Delivery of DNA vaccine using chitosan–tripolyphosphate (CS/TPP) nanoparticles in Asian sea bass, Lates calcarifer (Bloch, 1790) for protection against nodavirus infection

Abstract

Abstract The present study examines the efficacy of DNA vaccine against nodavirus through oral route using CS/TPP (chitosan–tripolyphosphate) nanoparticles encapsulation. The RNA2 capsid protein gene of nodavirus was used to construct DNA vaccine using pcDNA 3.1, a eukaryotic expression vector and the construct was named as pFNCPE. The size of the RNA2 capsid protein gene was 42 kDa and it was named as pFNCPE42. The CS/TPP nanoparticles were used to deliver the constructed plasmid. In vitro and in vivo expressions of FNCP (fish nodavirus capsid protein) gene were observed in sea bass kidney cell line (SISK) and in fish, respectively by fluorescent microscopy. The cytotoxicity of CS/TPP–pFNCPE42 DNA nanoparticles was evaluated by MTT assay using fish cell line. Distribution of DNA vaccines in different tissues was studied in fish fed with the pFNCPE42-DNA encapsulated in CS/TPP nanoparticles and the expression of the gene was confirmed by PCR, RT-PCR, immunohistochemistry and ELISA analysis. The results indicate that DNA vaccine can be easily delivered into fish by feeding with CS/TPP nanoparticles. After oral vaccination Asian sea bass were challenged with nodavirus by intramuscular injection. A relative percent survival (RPS) rate of 60.0% was recorded. This study suggested that CS/TPP nanoparticles were promising carriers for plasmid DNA vaccine and might be used to vaccinate fish by oral approach.