Salmon louse rhabdoviruses: Impact on louse development and transcription of selected Atlantic salmon immune genes. (September 2018) - Øvergård, Aina-Cathrine
Abstract: Recently, it has been shown that the salmon louse ( Lepeophtheirus salmonis ) is commonly infected by one or two vertically transmitted Lepeophtheirus salmonis rhabdoviruses (LsRVs). As shown in the present study, the viruses have limited effect on louse survival, developmental rate and fecundity. Since the LsRVs were confirmed to be present in the louse salivary glands, the salmon cutaneous immune response towards LsRV positive and negative lice was analyzed. In general, L. salmonis increased the expression of IL1β, IL8 and IL4/13A at the attachment site, in addition to the non-specific cytotoxic cell receptor protein 1 (NCCRP-1). Interestingly, LsRV free lice induced a higher skin expression of IL1β, IL8, and NCCRP-1 than the LsRV infected lice. The inflammatory response is important for louse clearance, and the present results suggest that the LsRVs can be beneficial for the louse by dampening inflammation. Further research is, however; needed to ascertain whether this is a direct modulatory effect of secreted virions, or if virus replication is altering the level of louse salivary gland proteins. Highlights: The Lepeopthteirus salmonis rhabdoviruses do not affect salmon louse development, size or fecundity. The Lepeopthteirus salmonis rhabdoviruses is localized to the salmon louse salivary gland. The response towards salmon louse includes an increase of IL1β, IL8, IL4/13A and NCCRP-1 mRNA at the lice attachment site. Higher levels of IL1β and IL8 were seen in response to virus free lice than virus infected lice.