Beating Cardiac Cell Cultures From Different Developmental Stages of Rainbow Trout as a Novel Approach for Replication of Cardiac Fish Viruses

Piscine orthoreovirus-1 and 3 (PRV-1, PRV-3) cause highly prevalent infection in cultured salmonids and can induce heart and skeletal muscle inflammation (HSMI) resulting in economic losses in aquaculture. However, to date, PRV-1 and PRV-3 have withstood replication in continuous cell lines. In this study, we used beating heart cell cultures obtained from different developmental stages of rainbow trout (Oncorhynchus mykiss) (RTC-L and RTC-A) and tested their ability to sustain replication of PRV-1 and PRV-3. Furthermore, we compared the replication pattern of the different viruses with those in the newly developed heart fibroblast cell line (RTH-F) and the traditional established rainbow trout gonad cell line (RTG-2). Neither RTCs nor RTH-F cell lines supported replication of PRV-1 and PRV-3. Comparative experiments showed varying susceptibility of the novel cultures to viral haemorrhagic septicaemia virus (VHSV), chum salmon reovirus (CSV), infectious pancreatic necrosis virus (IPNV), piscine myocarditis virus (PMCV), salmonid alphavirus 3 (SAV-3) and tilapia lake virus (TiLV), indicating their usability for work with multiple fish viruses. While confirming the difficulty of replicating PRV-1 and PRV-3, the results demonstrate the potential of novel heart-derived cell cultures as in vitro tools for studying fish viruses.