Derivation of two tilapia (Oreochromis niloticus) cell lines for efficient propagation of Tilapia Lake Virus (TiLV)

Tilapia Lake Virus (TiLV) has been associated with disease outbreaks in cultured tilapia worldwide. In this study, we developed and characterized two cell lines from the brain (OnlB) and liver (OnlL) of the Nile tilapia, Oreochromis niloticus for the efficient propagation of TiLV. Both the cells grew well in Leibovitz's - 15 (L-15) medium supplemented with 20% fetal bovine serum (FBS) and have been sub-cultured more than 45 times. Chromosome analysis of the cells revealed that both lines had normal diploid number (2n = 44). TiLV was isolated from diseased tilapia and continuously propagated for 20 passages in these cell lines. The maximum TiLV titer was 107.3±0.05 and 107.0±0.96 TCID50/ml, in OnlL and OnlB respectively. The TiLV isolate consistently produced the same CPE in all passages. In vivo challenge experiments using the TiLV infected cell culture supernatant reproduced symptoms of the disease in healthy tilapia, with mortality commencing 10 days post-infection and we were able to isolate TiLV from the challenged fish The above results suggest both cell lines are highly permissive for propagating TiLV and could be important tools for studying the molecular pathogenesis of TiLV infection.