Generation and Characterization of ORF55/ORF57-Deleted Recombinant ICyprinid herpesvirus/I 2 Mutants with Chimeric Capsid Protein Gene of Grouper Nervous Necrosis Virus

• Published in: Vaccines (Basel) 2023-12, Vol.12 (1)
• Main Authors: Feng, Zizhao, Cheng, Wenjie, Ma, Mingyang, Yu, Chenwei, Zhang, Ye, Lu, Liqun, Wang, Hao, Gui, Lang, Xu, Dan, Dong, Chuanfu
• Format: Article
• Language: English
• Subjects: Analysis; Design and construction; Genetic aspects; Herpesviruses; Pathogenic microorganisms; Vaccines
• ISSN: 2076-393X; 2076-393X
• DOI: 10.3390/vaccines12010043

Cyprinid herpesvirus 2 (CyHV-2) is a pathogen that causes significant losses to the global aquaculture industry due to mass mortality in crucian carp and goldfish. This study demonstrates that the ORF55/ORF57 deletion mutants CyHV-2-Δ55-CP and CyHV-2-Δ57-CP obtained through homologous recombination replicate effectively within the caudal fin of Carassius auratus gibelio (GiCF) cells and exhibit morphologies similar to the CyHV-2 wild-type strain. Both mutants demonstrated a decrease in virulence, with CyHV-2-Δ57-CP exhibiting a more significant reduction. This serves as a reference for the subsequent development of recombinant attenuated vaccines against CyHV-2. Additionally, both mutants expressed the inserted RGNNV-CP (capsid protein of Redspotted grouper nervous necrosis virus) fusion protein gene, and inoculation with CyHV-2-Δ57-CP-infected GiCF cell lysates elicited an antibody response in the grouper. These results indicate that, while ORF55 and ORF57 genes of CyHV-2 are not required for viral replication in vitro, they do play a role in virulence in vivo. Additionally, expression of foreign protein in CyHV-2 suggests that the fully attenuated mutant of CyHV-2 could potentially function as a viral vector for developing subunit vaccines or multivalent recombinant attenuated vaccines.