Antigenic Differences and Conservation among Placental Plasmodium falciparum–Infected Erythrocytes and Acquisition of Variant-Specific and Cross-Reactive Antibodies

• Published in: The Journal of infectious diseases Vol. 193; no. 5; pp. 721 - 730
• Main Authors: Beeson, James G., Mann, Emily J., Byrne, Timothy J., Caragounis, Aphrodite, Elliott, Salenna R., Brown, Graham V., Rogerson, Stephen J.
• Format: Journal Article
• Language: English
• Published: United States The University of Chicago Press 01.03.2006; University of Chicago Press; Oxford University Press
• Subjects: Adhesion; Agglutination; Agglutinins - blood; Animals; Antibodies; Antibodies, Protozoan - blood; Antibodies, Protozoan - immunology; Antigenic Variation - immunology; Antigens; Antiserum; Blotting, Western; Cell Adhesion; Chondroitin Sulfates - metabolism; Cross Reactions; Epitopes; Epitopes - immunology; Erythrocytes; Erythrocytes - parasitology; Female; Humans; Immunoglobulin G - blood; Malaria; Malaria, Falciparum - immunology; Malaria, Falciparum - parasitology; Parasites; Placenta - parasitology; Plasmodium falciparum; Plasmodium falciparum - immunology; Plasmodium falciparum - isolation & purification; Plasmodium falciparum - metabolism; Pregnancy; Pregnancy Complications, Parasitic - immunology; Pregnancy Complications, Parasitic - parasitology; Protozoan Proteins - biosynthesis; Protozoan Proteins - immunology; Protozoan Proteins - metabolism; Sulfates
• ISSN: 0022-1899; 1537-6613
• DOI: 10.1086/500145

BackgroundPregnant women are infected by Plasmodium falciparum with novel antigenic phenotypes that adhere to chondroitin sulfate A (CSA) and other receptors in the placenta. The diverse and variant parasite protein P. falciparum erythrocyte membrane protein 1 (PfEMP1), which is encoded by var genes, is a ligand for CSA and a major target of antibodies associated with protective immunity MethodsSerum samples from pregnant women exposed to malaria were tested for immunoglobulin G, adhesion-inhibitory antibodies, and agglutinating antibodies to different CSA-binding isolates expressing conserved var2csa-type genes and to parasite isolates from infected placentas. Parasite isolates also were examined to assess PfEMP1 expression, the effect of trypsin treatment of infected erythrocytes on parasite adhesion and cleavage of PfEMP1, and inhibition of adhesion by rabbit antiserum raised against a CSA-binding isolate ResultsFindings demonstrated that (1) there are significant antigenic differences between CSA-binding isolates that correspond with polymorphisms in var2csa; (2) there are differences in the properties of PfEMP1 and antibody reactivity between CSA-binding and placental isolates, which express multiple PfEMP1 forms; (3) acquired antibodies target diverse and cross-reactive epitopes expressed by CSA-binding infected erythrocytes, and cross-reactive antibodies are not necessarily cross-inhibitory; and (4) the breadth of antibody reactivity is greater among multigravidae than among primigravidae ConclusionsImmunity may be mediated by a repertoire of antibodies to diverse and common epitopes. Strategies based on vaccination with a single domain or isolate might be hindered by antigenic diversity