Development of a sea perch (Lateolabrax japonicus) fry cell line and its application to the study of fish virus-host interactions

We developed and characterized a new cell line from sea perch (Lateolabrax japonicus) fry (SPF). SPF cells were subcultured over 100 passages, and sequencing of the mitochondrial 18 s rRNA gene confirmed that SPF cells derived from Lateolabrax japonicus. SPF cells consisted predominantly of epithelial-like cells, and proliferated well in Leibovitz's L-15 medium supplemented with 15% fetal bovine serum at 28 degrees C. Karyotyping analysis indicated that the modal chromosome number was 48 at passage 55. Green fluorescence could be observed in pEGFP-N3 transfected SPF cells at passages 55. SPF cells showed susceptibility to sea perch iridovirus (SPIV), Singapore grouper iridovirus (SGIV), and red-spotted grouper nervous necrosis virus (RGNNV), which was demonstrated by the occurrence of severe cytopathic effects, increased viral protein synthesis, and abundant virus particles in the cytoplasm. Moreover, SPIV and SGIV infection in SPF cells caused profound alterations in the actin cytoskeleton, as evidenced by a significant decrease in the number of actin stress fibers. Of note, no apoptotic bodies were observed in either SGIV- or SPIV-infected cells, suggesting that these two viruses induced non-apoptotic cell death in vitro. Interferon-related genes were up-regulated in SPIV- or RGNNV-infected SPF cells, suggesting that the host interferon immune response was involved in SPIV or RGNNV infection. These results showed that our newly established SPF cell line was a useful tool for genetic manipulation, virus isolation, and functional studies of host-virus interactions.