Author: White, Nicholas J.; McGready, Rose M.; Nosten, Francois, H.
Year: 2008
Title: New Medicines for Tropical Diseases in Pregnancy: Catch-22
Journal: PLoS Medicine
Volume: 5
Issue: 6
Pages: e133
Date: June 01, 2008
URL: http://dx.doi.org/10.1371%2Fjournal.pmed.0050133

Author: Wang, Y.; Nair, S.; Nosten, F.; Anderson, T.
Year: 2008
Title: Multiple Displacement Amplification for Malaria Parasite DNA
Journal: J Parasitol
Pages: 1
Date: Jul 5
Abstract: Multiple displacement amplification (MDA) using Phi29 has proved to be an efficient, high fidelity method for whole genome amplification in many organisms. This project was designed to evaluate this approach for use with the malaria parasite, Plasmodium falciparum. In particular, we were concerned that the AT richness and presence of contaminating human DNA could limit efficiency of MDA in this system. We amplified 60 DNA samples using phi29 and scored 14 microsatellites, 9 SNPs and gene copy number at GTP-cyclohydrolase I both before and after MDA. We observed 100% concordance in 829 microsatellite genotypes and in 499 SNP genotypes. Furthermore, copy number estimates for GTP-cyclohydrolase I was correlated in pre-and post-amplification samples. These data confirm that MDA permits scoring of a range of different types of polymorphisms in P. falciparum malaria and can be used to extend the life of valuable DNA stocks.

Author: Tan, S. O.; McGready, R.; Zwang, J.; Pimanpanarak, M.; Sriprawat, K.; Thwai, K. L.; Moo, Y.; Ashley, E. A.; Edwards, B.; Singhasivanon, P.; White, N. J.; Nosten, F.
Year: 2008
Title: Thrombocytopaenia in pregnant women with malaria on the Thai-Burmese border
Journal: Malar J
Volume: 7
Pages: 209
Alternate Journal: Malaria journal
Abstract: BACKGROUND: Haematological changes associated with malaria in pregnancy are not well documented, and have focused predominantly on anaemia. Examined here is thrombocytopaenia in pregnant women infected with Plasmodium falciparum or Plasmodium vivax in a low transmission area on the north-western border of Thailand. METHODS: In this observational study we reviewed the platelet counts from routine complete blood count (CBC) in a cohort of healthy and malaria infected Karen pregnant women attending weekly antenatal clinics. A platelet count of 75,000/microL was the threshold at 2 standard deviations below the mean for healthy pregnant women used to indicate thrombocytopenia. Differences in platelet counts in non-pregnant and pregnant women were compared after matching for age, symptoms, malaria species and parasitaemia.
RESULTS: In total 974 pregnant women had 1,558 CBC measurements between February 2004 and September 2006. The median platelet counts (/microL) were significantly lower in patients with an episode of falciparum 134,000 [11,000-690,000] (N = 694) or vivax malaria 184,000 [23,000-891,000] (N = 523) compared to healthy pregnant women 256,000 [64,000-781,000] (N = 255), P < 0.05 for both comparisons. Plasmodium falciparum and P. vivax caused a 34% (95% CI 24-47) and 22% (95% CI 8-36) reduction in platelet count, respectively. Pregnant compared to non pregnant women were at higher risk OR = 2.27 (95%CI 1.16-4.4) P = 0.017, for thrombocytopaenia. Platelets counts were higher in first compared with subsequent malaria infections within the same pregnancy. Malaria associated thrombocytopaenia had a median [range] time for recovery of 7 234567891011121314 days which did not differ by antimalarial treatment (P = 0.86), or species (P = 0.63) and was not associated with active bleeding. CONCLUSION: Pregnant women become more thrombocytopenic than non-pregnant women with acute uncomplicated malaria. Uncomplicated malaria associated thrombocytopaenia is seldom severe. Prompt antimalarial treatment resulted in normalization of platelet counts within a week.

 Author: Suwanarusk, R.; Chavchich, M.; Russell, B.; Jaidee, A.; Chalfein, F.; Barends, M.; Prasetyorini, B.; Kenangalem, E.; Piera, K. A.; Lek-Uthai, U.; Anstey, N. M.; Tjitra, E.; Nosten, F.; Cheng, Q.; Price, R. N.
Year: 2008
Title: Amplification of pvmdr1 associated with multidrug-resistant Plasmodium vivax
Journal: J Infect Dis
Volume: 198
Issue: 10
Pages: 1558-64
Date: Nov 15
Abstract: BACKGROUND: Multidrug-resistant strains of Plasmodium vivax are emerging in Southeast Asia.
METHODS: In vitro drug susceptibility and pvmdr1 genotype were determined in P. vivax field isolates from Indonesia and Thailand. RESULTS: Increased pvmdr1 copy number was present in 21% of isolates from Thailand (15/71) and none from Indonesia (0/114; [Formula: see text]). Compared with Indonesian isolates, the median IC(50) of Thai isolates was lower for chloroquine (36 vs. 114 nmol/L; [Formula: see text]) but higher for amodiaquine (34 vs. 13.7 nmol/L; [Formula: see text]), artesunate (8.33 vs. 1.58 nmol/L; [Formula: see text]), and mefloquine (111 vs. 9.87 nmol/L; [Formula: see text]). In 11 cryopreserved Thai isolates, those with increased pvmdr1 copy number had a higher IC(50) for mefloquine (78.6 vs. 38 nmol/L for single-copy isolates; [Formula: see text]). Compared with isolates with the wild-type allele, the Y976F mutation of pvmdr1 was associated with reduced susceptibility to chloroquine (154 nmol/L [range, 4.6-3505] vs. 34 nmol/L [range, 6.7-149]; [Formula: see text]) but greater susceptibility to artesunate (1.8 vs. 9.5 nmol/L; [Formula: see text]) and mefloquine (14 vs. 121 nmol/L; [Formula: see text]).
CONCLUSIONS: Amplification of pvmdr1 and single-nucleotide polymorphisms are correlated with susceptibility of P. vivax to multiple antimalarial drugs. Chloroquine and mefloquine appear to exert competitive evolutionary pressure on pvmdr1, similar to that observed with pfmdr1 in Plasmodium falciparum.

Author: Poespoprodjo, J. R.; Fobia, W.; Kenangalem, E.; Lampah, D. A.; Warikar, N.; Seal, A.; McGready, R.; Sugiarto, P.; Tjitra, E.; Anstey, N. M.; Price, R. N.
Year: 2008
Title: Adverse pregnancy outcomes in an area where multidrug-resistant plasmodium vivax and Plasmodium falciparum infections are endemic
Journal: Clin Infect Dis
Volume: 46
Issue: 9
Pages: 1374-81
Abstract: BACKGROUND: Plasmodium falciparum infection exerts a considerable burden on pregnant women, but less is known about the adverse consequences of Plasmodium vivax infection. METHODS: In Papua, Indonesia, where multiple drug resistance to both species has emerged, we conducted a cross-sectional hospital-based study to quantify the risks and consequences of maternal malaria.
RESULTS: From April 2004 through December 2006, 3046 pregnant women were enrolled in the study. The prevalence of parasitemia at delivery was 16.8% (432 of 2570 women had infections), with 152 (35.2%) of these 432 infections being associated with fever. The majority of infections were attributable to P. falciparum (250 [57.9%]); 146 (33.8%) of the infections were attributable to P. vivax, and 36 (8.3%) were coinfections with both species. At delivery, P. falciparum infection was associated with severe anemia (hemoglobin concentration, <7 g/dL; odds ratio [OR], 2.8; 95% confidence interval [95% CI], 2.0-4.0) and a 192 g (95% CI, 119-265) reduction in mean birth weight (P<.001). P. vivax infection was associated with an increased risk of moderate anemia (hemoglobin concentration, 7-11 g/dL; OR, 1.8; 95% CI, 1.2-2.9; P=.01) and a 108 g (95% CI, 17.5-199) reduction in mean birth weight (P<.019). Parasitemia was associated with preterm delivery (OR, 1.5; 95% CI, 1.1-2.0; P=.02) and stillbirth (OR, 2.3; 95% CI, 1.3-4.1; P=.007) but was not associated with these outcomes after controlling for the presence of fever and severe anemia, suggesting that malaria increases the risk of preterm delivery and stillbirth through fever and contribution to severe anemia rather than through parasitemia per se. CONCLUSIONS: These observations highlight the need for novel, safe, and effective treatment and prevention strategies against both multidrug-resistant P. falciparum and multidrug-resistant P. vivax infections in pregnant women in areas of mixed endemicity.

Author: Plewes, K.; Lee, T.; Kajeechewa, L.; Thwin, M. M.; Lee, S. J.; Carrara, V. I.; Nosten, F.; McGready, R.
Year: 2008
Title: Low seroprevalence of HIV and syphilis in pregnant women in refugee camps on the Thai-Burma border
Journal: Int J STD AIDS
Volume: 19
Issue: 12
Pages: 833-7
Abstract: Refugee and migrant populations are considered to be at high risk from sexually transmitted infection (STI) and HIV. Cross-sectional surveys for syphilis and HIV were conducted in antenatal clinics (ANCs) on the Thai-Burmese border. In Mae La refugee camp, the seroprevalence of HIV and syphilis were 0.2% (one of 500) (95% CI 0-1.1) and 0% (0 of 404) (95% CI 0-0.9) in 1997; and 0.4% (two of 500) (95% CI 0.1-1.4) and 0.4% (three of 741) (95% CI 0.1-1.2) in 2005, respectively; syphilis seroprevalence in migrant women in 2005 was 0 (0 of 234) (95% CI 0-1.6). The seroprevalence was lower than that reported from surrounding ANCs for Thai or Burmese women. Focus group discussions with HIV-negative and -positive pregnant refugee women established that aspects of Karen culture and isolation (geographical and political) had a significant protective role from HIV and STI. This survey has resulted in programmatic changes in services to pregnant women in this area.

Author: Nair, S.; Miller, B.; Barends, M.; Jaidee, A.; Patel, J.; Mayxay, M.; Newton, P.; Nosten, F.; Ferdig, M. T.; Anderson, T. J.
Year: 2008
Title: Adaptive copy number evolution in malaria parasites
Journal: PLoS Genet
Volume: 4
Issue: 10
Abstract: Copy number polymorphism (CNP) is ubiquitous in eukaryotic genomes, but the degree to which this reflects the action of positive selection is poorly understood. The first gene in the Plasmodium folate biosynthesis pathway, GTP-cyclohydrolase I (gch1), shows extensive CNP. We provide compelling evidence that gch1 CNP is an adaptive consequence of selection by antifolate drugs, which target enzymes downstream in this pathway. (1) We compared gch1 CNP in parasites from Thailand (strong historical antifolate selection) with those from neighboring Laos (weak antifolate selection). Two percent of chromosomes had amplified copy number in Laos, while 72% carried multiple (2-11) copies in Thailand, and differentiation exceeded that observed at 73 synonymous SNPs. (2) We found five amplicon types containing one to greater than six genes and spanning 1 to >11 kb, consistent with parallel evolution and strong selection for this gene amplification. gch1 was the only gene occurring in all amplicons suggesting that this locus is the target of selection. (3) We observed reduced microsatellite variation and increased linkage disequilibrium (LD) in a 900-kb region flanking gch1 in parasites from Thailand, consistent with rapid recent spread of chromosomes carrying multiple copies of gch1. (4) We found that parasites bearing dhfr-164L, which causes high-level resistance to antifolate drugs, carry significantly (p = 0.00003) higher copy numbers of gch1 than parasites bearing 164I, indicating functional association between genes located on different chromosomes but linked in the same biochemical pathway. These results demonstrate that CNP at gch1 is adaptive and the associations with dhfr-164L strongly suggest a compensatory function. More generally, these data demonstrate how selection affects multiple enzymes in a single biochemical pathway, and suggest that investigation of structural variation may provide a fast-track to locating genes underlying adaptation.

Author: McGready, Rose; Tan, Saw Oo; Ashley, Elizabeth A.; Pimanpanarak, Mupawjay; Viladpai-nguen, Jacher; Phaiphun, Lucy; stefeld, Katja; Barends, Marion; Laochan, Natthapon; Keereecharoen, Lily; Lindegardh, Niklas; Singhasivanon, Pratap; White, Nicholas J.; Nosten, Francois
Year: 2008
Title: A Randomised Controlled Trial of Artemether-Lumefantrine Versus Artesunate for Uncomplicated Plasmodium falciparum Treatment in Pregnancy
Journal: PLoS Medicine
Volume: 5
Issue: 12
Pages: e253
Date: December 01, 2008
Abstract: BackgroundTo date no comparative trials have been done, to our knowledge, of fixed-dose artemisinin combination therapies (ACTs) for the treatment of Plasmodium falciparum malaria in pregnancy. Evidence on the safety and efficacy of ACTs in pregnancy is needed as these drugs are being used increasingly throughout the malaria-affected world. The objective of this study was to compare the efficacy, tolerability, and safety of artemether-lumefantrine, the most widely used fixed ACT, with 7 d artesunate monotherapy in the second and third trimesters of pregnancy.Methods and FindingsAn open-label randomised controlled trial comparing directly observed treatment with artemether-lumefantrine 3 d (AL) or artesunate monotherapy 7 d (AS7) was conducted in Karen women in the border area of northwestern Thailand who had uncomplicated P. falciparum malaria in the second and third trimesters of pregnancy. The primary endpoint was efficacy defined as the P. falciparum PCR-adjusted cure rates assessed at delivery or by day 42 if this occurred later than delivery, as estimated by Kaplan-Meier survival analysis. Infants were assessed at birth and followed until 1 y of life. Blood sampling was performed to characterise the pharmacokinetics of lumefantrine in pregnancy.
Both regimens were very well tolerated. The cure rates (95%; confidence interval) for the intention to treat (ITT) population were: AS7 89.2%; (82.3%;96.1%) and AL 82.0% (74.8%;89.3%), p = 0.054 (ITT); and AS7 89.7% (82.6%;96.8%) and AL 81.2%; (73.6%;88.8%), p = 0.031 (per-protocol population). One-third of the PCR-confirmed recrudescent cases occurred after 42 d of follow-up. Birth outcomes and infant (up to age 1 y) outcomes did not differ significantly between the two groups. The pharmacokinetic study indicated that low concentrations of artemether and lumefantrine were the main contributors to the poor efficacy of AL.
Conclusion: The current standard six-dose artemether-lumefantrine regimen was well tolerated and safe in pregnant Karen women with uncomplicated falciparum malaria, but efficacy was inferior to 7 d artesunate monotherapy and was unsatisfactory for general deployment in this geographic area. Reduced efficacy probably results from low drug concentrations in later pregnancy. A longer or more frequent AL dose regimen may be needed to treat pregnant women effectively and should now be evaluated. Parasitological endpoints in clinical trials of any antimalarial drug treatment in pregnancy should be extended to delivery or day 42 if it comes later.

Reference Type: Journal Article
Record Number: 338
Author: McGready, R.; Nosten, F.
Year: 2008
Title: Symptomatic malaria in pregnancy
Journal: J Obstet Gynaecol
Volume: 28
Issue: 4
Pages: 463
Date: May
Accession Number: 18604704
Notes: Comment

Author: Lindegardh, N.; Hanpithakpong, W.; Kamanikom, B.; Singhasivanon, P.; Socheat, D.; Yi, P.; Dondorp, A. M.; McGready, R.; Nosten, F.; White, N. J.; Day, N. P.
Year: 2008
Title: Major pitfalls in the measurement of artemisinin derivatives in plasma in clinical studies
Journal: J Chromatogr B Analyt Technol Biomed Life Sci
Volume: 876
Issue: 1
Pages: 54-60
Date: Dec 1
Abstract: A bioanalytical method for the analysis of artesunate (ARS) and its metabolite dihydroartemisinin (DHA) in human plasma using protein precipitation and liquid chromatography coupled to positive tandem mass spectroscopy was developed. The method was validated according to published US FDA-guidelines and showed excellent performance. However, when it was applied to clinical pharmacokinetic studies in malaria, variable degradation of the artemisinins introduced an unacceptable large source of error, rendering the assay useless. Haemolytic products related to sample collection and malaria infection degraded the compounds. Addition of organic solvents during sample processing and even low volume addition of the internal standard in an organic solvent caused degradation. A solid phase extraction method avoiding organic solvents eliminated problems arising from haemolysis induced degradation. Plasma esterases mediated only approximately 20% of ex vivo hydrolysis of ARS into DHA. There are multiple sources of major preventable error in measuring ARS and DHA in plasma samples from clinical trials. These various pitfalls have undoubtedly contributed to the large inter-subject variation in plasma concentration profiles and derived pharmacokinetic parameters for these important antimalarial drugs.

Author: Lee, S. J.; McGready, R.; Fernandez, C.; Stepniewska, K.; Paw, M. K.; Viladpai-Nguen, S. J.; Thwai, K. L.; Villegas, L.; Singhasivanon, P.; Greenwood, B. M.; White, N. J.; Nosten, F.
Year: 2008
Title: Chloroquine pharmacokinetics in pregnant and nonpregnant women with vivax malaria
Journal: Eur J Clin Pharmacol
Date: Jul 2
Abstract: PURPOSE: We compared the pharmacokinetics of chloroquine in pregnant and nonpregnant women treated for Plasmodium vivax malaria. METHODS: Twelve pregnant women and 15 nonpregnant women of child-bearing age with acute P. vivax malaria were treated with 25 mg chloroquine base/kg over 3 days on the northwestern border of Thailand. Blood concentrations of chloroquine and desethylchloroquine were measured using hydrophilic interaction liquid chromatography coupled with fluorescence detection. Twenty-five women completed the pharmacokinetic study. RESULTS: Although increasing gestational age was associated with reduced chloroquine [Formula: see text], there was no significant difference overall in the pharmacokinetics of chloroquine between pregnant and nonpregnant women. Fever was associated with lower chloroquine [Formula: see text] values. Desethylchloroquine area under the curve (AUC) values were not significantly affected by pregnancy. CONCLUSIONS: Pregnancy did not significantly affect blood concentrations of chloroquine or its metabolite, desethylchloroquine, in women with P. vivax malaria.

Author: Lee, Sue; Stepniewska, Kasia; Anstey, Nicholas; Ashley, Elizabeth; Barnes, Karen; Binh, Tran; D'Alessandro, Umberto; Day, Nicholas; de Vries, Peter; Dorsey, Grant; Guthmann, Jean-Paul; Mayxay, Mayfong; Newton, Paul; Nosten, Francois; Olliaro, Piero; Osario, Lyda; Pinoges, Loretxu; Price, Ric; Rowland, Mark; Smithuis, Frank; Taylor, Robert; White, Nicholas
Year: 2008
Title: The relationship between the haemoglobin concentration and the haematocrit in Plasmodium falciparum malaria
Journal: Malaria Journal
Volume: 7
Issue: 1
Pages: 149
Abstract: BACKGROUND:Malaria is a very important cause of anaemia in tropical countries. Anaemia is assessed either by measurement of the haematocrit or the haemoglobin concentration. For comparisons across studies, it is often necessary to derive one measure from the other.METHODS:Data on patients with slide-confirmed uncomplicated falciparum malaria were pooled from 85 antimalarial drug trials conducted in 25 different countries, to assess the haemoglobin/haematocrit relationship at different time points in malaria. Using a linear random effects model, a conversion equation for haematocrit was derived based on 3,254 measurements from various time points (ranging from day 0 to day 63) from 1,810 patients with simultaneous measurements of both parameters. Haemoglobin was also estimated from haematocrit with the commonly used threefold conversion.RESULTS:A good fit was obtained using Haematocrit = 5.62 + 2.60 * Haemoglobin. On average, haematocrit/3 levels were slightly higher than haemoglobin measurements with a mean difference (+/- SD) of -0.69 (+/- 1.3) for children under the age of 5 (n = 1,440 measurements from 449 patients).CONCLUSION:Based on this large data set, an accurate and robust conversion factor both in acute malaria and in convalescence was obtained. The commonly used threefold conversion is also valid.

Author: Harris, K. A.; Turner, P.; Green, E. A.; Hartley, J. C.
Year: 2008
Title: Duplex real-time PCR assay for detection of Streptococcus pneumoniae in clinical samples and determination of penicillin susceptibility
Journal: J Clin Microbiol
Volume: 46
Issue: 8
Pages: 2751-8
Date: Aug
Abstract: We have developed a duplex real-time PCR for the rapid diagnosis of Streptococcus pneumoniae infection from culture-negative clinical samples with the simultaneous determination of penicillin susceptibility. The assay amplifies a lytA gene target and a penicillin binding protein 2b (pbp2b) gene target in penicillin-susceptible organisms. The assay was shown to be sensitive (detects 0.5 CFU per PCR) and specific for the detection of S. pneumoniae DNA. The assay was validated by comparing pbp2b PCR results with MIC data for 27 S. pneumoniae isolates. All 5 isolates with penicillin MICs of > 1.0 mg/liter were pbp2b real-time PCR negative, as were 9 of the 10 isolates with penicillin MICs of 0.12 to 1.0 mg/liter. One isolate with a penicillin MIC of 0.12 to 1.0 mg/liter gave an equivocal pbp2b real-time PCR result. Twelve isolates were penicillin susceptible (MICs of < or = 0.06 mg/liter) and pbp2b real-time PCR positive. These data were used to establish an algorithm for the interpretation of penicillin susceptibility from the duplex PCR result. pbp2b real-time PCR results were also compared to an established PCR-restriction fragment length polymorphism (RFLP) method previously applied to these 27 isolates and 46 culture-negative clinical samples (containing S. pneumoniae DNA by broad-range 16S rRNA gene PCR). Discordant results were seen for four isolates and six culture-negative clinical samples, as PCR-RFLP could not reliably detect penicillin MICs of 0.12 to 1.0 mg/liter. We report prospective application of the duplex PCR assay to the diagnosis of S. pneumoniae infection from 200 culture-negative clinical specimens sent to the laboratory for diagnostic broad-range 16S rRNA gene PCR. One hundred six were negative in the duplex PCR. Ninety-four were lytA PCR positive, and 70 of these were also pbp2b PCR positive and interpreted as penicillin susceptible. Fourteen were pbp2b PCR negative and interpreted as having reduced susceptibility to penicillin. For the remaining 10 samples, susceptibility to penicillin was not determined.

Author: Carrara, V. I.; Phyo, A. P.; Nwee, P.; Soe, M.; Htoo, H.; Arunkamomkiri, J.; Singhasivanon, P.; Nosten, F.
Year: 2008
Title: Auditory assessment of patients with acute uncomplicated Plasmodium falciparum malaria treated with three-day mefloquine-artesunate on the north-western border of Thailand
Journal: Malar J
Volume: 7
Issue: 1
Pages: 233
Abstract: ABSTRACT: BACKGROUND: The use of artemisinin derivatives has increased exponentially with the deployment of artemisinin combination therapy (ACT) in all malarious areas. They are highly effective and are considered safe, but in animal studies artemisinin derivatives produce neurotoxicity targeting mainly the auditory and vestibular pathways. The debate remains as to whether artemisinin derivatives induce similar toxicity in humans. METHODS: This prospective study assessed the effects on auditory function of a standard 3-day oral dose of artesunate (4 mg/kg/day) combined with mefloquine (25 mg/kg) in patients with acute uncomplicated falciparum malaria treated at the Shoklo Malaria Research Unit, on the Thai-Burmese border. A complete auditory evaluation with tympanometry, audiometry and auditory brainstem responses (ABR) was performed before the first dose and seven days after initiation of the antimalarial treatment. RESULTS: Complete auditory tests at day 0 (D0) and day 7 (D7) were obtained for 93 patients. Hearing loss (threshold > 25 dB) on admission was common (57%) and associated with age only. No patient had a threshold change exceeding 10 dB between D0 and D7 at any tested frequency. No patient showed a shift in Wave III peak latency of more than 0.30 msec between baseline and D7. CONCLUSIONS: Neither audiometric or the ABR tests showed clinical evidence of auditory toxicity seven days after receiving oral artesunate and mefloquine.

Author: Bozdech, Z.; Mok, S.; Hu, G.; Imwong, M.; Jaidee, A.; Russell, B.; Ginsburg, H.; Nosten, F.; Day, N. P.; White, N. J.; Carlton, J. M.; Preiser, P. R.
Year: 2008
Title: The transcriptome of Plasmodium vivax reveals divergence and diversity of transcriptional regulation in malaria parasites
Journal: Proc Natl Acad Sci U S A
Volume: 105
Issue: 42
Pages: 16290-5
Date: Oct 21
Alternate Journal: Proceedings of the National Academy of Sciences of the United States of America
Abstract: Plasmodium vivax causes over 100 million clinical infections each year. Primarily because of the lack of a suitable culture system, our understanding of the biology of this parasite lags significantly behind that of the more deadly species P. falciparum. Here, we present the complete transcriptional profile throughout the 48-h intraerythrocytic cycle of three distinct P. vivax isolates. This approach identifies strain specific patterns of expression for subsets of genes predicted to encode proteins associated with virulence and host pathogen interactions. Comparison to P. falciparum revealed significant differences in the expression of genes involved in crucial cellular functions that underpin the biological differences between the two parasite species. These data provide insights into the biology of P. vivax and constitute an important resource for the development of therapeutic approaches.

Reference Type: Journal Article
Author: Tarning, J.; Ashley, E. A.; Lindegardh, N.; Stepniewska, K.; Phaiphun, L.; Day, N. P.; McGready, R.; Ashton, M.; Nosten, F.; White, N. J.
Year: 2008
Title: Population pharmacokinetics of piperaquine after two different treatment regimens with dihydroartemisinin-piperaquine in patients with Plasmodium falciparum malaria in Thailand
Journal: Antimicrob Agents Chemother
Volume: 52
Issue: 3
Pages: 1052-61
Abstract: The population pharmacokinetics of piperaquine in adults and children with uncomplicated Plasmodium falciparum malaria treated with two different dosage regimens of dihydroartemisinin-piperaquine were characterized. Piperaquine pharmacokinetics in 98 Burmese and Karen patients aged 3 to 55 years were described by a two-compartment disposition model with first-order absorption and interindividual random variability on all parameters and were similar with the three- and four-dose regimens. Children had a lower body weight-normalized oral clearance than adults, resulting in longer terminal elimination half-lives and higher total exposure to piperaquine (area under the concentration-time curve from 0 to 63 days [AUC day 0-63]). However, children had lower plasma concentrations in the therapeutically relevant posttreatment prophylactic period (AUC day 3-20) because of smaller body weight-normalized central volumes of distribution and shorter distribution half-lives. Our data lend further support to a simplified once-daily treatment regimen to improve treatment adherence and efficacy and indicate that weight-adjusted piperaquine doses in children may need to be higher than in adults.

Reference Type: Journal Article
Author: Sharrock, W. W.; Suwanarusk, R.; Lek-Uthai, U.; Edstein, M. D.; Kosiavasee, V.; Travers, T.; Jaidee, A.; Sriprawat, K.; Price, R. N.; Nosten, F.; Russell, B.
Year: 2008
Title: Plasmodium vivax trophozoites insensitive to chloroquine
Journal: Malar J
Volume: 7
Issue: 1
Pages: 94
Abstract: ABSTRACT: BACKGROUND: Plasmodium vivax is a major cause of malaria and is still primarily treated with chloroquine. Chloroquine inhibits the polymerization of haem to inert haemozoin. Free haem monomers are thought to catalyze oxidative damage to the Plasmodium spp. trophozoite, the stage when haemoglobin catabolism is maximal. However preliminary in vitro observations on P. vivax clinical isolates suggest that only ring stages (early trophozoites) are sensitive to chloroquine. In this study, the stage specific action of chloroquine was investigated in synchronous cryopreserved isolates of P. vivax. METHODS: The in vitro chloroquine sensitivity of paired ring and trophozoite stages from 11 cryopreserved P. vivax clinical isolates from Thailand and two Plasmodium falciparum clones (chloroquine resistant K1 and chloroquine sensitive FC27) was measured using a modified WHO microtest method and fluorometric SYBR Green I Assay. The time each stage was exposed to chloroquine treatment was controlled by washing the chloroquine off at 20 hours after the beginning of treatment. RESULTS: Plasmodium vivax isolates added to the assay at ring stage had significantly lower median IC50s to chloroquine than the same isolates added at trophozoite stage (median IC50 12 nM vs 415nM p<0.01). Although only 36% (4/11) of the SYBR Green I assays for P. vivax were successful, both microscopy and SYBR Green I assays indicated that only P. vivax trophozoites were able to develop to schizonts at chloroquine concentrations above 100nM. CONCLUSIONS: Data from this study confirms the diminished sensitivity of P. vivax trophozoites to chloroquine, the stage thought to be the target of this drug. These results raise important questions about the pharmacodynamic action of chloroquine, and highlight a fundamental difference in the activity of chloroquine between P. vivax and P. falciparum.

Reference Type: Journal Article
Author: Rijken, M. J.; McGready, R.; Boel, M. E.; Barends, M.; Proux, S.; Pimanpanarak, M.; Singhasivanon, P.; Nosten, F.
Year: 2008
Title: Dihydroartemisinin-piperaquine rescue treatment of multidrug-resistant Plasmodium falciparum malaria in pregnancy: a preliminary report
Journal: Am J Trop Med Hyg
Volume: 78
Issue: 4
Pages: 543-5
Date: Apr
Abstract: Dihydroartemisinin-piperaquine (DHA-PPQ) is a promising new artemisinin combination treatment. There are no published data on the intentional use of the drug in pregnancy. Between June 2006 and January 2007, 50 Karen pregnant women with recurrent P. falciparum infections, despite 7-day treatments with quinine or artesunate (+/-clindamycin) or both, were treated with DHA-PPQ. This rescue treatment was effective and well tolerated and there was no evidence of toxicity for the mothers or the fetus. The PCR adjusted cure rate by Kaplan Meier analysis at day 63 was 92.2% (95% CI: 76.9-97.4).
URL: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=18385345
Author Address: Shoklo Malaria Research Unit, Mae Sot, Tak, Thailand.

Reference Type: Journal Article
Author: Lwin, K. M.; Ashley, E. A.; Proux, S.; Silamut, K.; Nosten, F.; McGready, R.
Year: 2008
Title: Clinically uncomplicated Plasmodium falciparum malaria with high schizontaemia: a case report
Journal: Malar J
Volume: 7
Pages: 57
Abstract: BACKGROUND: The treatment options for acute Plasmodium falciparum malaria are based on the clinician classifying the patient as uncomplicated or severe according to the clinical and parasitological findings. This process is not always straightforward. CASE PRESENTATION: An adult male presented to a clinic on the western border of Thailand with a physical examination and P. falciparum trophozoite count (1.2% of infected red blood cells, IRBC) from malaria blood smear, consistent with a diagnosis of uncomplicated P. falciparum infection. However, the physician on duty treated the patient for severe malaria based on the reported P. falciparum schizont count, which was very high (0.3% IRBC), noticeably in relation to the trophozoite count and schizont:trophozoite ratio 0.25:1. On intravenous artesunate, the patient deteriorated clinically in the first 24 hours. The trophozoite count increased from 1.2% IRBC at baseline to 20.5% IRBC 18 hours following the start of treatment. By day three, the patient recovered and was discharged on day seven having completed a seven-day treatment with artesunate and mefloquine. CONCLUSION: The malaria blood smear provides only a guide to the overall parasite biomass in the body, due to the ability of P. falciparum to sequester in the microvasculature. In severe malaria, high schizont counts are associated with worse prognosis. In low transmission areas or in non-immune travelers the presence of schizonts in the peripheral circulation is an indication for close patient supervision. In this case, an unusually high schizont count in a clinically uncomplicated patient was indicative of potential deterioration. Prompt treatment with intravenous artesunate is likely to have been responsible for the good clinical outcome in this case.
Notes: United Kingdom Wellcome Trust
Journal Article
Research Support, Non-U.S. Gov't
England
URL: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=18402713
Author Address: Shoklo Malaria Research Unit, Mae Sot, Tak, 63110, Thailand. drkhin_mg_lwin@shoklo-unit.com

Reference Type: Journal Article
Author: Lek-Uthai, U.; Suwanarusk, R.; Ruengweerayut, R.; Skinner-Adams, T. S.; Nosten, F.; Gardiner, D. L.; Boonma, P.; Piera, K. A.; Andrews, K. T.; MacHunter, B.; McCarthy, J. S.; Anstey, N. M.; Price, R. N.; Russell, B.
Year: 2008
Title: HIV-1 protease inhibitors and clinical isolates of Plasmodium: Greater activity against P. vivax than P. falciparum
Journal: Antimicrob. Agents Chemother.
Date: April 28, 2008
Abstract: Recent studies using laboratory clones have demonstrated that several antiretroviral protease inhibitors inhibit the growth of Plasmodium falciparum at concentrations that may be of clinical significance, especially during HIV-1 and malaria co-infection. Using clinical isolates, we now demonstrate the in vitro effectiveness of two HIV-1 aspartic protease inhibitors (PIs); saquinavir (SQV) and ritonavir (RTV) against P. vivax (n=30) and P. falciparum (n=20) from populations subjected to high levels of mefloquine and artesunate pressure on the Thai-Burmese border. The median IC50 values of P. vivax to RTV and SQV were 2233nM (range; 732-7738nM) and 4230nM (range; 1326-8452nM) respectively, both within the therapeutic concentration range commonly found in patients treated with these PIs. RTV was four fold more effective at inhibiting P. vivax than P. falciparum compared to a two fold difference in SQV sensitivity. Increased Pfmdr1 copy number was present in 33% (3/9) of isolates and that of Pvmdr1 in 9% (2/22), but neither was associated with PI sensitivity. The inter-Plasmodium spp. variations in PI sensitivity indicate key differences between P. vivax and P. falciparum. PI-containing antiretroviral regimens may demonstrate prophylactic activity against both vivax and falciparum malaria in HIV-infected patients resident in areas where multi-drug resistant P. vivax or P. falciparum is found.
URL: http://aac.asm.org/cgi/content/abstract/AAC.00169-08v1

Reference Type: Journal Article
Author: Guthmann, J. P.; Pittet, A.; Lesage, A.; Imwong, M.; Lindegardh, N.; Min Lwin, M.; Zaw, T.; Annerberg, A.; de Radigues, X.; Nosten, F.
Year: 2008
Title: Plasmodium vivax resistance to chloroquine in Dawei, southern Myanmar
Journal: Trop Med Int Health
Volume: 13
Issue: 1
Pages: 91-8
Date: Jan
Abstract: OBJECTIVE: To assess the efficacy of chloroquine in the treatment of Plasmodium vivax malaria in in Dawei District, southern Myanmar. METHODS: Enrolled patients at Sonsinphya clinic >6 months of age were assessed clinically and parasitologically every week for 28 days. To differentiate new infections from recrudescence, we genotyped pre- and post-treatment parasitaemia. Blood chloroquine was measured to confirm resistant strains. RESULTS: Between December 2002 and April 2003, 2661 patients were screened, of whom 252 were included and 235 analysed. Thirty-four per cent (95% CI: 28.1-40.6) of patients had recurrent parasitaemia and were considered treatment failures. 59.4% of these recurrences were with a different parasite strain. Two (0.8%) patients with recurrences on day 14 had chloroquine concentrations above the threshold of 100 ng/ml and were considered infected with chloroquine resistant parasites. 21% of failures occurred during the first 3 weeks of follow-up: early recurrence and median levels of blood chloroquine comparable to those of controls suggested P. vivax resistance. CONCLUSIONS: Plasmodium vivax resistance to chloroquine seems to be emerging in Dawei, near the Thai-Burmese border. While chloroquine remains the first-line drug for P. vivax infections in this area of Myanmar, regular monitoring is needed to detect further development of parasite resistance.
URL: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=18291007
Author Address: Epicentre, Paris, France.

Reference Type: Journal Article
Author: Dondorp, A. M.; Lee, S. J.; Faiz, M. A.; Mishra, S.; Price, R.; Tjitra, E.; Than, M.; Htut, Y.; Mohanty, S.; Yunus, E. B.; Rahman, R.; Nosten, F.; Anstey, N. M.; Day, N. P.; White, N. J.
Year: 2008
Title: The relationship between age and the manifestations of and mortality associated with severe malaria
Journal: Clin Infect Dis
Volume: 47
Issue: 2
Pages: 151-7
Date: Jul 15
Accession Number: 18533842
Abstract: BACKGROUND: The reported case-fatality rate associated with severe malaria varies widely. Whether age is an independent risk factor is uncertain. METHODS: In a large, multicenter treatment trial conducted in Asia, the presenting manifestations and outcome of severe malaria were analyzed in relation to age. RESULTS: Among 1050 patients with severe malaria, the mortality increased stepwise, from 6.1% in children (age, <10 years) to 36.5% in patients aged >50 years (P<0.001). Compared with adults aged 21-50 years, the decreased risk of death among children (adjusted odds ratio, 0.06; 95% confidence interval, 0.01-0.23; P<0.001) and the increased risk of death among patients aged >50 years (adjusted odds ratio, 1.88; 95% confidence interval, 1.01-3.52; P<0.001) was independent of the variation in presenting manifestations. The incidence of anemia and convulsions decreased with age, whereas the incidence of hyperparasitemia, jaundice, and renal insufficiency increased with age. Coma and metabolic acidosis did not vary with age and were the strongest predictors of a fatal outcome. The number of severity signs at hospital admission also had a strong prognostic value. CONCLUSION: Presenting syndromes in severe malaria depend on age, although the incidence and the strong prognostic significance of coma and acidosis are similar at all ages. Age is an independent risk factor for a fatal outcome of the disease.
URL: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=18533842
Author Address: Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.

Reference Type: Journal Article
Author: Blacksell, S. D.; Luksameetanasan, R.; Kalambaheti, T.; Aukkanit, N.; Paris, D. H.; McGready, R.; Nosten, F.; Peacock, S. J.; Day, N. P.
Year: 2008
Title: Genetic typing of the 56-kDa type-specific antigen gene of contemporary Orientia tsutsugamushi isolates causing human scrub typhus at two sites in north-eastern and western Thailand
Journal: FEMS Immunol Med Microbiol
Volume: 52
Issue: 3
Pages: 335-42
Date: Apr
Abstract: Orientia tsutsugamushi is the causative agent of scrub typhus, a major cause of febrile illness in the rural areas of Southeast Asia. Twenty-three strains of O. tsutsugamushi were isolated from patients with scrub typhus in north-east (Udorn Thani province) and western Thailand (Tak province) between 2003 and 2005. The isolates were characterized by sequencing the entire ORF of the 56-kDa-type-specific antigen gene, followed by phylogenetic analysis. The majority (15/23) of isolates clustered with the Karp-type strain, six with a Gilliam-type strain and one each with the TA716- and TA763-type strains. Overall, there was considerable diversity in sequence, comparable to that seen in strains from across the rest of the scrub typhus-endemic world. There was no significant difference in the distributions of strains between the two provinces (P=0.08, Fisher's exact) nor a temporal change in distribution with year of isolation (P=0.80, Fisher's exact). Within this diversity there were also examples of isolates with identical 56-kDa genotypes that were cultured from patients from the same geographical areas.
URL: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=18312580
Author Address: Oxford Tropical Medicine Research Unit, Mahidol University, Bangkok, Thailand. stuart@tropmedres.ac

Reference Type: Journal Article
Author: Imwong, M.; Pukrittayakamee, S.; Pongtavornpinyo, W.; Nakeesathit, S.; Nair, S.; Newton, P.; Nosten, F.; Anderson, T. J.; Dondorp, A.; Day, N. P.; White, N. J.
Year: 2008
Title: Gene amplification of Plasmodium vivax multidrug resistance 1 gene in Thailand, Laos, and Myanmar
Journal: Antimicrob Agents Chemother
Date: Apr 28
Abstract: Plasmodium vivax mdr1 gene amplification, quantified by real time PCR, was significantly more common on the western Thailand border (6 of 66 samples), where mefloquine pressure has been intense, than elsewhere in Southeast Asia (3 of 149; p=0.02). Five coding mutations in pvmdr1, independent of gene amplification, were found also.
URL: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=18443118

Reference Type: Journal Article
Record Number: 331
Author: Blacksell, S. D.; Luksameetanasan, R.; Kalambaheti, T.; Aukkanit, N.; Paris, D. H.; McGready, R.; Nosten, F.; Peacock, S. J.; Day, N. P.
Year: 2008
Title: Genetic typing of the 56-kDa type-specific antigen gene of contemporary Orientia tsutsugamushi isolates causing human scrub typhus at two sites in north-eastern and western Thailand
Journal: FEMS Immunol Med Microbiol
Volume: 52
Issue: 3
Pages: 335-42
Date: Apr
Abstract: Orientia tsutsugamushi is the causative agent of scrub typhus, a major cause of febrile illness in the rural areas of Southeast Asia. Twenty-three strains of O. tsutsugamushi were isolated from patients with scrub typhus in north-east (Udorn Thani province) and western Thailand (Tak province) between 2003 and 2005. The isolates were characterized by sequencing the entire ORF of the 56-kDa-type-specific antigen gene, followed by phylogenetic analysis. The majority (15/23) of isolates clustered with the Karp-type strain, six with a Gilliam-type strain and one each with the TA716- and TA763-type strains. Overall, there was considerable diversity in sequence, comparable to that seen in strains from across the rest of the scrub typhus-endemic world. There was no significant difference in the distributions of strains between the two provinces (P=0.08, Fisher's exact) nor a temporal change in distribution with year of isolation (P=0.80, Fisher's exact). Within this diversity there were also examples of isolates with identical 56-kDa genotypes that were cultured from patients from the same geographical areas.
URL: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=18312580
Author Address: Oxford Tropical Medicine Research Unit, Mahidol University, Bangkok, Thailand. stuart@tropmedres.ac