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)

During the characterization of malaria vaccine candidate proteins, three metalloproteinases having a molecular mass of 220, 95 and 70 kDa were found to be co-isolated with the rhoptry-associated protein-1 (RAP-1) complex, but not with RAP-3 or gp195. These enzymes were also found in detergent extracts of saponin-lysed Plasmodium falciparum. Of nine proteinase inhibitors tested, only EDTA was found to abrogate activity. Dose-dependent curves were determined for several metal ions and cobalt was found to synergistically enhance enzyme activity. The gelatinases were immunoprecipitated with monospecific polyclonal antisera to macrophage and fibroblast gelatinase; however, these sera did not react with intracellular parasites by indirect immunofluorescence. These results indicate that the matrix metalloproteinases co-isolated with RAP-1 originate from human serum used to cultivate P. falciparum in vitro.
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PMID:Three matrix metalloproteinases form a non-covalent association with the rhoptry-associated protein-1 of Plasmodium falciparum. 147 99

A non-polymorphic antigen associated with the rhoptry organelles of Plasmodium falciparum has been purified by immunoaffinity chromatography. The antigen, RAP-1 (rhoptry associated protein-1), which is defined by monoclonal antibodies which inhibit parasite growth in vitro, is a multi-component antigen consisting of four major proteins of 80, 65, 42 and 40 kDa and two minor proteins of 77 and 70 kDa. These proteins were electro-eluted from preparative sodium dodecyl sulphate polyacrylamide gels and protected Saimiri sciureus monkeys from a lethal blood-stage infection of P. falciparum malaria. Sera from the protected animals recognized only proteins of the RAP-1 antigen when used to probe a Western blot of total parasite protein extract, confirming that RAP-1 is responsible for eliciting the protective immune response.
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PMID:A rhoptry antigen of Plasmodium falciparum is protective in Saimiri monkeys. 226 13

A well conserved 83-kDa apical membrane antigen of Plasmodium falciparum, PF83/AMA-1, is the analogue of PK66/AMA-1, a 66-kDa P. knowlesi protective merozoite protein. PK66/AMA-1 is expressed in late-stage schizonts; is localized within the merozoite apex; and is processed to a 44/42-kDa doublet at, or around, the time of schizont rupture. The processed forms can associate with the merozoite surface. We were interested to further analyze the timing of synthesis and processing, and subcellular localization of PF83/AMA-1, a malaria vaccine candidate, using monoclonal antibodies (mAbs) developed against PF83/AMA-1. Using [35S]methionine metabolically labeled asexual blood stage parasites, in combination with indirect single and dual immunofluorescence, we have determined that, in similar fashion to PK66/AMA-1, protein expression of PF83/AMA-1 is restricted to late-stage schizonts with greater than 8 nuclei. PF83/AMA-1 is post-synthetically processed rapidly by cleavage of an N-terminal peptide to a 66-kDa molecule. Both the 83- and the 66-kDa molecules are initially localized at the merozoite apex. In P. falciparum (7G8 strain and CVD-1 clone) the full-length 83-kDa molecule remains apically restricted following merozoite release. However, the processed 66-kDa form can become circumferentially associated with the merozoite surface at or around the time of schizont rupture and merozoite release. After merozoite invasion a processed form of PF83/AMA-1 is present in early ring stage parasites. Comparative analysis of a rhoptry associated protein RAP-1, shows a co-ordinated and compartmentalized release of rhoptry components.
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PMID:Differential localization of full-length and processed forms of PF83/AMA-1 an apical membrane antigen of Plasmodium falciparum merozoites. 783 84

The merozoite proteins merozoite surface protein 1 (MSP-1) and rhoptry-associated protein 1 (RAP-1) and synthetic peptides containing sequences of MSP-1, RAP-1, and erythrocyte-binding antigen 1, induced in vitro proliferative responses of lymphocytes collected from Ghanaian blood donors living in an area with a high rate of transmission of malaria. Lymphocytes from a large proportion of the Ghanaian blood donors proliferated in response to the RAP-1 peptide, unlike those of Danish control blood donors, indicating that this sequence contains a malaria-specific T-cell epitope broadly recognized by individuals living in an area with a high transmission rate of malaria. Most of the donor plasma samples tested contained immunoglobulin G (IgG) and IgM antibodies recognizing the merozoite proteins, while only a minority showed high IgG reactivity to the synthetic peptides.
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PMID:Specific T-cell recognition of the merozoite proteins rhoptry-associated protein 1 and erythrocyte-binding antigen 1 of Plasmodium falciparum. 841 48

Mice and rabbits immunized with recombinant forms of malaria vaccine candidate antigens rhoptry-associated proteins 1 and 2 (RAP-1, RAP-2 and rRAP-1, rRAP-2) produce antibodies at titres equivalent to monoclonal antibody ascites fluid raised against the native proteins. Sera from animals immunized with rRAP-1 contain antibodies which recognize the native protein by indirect immunofluorescence and immunoblotting, partially inhibit erythrocyte invasion in vitro and are long lasting. Epitope mapping shows these antibodies predominantly recognize epitopes in the N-terminal third of rRAP-1, some of which coincide with the targets of inhibitory monoclonal antibodies. By contrast, sera from animals immunized with rRAP-2 contain antibodies which recognize the recombinant but not the native protein.
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PMID:Immunogenicity of recombinant Plasmodium falciparum rhoptry associated proteins 1 and 2. 883 63

Naturally occurring antibody responses to Plasmodium falciparum rhoptry-associated proteins 1 and 2 (RAP-1 and RAP-2) were measured with recombinant and parasite-derived forms of the antigens. For comparative purposes, responses to multiple forms of three other malarial antigens were also examined. The sera of 100 Papua New Guineans were screened for antibodies. Eighty-six and 82% of individuals over 30 years of age had antibodies that recognized parasite-derived RAP-1 and RAP-2, respectively. Importantly, we found that recombinant and native antigens share linear epitopes seen by the human immune system; thus, the recombinant proteins may be adequate human immunogens. However, antibodies affinity purified on recombinant RAP-1 reacted with other antigens in addition to parasite-derived RAP-1. Thus, the antigenicity of RAP-1 may have been overestimated previously. The recognition of RAP-1 and RAP-2 correlated with age and with the recognition of recombinant forms of the ring-infected erythrocyte surface antigen, merozoite surface protein 1, and merozoite surface antigen 2 (MSA2) antigens. Antibodies to these antigens appear to be generated in response to the total exposure to malaria of the host. Antibodies to conserved regions of MSA2 had stronger correlations with both age and the recognition of other antigens than did the full-length recombinant MSA2 molecule. In contrast to results with the other antigens, there was no significant difference in the ages of individuals with a certain antibody titer to the full-length recombinant or parasite-derived MSA2 molecule, but antibodies to these two antigens did correlate with parasitemia. For all antigens tested, antibody levels after two infections can approach the peak levels of antibodies obtained in immune individuals.
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PMID:Assessment of the humoral immune response against Plasmodium falciparum rhoptry-associated proteins 1 and 2. 916 71

The frequency and level of cellular and humoral responses to seven synthetic peptides from asexual blood stages of Plasmodium falciparum were measured in two cohorts of children living in areas highly endemic for malaria in Gabon and Cameroon. A prospective longitudinal study was conducted for one year in these sites to examine the relationship between specific in vitro immune responses and susceptibility to clinical malaria. Clinical protection was related to high proliferative responses (merozoite surface antigen-1 [MSA-1] and MSA-2 peptides) as well as to elevated antibody levels (schizont extract, MSA-2, and rhoptry-associated protein-1 [RAP-1] peptides) in the village of Dienga, Gabon. Higher response rates of interferon-gamma but lower response rates of tumor necrosis factor-alpha to four and six peptides, respectively, were observed in Dienga than in Pouma that were independent of the older age of the Gabonese children. Age accounted only for the higher prevalence rate in Dienga of the antibody responders to the peptide from Pf155/ring-infected erythrocyte surface antigen (RESA). Our results support the inclusion of epitopes from MSA-1, MSA-2, RAP-1, and Pf155/RESA antigens in a subunit vaccine against malaria, but show that a longitudinal clinical, parasitologic, and immunologic study conducted according to identical criteria in two separate areas may lead to contrasting observations, demonstrating the geographic limitation of the interpretation of such results.
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PMID:Immune responses against Plasmodium falciparum asexual blood-stage antigens and disease susceptibility in Gabonese and Cameroonian children. 1049 96

A cross-sectional sero-epidemiological study was performed in Magoda, Tanzania, an area where malaria is holoendemic. Blood samples were collected from children (1-4 years) and tested for IgG antibody reactivity against 2 recombinant protein fragments of Plasmodium falciparum Rhoptry-Associated Protein-1 (rRAP-1). The data were related to the prevalence of malarial disease and single P. falciparum or mixed Plasmodium infections. Fever (> or = 37.5 degrees C) in combination with parasite densities > 5000/microliter were used to distinguish between children with asymptomatic malaria infections and those with acute clinical disease. Furthermore, C-reactive protein (CRP) was applied as a surrogate marker of malaria morbidity. The prevalence of Plasmodium infections was 96.0%. Eleven children were defined as clinical malaria cases, all with single P. falciparum infections. The density of P. falciparum was significantly lower in children with mixed Plasmodium infections compared to those with single P. falciparum infections. Children with asymptomatic P. falciparum infections had higher IgG reactivities to rRAP-1, compared to IgG reactivities of children with malarial disease. Children with mixed Plasmodium infections generally showed elevated IgG reactivity to rRAP-1, when compared to children with single P. falciparum infections. The possible relationship between mixed species infections, clinical outcome of the disease and antibody responses to RAP-1 is discussed.
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PMID:IgG reactivities against recombinant Rhoptry-Associated Protein-1 (rRAP-1) are associated with mixed Plasmodium infections and protection against disease in Tanzanian children. 1058 10

Several human genetic factors, including red blood cell polymorphisms (ABO blood group, sickle-cell trait, G6PD deficiency) as well as point mutations in the mannose binding protein (MBP) and in the promoter regions of both the TNF-alpha and NOS2 genes, influence the severity of disease due to infection with Plasmodium falciparum. We assessed their impact on mild P. falciparum malaria, as part of a longitudinal investigation of clinical, parasitological and immunological parameters in a cohort of 300 Gabonese schoolchildren. We found the following frequencies: blood group O (0.54), sickle-cell trait (0.23), G6PD deficiency (0.09), MBP gene mutations (0.34), TNF-alpha promoter mutations (at positions -238: 0.17 and -308: 0.22) and NOS2 promoter mutation (0.18). Blood group O or hemoglobin AA were associated with protection against higher parasitemia. Girls with normal G6PD enzyme activity were protected against clinical malaria attacks. In addition, we demonstrated for the first time that the mutation at position -238 of the gene coding for the promoter region of TNF-alpha was positively correlated with the level of the antibody response specific for epitopes of the antigens MSA-2 and RAP-1 of P. falciparum.
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PMID:Human genetic factors related to susceptibility to mild malaria in Gabon. 1119 74

Monoclonal antibodies (MAbs) specific for Plasmodium falciparum rhoptry-associated protein 1 (RAP-1) were generated and tested for inhibition of parasite growth in vitro. The majority of indirect immunofluorescence assay (IFA)-positive MAbs raised against recombinant RAP-1 positions 23 to 711 (rRAP-1(23-711)) recognized epitopes located in the immunodominant N-terminal third of RAP-1. MAbs specific for the building block 35.1 of the synthetic peptide malaria vaccine SPf66 also yielded an IFA staining pattern characteristic for rhoptry-associated proteins and reacted specifically with rRAP-1 and parasite-derived RAP-1 molecules p67 and p82. Cross-reactivity with RAP-1 was blocked by the 35.1 peptide. Epitope mapping with truncated rRAP-1 molecules and overlapping peptides identified the linear RAP-1 sequence Y218KYSL222 as a target of the anti-35.1 MAbs. This sequence lacks primary sequence similarity with the 35.1 peptide (YGGPANKKNAG). Cross-reactivity of the anti-35.1 MAbs thus appears to be associated with conformational rather than sequence homology. While the anti-35.1 MAb SP8.18 exhibited parasite growth-inhibitory activity, none of the tested anti-rRAP-1(23-711) MAbs inhibited parasite growth, independently of their fine specificity for the RAP-1 sequences at positions 33 to 42, 213 to 222, 243 to 247, 280 to 287, or 405 to 446. The growth-inhibitory activity of MAb SP8.18 was, however, accelerated by noninhibitory anti-RAP-1 MAbs. Results demonstrate that in addition to fine specificity, other binding parameters are also crucial for the inhibitory potential of an antibody.
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PMID:Rhoptry-associated protein 1-binding monoclonal antibody raised against a heterologous peptide sequence inhibits Plasmodium falciparum growth in vitro. 1125 20


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