Long dsRNAs promote an anti-viral response in Pacific oyster hampering ostreid herpesvirus 1 replication

Double-stranded RNA (dsRNA)-mediated genetic interference (RNAi) is a widely used reverse genetic tool for determining the loss-of-function phenotype of a gene. Here, the possible induction of an immune response by long dsRNA was tested in a marine bivalve (Crassostrea gigas), as well as the specific role of the subunit 2 of the nuclear factor kappa B inhibitor (I kappa B2). This gene is a candidate of particular interest for functional investigations in the context of oyster mass mortality events, as Cg-I kappa B2 mRNA levels exhibited significant variation depending on the amount of ostreid herpesvirus 1 (OsHV-1) DNA detected. In the present study, dsRNAs targeting Cg-I kappa B2 and green fluorescent protein genes were injected in vivo into oysters before being challenged by OsHV-1. Survival appeared close to 100% in both dsRNA-injected conditions associated with a low detection of viral DNA and a low expression of a panel of 39 OsHV-1 genes as compared with infected control. Long dsRNA molecules, both Cg-I kappa B2- and GFP-dsRNA, may have induced an anti-viral state controlling the OsHV-1 replication and precluding the understanding of the specific role of Cg-I kappa B2. Immune-related genes including Cg-I kappa B1, Cg-Rel1, Cg-IFI44, Cg-PKR and Cg-IAP appeared activated in the dsRNA-injected condition, potentially hampering viral replication and thus conferring a better resistance to OsHV-1 infection. We revealed that long dsRNA-mediated genetic interference triggered an anti-viral state in the oyster, emphasizing the need for new reverse genetics tools for assessing immune gene function and avoiding off-target effects in bivalves.


Anti-viral response, RNA interference, Inhibitor of NF-kappa B, Marine bivalve, Ostreid herpesvirus 1

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Pauletto Marianna, Segarra Amelie, Montagnani Caroline, Quillien Virgile, Faury Nicole, Le Grand Jacqueline, Miner Philippe, Petton Bruno, Labreuche Yannick, Fleury Elodie, Fabioux Caroline, Bargelloni Luca, Renault Tristan, Huvet Arnaud (2017). Long dsRNAs promote an anti-viral response in Pacific oyster hampering ostreid herpesvirus 1 replication. Journal Of Experimental Biology. 220 (20). 3671-3685. https://doi.org/10.1242/jeb.156299, https://archimer.ifremer.fr/doc/00409/52011/

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