We have tested the hypothesis that the flavivirus nonstructural protein NS3 is a viral proteinase that generates the termini of several nonstructural proteins by using an efficient in vitro expression system and monospecific antisera directed against the nonstructural proteins NS2B and NS3. A series of cDNA constructs was transcribed by using T7 RNA polymerase, and the RNA was translated in reticulocyte lysates. The resulting protein patterns indicated that proteolytic processing occurred in vitro to generate NS2B and NS3. The amino termini of NS2B and NS3 produced in vitro were found to be the same as the termini of NS2B and NS3 isolated from infected cells. Deletion analysis of cDNA constructs localized the protease domain within NS3 to the first 184 amino acids but did not eliminate the possibility that sequences within NS2B were also required for proper cleavage. Kinetic analysis of processing events in vitro and experiments to examine the sensitivity of processing to dilution suggested that an intramolecular cleavage between NS2A and NS2B preceded an intramolecular cleavage between NS2B and NS3. The data from these expression experiments confirm that NS3 is the viral proteinase responsible for cleavage events generating the amino termini of NS2B and NS3 and presumably for cleavages generating the termini of NS4A and NS5 as well.

We have investigated the plasma proteome by using 2D gel electrophoresis and MS from patients with severe acute respiratory syndrome (SARS). A complete proteomic analysis was performed on four patients with SARS in different time courses, and a total of 38 differential spots were selected for protein identification. Most of the proteins identified are acute phase proteins, and their presence represents the consequence of serial cascades initiated by SARS-coronavirus infection. There are several proteins that have never been identified in plasma before using 2D gel electrophoresis, among which peroxiredoxin II was chosen for further study by analyzing additional 20 plasma samples from patients with probable and suspected SARS and patients with fever, respectively. The results showed that the level of plasma peroxiredoxin II in patients with SARS is significantly high and could be secreted by T cells. Taken together, our findings indicate that active innate immune responses, along with the oxidation-associated injuries, may play a major role in the pathogenesis of SARS.proteomic techniques ͉ acute phase proteins ͉ peroxiredoxin II S evere acute respiratory syndrome (SARS) was first recognized at the end of 2002 in Guangdong, China, and since then the disease has spread to several countries. By late July 2003, Ͼ8,000 SARS cases and Ͼ700 SARS-related deaths were reported from Ͼ25 countries around the world, and no effective treatment has been established so far. Through extensive studies, the causative agent of SARS has been identified as a human SARS-coronavirus (SARS-CoV) (1-3). Although the complete genome sequence of SARS-CoV, the structure of the main protease (3CL protease), and the possible receptor have been determined (4-7), the pathogenesis of SARS is still not fully understood.Plasma proteins are useful targets for diagnostic, prognostic, and͞or therapeutic development. With proteomic tools available recently, profiling of human plasma proteome becomes more feasible in searching for disease-related markers (8). To explore the possible pathogenetic mechanisms involving the progression of SARS, we have analyzed the plasma proteins of 22 different plasma samples from four SARS patients in different time courses by using 2D gel electrophoresis (2DE) in combination with MS. The results showed that most of the plasma proteins found in patients with SARS are acute phase proteins (APPs) generated by inflammatory reactions during SARS-CoV-induced acute lung injuries. Materials and MethodsHuman Subjects. Four SARS patients with a total of 22 plasma samples were selected for complete proteomic analysis. These patients were infected by SARS-CoV through nosocomial transmission during one major SARS outbreak in one municipal hospital in Taipei. For comparison, plasma samples from six healthy individuals were used as controls. The protein concentration of each sample was determined by the standard Bradford method. The use of these samples was approved by the Review Board of the Tri-Service General Hospital, National Def...