Étude structurale et fonctionnelle du phénomène d'adhésion des norovirus sur des surfaces inertes et des aliments
|Advisor:||Jean, Julie; Fliss, Ismaïl|
|Abstract:||Human noroviruse has been the main cause of acute non-bacterial gastroenteritis in the world through all ages. Their growing incidence has been repeatedly associated with their ability to bind and persist on agrifood surfaces in food processing environments. However, the mechanism of their adhesion phenomenon remains unknown. This study was aimed at identifying structural, molecular and functional elements of human norovirus involved in their adhesion phenomenon. Prototypes as «virus-like particle» (VLPs) have been produced for human noroviruses GI.1 and GII.4 and feline calicivirus (FCV) using cell culture, purified by ultracentrifugation, and characterized with aspect to pH, ionic strength and temperature. In this characterization, their electrical charges and their size were analyzed using a Zeta NanoSizer ZS and their secondary and tertiary structures and stability were analyzed using circular dichroism and intrinsic fluorescence UV techniques, respectively. Their surface energies as well as surface energies of inert surfaces and fresh foods were estimated applying contact angle technic with a goniometer. The total interfacial free energy of interactions between the VLPs and the surfaces were estimated, and GII.4 VLPs adhesion assays perfomed in order to draw correlation between adhesion and structural, molecular and functional changes. Our results revealed that GII.4 VLPs adhesion was rather related to structural, molecular and functional changes than surface thermodynamic proprieties. Maxima observed at isoelectric point followed by decreases with pH and the increasing trend with increasing ionic strength indicate respectively the importance of acid base (hydrophobic) interactions and of van der Waals interactions in adhesion phenomenon. The adhesion on polyethylene and lettuce are seemingly related to hydrophobic interactions, while the adhesion on stainless steel is apparently controlled by van der Waals interactions. At low temperature, adsorption may rely on capsid external hydrophobic residues, while at high temperature, internal hydrophobic residues may plausibly play a part in the process upon denaturation of secondary and tertiary structures. The interactions mainly involved in GII.4 VLPs adsorption are hydrophobic and suggest the use of chaotropic agents to break efficiently adhesion mechanism and limit norovirus outbreaks.|
|Document Type:||Thèse de doctorat|
|Open Access Date:||23 April 2018|
|Collection:||Thèses et mémoires|
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