Gene Cloning and Expression of Major Capsid Protein of Large Yellow Croaker Iridovirus and Its Secretion Based on α‐hemolysin Transport System

Large yellow croaker iridovirus (LYCIV) is an important pathogen of mariculture fish. The complete gene of an important protective antigen, major capsid protein (MCP), of LYCIV was amplified by polymerase chain reaction and was cloned into pET‐16b for expression in Escherichia coli. The MCP‐encoded gene was in‐frame fused to the E. coliα‐hemolysin transport elements to construct the MCP secretory expression plasmid pMOhlyM, and its secretion characters in E. coli and attenuated Vibrio anguillarum MVAV6203 were investigated. With the aid of E. coliα‐hemolysin transport system, about 400 μg/L MCP was secreted into culture supernatant in E. coli, while intracellularly expressed MCP in MVAV6203 was not secreted. The study provides the foundation for attempts to secrete viral‐originated antigens by the E. coli HlyA transporter in bacterial hosts and to explore feasible ways to develop multivalent live vaccines against both bacterial and viral pathogens.