Expression of the Spike Protein of Murine Coronavirus JHM Using a Baculovirus Vector
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Coronaviruses are enveloped RNA viruses with single positive stranded genomic RNA of approximately 32 kilobases which encodes at least 3 structural proteins; a nucleocapsid protein (N), a matrix glycoprotein (M) and a spike glycoprotein (S), as well as several nonstructural proteins (1). The S protein forms the projecting spikes or peplomers on the surface of the virus particle (2). This protein is considered to be involved in the attachment of virus to susceptible cells, the induction of cell-to-cell fusion, and the induction of neutralizing antibodies (3,4). It is also believed that the S protein is important for determining the pathogenic potential of murine coronaviruses (5,6). For more detailed structural and functional analyses of S protein, we need to have large quantities of S protein uncontaminated with other viral proteins. For this purpose, we have sought to express the S gene product in a baculovirus expression vector. The Autographa californica nuclear polyhedrosis virus (AcNPV) insect baculovirus vector was chosen because of the high levels of foreign gene expression obtained using the AcNPV polyhedrin promoter (7). Also, translational modifications such as glycosylation, phosphorylation, and cleavage of the signal peptide are known to occur in this system. In this paper, we describe the expression of the MHV strain JHM (JHMV) S protein by recombinant baculovirus in insect cells, characterization of the protein and analysis of epitopes existing on the S protein.
KeywordsInsect Cell Recombinant Virus Recombinant Baculovirus Recombinant Baculoviruses Baculovirus Vector
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