Development of a mandarin fish Siniperca chuatsi fry cell line suitable for the study of infectious spleen and kidney necrosis virus (ISKNV)

Infectious spleen and kidney necrosis virus (ISKNV) is a typical species of the genus Megalocytivirus in the family Iridoviridae. However, until recently, no suitable piscine cell line is stably susceptible to ISKNV. Here, a continuous cell culture derived from the mandarin fish fry (MFF-1) was developed and has been subcultured over 60 passages during a period of 18 months. MFF-1 consists predominantly of epithelial-like cells and grows well in DMEM supplemented with 10% fetal bovine serum. MFF-1 could produce high titers of ISKNV by continuous viral passages which were further confirmed by indirect immunofluorescence assay and RT-PCR analysis. Flow cytometry analyse showed that approximately 80.3% cells could be infected by ISKNV at 3 days post-infection. Abundant ISKNV particles were observed in the cytoplasm of the ISKNV infected MFF-1 cells by transmission electron microscopy. Mandarin fish injected with the filtrate from the infected cell suspension developed clinical signs and died, which is in accordance with the infectious spleen and kidney necrosis virus disease (ISKNVD). In addition, apoptosis was observed in the MFF-1 cells upon ISKNV infection by FITC-annexin V staining. ISKNV was purified and the viral protein profiles were also determined in this research. To our knowledge, MFF-1 is the first cell line originated from mandarin fish and it can be an efficient tool for the study of ISKNV.