Functional and immunological characterization of the var2CSA-DBL5ɛ domain of a placental Plasmodium falciparum isolate

Gangnard, Stéphane; Ndam, Nicaise Tuikue; Gnidehou, Sédami; Quiviger, Michael; Juillerat, Alexandre; Faure, Grazyna; Baron, Bruno; Viwami, Firmine; Deloron, Philippe; Bentley, G.A.

doi:10.1016/j.molbiopara.2010.05.014

Cited by 9 publications

(15 citation statements)

References 34 publications

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“…The affinities of 3D7-DBL1X-2X and 3D7-DBL1X-3X for human placental CSPG are ∼5 times lower than that of 3D7-DBL1X-6ε, but ∼10 times higher than that of 3D7-DBL2X and ∼150 times higher than that of the single DBL domains FCR3-DBL3X and FCR3-DBL6ε. K D for the binding of DBL5ε, derived from the placental strain CYK39, for placental CSPG was reported as 140 µM [41], similar to that of the single 3D7-DBL3X and 3D7-DBL6ε domains. Thus, 3D7-DBL1X-2X is the shortest var2CSA recombinant protein with an affinity for human placental CSPG that is the most comparable with that of 3D7-DBL1X-6ε.…”

Section: Resultsmentioning

confidence: 71%

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Var2CSA Minimal CSA Binding Region Is Located within the N-Terminal Region

et al. 2011

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Var2CSA, a key molecule linked with pregnancy-associated malaria (PAM), causes sequestration of Plasmodium falciparum infected erythrocytes (PEs) in the placenta by adhesion to chondroitin sulfate A (CSA). Var2CSA possesses a 300 kDa extracellular region composed of six Duffy-binding like (DBL) domains and a cysteine-rich interdomain region (CIDRpam) module. Although initial studies implicated several individual var2CSA DBL domains as important for adhesion of PEs to CSA, new studies revealed that these individual domains lack both the affinity and specificity displayed by the full-length extracellular region. Indeed, recent evidence suggests the presence of a single CSA-binding site formed by a higher-order domain organization rather than several independent binding sites located on the different domains. Here, we search for the minimal binding region within var2CSA that maintains high affinity and specificity for CSA binding, a characteristic feature of the full-length extracellular region. Accordingly, truncated recombinant var2CSA proteins comprising different domain combinations were expressed and their binding characteristics assessed against different sulfated glycosaminoglycans (GAGs). Our results indicate that the smallest region within var2CSA with similar binding properties to those of the full-length var2CSA is DBL1X-3X. We also demonstrate that inhibitory antibodies raised in rabbit against the full-length DBL1X-6ε target principally DBL3X and, to a lesser extent, DBL5ε. Taken together, our results indicate that efforts should focus on the DBL1X-3X region for developing vaccine and therapeutic strategies aimed at combating PAM.

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Section: Resultsmentioning

confidence: 71%

“…K D values were determined from the concentration dependence of steady-state SPR response using the Biacore BIAEVALUATION 3.1 software.*: from reference [34].#: from reference [41].…”

Section: Resultsmentioning

confidence: 99%

Var2CSA Minimal CSA Binding Region Is Located within the N-Terminal Region

et al. 2011

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“…A pregnancy malaria vaccine is expected to induce immune responses with qualities similar to those of naturally acquired immunity, including broad recognition and functional activity against diverse placental parasites. Previous studies reported that immunization with recombinant VAR2CSA domains can elicit antibodies that recognize the surface of homologous (33)(34)(35) and heterologous (22,27,28,36,37) IRBCs. Naturally acquired antiadhesion antibodies are associated with protection from PM (29), and therefore, an effective PM vaccine should elicit antibodies that can inhibit parasite adhesion.…”

Section: Discussionmentioning

confidence: 99%

“…VAR2CSA specifically appears on the surface of CSA-binding infected erythrocytes (IEs) (16)(17)(18)(19)(20), and levels of antibody to VAR2CSA domains increase over successive pregnancies (21)(22)(23)(24), as women become resistant to pregnancy malaria. These properties have positioned VAR2CSA as the leading candidate for a PM vaccine.…”

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confidence: 99%

Multilaboratory Approach to Preclinical Evaluation of Vaccine Immunogens for Placental Malaria

et al. 2013

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f Pregnancy malaria is caused by Plasmodium falciparum-infected erythrocytes that adhere to the placental receptor chondroitin sulfate A (CSA) and sequester in the placenta; women become resistant to pregnancy malaria as they acquire antiadhesion antibodies that target surface proteins of placental parasites. VAR2CSA, a member of the P. falciparum EMP1 variant surface antigen family, is the leading candidate for a pregnancy malaria vaccine. Because VAR2CSA is a high-molecular-weight protein, a vaccine based on the full-length protein may not be feasible. An alternative approach has been to develop a vaccine targeting individual Duffy binding-like (DBL) domains. In this study, a consortium of laboratories under the Pregnancy Malaria Initiative compared the functional activity of antiadhesion antibodies elicited by different VAR2CSA domains and variants produced in prokaryotic and eukaryotic expression systems. Antisera were initially tested against laboratory lines of maternal parasites, and the most promising reagents were evaluated in the field against fresh placental parasite samples. Recombinant proteins expressed in Escherichia coli elicited antibody levels similar to those expressed in eukaryotic systems, as did the two allelic forms of the DBL4 and DBL5 domains. The procedures developed for this head-to-head comparison will be useful for future evaluation and down-selection of malaria vaccine immunogens.

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“…Previous studies identified two amino acid motifs in DBL3X that were over-represented in parasites isolated from Senegalese and Kenyan primigravid women (PG) [34],[35], suggesting that parasites with these motifs may bind more efficiently to placenta in women with limited immunity. Polymorphisms in DBL5ε have also been associated with the CSA-binding intensity of placental isolates [36], but a direct role for this domain in CSA-VAR2CSA interaction is unclear [17],[22],[23],[37]. Here, we hypothesized that polymorphisms in VAR2CSA may affect parasite densities in the placenta by altering the antigenicity of domains involved in the adhesion to CSA and their ability to escape immune recognition by the host.…”

Section: Introductionmentioning

confidence: 99%

VAR2CSA Signatures of High Plasmodium falciparum Parasitemia in the Placenta

et al. 2013

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Plasmodium falciparum infected erythrocytes (IE) accumulate in the placenta through the interaction between Duffy-binding like (DBL) domains of parasite-encoded ligand VAR2CSA and chondroitin sulphate-A (CSA) receptor. Polymorphisms in these domains, including DBL2X and DBL3X, may affect their antigenicity or CSA-binding affinity, eventually increasing parasitemia and its adverse effects on pregnancy outcomes. A total of 373 DBL2X and 328 DBL3X sequences were obtained from transcripts of 20 placental isolates infecting Mozambican women, resulting in 176 DBL2X and 191 DBL3X unique sequences at the protein level. Sequence alignments were divided in segments containing combinations of correlated polymorphisms and the association of segment sequences with placental parasite density was tested using Bonferroni corrected regression models, taking into consideration the weight of each sequence in the infection. Three DBL2X and three DBL3X segments contained signatures of high parasite density (P<0.003) that were highly prevalent in the parasite population (49–91%). Identified regions included a flexible loop that contributes to DBL3X-CSA interaction and two DBL3X motifs with evidence of positive natural selection. Limited antibody responses against signatures of high parasite density among malaria-exposed pregnant women could not explain the increased placental parasitemia. These results suggest that a higher binding efficiency to CSA rather than reduced antigenicity might provide a biological advantage to parasites with high parasite density signatures in VAR2CSA. Sequences contributing to high parasitemia may be critical for the functional characterization of VAR2CSA and the development of tools against placental malaria.

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Functional and immunological characterization of the var2CSA-DBL5ɛ domain of a placental Plasmodium falciparum isolate

Cited by 9 publications

References 34 publications

Var2CSA Minimal CSA Binding Region Is Located within the N-Terminal Region

Var2CSA Minimal CSA Binding Region Is Located within the N-Terminal Region

Multilaboratory Approach to Preclinical Evaluation of Vaccine Immunogens for Placental Malaria

VAR2CSA Signatures of High Plasmodium falciparum Parasitemia in the Placenta

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