Mechanisms and specificity of antiviral immune priming in a Lophtrochozoan, the Pacific oyster Crassostrea gigas

• Main Author: Lafont, Maxime
• Other Authors: Interactions Hôtes-Pathogènes-Environnements (IHPE), Université de Perpignan Via Domitia (UPVD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM), Université de Perpignan, Benjamin Gourbal, Caroline Montagnani
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2017
• Subjects: Immune priming; Antiviral mechanisms; Poly(I:C); Innate immunity; Pacific oyster; Immunité innée; Huître creuse; Priming immunitaire; Mécanismes antiviraux; [SDV.IMM]Life Sciences [q-bio]/Immunology; Pacific; Crassostrea gigas
• Online Access: https://theses.hal.science/tel-02426215; https://theses.hal.science/tel-02426215/document; https://theses.hal.science/tel-02426215/file/These_LAFONT_Maxime_2017.pdf

Since 2008, mass mortality events of multifactorial origin have affected the Pacific oyster Crassostrea gigas farms worldwide, in which a herpesvirus, the OsHV-1, can be considered as one of the major pathogens. The immunity of oysters, as for all invertebrates, is based on an innate immune system that has long been considered to be scarcely specific and to lack memory. However, in recent years this simplistic view has been questioned through studies that have demonstrated the existence of a specific immune response and memory. However, knowledge about the mechanisms underlying these phenomena still remains extremely fragmentary. The aim of this thesis was to characterize the antiviral immune priming and its mechanisms in the oyster against OsHV-1. By stimulating oysters with a viral mimic, poly(I:C), we have shown that this molecule specifically protects against OsHV-1 in controlled environment and in natural environment, protecting oysters from mass mortality events on the long term (min. 5 months) by improving oyster survival by almost 100% but does not protect against bacterial infection. A RNA-seq approach carried out during this thesis allowed us to identify different antiviral immune pathways regulated following the stimulation by poly(I:C). The regulation profiles are mostly maintained over time (at least 10 days), which could explain the observed protection. All these results show the existence of an effective antiviral immune priming phenomenon in a Lophotrochozoan and contribute to the understanding of the molecular mechanisms underlying this phenomenon. This work opens new perspectives hitherto unexplored to support oyster farming against this crisis. Depuis 2008, des épisodes de surmortalité massive d’origine multifactorielle, affectent mondialement les élevages de juvéniles d’huître creuse Crassostrea gigas dont le virus de type herpès, l’OsHV-1, peut être considéré comme un des agents pathogènes majeurs. L’immunité des huîtres, repose sur un système immunitaire inné et a longtemps été considéré ...