High-level expression of recombinant dengue viral NS-1 protein and its potential use as a diagnostic antigen

The prevalence of NS1 Ab response in patients with dengue viral infection a nd the potential of using recombinant NS1 protein as a diagnostic antigen f or dengue viral infection were investigated. In this study, the full-length and C-terminal half of NS1 proteins (rNS1, rNS1-C) were highly expressed ( 10-30 mg/l) and further purified and refolded. The good antigenicity of the full-length rNS1 protein was confirmed by interaction with 19 dengue NS1-s pecific monoclonal antibodies (MAbs) in ELISA; however, the antigenicity of rNS1-C was relatively lower. The full-length rNS1 antigen also differentia ted reliably between sera from dengue virus-infected patients and sera from normal controls. When rNS1 was used as an antigen to detect human anti-NS1 IgM and IgG Ab, the anti-NS1 Ab response was found in 15 of 17 patients (8 8%) with primary dengue infection and all 16 patients (100%) with secondary dengue infection. These results indicated that using the full-length rNS1 whose antigenicity is restored as ELISA antigen, a high anti-NS1 antibody p revalence could be detected in patients with either primary or secondary de ngue infection. This finding suggested that the anti-NSI antibody appeared not only in secondary and severe dengue virus infection and might not corre late the pathogenesis of dengue hemorrhagic fever. The study also verified that our purified NS1 protein showed similar immunological properties as na tive dengue viral proteins. Genetic engineering production of recombinant N S1 antigen could provide a safe and valuable resource for dengue virus sero diagnosis. (C) 2001 Wiley-Liss, Inc.