Whole-transcriptome analysis of Plasmodium falciparum field isolates: identification of new pathogenicity factors.

BACKGROUND: Severe malaria and one of its most important pathogenic processes, cerebral malaria, involves the sequestration of parasitized red blood cells (pRBCs) in brain postcapillary venules. Although the pathogenic mechanisms underlying malaria remain poorly characterized, it has been established that adhesion of pRBCs to endothelial cells (ECs) can result in cell apoptosis, which in turn may lead to disruption of the blood-brain barrier. The nature of the parasite molecules involved in the pathogenesis of severe malaria remains elusive.

METHODS: Whole-transcriptome profiling of nonapoptogenic versus apoptogenic parasite field isolates obtained from Gabonese children was performed with pan-genomic Plasmodium falciparum DNA microarrays; radiolabeled instead of fluorescent cDNAs were used to improve the sensitivity of signal detection.

RESULTS: Our methods allowed the identification of 59 genes putatively associated with the induction of EC apoptosis. Silencing of Plasmodium gene expression with specific double-stranded RNA was performed on 8 selected genes; 5 of these, named "Plasmodium apoptosis-linked pathogenicity factors" (PALPFs), were found to be linked to parasite apoptogenicity. Of these genes, 2 might act via parasite cytoadherence.

CONCLUSION: This is the first attempt to identify genes involved in parasite pathogenic mechanisms against human ECs. The finding of PALPFs illuminates perspectives for novel therapeutic strategies against cerebral complications of malaria.