Data/hora: 09/06/2024 06:00:29

Provedor de dados: 	5	
País: 	France	
Título: 	Etude de la réponse immunitaire chez l'huître Crassostrea gigas : caractérisation et fonctions de protéines de reconnaissance aux LPS et d'effecteurs antimicrobiens	
Autores: 	Gonzalez, Marcelo.	
Data: 	2005-11-23	
Ano: 	2005	
Palavras-chave: 	Defense peptides; Polysaccharides; LPS; Hemocytes; Immune response; Crassostrea gigas; Shellfish culture; LPS; Défensine; Peptides antimicrobiens; LBP; BPI; Superoxide dismutase; Hémocytes; Crassostrea gigas; Huître; Mollusque; Immunité.	
Resumo: 	Research on the immune response of oysters is motivated by the problems of infectious diseases potentially found in the farms. Over the course of the last few years, the development of genomic approaches has allowed us to make headway on characterising genes involved in the cup oyster's (Crassostrea gigas) innate immunity, particularly thanks to various programmes for analysing transcriptome, of type EST (Express Sequence Tag) and subtractive banks. Within the context of this work, over the course of which we have used the data from genomic research and we have also developed biochemical approaches, we were particularly interested in studying the proteins involved in reconnaissance reactions to LPS as well as to antimicrobial effectors. In an earlier part, we isolated, from the plasma, two proteins showing binding activities with the LPS of Gram-negative bacteria. We were able to identify the first isolated protein as being a Superoxide Dismutase of the extracellular type produced by haemocytes (Cg-EcSOD). Our results suggest that Cg-EcSOD has, in addition to its SOD activity, original LPS binding properties and could bind itself to haemocytes via a &amp;#946; integrin. The second protein, Cg-LBP (Lipopolysaccharide-Binding protein), isolated from the oyster's plasma, does not have any homology with the proteins from the databases and shows strong affinities for LPS. As far as the antimicrobial effectors are concerned, we characterised a gene coding a protein of type Bactericidal/Permeability Increasing protein, Cg-BPI, which is expressed in haemocytes and the epithelia as well as an antimicrobial peptide of type defensin (Cg-Def) from the oyster's mantle. Two other sequences of defensins (Cg-Defh) isolated from haemocytes were characterised. Functional studies of recombinant proteins show that Cg-BPI displays LPS binding properties as well as a permeabilisation of E. coli's external membrane. It is the first protein of type BPI characterised in an invertebrate. Defensin Cg-Def displays a spectrum of antimicrobial activity comparable to that of the other defensins of invertebrates. Gene expression analyses confirm that Cg-BPI and Cg-Def are expressed in a constitutive way at the oyster's epithelial level. However, the expression profiles of Cg-BPI and Cg-Defh after stimulation by bacteria show variations. All of the results obtained in the context of this thesis have allowed us to make headway in understanding the mechanisms set up in the oyster for controlling or eliminating potentially pathogenic micro-organisms.	
Tipo: 	Text	
Idioma: 	Francês	
Identificador: 	http://archimer.ifremer.fr/doc/2005/these-2098.pdf	
Editor: 	Université Montpellier II	
Relação: 	http://archimer.ifremer.fr/doc/00000/2098/	
Formato: 	application/pdf