Genomic and molecular characterization of a cyprinid herpesvirus 2 YC-01 strain isolated from gibel carp.

Cyprinid herpesvirus 2 (CyHV-2) is the pathogen of herpesviral hematopoietic necrosis (HVHN), causing the severe economic losses in farmed gibel carp (Carassius gibelio). Further exploration of the genome structure and potential molecular pathogenesis of CyHV-2 through complete genome sequencing, comparative genomics, and molecular characterization is required. Herein, the genome of a CyHV-2 YC-01 strain isolated from diseased gibel carp collected in Yancheng, Jiangsu Province, China was sequenced, then we analyzed the genomic structure, genetic properties, and molecular characterization. First, the complete YC-01 genome comprises 275,367 bp without terminal repeat (TR) regions, with 151 potential open reading frames (ORFs). Second, compared with other representative published strains of the genus Cyvirus, several evident variations are found in YC-01, particularly the orientation and position of ORF25 and ORF25B. ORF107 and ORF156 are considered as potential molecular genetic markers for YC-01. ORF55 (encoding thymidine kinase) might be used to distinguish YC-01 and ST-J1 from other CyHV-2 isolates. Third, phylogenetically, YC-01 clusters with the members of the genus Cyvirus (together with the other six CyHV-2 isolates). Fourth, 43 putative proteins are predicted to be functional and are mainly divided into five categories. Several conserved motifs are found in nucleotide, amino acid, and promoter sequences including cis-acting elements identification of YC-01. Finally, the potential virulence factors and linear B cell epitopes of CyHV-2 are predicted to supply possibilities for designing novel vaccines rationally. Our results provide insights for further understanding genomic structure, genetic evolution, and potential molecular mechanisms of CyHV-2.