京都大学 / 新制・課程博士 / 博士(理学) / 甲第25144号 / 理博第5051号 / 新制||理||1720(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)准教授 高山 浩司, 教授 田村 実, 教授 石田 厚 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

<p>Insects encounter many microorganisms in nature and to survive they have developed counter measures against the invading pathogens. In <i>Drosophila melanogaster</i> research on insect immunity has mainly been focused on infections by bacteria and fungi. We have explored the immune response against natural infections of the parasite <i>Octosporea muscaedomesticae</i> and the <i>Drosophila</i> C virus as compared to natural infections of bacteria and fungi. By using Affymetrix <i>Drosophila</i> GeneChips, we were able to obtain 48 genes uniquely induced after parasitic infection. It was also clearly shown that natural infections led to different results than when injecting the pathogens. </p><p>In order to search for the ultimate role of the lepidopteran protein hemolin, we used RNA interference (RNAi). We could show that injection of double stranded RNA (dsRNA) of <i>Hemolin</i> in pupae of <i>Hyalophora cecropia</i> led to embryonic malformation and lethality and that there was a sex specific difference. We continued the RNAi investigation of hemolin in another lepidopteran species, <i>Antheraea pernyi</i>, and discovered that hemolin was induced by dsRNA<i> per se</i>. A similar induction of hemolin was seen after infection with baculovirus and we therefore performed <i>in vivo</i> experiments on baculovirus infected pupae. We could show that a low dose of ds<i>Hemolin</i> prolonged the period before the <i>A. pernyi</i> pupae showed any symptoms of infection, while a high dose led to a more rapid onset of symptoms. By performing <i>in silico</i> analysis of the hemolin sequence from <i>A. pernyi</i> in comparison with other<i> Hemolin</i> sequences, it was possible to select a number of sites that either by being strongly conserved or variable could be important targets for future studies of hemolin function.</p>

Although the physiological consequences of Notch signaling in hematopoiesis have been extensively studied, the differential effects of individual notch cleavage products remain to be elucidated. Given that a disintegrin and metalloproteinase 10 (ADAM10) is a critical regulator of Notch and that its deletion is embryonically lethal, we generated transgenic mice that overexpress ADAM10 at early stages of lymphoid and myeloid development (A10Tg). ADAM10 transgene expression alters hematopoiesis post-hematopoietic Lineage-Sca-1+c-kit+ (LSK) subset differentiation but prior to lineage commitment of progenitor populations. This results in delayed T cell development, abrogated B2 cell development, and dramatic expansion of functionally active myeloid derived suppressor cells (MDSCs) in A10Tg mice. Given ADAM10’s role in Notch signaling, we hypothesized that the observed hematopoietic alterations may be a consequence of perturbed Notch signaling. In fact, blockade of ADAM10 (S2) rescues B cell development and reduces myeloid cells in A10Tg LSKs. Inhibition of γ-secretase (S3) in wild type (WT) LSKs results in enhanced myelopoiesis, mimicking the phenotype of A10Tg mice. Collectively, these findings indicate that the differential cleavage of Notch into S2 and S3 products regulated by ADAM10 is critical for hematopoietic cell-fate determination. Albeit arising in a tumor-free host, A10Tg MDSCs are functionally and phenotypically analogous to tumor-derived MDSCs. A10Tg MDSCs inhibit T cell activation in vitro, and inhibit adoptive immunotherapy (AIT) of metastatic melanoma in vivo, which can be reversed with MDSC depletion. Intriguingly, A10Tg mice are resistant to parasitic infection upon inoculation of Nippostrongylus brasiliensis. However, depletion of MDSCs abrogates this response, while adoptive transfer (AT) of MDSCs into WT mice increases their resistance. This polarized activity of MDSCs is heavily dependent upon interaction with mast cells (MCs). In fact, B16 melanoma cells metastasize more rapidly in WT mice infused with MDSCs when compared to MC-deficient mice (Kit Wsh/Wsh), with or without MDSC AT. Parallel to B16 progression, the ability of MDSCs to promote anti-Nb immunity is significantly diminished in MC-deficient (Kit Wsh/Wsh) mice even with MDSC AT. This augmentation of MDSC activity in the presence of MCs is further corroborated by in vitro co-culture assays that demonstrate a synergistic increase in cytokine production. Furthermore, MDSCs preferentially migrate to the liver in a MC-dependent manner. This interaction is mediated by MC-released histamine. In fact, MDSCs express histamine receptors (HR) and histamine induces MDSC survival, proliferation, and activation. We demonstrate that MDSC activity is abrogated with histamine blockade. Moreover, in humans, allergic patients present with an increase in MDSC population, and MDSCs purified from a stage I breast cancer patient exhibit increased survival in the presence of histamine. Taken together, our studies indicate that MCs and MC-released histamine are critical for the observed functional duality of MDSCs, ranging from immunosuppressive to immunosupportive, depending on the disease state.

A pattern-reconfigurable, low-profile, efficient, electrically small, near-field resonant parasitic (NFRP), Huygens source antenna is presented. The design incorporates both electric and magnetic NFRP elements. The electric ones are made reconfigurable by the inclusion of a set of p-i-n diodes. By arranging these electric and magnetic NFRP elements properly, a set of three Huygens sources are attained, each covering a 120 degrees sector. Pattern reconfigurability is obtained by switching the diodes on or off; it encompasses the entire 360 degrees azimuth range. A prototype was fabricated and tested. The numerical and experimental studies are in good agreement. The experimental results indicate that in each of its instantaneous states at f(0) = 1.564 GHz, the antenna provides uniform peak realized gains, front-toback ratios, and radiation efficiencies, respectively, as high as 3.55 dBi, 17.5 dB, and 84.9%, even though it is electrically small: ka = 0.92, and low profile: 0.05 lambda(0).

Nematodes of the genus Phasmarhabditis (Nematoda: Rhabditidae) are world-wide distributed molluscs´ parasites. Species P. hermaphrodita is the only commercially produced bio-agent for slug control. The aim of this thesis is to evaluate some ecologic characteristics of three newly described species of the genus Phasmarhabditis (P. bohemica, P. bonaquaense a P. apuliae) in polyxenic and monoxenic cultures. Three bacterial isolates, Pseudomonas sp., Acinetobacter sp. and Flavobacterium sp. were chosen for testing the monoxenic cultures. The growing ability of tested nematodes, the effect on the quality of progeny and the rate of development were examined on various organic substrates (compost, faeces of Deroceras slugs, homogenized Deroceras slugs, homogenized larvae of Galleria mellonella and homogenized pig kidney). Subsequently, the growth of nematodes was tested in solid and liquid media. The last experiment was focused on evaluating the impact of polyxenic and monoxenic nematode cultures on the mortality and feeding activity of Deroceras reticulatum and Cepaea hortensis. As is assumed in the results chapter, all examined species of nematodes are lethal facultative parasites of Deroceras spp. They are able to grow in broad spectre of organic substrates and bacteria which influence the production of the progeny, but the qualitative parameters of dauer juveniles remain more or less unaffected.

A prevalência de patógenos intestinais foi estudada entre os índios da etnia Tapirapé, da Amazônia mato-grossense, por meio de técnicas coproparasitológicas, imunológicas e moleculares. Do total de 1526 amostras, 83,35% apresentaram ao menos um parasito intestinal e 65% tinham mais de um parasito (poliparasitismo). Entamoeba coli foi o mais prevalente (827/1526 - 54,19%). Entamoeba histolytica/dispar (581/1526 - 38,07%), Giardia intestinalis (287/1526 - 18,81%), Blastocystis spp. (257/1526 - 16,84%) e Ancylostoma spp. (293/1526 - 19,20%) também foram freqüentes. Cistos de Giardia intestinalis foram seqüenciados utilizando os genes <font face=\"Symbol\">b-Giardina e gdh. Apenas os assemblages A e B foram encontrados, sendo que o assemblage A foi o mais prevalente. Análise molecular de Blastocystis spp. demonstrou que, por meio do gene SSU-rNA, o subtipo 1 foi o mais dominante entre os Tapirapé, seguido pelos subtipos 2 e 3. Com base nisso, G. intestinalis e Blastocystis spp. são potencialmente zoonóticos. Os resultados corroboram com outros estudos realizados na Amazônia brasileira. / The prevalence of intestinal pathogens was studied in indigenous of the Tapirapé ethnic from Amazon region of Mato Grosso State, using the coproparasitological, immunological and molecular. Of the total 1,526 fecal samples 83.35% had at least one intestinal parasite and 65% had more than one parasite (poliparasitism). The most prevalent parasite was Entamoeba coli (827/1526 - 54.19%). Entamoeba histolytica/dispar (581/1526 - 38, 07%), Giardia intestinalis (287/1526 - 18.81%), Blastocystis spp. (257/1526 - 16.84%) and Ancylostoma spp. (293/1526 -19.20%) were found too. Cysts of G. intestinalis were sequence by <font face=\"Symbol\">b-Giardina and GDH gene. Only assemblages A and B were found and assemblage A was the most prevalent. The molecular characterization of Blastocystis spp. by SSU-rRNA demonstrated that subtype 1 was dominant followed by subtypes 2 and 3. So, G. intestinalis and Blastocystis spp. are potentially zoonotic. The results are in agreement with previous studies conducted in the Brazilian Amazon.

Pratylenchus brachyurus é um dos nematóides mais disseminados na cultura do algodão nas áreas produtoras do Brasil. Sua patogenicidade ao algodoeiro, entretanto, é pouco estudada. Os objetivos deste trabalho foram: i) correlacionar níveis populacionais iniciais crescentes de P. brachyurus (0, 12.000, 30.000 e 75.000 exemplares/ planta) com os danos causados ao algodoeiro \'Delta Opal\'; ii) avaliar a patogenicidade de populações de P. brachyurus em algodoeiros \'Delta Opal\' e \'Fibermax 966\'; iii) testar cultivares de algodão em relação à reprodução de três populações de P. brachyurus ; iv) caracterizar a relação parasito-hospedeiro (em termos de suscetibilidade/resistência) de alguns adubos verdes, coberturas vegetais e pastagens a Pratylenchus brachyurus; v) caracterizar molecularmente populações de P. brachyurus, através de PCR-RFLP e seqüenciamento da região ITS-1 do rDNA. Os resultados sugerem que P. brachyurus é patógeno pouco agressivo da cultura do algodão, já que não se verificaram danos significativos às plantas em densidades populacionais do nematóide inferiores a 12.000 exemplares/ planta. Em relação às cultivares, todas foram suscetíveis a P. brachyurus . Entre as espécies vegetais testadas, as que se mostraram resistentes a P. brachyurus foram Crotalaria spectabilis, C. breviflora, amaranto \'BRS Alegria\', nabo forrageiro \'Comum\' e as cultivares de aveia preta Campeira Mor, IPFA 99006, Comum, CPAO 0010 e Garoa. As análises de PCRRFLP revelaram variabilidade genética entre as diferentes populações de P. brachyurus estudadas, em função dos diferentes padrões de bandas encontrados para as populações estudadas. O seqüenciamento da região ITS-1 do rDNA confirmou a variabilidade observada pela digestão enzimática, além de evidenciar heterogeneidade das regiões 18S e ITS-1 do rDNA de P. brachyurus / Although Pratylenchus brachyurus is widespread in Brazilian cotton fields, information about its importance as a cotton pathogen is scarce. The objectives of this work were: i) correlate crescent initial population densities (0; 12,000; 30,000; and 75,000 nematodes/ plant) with damage on cotton \'Delta Opal\'; ii) measure the pathogenic effect of P. brachyurus on cotton \'Delta Opal\' and \'Fibermax 966\'; iii) characterize the reaction of cotton cultivars to three populations of P. brachyurus ; iv) characterize the host reaction (in terms of susceptibility/ resistance) of some green manures, cover crops and pastures to two populations of P. brachyurus; v) characterize different populations of P. brachyurus by PCR-RFLP and sequencing of ITS-1 rDNA region. Results suggest that P. brachyurus is an eventual pathogen of cotton, since high population levels were necessary to reduce plant growth (< 12,000 nematodes/ plant). All cotton cultivars tested were rated as susceptible to P. brachyurus In relation to crop species tested, Crotalaria spectabilis, C. breviflora, amaranth \'BRS Alegria\', oil radish \'Comum\', and the black oat cultivars Campeira Mor, IPFA 99006, Comum, CPAO 0010, and Garoa were resistant to P. brachyurus PCR-RFLP showed intraspecific variability for different population of P. brachyurus studied. Sequencing of the ITS-1 rDNA region confirmed the results of the enzymatic digestion and demonstrated heterogeneity of 18S and ITS-1 rDNA regions of P. brachyurus.

No sistema imune de artrópodes, em contraste com o dos vertebrados, não ocorre uma resposta a antígenos por meio da produção de imunoglobulinas específicas contra agentes infecciosos. Portanto, a imunidade adaptativa está ausente, sendo que o sistema imune nesses animais baseia-se somente numa resposta inata. Os mecanismos presentes na resposta imune inata dos artrópodes incluem: (i) o sistema de coagulação; (ii) a cascata da profenoloxidase; (iii) a liberação de moléculas que possuem ação direta contra microorganismos dentre elas, os peptídeos antimicrobianos (PAMs). Estas moléculas podem ser constitutivas, como observado em aracnídeos, ou terem sua expressão induzida após desafio imune, como observado em alguns insetos. PAMs são moléculas anfipáticas, geralmente catiônicas e compostas por 9 a 100 resíduos. O estudo desses peptídeos, além de possibilitar a descoberta de novas moléculas que tenham modo de ação alternativo aos antibióticos convencionais, permite uma compreensão mais ampla do sistema imunológico de diferentes grupos de animais, bem como a origem dos seus mecanismos na história evolutiva. Neste trabalho foi utilizado o opilião Acutisoma longipes como modelo experimental para a caracterização de PAMs presentes na sua hemolinfa, tendo em vista que não há registros de estudos dessa natureza que utilizaram representantes da ordem Opiliones. Primeiramente, foi demonstrada a ocorrência de diversas frações, obtidas da purificação da hemolinfa, com atividade anti-M. luteus, consistidas por peptídeos que aparentemente são constitutivos. Uma das frações mostrou-se pura e apresentou um peptídeo de 2,1 kDa cuja estrutura primária, composta por 18 resíduos, foi completamente elucidada (SGYLPGKEYVYKYKGKVF) por sequenciamento de novo e sequenciamento do N-terminal. Este peptídeo linear foi nomeado longipina. O peptídeo sintético apresentou atividade antimicrobiana contra as bactérias Escherichia coli e Micrococcus luteus, e as leveduras Candida albicans e C. tropicalis, além de não apresentar atividade hemolítica na máxima concentração testada (100 mM). Foi demonstrado que a longipina liga-se preferencialmente a vesículas unilamelares grandes (LUVs), constituídas de fosfolipídios aniônicos (POPG), que mimetizam as cargas da superfície das células de microorganismos. A ligação do peptídeo a LUVs compostas, na razão molar de 1:1, por POPG e POPC (zwiteriônico) provoca o extravasamento de marcadores (carboxifluoresceína) aprisionados nos seus interiores. Esse peptídeo encontra-se majoritariamente desestruturado em solução ou na presença de sistema mimético composto somente por POPC. Porém, na sua ligação com POPG:POPC 1:1, adota estruturas b e estrutura relacionada à presente em agregados intermoleculares de fibras amiloides. / The arthropods immune system, in contrast to the vertebrates one, lacks a response to antigens through the production of specific immunoglobulins to fight against infectious agents. Therefore, the adaptive immunity is absent, and their immune system is only supported by an innate response. The mechanisms present in the arthropods innate immune response include: (i) the clotting system; (ii) the prophenoloxidase cascade; (ii) the release of molecules that can directly act against microorganisms among them, the antimicrobial peptides (AMPs). These molecules can be constitutive, as observed in arachnids, or have their expression induced upon imune challenge, as observed in some insects. AMPs are amphipathic molecules, usually cationic and formed by 9 to 100 residues. The study of these peptides, besides allowing the discovery of new molecules that exert their mode of action alternatively from the conventional antibiotics, permits a wider understanding of the immunological system from different groups of animals, as well as the origin of their mechanisms in the evolutionary history. The harvestman Acutisoma longipes was used in this work as na experimental model for the characterization of AMPs from its haemolymph, taking into account that there are no records of using representatives of the Opiliones order in such kind of study. Firstly, it was demonstrated the occurrence of several fractions, obtained from the haemolymph purification, that presented anti-M. luteus activity, consisted by peptides that are apparently constitutive. One of these fractions was pure and presented a 2.1 kDa peptide which had its primary structure, composed by 18 residues, completely elucidated by de novo and N-terminal sequencing (SGYLPGKEYVYKYKGKVF). This linear peptide was named longipin. The synthetic peptide presented antimicrobial activity against Escherichia coli and Micrococcus luteus bacteria and Candida albicans and C. tropicalis yeasts, in addition to the absence of hemolytic activity at the highest concentration used (100mM). It was shown that longipin preferentially binds to large unilamellar vesicles (LUVs), constituted by anionic phospholipds (POPG), that mimics the membrane surface of microbe cells. The peptide biding to LUVs composed, in 1:1 molar ratio, by POPG and POPC (zwitterionic) causes dye leakage (carboxyfluorescein) from their inside. This peptide in solution or in the presence of POPC solely containing mimic system is mostly unstructured. However, upon its binding to POPG:POPC 1:1, it adopts b and intermolecular aggregates amyloid-like fibrils structures.

Microrganismos formam associações com a maioria das espécies animais e um exemplo fascinante são as múltiplas interações nas colônias de formigas-cortadeiras. Os efeitos dessas interações (positivos e negativos) se manifestam na sanidade e desenvolvimento das colônias. Sendo assim, a compreensão das interações que ocorrem entre os microrganismos das colônias de formigas-cortadeiras A. sexdens é importante para fundamentar o controle biológico desta praga. Esse presente trabalho foi dividido em três capítulos. O primeiro capítulo objetivou comparar o desenvolvimento de colônias de Atta sexdens (Linnaeus) em contato com dois solos: (i) de área com ninhos e (ii) de área sem ninhos de formigas-cortadeiras. Foram conduzidos dois experimentos em laboratório. No experimento I, fêmeas recémfecundadas fundaram a colônia em pote com gesso e, após 106 dias, entraram em contato com solo. No experimento II, as fêmeas recém-fecundadas fundaram suas colônias diretamente no solo. A taxa de mortalidade de colônias, após 106 dias da revoada e se desenvolvendo em pote com gesso, foi de 28,6%. Quando se desenvolveram desde o início em contato com o solo, a taxa de mortalidade elevouse a 67,2 %. Os resultados confirmam que as colônias incipientes de A. sexdens sofrem forte pressão seletiva de microrganismos do solo no momento da fundação. No entanto, após o surgimento da força operária, mecanismos de defesa imune social, provavelmente, garantem o desenvolvimento da colônia a despeito da presença de microrganismos patogênicos no solo dos ninhos. O segundo capítulo objetivou isolar e identificar actinobactérias de solos de câmaras de jardim de fungos de A. sexdens e avaliar o efeito inibitório desses isolados sobre fungos associados às colônias de formigas-cortadeiras. Foram sequenciados o gene 16S rRNA de nove actinobactérias, sendo seis do gênero Streptomyces, duas do gênero Nocardia e uma do gênero Kitasatospora. Foi verificado que dois isolados de Streptomyces e um de Kitasatospora inibiram não só o fungo Escovopsis sp., como também o fungo entomopatogênico Metarhizium anisopliae e o fungo antagonista do cultivar simbionte de cortadeiras Trichoderma aff. strigosellum. Uma vez que não existem evidências de cultivo de actinobactérias na cutícula de operárias do gênero Atta, é possível hipotetizar que essas operárias estabeleçam simbiose temporária adaptativa com microrganismos do solo produtores de substâncias antifúngicas e antibióticas e que vivem em alguma parte de seu ninho ou mesmo no interior do seu corpo. Além disso, 10 os fungos patogênicos para colônias de formigas-cortadeiras presentes no solo adjacente ao ninho, apesar de constituírem um risco, podem ser controlados pelas secreções produzidas pelas operárias, bem como pelos metabólitos de algumas actinobactérias. O terceiro capítulo teve como objetivo verificar a aceitação e incorporação de iscas contendo micélio de Escovopsis sp. em colônias jovens de Atta sexdens. Verificou-se o transporte de iscas em todas as colônias do teste. Houve redução no peso do jardim de fungos das colônias que receberam iscas com Escovopsis sp., e aumento no peso do jardim de fungos de colônias que receberam tratamento controle. Conclui-se que a utilização de iscas com micélio de Escovopsis sp. foi satisfatória para introduzir o fungo parasita no jardim de fungos de colônias de Atta sexdens. / Microorganisms form associations with most animal species, and a fascinating example is the multiple interactions in the colonies of leaf-cutting ants. The effects of these interactions (positive and negative) are exhibited in the health and development of the colonies. Therefore, the understanding of the interactions that occur among the microorganisms into leaf-cutting ants colonies is important to support of biological control of this pest. This work was divided into three chapters. The first chapter aimed to compare the development of colonies of Atta sexdens (Linnaeus) in contact with two types of soil: (i) from an area used for nesting and (ii) from an area not used for nesting of leaf-cutting ants. Two experiments were conducted in the laboratory. In experiment I, newly fertilized females founded the colony in a plastic pot with gypsum and, after 106 days were transferred to a plastic pot with soil. In experiment II, newly fertilized females founded their colonies directly on the soil. Colony mortality rate 106 days after nuptial flight and founding in a plastic pot with gypsum was 28.6%. When they developed directly in contact with the soil, mortality rate increased to 67.2%. The results support that incipient colonies of A. sexdens undergo strong selective pressure from soil microorganisms at the time of foundation. However, after the emergence of the worker force, social immune defense mechanisms likely guarantee the development of the colony, despite the presence of pathogenic microorganisms in the soil of the nests. The second chapter aimed to isolate and identify actinobacteria from soils of fungi garden chambers of A. sexdens and to evaluate the inhibitory effect of these isolates on fungi associated with leaf-cutting colonies. To identify the isolates, the 16S rRNA gene was sequenced from nine actinobacteria: six of Streptomyces genus, two of Nocardia genus and one of Kitasatospora genus. Two Streptomyces and one Kitasatospora isolates inhibited not only the fungus Escovopsis sp., but also the entomopathogenic fungus Metarhizium anisopliae and the antagonistic fungus of the cultivar symbiont of leaf-cutting ant Trichoderma aff. strigosellum. Since there is no evidence of cultivation of actinobacteria on the Atta worker cuticle, it is possible that these workers establish temporary adaptive symbiosis with soil microorganisms producing antifungal and antibiotic substances and living in some part of their nest or even in the interior of their body. It can be hypothesized that pathogenic fungi present in the soil adjacent to the leaf-cutting ant nest, despite the risk they represent, are controlled by the secretions produced by the workers, as well as by the metabolites of some actinobacteria. The third chapter had the objective of verifying the acceptance and incorporation of baits containing mycelium of Escovopsis sp. by young colonies of A. sexdens. We verified the transport of baits in all tested colonies. There was a reduction in the weight of the fungus garden of the colonies that received baits with Escovopsis sp., and an increase in the weight of the fungus garden of colonies that received control treatment. It is concluded that the use of baits with mycelium of Escovopsis sp. was satisfactory to introduce the fungus parasite in the fungus garden of A. sexdens colonies.

A caracterização de sequências codificadoras presentes nas vizinhanças do gene META 1 permitiu a identificação de alguns genes expressos preferencialmente em estágios infectivos de L. (L.) amazonensis. Um dos genes presentes é regulado de forma distinta, observando-se maior abundância do RNA em formas amastigotas. Este gene foi denominado LaLRR17 por codificar uma proteína contendo em sua região central 6 repetições ricas em leucina (LRR). As LRR são motivos presentes em diversas famílias de proteínas e são responsáveis pela formação de uma estrutura capaz de estabelecer interações protéicas. A região central da proteína LRR17 apresentou similaridade com a porção carboxi-terminal da proteína NOD 3 humana. A proteína LRR17 foi localizada no citosol de macrófagos infectados com L. (L.) amazonensis. Para caracterizar a função da proteína LRR17 foram obtidas linhagens de L. (L.) amazonensis expressoras do gene LmjLRR17. Essas linhagens mutantes foram mais infectivas em macrófagos in vitro quando comparadas com a linhagem selvagem. Avaliamos também o papel das proteínas NOD 1 e NOD 2 na infecção por L. (L.) amazonensis e L. (L.) major para estabelecer a possível relação da proteína LRR17 na interação com essas vias de defesa celular do macrófago. / The characterization of coding sequences in the vicinity of the META 1 gene allowed the identification of some genes preferentially expressed in L. (L.) amazonensis infective stages. One of the identified transcripts presents a distinct pattern of expression with higher levels of mRNA in amastigotes. This gene was named LaLRR17 since it encodes a 72 kDa protein with 6 leucine-rich repeats (LRR) in its central region. Leucine-rich repeats (LRR) are present in several families of proteins and are responsible for the formation of a structure capable of establishing protein interactions. The central region of the LRR17 protein showed similarity with the carboxyl-terminal portion of the NOD 3 human protein. The LaLRR17 protein is secreted to the cytoplasm of L. (L.) amazonensis-infected macrophages. To characterize the function of the LRR17 protein we obtained strains of L. (L.) amazonensis expressing the LmjLRR17 gene. These mutant strains were more infective to macrophages in vitro when compared with the wild type strain. We also evaluated the role of NOD 1 and NOD 2 proteins in infections with L. (L.) amazonensis and L. (L.) major to investigate a possible role of the LRR17 protein in the interaction with these defense pathways in macrophages.