Abstract
Viral entry mechanisms of herpesviruses constitute a highly complex process which implicates several viral glycoproteins and different receptors on the host cell surfaces. This initial infection stage was currently undescribed for Ostreid herpes virus 1 (OsHV-1), a herpesvirus infecting bivalves including the Pacific oyster, Crassostrea gigas. To identify OsHV-1 glyproteins implicated in the attachment of the virus to oyster cells, three viral putative membrane proteins, encoded by ORF 25, 41, and 72, were selected and polyclonal antibodies against these targets were used to explore first interactions between the virus and host cells. In addition, effects of dextran sulfate, a negative charged sulfated polysaccharide, were investigated on OsHV-1 infection. Effects of antiviral antibodies and dextran sulfate were evaluated by combining viral DNA and RNA detection in spat (in vivo trials) and in oyster hemolymph (in vitro trials). Results showed that viral protein encoded by ORF 25 appeared to be involved in interaction between OsHV-1 and host cells even if other proteins are likely implicated, such as proteins encoded by ORF 72 and ORF 41. Dextran sulfate at 30 μg/mL significantly reduced the spat mortality rate in the experimental conditions. Taken together, these results contribute to better understanding the pathogenesis of the viral infection, especially during the first stage of OsHV-1 infection, and open the way toward new approaches to control OsHV-1 infection in confined facilities.
Highlights
Ostreid herpesvirus 1 (OsHV-1) has been a major threat to Pacific cupped oyster cultivation in Europe over the last decades, especially for French oyster farmers
As no spat mortality was recorded in different control conditions and viral DNA copies per nanogram of total DNA in dead oysters were log 4.8 ± 0.8, mortality observed in tested conditions was considered to be due to viral infection (Figure 1)
At 18 h post-incubation, the amount of OsHV-1 DNA was significantly higher in hemolymph from adult oysters presenting a high susceptibility to Ostreid herpes virus 1 (OsHV1) infection than those collected from adult oysters which are less susceptible to OsHV-1 infection (Figure 2)
Summary
Ostreid herpesvirus 1 (OsHV-1) has been a major threat to Pacific cupped oyster cultivation in Europe over the last decades, especially for French oyster farmers. Other studies focused on the OsHV-1 replication cycle by analyzing viral gene expression during an experimental OsHV-1 infection or in vitro approaches (Renault et al, 2011; Jouaux et al, 2013; Rosani et al, 2014; Segarra et al, 2014b; Morga et al, 2017). This knowledge was completed by recent results on tissue distribution of viral DNA, RNA and proteins (Schikorski et al, 2011a; Corbeil et al, 2015; Martenot et al, 2016; Segarra et al, 2016). The present study attempts to better understand these interactions at protein level by approaches not already used in this model
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