Single-Dose Tafenoquine to Prevent Relapse of Plasmodium vivax Malaria.

BACKGROUND: Treatment of Plasmodium vivax malaria requires the clearing of asexual parasites, but relapse can be prevented only if dormant hypnozoites are cleared from the liver (a treatment termed "radical cure"). Tafenoquine is a single-dose 8-aminoquinoline that has recently been registered for the radical cure of P. vivax. METHODS: This multicenter, double-blind, double-dummy, parallel group, randomized, placebo-controlled trial was conducted in Ethiopia, Peru, Brazil, Cambodia, Thailand, and the Philippines. We enrolled 522 patients with microscopically confirmed P. vivax infection (>100 to <100,000 parasites per microliter) and normal glucose-6-phosphate dehydrogenase (G6PD) activity (with normal activity defined as ≥70% of the median value determined at each trial site among 36 healthy male volunteers who were otherwise not involved in the trial). All patients received a 3-day course of chloroquine (total dose of 1500 mg). In addition, patients were assigned to receive a single 300-mg dose of tafenoquine on day 1 or 2 (260 patients), placebo (133 patients), or a 15-mg dose of primaquine once daily for 14 days (129 patients). The primary outcome was the Kaplan-Meier estimated percentage of patients who were free from recurrence at 6 months, defined as P. vivax clearance without recurrent parasitemia. RESULTS: In the intention-to-treat population, the percentage of patients who were free from recurrence at 6 months was 62.4% in the tafenoquine group (95% confidence interval [CI], 54.9 to 69.0), 27.7% in the placebo group (95% CI, 19.6 to 36.6), and 69.6% in the primaquine group (95% CI, 60.2 to 77.1). The hazard ratio for the risk of recurrence was 0.30 (95% CI, 0.22 to 0.40) with tafenoquine as compared with placebo (P<0.001) and 0.26 (95% CI, 0.18 to 0.39) with primaquine as compared with placebo (P<0.001). Tafenoquine was associated with asymptomatic declines in hemoglobin levels, which resolved without intervention. CONCLUSIONS: Single-dose tafenoquine resulted in a significantly lower risk of P. vivax recurrence than placebo in patients with phenotypically normal G6PD activity. (Funded by GlaxoSmithKline and Medicines for Malaria Venture; DETECTIVE ClinicalTrials.gov number, NCT01376167 .).

Plasmodium vivax Infection Impairs Regulatory T-Cell Suppressive Function During Acute Malaria.

The balance between pro- and antiinflammatory mechanisms is essential to limit immune-mediated pathology, and CD4+ forkhead box P3 (Foxp3+) regulatory T cells (Treg) play an important role in this process. The expression of inhibitory receptors regulates cytokine production by Plasmodium vivax-specific T cells. Our goal was to assess the induction of programmed death-1 (PD-1) and cytotoxic T-lymphocyte antigen (CTLA-4) on Treg during malaria and to evaluate their function. We found that P. vivax infection triggered an increase in circulating Treg and their expression of CTLA-4 and PD-1. Functional analysis demonstrated that Treg from malaria patients had impaired suppressive ability and PD-1+Treg displayed lower levels of Foxp3 and Helios, but had higher frequencies of T-box transcription factor+ and interferon-gamma+ cells than PD-1-Treg. Thus malaria infection alters the function of circulating Treg by triggering increased expression of PD-1 on Treg that is associated with decreased regulatory function and increased proinflammatory characteristics.

Induction of Inhibitory Receptors on T Cells During Plasmodium vivax Malaria Impairs Cytokine Production.

The function and regulation of the immune response triggered during malaria is complex and poorly understood, and there is a particular paucity of studies conducted in humans infected with Plasmodium vivax. While it has been proposed that T-cell-effector responses are crucial for protection against blood-stage malaria in mice, the mechanisms behind this in humans remain poorly understood. Experimental models of malaria have shown that the regulatory molecules, cytotoxic T-lymphocyte attenuator-4 (CTLA-4), lymphocyte activation gene-3 (LAG-3), and programmed death-1 (PD-1) are involved in the functional impairment of T cells during infection. Our goal was to define the role of these molecules during P. vivax malaria. We demonstrate that infection triggers the expression of regulatory molecules on T cells. The pattern of expression differs in CD4(+) and CD8(+) T cells. Higher frequencies of CD4(+) express more than 1 regulatory molecule compared to CD8(+) T cells. Moreover, lower proportions of CD4(+) T cells coexpress regulatory molecules, but are still able to proliferate. Importantly, simultaneously blockade of the CLTA-4, PD-1, and T-cell immunoglobulin and mucin-3 signaling restores the cytokine production by antigen-specific cells. These data support the hypothesis that upregulation of inhibitory receptors on T cells during P. vivax malaria impairs parasite-specific T-cell effector function.

CD4+ T cells apoptosis in Plasmodium vivax infection is mediated by activation of both intrinsic and extrinsic pathways.

BACKGROUND: Reduction in the number of circulating blood lymphocytes (lymphocytopaenia) has been reported during clinical episodes of malaria and is normalized after treatment with anti-malaria drugs. While this phenomenon is well established in malaria infection, the underlying mechanisms are still not fully elucidated. In the present study, the occurrence of apoptosis and its pathways in CD4+ T cells was investigated in naturally Plasmodium vivax-infected individuals from a Brazilian endemic area (Porto Velho - RO). METHODS: Blood samples were collected from P. vivax-infected individuals and healthy donors. The apoptosis was characterized by cell staining with Annexin V/FITC and propidium iodide and the apoptosis-associated gene expression profile was carried out using RT2 Profiler PCR Array-Human Apoptosis. The plasma TNF level was determined by ELISA. The unpaired t-test or Mann-Whitney test was applied according to the data distribution. RESULTS: Plasmodium vivax-infected individuals present low number of leukocytes and lymphocytes with a higher percentage of CD4+ T cells in early and/or late apoptosis. Increased gene expression was observed for TNFRSF1B and Bid, associated with a reduction of Bcl-2, in individuals with P. vivax malaria. Furthermore, these individuals showed increased plasma levels of TNF compared to malaria-naive donors. CONCLUSIONS: The results of the present study suggest that P. vivax infection induces apoptosis of CD4+ T cells mediated by two types of signaling: by activation of the TNFR1 death receptor (extrinsic pathway), which is amplified by Bid, and by decreased expression of the anti-apoptotic protein Bcl-2 (intrinsic pathway). The T lymphocytes apoptosis could reflect a strategy of immune evasion triggered by the parasite, enabling their persistence but also limiting the occurrence of immunopathology.

The CD14+CD16+ inflammatory monocyte subset displays increased mitochondrial activity and effector function during acute Plasmodium vivax malaria.

Infection with Plasmodium vivax results in strong activation of monocytes, which are important components of both the systemic inflammatory response and parasite control. The overall goal of this study was to define the role of monocytes during P. vivax malaria. Here, we demonstrate that P. vivax-infected patients display significant increase in circulating monocytes, which were defined as CD14(+)CD16- (classical), CD14(+)CD16(+) (inflammatory), and CD14loCD16(+) (patrolling) cells. While the classical and inflammatory monocytes were found to be the primary source of pro-inflammatory cytokines, the CD16(+) cells, in particular the CD14(+)CD16(+) monocytes, expressed the highest levels of activation markers, which included chemokine receptors and adhesion molecules. Morphologically, CD14(+) were distinguished from CD14lo monocytes by displaying larger and more active mitochondria. CD14(+)CD16(+) monocytes were more efficient in phagocytizing P. vivax-infected reticulocytes, which induced them to produce high levels of intracellular TNF-α and reactive oxygen species. Importantly, antibodies specific for ICAM-1, PECAM-1 or LFA-1 efficiently blocked the phagocytosis of infected reticulocytes by monocytes. Hence, our results provide key information on the mechanism by which CD14(+)CD16(+) cells control parasite burden, supporting the hypothesis that they play a role in resistance to P. vivax infection.

Low sensitivity of malaria rapid diagnostic tests stored at room temperature in the Brazilian Amazon Region.

INTRODUCTION: In remote areas of the Amazon Region, diagnosis of malaria by microscopy is practically impossible. This study aimed to evaluate the performance of two rapid diagnostic tests (RDTs) targeting different malaria antigens stored at room temperature in the Brazilian Amazon Region. METHODOLOGY: Performance of the OptiMal Pf/Pan test and ICT-Now Pf/Pan test was analyzed retrospectively in 1,627 and 1,602 blood samples, respectively. Tests were performed over a 15-month period. Kits were stored at room temperature in five community health centres located in the Brazilian Amazon Region. RDT results were compared with thick blood smear (TBS) results to determine sensitivity, specificity, and accuracy of the RDT. RESULTS: The sensitivities of the OptiMal Pf/Pan test were 79.7% for Plasmodium falciparum malaria diagnosis and 85.7% for non-P. falciparum infections. The results showed a crude agreement of 88.5% for P. falciparum, and 88.3% for non-P. falciparum infections (Kappa index = 0.74 and 0.75, respectively). For the ICT-Now Pf/Pan test (CI 95%), the sensitivities were 87.9% for P. falciparum malaria diagnosis and 72.5% for non-P. falciparum infection. Crude agreement between the ICT-Now Pf/Pan test and TBS was 91.4% for P. falciparum and 79.7% for non-P. falciparum infection. The Kappa index was 0.81 and 0.59 for the final diagnosis of P. falciparum and non-P. falciparum, respectively. Higher levels of parasitaemia were associated with higher crude agreement between RDT and TBS. CONCLUSIONS: The sensitivities of RDTs stored at room temperature over a 15-month period and performed in field conditions were lower than those previously reported.

Understanding the clinical spectrum of complicated Plasmodium vivax malaria: a systematic review on the contributions of the Brazilian literature.

The resurgence of the malaria eradication agenda and the increasing number of severe manifestation reports has contributed to a renewed interested in the Plasmodium vivax infection. It is the most geographically widespread parasite causing human malaria, with around 2.85 billion people living under risk of infection. The Brazilian Amazon region reports more than 50% of the malaria cases in Latin America and since 1990 there is a marked predominance of this species, responsible for 85% of cases in 2009. However, only a few complicated cases of P. vivax have been reported from this region. A systematic review of the Brazilian indexed and non-indexed literature on complicated cases of vivax malaria was performed including published articles, masters' dissertations, doctoral theses and national congresses' abstracts. The following information was retrieved: patient characteristics (demographic, presence of co-morbidities and, whenever possible, associated genetic disorders); description of each major clinical manifestation. As a result, 27 articles, 28 abstracts from scientific events' annals and 13 theses/dissertations were found, only after 1987. Most of the reported information was described in small case series and case reports of patients from all the Amazonian states, and also in travellers from Brazilian non-endemic areas. The more relevant clinical complications were anaemia, thrombocytopaenia, jaundice and acute respiratory distress syndrome, present in all age groups, in addition to other more rare clinical pictures. Complications in pregnant women were also reported. Acute and chronic co-morbidities were frequent, however death was occasional. Clinical atypical cases of malaria are more frequent than published in the indexed literature, probably due to a publication bias. In the Brazilian Amazon (considered to be a low to moderate intensity area of transmission), clinical data are in accordance with the recent findings of severity described in diverse P. vivax endemic areas (especially anaemia in Southeast Asia), however in this region both children and adults are affected. Finally, gaps of knowledge and areas for future research are opportunely pointed out.

Rapid turnover of Plasmodium falciparum var gene transcripts and genotypes during natural non-symptomatic infections.

The var genes of Plasmodium falciparum code for the antigenically variant erythrocyte membrane proteins 1 (PfEMP1), a major factor for cytoadherence and immune escape of the parasite. Herein, we analyzed the var gene transcript turnover in two ongoing, non-symptomatic infections at sequential time points during two weeks. The number of different circulating genomes was estimated by microsatellite analyses. In both infections, we observed a rapid turnover of plasmodial genotypes and var transcripts. The rapidly changing repertoire of var transcripts could have been caused either by swift elimination of circulating var-transcribing parasites stemming from different or identical genetic backgrounds, or by accelerated switching of var gene transcription itself.

Rapid turnover of Plasmodium falciparum var gene transcripts and genotypes during natural non-symptomatic infections

Os genes var de Plasmodium falciparum codificam as proteínas variantes da superfície do eritrócito infectado (PfEMP1). Neste estudo examinamos a mudança de transcritos destes genes var em duas infecções assintomáticas durante um curto prazo e estimamos simultaneamente o número de genomas circulantes nas mesmas amostras por análise de microssatélites. Nas duas infecções observamos uma rápida mudança de genótipos e transcritos de genes var. A mudança acelerada do repertório de transcritos possivelmente foi causada pela rápida eliminação de parasitas circulantes transcrevendo genes var a partir de genomas iguais ou diferentes, ou pela mudança acelerada da própria transcrição (switching) de genes var.

Seasonal malaria transmission and variation of anopheline density in two distinct endemic areas in Brazilian Amazonia.

Studies on seasonal anopheline fauna variation were performed in two distinct settlements in the State of Rondônia, Brazil: one at the Madeira River banks (Portuchuelo) with stable native Amazonian population; the other at an inland lumber-extracting farm (Urupá) in dry land, in which adults are mostly migrants. During a 6-yr period (1994-2000), 8,638 adult anophelines were collected: 2,684 in Urupá and 5,954 in Portuchuelo. Anopheles darlingi represented >95% of total mosquitoes caught. Dissection of 4,424 A. darlingi females yielded a very low sporozoite infection index below 0.1%. Oocysts were found in both localities in approximately 0.1% of dissected mosquitoes. Determination of the hour biting rates disclosed seasonal variations in both localities. However, in Portuchuelo, mosquito density peaked at the acme of the rainy season, whereas at Urupá it peaked in the dry season. The increase in mosquito density and incidence of malaria cases were coincident. The high mosquito densities observed in the riverine settlement of Portochuelo sector B, which permits evaluation in > 10,000 mosquitoes' bites/person/year, could explain, in spite of the low mosquito's infection index, the previously described development of natural immunity in the local population that is not observed in the dry land agroindustrial settlement of Urupá.

Infection of Anopheles darlingi fed on patients infected with Plasmodium vivax before and during treatment with chloroquine plus primaquine in Costa Marques, Rondônia, Brazil

Five patients with asexual and sexual parasites of Plasmodium vivax were treated orally with 600 mg chloroquine diphosphate (hour 0) followed with 300 mg at 8, 24 and 48 h later. Primaquine phospate, 15 mg, was administered concurrently at h 0 and 24 h intervals for 14 days. Anopheles darlingi were fed before the first dose (h-0.5) and 0.5, 1, 2, 4, 6, 8, 10, 12, 16, 20, 24, 36, 48, 60 and 72 h later. Mosquitoes were examined for oocysts on day 8 and for sporozoites on day 15 after infection. Four of the five patients studied were still infective to mosquitoes from 1-5 h after the first dose of chloroquine plus primaquine. One of these and one other patient, who vomited 15 min after the first dose, became inffective again at hours 10 and 12, respectively. Once produced, oocysts in mosquitoes fed on patients before, during and after chloroquine plus primaquine treatment appeared normal and produced sporozoite infected salivary glands. In view of these data , it is concluded that primaquine demonstrated rapid gametocytocidal activity and should be administred concurrently with chloroquine to reduce vivax malaria transmission

Procedência de pacientes portadores de leishmaniose tegumentar americana nas áreas endêmicas de três braços e corte de pedra, Estado da Bahia, Brasil / Origin of patients with american tegumentar leishmaniasis recorded in the endemic areas of Tres Braços and Corte de Pedra, Bahia State, Brazil

De acordo com o cadastro de 1416 pacientes portadores de leishmaniose tegumentar americana (L.T.A) referentes ao período de janeiro de 1976 a maio de 1987, os autores realizaram um levantamento da procedência dos casos dessa parasitose atendidos nas áreas endêmicas de Três Braços e Corte de Pedra no estado da Bahia. Os pacientes procediam de 24 dos 89 municípios que compöem a regiäo cacaueira da Bahia, destacando-se os municípios de Valença, Wenceslau Guimaräes e Teolândia como os de maior prevalência, somando juntos 923 casos (65,1%, com 520 destes residindo em umas poucas localidades contínuas entre si, formando uma área endêmica, com transmissäo ocorrendo provavelmente no peri, intradomicílio e nas lavouras de cacau e cravo localizadas nas encostas da floresta atlântica. Nota-se que a partir de 1983, houve um aumento do número de casos em toda a regiäo, havendo evidências da leishmaniose tegumentar americana comportar-se como uma doença ocupacional em toda a regiäo estudada

Aspectos psicossociais e estigmatizantes da leishmaniose cutâneo-mucosa / Psychosocial aspects and stigmatizing of mucocutaneous leishmaniasis

Os autores selecionaram 15 pacientes portadores de leishmaniose cutâneo-mucosa (LCM) forma grave, onde buscaram, através de entrevista psicológica, conhecer aspectos da vida de cada um, antes de contrair a doença, no decorrer e após o tratamento. Concomitantemente, realizaram 25 entrevistas com a comunidade onde residem os pacientes, com a intençäo de avaliar as reaçöes da mesma ao doente com leishmaniose. Constataram que entre os pacientes entrevistados: 14(93,3%) referiram algum tipo de modificaçäo no decorrer da doença; 11(73,3%) perceberam-se marginalizados; 9(60%) sentiram-se afastados do convívio da sociedade; 10(66,6%) tiveram dificuldade de retornar ao trabalho. Na comunidade, 11(44%) associam o portador da LCM a indivíduos que apresentam deformaçöes no corpo, 8(32%) têm receio de contrair a doença pelo caráter destrutivo das lesöes, 24(96%) referiram que os pacientes têm problemas de relacionamento social

Conceitos de uma populaçäo local a respeito da leishmaniose mucocutânea em uma área endêmica / Concepts among a local population regarding mucocutaneous leishmaniasis in an endemic area

Uma investigaçäo a respeito do que a populaçäo local pensa sobre vários aspectos da leishmaniose mucocutânea foi realizada em Três Braços, Bahia, uma área de alta prevalência de infecçäo por Leishmania braziliensis. Os resultados obtidos indicam que essa populaçäo tem um entendimento razoavelmente bom sobre alguns aspectos epidemiológicos e tratamento dessa doença, mas demonstram seu pouco conhecimento concernente à etiologia e prevençäo. Esses dados poderäo ser valiosos, no futuro, em um planejamento do controle de transmissäo da doença nesta comunidade