DAO 63:43-52 (2005)  -  doi:10.3354/dao063043

ABSTRACT: We studied the characteristics of rainbow trout serum (RTS) inhibitory activity against infectious pancreatic necrosis virus (IPNV). Serum inhibition was related to the serum source and host cell in which the virus had been propagated. IPNV was more efficiently inhibited by RTS in salmonid cell lines than in non-salmonid cell lines, with inhibition highest in rainbow trout gonad (RTG)-2 cells. The RTS sensitivity of the virus was modified by the cell line through which the virus passed, with multiple passages through Chinook salmon embryo (CHSE)-214 cells producing a virus that was less sensitive to RTS. The RTS inhibition level was dependent on cell density: at a cell density of ≤2 × 10⁵ cells ml^–1, inhibition was insignificant (tissue culture infective dose 50% = 10^–1.1 TCID₅₀ ml^–1 reduction); however, above a density of 3 × 10⁵ cells ml^–1, the inhibition level was very high (≥10^–6.3 TCID₅₀ ml^–1 reduction). The salmonid sera tested showed high inhibition, except for brook trout serum (BTS), while non-salmonid sera did not inhibit IPNV, replication on RTG-2 cells. Pretreatment of cultured cells with RTS prior to exposure did not affect inhibition of IPNV and thus did not mask a viral receptor. The RTS inhibition level was dependent on the time of serum addition, with inhibition being maintained for at least 16 h postinfection. Pretreatment of IPNV revealed that the virus is directly inhibited by RTS, and more strongly so when RTS is present during viral replication.

KEY WORDS: Infectious pancreatic necrosis · IPNV · Rainbow trout serum · Inhibition