The replication of mouse hepatitis virus strain JHM (MHV-JHM), a murine coronavirus, will be studied. The 5' termini of the virion and mRNAs will be sequenced. Molecular clones of the genome will be made and portions of these clones corresponding to the 5' termini of the mRNAs will also be sequenced. An in vitro RNA dependent RNA polymerase system will be established and the RNA products characterized by gel electrophoresis and hybridization. Temperature sensitive mutants with lesions in genes required for RNA synthesis will be examined in this system. Antibody made to synthetic peptides will also be used to attempt to disect the mechanism of MHV RNA synthesis. A persistently infected cell line which has been modulated by antibody will be examined to determine which genes are being expressed. Western blots will be used to examine MHV-specific proteins; Northern blots will be used to examine MHV-specific RNAs. We will examine persistently infected mice for the presence of CNS anti-MHV antibody, for the presence of infectious virus and for the presence of viral antigens.