An epitheloid morphology cell line designated TO-2 was established from ovary of healthy adult tilapia hybrid(Tilapia mossambica×T.nilotica).Using Leibovitz's L-15 medium with 10% fetal calf serum at 31°C, TO-2 cell line has been passed for 106 times since its initiation in October, 1981.The cells were demonstrated to be free of bacterial, fungal and mycoplasma contaminations.
Optimal temperature for TO-2 cell growth was 31°C. The cells are also able to grow at 15 or 24°C. However, in 37°C the cells grew very slowly and eventually died. The growth rate of the cells varied with different serum concentrations in culture media. At a low seeding density (1.6×10²-1.6×10³/25cm² flask), the plating efficiency was approximately 12%. Chromosome number at passage level of 80 ranged from 24 to 76 with a modal number of 40.
TO-2 cell line is susceptible to EVE, EVA, EVEX and IPNV.