Establishment of fin cell lines and their use to study the immune gene expression in cyprinid fishes with different ploidy in rhabdovirus infection

Triploid hybrid (3n = 150) of red crucian carp (female, 2n = 100) and allotetraploid (male, 4n = 200) display improved disease resistance and stress resistance than their parents. In order to elucidate their innate immune mechanisms, three novel cell lines from the caudal fin of red crucian carp, triploid hybrid and allotetraploid (named 2nFC, 3nFC and 4nFC accordingly) were established and characterized respectively. 2nFC, 3nFC and 4nFC showed fibroblast-like morphology and characteristics. They have been subcultured for more than 100 passages since the initial primary culture. Viral infection experiments showed that 2nFC, 3nFC and 4nFC were susceptible to spring viraemia of carp virus (SVCV) infection. Intriguingly, 3nFC performed the stronger resistance ability against SVCV than 2nFC and 4nFC, which indicated that 2nFC, 3nFC and 4nFC might be used as the suitable in vitro models for exploring and analyzing the differences among these three cyprinid fishes in antiviral innate immune mechanisms. Based on this, we analyzed the transcriptome profile of 2nFC, 3nFC and 4nFC in the context of SVCV infection. The KEGG enrichment analysis showed that the differentially expressed genes (DEGs) were primarily enriched to immune-related signaling pathways. However, some signaling pathways against viral infection were activated remarkably in 2nFC and 3nFC but not in 4nFC. Overall, the establishment of 2nFC, 3nFC and 4nFC provided us a suitable platform to elucidate the innate immunity of fishes with different ploidy and clear genetic relationship.