Rapid Diagnosis of Necrosis Nervous Virus Infection using Recombinant Single-chain Variable Fragment (scFv)

Many fishes have been infected with many kinds of marine pathogens and died, but marine viruses are most threatening pathogens. Marine viruses show a high lethality of ~70% but there is no therapeutic method for virus-infected fishes. Therefore, detection of marine viruses is very important issue for fish pathology. Marine virus Nervous Necrosis Virus (NNV), which is one of the most important marine viruses in Korea, infects high demanded fishes such as Paralichthys olivaceus and Scomber japonicas. NNV belongs to the family Nodaviridae, which has ssRNA (+) genome. This virus can be transmitted not only by tissues from infected fish but also by passive diffusion. Single Chain Variable Fragments (scFv) was chosen to detection and therapeutic methods in this study. Detection methods using scFvs has shown simplicity, speed, relatively high specificity and sensitivity than ordinary antibodies-using methods. To screen specific scFvs, viral coat protein as antigen is expressed by yeast surface display, which has advantages of post-translational process and efficient to use flow cytometry. scFvs expressed by phage display was used for ‘bio-panning’ process to get specific scFvs bound to antigen. After screening specific scFvs to antigen, they will be used to develop the marine virus detection kit.1

Rapid Diagnosis of Red Sea Bream Iridovirus Infection using Recombinant Single-chain Variable Fragment (scFv)

Red Sea bream Iridovirus (RSIV) is one of the most important marine viruses in Asia and infects high demanded fishes. RSIV spread rapidly in the sea around the world via various routes, such as ocean current, imported fishery products and ships’ ballast water discharged in ports. Therefore, the detection of RSIV is very important for food and economic security worldwide. Also, it is important for preservation of marine life. However, there are not any appropriate diagnostic methods for rapid diagnosis of marine viruses. In this study, scFv was used to solve this problem. Detection methods using scFvs are expected to show characteristics that more simplified, fast, specific and sensitive than ordinary antibodies-using methods. For selecting scFv recognizing target virus coat proteins, two display systems, phage display system and yeast surface display system, are used. First, viral coat proteins are expressed by yeast surface display which can express proteins with post-translational process. And then, scFv libraries, expressed by phage display, were screened against the viral coat proteins expressed by yeast for three rounds of panning. Finally, three scFvs are chosen for production as soluble antibody by E.coli and they will be used to develop the marine virus detection system. This strategy can be applied to other marine viruses threatening the health of ocean. Also it can provide easy and rapid virus specific scFv isolation and marine virus diagnosis application.1