Physiological change under OsHV-1 contamination in Pacific oyster Crassostrea gigas through massive mortality events on fields

Abstract

BackgroundMassive mortalities have been observed in France since 2008 on spat and juvenile Pacific oysters, Crassostrea gigas. A herpes virus called OsHV-1, easily detectable by PCR, has been implicated in the mortalities as demonstrated by the results of numerous field studies linking mortality with OsHV-1 prevalence. Moreover, experimental infections using viral particles have documented the pathogenicity of OsHV-1 but the physiological responses of host to pathogen are not well known.ResultsThe aim of this study was to understand mechanisms brought into play against the virus during infection in the field. A microarray assay has been developed for a major part of the oyster genome and used for studying the host transcriptome across mortality on field. Spat with and without detectable OsHV-1 infection presenting or not mortality respectively were compared by microarray during mortality episodes. In this study, a number of genes are regulated in the response to pathogen infection on field and seems to argue to an implication of the virus in the observed mortality. The result allowed establishment of a hypothetic scheme of the host cell’s infection by, and response to, the pathogen.ConclusionsThis response shows a “sensu stricto” innate immunity through genic regulation of the virus OsHV-1 life cycle, but also others biological processes resulting to complex interactions between host and pathogens in general.

Rearing practices identified as risk factors for ostreid herpesvirus 1 (OsHV-1) infection in Pacific oyster Crassostrea gigas spat

“…The seasonality of mortality outbreaks in spat and virus detection in relation to seawater temperature variation also suggests that OsHV-1 is able to reactivate from latency and that this is triggered by temperature increases (Le Deuff et al 1996, Burge et al 2006, Oden et al 2011. The identification of several OsHV-1 genes involved in latency maintenance or in the lytic phase (Jouaux et al 2013) strongly supports this hypothesis.…”

Infectious diseases in oyster aquaculture require a new integrated approach

“…OsHV-1 is detected in haemocytes 6 h following exposure of naive oysters in laboratory cohabitation studies, and these cells then transport the virus to target organs [26]. Infected cells transcribe viral genes, which leads to replication and release of the virus into the cytoplasm within 2-3 days [32,33]. The minimum infective dose, an important parameter for evaluating the potential for spread of viruses in their natural environment, is currently unknown for natural infections with OsHV-1.…”

Antiviral immunity in marine molluscs

“…and no studies of cephalopods. Studies investigating the antiviral response of molluscs have mainly focused on identifying antiviral compounds, measuring immune enzyme activity or characterizing the transcriptional response to OsHV-1 infection Dang et al, 2011Dang et al, , 2013Fleury & Huvet, 2012;Green & Montagnani, 2013;Green et al, 2014c;Jouaux et al, 2013;Moreau et al, 2015;Normand et al, 2014;Olicard et al, 2005a, b;Renault et al, 2011;Rosani et al, 2014;Segarra et al, 2014a, c). These studies suggest that the molluscan antiviral response has similarities to the vertebrate interferon pathway (Green & Montagnani, 2013).…”

“…In addition, mortality events of Crassostrea gigas were reported in 2010 from New Zealand and Australia in association with a virus closely related to mVar (Jenkins et al, 2013;Keeling et al, 2014). Numerous genomic and proteomic studies investigating the host-pathogen interactions of Crassostrea gigas and OsHV-1 have been undertaken (Corporeau et al, 2014;Du et al, 2013;Fleury & Huvet, 2012;Green & Montagnani, 2013;Jouaux et al, 2013;Normand et al, 2014;Renault et al, 2011;Segarra et al, 2014a, b, c;Tamayo et al, 2014). Acute viral necrosis virus (AVNV) is the causative agent of a serious disease of Chinese scallops, Chlamys farreri (Ren et al, 2013).…”