Briefly, pMH54
contains a T7 RNA polymerase promoter followed by a 9,139-nucleotide sequence
(11); pMH54 encodes the 5 end of the MHV genome fused in frame to
codon 28 of the hemagglutinin esterase pseudogene, followed by the spike and
the rest of the 3 end of the MHV-A59 genome and finally a poly(A) tail