The innate immune system of fish is critical for rapid detection and immediate response to infection, as well as to orchestrate the adaptive branch of the immune system. Rainbow trout Oncorhynchus mykiss ladderlectin and intelectin are plasma pattern recognition receptors (PRR) for bacterial and fungal pathogens of rainbow trout, but their role as PRRs for virus is unknown. Viral hemorrhagic septicemia virus (VHSV) IVb is a recently described fish pathogen in the Great Lakes, and rainbow trout can be experimentally infected. Using an indirect enzyme-linked immunosorbent assay, rainbow trout plasma ladderlectin significantly (p < 0.05) bound purified VHSV while int electin did not. In addition, plasma ladderlectin but not intelectin was eluted from a VHSV-conjugated Toyopearl column using EDTA. Protein identification was confirmed with polyclonal antiserum used with slot immunoblot, 1-dimensional sodium dodecyl sulphate polyacrylamide electrophoresis, and Western immunoblot.KEY WORDS: Oncorhychus mykiss · Pattern recognition receptor · Viral hemorrhagic septicemia virus · Innate immunity · Plasma proteins · Binding · Ladderlectin · Intelectin
Resale or republication not permitted without written consent of the publisherDis Aquat Org 95: [137][138][139][140][141][142][143] 2011 in rainbow trout by 7 d and lasting up to 21 d (Acosta et al. 2005). A DNA vaccine for VHSV conferred shortterm protection of rainbow trout Oncorhynchus mykiss from infection with heterologous rhabdoviruses and the unenveloped nodavirus of turbot (Sommerset et al. 2003). Resistance was hypothesized to be due to the initial inflammatory response that is likely to produce innate antiviral proteins such as interferon and Mx (Sommerset et al. 2003). Mx proteins are one of the major families of interferon-stimulated proteins resulting from innate immune recognition of viral infection (Ellis 2001). More recently, VHSV has been shown to stimulate multiple components of the innate immune system. In gilthead seabream Sparus aurata, VHSV has been shown to recruit and increase the activity of natural cytotoxic cells (NCC) (Esteban et al. 2008). Rainbow trout TLR9 was upregulated at the site of injection of VHSV glycoprotein G in muscle, suggesting the recruitment of dendritic cells to the site; in the head kidney and spleen there was transcriptional increase of tumor necrosis factor alpha and interleukin-6, which are cytokines known to be upregulated by TLR9 activated by unmethylated CpG DNA (Ortega-Villaizan et al. 2009). In addition, the RIG-I/MAVS pathway of double stranded RNA-stimulated interferon induction has been documented in numerous fish species (Biacchesi et al. 2009), and Mx transcript upregulation has been shown in rainbow trout (Acosta et al. 2005) in response to VHSV infection. In Japanese flounder Paralichthys olivaceus, VHSV infection upregulates the hepatic expression of C3 and complement regulatory proteins (Byon et al. 2006).Lectins are cell-associated or circulating proteins involved in recognition and binding of vir...