TABLE 1.

Protection against lethal virus challenge in immunized micea

Time of virus challenge after the last vaccination and immunogenNo. of survivors/no. testedbVirus titer in lungs [log10(PFU/g)]
10 LD50100 LD5010 LD50100 LD50
1 month
    Control0/90/97.9 ± 0.47.7 ± 0.5
    Inactivated virus0/90/97.5 ± 0.17.2 ± 0.3
    NS gene-deficient VLPs2/90/97.8 ± 0.67.6 ± 0.5
    NS2-knockout VLPs9/99/95.1 ± 1.2c5.2 ± 1.0c
3 months
    Control0/90/97.3 ± 0.27.0 ± 0.2
    Inactivated virus0/90/97.4 ± 0.27.1 ± 0.3
    NS gene-deficient VLPs1/90/97.1 ± 0.87.2 ± 0.3
    NS2-knockout VLPs8/98/93.7 ± 1.3d4.0 ± 1.1e
  • a Mice were challenged intranasally, under anesthesia, with 10 or 100 LD50 of the wild-type WSN virus at 1 or 3 months after the last vaccination. Virus titers in the lungs were determined 3 days after challenge.

  • b Mice were monitored for 14 days after challenge.

  • c Significantly different from the above three groups (P < 0.001) by Student’s t test.

  • d Significantly different from the above three groups (P < 0.02) by Student’s t test.

  • e Significantly different from the above three groups (P < 0.003) by Student’s t test.