Etude de la sialylation des anticorps en transplantation rénale

La présence d anticorps anti HLA/DSA est associée à une moindre fonction du greffon à long terme et à une augmentation de la prévalence du rejet chronique. Pourtant, malgré leur présence, certains patients greffés maintiennent une fonction stable de leur greffon des années après la transplantation. Notre objectif est de déterminer si la nature de ces anticorps et leur structure biochimique pourraient expliquer une activité biologique non agressive , voire protectrice de ces anticorps vis-à-vis du greffon rénal : un sucre, l acide sialique, présent sur la chaîne glycosylée du fragment Fc peut modifier la pathogénicité de l anticorps en favorisant la synthèse de récepteurs aux immunoglobulines de type inhibiteur Fc RIIB. L objectif était la mise au point d une méthode d'analyse de la sialylation des anticorps totaux et anti HLA, d étudier sa cinétique, de comparer le niveau de sialylation des anticorps anti-HLA et DSA dans une cohorte de patients ayant des anticorps anti-HLA/DSA : 55 patients ayant maintenu une bonne fonction rénale, 90 patients ayant dégradé leur fonction. Les premiers résultats sur une petite cohorte montrent une variation de la sialylation des IgG et anti HLA en fonction du temps et des données clinico biologiques. Cette étude devrait nous permettre de mieux comprendre les mécanismes responsables du développement du rejet chronique médié par les anticorps, première cause actuelle de perte tardive des greffons. Nos résultats pourraient également établir l analyse de la sialylation des anticorps totaux et anti HLA comme marqueur prédictif de la pathogénicité des anticorps en transplantation.TOURS-BU Sciences Pharmacie (372612104) / SudocSudocFranceF

Antibiorésistance en Equine : mythe ou réalité ?

National audienc

New methods to characterize bacterial biofilm, the example of Streptococcus equi

International audienceIntroduction: The biofilm allows multiple bacteria to survive in a hostile environment because it provides greater resistance to the host’s immune response, antibiotics, and disinfectants than bacteria in their free form. The biofilm is a complex heterogeneous structure consisting of one or more bacterial populations, embedded in a self-produced extracellular matrix, which could bind to a biotic or abiotic surface. Biofilms were first described in human medicine and found to be implicated in animal bacterial infections. Streptococcus equi subsp equi (SEE) is the causative agent of strangles and its persistence in guttural pouches of asymptomatic carriers plays an important role in the spread of the disease. SEE is a β-hemolytic and Lancefield’s group C Streptococcus found only in Equidae and believed to have evolved from an ancestral strain of Streptococcus equi subsp zooepidemicus (SEZ). This last is associated with a wide variety of diseases in horses and other animals including humans. While SEZ is able to produce biofilm, SEE’s ability to form it is still undescribed.Methods: Six SEE strains (isolated from carrier [10-146, 15-001, 58-450] and acute [8-550, 12-313, 39-275] strangle horses) and three SEZ [6-884, 10-150, 39-477] strains were used to analyze and compare their biofilm formation ability. All these strains have been isolated from guttural pouch washes of horses included in the first longitudinal field study on strangles in France, performed from 2016 to 2019. In vitro biofilm production by SEE et SEZ was characterized by four methodologies: 1) Crystal violet staining (CV), 2) Single-frequency impedance measurement (iCELLigence Real-Time Cell Analysis /RTCA instrument), 3) 3D inverted microscopy using live/dead staining, 4) the Bioflux 200 microfluidic system associated with microscopy. A strain of Pseudomonas aeruginosa known to produce biofilm was used as positive control and sterile media as a negative control. Three independent experiments with three replicates per strain were carried out for each protocol.Results: The ability of SEZ strains to produce biofilm was confirmed by all four methods. According to the results obtained, two groups could be distinguished among the SEE strains analyzed. The strains of group A, including strains 8-550, 12-313, and 15-001, presented small colonies and average biofilm with mean OD590 comprised between 0.205 and 0.218 by CV. The strains of group B, containing strains 10-146, 39275, and 58-450, presented the largest mucosal colonies and showed weak biofilm with a mean OD590 comprised between 0.0015 and 0.035. These observations were confirmed by impedance measurement, 3D microscopy, and Bioflux visualizations.Conclusion: Our study revealed that biofilm production in SEE was mainly associated with morphotypes. More investigations are necessary to understand the relationship between the biofilm production ability of isolated strains and the asymptomatic carrier/acute status of strangles horses.These same experiments were performed on other bacterial species such as Pseudomonas aeruginosa isolated from human and animal samples. The obtained results thus allow a better understanding of the biofilm formation mechanism and composition to consider new therapeutic strategies

Enjeux de la Gourme en France : dépistage et prévention

National audienceSouvent considérée comme banale et associée à un tableau clinique respiratoire, les professionnels de la filière équine oublient parfois que la Gourme, hautement contagieuse, peut provoquer des abcès purulents et que, dans les formes les plus graves, elle peut être mortelle. La bactérie responsable de cette infection est Streptococcus equisubsp equi(S. equi), elle se transmet par contact direct ou indirect. LABÉO a mené, entre 2016 et 2019, une étude de terrain afin de déterminer,pour cette infection, le test diagnostique le plus performant (bactériologie, sérologie et/ou amplification génique par PCR) à associer au bon prélèvement (écouvillon naso-pharyngé oulavage despoches gutturales). Les résultats montrent que le lavage est le meilleur prélèvement pour isoler des souches de chevaux malades (M) ou porteurs asymptomatiques(PA), et que la PCR est le test diagnostic à réaliser en première intention. La caractérisation plus fine des souches isolées n’a pas mis en évidence de nouveau variant circulant en France. Toutefois, une différence de profil entre souches isoléesde M et PA dans leur capacité à produire du biofilm a été observée tendant à démontrer que la formation de chondroïdes dans les poches gutturales de PApourrait ne pas être la seule forme de persistance de S. equ

Responses of diploid and triploid Pacific oysters Crassostrea gigas to Vibrio infection in relation to their reproductive status

Several Vibrio species are known to be pathogenic to the Pacific oyster Crassostrea gigas. Survival varies according to pathogen exposure and high mortality events usually occur in summer during gametogenesis. In order to study the effects of gametogenetic status and ploidy (a factor known to affect reproduction allocation in oysters) on vibriosis survival, we conducted two successive experiments. Our results demonstrate that a common bath challenge with pathogenic Vibrio splendidus and Vibrio aestuarianus on a mixture of mature, spawning and non-mature oysters can lead to significant mortality. Previous bath challenges, which were done using only non-mature oysters, had not produced mortality. Immunohisto-chemical analyses showed the affinity of Vibrio for gonadic tissues, highlighting the importance of sexual maturity for vibriosis infection processes in oysters. Mortality rate results showed poor repeatability between tanks, however, in this bath challenge. We then tested a standardized and repeatable injection protocol using two different doses of the same combination of two Vibrio species on related diploid and triploid oysters at four different times over a year. Statistical analyses of mortality kinetics over a 6-day period after injection revealed that active gametogenesis periods correspond to higher susceptibility to vibriosis and that there is a significant interaction of this seasonal effect with ploidy. However, no significant advantage of triploidy was observed. Triploid oysters even showed lower survival than diploid counterparts in winter. Results are discussed in relation to differing energy allocation patterns between diploid and triploid Pacific oysters. (C) 2010 Elsevier Inc. All rights reserved

: Dossier : Lutte contre l'antibiorésistance

Disponible uniquement sous abonnementNational audienceBiofilm is a community lifestyle that allows bacteria to survive in a hostile environment through greater resistance to host immune response, antimicrobial drug and disinfectants compared to bacteria in their free form. The biofilm is a complex heterogeneous structure consisting of one or more bacterial populations, embedded in a self-produced extracellular matrix, which has the ability to attach itself to a biotic or abiotic surface. First described in human medicine, biofilms are also involved in bacterial infections in animals and equine in particular. A better knowledge of these biofilms (training mechanism and composition) makes it possible today to consider new therapeutic strategies.Le biofilm est un mode de vie communautaire qui permet aux bactéries de survivre dans un environnement hostile grâce à une plus grande résistance à la réponse immunitaire de l’hôte, aux antibiotiques et aux désinfectants en comparaison des bactéries sous leur forme libre. Le biofilm est une structure hétérogène complexe constituée d’une ou de plusieurs populations bactériennes, enchâssées dans une matrice extracellulaire autoproduite, qui a la capacité de se fixer sur une surface biotique ou abiotique. D’abord décrits en médecine humaine, les biofilms sont également impliqués dans les infections bactériennes animales, équines notamment. Une meilleure connaissance de ces biofilms (mécanisme de formation et composition) permet aujourd’hui d’envisager de nouvelles stratégies thérapeutiques

Regulatory functions of B cells in allergic diseases

International audienceB cells are essentially described for their capacity to produce antibodies ensuring anti-infectious immunity or deleterious responses in the case of autoimmunity or allergy. However, abundant data described their ability to restrain inflammation by diverse mechanisms. In allergy, some regulatory B-cell subsets producing IL-10 have been recently described as potent suppressive cells able to restrain inflammatory responses both in vitro and in vivo by regulatory T-cell differentiation or directly inhibiting T-cell-mediated inflammation. A specific deficit in regulatory B cells participates to more severe allergic inflammation. Induction of allergen tolerance through specific immunotherapy induces a specific expansion of these cells supporting their role in establishment of allergen tolerance. However, the regulatory functions carried out by B cells are not exclusively IL-10 dependent. Indeed, other regulatory mechanisms mediated by B cells are (i) the production of TGF-β, (ii) the promotion of T-cell apoptosis by Fas-Fas ligand or granzyme-B pathways, and (iii) their capacity to produce inhibitory IgG4 and sialylated IgG able to mediate anti-inflammatory mechanisms. This points to Bregs as interesting targets for the development of new therapies to induce allergen tolerance. In this review, we highlight advances in the study of regulatory mechanisms mediated by B cells and outline what is known about their phenotype as well as their suppressive role in allergy from studies in both mice and humans

Characterisation of Mycoplasma spp. isolated in 2020 from respiratory tract samples of horses in France

International audienceBackground: With more than 100 species colonizing animal hosts, bacteria of the genus Mycoplasma include important livestock pathogens. They are wall-less and considered as the smallest organisms capable of autonomous growth in vitro. Because their isolation can be laborious, they often lagged behind other bacteria in terms of general knowledge and diagnosis. In horses, three species, namely Mycoplasma (M.) equirhinis, M. pulmonis and M. felis, have been reported from respiratory tract samples, with an unknown pathogenic role but a potential implication on poor-performance [1-2]. In our laboratory, amongst equine respiratory samples submitted routinely for diagnosis, 15% per year turned out to be positive by real-time PCR (rt-PCR) for Mycoplasma spp. but the corresponding species have not been explored yet. Objectives: The aim of this study was to evaluate the prevalence of different species in respiratory clinical samples and characterize their intra species diversity. Study Design: 687 samples (68% tracheal wash, 26% bronchoalveolar lavage and 6% others) collected in 2020 were analysed. Methods: Samples were analysed by culture, rt-PCR and identified by 16S rRNA sequencing. Isolates were subtyped when necessary. Results: To date, 126 samples (18.3%) were found positive by rtPCR and 30 strains have been isolated (still ongoing). A majority of M. equirhinis (42/126 samples and 24/30 strains) was identified, while M. pulmonis and M. felis have been detected only sporadically so far. Main limitation: A gold standard method for Mycoplasma spp. detection and identification in equine samples would be helpful. Conclusions: A Multi Locus Sequence Typing scheme is being developed to analyse the genetic heterogeneity of M. equirhinis isolates. Subtypes will be examined it in the light of their clinical history to have a first insight into the potential pathogenic role of M. equirhinis.1. Allam and Lemcke. doi: 10.1017/s00221724000469082. Antal et al. doi.org/10.1111/j.1439-0450.1988.tb00496.

Characterisation of Mycoplasma spp. isolated in 2020 from respiratory tract samples of horses in France

International audienceBackground: With more than 100 species colonizing animal hosts, bacteria of the genus Mycoplasma include important livestock pathogens. They are wall-less and considered as the smallest organisms capable of autonomous growth in vitro. Because their isolation can be laborious, they often lagged behind other bacteria in terms of general knowledge and diagnosis. In horses, three species, namely Mycoplasma (M.) equirhinis, M. pulmonis and M. felis, have been reported from respiratory tract samples, with an unknown pathogenic role but a potential implication on poor-performance [1-2]. In our laboratory, amongst equine respiratory samples submitted routinely for diagnosis, 15% per year turned out to be positive by real-time PCR (rt-PCR) for Mycoplasma spp. but the corresponding species have not been explored yet. Objectives: The aim of this study was to evaluate the prevalence of different species in respiratory clinical samples and characterize their intra species diversity. Study Design: 687 samples (68% tracheal wash, 26% bronchoalveolar lavage and 6% others) collected in 2020 were analysed. Methods: Samples were analysed by culture, rt-PCR and identified by 16S rRNA sequencing. Isolates were subtyped when necessary. Results: To date, 126 samples (18.3%) were found positive by rtPCR and 30 strains have been isolated (still ongoing). A majority of M. equirhinis (42/126 samples and 24/30 strains) was identified, while M. pulmonis and M. felis have been detected only sporadically so far. Main limitation: A gold standard method for Mycoplasma spp. detection and identification in equine samples would be helpful. Conclusions: A Multi Locus Sequence Typing scheme is being developed to analyse the genetic heterogeneity of M. equirhinis isolates. Subtypes will be examined it in the light of their clinical history to have a first insight into the potential pathogenic role of M. equirhinis.1. Allam and Lemcke. doi: 10.1017/s00221724000469082. Antal et al. doi.org/10.1111/j.1439-0450.1988.tb00496.

Characterisation of S. equi strains by whole genome sequencing isolated from 2016 to 2019 in France

International audienceBackground: The prevalence of strangles, one of the most frequently diagnosed infectious diseases of horses worldwide, remains underestimated in France, despite causing economic losses to the equine industry. Streptococcus equi subsp equi (S. equi) is the causative agent and its persistence in guttural pouches of sub-clinical carriers plays an important role in the spread of the disease.Objectives: The aim of this study was to use whole genome sequencing to understand the genetic relationships of S. equi isolates recovered in France from 2016 to 2019 and compare them with international data.Study design: Longitudinal field study.Methods: The French Network for epidemio-surveillance of equine diseases (RESPE), collected 55 isolates from 23 horses implicated in 13 different outbreaks. DNAs from 18 of these strains were extracted, purified and whole genome sequenced according to Illumina recommendations. Genomes were analysed using Pathogenwatch and visualised in Microreact.Results: All isolates were classified as ST-179, recognised as “classic” S. equi. Genomes clustered into BAPS2 (Bayesian Analysis of Population Structure) but fell into two groups. Sequences in the first group, from different outbreaks (two in 2016 and one in 2017), differed from only some SNPs across the core genome and their closest relatives were previously recovered from horses in the United Arab Emirates. The second group were most closely related to other strains from France, Belgium, Spain, Sweden and the United Kingdom.Main limitations: Not all available isolates have been sequenced to date and the history of the horses from which these isolates were derived requires further investigation.Conclusions: Genomic analyses are undergoing to understand the differences between isolates from horses with acute strangles and sub-clinical carriers, by highlighting differences in genes involved in virulence, resistance, persistence or evasion of the immune system