TABLE 2.

Virulence properties of YFV-17D variants in IFN-α/γ-R−/− mice

VirusE residue(s) different from 17DMortalityaAST (days) (SD)P valueb
r17D14/16d18.1 (2.4)
r17D-R52G5210/1017.7 (1.6)0.9
r17D-I173T17310/1015.1 (2.3) 0.01
r17D-T200K2009/1016.7 (1.2)0.2
r17D-F305S3058/816.3 (2.8)0.1
r17D-S325P3259/1016.1 (1.5)0.07
r17D-R380T3809/918.0 (2.5)1
r17D-dI/II/III52, 173, 200, 305, 325, 3809/911.6 (1.3) <0.0001
r17D-dIII305, 325, 3809/912.9 (2.6) 0.0006
r17D-dI/II52, 173, 2008/817.00.2c
r17D-S325P/R380T325, 3800/8NAe
r17D-dI/II/III-305F52, 173, 200, 325, 38010/1011.5 (2.1) <0.0001
  • a Mortality over 4 weeks is shown as the fraction of the total number of mice inoculated with 103 Vero PFU via the footpad; the specific infectivity of YFV-17D and variants corresponds to 2 × 103 to 5 × 103 genome equivalents/PFU.

  • b The P value was calculated using the Mann-Whitney ranking U test on survival times versus r17D; values under 0.05 are shown in bold.

  • c A P value of 0.001 was calculated when the survival times were tested against those of r17D-dI/II/III using the Mann-Whitney ranking U test.

  • d Combined data from three virulence determinations are shown.

  • e NA, not applicable.