TABLE 1.

Vaccination with the SEB fragments elicited no neutralizing antibodies

AgentAcute toxicity (no. live/no. dead)aEfficacy
TiterbInhibition of T-cell proliferation (%)c% Survivald
SEBv10/0>10597100
SEB1-9910/0>1053e0e
SEB66-24310/0>1050e0e
Both fragments10/0>1052e0e
WT SEB0/10>10595100
  • a Naïve mice were injected with 10 μg of SEBv, the SEB fragments, or WT SEB and a potentiating dose of LPS. Lethality was recorded 4 days after the challenge dose was administered.

  • b Mice were vaccinated intraperitoneally and boosted at 2 and 4 weeks. Ten days after the last vaccination, the mice were bled and serum titers against SEB were determined. The data are expressed as the reciprocal serum dilution resulting in an optical density twice that of the negative controls (ELISA wells containing either no toxin or no primary antibody).

  • c SEB (10 ng/ml) and sera that were obtained 2 weeks after the last vaccination were preincubated before they were added to splenic mononuclear cells. The data are expressed as the percentage of SEB stimulation, where inhibition = 100 − [(experimental counts per minute for sera from vaccinated mice)/(counts per minute for SEB in the presence of sera from naïve mice) × 100]. The standard errors of the means for triplicate wells were <10% for the calculated values.

  • d Mice were challenged with 2 μg of SEB per mouse (approximately 10 LD50) and a potentiating dose of LPS (75 μg) 2 weeks after the final boost, and lethality was recorded 4 days after the challenge dose was administered.

  • e The P value compared to SEBv was <0.001.