Innate Cell-Mediated Cytotoxic Activity of European Sea Bass Leucocytes Against Nodavirus-Infected Cells: A Functional and RNA-seq Study

Abstract

Nervous necrosis virus (NNV) causes high mortalities in several marine species. We aimed to evaluate the innate cell-mediated cytotoxic (CMC) activity of head-kidney leucocytes (HKLs) isolated from naïve European sea bass (Dicentrarchus labrax) and gilthead seabream (Sparus aurata), a very susceptible and resistant fish species to NNV, respectively, against fish cell lines infected with NNV. Seabream HKLs showed significantly increased innate CMC activity against NNV-infected cells, compared to those uninfected, while sea bass HKLs failed to do so. Thus, we performed a RNA-seq study to identify genes related to the CMC activity of sea bass leucocytes. Thus, we found that sea bass HKLs incubated with DLB-1 cells alone (CMC_DLB1) or with NNV-infected DLB-1 cells (CMC_DLB1-NNV) showed very similar transcriptomic profiles and the GO analysis revealed that most of the up-regulated genes were related to immunity. Strikingly, when the CMC samples with and without NNV were compared, GO analysis revealed that most of the up-regulated genes in CMC_DLB1-NNV samples were related to metabolism and very few to immunity. This is also in agreement with the functional data. These data point to the escape of CMC activity by NNV infection as an important factor involved in the high susceptibility to nodavirus infections of European sea bass.

Betanodavirus and VER Disease: A 30-year Research Review

“…Gene ontology enrichment revealed the down-regulation of transcripts related to the cytoskeleton and vesicle biology, suggesting that the failure of vesicle transport upon NNV infection could be a major mechanism behind the pathogenic effects on the fish nervous system [232]. In another study also performed with DLB-1 cells, the transcriptomic profiles obtained from European sea bass head-kidney leucocytes incubated with NNV infected and uninfected cells were very similar, supporting that cell-mediated cytotoxic activity in sea bass is not primed upon NNV infection [231]. Other cells used for transcriptome analysis were Asian seabass (Lateolabrax japonicus) epithelial cells (SB) [229], grouper kidney (GK) cells [228] and Lateolabrax japonicus brain cells (LJB) [233].…”

“…In recent years, a great deal of progress has been made on high-throughput tools for sequencing the transcriptome (RNA-Seq), enabling genome-wide transcriptomic analysis and providing valuable information for understanding virus-host interactions [227]. Different transcriptomic analyses have been performed on both NNV-infected cells [228][229][230][231][232][233] and fish [234][235][236][237][238].…”

Identification and Regulation of Interleukin-17 (IL-17) Family Ligands in the Teleost Fish European Sea Bass

“…Sequences for IL-17 ligands were searched in internal RNA-seq experiments [44,45] and in the European sea bass genome project database (http://seabass.mpipz.mpg.de/). The identified mRNA sequences were detected, and putative proteins were predicted within the ExPASy Molecular Biology server (http://us.expasy.org).…”

Inhibition of Cyclophilin A on the replication of red spotted grouper nervous necrosis virus associates with multiple pro-inflammatory factors

“…Interestingly, the expression of RGNNV and CypA were gradual and significantly increased in GF-1 cells till 12 hpi. However, the substantial decrease at 24 hpi remains unclear, further transcriptomic and gene expression investigations might reveal the exact immune mechanisms of GF-1 cells related to RGNNV infection, as observed by Pozo and colleagues in European sea bass (Dicentrarchus labrax) and gilthead seabream (Sparus aurata) head-kidney leucocytes (HKLs) infected with NNV [41]. The expression pattern of GF-CypA was added to the universality and the importance of the role-played by Cyclophilin A family.…”