Biomedicine

Placental Malaria

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Science  12 Jul 2002:
Vol. 297, Issue 5579, pp. 161
DOI: 10.1126/science.297.5579.161c

Pregnant women are particularly vulnerable to malaria because Plasmodium parasites, usually resident in red blood cells, readily respond by switching tissue tropism to colonize the placenta, where heavy infections develop with malign consequences for mother and child. Infected red blood cells display adhesive parasite ligands, encoded by the var genes, on their surface. These ligands mediate attachment to vascular epithelium, thus ensuring the parasites are sequestered and can avoid clearance via the spleen. The adhesive ligands mediate tissue tropism and, like many Plasmodium proteins, have a huge capacity for variation—another means of immune evasion. Malaria parasites respond to pregnancy by switching expression to a surprisingly conserved gene, varCSA, encoding a ligand for chondroitin sulfate A, which is present in the placenta. Vázquez-Macías et al. have shown that, unlike most subtelomeric genes, varCSA is transcribed in the opposite direction to other var genes and is under the control of a distinct flanking element. These attributes might explain its conservation among genetically distinct malaria strains and might offer a route to therapy. — CA

Mol. Microbiol.45, 155 (2002).

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