Die Arbeit hatte zum Ziel, ein In-vitro-Infektionsmodell für den protozoären Durchfallerreger Cryptosporidium parvum zu optimieren und dahingehend zu testen, ob es für eine quantitative Beurteilung der Infektiosität von Kryptosporidienoozysten eingesetzt werden kann. Die verwendeten Oozysten wurden zuvor im Zuge einer Passagierung im Kalb vermehrt, aus dem Kot isoliert, aufgereinigt und zur Infektion einer humanen ileocaecalen Adenokarzinomzelllinie (HCT-8) verwendet Die Kultivierung erfolgte über 48 Stunden in Mikrotiterplatten mit jeweils 24 Kavitäten. Die DNA infizierter Zellen und nichtinfizierter Kontrollen wurde anschließend isoliert und die parasitenspezifische DNA in der real-time PCR quantifiziert. Die gewählten Primer-Sonden-Kombinationen erlaubten eine spezifische Amplifikation der Erreger-DNA. In der Optimierung wurden das Brilliant®QPCR Core Reagent Kit, der ABsoluteTMQPCR sowie zwei verschiedene Oligonukleotidkombinationen untersucht. Durch die Klonierung einer Sequenz im Target-Gen und die Herstellung einer Titrationsreihe aus dieser klonierten DNA gelang es, den für die Vergleichbarkeit unerlässlichen homogenen Standard zu gewinnen. Der In-vitro-Vitalitätsassay wurde außerdem auf seine praktische Anwendbarkeit hin geprüft. Es wurde einerseits eine Desinfektionsmittelprüfung mit Chlorokresol (Neopredisan®135-E), andererseits ein Versuch zur thermischen Inaktivierung, beide unter Nutzung dreier verschiedener C. parvum-Chargen (LE-06-Cp-05/0, LE-07-Cp-05/2 vom Isolat A, LE-06-Cp-05/2 vom Isolat B), vollzogen. Die Überbewertung der Infektiosität der Oozysten durch die Betrachtung der Exzystierung konnte anhand der parallel zur DNA-Quantifizierung ermittelten Exzystierungsraten gezeigt werden. Die Exzystierungshemmung lag in jedem Versuch deutlich unter den in der real-time PCR berechneten Inaktivierungsraten. Je nach verwendeter Oozystencharge lieferte die Desinfektion mit 4 % Neopredisan®135-E Inaktivierungsraten, die zwischen 90 und 100 % bei einstündiger Einwirkzeit lagen. Mit steigender Dauer der Inkubation stieg erwartungsgemäß auch der Grad der Inaktivierung. Die Anwendung der 1 %igen Verdünnung resultierte in einer deutlich gesteigerten Exzystierungsrate gegenüber der unbehandelten Kontrolle sowie in stark variierenden Inaktivierungsraten (24 - 91,5 %). Es konnte gezeigt werden, dass mit Neopredisan®135-E unter den gewählten Inkubationsbedingungen zwar eine gute, aber keine vollständige Inaktivierung der C. parvum-Oozysten erfolgt. Eine suboptimale Wirkung zeigte sich in einer hohen Varianz der Einzelmesswerte. Die Vitalitätsraten betrugen nach einstündiger Inkubation der Oozysten bei 38°C noch 100 %, nach 24 Stunden waren diese bereits auf 5 - 23 % abgesunken. Es scheint, als würden mesophile Verhältnisse die Exzystierung der Sporozoiten anregen und bei längerer Konditionierung eine Erschöpfung des Stoffwechsels der Entwicklungsstadien herbeiführen. Die Inaktivierungsrate bei 55°C lag zwischen 96 und 100 %. Bei thermophiler Konditionierung wurde in drei von sieben Fällen, nach der Inkubation in Neopredisan®135-E nur in einer der sieben Untersuchungen ein vollständiger Vitalitätsverlust beobachtet. Die vorgestellte Methode erwies sich als gut reproduzierbar, sensitiv und schnell. Die In-vitro-Kultivierung des Erregers C. parvum ließ sich mit der real-time PCR, welche eine absolute Quantifizierung erlaubte, gut in Einklang bringen. Die Verwendung der In-vitro-Kultur als lebendes System ließ eine gewisse Variabilität der Ergebnisse zwischen einzelnen Untersuchungen erwarten, die sich aber in einem akzeptablen Bereich bewegten. Eine weitere Optimierung im Sinne einer Sensitivitätssteigerung bei akzeptabler Störanfälligkeit und Variabilität ist anzustreben.

Cryptosporidium parvum is an obligatory intracellular parasitic protist that belongs to the phylum Apicomplexa. Cryptosporidiosis is an infection for which no satisfactory efficient curative treatment is known, especially in immunocompromised individuals. Furthermore, the parasite oocysts show considerable tenacity in the environment. Therefore, new potent drugs along with a simple and reliable experimental model for evaluation of anticryptosporidial measures are urgently needed. The present studies were undertaken to establish a combined cell culture and quantitative PCR assay (cc-qPCR) to assess efficacy of pharmacological compounds against C. parvum. Human ileocecal adenocarcinoma cells (HCT-8) were selected for culture of C. parvum. Oocysts were excysted directly on confluent monolayers for infection. After 3 h of incubation the non invasive parasite remains were removed by washing. At the end of the incubation period the cells were harvested and subjected to DNA extraction. Real time PCR was performed to quantify the target parasite DNA (fragments of 70 kDa heat shock protein gene) copy numbers. Each reaction was run in triplicate. A standard curve calculated on the basis of serial dilutions of plasmid DNA or infected control culture DNA was run in each experiment. A series of oocyst suspensions were applied to cell cultures to determine the sensitivity of the cc-qPCR assay and also to generate a calibration curve to calculate the infectivity of oocysts. A dilution series of heat inactivated oocysts (70°C for 1 h) were used to determine the size of the oocyst inoculum at which complete elimination of extracellular parasite material by washing is reliably achieved. The results obtained by the assays were reproducible and the method sensitive with a detection limit of infection with 10 oocysts 48 h post infection (p.i.) and with 100 oocysts 24 h p.i. Percent effects of drugs and disinfectants were enumerated by comparing DNA copies between treated and non treated samples. The suitability of cc-qPCR for screening of pharmacological compounds was validated by confirming the in vitro efficacy of monensin (98.15% ± 1.09 at 0.144 µM) and halofuginone (98.05% ± 0.59 at 25 µM) over the entire incubation period with a dose dependent reduction of parasite multiplication demonstrated 27 h p.i. The inhibition of parasite proliferation by 0.144 µM monensin in the period from 3 h p.i (time defined to represent the initial level of parasite development before drug application) to 27 h p.i. or 45 h p.i. was 97 and 99% respectively, and by 25 µM halofuginone 99% (27 h p.i.). Hexadecylphosphocholine (miltefosine), a new anti-leishmanial compound, was tested against cryptosporidia and provided a maximum of 98% reduction of parasite multiplication at 45 h p.i. The potential activity of curcumin (extract from the herb Curcuma longa) against C. parvum was also evaluated by cc-qPCR. Curcumin appeared to be sensitive to degradation after prolonged incubation and the observed inhibition of multiplication of C. parvum was significantly increased when medium was replaced by fresh medicated medium after 12 h of exposure. The effects on parasite multiplication (>95% inhibition with IC50 value of 13 µM) and on sporozoite invasion (assessed 3 h p.i.; 65% inhibition at 200 µM) suggest that further exploration of anticryptosporidial efficacy of curcumin may be rewarding. The cc-qPCR was further optimized to analyse inactivation measures directed against oocysts of C. parvum. The suitability of the assay for assessment of inactivation measures was confirmed by the reproducible demonstration of effectiveness of cresolic disinfectants at the recommended concentration of 4% and incubation period of 2 h (Neopredisan® 135-1, Menno Chemie, Norderstedt, Germany: 99.91% ± 0.08; Aldecoc® TGE, EWABO Chemikalien GmbH & Co. KG, Wietmarschen, Germany: 99.91± 0.05) and by using thermally inactivated oocysts (complete inactivation by 56°C and 70°C for 20 min). Based on the in vitro results and previously obtained data from the chicken infection model 99.5% inactivation is proposed as a suitable threshold value that needs to be consistently exceeded by a product to be considered efficient. Application of Neopredisan® 135- 1 and Aldecoc® TGE (4% for 2h) consistently inactivated more than 99.5% of oocysts while other disinfectants that are not certified as anticoccidial products like Aldecoc® XD (EWABO Chemikalien GmbH & Co. KG, Wietmarschen, Germany) and IGAVET® FF spezial (COS OHLSEN Chemie & Gerätevertrieb GmbH, Geltorf-Esprehm, Germany) and bleach (sodium hypochlorite) did not. It can be concluded that the cc-qPCR method is suited to easily and reliably assess anticryptosporidials in vitro. The method demonstrated that miltefosine and curcumin display anticryptosporidial efficacy under the applied conditions. The cc-qPCR is a highly standardized method supposedly appropriate to replace the chicken infection model for Eimeria tenella as currently practised for certification of anticoccidial disinfectants according to the guidelines of DVG (German Veterinary Society).

The emergence of MNAzymes (Multi-component nucleic acid enzymes) provides a new approach for detection of target analytes in various applications. In this thesis, three novel MNAzyme-based methodologies were developed to expand the range of the applications of MNAzymes. MNAzymes can be coupled with DNA or RNA ligands called aptamers to generate an apta-MNAzyme system, which can be used for the detection of non-nucleic target analytes such as small molecules and proteins. Direct detection using apta-MNAzyme system is performed in a format, which was isothermal, fluorescent, rapid, and requires no protein enzymes. Apta-MNAzymes can be coupled with a signal amplification cascade to increase the sensitivity of the reaction. Another MNAzyme-based methodology termed truncated MNAzyme arm system was developed to discriminate the presence of a single base mismatch of two closely related sequences. The system employs a partzyme with a truncated sensor arm and a stabiliser oligonucleotide that binds adjacently to the truncated sensor arm to stabilise the active MNAzyme structure. Truncated MNAzyme real-time PCR system is capable of discriminating the presence of a single base mismatch in a target DNA with high specificity and sensitivity (down to approximately 10 gene copies). The generic nature of the system enables simultaneous detection of three SNP targets in a multiplex format. MNAzymes was also investigated with various strategies to discriminate DNA sequences that are either methylated or unmethylated. In this thesis, bisulphite-treated DNA samples present in as low as 0.032 % of methylated DNA in a background of unmethylated DNA were discriminated using MNAzyme real-time methylation specific PCR (MSP) system. Furthermore, the presence of 5-methylcytosines in a target sequence increases the melting temperature of the duplex DNA. This was exploited further to directly discriminate DNA methylation status of target sequences using the truncated MNAzyme arm system without the need for bisulphite modification. Findings in this thesis have broadened the scope of MNAzymes as versatile tools for many possible applications and flexible alternative to the current technologies.

No description available.

Nitrification, a key step in biological nitrogen removal processes, is the oxidation of ammonia into nitrate performed by ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) under aerobic condition. Researchers have focused on factors affecting the performance of nitrification for decades, but the inorganic carbon limitation on nitrification had been neglected. However, the increase in nitrogen in wastewater has increased the need to evaluate and improve our understanding of this limitation. In a previous research, the hypothesis that different inorganic carbon concentrations would enrich different AOB populations has been examined. In this study, the focus was on the effect of inorganic carbon concentration on NOB, which has a close relationship with AOB. Two 5L lab–scale continuous–flow stirred tank reactors (CSTR) were operated to evaluate the nitrification performance and microbial ecology of nitrifier populations acclimated under inorganic carbon sufficient (high–IC) and limited (low–IC) conditions for approximately 700 days. During the operation period, both bioreactors were able to maintain satisfactory nitrification efficiency higher than 95% at an influent ammonium concentration of 250 mg–N/L. Nitrate was the major end product and no significant nitrite accumulation was observed. To evaluate the effects of inorganic carbon on NOB community structures, cloning/sequencing and real–time PCR were applied to target and quantify the two common NOB genera, Nitrospira and Nitrobacter, as no molecular probe targeting all known NOB is available presently. The results showed that these two genera were both found in the two reactors. Nitrospira was the dominant NOB population in the high–IC bioreactor, while Nitrobacter was dominant in the low–IC one after one year acclimation. Kinetic analysis revealed that NOB enriched in the two reactors have different kinetic performances. However, IC concentration did not show a significant impact on the nitrite oxidizing kinetics of NOB in the batch tests.

The aim of my thesis on topic The effect of n-3 polyunsaturated fatty acids in the diet of rats on expression of selected genes was to investigate the effect of eicosapentaenoic acid (EPA) and docosapentaenoic acid (DHA) on the expression of genes which encode GPR120, AdipoR1 and AdipoR2 receptors in relation to suppress low-grade chronic inflammation in organism to reduce the risk of atherosclerosis by dietary intervention in rats. Rats were fed by a mixture MYPO with 6 % safflower oil (diet S), 6 % fish oil (diet F) or 6 % of oil from algae Schizochytrium (diet A). Gene expression was measured by quantitative real-time PCR method and the results were evaluated by using the software qbase + (Biogazelle NV). Relative expression of GPR120 gene was in F diet 88 % (P > 0,05), in A diet 93 % (P > 0,05) in comparison with control group (100 %). Relative expression of ADIPOR1 gene was in F diets and A diet 82 % (P < 0,05) in comparison with the control group. For ADIPOR2 gene relative expression was 71 % (P < 0,05) in diet F and 68 % (P < 0,05) in diet A. The results were contrary to our hypothesis. However, they exactly match the results of other studies in the available literature. It would be appropriate to carry out further studies on this issue.

A subject of the diploma thesis was the optimization of a procedure of detecting a phytoplasma Candidatus Phytoplasma mali using woody indicator Golden Delicious in greenhouse conditions as an alternative method to the phytoplasma presence testing by biological indexing in field conditions. To control the presence of phytoplasma in the experimental plants, molecular method of real-time PCR was used. The experiment was set up on the demonstration area of the Department of Breeding and Propagation of Horticultural Plants in the grounds of Mendel University in Brno. Three different ways of transferring of the phytoplasma infection were compared: method of parallel grafting of the tested variety and of the indicator on the seedling in the period of dormancy (method number 1), method of summer budding of the tested variety on indicator grafted on the seedling in the period of dormancy (method number 2), and method of double summer budding of the indicator and of the tested variety on the seedling (method number 3). On a woody indicator Golden Delicious, varieties Virgin Czech, Canadian rennet, Gascoigne, Ribston and Boskoop were tested, 10 plants of each variety. The experiment lasted 10 months. A total of 150 tested plants were assessed by a visual inspection of the symptoms presence. During the monitoring period, none of the tested plants showed typical symptoms of the apple proliferation. Presence of the Candidatus Phytoplasma mali was verified using real-time PCR method in 60 tested (indicator) plants. The infection was confirmed in 12 of the indicator plants. The detected quantities of the phytoplasma in the tissues however reached very low values. The highest number of the infected plants was found in tests of the Gascoigne variety, established by the method of double summer budding of the indicator and of the tested variety on the seedling (method number 3). This method provided the most successful inoculation of the indicator by the phytoplasma. Based on the results obtained during the presented study, it can be declared that biological testing of the phytoplasma presence using short-term greenhouse tests is not reliable. When using testing with the indicator ´Golden Delicious´, it is recommended to realize the experiments for at least two growing seasons, as it is in the field tests. Due to the fact that during the time-limited realization period of the experiment in this study it was found that the phytoplasma was not sufficiently propagated, the final results of the comparison of the indicator plants inoculation methods will be available at the end of autumn of 2017.

O circovírus suíno tipo 2 (PCV2) é o principal agente da síndrome multissistêmica do definhamento do suíno (SMDS), uma doença mundialmente disseminada e que provoca perdas econômicas significativas para a suinocultura. Visando contribuir no diagnóstico da síndrome, o presente trabalho padronizou e comparou testes para a detecção do PCV2. Para isso, foram utilizadas as técnicas de amplificação por círculo rolante (ACR) e variações da PCR (convencional, tempo-real e competitiva). Utilizando a ACR foi possível obter a amplificação total de genomas do PCV2, os quais foram clonados, sequenciados e agrupados no genótipo PCV2b. Os genomas clonados foram isolados, recircularizados e transfectados em células PK-15. Este procedimento possibilitou a recuperação do vírus infeccioso em títulos de até 105,55 DICC50/mL. Portanto, a ACR foi uma ferramenta útil em estratégias de isolamento e sequenciamento do vírus. No entanto, a ACR foi menos sensível que a PCR para fins de detecção do PCV2. No segundo estudo, buscando métodos auxiliares no diagnóstico da SMDS, dois ensaios para a quantificação do PCV2 foram desenvolvidos. Estes ensaios foram baseados nas técnicas de PCR competitivo (cPCR) e de PCR em tempo real. Visando determinar qual seria o mais adequado para estimar a carga viral do PCV2, os dois métodos foram comparados. Ambos os ensaios foram capazes de detectar diferenças significativas entre o número de cópias de DNA de PCV2 encontradas em tecidos de animais saudáveis e acometidos pela SMDS (≥ 2,5 log10). No entanto, uma diferença média de 1,8 log10 na carga viral foi encontrada entre ensaios, onde as maiores cargas virais foram detectadas pela PCR em tempo real. Outro objetivo deste trabalho foi gerar vacinas baseadas na proteína do capsídeo (Cap) do PCV2. Assim, no terceiro estudo, três baculovírus recombinantes foram construídos de modo a expressar a proteína Cap. Em dois recombinantes, a seqüência de nucleotídeos do peptídeo sinal (PS) da glicoproteína I do herpesvírus bovino (BoHV-gI) foi inserida na extremidade 5’ do gene cap (ORF2). Além disso, um recombinante contendo a seqüência de nucleotídeos do PS foi construído sem o sinal de localização nuclear (NLS) de proteína Cap. Através do ensaio de imunoperoxidase em monocamada (IPMA), antígenos de PCV2 foram detectados em células Sf21 infectadas pelos três vírus recombinantes. Este resultado sugere que os recombinantes construídos são potenciais candidatos vacinais, uma vez que eles foram capazes de produzir antígenos de PCV2. / Porcine circovirus type 2 (PCV2) is the major agent of postweaning multisystemic wasting syndrome (PMWS), a worldwide spread disease that causes significant economic losses to the swine productive chain. Aiming to contribute in the diagnosis of the syndrome, this thesis compared and developed tests for PCV2 detection. For this, multiply-primed rolling-circle amplification (MPRCA) and PCR-based assays (conventional, real-time and competitive) were tested. The MPRCA allowed amplifying the full-length PCV2 genomes, which were cloned, sequenced and grouped on PCV2b genotype. The cloned genomes were isolated from the plasmids, recircularized and used for transfection in PK-15 cells. This procedure led to the production of infectious virus to titres up to 105.55 TCID50/mL. It was concluded that MPRCA is a useful tool to amplify PCV2 genomes in sight of sequencing and virus isolation strategies. However, it was less sensitive than PCR for diagnostic purposes. In the second study, searching for methods in support to PMWS diagnosis, two PCR assays were developed: a competitive PCR (cPCR) and a SYBR green real-time PCR. The quantitative PCR methods were compared to determine which would be more suitable to estimate the PCV2 DNA load. Both assays were able to detect significant differences between the numbers of PCV2 DNA copies found in tissues of PMWS-affected and non-PMWS-affected pigs (≥2.5 log10). However, a mean difference of 1.8 log10 on the viral load was found between assays, where the highest viral loads were detected by SYBR green real-time PCR. In the work outlined herein, another purpose was to generate vaccine candidates based on PCV2 capsid protein (Cap). Therefore, in the third study, three types of recombinant baculoviruses were constructed to express the Cap protein. In two recombinants, the nucleotide sequence from the signal peptide (SP) of bovine herpesvirus glycoprotein I (BoHV-gI) was inserted at the 5’ end of the cap gene (ORF2). Additionally, one recombinant containing the SP nucleotide sequence was constructed lacking the nuclear localization signal (NLS) of Cap protein. Through immunoperoxidase monolayer assay (IPMA), the PCV2 antigen was detected in Sf21 cells infected by the three recombinant viruses. This result suggests that the recombinants here constructed are potential vaccine candidates, once they were able to produce PCV2 antigens.

Submitted by Hiolanda Rêgo (hiolandarego@gmail.com) on 2018-02-05T14:14:00Z No. of bitstreams: 1 Dissertação_ICS_ ROCHA, D. J. P. G..pdf: 4034030 bytes, checksum: 7085be9f2fda81bc8248196d4b4e6988 (MD5) / Made available in DSpace on 2018-02-05T14:14:00Z (GMT). No. of bitstreams: 1 Dissertação_ICS_ ROCHA, D. J. P. G..pdf: 4034030 bytes, checksum: 7085be9f2fda81bc8248196d4b4e6988 (MD5) / CNPQ / O método mais comum de normalização em ensaios de quantificação relativa da expressão gênica por PCR quantitativa em tempo real (qPCR) faz uso de um gene de referência, que deve manter sua expressão estável sob diferentes condições experimentais. Em uma meta-análise da literatura e banco de dados de experimentos de análise de expressão gênica em bactérias, os genes gyrA (DNA gyrase subunidade A), gyrB (DNA gyrase subunidade B), dnaG (DNA primase), era (GTPase era) e secA (translocase proteica subunidade secA), figuram entre os mais estáveis em diversas condições experimentais. Neste cenário, este estudo se propõe a desenvolver e construir um conjunto de primers universais para esses genes de referência a partir de organismos modelo de grupos bacterianos de interesse clínico e biotecnológico. As ferramentas de alinhamento, ClustalOmega e PCR virtual, Primer-Blast foram utilizadas para encontrar regiões conservadas entre os genes candidatos em diferentes organismos bacterianos. Dentro do complexo Mycobacterium tuberculosis, todos os genes apresentaram homologia suficiente para o desenho de primers universais, enquanto que em outros grupos bacterianos a homologia de sequência foi restrita a algumas espécies. Potenciais primers universais foram desenhados para diferentes grupos bacterianos e os primers para a família Enterobacteriaceae foram validados por RT-qPCR em Escherichia coli; os resultados foram comparados contra o gene comumente usado, 16S rRNA. Os primers testados apresentaram eficiências de amplificação dentro dos limites esperados e as expressões dos genes de referência foram estáveis nas condições estudadas, tendo sido o gene dnaG o mais estável, de acordo com os softwares NormFinder e RefFinder. Conclui-se que é possível desenhar primers universais funcionais para normalização de RT-qPCR em grupos bacterianos específicos, contudo o baixo nível de conservação gênica de determinados genes pode limitar suas utilizações.

Submitted by Ana Maria Fiscina Sampaio (fiscina@bahia.fiocruz.br) on 2014-05-20T17:14:19Z No. of bitstreams: 1 Adenizar Delgado das Chagas Jr. Avanços... 2014..pdf: 11153892 bytes, checksum: 48154dea65a7a4a32a54408e694c5d30 (MD5) / Made available in DSpace on 2014-05-20T17:14:20Z (GMT). No. of bitstreams: 1 Adenizar Delgado das Chagas Jr. Avanços... 2014..pdf: 11153892 bytes, checksum: 48154dea65a7a4a32a54408e694c5d30 (MD5) Previous issue date: 2014 / Fundação Oswaldo Cruz. Centro de Pesquisa Gonçalo Moniz. Salvador, BA, Brasil / A leptospirose é uma zoonose causada por espiroquetas patogênicas pertencentes ao gênero Leptospira. O modelo da doença em camundongos tem vantagens devido à ampla gama de ferramentas genéticas e imunológicas disponíveis para pesquisas básicas. A maior limitação na conduta clínica e na pesquisa experimental da leptospirose é o fraco desempenho dos métodos disponíveis para detecção direta e para quantificação de leptospiras. Foi incluído nesta tese um conjunto de três manuscritos que visam investigar o desfecho da infecção pela cepa virulenta de Leptospira interrogans nas linhagens de camundongos selvagens (A, CBA, BALB/c e C57BL/6), em camundongos óxido nítrico sintase induzível (iNOS) Knockout (KO), camundongos gene ativador de recombinação 1 (RAG1) KO , camundongos CB17 com imunodeficiência combinada grave (SCID), e os seus respectivos controles selvagens C57BL/6 e BALB/c. Investigar a confiabilidade do método de quantificação do imprint (IM), comparando os resultados obtidos com esta técnica aos obtidos com a utilização do PCR em tempo real (qPCR) para detectar e quantificar leptospiras em amostras de rim de ratos e hamsters experimentalmente infectados. Como esperado, nenhuma das linhagens de camundongos selvagens foram suscetíveis à leptospirose letal. A linhagem A e C57BL/6 exibiram altas cargas de Leptospira nas amostras de rim e as linhagens CBA e C57BL/6 desenvolveram lesões inflamatórias graves, enquanto a linhagem BALB/c provou ser a mais resistente apresentando leptospirose subclínica. Os camundongos iNOS KO e selvagem sobreviveram sem sintomas clínicos de leptospirose. A frequência e gravidade das nefrites foram significantemente menores nos camundongos iNOS KO. Todos os animais RAG1 KO e SCID morreram de leptospirose aguda, enquanto que todos os camundongos selvagens sobreviveram. A hemorragia pulmonar foi observada em 57 e 94% dos camundongos RAG 1 KO e em 83 e 100% dos camundongos SCID, usando doses de inóculos de 107 e 106 leptospiras, respectivamente. Não houve evidências de hemorragia pulmonar nos controles selvagens. Nos modelos de infecção agudo e crônico, houve correlação positiva estatisticamente significante (P < 0,05) na quantificação de leptospiras pelos métodos do qPCR e do IM. Como conclusão geral, a linhagem de camundongos A pode ser a linhagem de escolha em estudos na qual se pretende recuperar um grande número de leptospiras de rins colonizados. As linhagens CBA e C57BL/6 desenvolveram, com maior frequência, lesões inflamatórias e podem ser as mais adequadas para estudos de leptospirose associados com nefrite intersticial. A linhagem BALB/c é a mais indicada para estudar mecanismos que envolvam a imunidade inata e/ou a rápida resposta imune adaptativa. A ausência do gene do iNOS no modelo murino resultou em uma diminuição significativa da suscetibilidade para o desenvolvimento da nefrite intersticial. Além disso, a ausência de linfócitos B e T funcionais não impediu a ocorrência de hemorragia pulmonar. Estes dados fornecem fortes evidências de que a hemorragia pulmonar na leptospirose não está relacionada apenas a mecanismos autoimunes. Para a detecção e quantificação de leptospiras o método do imprint foi equivalente ao qPCR. / Leptospirosis is a zoonosis caused by pathogenic spirochaetes belonging to the genus Leptospira. The mouse disease model is advantagous due to the broad array of immunological and genetic tools available for basic research. A major limitation in the clinical management and experimental research of leptospirosis is the poor performance of the available methods in the direct detection and quantification of leptospires. This thesis includes three manuscripts that investigate the outcome of infection by a virulent strain of Leptospira interrogans in wildtype mice strains: A, CBA, BALB/c and C57BL/6; in iNOS knockout (KO) mice, recombination activating gene 1 (RAG1) KO mice and CB17 severe combined immunodeficiency (SCID) mice. To investigate whether the imprint method (IM) of quantification was reliable we compared it with against real time PCR (qPCR) for the detection and quantification of leptospires in kidney samples from rats and hamsters. As expected, none of the wildtype mice were susceptible to lethal leptospirosis. The A and C57BL/6 strains exhibited high leptospiral loads in the kidney samples and the CBA and C57BL/6 strains developed severe inflammatory lesions, whilst the BALB/c strain proved to be the most resistant to subclinical leptospirosis. The iNOS KO mice survived with no clinical symptoms of leptospirosis. The frequency and severity of nephritis was significantly lower in the iNOS KO mice. All of the RAG 1 KO and SCID animals died of acute leptospirosis, whereas all of the wildtype mice survived. Pulmonary haemorrhage was observed in 57 and 94% of Rag1 KO mice and in 83 and 100% of SCID mice, using inoculum doses of 107 and 106 leptospires, respectively. There was no evidence of pulmonary haemorrhage in the wildtype controls. In both the acute and chronic infection models, the correlation between quantification by qPCR and the IM was found to be positive and statistically significant (P < 0.05). In conclusion, the mouse A strain would be the strain of choice in studies requiring the recovery of a large number of leptospires from colonized kidneys. The CBA and C57BL/6 strains developed more inflammatory lesions and would be the most suitable for studies of leptospirosis associated with interstitial nephritis. The BALB/c strain appeared to be the most suitable for studying mechanisms involving innate immunity and/or rapid adaptive immune response. The absence of the iNOS gene in the murine model resulted in a significant decrease in susceptibility to the development of interstitial nephritis. Furthermore, the absence of functional B and T lymphocytes did not prevent the occurrence of pulmonary hemorrhage. These data provide strong evidence that pulmonary hemorrhage in leptospirosis is not only related to autoimmune mechanisms. For the detection and quantification of leptospires the imprint method was quivalent to that of qPCR. Keywords: