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Cell-mediated cytotoxicity (CMC) is essential in eradicating virus-infected cells, involving CD8+ T lymphocytes (CTLs) and natural killer (NK) cells, through the activation of different pathways. This immune response is well-studied in mammals but scarcely in teleost fish. Our aim was to investigate the adaptive CMC using head-kidney (HK) cells from European sea bass infected at different times with nodavirus (NNV), as effector cells, and the European sea bass brain cell line (DLB-1) infected with different NNV genotypes, as target cells. Results showed low and unaltered innate cytotoxic activity through the infection time. However, adaptive CMC against RGNNV and SJNNV/RGNNV-infected target cells increased from 7 to 30 days post-infection, peaking at 15 days, demonstrating the specificity of the cytotoxic activity and suggesting the involvement of CTLs. At transcriptomic level, we observed up-regulation of genes related to T cell activation, perforin/granzyme and Fas/FasL effector pathways as well as apoptotic cell death. Further studies are necessary to understand the adaptive role of European sea bass CTLs in the elimination of NNV-infected cells. [Display omitted] • Head-kidney cells from RGNNV-infected European sea bass display cell-mediated cytotoxicity (CMC). • CMC response is specific against RGNNV capsid protein expressing target cells. • Adaptive CMC peaks after 15 days of infection. • Genes related to perforin/granzyme and Fas/FasL pathways were up-regulated during the CMC response. [ABSTRACT FROM AUTHOR]

Mammalian interleukin-1β (IL-1β) is a secretory cytokine lacking a signal peptide, which does not follow the classical endoplasmic reticulum to Golgi pathway of secretion. Its post-translational processing by IL-1β-converting enzyme (ICE) and subsequent release from activated macrophages requires ATP acting on P2X7 receptors. Little information is available on the production and release of fish IL-1β, but the IL-1β gene sequences reported to date lack a conserved ICE recognition site. We show for the first time that lipopolysaccharide (LPS)/macrophage-activating factor/bacterial DNA (VaDNA)-primed immune cells of the marine fish gilthead seabream (Sparus aurata) accumulate intracellular IL-1β as a ∼30 kDa polypeptide (proIL-1β). The combination of LPS and VaDNA was found to be synergistic, suggesting that each ligand is recognized by a different pattern recognition receptor. More importantly, addition of extracellular ATP does not promote IL-1β secretion by immune cells and fails to induce phosphatidylserine flip. In contrast, gilthead seabream SAF-1 fibroblasts shed microvesicles containing a 22 kDa IL-1β form within 30 min of activation with ATP. Notably, the post-translational processing of IL-1β by SAF-1 cells is abrogated by a specific ICE inhibitor. [Copyright &y& Elsevier]