Investigação epidemiológica de patógenos virais associados a manifestações no trato gastrintestinal, em crianças , na Zona da Mata Mineira

-A gastrenterite viral é uma doença comum, que ocorre tanto em países desenvolvidos quanto naqueles em desenvolvimento, sendo que nestes últimos, a doença se mantém como uma das principais causas de mortalidade infantil. Embora os rotavírus sejam os principais agentes envolvidos, merecem destaque também, os adenovírus e os astrovírus. Este trabalho teve como objetivos detectar a presença de rotavírus, adenovírus e astrovírus em casos de gastrenterite infantil; caracterizar as amostras de rotavírus detectadas; avaliar a prevalência e a sazonalidade dessas infecções. Espécimes fecais foram obtidos de crianças de 0 a 5 anos, com quadro de gastrenterite, atendidas em unidades de saúde das redes pública e privada, localizadas em Juiz de Fora, no período de 2005 a 2006. Suspensões fecais a 10% em tampão Tris-HCl-Ca, pH 7,2, clarificadas, foram testadas através de um ensaio imunoenzimático, para a detecção de rotavírus e adenovírus (EIERA). Todas as suspensões, com exceção daquelas positivas para adenovírus, foram submetidas à técnica de extração do RNA viral com tampão isotiocianato de guanidina, associado à sílica. A caracterização eletroforética do RNA das amostras positivas para rotavírus foi realizada através da técnica de eletroforese em gel de poliacrilamida (EGPA), enquanto a detecção dos astrovírus foi realizada através da técnica de reação em cadeia da polimerase, precedida de transcrição reversa (RT-PCR). A presença de rotavírus foi pesquisada em 338 espécimes fecais, tendo sido encontradas 61 amostras positivas (18,04%), a maioria delas entre julho e agosto, meses mais frios e secos do ano. A análise eletroforética destas, mostrou a circulação de amostras com perfis característicos de rotavírus do grupo A, todas de perfil longo, em 2005 e, em 2006, perfis longos e curtos, com predominância dos últimos. Os adenovírus foram pesquisados em 316 espécimes, tendo sido detectadas 17 amostras positivas (5,38%) e embora as infecções tenham sido registradas em diferentes meses do ano, em 2006, verificou-se uma maior ocorrência em maio. A maioria das amostras positivas para rotavírus e adenovírus foi encontrada em crianças com até 24 meses de idade. A pesquisa para detecção de astrovírus foi realizada em 90 amostras fecais, tendo sido encontrada uma positiva (1,11%), detectada no mês de setembro de 2005. O presente estudo reforça a importância do envolvimento destes vírus em casos brandos e severos de doença diarréica infantil. Dada a relevância das gastrenterites virais em todo o mundo, a realização de levantamentos epidemiológicos contínuos é importante, pois contribuem para a obtenção de dados, necessários para o desenvolvimento e acompanhamento de medidas de prevenção

Heterologous expression, purification and search for inhibitors of the NTPDase-1 of Trypanosoma cruzi

A Doença de Chagas é uma antropozoonose causada por Trypanosoma cruzi, um protozoário flagelado da ordem Kinetoplastida. T. cruzi possui em sua superfície uma ectonucleotidase denominada NTPDase-1. As ectonucleotidases da família E-NTPDases são enzimas capazes de hidrolisar nucleotídeos tri e/ou difosfatados, que podem ser degradados a nucleosídeos por outras ectonucleotidases. Os nucleotídeos extracelulares atuam como sinalizadores em vários processos celulares, como modulação da resposta imune de hospedeiros mamíferos. A hidrólise de ATP extracelular possui papel na infectividade e virulência do T. cruzi, bem como para outros parasitos, como Leishmania, Trichomonas, Toxoplasma, Entamoeba e outros. Por isso, as NTPDases são consideradas um alvo em potencial para o desenho racional de novas drogas para uso no tratamento da doença de Chagas. Neste trabalho realizamos a purificação parcial da NTPDase-1 e produzimos anticorpos policlonais contra ela. Além disso, avaliamos a estabilidade da sua atividade com relação à temperatura e tempo de armazenamento, estado de oligomerização, padronizamos um ensaio de inibição enzimática e realizamos uma triagem de análogos sintéticos de adenina como possíveis inibidores da NTPDase-1. Foi possível observar que a temperatura de armazenamento influenciou a atividade enzimática ao longo do tempo, sendo a temperatura de 4ºC a que melhor preservou tal atividade. A amostra protéica purificada é heterogênea, apresentando oligômeros inativos e monômeros e/ou dímeros ativos. A atividade ATPásica pode ser inibida por adenina e análogos e essa inibição parece ser do tipo competitiva.The Chagas’ Disease is an antropozoonose caused by Trypanosoma cruzi, a flagellate protozoan of order Kinetoplastida. T. cruzi presents an ectonucleotidase on its surface, named NTPDase-1. The ectonucleotidases of the E-NTPDase family are enzymes capable of hydrolyse nucleotides tri and/or diphosphates that can be degraded to nucleosides by other ectonucleotidases. Extracellular nucleotides act as signaling molecules in several celullar processes, such as modulation of immune response of mammalian hosts. The ATPe hydrolysis plays a role on T. cruzi infectivity and virulence, as in other parasites such as, Leishmania, Trichomonas, Toxoplasma and Entamoeba. Therefore, NTPDases are taken as potencial targets for the rational design of new drugs for the treatment of Chagas’ disease. In this work we performed the parcial purification of TcNTPDase-1 and produced polyclonal antibodies against it. Futhermore, we evaluated the stability of its activity with respect to time and temperature of storage, standardized an inhibition assay and performed a screening of synthetic adenine analogues as potential inhibitors of NTPDase-1. It was observed that the storage temperature influenced the enzyme activity over time, and temperature of 4 º C was the most efficient to preserve this activity. The purified protein sample is heterogeneous, with inactive oligomers and active monomers and/or dimers. The ATPase activity can be inhibited by adenine and analogues and this inhibition seems to be competitive.Coordenação de Aperfeiçoamento de Pessoal de Nível Superio

Biological and biochemical study of Trypanosoma cruzi and Leishmania infantum chagasi NTPDases and search for new compounds for the treatment of Chagas disease

As doenças tropicais negligenciadas persistem ainda como graves problemas de saúde pública em vários países, incluindo o Brasil. Dentre elas estão: a doença de Chagas e as Leishmanioses, causadas por Trypanosoma cruzi e espécies do gênero Leishmania, respectivamente. As ectonucleotidases da família das E- NTPDases são enzimas capazes de hidrolisar nucleotídeos tri e/ou difosfatados, que atuam como sinalizadores em vários processos celulares. A hidrólise de ATP extracelular possui papel na infectividade e virulência de T. cruzi, bem como para Leishmania. As enzimas NTPDase-1 de T. cruzi (TcNTPDase-1) e NTPDase-2 de Leishmania infantum chagasi (LicNTPDase-2) demonstraram serem moléculas pró-adesão, agindo como facilitadores na infecção de células VERO e macrófagos, respectivamente. Uma expressão ubíqua dessas duas enzimas sugere ainda que elas podem estar envolvidas em diferentes processos biológicos, e apresentar funções desconhecidas. A detecção da LicNTPDase-2 em tecidos de cães diagnosticados com leishmaniose visceral, indica uma importância das ENTPDases na infecção natural. A descoberta de moléculas envolvidas com o processo de infecção é uma alternativa em potencial para o desenho racional de novas drogas. Para a doença de Chagas, atualmente, somente duas drogas são utilizadas para o tratamento, porém ambas apresentam sérios efeitos colaterais e não são efetivas na fase crônica da doença. Sendo assim, é urgente o desenvolvimento de um tratamento menos nocivo e mais eficiente. A TcNTPDase-1 recombinante foi expressa e purificada, e foram encontrados extratos capazes de abolir totalmente sua atividade nucleotidásica. A partir de um desses extratos foi extraído o composto puro bioativo responsável pela inibição. A ligação deste composto ao sítio ativo da enzima foi avaliada por modelagem molecular. Esses e outros extratos e vicompostos foram testados sobre o parasito e células de mamíferos. Um composto da classe das isobenzofuranonas apresentou eficiência contra os parasitos comparável à da droga de referência, o benzonidazol. A baixa toxicidade apresentada pelo composto para as células hospedeiras foi revertida ao final de 72 horas. O estudo desses compostos e sua modificação e otimização poderia fornecer ferramentas para o desenvolvimento de novos compostos, com potencial para uma nova droga para o tratamento da doença de Chagas.Neglected tropical diseases persist as major public health problem in many countries, including Brazil. These include: Chagas disease and Leishmaniasis, caused by Trypanosoma cruzi and Leishmania species, respectively. The ectonucleotidases of the E-NTPDase family are enzymes that hydrolyze tri and / or diphosphate nucleotides, which act as signaling molecules in various cellular processes. Extracellular ATP hydrolysis has role in infectivity and virulence of T. cruzi and Leishmania. The enzymes NTPDase-1 of T. cruzi (TcNTPDase-1) and NTPDase-2 of Leishmania infantum chagasi (LicNTPDase-2) were demonstrated to be pro- adhesion molecules, acting as facilitators at the infection of VERO cells and macrophages, respectively. A ubiquitous expression of these two enzymes suggests that they may be involved in different biological processes, and present unknown functions. Detection of LicNTPDase-2 in dog tissues diagnosed with visceral leishmaniasis indicates an importance of ENTPDases in natural infection. The discovery of molecules involved in the infection process is a potential alternative to rational design of new drugs. For Chagas disease, currently, only two drugs are used for treatment, but both have serious side effects and are not effective in the chronic phase of the disease. Therefore, it is urgent to develop a less harmful and more efficient treatment. Recombinant TcNTPDase-1 was expressed and purified, and a few extracts were able to abolish its ectonucleotidase activity. From one of these extracts was extracted a pure bioactive compound, responsible for the inhibition. The binding of this compound to the active site of the enzyme, was evaluated by molecular modeling. These and other extracts and compounds were tested upon the parasite and mammalian cells. A compound of the isobenzofuranonas class presented efficiency against the parasites comparable to the reference drug, benznidazole. The low toxicity of the compound toward host cells was reversed after 72 hours. The study of these compounds and their modification and optimization viiicould provide tools for the development of new compounds with potential for a new drug for the treatment of Chagas disease.Conselho Nacional de Desenvolvimento Científico e Tecnológic

Immobilization of NTPDase-1 from Trypanosoma cruzi and Development of an Online Label-Free Assay

The use of IMERs (Immobilized Enzyme Reactors) as a stationary phase coupled to high performance chromatographic systems is an interesting approach in the screening of new ligands. In addition, IMERs offer many advantages over techniques that employ enzymes in solution. The enzyme nucleoside triphosphate diphosphohydrolase (NTPDase-1) from Trypanosoma cruzi acts as a pathogen infection facilitator, so it is a good target in the search for inhibitors. In this paper, immobilization of NTPDase-1 afforded ICERs (Immobilized Capillary Enzyme Reactors). A liquid chromatography method was developed and validated to monitor the ICER activity. The conditions for the application of these bioreactors were investigated, and excellent results were obtained. The enzyme was successfully immobilized, as attested by the catalytic activity detected in the TcNTPDase-1-ICER chromatographic system. Kinetic studies on the substrate ATP gave KM of 0.317 ± 0.044 mmol·L−1, which still presented high affinity compared to in solution. Besides that, the ICER was stable for 32 days, enough time to investigate samples of possible inhibitors, including especially the compound Suramin, that inhibited 51% the enzyme activity at 100 µmol·L−1, which is in accordance with the data for the enzyme in solution

Study of the circulation dynamic of rotavirus sample through their electropherotypes

An epidemiological study was carried out to detect rotavirus associated with cases of acute childhood diarrhea and to observe the circulation dynamics of these viruses on the basis of the electrophoresis profiles of the samples. The fecal specimens were obtained from 0-5-year-old children during 2005 and 2006. Among 55 positive samples detected through an immunoenzymatic test, which were subjected to the technique of electrophoresis in gel of polyacrylamide, it was possible to define the electrophoresis profile of 37 (62 %), with eight distinct profiles observed, all compatible with rotavirus of group A. This allowed the study of the profiles to accompany the dynamics of their circulation, showing that in 2005, all the samples presented long profiles, so-called L1 to L4. Samples of profile L2 appeared in the May and predominated up to August, being substituted by samples of profile L1 and L4 which co-circulated in September. In 2006, a few samples of long profile (L1 and L2) were detected, completing a total of 14 % (3/22), which circulated in May and June. Most of the positive samples of this year (86 % = 19/22) presented short profiles, substituting for those of long profile, from July. The co-circulation of samples with different short and long profiles reveals the extensive genetic variability which the rotavirus can present, within the same period.KEYWORDS: Diarrhea. Rotavirus. Electrophoresis

Label-free assay based on immobilized capillary enzyme reactor of Leishmania infantum nucleoside triphosphate diphosphohydrolase (LicNTPDase-2-ICER-LC/UV)

Nucleoside triphosphate diphosphohydrolase (NTPDase) is an enzyme belonging to the apyrase family that participates in the hydrolysis of the nucleosides di- and triphosphate to the corresponding nucleoside monophosphate. This enzyme underlies the virulence of parasites such as Leishmania. Recently, an NTPDase from Leishmania infantum (LicNTPDase-2) was cloned and expressed and has been considered as a new drug target for the treatment of leishmaniasis. With the intent of developing label-free online screening methodologies, LicNTPDase-2 was covalently immobilized onto a fused silica capillary tube in the present study to create an immobilized capillary enzyme reactor (ICER) based on LicNTPDase-2 (LicNTPDase-2-ICER). To perform the activity assays, a multidimensional chromatographic method was developed employing the LicNTPDase-2-ICER in the first dimension, and an analytical Ascentis C8 column was used in the second dimension to provide analytical separation of the substrates and products. The validated LicNTPDase-2-ICER method provided the following kinetic parameters of the immobilized enzyme: KM of 2.2 and 1.8 mmol L^−1 for the ADP and ATP substrates, respectively. Suramin (1 mmol L^−1) was also shown to inhibit 32.9% of the enzymatic activity. The developed method is applicable to kinetic studies and enables the recognition of the ligands. Furthermore, a comparison of the values of LicNTPDase-2-ICER with those obtained with an LC method using free enzyme in solution showed that LicNTPDase-2-ICER-LC/UV was an accurate and reproducible method that enabled automated measurements for the rapid screening of ligands

The Antileishmanial Potential of C-3 Functionalized Isobenzofuranones against Leishmania (Leishmania) Infantum Chagasi

Leishmaniases are diseases caused by protozoan parasites of the genus Leishmania. Clinically, leishmaniases range from cutaneous to visceral forms, with estimated global incidences of 1.2 and 0.4 million cases per year, respectively. The treatment of these diseases relies on multiple parenteral injections with pentavalent antimonials or amphotericin B. However, these pharmaceuticals are either too toxic or expensive for routine use in developing countries. These facts call for safer, cheaper, and more effective new antileishmanial drugs. In this investigation, we describe the results of the assessment of the activities of a series of isobenzofuran-1(3H)-ones (phtalides) against Leishmania (Leishmania) infantum chagasi, which is the main causative agent of visceral leishmaniasis in the New World. The compounds were tested at concentrations of 100, 75, 50, 25 and 6.25 µM over 24, 48, and 72 h. After 48 h of treatment at the 100 µM concentration, compounds 7 and 8 decreased parasite viability to 4% and 6%, respectively. The concentration that gives half-maximal responses (LC50) for the antileishmanial activities of compounds 7 and 8 against promastigotes after 24 h were 60.48 and 65.93 µM, respectively. Additionally, compounds 7 and 8 significantly reduced parasite infection in macrophages

Trypanosoma cruzi nucleoside triphosphate diphosphohydrolase 1 (TcNTPDase-1) biochemical characterization, immunolocalization and possible role in host cell adhesion.

Previous work has suggested that Trypanosoma cruzi diphosphohydrolase 1 (TcNTPDase-1) may be involved in the infection of mammalian cells and serve as a potential target for rational drug design. In this work, we produced recombinant TcNTPDase-1 and evaluated its nucleotidase activity, cellular localiza- tion and role in parasite adhesion to mammalian host cells. TcNTPDase-1 was able to utilize a broad range of triphosphate and diphosphate nucleosides. The enzyme’s Km for ATP (0.096mM) suggested a capabil-ity to influence the host’s ATP-dependent purinergic signaling. The use of specific polyclonal antibodies allowed us to confirm the presence of TcNTPDase-1 at the surface of parasites by confocal and electron microscopy. In addition, electron microscopy revealed that TcNTPDase-1 was also found in the flagellum, flagellum insertion region, kinetoplast, nucleus and intracellular vesicles. The presence of this enzyme in the flagellum insertion region and vesicles suggests that it may have a role in nutrient acquisition, and the widespread distribution of TcNTPDase-1 within the parasite suggests that it may be involved in other biological process. Adhesion assays using anti-TcNTPDase-1 polyclonal antibodies as a blocker or purified recombinant TcNTPDase-1 as a competitor revealed that the enzyme has a role in parasite–host cell adhesion. These data open new frontiers to future studies on this specific parasite–host interaction and other unknown functions of TcNTPDase-1 related to its ubiquitous localization

Leishmania infantum ecto-nucleoside triphosphate diphosphohydrolase-2 is an apyrase involved in macrophage infection and expressed in infected dogs

Visceral leishmaniasis is an important tropical disease, and Leishmania infantum chagasi (synonym of Leishmania infantum) is the main pathogenic agent of visceral leishmaniasis in the New World. Recently, ecto-nucleoside triphosphate diphosphohydrolases (E-NTPDases) were identified as enablers of infection and virulence factors in many pathogens. Two putative E-NTPDases (∼70 kDa and ∼45 kDa) have been found in the L. infantum genome. Here, we studied the ∼45 kDa E-NTPDase from L. infantum chagasi to describe its natural occurrence, biochemical characteristics and influence on macrophage infection. We used live L. infantum chagasi to demonstrate its natural ecto-nucleotidase activity. We then isolated, cloned and expressed recombinant rLicNTPDase-2 in bacterial system. The recombinant rLicNTPDase-2 hydrolyzed a wide variety of triphosphate and diphosphate nucleotides (GTP> GDP  =  UDP> ADP> UTP  =  ATP) in the presence of calcium or magnesium. In addition, rLicNTPDase-2 showed stable activity over a pH range of 6.0 to 9.0 and was partially inhibited by ARL67156 and suramin. Microscopic analyses revealed the presence of this protein on cell surfaces, vesicles, flagellae, flagellar pockets, kinetoplasts, mitochondria and nuclei. The blockade of E-NTPDases using antibodies and competition led to lower levels of parasite adhesion and infection of macrophages. Furthermore, immunohistochemistry showed the expression of E-NTPDases in amastigotes in the lymph nodes of naturally infected dogs from an area of endemic visceral leishmaniasis. In this work, we cloned, expressed and characterized the NTPDase-2 from L. infantum chagasi and demonstrated that it functions as a genuine enzyme from the E-NTPDase/CD39 family. We showed that E-NTPDases are present on the surface of promastigotes and in other intracellular locations. We showed, for the first time, the broad expression of LicNTPDases in naturally infected dogs. Additionally, the blockade of NTPDases led to lower levels of in vitro adhesion and infection, suggesting that these proteins are possible targets for rational drug design

Phylogenetic tree using representatives of the ENTPDases from mammals and Trypanosomatids (<i>Leishmania</i> and <i>T. cruzi</i>).

<p>ENTPDase sequences were aligned by the CLC workbench program and used to construct the phylogenetic tree using the Neighbor Joining method with bootstrap analysis (number in the branches). <i>Mus musculus</i> (Mm); <i>Homo sapiens</i> (Hs). Trypanosomatids have two ENTPDases with exception of <i>T. cruzi</i>, which has only one ENTPDase in databank. Trypanosomatid ENTPDases are more similar to mammalian ENTPDases isoforms 5 and 6 and are grouped at the upper branch of the tree.</p