Figure 1.

Recombinant viruses with an FL expression cassette at different genomic locations.
A. The genomic organization of the recombinant wild‐type MHV (MHV‐A59) and of the recombinant viruses carrying an FL expression cassette. The numbers designate the genes encoding the non‐structural proteins, while genes encoding the spike (S) protein, envelope (E) protein, membrane (M) protein, haemagglutinin‐esterase (HE) protein, and nucleocapsid (N) protein are indicated by their abbreviations. Srec indicates the S gene carrying the mutations that are responsible for the extended host range. The 5′‐ and 3′‐untranslated regions (UTR) are also designated.
B. The growth kinetics of the MHV recombinants. LR7 cells were infected with each recombinant MHV at a multiplicity of infection of 1. Viral infectivity in the cell culture media at different times post infection was determined by a quantal assay on LR7 cells, and TCID₅₀ values were calculated.
C. In parallel, the intracellular expression of luciferase in relative light units (RLU) was determined as described in the Experimental procedures. Standard deviations (n = 3) are indicated.