Transmission-blocking compound candidates against Plasmodium vivax using P. berghei as an initial screening

BACKGROUND Different strategies for improvement of malaria control and elimination are based on the blockage of malaria parasite transmission to the mosquito vector. These strategies include the drugs that target the plasmodial sexual stages in humans and the early developmental stages inside mosquitoes. OBJECTIVES Here we tested Malaria Box compounds in order to evaluate their activity against male and female gametocytes in Plasmodium berghei, mosquito infection in P. vivax and ookinete formation in both species. METHODS/FINDINGS The membrane feeding assay and the development of ookinetes by a 24 h ex vivo culture and the ookinete yield per 1000 erythrocytes were used to test transmission-blocking potential of the Malaria Box compounds in P. vivax. For P. berghei we used flow cytometry to evaluate male and female gametocyte time course and fluorescence microscopy to check the ookinete development. The two species used in this study showed similar results concerning the compounds' activity against gametocytes and ookinetes, which were different from those in P. falciparum. In addition, from the eight Malaria Box compounds tested in both species, compounds MMV665830, MMV665878 and MMV665941 were selected as a hit compounds due the high inhibition observed. CONCLUSION Our results showed that P. berghei is suitable as an initial screening system to test compounds against P. vivax.

Increased platelet distribution width and reduced IL-2 and IL-12 are associated with thrombocytopenia in Plasmodium vivax malaria

BACKGROUND Thrombocytopenia in malaria involves platelet destruction and consumption; however, the cellular response underlying this phenomenon has still not been elucidated. OBJECTIVE To find associations between platelet indices and unbalanced Th1/Th2/Th17 cytokines as a response to thrombocytopenia in Plasmodium vivax infected (Pv-MAL) patients. METHODS Platelet counts and quantification of Th1/Th2/Th17 cytokine levels were compared in 77 patients with uncomplicated P. vivax malaria and 37 healthy donors from the same area (endemic control group - ENCG). FINDINGS Thrombocytopenia was the main manifestation in 55 patients, but was not associated with parasitaemia. The Pv-MAL patients showed increases in the mean platelet volume (MPV), which may be consistent with larger or megaplatelets. Contrary to the findings regarding the endemic control group, MPV and platelet distribution width (PDW) did not show an inverse correlation, due the increase in the heterogeneity of platelet width. In addition, the Pv-MAL patients presented increased IL-1β and reduced IL-12p70 and IL-2 serum concentrations. Furthermore, the reduction of these cytokines was associated with PDW values. MAIN CONCLUSIONS Our data demonstrate that an increase in MPV and the association between reductions of IL-2 and IL-12 and PDW values may be an immune response to thrombocytopenia in uncomplicated P. vivax malaria.

A decade of malaria during pregnancy in Brazil: what has been done concerning prevention and management

In Brazil, malaria remains a disease of major epidemiological importance because of the high number of cases in the Amazonian Region. Plasmodium spp infections during pregnancy are a significant public health problem with substantial risks for the pregnant woman, the foetus and the newborn child. In Brazil, the control of malaria during pregnancy is primarily achieved by prompt and effective treatment of the acute episodes. Thus, to assure rapid diagnosis and treatment for pregnant women with malaria, one of the recommended strategy for low transmission areas by World Health Organization and as part of a strategy by the Ministry of Health, the National Malaria Control Program has focused on integrative measures with woman and reproductive health. Here, we discuss the approach for the prevention and management of malaria during pregnancy in Brazil over the last 10 years (2003-2012) using morbidity data from Malaria Health Information System. Improving the efficiency and quality of healthcare and education and the consolidation of prevention programmes will be challenges in the control of malaria during pregnancy in the next decade.

Antibody recognition of Plasmodium falciparum infected red blood cells by symptomatic and asymptomatic individuals in the Brazilian Amazon

In the Amazon Region, there is a virtual absence of severe malaria and few fatal cases of naturally occurring Plasmodium falciparum infections; this presents an intriguing and underexplored area of research. In addition to the rapid access of infected persons to effective treatment, one cause of this phenomenon might be the recognition of cytoadherent variant proteins on the infected red blood cell (IRBC) surface, including the var gene encoded P. falciparum erythrocyte membrane protein 1. In order to establish a link between cytoadherence, IRBC surface antibody recognition and the presence or absence of malaria symptoms, we phenotype-selected four Amazonian P. falciparum isolates and the laboratory strain 3D7 for their cytoadherence to CD36 and ICAM1 expressed on CHO cells. We then mapped the dominantly expressed var transcripts and tested whether antibodies from symptomatic or asymptomatic infections showed a differential recognition of the IRBC surface. As controls, the 3D7 lineages expressing severe disease-associated phenotypes were used. We showed that there was no profound difference between the frequency and intensity of antibody recognition of the IRBC-exposed P. falciparum proteins in symptomatic vs. asymptomatic infections. The 3D7 lineages, which expressed severe malaria-associated phenotypes, were strongly recognised by most, but not all plasmas, meaning that the recognition of these phenotypes is frequent in asymptomatic carriers, but is not necessarily a prerequisite to staying free of symptoms. .

Análise dos mecanismos imunológicos gerados pela imunizaçäo experimental contra doença de Chagas e malária / Analysis of the immunological mechanisms generated by experimental immunization against Chagas' disease and malaria

Durante a tese de Mestrado, eu descrevi que a imunizaçao de camundongos BALB/c com um plasmídio contendo o gene da trans-sialidase foi capaz de induzir imunidade protetora contra a infecçao pelo Trypanosoma cruzi. Baseados nos resultados obtidos anteriormente, a primeira parte deste trabalho teve o intuito de analisar a imunidade celular induzida pela vacinaçao genética com o gene da TS. Observamos em animais imunizados a presença de esplenócitos CD4+ e CD8+ específicos para a TS e que produziam IFN-g, mas nao IL-4 ou IL-10. Posteriormente, estes linfócitos T foram caracterizados a nível clonal, e os clones de linfócitos T CD4+ citotóxicos secretavam IFN-g mas nao IL-4 ou IL-10, sendo definido portanto como Th1. Obtivemos também clones Th2 secretores de IL-4 e IL-10, mas nao de IFN-g Todos os clones T CDB+ gerados apresentaram atividade citotóxica in vitro e foram capazes de secretar IFN-g, mas nao IL-4 ou IL-10. 0 mais importante foi o fato que clones T CD4+ Th1 ou CD8+ Tc1 foram capazes de inibir, respectivamente, o desenvolvimento in vitro do T. cruzi em culturas de macrófagos ou fibroblastos infectados. Estes resultados mostraram que a imunizaçao genética é capaz de induzir linfócitos T CD4+ Th1 e CD8+ Tc1 potencialmente protetores, reforçando assim a possibilidade do uso desta estratégia de imunizaçao no desenvolvimento de uma vacina preventiva ou terapêutica contra doença de Chagas. Na segunda parte deste trabalho, reavaliamos a capacidade da imunizaçao com plasmídios contendo o gene da proteína do circumsporozoíta (CS) de Plasmodium yoelii com o intuito de aprofundar os estudos dos mecanismos imunológicos induzidos pela vacinaçao genética contra malária experimental. Entretanto, ao contrário do que está descrito na literatura, fomos incapazes de induzir imunidade protetora contra a infecçao experimental. A ausência de proteçao em nossos experimentos nao estava relacionada com a falta de resposta imune. Entretanto, observamos que os anticorpos induzidos pela imunizaçao com o gene da proteína CS nao foram capazes de inibir a penetraçao de esporozoítas em culturas de hepatócitos. Além de anticorpos, observamos a presença de linfócitos T CD8+ produtores de IFN-g e capazes de reconhecer o epítopo citotóxico da proteína CS. 0 número destas células produtoras de IFN-g no baço de animais imunizados foi semelhante ao descrito por outros grupos utilizando o mesmo gene. Nossos resultados sugerem que a...