FIG. 9.
Reduced virulence of the ΔHVR2 mutant. Six-week-old, female BALB/c mice, in groups of eight, were inoculated intranasally with 5 × 103 PFU (A and B), 5 × 104 PFU (C and D), or 5 × 105 PFU (E and F) of wild-type or ΔHVR2 virus. A group of four mock-inoculated mice was inoculated with tissue culture supernatant. Mice were weighed and observed for clinical signs daily. (A, C, and E) Percentage of original weight (± standard deviation). (B, D, and F) Average clinical disease scores, as defined in Materials and Methods. The same mock-inoculated group is shown in all panels for comparison to each of the viral dose groups.