Aquatic birnavirus induces apoptosis through activated caspase‐8 and ‐3 in a zebrafish cell line

Abstract

In this study, the possible influence of temperature on infectious pancreatic necrosis virus (IPNV)-induced apoptosis in a zebrafish liver epithelium (ZLE) cell line was investigated. At a lower temperature (18 degrees C), there was expression of viral proteins VP2 and VP3 at 4 h post-infection (p.i.). At this time no expression was found in the high temperature group at 28 degrees C. The cell survival ratio was 52 and 18% at 24 and 48 h p.i., respectively, during IPNV infection at 18 degrees C. In addition, we assayed for apoptosis in IPNV-infected cells with terminal deoxynucleotidyl transferase (TdT)-mediated end labelling (TUNEL) of DNA at different dosages of virus. We found a ratio of apoptotic cells of 8 and 25% at 12 and 18 h p.i., respectively, in the multiplicity of infection (MOI) 1 group. The MOI 10 group had 20 and 45% apoptotic cells at 12 and 18 h, respectively. Furthermore, at 18 degrees C IPNV activated the caspase-8 and 3 from 1.5 to 2 times at 12 and 18 h p.i., respectively. Taken together, these findings suggest that successful virus replication occurs at the low temperature (18 degrees C) compared with the non-permissive temperature of 28 degrees C. Thus, IPNV replication is capable of activating caspase-8 and -3 and inducing host apoptosis.

Aquatic birnavirus capsid protein, VP3, induces apoptosis via the Bad-mediated mitochondria pathway in fish and mouse cells

“…Cleavage of synthetic caspase-9 (LEHD-AMC) and caspase-3 (DEVD-ABC) substrates were analyzed to determine caspase activation. Cleavage after the second Asp residue produced free AFC [19], with the amount of detected fluorescence directly proportional to the level of caspase activity. Fluorogenic substrate assay experiments were performed at the same time.…”

“…IPNV induced cell death through caspase-8 and caspase-3 activation [19], and the transcription factor, NF-kB, was activated by tyrosine kinase upon IPNV infection [20]. In addition, IPNV can up-regulate expression of host annexin 1, an anti-apoptotic factor that enhances cell viability [21].…”

Activation of cytokine expression occurs through the TNFα/NF-κB-mediated pathway in birnavirus-infected cells

“…The expression level of the anti-apoptotic Bcl-2 gene Mcl-1 has been shown to be downregulated following IPNV infection [9]. The initiator caspase 8 and effector caspase 3 are activated and promote host cell apoptosis during IPNV pathogenesis [10]. The apoptosis induced by IPNV occurs via a viral receptor that triggers the expression of the death gene Bad, possibly through a tyrosine kinase-dependent pathway [11].…”

Identification of Aquatic Birnavirus VP3 Death Domain and Its Dynamic Interaction Profiles in Early and Middle Replication Stages in Fish Cells

“…It induces apoptotic cell death in CHSE-214 cells Hong et al, 1999a;Hong et al, 1999b) and zebrafish ZLE cells (Hong et al, 2005). In summary, we provided evidence that IPNV minor capsid proteins were specifically involved in the induction of necrotic cell death.…”

“…Previously, it was found that IPNV-induced apoptosis Hong, et al, 1999a;Hong et al, 1999b;Hong and Wu, 2002) may be mediated through activation of caspase-8 and -3 (Hong et al, 2005) and requires new protein synthesis (Hong et al, 1999). This pathway may be triggered through NF-κB transcription factor transactivation of downstream effector genes such as Bad (Hong et al, 2008).…”