Production of recombinant vaccine using capsid gene of nodavirus to protect Asian sea bass, Lates calcarifer (Bloch, 1790)

Fish nodavirus (betanodavirus), a viral pathogen responsible for viral nervous necrosis (VNN) was isolated from infected Asian sea bass (Lates calcarifer). The capsid protein gene of nodavirus was amplified and cloned in pRSET B, a prokaryotic expression vector. The construct was named as r-FNCP. The size of the capsid protein was 42 kDa and it was named as r-FNCP42. The r-FNCP42 protein was expressed as a protein with a 6-histidine tag in Escherichia coli BL21 with IPTG induction. Polyclonal antiserum was raised against this recombinant protein in rabbits and it recognized r-FNCP42 protein. The gene encoding capsid protein (FNCP-42) nucleotide sequence was cloned and its sequence was analysed with sequences of other isolates such as Taiwan, Malaysia, Singapore and France available in the GenBank using Bioinformatics tools such as BLASTn, clustal W analysis. Homology comparison showed 98-99% identity with other isolates. Asian sea bass was immunized with purified r-FNCP42 mixed with complete adjuvant at a dose of 50 μg per fish and was challenged with nodavirus by intramuscular injection. The vaccinated sea bass was protected from nodaviral infection and 76% of relative percent survival (RPS) was recorded.