Development of a highly permissive cell line from spotted knifejaw (Oplegnathus punctatus) for red sea bream iridovirus

We developed a cell line (SKF-9) from spotted knifejaw (Oplegnathus punctatus), which is highly susceptible to red sea bream iridovirus (RSIV). Cytopathic effect (CPE) characterized by rounding and enlargement was clearly observed in RSIV-infected SKF-9 cells. The amount of viral production of SKF-9 cells was approximately 100 times greater than that of GF cells, which is conventionally used for RSIV research. The viral titer was not decreased through passages using SKF-9 cells, whereas a considerable reduction in the titer was observed when GF cells were used. On the other hand, control of appropriate passage numbers (< 50) of the cell line was important to maintain the high permissiveness of SKF-9. Mortality rate was 100% when culture supernatant of RSIV propagated with SKF-9 cells was injected into spotted knifejaw with dilutions of 100, 10− 5, and 10− 6. Thus, the SKF-9 cell line can be a useful tool for research of RSIV (and ISKNV) and for vaccine production.