Fig. 7
Quantitative analysis of the individual parasite burden and thus inferred plasmid retention. Proportion of parasite total burden in the spleen of BALB/c mice infected with LV9 NMT+/HYG [NMT-TK], LV9 ΔNMT [NMT-TK], LV9 ΔNMT [NMT-TK][NMT-tdtom] or LV9 ΔNMT [NMT-TK][tdtom] are selected for by limiting dilution assay with the appropriate drugs. a Selection for the presence of plasmid coding for NMT, TK and GFP. Upon treatment with GCV for 28 days (3 mg/kg per day− b.i.d; open symbols), parasites have almost entirely lost the plasmid encoding for TK, NMT, GFP.b Selection for the presence of the plasmid coding for NMT and tdtom or tdtom alone. Upon GCV treatment, there were ~100 times more parasites present if an additional NMT allele/gene was encoded. No significant difference between the untreated and treated group was observed. However, if no additional NMT allele/gene was present, parasites, survival was less (untreated group) and upon GCV treatment, those parasites were not detectable. c Selection for the presence of parasites positive for both plasmids, i.e. encoding NMT, TK & GFP and NMT & tdtom or only tdtom. Upon GCV treatment, only a few parasites were present in the spleen encoding for both plasmids. There were more parasites in the spleen in the group not encoding for a second NMT gene carrying both plasmids. However this number was not significant (Mann–Whitney test *P < 0.5, **P < 0.05)