Chinese Giant Salamander (Andrias davidianus) Iridovirus Infection Leads to Apoptotic Cell Death through Mitochondrial Damage, Caspases Activation, and Expression of Apoptotic-Related Genes

Abstract

Chinese giant salamander iridovirus (GSIV) is the causative pathogen of Chinese giant salamander (Andrias davidianus) iridovirosis, leading to severe infectious disease and huge economic losses. However, the infection mechanism by GSIV is far from clear. In this study, a Chinese giant salamander muscle (GSM) cell line is used to investigate the mechanism of cell death during GSIV infection. Microscopy observation and DNA ladder analysis revealed that DNA fragmentation happens during GSIV infection. Flow cytometry analysis showed that apoptotic cells in GSIV-infected cells were significantly higher than that in control cells. Caspase 8, 9, and 3 were activated in GSIV-infected cells compared with the uninfected cells. Consistently, mitochondria membrane potential (MMP) was significantly reduced, and cytochrome c was released into cytosol during GSIV infection. p53 expression increased at an early stage of GSIV infection and then slightly decreased late in infection. Furthermore, mRNA expression levels of pro-apoptotic genes participating in the extrinsic and intrinsic pathway were significantly up-regulated during GSIV infection, while those of anti-apoptotic genes were restrained in early infection and then rose in late infection. These results collectively indicate that GSIV induces GSM apoptotic cell death involving mitochondrial damage, caspases activation, p53 expression, and pro-apoptotic molecules up-regulation.

Bcl-xL Reduces Chinese Giant Salamander Iridovirus-Induced Mitochondrial Apoptosis by Interacting with Bak and Inhibiting the p53 Pathway

“…To date, no effective prevention and treatment methods are available for GSIV infection. In our previous study, GSIV infection triggered typical apoptotic cell death through both the extrinsic and intrinsic pathways [23]. In addition, the protein levels of p53 increased during GSIVinduced apoptosis.…”

“…In carp, Spring viremia of carp virus (SVCV) degraded p53 early during infection, while an increase in p53 was observed late in the infection process [32]. In our previous study, the protein level of p53 was upregulated following GSIV-induced apoptosis [23]. BCL-2 proteins such as Bax/Bak are believed to be the downstream effectors of the tumor suppressor p53 [33].…”

“…After propagation of positive transformants, Isopropyl β-d-1-thiogalactopyranoside induction, recombinant protein purification, and quantification of their concentrations, the purified rAdBcl-xL was immunized separately into rabbits four times to acquire polyclonal antibodies. For Bcl-xL protein expression analysis, samples of GSM cells after GSIV infection (multiplicity of infection (MOI) = 0.5) at different time points were prepared, as reported previously [23]. Briefly, after harvesting and lysis using SDS Lysis Buffer (Beyotime, Jiangsu, China), the samples were suspended in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) sample loading buffer and heated at 95 • C for 5 min.…”

Largemouth Bass Virus Infection Induced Non-Apoptotic Cell Death in MsF Cells

“…Among them, Ranaviruses have a broad host range, including teleost, amphibians, and reptiles [ 18 ]. To demonstrate the mechanism of ranaviruses pathogenesis, the mode of cell death induced by ranaviruses was gradually investigated, including Rana grylio virus (RGV) [ 19 ], Frog virus 3 (FV3) [ 20 ], grouper iridovirus (GIV) [ 21 ], epizootic hematopoietic necrosis virus (EHNV) [ 22 ], and Chinese giant salamander iridovirus (GSIV) [ 23 ]. Interestingly, the outcome of cell death induced by SGIV (fish ranavirus) was cell type dependent [ 24 ].…”

Glycosylphosphatidylinositol Mannosyltransferase Ⅰ Protects Chinese Giant Salamander, Andrias davidianus, against Iridovirus

“…In recent years, the outbreak of the Chinese giant salamander iridovirus (GSIV) brought great losses to the breeding industry, and there is no medical treatment for this disease. GSIV, a member of the genus Ranavirus and belonging to the iridovirus family, is a double-stranded DNA virus with icosahedral symmetry and a diameter of approximately 140 nm [ 19 , 20 , 21 ]. The GSIV infection of Chinese giant salamanders causes anorexia, lethargy, skin ulceration, and tissue necrosis, and the mortality rate of giant salamanders infected with iridovirus is more than 90% [ 22 ].…”