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Query: UMLS:C0024530 (malaria)
 44,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To investigate whether soluble Plasmodium falciparum antigens possess endotoxin-like properties, the interaction of Limulus amoebocyte lysate (LAL) with defined soluble antigens from Plasmodium falciparum was studied by various crossed immunoelectrophoretic methods and immunoblotting. The soluble P. falciparum antigens were purified by affinity chromatography using human IgG from malaria-immune adults as ligand. Of eight possible antigens, at least three were affected by LAL, as indicated by disappearance of these antigens in the precipitation pattern, after the reaction with LAL. One of the LAL-reactive antigens is a heat-stable glycoprotein with the presence of both hydrophilic and hydrophobic regions in its structure. This antigen shows a strong reaction with polymyxin B, and antibodies against it have been shown to be inhibitory to the growth of P. falciparum in culture. It is concluded that LAL reacts with several soluble antigens from P. falciparum and it is suggested that these antigens participate in the induction of protective immunity to malaria, and consequently that one or more of the soluble antigens are candidates for a malaria vaccine.
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PMID:Demonstration of soluble Plasmodium falciparum antigens reactive with Limulus amoebocyte lysate and polymyxin B. 306 30

A murine monoclonal antibody has been used to characterise a 45,000 Da antigen that is associated with the surface membrane of merozoites of the human malaria parasite Plasmodium falciparum. The antigen is a glycoprotein and incorporates myristic acid.
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PMID:Studies on glycoproteins in the human malaria parasite Plasmodium falciparum. Identification of a myristilated 45kDa merozoite membrane glycoprotein. 332 10

Vaccination trials have shown that a purified, 74 kDa glycoprotein, GP74, isolated from the host cell membrane of Plasmodium knowlesi-infected rhesus erythrocytes, can provide protective immunity against P. knowlesi malaria. We have extended this work by a tryptic peptide analysis of the disposition of GP74 in the host cell membrane. Of the 18 peptides characterized by high-performance liquid chromatography only four were accessible to lactoperoxidase-catalyzed radioiodination of non-leaky, schizont-infected host cells from the extracellular space. Metabolic labeling with radioactive glucosamine indicates that two of the surface exposed peptides are glycopeptides, and one of these, peptide 12 appears to carry a dominant antigenic site, according to its reactivity with immunoglobulin from sera of monkeys protected against P. knowlesi malaria.
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PMID:Membrane orientation and antigenic peptides of an immunoprotective 74 kDa Plasmodium knowlesi glycoprotein. 373 96

The protozoan parasite Trypanosoma brucei is transmitted between mammalian hosts by the tsetse fly (Glossina spp.). Trypanosomes ingested by the fly undergo a number of changes in the insect midgut during differentiation to procyclic forms. These include the loss of the variant specific glycoprotein (VSG) coat and the appearance of a common set of procyclic surface antigens. In order to investigate genes other than VSG genes which are expressed only at certain stages of the life cycle, the first cDNA specific to procyclic culture form trypanosomes (equivalent to the stage found in the insect midgut) has been characterized. The encoded polypeptide shows several characteristics of membrane proteins, but its most striking feature is the presence of a repetitive amino-acid sequence in which there are 22 tandem repeats of the dipeptide-Glu-Pro-. Related genes are also found in other trypanosome species and in leishmania. This gene shows many similarities to a number of surface antigen genes described in malaria and, more recently, Trypanosoma cruzi. This is the first example of a repetitive sequence in a parasite protein which is present only in the insect vector, and which therefore cannot be implicated in the mammalian host immune response.
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PMID:Expression of a polypeptide containing a dipeptide repeat is confined to the insect stage of Trypanosoma brucei. 380 22

Monoclonal antibodies (MAbs) which are reactive with several antigenically distinct variable antigen types were prepared by immunization with Trypanosoma brucei rhodesiense. Certain MAbs were shown to be specific for members of the genus Trypanosoma and not reactive with Leishmania spp. or Plasmodium falciparum by the indirect immunofluorescence assay. These genus-specific MAbs were used to identify the molecular location of these invariant antigen determinants in whole T. brucei rhodesiense antigen preparations. Two monoclonals reacted with a low-molecular-weight doublet of approximately 22,000 relative molecular weight on Western blots of whole trypanosome antigen preparations separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These determinants did not appear to be on the variable surface glycoprotein molecule and were destroyed by trypsin digestion. Binding studies in which live, DEAE-purified, bloodstream trypanosomes were exposed to invariant antigen-specific MAbs suggested these determinants were accessible on living trypanosomes. Genus-specific MAbs also reacted with determinants present in sera from African trypanosomiasis patients in a dot immunobinding assay but not sera from patients with malaria or leishmaniasis. These results suggest that certain invariant molecules of African trypanosomes are immunogenic, possibly accessible on the trypanosome surface, and may be present as circulating invariant antigen in trypanosomiasis patients.
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PMID:Molecular identity and location of invariant antigens on Trypanosoma brucei rhodesiense defined with monoclonal antibodies reactive with sera from trypanosomiasis patients. 390 17

The aim of this article is to review the role of monoclonal antibodies as a tool in malaria research. In particular we concentrate on a monoclonal antibody directed against a functional epitope on the merozoite surface. This antibody blocked the invasion of merozoites into the red blood cells by causing agglutination of the parasite. The antigenic determinant recognized by this mcAb, 13C11, is located on a major 230 K dalton glycoprotein of the mature Plasmodium knowlesi parasite. Using the 13C11 monoclonal antibody it was possible to follow the synthesis and insertion of this glycoprotein into the schizont membrane. The relation between the intraerythrocyte schizont and the extraerythrocyte merozoite components recognized by the 13C11 were defined. Furthermore, 13C11 was used to analyze the processing of the 230 Kd plasma-membrane component to lower molecular weight products which were present on the surface of the invasive merozoite and which might play a role in the invasion process.
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PMID:Monoclonal antibodies. A tool in malaria research. 608 4

During malaria and other infections, the plasma concentration of alpha 1-acid glycoprotein (AGP) increases 3- to 4-fold, but the function of this glycoprotein has been unknown. This study demonstrates, by in vitro culture of the malaria parasite Plasmodium falciparum, that the AGP concentration achieved during malaria is sufficient to inhibit parasite multiplication by 80%. It was found that the inhibitory activity of AGP depends on and is a function of its sialic acid complement (12-16 mol/mol) and its higher-order structure. AGP acts by blocking parasite-erythrocyte interaction during the invasion process. These findings indicate a function for AGP with definite in vivo significance. Moreover, they reveal an important protective response to malaria and perhaps other infectious diseases.
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PMID:Control of malaria virulence by alpha 1-acid glycoprotein (orosomucoid), an acute-phase (inflammatory) reactant. 635 Oct 60

The sixth meeting of the Scientific Working Group on the Immunology of Malaria reviewed studies on the identification and analysis of malarial antigens of asexual blood stages and sexual stages (gametes, zygotes, ookinetes) that may be exploited as targets for vaccination. Several proteins have been identified on the surface of mature schizonts and free merozoites, some of which can be recognized by antibodies which block in vitro parasite growth. Immunization of rodents and monkeys with purified antigens from the parasite surface membrane has conferred substantial immunity against subsequent challenge. A new class of malarial antigens has been identified which bind specifically to glycophorin, the major erythrocyte glycoprotein; these antigens are on the merozoite surface and it is possible that they mediate attachment to erythrocytes. Antibodies against these proteins also block parasite growth in vitro. The Plasmodium falciparum S-antigens have been characterized biochemically and the genes for two of these proteins sequenced. Several antigens have been localized in the invasion process, and monoclonal antibodies against these proteins block in vitro growth. Malarial antigens on the surface of P. falciparum trophozoite and schizont-infected erythrocytes may be involved in the cytoadherence of infected erythrocytes to endothelial cells. Surface antigens on gametes and zygotes of P. gallinaceum and P. falciparum have been shown to be the targets of transmission-blocking immunity. Monoclonal antibodies specific for these antigens block fertilization in the mosquito midgut. Transmission of P. gallinaceum can also be blocked by an antibody that blocks development of zygotes into ookinetes. Studies on the transmission of P. yoelii have identified a gamete protein that immunizes mice against transmission to mosquitos.
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PMID:Recent progress in the development of malaria vaccines: memorandum from a WHO meeting. 639 15

Membrane glycoprotein synthesis by Plasmodium falciparum was determined by metabolic labelling in the presence of 74 kBq/ml (2.5 muCi/ml) glucosamine-(3)H. Five major glycoprotein bands and four minor ones were demonstrated. A control experiment using normal, outdated, human erythrocytes indicates that there was no incorporation of the labelled glucosamine into the erythrocyte membrane. It was also demonstrated that the rate of membrane glycoprotein synthesis by mature parasites of the trophozoite and schizont stages was twice that of the ring-stage parasites. Cytochemical surface-labelling experiments had led to the conclusion that the membrane of malaria parasites contains little or no glycoprotein. Our studies indicate, however, that there is significant synthesis of membrane glycoprotein by the parasite and that this can be metabolically labelled and measured by using radioactive glucosamine as precursor of the glycoprotein.
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PMID:Labelling of membrane glycoproteins of cultivated Plasmodium falciparum. 699 92

The surface proteins and glycoproteins of red cells from Plasmodium berghei-infected blood have been radio-isotope labelled and compared with those of normal mouse erythrocytes using the following protein labelling probes: lactoperoxidase-catalysed radio-iodination of tyrosyl residues, periodate oxidation and NaB3H4 reduction of sialic acid and oxidation of galactosyl/N-acetylgalactosaminyl residues by galactose oxidase with subsequent NaB3H4 reduction. During P. berghei infection, new tyrosyl-labelled proteins with apparent molecular weights (Mr) of 60 000, 54 000, 40 000 and 27 500 appeared on the surface of most, if not all, red cells in the blood. Purified multinucleate cells (mostly reticulocytes) differed only in that they also had a surface protein with Mr of 83 000. However, this molecule is thought to be specific to mouse reticulocytes rather than derived from parasites. In contrast to the relatively minor changes detected with radio-iodination, striking changes in glycoprotein radio-isotope labelling resulted from infection. All of the red cells in infected blood of greater than 20% parasitaemia lost their periodate-sensitive glycoprotein sialic acid. With some samples there was little change in glycoprotein labelling by the galactose oxidase method, provided neuraminidase was also added. Modification of the exocyclic hydroxyls of sialic acid is postulated to account for this. Other blood samples exhibited a dramatic loss of galactose oxidase-dependent labelling. It is suggested that these observations may relate to the excessive red cell destruction of uninfected as well as infminidase was also added. Modification of the exocyclic hydroxyls of sialic acid is postulated to account for this. Other blood samples exhibited a dramatic loss of galactose oxidase-dependent labelling. It is suggested that these observations may relate to the excessive red cell destruction of uninfected as well as infminidase was also added. Modification of the exocyclic hydroxyls of sialic acid is postulated to account for this. Other blood samples exhibited a dramatic loss of galactose oxidase-dependent labelling. It is suggested that these observations may relate to the excessive red cell destruction of uninfected as well as infected cells which has been inferred in many haemosporidial infections, including malaria.
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PMID:Characterization of surface proteins and glycoproteins on red blood cells from mice infected with haemosporidia: Plasmodium berghei infections of BALB/c mice. 700


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