Fg40 fragment contains the intact C-terminal serine protease domain but not the N-terminal domain mediating C1s interaction with the other C1 subunits, C1r, and C1q. Thus, Fg40 enzymatic activity escapes the normal physiological control of C1s activity within C1, potentially providing a loss-of-control. Comparative enzymatic analyses show that Fg40 retains the native esterolytic activity of C1s, as well as its cleavage efficiency toward the ancillary alarmin HMGB1 substrate, for example, whereas the nominal complement C4 activation cleavage is impaired. These new results open the way to further molecular explorations possibly involving subsidiary C1s targets., (Copyright © 2019 Bally, Dalonneau, Chouquet, Gröbner, Amberger, Kapferer-Seebacher, Stoiber, Zschocke, Thielens, Rossi and Gaboriaud.)
- Published
- 2019
- Full Text
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44. Corrigendum: C1R Mutations Trigger Constitutive Complement 1 Activation in Periodontal Ehlers-Danlos Syndrome.
- Author
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Gröbner R, Kapferer-Seebacher I, Amberger A, Redolfi R, Dalonneau F, Björck E, Milnes D, Bally I, Rossi V, Thielens N, Stoiber H, Gaboriaud C, and Zschocke J
- Abstract
[This corrects the article DOI: 10.3389/fimmu.2019.02537.]., (Copyright © 2019 Gröbner, Kapferer-Seebacher, Amberger, Redolfi, Dalonneau, Björck, Milnes, Bally, Rossi, Thielens, Stoiber, Gaboriaud and Zschocke.)
- Published
- 2019
- Full Text
- View/download PDF
45. C1R Mutations Trigger Constitutive Complement 1 Activation in Periodontal Ehlers-Danlos Syndrome.
- Author
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Gröbner R, Kapferer-Seebacher I, Amberger A, Redolfi R, Dalonneau F, Björck E, Milnes D, Bally I, Rossi V, Thielens N, Stoiber H, Gaboriaud C, and Zschocke J
- Subjects
- Cells, Cultured, Complement Activation, Complement C1r genetics, Ehlers-Danlos Syndrome genetics, Fibroblasts immunology, Humans, Mutation, Periodontal Diseases genetics, Complement C1 immunology, Complement C1r immunology, Ehlers-Danlos Syndrome immunology, Periodontal Diseases immunology
- Abstract
Heterozygous missense or in-frame insertion/deletion mutations in complement 1 subunits C1r and C1s cause periodontal Ehlers-Danlos Syndrome (pEDS), a specific EDS subtype characterized by early severe periodontal destruction and connective tissue abnormalities like easy bruising, pretibial haemosiderotic plaques, and joint hypermobility. We report extensive functional studies of 16 C1R variants associated with pEDS by in-vitro overexpression studies in HEK293T cells followed by western blot, size exclusion chromatography and surface plasmon resonance analyses. Patient-derived skin fibroblasts were analyzed by western blot and Enzyme-linked Immunosorbent Assay (ELISA). Overexpression of C1R variants in HEK293T cells revealed that none of the pEDS variants was integrated into the C1 complex but cause extracellular presence of catalytic C1r/C1s activities. Variants showed domain-specific abnormalities of intracellular processing and secretion with preservation of serine protease function in the supernatant. In contrast to C1r wild type, and with the exception of a C1R missense variant disabling a C1q binding site, pEDS variants had different impact on the cell: retention of C1r fragments inside the cell, secretion of aggregates, or a new C1r cleavage site. Overexpression of C1R variants in HEK293T as well as western blot analyses of patient fibroblasts showed decreased levels of secreted C1r. Importantly, all available patient fibroblasts exhibited activated C1s and activation of externally added C4 in the supernatant while control cell lines secreted proenzyme C1s and showed no increase in C4 activation. The central elements in the pathogenesis of pEDS seem to be the intracellular activation of C1r and/or C1s, and extracellular presence of activated C1s that independently of microbial triggers can activate the classical complement cascade., (Copyright © 2019 Gröbner, Kapferer-Seebacher, Amberger, Redolfi, Dalonneau, Björck, Milnes, Bally, Rossi, Thielens, Stoiber, Gaboriaud and Zschocke.)
- Published
- 2019
- Full Text
- View/download PDF
46. Interaction of C1q With Pentraxin 3 and IgM Revisited: Mutational Studies With Recombinant C1q Variants.
- Author
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Bally I, Inforzato A, Dalonneau F, Stravalaci M, Bottazzi B, Gaboriaud C, and Thielens NM
- Subjects
- Amino Acid Substitution, Animals, C-Reactive Protein genetics, C-Reactive Protein immunology, CHO Cells, Complement C1q genetics, Complement C1q immunology, Cricetulus, Humans, Immunoglobulin M immunology, Recombinant Proteins chemistry, Recombinant Proteins genetics, Recombinant Proteins immunology, Serum Amyloid P-Component genetics, Serum Amyloid P-Component immunology, C-Reactive Protein chemistry, Complement C1q chemistry, Immunoglobulin M chemistry, Mutation, Missense, Serum Amyloid P-Component chemistry
- Abstract
Pentraxins and complement defense collagens are soluble recognition proteins that sense pathogens and altered-self elements, and trigger immune responses including complement activation. PTX3 has been shown to interact with the globular recognition domains (gC1q) of the C1q protein of the classical complement pathway, thereby modulating complement activity. The C1q-PTX3 interaction has been characterized previously by site-specific mutagenesis using individual gC1q domains of each of the three C1q chains. The present study is aimed at revisiting this knowledge taking advantage of full-length recombinant C1q. Four mutations targeting exposed amino acid residues in the gC1q domain of each of the C1q chains (Lys
A200 Asp-LysA201 Asp, ArgB108 Asp-ArgB109 Glu, TyrB175 Leu, and LysC170 Glu) were introduced in recombinant C1q and the interaction properties of the mutants were analyzed using surface plasmon resonance. All C1q mutants retained binding to C1r and C1s proteases and mannose-binding lectin-associated serine proteases, indicating that the mutations did not affect the function of the collagen-like regions of C1q. The effect of these mutations on the interaction of C1q with PTX3 and IgM, and both the PTX3- and IgM-mediated activation of the classical complement pathway were investigated. The LysA200 Asp-LysA201 Asp and LysC170 Glu mutants retained partial interaction with PTX3 and IgM, however they triggered efficient complement activation. In contrast, the ArgB108 Asp-ArgB109 Glu mutation abolished C1q binding to PTX3 and IgM, and significantly decreased complement activation. The TyrB175 Leu mutant exhibited decreased PTX3- and IgM-dependent complement activation. Therefore, we provided evidence that, in the context of the full length C1q protein, a key contribution to the interaction with both PTX3 and IgM is given by the B chain Arg residues that line the side of the gC1q heterotrimer, with a minor participation of a Lys residue located at the apex of gC1q. Furthermore, we generated recombinant forms of the human PTX3 protein bearing either D or A at position 48, a polymorphic site of clinical relevance in a number of infections, and observed that both allelic variants equally recognized C1q.- Published
- 2019
- Full Text
- View/download PDF
47. C1q restrains autoimmunity and viral infection by regulating CD8 + T cell metabolism.
- Author
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Ling GS, Crawford G, Buang N, Bartok I, Tian K, Thielens NM, Bally I, Harker JA, Ashton-Rickardt PG, Rutschmann S, Strid J, and Botto M
- Subjects
- Animals, Autoantibodies immunology, Autoimmunity genetics, Complement C1q genetics, Complement C3 genetics, Complement C3 physiology, Complement Pathway, Classical genetics, Complement Pathway, Classical immunology, Disease Models, Animal, Immunoglobulins immunology, Immunologic Memory immunology, Lupus Erythematosus, Systemic genetics, Lymphocytic Choriomeningitis genetics, Mice, Mice, Mutant Strains, Autoimmunity immunology, CD8-Positive T-Lymphocytes metabolism, Complement C1q physiology, Lupus Erythematosus, Systemic immunology, Lymphocytic Choriomeningitis immunology
- Abstract
Deficiency of C1q, the initiator of the complement classical pathway, is associated with the development of systemic lupus erythematosus (SLE). Explaining this association in terms of abnormalities in the classical pathway alone remains problematic because C3 deficiency does not predispose to SLE. Here, using a mouse model of SLE, we demonstrate that C1q, but not C3, restrains the response to self-antigens by modulating the mitochondrial metabolism of CD8
+ T cells, which can themselves propagate autoimmunity. C1q deficiency also triggers an exuberant effector CD8+ T cell response to chronic viral infection leading to lethal immunopathology. These data establish a link between C1q and CD8+ T cell metabolism and may explain how C1q protects against lupus, with implications for the role of viral infections in the perpetuation of autoimmunity., (Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)- Published
- 2018
- Full Text
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48. C1q and Mannose-Binding Lectin Interact with CR1 in the Same Region on CCP24-25 Modules.
- Author
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Jacquet M, Cioci G, Fouet G, Bally I, Thielens NM, Gaboriaud C, and Rossi V
- Subjects
- Complement C1q genetics, Complement C1q immunology, Humans, Lectins chemistry, Lectins genetics, Lectins immunology, Mannose-Binding Lectin genetics, Mannose-Binding Lectin immunology, Peptides genetics, Peptides immunology, Protein Binding, Protein Domains, Protein Structure, Secondary, Receptors, Complement 3b genetics, Receptors, Complement 3b immunology, Ficolins, Complement C1q chemistry, Mannose-Binding Lectin chemistry, Peptides chemistry, Receptors, Complement 3b chemistry
- Abstract
Complement receptor type 1 (CR1) is a multi modular membrane receptor composed of 30 homologous complement control protein modules (CCP) organized in four different functional regions called long homologous repeats (LHR A, B, C, and D). CR1 is a receptor for complement-opsonins C3b and C4b and specifically interacts through pairs of CCP modules located in LHR A, B, and C. Defense collagens such as mannose-binding lectin (MBL), ficolin-2, and C1q also act as opsonins and are involved in immune clearance through binding to the LHR-D region of CR1. Our previous results using deletion variants of CR1 mapped the interaction site for MBL and ficolin-2 on CCP24-25. The present work aimed at deciphering the interaction of C1q with CR1 using new CR1 variants concentrated around CCP24-25. CR1 bimodular fragment CCP24-25 and CR1 CCP22-30 deleted from CCP24-25 produced in eukaryotic cells enabled to highlight that the interaction site for both MBL and C1q is located on the same pair of modules CCP24-25. C1q binding to CR1 shares with MBL a main common interaction site on the collagen stalks but also subsidiary sites most probably located on C1q globular heads, contrarily to MBL.
- Published
- 2018
- Full Text
- View/download PDF
49. Structural and Functional Characterization of a Single-Chain Form of the Recognition Domain of Complement Protein C1q.
- Author
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Moreau C, Bally I, Chouquet A, Bottazzi B, Ghebrehiwet B, Gaboriaud C, and Thielens N
- Abstract
Complement C1q is a soluble pattern recognition molecule comprising six heterotrimeric subunits assembled from three polypeptide chains (A-C). Each heterotrimer forms a collagen-like stem prolonged by a globular recognition domain. These recognition domains sense a wide variety of ligands, including pathogens and altered-self components. Ligand recognition is either direct or mediated by immunoglobulins or pentraxins. Multivalent binding of C1q to its targets triggers immune effector mechanisms mediated via its collagen-like stems. The induced immune response includes activation of the classical complement pathway and enhancement of the phagocytosis of the recognized target. We report here, the first production of a single-chain recombinant form of human C1q globular region (C1q-scGR). The three monomers have been linked in tandem to generate a single continuous polypeptide, based on a strategy previously used for adiponectin, a protein structurally related to C1q. The resulting C1q-scGR protein was produced at high yield in stably transfected 293-F mammalian cells. Recombinant C1q-scGR was correctly folded, as demonstrated by its X-ray crystal structure solved at a resolution of 1.35 Å. Its interaction properties were assessed by surface plasmon resonance analysis using the following physiological C1q ligands: the receptor for C1q globular heads, the long pentraxin PTX3, calreticulin, and heparin. The 3D structure and the binding properties of C1q-scGR were similar to those of the three-chain fragment generated by collagenase digestion of serum-derived C1q. Comparison of the interaction properties of the fragments with those of native C1q provided insights into the avidity component associated with the hexameric assembly of C1q. The interest of this functional recombinant form of the recognition domains of C1q in basic research and its potential biomedical applications are discussed.
- Published
- 2016
- Full Text
- View/download PDF
50. Deciphering the fine details of c1 assembly and activation mechanisms: "mission impossible"?
- Author
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Gaboriaud C, Ling WL, Thielens NM, Bally I, and Rossi V
- Abstract
The classical complement pathway is initiated by the large (~800 kDa) and flexible multimeric C1 complex. Its catalytic function is triggered by the proteases hetero-tetramer C1r2s2, which is associated to the C1q sensing unit, a complex assembly of 18 chains built as a hexamer of heterotrimers. Initial pioneering studies gained insights into the main architectural principles of the C1 complex. A dissection strategy then provided the high-resolution structures of its main functional and/or structural building blocks, as well as structural details on some key protein-protein interactions. These past and current discoveries will be briefly summed up in order to address the question of what is still ill-defined. On a functional point of view, the main molecular determinants of C1 activation and its tight control will be delineated. The current perspective remains to decipher how C1 really works and is controlled in vivo, both in normal and pathological settings.
- Published
- 2014
- Full Text
- View/download PDF
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