FIG. 3.

Quantitative PCR analysis of genetically mixed strain infections of P. c. chabaudi in immune mice. (a) Percentages of parasitemia on a log scale for groups of AJ- or CB-immunized mice. The infection in mouse 18 resolved to subpatent levels by day 7 and could not be used in the analyses after that day. (b and c) Proportions of each strain of P. c. chabaudi, measured by RTQ-PCR, in three mice immunized with (b) CB or (c) AJ by two successive drug-treated bouts of parasitemia with the homologous strain. The mixed strain challenge was administered 43 days later for AJ-immunized mice or 45 days later for CB-immunized mice and comprised approximately equal proportions of homologous and heterologous strains amounting to a total of 5 × 10⁶ parasites per inoculum (see Materials and Methods). No error bars are shown for the RTQ-PCR measurements as no DNA derived from the homologous strain was found in any of the samples analyzed over the 6 days where the parasitemia of the mice was high enough to be able to extract sufficient genomic DNA for quantitative analysis. The data shown in panel b comprise results from three mice for days 3 to 6 (mice 18, 19, and 20) and from two mice for days 7 and 8 (mice 18 and 20). (e and f) Proportions of each strain were measured by RTQ-PCR (another experiment) for (e) three mice made immune to AJ or (f) one mouse made immune to AQ (mouse number 21) by two successive drug-treated bouts of parasitemia with the homologous strain administered 43 days later for AJ or 45 days later for AQ. The mixed strain challenge comprised 5 × 10⁶ parasites, approximately half of which were the homologous strain and half the heterologous strain (see Materials and Methods). (d) Parasitemias for the mice described for panels e and f, monitored over the period when the mice were parasitemic.