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Prepublished online as a Blood First Edition Paper on August 15, 2002; DOI 10.1182/blood-2002-06-1725.
RED CELLS
From the Immunology Research Group, University of
Calgary, Calgary, AB, Canada; Laboratory for Parasitic
Diseases and Malaria Vaccine Development Unit, National Institute of
Allergy and Infectious Diseases, National Institutes of Health,
Bethesda, MD; Department of Medicine, University of Alberta, Edmonton,
AB, Canada; and Faculty of Tropical Medicine, Mahidol
University, Bangkok, Thailand.
The parasite ligand Plasmodium falciparum erythrocyte
membrane protein 1 (PfEMP1) and host endothelial receptors represent potential targets for antiadhesive therapy for cytoadherence. In the
present study, the major host receptor CD36 was targeted in vitro and
in vivo with a recombinant peptide, PpMC-179, corresponding to the
minimal CD36-binding domain from the cysteine-rich interdomain region 1 (CIDR1) within the MCvar1 PfEMP1. The in vitro inhibitory effect of PpMC-179 on human dermal microvascular endothelial
cells (HDMECs) expressing multiple relevant adhesion molecules
was investigated using a parallel-plate flow chamber. Pretreatment of
endothelial monolayers with PpMC-179 (2 µM) inhibited the adhesion of
infected erythrocytes (IRBCs) from all clinical isolates tested by
84.4% on resting and 62.8% on tumor necrosis factor Plasmodium falciparum malaria is an
acute febrile illness characterized by fever, chills, headache, anemia,
and splenomegaly. In some patients, particularly in nonimmune
individuals, the infection can become severe and complicated by
multiorgan dysfunction.1 Death most commonly results from
cerebral malaria, severe anemia, metabolic acidosis, or pulmonary
edema. Although the underlying mechanisms leading to severe falciparum
malaria and death are still not completely understood, there is little
doubt that much of the pathogenicity of P falciparum depends
on its unique ability to adhere to host vascular endothelium and
syncytiotrophoblasts in the placenta, a characteristic not shared with
the other 3 species of human malaria parasites.2 Although
antimalarial drug therapy can be very effective, its use has been
hampered by the emergence of multiple drug resistance and the length of time required until drug therapy becomes effective. This is
particularly true in comatose patients in whom an immediate effect may
be lifesaving. One possible therapy that might stop the chain of
pathophysiologic events is the reversal of parasite sequestration.
Cytoadherence on vascular endothelium is mediated by a number of
adhesion molecules in a synergistic fashion under flow conditions in
vitro and in vivo, mimicking the adhesive events in the leukocyte recruitment cascade.3-6 Infected red blood cells (IRBCs)
can tether and roll on several host receptors including intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and P-selectin. These low-affinity interactions do not by
themselves lead to the arrest of the interacting cells but enhance the
subsequent adhesion of nearly all clinical isolates tested to CD36.
ICAM-1 and VCAM-1 mediate their effect by increasing the percentage of
rolling cells that become adherent, whereas P-selectin increases the
total number of rolling and adherent IRBCs.6 Peptide
mapping studies on CD36 reveal that residues 145 to 171 are important
for IRBC adhesion.7 Furthermore, adhesion by diverse
P falciparum clones and isolates to CD36 can be inhibited by
monoclonal antibody (mAb) OKM5 that is thought to bind to residues 155 to 183.8
P falciparum erythrocyte membrane protein 1 (PfEMP1) is the
parasite protein directly involved in adhesive interactions with microvascular endothelium.9 PfEMP1 is a highly variable
protein encoded by the large var gene
family.10,11 A single IRBC only expresses one var
gene product during the mature stages of the parasite, whereas the
remaining genes in this family are inactivated by an as yet unknown
silencing mechanism.12 However, a single parasite clone
can bind to more than one receptor molecule through its distinct
binding modules: the Duffy binding-like domains (DBLs) and the
cysteine-rich interdomain regions (CIDRs).12-14 A critical region of PfEMP1 involved in binding to CD36 is localized to a 179-amino acid sequence within the CIDR1 region.15 The
recombinant 179-amino acid peptide (r179) from the Malayan Camp (MC)
var1 gene has been shown to bind to CD36 and inhibit and
reverse the adhesion of several CD36-binding laboratory-adapted
parasite strains in static and flow chamber-based assays in
vitro.16
Unlike the broad-range effect of the r179 on parasite adhesion,
antibodies against r179 appear to be primarily strain specific and
inhibit the binding of parasites expressing the homologous region.10,15,17 Immunization of Aotus monkeys with this
region also generated a strain-specific immune response that protected from challenge with the homologous strain but not from the heterologous virulent FVO strain.18 Collectively, the results suggest
that targeting CD36 with r179 may be more effective for inhibiting the
adhesion of diverse parasite isolates than antibodies against this
region of PfEMP1.
In this study, we tested the antiadhesive effects of the recombinant
peptide r179 expressed in yeasts (PpMC-179) on clinical parasite
isolates. Experiments were conducted in a parallel-plate flow chamber
in vitro using microvascular endothelium,5 and in a
human/severe combined immunodeficiency (SCID) mouse chimeric model in
vivo.6 This human/SCID mouse model allowed us to directly visualize IRBC-endothelial cell interactions in an intact human microvasculature in a skin graft and to verify the ability of PpMC-179
to inhibit and reverse IRBC adhesion in vivo. The results indicate that
the adhesion of clinical parasite isolates to microvascular endothelium
was inhibited and reversed by PpMC-179 both in vitro and in vivo.
The finding strongly suggests that PpMC-179 may be a suitable
therapeutic agent for antiadhesive therapy.
Tissue culture reagents
Parasites
Production in Pichia pastoris and purification of PpMC-179 from P falciparum The recombinant PpMC-179 protein was expressed in P pastoris. In brief, a synthetic gene of the MC-179 (optimized for codon usage in P pastoris and containing a His6-tag on the C-terminus) was cloned into pPIC9K vector containing the -factor secretion signal that directs the recombinant
protein into the secretory pathway. The protein was expressed in shaker
flasks and harvested at 48 hours after induction. The protein was
purified using nickel-nitriltriacetic acid-agarose (Ni-NTA) followed by
size exclusion chromatography on a Superdex 75 column (Amersham
Pharmacia Biotech, Piscataway, NJ) and reversed phase high-performance
liquid chromatography (HPLC) using a C4 column (Grace Vydac,
Hesperia, CA).
Protein characterization Proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) on 4% to 20% gradient gels (Invitrogen, San Diego, CA) as per the manufacturer's instructions. Gels were either stained with Coomassie brilliant blue or prepared for electrophoretic transfer to polyvinylidene difluoride (PVDF) membranes. Amino acid sequencing of samples bound to PVDF by automated Edman degradation and electron spray mass spectroscopy analysis of liquid samples were performed at the Biological Resources Branch, National Institute of Allergy and Infectious Diseases. Protein concentrations were determined using the bicinchoninic acid protein assay (Pierce, Rockford, IL).CD36-binding assay PpMC-179 was assayed for binding to CD36 using a protocol similar to that previously described.15 Briefly, various amounts of PpMC-179 (5-0.05 µg) were bound to 50 µL Ni-NTA beads (Qiagen, Mississauga, ON, Canada) in phosphate-buffered saline (PBS). Soluble recombinant CD3610 was added to the beads and incubated with shaking at 25°C for 2 hours. Beads were washed extensively with PBS and proteins bound were eluted by boiling in SDS-PAGE sample buffer. Proteins were separated on gels and transferred to PVDF as above; Western blots were performed by standard methods. CD36 bound on the membrane was detected by incubating blots with a monoclonal antibody termed MoAb-17915 followed by incubation with horseradish peroxidase (HRP)-conjugated goat antimouse IgG (Kirkegaard and Perry Laboratories, Gaithersburg, MD). Blots were developed using the enhanced chemiluminescence (ECL) detection system (Qiagen) according to the manufacturer's instructions.Adhesion inhibition assay The blockade of IRBC adhesion to CD36 protein by PpMC-179 was tested using the CD36-binding parasite line FMG as described.15 Briefly, recombinant CD36 was captured on a Falcon 1001 Petri dish by the MoAb-179. Blocking solutions containing 1% bovine serum albumin (BSA) alone in RPMI 1640, pH 6.8, or BSA plus PpMC-179 (50 µg/mL), or BSA plus yPyCSP (50 µg/mL) were added to the immobilized protein for 1 hour at room temperature. After washing, IRBCs from FMG strain were added at 3% parasitemia and 2% hematocrit in blocking solution. Binding was allowed to proceed for 1 hour at room temperature. Nonadherent IRBCs were washed off, and the adherent IRBCs were fixed in 2% glutaraldehyde and stained with Giemsa. Three high-power fields (× 40) in duplicate spots were counted.Antibody and cytokine The anti-ICAM-1 mAb 84H10, known to inhibit IRBC interactions with ICAM-1, was purchased from R & D Systems (Minneapolis, MN). Recombinant tumor necrosis factor (TNF-) was purchased from BD
Biosciences (Bedford, MA). The concentration of cytokine used for the
stimulation of human dermal microvascular endothelial cells (HDMECs) in
35-mm tissue culture dishes (Corning, NY) was TNF- 10 ng/mL for 24 hours. For in vivo experiments, 100 ng TNF- in 50 µL sterile PBS
was injected intradermally at the edge of the human skin graft 4 hours
prior to the start of the experiments.
Endothelial cell culture HDMECs were harvested from discarded neonatal human foreskins using 0.5 mg/mL type IA collagenase (Boerhringer Mannheim Biochemicals, Indianapolis, IN) as described previously.5 The protocol was approved by the Conjoint Health Research Ethics Board of the University of Calgary. The cells were maintained in endothelial basal medium (EBM) (Biowhittaker, Walkerville, MD) with supplements provided by the manufacturer. Experiments were performed with cells from passages 1 to 5 on which adhesion molecule expression was shown to be stable.5 We and others have shown previously that HDMECs express CD36 and ICAM-1 constitutively.5,21,22 Stimulation with TNF- for 4 hours up-regulates ICAM-1 expression,
and at 24 hours, ICAM-1 expression is further augmented, whereas VCAM-1 expression is induced.5,22 In inhibition studies, HDMEC
monolayers were preincubated with 2 µM PpMC-179 with or without 5 µg/mL anti-ICAM-1 mAb for 30 minutes at 37°C before being used in
flow chamber experiments.
Adhesive interactions under flow conditions in vitro IRBC-endothelial cell interactions at fluid shear stresses approximating those in the microvasculature were studied using a parallel plate flow chamber as described.5 In previous studies, we have established that infusion of a 1% IRBC suspension over endothelial cell monolayers at 1 dyne/cm2 allowed us to optimally visualize the adhesive interactions in real time. A rolling IRBC was defined as one that displayed a typical end-on-end rolling motion at a velocity of less than 150 µm/s, compared to a centerline red blood cell flow rate of more than 1000 µm/s and a velocity of more than 150 µm/s for noninteracting cells in close proximity to the endothelial monolayer. The flux of rolling IRBCs was determined as the number that rolled past a fixed line on the monitor screen for the duration of the experiment and expressed as the number of rolling IRBC/min/mm2. An IRBC was considered adherent if it remained stationary for more than 10 seconds, and the results were expressed as the number of adherent IRBCs per square millimeter of surface area.Preparation of human skin graft in SCID mice CB-17 SCID/beige mice (Harlan Teklad, Madison, WI) were grafted with split-thickness human skin as described previously23 under a protocol approved by the Animal Care Committee and the Conjoin Health Research Ethics Board of the University of Calgary. Briefly, split-thickness grafts were prepared using a 1-mm dermatome from discarded human skin from donors undergoing plastic surgery. Recipient mice were anesthetized using halothane. A 0.5 × 0.5-cm defect was excised from the posterior thorax and covered with human skin anchored using skin staples (US Surgical, Norwalk, CT). The graft was allowed to heal for 3 weeks before the animal was used for intravital microscopy experiments. The microvessels in the human skin graft express human platelet-endothelial cell adhesion molecule 1 (PECAM-1), CD36, ICAM-1, and E-selectin by immunohistochemical staining.6,21Intravital microscopy Animals were prepared for intravital microscopy as previously described.6 The procedure was approved by the Animal Care Committee, University of Calgary. Briefly, the jugular vein of anesthetized animals was cannulated for administration of additional anesthetic, boluses of IRBCs, and recombinant peptide. A midline dorsal incision was made from the neck to the lower back, without disrupting the lateral dermal blood supply. The skin was reflected onto a pedestal and examined using an upright microscope (Nikon Optiphot) with a × 20 water-immersion objective (Nikon). To identify human vessels, 100 µg fluorescein isothiocyanate (FITC)-Ulex europaeus (Sigma Aldrich, St Louis, MO) was injected intravenously immediately before microscopic visualization. FITC-derived fluorescence was visualized by epi-illumination at 450 to 490 nm, using a 520-nm emission filter. IRBCs, but not noninfected red cells, were labeled with the nuclear dye rhodamine 6G (25 µg/mL) and visualized by excitation at 510 to 560 nm, using a 590-nm emission filter. Each 200-µL bolus of IRBCs contained IRBCs at approximately 50% hematocrit and 5% to 7% parasitemia. Images of the labeled IRBCs and human microvessels were visualized using a silicon-intensified CCD camera (C-2400-08; Hamamatsu Photonics, Hamamatsu City, Japan) and recorded with a VCR for playback analysis. The numbers of rolling and adherent IRBCs were determined off-line. IRBC rolling was expressed as rolling flux fraction, determined by counting the IRBCs interacting in an individual vessel over the period of observation and expressing this relative to the total number of IRBCs passing through the vessel over the same period (determined by frame-by-frame analysis). IRBCs that remained stationary on the vascular wall for at least 30 seconds were defined as adherent. Adhesive interactions in 3 to 7 postcapillary venules per skin graft were counted.Statistical analysis All data are presented as mean ± SEM. In the in vivo experiments, n values are based on the total number of vessels observed in the skin grafts of 1 or 2 mice studied under each condition for each clinical isolate.24 Data between 2 groups were compared by Student t test for paired samples. P .05 was considered statistically significant.
PpMC-179 purification and characterization The final purified product is shown in Figure 1A. N-terminal sequence analysis of the first 12 amino acid residues of the purified PpMC-179 yielded the sequence YVEDKIMSYNAF (single-letter amino acid codes). The first 2 amino acids correspond to the SnaB1 cloning site in the pPIC9K vector, proving that the-factor secretion signal was
efficiently removed during secretion from the cell. The next 10 amino
acids represent the N-terminus of MC-179. There are no glycosylation
sites on the y179 sequence, which is consistent with the molecular size
of about 22 kDa as determined by electron spray mass spectroscopy.
CD36 binding PpMC-179 was tested for its ability to bind to CD36 to determine whether it had the correct conformation. Because the protein was purified under potentially denaturing conditions by reversed phase chromatography, the final product was compared for binding to the protein purified by size exclusion. Results of the assay demonstrate that PpMC-179 bound to CD36 in a dose-dependent manner (Figure 1B). Furthermore, the product purified by reverse phase bound to CD36 at least as well, if not better, than the protein purified by size exclusion. This may reflect the higher purity and subsequent higher specific activity of the reverse phase-purified protein. CSA-163 produced in Saccharomyces cerevisiae (C.B., unpublished data, 2000) was used as the negative control in the assay. This protein is the homologous region to MC-179 in the CIDR1 domain from the FCR3-CSA strain of P falciparum. This CIDR1 domain is known not to bind to CD3625 and served to demonstrate the specificity of the assay to detect proteins that specifically bind to CD36. Furthermore, PpMC-179 inhibited the binding of IRBCs from the FMG strain to recombinant CD36 in a static binding assay, whereas an unrelated yeast recombinant protein yPyCSP had no effect (Table 1).
Inhibition of IRBC cytoadherence on HDMECs by recombinant PpMC-179 in vitro We first tested if PpMC-179 was capable of inhibiting the rolling and adhesion of IRBCs from clinical parasite isolates on HDMECs in vitro. Resting endothelial monolayers were preincubated with 2 µM PpMC-179 for 30 minutes prior to flow chamber experiments. In the 7 minutes of IRBC infusion, PpMC-179 inhibited adhesion by 84.4% (Figure 2A) and the total number of adherent IRBCs decreased from 96.8 ± 20.5 to 15.1 ± 9.0/mm2 (P < .01). The results presented in Figure 2, panels A and B, are the means of 4 independent experiments with 3 different clinical isolates. Rolling flux, however, was not significantly affected by PpMC-179, suggesting that the same number of IRBCs interacted with the endothelium and that in the absence of CD36, IRBC rolling could be mediated by other adhesion molecules such as ICAM-1 (Figure 2B).
On TNF- Inhibition of IRBC cytoadherence in human microvasculature by recombinant PpMC-179 in vivo To determine if PpMC-179 could inhibit the adhesive interactions between IRBCs and human microvessels in vivo, we measured the adhesive interactions of IRBCs in the microvasculature of human skin grafted onto an SCID mouse by intravital microscopy. The receptor profiles of the parasite isolates used in these experiments are given in Table 2. In inhibition experiments, the grafted mice received a bolus of 2 µM PpMC-179 via the jugular vein. The peptide was allowed to circulate for 10 to 15 minutes before the administration of a bolus of IRBCs. Rolling and adhesion of IRBCs in 3 animals treated with PpMC-179 were compared to that observed in 4 untreated animals. The results show that firm adhesion was inhibited from a baseline of 1.4 ± 0.24 to 0.18 ± 0.13 IRBC/100 µm for parasite isolate P00-24 (P < .01) and 1.94 ± 0.13 to 0.28 ± 0.13 IRBC/100 µm for P99-14 (P < .001; Figure 3A). The drop in adhesion represented an inhibition of 87.1% and 85.5%, respectively. However, the effect of PpMC-179 on the rolling flux fraction was different between the 2 parasites isolates. Isolate P00-24 showed a significant increase of the rolling flux fraction from 1.46 ± 0.77 to 6.02 ± 2.0 (P < .05), whereas the rolling of P99-14 did not appear to be affected (Figure 3B). The lack of effect of CD36 blockade on the rolling of P99-14 is consistent with the comparatively low interaction of P99-14 with ICAM-1 (Table 2).
The peptide PpMC-179 was next tested for its ability to inhibit
cytoadherence in TNF- Videotaped images depicting the rolling and adhesion of IRBCs on human
microvessels in the absence or presence of PpMC-179 are shown in Figure
4. Adherent and rolling cells appeared
round, whereas fast rolling and noninteracting cells appeared as
streaks. Figure 4, panels A and B, show a number of adherent IRBCs that remained stationary for at least 30 seconds (indicated by arrows), whereas several others rolled for short distances in that duration. The
situation was quite different when PpMC-179 was administered 10 to 15 minutes before the bolus of IRBCs (Figure 4C,D). The IRBCs were no
longer able to adhere, although some of them still rolled, whereas
others became noninteracting.
Reversal of IRBC cytoadherence in human microvasculature by recombinant PpMC-179 in vivo To determine if PpMC-179 was able to detach IRBCs that were already adherent, a bolus of IRBCs was allowed to circulate and adhere within the human microvasculature for 5 to 10 minutes prior to the administration of 2 µM PpMC-179. In control animals, the number of circulating IRBCs gradually decreased over 15 to 20 minutes due to IRBC adhesion within the human microvasculature, as well as trapping in the mouse liver and spleen (M.H. et al, unpublished observation, 2000). In contrast, in 3 animals that received PpMC-179 after IRBCs were allowed to adhere, the number of adherent IRBCs dropped within 5 minutes (Figure 5A) from 1.4 ± 0.2 to 0.4 ± 0.2 IRBC/100 µm for P00-24 (P < .01) and from 2.0 ± 0.3 to 0.2 ± 0.2 IRBC/100 µm for P98-10 (P < .01). This represents a 71.4% and a 90.0% reversal of cytoadherence, respectively, and an average reversal of 80.7% (Figure 5A). As IRBCs became detached, the rolling flux fraction increased markedly (P < .05) for P98-10 but not for isolate P00-24 (Figure 5B). Interestingly, P98-10 had the highest binding of the 5 clinical isolates tested to ICAM-1 transfectants under static conditions (Table 2).
Reversal experiments were also conducted in skin grafts treated with
TNF-
Antimalarial drugs are the mainstay of treatment for P
falciparum infections. However, for some patients this
intervention may come too late to save their lives. This is
particularly true for comatose patients and for those developing
life-threatening syndromes before antimalarial agents become effective.
The spread of drug-resistant parasites increases the likelihood of such
events and requires the development of novel adjunct therapies to
rapidly halt the disease process. In the past few years, anticytokine therapy in the form of anti-TNF- With increasing understanding of the molecular mechanisms of cytoadherence, an alternative therapeutic modality for severe falciparum malaria might be antiadhesive therapy. This type of therapy has been shown to be efficacious in inflammatory diseases such as rheumatoid arthritis in which the recruitment of lymphocytes to the synovium is successfully inhibited by antileukocyte function associated antigen 1 (anti-LFA-1) antibody.31 Soluble ICAM-1 has also been used successfully to inhibit the binding of rhinovirus, the causative agent of the common cold, to nasal epithelium.32 There is also precedent in the use of antiadhesive therapy in the treatment of malaria in animal models. In Aotus and Saimiri monkeys infected with P falciparum, passive transfer of hyperimmune sera resulted in parasite detachment and subsequent clearance by the spleen.33,34 In addition, it has been reported that soluble chondroitin sulfate A (CSA) was able to inhibit and reverse adhesion of CSA-adherent parasites in splenectomized Saimiri monkeys.35 However, the degree of detachment in these studies was not established. Among the various host receptors, adhesion to CD36 appears to be a
vital component for parasite sequestration in microvasculature beds.
With few exceptions, all nonplacental parasites, including those from
patients with cerebral malaria, exhibit binding to CD36. This
interaction is mediated by the M2 region of the CIDR1 domain of
PfEMP1.36 In this study, we show that a 179-amino acid
peptide from the CIDR domain of MCvar1 PfEMP1
inhibited and reversed the adhesion of IRBCs from multiple clinical
parasite isolates to HDMECs under flow conditions in vitro and to human microvessels in skin grafts on SCID mice in vivo. This is the first
demonstration that cytoadherence of diverse wild-type parasite strains
on a physiologic substratum can be inhibited by a single parasite
protein under shear stress. On HDMEC monolayers in vitro, the peptide
was effective in inhibiting IRBC adhesion on resting endothelium and
acted in concert with an anti-ICAM-1 antibody on endothelium that had
been stimulated with TNF- More striking was the observation that PpMC-179 could rapidly detach
already adherent IRBCs in vivo, suggesting that the peptide can have
both a preventive and curative role in relation to cytoadherence. No
further IRBC adhesion occurred once they were displaced, even when a
second bolus of IRBCs was administered after the peptide. The rapid
reversal within 5 minutes was different from previous results from an
in vitro flow chamber assay in which perfusion of recombinant peptide
for over 2 hours was needed for reversal.16 We believe
that the human microvasculature in the human/SCID mouse chimera used in
this study represents a much more physiologic model for cytoadherence
than immobilized CD36 protein in a flow chamber. Nevertheless, we
recognize that even the human/SCID mouse model has its limitations.
Reversal of adhesion was substantial but never complete and may not be
sufficient for altering the course of disease progression. In addition,
questions remain regarding the importance of CD36 binding in adhesion
to cerebral microvascular endothelium that expresses very little CD36
by immunohistochemical staining.37 On the other hand, a
low level of CD36 expression might well be sufficient to mediate
cytoadherence to brain microvasculature through the synergistic
interactions with other adhesion molecules. This possibility is
consistent with our observation that IRBC binds preferentially to CD36
on TNF- In conclusion, we demonstrated that it is possible to inhibit and reverse parasite sequestration with a small functional peptide from PfEMP1 in vivo. The peptide has an inhibitory effect on all parasite isolates tested. The finding strongly suggests that antiadhesive therapy based on PpMC-179 is feasible and will offer a therapeutic intervention with immediate effect.
The authors are grateful to Dr Robert Lindsay, Department of Surgery, Foothills Hospital and Dr Caroline Lane, Valley View Family Practice Clinic, Calgary, AB, Canada for providing the skin specimens.
Submitted June 12, 2002; accepted July 31, 2002.
Prepublished online as Blood First Edition Paper, August 15, 2002; DOI 10.1182/blood-2002-06-1725.
Supported by a group grant from the Canadian Institutes of Health Research, the Alberta Heritage Foundation for Medical Research, AB, Canada, and a Faculty of Medicine Endowment Award, University of Calgary, Calgary, AB, Canada. P.K. is a scientist of the Canadian Institutes of Health Research and holds a Canada Research Chair in Immunology, M.H. is a Senior Scholar of the Alberta Heritage Foundation for Medical Research (AHFMR), and B.G.Y. is supported by a studentship from AHFMR.
The publication costs of this article were defrayed in part by page charge payment. Therefore, and solely to indicate this fact, this article is hereby marked "advertisement" in accordance with 18 U.S.C. section 1734.
Reprints: May Ho, Department of Microbiology and Infectious Diseases, 3330 Hospital Dr NW, Calgary, AB, Canada T2N 4N1; e-mail: mho{at}ucalgary.ca.
1. White NJ, Ho M. The pathophysiology of malaria. Adv Parasitol. 1992;31:83-173[Medline] [Order article via Infotrieve]. 2. MacPherson GG, Warrell MJ, White NJ, Looareesuwan S, Warrell DA. Human cerebral malaria. A quantitative ultrastructural analysis of parasitized erythrocyte sequestration. Am J Pathol. 1985;119:385-401[Abstract]. 3. Udomsangpetch R, Reinhardt PH, Schollaardt T, Elliott JF, Kubes P, Ho M. Promiscuity of clinical Plasmodium falciparum isolates for multiple adhesion molecules under flow conditions. J Immunol. 1997;158:4358-4364[Abstract].
4.
Ho M, Schollaardt T, Niu X, Looareesuwan S, Patel KD, Kubes P.
Characterization of Plasmodium falciparum-infected erythrocyte and P-selectin interaction under flow conditions.
Blood.
1998;91:4803-4809
5.
Yipp BG, Anand S, Schollaardt T, Patel KD, Looareesuwan S, Ho M.
Synergism of multiple adhesion molecules in mediating cytoadherence of Plasmodium falciparum-infected erythrocytes to microvascular endothelial cells under flow.
Blood.
2000;96:2292-2298
6.
Ho M, Hickey MJ, Murray AG, Andonegui G, Kubes P.
Visualization of Plasmodium falciparum-endothelium interactions in human microvasculature: mimicry of leukocyte recruitment.
J Exp Med.
2000;192:1205-1211
7.
Baruch DI, Ma XC, Pasloske B, Howard RJ, Miller LH.
CD36 peptides that block cytoadherence define the CD36 binding region for Plasmodium falciparum-infected erythrocytes.
Blood.
1999;94:2121-2127
8.
Navazo MD, Daviet L, Savill J, Ren Y, Leung LL, McGregor JL.
Identification of a domain (155- 183) on CD36 implicated in the phagocytosis of apoptotic neutrophils.
J Biol Chem.
1996;271:15381-15385
9.
Magowan C, Wollish W, Anderson L, Leech J.
Cytoadherence by Plasmodium falciparum-infected erythrocytes is correlated with the expression of a family of variable proteins on infected erythrocytes.
J Exp Med.
1988;168:1307-1320 10. Baruch DI, Pasloske BL, Singh HB, et al. Cloning the P falciparum gene encoding PfEMP1, a malarial variant antigen and adherence receptor on the surface of parasitized human erythrocytes. Cell. 1995;82:77-87[CrossRef][Medline] [Order article via Infotrieve]. 11. Su XZ, Heatwole VM, Wertheimer SP, et al. The large diverse gene family var encodes proteins involved in cytoadherence and antigenic variation of Plasmodium falciparum-infected erythrocytes. Cell. 1995;82:89-100[CrossRef][Medline] [Order article via Infotrieve]. 12. Scherf A, Hernandez-Rivas R, Buffet P, et al. Antigenic variation in malaria: in situ switching, relaxed and mutually exclusive transcription of var genes during intra-erythrocytic development in Plasmodium falciparum. EMBO J. 1998;17:5418-5426[CrossRef][Medline] [Order article via Infotrieve].
13.
Baruch DI, Gormely JA, Ma C, Howard RJ, Pasloske BL.
Plasmodium falciparum erythrocyte membrane protein 1 is a parasitized erythrocyte receptor for adherence to Cd36, thrombospondin, and intercellular adhesion molecule 1.
Proc Natl Acad Sci U S A.
1996;93:3497-3502 14. Smith JD, Gamain B, Baruch DI, Kyes S. Decoding the language of var genes and Plasmodium falciparum sequestration. Trends Parasitol. 2001;17:538-545[CrossRef][Medline] [Order article via Infotrieve].
15.
Baruch DI, Ma XC, Singh HB, Bi X, Pasloske BL, Howard RJ.
Identification of a region of PfEMP1 that mediates adherence of Plasmodium falciparum infected erythrocytes to CD36: conserved function with variant sequence.
Blood.
1997;90:3766-3775 16. Cooke BM, Nicoll CL, Baruch DI, Coppel RL. A recombinant peptide based on PfEMP-1 blocks and reverses adhesion of malaria-infected red blood cells to CD36 under flow. Mol Microbiol. 1998;30:83-90[CrossRef][Medline] [Order article via Infotrieve].
17.
Gamain B, Miller LH, Baruch DI.
The surface variant antigens of Plasmodium falciparum contain cross-reactive epitopes.
Proc Natl Acad Sci U S A.
2001;98:2664-2669
18.
Baruch DI, Gamain B, Barnwell JW, et al.
Immunization of Aotus monkeys with a functional domain of the Plasmodium falciparum variant antigen induces protection against a lethal parasite line.
Proc Natl Acad Sci U S A.
2002;99:3860-3865 19. World Health Organization. Severe falciparum malaria. Tran R Soc Trop Med Hyg. 2000;94(suppl 1):S1-S90[Medline] [Order article via Infotrieve].
20.
Udomsangpetch R, Taylor BJ, Looareesuwan S, White NJ, Elliott JF, Ho M.
Receptor specificity of clinical Plasmodium falciparum isolates: nonadherence to cell-bound E-selectin and vascular cell adhesion molecule-1.
Blood.
1996;88:2754-2760 21. Petzelbauer P, Bender JR, Wilson J, Pober JS. Heterogeneity of dermal microvascular endothelial cell antigen expression and cytokine responsiveness in situ and in cell culture. J Immunol. 1993;151:5062-5072[Abstract]. 22. McCormick CJ, Craig A, Roberts D, Newbold CI, Berendt AR. Intercellular adhesion molecule-1 and CD36 synergize to mediate adherence of Plasmodium falciparum-infected erythrocytes to cultured human dermal microvascular endothelium. J Clin Invest. 1997;100:2521-2529[Medline] [Order article via Infotrieve].
23.
Murray AG, Petzelbauer P, Hughes CC, Costa J, Askenase P, Pober JS.
Human T-cell-mediated destruction of allogeneic dermal microvessels in a severe combined immunodeficient mouse.
Proc Natl Acad Sci U S A.
1994;91:9146-9150 24. Forlow SB, White EJ, Barlow SC, et al. Severe inflammatory defect and reduced viability in CD18 and E-selectin double-mutant mice. J Clin Invest. 2000;106:1457-1466[Medline] [Order article via Infotrieve].
25.
Gamain B, Smith JD, Miller LH, Baruch DI.
Modifications in the CD36 binding domain of the Plasmodium falciparum variant antigen are responsible for the inability of chondroitin sulfate A adherent parasites to bind CD36.
Blood.
2001;97:3268-3274 26. Day NP, Hien TT, Schollaardt T, et al. The prognostic and pathophysiological role of pro- and anti-inflammatory cytokines in severe malaria. J Infect Dis. 1999;180:1288-1297 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Abstract
Introduction
