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Leimanis M.L.,Shoklo Malaria Research Unit | Jaidee A.,Shoklo Malaria Research Unit | Sriprawat K.,Shoklo Malaria Research Unit | Kaewpongsri S.,Shoklo Malaria Research Unit | And 8 more authors.
Antimicrobial Agents and Chemotherapy | Year: 2010

The novel organometallic chloroquine analog ferroquine (SSR 97193) is effective against chloroquine-resistant Plasmodium falciparum. The ex vivo efficacy of ferroquine against Plasmodium vivax isolates was tested. Ferroquine has a potent ex vivo effect on P. vivax schizont maturation (median 50% inhibitory concentration, 15 nM; n = 42). No significant cross-sensitivity between ferroquine and other antimalarials was detected. This drug may be a suitable replacement for chloroquine in the treatment of drug-resistant P. vivax malaria. Copyright © 2010, American Society for Microbiology. All Rights Reserved. Source


Kosaisavee V.,Mahidol University | Lek-Uthai U.,Mahidol University | Suwanarusk R.,Agency for Science, Technology and Research Singapore | Gruner A.C.,Agency for Science, Technology and Research Singapore | And 6 more authors.
PLoS ONE | Year: 2012

Background: Plasmodium vivax merozoites specifically invade reticulocytes. Until recently, two reticulocyte-binding proteins (Pvrbp1 and Pvrbp2) expressed at the apical pole of the P. vivax merozoite were considered to be involved in reticulocyte recognition. The genome sequence recently obtained for the Salvador I (Sal-I) strain of P. vivax revealed additional genes in this family, and in particular Pvrbp2a, Pvrbp2b (Pvrbp2 has been renamed as Pvrbp2c) and two pseudogenes Pvrbp2d and Pvrbp3. It had been previously found that Pvrbp2c is substantially more polymorphic than Pvrbp1. The primary goal of this study was to ascertain the level of polymorphism of these new genes. Methodology/Principal Findings: The sequence of the Pvrbp2a, Pvrbp2b, Pvrbp2d and Pvrbp3 genes were obtained by amplification/cloning using DNA purified from four isolates collected from patients that acquired the infection in the four cardinal regions of Thailand (west, north, south and east). An additional seven isolates from western Thailand were analyzed for gene copy number variation. There were significant polymorphisms exhibited by these genes (compared to the reference Sal-I strain) with the ratio of mutations leading to a non-synonymous or synonymous amino acid change close to 3:1 for Pvrbp2a and Pvrbp2b. Although the degree of polymorphism exhibited by these two genes was higher than that of Pvrbp1, it did not reach the exceptional diversity noted for Pvrbp2c. It was interesting to note that variations in the copy number of Pvrbp2a and Pvrbp2b occurred in some isolates. Conclusions/Significance: The evolution of different members of the Pvrbp2 family and their relatively high degree of polymorphism suggests that the proteins encoded by these genes are important for parasite survival and are under immune selection. Our data also shows that there are highly conserved regions in rbp2a and rbp2b, which might provide suitable targets for future vaccine development against the blood stage of P. vivax. © 2012 Kosaisavee et al. Source


Burgoine K.L.,Shoklo Malaria Research Unit | Burgoine K.L.,University of Oxford | Bancone G.,Shoklo Malaria Research Unit | Bancone G.,Mahidol University | And 3 more authors.
Malaria Journal | Year: 2010

Background: Primaquine is currently the only medication used for radical cure of Plasmodium vivax infection. Unfortunately, its use is not without risk. Patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency have an increased susceptibility to haemolysis when given primaquine. This potentially fatal clinical syndrome can be avoided if patients are tested for G6PD deficiency and adequately informed before being treated. Case presentation. A 35-year old male presented to our clinic on the Thai-Burmese border with a history and clinical examination consistent with intravascular haemolysis. The patient had been prescribed primaquine and chloroquine four days earlier for a P. vivax infection. The medication instructions had not been given in a language understood by the patient and he had not been tested for G6PD deficiency. The patient was not only G6PD deficient but misunderstood the instructions and took all his primaquine tablets together. With appropriate treatment the patient recovered and was discharged home a week later. Conclusions. Whilst primaquine remains the drug of choice to eradicate hypnozoites and control P. vivax transmission, the risks associated with its use must be minimized during its deployment. In areas where P. vivax exists, patients should be tested for G6PD deficiency and adequately informed before administration of primaquine. © 2010 Burgoine et al; licensee BioMed Central Ltd. Source


Canavati S.,Mahidol University | Plugge E.,University of Oxford | Suwanjatuporn S.,Mahidol University | Sombatrungjaroen S.,Mahidol University | Nostenc F.,Center for Clinical Vaccinology and Tropical Medicine
Bulletin of the World Health Organization | Year: 2011

Problem Immunization is a cost-effective means of improving child survival but implementation of programmes in low- and middleincome countries is variable. Children of migrants are less likely to be immunized. Approach The qualitative study aimed to identify barriers to the successful implementation of migrant immunization programmes in Tak province, Thailand. We ran a total of 53 focus groups involving 371 participants in three sites. Local setting Tak province in Thailand borders Myanmar and has an estimated 200 000 migrants from Myanmar. Vaccine-preventable diseases are a documented cause of morbidity in this population but there is no systematic or coordinated immunization programme in the area. Relevant changes As a result of the findings, the subsequent immunization campaign targeted children in school to overcome those barriers of distance to immunization services, fear of arrest, not remembering immunization appointments, and the disruption of parental work. The campaigns also included immunization education for both parents and teachers. Lessons learnt Migrant parents identified similar barriers to accessing childhood immunization programmes as migrant populations elsewhere in the world, although a unique barrier identified by parents from Myanmar was 'fear of arrest'. The subsequent schoolbased strategy to overcome these barriers appears to be effective. Source


Ch'Ng J.-H.,National University of Singapore | Mok S.,Nanyang Technological University | Bozdech Z.,Nanyang Technological University | Lear M.J.,Tohoku University | And 5 more authors.
Scientific Reports | Year: 2013

Due to the widespread prevalence of resistant parasites, chloroquine (CQ) was removed from front-line antimalarial chemotherapy in the 1990s despite its initial promise of disease eradication. Since then, resistance-conferring mutations have been identified in transporters such as the PfCRT, that allow for the efflux of CQ from its primary site of action, the parasite digestive vacuole. Chemosensitizing/chemoreversing compounds interfere with the function of these transporters thereby sensitizing parasites to CQ once again. However, compounds identified thus far have disappointing in vivo efficacy and screening for alternative candidates is required to revive this strategy. In this study, we propose a simple and direct means to rapidly screen for such compounds using a fluorescent-tagged CQ molecule. When this screen was applied to a small library, seven novel chemosensitizers (octoclothepin, methiothepin, metergoline, loperamide, chlorprothixene, L-703,606 and mibefradil) were quickly elucidated, including two which showed greater potency than the classical chemosensitizers verapamil and desipramine. Source

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