Coronavirus induction of class I major histocompatibility complex expression in murine astrocytes is virus strain specific

As Coronaviridae, all MHV strains are enveloped viruses that contain a single-stranded, positive-sense ILNA genome of 31-kb that is expressed as 7 or 8 mRNAs encoding both structural and nonstructural proteins (11) . The structural proteins have been well characterized, and include the nucleocapsid (N) protein, which interacts with the viral RNA, and two envelope glycoproteins, the spike (S) and membrane (M) proteins. The S protein forms the virion surface spikes and is responsible for binding the cellular MHV receptor, inducing cell-to-cell fusion and providing a target for neutralizing antibodies. It is the least conserved of the structural proteins among the MHV strains (12) (13) (14) (15) (16) . M interacts with the N protein-R.NA comply, and may be involved in virus assembly. It is the most conserved structural protein among the MHV. A third envelope glycoprotein, hemagglutinin-esterase (HE), has been identified in MHV-S and several JHMV isolates, and may participate in the pathogenesis of JHMV infection in the central nervous system (CNS) (11, 17) . Nonstructural proteins include an RNA-dependent RNA polymerase, and three additional proteins that do not appear to be required for viral replication, but whose functions and biological activities have not been identified.