Comparison of Immune Response Between Escherichia coli-Derived Recombinant Subunit Vaccine and Formol-Inactivated Whole Particle Vaccine Against Viral Haemorrhagic Septicaemia Virus (VHSV) in Rainbow Trout

Abstract

Viral haemorrhagic septicaemia (VHS) is a serious disease of finfish with a high mortality rate (70%) worldwide. It is caused by infectious viral haemorrhagic septicaemia virus (VHSV). No commercial vaccine is available against VHSV so far. In the present study, we aimed to develop a sustainable recombinant subunit vaccine against a local isolate of VHSV belonging to the genogroup Ie. In order to develop a recombinant vaccine against VHSV genogroup Ie, a cDNA construct of the VHSV gG gene was amplified by reverse transcriptase-polymerase chain reaction (RT-PCR) and cloned into an Escherichia coli expression vector (pET-28a) to express recombinant protein products. In addition, a formol-inactivated whole particle vaccine was prepared. Subsequently, rainbow trout (17-60 g) were vaccinated by injecting purified recombinant VHSV gG proteins with an adjuvant (montanide) and the formol-inactivated whole particle vaccine and then challenged with moderately virulent VHSV. At the end of the trial, the mortality rate was found to be 10% (RPS 33.3%) in the recombinant vaccine group, while no mortality was detected (RPS 100%) in the formol-inactivated whole particle vaccine group. The recombinant subunit vaccine did not provide as much protection as the inactivated whole particle vaccine, even if the desired antibody production and viral load decreased.