Abstract
In the current era of malaria eradication, reducing transmission is critical. Assessment of transmissibility requires tools that can accurately identify the various developmental stages of the malaria parasite, particularly those required for transmission (sexual stages). Here, we present a method for estimating relative amounts of Plasmodium falciparum asexual and sexual stages from gene expression measurements. These are modeled using constrained linear regression to characterize stage-specific expression profiles within mixed-stage populations. The resulting profiles were analyzed functionally by gene set enrichment analysis (GSEA), confirming differentially active pathways such as increased mitochondrial activity and lipid metabolism during sexual development. We validated model predictions both from microarrays and from quantitative RT-PCR (qRT-PCR) measurements, based on the expression of a small set of key transcriptional markers. This sufficient marker set was identified by backward selection from the whole genome as available from expression arrays, targeting one sentinel marker per stage. The model as learned can be applied to any new microarray or qRT-PCR transcriptional measurement. We illustrate its use in vitro in inferring changes in stage distribution following stress and drug treatment and in vivo in identifying immature and mature sexual stage carriers within patient cohorts. We believe this approach will be a valuable resource for staging lab and field samples alike and will have wide applicability in epidemiological studies of malaria transmission.
Highlights
One of the tenets of the recently released Malaria Eradication Research Agenda is the development of new diagnostics addressing transmission reduction [1]
Individuals harboring the Plasmodium falciparum transmissible parasite stage, or gametocyte, are the primary reservoir for malaria transmission, and proper surveillance of gametocyte carriers is critical to transmission reduction
The human malaria parasite Plasmodium falciparum is transmitted through a mosquito vector and causes over half a million deaths per year
Summary
One of the tenets of the recently released Malaria Eradication Research Agenda (malERA) is the development of new diagnostics addressing transmission reduction [1]. Surveillance is difficult, because gametocytes comprise only a small fraction of the total body parasite load during active infection and are only observed in the bloodstream in their mature form, while developing stages are sequestered in tissues [2] For these reasons, quantifying gametocytes in mixed parasite populations has been an ongoing challenge ever since they were first identified more than a century ago. The switch between asexual replication and sexual development does not occur ubiquitously in vivo or in vitro, as even the most synchronized gametocyte induction protocols result in partially asynchronous and mixed gametocyte stages [3,6] This problem is compounded in vivo, as blood sampled during infection is likely to contain both gametocyte and asexual parasite populations, leading to a highly convolved transcriptional mixture
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
