Design, construction and expression of recombinant vector containing the rabies virus nucleoprotein gene

Rabies is an acute encephalitis that causes more than 60,000 deaths worldwide. The only way to save individuals bitten by a rabies-infected animal is the timely use of effective vaccines. Treatment with new generation vaccines is expensive. Therefore, there is a global movement towards the production of less expensive vaccines which retain and improve upon the quality and effectiveness of the vaccine. Production and evaluation of non-classical vaccines is one of the approaches taken in this regard. In this study, we describe a new eukaryotic expression system to express the nucleoprotein N gene of rabies virus which, if suitable, may be evaluated for anti-rabies vaccine production. The complete sequence of the N gene of rabies virus PV subtype was amplified by real-time polymerase chain reaction and cloned into the pCDNA3.1(+) vector. The cloned gene was excised from the vector by restriction enzyme digestion and sequenced. Due to mutations detected in the N gene, the gene coding sequence was purchased as a recombinant pGH/N vector. Vector pGH/N was amplified and following enzymatic digestion, the excised N gene was once again cloned into vector pCDNA3.1(+). Successful cloning was confirmed using restriction digests and quick check. The recombinant vector pCDNA3.1(+)/N was transformed into cultured BSR cells and protein N expression was analyzed using fluorescent antibody test (FAT). Electrophoresis confirmed amplification of the nucleoprotein N gene and subsequent restriction enzyme digestion showed that the N gene had been successfully cloned into the recombinant pCDNA3.1(+)/N vector. However, DNA sequencing revealed the presence of mutations within the N gene. Restriction digest of the commercial pGH/N vector showed that the N gene had been excised from the vector. Successful cloning of the N gene into the pCDNA3.1(+) expression vector was confirmed using restriction digests and quick check. Protein expression in BSR cells was assayed by immunostaining with anti-ribonucleocapsid FITC-conjugated antibody and visually confirmed by fluorescence microscopy. This study showed that the protein N of rabies virus subtype PV can be expressed in a eukaryotic expression system using the pCDNA3.1(+) expression vector.