and has been
described previously (5); for simplicity we will refer to this strain here as RA59-
gfp (4, 8).
Selection of the RA59-gfp/gp33
recombinant MHV-A59 expressing
the LCMV gp33 epitope as a fusion protein with GFP is described in the next
paragraph. fMHV (obtained from Paul Masters, New York State Department of
Health, Albany) is a recombinant MHV-A59 which contains the ectodomain of
the feline infectious peritonitis virus spike glycoprotein in place of that of the
MHV spike (11). MHV stocks were prepared in 17Cl-1 cells and titrated by
plaque assay in murine L2 cells