Table 2. Immunization with p36p sporozoites protects against a subsequent infection with WT sporozoites
Time of challenge, days after final immunization
No. protected (no. challenged)
Experiment no. Mouse strain Immunization,* RAS/p36p × 103 Challenge dose, WT × 103 Control RAS p36p
1 BALB/c 100 50 10 0 (10) ND 18 (20)
2 BALB/c 50 25 10 0 (15) 15 (15) 15 (15)
3 BALB/c 50 10 10 0 (5) ND 5 (5)
3 BALB/c 50 10 30 0 (5) ND 5 (5)
3 BALB/c 50 10 60 0 (5) ND 5 (5)
3 BALB/c 50 10 120 0 (5) ND 5 (5)
4 BALB/c 50 1,000 iRBC 10 0 (3) 0 (5) 0 (4)
1 C57BL6 50 10 10 0 (3) 0 (3) 0 (1)
1 C57BL6 50/20 10 10 0 (3) 1 (3) 1 (4)
1 C57BL6 50/20/20 10 10 0 (5) 5 (5) 4 (4)
1 C57BL6 50/20/20 10 30 0 (5) 5 (5) 5 (5)
  • * Groups of mice were immunized intravenously with one of PBS (control), RAS, or p36p sporozoites isolated from different mos quito batches. Multiple immunizations with RAS or p36p sporozoites were administered at 7-day intervals.

  • Mice were challenged with WT sporozoites or parasite infected red blood cell (iRBC) stages and the prepatent period monitored by either counting Giemsa-stained bloodsmears or FACS analysis. All control, unimmunized mice became positive on day 4 or 5 after challenge. Sporozoites were isolated from different mosquito batches.