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)

Antigenic polymorphism and HLA restriction may limit the immunogenicity of a subunit vaccine against liver-stage Plasmodium falciparum. We examined 59 clinical isolates and five laboratory clones of P. falciparum for polymorphism in the N- and C-terminal regions of LSA-1, evaluated binding of the corresponding peptides to selected HLA class I alleles, and measured IFN-gamma responses in residents of a malaria-endemic area of Papua New Guinea where HLA-A*1101, -24, -B13, and -B40 are the most common class I alleles. LSA-1 polymorphism was limited to a single non-synonymous mutation encoding serine (S), proline (P), or threonine (T) at amino acid 85. Nine-mer 84-92 peptides with S, T, or P at the primary anchor position bound differentially to HLA-A11, -A2, and -B7. IFN-gamma ELISPOT responses increased with age in malaria-exposed subjects: 14-16% and 30-36% of 2-5- and 6-54-year-olds, respectively, had > or =10 IFN-gamma-secreting cells/106 peripheral blood mononuclear cells when stimulated with at least one peptide variant (P<0.05). IFN-gamma responses to all three peptides were also greater for older than younger individuals. No children < 3 years old had lymphocytes that responded to all three 84-92 peptides, whereas 45% of adults (mean age 48 years) had aggregated IFN-gamma responses. These data support the notion that age-related cumulative exposure to P. falciparum increases the frequency of IFN-gamma responses to polymorphic epitopes of liver-stage antigens such as LSA-1.
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PMID:Influence of age and HLA type on interferon-gamma (IFN-gamma) responses to a naturally occurring polymorphic epitope of Plasmodium falciparum liver stage antigen-1 (LSA-1). 1101 24

In the present study, HLA associations among the cohort of 171 severe P. falciparum malaria patients were compared with that of 101 normal sex, age and ethnically matched control samples. All these individuals lived in Mumbai in an area of low and seasonal P. falciparum transmission. HLA A, B, DRB1 and DQB1 antigens were serologically (A and B) and molecularly (DRB and DQB) determined using isolated lymphocytes and genomic DNA following the microlymphocytotoxicity assay and PCR-SSP techniques. Significant differences were observed between patients with malaria and controls in the following groups of alleles: A3, B27, B49, DRB1*04, and DRB1*0809 were increased, while A19, A34, B18, B37, and DQB1*0203 were decreased. HLA B49 and DRB1*0809 were found to be positively associated with the complicated severe malaria patients (OR = 13.88; p < 0.0001). HLA A19, B5 and B13 were protective in patients with high parasite index (> 2%). These observations revealed the importance of ethnic background, which has to be taken into consideration while developing an ideal malaria vaccine. Further, when compared to HLA associations of other world populations the present study indicates the relative importance of different HLA alleles that may vary in different populations.
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PMID:HLA associations in P. falciparum malaria patients from Mumbai, western India. 1468 15

Parasites have exploited unique energy metabolic pathways as adaptations to the natural host habitat. In fact, the respiratory systems of parasites typically show greater diversity in electron transfer pathways than do those of host animals. These unique aspects of parasite mitochondria and related enzymes may represent promising targets for chemotherapy. Natural products have been recognized as a source of the candidates of the specific inhibitors for such parasite respiratory chains. Chalcones was recently evaluated for its antimalarial activity in vitro and in vivo. However, its target is still unclear in malaria parasites. In this study, we investigated that licochalcone A inhibited the bc1 complex (ubiquinol-cytochrome c reductase) as well as complex II (succinate ubiquinone reductase, SQR) of Plasmodium falciparum mitochondria. In particular, licochalcone A inhibits bc1 complex activity at very low concentrations. Because the property of the P. falciparum bc1 complex is different from that of the mammalian host, chalcones would be a promising candidate for a new antimalarial drug.
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PMID:Parasite mitochondria as a target of chemotherapy: inhibitory effect of licochalcone A on the Plasmodium falciparum respiratory chain. 1638 76

In the intraerythrocytic stages of malaria parasites, mitochondria lack obvious cristae and are assumed to derive energy through glycolysis. For understanding of parasite energy metabolism in mammalian hosts, we isolated rodent malaria mitochondria from Plasmodium yoelii yoelii grown in mice. As potential targets for antiplasmodial agents, we characterized two respiratory dehydrogenases, succinate:ubiquinone reductase (complex II) and alternative NADH dehydrogenase (NDH-II), which is absent in mammalian mitochondria. We found that P. y. yoelii complex II was a four-subunit enzyme and that kinetic properties were similar to those of mammalian enzymes, indicating that the Plasmodium complex II is favourable in catalysing the forward reaction of tricarboxylic acid cycle. Notably, Plasmodium complex II showed IC(50) value for atpenin A5 three-order of magnitudes higher than those of mammalian enzymes. Divergence of protist membrane anchor subunits from eukaryotic orthologs likely affects the inhibitor resistance. Kinetic properties and sensitivity to 2-heptyl-4-hydroxyquinoline-N-oxide and aurachin C of NADH: ubiquinone reductase activity of Plasmodium NDH-II were similar to those of plant and fungus enzymes but it can oxidize NADPH and deamino-NADH. Our findings are consistent with the notion that rodent malaria mitochondria are fully capable of oxidative phosphorylation and that these mitochondrial enzymes are potential targets for new antiplasmodials.
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PMID:Mitochondrial dehydrogenases in the aerobic respiratory chain of the rodent malaria parasite Plasmodium yoelii yoelii. 1906 Mar 9

Malaria parasites in human hosts depend on glycolysis for most of their energy production, and the mitochondrion of the intraerythrocytic form is acristate. Although the genes for all tricarboxylic acid (TCA) cycle members are found in the parasite genome, the presence of a functional TCA cycle in the intraerythrocytic stage is still controversial. To elucidate the physiological role of Plasmodium falciparum mitochondrial complex II (succinate-ubiquinone reductase (SQR) or succinate dehydrogenase (SDH)) in the TCA cycle, the gene for the flavoprotein subunit (Fp) of the enzyme, pfsdha (P.falciparum gene for SDH subunit A, PlasmoDB ID: PF3D7_1034400) was disrupted. SDH is a well-known marker enzyme for mitochondria. In the pfsdha disruptants, Fp mRNA and polypeptides were decreased, and neither SQR nor SDH activity of complex II was detected. The suppression of complex II caused growth retardation of the intraerythrocytic forms, suggesting that complex II contributes to intraerythrocytic parasite growth, although it is not essential for survival. The growth retardation in the pfsdha disruptant was rescued by the addition of succinate, but not by fumarate. This indicates that complex II functions as a quinol-fumarate reductase (QFR) to form succinate from fumarate in the intraerythrocytic parasite.
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PMID:Toward understanding the role of mitochondrial complex II in the intraerythrocytic stages of Plasmodium falciparum: gene targeting of the Fp subunit. 2269 72