Establishment of a new intestinal cell line from the grouper (Epinephelus coioides) for aquatic virus pathogenesis

A new cell line (ECGI-21) was developed from the intestine of grouper (Epinephelus coioides). The cell line was routinely grown in Leibovitz's L-15 medium supplemented with 15% fetal bovine serum (FBS) at 28 °C. ECGI-21 cells had an epithelioid morphology. At present, the cell line has been stably passed over 80 generations and has been successfully cryopreserved. The origin of grouper was confirmed by the sequence of 18S ribosomal RNA (18S rRNA). Chromosome analysis indicated that the modal chromosome number was 48. The green fluorescence signals were detected when pEGFP-N3 was transfected into ECGI-21 cells. Moreover, the ECGI-21 cells were susceptible to Singapore grouper iridovirus (SGIV) and Red-spotted grouper nervous necrosis virus (RGNNV), which was demonstrated by the presence of a significant cytopathic effect (CPE), increased expression of viral proteins after viral infection. Meantime, abundant viral particles were observed in the cells infected with SGIV and RGNNV by electron microscopy. Furthermore, virus replication significantly increased the level of interferon (IFN) related signaling molecules and pro-inflammatory cytokine expression in cells. In summary, ECGI-21 cell line was established and become the first stable intestinal cell line from marine fish. It provides a useful tool for studying problems of gastrointestinal health, viral pathogenesis and virus-host interaction in vitro.