Establishment and characterization of a new cell line (SSP‐9) derived from Atlantic salmon Salmo salar that expresses type I if n

In the present work, the establishment and biological characterization of a new cell line, SSP‐9, derived from the pronephros of the Atlantic salmon Salmo salar, are reported. These cells grew well in Leibovitz's (L15) medium supplemented with 10% foetal calf serum at temperatures from 15 to 25° C, and they have been sub‐cultured over 100 passages to produce a continuous cell line with an epithelial‐like morphology. The SSP‐9 cells attached and spread efficiently at different plating densities, retaining 80% of cell viability after storage in liquid nitrogen. When karyotyped, the cells had 40–52 chromosomes, with a modal number of 48. Viral susceptibility tests showed that SSP‐9 cells were susceptible to infectious pancreatic necrosis virus and infectious haematopoietic necrosis virus, producing infectious virus and regular cytopathic effects. Moreover, these cells could be stimulated by poly I:C, showing significant up‐regulation in the expression of the genes that regulate immune responses, such as ifn and mx‐1. SSP‐9 cells constitutively express genes characteristic of macrophages, such as major histocompatibility complex (mhc‐II) and interleukin 12b (il‐12b), and flow cytometry assays confirmed that SSP‐9 cells can be permanently transfected with plasmids expressing a reporter gene. Accordingly, this new cell line is apparently suitable for transgenic manipulation, and to study host cell–virus interactions and immune processes.