FIG. 4.

The role of CSP in sterile protection. Groups of 5 BALB/c mice, each immunized by Spz plus CQ with either P. berghei, P. berghei[PyCS], or P. yoelii, were challenged with either 100 sporozoites (P. yoelii) or 5,000 sporozoites (P. berghei or P. berghei[PyCS]) at least 25 days after immunization. The presence of parasites in the blood was monitored in each animal by microscopic examination of Giemsa-stained blood smears. All control mice treated with chloroquine alone (None) developed patent blood stage parasitemia after sporozoite challenge. Protection was defined as the percentage of mice that did not develop patent blood stage parasitemia over 10 days postchallenge. The data are the cumulative results of two experiments with 5 mice per group and per experiment.