Construction of a severe acute respiratory syndrome coronavirus infectious cDNA clone and a replicon to study coronavirus RNA synthesis

The engineering of a full-length infectious cDNA clone and a functional replicon of the severe acute respiratory syndrome coronavirus (SARS-CoV) Urbani strain as bacterial artificial chromosomes (BACs) is described in this study. In this system, the viral RNA was expressed in the cell nucleus under the control of the cytomegalovirus promoter and further amplified in the cytoplasm by the viral replicase. Both the infectious clone and the replicon were fully stable in Escherichia coli. Using the SARS-CoV replicon, we have shown that the recently described RNA-processing enzymes exoribonuclease, endoribonuclease, and 2′-O-ribose methyltransferase were essential for efficient coronavirus RNA synthesis. The SARS reverse genetic system developed as a BAC constitutes a useful tool for the study of fundamental viral processes and also for developing genetically defined vaccines. Copyright © 2006, American Society for Microbiology. All Rights Reserved.This work was supported by grants from the Ministerio de Educación y Ciencia of Spain (BIO2004-00636), the European Community (Frame VI, Projects DISSECT SP22-CT-2004-511060 and RIVIGENE SSPE-CT2005-022639), and Fort Dodge Veterinaria