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PubMed1981

Chloroquine resistant Plasmodium falciparum infection from Lampung and South Sumatra, Indonesia.

A report was made of 4 cases of chloroquine resistant Plasmodium falciparum infections. The infections, detected in Jakarta, were imported from Kotabumi, Tanjung Karang, the Island of Pidada in the Lampung Province and from Pangkalpinang on the Island Bangka in the Province of South Sumatra. Treatment with courses of 1500 mg chloroquine base and with increased dosages up to 2250 mg base failed to cure the patients. The chloroquine sensitivity test in vitro was carried out in 3 patients, which showed that the Plasmodium falciparum strains were resistant to chloroquine at the R I level. The strains appeared to be similar to the Malaya Camp strain. In vivo observations revealed that the parasites were resistant at the R I level with a delayed recrudescence. The chloroquine resistant falciparum malaria cases, acquired in South Sumatra, may therefore be regarded as the first reported cases from a focus outside the already known two foci in Indonesia, namely East Kalimantan and Irian Jaya. It may be expected that chloroquine resistant Plasmodium falciparum will be encountered in other parts of Indonesia in the near future. The use of a combination of sulfadoxine and pyrimethamine should not be recommended in Indonesia because chloroquine is still considered the drug of choice against all malaria infections in Indonesia.

Adult↗
PubMed1980

[Experimental production of variants with lowered preference for polychromatophilic erythrocytes in Plasmodium yoelii (author's transl)].

After 25 massive passages of a Plasmodium yoelii-population (strain 17X) in the phase of high parasitization of mature erythrocytes, parasites with markedly lowered preference for immature erythrocytes could be isolated. Of 3 isolates in 3 independent experiments, one showed a distinctly lower preference than the other two. With very high infecting doses, the isolates caused in most mice high parasitization of mature erythrocytes and death. The original strain had been kept in mice by passage of a few parasites every 1--2 weeks for several months; on testing it exhibited a somewhat lower preference for immature erythrocytes and less polyparasitization of immature erythrocytes for a given multiplicity. Polyparasitization seemed to be unaltered in the 3 isolates. Antiserum against Plasmodium yoelii inhibited 2 tested isolates more than the modified original strain. These observations suggest that Plasmodium yoelii merozites may exist in several types differing in their relative affinity for mature erythrocytes, antibodies and parasitized immature erythrocytes. Different types should become predominant under different selective pressures. The different types are probably formed by mutations determining alterations in molecules of the merozoite surface.

Animals↗
PubMed1995

Mixed Plasmodium infection in rural children of Zambia.

A total of 210 blood slides from rural children in Samfya District were examined for malaria parasites. One hundred and seventy two were positive for malaria parasites giving a prevalence of 819 pc. Among the children less than one year of age, the prevalence of mixed Plasmodium infection was 124 pc. For children one year and above, the prevalence of mixed Plasmodium infection was 227 pc. There was a statistically significant difference between these two prevalence rates of mixed Plasmodium infection.

Age Distribution↗
PubMed1994

[Molecular recognition between GlcNAc and Plasmodium falciparum merozoites].

In this study p-aminophenyl-2-acetamido-2-deoxy-beta-D-glucopyranoside was bound covalently to bovine serum albumin (BSA) to form neoglycoprotein (GlcNAc-BSA). The antigenicity of BSA and the pyranose structure of the sugar was preserved. By using the neoglycoprotein antibody against BSA and staphylococcal protein A-gold (SPA-gold), Plasmodium falciparum FCC-1/HN merozoites were immunolabeled. The labelled sample was observed under transmission electron microscope (TEM). The TEM pictures showed that colloidal gold pellets were distributed all over the merozoite surface. This is the first report on the direct experimental evidence of molecular recognition between GlcNAc-BSA (or GlcNAc) and Plasmodium falciparum merozoites. But free GlcNAc or even GlcN can inhibit the immunolabeleation. The results support the hypothesis that, besides N-acetylneuraminic acid, GlcNAc is involved as another recognized site on GPA for Plasmodium falciparum. Thus we further confirmed that N-acetyl of GlcNAc is not necessary for the recognition.

Acetylglucosamine↗
PubMed1994

A species of Plasmodium from sandhill cranes in Florida.

Infections of a species of Plasmodium (subgenus Giovannolaia) were diagnosed in 3 sandhill cranes (Grus canadensis) from north-central Florida. This parasite is close morphometrically to Plasmodium polare; this finding constitutes the first report of a species of Plasmodium from sandhill cranes in North America.

Animals↗
PubMed1994

Presbytis entellus, a new experimental host for Plasmodium fragile.

The course of blood-induced Plasmodium fragile infection in 3 simian hosts, Macaca radiata (bonnet monkey), Macaca mulatta (rhesus monkey), and Presbytis entellus (Indian langur), was studied. The infection in 8 bonnet monkeys was very mild and nonfatal. In M. mulatta, P. fragile produced acute initial infection followed by anemia and death in 3 of 6 monkeys. The parasite has a relatively high level of virulence for P. entellus, a new experimental host for P. fragile, in which peak parasitemia ranging between 15 and 75% was recorded, and the infection was uniformly fatal. Plasmodium fragile infection in P. entellus can serve as an ideal biological counterpart to human Plasmodium falciparum.

Animals↗
PubMedDate not supplied

Management of chloroquine-resistant Plasmodium falciparum malaria in a pregnant Ethiopian immigrant--a case report.

Plasmodium falciparum malaria is infrequently recognized in Israel as a cause of infection during pregnancy. We expect that with increasing frequency physicians in Israel will confront patients with malaria. Special concern should be given to malaria in pregnancy because of its serious complications. Thus, prompt diagnosis and treatment are essential. While chloroquine is safe for use in pregnancy, drug resistance is common, especially with Plasmodium falciparum. There is concern about the safety of other antimalarial agents during pregnancy. We recently observed a case of chloroquine-resistant Plasmodium falciparum malaria during pregnancy in a new immigrant primigravida from Ethiopia. Malaria in patients from endemic regions is less severe than in nonimmune hosts. Therefore, we elected to follow the patient's parasitemia periodically without additional antimalarial treatment until after delivery.

Adolescent↗
PubMed1996

Structural features of the large subunit rRNA expressed in Plasmodium falciparum sporozoites that distinguish it from the asexually expressed subunit rRNA.

The developmentally regulated transcription of at least two distinct sets of nuclear-encoded ribosomal RNAs is detected in Plasmodium species. The identification of functional differences between the two sets of rRNAs is of interest. To facilitate the search for such differences, we have identified the 5.8S and 28S rRNAs from Plasmodium falciparum that are expressed in the sporozoite stage (S gene) of the parasites' life cycle in the mosquito host and compare them to transcripts expressed in the red blood cells (A gene) of the vertebrate host. This completes the first set of A- and S-type nuclear-encoded rRNA genes for a Plasmodium species. Analysis of the predicted secondary structures of the two units reveals the majority of differences between the A- and S-type genes occur in regions previously known to be variable. However, the predicted secondary structure of both 28S rRNAs indicates 11 positions within conserved areas that are not typical of eucaryotic rRNAs. Although the A-type gene resembles almost all eucaryotes, being atypical in only 4 of the 11 positions, the S gene is variant in 8 of the 11 positions. In three of these positions, the S-type gene resembles the consensus nucleotides for the 23S rRNA from Eubacteria and/or Archaea. A few differences occur in regions associated with ribosome function, in particular the GTPase site where the S-type differs in a base pair and loop from all known sequences. Further, the identification of compensatory changes at conserved points of interactions between the 5.8S-28S rRNAs indicates that transcripts from A- and S-units should not be interchangeable.

Animals↗
PubMed1996

Wistar rat-Plasmodium berghei model does not approximate human congenital malaria.

Until recently, congenital malaria was thought to be rare. Now, several reports suggest that more than 10% of newborns in some settings are parasitemic. The pathophysiology of transplacental transmission of Plasmodium is not well understood, and no animal model of congenital malaria exists. A rodent model of malaria in pregnant females, however, has been developed. In an effort to test the usefulness of this model in the study of congenital malaria, Wistar rats were injected intraperitoneally with approximately 10(6) NYU-2 strain Plasmodium berghei-infected erythrocytes at various times relative to conception. Perinatal maternal and neonatal blood was tested for the presence of parasites. Two rats infected preconceptually, 1 at 29 and the other at 11 days prior to mating, delivered aparasitemic pups. Fourteen rats were inoculated during gestation. Five of 5 rats infected on the fifth gestational day succumbed prior to delivery; 1 fetus was parasitemic. Offspring of females infected on the 9th, 10th, 12th, and 14th days of gestation were aparasitemic at birth. Four rats conceived after an initial Plasmodium infection had waned and were reinfected during pregnancy; none of their pups showed evidence of parasitemia. Thus, though rare, transplacental passage of malaria parasites can occur in rats. The Wistar rat-P. berghei model of gestational malaria, however, does not seem to be useful for the study of congenital malaria.

Animals↗
PubMed1996

Human erythroid spectrin alpha subunit and its SH3 domain are sensitive to acidic Plasmodium falciparum proteolytic activity.

Many proteases play a crucial role in the Plasmodium intraerythrocytic life cycle. Spectrin depletion, one of the major events involved in parasite release from the red blood cell, results from proteolytic activities associated with the presence of the intracellular parasite. Here, we describe a new acidic proteolytic activity from Plasmodium falciparum, whose target is the alpha-subunit of human spectrin. Immunoblotting experiments with antibodies specific for the tryptic peptides of the alpha-chain and in vitro proteolysis tests on recombinant peptides from different regions of the spectrin alpha subunit demonstrated that cleavage sites for the parasite proteolytic activity were localized within the SH3 motif of the alpha-chain sequence. Remarkably, this Plasmodium protease activity on spectrin SH3 substrate was unable to cleave the SH3 from fodrin, a non-erythroid spectrin.

Animals↗
PubMed1998

Citalopram enhances the activity of chloroquine in resistant plasmodium in vitro and in vivo.

Citalopram, is an extremely potent inhibitor of neuronal serotonin reuptake. It is structurally unrelated to other antidepressants, but it contains the chemical features associated with reversal of drug resistance and exhibits minimal cardiotoxic side effects and fewer of the anticholinergic and adrenolytic side effects associated with other psychotropic agents. Sensitivity tests to citalopram alone and in combination with chloroquine were performed against chloroquine-resistant and chloroquine-sensitive strains of Plasmodium falciparum and Plasmodium chabaudi. Citalopram alone showed intrinsic activity against the chloroquine-resistant strains of P. falciparum (IC50 = 1.51 +/- .6 microM) but only limited activity against the chloroquine-sensitive strain (IC50 = 33.27 +/- 5.87 microM) and no activity in vivo. The interaction of chloroquine and citalopram in vitro resulted in a synergistic response in the chloroquine-resistant strain but there was no interaction between the drugs in the chloroquine-sensitive strain--a pattern found with other reversal agents. Citalopram enhanced chloroquine susceptibility in both strains of P. chabaudi, however, the potentiating effect was seen at lower doses in the chloroquine-resistant strain. The results of this study suggest that citalopram may have potential as a chemosensitizer in Plasmodium infections on the basis of the low toxicity of citalopram at concentrations potentiating chloroquine activity both in vitro and in vivo.

Animals↗
PubMed1998

[ParaSight F in the diagnosis of Plasmodium falciparum malaria].

The ParaSight F is a new diagnostic test for Plasmodium falciparum infections and is based on the detection of a trophozoite-derived antigen, the histidine rich protein II (HRP-II). To assess the usefulness of this test, we conducted a prospective study and analyzed 62 blood specimens from 38 patients, using thin blood films, thick blood films and the ParaSight F test. Compared to thick blood film, on samples taken before and during treatment, the ParaSight F test had 86.4% sensitivity and 100% specificity. In 31.5% of P. falciparum infected patients, parasitemia was lower than 1 parasite/1000 red blood cells, with all specimens being positive by the ParaSight F test. In 15 cases, specimens were negative by thin blood film, but were positive by thick blood film and by the ParaSight F test. Two patients had, after their treatment was started, positive results by ParaSight F and negative results by thick blood film. Cross-reactivity occurred neither with other Plasmodium species, nor in cases of severe inflammatory syndrome. Persistence of antigenemia was monitored in 14 patients receiving quinine. At day five of treatment, antigenemia persisted in seven patients. In conclusion, the ParaSight F test does not allow following up the efficacy of treatment, identifying other Plasmodium species, or assessing parasitemia. However, because this test is easy to perform and has good sensitivity and specificity, it is a useful tool in emergent context, in cases of parasitemia lower than the thin blood film threshold, and in cases morphologically difficult to decipher.

Animals↗
PubMed1998

[Considering disparities in resistance of Plasmodium falciparum in Africa in chemoprevention decisions].

OBJECTIVES: Assess the efficacy of preventive and curative treatments of imported malaria. METHODS: The in vitro drug susceptibility of mefloquine, chloroquine and cycloguanil was determined against African isolates of Plasmodium falciparum from imported malaria cases by an isotopic in vitro test or a genomic approach. RESULTS: Plasmodium falciparum resistance to mefloquine, chloroquine or to the dihydrofolate reductase inhibitor was present in 5.2%, 46% and 42% of isolates respectively. Plasmodium falciparum drug resistance to chloroquine or antifolinics was more frequent in permanent than in seasonal malarial transmission areas. Simultaneous resistance to chloroquine and antifolinics was observed in 17% of isolates between 1991 and 1994 and in 28% between 1995 and 1997.

Africa↗
PubMed2000

Expression and one-step purification of Plasmodium proteins in dictyostelium.

Nearly full-length Circumsporozoite protein (CSP) from Plasmodium falciparum, the C-terminal fragments from both P. falciparm and P. yoelii CSP and a fragment comprising 351 amino acids of P.vivax MSPI were expressed in the slime mold Dictyostelium discoideum. Discoidin-tag expression vectors allowed both high yields of these proteins and their purification by a nearly single-step procedure. We exploited the galactose binding activity of Discoidin Ia to separate the fusion proteins by affinity chromatography on Sepharose-4B columns. Inclusion of a thrombin recognition site allowed cleavage of the Discoidin-tag from the fusion protein. Partial secretion of the protein was obtained via an ER independent pathway, whereas routing the recombinant proteins to the ER resulted in glycosylation and retention. Yields of proteins ranged from 0.08 to 3 mg l(-1) depending on the protein sequence and the purification conditions. The recognition of purified MSPI by sera from P. vivax malaria patients was used to confirm the native conformation of the protein expressed in Dictyostelium. The simple purification procedure described here, based on Sepharose-4B, should facilitate the expression and the large-scale purification of various Plasmodium polypeptides.

Animals↗
PubMed1999

Mosquito-Plasmodium interactions in response to immune activation of the vector.

During the development of Plasmodium sp. within the mosquito midgut, the parasite undergoes a series of developmental changes. The elongated ookinete migrates through the layers of the midgut where it forms the oocyst under the basal lamina. We demonstrate here that if Aedes aegypti or Anopheles gambiae, normally susceptible to Plasmodium gallinaceum and P. berghei, respectively, are immune activated by the injection of bacteria into the hemocoel, and subsequently are fed on an infectious bloodmeal, there is a significant reduction in the prevalence and mean intensity of infection of oocysts on the midgut. Only those mosquitoes immune activated prior to, or immediately after, parasite ingestion exhibit this reduction in parasite development. Mosquitoes immune activated 2-5 days after bloodfeeding show no differences in parasite burdens compared with naive controls. Northern analyses reveal that transcriptional activity for mosquito defensins is not detected in the whole bodies of Ae. aegypti from 4 h to 10 days after ingesting P. gallinaceum, suggesting that parasite ingestion, passage from the food bolus through the midgut, oocyst formation, and subsequent release of sporozoites into the hemolymph do not induce the production of defensin. However, reverse transcriptase-PCR of RNA isolated solely from the midguts of Ae. aegypti indicates that transcription of mosquito defensins occurs in the midguts of naive mosquitoes and those ingesting an infectious or noninfectious bloodmeal. Bacteria-challenged Ae. aegypti showed high levels of mature defensin in the hemolymph that correlate with a lower prevalence and mean intensity of infection with oocysts. Because few oocysts were found on the midgut of immune-activated mosquitoes, the data suggest that some factor, induced by bacterial challenge, kills the parasite at a preoocyst stage.

Aedes↗
PubMedDate not supplied

A comparison of two DNA probes, one specific for Plasmodium falciparum and one with wider reactivity, in the diagnosis of malaria.

The sensitivity and specificity of 2 probes for the detection of malarial infection was studied. 399 blood samples from Gambian children were tested in a deoxyribonucleic acid (DNA) hybridization assay, and the results compared with the microscopical findings from thick blood films. 8 additional pure Plasmodium malariae and 14 pure P. vivax samples were also assayed. One probe, containing a 21 base pair tandem repeat and highly specific for P. falciparum, detected this species in all except 2 of 74 samples with a parasitaemia of 250 per microliter or more; the overall sensitivity of the probe was 76%. The other probe, a 6 kilobase pair organelle DNA, is conserved in all Plasmodium species so far tested. Its sensitivity for P. falciparum was lower than the 21 base pair repeat, but it detected P. vivax and P. malariae at low levels of parasitaemia, and thus could be useful in field studies.

Animals↗
PubMed1991

Identification of a common Plasmodium epitope (CPE) recognised by a pan-specific inhibitory monoclonal antibody.

A Plasmodium falciparum genomic expression library was screened with a monoclonal antibody produced from mice infected with Plasmodium yoelii. Eleven unique clones were isolated all of which contained the sequence NKND, IKND or KKND. This sequence was confirmed as the epitope of M26-32 by testing a series of overlapping peptides and the allowable substitutions determined by testing the binding of M26-32 to peptides containing all possible single amino acid replacements of NKND. Potential epitopes of M26-32 occur in many plasmodial proteins and this is consistent with the large number of proteins recognised in these parasites by Western blotting. Since this monoclonal antibody shows marked in vitro inhibition of P. falciparum growth, these data suggest that an anti-malarial vaccine may be produced by targeting such common plasmodial epitopes without necessarily identifying the corresponding antigens.

Amino Acid Sequence↗
PubMed1994

Characterization of phosphatidylinositol synthase and evidence of a polyphosphoinositide cycle in Plasmodium-infected erythrocytes.

Plasmodium knowlesi-infected erythrocytes possess a membranous cytidine 5'-diphospho-1,2-diacyl-sn-glycerol: myoinositol 3-phosphatidyl transferase (PI synthase) (EC 2.7.8.11) activity of 10 +/- 1.7 nmol min-1 per 10(10) infected cells. The activity was successfully solubilized with 40 mM n-octyl-beta-D-glucopyranoside in the presence of bivalent metal ions which were absolutely required for activity. The optimal pH was 8 and the apparent Ks for Mn2+ was 0.1 mM. Mg2+ allowed two-fold higher PI synthase activity, with an optimum above 100 mM. Calcium alone was ineffective while at 2 mM it inhibited solubilized PI synthase activity in the presence of 100 mM Mg2+. Enzymatic activity was fully dependent on CDP-diacylglycerol and inositol with apparent Km of 0.16 +/- 0.1 mM and 1 +/- 0.5 mM respectively. Affinity chromatography clearly showed CDP-diacylglycerol-dependent interactions of PI synthase with CDP-diacylglycerol Sepharose. However, elution of enzymatic activity in an active form was unsuccessful while SDS-PAGE of the eluate showed one apparent band. Incubations of Plasmodium falciparum-infected erythrocytes with 32P or [3H]inositol revealed de novo biosynthesis of phosphatidylinositol, phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate which appeared to predominate in the second half of the asexual cellular cycle. Ionomycin, a calcium ionophore, induced Li(+)-sensitive production of radioactive inositol phosphates, with neo-synthesized inositol 1,4,5-trisphosphate accumulation being the highest.

Animals↗