Clinical Pathology - Research Publications

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Start date: 1980 × End date: 1999 × Author: Brown, Graham ×

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    Plasmodium Falciparum: Cytoadherence occurring in the absence of knobs uses the thrombospondin receptor (CD36)
    Biggs, BA ; Culvenor, JG ; Ng, J ; Kemp, DJ ; Boyd, A ; Brown, GV (Elsevier BV, 1990)
    P. falciparum is the cause of the lethal form of malaria which results in thousands of deaths each year. The primary cause of death, cerebral malaria, is associated with the sequestration of erythrocytes infected with the mature stages of P. falciparum (trophozoites and schizonts) in the post capillary venules of the brain. The identification of the parasite protein(s) involved in this process will provide important vaccine candidate molecules and knowledge about the pathological processes involved in cell-cell adhesion in general. The mechanism of cytoadherence is studied in vitro using cultured lines of P. falciparum which bind to umbilical vein endothelial cells and C32 amelanotic melanoma cells. Mature stages of the parasite may induce knob-like protrusions in the erythrocyte membrane, and it was previously thought that ‘knobs’ were necessary although not sufficient for cytoadherence to occur both in vitro and during natural infection. We have derived a clone of the Brazilian isolate of P. falciparum, ITG2F6, and selected for cytoadherence by repeated passage over amelanotic melanoma cells. Chromosome analysis using pulsed-field gradient electrophoresis and DNA amplification using the polymerase chain reaction reveal that this clone has deleted the gene coding for knobs. Furthermore, cytoadherence which is independent of knobs occurs via the receptor for the platelet protein, thrombospondin.
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    Plasmodium falciparum: Cytoadherence of a knobless clone
    BIGGS, BA ; CULVENOR, JG ; NG, JS ; KEMP, DJ ; BROWN, GV (Elsevier, 1989-07)
    Sequestration of Plasmodium falciparum-infected erythrocytes is crucial to parasite survival as it prevents destruction in the liver and spleen. Knobs have been considered necessary but not sufficient for cytoadherence to vascular endothelial cells in vivo and to melanoma or umbilical vein endothelial cells in vitro. We describe here a knobless clone that cytoadheres strongly to C32 melanoma cells. This clone cannot express the knob-associated histidine-rich protein (KAHRP) due to the deletion of the KAHRP gene. Our results raise the possibility of an alternative mechanism for in vitro cytoadherence and suggest that the use of long term cultured isolates and melanoma cells as a model for cytoadherence in vivo may be misleading.
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    Localization of the ring-infected erythrocyte surface antigen (RESA) of Plasmodium falciparum in merozoites and ring-infected erythrocytes.
    Brown, GV ; Culvenor, JG ; Crewther, PE ; Bianco, AE ; Coppel, RL ; Saint, RB ; Stahl, HD ; Kemp, DJ ; Anders, RF (Rockefeller University Press, 1985-08-01)
    Immunoelectron microscopy with protein A gold has been used to determine the subcellular location of the ring-infected erythrocyte surface antigen (RESA) of Plasmodium falciparum. RESA was associated with dense vesicles presumed to be micronemes within merozoites. RESA was not detected on the surface of merozoites but was located at the membrane of erythrocytes infected with ring-stage parasites. RESA within merozoites was largely soluble in the nonionic detergent Triton X-100, but was insoluble in this detergent when associated with the erythrocyte membrane.