Plasmodium falciparumIsolates from Infected Pregnant Women and Children Are Associated with Distinct Adhesive and Antigenic Properties

Abstract

Plasmodium falciparum malaria during pregnancy is an important cause of maternal and infant morbidity and mortality. Accumulation of large numbers of P. falciparum-infected erythrocytes in the maternal blood spaces of the placenta may be mediated by adhesion of infected erythrocytes to molecules presented on the syncytiotrophoblast surface. In this study, isolates from placentas and peripheral blood of infected pregnant women and from children were tested for binding to purified receptors and for agglutination with adult sera. Results suggest that adhesion to chondroitin sulfate A may be involved in placental parasite sequestration in most cases, but other factors are also likely to be important. Agglutination assay results suggest that parasites infecting pregnant women are antigenically distinct from those common in childhood disease. The prevalence of agglutinating antibodies to pregnancy isolates was generally low, but it was highest in multigravidae who are likely to have had the greatest exposure.

Adhesion Specificities of Plasmodium falciparum-Infected Erythrocytes Involved in the Pathogenesis of Pregnancy-Associated Malaria

“…4 Furthermore, the VSA expressed by placental and CSA-adhering IEs (VSA PAM ) are antigenically completely distinct from other VSA. 5,6 These findings suggest that the reason why pregnant women become susceptible to P. falciparum malaria despite previously acquired protective immunity to the disease is not due to pregnancy-related immunosuppression as previously thought. Rather, the parasites causing PAM express VSA (VSA PAM ), which is not expressed by parasites infecting nonpregnant individuals and to which primigravidae consequently have no pre-existing immunity.…”

Multiplicity of Plasmodium falciparum infection in pregnancy.

“…This hypothesis is supported by a recent study. 31 It demonstrated that parasites found in pregnant women were antigenically distinct from those common in children in the study area, and that the prevalence of agglutinating antibodies against these strains increased with gravidity. In hyperendemic areas, women usually acquire such antibodies during their first or second pregnancies.…”

Plasmodium falciparum dihydrofolate reductase alleles and pyrimethamine use in pregnant Ghanaian women.

“…35 In a given transmission area, parasites with specific receptors to placental tissue have an increased chance to establish themselves in the otherwise semi-immune pregnant host. [36][37][38] With successive pregnancies, immune mechanisms against these particular strains develop; infections become rarer and may increasingly comprise parasite genotypes also present in nonpregnant individuals. 38,39 If drug consumption propagates resistance in parasites able to adhere to placental ligands, it seems conceivable that this resistance is further selected within the group of pregnant women.…”