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Etude de la variole ovine en Tunisie et caractérisation des protéines virales impliquées dans la réponse immunitaire anti-capripoxvirus

Abstract : The sheep pox virus is omnipresent in small ruminant farms in North African countries andparticularly in Tunisia despite the annual vaccination campaigns set up by the Tunisian veterinaryauthorities. The optimization of the used vaccine strain involves the development of the so-called newgeneration vaccines such as subunit vaccines and this, using proteins recognized to induce a protectivehumoral response in the immunized animal. This could be considered as an alternative to currentcontrol strategies limiting virus spread in Tunisia. Few data exist on protective antigens specific toviruses in the genus Capripoxvirus. By homology to vaccinia virus proteins, this thesis work hastargeted four proteins in the genus Capripoxvirus belonging to the potentially immuno-dominantcontagious nodular dermatosis virus named LSDV60, LSDV117, LSDV122 and LSDV141respectively homologues of proteins L1, A27, A33 and B5. First, an in silico structural analysis hasallowed to identify the essential domains of each protein and to check the conservation rate of theseproteins among different viruses belonging to the poxvirus family. A thorough structural analysisidentifying the primary, secondary and tertiary structure of the A27 protein was conducted. Followingthis structural study, the proteins were produced in two different expression systems, namely theeukaryotic system and the baculovirus-insect cell system, in order to characterize their antigenicity tosera from immunized or proven animals. The recognition of the proteins of interest in the eukaryoticexpression vector has not been conclusive. On the other hand, the BEVS expression systemsuccessfully allowed the production of the A27 protein (L1, A33 and B5 in progress) in a solubleform, which was correctly recognized by sera from challenged naïve goats. Identifying trimeric andhexameric forms confirms its antigenicity. An immunodetection of the peptides corresponding toprotein A27 synthesized on membranes (PepScan) combined with an in silico analysis led to identifyzones capable of constituting recognized epitopic regions located predominantly in part N-terminal ofthe protein.
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Faten Ben Chehida Regaya. Etude de la variole ovine en Tunisie et caractérisation des protéines virales impliquées dans la réponse immunitaire anti-capripoxvirus. Médecine vétérinaire et santé animale. Université Montpellier; Faculté des sciences de Bizerte (Tunisie), 2017. Français. ⟨NNT : 2017MONTT021⟩. ⟨tel-02936259⟩

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