Social Sciences and Malaria

The impact of insecticide-treated bednets on malaria and anaemia in pregnancy in Kassena-Nankana district, Ghana: A randomized controlled trial

Browne E.N.L.; Maude G.H.; Binka F.N.
EMAIL: [email protected]

The impact of insecticide-treated bednet use on malaria and anaemia in pregnancy was assessed, as a supplementary study, in a major WHO/TDR-supported bednet trial in northern Ghana between July 1994 and April 1995. The study area was divided into 96 clusters of compounds, with 48 clusters being randomly allocated to intervention. All pregnant women were included in the study but the focus was on primigravidae and secundigravidae. 1961 pregnant women were recruited into the study – 1033 (52.7%) in the treated bednet group and 928 (47.3%) in the no net group. 1806 (92.1%) had blood taken for malaria microscopy and haemoglobin determination in the third trimester. Pregnancy outcomes were reported for 847 women. The characteristics of women in intervention and control groups were comparable. The odds ratios, with 95% confidence interval (CI), for different study endpoints were, for Plasmodium falciparum parasitaemia – 0.89 (0.73, 1.08), for anaemia – 0.88 (0.70, 1.09), for low birthweight (LBW) – 0.87 (0.63, 1.19), indicating no benefit for treated bednet use. Effective net use by parity varied from 42% in primigravidae to 63% in multigravidae, in spite of free nets and insecticide impregnation. The main reasons for not using a net were warm weather and perceived absence of mosquito biting. Chloroquine use in pregnancy was low and comparable in both groups. Implications of findings for malaria control in pregnancy and further research are discussed.

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Am J Public Health 2001 Oct;91(10):1617-24Community health worker performance in the management of multiple childhood illnesses: Siaya District, Kenya, 1997-2001.

Kelly JM, Osamba B, Garg RM, Hamel MJ, Lewis JJ, Rowe SY, Rowe AK, Deming MS.

Division of Parasitic Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, 4770 Buford Highway NE, Atlanta, GA 30341-3724, USA. 
Email: [email protected]
OBJECTIVES: To characterize community health worker (CHW) performance using an algorithm for managing common childhood illnesses in Siaya District, Kenya, we conducted CHW evaluations in 1998, 1999, and 2001. METHODS: Randomly selected CHWs were observed managing sick outpatient and inpatient children at a hospital, and their management was compared with that of an expert clinician who used the algorithm. RESULTS: One hundred, 108, and 114 CHWs participated in the evaluations in 1998, 1999, and 2001, respectively. The proportions of children treated “adequately” (with an antibiotic, antimalarial, oral rehydration solution, or referral, depending on the child’s disease classifications) were 57.8%, 35.5%, and 38.9%, respectively, for children with a severe classification and 27.7%, 77.3%, and 74.3%, respectively, for children with a moderate (but not severe) classification. CHWs adequately treated 90.5% of malaria cases (the most commonly encountered classification). CHWs often made mistakes assessing symptoms, classifying illnesses, and prescribing correct doses of medications. CONCLUSIONS: Deficiencies were found in the management of sick children by CHWs, although care was not consistently poor. Key reasons for the deficiencies appear to be guideline complexity and inadequate clinical supervision; other possible causes are discussed.

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PubMed

J Med Entomol 2001 Sep;38(5):763-7Analysis of salivary gland proteins of the mosquito Anopheles darlingi (Diptera: Culicidae).

Moreira CK, Marrelli MT, Lima SP, Marinotti O.

Departamento de Parasitologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, SP, Brazil.

The salivary proteins of Anopheles darlingi Root, the principal vector of malaria in the Amazon Region, Brazil, were analyzed. Comparison of the protein profiles between adult males and females revealed that most of the polypeptides are present in both sexes, but female-specific polypeptides also were observed. SDS-PAGE analysis of sugar-fed female mosquitoes with ages varying from 1 to 10 d after adult emergence indicated that the proteins start to be accumulated in the first day of life and are present throughout the period analyzed. Analysis of blood-fed mosquitoes showed no differences in salivary proteins when compared with sugar fed ones, suggesting that there is no specific protein induced by blood. The protein profiles of the salivary glands dissected from wild-caught female mosquitoes from different geographical regions of Brazil were compared and some differences were observed.

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J Med Entomol 2001 Sep;38(5):613-22Deltamethrin treated bednets for control of malaria transmitted by Anopheles culicifacies (Diptera: Culicidae) in India.

Yadav RS, Sampath RR, Sharma VP.

Malaria Research Center, Field Station, Rourkela, Orissa, India. 
Email: [email protected]
In a malaria endemic area in Orissa state in eastern India baseline (November 1989 to October 1990) malaria incidence ranged front 215 to 328 cases/1,000 population/yr in different groups of villages. In November 1990, nylon bednets treated with deltamethrin at 25 mg/m2 were given out in two villages (population 1062), untreated bednets were given out in five villages (population 1,226) and in one village (population 786) nets were not given. Nets were retreated in October 1991 and June 1992 in treated-net villages. The trial continued until October 1992. The treated nets caused significant reduction in indoor resting density, biting (landing), light trap catches, human engorgement rate, and parous rate of malaria vector Anopheles culicifacies Giles as compared with untreated nets or no nets. Untreated nets also caused reductions in biting and indoor density. Treated nets retained insecticidal action well over 6 mo. In the final year, malaria incidence was reduced 8.9% in the no-net village, 34.9% in the villages with untreated nets, and 59.1% in villages with treated nets. The relative risk of malaria and parasite rates declined significantly in villages with treated nets. Pediatric splenomegaly rate did not change in the no-net village, increased significantly in villages with untreated nets, but decreased significantly in those with treated nets. Treated nets also reduced pediatric anemia rates, but Hb concentration increased in all villages. Considering the benefits of treated bednets and development of resistance among vectors to DDT and malathion, bednets treated with deltamethrin could be an effective alternative strategy to control malaria in forested areas in India.

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Trans R Soc Trop Med Hyg 2001 Jul-Aug;95(4):433-8A trial of proguanil-dapsone in comparison with sulfadoxine-pyrimethamine for the clearance of Plasmodium falciparum infections in Tanzania.

Mutabingwa TK, Maxwell CA, Sia IG, Msuya FH, Mkongewa S, Vannithone S, Curtis J, Curtis CF.

Amani Medical Research Centre, Box 4, Amani, Tanga, Tanzania.

Considerable levels of resistance to sulfadoxine-pyrimethamine (SP) have been reported in Plasmodium falciparum in north-eastern Tanzania, and the identification of a suitable antimalarial to replace SP is now a high priority. We conducted a trial in July 2000 to determine the efficacy of proguanil (PG) plus dapsone (DS), compared with that of SP, for the treatment of asymptomatic falciparum infection. A total of 220 children with parasitaemia > or = 2000 per microL completed the study; 112 had received a single dose of SP (dosage calculated for pyrimethamine 1.25 mg/kg and sulfadoxine 25 mg/kg) and 108 had taken PG 10 mg/kg with DS 2.5 mg/kg each day for 3 days. Clearance of asexual parasites at day 7 was 14.3% with SP, but 93.5% with PG-DS. The remarkably high failure rate with SP was not associated with occurrence of leucine substitution at position 164 of the dhfr gene. Both treatment regimens were well tolerated. Compared with available data on another antifolate combination, chlorproguanil-dapsone (‘Lapdap’), PG-DS was slightly but significantly inferior in achieving parasite clearance (99.5% versus 93.5%). The estimated cost of a 3-day course of PG-DS treatment for a child weighing 18 kg is US $0.15. With the rising incidence of SP-resistant P. falciparum infection, PG-DS could provide an effective, affordable and already available therapeutic alternative for malaria in East Africa at least until chlorproguanil-dapsone is registered.

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Trans R Soc Trop Med Hyg 2001 Jul-Aug;95(4):429-32Causal prophylactic efficacy of atovaquone-proguanil (Malarone) in a human challenge model.

Berman JD, Nielsen R, Chulay JD, Dowler M, Kain KC, Kester KE, Williams J, Whelen AC, Shmuklarsky MJ.

Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA. 
Email: jonathan.b[email protected]
Plasmodia infect the liver for about 7 days before subsequently infecting the blood. Present prophylaxis against Plasmodium falciparum malaria employs agents that primarily kill blood stages and must be continued for 28 days after the last exposure. Atovaquone-proguanil (Malarone) is a new antimalarial agent that is licensed in 35 countries as treatment against blood-stage infection, but its components (atovaquone and proguanil) have separately been shown to be active also against liver stages. To determine whether atovaquone-proguanil is sufficiently active against liver stages to be discontinued 7 days after exposure, we challenged 16 volunteers with P. falciparum via infected mosquitoes. Twelve volunteers received atovaquone-proguanil (1 tablet daily) on the day prior to challenge, on the day of challenge, and for the next 6 days; 4 volunteers received matching placebo. All placebo volunteers demonstrated parasitaemia and malarial symptoms beginning on days 11-12 after challenge. No atovaquone-proguanil volunteer acquired malaria. Atovaquone-proguanil is the first licensed antimalarial agent that kills P. falciparum in the liver and that may be discontinued 7 days after the last exposure.

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Trans R Soc Trop Med Hyg 2001 Jul-Aug;95(4):424-8The safety of the combination artesunate and pyrimethamine-sulfadoxine given during pregnancy.

Deen JL, von Seidlein L, Pinder M, Walraven GE, Greenwood BM.

Medical Research Council Laboratories, Farafenni Field Station, P. O. Box 273, Banjul, The Gambia, West Africa.

Malaria during pregnancy is associated with an increased risk of severe anaemia and low-birthweight babies. Effective intermittent therapy with pyrimethamine-sulfadoxine (PSD) decreases parasitaemia and severe anaemia and improves birthweight in areas where Plasmodium falciparum is sensitive to this drug. Increasing resistance to PSD is a concern and alternative antimalarial regimens during pregnancy are needed. Artesunate with PSD is a promising antimalarial combination but few data are available on the safety of artemisinins when taken during pregnancy. Outcome of pregnancy was evaluated for 287 women in The Gambia who were exposed in June 1999 to a single dose of the combination artesunate and PSD during a mass drug administration and 172 women who were not exposed. Women who received placebo (40) and those who did not participate in the mass drug administration (132) comprised the non-exposed group. There was no difference in the proportion of abortions, stillbirths, or infant deaths among those exposed or not exposed to the drugs. The mean weight of 18 infants born to mothers who had received artesunate and PSD during the third trimester was 3.10 kg compared to a mean weight of 2.62 kg of the 10 infants of untreated mothers (adjusted P value = 0.05). We found no evidence of a teratogenic or otherwise harmful effect of gestational exposure to artesunate and PSD. Treatment of a self-selected group of pregnant women with PSD and artesunate during pregnancy was associated with a greater birthweight, which may have resulted from clearance of malaria parasites. However, the influence of confounding factors cannot be excluded.

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Trans R Soc Trop Med Hyg 2001 Jul-Aug;95(4):391-7The detection of Plasmodium falciparum and P. vivax in DNA-extracted blood samples using polymerase chain reaction.

Zaman S, Tan L, Chan HH, Aziz L, Abdul-Samat S, Wahid R, Kamal A, Ahmed M, Zaman V.

Centre for Life Sciences and Chemical Technology, Ngee Ann Polytechnic, 535 Clementi Road, Singapore 599489, Singapore. 
Email: [email protected]
Seventeen pairs of published primer sets were compared for their relative sensitivity to detect malaria DNA extracted from blood samples, which were obtained from Pakistani patients suffering from malaria. The primer sets investigated consisted of: (i) 9 pairs of direct primers and 3 sets of nested primers for detecting Plasmodium falciparum, (ii) 2 pairs of direct primers and 2 sets of nested primers for detecting P. vivax, and (iii) 1 set of multiplex primers for detecting both P. falciparum and P. vivax, simultaneously. After a miniscreen of 9 DNA-extracted blood samples using the 17 primer sets stated above, 5 primer sets were short-listed (based on their superior sensitivity) and used for a maxi-screen of DNA extracted from 126 microscopy-positive blood samples from Pakistan, with the following results. (i) For the detection of P. falciparum, the direct primer pair ‘PF1 + PF2’ gave a sensitivity of 95% and the nested primer set ‘RIT405 + RIT406/RIT371 + RIT372’ gave a sensitivity of 97%. (ii) For the detection of P. vivax, the direct primer pair ‘Forward + Reverse’ and the nested primer set ‘PLF + UNR/PLF + VIR’ both gave a sensitivity of 94%. (iii) The nested multiplex primer set ‘rPLU5 + rPLU6/rFAL1 + rFAL2 + rVIV1 + rVIV2’ gave a sensitivity of 97% and 96% for P. falciparum and P. vivax, respectively. It was concluded that the nested multiplex primer set was the most optimal primer set to use for the detection of malaria DNA extracted from blood samples. Furthermore, the nested multiplex primer set has the advantage of simultaneously detecting and differentiating between P. vivax and P. falciparum.

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Trans R Soc Trop Med Hyg 2001 Jul-Aug;95(4):353-60Insecticide-treated materials, mosquito adaptation and mass effect: entomological observations after five years of vector control in Burkina Faso.

Ilboudo-Sanogo E, Cuzin-Ouattara N, Diallo DA, Cousens SN, Esposito F, Habluetzel A, Sanon S, Ouedraogo AP.

Centre National de Recherche et de Formation sur le Paludisme, 01 B.P. 2208, Ouagadougou 01, Burkina Faso. 
Email: [email protected]
Insecticide-treated bednets and curtains have been shown to be successful in reducing malaria transmission and child mortality in Africa over periods of up to 2 years. A major concern relating to this approach is that, in time, it will be compromised by the selection of mosquito genotypes that are resistant at the biochemical or behavioural level. We report entomological data from a large area in Burkina Faso where insecticide-treated curtains have been in use for up to 5 years. Longitudinal indoor and outdoor CDC light-trap catches were performed in 4 sentinel villages. In addition cross-sectional surveys using indoor spray catches and outdoor CDC light-trap catches were performed each September in a larger number of villages, including 8 located outside the intervention area. We found no evidence of the selection of mosquito phenotypes that might compromise the intervention. Indoor and outdoor vector densities remained very low after 5 years of intervention, both compared with pre-intervention levels and with concurrent levels outside the intervention area. We found no evidence of a switch to outdoor rather than indoor biting. The proportion of blood meals taken on humans may have decreased but our data are inconclusive on this point. We observed higher vector densities and sporozoite rates at the periphery of the intervention zone than at the centre, which may reflect re-invasion of peripheral villages by mosquitoes from outside the intervention area. In ‘real life’ programmes, with perhaps patchy, less than optimal coverage, the protection against malaria transmission provided to individuals using insecticide-treated materials may be less than that achieved in the randomized controlled trials which demonstrated an impact of insecticide-treated materials on child mortality.

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Trans R Soc Trop Med Hyg 2001 Jul-Aug;95(4):345-6Rational use of drugs against Plasmodium falciparum.

Warhurst DC, Duraisingh MT.

Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK. 
Email: [email protected]
Recent studies on resistance to blood schizontocides in Plasmodium falciparum give a rational basis for the use of artemisinins combined with arylaminoalcohols for the treatment of uncomplicated chloroquine-resistant malaria in Africa. In areas where such combinations are introduced, there is reason to believe that the continued use of chloroquine in the community will help protect the new drugs from resistance. In view of several laboratory studies, combinations of artemisinins with antifolates or chloroquine pose a risk of antagonistic interaction. This can be avoided by use of the artemisinin and the companion drug sequentially.

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Ann Trop Paediatr 2001 Sep;21(3):211-22A randomised, double-blind, placebo-controlled clinical trial of vitamin A in severe malaria in hospitalised Mozambican children.

Varandas L, Julien M, Gomes A, Rodrigues P, Van Lerberghe W, Malveiro F, Aguiar P, Kolsteren P, Van Der Stuyft P, Hilderbrand K, Labadarios D, Ferrinho P.

Health Systems Unit and Centre for Malaria and other Tropical Diseases, Institute of Hygiene and Tropical Medicine, New University of Lisbon, Portugal. 
Email: [email protected]
This paper reports a randomised, double-blind, placebo-controlled clinical trial of the effect of routine vitamin A supplementation given on admission to children with severe malaria with regard to survival, recovery during hospitalisation and outcome 6 weeks after discharge. Children aged between 6 and 72 months admitted to the paediatric wards of the Central Hospital of Maputo (CHM), Mozambique with a diagnosis of severe malaria were randomly assigned either to a control group (placebo) or an experimental group (vitamin A) and were followed up 6 weeks after discharge. There were 280 children in the experimental and 290 in the placebo group. Seven (2.5%) and 13 (4.5%) children died in the experimental and the placebo groups, respectively, a relative risk of death of 0.56 (95% CI 0.23-1.38, p = 0.201). During the 1st 5 hours of admission, the relative risk of death in the vitamin A-supplemented group was 2.54 (0.50-12.96); after 5 hours of admission it was 0.19 (95% CI 0.04-0.85; p = 0.015). In the supplemented group, 4/82 (4.9%) of the children developed neurological sequelae vs 2/78 (2.6%) in the placebo group (RR = 1.90; 95% CI 0.36-10.09; p = 0.682). Although the overall reduction in the risk of death observed for all children receiving vitamin A is not statistically significant, it might be clinically important. This finding cannot, however, be accepted as a firm conclusion and requires validation by future trials.

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Science 2001 Sep 28;293(5539):2370-1Malaria research: two new steps toward a ‘better mosquito’.

Enserink M.

BARCELONA, SPAIN–Scientists have long fantasized about the ultimate method to eradicate malaria: replacing existing mosquito populations with ones unable to spread the disease. At a meeting here last week, researchers presented two studies that could help edge that dream closer to reality. Some researchers hailed the new studies as milestones, but skeptics warned that the strategy may never work in practice.

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J Assoc Physicians India 2001 Jul;49:692-6A multicentric study with arteether in patients of uncomplicated falciparum malaria.

Asthana OP, Srivastava JS, Kamboj VP, Valecha N, Sharma VP, Gupta S, Pande TK, Vishwanathan KA, Mahapatra KM, Nayak NC, Mahapatra PK, Mahanta J, Srivastava VK, Vasdev, Singh N, Shukla MM, Balsara AB, Mishra SK, Satpathy SK, Mohanty S, Dash B.

Central Drug Research Institute, Lucknow, India.

Two hundred and sixty seven patients of uncomplicated P. falciparum malaria completed study in a multicentric phase III clinical trial of Arteether. Arteether was given intramuscularly in a dose of 150 mg daily for three consecutive days. Each patient was followed upto 28 days of alpha, beta arteether therapy. The cure rate was 97% with fever clearance time between 1-7 days (24-168 hours) and parasite clearance time between 1-3 days (24-72 hours). Parasite reappearance rate was found to be 3% and reported at only three of the centres. Following the treatment no adverse effect was observed on haematological, biochemical and vital clinical parameters.

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Saudi Med J 2001 Aug;22(8):690-3Efficacy of Sulphadoxine and Pyrimethamine, Doxycycline and their combination in the treatment of chloroquine resistant Falciparum Malaria.

Elkheir HK, Elkarim EF, Eltayeb IB, Elkadaru AE, Babiker HA, Ibrahim AM.

Faculty of Pharmacy, University of Khartoum, Khartoum, Sudan.

OBJECTIVE: The present in vivo study evaluates the efficacy of sulphadoxine/pyrimethamine, doxycycline and their combination in the treatment of Sudanese patients infected by chloroquine resistant falciparum malaria. METHODS: Febrile patients with positive blood smears of Plasmodium falciparum were given chloroquine 25mg-base/kg body weight and followed up for 3 days. Patients with recrudescence due to chloroquine resistance were readmitted for test treatment. Using simple number randomization patients were divided into groups, A, B and C. These were treated with doxycycline, sulphadoxine/ pyrimethamine and a combination therapy of sulphadoxine/pyrimethamine plus doxycycline. Doxycycline was initially administered as a single dose of 200mg followed by 100mg daily for 6 days whereas sulphadoxine/pyrimethamine was given as a single dose of sulphadoxine 1500mg and pyrimethamine 75mg. Patients of group C received the combination therapy of sulphadoxine/pyrimethamine and doxycycline. Clinical observations and examination of blood films were carried out for each patient daily for 6 days and thereafter weekly for 4 weeks. RESULTS: A high level of chloroquine resistance (75%) was documented amongst 280 patients (age 15-53 years) visiting Omdurman Hospital of Endemic Diseases during 1996-1998. The study demonstrated that only 46% and 78% of the patients were cured after 4 days of treatment by doxycycline and sulphadoxine/pyrimethamine. Patients treated with sulphadoxine/pyrimethamine in combination with doxycycline had a cure rate of 90% and 100% after 3-4 days of treatment, a single recrudescent case was detected on day 6. No relapses occurred during the follow up period. All patients were successfully treated by all regimens with the exception of one case treated by doxycycline. All treatments were well tolerated but a few cases had complaints of nausea. CONCLUSION: The combination therapy of doxycycline/sulphadoxine/pyrimethamine appeared to be significantly effective in the treatment of patients with chloroquine resistant falciparum malaria without causing any serious side effects. Such a combination regimen has the advantages of being available at a reasonable cost and less prone to development of resistance.

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Parasitol Res 2001 Sep;87(9):715-21Immune-mediated parasite clearance in mice infected with Plasmodium berghei following treatment with manzamine A.

Ang KK, Holmes MJ, Kara UA.

Department of Biological Sciences, National University of Singapore, Singapore. Email: [email protected]
Manzamine A, a sponge-derived alkaloid, was recently shown to possess in vivo antimalarial activity against the blood stages of the rodent malaria parasite Plasmodium berghei. A single intraperitoneal dose of 100 micromol/kg of manzamine A suppressed parasite growth but was followed by parasite recrudescence. Forty percent of mice with recrudescing parasites were able to recover and clear the fulminating parasitaemia. Examination of sera from these mice revealed that infected mice treated with manzamine A had a suppressed IFN-gamma production but an increase in their IL-10 and IgG production. The prolonged survival of infected mice treated with manzamine A and the eventual clearance of recrudescing parasites in some of these mice involve a down-regulation of Thl responses and a switch to antibody dependent-Th2 responses.

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Vaccine 2001 Oct 12;20(1-2):275-80Enhancement of the immune response in rabbits to a malaria DNA vaccine by immunization with a needle-free jet device.

Aguiar JC, Hedstrom RC, Rogers WO, Charoenvit Y, Sacci JB, Lanar DE, Majam VF, Stout RR, Hoffman SL.

Malaria Program, Naval Medical Research Center, 503 Robert Grant Avenue, 20910-7500, Silver Spring, MD, USA

We compared the needle free jet device device Biojector with syringe/needle as a method to administer a DNA vaccine encoding the Plasmodium falciparum circumsporozoite protein (PfCSP) in albino rabbits. A group of three rabbits was injected by the intramuscular (IM) route using a syringe/needle combination, a second group IM with the Biojector device and a third group both IM and intradermal (ID) using the Biojector. When animals were immunized with the Biojector IM or IM/ID as compared to the syringe/needle IM, we observed 10- and 50-fold greater antibody titers, as measured by enzyme immunoassay (EIA) and indirect fluorescence antibody test (IFAT), respectively. We also observed that the Biojector conferred a greater ability to prime the immune system as compared with the needle. The subsequent boosting of all animals with a recombinant canary pox virus (ALVAC) expressing PfCSP induced significantly higher titers in both Biojector groups of rabbits as compared with the needle and naive animals. These results provided the foundation for a clinical trial using the same regime.

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Eur Cytokine Netw 2001 Jul-Aug;12(3):528-36Protection of mice from malaria after co-administration of recombinant mouse granulocyte-macrophage colony- stimulating factor and methionine-enkephalin.

Singh PP, Singh S.

Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Sector-67, Phase-X, SAS Nagar-160 062, India.

The protective effect of co-administration of recombinant mouse granulocyte-macrophage colony-stimulating factor (rmGM-CSF) and synthetic peptide met-enkephalin (M-ENK) against blood-induced Plasmodium berghei infection in Swiss mice was investigated. Mice co-administered with rmGM-CSF (10.0 mug/kg) and M-ENK (2.0 mg/kg) x 3/day, i.p., beginning on day -1 and continuing through day +4 after the initiation of infection, showed significant suppression (p < 0.05) (sometimes even complete elimination) of parasitaemia compared to vehicle-treated controls. However, when administered separately, neither of these agents induced any detectable protective effect. Surprisingly, mice similarly co-administered with rmGM-CSF (10.0 mug/kg) and higher doses of M-ENK (10.0 mg/kg), showed no protection. Polyclonal neutralizing (100%) antibody to rmGM-CSF abrogated the combined protective effect of these agents. Additionally, naloxone (10.0 mg/kg/day x 6, i.p.), a non-selective, opioid receptor antagonist, also blocked the combined protection. Mice that survived the challenge showed a significant increase (p < 0.05) in total circulating leukocytes counts, and the pool-size and the phagocytic activity of both the peritoneal and splenic macrophages, ex vivo. Silica (3.0 mg/mouse, i.v.) abrogated the combined protective effect of rmGM-CSF and M-ENK. These results indicate that co-administration of rmGM-CSF and dose dependent quantities of M-ENK in P. berghei-infected mice can protect against malaria, apparently through macrophage-mediated mechanisms.

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J Inorg Biochem 2001 Sep;86(2-3):617-25A spectroscopic investigation of the binding interactions between 4,5-dihydroxyxanthone and heme.

Xu Kelly J, Winter R, Riscoe M, Peyton DH.

Department of Chemistry, Portland State University, PO Box 751, 97207-0751, Portland, OR, USA

In order to investigate one possible mechanism by which xanthones inhibit growth of malaria-causing Plasmodium parasites, optical and NMR spectroscopic studies were performed on a prototypic xanthone, 4,5-dihydroxyxanthone (45X2), upon its complexation to heme. The 45X2&z.ccirf;heme complex stoichiometry in aqueous solution was found to be 1:2; this interaction was non-cooperative, and exhibited a very similar heme complex dissociation constant (K(d)=5.1×10(-6)) as observed for the common antimalarial agents, chloroquine and quinine. The 45X2&z.ccirf;heme(2) complex formation was found to be both pH- and solvent-dependent, with clear evidence of the xanthone carbonyl moiety coordinating with the iron of heme. Hydrogen bonding between the hydroxyl groups of 45X2 and the propionate side chains of heme, as well as pi-pi stacking between both aromatic systems appeared to contribute to the overall stability of the 45X2&z.ccirf;heme(2) complex, as judged by 1H NMR. It was concluded that 45X2 forms a complex with a heme dimer in aqueous solution, and that this interaction can be generalized to account for its in vivo detrimental effect of parasite growth through an effective inhibition of hemozoin aggregate formation.

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Int J Parasitol 2001 Oct;31(12):1381-91Vesicle-mediated trafficking of parasite proteins to the host cell cytosol and erythrocyte surface membrane in Plasmodium falciparum infected erythrocytes.

Taraschi TF, Trelka D, Martinez S, Schneider T, O’Donnell ME.

Department of Pathology, Anatomy & Cell Biology, Jefferson Medical College, Thomas Jefferson University, 1020 Locust Street, 19107, Philadelphia, PA, USA

During the development of the asexual stage of the malaria parasite, Plasmodium falciparum, the composition, structure and function of the host cell membrane is dramatically altered, including the ability to adhere to vascular endothelium. Crucial to these changes is the transport of parasite proteins, which become associated with or inserted into the erythrocyte membrane. Protein and membrane targeting beyond the parasite plasma membrane must require unique pathways, given the parasites intracellular location within a parasitophorous vacuolar membrane and the lack of organelles and biosynthetic machinery in the host cell necessary to support a secretory system. It is not clear how these proteins cross the parasitophorous vacuolar membrane or how they traverse the erythrocyte cytosol to reach their final destinations. The identification of: (1) a P. falciparum homologue of the protein Sar1p, which is an essential component of the COPII-based secretory system in mammalian cells and yeast and (2) electron-dense, possibly coated, secretory vesicles bearing P. falciparum erythrocyte membrane protein 1 and P. falciparum erythrocyte membrane protein 3 in the host cell cytosol of P. falciparum infected erythrocytes recently provided the first direct evidence of a vesicle-mediated pathway for the trafficking of some parasite proteins to the erythrocyte membrane. The major advance in uncovering the parasite-induced secretory pathway was made by incubating infected erythrocytes with aluminium tetrafluoride, an activator of guanidine triphosphate-binding proteins, which resulted in the accumulation of the vesicles into multiple vesicle strings. These vesicle complexes were often associated with and closely abutted the erythrocyte membrane, but were apparently prevented from fusing by the aluminium fluoride treatment, making their capture by electron microscopy possible. It appears that malaria parasites export proteins into the host cell cytosol to support a vesicle-mediated protein trafficking pathway.

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Int J Parasitol 2001 Oct;31(12):1371-9

Plasmodium falciparum signal sequences: simply sequences or special signals?

Nacer A, Berry L, Slomianny C, Mattei D.

Unite de Biologie des Interactions Hote-Parasite, CNRS URA 1960, Institut Pasteur, 75724, Paris, France

The malaria parasite, Plasmodium falciparum, synthesises and exports several proteins inducing morphological and biochemical modifications of erythrocytes during the erythrocytic cycle. The protein trafficking machinery of the parasite is similar to that of other eukaryotic cells in several ways. However, some unusual features are also observed. The secretion of various polypeptides was inhibited when P. falciparum-infected erythrocytes were incubated with Brefeldin A. Immunoelectron microscopy studies revealed substantial morphological changes in the endoplasmic reticulum following exposure of parasitised erythrocytes to the drug. Immunofluorescence studies of Brefeldin A-treated parasites suggest that polypeptide sorting to different intracellular destinations begins at the endoplasmic reticulum. The parasite also secretes polypeptides by a Brefeldin A-insensitive route that bypasses the classical endoplasmic reticulum-Golgi complex pathway.

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Int J Parasitol 2001 Oct;31(12):1331-42Transport proteins of Plasmodium falciparum: defining the limits of metabolism.

Krishna S, Webb R, Woodrow C.

Department of Infectious Diseases, St. George’s Hospital Medical School, Cranmer Terrace, SW17 ORE, London, UK

In this review we give an account of transport processes occurring at the membrane interface that separates the asexual stage of Plasmodium falciparum from its host, the infected erythrocyte, and also describe proteins whose activities may be important at this location. We explain the potential clinical value of such studies in the light of the current spread of parasite resistance to conventional antimalarial strategies. We discuss the uptake of substrates critical to the survival of the intracellular malaria parasite, and also the parasite’s homeostatic and disposal mechanisms. The use of the Xenopus laevis expression system in the characterisation of a hexose transporter (‘PfHT1’) and a Ca(2+) ATPase (‘PfATP4’) of the parasite plasma membrane are described in detail.