Fig. 6.

Virulence of CPXV mutant and revertant strains in mice: (A) weight loss comparison. BALB/cJ (5–7 weeks old) mice were inoculated i.n. with PBS (mock) or 10⁶ PFU of the cloned CPXV 91/3, the two deletion mutants (ΔATI and ΔA26) and the two revertants (ATIRev and A26Rev). The weight loss data (average weight loss with standard error of the means) was generated from two independent experiments with a total of 15 mice and plus error bars are shown. The baseline used for calculation was obtained by weighing each mouse on the two successive days prior to infection. The asterisks indicate significant difference (p<0.05) between the weight loss of mice infected with ΔATI and each of the other viruses. (B) Virus titers in organs. Mice (n=5 per group) were infected as in panel A and sacrificed on days 1, 3, 5 and 10. The lungs and nasal turbinates were homogenized and the virus titers determined by plaque assay on BS-C-1 cells. The average titers (total for the turbinates and per gram for the lung) with standard error of the means were calculated and the plus bars are shown. For turbinates, asterisks on day 3 of ΔATI infection and 3, 5 and 10 of ΔA26 infection indicate significant differences (p<0.05) from CPXV 91/3, ATIRev and A26Rev. For lungs, asterisks on days 3, 5 and 10 of ΔATI infection indicate significant differences (p<0.05) from CPXV 91/3, ATIRev, A26Rev and ΔA26.