Dissertations / Theses on the topic 'Hemolytic uremic syndrome Prevention'

"February 2003." Addendum and corrigenda inserted at back Includes bibliographical references (leaves 249-272) Aims to identify and characterise potential virulence-associated factors from the locus of enterocyte effacement-negative shiga-toxigenic Escherichia coli O113:H21 strain 98NK2 which was responsible for an outbreak of haemolytic uremic syndrome. Particular attention was focused on putative virulence genes encoded on the megaplasmid of this strain.

Atypical hemolytic uremic syndrome (aHUS) is characterized by acute renal failure, thrombocytopenia, and microangiopathic hemolytic anemia. aHUS is far less common and more severe than typical HUS, which is caused by E. coli infection and manifests as diarrheal illness. The pathogenesis of the disease is linked to dysregulation of the alternative pathway of the complement cascade. Mutations in the complement regulators factor H (CFH), membrane cofactor protein (MCP), factor B (CFB), and factor I (CFI) have been implicated in aHUS. These loss or gain of function mutations lead to uncontrolled complement activity and immune-mediated host cell damage. Establishing a genetic etiology is important as it helps to direct treatment during the acute phase of disease and when transplantation is considered. It has been shown in previous studies that the age of onset as well the severity of the disease is correlated with the type of mutation a patient is found to carry. In forty percent of aHUS patients a mutation in CFH, MCP, CFB, CFI, C3 or THBD is not detected. These data strongly suggest that other genetic factors are involved in the pathogenesis of aHUS and that comprehensive mutation detection in aHUS patients is essential to provide diagnostic and prognostic information, and improve their clinical care. My thesis work has aimed to identify the other genetic contributors to this disease. To achieve this goal we began by screening the largest American cohort of aHUS patients for mutations in CFH, MCP, CFB, CFI, C3, THBD as well as CFHR5. This study identified over thirty novel mutations and suggests a more comprehensive genetic screening method that would better serve patients. To complement these studies multiplex ligation-dependent probe amplification was used to detect genetic rearrangements within the factor H related genes. A number of unique fusion proteins were seen in aHUS patients, all of which are predicted to affect the function of CFH. To discover mutations in novel genes that are causally related to aHUS, we have optimized a platform called CASCADE (Capture and Sequencing of Complement-Associated Disease Exons), which is based on targeted-genome capture and next-generation sequencing. This study revealed an unexpected role for ADAMTS13 and other genes in the coagulation pathway as modifiers of aHUS. Using functional assays we show two of the ADAMTS13 variants alter the behavior of this protein. This work has changed how we view this disease by identifying several novel candidate genes, for which we hope future analysis will lead to a better understanding of their role in aHUS. Using this knowledge we can provide better and more personalized treatments for patients.

Atypical hemolytic uremic syndrome (aHUS) is a rare renal disorder characterized by thrombotic microangiopathy, thrombocytopenia, and acute kidney injury. Its pathogenesis has been attributed to a ‘triggering' event that leads to dysregulation of the complement cascade at the level of the endothelial cell surface. Consistent with this understanding of the disease, mutations in complement genes have been definitively implicated in aHUS. However, the existence of other genetic contributors is supported by two observations. First, in ~50% of cases, disease-causing variants are not identified in complement genes, and second, disease penetrance is typically incomplete and highly variable. To test this hypothesis, we identified pathways established to have crosstalk with the complement cascade, focusing initially on the coagulation pathway. Using targeted genomic enrichment and massively parallel sequencing we screened 36 European-American patients with sporadic aHUS patients for genetic variants in 85 complement and coagulation genes, identifying deleterious rare variants in several coagulation genes. The most frequently mutated coagulation gene in our study cohort was PLG, which encodes a zymogen of plasmin and plays key role in fibrinolysis. These results implicate the coagulation pathway in the pathogenesis of aHUS. Based on this outcome, we developed a clinical genetic testing panel to screen disease-related genes in a group of ultra-rare complement-mediated diseases that includes, in addition to aHUS, thrombotic thrombocytopenic purpura (TTP), C3 glomerulonephritis (C3GN) and dense deposit disease (DDD) patients. Data from 193 patients validate the usage of this panel in clinical practice and also provide confirmatory insight into the pathogeneses of these diseases. Specifically, we found that in aHUS and TTP patients, variants were frequently identified in complement regulator genes, while in C3GN and DDD patients, variants were additionally found in C3 convertase genes. To understand variability in disease penetrance, we completed targeted genetic screening in two aHUS families grossly discordant for disease penetrance, identifying in one family a co-segregating Factor X-deficiency variant (F10 p.Glu142Lys) that abrogated the effect of the complement mutation. Functional studies of the F10 p.Glu142Lys variant show that it decreases Factor X activity predicting to a hypo-coagulable state and further illustrating the importance of complement-coagulation crosstalk in exacerbating, but also mitigating the aHUS phenotype. In our final studies, we have sought to complete a comprehensive analysis for other potentially related pathways by using bioinformatics to identify candidate pathways coupled with whole exome sequencing. Preliminary data from 43 aHUS patients and 300 controls suggest that pathways for dermatan and heparan sulfate synthesis, which are relevant to the formation of the extra-cellular matrix and cell surface adhesion, may be implicated in the aHUS.

Atypical hemolytic uremic syndrome (aHUS) is a rare form of thrombotic microangiopathy characterized by renal failure and determined by genetic and acquired defects of alternative pathway (AP) of the complement system. Autoantibodies against factor H (anti-FHs), a regulator of the AP, were reported in 10% of patients, and are associated with the deficiency of factor H related 1 (FHR1), a FH homologous protein. The aim of this thesis was to evaluate the contribution of genetics to the development of anti-FHs in aHUS. Thirty patients affected by aHUS resulted positive for anti-FHs (9.8%) and FHR1 deficiency was present in 83.3% of them. A healthy control also showed anti-FHs in concomitance with FHR1 deficiency documenting that the lack of FHR1 strongly predisposed to anti-FH development also in healthy subjects although this condition was not sufficient for the disease manifestation. The presence of infectious prodromal signs and an age at the disease onset around 8 years indicated that common infections may trigger the development of autoantibodies in subjects with at risk genetic background. Likely pathogenetic variants in complement genes were observed in 37% of our patients with anti-FHs. At variance, common variants in complement genes did not seem to contribute to the disease, as documented by comparing patients with super controls, unaffected subjects carrying FHR1 deficiency. Finally, I report that the HLA-DRB1*11:04 allele could be a predisposing genetic variant for anti-FH associated aHUS. Further works will be necessary to confirm this finding and to explore the presence of other genetic susceptibility factors that, in combination with the HLA-DRB1*11:04 allele and the FHR1 deficiency, could increase the risk for anti-FHs.

BACKGROUND: Over the past 5 years, 634 cases of Shigatoxin E. coli (STEC) infection were reported to Tennessee Health Department 1. At our local children’s hospital, 4-5 children are hospitalized with STEC infection each year. Some of these children had no history of ingesting food items that could have placed them at risk to develop STEC infection; however, there are other ways that humans could get infected, such as exposure to contaminated water from cattle farms 2. GOALS: To determine if bodies of water in the city are contaminated with STEC. METHODS: Fifty (50) ml of water samples were collected from selected areas of Johnson City, TN. Samples were inoculated to Sorbitol McConkey Agar (SMA) plates under sterile techniques & incubated at 36C for 18 hours under aerobic conditions. RESULTS: Table 1 E. coli Strains Isolated from Water Samples Colony Types Founders Park Sinking Creek Carroll Creek Cherokee Creek Colorless (STEC) 14 (3.5) 24 (6) 32 (8) 35 (8.75) Pink (Non-STEC ) 8 (2) 3 (0.75) 7 (1.75) 4(1) DISCUSSION/ CONCLUSION: All sampled sites were positive for STEC. STEC is a normal flora of the gastrointestinal tract of cattle. Around city neighborhoods are pastures, as cattle farming is a major livelihood in Northeastern, TN. It is highly possible that water runoff from these pastures contaminates the waters around the city. Public health measures should be undertaken to inform the community that these waters are contaminated with STEC to prevent STEC infection. References: Reportable Conditions. TN Epi-news, TN Health Dept Issue 3, Volume 9, 2016 Escherichia coli O157:H7 Infections in Children Associated with Raw Milk & Raw Colostrum From Cows—California, 2006. MMWR Weekly, 57(23); 625-628, June 23, 2008.

A Síndrome Hemolítica Urêmica (SHU) é a principal doença associada à infecção com linhagens de Escherichia coli produtoras de toxina de Shiga (Stx), doença para qual não há uma vacina ou tratamento específico. A toxina Stx é formada por uma subunidade A enzimaticamente ativa e uma B pentamérica responsável pela ligação da toxina na célula hospedeira. Neste trabalho propomos o uso de Bacillus subtilis, uma bactéria não patogênica e formadora de esporos, como veículo vacinal para a expressão de formas atóxicas da Stx2, sob o controle de um promotor induzível por estresse (PgsiB). Camundongos BALB/c imunizados com células vegetativas ou esporos das linhagens vacinais de B. subtilis, por diferentes vias, induziram baixos níveis de anticorpos anti-Stx em soro (IgG) e fezes (IgA). Avaliamos também o potencial imunogênico da Stx gerada em linhagens recombinates de E. coli, mas os anticorpos gerados não foram capazes de neutralizar a toxina nativa. Os resultados indicam que formas alternativas de expressão e/ou o uso de adjuvantes são necessárias para gerar formulações vacinais eficazes contra a SHU.
The Hemolytic Uremic Syndrome (HUS) is the main disease associated with infections with Shiga toxin (Stx) - producing Escherichia coli strain and no effective vaccine or treatment exist. The Stx toxin consist of an enzymatically active A subunit and a pentameric B subunit responsible toxin binding to host cells. In this work we propose the use of Bacillus subtilis, a harmless spore form bacteria as a vaccine vehicle for the expression atoxic forms of Stx2, under the control of stress inducible (PgsiB) promoter. BALB/c mice immunized with vegetative cells and spores of the B. subtilis vaccine strain using different immunization routes elicited low specific antibody levels at serum (IgG) or fecal extracts (IgA). We also investigated the immunogenic potencial of StxB purified from recombinant E. coli strain, but the induced anti-StxB antibodies did not neutralize the native toxin. The results indicate that alternative expression system or the incorporation of the adjuvants are required for the generation of vaccine formulation active against HUS.

Thesis (M.P.H.)--Georgia State University, 2009.
Title from file title page (Digital Archive@GSU, viewed June 16, 2010) Karen Giseker, committee chair; Peter Gerner-Smidt, committee member. Includes bibliographical references (p. 101-105).

Escherichia coli é um microrganismo presente no trato intestinal do homem e de animais de sangue quente, fazendo parte da microbiota, coexistindo sem causar danos ao hospedeiro. No entanto, algumas linhagens desse microrganismo podem ser patogênicas e causar doenças tanto ao homem como aos animais. E. coli produtoras de toxina de Shiga (STEC), consideradas patógenos de origem alimentar, podem causar desde diarréias brandas até severas e sanguinolentas a complicações graves, como colite hemorrágica (HC), síndrome urêmica hemolítica (HUS) e púrpura trombótica trombocitopênica (TTP). O gado é considerado um importante reservatório deste patógeno e a contaminação de seres humanos ocorre, na maioria das vezes, através do consumo de alimentos ou água contaminados. O presente trabalho teve como objetivos avaliar a ocorrência de E. coli O157:H7 e outras STEC em amostras de couro de animais bovinos e de suas respectivas carcaças, na etapa de pré-evisceração, e meia-carcaças, na etapa de pós-evisceração; identificar os genes que codificam para os fatores de virulência (stx1 , stx2, eaeA e ehxA) dos isolados obtidos; evidenciar cepas de E. coli O157:H7 através da pesquisa do gene uidA; identificar os sorotipos dos isolados; verificar a citotoxicidade dos isolados de STEC em células Vero e avaliar a sensibilidade a diferentes antibióticos. De 198 animais amostrados, sete (3,5%) apresentaram cepas de STEC. Em seis (3%) destes, STEC foi detectada no couro e em um (0,5%) foi isolada de meia-carcaça, não tendo sido detectada em amostras de carcaça. As 23 cepas isoladas do couro apresentaram o perfil stx2, eaeA, uidA e ehxA, podendo ser consideradas E. coli enterohemorrágica (EHEC), e a isolada de meia carcaça apresentou o perfil stx2, uidA e ehxA. Das 24 cepas isoladas, 13 (54,2%) pertenciam ao sorotipo O157:H7. Além deste sorotipo, foram isoladas cepas de outros sorotipos previamente descritos e associados a doenças humanas severas no Brasil e em outros países, como O174:H21, O6:H49, ONT:H7, ONT:H8 e OR:H10. Dos sete animais com cepas positivas para stx2e ehxA, cinco (71,4%) apresentaram cepas com atividade citotóxica em células Vero e um (14,2%) apresentou cepas positivas na avaliação da produção de entero-hemolisina. Com relação ao teste com antibióticos, quatro (16,7%) das 24 cepas testadas apresentaram resistência a um ou mais antibióticos, sendo três (12,5%) a estreptomicina e uma (4,2%) a estreptomicina e ampicilina. Diante destes resultados, pode-se dizer que a produção de entero-hemolisina e a pesquisa dos genes ehxA e uidA não demonstraram ser bons marcadores na pesquisa do sorotipo O157:H7. A presença de cepa de STEC na meia-carcaça alerta para a necessidade de vigilância da presença destes microrganismos, uma vez que eles poderiam contaminar o produto final, colocando em risco a saúde do consumidor.
Escherichia coli is a microorganism present in the intestinal tract of humans and warm-blood animals, being part of the normal microbiota and harmless to the host. However, some strains are able to cause human and animal infections. Shiga toxin-producing E. coli (STEC), regarded as foodborne pathogens, can cause since mild or severe and bloody diarrhea to major complications, such as hemorrhagic colitis (HC), hemolytic-uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP). Cattle are considered the main reservoir of this pathogen and the transmission to humans happens, most of the times, due to the consumption of contaminated food or water. The aim of the present research was to determine the prevalence of E. coli O157:H7 and other STEC on hide samples of beef cattle and on their corresponding carcasses, sampled prior to evisceration, and half-carcasses, sampled after evisceration; identity the genes that code for the virulence factors (stx1, stx2, eaeA e ehxA) of the isolates; detect E. coli O157:H7 strains using the gene uidA as epidemiological marker; identify the serotypes of the STEC isolates; verify the citotoxicity of the isolates in Vero cells and evaluate their resistance to different antibiotics. From 198 animals sampled, seven (3.5%) carried STEC strains. In six (3%) of them, STEC was detected on hide and in one (0.5%) it was isolated from half-carcass. The 23 strains isolated from hide presented the profile stx2, eaeA, uidA e ehxA, and were regarded as enterohemorrhagic Escherichia coli (EHEC), and the one isolated from half-carcass presented the profile stx2, uidA e ehxA. From the 24 isolated strains, 13 (54.2%) belonged to the serotype O157:H7. Besides this serotype, other strains belonging to serotypes that have been previously described and associated with severe human infections in Brazil and other countries, such as O174:H21 , O6:H49, ONT:H7, ONT:H8 and OR:H10, were isolated. From seven animals with strains harboring stx2, and ehxA, five (71.4%) presented verocytotoxigenic strains and one (14.2%) presented enterohemolisin producing strains. Regarding the antibiotics tested, four (16.7%) of the 24 isolated strains were resistant to some antibiotic, being three (12.5%) to streptomycin and one (4.2%) to streptomycin and ampicilin. Faced with these results, the production of enterohemolisin and the search of the genes ehxA and uidA can not be considered good epidemiological markers for the serotype O157:H7. The isolation of STEC strain from the half-carcass alerts for the need of surveillance on the presence of these microorganisms, since they may contaminate the final product, representing a risk to consumers health.

As Escherichia coli produtoras da toxina Shiga (STEC) são importantes patógenos humanos, causando desde diarréias até a síndrome hemolítica urêmica (SHU). Há diversos sorotipos associados a SHU, tais como O157:H7 e O113:H21. No Brasil o sorotipo O113:H21 ainda não aparece associado a SHU, embora seja frequentemente isolado de carcaças e fezes bovinas. Nosso grupo já investigou comparativamente as redes de coexpressão gênica (RCG) de STEC EH41 (associado à SHU) e Ec472/01 (isolado de fezes bovinas). A análise comparativa do perfil transcricional de EH41 e Ec472/01 revelou que somente EH41 expressa um conjunto de genes que inclui o regulador transcricional dicA. A maioria destes genes está situada em um único módulo transcricional e podem estar associados a fatores de virulência. Assim, este trabalho centrou-se numa abordagem de biologia de sistemas, integrando análises genômica e fenotípica da resposta de enterócitos Caco-2 à EH41 e Ec472/01. A análise genômica baseou-se no estudo temporal de RCG para compreender os mecanismos moleculares envolvidos na patogenicidade desses dois isolados. As alterações fenotípicas ocorridas nas células Caco-2 ao longo da exposição a cada um dos isolados de STEC foram visualizadas através de MEV. A análise genômica mostrou que o mecanismo molecular da resposta de Caco-2 durante a interação com EH41 ou Ec472/01 é claramente distinto. Nas redes do grupo Caco-2/EH41 as alterações topológicas incluíram a perda do status scale free e a sua recuperação, com o estabelecimento de uma nova hierarquia de genes na rede. Esses resultados se enquadram no modelo de redes para transição saúde-doença: a nova rede representa a resposta adaptativa da célula ao patógeno, o que não significa um retorno à normalidade. Já no grupo Caco-2/Ec472 as redes, após a perda do status scale free, não recuperam esse status até o final do período estudado, o que sugere um estado de transição mais prolongado para reorganização da hierarquia da rede. Mais ainda, através da caracterização dos módulos transcricionais, foi possível compreender dinamicamente os mecanismos moleculares envolvidos na resposta diferencial de Caco-2 aos dois isolados aqui estudados. STEC EH41 induz rapidamente a resposta inflamatória e apoptótica a partir da primeira hora de interação enterócito-bactéria. Por outro lado, células Caco-2 em contato com Ec472/01 ativam, a partir de uma hora, a fagocitose e, a partir da segunda hora, expressam moduladores da homeostase imune. A análise fenotípica das células Caco-2 mostrou, de forma nítida, uma maior destruição dos microvilos dos enterócitos em contato com EH41 do que com Ec472/01. Integrando os resultados genômicos e fenotípicos pode-se concluir que EH41 induz em Caco-2 - em comparação com Ec472/01 - maiores e mais rápidas alterações na expressão gênica global, além de uma resposta inflamatória e apoptótica excessiva, levando assim a alterações morfológicas mais pronunciadas nas células Caco-2. Em seu conjunto, esses resultados contribuem para uma melhor compreensão dos mecanismos moleculares envolvidos na patogenicidade das STECs associadas à SHU. Assim, as perspectivas de desenvolvimento deste trabalho deverão incluir a investigação de fatores de virulência e vias moleculares envolvidas na indução das respostas imunes que podem conduzir à SHU
Shiga toxin-producing Escherichia coli (STEC) O113:H21 strains are associated with human diarrhea and some of these strains may cause hemolytic uremic syndrome (HUS). In Brazil O113:H21 strains are commonly found in cattle but, so far, were not isolated from HUS patients. Previously, our group conducted comparative gene co-expression network (GCN) analyses of two O113:H21 STEC strains: EH41, isolated from a HUS patient in Australia, and Ec472/01, isolated from bovine feces in Brazil. Differential transcriptome profiles for EH41 and Ec472/01 revealed a gene set exclusively expressed in EH41, which includes the dicA putative virulence factor regulator. GCN analysis showed that this set of genes constitutes an EH41 specific transcriptional module which may be associated to virulence factors. Therefore, in the present work a system biology approach was conducted to investigate the differential Caco-2 response - genomic and phenotypic - to EH41 (Caco-2/EH41) or to Ec472/01 (Caco- 2/Ec472) along enterocyte-bacteria interaction. The genomic analysis was based on temporal GCN data in order to gain a better understanding on the molecular mechanisms underlying the capacity to cause HUS. The phenotypic alterations in Caco-2 during enterocyte-bacteria interaction were assessed by scanning electronic microscopy (SEM). The genomic analysis showed that the molecular mechanism of Caco-2 response to EH41 or to Ec472/01 during enterocyte-bacteria interaction is clearly different. The GCN topological analyses for Caco-2/EH41 group revealed loss of the scale-free status after one hour of interaction, persistence of this condition along the second hour and establishment of a new gene hierarchy thereafter. These events resemble the network mechanism of health-disease transition. The new established network represents an adaptive cell response to the pathogen and not the return to a \"normal\" state. Conversely, the networks for Caco-2/Ec472 group showed a slow and progressive loss of the scale-free status without its restoration at the end of the time interval here studied. Through transcriptional module characterization it was possible to reveal the dynamic of the molecular mechanism involved in the Caco-2 differential responses to the STEC isolates. EH41 induces a rapid inflammatory and apoptotic response just after the first hour of enterocyte-bacteria interaction. Instead, the Caco-2 response to Ec472/01 is characterized by phagocytosis activation at the first hour, followed by the expression of immune response modulators after the second hour. SEM phenotypic analysis of Caco-2 cells along enterocyte-bacteria interaction showed more intense microvilli destruction in cells exposed to EH41, when compared to cells exposed to Ec472/01. The integration of genomic and phenotypic data allowed us to conclude that EH41, comparatively to Ec472/01, induces greater and precocious global gene expression alterations in Caco-2, what is related to excessive inflammatory and apoptotic responses. These responses are associated with the pronounced morphological alterations observed by SEM in Caco-2 cells exposed to EH41. Altogether, these results contribute for a better understanding of the molecular mechanism involved in STEC pathogenicity associated to HUS. Therefore, the future perspectives for the development of the present work should include the investigation of virulence factors and molecular pathways involved in the induction of immune responses leading to HUS

Enterohemorrhagic Escherichia coli (EHEC) colonizes the intestine and produces the phage-encoded Shiga toxin (Stx) which is absorbed systemically and can lead to hemolytic uremic syndrome (HUS) characterized by hemolytic anemia, thrombocytopenia, and renal failure. EHEC, and two related pathogens, Enteropathogenic E. coli (EPEC), and the murine pathogen, Citrobacter rodentium, are attaching and effacing (AE) pathogens that intimately adhere to enterocytes and form actin “pedestals” beneath bound bacteria. The actin pedestal, because it is a unique characteristic of AE pathogens, has been the subject of intense study for over 20 years. Investigations into the mechanism of pedestal formation have revealed that to generate AE lesions, EHEC injects the type III effector, Tir, into mammalian cells, which functions as a receptor for the bacterial adhesin intimin. Tir-intimin binding then triggers a signaling cascade leading to pedestal formation. In spite of these mechanistic insights, the role of intimin and pedestal formation in EHEC disease remains unclear, in part because of the paucity of murine models for EHEC infection. We found that the pathogenic significance of EHEC Stx, Tir, and intimin, as well as the actin assembly triggered by the interaction of the latter two factors, could be productively assessed during murine infection by recombinant C. rodentium expressing EHEC virulence factors. Here we show that EHEC intimin was able to promote colonization of C. rodentium in conventional mice. Additionally, previous in vitro data indicates that intimin may have also function in a Tir-independent manner, and we revealed this function using streptomycin pre-treated mice. Lastly, using a toxigenic C. rodentium strain, we assessed the function of pedestal formation mediated by Tir-intimin interaction and found that Tir-mediated actin polymerization promoted mucosal colonization and a systemic Stx-mediated disease that shares several key features with human HUS.

Enterohemorrhagic E. coli (EHEC) infections are a leading cause of foodborne illness in the United States. Shiga-like toxins are produced that can cause hemorrhagic colitis and can lead to dangerous complications, such as acute kidney injury and hemolytic uremic syndrome (HUS). There are currently no specific treatments for HUS, and therefore more research into EHEC and HUS needs to be done. Our study focuses on Shiga-like toxin induction of endoplasmic reticulum (ER) stress in in vitro and in vivo systems, using human monocyte-like THP-1 cells and a non-human primate model of HUS. We used qPCR to determine the levels of ER stress marker expression induced by both Shiga-like toxin 1 (Stx1) and Shiga-like toxin 2 (Stx2) challenges. We also looked at ER stress marker expression in non-human primates that survived a lethal Stx2 challenge after being given a Stx2 binding tetravalent peptide. We expected to see increased ER stress marker expression in THP-1 cells challenged with both Shiga-like toxins and in animals that received lethal doses of the toxins. Although results were inconclusive for THP-1 cell experiments, our preliminary non-human primate data suggest that the timing of ER stress marker production is important, and Shiga-like toxins may suppress the unfolded protein response (UPR) in some baboon tissues. We also show that the therapeutic peptide TVP may reverse this UPR suppression and relieve ER stress leading to animal survival. Our study, along with the current literature, shows that Shiga-like toxin induced ER stress is a promising area for future study.

Background: Atypical hemolytic uremic syndrome is a rare variant of thrombotic microangiopathy characterized by microangiopathic hemolytic anemia, thrombocytopenia and, occasionally, acute renal failure. This condition is often idiopathic and may also be secondary to other pathologies or due to genetic causes - variants in the complement genes (C3, CFB, CFH, CFI, MCP, THBD). These changes, in most cases, lead to hyperactivation of the pathway complement and consequently result in the formation of microvascular thrombi that affect, mainly, the renal function. However, other possible genetic causes of this pathology have emerged recently, in genes not related to complement, VTN, PLG, among other coagulation genes. Objectives and Methods: In order to deepen the genotype/phenotype correlation in patients with aHUS, we analyzed 45 genes in 50 patients using Sanger sequencing for the VTN gene and a custom next generation sequencing gene panel (NGS) for PLG and other coagulation genes. Results: In total, 53 different rare variants were identified in VTN, PLG, ADAMTS13, ANKRD26, F5, F7, F8, F10, F13A1, FGA, FGB, FGG, GP6, ITGA2B, ITGB3, NBEAL2, PLAT, PROC, PROS1, SERPINC1, SERPINE1, SERPINF2, TUBB1 and VWF. Of which we identified 8 pathogenic variants, 11 probably pathogenic, 14 uncertain significance and 20 probably benign. Conclusions: This study did not imply VTN and PLG in particular as important contributors to aHUS. However, we found variants in several genes that could be a genetic background in these patients, and to have a cumulative effect on both systems - coagulation and complement.
Introdução: A síndrome hemolítica urémica atípica é uma variante rara de microangiopatia trombótica caracterizada por anemia hemolítica microangiopática, trombocitopenia e, por vezes, insuficiência renal aguda. Esta patologia é frequentemente idiopática, podendo também ser secundária a outras patologias ou devida a causas genéticas – variantes nos genes do complemento (C3, CFB, CFH, CFI, MCP, THBD). Estas alterações, na maioria dos casos, originam a hiperativação da via alternativa do complemento e consequentemente resultam em formação de trombos microvasculares que afetam, principalmente, a função renal. No entanto, recentemente surgiram outras possíveis causas genéticas desta patologia, em genes não relacionados com o complemento, VTN, PLG, entre outros genes de coagulação. Objetivos e Métodos: Com o objetivo de analisar a correlação genótipo/fenótipo em pacientes com SHUa, analisámos 45 genes em 50 pacientes, utilizando a sequenciação Sanger para o gene VTN e um painel de genes personalizado de sequenciação de próxima geração (NGS) para o PLG e outros genes de coagulação. Resultados: No total, foram identificadas 53 variantes raras diferentes em VTN, PLG, ADAMTS13, ANKRD26, F5, F7, F8, F10, F13A1, FGA, FGB, FGG, GP6, ITGA2B, ITGB3, NBEAL2, PLAT, PROC, PROS1, SERPINC1, SERPINE1, SERPINF2, TUBB1 e VWF. Das quais, identificámos 8 variantes patogénicas, 11 provavelmente patogénicas, 14 de significado incerto e 20 provavelmente benignas. Conclusões: Este estudo não implicou os genes VTN e PLG, em particular, como importantes contribuintes para SHUa. Contudo, encontrámos variantes em vários genes que poderão constituir uma predisposição genética nestes doentes, e ter um efeito cumulativo em ambos os sistemas - coagulação e complemento.
Mestrado em Bioquímica

Typical Hemolytic Uremic Syndrome (HUS) presents as a complication of infection with Shiga-toxin producing E. coli (STEC). While there are many animal models for infection, few show true signs of HUS. Additionally, these models differ greatly from the clinical presentation that affects small children and elderly populations. Immunohistochemical assays of tissues from a known HUS model may provide insight into molecular changes associated with the condition, particularly as it pertains to clotting factors. In this study, tissue factor (TF) was investigated in the kidneys of non-human primates previously injected with Shiga-Toxin 2 (STX2). The animals’ condition was indicative of HUS through three main clinical signs: thrombocytopenia, hemolytic anemia and decreased kidney function. Tissue factor antigen in the kidneys varies between animals that exhibited HUS when compared to those that had recovered or treated with anti-STX2 antibody. Overall, tissue factor is strongly detected in the renal tubules of those afflicted with HUS; tissue factor was not strongly expressed in the glomerular epithelial space, as it was in recovered, clinically healthy animals. This suggests a change throughout the time course of disease and recovery. Investigating tissue factor’s role, if any, in the pathology of the disease could lead to new therapeutics. Although many types of treatments have been suggested and tried, the primary clinical procedure is to administer fluids and allow symptoms to subside. With increasing knowledge about HUS through studies like these, we can hope to gain insight into potent therapeutics and therefore, save lives associated with typical HUS.

Sub-acute/chronic inflammatory diseases are often associated with altered inflammatory response, leading to increased host vulnerability to secondary inflammatory challenges. In the first study, by employing streptozotocin (STZ)-induced diabetes in mice, we further investigate mechanisms leading to enhanced polymorphonuclear leukocytes (PMN) response under hyperglycemia. We show that existence of a proinflammatory state associated with broad increases of macrophages in various organs plays a dominant role in promoting PMN response in diabetic mice. Studies of PMN infiltration during zymosan-induced peritonitis reveal that hyperglycemia enhances PMN recruitment through increasing F4/80+ macrophages in the peritoneal cavity. Insulin reversal of hyperglycemia reduces peritoneal macrophage numbers and ameliorates PMN infiltration. Significantly increased macrophages are also observed in the liver, kidneys, and intestines under hyperglycemia, and are attributable to exacerbated nephropathy and colitis when respective inflammatory conditions are induced. We also find that significant monocytosis of inflammatory F4/80+Gr-1+ monocytes from the spleen and macrophage proliferation in situ synergistically contribute to the increased macrophage population under hyperglycemia. In conclusion, our results demonstrate that STZ-induced hyperglycemic/diabetic mice develop a systemic proinflammatory state mediated by broad infiltration of macrophages. In the second study, we focus on the identification of the carrier that binds to and delivers Shiga toxin 2(Stx2) to the target organ causing hemolytic uremic syndrome (HUS). By employing a murine HUS model through co-injection of LPS-Stx2, we show that, adoptive transfer of CD11b+ leukocytes, but not CD11b- leukocytes, RBC, platelets or plasma, isolated from mice with HUS induces HUS in healthy recipients. Interestingly, we find that LPS priming of mice significantly promotes CD11b+ leukocytes binding to Stx2. Compared to CD11b+ leukocytes from mice without LPS priming, CD11b+ leukocytes isolated from mice after LPS priming demonstrate higher frequencies of toxin binding and augmented potency to induce HUS. In sum, our results demonstrate peripheral CD11b+ myeloid leukocytes act as effective Stx2 carriers that deliver toxin to kidneys causing HUS and that LPS-induced inflammation enhances the carrier capacity and aggravates HUS.

Enterohemorrhagic E. coli (EHEC) infection is a leading cause of acute kidney failure in otherwise healthy children, and a leading cause of foodborne illness with an outsized economic impact from outbreaks. EHEC secrete two Shiga-like toxins (Stx1 and Stx2) which are AB5 holotoxins that inhibit protein synthesis in cells expressing the toxin receptor Gb3. Infection with EHEC typically begins with a diarrheal prodrome that can progress in 5-15% of cases to hemolytic uremic syndrome (HUS), a clinical diagnosis characterized by thrombocytopenia, hemolytic anemia, and thrombotic microangiopathy. Historically, strains of EHEC expressing Stx2 have been associated with more severe disease. We hypothesized that tissue injury due to the toxins leads to the release of damage-associated molecular patterns (DAMPs), which act through inflammatory receptors to promote the endothelial dysfunction that drives this disease alongside the inciting Shiga toxins. Here we demonstrate that two well-characterized DAMPs, extracellular histones and HMGB1, are produced in two different mouse models when Stx2 is present; one model represents challenge with the toxin alone, and the second model introduces toxin through secretion with a lysogenized bacterium, C. rodentium, mimicking EHEC colonization. We investigate whether Stx1, Stx2, or histones affect the endothelial expression of well-characterized members of the protein C pathway, namely the endothelial protein C receptor (ECPR), protease-activated receptor 1 (PAR1), and thrombomodulin (TM), on human aortic (HAEC) and human renal glomerular endothelial cells (HRGEC). We show that Stx and/or histones reduce endothelial expression of these anti-coagulant molecules and histones dramatically increase expression of pro-thrombotic PAR-1. These changes lead to physiologically important decreases in activated protein C (APC), a critical anti-coagulant and cytoprotective molecule. Finally, we demonstrate that histones exacerbate thrombin's barrier-disruptive effects on the endothelium, and prevent APC's protective effects. These data provide novel mechanistic insight into the endothelial dysfunction that characterizes HUS and also provide a new perspective on systemic consequences of the bacterial Shiga toxins that might drive organ injury in susceptible patients.

Since Shiga-toxigenic Escherichia coli (STEC) strains are not considered to be enteroinvasive, the mechanism(s) by which Shiga toxin (Stx) gains access to the circulation and to target tissues expressing its target receptor Gb3 is crucial to the disease process. There is increasing evidence that by facilitating translocation of Stx across the intestinal epithelium and by transporting bound toxin to remote sites such as the renal endothelium, polymorphonuclear leucocytes (PMNs) play a key role in the pathogenesis of serious STEC disease. Plasma levels of PMN-attracting CXC chemokines such as IL-8 also appear to correlate in humans with the severity of disease. Thus, the capacity of STEC strains to elicit CXC chemokine responses in intestinal epithelial cells may be a crucial step in pathogenesis. In order to determine which STEC factor(s) are responsible for the induction of CXC chemokine responses by intestinal epithelial (HCT-8) cells, a real-time reverse transcription PCR assay was developed to quantitatively measure relative expression of chemokine mRNA for IL-8, ENA-78, GCP-2, MGSA, MIP-2α and MIP-2β. Similarly, a commercially available sandwich ELISA was used to measure levels of IL-8 protein secreted by HCT-8 cells in response to infection with STEC. When HCT-8 cells were infected with the wellcharacterised locus of enterocyte effacement (LEE)-negative O113:H21 strain 98NK2 or the LEE-positive STEC strain EDL933, there were significant differences in the levels of chemokine mRNA and IL-8 protein expression. In particular, the LEE-negative strain 98NK2 induced significantly higher and earlier levels of chemokine mRNAs, including IL-8, MIP-2α and MIP-2β at 1 and 4 h, and ENA-78 at 4 h. However, EDL933 elicited no significant upregulation of any of the chemokine mRNAs at 1 h, and only modest increases in IL-8, MIP-2α and MIP-2β by 4 h, post-infection. These results were confirmed by IL-8 ELISA which showed that 98NK2 elicited significant levels of IL-8 protein by 2 h post-infection, and remained high until 4 h post-infection. In comparison, EDL933 did not elicit significant IL-8 induction over that of control cells, even at 4 h post-infection. When a range of STEC isolates from clinical samples were tested for their capacity to induce chemokine production in HCT-8 cells, highly significant differences were observed between the strains. Infection of HCT-8 cells with a range of LEE-negative STEC strains isolated from patients with severe STEC disease resulted in significantly higher and earlier upregulation of IL-8 and MIP-2α mRNA than that elicited by several LEE-positive STEC strains. Similarly, levels of IL-8 protein in LEE-negative STEC-infected HCT-8 culture supernatants were significantly higher than in LEE-positive STEC-infected culture supernatants. Only one LEE-positive strain, an O26 strain 95ZG1, was capable of inducing chemokine responses comparable to that induced by infection with the LEE-negative STEC strains. These results were also shown not to be attributable to differences in the adherence, initial doses or growth of the strains during the assay, or to a loss of viability of the HCT-8 cells. These results, therefore, suggest that there may be interesting differences in the ability of STEC strains to induce chemokine production in intestinal epithelial cells. The factor(s) that contribute to chemokine induction by epithelial cells in response to STEC were then examined. The difference in responses could not be attributed to the expression or non-expression of LEE genes, the presence or absence of an STEC megaplasmid or to differences in O serogroup. Although purified Stx1 and Stx2 were able to induce IL-8 and MIP-2α mRNA, and IL-8 protein, the levels of chemokine induction in response to wild-type STEC did not correlate with the type or amount of Stx produced by these strains in vitro. Similarly, deletion of the single stx2 gene from 98NK2 had no significant effect on chemokine induction compared to wild-type 98NK2-infected HCT-8 cells. Interestingly, several of the LEE-negative STEC strains eliciting the strongest chemokine responses belonged to flagellar serotype H21. Incubation of HCT-8 cells with purified H21 flagella elicited IL-8 and MIP-2α mRNA responses similar to those seen in the presence of the most potent LEE-negative STEC strains. Deletion of the fliC gene largely abolished the capacity of 98NK2 to elicit IL-8 and MIP-2α mRNA and IL-8 protein responses in HCT-8 cells. Similarly, deletion of both stx2 and fliC from 98NK2 elicited a response similar to that observed with deletion of fliC alone. Flagella were then purified from the high chemokine-inducing STEC strains 95HE4 (O91:H7) and 95ZG1 (O26:H11). Purified H7 and H11 flagella were similarly able to induce both IL-8 and MIP-2α mRNA, and IL-8 protein, in HCT-8 cells at levels similar to their respective wild-type strains. Deletion of fliC from two other STEC strains, 97MW1 (O113:H21) and 86-24 (O157:H7), confirmed that flagellin was responsible for the majority of chemokine responses in these wild-type strains. However, an inability of EDL933 to induce these responses was unexpected and later found to be due to a lack of expression of H7 flagella by this strain. Purified H21 FliC (His6-FliC) alone was able to induce chemokine production (including IL-8, MIP-2α and MIP-2β at 1 and 4 h, and ENA-78 at 4 h) by HCT-8 cells at similar levels to that observed for 98NK2. Taken together, these data suggest that although Stx is capable of inducing CXC chemokine responses, the elevated responses observed in cells infected with certain STEC strains are largely attributable to the production of flagellin. Purified His6-H21 flagellin was also able to induce p38 MAPK activation in vitro and IL-8 and MIP-2α mRNA were superinduced in the presence of both Stx2 and H21 flagellin. Blockade of the p38 pathway with SB203580 resulted in a down-regulation of IL-8 protein levels (by up to 61%) in response to H21 flagellin, but not IL-8 mRNA, suggesting that this inhibition may occur post-transcriptionally. Blocking the ERK and JNK pathways similarly decreased IL-8 secretion in response to H21 flagellin, suggesting that all three MAPK pathways are involved in this response. Indeed, concurrent inhibition of all three pathways resulted in virtually complete inhibition of IL-8 protein production (98%). Transfected HeLa and MDCK cells stably expressing TLR5 activated p38 in the presence of purified H21 flagellin, whereas dominant-negative (DN) TLR5-expressing cells did not, supporting previous studies that show that flagellin acts via TLR5. These data suggest that TLR5 and the p38, ERK and JNK MAPK pathways all play an important role in the response of intestinal epithelial cells to H21 flagellin from STEC, and that the combined effects of Stx and flagellin on host intestinal epithelial cells may result in an augmented inflammatory response. A role for flagellin in virulence was then investigated. BALB/c mice were orally inoculated with wild-type 98NK2 or 98NK2ΔfliC. Of the 16 mice challenged with the wildtype strain 98NK2, 9 (56%) died during the experiment (median survival time 7.6 days). However, only 3 of 16 mice (19%) challenged with 98NK2ΔfliC died (median survival time > 14 days). The difference in survival rate was statistically significant. No significant differences in the level of intestinal colonisation of 98NK2 or 98NK2ΔfliC were observed. Thus, flagellin directly contributes to the virulence of STEC in streptomycin-treated mice. Since the streptomycin-treated mouse is a model for systemic Stx-mediated pathology, these results suggest that the pro-inflammatory effects of flagellin play an important role in the pathogenesis of Stx-mediated STEC disease in vivo.
Thesis (Ph.D.)--School of Molecular and Biomedical Science, 2004.

BACKGROUND: Shiga toxin (Stx)-producing enterohemorrhagic Escherichia coli (EHEC) are emerging food- and water- borne pathogens and a leading cause of acute renal failure in otherwise healthy children. Ribotoxic Shiga toxins are the primary virulence factors and are responsible for the potentially lethal EHEC complication of hemolytic uremic syndrome (HUS). HUS, defined clinically by microangiopathic hemolytic anemia, thrombocytopenia and thrombotic microangiopathy which contribute to acute kidney injury or renal failure, is associated with significant patient morbidity. No pathogen- or toxin- specific therapeutic exists, and antibiotic use is contraindicated. Understanding the molecular mechanisms of Stx toxicity could lead to the development of Stx specific therapies. HYPOTHESIS: Experimental evidence suggests a role for leukocytes in systemic Stx2 trafficking and in Stx2 mediated kidney pathology. Cell stress responses, such as the ER stress response and ribosomal stress response, are hypothesized to induce apoptosis, and ultimately cell death, contributing to kidney injury; however these processes have only been described in vitro. If leukocyte and kidney cell stress responses are playing significant roles in in vivo Stx2 kidney injury, then down-regulation of these processes may provide therapeutic benefit. RESULTS: Mice injected with Stx2 or infected with Stx2-producing bacteria developed lethal kidney injury as judged by biomarkers and histopathology. Experimentally induced leukopenia did not alter kidney injury in either model, but did cause striking increases in the intestinal bacterial colonization which was dependent on the presence of Stx2. No Stx binding capacity was observed for either murine or human leukocytes ex vivo. Transcriptional evidence of kidney ER stress and apoptotic biomarkers were observed in both models of Stx2-mediated kidney injury, but down-regulation of these processes did not yield therapeutic benefit. CONCLUSIONS: Contrary to the current disease paradigm, no major role for leukocytes in systemic Stx2 trafficking or kidney injury was observed in vivo, but a novel role for host immune responses to Stx2 in the control of intestinal colonization by Stx2-producing bacteria was identified. Cell stress and apoptosis is induced by Stx2 in vivo but prevention of these is not sufficient to appreciably alter organ injury or survival in the murine models.

Normal endothelial cell function is controlled in part by a tightly regulated balance between angiopoietin-1 and -2 (Ang-1 and Ang-2). Angiopoietin dysregulation (decreased Ang-1 and increased Ang-2) leads to an activated endothelium that is contractile, adhesive, and prothrombotic. Since an activated endothelial phenotype is seen in invasive group A streptococcal infection, E. coli O157:H7-induced hemolytic-uremic syndrome (HUS), and sepsis, we hypothesized that angiopoietin dysregulation might also be present in these syndromes, and to that end, measured angiopoietin levels in several well-characterized patient cohorts. Decreased Ang-1 and/or increased Ang-2 were found in all three syndromes, and were predictive of clinical outcome in HUS and sepsis. The prognostic utility of Ang-2 in sepsis was further enhanced by combination with biomarkers of inflammation. Angiopoietin dysregulation may therefore represent a shared final common pathway to endothelial activation as well as a clinically useful prognostic biomarker in streptococcal toxic shock, HUS, and sepsis.