Table 4.
Mice that survive primary LVS infection survive high-level secondary challenge with F. tularensis LVSa
| Expt no. | Strain | Primary infection (CFU) | Secondary challenge (CFU) | No. of survivors/total no. infected |
|---|---|---|---|---|
| 1 | C57BL/6 | PBS | 5 × 106 i.p. | 0/5 |
| C57BL/6 | 104 i.d. | 5 × 106 i.p. | 4/5 | |
| IL-6 KO | 104 i.d. | 5 × 106 i.p. | 4/5 | |
| 2 | C57BL/6 | PBS | 106 i.p. | 0/3 |
| C57BL/6 | PBS | 8 × 107 i.n. | 0/3 | |
| C57BL/6 | 102 i.d. | 106 i.p. | 4/5 | |
| IL-6 KO | 102 i.d. | 106 i.p. | 4/4 | |
| C57BL/6 | 102 i.d. | 8 × 107 i.n. | 5/5 | |
| IL-6 KO | 102 i.d. | 8 × 107 i.n. | 3/4 | |
| C57BL/6 | 102 i.n. | 106 i.p. | 5/5 | |
| IL-6 KO | 102 i.n. | 106 i.p. | 4/4 |
a
Wild-type C57BL/6 and IL-6 KO mice were vaccinated by primary i.d. infection with F. tularensis LVS (104 or 102 CFU, as indicated), by intranasal infection (102 CFU), or with PBS as a control. Eight (experiment 1) or 12 (experiment 2) weeks later, surviving mice were challenged i.p. with 1 × 106 to 5 × 106 LVS i.p. or with 8 × 107 LVS i.n., as indicated.