Plasmodium falciparum: analysis of transcribed var gene sequences in natural isolates from the Brazilian Amazon region

Abstract

Parasite isolates from Brazilian Western Amazonian patients suffering from uncomplicated falciparum malaria were matured in vitro and their var gene transcripts were analysed by RT-PCR and sequencing. Additionally, the cytoadherence patterns of these isolates were determined by panning techniques using transfected CHO cell lines expressing different surface receptors. All of the isolates tested showed between 4 and 13 different var gene transcripts per isolate. Several of these transcripts were present in more than one isolate and three sequences appeared to be preferentially expressed in natural infections. In most of the isolates, cytoadherence occurred to the receptors ICAM-1 and CD36. Several isolates showed a multiadherent profile. Analysis of MSP1 and MSP2 allelic polymorphism indicated polyclonal infections, that could be responsible for the multiadherent phenotype.