TABLE 4.

Cross-protective immunity of PspA/EF3296 immunization in CBA/N mice

Immunogena and strain (capsular type)PspA clade(s)bMedian no. of days to deathcP valueAlive/dead ratiodP value
NonimmuneImmuneNonimmuneImmune
SW111
    A66.1 (3)1 + 2e240.6220:73:40.191
    BG7322 (6B)26210.0180:76:10.005
    3JYP2670 (3)41210.0020:75:20.020
    ATCC 6303 (3)5221<0.0010:77:0<0.001
HR101
    A66.1 (3)1 + 2221.0000:70:71.000
    BG7322 (6B)2560.3790:70:71.000
    3JYP2670 (3)4110.9450:70:71.000
    ATCC 6303 (3)5230.0020:70:71.000
HR107
    A66.1 (3)1 + 2230.6920:50:51.000
    BG7322 (6B)26210.0160:53:20.167
    3JYP2670 (3)4221<0.0010:109:1<0.001
    ATCC 6303 (3)52210.0160:53:20.167
HR108
    A66.1 (3)1 + 2220.720:80:81.000
    BG7322 (6B)23.5210.0150:86:20.007
    3JYP2670 (3)4121<0.0010:86:20.007
    ATCC 6303 (3)5121<0.0010:76:10.026
  • a Mice were immunized and boosted 2 weeks apart with 1 μg of protein and challenged 2 weeks after the boost.

  • b Clades 1 and 2 are in family 1; clades 3, 4, and 5 are in family 2. For protection against family 2, clade 3 strain EF3296, see Table 2.

  • c Median numbers of days to death were compared between immune and nonimmune mice with the two-tailed Mann-Whitney U test (nonparametric, two-sample rank test). Boldface P values indicate significant differences.

  • d Fisher's exact test was used to compare alive/dead ratios of immune and nonimmune mice in survival experiments. Boldface P values indicate significant differences.

  • e A66.1 expresses both clade 1 and clade 2 PspA proteins (10).