Table 1.
Immunization with palm- sporozoites confers potent protection against reinfection
| Challenge | palm- immunizationa | # Protected/# Challengedb | Prepatency (days)c |
|---|---|---|---|
| Exposure to five infected mosquitoes | 2 × 10 000 spz | 20/20 (100%) | – |
| 2 × 1000 spz | 0/2 (0%) | 6.0 | |
| naïve | 0/10 (0%)d | 4.0 | |
| Intravenous injection of 10 000 sporozoites | 2 × 10 000 spz | 5/5 (100%) | – |
| naïve | 0/6 (0%) | 3.0 | |
| Intravenous injection of 10 000 sporozoites (day 110)e | 2 × 10 000 spz | 6/7 (86%) | 8.0 |
| naïve | 0/3 (0%) | 3.0 | |
| Intravenous injection of 10 blood-stage parasitesf | 2 × 10 000 spz | 0/4 (0%) | 6.0 |
| naïve | 0/5 (0%) | 6.0 |
a
Age-matched female C57BL/6 mice were immunized with palm- sporozoites (spz) in the numbers indicated. The immunization protocol is described in the Experimental procedures section.
b
Animals were checked for parasitaemia by daily examination of Giemsa-stained blood smears.
c
Prepatency is the time until detection of the first parasite in the peripheral blood.
d
One additional naïve mouse (not included) stayed initially malaria-free but became positive at day 3 after intravenous re-challenge.
e
Challenge at 110 days after the last immunization.
f
The immunized mice were previously shown to be fully protected against ‘by bite’ challenge.