Table 3.

Duration of immunity to pcDNA3JEME in BALB/c micea

Interval between immunization and challenge (mo)bImmunogenNEUT titerc at daydSurvi- vale
−24821
1pcDNA3JEME1:101:1601:3201:6402/2
1PBS<1:101:101:10NAf 0/2
2pcDNA3JEME<1:101:1601:6401:6402/2
4pcDNA3JEME1:101:1601:6401:6402/2
4PBS<1:101:10NANA0/2
6pcDNA3JEME1:101:6401:1,280≥1:1,2802/2
  • a The duration was demonstrated by protection from challenge and anamnestic antibody response at up to 6 months following a single immunization.

  • b Groups of two male BALB/c mice were inoculated with PBS or 100 μg of pcDNA3JEME at 6 weeks of age and then challenged 1, 2, 4, or 6 months later.

  • c Represented as the serum dilution yielding a 90% reduction in plaque number.

  • d Days relative to challenge. Day −2 indicates 2 days before challenge.

  • e Number of surviving mice/total number of mice tested 21 days after challenge with the same dose of the P3 strain of JE virus as was used for the challenge of ICR mice (Table 2).

  • f NA, serum was not available due to the death of mice. Two mice immunized with PBS 1 month earlier died on days 6 and 10, and two mice immunized with PBS 4 months earlier died on days 6 and 8.