Cloning and expression of the nucleoprotein gene (NP) of newcastle disease virus (NDV) in Escherichia coli for immunodiagnosis application

The nucleocapsid protein (NP) of newcastle disease virus (NDV) is an important antigen to develop a serologic assay on account of its highly conserved sequences and high immunogenicity. This study aimed at expressing the gene of the NP of NDV in a heterologous system (Escherichia coli), using the appropriate vector. The NDV-NP protein was expressed as a fusion recombinant protein containing SUMO peptide and poly-histidine tags. This recombinant nucleocapsid protein (rNP) was expressed in a soluble form which was easily purified and showed the ability to react with chicken anti-NDV polyclonal antibodies. An indirect ELISA method based on the adsorption of an antigen composed by NP (rNP-NDV-ELISA) was developed. By comparing this rNP-NDV-ELISA with haemagglutination-inhibition test (HI) high and significant correlation with the HI (r = 0.83) was found. In addition to, high sensitivity (88.9%), specificity (95.5%), accuracy (90.4%) and agreement (0.85) were obtained. In conclusion the results indicated that the cloning and expression procedures used in this study provided a rNP that shared the major epitopes with the homologous viral protein and has the potential to be applied in ELISA for the immunodiagnosis of the important newcastle disease.