[Studies of the duration of the course of Plasmodium vivax, Plasmodium falciparum and Plasmodium malariae infections].
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Humans↗
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[Action of combined primaquine-pyrimethamine. II. Human infections by Plasmodium vivax & Plasmodium falciparum].
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Antimalarials↗
[Infection of Anopheles (Kerteszia) cruzii by Plasmodium vivax and Plasmodium vivax variant VK247 in the municipalities of São Vicente and Juquitiba, São Paulo].
Sporadic cases of autochthonous malaria have been recorded in São Paulo State, located in the Southeast region of Brazil. These cases are characterized by their benign course, low parasitemia, and mild symptomatology and have been identified as vivax malaria. Little is known about the symptoms and immune response elicited in humans by the variants Plasmodium vivax VK247 and P. vivax-like human malaria parasites. These variants are transmitted by Anopheles (Kerteszia) cruzii, one of the most common species of mosquitoes in the Southeast of Brazil. The objective of the study described in this paper was to investigate infection in anophelines using ELISA immunoenzymatic assay with specific monoclonal antibodies directed against the repetitive regions of the circumsporozoite protein in classic P. vivax, P. brasilianum/P. malariae, and P. vivax VK247. Between 1991 and 1993, mosquitoes were collected in São Vicente and Juquitiba, municipalites located in a remnant of the Brazilian Atlantic forest in São Paulo State, an ecosystem rich in plants of the Bromeliaceae family. These plants function as nurseries for immature forms of anophelines of the subgenus Kerteszia. Of 1,117 An. (Ker.) cruzii captured in São Vicente, 0.179% were positive for classic P. vivax. In Juquitiba, of 1,161 An. (Ker.) cruzii, 0.086% were positive for P. vivax VK247, confirming the presence of this variant in the region. Although the infection rate is low, the high density of these mosquitoes and their voracity (they exhibit 24-h biting activity) could compensate for the low percentage of infected specimens.
Animals↗
[Comparative analysis at the nucleotide level of the genes encoding the lactate dehydrogenase enzyme of Plasmodium vivax and Plasmodium falciparum.].
In this study, the nucleotide sequence of the enzyme lactate dehydrogenase from Plasmodium vivax has been compared to the same enzyme from another malaria parasite Plasmodium falciparum. It was found that the identity between two sequences was 74.8%. The percentage of the GC value was found to be higher in the Plasmodium vivax lactate dehydrogenase (46.6%) than in that of Plasmodium falciparum (33%). The nucleotide sequence that corresponds to the 5 amino acid insertion in Plasmodium lactate dehydrogenase is also present in Plasmodium vivax. This site will be targeted in the design of novel antimalarials for Plasmodium vivax as has been for Plasmodium falciparum.
English Abstract↗
Identification, expression, localization and serological characterization of a tryptophan-rich antigen from the human malaria parasite Plasmodium vivax.
Plasmodium vivax is most common but non-cultivable human malaria parasite which is poorly characterized at the molecular level. Here, we describe the identification and characterization of a P. vivax Tryptophan-Rich Antigen (PvTRAg) which contains unusually high (8.28%) tryptophan residues and is expressed by all blood stages of the parasite. The pvtrag gene comprises a 978bp open reading frame interrupted by two introns. The first intron is located in the 5'-untranslated region while the second one is positioned 174bp downstream to the ATG codon. The encoded approximately 40kDa protein contains a transmembrane domain near the N-terminus followed by a tryptophan-rich domain with significantly high surface probability and antigenic index. It is localized in the parasite cytoplasm as well as in the cytoplasm of the parasitized erythrocyte. The purified E. coli expressed recombinant PvTRAg protein showed a very high seropositivity rate for the presence of antibodies amongst the P. vivax patients, indicating that the antigen generates significant humoral immune response during the natural course of P. vivax infection. Analysis of various field isolates revealed that the tryptophan-rich domain is highly conserved except for three-point mutations. The PvTRAg could be a potential vaccine candidate since similar tryptophan-rich antigens of P. yoelii have shown protection against malaria in murine model.
Amino Acid Sequence↗
Antigenic properties of the merozoite surface protein 1 gene of Plasmodium vivax.
Plasmodium vivax is responsible for an approximate 35 million yearly human cases of malaria. Unfortunately, due to the low mortality rate associated with it and the difficulties of continuously in vitro culturing of this parasite, vaccine development against this human malaria has been largely neglected. In here, the antigenic properties of the merozoite surface protein 1 gene of P. vivax (PvMSP-1), were studied. Thus, seven recombinant bacterial plasmids coding different regions of the PvMSP-1 protein were constructed and used to immunize BALB/c mice. The results demonstrated that a plasmid encoding the entire N-terminus comprising 682 amino acids and a plasmid encoding the C-terminus including the two juxtaposed epidermal growth factor (EGF)-like domains fused to the Hepatitis B surface antigen, were antigenic. Moreover, the elicited immune responses were similar to those reported for these same PvMSP-1 regions in natural human infections.
Animals↗
In vitro culture of two populations (dividing and nondividing) of exoerythrocytic parasites of Plasmodium vivax.
Plasmodium vivax sporozoites invaded human hepatoma cells and differentiated into 2 types of exoerythrocytic (EE) parasites. One group was composed of actively dividing schizonts, which released merozoites after 9 days of culture. The second group was nondividing and persisted after the primary schizonts disappeared from the culture. EE schizonts progressively lost reactivity to monoclonal antibodies to the surface-protective protein antigen of P. vivax sporozoites, but the persisting parasites remained strongly reactive. In the 2 strains of P. vivax studied, the ratio of schizonts to persisting parasites was approximately equal.
Animals↗
Sequence of the immunodominant epitope for the surface protein on sporozoites of Plasmodium vivax.
Plasmodium vivax is one of the four malaria parasites that cause disease in humans. The structure of the immunodominant repeating peptide of the circumsporozoite (CS) protein of P. vivax was determined. A fragment of P. vivax DNA that encodes this tandemly repeating epitope was isolated by use of an oligonucleotide probe whose sequence is thought to be conserved in CS protein genes. DNA sequence analysis of the P. vivax clone indicates that the CS repeat is nine amino acids in length (Gly-Asp-Arg-Ala-Asp-Gly-Gln-Pro-Ala). The structure of the repeating region was confirmed with synthetic peptides and monoclonal antibodies directed against P. vivax sporozoites. This information should allow synthesis of a vaccine for P. vivax that is similar to the one being tested for P. falciparum.
Amino Acid Sequence↗
Pyrimethamine and WR99210 exert opposing selection on dihydrofolate reductase from Plasmodium vivax.
Plasmodium vivax is a major public health problem in Asia and South and Central America where it is most prevalent. Until very recently, the parasite has been effectively treated with chloroquine, but resistance to this drug has now been reported in several areas. Affordable alternative treatments for vivax malaria are urgently needed. Pyrimethamine-sulfadoxine is an inhibitor of dihydrofolate reductase (DHFR) that has been widely used to treat chloroquine-resistant Plasmodium falciparum malaria. DHFR inhibitors have not been considered for treatment of vivax malaria, because initial trials showed poor efficacy against P. vivax. P. vivax cannot be grown in culture; the reason for its resistance to DHFR inhibitors is unknown. We show that, like P. falciparum, point mutations in the dhfr gene can cause resistance to pyrimethamine in P. vivax. WR99210 is a novel inhibitor of DHFR, effective even against the most pyrimethamine-resistant P. falciparum strains. We have found that it is also an extremely effective inhibitor of the P. vivax DHFR, and mutations that confer high-level resistance to pyrimethamine render the P. vivax enzyme exquisitely sensitive to WR99210. These data suggest that pyrimethamine and WR99210 would exert opposing selective forces on the P. vivax population. If used in combination, these two drugs could greatly slow the selection of parasites resistant to both drugs. If that is the case, this novel class of DHFR inhibitors could provide effective and affordable treatment for chloroquine- and pyrimethamine-resistant vivax and falciparum malaria for many years to come.
Alleles↗
High prevalence of asymptomatic Plasmodium vivax and Plasmodium falciparum infections in native Amazonian populations.
The epidemiology of malaria in 2 riverine localities in Rondĵnia, Brazilian western Amazĵnia, was assessed by a 1-year study at Portuchuelo, and a cross-sectional survey at riverine communities at Rio Machado (= Ji-Parana). Plasmodium spp. infections were diagnosed by light microscopy and by polymerase chain reaction (PCR) amplification of ribosomal DNA. PCR was 6-7 times more efficient than microscopy for detecting plasmodial infections. Both Plasmodium vivax and Plasmodium falciparum infections occurred as asymptomatic and symptomatic forms of the disease. The relation between symptomatic and asymptomatic clinical forms was roughly similar for both species of Plasmodium. Symptomless patients were monitored for 2 months. The prevalence of symptomless infections was 4-5 times higher than the symptomatic ones--respectively, 20% and 4.6% for Portuchuelo and 49.5% and 10% for Ji-Parana. Symptomatic malaria occurred mostly in patients in younger age groups. In contrast, there was a significant association of symptomless malaria with older age groups (medians of 26.5 and 21 years, respectively, for Portuchuelo and Ji-Parana), whereas the age medians for symptomatic malaria were 14 and 8 years, respectively, in the 2 regions. Symptomatic malaria also was more prevalent in groups living for shorter times in Amazĵnia (13 and 4 years, respectively, for Portuchuelo and Ji-ParanA) as compared with symptomless malaria, which was more prevalent in groups living for longer periods in the region (medians of 25.5 and 18 years, respectively, for Portuchuelo and Ji-Paraná). The high prevalence of symptomless malaria may pose new problems for the currently adopted strategy for the control of malaria in the Amazonian region, which is essentially based on the treatment of symptomatic patients.
Adolescent↗
Overcoming cloning problems by staining agarose gels with crystal violet instead of ethidium bromide in lactate dehydrogenase gene from Plasmodium vivax and Plasmodium falciparum.
In this study, lactate dehydrogenase gene from Plasmodium vivax has been tried to subclone into an expression vector. Some of the Plasmodium falciparum lactate dehydrogenase mutant genes have also been tried to clone and subclone into a vector, but we failed to clone or subclone either of the genes. DNA visualisation in electrophoretic gels typically requires UV radiation and the fluorecent dye ethidium bromide. A crystal violet-stained gel was run instead of an ethidium bromide gel and so avoided the use of UV radiation. This enabled us to clone or subclone both Plasmodium vivax lactate dehydrogenase gene and Plasmodium falciparum lactate dehydrogenase mutant genes into any desired vector.
Animals↗
[Malaria attack: a very late relapse due to Plasmodium vivax].
Plasmodium vivax malaria late-forms rarely exceed two years--the authors reported a late-form more than twenty years after a stay in endemic area. This late-form occurred in an immunocompromised patient with two terminal-stage neoplasia receiving radio, chimio corticotherapy associated with anemia and thrombopenia. Repeated-tests allowed the diagnostic.
Adenocarcinoma↗
Blood-stage dynamics and clinical implications of mixed Plasmodium vivax-Plasmodium falciparum infections.
We present a mathematical model of the blood-stage dynamics of mixed Plasmodium vivax-Plasmodium falciparum malaria infections in humans. The model reproduces features of such infections found in nature and suggests several phenomena that may merit clinical attention, including the potential recrudescence of a long-standing, low-level P. falciparum infection following a P. vivax infection or relapse and the capacity of an existing P. vivax infection to reduce the peak parasitemia of a P. falciparum superinfection. We simulate the administration of antimalarial drugs, and illustrate some potential complications in treating mixed-species malaria infections. Notably, our model indicates that when a mixed-species infection is misdiagnosed as a single-species P. vivax infection, treatment for P. vivax can lead to a surge in P. falciparum parasitemia.
Animals↗
Stage-specific and species-specific antigens of Plasmodium vivax and Plasmodium ovale defined by monoclonal antibodies.
Monoclonal antibodies (MAbs) were produced against the asexual blood stages of Plasmodium vivax and Plasmodium ovale and used to define antigens of plasmodial parasites in an indirect fluorescent antibody assay. The anti-P. vivax MAbs produced two distinct patterns in the indirect fluorescent antibody assay. Four patterns were found with the anti-P. ovale MAbs. Species-specific epitopes were defined for P. vivax and P. ovale; epitopes shared among all four species of human malaria parasites were also defined. Some of the anti-P. vivax MAbs reacted only with mature stages, and others reacted with all asexual stages. No asexual blood-stage specificity could be found with the anti-P. ovale antibodies. Five of the anti-P. vivax MAbs and three of the anti-P. ovale MAbs also reacted with sporozoites.
Animals↗
Detection of Plasmodium vivax and Plasmodium falciparum circumsporozoite antigen in anopheline mosquitoes collected in southern Thailand.
During a 13-month study on the ecology of malaria vectors in five villages in southern Thailand, Anopheles specimens collected on human-bait, bovid-bait, and in light traps were tested for the presence of Plasmodium vivax and P. falciparum circumsporozoite antigen by enzyme-linked immunosorbent assay. Plasmodium vivax antigen was detected in seven specimens and P. falciparum in 21 specimens, together representing 0.4% of the 7,938 specimens tested. In one village, Palao-U, circumsporozoite antigen was detected in 16 (0.7%) of the 2,196 specimens tested. In this village, combined rates of infection with P. falciparum and P. vivax were 0.6% for An. minimus, 1.1% for An. sawadwongporni, and 1.5% for An. maculatus. Circumsporozoite antigen was also detected in An. dirus, An. nivipes, An. barbirostris group, and An. hyrcanus group specimens. Combined P. falciparum and P. vivax entomologic inoculation rates in the wet season (March-October) were 0.05 for An. minimus, An. maculatus, and An. dirus, but 0 for An. sawadwongporni. Rates were higher in the dry season (November-February): 0.26 for An. minimus, 0.13 for An. maculatus, 0.13 for An. sawadwongporni, and 0 for An. dirus. The vectorial capacity, calculated based on human biting rate and rate of survival, of An. minimus during the dry season was more than two-fold higher than that of An. maculatus, the species with the second highest vectorial capacity.
Animals↗
Mapping regions containing binding residues within functional domains of Plasmodium vivax and Plasmodium knowlesi erythrocyte-binding proteins.
Invasion of erythrocytes by malaria parasites is mediated by specific molecular interactions. Whereas Plasmodium vivax and Plasmodium knowlesi use the Duffy blood group antigen, Plasmodium falciparum uses sialic acid residues of glycophorin A as receptors to invade human erythrocytes. P. knowlesi uses the Duffy antigen as well as other receptors to invade rhesus erythrocytes by multiple pathways. Parasite ligands that bind these receptors belong to a family of erythrocyte-binding proteins (EBP). The EBP family includes the P. vivax and P. knowlesi Duffy-binding proteins, P. knowlesi beta and gamma proteins, which bind alternate receptors on rhesus erythrocytes, and P. falciparum erythrocyte-binding antigen (EBA-175), which binds sialic acid residues of human glycophorin A. Binding domains of each EBP lie in a conserved N-terminal cysteine-rich region, region II, which contains around 330 amino acids with 12 to 14 conserved cysteines. Regions containing binding residues have now been mapped within P. vivax and P. knowlesi beta region II. Chimeric domains containing P. vivax region II sequences fused to P. knowlesi beta region II sequences were expressed on the surface of COS cells and tested for binding to erythrocytes. Binding residues of P. vivax region II lie in a 170-aa stretch between cysteines 4 and 7, and binding residues of P. knowlesi beta region II lie in a 53-aa stretch between cysteines 4 and 5. Mapping regions responsible for receptor recognition is an important step toward understanding the structural basis for the interaction of these parasite ligands with host receptors.
Animals↗
Evaluation of the OptiMAL test for rapid diagnosis of Plasmodium vivax and Plasmodium falciparum malaria.
The development of rapid and specific diagnostic tests to identify individuals infected with malaria is of paramount importance in efforts to control the severe public health impact of this disease. This study evaluated the ability of a newly developed rapid malaria diagnostic test, OptiMAL (Flow Inc., Portland, Oreg.), to detect Plasmodium vivax and Plasmodium falciparum malaria during an outbreak in Honduras. OptiMAL is a rapid (10-min) malaria detection test which utilizes a dipstick coated with monoclonal antibodies against the intracellular metabolic enzyme parasite lactate dehydrogenase (pLDH). Differentiation of malaria parasites is based on antigenic differences between the pLDH isoforms. Since pLDH is produced only by live Plasmodium parasites, this test has the ability to differentiate live from dead organisms. Results from the OptiMAL test were compared to those obtained by reading 100 fields of traditional Giemsa-stained thick-smear blood films. Whole-blood samples were obtained from 202 patients suspected of having malaria. A total of 96 samples (48%) were positive by blood films, while 91 (45%) were positive by the OptiMAL test. The blood films indicated that 82% (79 of 96) of the patients were positive for P. vivax and 18% (17 of 96) were infected with P. falciparum. The OptiMAL test showed that 81% (74 of 91) were positive for P. vivax and 19% (17 of 91) were positive for P. falciparum. These results demonstrated that the OptiMAL test had sensitivities of 94 and 88% and specificities of 100 and 99%, respectively, when compared to traditional blood films for the detection of P. vivax and P. falciparum malaria. Blood samples not identified by OptiMAL as malaria positive normally contained parasites at concentrations of less than 100/microl of blood. Samples found to contain P. falciparum were further tested by two other commercially available rapid malaria diagnostic tests, ParaSight-F (Becton Dickinson, Cockeysville, Md.) and ICT Malaria P.f. (ICT Diagnostics, Sydney, Australia), both of which detect only P. falciparum. Only 11 of the 17 (65%) P. falciparum-positive blood samples were identified by the ICT and ParaSight-F tests. Thus, OptiMAL correctly identified P. falciparum malaria parasites in patient blood samples more often than did the other two commercially available diagnostic tests and showed an excellent correlation with traditional blood films in the identification of both P. vivax malaria and P. falciparum malaria. We conclude that the OptiMAL test is an effective tool for the rapid diagnosis of malaria.
Humans↗
[Construction of a cDNA library of the erythrocytic stage of Plasmodium vivax].
Plasmodium vivax-infected blood samples were collected from patients in the field during malaria transmission season. Total RNA of the parasites was extracted by guanidine HCl/cesium chloride centrifugation. mRNA was purified through oligo-dT cellulose. Double stranded cDNA were synthesized with AMV reverse transcriptase by Huynh's method. lambda gt11 phage was used as the vector. A cDNA library of the erythrocytic stage P. vivax was constructed after recombination of DNA and package in vitro.
Animals↗