Innate immunity to Paracoccidioides brasiliensis infection

Innate immunity is based in pre-existing elements of the immune system that directly interact with all types of microbes leading to their destruction or growth inhibition. Several elements of this early defense mechanism act in concert to control initial pathogen growth and have profound effect on the adaptative immune response that further develops. Although most studies in paracoccidioidomycosis have been dedicated to understand cellular and humoral immune responses, innate immunity remains poorly defined. Hence, the main purpose of this review is to present and discuss some mechanisms of innate immunity developed by resistant and susceptible mice to Paracoccidioides brasiliensis infection, trying to understand how this initial host-pathogen interface interferes with the protective or deleterious adaptative immune response that will dictate disease outcome. An analysis of some mechanisms and mediators of innate immunity such as the activation of complement proteins, the microbicidal activity of natural killer cells and phagocytes, the production of inflammatory eicosanoids, cytokines, and chemokines among others, is presented trying to show the important role played by innate immunity in the host response to P. brasiliensis infection.

Proteomic analysis reveals suppression of bark chitinases and proteinase inhibitors in citrus plants affected by the citrus sudden death disease

Citrus sudden death (CSD) is a disease of unknown etiology that greatly affects sweet oranges grafted on Rangpur lime rootstock, the most important rootstock in Brazilian citriculture. We performed a proteomic analysis to generate information related to this plant pathogen interaction. Protein profiles from healthy, CSD-affected and CSD-tolerant stem barks, were generated using two-dimensional gel electrophoresis. The protein spots were well distributed over a pI range of 3.26 to 9.97 and a molecular weight (MW) range from 7.1 to 120 kDa. The patterns of expressed proteins on 2-DE gels made it possible to distinguish healthy barks from CSD-affected barks. Protein spots with MW around 30 kDa and pI values ranging from 4.5 to 5.2 were down-regulated in the CSD-affected rootstock bark. This set of protein spots was identified as chitinases. Another set of proteins, ranging in pI from 6.1 to 9.6 with an MW of about 20 kDa, were also suppressed in CSD-affected rootstock bark; these were identified as miraculin-like proteins, potential trypsin inhibitors. Downregulation of chitinases and proteinase inhibitors in CSD-affected plants is relevant since chitinases are well-known pathogenesis-related protein, and their activity against plant pathogens is largely accepted.

alpha-Hydroxynitrile lyase protein from Xylella fastidiosa: Cloning, expression, and characterization

Xylella fastidiosa is a xylem-restricted plant pathogen that causes a range of diseases in several and important crops. Through comparative genomic sequence analysis many genes were identified and, among them, several potentially involved in plant-pathogen interaction. The experimental determination of the primary sequence of some markedly expressed proteins for X fastidiosa and the comparison with the nucleic acids sequence of genome identified one of them as being SCJ21.16 (XFa0032) gene product. The comparative analysis of this protein against SWISSPROT database, in special, resulted in similarity with a-hydroxynitrile lyase enzyme (HNL) from Arabidopsis thaliana, causing interest for being one of the most abundant proteins both in the whole cell extract as well as in the extracellular protein fraction. It is known that HNL enzyme are involved in a process termed ""cyanogenesis"", which catalyzes the dissociation of alpha-hydroxinitrile into carbonyle and HCN when plant tissue is damaged. Although the complete genome sequences of X.fastidiosa are available and the cyanogenesis process is well known, the biological role of this protein in this organism is not yet functionally characterized. In this study we presented the cloning, expression, characterization of recombinant HNL from X fastidiosa, and its probable function in the cellular metabolism. The successful cloning and heterologous expression in Escherichia coli resulted in a satisfactory amount of the recombinant HNL expressed in a soluble, and active form giving convenient access to pure enzyme for biochemical and structural studies. Finally, our results confirmed that the product of the gene XFa0032 can be positively assigned as FAD-independent HNLs. (C) 2009 Elsevier Ltd. All rights reserved.

Postharvest harpin or Bacillus thuringiensis treatments suppress citrus black spot in 'Valencia' oranges

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Requirement for cobalamin by Salmonella enterica serovars Typhimurium, Pullorum, Gallinarum and Enteritidis during infection in chickens

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Transcription profiling of signal transduction-related genes in sugarcane tissues

A collection of 237,954 sugarcane ESTs was examined in search of signal transduction genes. Over 3,500 components involved in several aspects of signal transduction, transcription, development, cell cycle, stress responses and pathogen interaction were compiled into the Sugarcane Signal Transduction (SUCAST) Catalogue. Sequence comparisons and protein domain analysis revealed 477 receptors, 510 protein kinases, 107 protein phosphatases, 75 small GTPases, 17 G-proteins, 114 calcium and inositol metabolism proteins, and over 600 transcription factors. The elements were distributed into 29 main categories subdivided into 409 sub-categories. Genes with no matches in the public databases and of unknown function were also catalogued. A cDNA microarray was constructed to profile individual variation of plants cultivated in the field and transcript abundance in six plant organs (flowers, roots, leaves, lateral buds, and 1(st) and 4(th) internodes). From 1280 distinct elements analyzed, 217 (17%) presented differential expression in two biological samples of at least one of the tissues tested. A total of 153 genes (12%) presented highly similar expression levels in all tissues. A virtual profile matrix was constructed and the expression profiles were validated by real-time PCR. The expression data presented can aid in assigning function for the sugarcane genes and be useful for promoter characterization of this and other economically important grasses.

Análise do perfil de expressão dos genes da cana-de-açúcar envolvidos na interação com Leifsonia xyli subsp: xyli

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Avaliação de métodos de inoculação de Phytophthora parasitica em plântulas e plantas jovens de citros

Este trabalho teve como objetivo avaliar métodos de inoculação de Phytophthoraparasitica em plântulas e plantas jovens de citros (Citrus spp.) visando sua utilização em estudos de resistência de porta-enxertos à gomose de Phytophthora. Os métodos de inoculação testados foram: contato planta sem ferimento-patógeno, casca destacada, inserção de disco de meio de cultura contendo micélio sob a casca, método do disco e inserção de agulha e palito infestados em plântulas e plantas jovens de citros. A resistência de genótipos à gomose pode ser avaliada em plântulas in vitro, através de inserção de agulha infestada. O método do disco e o da inserção sob casca foram os melhores quando utilizados em plantas jovens. A medida da área total da lesão é a variável ideal para avaliação da doença. No entanto, o comprimento da lesão pode ser utilizado na avaliação da doença em plântulas, plantas jovens e no campo.

Road-killed wild animals: a preservation problem useful for eco-epidemiological studies of pathogens

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Partial characterization of proteolytic activity in Giardia duodenalis purified proteins

O presente estudo consiste em uma caracterização preliminar da atividade proteolítica de frações de proteínas purificadas a partir de lisados de trofozoítos de cepa isolada e axenizada no Brasil. Frações obtidas por cromatografia líquida (FPLC) foram analisadas quanto ao perfil eletroforético em géis de poliacrilamida (SDS-PAGE) e a atividade proteolítica foi avaliada em géis contendo gelatina como substrato. A caracterização das enzimas foi realizada a partir da análise do efeito de inibidores sintéticos de cisteína-proteases (E-64, IAA), serina-proteases (PMSF), serina e cisteína-proteases (TPCK, TLCK, elastatinal), metalo-proteases (EDTA) e aspartil proteases (pepstatina) sobre a degradação do substrato. Entre 30 frações eluídas, bandas de proteínas foram observadas em oito delas, entretanto, atividade proteolítica foi detectada apenas nas frações 23, 24, 25 e 26. O perfil eletroforético das proteínas revelou poucas bandas distribuídas na faixa de 45 a 18 kDa. Os zimogramas revelaram zonas de proteólise na faixa de aproximadamente 62 a 35 kDa, entretanto destacaram-se as bandas de hidrólise de 62, 55, 53, 50, 46 e 40 kDa. Nos ensaios de inibição, a proteólise foi marcantemente inibida por E-64, TPCK, TLCK e elastatinal. Redução discreta da proteólise foi observada com IAA e PMSF, enquanto que EDTA e pepstatina não promoveram alteração dos perfis de hidrólise. Estas observações são relevantes, especialmente se considerarmos que para elucidar o envolvimento das proteases na relação parasita-hospedeiro, a purificação dessas moléculas é um requisito importante.

Proteomic analysis reveals suppression of bark chitinases and proteinase inhibitors in citrus plants affected by the citrus sudden death disease

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Immunity in plants and animals: common ends through different means using similar tools

A comparative approach is potentially useful for understanding the role of mammal innate immunity role in stimulating adaptive immunity as well as the relationship between these two types of immune strategies. Considerable progress has been made in the elucidation of the co-ordinated events involved in plant perception of infection and their mobilisation of defence responses. Although lacking immunoglobulin molecules, circulating cells, and phagocytic processes, plants successfully use pre-formed physical and chemical innate defences, as well as inducible adaptive immune strategies. In the present paper, we review some shared and divergent immune aspects present in both animals and plants. (C) 2002 Elsevier B.V. All rights reserved.

Implications of genetic variability of Trypanosoma cruzi for the pathogenesis of Chagas disease

O Trypanosoma cruzi, agente etiológico da doença de Chagas, apresenta elevado grau de variabilidade genética intra-específica, com possíveis implicações na forma clínica da doença, como o desenvolvimento de cardiopatia, do megaesôfago e do megacólon de forma isolada ou em associação. Este tropismo tecidual envolvido na patogênese da doença não está totalmente esclarecido. Assim, nesta revisão são abordados alguns aspectos referentes à diversidade genética dos parasitas isolados, às formas clínicas da doença de Chagas, ao processo de infecção do parasita na célula hospedeira e resposta imune. Outros aspectos também são enfocados, como os fatores imunossupressivos liberados pelo parasita que atuam na regulação das respostas imunes, a inibição da apoptose da célula hospedeira, assim como da patogênese do megaesôfago chagásico que pode estar relacionada à interação hospedeiro- parasita e sua associação com risco aumentado para o desenvolvimento do carcinoma epidermóide do esôfago. Porém, apesar dos avanços no entendimento desta doença, ainda não é possível estabelecer o verdadeiro perfil da variabilidade genética do parasita com a forma clínica da doença de Chagas.

alpha-Hydroxynitrile lyase protein from Xylella fastidiosa: Cloning, expression, and characterization

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Implicações da agregação espacial de parasitas para a dinâmica populacional na interação hospedeiro-parasita

Some aspects of the widely observed over-dispersed pattern of the distribution of parasites within the host population are examined. It has been established in the parasitological literature that most hosts usually harbour few parasites, while only few hosts harbour a large proportion of the parasite population. Factors that may influence the pattern of distribution of parasites, the relation between the level of parasite aggregation and the prevalence of infection, and changes in this level of aggregation as a function of host age are analysed. Factors which determine the diversity of species in parasite communities are presented, and aspects of exploitative and interference competition among parasites and their relations with biological control procedures are also considered. Attention is also focused on the regulatory and destabilizing processes influencing the dynamic behaviour of host-parasite population interactions.