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)

Molecular genetic studies of the human malaria parasite Plasmodium falciparum have been hampered in part due to difficulties in stably cloning and propagating parasite genomic DNA in bacteria. This is thought to be a result of the unusual A+T bias (>80%) in the parasite's DNA. Pulsed-field gel electrophoretic separation of P. falciparum chromosomes has shown that large chromosomal polymorphisms, resulting from the deletion of DNA from chromosome ends, frequently occur. Understanding the biological implications of this chromosomal polymorphism will require the analysis of large regions of genomic, and in particular telomeric, DNA. To overcome the limitations of cloning parasite DNA in bacteria, we have cloned genomic DNA from the P. falciparum strain FCR3 in yeast as artificial chromosomes. A pYAC4 library with an average insert size of approximately 100 kb was established and found to have a three to fourfold redundancy for single-copy genes. Unlike bacterial hosts, yeast stably maintain and propagate large tracts of parasite DNA. Long-range restriction enzyme mapping of YAC clones demonstrates that the cloned DNA is contiguous and identical to the native parasite genomic DNA. Since the telomeric ends of chromosomes are underrepresented in YAC libraries, we have enriched for these sequences by cloning P. falciparum telomeric DNA fragments (from 40 to 130 kb) as YACs by complementation in yeast.
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PMID:Characterization of yeast artificial chromosomes from Plasmodium falciparum: construction of a stable, representative library and cloning of telomeric DNA fragments. 142 49

A two-phase study was initiated to delineate the peripheral blood lymphocyte populations present in owl monkeys and to correlate those populations with immune response and parasitism during malaria infection. The goal of phase I of the study was to elucidate a monoclonal antibody panel that could be used to characterize peripheral blood mononuclear cell (PBMC) populations with flow cytometric techniques. Forty-two monoclonal antibodies (reported to be reactive with human and macaque lymphocyte antigens) were screened for activity to owl monkey PBMC. Eleven monoclonals were found to react: anti-H42A (MHC Class II DP-like); anti-TH14B (MHC Class II DR-like); and anti-TH81A5 (MHC Class II DQ-like); anti-H58A (MHC Class I); anti-DH59B (granulocyte and monocyte); anti-B1 (B cell); anti-T4 (CD4); anti-Leu3a (CD4); anti-Leu11a (CD16); anti-60.3 (CD18); and anti-OKM1 (NK and monocyte). In a preliminary retrospective study correlating antibody titers, parasitemia values, and MHC Class I and Class II marker profiles on PBMC to test antigens used in malaria vaccine trials, a significant negative association was observed between cells bearing MHC Class II molecules and the other elements of the comparison. In summary, an appropriate panel of monoclonal antibodies has been identified for characterizing PBMC in owl monkeys, and preliminary studies indicate a possible association between clinical outcome and expressed phenotypic PBMC markers.
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PMID:Immunophenotypic characterization of owl monkey peripheral blood mononuclear cells. 162 63

To investigate the genetic basis of drug resistance in human malaria parasites, we have sequenced the entire dihydrofolate reductase thymidylate synthetase DHFR-TS bifunctional gene from the highly pyrimethamine-resistant K1 isolate of Plasmodium falciparum. The protein is predicted to consist of 607 amino acids (aa), (71,685 Da), with an N-terminal methionine encoded by the second start codon of the open reading frame. Compared to the sequence from drug-sensitive parasites, there are two nucleotide changes in the coding region which bring about a substitution of Arg for Cys at aa position 59 and Asn for Thr at aa position 108. Both changes occur in regions of the DHFR domain involved in inhibitor and cofactor binding and are hence strongly implicated in drug resistance. The gene is present as a single copy in both K1 and drug-sensitive FCR3 isolates, and is assigned to chromosome 4. Codon usage follows the pattern observed in that of malarial surface antigen genes, with the exception fo codons corresponding to Val and Pro. The Asn and Lys contents of the predicted protein are exceptionally high, these residues being particularly concentrated in the DHFR and junction domains.
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PMID:Characterisation of the dihydrofolate reductase-thymidylate synthetase gene from human malaria parasites highly resistant to pyrimethamine. 266 50

We report the isolation of cDNA clones for a Plasmodium falciparum gene that encodes the complete amino acid sequence of a previously identified exported blood stage antigen. The Mr of this antigen protein had been determined by sodium dodecylsulphate-polyacrylamide gel electrophoresis analysis, by different workers, to be 113,000, 126,000, and 140,000. We show, by cDNA nucleotide sequence analysis, that this antigen gene encodes a 989 amino acid protein (111 kDa) that contains a potential signal peptide, but not a membrane anchor domain. In the FCR3 strain the serine content of the protein was 11%, of which 57% of the serine residues were localized within a 201 amino acid sequence that included 35 consecutive serine residues. The protein also contained three possible N-linked glycosylation sites and numerous possible O-linked glycosylation sites. The mRNA was abundant during late trophozoite-schizont parasite stages. We propose to identity this antigen, which had been called p126, by the acronym SERA, serine-repeat antigen, based on its complete structure. The usefulness of the cloned cDNA as a source of a possible malaria vaccine is considered in view of the previously demonstrated ability of the antigen to induce parasite-inhibitory antibodies and a protective immune response in Saimiri monkeys.
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PMID:Amino acid sequence of the serine-repeat antigen (SERA) of Plasmodium falciparum determined from cloned cDNA. 284 41

DNA encoding an antigen of 101,000 apparent molecular weight from the human malaria parasite Plasmodium falciparum was cloned and sequenced. Genomic DNA from the Camp strain covering the complete coding region along with cDNA from the FCR3 strain covering 81% of the coding region were obtained. The cloned DNA specified a full-length protein of 743 amino acids which included two tandemly repeated regions, one near the amino terminus containing eight hexapeptide repeats of sequence TVNDEDED, and the second near the carboxyl terminus containing primarily KE and KEE repeats. The latter repeated region is encoded by a 174-base stretch of mRNA containing only a single pyrimidine. Except for a putative leader sequence located at the amino terminus of the protein, the protein is hydrophilic and highly charged with a calculated isoelectric point of 5.6. Sequences from the Camp and FCR3 strains are very close and are also nearly identical to the partial cDNA sequence of the acidic basic repeated antigen (ABRA) protein from the FC27 strain (Stahl, H.D., Bianco, A.E., Crewther, R.F., Anders, R.F., Kyne, A.P., Coppel, R. L., Mitchell, G.F., Kemp, D.J., and Brown, G.V. (1986) Mol. Biol. Med. 3, 351-368). ABRA was previously shown to be located at the merozoite surface and in the parasitophorous vacuole. Because of its location and because it becomes complexed to merozoites when schizonts rupture in the presence of immune serum, ABRA is a candidate component of a malaria vaccine.
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PMID:Primary structure of a Plasmodium falciparum malaria antigen located at the merozoite surface and within the parasitophorous vacuole. 304 68

Human neutrophil elastase (HNE) has been well-studied with respect to its role in pathologic states, but less is known about the physiologic functions of this important granulocyte enzyme. In the present study, we show that HNE can degrade the major circumsporozoite protein of the infective (sporozoite) stage of Plasmodium vivax malaria, and that this enzyme can also interfere with the cytoadherence of human E infected with Plasmodium falciparum (strain K+ FMG-FCR3) (IE). Cytoadherence reactions are not only blocked by treatment of IE with as little as 10 fg HNE/IE, but already adherent IE are also removed by the enzyme. Normal E surface Ag are not extensively destroyed by these doses of HNE. This suggests that the effect of HNE on cytoadherence is selective and probably due to degradation of the malarial Ag exported to the IE surface and responsible for the formation of "recognition knobs" upon which the cytoadherence reaction depends. This conclusion, in turn, was supported by the results of Western blot analysis showing that HNE degrades a high m.w. Ag found exclusively in membrane extracts of IE. Our results suggest that one physiologic role of HNE may be degradation of parasitic antigens during host defense against malaria.
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PMID:Degradation of plasmodial antigens by human neutrophil elastase. 329 93

Stable human hybridomas were generated that produced inhibitory anti-Plasmodium falciparum monoclonal antibodies. Peripheral blood lymphocytes, obtained from adults in Liberia, a malaria endemic area, were immortalized with Epstein-Barr virus and then fused with KR4, a human, lymphoblastoid cell line. Stable hybridomas that produced anti-P. falciparum monoclonal antibody were identified by an ELISA assay that used the trophozoite and schizont antigens of both the Honduras I and FCR3 parasite strains. Monoclonal antibodies produced by selected hybridomas derived from lymphocytes of two individuals were subsequently studied. The anti-parasite antibodies were produced at 1-3 micrograms/ml in culture supernatants. All of the monoclonal antibodies bound specifically to trophozoites and schizonts of both strains of parasite in an indirect immunofluorescence assay and inhibited production of ring stage parasites by more than 90% when added to trophozoite or schizont containing erythrocytes in culture. Western immunoblot analysis of antigens obtained from trophozoites and schizonts (parasite age span of 36 to 48 h) was performed using either affinity purified or ammonium sulfate-concentrated monoclonal antibody. Antibody from three hybridomas which bound primarily to antigens of the Honduras 1 strain had Mr of approximately 140,000, 130,000 and 123,000.
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PMID:Plasmodium falciparum-inhibitory monoclonal antibodies produced by human hybridomas. 329 24

The intraerythrocytic development of the malaria parasite is accompanied by distinct morphological and biochemical changes in the host cell membrane, yet little is known about development-related alterations in the transbilayer organization of membrane phospholipids in parasitized cells. This question was examined in human red cells infected with Plasmodium falciparum. Normal red cells were infected with strain FCR3 or with clonal derivatives that either produce (K+) or do not produce (K-) knobby protuberances on the infected red cells. Parasitized cells were harvested at various stages of parasite development, and the bilayer orientation of red cell membrane phospholipids was determined chemically using 2,4,6-trinitrobenzene sulphonic acid (TNBS) or enzymatically using bee venom phospholipase A2 (PLA2) and sphingomyelinase C (SMC). We found that parasite development was accompanied by distinct alterations in the red cell membrane transbilayer distribution of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylserine (PS). Increases in the exoplasmic membrane leaflet exposure of PE and PS were larger in the late-stage parasitized cells than in the early-stage parasitized cells. Similar results were obtained for PE membrane distribution using either chemical (TNBS) or enzymatic (PLA2 plus SMC) methods, although changes in PS distribution were observed only with TNBS. Uninfected cohort cells derived from mixed populations of infected and uninfected cells exhibited normal patterns of membrane phospholipid organization. The observed alterations in P falciparum-infected red cell membrane phospholipid distribution, which is independent of the presence or absence of knobby protuberances, might be associated with the drastic changes in cell membrane permeability and susceptibility to early hemolysis observed in the late stages of parasite development.
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PMID:Altered plasma membrane phospholipid organization in Plasmodium falciparum-infected human erythrocytes. 354 79

The present study was to evaluate the soluble antigen prepared from the in-vitro cultured P. falciparum (FCR3) as an alternative source of antigen to those obtained from in-vivo models for enzyme linked immunosorbent assay (ELISA) in serology of malaria. Results obtained on known positive and negative reference sera revealed good correlation between the ELISA and the indirect fluorescent antibody (IFA) technique (rs = 0.797; p less than 0.001). However such close correlation was not observed on six local sera from patients whose peripheral blood smear showed ring stage of P. falciparum (rs = 0.43; p greater than 0.05), though all the six sera were positive by the IFA and ELISA tests. Test was repeated to establish its reproducibility. The results indicate that antigen prepared from in vitro culture and stored in liquid nitrogen was found sensitive in ELISA for serology of malaria.
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PMID:Evaluation of a crude soluble antigen from in-vitro culture of Plasmodium falciparum for ELISA. 676 15

Cerebral malaria is probably related to an overstimulation of the immune system and the cytokine network. We have previously demonstrated that tumour necrosis factor (TNF) secretion by human macrophages can be induced by soluble and heat-stable malarial antigens. Indirect evidence from epidemiological and in vitro studies suggests that Pf155/RESA can be considered as a candidate for triggering TNF secretion. Thus we conducted experiments to investigate the relationship between Pf155/RESA and TNF production. The SGE1 strain of Plasmodium falciparum was compared with the P. falciparum FCR3 strain, which does not express Pf155/RESA protein, for ability to induce TNF secretion by normal human macrophages in vitro. Synthetic peptides from the Pf155/RESA antigen ((EENV)4, (EENVEHDA)4, (DDEHVEEPTVA)3), were used in some experiments. TNF levels were measured by an immunoradiometric assay. We observed that the RESA-defective strain induces lower levels of TNF after schizont rupture than the SGE1 strain. Moreover, substantial TNF secretion was detected when macrophages were incubated with all three peptides, maximum levels being obtained with the (EENV)4 peptide. Although previous reports have described TNF-inducing activity of phospholipid from P. falciparum, these findings strengthen the evidence for Pf155/RESA antigens also being involved in TNF production during malaria.
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PMID:Ring-infected erythrocyte surface antigen (Pf/155RESA) induces tumour necrosis factor-alpha production. 768 75


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