Walleye (Sander vitreus M.) are valuable in commercial and recreational fisheries and are affected by bacterial, fungal and viral disease. Pattern recognition receptors (PRRs) are germline-encoded and constitutively expressed and bind non-self or altered-self for immune recognition. Walleye were hypothesised to have circulating PRRs that were capable of binding diverse pathogens. These PRRs were hypothesised to increase with infection, be distributed in immunologically relevant tissues and to be strain and age specific. PRR binding was measured by affinity chromatography, plasma binding assays,SDS-PAGE, Western blots, ELISA, PCR, and immunohistochemistry. ELISA and affinity chromatography assays were developed in rainbow trout (Oncorhynchus mykiss) with known PRRs. Trout ladderlectin was confirmed as a PRR binding viral hemorrhagic septicemia virus (VHSV). These techniques were adapted to walleye using Flavobacterium columnare, chitin, VHSV and Sepharose resin. A 22 kDa protein bound to F. columnare, a 17 kDa protein bound to chitin and a 34 kDa protein bound to VHSV were identified as similar to bass apolipoprotein, carp C3 and rainbow trout intelectin, respectively. PCR and 3'-RACE-PCR were used to generate nucleotide sequence to confirm identity of walleye apolipoprotein and mannose-binding lectin (MBL)-like protein from the intelectin-like sequence. Two rabbit polyclonal antibodies were raised to 34 and 67 kDa MBL amino acid sequences and used to verify MBL-like protein as a PRR for VHSV. Healthy walleye MBL-like protein plasma concentration was 7.5 ng/ml. Significant differences were found between geographically distant strains of walleye. An ELISA demonstrated that MBL-like protein had significant differences in binding affinity between multiple strains of VHSV and different viruses found in Ontario. MBL-like protein plasma levels increased with initial infection of naïve fish with waterborne and IP VHSV (107 pfu) but did not change with IP reinfection. Previous infection with VHSV significantly decreased walleye mortality. IHC of walleye shows MBL-like protein is distributed in epithelial surfaces, primarily skin, oropharynx, gill, gastrointestinal system, renal nephrons, connective tissue of gonads and plasma. There was no qualitative difference in MBL-like protein tissue distribution in healthy and VHSV-infected walleye. This is the first evidence for fish lectins binding viruses.

A hemostasia envolve diversos eventos fisiológicos desencadeados após a ruptura da integridade vascular. Durante estes processos, os glicosaminoglicanos, incluindo a heparina e o heparan sulfato, desempenham funções fisiológicas fundamentais. Particularmente a heparina, isolada no início do século XX, permanece até os dias atuais como um dos mais eficientes agentes terapêuticos de ação antitrombótica. As cadeias polissacarídicas destes glicosaminoglicanos são clivadas por liases, denominadas heparinases, através de um mecanismo de eliminação. As heparinases, identificadas inicialmente na bactéria do solo Flavobacterium heparinum (sinonímia: Pedobacter heparinus), diferem em tamanho, carga e grau de especificidade pela sequência dissacarídica do substrato. Possuem importantes aplicações na terapêutica, diagnóstico e também na produção de heparinas de baixo peso molecular (HBPM). Dentre as heparinases já descritas para F. heparinum a enzima do tipo II é a menos específica, sendo capaz de clivar ligações glicosídicas do tipo 1-4 entre a glicosamina e ácido urônico (idurônico ou glicurônico), presentes na heparina e no heparan sulfato. Entretanto, o processo de reconhecimento enzima-substrato neste sistema é ainda pouco conhecido. Particularmente com relação à dependência por metais, esta enzima tem sua atividade inibida pela presença do íon cálcio que, em contrapartida, é importante para a atividade das heparinases dos tipos I e III. A heparinase II é uma glicoproteína e apresenta um sítio de ligação ao íon zinco, o qual exerce uma importante função de manutenção da integridade da estrutura protéica. Desta forma, o presente trabalho tem por objetivo a caracterização estrutural e conformacional da enzima heparinase II e, a partir destas informações, subsidiar o entendimento do reconhecimento e especificidade da interação enzima-substrato, fundamentando um planejamento racional de novos ligantes. Empregando-se a Dinâmica Molecular (MD), quatro sistemas envolvendo a enzima foram estudados, considerando-se a presença ou ausência de íons Ca+² e Zn+² e da estrutura de glicosilação. Os dados obtidos indicam que a presença do íon Zn+² pode estar envolvida no controle da flexibilidade da estrutura protéica em regiões específicas da heparinase II. Em contrapartida, a presença do íon Ca+² promove um acréscimo significativo na flexibilidade em regiões equivalentes àquelas do Zn+², relacionada à influência do íon no sítio catalítico da enzima. Adicionalmente, a presença da O-glicosilação parece ser capaz de promover uma estabilização adicional da estrutura secundária da proteína, sugerindo um papel na estabilidade conformacional da mesma. Globalmente, os resultados indicam que simulações de MD podem ser utilizadas para representar adequadamente a conformação de glicoproteínas como a heparinase II, permitindo a caracterização de diversas propriedades, como a quantificação de suas interações com cofatores metálicos e o papel de seu sítio de glicosilação. Cria-se, portanto, uma sólida base para o estudo das demais heparinases, de suas respectivas especificidades e, por fim, para o planejamento racional de novos candidatos a agentes moduladores dos processos hemostáticos. / The hemostasis comprises important physiologic events following the rupture of vascular integrity. During these processes, heparin and heparan sulfate glycosaminoglycans (HSGAG) presents important physiological functions. In particular heparin, isolated in the beginning of the XX century, remains until today as one of the most efficient antithrombotic therapeutic agents. The polysaccharide chains of these HSGAGs are cleaved by lyases, named heparinases, through an elimination mechanism. The heparinases, first identified in the soil bacterium Flavobacterium heparinum (also named Pedobacter heparinus), differ in size, charge and substrate specificity. They have important applications, such as therapeutic, diagnostic and production of low molecular weight heparins (LMWH). Within the heparinases from F. heparinum, the type II enzyme has the broadest substrate specificity, being capable of cleavage upon the (1-4) glycosidic linkages between glucosamine and uronic acid (either glucuronic or iduronic) residues contained by heparin and heparan sulfate. However, the enzyme-substrate recognition process is poorly structurally described. Mainly in relation of the metals dependence, this enzyme has its activity inhibited by the presence of the calcium ion which, in opposite, is important for heparinanses I and III activities. The heparinase II is a glycoprotein and shows a zinc ion binding site, which plays an important role in the protein structure maintenance. Thus, the current work aims to characterize the structure and conformation of heparinase II enzyme and, based on this information, support the understanding of the recognition and specificity of the enzyme-substrate interaction, and further the rational design of new ligands of the enzyme. Using molecular dynamics (MD) calculations, four systems were studied, considering the presence or absence of Ca+² and Zn+² ions and the glycosylation structure. The obtained data indicates that the presence of a Zn+² ion may be involved in the control of the protein flexibility at some specific regions of the heparinase II. In opposite, the Ca+² presence promotes a significant increase of the flexibility on the same regions, related to the influence of this ion in the enzyme active site. Additionally, the O-glycosylation seems to be capable to promote an additional stabilization of the protein secondary structure, what may indicate its role as an element that contributes to the conformational stability of the protein. Altogether the results show that MD simulations can be used to correctly represent the glycoprotein conformations, such as heparinase II, allowing characterizing its properties, as well as quantifying its interactions with metallic cofators and the role of the glycosylation site. Thus, is generated a solid basis to the study of the other heparinases, their respective specificities, and finally to the design of new candidates to hemostatic process modulating agents.

A hemostasia envolve diversos eventos fisiológicos desencadeados após a ruptura da integridade vascular. Durante estes processos, os glicosaminoglicanos, incluindo a heparina e o heparan sulfato, desempenham funções fisiológicas fundamentais. Particularmente a heparina, isolada no início do século XX, permanece até os dias atuais como um dos mais eficientes agentes terapêuticos de ação antitrombótica. As cadeias polissacarídicas destes glicosaminoglicanos são clivadas por liases, denominadas heparinases, através de um mecanismo de eliminação. As heparinases, identificadas inicialmente na bactéria do solo Flavobacterium heparinum (sinonímia: Pedobacter heparinus), diferem em tamanho, carga e grau de especificidade pela sequência dissacarídica do substrato. Possuem importantes aplicações na terapêutica, diagnóstico e também na produção de heparinas de baixo peso molecular (HBPM). Dentre as heparinases já descritas para F. heparinum a enzima do tipo II é a menos específica, sendo capaz de clivar ligações glicosídicas do tipo 1-4 entre a glicosamina e ácido urônico (idurônico ou glicurônico), presentes na heparina e no heparan sulfato. Entretanto, o processo de reconhecimento enzima-substrato neste sistema é ainda pouco conhecido. Particularmente com relação à dependência por metais, esta enzima tem sua atividade inibida pela presença do íon cálcio que, em contrapartida, é importante para a atividade das heparinases dos tipos I e III. A heparinase II é uma glicoproteína e apresenta um sítio de ligação ao íon zinco, o qual exerce uma importante função de manutenção da integridade da estrutura protéica. Desta forma, o presente trabalho tem por objetivo a caracterização estrutural e conformacional da enzima heparinase II e, a partir destas informações, subsidiar o entendimento do reconhecimento e especificidade da interação enzima-substrato, fundamentando um planejamento racional de novos ligantes. Empregando-se a Dinâmica Molecular (MD), quatro sistemas envolvendo a enzima foram estudados, considerando-se a presença ou ausência de íons Ca+² e Zn+² e da estrutura de glicosilação. Os dados obtidos indicam que a presença do íon Zn+² pode estar envolvida no controle da flexibilidade da estrutura protéica em regiões específicas da heparinase II. Em contrapartida, a presença do íon Ca+² promove um acréscimo significativo na flexibilidade em regiões equivalentes àquelas do Zn+², relacionada à influência do íon no sítio catalítico da enzima. Adicionalmente, a presença da O-glicosilação parece ser capaz de promover uma estabilização adicional da estrutura secundária da proteína, sugerindo um papel na estabilidade conformacional da mesma. Globalmente, os resultados indicam que simulações de MD podem ser utilizadas para representar adequadamente a conformação de glicoproteínas como a heparinase II, permitindo a caracterização de diversas propriedades, como a quantificação de suas interações com cofatores metálicos e o papel de seu sítio de glicosilação. Cria-se, portanto, uma sólida base para o estudo das demais heparinases, de suas respectivas especificidades e, por fim, para o planejamento racional de novos candidatos a agentes moduladores dos processos hemostáticos. / The hemostasis comprises important physiologic events following the rupture of vascular integrity. During these processes, heparin and heparan sulfate glycosaminoglycans (HSGAG) presents important physiological functions. In particular heparin, isolated in the beginning of the XX century, remains until today as one of the most efficient antithrombotic therapeutic agents. The polysaccharide chains of these HSGAGs are cleaved by lyases, named heparinases, through an elimination mechanism. The heparinases, first identified in the soil bacterium Flavobacterium heparinum (also named Pedobacter heparinus), differ in size, charge and substrate specificity. They have important applications, such as therapeutic, diagnostic and production of low molecular weight heparins (LMWH). Within the heparinases from F. heparinum, the type II enzyme has the broadest substrate specificity, being capable of cleavage upon the (1-4) glycosidic linkages between glucosamine and uronic acid (either glucuronic or iduronic) residues contained by heparin and heparan sulfate. However, the enzyme-substrate recognition process is poorly structurally described. Mainly in relation of the metals dependence, this enzyme has its activity inhibited by the presence of the calcium ion which, in opposite, is important for heparinanses I and III activities. The heparinase II is a glycoprotein and shows a zinc ion binding site, which plays an important role in the protein structure maintenance. Thus, the current work aims to characterize the structure and conformation of heparinase II enzyme and, based on this information, support the understanding of the recognition and specificity of the enzyme-substrate interaction, and further the rational design of new ligands of the enzyme. Using molecular dynamics (MD) calculations, four systems were studied, considering the presence or absence of Ca+² and Zn+² ions and the glycosylation structure. The obtained data indicates that the presence of a Zn+² ion may be involved in the control of the protein flexibility at some specific regions of the heparinase II. In opposite, the Ca+² presence promotes a significant increase of the flexibility on the same regions, related to the influence of this ion in the enzyme active site. Additionally, the O-glycosylation seems to be capable to promote an additional stabilization of the protein secondary structure, what may indicate its role as an element that contributes to the conformational stability of the protein. Altogether the results show that MD simulations can be used to correctly represent the glycoprotein conformations, such as heparinase II, allowing characterizing its properties, as well as quantifying its interactions with metallic cofators and the role of the glycosylation site. Thus, is generated a solid basis to the study of the other heparinases, their respective specificities, and finally to the design of new candidates to hemostatic process modulating agents.

Orientador: Manoel Victor Franco Lemos / Banca: Maria Inês Tiraboshi Ferro / Banca: Maria José Tavares Ranzani de Paiva / Resumo: Dentre as enfermidades de importância na piscicultura, destaca-se a columnariose, cujo agente etiológico é a Flavobacterium columnare, bactéria de ampla distribuição geográfica, responsável por um elevado número de mortalidade em peixes de várias espécies, principalmente em condições intensivas de criação. Visando o melhor conhecimento desta bactéria para desenvolvimento de métodos de diagnóstico e controle da doença, os objetivos deste estudo foram isolar, caracterizar bioquímica e molecularmente por PCR-RFLP do gene 16S rDNA de F. columnare, detectar fenotipicamente a formação de cápsulas destes isolados pelo teste Agar vermelho congo, e avaliar a composição do EPS quando produzidos por meio de cromatografia líquida de alta eficiência. Ao todo foram obtidos 37 isolados e a caracterização bioquímica indica que os isolamentos são classificados como F. columnare. O filograma gerado pela técnica de PCR-RFLP mostrou três principais ramificações entre os isolados de F. columnare. Os testes comprovaram que a presença de cápsula na célula bacteriana não está diretamente relacionada à formação de biofilme, e o monossacarídeo preponderante em F. columnare é a glicose.Portanto, a utilização da PCR-RFLP para a identificação da bactéria apresentou-se como ferramenta mais rápida que as técnicas bioquímicas atuais e os dados referentes a produção de biofilme são relevantes para futuros estudos que busquem métodos enzimáticos para impedimento da aderência e formação de biofilmes destes patógenos aquáticos em sistemas de aqüicultura e consequentemente a prevenção da columnariose / Abstract: Columnaris disease stands out among the illnesses of importance in fish breeding, its etiological agent is Flavobacterium columnare, which has been recognized as a worldwide pathogen, responsible for high degree of mortality in many fish species, especially in conditions of intensive breed. Looking for a better knowledge of this bacteria and aiming to develop diagnosis methods and disease control, the objectives of this study were to isolate, to biochemistry and molecularly characterize by 16S rDNA gene PCR-RFLP of F. columnare, to detect phenotipically the formation of capsules by the agar Congo red method, and to evaluate the EPS composition by high-performance liquid chromatography. There were obtained 37 isolates and the biochemistry characterization indicated that the isolates were classified as F. columnare. The phylogenetic tree generated by PCR-RFLP technique showed three main branches among the F. columnare isolates. The presence of capsule on the bacterial cells has not a direct relationship to biofilm formation, and considering its composition it was observed that the preponderant monosaccharide is glucose. Therefore, the PCR-RFLP alternative to identify this bacteria presented itself as a faster tool than actual biochemical techniques and the results regarding to biofilm production are relevant to future studies that search for enzymatic methods to abolish the adherence and biofilm formation by this aquatic pathogen in aquaculture systems, and, consequently, columnaris disease prevention / Mestre

A hemostasia envolve diversos eventos fisiológicos desencadeados após a ruptura da integridade vascular. Durante estes processos, os glicosaminoglicanos, incluindo a heparina e o heparan sulfato, desempenham funções fisiológicas fundamentais. Particularmente a heparina, isolada no início do século XX, permanece até os dias atuais como um dos mais eficientes agentes terapêuticos de ação antitrombótica. As cadeias polissacarídicas destes glicosaminoglicanos são clivadas por liases, denominadas heparinases, através de um mecanismo de eliminação. As heparinases, identificadas inicialmente na bactéria do solo Flavobacterium heparinum (sinonímia: Pedobacter heparinus), diferem em tamanho, carga e grau de especificidade pela sequência dissacarídica do substrato. Possuem importantes aplicações na terapêutica, diagnóstico e também na produção de heparinas de baixo peso molecular (HBPM). Dentre as heparinases já descritas para F. heparinum a enzima do tipo II é a menos específica, sendo capaz de clivar ligações glicosídicas do tipo 1-4 entre a glicosamina e ácido urônico (idurônico ou glicurônico), presentes na heparina e no heparan sulfato. Entretanto, o processo de reconhecimento enzima-substrato neste sistema é ainda pouco conhecido. Particularmente com relação à dependência por metais, esta enzima tem sua atividade inibida pela presença do íon cálcio que, em contrapartida, é importante para a atividade das heparinases dos tipos I e III. A heparinase II é uma glicoproteína e apresenta um sítio de ligação ao íon zinco, o qual exerce uma importante função de manutenção da integridade da estrutura protéica. Desta forma, o presente trabalho tem por objetivo a caracterização estrutural e conformacional da enzima heparinase II e, a partir destas informações, subsidiar o entendimento do reconhecimento e especificidade da interação enzima-substrato, fundamentando um planejamento racional de novos ligantes. Empregando-se a Dinâmica Molecular (MD), quatro sistemas envolvendo a enzima foram estudados, considerando-se a presença ou ausência de íons Ca+² e Zn+² e da estrutura de glicosilação. Os dados obtidos indicam que a presença do íon Zn+² pode estar envolvida no controle da flexibilidade da estrutura protéica em regiões específicas da heparinase II. Em contrapartida, a presença do íon Ca+² promove um acréscimo significativo na flexibilidade em regiões equivalentes àquelas do Zn+², relacionada à influência do íon no sítio catalítico da enzima. Adicionalmente, a presença da O-glicosilação parece ser capaz de promover uma estabilização adicional da estrutura secundária da proteína, sugerindo um papel na estabilidade conformacional da mesma. Globalmente, os resultados indicam que simulações de MD podem ser utilizadas para representar adequadamente a conformação de glicoproteínas como a heparinase II, permitindo a caracterização de diversas propriedades, como a quantificação de suas interações com cofatores metálicos e o papel de seu sítio de glicosilação. Cria-se, portanto, uma sólida base para o estudo das demais heparinases, de suas respectivas especificidades e, por fim, para o planejamento racional de novos candidatos a agentes moduladores dos processos hemostáticos. / The hemostasis comprises important physiologic events following the rupture of vascular integrity. During these processes, heparin and heparan sulfate glycosaminoglycans (HSGAG) presents important physiological functions. In particular heparin, isolated in the beginning of the XX century, remains until today as one of the most efficient antithrombotic therapeutic agents. The polysaccharide chains of these HSGAGs are cleaved by lyases, named heparinases, through an elimination mechanism. The heparinases, first identified in the soil bacterium Flavobacterium heparinum (also named Pedobacter heparinus), differ in size, charge and substrate specificity. They have important applications, such as therapeutic, diagnostic and production of low molecular weight heparins (LMWH). Within the heparinases from F. heparinum, the type II enzyme has the broadest substrate specificity, being capable of cleavage upon the (1-4) glycosidic linkages between glucosamine and uronic acid (either glucuronic or iduronic) residues contained by heparin and heparan sulfate. However, the enzyme-substrate recognition process is poorly structurally described. Mainly in relation of the metals dependence, this enzyme has its activity inhibited by the presence of the calcium ion which, in opposite, is important for heparinanses I and III activities. The heparinase II is a glycoprotein and shows a zinc ion binding site, which plays an important role in the protein structure maintenance. Thus, the current work aims to characterize the structure and conformation of heparinase II enzyme and, based on this information, support the understanding of the recognition and specificity of the enzyme-substrate interaction, and further the rational design of new ligands of the enzyme. Using molecular dynamics (MD) calculations, four systems were studied, considering the presence or absence of Ca+² and Zn+² ions and the glycosylation structure. The obtained data indicates that the presence of a Zn+² ion may be involved in the control of the protein flexibility at some specific regions of the heparinase II. In opposite, the Ca+² presence promotes a significant increase of the flexibility on the same regions, related to the influence of this ion in the enzyme active site. Additionally, the O-glycosylation seems to be capable to promote an additional stabilization of the protein secondary structure, what may indicate its role as an element that contributes to the conformational stability of the protein. Altogether the results show that MD simulations can be used to correctly represent the glycoprotein conformations, such as heparinase II, allowing characterizing its properties, as well as quantifying its interactions with metallic cofators and the role of the glycosylation site. Thus, is generated a solid basis to the study of the other heparinases, their respective specificities, and finally to the design of new candidates to hemostatic process modulating agents.

No description available.

Flavobacterium columnare yra gerai žinomas patogenas sukeliantis kolumnariozę, ir kurio sukeliama liga paliečia gėlavandenes žuvis: tiek akvariumines, tiek žuvivaisos įmonėse, tiek gyvenančias natūraliose gamtinėse sąlygose. Bakteriją pirmą kartą 1922 metais aprašė Herber Spencer Davis, ir jai suteikė pavadinimą, kuris vėliau kelis kartus keitėsi (Bacillus columnaris, Cytophaga columnaris, Chondrococcus columnaris, Flexibacter columnaris) kol buvo pripažintas Flavobacterium columnare pavadinimas, kuris dabar naudojamas. Jungtinėse Amerikos Valstijose ši bakterija atneša labai didžiulius nuostolius. Registruotais duomenimis 2003 m. kolumnaris liga nusinešė daugiau nei 30 milijonų JAV dolerių vien tik iš šamų pramonės. F. columnare dažniausiai pasižymi tuo, kad sukelia žiaunų nekrozę, pelekų erozijas ir žvynų pažeidimus. Išauginta ant Cytophaga agaro kolonija dažniausiai būna rizoidinio tipo, adhezyvi, gelsvos spalvos (dėl pigmento fleksirubinino). Raudonųjų Kongo dažų absorbcija – vienas labiausiai patikimiausių biocheminių testų. Taip pat egzistuoja ir kiti diagnozavimo metodai – serologiniai, molekuliniai. Šios ligos prevencijai reikia reguliariai naudoti kalio permanganatą, vario sulfatą ar kitą dezinfekcinę medžiagą, kuri naikina F. columnare bakterijas. Jei tenka gydyti – visai neseniai pasirodė tyrimai, kuriuose buvo aprašytas fagų panaudojimas. Jie pasižymi kolonijų augimą stabdančiu ar bakterijas naikinančiu poveikiu, tačiau dar reikia atlikti daugybę tyrimų norint... [toliau žr. visą tekstą] / Flavobacterium columnare is a well known worldwide pathogen, causative agent of Columnaris disease, elicting significant problems in freshwater fish including aquariums, culture places, natural surroundings. The first time the bacteria was described and named by Herber Spencer Davis. The name has changed for several times till reached the one is used now (Bacillus columnaris, Cytophaga columnaris, Chondrococcus columnaris, Flexibacter columnaris). In the industry of USA catfish this pathogen causes millions of dollars of losses. According to the statistics of the year 2003, the industry lost more than 30 millions of dollars of income. F. columnare in fish infections may cause skin lesions, fin erosions and gill necrosis, with a high degree of mortality. Cultured on Cytophaga agar grows mostly in rhizoit type very much adhesive collonies coloured in yellow due to pigment flexirubinin. One of the most revieling biochemical tests – absorbance of Congo red dye. Also it can be diagnosed by many serological and molecular assays. Preventive control should be used regularly involving potassium permanganate, copper sulphate or other desinfecant, which is available for F. columnare on the market. The latest treatment described for columnariosis is based upon phages which prevent the growth of F. columnare or kill it, but there are many studies to be done before making any conlusions. The aim of the research – to evaluate morfophysiological status and infestation with Flavobacterium... [to full text]

La santé des cheptels et la maîtrise des maladies est un enjeu majeur de compétitivité des élevages et de durabilité des filières. Les maladies d'origine bactérienne sont responsables de pertes économiques importantes en pisciculture. La bactérie Flavobacterium psychrophilum, qui touche l’ensemble des salmonidés et plus particulièrement la truite arc-en-ciel (Oncorhynchus mykiss),est très largement distribuée dans le monde et en France. En l'absence de vaccin commercial efficace, la maladie est jusqu’à présent systématiquement combattue à l'aide de traitements antibiotiques. Dans un contexte d’antibiorésistance croissante, il est nécessaire de trouver d’autres moyens de lutte et la sélection d'animaux naturellement plus résistants constitue une priorité pour la filière trutticole française. Si le caractère héritable de la résistance à la maladie est bien démontré chez la truite, une meilleure connaissance de ses différentes composantes et des déterminismes génétiques sous-jacents est nécessaire pour optimiser les modalités d’introduction de la résistance dans les objectifs des schémas de sélection conduits par les entreprises françaises.Dans ce contexte, l’objectif de cette thèse est d’étudier le déterminisme génétique de différentes composantes de la réponse à l’infection par F. psychrophilum par une approche de cartographie de QTL (quantitative trait locus) ; puis d’évaluer dans quelle mesure ces déterminismes dépendent des protocoles infectieux utilisés pour tester la résistance.Pour ce faire, nous avons combiné les résultats obtenus avec des infections expérimentales par injection et balnéation et une infection naturelleEn utilisant, d’une part des croisements expérimentaux entre lignées isogéniques à la résistance contrastée et d’autre part, avec une lignée commerciale élevée dans une entreprise de sélection française.Nous mettons en évidence que la réponse de la truite arc-en-ciel à l’infection par F. psychrophilum est un caractère complexe, contrôlé par un grand nombre de QTL d’effet modéré et en interaction. Nos résultats suggèrent également que les différentes composantes de la réponse à l’infection (résistance, endurance, résilience, portage) sont en partie contrôlées par des déterminants génétiques différents, et que certains mécanismes de défense contre l’infection par F. psychrophilum dépendent de la voie d’infection (infection par balnéation ou par injection). Cette étude ouvre la voie à une meilleure compréhension des mécanismes immunitaires sous-jacents à la réponse de la truite arc-en-ciel à l’infection par F. psychrophilum, et constitue une première étape vers la mise en place de la sélection génomique pour la résistance à F. psychrophilum dans les populations de truites françaises. / Health management and disease control are of both major economic and environmental concerns for animal production systems. Bacterial diseases are responsible for important economic losses in fish farming. Flavobacterium psychrophilum, the causative agent of bacterial cold water disease (BCWD), affects particularly rainbow trout (Oncorhynchus mykiss) and is found worldwide where salmonids are raised. As no commercial vaccine is available at the moment, the only way to fight BCWD remains through the use of antibiotic treatments. In a context of growing antibiotic resistance threat, additional methods to tackle fish disease are highly needed. Improving the natural host defense mechanisms against infectious pathogens through selective breeding is one of the priorities for French trout farmers. Moderate heritabilities were estimated for resistance against BCWD, indicating that selective breeding is a promising approach to improve trout defense mechanisms against F. psychrophilum. In order to implement disease resistance in French breeding schemes, we need to better understand the genetic determinism of this trait.In this context, the objective of this PhD is to study genetic determinism of different components of trout response to different infection protocols with F. psychrophilum using a QTL (Quantitative Trait Loci) mapping approach.To do so we used three experimental crosses between isogenic lines of trout with contrasting susceptibility. Finally, a study on a commercial line under selection in a French breeding company was performed after a natural disease outbreak to validate the interest of QTL previously detected.In this study, we showed that an important number of interacting QTL controls rainbow trout response to infection with F. psychrophilum. Our results suggest that different components of response to infection (resistance, endurance, resilience, bacterial load) might be controlled by different genetic determinisms. We also showed that different infection protocols trigger different immune mechanisms that may be specific to the route of entry of the pathogen. This study paves the way toward a better understanding of underlying immune mechanisms of rainbow trout response to F. psychrophilum. Finally, this study is the first step toward implementing genomic selection of resistance to BCWD in French rainbow trout population.

Flavobacterium psychrophilum est l’agent pathogène des flavobactérioses d’eau froide touchant essentiellement les salmonidés dont la truite arc-en-ciel Oncorhynchus mykiss d’élevage. Cette bactérie Gram négative a un très fort impact économique en aquaculture car elle peut causer jusqu'à 70 % de mortalité dans les bassins d’élevage. La flavobactériose se décline sous deux formes pathologiques : la maladie de l’eau froide touchant les poissons adultes et le syndrome de l’alevin de truite arc-en-ciel touchant les juvéniles.Au cours de se travail, une méthode de PCR quantitative a été proposée. Elle permet en moins de trois heures de détecter et de quantifier un nombre de copies du gène codant l’ARNr 16S de la bactérie dans les tissus du poisson. Cette méthode a été testée sur différentes suspensions bactériennes (F. psychrophilum, autres flavobactéries, autres pathogènes) afin d’en valider la spécificité. La sensibilité de la méthode de détection a été évaluée à 1 et 2 bactéries par PCR en fonction de la matrice biologique utilisée.Une étude écotoxicologique a été menée et montre d’une part que F. psychrophilum est une bactérie hyper-sensible au cadmium comparée aux autres bactéries Gram négatives. Sa croissance est diminuée d’un facteur 2 en présence d’une contamination au Cd à 0,4 µM. D’autre part, nous avons constaté qu’une contamination de truites juvéniles par 1 µg CdCl2/L (2 mois) et une injection de 5 × 107 flavobactéries par individu (1 mois) ne provoque aucune mortalité. L’expression génique mesurée sur ses poissons démontre que le cadmium peut avoir des effets contradictoires sur le système immunitaire du poisson, pouvant soit exacerber ou diminuer la réponse immunitaire selon l’organe considéré. Un travail comparatif de la prévalence de la flavobactérie dans 7 sites aquacoles d’Aquitaine a démontré que la flavobactérie est omniprésente et que sa pathogénicité est contrôlée par le système immunitaire des poissons en bonne santé apparente. L’expression génique mesurée sur les poissons malades et apparemment sains nous apporte deux informations importantes : 1/ les gènes codant pour la métallothionéine A et l’interleukine 1-β sont de bons bio-marqueurs de la maladie et 2/ la répression des gènes codant pour le complexe majeur d’histocompatibilité 2-β, le facteur de croissance transformant β, le cluster de différentiation 8-α et l’immunoglobuline T dans la rate des poissons malades montre un effondrement du système immunitaire acquis nous permettant d’émettre l’hypothèse que ce phénomène déclenche l’apparition de la maladie. Ainsi, F. psychrophilum aurait un comportement de pathogène à virulence latente.Afin d’imaginer de nouvelles mesures prophylactiques et pour mieux comprendre la pathogénicité de la bactérie, une analyse du protéome de la membrane externe couplée à l’annotation du génome séquencé a été effectuée. Il a été identifié entre autres 1/ des protéines d’adhésion et d’invasion des tissus et 2/ des protéines d’acquisition de métabolites de l’hôte. De plus, un nombre important de protéines immunogènes chez la truite potentiellement utilisable dans un cocktail vaccinant a été détecté. Afin de chercher un vecteur pour ce cocktail, des nanoparticules d’acide γ-glutamique et phénylalanine d’environ 100 à 200 nm de diamètre ont été synthétisées. Ces dernières constituent une approche séduisante pour vacciner les poissons avec des antigènes de F. psychrophilum encapsulés puis incorporés dans la nourriture. / Flavobacterium psychrophilum is the causative agent of cold water flavobacteriosis, a condition affecting mostly salmonid fish, including the farmed rainbow trout Oncorhynchus mykiss. This Gram negative bacterium can cause up to 70% mortality in breeding tanks and has a very strong economic impact on the fish farming industry. Flavobacteriosis can take two pathological forms: the cold water disease affecting adult fish and the rainbow trout fry syndrome affecting juveniles.In the present study, a method of quantitative PCR was devised that allowed for the detection and the quantification, within three hours, of the 16S rRNA copy number in fish tissues. This method’s specificity was confirmed through the use of various bacterial suspensions (F.psychrophilum, others flavobacteria and others pathogens) and its detection limit was estimated to be 1 and 2 bacteria in broth and in biological matrices, respectively.An ecotoxicological study was then performed that showed that, on the one hand, F. psychrophilum is cadmium hypersensitive compared to others Gram negative bacteria because its growth rate, compared to a control, is decreased by a factor 2 at a cadmium concentration of 0,4 µM. On the other hand, we observed that subjecting rainbow trout juveniles to a concentration of 1 µg CdCl2/L for2 months prior to an injection of 5 × 107 F. psychrophilum by fish didn’t lead to any mortality. The gene expression which was measured on these fish demonstrated that cadmium can have contradictory effects on the immune system of fish, which could enhance or decrease the immune response depending of the organ. A comparative work of the prevalence of flavobacteria in 7 fish farms within the Aquitaine region (France) demonstrated that the bacterium was endemic and present in asymptomatic fish. Gene expression levels were measured on diseased and asymptomatic fish and demonstrated that the genes metallothionein A and interleukine 1-β were good biomarkers of the disease and that repression of the genes major histocompatibility complex 2-β, transforming growth factor -β, cluster of differentiation α and immunoglobulin T in the spleen of diseased fish was indicative of a collapse of the acquired immune system. We therefore hypothesized that this event marked the beginning of the disease and that F. psychrophilum is mostly an opportunistic pathogen.To prepare the development of new prophylactic techniques and to understand better the bacterium pathogenicity, an analysis of the outer membrane proteome coupled with sequencing of the bacterial genome was also performed. Furthermore, a significant number of immunogenic proteins were identified as good candidates for the preparation of a vaccine. Finally, γ-glutamic acid and phenylalanine nanoparticles of about 100 - 200 nm in diameter were synthesized to serve as potential vector for this vaccine. These nanoparticles should be tested to administrate F. psychrophilum antigens to fish through the digestive route.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 4 uppsatser.