Figure 2. Chloroquine permits transient blood-stage parasitemia during each immunization.
The number of parasitized erythrocytes (pE) per ml of whole blood was enumerated by quantitative RealTime PCR after each CPS immunization (i1, i2, i3) with P. chabaudi AS-infected mosquito bites under chloroquine (CQ) cover. The number of pE (at the late trophozoite stage) was quantified immediately before merozoite egress from the liver, at 48 hr post mosquito transmission (erythrocytic cycle 0), and then every 24 hr until erythrocytic replication cycle 4. Daily parasitemia of 10 CPS immunized mice (each color represents an individual mouse) are shown. Blood-stage parasites were detected within the first erythrocytic cycle after every immunization in all but one mouse after the final immunization. Gray bars represent the mean parasitemia in the first erythrocytic cycle of naive mice infected as controls for mosquito transmission efficiency separate with each immunization (n = 3–5). Significant differences in the number of blood-stage parasites in the first erythrocytic cycle between naive and CPS immunized mice are indicated (Mann Whitney test, **p ≤ 0.01).