Alternative cell line for the isolation of salmonid alphavirus-1

Abstract

Salmonid alphavirus (SAV) has recently become an economically important pathogen in salmonid aquaculture in Europe. Subtype SAV-1 causes salmon pancreas disease (SPD) in Atlantic salmon in Scotland and Ireland, and was first isolated on Chinook salmon embryo-214 (CHSE-214) cells in 1995 in Ireland; several established cell lines have since been tested for viral growth, although the ability of these cell lines to support primary virus isolation has not being examined. In the present study, CHSE-214, Chum salmon heart -1 (CHH-1) and Salmon head kidney -1 (SHK-1) cell lines were evaluated for isolation of SAV-1 from kidney samples of experimentally infected Atlantic salmon (Salmo salar). The presence of infection in these samples was confirmed both by cell culture and reverse transcription polymerase chain reaction (RT-PCR). Homogenates of kidney from fish 3 days post-infection (p.i.) were inoculated onto the three cell lines and the development of a cytopathic effect (CPE) recorded. The CHH-1 cells produced a rapid CPE from Day 6 p.i., while the CHSE-214 cells showed the presence of a CPE from Day 10 p.i. In comparison, a CPE developed much later in the SHK-1 cells, from Day 20 p.i. The virus was successfully isolated on all three cell lines in subsequent passages, indicating that CHSE-214, CHH-1, and SHK-1 cells can be used for the isolation and culture of SAV-1. The CHH-1 cell line, however, has proven the most useful, since the CPE developed the quickest in this cell line.