Pseudotyped virus to study SARS virus entry

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The etiologic agent involved in severe acute respiratory syndrome (SARS) has been identified as a coronavirus (SARS-CoV). Though the complete genomic sequence has been determined in a short time, there are still large gaps in the understanding of functions of the viral proteins which is necessary to develop antiviral strategies. The surface glycoprotein S is of major importance for the pathogenesis of coronaviruses. It is the main target of the protective immune response elicited by a coronavirus infection. Furthermore it is involved in the early and late stages of the replication cycle. In the initiation of an infection, the S protein mediates the binding of the virion to receptors on the cell surface and the subsequent fusion event between the viral and the cellular membrane. We plan to use our expertise to generate vesicular stomatitis virus (VSV) pseudotypes that contain the S protein of SARS-CoV instead of the VSV G protein. In place of the G gene, the VSV genome contains the GFP gene the expression of which allows easy detection of infected cells by fluorescence microscopy. As the S protein is provided in trans by cotransfection of the corresponding gene, the pseudotypes are only able to perform a single replication cycle. Newly formed virions do not contain a surface glycoprotein and therefore are not infectious. This approach allows to analyze the S protein independent of other viral proteins and it can be applied at lower biosafety level conditions than are required for experiments performed with SARS-CoV. The pseudotypes will used to analyze the function of the S protein in the interaction with target cells. Furthermore, the potential of these virus-like particles as a vaccine against SARS-CoV infection will be analyzed in mice and monkeys. Pseudotypes should also be an interesting tool to screen for antivirals directed against the S protein of SARS-CoV.