Autophagy Delays Apoptotic Cell Death Induced by Siniperca chuatsi Rhabdovirus in Epithelioma Papulosum Cyprinid Cells

Autophagy and apoptosis are two key cell fate determination pathways, which play vital roles in the interaction between viruses and host cells. Previous research had confirmed that one strain of fish rhabdoviruses, Siniperca chuatsi rhabdovirus (SCRV), could induce apoptosis and autophagy after infection. In the current study, we continued to analyze the interaction of autophagy and apoptosis in SCRV-infected EPC cell lines after treatment with different autophagy or apoptosis inhibitors. We found that SCRV infection could activate the mitochondrial apoptotic pathway by the detection of the activities of the caspase-3 and caspase-9 and by flow cytometry analysis in JC-1-stained cells, respectively. Furthermore, no significant autophagy-related factors were disturbed in SCRV-infected cell after apoptosis inhibitor Z-VAD-FMK treatment, while autophagy inducer rapamycin could obviously delay the occurrence of CPE and cell death. Meanwhile, rapamycin was able to reduce the proportion of apoptotic cells. Besides that, rapamycin could disturb the expression of p62 and LC3B-II, and the transcription level of SCRV nucleoprotein mRNA. The progeny virus titers did not show a big difference between the rapamycin treatment or without it. Collectively, our data preliminarily confirmed that SCRV-activated autophagy could delay apoptosis in EPC cells and may not affect virus production. Further study may need to focus on the crosstalk regulation and its roles on the SCRV infection.