Social Sciences and Malaria 

Compliance to correct dose of chloroquine in uncomplicated malaria correlates with improvement in the condition of rural Nigerian children

OKONKWO P O; AKPALA C O; OKAFOR H U; MBAH A U; NWAIWU O

Department of Pharmacology and Therapeutics, University of Nigeria Teaching Hospital, PMB 01129, Enugu, Nigeria; Department of Community Medicine, University of Nigeria Teaching Hospital, PMB 01129, Enugu, Nigeria; Department of Paediatrics, University of Nigeria Teaching Hospital, PMB 01129, Enugu, Nigeria

Non-compliance to correct dosing is thought to be one of the main causes of treatment failure of chloroquine in the home management of childhood malaria. There are few studies of compliance to drugs used for tropical diseases. In order to study compliance in the rural setting, chloroquine syrup was packaged with a novel pictorial insert for compliance to correct dosing. Compliance was assessed in a field trial in September 1996-December 1997, involving 632 children with uncomplicated malaria in Udi local government area in Nigeria. Written informed consent was obtained from mothers/guardians before children were enrolled in the study. There were 3 arms to the trial: control villages (group I) received chloroquine syrup without further intervention, group II received a pictorial insert with chloroquine syrup, and group III received chloroquine syrup, the pictorial insert and verbal instructions. Each group was made up of 3 health centres. Compliance was assessed by volumetric measurement of the chloroquine syrup left in 30-mL bottles and by questionnaires administered to mothers/helpers of the children. Control villages recorded full compliance for 36.5 +- 4.4% of the children, group II for 51.9 +- 7.9% and group III for 73.3 +- 4.2%, There was a significant correlation (P < 0.0001) between full compliance, improvement and time for improvement of the condition. This study is deemed important because it focuses on children, who bear the greatest burden of malaria. It is unique for introducing a pictorial insert that illiterate villagers, who may not understand the use of age or weight in drug dispensing, may utilize as a substitute.

Tropical medicine & international health, 2001, 6 (7) 496-504

Improving adherence to malaria treatment for children: the use of pre-packed chloroquine tablets vs. chloroquine syrup 

ANSAH E K; GYAPONG J O; AGYEPONG I A; EVANS D B 

Dangme West District, Ministry of Health, Dodowa, Ghana; Health Research Unit, Ministry of Health, Accra, Ghana; Global Programme on Evidence for Health Policy (GPE), World Health Organization, Geneva, Switzerland

Malaria is a major cause of morbidity and mortality among children under five in sub-Saharan Africa. Prompt diagnosis and adequate treatment of acute clinical episodes are essential to reduce morbidity and prevent complications and mortality. In many countries, chloroquine syrup is the mainstay of malaria treatment for children under five. Not only is syrup more expensive than tablets, adherence to the prescribed dose at home is a problem because mothers use wrongly sized measuring devices or have difficulty with the instructions. We investigated the impact of introducing pre-packed tablets for children on adherence to treatment and compared the total cost of the tablets with that of syrup. Children aged 0-5 years diagnosed with malaria at the clinic over a 6-week period received either pre-packed tablets or syrup by random assignment. The principal caregivers were interviewed at home on day 4 after attending the clinic. Of the 155 caregivers given pre-packed tablets, 91% (n = 141) adhered to the recommended dosage, while only 42% (n = 61) of 144 who were provided syrup did. Only 20% of caregivers who received syrup used an accurate 5 ml measure. The cost of treatment with tablets was about one-quarter that of syrup and 62% (n = 96) of caregivers preferred tablets. Pre-packed chloroquine tablets are a viable alternative to syrup.Parassitologia 2000 Dec;42(3-4):255-90

The community-based malaria control programme in Tigray, northern Ethiopia. A review of programme set-up, activities, outcomes and impact.

Ghebreyesus TA, Witten KH, Getachew A, Yohannes AM, Tesfay W, Minass M, Bosman A, Teklehaimanot A.

Tigray Health Bureau, PO Box 7, Mekelle, Ethiopia. 
Email: [email protected]

Tigray, the northernmost state of Ethiopia, has a population of 3.5 million, 86% rural, and 56% living in malarious areas. In 1992 a Community-Based Malaria Control Programme was established to provide region-wide and sustained access to early diagnosis and treatment of malaria at the village level. 735 volunteer community health workers (CHWs) serve 2,327 villages with a population of 1.74 million, treating an average of 489,378 patients yearly from 1994 to 1997. Recognition of clinical malaria is similar for CHWs and health staff at clinics where there is no access to microscopy. In 1996 a pilot community-financing scheme of insecticide-treated bednets was well accepted, but re-impregnation rates fell in 1998 because of war-related social upheaval. Indicators from health institutions show a progressive increase in malaria morbidity from 1994 to 1998. Repeated mortality surveys show a 40% reduction in death rates in under-5 children from 1994 to 1996 and a 10% increase from 1996 to 1998. These trends may be related to increased malaria transmission with water resources development, increased seasonal labour migration to malarious lowlands, prolongation of the transmission season with climate changes, and increasing chloroquine resistance throughout Ethiopia. Progressive extension of CHW services to ensure better coverage of women, children, migrant workers and communities near water development projects, change to first-line treatment with sulfadoxine-pyrimethamine, extension of the impregnated bednet initiative, and development of a regional warning system for epidemics should result in a greater impact on morbidity and mortality.

PMID: 11686085 [PubMed – in process]

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Cent Afr J Med 2000 Oct;46(10):268-70

Utilisation of malarial drugs at a household level: results from a KAP study in Choma, southern province and Mporokoso, northern province of Zambia.

Kaona F, Siajunza MT, Manyando C, Khondowe S, Ngoma GK.

Department of Public Health, Tropical Diseases Research Centre, P O Box 71769, Ndola, Zambia.

OBJECTIVES: To describe and document knowledge and use of anti-malarial drugs at household level in rural Zambia. DESIGN: Cross sectional study. SETTING: Community based. SUBJECTS: Data was collected from 392 male and 415 female respondents. MAIN OUTCOME MEASURES: Percentage of respondents knowing the cause of malaria and using modern health facilities. RESULTS: The median age of respondents in Choma was 37(Q1 = 27, Q3 = 52) while that for Mporokoso respondents was 34(Q1 = 26, Q3 = 47), (p < 0.001). There was no association between educational level and knowledge of causes of malaria (p = 0.674). Fever was significantly (p < 0.001) associated with malaria (20.4% in Choma, 80.6% in Mporokoso). However, only 1% in both areas mentioned the mosquito as a vector for malaria. The majority of residents (59.5%) went to the hospital when they suffered from malaria. Only 7% mentioned the use of traditional medicine. There was an association between the level of education and taking preventive measures against malaria in all the communities (p < 0.001). Respondents did not mention the use of treated mosquito nets. CONCLUSION: Residents in both Choma and Mporokoso did not know the cause of malaria. The use of treated mosquito nets is rare. Production of information, education, communication (IEC) health materials and recruitment of a village health educator is recommended.

PMID: 11682934 [PubMed – in process]

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PubMed

Proc Natl Acad Sci U S A 2001 Oct 30

Full-text at: http://www.pnas.org

Targeting Plasmodium ligands on mosquito salivary glands and midgut with a phage display peptide library.

Ghosh AK, Ribolla PE, Jacobs-Lorena M.

Department of Genetics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-4955.

Despite vast efforts and expenditures in the past few decades, malaria continues to kill millions of persons every year, and new approaches for disease control are urgently needed. To complete its life cycle in the mosquito, Plasmodium, the causative agent of malaria, has to traverse the epithelia of the midgut and salivary glands. Although strong circumstantial evidence indicates that parasite interactions with the two organs are specific, hardly any information is available about the interacting molecules. By use of a phage display library, we identified a 12-aa peptide-salivary gland and midgut peptide 1 (SM1)-that binds to the distal lobes of the salivary gland and to the luminal side of the midgut epithelium, but not to the midgut surface facing the hemolymph or to ovaries. The coincidence of the tissues with which parasites and the SM1 peptide interact suggested that the parasite and peptide recognize the same surface ligand. In support of this hypothesis, the SM1 peptide strongly inhibited Plasmodium invasion of salivary gland and midgut epithelia. These experiments suggest a new strategy for the genetic manipulation of mosquito vectorial capacity.

PMID: 11687659 [PubMed – as supplied by publisher]

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Clin Diagn Lab Immunol 2001 Nov;8(6):1289-1291

Insecticide-Treated Bed Nets Reduce Plasma Antibody Levels and Limit the Repertoire of Antibodies to Plasmodium falciparum Variant Surface Antigens.

Askjaer N, Maxwell C, Chambo W, Staalsoe T, Nielsen M, Hviid L, Curtis C, Theander TG.

Centre for Medical Parasitology at Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), and Institute for Medical Microbiology and Immunology, University of Copenhagen, Copenhagen, Denmark; London School of Hygiene, Amani Medical Research Centre, Amani, Tanzania.

The use of insecticide-treated bed nets (ITN) has been documented to reduce malaria morbidity and mortality in areas with endemic malaria, but concerns have been raised that ITN usage could affect the acquisition of malaria immunity. Several lines of evidence have indicated that antibodies against variant surface antigens (VSA) are important in the development of naturally acquired immunity to Plasmodium falciparum malaria and may thus be good indicators of immune status. We have compared the levels of VSA antibodies in plasma from children who have used ITN for 4 years to levels in plasma from children from a nearby village not using ITN. A total of 97 plasma samples were analyzed using 13 different P. falciparum isolates. We found that the children using ITN had significantly lower VSA antibody levels and recognized a smaller proportion of the VSA expressed by the tested parasite isolates than children not using ITN.

PMID: 11687480 [PubMed – as supplied by publisher]

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Clin Diagn Lab Immunol 2001 Nov;8(6):1164-1170

Anemia and Interleukin-10, Tumor Necrosis Factor Alpha, and Erythropoietin Levels among Children with Acute, Uncomplicated Plasmodium falciparum Malaria.

Nussenblatt V, Mukasa G, Metzger A, Ndeezi G, Garrett E, Semba RD.

Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins School of Medicine, Baltimore, Maryland.

Anemia is an important complication of malaria, and its pathogenesis is not well understood. To gain insight into potential age-related relationships between tumor necrosis factor alpha (TNF-alpha), interleukin 10 (IL-10), erythropoietin, and anemia during acute malaria, 273 children of ages 12 to 120 months presenting with acute, uncomplicated malaria in Kampala, Uganda, were monitored at enrollment and 3 and 7 days later. Younger children had higher geometric mean erythropoietin, TNF-alpha, and alpha(1)-acid glycoprotein (AGP) concentrations than older children. Univariate regression analysis revealed that age, log(10) erythropoietin levels, IL-10/TNF-alpha ratio, and AGP levels were each significantly associated with hemoglobin levels at baseline. Hemoglobin concentrations were inversely correlated with the log(10) erythropoietin level at all three visits. For the older age groups, higher levels of TNF-alpha were significantly associated with higher IL-10 levels at all three visits, but this relationship was significant only at baseline for younger children. These data suggest that younger children do not maintain IL-10 production in response to the inflammatory process, and this mechanism may contribute to the more severe anemia found in younger children. Acute malaria is an illness whose incidence and severity are largely age dependent. Further studies are needed to understand the relationships between age-related immune responses to malaria and their role in the pathogenesis of malarial anemia.

PMID: 11687458 [PubMed – as supplied by publisher]

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Cochrane Database Syst Rev 2001;4:CD000386

Chloroquine or amodiaquine combined with sulfadoxine-pyrimethamine for treating uncomplicated malaria (Cochrane Review).

McIntosh HM.

NHS Centre for Reviews and Dissemination, York, UK, YO10 5DD. Email: [email protected]

BACKGROUND: Amodiaquine and chloroquine give fast relief from malaria symptoms, particularly fever. When used alone in areas where there is some parasite resistance they do not completely clear parasites from the blood in all cases, and so not all patients are cured of infection. The major disadvantage of using sulfadoxine-pyrimethamine alone is that it takes a relatively long time to relieve fever. OBJECTIVES: To assess the effectiveness of chloroquine or amodiaquine given with sulfadoxine-pyrimethamine to treat uncomplicated falciparum malaria. SEARCH STRATEGY: The Cochrane Infectious Diseases Group trials register, the Cochrane Controlled Trials Register, MEDLINE, EMBASE, Science Citation Index, African Index Medicus and LILACS were searched. Experts in the field and drug companies were contacted. SELECTION CRITERIA: Randomised and quasi-randomised trials of chloroquine or amodiaquine given with sulfadoxine-pyrimethamine compared with either drug alone in adults or children with confirmed uncomplicated falciparum malaria. DATA COLLECTION AND ANALYSIS: Two people independently applied the inclusion criteria. Data were extracted by the reviewer and checked independently by another person. MAIN RESULTS: Seven trials were included (1277 patients in total). Fever clearance time was shortened by combination therapy compared to sulfadoxine-pyrimethamine alone. Parasite clearance at day seven follow-up was not significantly different for chloroquine or amodiaquine treatment with or without sulfadoxine-pyrimethamine. Parasite clearance at day 28 was better with combination therapy compared to chloroquine or amodiaquine alone, but not significantly better than sulfadoxine-pyrimethamine alone. There was no evidence from the included trials of serious side effects with combination treatment. REVIEWER’S CONCLUSIONS: In areas where chloroquine or amodiaquine are still effective, despite some degree of resistance, using these drugs in combination with sulfadoxine-pyrimethamine, rather than sulfadoxine-pyrimethamine alone, may make people feel better faster and improve sustained parasites clearance.

PMID: 11687077 [PubMed – as supplied by publisher]

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Parassitologia 2000 Dec;42(3-4):197-203

Site-based study on polymorphism of Plasmodium falciparum MSP-1 and MSP-2 genes in isolates from two villages in Central Africa.

Ntoumi F, Ngoundou-Landji J, Lekoulou F, Luty A, Deloron P, Ringwald P.

Centre International de Recherches Medicales de Franceville (CIRMF), BP 769, Franceville, Gabon. 
Email: [email protected]

We investigated Plasmodium falciparum genetic diversity in isolates collected from school-going residents aged from 5 to 15 years in the village of Pouma (Cameroon, Central Africa). Seventy-six children were grouped according to the clinical status. Asymptomatic status was defined as parasite carriage in the absence of any clinical symptom and malaria symptomatic status with patent parasitemia over 5000 parasites/microliter of blood and an axillary temperature > 37.5 degrees C. Parasite DNA was analysed prior to malaria treatment. Genotyping of the P. falciparum merozoite surface proteins (MSP) 1 and 2 was performed by polymerase chain reaction using allele-specific primers. K1, MAD20, Ro33 and 3D7/CAMP, FC27 allelic families were attributed to MSP-1 and MSP-2 genes, respectively. No association was found between P. falciparum MSP-1 and MSP-2 genotypes and the clinical status of children. Mixed P. falciparum infections were detected in 78% of overall samples and all isolates from symptomatic children contained more than 1 clone. The results obtained in the village of Pouma were compared to those of the village of Dienga in Gabon where a similar study, using the same genotyping methods, had been carried out in the same age group of schoolchildren. Data are interpreted in the context of malaria epidemiology in both settings.

PMID: 11686079 [PubMed – in process]

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J Exp Biol 2001 Aug;204(Pt 16):2773-80

Malaria-induced apoptosis in mosquito ovaries: a mechanism to control vector egg production.

Hopwood JA, Ahmed AM, Polwart A, Williams GT, Hurd H.

Centre for Applied Entomology and Parasitology, Keele University, Staffordshire, UK.

Many insects are able to adjust their egg production according to physiological conditions such as nutrient supply and mating success. One way in which this is achieved is by resorption of some, or all, of the ovarian follicles at some stage during oogenesis. We have shown that the mosquito Anopheles stephensi responds in this manner when ookinetes of the malaria parasite Plasmodium yoelii nigeriensis first begin to invade the midgut. Little is known about the initiation and regulation of follicle resorption in any insect. Here, we demonstrate that there is a significant positive correlation between follicle resorption and the presence of follicular epithelial cells that are undergoing apoptosis. The parasite causes significantly more follicles to contain apoptotic cells from 16h post-infection onwards. Injection of a caspase inhibitor immediately after feeding on an infective blood meal prevents parasite-induced resorption of follicles and thus demonstrates that apoptosis precedes resorption. Ultrastructural studies show that patches of follicular epithelial cells contain condensed nuclear chromatin, a characteristic of apoptosis, and that no patency develops in these cells. Our work suggests that apoptosis plays a role in malaria-initiated inhibition of mosquito oogenesis and that caspase is central to this process. Follicle resorption is one of the main factors contributing to malaria-induced fecundity reduction in mosquitoes.

PMID: 11683433 [PubMed – in process]

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J Biol Chem 2001 Nov 2;276(44):41095-41099

Localization of the Plasmodium falciparum PfNT1 Nucleoside Transporter to the Parasite Plasma Membrane.

Rager N, Mamoun CB, Carter NS, Goldberg DE, Ullman B.

Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon 97201, the Center for Microbial Pathogenesis, University of Connecticut School of Medicine, Farmington, Connecticut 06030, and the Howard Hughes Medical Institute, Departments of Molecular Microbiology and Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.

Nutrient transporters play critical roles in parasite metabolism, but the membranes in which they reside have not been clearly defined. The transport of purine nutrients is crucial to the survival of the malaria parasite Plasmodium falciparum, and nucleoside transport activity has been associated with a number of different membrane components within the parasitized erythrocyte. To determine the location of the PfNT1 nucleoside transporter, the first component of the nucleoside permeation pathway to be studied at the molecular level in P. falciparum (Carter, N. S., Ben Mamoun, C., Liu, W., Silva, E. O., Landfear, S. M., Goldberg, D. E., and Ullman, B. (2000) J. Biol. Chem. 275, 10683-10691), polyclonal antisera against the NH(2)-terminal 36 amino acids of PfNT1 were raised in rabbits. Western blot analysis of parasite lysates revealed that the antibodies were specific for PfNT1 and that the level of PfNT1 protein in the infected erythrocyte is regulated in a stage-specific fashion. The amount of PfNT1 polypeptide increases dramatically during the early trophozoite stage and reaches its maximal level in the late trophozoite and schizont stages. Deconvolution and immunoelectron microscopy using these monospecific antibodies revealed that PfNT1 localizes predominantly, if not exclusively, to the plasma membrane of the parasite and not to the parasitophorous vacuolar or erythrocyte membranes.

PMID: 11682491 [PubMed – as supplied by publisher]

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Trop Med Int Health 2001 Oct;6(10):779-86

An empirical malaria distribution map for West Africa.

Kleinschmidt I, Omumbo J, Briet O, van de Giesen N, Sogoba N, Mensah NK, Windmeijer P, Moussa M, Teuscher T.

South African Medical Research Council, Congella, Durban, South Africa. 
Email: [email protected]

The objective of this study was to produce a malaria distribution map that would constitute a useful tool for development and health planners in West Africa. The recently created continental database of malaria survey results (MARA/ARMA 1998) provides the opportunity for producing empirical models and maps of malaria distribution at a regional and eventually at a continental level. This paper reports on the mapping of malaria distribution for sub-Saharan West Africa based on these data. The strategy was to undertake a spatial statistical analysis of malaria parasite prevalence in relation to those potential bio-physical environmental factors involved in the distribution of malaria transmission intensity which are readily available at any map location. The resulting model was then used to predict parasite prevalence for the whole of West Africa. We also produced estimates of the proportion of population of each country in the region exposed to various categories of risk to show the impact that malaria is having on individual countries. The data represent a very large sample of children in West Africa. It constitutes a first attempt to produce a malaria risk map of the West African region, based entirely on malariometric data. We anticipate that it will provide useful additional guidance to control programme managers, and that it can be refined once sufficient additional data become available.

PMID: 11679126 [PubMed – in process]

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Trop Med Int Health 2001 Oct;6(10):770-8

Malaria in pregnancy: adverse effects on haemoglobin levels and birthweight in primigravidae and multigravidae.

Shulman CE, Marshall T, Dorman EK, Bulmer JN, Cutts F, Peshu N, Marsh K.

London School of Hygiene and Tropical Medicine, London, UK. Email: [email protected]

BACKGROUND: In areas of endemic transmission, malaria in pregnancy is associated with severe maternal anaemia and low birthweight babies. The prevalence of infection is highest in primigravidae (PG), and hence control efforts are usually geared towards this high risk group. Using a sensitive measure of placental infection, we investigated the relationship between active-acute, active-chronic and past placental infection with maternal anaemia and low birthweight in women of all gravidities. METHODS: Between January 1996 and July 1997, 912 women delivering in Kilifi District Hospital, Kenya, were recruited. Haemoglobin and peripheral malaria slides were taken prior to delivery, placental biopsies and smears were taken at the time of delivery and birthweight and maternal height and weight were measured soon after birth. Information was obtained on socio-economic and educational status. The association between placental malaria, severe anaemia and low birthweight was investigated for women of different gravidities. FINDINGS: By placental histology, the prevalence of active or past malaria in all gravidities was high, ranging from 64% in PG to 30% in gravidities 5 and above. In gravidities 1-4, active malaria infection was associated with severe maternal anaemia, adjusted OR 2.21 (95% CI 1.36, 3.61). There was a significant interaction between chronic or past malaria and severe anaemia in their effects on birthweight, whereby the risk of low birthweight was very high in women with both chronic or past placental malaria and severe anaemia: OR 4.53 (1.19, 17.2) in PG; 13.5 (4.57, 40) in gravidities 2-4. INTERPRETATION: In this area of moderate malaria transmission, women of all parities have substantially increased risk of low birthweight and severe anaemia as a result of malaria infection in pregnancy. The risk of low birthweight is likely to be particularly high in areas with a high prevalence of severe anaemia.

PMID: 11679125 [PubMed – in process]

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Trop Med Int Health 2001 Oct;6(10):761-6

Population structure of Plasmodium falciparum isolates during an epidemic in southern Mauritania.

Jordan S, Jelinek T, Aida AO, Peyerl-Hoffmann G, Heuschkel C, el Valy AO, Christophel EM.

Department of Infectious Diseases and Tropical Medicine, University of Munich, Munich, Germany.

While the population structure of Plasmodium falciparum is well analysed in selected areas with high malaria endemicity in East and West Africa, only limited data are available for low endemicity regions bordering the Saharan desert. This is one of the first studies for the Sahel, where atypically strong rainfalls in 1998 and 1999 led to a severe outbreak of falciparum malaria in south-east Mauritania. During a study on in vivo-drug resistance against chloroquine we collected blood samples of patients with fever in two medical centres located in non-endemic and hypoendemic areas. We analysed 386 samples by polymerase chain reaction for infection with P. falciparum, and 173 (45%) tested positive. The isolates were genotyped for three polymorphic genetic markers: merozoite surface protein 1 (MSP1), MSP2 and glutamate-rich protein (GLURP). Differences between the two regions could be shown in either number of clones per infection or in their distribution on the different allelic groups. While the mean minimal number of clones in the non-endemic region around Aioun was 1.57, blood samples collected in the hypoendemic region around Kobeni showed multiple infections with an average of 2.34 clones (P < 0.001). In addition, clear differences between endemic regions were apparent in three of the investigated allelic groups: RO33 of the MSP1 gene and FC and Indochina of the MSP2 gene.

PMID: 11679123 [PubMed – in process]

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Trop Med Int Health 2001 Oct;6(10):756-60

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

Eberl KJ, Jelinek T, Aida AO, Peyerl-Hoffmann G, Heuschkel C, el Valy AO, Christophel EM.

Department of Infectious Diseases and Tropical Medicine, University of Munich, Munich, Germany.

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.

PMID: 11679122 [PubMed – in process]

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Trop Med Int Health 2001 Oct;6(10):749-55

Plasmodium falciparum pfcrt and pfmdr1 polymorphisms are associated with the pfdhfr N108 pyrimethamine-resistance mutation in isolates from Ghana.

Mockenhaupt FP, Eggelte TA, Till H, Bienzle U.

Institut fur Tropenmedizin, Medizinische Fakultat Charite, Humboldt Universitat zu Berlin, Germany. 
Email: [email protected]

The Plasmodium falciparum chloroquine resistance transporter gene (pfcrt) T76 and multidrug resistance gene analogue (pfmdr1) Y86 mutations are associated with chloroquine(CQ)-resistance. In isolates from 172 pregnant women living in the area of Agogo, Ghana, pfcrt T76 was detected in 69% and pfmdr1 Y86 in 66%. Pfcrt T76 but not pfmdr1 Y86 was more prevalent in samples from women with residual CQ in urine or serum. Parasite densities and multiplicity of infection of pfmdr wild type but not of resistant isolates were reduced by CQ. Adjusted for CQ and pyrimethamine (PYR) in urine, the P. falciparum dihydrofolate reductase (pfdhfr) N108 mutation which confers PYR-resistance was 3.1 and 3 times, respectively, more likely to be detected in isolates containing pfcrt and pfmdr1 mutations than in those comprising wild type alleles. Pfcrt, pfmdr, and pfdhfr mutations are frequent in P. falciparum from this part of Ghana which may limit the choice of drugs for the prevention of malaria in pregnancy. The association of CQ- and PYR-resistance mutations independent of recent drug use could indicate accelerated development of resistance to structurally unrelated drugs. Alternatively, it may reflect selection of resistance in persisting infections due to no longer detectable drug pressure.

PMID: 11679121 [PubMed – in process]

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Clin Exp Immunol 2001 Oct;126(1):69-75

West African donors have high percentages of activated cytokine producing T cells that are prone to apoptosis.

Kemp K, Akanmori BD, Hviid L.

Centre for Medical Parasitology at the Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), Denmark. 
Email: [email protected]

Persistent immune activation has been suggested to affect the subset composition and activation status of peripheral blood cells. In this study we have compared peripheral blood mononuclear cells (PBMC) from a group of Ghanaians living in an area with high prevalence of malaria, mycobacteria, EBV and helmintic infections to a group of European counterparts. Our hypothesis was that persistent challenge with microorganisms is associated with increased production of cytokines and increased susceptibility of periphery cells to undergo apoptosis. We observed an increased frequency of activated T cells and a higher frequency of IL-4- but not IFN-gamma-producing cells in the periphery of the Ghanaians. The IL-4 was produced mainly by CD4+ cells, in contrast to IFN-gamma which was produced equally by CD4+, CD8+ and TCR-gammadelta+ cells. The frequencies of cytokine-producing cells were highly correlated to the frequencies of activated cells. Finally, cells from Ghanaians were more susceptible to activation-induced apoptosis. These results may explain why some epidemic diseases seem to have a different mode of transmission in Africa compared to the western world, and may thus be of importance when vaccine strategies are considered in Africa.

PMID: 11678901 [PubMed – in process]

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Parasitology 2001 Oct;123(Pt 4):337-46

Pharmacokinetic-pharmacodynamic modelling of the antimalarial activity of mefloquine.

Hoshen MB, Stein WD, Ginsburg HD.

Department of Biological Chemistry, Institute of Life Sciences, The Hebrew University of Jerusalem, Israel.

Treatment protocols for the chemotherapy of malaria are usually acquired through clinical trials. Once pharmacokinetic and pharmacodynamic information becomes available, it is possible to use mathematical modelling for testing these protocols and, possibly, for improving them. In this report the case of monotherapy by mefloquine is analysed. Published pharmacokinetic and clinical results are used to derive the essential model parameters such as kill rate, parasite growth rates, drug sensitivity and the pharmacokinetic parameters. Good agreement is obtained between clinical results and simulated parasite numbers using the derived parameters. It is demonstrated that the 2 exponential kinetics of mefloquine elimination can be reduced to an operational single exponent for pharmacodynamic modelling by educated choice of sampling times of plasma drug concentration. It is deduced that a second drug dose, at a properly chosen time-interval, results in radical cure even when resistant parasites are present and at maximal parasite growth rates such as those found in non-immune patients. Finally, a table is provided for guiding the optimal choice of dosing intervals under different values of population pharmacokinetics, drug resistance and individual immunity parameters.

PMID: 11676365 [PubMed – in process]

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Parasitology 2001 Oct;123(Pt 4):331-6

Amplified fragment length polymorphism (AFLP) protocol for genotyping the malarial parasite Plasmodium falciparum.

Rubio JM, Berzosa PJ, Benito A.

Department of Parasitology, National Center for Microbiology, National Institute of Health Carlos III, Madrid, Spain.

We have established an amplified fragment length polymorphism (AFLP) protocol for identifying anonymous polymorphic loci of the malarial parasite, Plasmodium falciparum. The method consists of the following steps (i) digestion and ligation in one reaction; (ii) selective fluorescence forward primers labelled; (iii) PCR products resolved in polyacrylamide gels using the ABIPRISM 377 XL DNA sequencer and, (iv) the use of Genescan software to size the fragments. This standardized protocol distinguished between 2 standard reference clones of P. falciparum from West African and Southeast Asian and 2 Central African isolates from patients with clinical malaria. The AFLP protocol resulted in evenly distributed and reproducible band patterns for amplified fragments ranking from 163 to 489 bp long +/-0.5 S.D. The primer Tru ACA labelled with the phosphoramidite 6-carboxifluorescein (FAM-blue) was easy to interpret, with a maximum of 53 bands per clone and of 81 per isolate (mixed falciparum populations) whereas the primer Tru AG labelled with the hexachlorinated analogue (HEX-green) showed a less clear pattern of bands and reproducibility than Tru ACA.

PMID: 11676364 [PubMed – in process]

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Blood 2001 Nov 1;98(9):2859-61

Peripheral blood dendritic cells in children with acute Plasmodium falciparum malaria.

Urban BC, Mwangi T, Ross A, Kinyanjui S, Mosobo M, Kai O, Lowe B, Marsh K, Roberts DJ.

Weatherall Institute of Molecular Medicine, Nuffield Department of Clinical Medicine, and National Blood Service, John Radcliffe Hospital, University of Oxford, United Kingdom; and Wellcome Trust Research Laboratories/KEMRI, Kilifi, Kenya.

The importance of dendritic cells (DCs) for the initiation and regulation of immune responses not only to foreign organisms but also to the self has raised considerable interest in the qualitative and quantitative analysis of these cells in various human diseases. Plasmodium falciparum malaria is characterized by the poor induction of long-lasting protective immune responses. This study, therefore, investigated the percentage of peripheral blood DCs as lineage marker-negative and HLA-DR(+) or CD83(+) cells in healthy children and in children suffering from acute malaria in Kilifi, Kenya. Comparable percentages of CD83(+) DCs were found in peripheral blood of healthy children and children with malaria. However, the percentage of HLA-DR(+) peripheral blood DCs was significantly reduced in children with malaria. The results suggest that a proportion of peripheral blood DCs may be functionally impaired due to the low expression of HLA-DR on their surface. (Blood. 2001;98:2859-2861)

PMID: 11675362 [PubMed – in process]

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Lancet 2001 Oct 13;358(9289):1218-23

Chlorproguanil-dapsone for treatment of drug-resistant falciparum malaria in Tanzania.

Mutabingwa T, Nzila A, Mberu E, Nduati E, Winstanley P, Hills E, Watkins W.

National Institute for Medical Research, Amani-Tanga, Tanzania. Email: [email protected]

BACKGROUND: Resistance to the affordable malaria treatments chloroquine and pyrimethamine-sulfadoxine is seriously impeding malaria control through treatment in east Africa. We did an open, alternate drug allocation study to assess the efficacy of chlorproguanil-dapsone in the treatment of falciparum malaria clinically resistant to pyrimethamine-sulfadoxine. METHODS: Children younger than 5 years with non-severe falciparum malaria, attending Muheza district hospital in Tanzania, were treated with the standard regimen of pyrimethamine-sulfadoxine. Patients whose clinical symptoms resolved but who remained parasitaemic 7 days after pyrimethamine-sulfadoxine were followed up for 1 month. Clinical malaria episodes were retreated with either single dose pyrimethamine-sulfadoxine or a 3-day regimen of chlorproguanil-dapsone. Those with parasitaemia after 7 days were treated with chlorproguanil-dapsone. Parasite DNA was collected on day 7 after first treatment with pyrimethamine-sulfadoxine and we looked for point mutations in the genes encoding dihydrofolate reductase (dhfr) and dyhydropteroate synthetase (dhps). FINDINGS: 360 children were enrolled and treated with pyrimethamine-sulfadoxine. On day 7, 192 (55%) of 348 had cleared parasitaemia. Of the remaining 156 parasitaemic children, 140 (90%) were followed up to day 28, and 92 (66%) of 140 developed clinical malaria. These 92 patients were alternately retreated with either pyrimethamine-sulfadoxine (46) or chlorproguanil-dapsone (46). 28 (61%) of 46 children retreated with pyrimethamine-sulfadoxine were still parasitaemic at day 7, compared with three (15%) of 46 children retreated with chlorproguanil-dapsone. Resistance to pyrimethamine-sulfadoxine increased from 45% (156/348) at the first treatment to 61% (28/46) after retreatment. 83 of 85 parasite isolates collected after the first pyrimethamine-sulfadoxine treatment, and before and after the second treatments with pyrimethamine-sulfadoxine and chlorproguanil-dapsone showed triple-mutant dhfr alleles, associated with a variety of dhps mutations. INTERPRETATION: Most patients treated with pyrimethamine-sulfadoxine, who remain parasitaemic at day 7, develop new malaria symptoms within 1 month. Chlorproguanil-dapsone was a practicable therapy under these circumstances. Analysis of parasite dhfr and dhps before and after treatment supports the view that pyrimethamine-sulfadoxine resistance in this part of Africa is primarily due to parasites with three mutations in the dhfr domain.

PMID: 11675058 [PubMed – in process]

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Vaccine 2001 Nov 12;20(3-4):630-4

Circumvention of MHC class II restriction by genetic immunization.

Schuler K, Lu C, Chang HD, Croft M, Zanetti M, Gerloni M.

Department of Medicine and Cancer Center, University of California, San Diego 9500 Gilman Drive, 92093-0837, La Jolla, CA, USA

The fate of T cell responses to peptide-based vaccination is subject to constraints by the major histocompatibility complex (MHC), MHC restriction. Using as a model system of T and B cell epitopes from the circumsporozoite protein of Plasmodium falciparum malaria parasite, we show that vaccination by somatic transgene immunization readily primes Balb/c mice (H-2(d)) a strain previously reported to be non-responder to immunization with a synthetic peptide vaccine encompassing these epitopes. Following genetic vaccination Balb/c mice developed a primary T cell response comparable to that of the responder strain C57Bl/6 (H-2(b)). Following booster immunization on day 45 Balb/c mice responded with a typical T cell memory response. Priming induced the formation of specific antibodies, which rose sharply after booster immunization. These findings suggests that genetic immunization can circumvent MHC class II restriction.

PMID: 11672931 [PubMed – in process]

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Vaccine 2001 Nov 12;20(3-4):385-96

Comparison of the immunogenic properties of recombinant proteins representing the Plasmodium vivax vaccine candidate MSP1(19) expressed in distinct bacterial vectors.

Cunha MG, Rodrigues MM, Soares IS.

Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de Sao Paulo-Escola Paulista de Medicina, Rua Botucatu 862, 6th Floor, 04023-062, SP, Sao Paulo, Brazil

The 19kDa C-terminal region of the merozoite surface protein 1 (MSP1(19)) is one of the most promising vaccine candidates against the erythrocytic forms of malaria. In the present study, we used three different Escherichia coli expression vectors to generate five recombinant proteins representing the MSP1(19) of Plasmodium vivax. These proteins were compared for reactivity with a panel of sera from individuals naturally exposed to P. vivax and for their immunogenicity in mice. Among the proteins studied, MSP1(19) expressed by the vector pET (His(6)-MSP1(19)) was better recognized by the antibodies of several individuals exposed to P. vivax. The addition of the T-cell Pan-allelic DR epitope (PADRE) did not alter the recognition of this recombinant protein by human antibodies. Although recombinant proteins were immunogenic to mice, immunization with MSP1(19) expressed by the pET or pGEX vectors induced significantly higher antibody titers than a protein produced by the pMAL vector. The antibody immune response elicited by His(6)-MSP1(19) containing the PADRE epitope was compared using different adjuvant formulations. After only two immunizing doses, antibody titers induced in the presence of the adjuvants TiterMax, MPL/TDM/CWS or alum plus CpG ODN 1826 were as high as titers generated by complete Freund’s adjuvant. We concluded that, among the bacterial recombinant proteins, MSP1(19) expressed by the vector pET should be selected for further evaluation in pre-clinical immunizations against P. vivax.

PMID: 11672901 [PubMed – in process]

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Ann Trop Med Parasitol 2001 Sep;95(6):549-58

Randomized comparison of chloroquine and amodiaquine in the treatment of acute, uncomplicated, Plasmodium falciparum malaria in children.

Sowunmi A, Ayede AI, Falade AG, Ndikum VN, Sowunmi CO, Adedeji AA, Falade CO, Happi TC, Oduola AM.

Department of Pharmacology and Therapuetics and Postgraduate Institute for Medical Research and Training, University College Hospital, Ibadan, Nigeria.

The increasing resistance of Plasmodium falciparum to chloroquine (CQ) has created an urgent need for the evaluation of alternative, effective, safe, cheap, readily available and affordable antimalarial treatments. In the present study, the efficacy of amodiaquine (AQ) in the treatment of acute, symptomatic, uncomplicated, P. falciparum malaria was compared with that of CQ, each drug being given at 10 mg/kg per day for 3 days (days 0, 1 and 2). The 210 subjects (104 given AQ and 106 CQ) were Nigerian children aged 5 months-12 years. Fever-clearance times (FCT), parasite densities on days 1-4 and parasite-clearance times (PCT) were all significantly lower with AQ than with CQ. Mean (S.D.) PCT, for example, were 2.6 (0.8) days with AQ and 3.0 (1.0) days with CQ (P = 0.001). The cure rates obtained on days 14, 21 and 28 – 98.1% v. 79.3% (P =0.000), 97.1% v. 64.2% (P = 0.00001) and 95.2% v. 58.5% (P = 0.0000000) with AQ and CQ, respectively – were all also significantly higher with AQ. All but two of the 20 subjects who were considered CQ-treatment failures by day 14 (i.e. two RIII, two RII and 16 RI) responded to subsequent treatment with AQ, with PCT (but not FCT) significantly shorter than during their initial treatment with CQ. In siblings in whom there was clustering of infections, the cure rates were 100% with AQ (N =12) and 63.6% with CQ (N = 11; P = 0.03). Adverse reactions to CQ and AQ were similar and tolerable: pruritus in 10 and 11 children in the AQ and CQ groups, respectively, and gastro-intestinal disturbances which occurred in three children from each group. Haematological parameters were not adversely affected by either drug. At least in the setting of the present study, AQ appears more effective than CQ, effective against CQ-resistant infections, and well tolerated by children with acute, uncomplicated, P. falciparum malaria. It may therefore be useful as an alternative to CQ in areas of CQ resistance.

PMID: 11672461 [PubMed – in process]

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Clin Infect Dis 2001 Nov 15;33(10):1774-7

Age as a Risk Factor for Severe Plasmodium falciparum Malaria in Nonimmune Patients.

Schwartz E, Sadetzki S, Murad H, Raveh D.

Center for Geographic Medicine and Department of Medicine C, Chaim Sheba Medical Center, Tel Hashomer, Israel. 
Email: [email protected]

In this nationwide, cross-sectional study, we evaluated the influence of age and other factors that affect clinical outcome of Plasmodium falciparum malaria in nonimmune patients. Of 135 patients with P. falciparum malaria, 84 (62%) were <40 years old, and only 5% of the patients in this age group developed severe malaria, compared with 18% of the subjects who were >/=40 years of age (odds ratio, 4.29); moreover, all deaths occurred in the latter group. Male subjects did not differ from female subjects with regard to severity of disease.

PMID: 11641827 [PubMed – in process]

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Sante 2001 May;11(3):145-153

[Intrarectal administration of quinine: an early treatment for severe malaria in children?]

[Article in French]

Barennes H, Kailou D, Pussard E, Munjakazi JM, Fernan M, Sherouat H, Sanda A, Clavier F, Verdier F.

Centre Muraz, BP 153, Bobo Dioulasso, Burkina Faso.

Delay for treatment of severe malaria is the cause of an important chilhood mortality in Africa especially in rural zone when health facilities and accessibility are scarce. Intrarectal treatment is of particular interest in children as a non agressive, painless and easy treatment. It can be used as early treatment and could decrease the lethality of severe malaria. We recently showed the kinetic profile, the optimal regimen and the clinical efficacy of intrarectal quinine (QIR) using Quinimax? (Sanofi, Gentilly France) 20 mg/kg in solution with 2 ml of water. From 1994 to 1996 two open clinical trials were performed in Niger in children (2-15 years). QIR was compared with intraveinous infusion in cerebral malaria (n = 76) and with intramuscular quinine in severe malaria (n = 57). A three daily QIR administration (20 mg/kg followed by 15 mg/kg/8 h) was used in cerebral malaria; a two daily administration in severe malaria (30 mg/kg followed by 20 mg/kg/12 h). Symptomatic treatment was associated for hyperthermia, hypoglycemia, anemia and seizures. Results. In the cerebral malaria study 58 children presented a Blantyre coma score below 3. Four children in the IR group and 9 children in the infusion group died (P > 0.05). Evolution was similar in both treatment groups: temperature clearance (< 37.5 C) 39.0 +/- 15.2 h and 37.1 +/- 16.5 h; return to consciousness 34.6 +/- 12.8 h and 33.0 +/- 14.1 h; decrease to 50% of the initial parasites count: 15.5 +/- 11.5 h and 13.8 +/- 10.0 h. Residual blood quinine concentrations at 48 hours were similar 7.4 +/- 3.7 mg/l and 7.2 +/- 2.9 mg/l. In the severe malaria study, the mortality was 0 and 7.6% in the QIR and IM group respectively (P > 0.005). Evolution was similar in both treatment groups: temperature clearance (< 37.5 C) 38.7 +/- 22.8 h and 38.6 +/- 22.2 h; return to consciousness 26.8 +/- 13.9 h and 27.6 +/- 9.9 h for the 16 children in coma. The evolution under QIR treatment was also similar with that described with the other quinine routes. QIR allows an efficious treatment particularly when correct infusion cannot be performed. The efficacy, the simplicity and the good tolerance of QIR are of major concern to decrease the mortality of severe malaria due to delay for treatment and to decrease the side-effects due to intramuscular administrations of quinine in Africa.

PMID: 11641075 [PubMed – as supplied by publisher]

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Proc Natl Acad Sci U S A 2001 Oct 23;98(22):12630-5

Full-text at: http://www.pnas.org

Gambicin: A novel immune responsive antimicrobial peptide from the malaria vector Anopheles gambiae.

Vizioli J, Bulet P, Hoffmann JA, Kafatos FC, Muller HM, Dimopoulos G.

Institut de Biologie Moleculaire et Cellulaire, 15 Rue Rene Descartes, 67084 Strasbourg Cedex, France; and European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany.

A novel mosquito antimicrobial peptide, gambicin, and the corresponding gene were isolated in parallel through differential display-PCR, an expressed sequence tag (EST) project, and characterization of an antimicrobial activity in a mosquito cell line by reverse-phase chromatography. The 616-bp gambicin ORF encodes an 81-residue protein that is processed and secreted as a 61-aa mature peptide containing eight cysteines engaged in four disulfide bridges. Gambicin lacks sequence homology with other known proteins. Like other Anopheles gambiae antimicrobial peptide genes, gambicin is induced by natural or experimental infection in the midgut, fatbody, and hemocyte-like cell lines. Within the midgut, gambicin is predominantly expressed in the anterior part. Both local and systemic gambicin expression is induced during early and late stages of natural malaria infection. In vitro experiments showed that the 6.8-kDa mature peptide can kill both Gram-positive and Gram-negative bacteria, has a morphogenic effect on a filamentous fungus, and is marginally lethal to Plasmodium berghei ookinetes. An oxidized form of gambicin isolated from the cell line medium was more active against bacteria than the nonoxidized form from the same medium.

PMID: 11606751 [PubMed – in process]

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Mol Biochem Parasitol 2001 Oct 1;117(2):161-8

Transglutaminase in Plasmodium parasites: activity and putative role in oocysts and blood stages.

Adini A, Krugliak M, Ginsburg H, Li L, Lavie L, Warburg A.

Department of Parasitology, The Kuvin Center for the Study of Infectious and Tropical Diseases, Hebrew University-Hadassah Medical School, P.O. Box 12272, Ein Kerem, 91120, Jerusalem, Israel

Transglutaminase was identified in malaria parasites by immunofluorescence microscopy using alpha-transglutaminase antiserum. Functional enzyme was demonstrated in vivo and in vitro using labeled polyamines that become incorporated into protein substrates through TGase activity. In Plasmodium falciparum intraerythrocytic parasites, transglutaminase activity was stage-dependent: it was weak in ring-forms but much stronger in trophozoites and schizonts. High levels of activity were detected in P. gallinaceum zygotes and ookinetes and in capsules of oocysts developing on mosquito midguts. Unlike most known transglutaminases, the enzymatic activity in Plasmodium was Ca(2+)-independent. Furthermore, levels of activity were similar at 37 and 26 degrees C. Parasite transglutaminase may be responsible for the modification of erythrocytic cytoskeleton in infected cells and it may facilitate the construction of oocyst capsules by cross-linking mosquito-derived basement membrane components with Plasmodium-derived proteins.

PMID: 11606226 [PubMed – in process]

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Mol Biochem Parasitol 2001 Oct 1;117(2):155-60

Puromycin-N-acetyltransferase as a selectable marker for use in Plasmodium falciparum.

de Koning-Ward TF, Waters AP, Crabb BS.

The Walter and Eliza Hall Institute of Medical Research, PO Royal Melbourne Hospital, Vic. 3050, Melbourne, Australia

The limited number of selectable markers available for malaria transfection has hindered extensive manipulation of the Plasmodium falciparum genome and subsequently thorough genetic analysis of this organism. In this paper, we demonstrate that P. falciparum is highly sensitive to the drug puromycin, but that transgenic expression of the puromycin-N-acetyltransferase (PAC) gene from Streptomyces alboninger confers resistance to this drug with the IC(50) and IC(90) values increasing approximately 3- and 7-fold, respectively in PAC-expressing parasites. Despite this relatively low level of resistance, parasite populations transfected with the PAC selectable marker and selected directly on puromycin emerged at the same rate post-transfection as human dihydrofolate reductase (hDHFR)-expressing parasites, selected independently with the anti-folate drug WR99210. Transfected parasites generally maintained the PAC expression plasmid episomally at between two and six copies per parasite. We also demonstrate by cycling transfected parasites in the presence and absence of puromycin for several weeks, that the PAC selectable marker can be used for gene-targeting. Since the mode of action of puromycin is distinct from other drugs currently used for the stable transfection of P. falciparum, the PAC selectable marker should also have applicability for use in conjunction with other positive selectable markers, thereby increasing the possibilities for more complex functional studies of this organism.PMID: 11606225 [PubMed – in process]

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Mol Biochem Parasitol 2001 Oct 1;117(2):121-8

Calcium regulation in the intraerythrocytic malaria parasite Plasmodium falciparum.

Alleva LM, Kirk K.

School of Biochemistry and Molecular Biology, Faculty of Science, The Australian National University, ACT 0200, Canberra, Australia

The regulation of intracellular Ca(2+) in the intraerythrocytic form of the human malaria parasite, Plasmodium falciparum, was investigated using parasites ‘isolated’ from their host cells by saponin-permeabilisation of the erythrocyte membrane. The isolated parasites maintained tight control over their resting cytosolic Ca(2+) concentration which ranged from approximately 100 nM in the absence of extracellular Ca(2+) to approximately 700 nM in the presence of 1 mM extracellular Ca(2+). The parasite has two functionally discrete intracellular Ca(2+) stores. One is an ‘endoplasmic reticulum (ER)-like’ store, the other an ‘acidic store’. The ER-like store was discharged by cyclopiazonic acid (CPA), an inhibitor of sarco/endoplasmic reticulum Ca(2+)-ATPases (SERCAs) of animal and plant cells, but not by thapsigargin (TG), a more specific inhibitor of SERCAs of animal cells. The acidic store was discharged by nigericin and by NH(4)(+). The amount of Ca(2+) in the ER-like store increased with increasing extracellular Ca(2+) concentration, whereas the amount of Ca(2+) in the acidic store did not. Ca(2+) released from the ER-like store by CPA was cleared from the parasite cytosol by uptake into the acidic store (over a range of extracellular Ca(2+) concentrations), consistent with the acidic store serving as a Ca(2+) reservoir within the intracellular parasite.

PMID: 11606221 [PubMed – in process]