Application of antibodies against nonstructural protein 2B of dengue serotype 2 virus induced by DNA immunisation or recombinant protein NS 2B immunisation in BALB/c mice

To investigate the structure and function of nonstructural (NS) protein 2B of the dengue serotype 2 virus (DV2) during infection, polyclonal antibodies (Abs) against DV2 NS2B were prepared by immunisation with NS2B protein or by DNA immunisation. The full-length NS2B gene was cloned and inserted into the prokaryotic expression vector pQE31, resulting in a vector, named pQE-NS2B, or into the eukaryotic expression vector pCAGGS-P7, resulting in the vector pCAG-NS2B. The pQE-NS2B vector was transfected into Escherichia coli JM109, and recombinant NS2B protein was obtained by Ni2+–NTA agarose affinity chromatography. Vero cells transfected with pCAG-NS2B showed that NS2B protein can be expressed in eukaryotic cells. Finally, mice were immunised with the recombinant NS2B protein or pCAG-NS2B. Anti-NS2B sera from the immunised mice could specifically react with DV2 NS2B proteins, as visualised by fluorescence staining and Western blotting. Immunisation with NS2B protein induced a higher titre of the antibody than that induced by DNA immunisation. These data indicate that our antisera against DV2 NS2B can recognise both the natural and denatured NS2B protein. Based on these results, the polyclonal Abs could be used as a tool for studying the role of NS2B in the pathogenesis of DV2.