chondroitin-sulfates and Malaria

Topics: Animals; Cell Adhesion; Chondroitin Sulfates; Erythrocytes; Female; Humans; Malaria; Placenta; Plasmodium falciparum; Pregnancy; Pregnancy Complications, Parasitic

Topics: Animals; Antibodies, Protozoan; Antigenic Variation; Antigens, Protozoan; Chondroitin Sulfates; Erythrocytes; Female; Humans; Malaria; Placenta; Plasmodium falciparum; Plasmodium vivax; Pregnancy; Pregnancy Complications, Parasitic; Protozoan Proteins

Adherence of Plasmodium falciparum-infected erythrocytes (PRBCs) to the microvascular endothelium of specific organs and consequent sequestration is believed to be responsible for the development of malaria pathology. A number of studies have shown that cell adhesion molecules expressed on the surface of endothelial cells mediate the adherence. Recent studies indicate that a subpopulation of PRBCs adhere to chondroitin 4-sulfate (C4S). This adhesion can be effectively inhibited by C4S oligosaccharides. In pregnant women, the placenta specifically selects C4S-adherent PRBCs, and thus these phenotypes multiply and sequester in the intervillous spaces. Over successive pregnancies, women develop a protective humoral response to the C4S-adhesion phenotype. Disruption of C4S-mediated PRBCs adhesion using either a C4S oligosaccharide mimetic or an antiC4S-adhesion vaccine can be an efficient strategy for the treatment of malaria caused by C4S-adherent P. falciparum.

Topics: Animals; Antigens, Protozoan; Carbohydrate Sequence; Cell Adhesion; Chondroitin Sulfates; Erythrocytes; Female; Glycosaminoglycans; Humans; Malaria; Models, Chemical; Molecular Sequence Data; Plasmodium falciparum; Pregnancy; Time Factors

VAR2CSA, a multidomain Plasmodium falciparum protein, mediates the adherence of parasite-infected red blood cells to chondroitin 4-sulfate (C4S) in the placenta, contributing to placental malaria. Therefore, detailed understanding of VAR2CSA structure likely help developing strategies to treat placental malaria. The VAR2CSA ectodomain consists of an N-terminal segment (NTS), six Duffy binding-like (DBL) domains, and three interdomains (IDs) present in sequence NTS-DBL1x-ID1-DBL2x-ID2-DBL3x-DBL4ε-ID3-DBL5ε-DBL6ε. Recent electron microscopy studies showed that VAR2CSA is compactly organized into a globular structure containing C4S-binding channel, and that DBL5ε-DBL6ε arm is attached to the NTS-ID3 core structure. However, the structural elements involved in inter-domain interactions that stabilize the VAR2CSA structure remain largely not understood. Here, limited proteolysis and peptide mapping by mass spectrometry showed that VAR2CSA contains several inter-domain disulfide bonds that stabilize its compact structure. Chemical crosslinking-mass spectrometry showed that all IDs interact with DBL4ε; additionally, IDs interact with other DBL domains, demonstrating that IDs are the key structural scaffolds that shape the functional NTS-ID3 core. Ligand binding analysis suggested that NTS considerably restricts the C4S binding. Overall, our study revealed that inter-domain disulfide bonds and interactions between IDs and DBL domains contribute to the stability of VAR2CSA structural architecture and formation of C4S-binding channel.

Topics: Antigens, Protozoan; Chondroitin Sulfates; Disulfides; Erythrocytes; Female; Humans; Malaria; Malaria, Falciparum; Placenta; Plasmodium falciparum; Pregnancy; Protein Structure, Tertiary

Baculovirus vectors (BVs) are able to use for gene transduction in mammalian cells and are recognized as growing viral vectors for cancer gene therapy applications. The transduction efficiency of BVs varies among cancer cell types. To improve the transduction efficiency of BVs in human cancer cells, BV displaying malarial variant surface antigen 2-chondroitin sulfate A (var2CSA) molecules was developed in this study. Var2CSA plays a critical role in the sequestration of Plasmodium falciparum-infected erythrocytes in the placenta. Moreover, var2CSA binds to cancer cells via placenta-like chondroitin sulfate A (CSA), but not to non-cancer cells. Var2CSA BV showed significantly higher gene transduction than control BV in HepG2 and Huh7 cells, human hepatic cancer cells as well as AsPC-1 cells, human pancreatic cancer cells. The transduction efficiency of var2CSA BV was significantly inhibited by the anti-gp64 antibody, free heparin, and CSA. The results of this study suggest that var2CSA BV would be an improved vector for cancer gene therapies, especially in the treatment of hepatic and pancreatic cancers.

Topics: Animals; Antigens, Surface; Baculoviridae; Cell Line, Tumor; Chondroitin Sulfates; Female; Genetic Vectors; Humans; Liver Neoplasms; Malaria; Pancreatic Neoplasms; Pregnancy; Transduction, Genetic

VAR2CSA is the Plasmodium falciparum variant surface antigen that mediates binding of infected erythrocytes to chondroitin sulfate A (CSA) and their sequestration in intervillous spaces of the placenta, leading to placental malaria (PM). Relatively high polymorphism in VAR2CSA sequences has hindered development of a vaccine that induces broadly neutralizing immunity. Recent research has highlighted that a broadly reactive human monoclonal antibody, called PAM1.4, binds to multiple conserved residues of different subfragments of VAR2CSA, forming a conformational epitope. In this short perspective, we describe evidence that residues located in the interdomain-1 fragment of VAR2CSA within the PAM1.4 binding epitope might be critical to broad reactivity of the antibody. Future investigation into broadly reactive anti-VAR2CSA antibodies may be important for the following: (1) identification of similar conformation epitopes targeted by broadly neutralizing antibodies; and (2) understanding different immune evasion mechanisms used by placenta-binding parasites through VAR2CSA polymorphism in critical epitopes.

Topics: Antibodies, Protozoan; Antigens, Protozoan; Chondroitin Sulfates; Epitopes; Erythrocytes; Female; Humans; Malaria; Malaria Vaccines; Malaria, Falciparum; Placenta; Plasmodium falciparum; Pregnancy

Malaria infected erythrocytes utilize the parasite protein VAR2CSA to bind to a unique presentation of chondroitin sulfate (CS) for their placenta specific tropism. Interestingly, many cancers express a similar form of CS, thereby termed oncofetal CS (ofCS). The distinctive tropism of malaria infected erythrocytes and the identification of oncofetal CS, therefore, represent potentially potent tools for cancer targeting. Here we describe an intriguing drug delivery platform that effectively mimics infected erythrocytes and their specificity for ofCS. We used a lipid catcher-tag conjugation system for the functionalization of erythrocyte membrane-coated drug carriers with recombinant VAR2CSA (rVAR2). We show that these malaria mimicking erythrocyte nanoparticles (MMENPs) loaded with docetaxel (DTX) specifically target and kill melanoma cells

Topics: Antigens, Protozoan; Biomimetics; Chondroitin Sulfates; Erythrocytes; Humans; Malaria; Malaria, Falciparum; Melanoma; Plasmodium falciparum

Plasmodium falciparum-infected red blood cells (iRBCs) bind and sequester in deep vascular beds, causing malaria-related disease and death. In pregnant women, VAR2CSA binds to chondroitin sulfate A (CSA) and mediates placental sequestration, making it the major placental malaria (PM) vaccine target.. In this study, we characterize an invariant protein associated with PM called P falciparum chondroitin sulfate A ligand (PfCSA-L).. Recombinant PfCSA-L binds both placental CSA and VAR2CSA with nanomolar affinity, and it is coexpressed on the iRBC surface with VAR2CSA. Unlike VAR2CSA, which is anchored by a transmembrane domain, PfCSA-L is peripherally associated with the outer surface of knobs through high-affinity protein-protein interactions with VAR2CSA. This suggests that iRBC sequestration involves complexes of invariant and variant surface proteins, allowing parasites to maintain both diversity and function at the iRBC surface.. The PfCSA-L is a promising target for intervention because it is well conserved, exposed on infected cells, and expressed and localized with VAR2CSA.

Topics: Antibodies, Protozoan; Antigens, Protozoan; Chondroitin Sulfates; Erythrocytes; Female; Humans; Malaria; Malaria Vaccines; Malaria, Falciparum; Placenta; Plasmodium falciparum; Pregnancy

Contracting malaria during pregnancy – especially a first pregnancy – can lead to a severe, placental form of the disease that is often fatal. Red blood cells infected with the malaria parasite

Topics: Antibodies, Protozoan; Antigens, Protozoan; Antigens, Surface; Broadly Neutralizing Antibodies; Chondroitin Sulfates; Epitopes; Erythrocytes; Female; Humans; Immunoglobulin G; Malaria; Malaria Vaccines; Malaria, Falciparum; Placenta; Plasmodium falciparum; Pregnancy

Plasmodium falciparum-infected erythrocytes that display the variant surface antigen VAR2CSA bind chondroitin sulfate A (CSA) to sequester in placental intervillous spaces, causing severe sequelae for mother and offspring. Here, we establish a placental malaria (PM) monkey model. Pregnant Aotus infected with CSA-binding P. falciparum CS2 parasites during the third trimester developed pronounced sequestration of late-stage parasites in placental intervillous spaces that express VAR2CSA and bind specifically to CSA. Similar to immune multigravid women, a monkey infected with P. falciparum CS2 parasites over successive pregnancies acquired antibodies against VAR2CSA, with potent functional activity that was boosted upon subsequent pregnancy infections. Aotus also developed functional antibodies after multiple acute PM episodes and subsequent VAR2CSA immunization. In summary, P. falciparum infections in pregnant Aotus monkeys recapitulate all the prominent features of human PM infection and immunity, and this model can be useful for basic mechanistic studies and preclinical studies to qualify candidate PM vaccines. Clinical Trials Registration: NCT02471378.

Topics: Animals; Antibodies, Protozoan; Antigens, Protozoan; Aotidae; Chondroitin Sulfates; Erythrocytes; Female; Humans; Malaria; Malaria, Falciparum; Placenta; Plasmodium falciparum; Pregnancy; Pregnancy Complications, Parasitic

The human placenta is a critical organ, mediating the exchange of nutrients, oxygen, and waste products between fetus and mother. Placental malaria (PM) resulted from Plasmodium falciparum infections causes up to 200 thousand newborn deaths annually, mainly due to low birth weight, as well as 10 thousand mother deaths. In this work, a placenta-on-a-chip model is developed to mimic the nutrient exchange between the fetus and mother under the influence of PM. In this model, trophoblasts cells (facing infected or uninfected blood simulating maternal blood and termed "trophoblast side") and human umbilical vein endothelial cells (facing uninfected blood simulating fetal blood and termed "endothelial" side) are cultured on the opposite sides of an extracellular matrix gel in a compartmental microfluidic system, forming a physiological barrier between the co-flow tubular structure to mimic a simplified maternal-fetal interface in placental villi. The influences of infected erythrocytes (IEs) sequestration through cytoadhesion to chondroitin sulfate A (CSA) expressed on the surface of trophoblast cells, a critical feature of PM, on glucose transfer efficiency across the placental barrier was studied. To create glucose gradients across the barrier, uninfected erythrocyte or IE suspension with a higher glucose concentration was introduced into the "trophoblast side" and a culture medium with lower glucose concentration was introduced into the "endothelial side". The glucose levels in the endothelial channel in response to CSA-adherent erythrocytes infected with CS2 line of parasites in trophoblast channel under flow conditions was monitored. Uninfected erythrocytes served as a negative control. The results demonstrated that CSA-binding IEs added resistance to the simulated placental barrier for glucose perfusion and decreased the glucose transfer across this barrier. The results of this study can be used for better understanding of PM pathology and development of models useful in studying potential treatment of PM.

Topics: Chondroitin Sulfates; Female; Glucose; Human Umbilical Vein Endothelial Cells; Humans; Infant, Newborn; Malaria; Microfluidics; Placenta; Pregnancy

Malaria during pregnancy is a major global health problem caused by infection with Plasmodium falciparum parasites. Severe effects arise from the accumulation of infected erythrocytes in the placenta. Here, erythrocytes infected by late blood-stage parasites adhere to placental chondroitin sulphate A (CS) via VAR2CSA-type P. falciparum erythrocyte membrane protein 1 (PfEMP1) adhesion proteins. Immunity to placental malaria is acquired through exposure and mediated through antibodies to VAR2CSA. Through evolution, the VAR2CSA proteins have diversified in sequence to escape immune recognition but retained their overall macromolecular structure to maintain CS binding affinity. This structural conservation may also have allowed development of broadly reactive antibodies to VAR2CSA in immune women. Here we show the negative stain and cryo-EM structure of the only known broadly reactive human monoclonal antibody, PAM1.4, in complex with VAR2CSA. The data shows how PAM1.4's broad VAR2CSA reactivity is achieved through interactions with multiple conserved residues of different sub-domains forming conformational epitope distant from the CS binding site on the VAR2CSA core structure. Thus, while PAM1.4 may represent a class of antibodies mediating placental malaria immunity by inducing phagocytosis or NK cell-mediated cytotoxicity, it is likely that broadly CS binding-inhibitory antibodies target other epitopes at the CS binding site. Insights on both types of broadly reactive monoclonal antibodies may aid the development of a vaccine against placental malaria.

Topics: Antibodies, Monoclonal; Antibodies, Protozoan; Antigens, Protozoan; Chondroitin Sulfates; Cryoelectron Microscopy; Epitopes; Erythrocytes; Female; Humans; Malaria; Malaria, Falciparum; Placenta; Plasmodium falciparum; Pregnancy

In this work the DBL3x domain of the erythrocyte membrane protein from

Topics: Animals; Antigens, Protozoan; Chondroitin Sulfates; Erythrocytes; Female; Glycosaminoglycans; Humans; Malaria; Malaria, Falciparum; Membrane Proteins; Molecular Docking Simulation; Molecular Dynamics Simulation; Phosphates; Placenta; Plasmodium falciparum; Pregnancy; Pregnancy Complications, Parasitic; Protozoan Proteins; Sulfates

As an immune evasion and survival strategy, the Plasmodium falciparum malaria parasite has evolved a protein named VAR2CSA. This protein mediates sequestration of infected red blood cells in the placenta through the interaction with a unique carbohydrate abundantly and exclusively present in the placenta. Cancer cells were found to share the same expression of this distinct carbohydrate, termed oncofetal chondroitin sulfate on their surface. In this study we have used a protein conjugation system to produce a bispecific immune engager, V-aCD3, based on recombinant VAR2CSA as the cancer targeting moiety and an anti-CD3 single-chain variable fragment linked to a single-chain Fc as the immune engager. Conjugation of these two proteins resulted in a single functional moiety that induced immune mediated killing of a broad range of cancer cells in vitro and facilitated tumor arrest in an orthotopic bladder cancer xenograft model.

Topics: Chondroitin Sulfates; Erythrocytes; Female; Humans; Malaria; Malaria, Falciparum; Placenta; Plasmodium falciparum; Pregnancy; Protozoan Proteins; Recombinant Proteins

The adaptation of existing antimalarial nanocarriers to new Plasmodium stages, drugs, targeting molecules, or encapsulating structures is a strategy that can provide new nanotechnology-based, cost-efficient therapies against malaria. We have explored the modification of different liposome prototypes that had been developed in our group for the targeted delivery of antimalarial drugs to Plasmodium-infected red blood cells (pRBCs). These new models include: (i) immunoliposome-mediated release of new lipid-based antimalarials; (ii) liposomes targeted to pRBCs with covalently linked heparin to reduce anticoagulation risks; (iii) adaptation of heparin to pRBC targeting of chitosan nanoparticles; (iv) use of heparin for the targeting of Plasmodium stages in the mosquito vector; and (v) use of the non-anticoagulant glycosaminoglycan chondroitin 4-sulfate as a heparin surrogate for pRBC targeting. The results presented indicate that the tuning of existing nanovessels to new malaria-related targets is a valid low-cost alternative to the de novo development of targeted nanosystems.

Topics: Animals; Antimalarials; Chondroitin Sulfates; Drug Delivery Systems; Humans; Liposomes; Malaria; Mice; Nanoparticles

Plasmodium falciparum infection during pregnancy leads to abortions, stillbirth, low birth weight, and maternal mortality. Infected erythrocytes (IEs) accumulate in the placenta by adhering to chondroitin sulfate A (CSA) via var2CSA protein exposed on the P. falciparum IE membrane. Plasmodium berghei IE infection in pregnant BALB/c mice is a model for severe placental malaria (PM). Here, we describe a transgenic P. berghei parasite expressing the full-length var2CSA extracellular region (domains DBL1X to DBL6ε) fused to a P. berghei exported protein (EMAP1) and characterize a var2CSA-based mouse model of PM. BALB/c mice were infected at midgestation with different doses of P. berghei-var2CSA (P. berghei-VAR) or P. berghei wild-type IEs. Infection with 10(4) P. berghei-VAR IEs induced a higher incidence of stillbirth and lower fetal weight than P. berghei At doses of 10(5) and 10(6) IEs, P. berghei-VAR-infected mice showed increased maternal mortality during pregnancy and fetal loss, respectively. Parasite loads in infected placentas were similar between parasite lines despite differences in maternal outcomes. Fetal weight loss normalized for parasitemia was higher in P. berghei-VAR-infected mice than in P. berghei-infected mice. In vitro assays showed that higher numbers of P. berghei-VAR IEs than P. berghei IEs adhered to placental tissue. Immunization of mice with P. berghei-VAR elicited IgG antibodies reactive to DBL1-6 recombinant protein, indicating that the topology of immunogenic epitopes is maintained between DBL1-6-EMAP1 on P. berghei-VAR and recombinant DBL1-6 (recDBL1-6). Our data suggested that impairments in pregnancy caused by P. berghei-VAR infection were attributable to var2CSA expression. This model provides a tool for preclinical evaluation of protection against PM induced by approaches that target var2CSA.

Topics: Animals; Antibodies, Protozoan; Antigens, Protozoan; Chondroitin Sulfates; Disease Models, Animal; Epitopes; Erythrocytes; Female; Fetal Weight; Immunization; Immunoglobulin G; Malaria; Malaria, Falciparum; Mice; Mice, Inbred BALB C; Parasite Load; Parasitemia; Placenta; Plasmodium berghei; Plasmodium falciparum; Pregnancy; Pregnancy Complications, Parasitic; Protein Domains; Recombinant Fusion Proteins; Stillbirth

Placental malaria (PM) is characterized by infected erythrocytes (IEs) that selectively bind to chondroitin sulfate A (CSA) and sequester in placental tissue. Variant surface antigen 2-CSA (VAR2CSA), a Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) protein family member, is expressed on the surface of placental IEs and mediates adherence to CSA on the surface of syncytiotrophoblasts. This transmembrane protein contains 6 Duffy binding-like (DBL) domains which might contribute to the specific adhesive properties of IEs. Here, we use laboratory isolate 3D7 VAR2CSA DBL domains expressed in Escherichia coli to generate antibodies specific for this protein. Flow cytometry results showed that antibodies generated against DBL4ε, DBL5ε, DBL6ε, and tandem double domains of DBL4-DBL5 and DBL5-DBL6 all bind to placental parasite isolates and to lab strains selected for CSA binding but do not bind to children's parasites. Antisera to DBL4ε and to DBL5ε inhibit maternal IE binding to placental tissue in a manner comparable to that for plasma collected from multigravid women. These antibodies also inhibit binding to CSA of several field isolates derived from pregnant women, while antibodies to double domains do not enhance the functional immune response. These data support DBL4ε and DBL5ε as vaccine candidates for pregnancy malaria and demonstrate that E. coli is a feasible tool for the large-scale manufacture of a vaccine based on these VAR2CSA domains.

Topics: Adult; Animals; Antibodies, Protozoan; Antigens, Protozoan; Cell Adhesion; Chondroitin Sulfates; Escherichia coli; Female; Gene Expression; Humans; Infant, Newborn; Malaria; Malaria Vaccines; Placenta; Plasmodium falciparum; Pregnancy; Protein Structure, Tertiary; Rats; Recombinant Fusion Proteins; Vaccines, Synthetic

Pregnancy-associated malaria (PAM) is a serious consequence of the adhesion to the placental receptor chondroitin sulfate A (CSA) of Plasmodium falciparum-infected erythrocytes (PE) expressing the large cysteine-rich multi-domain protein var2CSA. Women become resistant to PAM, and develop strain-transcending immunity against CSA-binding parasites. The identification of var2CSA regions that could elicit broadly neutralizing and adhesion-blocking antibodies is a key step for the design of prophylactic vaccine strategies.. Escherichia coli expressed var2CSA DBL domains were refolded and purified prior to immunization of mice and a goat. Protein-G-purified antibodies were tested for their ability to block FCR3(CSA)-infected erythrocytes binding to placental (BeWo) and monkey brain endothelial (ScC2) cell lines using a flow cytoadhesion inhibition assay mimicking closely the physiological conditions present in the placenta at shear stress of 0.05 Pa. DBL5-ε, DBL6-ε and DBL5-6-ε induced cross-reactive antibodies using Alum and Freund as adjuvants, which blocked cytoadhesion at values ranging between 40 to 96% at 0.5 mg IgG per ml. Importantly, antibodies raised against recombinant DBL5-ε from 3 distinct parasites genotypes (HB3, Dd2 and 7G8) showed strain-transcending inhibition ranging from 38 to 64% for the heterologuous FCR3(CSA).. Using single and double DBL domains from var2CSA and Alum as adjuvant, we identified recombinant subunits inducing an immune response in experimental animals which is able to block efficiently parasite adhesion in a flow cytoadhesion assay that mimics closely the erythrocyte flow in the placenta. These subunits show promising features for inclusion into a vaccine aiming to protect against PAM.

Topics: Animals; Antibodies, Protozoan; Antigens, Protozoan; Cell Adhesion; Cell Line; Chondroitin Sulfates; Disease Models, Animal; Female; Flow Cytometry; Humans; Malaria; Mice; Mice, Inbred BALB C; Placenta; Plasmodium falciparum; Pregnancy; Pregnancy Complications, Parasitic; Protein Structure, Tertiary; Recombinant Proteins; Saimiri; Species Specificity

Surface proteins from Plasmodium falciparum are important malaria vaccine targets. However, the surface proteins previously identified are highly variant and difficult to study. We used tandem mass spectrometry to characterize the variant antigens (Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1)) expressed on the surface of malaria-infected erythrocytes that bind to chondroitin sulfate A (CSA) in the placenta. Whereas PfEMP1 variants previously implicated as CSA ligands were detected, in unselected parasites four novel variants were detected in CSA-binding or placental parasites but not in unselected parasites. These novel PfEMP1 variants require further study to confirm whether they play a role in placental malaria.

Topics: Animals; Chondroitin Sulfates; Electrophoresis, Polyacrylamide Gel; Erythrocyte Membrane; Erythrocytes; Female; Malaria; Malaria Vaccines; Placenta; Plasmodium falciparum; Pregnancy; Pregnancy Complications, Parasitic; Protozoan Proteins; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization

The Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) family is a highly polymorphic class of variant surface antigens encoded by var genes that play an important role in malaria pathogenesis. This report describes the unexpected finding that 1 of the var genes encoding a PfEMP1 variant that binds to the host receptor chondroitin sulfate A (CSA) and is implicated in malaria in pregnancy is well conserved among P. falciparum isolates worldwide. The N-terminal domains of this PfEMP1 variant are especially highly conserved, whereas the functional CSA binding domain is more variable. Analysis of var gene expression in placental parasites from primigravid women in Malawi did not support a role for this conserved gene in placental infection but identified a second commonly occurring var gene. These results indicate the need for reevaluation of previous assumptions of a minimal overlap between var gene repertoires from different parasite isolates.

Topics: Animals; Base Sequence; Binding Sites; Chondroitin Sulfates; DNA, Protozoan; Female; Humans; Malaria; Molecular Sequence Data; Placenta; Plasmodium falciparum; Polymerase Chain Reaction; Pregnancy; Pregnancy Complications, Parasitic; Protozoan Proteins

Adherence of parasite-infected erythrocytes (IEs) to the microvascular endothelium of various organs, a process known as sequestration, is a feature of Plasmodium falciparum malaria. This event is mediated by specific adhesive interactions between parasite proteins, expressed on the surface of IEs, and host molecules. P. falciparum IEs can bind to purified chondroitin sulfate A (CS-A), to the proteoglycan thrombomodulin through CS-A side chains, and to CS-A present on the surface of brain and lung endothelial cells and placental syncytiotrophoblasts. In order to identify structural characteristics of CS-A important for binding, oligosaccharide fragments ranging in size from 2 to 20 monosaccharide units were isolated from CS-A and CS-C, following controlled chondroitin lyase digestion, and used as competitive inhibitors of IE binding to immobilized ligands. Inhibition of binding to CS-A was highly dependent on molecular size: a CS-A tetradecasaccharide fraction was the minimum length able to almost completely inhibit binding. The effect was dose dependent and similar to that of the parent polysaccharide, and the same degree of inhibition was not found with the CS-C oligosaccharides. There was no effect on binding of IEs to other ligands, e.g., CD36 and intercellular adhesion molecule 1. Hexadeca- and octadecasaccharide fractions of CS-A were required for maximum inhibition of binding to thrombomodulin. Analyses of oligosaccharide fractions and polysaccharides by electrospray mass spectrometry and high-performance liquid chromatography suggest that the differences between the activities of CS-A and CS-C oligosaccharides can be attributed to differences in sulfate content and sulfation pattern and that iduronic acid is not involved in IE binding.

Topics: CD36 Antigens; Chondroitin Sulfates; Erythrocytes; Humans; Intercellular Adhesion Molecule-1; Malaria; Oligosaccharides; Thrombomodulin

Topics: Animals; Chondroitin Sulfates; Erythrocytes; Female; Gravidity; Humans; Malaria; Malaria, Falciparum; Placenta; Plasmodium falciparum; Pregnancy; Pregnancy Complications, Parasitic

Topics: Animals; CD36 Antigens; Chondroitin Sulfates; Erythrocytes; Female; Genes, Protozoan; Humans; Malaria; Malaria, Falciparum; Placenta; Plasmodium; Plasmodium falciparum; Pregnancy; Pregnancy Complications, Parasitic

Adhesion of parasitized red blood cells (PRBCs) to microvascular endothelial cells (ECs) is a distinctive feature of Plasmodium falciparum malaria and is a central event in the development of life-threatening complications such as cerebral malaria. PRBCs adhere to several EC-expressed molecules in vitro, but the relative importance of these interactions in vivo remains unclear. Chondroitin sulfate A (CSA) is the most recent EC surface-associated molecule to be implicated in the adhesive process. Accordingly, we have studied adhesion of PRBCs to CSA in vitro using a parallel-plate flow chamber. Under controlled flow conditions, PRBCs adhered to CSA in a concentration-dependent manner at wall-shear stresses up to 0.2 Pa, a value that is within the physiological range for venules. Once adhered, PRBCs remained stationary (rather than rolling) and continued to remain stationary even when the wall-shear stress was raised to supravenular levels. The adhesive interaction was strong and a proportion of adherent PRBCs could withstand detachment at stresses up to 2.5 Pa. Soluble CSA at pharmacological concentrations prevented adhesion of flowing PRBCs in a concentration-dependent manner but failed to reverse established adhesion. Adhesion of PRBCs to CSA could contribute to the pathogenesis of malaria, and soluble CSA may have a useful therapeutic effect.

Topics: Cell Adhesion; Chondroitin Sulfates; Dose-Response Relationship, Drug; Erythrocytes; Hemorheology; Humans; Malaria; Stress, Mechanical