A Novel Specific Single-Chain Variable Fragment Diagnostic System for Viral Hemorrhagic Septicemia Virus

Viral hemorrhagic septicemia virus (VHSV), one of the most important viral marine pathogens worldwide, has a broad range of hosts, such as members of the families Salmonidae and Paralichthyidae. In addition to being highly contagious, VHSV causes high lethality. The transmission of VHSV can be both vertical and horizontal. In fish, the resolution of VHSV infection is challenging. Thus, early diagnosis of VHSV infections is critical, especially in fish farms that have a high population of juvenile fish. Serological methods are commonly used to detect viral antigens. However, limited serological methods are available for marine viruses. In this study, a VHSV-specific single-chain variable fragment (scFv), E5, was selected using the yeast surface display and phage display systems. scFv, a type of recombinant antibody, comprises a variable heavy chain ([Formula: see text]) and a variable light chain ([Formula: see text]) connected by a polypeptide linker. An scFv clone was selected from the VHSV glycoprotein-expressing yeast cells using the bio-panning method. The scFv-encoding gene was subcloned and expressed in the Escherichia coli expression system. The binding affinity of the expressed and purified scFv protein was determined using an enzyme-linked immunosorbent assay and western blotting. Thus, this study reported a method to identify VHSV-specific scFv using bio-panning that can be utilized to develop a diagnostic system for other viruses.