Browsing by Author "Serafim, Tiago Donatelli"
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Item Ecto-nucleotidase activities of promastigotes from leishmania (Viannia) braziliensis relates to parasite infectivity and disease clinical outcome.(2012) Leite, Pauline Martins; Gomes, Rodrigo Saar; Figueiredo, Amanda Braga de; Serafim, Tiago Donatelli; Tafuri, Wagner Luiz; Gomes, Carolina Cavaliéri; Moura, Sandra Aparecida Lima de; Fietto, Juliana Lopes Rangel; Melo, Maria Norma; Dias, Fátima Ribeiro; Oliveira, Milton Adriano Pelli de; Rabello, Ana Lúcia Teles; Afonso, Luís Carlos CroccoBackground: Leishmania (Viannia) braziliensis has been associated with a broad range of clinical manifestations ranging from a simple cutaneous ulcer to destructive mucosal lesions. Factors leading to this diversity of clinical presentations are not clear, but parasite factors have lately been recognized as important in determining disease progression. Given the fact that the activity of ecto-nucleotidases correlates with parasitism and the development of infection, we evaluated the activity of these enzymes in promastigotes from 23 L. braziliensis isolates as a possible parasite-related factor that could influence the clinical outcome of the disease. Methodology/Principal Findings: Our results show that the isolates differ in their ability to hydrolyze adenine nucleotides. Furthermore, we observed a positive correlation between the time for peak of lesion development in C57BL/6J mice and enzymatic activity and clinical manifestation of the isolate. In addition, we found that L. (V.) braziliensis isolates obtained from mucosal lesions hydrolyze higher amounts of adenine nucleotides than isolates obtained from skin lesions. One isolate with high (PPS6m) and another with low (SSF) ecto-nucleotidase activity were chosen for further studies. Mice inoculated with PPS6m show delayed lesion development and present larger parasite loads than animals inoculated with the SSF isolate. In addition, PPS6m modulates the host immune response by inhibiting dendritic cell activation and NO production by activated J774 macrophages. Finally, we observed that the amastigote forms from PPS6m and SSF isolates present low enzymatic activity that does not interfere with NO production and parasite survival in macrophages. Conclusions/Significance: Our data suggest that ecto-nucleotidases present on the promastigote forms of the parasite may interfere with the establishment of the immune response with consequent impaired ability to control parasite dissemination and this may be an important factor in determining the clinical outcome of leishmaniasis.Item Immune response to Leishmania (Leishmania) chagasi infection is reduced in malnourished BALB/c mice.(2010) Serafim, Tiago Donatelli; Malafaia, Guilherme; Silva, Marcelo Eustáquio; Pedrosa, Maria Lúcia; Rezende, Simone AparecidaProtein-energy malnutrition and micronutrient deficiencies may down-regulate immune response and increase morbidity and mortality due to infection. In this study, a murine model was used to study the effects of protein, iron and zinc deficiencies on the immune response to Leishmania (Leishmania) chagasi infection. Mice were initially fed a standard diet or with a diet containing 3% casein but deficient in zinc and iron. After malnutrition was established, mice were inoculated with L. chagasi and sacrificed four weeks later in order to evaluate liver and spleen parasite loads and serum biochemical parameters. Significant decreases in liver and spleen weight, an increase in the parasite loads in these organs and decreases in serum protein and glucose concentrations in malnourished animals were observed. Furthermore, the production of interferon-gamma by spleen cells from infected malnourished mice stimulated by Leishmania antigen was significantly lower compared with that in control diet mice. These data suggest that malnutrition alters the immune response to L. chagasi infection in the BALB/c model and, in association with the effects on biochemical and anatomical parameters of the host, favored increases in the parasite loads in the spleens and livers of these animals.Item Leishmania amazonensis impairs DC function by inhibiting CD40 expression via A2B adenosine receptor activation.(2012) Figueiredo, Amanda Braga de; Serafim, Tiago Donatelli; Silva, Eduardo de Almeida Marques da; Fernandes, José Roberto Meyer; Afonso, Luís Carlos CroccoDendritic cells (DCs) play an essential role in the modulation of immune responses and several studies have evaluated the interactions between Leishmania parasites and DCs. While extracellular ATP exhibits proinflammatory properties, adenosine is an important anti-inflammatory mediator. Here we investigated the effects of Leishmania infection on DC responses and the participation of purinergic signalling in this process. Bone marrowderived dendritic cells (BMDCs) from C57BL/6J mice infected with Leishmania amazonensis, Leishmania braziliensis or Leishmania major metacyclic promastigotes showed decreased major histocompatibility complex (MHC) class II and CD86 expression and increased ectonucleotidase expression as compared with uninfected cells. In addition, L. amazonensis-infected DCs, which had lower CD40 expression, exhibited a decreased ability to induce T-cell proliferation. The presence of MRS1754, a highly selective A2B adenosine receptor antagonist at the time of infection increased MHC class II, CD86 and CD40 expression in L. amazonensis-infected DCs and restored the ability of the infected DCs to induce T-cell proliferation. Similar results were obtained through the inhibition of extracellular ATP hydrolysis using suramin. In conclusion, we propose that A2B receptor activation may be used by L. amazonensis to inhibit DC function and evade the immune response.Item Leishmania metacyclogenesis is promoted in the absence of purines.(2012) Serafim, Tiago Donatelli; Figueiredo, Amanda Braga de; Costa, Pedro Augusto Carvalho; Silva, Eduardo de Almeida Marques da; Gonçalves, Ricardo; Moura, Sandra Aparecida Lima de; Gontijo, Nelder de Figueiredo; Silva, Sydnei Magno da; Michalick, Marilene Susan Marques; Fernandes, José Roberto Meyer; Carvalho, Roberto Paes de; Uliana, Silvia Reni Bortolin; Fietto, Juliana Lopes Rangel; Afonso, Luís Carlos CroccoLeishmania parasites, the causative agent of leishmaniasis, are transmitted through the bite of an infected sand fly. Leishmania parasites present two basic forms known as promastigote and amastigote which, respectively, parasitizes the vector and the mammalian hosts. Infection of the vertebrate host is dependent on the development, in the vector, of metacyclic promastigotes, however, little is known about the factors that trigger metacyclogenesis in Leishmania parasites. It has been generally stated that ‘‘stressful conditions’’ will lead to development of metacyclic forms, and with the exception of a few studies no detailed analysis of the molecular nature of the stress factor has been performed. Here we show that presence/absence of nucleosides, especially adenosine, controls metacyclogenesis both in vitro and in vivo. We found that addition of an adenosine-receptor antagonist to in vitro cultures of Leishmania amazonensis significantly increases metacyclogenesis, an effect that can be reversed by the presence of specific purine nucleosides or nucleobases. Furthermore, our results show that proliferation and metacyclogenesis are independently regulated and that addition of adenosine to culture medium is sufficient to recover proliferative characteristics for purified metacyclic promastigotes. More importantly, we show that metacyclogenesis was inhibited in sand flies infected with Leishmania infantum chagasi that were fed a mixture of sucrose and adenosine. Our results fill a gap in the life cycle of Leishmania parasites by demonstrating how metacyclogenesis, a key point in the propagation of the parasite to the mammalian host, can be controlled by the presence of specific purines.Item A metaciclogênese em Leishmania é promovida na ausência de purinas.(Programa de Pós-Graduação em Ciências Biológicas. Núcleo de Pesquisas em Ciências Biológicas, Pró-Reitoria de Pesquisa e Pós Graduação, Universidade Federal de Ouro Preto., 2012) Serafim, Tiago Donatelli; Afonso, Luís Carlos CroccoParasitos do gênero Leishmania são agentes causadores de um espectro de doenças, caracterizadas por lesões cutâneas graves (localizadas ou difusas) até ao potencialmente fatal acometimento de vísceras, coletivamente conhecido como leishmanioses. Estas doenças têm início quando formas infecciosas do parasito. promastigotas metacíclicas, são transmitidas pela picada de um flebotomíneo infectado para o hospedeiro mamífero. Há muito que se sabe que o desenvolvimento no vetor dessas formas, processo conhecido como metaciclogênese, é vital para o ciclo de vida do protozoário e concomitante surgimento da doença no homem, porém, pouco se sabe sobre os fatores que proporcionam seu aparecimento. Tem sido geralmente estabelecido que "condições de estresse" irão conduzir ao desenvolvimento de formas metacíclicas e com a exceção de alguns estudos nenhuma análise detalhada da natureza molecular do fator de estresse tem sido realizada. Neste trabalho, mostramos que a presença/ausência de nucleosídeos, em particular a adenosina, controla a metaciclogênese em Leishmania tanto in vitro quanto in vivo. Nós descobrimos que a adição de um antagonista de receptor de adenosina em culturas de Leishmania amazonensis aumenta significativamente a metaciclogênese, um efeito que pode ser revertido pela presença de determinados nucleosídeos de purina ou nucleobases. Além disso, nossos resultados mostram que a proliferação e metaciclogênese são reguladas independentemente e que a adição de adenosina no meio de cultura é suficiente para recuperar características proliferativas em promastigotas metacíclicos purificados. Mais importante, demonstramos que a metaciclogênese foi inibida em fêmeas de Lutzomyia longipalpis infectadas com Leishmania infantum chagasi que foram alimentadas com uma mistura de sacarose e adenosina. Esses resultados preenchem uma lacuna de conhceimento no ciclo de vida destes parasitos, demonstrando como a metaciclogênese, um ponto chave na propagação do parasito ao hospedeiro mamífero, pode ser controlada pela presença de purinas.Item Protein-energy malnutrition decreases immune response to Leishmania chagasi vaccine in BALB/c mice.(2009) Malafaia, Guilherme; Serafim, Tiago Donatelli; Silva, Marcelo Eustáquio; Pedrosa, Maria Lúcia; Rezende, Simone AparecidaProtein-energy malnutrition and visceral leishmaniasis are important problems of public health affecting millions of people worldwide. Vaccine efficacy depends on the ability of individuals to mount an appropriate immune response and may be inadequate in malnourished persons. In this study, we used a mouse model to verify the effect of combined protein, iron and zinc deficiency in the response to Leishmania chagasi antigen vaccine. BALB/c mice were fed with a low-protein (3% casein), iron- and zinc-deficient diet or control diet (14% casein and sufficient in zinc and iron). After malnutrition establishment, mice were vaccinated subcutaneously with L. chagasi Ag plus saponin. After vaccination, mice were nutritionally repleted and then all mice were challenged with L. chagasi promastigotes. Four weeks later, liver and spleen parasite load was evaluated. Our data show that vaccine caused a significant reduction in parasite load in spleen and liver from mice fed with control diet. However, splenic parasitism was increased in mice fed with deficient diet and this diet caused a reduction in splenocyte IFN-γ production in response to the vaccine in repleted mice. These data suggest that malnutrition may alter immune response to L. chagasi vaccine in BALB/c model of infection, even after nutritional repletion.Item Successful vaccination against Leishmania chagasi infection in BALB/c mice with freeze-thawed Leishmania antigen and Corynebacterium parvum.(2007) Vilela, Márcia de Carvalho; Gomes, Daniel Cláudio de Oliveira; Silva, Eduardo de Almeida Marques da; Serafim, Tiago Donatelli; Afonso, Luís Carlos Crocco; Rezende, Simone AparecidaThis study evaluated the potential of a Leishmania antigen vaccine in protecting BALB/c mice against Leishmania chagasi. Mice received two subcutaneous doses of L. amazonensis vaccine with Corynebacterium parvum and subsequent boost was done without adjuvant. One week later, mice were challenged with L. chagasi. We observed that this vaccine caused a significant reduction in parasite load in liver and spleen and induced a high production of IFN-_ and IL-4 by spleen cells from vaccinated mice in response to Leishmania antigen. Together, our data show that this vaccine is capable of inducing a Th1/Th2 response that is important to control parasite replication.