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Malaria Journal

, 7:243

First Online: 24 November 2008Received: 06 June 2008Accepted: 24 November 2008

Abstract

BackgroundPlatelet-mediated clumping of Plasmodium falciparum-infected erythrocytes IE is a parasite adhesion phenotype that has been associated with severe malaria in some, but not all, field isolate studies. A variety of experimental conditions have been used to study clumping in vitro, with substantial differences in parasitaemia Pt, haematocrit Ht, and time of reaction between studies. It is unknown whether these experimental variables affect the outcome of parasite clumping assays.

MethodsThe effects of Pt 1, 4 and 12%, Ht 2, 5 and 10% and time 15 min, 30 min, 1 h, 2 h on the clumping of P. falciparum clone HB3 were examined. The effects of platelet freshness and parasite maturity were also studied.

ResultsAt low Ht 2%, the Pt of the culture has a large effect on clumping, with significantly higher clumping occurring at 12% Pt mean 47% of IE in clumps compared to 4% Pt mean 26% IE in clumps or 1% Pt mean 7% IE in clumps ANOVA, p = 0.0004. Similarly, at low Pt 1%, the Ht of the culture has a large effect on clumping, with significantly higher clumping occurring at 10% Ht mean 62% IE in clumps compared to 5% Ht mean 25% IE in clumps or 2% Ht mean 10% IE in clumps ANOVA, p = 0.0004. Combinations of high Ht and high Pt were impractical because of the difficulty assessing clumping in densely packed IE and the rapid formation of enormous clumps that could not be counted accurately. There was no significant difference in clumping when fresh platelets were used compared to platelets stored at 4°C for 10 days. Clumping was a property of mature pigmented-trophozoites and schizonts but not ring stage parasites.

ConclusionThe Pt and Ht at which in vitro clumping assays are set up have a profound effect on the outcome. All previous field isolate studies on clumping and malaria severity suffer from potential problems in experimental design and methodology. Future studies of clumping should use standardized conditions and control for Pt, and should take into account the limitations and variability inherent in the assay.

Electronic supplementary materialThe online version of this article doi:10.1186-1475-2875-7-243 contains supplementary material, which is available to authorized users.

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Autor: Mònica Arman - J Alexandra Rowe

Fuente: https://link.springer.com/







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