Establishment of a cell line from the head kidney of giant grouper (Epinephelus lanceolatus) and its susceptibility to fish viruses

Grouper is an important marine fish mainly cultured in China and Southeast Asia. Here, a continuous cell line, named as ELHK, was established from head kidney of giant grouper (Epinephelus lanceolatus). The origin of cell line was confirmed by sequencing of 18s rRNA genes. ELHK cells consisted predominantly of fibroblast-like cells, and multiplied well in Leibovitz's L-15 medium supplemented with 10% fetal bovine serum at 28 degrees C. Karyotyping analysis indicated that the modal chromosome number of ELHK cell was 60 at 50 passages. The cells were successfully transfected with GFP reporter gene suggesting that ELHK cell could be used for exogenous gene expression in vitro. Moreover, ELHK cells was susceptible to Singapore grouper iridovirus (SGIV) and red-spotted grouper nervous necrosis virus (RGNNV), demonstrated by the occurrence of cytopathic effects (CPEs) and increased transcription of the viral genes during virus infection. Furthermore, numerous viral particles were observed in SGIV- or RGNNV-infected ELHK cells using electron microscopy, which further confirmed that ELHK cells could be used for fish virus propagation in vitro. In addition, quantitative PCR analysis indicated that SGIV and RGNNV infection in ELHK cells significantly increased the transcripts of several interferon- or proinflammation-related cytokines, suggested that both of them up-regulated host interferon and inflammatory immune response in vitro. Taken together, our established ELHK cell line could be used as an in vitro tool for gene expression, as well as virus propagation and virus-host interaction studies.