Treatments to control infectious diseases in aquacultured fish commonly focus on the use of antibiotics (which are ineffective against viruses) and inorganic disinfectants. Currently, antiviral treatments are not available for use in aquaculture. The use of plasmid vectors to overexpress antiviral proteins in fish has been reported, with positive results against viral infections.
The aim of this work was to overexpress the antiviral proteins interferon-induced protein with tetratricopeptide repeats 5 (IFIT5) and natural killer enhancing factor (NKEF) using plasmid vectors (pIFIT5 and pNKEF ) as novel therapeutic agents against viral infections. The antiviral activity of pIFIT5 against viral hemorrhagic septicemia virus (VHSV) and infectious pancreatic necrosis virus (IPNV) was evaluated in vitro in epithelioma papulosum cyprinid and Chinook salmon embryo cell lines. Moreover, pNKEF antiviral activity against IPNV was also evaluated. Results showed that pIFIT5 had antiviral activity against both viruses, but pNKEF did not protect against IPNV. In addition, we evaluated the use of pIFIT5 and pNKEF constructs as therapeutics in rainbow trout. Biodistribution assays demonstrated systemic distribution of the IFIT5 and NKEF proteins in rainbow trout injected with the plasmids, and pIFIT5 and pNKEF triggered an immune response in the injected fish. In a pilot study, we evaluated the level of protection conferred by pIFIT5 and pNKEF against VHSV in rainbow trout . Together, these results suggest the potential of pIFIT5 and pNKEF as therapeutic agents in aquaculture.