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

Abstract

Largemouth bass virus (LMBV), belonging to the genus Ranavirus, causes high mortality and heavy economic losses in largemouth bass aquaculture. In the present study, a novel cell line, designated as MsF, was established from the fin of largemouth bass (Micropterus salmoides), and applied to investigate the characteristics of cell death induced by LMBV. MsF cells showed susceptibility to LMBV, evidenced by the occurrence of a cytopathic effect (CPE), increased viral gene transcription, protein synthesis, and viral titers. In LMBV-infected MsF cells, two or more virus assembly sites were observed around the nucleus. Notably, no apoptotic bodies occurred in LMBV-infected MsF cells after nucleus staining, suggesting that cell death induced by LMBV in host cells was distinct from apoptosis. Consistently, DNA fragmentation was not detected in LMBV-infected MsF cells. Furthermore, only caspase-8 and caspase-3 were significantly activated in LMBV-infected MsF cells, suggesting that caspases were involved in non-apoptotic cell death induced by LMBV in host cells. In addition, the disruption of the mitochondrial membrane potential (ΔΨm) and reactive oxygen species (ROS) generation were detected in both LMBV-infected MsF cells and fathead minnow (FHM) cells. Combined with our previous study, we propose that cell death induced by LMBV infection was cell type dependent. Although LMBV-infected MsF cells showed the characteristics of non-apoptotic cell death, the signal pathways might crosstalk and interconnect between apoptosis and other PCD during LMBV infection. Together, our results not only established the in vitro LMBV infection model for the study of the interaction between LMBV and host cells but also shed new insights into the mechanisms of ranavirus pathogenesis.

Characterization of the expression stability of largemouth bass (Micropterus salmoides) candidate reference genes by qRT-PCR during viral infection

“…Largemouth bass, an important freshwater commercial species in China, is suffering from severe virus-induced diseases [25] . Few report investigated the host immune mechanism during virus infection.…”

Experimental evidence of effective disinfectant to control the transmission of Micropterus salmoides rhabdovirus

“…However, the expansion of breeding scale and breeding density has come along with a variety of diseases. In addition to bacterial and parasitic diseases, largemouth bass is susceptible to a variety of viruses (Ho et al., 2018; Sibley et al., 2016; Yang, Guo, et al., 2022; Yang, Xu, et al., 2022).…”

“…In order to prevent and control the transmission of MSRV disease, some studies have focus on immunization and drug screening. The DNA vaccine and subunit vaccine prepared with glycoprotein of MSRV had good immune protection effects against MSRV infection (Guo et al., 2020; Xu et al., 2022; Yang, Guo, et al., 2022; Yang, Xu, et al., 2022). In addition, Chinese herbal medicine (magnolol derivatives) and antiviral drug (ribavirin and 8‐hydroxyquinoline) could decrease tissue viral nucleic acids, and improve the survival rate of largemouth bass after MSRV infection (Jin et al., 2022; Li et al., 2022; Yang et al., 2021).…”