Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0024530 (malaria)
 44,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Adhesion of mature Plasmodium falciparum parasitized erythrocytes to microvascular endothelial cells or to placenta contributes directly to the virulence and severe pathology of P falciparum malaria. Whereas CD36 is the major endothelial receptor for microvasculature sequestration, infected erythrocytes adhering in the placenta bind chondroitin sulfate A (CSA) but not CD36. Binding to both receptors is mediated by different members of the large and diverse protein family P falciparum erythrocyte membrane protein-1 (PfEMP-1) and involves different regions of the molecule. The PfEMP-1-binding domain for CD36 resides in the cysteine-rich interdomain region 1 (CIDR-1). To explore why CSA-binding parasites do not bind CD36, CIDR-1 domains from CD36- or CSA-binding parasites were expressed in mammalian cells and tested for adhesion. Although CIDR-1 domains from CD36-adherent strains strongly bound CD36, those from CSA-adherent parasites did not. The CIDR-1 domain has also been reported to bind CSA. However, none of the CIDR-1 domains tested bound CSA. Chimeric proteins between CIDR-1 domains that bind or do not bind CD36 and mutagenesis experiments revealed that modifications in the minimal CD36-binding region (M2 region) are responsible for the inability of CSA-selected parasites to bind CD36. One of these modifications, mapped to a 3-amino acid substitution in the M2 region, ablated binding in one variant and largely reduced binding of another. These findings provide a molecular explanation for the inability of placental sequestered parasites to bind CD36 and provide additional insight into critical residues for the CIDR-1/CD36 interaction.
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PMID: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. 1134 58

The major surface protein of malaria sporozoites, the circumsporozoite protein, binds to heparan sulfate proteoglycans on the surface of hepatocytes. It has been proposed that this binding event is responsible for the rapid and specific localization of sporozoites to the liver after their injection into the skin by an infected anopheline mosquito. Previous in vitro studies performed under static conditions have failed to demonstrate a significant role for heparan sulfate proteoglycans during sporozoite invasion of cells. We performed sporozoite attachment and invasion assays under more dynamic conditions and found a dramatic decrease in sporozoite attachment to cells in the presence of heparin. In contrast to its effect on attachment, heparin does not appear to have an effect on sporozoite invasion of cells. When substituted heparins were used as competitive inhibitors of sporozoite attachment, we found that sulfation of the glycosaminoglycan chains at both the N- and O-positions was important for sporozoite adhesion to cells. We conclude that the binding of the circumsporozoite protein to hepatic heparan sulfate proteoglycans is likely to function during sporozoite attachment in the liver and that this adhesion event depends on the sulfated glycosaminoglycan chains of the proteoglycans.
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PMID:The binding of the circumsporozoite protein to cell surface heparan sulfate proteoglycans is required for plasmodium sporozoite attachment to target cells. 1135 23

One hundred and two children aged 0-10 years with cerebral malaria (Blantyre coma score of 2 or less) were randomly treated either with intramuscular arteether (3.2 mg/kg on Day 0, followed by 1.6 mg/kg on Days 1 to 4) or intravenous (i.v.) quinine dihydrochloride (20 mg of the salt/kg, followed by 10 mg of the salt/kg every 8 hr up to Day 6). Treatment with oral quinine sulfate (10 mg/kg every 8 hr) was substituted for i.v. quinine when the patient was able to take oral medicine. All patients were followed up in the hospital for 7 days; thereafter, they were treated as outpatients on Days 14, 21, and 28. Mortality rate, the main efficacy parameter, was 11.8% lower in the arteether treatment group than in the quinine group (15.7% versus 27.4%); however, the difference was not significant (P = 0.25). Means for fever clearance time, coma resolution time, and parasite clearance time were similar in the 2 treatment groups (42.2 +/- 34.9 hr; 34.8 +/- 18.8 hr, and 46.3 +/- 28.5 hr, respectively for arteether, versus 45.0 +/- 26.7 hr; 30.3 +/- 18.9 hr, and 40.7 +/- 18.9 hr, respectively, for quinine). At 28 days, the cure rates were 73.2% and 64.9% for the arteether and quinine treatment groups, respectively. Arteether is safe and therapeutically at least as effective as quinine for the treatment of cerebral malaria in children in Cameroon. Because of its ease of administration, arteether appears to be suited for use in the rural zones where monitoring facilities do not exist.
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PMID:Clinical trial of beta-arteether versus quinine for the treatment of cerebral malaria in children in Yaounde, Cameroon. 1146 8

Chloroquine and its derivative, hydroxychloroquine sulfate, have been used in treating malaria, dermatitides of systemic lupus erythematosus and rheumatoid arthritis. Hydroxychloroquine retinopathy is uncommon in Taiwan. Here we report a patient with hydroxychloroquine retinopathy which progressed even after discontinuation of hydroxychloroquine. A 42-year-old woman had systemic lupus erythematosus for twenty years. She had been treated with 200 to 400 mg of hydroxychloroquine per day (4 to 8 mg/kg of body weight/day) with a cumulative dose of 657 g. After bull's-eye maculopathy was found, hydroxychloroquine was discontinued. Her medical history revealed no chloroquine administration and no other systemic disease. Five years after cessation of the therapy, her visual acuity and visual fields continued to deteriorate. Ophthalmoscopic examination revealed the hydroxychloroquine retinopathy had advanced. To the best of our knowledge, the progression of hydroxychloroquine retinopathy after discontinuation of medications is a rare phenomenon. Regular ophthalmologic examinations should be performed for patients on hydroxychloroquine regimens because there is no satisfactory treatment for hydroxychloroquine retinal toxicity. Ophthalmologists, dermatologists and rheumatologists should monitor for ocular toxicity of hydroxychloroquine carefully.
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PMID:Progression of hydroxychloroquine retinopathy after discontinuation of therapy: case report. 1148 Mar 31

Otherwise clinically immune women in areas endemic for malaria are highly susceptible to Plasmodium falciparum malaria during their first pregnancy. Pregnancy-associated malaria (PAM) is characterized by placental accumulation of infected erythrocytes that adhere to chondroitin sulfate A (CSA). Susceptibility to PAM decreases with increasing parity, apparently due to acquisition of antibodies directed against the variant surface antigens (VSAs) that mediate the adhesion to CSA (VSA(CSA)). This study found that levels of VSA(CSA)-specific antibodies depend on endemicity, that anti-VSA(CSA) IgG is acquired during gestation week 20, and that plasma levels of the antibodies decline during the postpartum period. There is evidence that VSA(CSA)-specific antibodies are linked to placental infection and that high antibody levels contribute to the control of placental infection by inhibiting parasite adhesion to CSA. Data suggest that VSA(CSA) is a target for vaccination against PAM.
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PMID:Acquisition and decay of antibodies to pregnancy-associated variant antigens on the surface of Plasmodium falciparum-infected erythrocytes that protect against placental parasitemia. 1149 67

Circumsporozoite (CS) protein is a predominant surface antigen of malaria sporozoites, the infective form of the parasite, and has been used for making anti-malaria vaccines. For the first time we have examined the interaction of CS protein with various glycosaminoglycans in real time using surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC). Heparin was the best binder among the glycosaminoglycans tested and bound to CS protein with nanomolar affinity. Using purified and structurally defined small heparin oligosaccharides, we identified a decasaccharide to be the minimum sized CS protein-binding sequence. In an indirect competition assay, this decasaccharide blocked the CS protein interaction with HepG2 cells with an ID(50) of less than 60 nM. The decasaccharide has a structure commonly found in hepatic heparan sulfate, and the same sequence has recently been shown to bind specifically to apolipoprotein E. Examination of porcine liver heparan sulfate in this indirect competition assay showed that it and heparin were the only glycosaminoglycans that could effectively block CS protein interaction with HepG2 cells in culture. These data support the hypothesis that the invasion of liver cells by the parasite shares a common mechanism with the hepatic uptake of lipoprotein remnants from the blood.
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PMID:Direct measurement of the interactions of glycosaminoglycans and a heparin decasaccharide with the malaria circumsporozoite protein. 1156 May

During pregnancy, Plasmodium falciparum-infected erythrocytes sequester in the placenta by adhering to chondroitin 4-sulfate, creating a risk factor for both the mother and the fetus. The primigravidae are at higher risk for placental malaria than the multigravidae. This difference in susceptibility has been attributed to the lack of antibodies that block the adhesion of infected erythrocytes to placental chondroitin 4-sulfate in primigravid women. However, recent results show that many primigravidae at term have antibody levels similar to those of multigravidae, and thus the significance of antiadhesion antibodies in providing protection against malaria during pregnancy remains unclear. In this study, we analyzed plasma samples from women of various gravidities at different gestational stages for antiadhesion antibodies. The majority of women, regardless of gravidity, had similar levels of antibodies at term. Most primigravidae had low levels of or no antiadhesion antibodies prior to ~20 weeks of pregnancy and then produced antibodies. Multigravidae also lacked antibodies until ~12 weeks of pregnancy, but thereafter they efficiently produced antibodies. In pregnant women who had placental infection at term, higher levels of antiadhesion antibodies correlated with lower levels of placental parasitemia. The difference in kinetics of antibody production between primigravidae and multigravidae correlated with the prevalence of malaria in these groups, suggesting that antibodies are produced during pregnancy in response to placental infection. The early onset of efficient antibody response in multigravidae and the delayed production to antibodies in primigravidae appear to account for the gravidity-dependent differential susceptibilities of pregnant women to placental malaria.
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PMID:Gravidity-dependent production of antibodies that inhibit binding of Plasmodium falciparum-infected erythrocytes to placental chondroitin sulfate proteoglycan during pregnancy. 1170 24

To compare the effectiveness and safety of quinine sulfate and artesunate with mefloquine for treating second trimester pregnancy in women who suffered from Plasmodium falciparum malaria. The prospective study was done in Srisangwal Hospital, Mae Hong Son, Thailand. Sixty, second to third trimester pregnant patients with P. falciparum infection, were recruited at random. They received either quinine sulfate 10 mg/kg/day for at least 7 days, 29 women (group I), or oral artesunate 2 mg/kg as the first dose, 1 mg/kg every 12 hours orally for at least 5 days together with split doses of mefloquine, 15 mg/kg and 6 hours later 10 mg/kg orally 1 day after artesunate was stopped, 28 women (group II). Three cases (5%) were lost to follow-up before delivery, one case in group I and two cases in group II. After treatment, the mean hematocrit of group I was significantly less than group II (p = 0.000). The PCT (parasite clearance time) and FCT (fever clearance time) of group II were significantly shorter than group I (p = 0.000). None of the patients in both groups had recrudescences within 28 days. Group I had more adverse effects than group II. No adverse neurological effects in pregnancy were found in both groups. The calcification of placenta and IUGR (Intrauterine growth retard) were not different between the two groups (p = 0.964, 0.363 respectively). The PCT was not different between the calcified placenta group and normal placenta group (p = 0.058), but the TTPP (Total time of parasite presentation) was (p = 0.000). TTPP related to low birth weight and low apgar score at 1 minute might be the cause (p = 0.000, 0.000 F = 5.261, 21.627 respectively). TTPP and PCT related to neonatal blood pH and caused low neonatal blood pH (p = 0.000, 0.001 F = 24.351, 11.162 respectively). The physical and neurological development of the babies at 2, 4, 6 and 12 months follow-up, were normal and there were no congenital abnormalities in either group. TTPP relating to fetal outcome, the longer the TTPP, the worse the fetal outcome, so we should diagnose early and treat P. falciparum malaria in pregnancy to prevent fetal jeopardy. Artesunate with mefloquine could shorten the PCT more than quinine sulfate in pregnancy, so the fetal outcome was better than that of quinine sulfate. In cases of prolonged infection before treatment, artesunate might be the alternative treatment of P. falciparum malaria in pregnancy. However, its safety should be carefully studied further with a larger sample size.
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PMID:Randomized trial of artesunate and mefloquine in comparison with quinine sulfate to treat P. falciparum malaria pregnant women. 1180 Mar 3

Quinine sulfate has been the drug of choice for the treatment of the ever-increasing number of cases of falciparum malaria in tropical countries. Because of the spectrum of adverse effects produced by the drug in the so-called cinchona syndrome, the variation in its pharmacokinetics during the episodes of falciparum malaria, and the different therapeutic regimens proposed in different countries, the authors monitored quinine plasma concentrations in daily samples of 20 men of the Amazon region in Brazil with nonsevere falciparum malaria who were administered 1 g quinine sulfate every 12 hours for 7 days. Three blood samples were collected from each patient each day: two immediately before administration of the drug (7 am and 7 pm) and one at 11 am. A total of 440 samples were analyzed by a validated method developed in the authors' laboratories using the high-performance liquid chromatographic technique. The overall quinine plasma levels obtained varied from 1.52 to 16.89 microg/mL. From the second day of treatment, overall levels varied from 2.33 to 14.29 microg/mL; the peak concentrations showed values from 4.22 to 16.89 microg/mL, showing the efficacy of the therapeutic regimen used. Adverse effects (signs and symptoms of cinchonism) were observed in all patients. However, no cases of hypoglycemia were detected. Intrapatient comparisons of the obtained quinine plasma concentrations were statistically significant. The quinine dose may be reduced on day 4 of treatment when asexual parasitemia is absent. This way, no resistance to the drug is observed, cinchonism can be minimized, and good adherence to the regimen is obtained.
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PMID:Drug monitoring of quinine in men with nonsevere falciparum malaria: study in the Amazon region of Brazil. 1180 92

Malaria results in up to 2.5 million deaths annually, with young children and pregnant women at greatest risk. The great majority of severe disease is caused by Plasmodium falciparum. A characteristic feature of infection with Pfalciparum is the accumulation or sequestration of parasite-infected red blood cells (RBCs) in various organs, such as the brain, lung and placenta, and together with other factors is important in the pathogenesis of severe forms of malaria. Sequestration results from adhesive interactions between parasite-derived proteins expressed on the surface of infected RBCs and a number of host molecules on the surface of endothelial cells, placental cells and uninfected RBCs. Some receptors for parasite adhesion have been implicated in particular malaria syndromes, such as intercellular adhesion molecule 1 in cerebral malaria and chondroitin sulfate A and hyaluronic acid in placental infection. The principal parasite ligand and antigen on the RBC surface, P falciparum erythrocyte membrane protein 1 encoded by a multigene family termed var, is clonally variant, enabling evasion of specific immune responses. An understanding of these host-parasite interactions in the context of clinical disease and immunity may reveal potential targets to prevent or treat severe forms of malaria.
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PMID:Pathogenesis of Plasmodium falciparum malaria: the roles of parasite adhesion and antigenic variation. 1191 43


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