FIG. 5.

Structures of the genomes of recombinant viruses. The genome structures of the recombinant viruses are shown as combinations of OM (closed boxes) and SA (open boxes) sequences. Nucleotide sequence differences that resulted in amino acid differences between OM and SA are shown on the OM and SA genomes. Cleavage sites of restriction enzymes used for allele replacement experiments are denoted by the names of the enzymes with the relevant nucleotide positions. The nomenclature for virus strains indicated on the left is explained in Materials and Methods. The LD₅₀ (PFU) of each virus obtained from mouse neurovirulence testing following inoculation via the intraspinal route is shown on the right. P1, P2, P3, and UTR are defined in the legend for Fig. 4.