EHP Library Malaria Bulletin, Feb 6 – 13, 2001

Social Sciences and Malaria

BMJ 2001 Feb 10;322(7282):316B

Mouthwash may treat malaria.
Berger A

Full text article at http://www.bmj.com

BMJ 2001 Feb 3;322(7281):249-250

Insecticide treated bed nets to prevent malaria. The challenge lies in implementation.
D’Alessandro U

Department Parasitology, Prince Leopold Institute of Tropical Medicine, B-2000 Antwerp, Belgium 
Email: [email protected]

(full-text at: http://www.bmj.com)

BMJ 2001 Feb 3;322(7281):270-273

Impact on malaria morbidity of a programme supplying insecticide treated nets in children aged under 2 years in Tanzania: community cross sectional study.
Abdulla S, Schellenberg JA, Nathan R, Mukasa O, Marchant T, Smith T, Tanner M, Lengeler C

Ifakara Health Research and Development Centre, PO Box 53, Ifakara, Tanzania.

(full-text at http://www.bmj.com)
Objective: To assess the impact of a social marketing programme for distributing nets treated with insecticide on malarial parasitaemia and anaemia in very young children in an area of high malaria transmission. Design: Community cross sectional study. Annual, cross sectional data were collected at the beginning of the social marketing campaign (1997) and the subsequent two years. Net ownership and other risk and confounding factors were assessed with a questionnaire. Blood samples were taken from the children to assess prevalence of parasitaemia and haemoglobin levels. Setting: 18 villages in the Kilombero and Ulanga districts of southwestern Tanzania. Participants: A random sample of children aged under 2 years. Main outcome measures: The presence of any parasitaemia in the peripheral blood sample and the presence of anaemia (classified as a haemoglobin level of <80 g/l). Results: Ownership of nets increased rapidly (treated or not treated nets: from 58% to 83%; treated nets: from 10% to 61%). The mean haemoglobin level rose from 80 g/l to 89 g/l in the study children in the successive surveys. Overall, the prevalence of anaemia in the study population decreased from 49% to 26% in the two years studied. Treated nets had a protective efficacy of 62% (95% confidence interval 38% to 77%) on the prevalence of parasitaemia and of 63% (27% to 82%) on anaemia. Conclusions: These results show that nets treated with insecticide have a substantial impact on morbidity when distributed in a public health setting.

Trop Med Int Health 2000 Dec;5(12):876-881

Child malaria treatment practices among mothers in the district of Yanfolila, Sikasso region, Mali.
Thera M, D’Alessandro U, Ouedraogo A, Packou J, Souleymane O, Fane M, Ade G, Alvez F, Doumbo O

Faculte de Medecine de Pharmacie et d’Odontostomatologie/Departement de l’Epidemiologie des Affections Parasitaires, Bamako, Mali; Department of Parasitology, Prince Leopold Institute of Tropical Medicine, Antwerp, Belgium; Service Sociosanitaire de Cercle, Sikasso, Mali; CHR Koudougou, Burkina Faso; Programme National de Lutte contre le Paludisme, Libreville, Gabon; Moughataa de Maghama, Gorgol, Mauritanie; Programme National de Lutle contre le Paludisme, Bamaka, Mali; Cotonou, Benin.

We studied child malaria treatment practices among mothers living in the District of Yanfolila in southern Mali. For sampling, we first chose five of 13 health areas with probability proportional to size. Then villages, compounds and mothers with at least one child aged 1-5 years were randomly chosen. We assessed the spleen size of one 1-5 year-old child of each mother, collected a thick blood film and recorded the body temperature of every child whose mother thought he/she was sick. 399 mothers in 28 villages were interviewed with a structured questionnaire divided into two parts. If the child had had soumaya (a term previously associated with uncomplicated malaria) during the past rainy season, we asked about signs and symptoms, health-seeking behaviour (who the mother consulted first) and treatment. If not, information about knowledge of the disease and treatment to be given was collected. 86% of the mothers interviewed stated that their child had been sick and almost half of them had had soumaya. All mothers named at least one sign by which they recognized the disease. Vomiting, fever and dark urine/yellow eyes/jaundice were the three most common signs mentioned. 75.8% managed their child’s disease at home and used both traditional and modern treatment. The most common anti-malarial drug was chloroquine, often given at inappropriate dosage. The sensitivity and specificity of the mothers’ diagnosis was poor, although this might be explained by the large percentage of children who had already been treated at the time of the interview. The results of our survey call for prompt educational action for the correct treatment of uncomplicated malaria/soumaya, particularly for mothers and possibly for shopkeepers. The high spleen rate (58.1%) among randomly selected children confirms that malaria is a common disease in this area. Improved case-management at home could only be beneficial.

Trop Med Int Health 2000 Dec;5(12):865-875

Treatment for clinical malaria is sought promptly during an epidemic in a highland region of Uganda.
Lindblade KA, O’Neill DB, Mathanga DP, Katungu J, Wilson ML

Department of Epidemiology, School of Public Health, University of Michigan, Ann Arbor, USA; CDC/KEMRI, Kisumu, Kenya; School of Law, University of Michigan, Ann Arbor, USA; Kabale District Medical Office, Kabale, Uganda.

Early diagnosis of malaria followed by appropriate treatment can help reduce related morbidity and mortality as well as interrupt transmission. Previous studies of household responses to malaria have tended to focus on endemic areas where the burden of this disease is greatest. With the apparent increasing frequency of epidemics in African highlands, a better understanding of treatment behaviours in areas of unstable transmission may be important to future public health interventions. This study was undertaken following a serious epidemic of malaria in the highlands of south-western Uganda. Our objectives were to characterize actions taken by both adults and caretakers of children </=5 years old during their most recent episode of self-diagnosed malaria, and to identify factors that were associated with prompt treatment at a health facility. A survey of 300 households selected in a 2-stage cluster sampling procedure produced 453 adult respondents and 133 caretakers of children </=5 years old. We found that almost 65% of adults and 62% of children who had experienced an episode of malaria in the last year (most during the epidemic) had sought treatment from a health facility first as opposed to self-treatment. Most of these people had visited the health facility within 1 day of symptom onset. By the end of their malaria episode, over 87% of adults and 80% of children had visited a health facility at least once. Factors associated with prompt presentation at a health facility included severity of illness, household proximity to a health facility, and knowledge of malaria prevention methods. Our results indicate that there is an important role for the formal health care system in mitigating morbidity and mortality and reducing transmission during malaria epidemics in Uganda.

J Ethnopharmacol 2001 Feb;74(2):195-204

In vitro screening of Indian medicinal plants for antiplasmodial activity.
Simonsen HT, Nordskjold JB, Smitt UW, Nyman U, Palpu P, Joshi P, Varughese G

Department of Medicinal Chemistry, Royal Danish School of Pharmacy, Group of Pharmacognosy, Universitetsparken 2, 2100, Copenhagen, Denmark

Plants traditionally used in India to treat fever or malaria were examined in vitro for antiplasmodial properties against Plasmodium falciparum. Of 80 analysed ethanol extracts, from 47 species, significant effects were found for 31 of the extracts. These represent 23 different species from 20 families. Of the active species 20 were tested against P. falciparum for the first time. The following five species seems to be of special interest for further antimalarial studies, Casearia elliptica, Holarrhena pubescens, Pongamia pinnata, Soymida febrifuga, and Plumbago zeylanica.

J Ethnopharmacol 2001 Feb;74(2):141-148

Antimalarial activity of Ajuga remota Benth (Labiatae) and Caesalpinia volkensii Harms (Caesalpiniaceae): in vitro confirmation of ethnopharmacological use.
Kuria KA, De Coster S, Muriuki G, Masengo W, Kibwage , Hoogmartens J, Laekeman GM

Faculty of Pharmacy, University of Nairobi, Nairobi, Kenya

Field trips to herbalists’ practices in an area about 200 miles around Nairobi (Kenya) enabled us to make a list of medicinal plant species preferentially used to treat malaria. Ajuga remota and Caesalpinia volkensii were further investigated as being the most frequently used species. Aqueous decoctions, ethanol macerates, and petroleum ether, methanol and water Soxhlet extracts of these plants were further tested for their in vitro antimalarial properties in a chloroquine sensitive (FCA/20GHA) and resistant (W2) strain of Plasmodium falciparum. The activity was assessed by the parasite lactate dehydrogenase (pLDH) assay method. There was a concentration-dependent inhibition by the vegetal extracts of both plants. The IC(50) of the most active A. remota extract (ethanol macerate) was 55 and 57 ?g/ml against FCA/20GHA and W2, respectively. For C. volkensii, it was the Soxhlet-water extract which was most active against FCA/20GHA with an IC(50) of 404 ?g/ml while the petroleum ether extract exhibited the most activity against W2 with an IC(50) of 250 ?g/ml. Further phytochemical work is being done in order to identify the active principles.

PubMed – Feb 6 – Feb 13, 2001

Yeast 2001 Jan 30;18(2):137-150

Structural conformers produced during malaria vaccine production in yeast.
Stowers AW, Zhang Y, Shimp RL, Kaslow DC

Malaria Vaccine Development Unit, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA.

A recombinant protein expression system based on Saccharomyces cerevisiae has been used to express malarial vaccine candidate antigens. The antigens so produced have been used in three Phase 1 clinical trials and numerous preclinical non-human primate trials. Further Phase I trials are planned using these candidate vaccine antigens. These molecules were identified as attractive candidates for antimalarial vaccines, as they are all surface-exposed at some stage in the parasite’s life cycle. They all share an unusual structural feature: epidermal growth factor (EGF)-like motifs. When these proteins are expressed in our S. cerevisiae expression system, they are produced as a series of stable structural conformers, each with a different disulphide bonding pattern. This leads to both biochemical and, more importantly, antigenic differences between the conformers (e.g. presence or absence of an antibody B cell epitope). These findings have important ramifications for other EGF-domain-containing proteins expressed in S. cerevisiae, or for proteins which contain other cysteine-folding motifs not normally expressed by this organism, both for vaccine production or for research/reagent purposes. Copyright 2000 John Wiley & Sons, Ltd.

Eur J Immunol 2001 Jan;31(1):72-81

Low CD4(+) T cell responses to the C-terminal region of the malaria merozoite surface protein-1 may be attributed to processing within distinct MHC class II pathways.
Quin SJ, Seixas EM, Cross CA, Berg M, Lindo , Stockinger B, Langhorne J

National Institute for Medical Research, The Ridgeway, Mill Hill, London, GB.

The C-terminal fragment of merozoite surface protein-1 (MSP-1) of the mouse malaria parasite Plasmodium chabaudi chabaudi (AS) stimulates a weak CD4 T cell response when compared to the response to a more structurally simple region of the molecule. The tertiary structure of the C-terminal region of MSP-1 is maintained by five disulfide bonds. A peptide from this region could only be processed and loaded onto newly synthesized MHC class II molecules, whereas a peptide from the structurally simple region was available for loading onto recycling MHC class II. CD4(+) T cell hybridomas took longer to recognize an epitope derived from the disulfide-bonded region whether native parasite or recombinant MSP-1 antigen was used. Reduction of disulfide bonds in the C-terminal region subsequently allowed peptides to be loaded onto recycling MHC class II and greatly enhanced the rapidity of the T cell response. These data demonstrate that differential processing occurs intramolecularly in MSP-1, which may be responsible for the observed weak CD4 T cell responses against this region. The consequences of this in vivo may be that limited T cell help is available for protective antibody production which has important implications for designing vaccines based on MSP-1.

Trop Med Int Health 2000 Dec;5(12):860-864

Chloroquine is not a risk factor for seizures in childhood cerebral malaria.
Crawley J, Kokwaro G, Ouma D, Watkins W, Marsh K

KEMRI Centre for Geographic Medicine Research (Coast), Kilifi, Kenya; Nuffield Department of Clinical Medicine, University of Oxford, UK; Wellcome Trust Research Laboratories, Nairobi, Kenya; Department of Pharmacology and Therapeutics, University of Liverpool, UK.

OBJECTIVES: There are a number of case reports in the medical literature suggesting an association between the ingestion of chloroquine and subsequent seizure activity. Our study was designed to investigate the relationship between blood levels of chloroquine (CQ), its metabolite desethylchloroquine (DCQ), and seizures in children admitted to hospital with cerebral malaria. METHODS: Serial blood levels of CQ and DCQ were measured over the first 24 h of hospital admission in children with cerebral malaria. The number and duration of all seizures was recorded, and statistical analysis subsequently performed to determine the relationship between seizure activity and blood concentrations of CQ and DCQ. RESULTS: Chloroquine was detected in 92% (100/109) of admission blood samples. 54% (59/109) of the patients had one or more seizures after admission, while 8% (9/109) had an episode of status epilepticus. Median (interquartile range) baseline concentrations of CQ and DCQ were, respectively, 169.4 ?g/ml (75.1-374.9) and 352.3 ?g/ml (81.9-580.1) for those children who had seizures after admission, compared to CQ 227.5 ?g/ml (79.4-430.2) and DCQ 364.0 ?g/ml (131.3-709.4) for those who did not have seizures (P > 0.5 for all comparisons). Baseline concentrations of CQ and DCQ were not significantly associated with the occurrence of seizures lasting for 5 min or more. The nine children who had an episode of status epilepticus had significantly lower median admission levels of CQ than those without status epilepticus: 75.1 ?g/l (7.4-116.5) vs. 227.5 ?g/l (85.6-441.2), P = 0.02. Multivariate logistic regression analysis, taking into account factors likely to affect the risk of seizures in hospital, failed to change the significance of these results. CONCLUSIONS: These findings suggest that chloroquine does not play an important role in the aetiology of seizures in childhood cerebral malaria.

Acta Obstet Gynecol Scand 2001 Jan;80(1):18-26

Anemia in pregnancy in the highlands of Tanzania.
Hinderaker SG, Olsen BE, Bergsjo P, Lie RT, Gasheka P, Kvale G

Centre for International Health, University of Bergen, Norway and Haydom Lutheran Hospital, Tanzania.

BACKGROUND: Anemia in pregnancy is common in Tanzania, but many areas have not been investigated. This study describes prevalence and determinants of anemia among rural pregnant women living at 1300-2200 meters above sea level in Northern Tanzania. METHODS: Three thousand eight hundred and thirty-six pregnant women from two rural divisions of Mbulu and Hanang districts attending ANCantenatal clinic between January 1995 and March 1996 were assessed in a cross-sectional study. Blood samples were examined for hemoglobin concentration (Hb) and thick blood slide (BS) for malaria. Information on date of examination, village, age, ethnic and religious affiliation, gestational age, and parity was recorded. Altitude was derived from official maps. Main outcome measures were mean Hb level and risk of anemia defined as a Hb of less than 9.0 g/dl. RESULTS: Hb levels ranged from 4.5 to 18.1 g/dl, and mean was 12.1 g/dl. Twenty-three per cent had a Hb of less than 11 g/dl, 4.6% less than 9 g/dl and 0.5% less than 7 g/dl; standardized to sea level 36.1%, 8.8%, and 1.1%, respectively. The mean Hb increased by 0.3 g/dl per 200 m increased altitude, and the risk of anemia decreased with a factor of 0.6 per 200 m increased altitude. We found higher risk of anemia at higher maternal age (1.2 times increased risk per 5 years). Furthermore, the Datoga tribe had twice the risk of anemia compared with the Iraqw. The risk of anemia was only half at 3-4 months of gestation compared to at 7-8 months. The risk increased six-fold in the rainy season of 1995, and the risk was almost double among those with malaria parasitemia. CONCLUSIONS: Anemia in pregnancy was common in this area of high altitude in rural Tanzania, but less prevalent than indicated by studies from most other parts of the country. The study confirms that preventing anemia is a challenge in preventive antenatal care in the highlands of Tanzania. Studies focussing on the specific etiologic agents are needed.

Insect Biochem Mol Biol 2001 Mar;31(3):257-262

Serine proteases as mediators of mosquito immune responses.
Gorman MJ, Paskewitz SM

Department of Entomology, University of Wisconsin, 1630 Linden Drive, WI 53706, Madison, USA

Serine proteases regulate several invertebrate defense responses, including hemolymph coagulation, antimicrobial peptide synthesis, and melanization of pathogen surfaces. These processes require the presence of serine proteases in the hemolymph where they can rapidly activate immune pathways in response to pathogen detection. Hemolymph coagulation in the horseshoe crab is controlled by several serine proteases, including two that are pathogen recognition molecules and two in the clip domain family of serine proteases. The antimicrobial peptide synthesis and melanization pathways include clip domain proteases as well as other, uncharacterized serine proteases. We have identified five serine proteases from the hemolymph of the mosquito, Anopheles gambiae. One, Sp22D, is a large protease with potential pathogen binding domains. Sp22D is expressed in three tissues that have immune functions (midgut epithelium, fat body, and hemocytes), and its transcript abundance increases after immune challenge. Sp14A, Sp14D1, and Sp14D2 are clip domain serine proteases that are similar to enzymes with presumed roles in melanization or antimicrobial peptide synthesis. They undergo changes in transcript abundance in response to infection with bacteria or malaria parasites, and they reside in a chromosomal region that has been associated with melanization of parasites. Sp18D, also a clip domain protease, is similar to a Manduca protease with a likely role in immunity, but immune challenge does not affect its mRNA abundance.

Insect Biochem Mol Biol 2001 Mar;31(3):241-248

The defensin peptide of the malaria vector mosquito Anopheles gambiae: antimicrobial activities and expression in adult mosquitoes.
Vizioli J, Richman AM, Uttenweiler-Joseph S, Blass C, Bulet P

UPR CNRS 9022, Institut de Biologie Moleculaire et Cellulaire, 15, rue Rene Descartes, 67084 Cedex, Strasbourg, France

A recombinant Anopheles gambiae defensin peptide was used to define the antimicrobial activity spectrum against bacteria, filamentous fungi and yeast. Results showed that most of the Gram-positive bacterial species tested were sensitive to the recombinant peptide in a range of concentrations from 0.1 to 0.75 ?M. No activity was detected against Gram-negative bacteria, with the exception of some E. coli strains. Growth inhibitory activity was detected against some species of filamentous fungi. Defensin was not active against yeast. The kinetics of bactericidal and fungicidal effects were determined for Micrococcus luteus and Neurospora crassa, respectively. Differential mass spectrometry analysis was used to demonstrate induction of defensin in the hemolymph of bacteria-infected adult female mosquitoes. Native peptide levels were quantitated in both hemolymph and midgut tissues. The polytene chromosome position of the defensin locus was mapped by in situ hybridization.

Insect Biochem Mol Biol 2001 Mar;31(3):231-240

Spatial distribution of factors that determine sporogonic development of malaria parasites in mosquitoes.
Shahabuddin M, Costero A

Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, MD 20892-0425, Bethesda, USA]

Mosquitoes transmit malaria, but only a few species permit the complete development and transmission of the parasite. Also, only a fraction of the ingested parasites develop in the vector. The attrition occurs in different compartments during the parasite’s complex developmental scheme in the insect. A number of factors, both physical and biochemical, that affect the development have been proposed or demonstrated. Each of these factors is located within a specific space in the insect. We have divided this space into six compartments, which are distinct in their biochemical and biophysical nature: Endoperitrophic space, Peritrophic matrix, Ectopretrophic space, Midgut epithelium, Haemocoel and Salivary gland. Because factors that influence a particular stage of parasite development share the same microenvironment within these compartments, they must be considered collectively to exploit them for designing effective transmission blocking strategies. In this article we discuss these factors according to their spatial location in the mosquito.

Mol Biochem Parasitol 2001 Jan 15;112(1):91-101

The merozoite surface protein 6 gene codes for a 36 kDa protein associated with the Plasmodium falciparum merozoite surface protein-1 complex.
Trucco C, Fernandez-Reyes D, Howell S, Stafford WH, Scott-Finnigan TJ, Grainger M, Ogun SA, Taylor WR, Holder AA

Division of Parasitology, National Institute for Medical Research, Mill Hill, London, UK

A complex of non-covalently bound polypeptides is located on the surface of the merozoite form of the human malaria parasite Plasmodium falciparum. Four of these polypeptides are derived by proteolytic processing of the merozoite surface protein 1 (MSP-1) precursor. Two components, a 22 and a 36 kDa polypeptide are not derived from MSP-1. The N-terminal sequence of the 36 kDa polypeptide has been determined, the corresponding gene cloned, and the protein characterised. The 36 kDa protein consists of 211 amino acids and is derived from a larger precursor of 371 amino acids. The precursor merozoite surface protein 6 (MSP-6) has been designated, and the 36 kDa protein, MSP-6(36). Mass spectrometric analysis of peptides released from the polypeptide by tryptic digestion confirmed that the gene identified codes for MSP-6(36). Antibodies were produced to a recombinant protein containing the C-terminal 45 amino acid residues of MSP-6(36). In immunofluorescence studies these antibodies bound to antigen at the parasite surface or in the parasitophorous vacuole within schizonts, with a pattern indistinguishable from that of antibodies to MSP-1. MSP-6(36) was present in the MSP-1 complex immunoprecipitated from the supernatant of in vitro parasite cultures, but was also immunoprecipitated from this supernatant in a form not bound to MSP-1. Examination of the MSP-6 gene in three parasite lines detected no sequence variation. The sequence of MSP-6(36) is related to that of the previously described merozoite surface protein 3 (MSP-3). The MSP-6(36) amino acid sequence has 50% identity and 85% similarity with the C-terminal region of MSP-3. The proteins share a specific sequence pattern (ILGWEFGGG-[AV]-P) and a glutamic acid-rich region. The remainder of MSP-6 and MSP-3 are unrelated, except at the N-terminus. Both MSP-6(36) and MSP-3 are partially associated with the parasite surface and partially released as soluble proteins on merozoite release. MSP-6(36) is a hydrophilic negatively charged polypeptide, but there are two clusters of hydrophobic amino acids at the C-terminus, located in two amphipathic helical structures identified from secondary structure predictions. It was suggested that this 35 residue C-terminal region may be involved in MSP-6(36) binding to MSP-1 or other molecules; alternatively, based on the secondary structure and coil formation predictions, the region may form an intramolecular anti-parallel coiled-coil structure.

Mol Biochem Parasitol 2001 Jan 15;112(1):29-37

Biosynthesis of glycosphingolipids de-novo by the human malaria parasite Plasmodium falciparum.
Gerold P, Schwarz RT

Med. Zentrum fur Hygiene und Med. Mikrobiologie, Philipps-Universitat, Robert-Koch-Strasse 17, 35037, Marburg, Germany

Glycolipids are important components of cellular membranes involved in various biological functions. In this report we describe the identification of the de-novo synthesis of glycosphingolipids by intraerythrocytic, asexual stages of the malaria parasite, Plasmodium falciparum. Parasite-specific glycolipids were identified in organic solvent extracts of parasites metabolically labeled with tritiated serine and glucosamine and characterised as sphingolipids based on their insensitivity towards alkaline treatment. While the de-novo synthesis of parasite glycosphingolipids was affected by fumonisin B1, threo-PPMP, cyclo-serine and myriocin, these well established inhibitors of de-novo ceramide biosynthesis were unable to arrest the intraerythrocytic development of the parasites in culture.

J Insect Physiol 2001 Apr;47(4-5):455-464

Olfactory receptors on the antennae of the malaria mosquito Anopheles gambiae are sensitive to ammonia and other sweat-borne components.
Meijerink J, Braks MA, Van Loon JJ

Laboratory of Entomology, Wageningen University, PO Box 8031, 6700 EH, Wageningen, The Netherlands

Electrophysiological studies on female An. gambiae s.s. mosquitoes revealed a receptor neuron within a subpopulation of the antennal grooved-peg sensilla sensitive to the odour of incubated sweat, but not responding to fresh sweat. This receptor neuron was sensitive to ammonia as well, a sweat-borne component which attracts female An. gambiae in a windtunnel bioassay. Neurons innervating a different subpopulation of grooved-peg sensilla did not show a response to incubated sweat. In the latter sensilla, however, one type of neuron responded to water or water containing solutions, while another receptor neuron was inhibited when stimulated with dry air, ether or ethanol. Neurons innervating sensilla trichodea, a more abundant antennal type of olfactory sensillum, did not respond to fresh or incubated sweat at the doses offered. However, receptor neurons within the sensilla trichodea responded with excitation to several sweat-borne components. A subpopulation of the sensilla trichodea was innervated by neurons sensitive to geranyl acetone. A second subpopulation housed receptor neurons sensitive to indole. 3-Methyl-1-butanol and 6-methyl-5-hepten-2-one evoked excitation of receptor neurons within both subpopulations of sensilla trichodea. Neurons were most sensitive to indole and geranyl acetone with a threshold of 0.01%. These findings are discussed in the context of host-seeking behaviour.

Microbes Infect 2000 Dec;2(15):1789-1798

Polar Plasmodium falciparum lipids induce lipogenesis in rat adipocytes in vitro.
Zakeri S, Taylor K, Goad JL, Hommel M

Molecular Biology and Immunology Division, Liverpool School of Tropical Medicine, University of Liverpool, Pembroke Place, L3 5QA, Liverpool, UK

Previous studies have shown that ‘toxic malarial antigens’ released by Plasmodium yoelii can induce hypoglycaemia in mice and act synergistically with insulin in stimulating lipogenesis in rat adipocytes in vitro. In this study, it was shown that similar bioactivity could be detected in Plasmodium falciparum culture supernatant, and the molecular basis of this activity was further investigated. Boiled spent culture medium from P. falciparum cultures (‘BS-Pf’) (exclusively released into the culture supernatant when schizonts rupture) acts in synergy with insulin to increase lipogenesis in a rat adipocyte assay by more than 250% (P < 0.001). Control preparations prepared from non-parasitized erythrocytes grown under similar conditions had no effect (P < 0.001). While contamination with mycoplasma has previously been shown to interfere with the interpretation of data obtained with other molecules thought to be released from P. falciparum in culture, including those inducing TNF-alpha and NO production by macrophages, such contamination was unequivocally ruled out here. BS-Pf alone did not stimulate the lipogenesis in short-term assays (less than 4 h), while long-term exposure of rat adipocytes to BS-Pf alone (12-24 h) caused a stimulation of lipogenesis at a level comparable to that observed with insulin. Furthermore, lipogenesis-inducing activity was also detected in the serum of squirrel monkeys infected with different species of malaria parasites (P. vivax, P. falciparum and P. brasilianum). Preliminary biochemical characterization showed that the biological activity was found in the solvent-extracted polar lipid fraction of boiled supernatant of P. falciparum cultures. All the different polar lipid fractions, collected from silica gel column chromatography, showed a comparable lipogenesis-inducing activity. Enzymatic treatment by phospholipase C of the lipid fraction, which co-migrated with the phosphatidylcholine standard, showed that the activity of the fraction was associated with the 1,2-diacylglycerol (1,2-DAG) moieties released from polar lipids. When this exogenous 1,2-DAG was added to the adipocyte cultures (short- and long-term cultures), it induced stimulation of lipogenesis in rat adipocytes, while no lipogenic activity was obtained from bacterial polar lipids and 1,2-DAG isolated from unparasitized erythrocytes. The importance of these findings is discussed with reference to other toxic malarial antigens and also to the potential role of these molecules in the induction of hypoglycaemia in the severe forms of malaria.

Acta Trop 2001 Jan 15;78(1):3-9

rDNA-ITS2 polymerase chain reaction assay for the sibling species of Anopheles fluviatilis.
Manonmani A, Townson H, Adeniran T, Jambulingam P, Sahu S, Vijayakumar T

Vector Control Research Centre (ICMR), Medical Complex, Indira Nagar, -605 006, Pondicherry, India

Species-specific differences in the nucleotide sequences of the second internal transcribed spacer (ITS2) region of the ribosomal DNA (rDNA) were used to develop a diagnostic polymerase chain reaction (PCR) assay for two of the sibling species of the Anopheles fluviatilis complex, members of which are major vectors of malaria in central and northern parts of India. This assay consisted of a three primer reaction, which could amplify the DNA of both the species producing fragments of two distinct sizes, 350 bp for species X and 450 bp for species Y, respectively. The assay was found to be highly specific and sensitive.

FEMS Microbiol Lett 2001 Jan 10;194(2):175-179

Antibodies detected against Plasmodium falciparum haemozoin with inhibitory properties to cytokine production.
Biswas S, Karmarkar MG, Sharma YD

Haemozoin, the malaria pigment, regulates the synthesis of several host cytokines and has been found to be associated with the disease severity. Here we describe that malarial patients produce a significant amount of anti-haemozoin IgM antibodies. Levels of these antibodies were higher among the complicated Plasmodium falciparum cases compared to the non-complicated P. falciparum group and Plasmodium vivax patients. The P. falciparum haemozoin also induced the synthesis of tumour necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) by the monocytes of the healthy individuals, but the production of these cytokines by the monocytes was inhibited in the presence of the anti-haemozoin IgM antibodies. Therefore, it seems that the host produces these antibodies (mainly IgM types) during malarial infection that can influence the progression of the disease by inhibiting the production of cytokines.

Gene 2000 Dec 30;261(1):161-170

Genetic variation and the recent worldwide expansion of Plasmodium falciparum.
Ayala FJ, Rich SM

Department of Ecology and Evolutionary Biology, University of California, CA 92697-2525, Irvine, USA

Plasmodium falciparum, the agent of human malignant malaria, diverged from Plasmodium reichenowi, the chimpanzee parasite, about the time the human and chimpanzee lineages diverged from each other. The absence of synonymous nucleotide variation at ten loci indicates that the world populations of P. falciparum derive most recently from one single strain, or ‘cenancestor,’ which lived a few thousand years ago. Antigenic genes of P. falciparum (such as Csp, Msp-1, and Msp-2) exhibit numerous polymorphisms that have been estimated to be millions of years old. We have discovered in these antigenic genes short repetitive sequences that distort the alignment of alleles and account for the apparent old age of the polymorphisms. The processes of intragenic recombination that generate the repeats occur at rates about 10(-3) to 10(-2), several orders of magnitude greater than the typical mutational process of nucleotide substitutions. We conclude that the antigenic polymorphisms of P. falciparum are consistent with a recent expansion of the world populations of the parasite from a cenancestor that lived in tropical Africa a few thousand years ago.

Mol Biochem Parasitol 2000 Dec 1;111(2):447-451

Synonymous and non-synonymous mutations in a region of the Plasmodium chabaudi genome and evidence for selection acting on a malaria vaccine candidate.
Black CG, Coppel RL

Department of Microbiology, P.O. Box 53, Monash University, Vic. 3800, Australia

Mol Biochem Parasitol 2000 Dec 1;111(2):377-390

Expression and one-step purification of Plasmodium proteins in Dictyostelium.
van Bemmelen MX, Beghdadi-Rais C, Desponds C, Vargas E, Herrera S, Reymond CD, Fasel N

Institut de Biologie Cellulaire et de Morphologie, Universite de Lausanne, Rue du Bugnon 9, CH-1005, Lausanne, Switzerland

Nearly full-length Circumsporozoite protein (CSP) from Plasmodium falciparum, the C-terminal fragments from both P. falciparum and P. yoelii CSP and a fragment comprising 351 amino acids of P.vivax MSP1 were expressed in the slime mold Dictyostelium discoideum. Discoidin-tag expression vectors allowed both high yields of these proteins and their purification by a nearly single-step procedure. We exploited the galactose binding activity of Discoidin Ia to separate the fusion proteins by affinity chromatography on Sepharose-4B columns. Inclusion of a thrombin recognition site allowed cleavage of the Discoidin-tag from the fusion protein. Partial secretion of the protein was obtained via an ER independent pathway, whereas routing the recombinant proteins to the ER resulted in glycosylation and retention. Yields of proteins ranged from 0.08 to 3mgl(-1) depending on the protein sequence and the purification conditions. The recognition of purified MSP1 by sera from P. vivax malaria patients was used to confirm the native conformation of the protein expressed in Dictyostelium. The simple purification procedure described here, based on Sepharose-4B, should facilitate the expression and the large-scale purification of various Plasmodium polypeptides.

Cell 2001 Jan 12;104(1):153-164

A Central Role for P48/45 in Malaria Parasite Male Gamete Fertility.
van Dijk MR, Janse CJ, Thompson J, Waters AP, Braks JA, Dodemont HJ, Stunnenberg HG, van Gemert G, Sauerwein RW, Eling W

Laboratory for Parasitology, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands

Fertilization and zygote development are obligate features of the malaria parasite life cycle and occur during parasite transmission to mosquitoes. The surface protein PFS48/45 is expressed by male and female gametes of Plasmodium falciparum and PFS48/45 antibodies prevent zygote development and transmission. Here, gene disruption was used to show that Pfs48/45 and the ortholog Pbs48/45 from a rodent malaria parasite P. berghei play a conserved and important role in fertilization. p48/45(-) parasites had a reduced capacity to produce oocysts in mosquitoes due to greatly reduced zygote formation. Unexpectedly, only male gamete fertility of p48/45(-) parasites was affected, failing to penetrate otherwise fertile female gametes. P48/45 is shown to be a surface protein of malaria parasites with a demonstrable role in fertilization.

Cell Immunol 2001 Jan 10;207(1):28-35

Association of Intermediate T Cell Receptor Cells, Mainly Their NK1.1(-) Subset, with Protection from Malaria.
Weerasinghe A, Sekikawa H, Watanabe H, Kaiissar Mannoor M, Morshed SR, Halder RC, Kawamura T, Kosaka T, Miyaji C, Kawamura H, Seki S, Abo T

Department of Immunology, Niigata University School of Medicine, Niigata, 951-8510

Mice were infected with Plasmodium (P.) yoelii blood-stage parasites. Both the liver and spleen were the sites of inflammation during malarial infection at the beginning of day 7. The major expanding cells were found to be NK1.1(-) intermediate alphabetaTCR (alphabetaTCR(int)) in the liver and spleen, although the population of NK1.1(+) alphabetaTCR(int) cells remained constant or slightly increased. These TCR(int) cells are of extrathymic origin or are generated by an alternative intrathymic pathway and are distinguished from conventional T cells of thymic origin. During malarial infection, the population of conventional T cells did not increase at all. TCR(int) cells purified from the liver of mice which had recovered from P. yoelii infection protected mice from malaria when they were transferred into 6.5-Gy-irradiated mice. Interestingly, the immunity against malaria seemed to disappear as a function of time after recovery, namely, mice which had recovered from malaria 1 year previously again became susceptible to malarial infection. The present results suggest that TCR(int) cells are intimately associated with protection against malarial infection and, therefore, that mice which had recovered from malaria 1 year previously lost such immunity. Copyright 2001 Academic Press.

Nucleic Acids Res 2001 Feb 1;29(3):850-853

Transformation of malaria parasites by the spontaneous uptake and expression of DNA from human erythrocytes.
Deitsch KW, Driskill CL, Wellems TE

Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.

The uptake and expression of extracellular DNA has been established as a mechanism for horizontal transfer of genes between bacterial species. Such transfer can support acquisition of advantageous elements, including determinants that affect the interactions between infectious organisms and their hosts. Here we show that erythrocyte-stage Plasmodium falciparum malaria parasites spontaneously take up DNA from the host cell cytoplasm into their nuclei. We have exploited this finding to produce levels of reporter expression in P.falciparum that are substantially improved over those obtained by electroporation protocols currently used to transfect malaria parasites. Parasites were transformed to a drug-resistant state when placed into cell culture with erythrocytes containing a plasmid encoding the human dihydrofolate reductase sequence. The findings reported here suggest that the malaria genome may be continually exposed to exogenous DNA from residual nuclear material in host erythrocytes.

PMID: 11160909

Nucleic Acids Res 2001 Feb 1;29(3):716-724

An alteration in concatameric structure is associated with efficient segregation of plasmids in transfected Plasmodium falciparum parasites.
O’Donnell RA, Preiser PR, Williamson DH, Moore PW, Cowman AF, Crabb BS

Department of Microbiology and Immunology and the CRC for Vaccine Technology, The University of Melbourne, VIC 3010, Australia, Division of Parasitology, The National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK and The Walter and Eliza Hall Institute of Medical Research, PO Royal Melbourne Hospital, Melbourne, VIC 3050, Australia.

Transfection of the human malaria parasite Plasmodium falciparum is currently performed with circularised plasmids that are maintained episomally in parasites under drug selection but which are rapidly lost when selection pressure is removed. In this paper, we show that in instances where gene targeting is not favoured, transfected plasmids can change to stably replicating forms (SRFs) that are maintained episomally in the absence of drug selection. SRF DNA is a large concatamer of the parental plasmid comprising at least nine plasmids arranged in a head-to-tail array. We show as well that the original unstable replicating forms (URFs) are also present as head-to-tail concatamers, but only comprise three plasmids. Limited digestion and gamma irradiation experiments revealed that while URF concatamers are primarily circular, as expected, SRF concatamers form a more complex structure that includes extensive single-stranded DNA. No evidence of sequence rearrangement or additional sequence was detected in SRF DNA, including in transient replication experiments designed to select for more efficiently replicating plasmids. Surprisingly, these experiments revealed that the bacterial plasmid alone can replicate in parasites. Together, these results imply that transfected plasmids are required to form head-to-tail concatamers to be maintained in parasites and implicate both rolling-circle and recombination-dependent mechanisms in their replication.

J Nutr 2001 Feb;131(2):636S-648S

An Analysis of Anemia and Child Mortality.
Brabin BJ, Premji Z, Verhoeff F

Liverpool School of Tropical Medicine, Liverpool, England and University of Amsterdam, Emma Kinderziekenhuis, Academic Medical Centre, Amsterdam, Netherlands. College of Health Sciences, Muhimbili University, Dar-es-Salaam, Tanzania. Department of Paediatrics, Leiden University Medical Centre, Leiden, Netherlands.

The relationship of anemia as a risk factor for child mortality was analyzed by using cross-sectional, longitudinal and case-control studies, and randomized trials. Five methods of estimation were adopted: 1) the proportion of child deaths attributable to anemia; 2) the proportion of anemic children who die in hospital studies; 3) the population-attributable risk of child mortality due to anemia; 4) survival analyses of mortality in anemic children; and 5) cause-specific anemia-related child mortality. Most of the data available were hospital based. For children aged 0-5 y the percentage of deaths due to anemia was comparable for reports from highly malarious areas in Africa (Sierra Leone 11.2%, Zaire 12.2%, Kenya 14.3%). Ten values available for hemoglobin values <50 g/L showed a variation in case fatality from 2 to 29.3%. The data suggested little if any dose-response relating increasing hemoglobin level (whether by mean value or selected cut-off values) with decreasing mortality. Although mortality was increased in anemic children with hemoglobin <50 g/L, the evidence for increased risk with less severe anemia was inconclusive. The wide variation for mortality with hemoglobin <50 g/L is related to methodological variation and places severe limits on causal inference; in view of this, it is premature to generate projections on population-attributable risk. A preliminary survival analysis of an infant cohort from Malawi indicated that if the hemoglobin decreases by 10 g/L at age 6 mo, the risk of dying becomes 1.72 times higher. Evidence from a number of studies suggests that mortality due to malarial severe anemia is greater than that due to iron-deficiency anemia. Data are scarce on anemia and child mortality from non-malarious regions. Primary prevention of iron-deficiency anemia and malaria in young children could have substantive effects on reducing child mortality from severe anemia in children living in malarious areas.

J Nutr 2001 Feb;131(2):616S-635S

Iron and Its Relation to Immunity and Infectious Disease.
Oppenheimer SJ

Green College, Oxford, UK.

The continuing unresolved debate over the interaction of iron and infection indicates a need for quantitative review of clinical morbidity outcomes. Iron deficiency is associated with reversible abnormalities of immune function, but it is difficult to demonstrate the severity and relevance of these in observational studies. Iron treatment has been associated with acute exacerbations of infection, in particular, malaria. Oral iron has been associated with increased rates of clinical malaria (5 of 9 studies) and increased morbidity from other infectious disease (4 of 8 studies). In most instances, therapeutic doses of oral iron were used. No studies in malarial regions showed benefits. Knowledge of local prevalence of causes of anemia including iron deficiency, seasonal malarial endemicity, protective hemoglobinopathies and age-specific immunity is essential in planning interventions. A balance must be struck in dose of oral iron and the timing of intervention with respect to age and malaria transmission. Antimalarial intervention is important. No studies of oral iron supplementation clearly show deleterious effects in nonmalarious areas. Milk fortification reduced morbidity due to respiratory disease in two very early studies in nonmalarious regions, but this was not confirmed in three later fortification studies, and better morbidity rates could be achieved by breast-feeding alone. One study in a nonmalarious area of Indonesia showed reduced infectious outcome after oral iron supplementation of anemic schoolchildren. No systematic studies report oral iron supplementation and infectious morbidity in breast-fed infants in nonmalarious regions.

J Nutr 2001 Feb;131(2):604S-615S

An Analysis of Anemia and Pregnancy-Related Maternal Mortality.
Brabin BJ, Hakimi M, Pelletier D

Liverpool School of Tropical Medicine, Liverpool, England and University of Amsterdam, Emma Kinderziekenhuis, Academic Medical Centre, Amsterdam, Netherlands. Gadjah Mada University, Yogyakarta, Indonesia. Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853.

The relationship of anemia as a risk factor for maternal mortality was analyzed by using cross-sectional, longitudinal and case-control studies because randomized trials were not available for analysis. The following six methods of estimation of mortality risk were adopted: 1) the correlation of maternal mortality rates with maternal anemia prevalence derived from national statistics; 2) the proportion of maternal deaths attributable to anemia; 3) the proportion of anemic women who die; 4) population-attributable risk of maternal mortality due to anemia; 5) adolescence as a risk factor for anemia-related mortality; and 6) causes of anemia associated with maternal mortality. The average estimates for all-cause anemia attributable mortality (both direct and indirect) were 6.37, 7.26 and 3.0% for Africa, Asia and Latin America, respectively. Case fatality rates, mainly for hospital studies, varied from <1% to >50%. The relative risk of mortality associated with moderate anemia (hemoglobin 40-80 g/L) was 1.35 [95% confidence interval (CI): 0.92-2.00] and for severe anemia (<47 g/L) was 3.51 (95% CI: 2.05-6.00). Population-attributable risk estimates can be defended on the basis of the strong association between severe anemia and maternal mortality but not for mild or moderate anemia. In holoendemic malarious areas with a 5% severe anemia prevalence (hemoglobin <70 g/L), it was estimated that in primigravidae, there would be 9 severe-malaria anemia-related deaths and 41 nonmalarial anemia-related deaths (mostly nutritional) per 100,000 live births. The iron deficiency component of these is unknown.

J Immunol 2001 Feb 1;166(3):1945-1950

Host Responses to Plasmodium yoelii Hepatic Stages: A Paradigm in Host-Parasite Interaction.
Lau AO, Sacci JB, Azad AF

Department of Microbiology and Immunology, University of Maryland, School of Medicine, Baltimore, MD 21201. Malaria Program, Naval Medical Research Center, Silver Spring, MD 20910.

The liver stage of malaria, caused by the genus PLASMODIUM:, is clinically silent, but immunologically significant. Ample evidence exists for an effective CD8(+) T cell response to this stage as well as the involvement of gammadeltaT cells and NK1.1(int) cells in immunized animal models. In contrast, there is little information concerning responses in a naive host. Here we report that several host gene expressions in the liver, spleen, and kidney of BALB/c mice are altered during the liver stage of PLASMODIUM: yoelii infection. Really interesting new gene 3 (Ring3), semaphorin subclass 4 member G, glutamylcysteine synthetase, and p45 NF erythroid 2 were all up-regulated 24 h after infection with P. yoelii. Semaphorin subclass 4 member G expression was elevated in the kidney, whereas Ring3 was elevated in both spleen and kidney. The expression of TNF-alpha (TNF-alpha and IFN-gamma) were down-regulated in all three tissues tested except in infected spleen where IFN-gamma was elevated. P. yoelii-related host gene changes were compared with those in Toxoplasma gondii-infected livers. Ring3 expression increased 5-fold over control values, whereas expression of the other transcripts remained unchanged. TNF-alpha and IFN-gamma expressions were increased in the Toxoplasma-infected livers. The uniform increase of Ring3 expression in both PLASMODIUM:- and Toxoplasma-infected livers suggests an innate immune response against parasitic infections, whereas the other gene expression changes are consistent with PLASMODIUM: parasite-specific responses. Taken together, these changes suggest the immune responses to P. yoelii infection are both parasite and organ specific.

Infect Immun 2001 Feb;69(2):1207-1211

Differential Patterns of Human Immunoglobulin G Subclass Responses to Distinct Regions of a Single Protein, the Merozoite Surface Protein 1 of Plasmodium falciparum.
Cavanagh DR, Dobano C, Elhassan IM, Marsh K, Elhassan A, Hviid L, Khalil EA, Theander TG, Arnot DE, McBride JS

Institute of Cell, Animal and Population Biology, Division of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, Scotland.

Comparisons of immunoglobulin G (IgG) subclass responses to the major polymorphic region and to a conserved region of MSP-1 in three cohorts of African villagers exposed to Plasmodium falciparum revealed that responses to Block 2 are predominantly IgG3 whereas antibodies to MSP-1(19) are mainly IgG1. The striking dominance of IgG3 to Block 2 may explain the short duration of this response and also the requirement for continuous stimulation by malaria infection to maintain clinical immunity.

Infect Immun 2001 Feb;69(2):996-1001

Familial Correlation of Immunoglobulin G Subclass Responses to Plasmodium falciparum Antigens in Burkina Faso.
Aucan C, Traore Y, Fumoux F, Rihet P

Universite de la Mediterranee, EA 864, Marseille, France.

Host genes are thought to determine the immune response to malaria infection and the outcome. Cytophilic antibodies have been associated with protection, whereas noncytophilic antibodies against the same epitopes may block the protective activity of the protective ones. To assess the contribution of genetic factors to immunoglobulin G (IgG) subclass responses against conserved epitopes and Plasmodium falciparum blood-stage extracts, we analyzed the isotypic distribution of the IgG responses in 366 individuals living in two differently exposed areas in Burkina Faso. We used one-way analysis of variance and pairwise estimators to calculate sib-sib and parent-offspring correlation coefficients, respectively. Familial patterns of inheritance of IgG subclass responses to defined antigens and P. falciparum extracts appear to be similar in the two areas. We observed a sibling correlation for the IgG, IgG1, IgG2, IgG3, and IgG4 responses directed against ring-infected-erythrocyte surface antigen, merozoite surface protein 1 (MSP-1), MSP-2, and P. falciparum extract. Moreover, a parent-offspring correlation was found for several IgG subclass responses, including the IgG, IgG1, IgG2, IgG3, and IgG4 responses directed against conserved MSP-2 epitopes. Our results indicated that the IgG subclass responses against P. falciparum blood-stage antigens are partly influenced by host genetic factors. The localization and identification of these genes may have implications for immunoepidemiology and vaccine development.

Antimicrob Agents Chemother 2001 Feb;45(2):509-516

Bioavailability and Preliminary Clinical Efficacy of Intrarectal Artesunate in Ghanaian Children with Moderate Malaria.
Krishna S, Planche T, Agbenyega T, Woodrow C, Agranoff D, Bedu-Addo G, Owusu-Ofori AK, Appiah JA, Ramanathan S, Mansor SM, Navaratnam

Department of Infectious Diseases, St. George’s Hospital Medical School, London SW17 ORE, United Kingdom.

We report the first detailed pharmacokinetic assessment of intrarectal (i.r.) artesunate (ARS) in African children. Artesunate was given intravenously (i.v.; 2.4 mg/kg of body weight) and i.r. (10 or 20 mg/kg formulated as 50- or 200-mg suppositories [Rectocaps]) in a crossover study design to 34 Ghanaian children with moderate falciparum malaria. The median relative bioavailability of dihydroartemisinin (DHA), the active antimalarial metabolite of ARS, was higher in the low-dose i.r. group (10 mg/kg) than in the high-dose i.r. group (20 mg/kg) (58 versus 23%; P = 0.018). There was wide interpatient variation in the area under the concentration-time curve after i.r. ARS administration (up to 9-fold in the high-dose group and 20-fold in the low-dose group). i.r. administered ARS was more rapidly absorbed in the low-dose group than the high-dose group (median [range] absorption half-lives, 0.7 h [0.3 to 1.24 h] versus 1.1 h [0.6 to 2.7 h] [P = 0.023]. i.r. administered ARS was eliminated with a median (range) half-life of 0.8 h (0.4 to 2.7 h) (low-dose group and 0.9 h (0.1 to 2.5 h) (high-dose group) (P = 1). The fractional clearances of DHA were 3.9, 2.6, and 1.5 liters/kg/h for the 20-mg/kg, 10-mg/kg and i.v. groups, respectively (P = 0.001 and P = 0.06 for the high-and low-dose i.r. groups compared with the i.v. groups, respectively). The median volumes of distribution for DHA were 1.5 liters kg (20 mg/kg, i.r. group), 1.8 liters/kg (10 mg/kg, i.r. group), and 0.6 liters/kg (i.v. group) (P < 0.05 for both i.r. groups compared with the i.v. group). Parasite clearance kinetics were comparable in all treatment groups. i.r. administered ARS may be a useful alternative to parenterally administered ARS in the management of moderate childhood malaria and should be studied further.

Genetics 2001 Feb;157(2):743-750

Gene Flow Among Populations of the Malaria Vector, Anopheles gambiae, in Mali, West Africa.
Taylor C, Toure YT, Carnahan J, Norris DE, Dolo G, Traore SF, Edillo FE, Lanzaro GC

Department of Organismic Biology, Ecology and Evolution, University of California, Los Angeles, California 90095-1606.

The population structure of the Anopheles gambiae complex is unusual, with several sibling species often occupying a single area and, in one of these species, An. gambiae sensu stricto, as many as three “chromosomal forms” occurring together. The chromosomal forms are thought to be intermediate between populations and species, distinguishable by patterns of chromosome gene arrangements. The extent of reproductive isolation among these forms has been debated. To better characterize this structure we measured effective population size, N(e), and migration rates, m, or their product by both direct and indirect means. Gene flow among villages within each chromosomal form was found to be large (N(e)m > 40), was intermediate between chromosomal forms (N(e)m approximately 3-30), and was low between species (N(e)m approximately 0.17-1.3). A recently developed means for distinguishing among certain of the forms using PCR indicated rates of gene flow consistent with those observed using the other genetic markers.

Immunogenetics 2000 Mar;51(3):219-30

Sequence and diversity of DRB genes of Aotus nancymaae, a primate model for human malaria parasites.
Nino-Vasquez JJ, Vogel D, Rodriguez R, Moreno A, Patarroyo ME, Pluschke G, Daubenberger CA

Instituto de Inmunologia, Hospital San Juan de Dios, Universidad Nacional de Colombia, Santafe de Bogota, DC. Email: [email protected]


The New World primate Aotus nancymaae is susceptible to infection with the human malaria parasite Plasmodium falciparum and Plasmodium vivax and has therefore been recommended by the World Health Organization as a model for evaluation of malaria vaccine candidates. We present here a first step in the molecular characterization of the major histocompatibility complex (MHC) class II DRB genes of Aotus nancymaae (owl monkey or night monkey) by nucleotide sequence analysis of the polymorphic exon 2 segments. In a group of 15 nonrelated animals captivated in the wild, 34 MHC DRB alleles could be identified. Six allelic lineages were detected, two of them having human counterparts, while two other lineages have not been described in any other New World monkey species studied. As in the common marmoset, the diversity of DRB alleles appears to have arisen largely by point mutations in the beta-pleated sheets and by frequent exchange of fixed sequence motifs in the alpha-helical portion. Pairs of alleles differing only at amino acid position b86 by an exchange of valine to glycine are present in Aotus, as in humans. Essential amino acid residues contributing to MHC DR peptide binding pockets number 1 and 4 are conserved or semiconserved between HLA-DR and Aona-DRB molecules, indicating a capacity to bind similar peptide repertoires. These results support fully our using Aotus monkeys as an animal model for evaluation of future subunit vaccine candidates.