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PubMed2002

[In vivo sensitivity of Plasmodium falciparum to amino-4-quinolines and sulfadoxine pyrimethamine in Agou (Ivory Coast)].

A comparative study of the in vivo sensitivity of Plasmodium falciparum to amodiaquine versus chloroquine has been made among children in Agou (south Côte d'Ivoire). In case of resistance to these drugs, the association of sulfadoxine-pyrimethamine was administered and followed by a J14 checking. We have noticed: (1) 8.47% of amodiaquine resistance versus 36.96% of chloroquine resistance (all these resistances are from type II), (2) a good clinical efficiency of the 4 amino quinolines. Only 1.69% of the subjects having resistant stocks to amodiaquine have gone feverish down to J7 whereas 10.47% of subjects have clinically resisted to chloroquine, (3) a good tolerance of drugs and an excellent clinical and parasitological efficiency of the second intention treatment. These data are in favour of using first the 4 amino quinolines (particularly the amodiaquine) in the treatment of simple bout of malaria to Plasmodium falciparum in this region. In case of resistance to these drugs, we recommend the combination sulfadoxine-pyrimethamine.

Adolescent↗
PubMed1988

Stage-dependent processing and localization of a Plasmodium falciparum protein of 130,000 molecular weight.

A Plasmodium falciparum protein of 130,000 molecular weight (m.w.) has been identified, cloned in Escherichia coli, and completely sequenced (Kochan et al. 1986). The protein appeared to bind to soluble glycophorin, a host erythrocyte surface protein. In the present study, extracts of parasites from different intraerythrocytic stages were immunoblotted with antibodies, raised against a 30,000 m.w. fusion protein corresponding to the 3' end of the 130,000 m.w. protein. It was demonstrated that the protein is synthesized at the trophozoite stage, accumulates at the schizont stage, and is processed at the merozoite stage to a triplet of three polypeptides. The processed proteins are present in the culture supernatant at the time of merozoite burst from the red cell. Immunofluorescent staining of the parasite at different intracellular stages indicates that the protein is localized on the parasite at the trophozoite stage. At late trophozoite stage, it appears to be transported to the erythrocyte cytoplasm, where it is present in small vesicles or inclusions. In mature schizonts the protein accumulates around the plasma membrane of the erythrocyte. At the segmenter stage, just prior to merozoite release, it appears also to surround the intracellular merozoite, as well as the erythrocyte plasma membrane. The soluble 130,000 m.w. protein binds to erythrocytes but binds significantly greater to erythrocyte membranes, suggesting it binds to an internal domain of glycophorin rather than the domain exposed on the surface. The 130,000 m.w. protein is present in 11 different geographic isolates of P. falciparum from diverse geographic origins. Its molecular weight is similar in all isolates.

Animals↗
PubMed1985

Sensitivity of Plasmodium falciparum to antimalarial drugs in Colombia.

Sensitivity of Plasmodium falciparum to several antimalarial drugs was determined by in vitro and in vivo tests. Chloroquine resistance in vitro was detected in 97 of 101 patients from different geographic areas of Colombia. Sensitivity to amodiaquine in vitro was observed in 29 of 30 P. falciparum isolates. In vitro sensitivity to amodiaquine was observed in 16 patients infected with chloroquine-resistant P. falciparum. In vitro sensitivity to quinine was demonstrated in 57 P. falciparum isolates. Two infections from the Amazon base (2/24) were resistant to mefloquine in vitro at concentrations of 5.7 and 16 pmol/well. Resistance to Fansidar, a sulfadoxine-pyrimethamine combination, was described in 9 patients from the Amazon region. One patient showed recrudescence of the infection 41 days after treatment. The current distribution and degree of resistance of P. falciparum to widely used antimalarial drugs requires the evaluation of therapeutic schemes based on combinations of fast blood schizontocides with slow acting drugs. These associations may reduce the development of multidrug-resistant isolates and retard the spread of resistant populations of P. falciparum parasites.

Amodiaquine↗
PubMed1991

7H8/6, a multicopy DNA probe for distinguishing isolates of Plasmodium falciparum.

A method using DNA fingerprinting to distinguish Plasmodium falciparum isolates has been developed using a clone, 7H8/6, isolated by screening a genomic expression library of the Malayan Camp strain with a monoclonal antibody. Unlike other P. falciparum DNA probes that contain internally repetitive sequences, this probe contains a single full-length open reading frame and lacks any repetitive sequences. Chromosome mapping located the hybridizing sequences to most chromosomes. 7H8/6 sequences are located at sites near the subtelomeric regions, although they are further from the telomeres than the subtelomeric repetitive sequences rep20. The probe gave multiple polymorphic bands on Southern blots of genomic DNA allowing all unrelated isolates tested to be readily distinguished. Hybridization patterns of parent and progeny from the genetic cross of two P. falciparum clones showed that most bands were inherited independently and no new bands were generated during the cross. This probe is useful for distinguishing isolates of P. falciparum and also for analyzing relationships between closely related isolates.

Animals↗
PubMed1993

In vitro sensitivity of southern African isolates of Plasmodium falciparum to halofantrine.

Twenty southern African isolates of Plasmodium falciparum and a 'control' Gambian strain were tested in vitro for their sensitivity to halofantrine. The concentration required to inhibit 50% of parasite growth, the IC50, ranged from 0.039 to 15.000 nmol/litre, with a mean of 4.619 nmol/litre. These IC50 values were comparable with those obtained in studies carried out in West Africa but were higher than the IC50 of South-East Asian isolates. All 21 isolates examined in the present study had minimum inhibitory concentrations (MIC) of 32 nmol/litre or less, with a median MIC value of 8 nmol/litre. Halofantrine was equally active against chloroquine-sensitive and chloroquine-resistant isolates and was also active against pyrimethamine-resistant strains. Indications are that this drug would be suitable for the treatment of P. falciparum malaria in the southern African region.

Africa, Southern↗
PubMed2001

Prevalence of polymorphisms in the dihydrofolate reductase and dihydropteroate synthetase genes of Plasmodium falciparum isolates from southern Mauritania.

The increasing resistance of Plasmodium falciparum in the treatment of uncomplicated malaria with pyrimethamine/sulphadoxine has been associated in several studies with the occurrence of point mutations in the genes of dihydrofolate reductase (DHFR) and dihydropteroate synthetase (DHPS). In this study, the prevalence of these mutations was examined in samples from south-east Mauritania, where atypically strong rainfalls in 1998 and 1999 led to a severe outbreak of falciparum malaria. We analysed 386 samples by polymerase chain reaction (PCR) for infection with P. falciparum, of which 162 (41.97%) were positive. These isolates were examined for point mutations in the genes of DHFR (codons 16, 51, 59, 108 and 164) and DHPS (codons 436, 437, 540, 581 and 613) by nested PCR and subsequent mutation-specific restriction enzyme digest. We found a low overall prevalence of DHFR gene mutations (up to 18.6% of isolates), but a high overall prevalence of DHPS gene mutations (up to 49.1% of isolates). Thus, emerging resistance to antifolate drugs may be expected to develop soon in the investigated area. This study demonstrates the utility of simple, relatively rapid and inexpensive molecular methods and their application in surveillance programmes. Testing for prevalence of point mutations conferring antifolate resistance might help to identify the developing of drug resistance at a very early stage.

Adolescent↗
PubMed2006

Protein targeting to destinations of the secretory pathway in the malaria parasite Plasmodium falciparum.

The secretory pathway in the malaria parasite Plasmodium falciparum has many unique aspects in terms of protein destinations and trafficking mechanisms. Recently, several exciting insights into protein trafficking within this intracellular parasite have been unveiled: these include signals that are required for targeting of proteins to the red blood cell and the relict plastid (known as the apicoplast); and the elucidation of the pathways of the haemoglobin proteases targeted to the food vacuole. Protein-targeting to the apical organelles in P. falciparum, however, is still not very well understood, but available research offers a tantalising glimpse of the system.

Animals↗
PubMed1983

Isolation and characterization of the plasma membrane of human erythrocytes infected with the malarial parasite Plasmodium falciparum.

Human erythrocytes infected with the malarial parasite Plasmodium falciparum were labeled metabolically with a mixture of 15 radioactive amino acids. When synchronously growing parasites were at the schizont stage of development infected cells were concentrated and purified by using a Percoll-Hypaque gradient. The plasma membrane of the infected erythrocyte, isolated by binding cells to a solid support (Affi-Gel 731, Bio-Rad), was less than 1% contaminated with parasite membranes. Erythrocyte membrane proteins were analyzed by polyacrylamide gel electrophoresis and autoradiography. Despite the high sensitivity of the procedure, there was no evidence for the insertion of parasite proteins into the infected host cell membrane. One possible exception is a Mr 230,000 parasite protein present maximally as 9,000 copies per infected erythrocyte membrane. Moreover, no differences in the membrane proteins were observed between a highly knobby clone and a knobless clone of the same strain of P. falciparum. These findings appear to rule out the presence of parasite protein(s) playing a structural role in the formation of knobs on the erythrocyte surface and question whether the antigenic determinants on the P. falciparum-infected erythrocyte are of parasite origin or whether such antigens represent newly exposed or chemically modified erythrocyte determinants.

Erythrocyte Membrane↗
PubMed2005

Fibrinolytic activity in children with Plasmodium falciparum malaria.

BACKGROUND: Malaria infection is still one of the major causes of morbidity and mortality among the under five year children in tropical Africa. Clinical and laboratory methods of assessing the risk factors for severity in order to adequately manage these children, therefore needs to be identified so that prompt and adequate treatment can be instituted early. Fibrinolytic activity has been postulated as one of the risk factors associated with severity of malaria infection. OBJECTIVE: To measure fibrinolytic activity euglobulin lysis time, (ELT) and fibrinogen levels in 50 Nigerian children with Plasmodium falciparum infection. DESIGN: A cross sectional study. SETTING: University of Benin Teaching Hospital, Benin City, Nigeria between January and December 2002. SUBJECTS: Fifty Nigerian children who were admitted with Plasmodium falciparum malaria infection in the paediatric wards of the hospital were recruited into the study. Thirty-four apparently healthy children who did not have malaria fever but who came for growth monitoring exercise and had some investigations done as part of this exercise were used as control for the study. The fibrinolytic activity in all the 84 children (both that had malaria infection and those who did not have malaria infection) were estimated by measuring the euglobulin lysis time (ELT). The fibrinogen levels in all the children were also estimated. The packed cell volume of the children was determined and some severely anaemic children had blood transfusions. RESULTS: Euglobin lysis time (ELT) was found to be higher in children with Plasmodium falciparum malaria infection (430 +/- 149) than in the controls (158 +/- 21.7, P< 0.01). Fibrinogen levels of 3.40 +/- 0.98 in children with malaria infection were high when compared to 2.21 +/- 0.81 in the controls. The children with malaria infection therefore had a decreased fibrinolytic activity and a proportionately high fibrinogen level. The average packed cell volume of the children with malaria infection was 29.64 +/- 2.13 while in the control it was 36.41 +/- 3.24. The study also showed that 50% of children with malaria had severe anaemia and subsequently had blood transfusions. Twenty percent of those who had transfusions died while being transfused. CONCLUSION: Children who have malaria infection have decreased fibrinolytic activity and proportionately high fibrinogen level which may contribute to the possible thromboembolic process in these children and hence higher risk of mortality from Plasmodium falciparum malaria infection.

Blood Coagulation Tests↗
PubMed2001

Partial purification of mitochondrial DNA topoisomerase II from Plasmodium falciparum and its sensitivity to inhibitors.

Mitochondria of Plasmodium falciparum (K1 strain) were isolated by differential centrifugation. Mitochondrial DNA topoisomerase II from P. falciparum was partially purified using fast protein liquid chromatography(FPLC). Parasite mitochondria contained approximately 8% of DNA topoisomerase II activity compared with its nuclear fraction. The effects of fluoroquinolones, inhibitors of bacterial DNA topoisomerase II or DNA gyrase, against partially purified P. falciparum mitochondrial DNA topoisomerase II were investigated using a decatenation assay. Minimum inhibitory concentrations (MIC) of ofloxacin, ciprofloxacin and norfloxacin were > 1, 10 and 100 mM, compared with that of >0.5 and 10 mM for eukaryotic DNA topoisomerase II inhibitor etoposide (VP-16) and amsacrine, respectively. The results indicate that partially purified mitochondrial DNA topoisomerase II was insensitive to fluoroquinolones and it is suggested that their inhibitory effects on P. falciparum growth may be directed against plastid DNA topoisomerase II.

Animals↗
PubMed1998

Transport and metabolism of the essential vitamin pantothenic acid in human erythrocytes infected with the malaria parasite Plasmodium falciparum.

The growth of the human malaria parasite, Plasmodium falciparum, within its host erythrocyte is reliant on the uptake of a number of essential nutrients from the extracellular medium. One of these is pantothenic acid, a water-soluble vitamin that is a precursor of coenzyme A. In this study we show that normal uninfected erythrocytes are impermeable to pantothenate but that the vitamin is taken up rapidly into malaria-infected cells via a transport pathway that has the characteristics (furosemide sensitivity, nonsaturability) of previously characterized, broad specificity permeation pathways induced by the intracellular parasite in the host cell membrane. The transport of pantothenate therefore constitutes a critical physiological role for these pathways. Inside the parasitized cell pantothenate undergoes phosphorylation, the first step in its conversion to coenzyme A. Parasites within saponin-permeabilized erythrocytes were shown to take up and phosphorylate pantothenate, consistent with the intracellular parasite having both a pantothenate transporter and a pantothenate kinase. Comparisons of the rate of phosphorylation of pantothenate by lysates prepared from uninfected and infected erythrocytes revealed that the pantothenate kinase activity of the P. falciparum trophozoite is some 10-fold higher than that of its host cell and that most, if not all, of the phosphorylation of pantothenate within the malaria-infected cell occurs within the intracellular parasite. These results contrast with those of previous studies in which it was proposed that the avian malaria parasite Plasmodium lophurae lacks pantothenate kinase (as well as the other enzymes for the synthesis of coenzyme A) and is reliant upon the uptake of preformed coenzyme A from the host cell cytosol.

Animals↗
PubMed1996

[Immunogenicity of recombinant S. typhimurium ex. pressing a hybrid antigen of Plasmodium falciparum].

We have expressed a 74-peptide hybrid Plasmodium falciparum antigen as fusion protein in attenuated Salmonella typhimurium SL3261. Live organisms were orally immunized Rabbits with a dose of 2 x 10(9)cfu. Specific anti-serum were detected by ELISA after immunization. Obvious Delayed type hypersensitivity (DTH) could be induced by PfAg and GZ-C antigen. The recombinant vaccine had no evident side-effects to the hosts. Our studies indicate that attenuated Salmonella typhimurium SL3261 can express synthetic P. falciparum antigen with several epitopes and live organisms can activate special cell-mediated immunity and humoral immunity.

Animals↗
PubMed1988

The three 5S rRNA genes from the human malaria parasite Plasmodium falciparum are linked.

5S rRNA and rDNA from Plasmodium falciparum have been characterized. The 5S rRNA transcripts isolated from erythrocytic stage parasites are composed of three distinct subclasses, 117-119 nucleotides in length, which are identical in sequence with the exception of one or two additional uridine residues at the 3' terminus. Southern blot analysis of genomic DNA identified three 5S rRNA gene classes which are clustered within 1.5 kb of DNA. Cloning and sequence analyses of the 5S rDNA revealed identical coding regions surrounded by divergent extremely A+T rich flanking sequences (greater than 90%). Typical PolIII termination signals (6-8) T residues abut each coding region. Copy number analysis indicates that P. falciparum contains only three 5S rRNA genes, the lowest number reported for any organism.

Animals↗
PubMed1993

Drug resistance and the P-glycoprotein homologues of Plasmodium falciparum.

The chloroquine resistance phenotype of Plasmodium falciparum shares many similarities to multi-drug resistance in tumour cells and this has led to the identification of two mdr-like genes (pfmdr1, pfmdr2) from this human pathogen. The pfmdr1 gene has been linked to the chloroquine resistance phenotype, although a genetic cross appears to contradict these results. Analysis of drug resistant mutants selected in vitro has shown that the level of expression of the pfmdr1 gene can affect resistance to chloroquine, mefloquine, halofantrine and quinine. Mefloquine isolates from the field appear to always contain amplified levels of the pfmdr1 gene and also overexpress the transcript. They are also resistant to halofantrine suggesting a true multi-drug resistant phenotype.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

Serum protein concentrations in Plasmodium falciparum malaria.

In patients with uncomplicated Plasmodium falciparum infection cytokine-mediated serum protein levels of C-reactive protein (CRP), coeruloplasmin (COE), beta 2-microglobulin (B2M), alpha 1-acid glycoprotein (AAG), alpha 1-antitrypsin (AAT), haptoglobin (HPT), prealbumin (PRE), retinol binding protein (RBP), albumin (ALB) and transferrin (TRF) were measured in an endemic area of the Amazonian rain forest. Semi-immune (SI) and nonimmune (NI) patients were investigated. In both patient groups the serum concentrations of CRP, COE and B2M were elevated on admission. In addition AAG and AAT concentrations were increased in NI patients compared to control subjects. Significantly lower serum concentrations of HPT, PRE, RBP, ALB and TRF were seen in both patient groups during the acute phase of the disease, and were more pronounced in NI patients. After a 28-day follow-up, AAT and B2M were normal in SI patients but HPT, AAT and B2M were still significantly altered in NI patients.

Acute-Phase Proteins↗
PubMed2005

Naturally acquired immunity to Plasmodium falciparum malaria in Africa.

Infection by Plasmodium falciparum parasites can lead to substantial protective immunity to malaria, and available evidence suggest that acquisition of protection against some severe malaria syndromes can be fairly rapid. Although these facts have raised hopes that the development of effective vaccines against this major cause of human misery is a realistic goal, the uncertainty regarding the antigenic targets of naturally acquired protective immunity and the immunological mechanisms involved remain major vaccine development obstacles. Nevertheless, a coherent theoretical framework of how protective immunity to P. falciparum malaria is acquired following natural exposure to the parasites is beginning to emerge, not least thanks to studies that have combined clinical and epidemiological data with basic immunological research. This framework involves IgG with specificity for clonally variant antigens on the surface of the infected erythrocytes, can explain some of the difficulties in relating particular immune responses with specificity for well-defined antigenic targets to clinical protection, and suggests a radically new approach to controlling malaria-related morbidity and mortality by immunological means.

Africa↗
PubMedDate not supplied

Comparative evaluation of four techniques for the diagnosis of Plasmodium falciparum infections.

Four diagnostic techniques for Plasmodium falciparum infection were evaluated against serial parasite dilutions and on identical field samples. These were (i) Giemsa-stained thick blood films (GTF), (ii) acridine orange-stained thick (AOTF) and thin (AOTnF) blood films, (iii) the quantitative buffy coat technique (QBC); and (iv) the ParaSight-F dipstick test (PS). PS had a consistently higher sensitivity and speed, was easiest to learn, and required no laboratory facility. The 100% sensitivity cut-off points against known parasite densities (per mm3) were: PS, 30; GTF, 84; QBC, 84; AOTnF, 84; AOTF, 149. In the field study, test sensitivities compared with examination of 800 microscope fields of a Giemsa-stained thin blood film were PS, 96.6%; AOTF, 93.1%; GTF, 91.4%; QBC, 89.7%; AOTnF, 82.8%. In the dilution study, one false positive result was recorded with QBC; in the field study there was one false positive each with PS, AOTnF and AOTF. When a newly trained microscopist examined samples of the parasite dilutions, the 100% sensitivity cut-off points were AOTF, 84; GTF, 140; QBC, 390. Total handling time was shortest with PS regardless of whether samples were processed individually or in batches of 10 or 100. The ParaSight-F test is recommended as the diagnostic tool for the future.

Enzyme-Linked Immunosorbent Assay↗