Abstract

A new cell line (KoG) was developed from the gill of koi, Cyprinus carpio. KoG cells were composed of epithelial-like cells and fibroblast-like cells. The cells were maintained well at 25°C in Leibovitz L15 medium supplemented with 10% fetal calf serum. Chromosome analysis showed that the KoG cells had 43 diploid chromosomes at passage 40. The KoG cells were used to test the susceptibility of a koi herpesvirus isolate using a Taiwanese koi herpesvirus isolate (strain TW BL98). The KHV-infected KoG cells revealed vacuolation in the cytoplasm and marginal hyperchromation in the nucleus, which was confirmed by an indirect immunofluorescence assay and transmission electron microscopy. A multistep growth curve showed the virus reaching the highest titer of 10^6.2 TCID₅₀/ml at 5 days post inoculation. Sequence analysis targeting the alleles of the two molecular markers indicated that the Taiwanese isolate displayed the I⁺⁺II⁺ allele and of the Asian lineage, which was identical to a Japanese strain (Asian genotype variant 1). Collectively, our results demonstrate that the KoG cells may provide a tool for the replication of KHV andthe Taiwanese isolate belongs to a typical Asian genotype.

Key words: Taiwan, KoG cell line, koi herpesvirus, phylogenetic analysis.

Abbreviation

Abbreviations: KHV, Koi herpesvirus; CyHV-3, cyprinid herpesvirus-3; IFA, indirect immunofluorescence assay; KoG, koi gill cell; CPE, cytopathic effect.