Authors

Discussion

Genetic linkage analysis of the cloned progeny of Plasmodium chabaudi chabaudi genetic crosses has historically been used to determine loci responsible for drug resistance and drug sensitivity, most notably in pyrimethamine and chloroquine resistance phenotypes. The usefulness of P. c. chabaudi strains for such experimental evolution studies stems from their genetic diversity. For example, pyrimethamine-resistant P. c. chabaudi strain 47AS and pyrimethamine-sensitive P. c. chabaudi strain 10AJ differ by >144k single nucleotide polymorphisms (SNPs), equating to approximately 1 SNP every 100 bp. Coupled with the ability to genetically cross and transmit these rodent malaria strains through Anopheles mosquitoes, genetic analyses such as quantitative trait loci (QTL) analysis and linkage group selection (LGS) have been possible in this Plasmodium species, while such experiments are not possible in experimental strains of P. berghei or P. falciparum. 

Using genetic crosses of two divergent P. c. chabaudi (AS and AJ) strains, we aim to investigate gene expression regulation during zygote-to-ookinete development in vivo in the Anopheles stephensi mosquito midgut, paying particular attention to maternal and paternal allele inheritance. In addition, should either of these strains fail to transmit or cross-fertilise, we have acquired, and transmitted through An. stephensi mosquitoes for the first time, the P. chabaudi subspecies isolate P. c. esekanensis EF. 

These data represent the establishment of the full P. c. chabaudi life cycle and the first generation of P. c. chabaudi genetic crosses at the University of Glasgow. This study also demonstrates the first transmission of P. c. esekanensis EF in an experimental setting. Using female Theiler’s Original (TO) mice housed under normal light conditions, we have measured the synchronicity of morphological stages across the intraerythrocytic developmental cycle (IDC), quantified gametocytaemia over 24 hours, and demonstrated transmission of three P. c. chabaudi strains (PccAS, PccAJ, and PcEF) through An. stephensi mosquitoes. Further optimisation of ookinete generation and purification is underway, with finalised protocols providing new avenues by which the P. c. chabaudi malaria model can be used to investigate the evolution and pathogenesis of Plasmodium parasites.