Adaptation and multiplication rate variation in the human malaria parasite
Adaptation and multiplication rate variation in the human malaria parasite Plasmodium falciparum
It is important to understand variation in malaria parasite reproductive rates in different environments, particularly in areas of Africa where there is a wide spectrum of transmission intensity and infection incidence. Different approaches will be illustrated with some recent results we have obtained working with colleagues in the region.
Genome sequence analyses of parasites at multiple sites throughout West Africa indicate a small number of discrete gene loci that have been under varying local selection, including genes involved in parasite sexual differentiation. Identifying functional differences between the allelic sequences is a priority to understand how parasites in particular populations have adapted differently.
Independently, direct measurements made of asexual blood stage multiplication rates of long-term laboratory adapted P. falciparum clones and new clinical isolates from West Africa have been measured. Multiplication rates of new clinical isolates after a few weeks of culture showed a wide spectrum of replication rates, with the entire range being lower than for the long-term laboratory adapted clones. Multiplication rates of many isolates increased over several months of culture, by which stage we have shown that new mutants can attain high frequencies, the analysis of which will also identify genes affecting multiplication in different environments.
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