Localization of Shiga toxins of enterohaemorrhagic Escherichia coli in kidneys of paediatric and geriatric patients with fatal haemolytic uraemic syndrome

Pharmacological Management of Atypical Hemolytic Uremic Syndrome in Pediatric Patients: Current and Future

Atypical hemolytic uremic syndrome is a thrombotic microangiopathy characterized by hemolysis, thrombocytopenia, and acute kidney injury, usually caused by alternative complement system overactivation due to pathogenic genetic variants or antibodies to components or regulatory factors in this pathway. Previously, a lack of effective treatment for this condition was associated with mortality, end-stage kidney disease, and the risk of disease recurrence after kidney transplantation. Plasma therapy has been used for atypical hemolytic uremic syndrome treatment with inconsistent results. Complement-blocking treatment changed the outcome and prognosis of patients with atypical hemolytic uremic syndrome. Early administration of eculizumab, a monoclonal C5 antibody, leads to improvements in hematologic, kidney, and systemic manifestations in patients with atypical hemolytic uremic syndrome, even with apparent dialysis dependency. Pre- and post-transplant use of eculizumab is effective in the prevention of atypical hemolytic uremic syndrome recurrence. Evidence on eculizumab use in secondary hemolytic uremic syndrome cases is controversial. Recent data favor the restrictive use of eculizumab in carefully selected atypical hemolytic uremic syndrome cases, but close monitoring for relapse after drug discontinuation is emphasized. Prophylaxis for meningococcal infection is important. The long-acting C5 monoclonal antibody ravulizumab is now approved for atypical hemolytic uremic syndrome treatment, enabling a reduction in the dosing frequency and improving the quality of life in patients with atypical hemolytic uremic syndrome. New strategies for additional and novel complement blockage medications in atypical hemolytic uremic syndrome are under investigation.

The association between E. coli exceedances in drinking water supplies and healthcare utilisation of older people

Evidence concerning the effects of indicators of waterborne pathogens on healthcare systems is of importance for policymaking, future infrastructure considerations and healthcare planning. This paper examines the association between the detection of E. coli in water tests associated with drinking water supplies and the use of healthcare services by older people in Ireland. Uniquely, three sources of data are linked to conduct the analysis. Administrative records of E. coli exceedances recorded from routine water quality tests carried out by Ireland’s Environmental Protection Agency are first linked to maps of water systems infrastructure in Ireland. Then, residential addresses of participants of The Irish Longitudinal Study of Ageing (TILDA), a nationally representative survey of over 50-year-olds in Ireland, are linked to the water systems dataset which has the associated water quality monitoring information. Multivariate regression analysis estimates a greater incident rate ratio (IRR) of General Practitioner (GP) visits in the previous year where E. coli is detected in the water supply associated with an older person’s residence (Incidence Rate Ratio (IRR) 1.118; [95% Confidence interval (CI): 1.019–1.227]), controlling for demographic and socio-economic factors, health insurance coverage, health, and health behaviours. Where E. coli is detected in water, a higher IRR is also estimated for visits to an Emergency Department (IRR: 1.292; [95% CI: 0.995–1.679]) and nights spent in hospital (IRR: 1.351 [95% CI: 1.004–1.818]).

Spatiotemporal Dynamics of Sporadic Shiga Toxin-Producing Escherichia coli Enteritis, Ireland, 2013-2017

The Republic of Ireland regularly reports the highest annual crude incidence rates of Shiga toxin–producing Escherichia coli (STEC) enteritis in the European Union, ≈10 times the average. We investigated spatiotemporal patterns of STEC enteritis in Ireland using multiple statistical tools. Overall, we georeferenced 2,755 cases of infection during January 2013–December 2017; we found >1 case notified in 2,340 (12.6%) of 18,641 Census Small Areas. We encountered the highest case numbers in children 0–5 years of age (n = 1,101, 39.6%) and associated with serogroups O26 (n = 800, 29%) and O157 (n = 638, 23.2%). Overall, we identified 17 space-time clusters, ranging from 2 (2014) to 5 (2017) clusters of sporadic infection per year; we detected recurrent clustering in 3 distinct geographic regions in the west and mid-west, all of which are primarily rural. Our findings can be used to enable targeted epidemiologic intervention and surveillance.

Postdiarrheal hemolytic uremic syndrome in Egyptian children: An 11-year single-center experience

Hemolytic-uremic syndrome (HUS) is a leading cause of childhood acute kidney injury (AKI) worldwide, with its postdiarrheal (D+HUS) form being the most common. Scarce data are available regarding D+HUS epidemiology from developing countries. This study aims to reveal the characterization of D+ HUS in Egyptian children. This is a retrospective study of all children with D+HUS admitted to a tertiary pediatric hospital in Egypt between 2007 and 2017. The study included epidemiological, clinical and laboratory data; management details; and outcomes. A cohort of 132 children aged 4months to 12 years was analyzed. Yearly incidence peaked in 2017, and spring showed the highest peak. All cases had a diarrheal prodrome that was bloody in 83% of the cases. Edema and decreased urine output were the most frequent presentations (50.3% and 42.4%, respectively). Escherichia coli was detected in 56 cases. Dialysis was performed in 102 cases. Eight patients died during acute illness, while five patients experienced long-term sequels. Lactate dehydrogenase (LDH) positively correlated with serum creatinine and negatively correlated with reticulocytic count. Univariate analysis showed that longer anuria duration, short duration between diarrheal illness and development of AKI (P = 0.001), leukocyte count above 20 × 10⁹ cells/L (P ≤ 0.001), platelet count below 30 × 10⁹ cells/L (P = 0.02), high LDH levels (P = 0.02) and hematocrit above 30% (P = 0.0001), need for dialysis (P = 0.03), and neurological involvement (P ≤ 0.001) were associated with unfavorable outcomes. This is the first report with a detailed insight into the epidemiology of D+HUS in Egyptian children. The incidence of D+HUS is increasing in our country due to increased awareness of the disease and the poor public health measures. Anuria duration, leukocyte count, and neurological involvement are predictors of poor outcome in the current work, and LDH is introduced as a marker of disease severity.

Molecular Biology of Escherichia Coli Shiga Toxins' Effects on Mammalian Cells

Shiga toxins (Stxs), syn. Vero(cyto)toxins, are potent bacterial exotoxins and the principal virulence factor of enterohemorrhagic Escherichia coli (EHEC), a subset of Shiga toxin-producing E. coli (STEC). EHEC strains, e.g., strains of serovars O157:H7 and O104:H4, may cause individual cases as well as large outbreaks of life-threatening diseases in humans. Stxs primarily exert a ribotoxic activity in the eukaryotic target cells of the mammalian host resulting in rapid protein synthesis inhibition and cell death. Damage of endothelial cells in the kidneys and the central nervous system by Stxs is central in the pathogenesis of hemolytic uremic syndrome (HUS) in humans and edema disease in pigs. Probably even more important, the toxins also are capable of modulating a plethora of essential cellular functions, which eventually disturb intercellular communication. The review aims at providing a comprehensive overview of the current knowledge of the time course and the consecutive steps of Stx/cell interactions at the molecular level. Intervention measures deduced from an in-depth understanding of this molecular interplay may foster our basic understanding of cellular biology and microbial pathogenesis and pave the way to the creation of host-directed active compounds to mitigate the pathological conditions of STEC infections in the mammalian body.

Treatment and management of children with haemolytic uraemic syndrome

Haemolytic uraemic syndrome (HUS), comprising microangiopathic haemolytic anaemia, thrombocytopaenia and acute kidney injury, remains the leading cause of paediatric intrinsic acute kidney injury, with peak incidence in children aged under 5 years. HUS most commonly occurs following infection with Shiga toxin-producing Escherichia coli (STEC-HUS). Additionally, HUS can occur as a result of inherited or acquired dysregulation of the alternative complement cascade (atypical HUS or aHUS) and in the setting of invasive pneumococcal infection. The field of HUS has been transformed by the discovery of the central role of complement in aHUS and the dawn of therapeutic complement inhibition. Herein, we address these three major forms of HUS in children, review the latest evidence for their treatment and discuss the management of STEC infection from presentation with bloody diarrhoea, through to development of fulminant HUS.

Immunogenicity of the nanovaccine containing intimin recombinant protein in the BALB/c mice

Purpose

Escherichia coli O157:H7 is one of the most important pathogens which create hemorrhagic colitis and hemolytic uremic syndrome in human. It is one of the most prevalent causes of diarrhea leading to death of many people every year. The first diagnosed gene in the locus of enterocyte effacement pathogenicity island is eae gene. The product of this gene is a binding protein called intimin belonging to the group of external membrane proteins regarded as a good stimulants of the immune system. Chitosan with its lipophilic property is an environmentally friendly agent able to return to the environment.

Materials and Methods

Intimin recombinant protein was expressed in pET28a vector with eae gene and purification was performed using Ni-NTA and finally the recombinant protein was approved through western blotting. This protein was encapsulated using chitosan nanoparticles and the size of nanoparticles was measured by Zetasizer. Intimin encapsulated was prescribed for three sessions among three groups of oral, injection, and oral-injection using Chitosan nanoparticles. Challenge was performed for all three groups with 10⁸E. coli O157:H7 bacteria.

Results

Intimin produced by chitosan nanoparticles improves immunological responses through the adjuvant nature of chitosan nanoparticles. Chitosan may be used as a carrier for transportation of the prescribed vaccine. Among the mice, encapsulated intimin could be able to provide suitable titers of IgG and IgA by the aid of chitosan nanoparticles. Results of mice challenge showed that decreased the bacterial shedding significantly.

Conclusion

Results showed that the chitosan nanovaccine with intimin protein may be used as a suitable candidate vaccine against E. coli O157:H7.

Haemolytic uraemic syndrome

Haemolytic uraemic syndrome (HUS) is defined by the simultaneous occurrence of nonimmune haemolytic anaemia, thrombocytopenia and acute renal failure. This leads to the pathological lesion termed thrombotic microangiopathy, which mainly affects the kidney, as well as other organs. HUS is associated with endothelial cell injury and platelet activation, although the underlying cause may differ. Most cases of HUS are associated with gastrointestinal infection with Shiga toxin-producing enterohaemorrhagic Escherichia coli (EHEC) strains. Atypical HUS (aHUS) is associated with complement dysregulation due to mutations or autoantibodies. In this review, we will describe the causes of HUS. In addition, we will review the clinical, pathological, haematological and biochemical features, epidemiology and pathogenetic mechanisms as well as the biochemical, microbiological, immunological and genetic investigations leading to diagnosis. Understanding the underlying mechanisms of the different subtypes of HUS enables tailoring of appropriate treatment and management. To date, there is no specific treatment for EHEC-associated HUS but patients benefit from supportive care, whereas patients with aHUS are effectively treated with anti-C5 antibody to prevent recurrences, both before and after renal transplantation.

Increased EHEC survival and virulence gene expression indicate an enhanced pathogenicity upon simulated pediatric gastrointestinal conditions

BACKGROUND

Enterohemorrhagic Escherichia coli (EHEC) are major foodborne pathogens that constitute a serious public health threat, mainly in young children. Shiga toxins (Stx) are the main virulence determinants of EHEC pathogenesis but adhesins like intimin (eae) and Long polar fimbriae (Lpf) also contribute to infection. The TNO GastroIntestinal Model (TIM) was used for a comparative study of EHEC O157:H7 survival and virulence under adult and child digestive conditions.

METHODS

Survival kinetics in the in vitro digestive tract were determined by plating while bacterial viability was assessed by flow cytometry analysis. Expression of stx, eae, and lpf genes was followed by reverse transcriptase-quantitative PCR (RT-qPCR) and Stx production was measured by ELISA (enzyme-linked immunosorbent assay).

RESULTS

Upon gastrointestinal passage, a higher amount of viable cells was found in the simulated ileal effluents of children compared to that of adults (with 34 and 6% of viable cells, respectively). Expression levels of virulence genes were up to 125-fold higher in children. Stx was detected only in child ileal effluents.

CONCLUSION

Differences in digestive physicochemical parameters may partially explain why children are more susceptible to EHEC infection than adults. Such data are essential for a full understanding of EHEC pathogenesis and would help in designing novel therapeutic approaches.

Animal Models of Enterohemorrhagic Escherichia coli Infection

The first major outbreaks caused by enterohemorrhagic Escherichia coli (EHEC) raised public and medical awareness of the risks associated with acquiring this potentially deadly infection. The widespread presence of these organisms in the environment, the severity of the clinical sequelae, and the lack of treatment options and effective preventive measures demand that we obtain a better understanding of how this group of organisms cause disease. Animal models allow study of the processes and factors that contribute to disease and, as such, form a valuable tool in the repertoire of infectious disease researchers. Yet despite more than 30 years of research, it seems that no single model host reproduces the full spectrum of clinical disease induced by EHEC in humans. In the first part of this review, a synopsis of what is known about EHEC infections is garnered from human outbreaks and biopsy specimens. The main features and limitations of EHEC infection models that are based on the three most commonly used species (pigs, rabbits, and mice) are described within a historical context. Recent advances are highlighted, and a brief overview of models based on other species is given. Finally, the impact of the host on moderating EHEC infection is considered in light of growing evidence for the need to consider the biology and virulence strategies of EHEC in the context of its niche within the intestine.

Enterohemorrhagic Escherichia coli Pathogenesis and the Host Response

Enterohemorrhagic Escherichia coli (EHEC) is a highly pathogenic bacterial strain capable of causing watery or bloody diarrhea, the latter termed hemorrhagic colitis, and hemolytic-uremic syndrome (HUS). HUS is defined as the simultaneous development of non-immune hemolytic anemia, thrombocytopenia, and acute renal failure. The mechanism by which EHEC bacteria colonize and cause severe colitis, followed by renal failure with activated blood cells, as well as neurological symptoms, involves the interaction of bacterial virulence factors and specific pathogen-associated molecular patterns with host cells as well as the host response. The innate immune host response comprises the release of antimicrobial peptides as well as cytokines and chemokines in addition to activation and/or injury to leukocytes, platelets, and erythrocytes and activation of the complement system. Some of the bacterial interactions with the host may be protective in nature, but, when excessive, contribute to extensive tissue injury, inflammation, and thrombosis, effects that may worsen the clinical outcome of EHEC infection. This article describes aspects of the host response occurring during EHEC infection and their effects on specific organs.

Complement Interactions with Blood Cells, Endothelial Cells and Microvesicles in Thrombotic and Inflammatory Conditions

The complement system is activated in the vasculature during thrombotic and inflammatory conditions. Activation may be associated with chronic inflammation on the endothelial surface leading to complement deposition. Complement mutations allow uninhibited complement activation to occur on platelets, neutrophils, monocytes, and aggregates thereof, as well as on red blood cells and endothelial cells. Furthermore, complement activation on the cells leads to the shedding of cell derived-microvesicles that may express complement and tissue factor thus promoting inflammation and thrombosis. Complement deposition on red blood cells triggers hemolysis and the release of red blood cell-derived microvesicles that are prothrombotic. Microvesicles are small membrane vesicles ranging from 0.1 to 1 μm, shed by cells during activation, injury and/or apoptosis that express components of the parent cell. Microvesicles are released during inflammatory and vascular conditions. The repertoire of inflammatory markers on endothelial cell-derived microvesicles shed during inflammation is large and includes complement. These circulating microvesicles may reflect the ongoing inflammatory process but may also contribute to its propagation. This overview will describe complement activation on blood and endothelial cells and the release of microvesicles from these cells during hemolytic uremic syndrome, thrombotic thrombocytopenic purpura and vasculitis, clinical conditions associated with enhanced thrombosis and inflammation.

Risk of haemolytic uraemic syndrome caused by shiga-toxin-producing Escherichia coli infection in adult women in Japan

Shiga-toxin-producing Escherichia coli (STEC) infections usually cause haemolytic uraemic syndrome (HUS) equally in male and female children. This study investigated the localization of globotriaosylceramide (Gb3) in human brain and kidney tissues removed from forensic autopsy cases in Japan. A fatal case was used as a positive control in an outbreak of diarrhoeal disease caused by STEC O157:H7 in a kindergarten in Urawa in 1990. Positive immunodetection of Gb3 was significantly more frequent in female than in male distal and collecting renal tubules. To correlate this finding with a clinical outcome, a retrospective analysis of the predictors of renal failure in the 162 patients of two outbreaks in Japan was performed: one in Tochigi in 2002 and the other in Kagawa Prefecture in 2005. This study concludes renal failure, including HUS, was significantly associated with female sex, and the odds ratio was 4·06 compared to male patients in the two outbreaks. From 2006 to 2009 in Japan, the risk factor of HUS associated with STEC infection was analysed. The number of males and females and the proportion of females who developed HUS were calculated by age and year from 2006 to 2009. In 2006, 2007 and 2009 in adults aged >20 years, adult women were significantly more at risk of developing HUS in Japan.

Management of hemolytic uremic syndrome

Hemolytic uremic syndrome (HUS) is a disease characterized by hemolysis, thrombocytopenia, and acute kidney injury, although other organs may be involved. Most cases are due to infection with Shiga toxin-producing Escherichia coli (STEC). Early identification and initiation of best supportive care, with microbiological input to identify the pathogen, result in a favorable outcome in most patients. The remaining 10% of HUS cases are classed together as atypical HUS and have a diverse etiology. The majority are due to inherited or acquired abnormalities that lead to a failure to control complement activation. Atypical HUS occurring in other situations (for example, related to pregnancy or kidney transplantation) may also involve excessive complement activation. Plasma therapies can reverse defective complement control, and it is now possible to specifically target complement activation. This has led to improved outcomes in patients with atypical forms of HUS. We will review our current understanding of the pathogenesis of HUS and how this has led to advances in patient care.

Shiga Toxin (Stx) Classification, Structure, and Function

Shiga toxin (Stx) is one of the most potent bacterial toxins known. Stx is found in Shigella dysenteriae 1 and in some serogroups of Escherichia coli (called Stx1 in E. coli). In addition to or instead of Stx1, some E. coli strains produce a second type of Stx, Stx2, that has the same mode of action as Stx/Stx1 but is antigenically distinct. Because subtypes of each toxin have been identified, the prototype toxin for each group is now designated Stx1a or Stx2a. The Stxs consist of two major subunits, an A subunit that joins noncovalently to a pentamer of five identical B subunits. The A subunit of the toxin injures the eukaryotic ribosome and halts protein synthesis in target cells. The function of the B pentamer is to bind to the cellular receptor, globotriaosylceramide, Gb3, found primarily on endothelial cells. The Stxs traffic in a retrograde manner within the cell, such that the A subunit of the toxin reaches the cytosol only after the toxin moves from the endosome to the Golgi and then to the endoplasmic reticulum. In humans infected with Stx-producing E. coli, the most serious manifestation of the disease, hemolytic-uremic syndrome, is more often associated with strains that produce Stx2a rather than Stx1a, and that relative toxicity is replicated in mice and baboons. Stx1a and Stx2a also exhibit differences in cytotoxicity to various cell types, bind dissimilarly to receptor analogs or mimics, induce differential chemokine responses, and have several distinctive structural characteristics.

Direct acute tubular damage contributes to Shigatoxin-mediated kidney failure

The pathogenesis and therapy of Shigatoxin 2 (Stx2)-mediated kidney failure remain controversial. Our aim was to test whether, during an infection with Stx2-producing E. coli (STEC), Stx2 exerts direct effects on renal tubular epithelium and thereby possibly contributes to acute renal failure. Mice represent a suitable model because they, like humans, express the Stx2-receptor Gb3 in the tubular epithelium but, in contrast to humans, not in glomerular endothelia, and are thus free of glomerular thrombotic microangiopathy (TMA). In wild-type mice, Stx2 caused acute tubular dysfunction with consequent electrolyte disturbance, which was most likely the cause of death. Tubule-specific depletion of Gb3 protected the mice from acute renal failure. In vitro, Stx2 induced secretion of proinflammatory cytokines and apoptosis in human tubular epithelial cells, thus implicating a direct effect of Stx2 on the tubular epithelium. To correlate these results to human disease, kidney biopsies and outcome were analysed in patients with Stx2-associated kidney failure (n = 11, aged 22–44 years). The majority of kidney biopsies showed different stages of an ongoing TMA; however, no glomerular complement activation could be demonstrated. All biopsies, including those without TMA, showed severe acute tubular damage. Due to these findings, patients were treated with supportive therapy without complement-inhibiting antibodies (eculizumab) or immunoadsorption. Despite the severity of the initial disease [creatinine 6.34 (1.31–17.60) mg/dl, lactate dehydrogenase 1944 (753–2792) U/l, platelets 33 (19–124)/nl and haemoglobin 6.2 (5.2–7.8) g/dl; median (range)], all patients were discharged after 33 (range 19–43) days with no neurological symptoms and no dialysis requirement [creatinine 1.39 (range 0.84–2.86) mg/dl]. The creatinine decreased further to 0.90 (range 0.66–1.27) mg/dl after 24 months. Based on these data, one may surmise that acute tubular damage represents a separate pathophysiological mechanism, importantly contributing to Stx2-mediated acute kidney failure. Specifically in young adults, an excellent outcome can be achieved by supportive therapy only. © 2014 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Protection of human podocytes from shiga toxin 2-induced phosphorylation of mitogen-activated protein kinases and apoptosis by human serum amyloid P component

Hemolytic uremic syndrome (HUS) is mainly induced by Shiga toxin 2 (Stx2)-producing Escherichia coli. Proteinuria can occur in the early phase of the disease, and its persistence determines the renal prognosis. Stx2 may injure podocytes and induce proteinuria. Human serum amyloid P component (SAP), a member of the pentraxin family, has been shown to protect against Stx2-induced lethality in mice in vivo, presumably by specific binding to the toxin. We therefore tested the hypothesis that SAP can protect against Stx2-induced injury of human podocytes. To elucidate the mechanisms underlying podocyte injury in HUS-associated proteinuria, we assessed Stx2-induced activation of mitogen-activated protein kinases (MAPKs) and apoptosis in immortalized human podocytes and evaluated the impact of SAP on Stx2-induced damage. Human podocytes express Stx2-binding globotriaosylceramide 3. Stx2 applied to cultured podocytes was internalized and then activated p38α MAPK and c-Jun N-terminal kinase (JNK), important signaling steps in cell differentiation and apoptosis. Stx2 also activated caspase 3, resulting in an increased level of apoptosis. Coincubation of podocytes with SAP and Stx2 mitigated the effects of Stx2 and induced upregulation of antiapoptotic Bcl2. These data suggest that podocytes are a target of Stx2 and that SAP protects podocytes against Stx2-induced injury. SAP may therefore be a useful therapeutic option.

Hemolytic uremic syndrome

Hemolytic uremic syndrome (HUS) is a thrombotic microangiopathy defined by thrombocytopenia, nonimmune microangiopathic hemolytic anemia, and acute renal failure. The most frequent form is associated with infections by Shiga-like toxin-producing bacteria (STEC-HUS). Rarer cases are triggered by neuraminidase-producing Streptococcus pneumoniae (pneumococcal-HUS). The designation of aHUS is used to refer to those cases in which an infection by Shiga-like toxin-producing bacteria or S. pneumoniae can be excluded. Studies performed in the last two decades have documented that hyperactivation of the complement system is the pathogenetic effector mechanism leading to the endothelial damage and the microvascular thrombosis in aHUS. Recent data suggested the involvement of the complement system in the pathogenesis of STEC-HUS and pneumococcal-HUS as well. Clinical signs and symptoms may overlap among the different forms of HUS; however, pneumococcal-HUS and aHUS have a worse prognosis compared with STEC-HUS. Early diagnosis and identification of underlying pathogenetic mechanism allows instating specific support measures and therapies. In clinical trials in patients with aHUS, complement inhibition by eculizumab administration leads to a rapid and sustained normalization of hematological parameters with improvement in long-term renal function. This review summarizes current concepts about the epidemiological findings, the pathological and clinical aspects of STEC-HUS, pneumococcal-HUS, and aHUS, and their diagnosis and management.

Genome Sequence of Escherichia coli O157:H7 Strain 2886-75, Associated with the First Reported Case of Human Infection in the United States

First identified in 1982 as a human pathogen, enterohemorrhagic Escherichia coli of the O157:H7 serotype is a major cause of food-borne acquired human infections. Here, we report the genome sequence of the first known strain of this serotype isolated in the United States.

Distinct renal pathology and a chemotactic phenotype after enterohemorrhagic Escherichia coli shiga toxins in non-human primate models of hemolytic uremic syndrome

Enterohemorrhagic Escherichia coli cause approximately 1.5 million infections globally with 176,000 cases occurring in the United States annually from ingesting contaminated food, most frequently E. coli O157:H7 in ground beef or fresh produce. In severe cases, the painful prodromal hemorrhagic colitis is complicated by potentially lethal hemolytic uremic syndrome (HUS), particularly in children. Bacterial Shiga-like toxins (Stx1, Stx2) are primarily responsible for HUS and the kidney and neurologic damage that ensue. Small animal models are hampered by the inability to reproduce HUS with thrombotic microangiopathy, hemolytic anemia, and acute kidney injury. Earlier, we showed that nonhuman primates (Papio) recapitulated clinical HUS after Stx challenge and that novel therapeutic intervention rescued the animals. Here, we present detailed light and electron microscopic pathology examination of the kidneys from these Stx studies. Stx1 challenge resulted in more severe glomerular endothelial injury, whereas the glomerular injury after Stx2 also included prominent mesangiolysis and an eosinophilic inflammatory infiltration. Both toxins induced glomerular platelet-rich thrombi, interstitial hemorrhage, and tubular injury. Analysis of kidney and other organs for inflammation biomarkers showed a striking chemotactic profile, with extremely high mRNA levels for IL-8, monocyte chemoattractant protein 1, and macrophage inflammatory protein 1α and elevated urine chemokines at 48 hours after challenge. These observations give unique insight into the pathologic consequences of each toxin in a near human setting and present potential pathways for therapeutic intervention.

Shiga toxins and the pathophysiology of hemolytic uremic syndrome in humans and animals

Food-borne diseases are estimated at 76 million illnesses and 5000 deaths every year in the United States with the greatest burden on young children, the elderly and immunocompromised populations. The impact of efficient food distribution systems and a truly global food supply ensures that outbreaks, previously sporadic and contained locally, are far more widespread and emerging pathogens have far more frequent infection opportunities. Enterohemorrhagic E. coli is an emerging food- and water-borne pathogen family whose Shiga-like toxins induce painful hemorrhagic colitis with potentially lethal complications of hemolytic uremic syndrome (HUS). The clinical manifestations of Shiga toxin-induced HUS overlap with other related syndromes yet molecular mechanisms differ considerably. As discussed herein, understanding these differences and the novel properties of the toxins is imperative for clinical management decisions, design of appropriate animal models, and choices of adjunctive therapeutics. The emergence of new strains with rapidly aggressive virulence makes clinical and research initiatives in this field a high public health priority.

Renal and neurological involvement in typical Shiga toxin-associated HUS

Shiga toxin-producing Escherichia coli-associated haemolytic uraemic syndrome (STEC-HUS) is one of the most important causes of acute kidney injury in patients of all ages, especially in children. It can occur sporadically or in outbreaks. STEC-HUS is a systemic illness caused by toxin-mediated injury to the vascular endothelium and a generalized inflammatory response. The kidney and the brain are the two primary target organs. Nearly 40% of patients with STEC-HUS require at least temporary renal replacement therapy and up to 20% will have permanent residual kidney dysfunction. Neurological injury can be sudden and severe and is the most frequent cause of acute mortality in patients with STEC-HUS. Over the past 30 years, a wide range of inflammatory mediators have been linked to the pathogenesis of STEC-HUS and associated renal and neurological complications. Recently, evidence has accumulated that abnormal activation of the alternative pathway of complement occurs in patients with STEC-HUS. In the large outbreak of STEC-HUS caused by E. coli O104:H4 that occurred in Germany in May 2011, a large number of patients received eculizumab, a monoclonal antibody directed against C5, in an open-label manner. We describe the experience with eculizumab under these emergent circumstances at one large centre.

Protective effects of lactoferrin chimera and bovine lactoferrin in a mouse model of enterohaemorrhagic Escherichia coli O157:H7 infection

Mice orally infected with enterohaemorrhagic Escherichia coli (EHEC) O157:H7 were used to evaluate the activity of bovine lactoferrin (bLF) and the synthetic peptide LFchimera. Groups of BALB/c mice inoculated intragastrically with EHEC O157:H7 showed chronic intestinal infection with the pathogen that persisted over 6 days and resulted in a high mortality rate (90%). LFchimera and kanamycin significantly decreased (40%) this mortality rate (P = 0.028). On the other hand, although mice administered with bLF showed an important reduction in mortality (50%), this was not statistically significant (P = 0.070). In infected and untreated mice, severe tubular necrosis, glomerular lesions, and moderate intratubular hyaline casts were found in the kidney. However, in the bLF and LFchimera groups we found a reduction in the damage and a substantial decrease in the bacterial concentration excreted in feces 48 h after infection. Furthermore, sepsis caused by EHEC was reduced by the treatments, evidenced by the fact that bacteria were not detected in the kidney or liver 72 h after infection. The results suggest the bLF and LFchimera could have potential as therapeutics in EHEC infections.

Shiga toxin pathogenesis: kidney complications and renal failure

The kidneys are the major organs affected in diarrhea-associated hemolytic uremic syndrome (D(+)HUS). The pathophysiology of renal disease in D(+)HUS is largely the result of the interaction between bacterial virulence factors such as Shiga toxin and lipopolysaccharide and host cells in the kidney and in the blood circulation. This chapter describes in detail the current knowledge of how these bacterial toxins may lead to kidney disease and renal failure. The toxin receptors expressed by specific blood and resident renal cell types are also discussed as are the actions of the toxins on these cells.

Differential response of the human renal proximal tubular epithelial cell line HK-2 to Shiga toxin types 1 and 2

Shiga toxins (Stxs) are expressed by the enteric pathogens Shigella dysenteriae serotype 1 and certain serotypes of Escherichia coli. Stx-producing bacteria cause bloody diarrhea with the potential to progress to acute renal failure. Stxs are potent protein synthesis inhibitors and are the primary virulence factors responsible for renal damage that may follow diarrheal disease. We explored the use of the immortalized human proximal tubule epithelial cell line HK-2 as an in vitro model of Stx-induced renal damage. We showed that these cells express abundant membrane Gb(3) and are differentially susceptible to the cytotoxic action of Stxs, being more sensitive to Shiga toxin type 1 (Stx1) than to Stx2. At early time points (24 h), HK-2 cells were significantly more sensitive to Stxs than Vero cells; however, by 72 h, Vero cell monolayers were completely destroyed while some HK-2 cells survived toxin challenge, suggesting that a subpopulation of HK-2 cells are relatively toxin resistant. Fluorescently labeled Stx1 B subunits localized to both lysosomal and endoplasmic reticulum (ER) compartments in HK-2 cells, suggesting that differences in intracellular trafficking may play a role in susceptibility to Stx-mediated cytotoxicity. Although proinflammatory cytokines were not upregulated by toxin challenge, Stx2 selectively induced the expression of two chemokines, macrophage inflammatory protein-1α (MIP-1α) and MIP-1β. Stx1 and Stx2 differentially activated components of the ER stress response in HK-2 cells. Finally, we demonstrated significant poly(ADP-ribose) polymerase (PARP) cleavage after exposure to Stx1 or Stx2. However, procaspase 3 cleavage was undetectable, suggesting that HK-2 cells may undergo apoptosis in response to Stxs in a caspase 3-independent manner.

Advances in our understanding of the pathogenesis of glomerular thrombotic microangiopathy

Glomerular thrombotic microangiopathy is a hallmark feature of haemolytic uraemic syndrome, the leading cause of acute renal failure in childhood. This paper is a review of the different mechanistic pathways that lead to this histological picture in the kidney. It will focus on atypical HUS and complement dysregulation, but will also highlight some other recent advances in our understanding of this condition, including the potential role of the molecule vascular endothelial growth factor-A (VEGF-A).

Escherichia coli Shiga Toxin Mechanisms of Action in Renal Disease

Shiga toxin-producing Escherichia coli is a contaminant of food and water that in humans causes a diarrheal prodrome followed by more severe disease of the kidneys and an array of symptoms of the central nervous system. The systemic disease is a complex referred to as diarrhea-associated hemolytic uremic syndrome (D⁺HUS). D⁺HUS is characterized by thrombocytopenia, microangiopathic hemolytic anemia, and acute renal failure. This review focuses on the renal aspects of D⁺HUS. Current knowledge of this renal disease is derived from a combination of human samples, animal models of D⁺HUS, and interaction of Shiga toxin with isolated renal cell types. Shiga toxin is a multi-subunit protein complex that binds to a glycosphingolipid receptor, Gb3, on select eukaryotic cell types. Location of Gb3 in the kidney is predictive of the sites of action of Shiga toxin. However, the toxin is cytotoxic to some, but not all cell types that express Gb3. It also can cause apoptosis or generate an inflammatory response in some cells. Together, this myriad of results is responsible for D⁺HUS disease.

Pathogenesis of Escherichia coli O157:H7 strain 86-24 following oral infection of BALB/c mice with an intact commensal flora

Escherichia coli O157:H7 is a food-borne pathogen that can cause hemorrhagic colitis and, occasionally, hemolytic uremic syndrome, a sequela of infection that can result in renal failure and death. Here we sought to model the pathogenesis of orally-administered E. coli O157:H7 in BALB/c mice with an intact intestinal flora. First, we defined the optimal dose that permitted sustained fecal shedding of E. coli O157:H7 over 7 days ( approximately 10(9) colony forming units). Next, we monitored the load of E. coli O157:H7 in intestinal sections over time and observed that the cecum was consistently the tissue with the highest E. coli O157:H7 recovery. We then followed the expression of two key E. coli O157:H7 virulence factors, the adhesin intimin and Shiga toxin type 2, and detected both proteins early in infection when bacterial burdens were highest. Additionally, we noted that during infection, animals lost weight and approximately 30% died. Moribund animals also exhibited elevated levels of blood urea nitrogen, and, on necropsy, showed evidence of renal tubular damage. We conclude that conventional mice inoculated orally with high doses of E. coli O157:H7 can be used to model both intestinal colonization and subsequent development of certain extraintestinal manifestations of E. coli O157:H7 disease.

Hemolytic uremic syndrome (HUS)--incidence and etiologies at a regional Children's Hospital in 2001-2006

Hemolytic uremic syndrome (HUS) is a serious health concern in children. HUS has primarily been linked to Escherichia coli O157:H7 infections, but non-O157 strains are gaining attention. Hemolytic anemia, thrombocytopenia, and acute renal failure are the characteristics of the syndrome. This study investigated the incidence of HUS at a regional Children's Hospital between 2001 and 2006 by retrospective review. Cases of HUS were investigated for outcomes based on stool culture and an association of acute pancreatitis. A total of 44 cases were identified, of which 57% were female and 43% were male, with an age distribution of 13 months to 17 years and a median age of 3.44 years. Data revealed 13 cases in 2006 compared to two cases in 2001, with 84% of all illnesses occurring in the summer and fall seasons. The median duration of thrombocytopenia was eight days and 50% of all cases required dialysis. E. coli O157:H7 was the predominant pathogen; however, 53% of the cases had unknown etiology. This data may suggest a growing number of cases from 2001 to 2006 and a role for agents other than E. coli O157:H7. E. coli O157:H7 caused longer intensive care unit (ICU) stay. No association between HUS and acute pancreatitis was found.

Shiga toxin 2 targets the murine renal collecting duct epithelium

Hemolytic-uremic syndrome (HUS) caused by Shiga toxin-producing Escherichia coli infection is a leading cause of pediatric acute renal failure. Bacterial toxins produced in the gut enter the circulation and cause a systemic toxemia and targeted cell damage. It had been previously shown that injection of Shiga toxin 2 (Stx2) and lipopolysaccharide (LPS) caused signs and symptoms of HUS in mice, but the mechanism leading to renal failure remained uncharacterized. The current study elucidated that murine cells of the glomerular filtration barrier were unresponsive to Stx2 because they lacked the receptor glycosphingolipid globotriaosylceramide (Gb(3)) in vitro and in vivo. In contrast to the analogous human cells, Stx2 did not alter inflammatory kinase activity, cytokine release, or cell viability of the murine glomerular cells. However, murine renal cortical and medullary tubular cells expressed Gb(3) and responded to Stx2 by undergoing apoptosis. Stx2-induced loss of functioning collecting ducts in vivo caused production of increased dilute urine, resulted in dehydration, and contributed to renal failure. Stx2-mediated renal dysfunction was ameliorated by administration of the nonselective caspase inhibitor Q-VD-OPH in vivo. Stx2 therefore targets the murine collecting duct, and this Stx2-induced injury can be blocked by inhibitors of apoptosis in vivo.

Virulence traits associated with verocytotoxigenic Escherichia coli O157 recovered from freshwater biofilms

AIM

To investigate whether epilithic biofilms in freshwater streams in a mixed UK agricultural river catchment harbour Escherichia coli O157, and if so, whether they demonstrate an association with those excreted by grazing farm animals.

METHODS AND RESULTS

Flint shingle, native to the study site, was used as a surface for biofilm development within cages of metal lath set into a stream bed at four locations on a chalkland farm. Shingle was collected from all sites once a month, as were pooled faecal samples from five farm animal populations. Subpopulations of E. coli, including E. coli O157 that demonstrated significant phenotypic and genotypic similarity with animal faecal isolates (t-test, P = 0.05) were isolated. Of 1002 E. coli isolates from biofilms and animal faeces, 48 were confirmed as the O157 strain by latex agglutination. The presence of five virulence traits associated with incidence of human disease was tested using PCR. Stx(2) was the most frequently isolated single gene (30 isolates), while stx(1) was the least frequently recovered (four isolates).

CONCLUSION

Escherichia coli O157, expressing up to four virulence factors associated with human disease, reside within freshwater biofilms in this agricultural environment.

SIGNIFICANCE AND IMPACT OF THE STUDY

Aquatic biofilms may potentially act as a reservoir for these pathogens, and the implications of the findings for the protection of drinking water resources should be further investigated.

Interactions of Shiga-like toxin with human peripheral blood monocytes

The cytotoxic effect of Shiga-like toxin (Stx; produced by certain Escherichia coli strains) plays a central role in typical hemolytic uremic syndrome (HUS). It damages the renal endothelium by inhibiting the cellular protein synthesis. Also, the monocyte has a specific receptor for Stx but is not sensitive for the cytotoxic effect. In this work, monocytes were studied as a potential transporter for Stx to the renal endothelium. Coincubation of isolated human monocytes loaded with Stx and target cells (vero cells and human umbilical vascular endothelial cells) were performed. Transfer was determined by measuring the protein synthesis of target cells and by flow cytometry. Furthermore, the effect of a temperature shift on loaded monocytes was investigated. Stx-loaded monocytes reduced the protein synthesis of target cells. After adding an antibody against Stx, incomplete recovery occurred. Also, adding only the supernatant of coincubation was followed by protein synthesis inhibition. Stx detached from its receptor on the monocyte after a change in temperature, and no release was detected without this temperature shift. Although the monocyte plays an important role in the pathogenesis of HUS, it has no role in the transfer of Stx.

A murine model of HUS: Shiga toxin with lipopolysaccharide mimics the renal damage and physiologic response of human disease

Hemolytic uremic syndrome (HUS), which is caused by Shiga toxin-producing Escherichia coli infection, is the leading cause of acute renal failure in children. At present, there is no complete small animal model of this disease. This study investigated a mouse model using intraperitoneal co-injection of purified Shiga toxin 2 (Stx2) plus LPS. Through microarray, biochemical, and histologic analysis, it was found to be a valid model of the human disease. Biochemical and microarray analysis of mouse kidneys revealed the Stx2 plus LPS challenge to be distinct from the effects of either agent alone. Microarrays identified differentially expressed genes that were demonstrated previously to play a role in this disease. Blood and serum analysis of these mice showed neutrophilia, thrombocytopenia, red cell hemolysis, and increased serum creatinine and blood urea nitrogen. In addition, histologic analysis and electron microscopy of mouse kidneys demonstrated glomerular fibrin deposition, red cell congestion, microthrombi formation, and glomerular ultrastructural changes. It was established that this C57BL/6 mouse is a complete model of HUS that includes the thrombocytopenia, hemolytic anemia, and renal failure that define the human disease. In addition, a time course of HUS disease progression that will be useful for identification of therapeutic targets and development of new treatments for HUS is described.

Procalcitonin in children with Escherichia coli O157:H7 associated hemolytic uremic syndrome

Shiga toxin producing Escherichia coli (STEC) are noninvasive enteric pathogens that may cause hemorrhagic colitis (HC) and diarrhea-associated hemolytic uremic syndrome (D+ HUS). We hypothesized that development of D+ HUS is associated with increased serum procalcitonin (PCT) levels. PCT was measured by an immunoluminometric assay in 113 patients. Concentrations of PCT were different in normal controls, disease control groups (rotavirus enteritis, HC due to non-STEC pathogens, chronic renal failure), and children with uncomplicated O157:H7 HC or D+ HUS. Children with D+ HUS showed higher PCT levels than those with uncomplicated O157:H7 HC, and increased concentrations were noted in cases requiring peritoneal dialysis. Severely increased concentrations were observed in children with D+ HUS on d 5 or 6 after the onset of enteritis, whereas serial measurements in those with uncomplicated O157:H7 HC remained within the normal range throughout the first week of illness. PCT was correlated with serum concentrations of lipopolysaccharide (LPS)-binding protein and serum levels of alanine aminotransferase. Using two separate sets of real-time PCR primers, we were unable to detect elevated PCT mRNA transcripts in nonadherent undifferentiated (monocytic) or differentiated (macrophage-like) THP-1 cells stimulated with purified Shiga toxin-1 and/or LPS. Our data show that serum levels of PCT are associated with the severity of illness in children with D+ HUS. Further studies are needed to determine the role of PCT in the pathogenesis of thrombotic microangiopathy associated to childhood D+ HUS.

Differential carbohydrate epitope recognition of globotriaosyl ceramide by verotoxins and a monoclonal antibody. Role in human renal glomerular binding

The role of renal expression of the glycosphingolipid verotoxin receptor, globotriaosylceramide, in susceptibility to verotoxin-induced hemolytic uremic syndrome is unclear. We show that a single glycosphingolipid can discriminate multiple specific ligands. Antibody detection of globotriaosylceramide in renal sections does not necessarily predict verotoxin binding. The deoxyglobotriaosylceramide binding profile for verotoxin 1, verotoxin 2 and monoclonal anti-globotriaosylceramide are distinct. Anti-globotriaosylceramide had greater dependency on the intact alpha-galactose and reducing glucose of globotriaosylceramide than verotoxin 1, while verotoxin 2 was intermediate. These ligands differentially stained human kidney sections. Glomerulopathy is the primary verotoxin-associated pathology in hemolytic uremic syndrome. For most samples, verotoxin 1 immunostaining within adult glomeruli was observed (type A). Some samples, however, lacked glomerular binding (type B). Anti-globotriaosylceramide (and less effectively, verotoxin 2) stained all glomeruli. Verotoxin 1/anti-globotriaosylceramide tubular staining was comparable. Type B glomerular/tubular globotriaosylceramide showed minor, but significant, fatty acid compositional differences. Verotoxin 1 type B glomerular binding became evident following pretreatment with cold acetone, or methyl-beta-cyclodextrin, used to deplete cholesterol. Direct visualization, using fluorescein isothiocyanate-verotoxin 1B, showed paediatric, but no adult glomerular staining; this was confirmed by anti-fluorescein isothiocyanate immunostaining. Acetone induced fluorescein isothiocyanate-verotoxin 1B glomerular staining in type A, but poorly in type B samples. Comparison of fluorescein isothiocyanate-verotoxin 1B and native verotoxin 1B deoxyglobotriaosylceramide analogue binding showed an alteration in subspecificity. These studies indicate a marked heterogeneity of globotriaosylceramide expression within renal glomeruli and differential binding of verotoxin 1/verotoxin 2/anti-globotriaosylceramide to the same glycosphingolipid. Verotoxin 1 derivatization can induce subtle changes in globotriaosylceramide binding to significantly affect tissue binding. Heterogeneity in glomerular globotriaosylceramide expression may play a significant (cholesterol-dependent?) role in determining renal pathology following verotoxemia.

Epidemiology and spectrum of disease of Escherichia coli O157

PURPOSE OF REVIEW

The Shiga toxin-producing Escherichia coli strains, such as E. coli O157:H7, have emerged as major diarrheal pathogens both in the United States and elsewhere. These organisms are important because gastrointestinal infection (afebrile hemorrhagic colitis) can trigger microangiopathic hemolytic anemia and renal failure (hemolytic uremic syndrome). Understanding the pathophysiology of this illness is likely to lead to important new treatment interventions.

RECENT FINDINGS

It is now recognized that children with hemorrhagic colitis routinely develop a spectrum of coagulation abnormalities and that only a fraction of children develop full blown hemolytic uremic syndrome. Individual variability in expression of inflammatory mediators is likely to be a key element in determining which children progress to the severe end of the spectrum of disease. The value of antibiotic therapy is unknown.

SUMMARY

The pathophysiology of HUS remains incompletely understood. The lag between onset of diarrhea and onset of HUS represents an opportunity to intervene and prevent renal failure. However, there currently is no way to prevent such life threatening complications. The management should focus on diagnosis and close observation so that early intervention can prevent complications.

Verotoxin 1 binding to intestinal crypt epithelial cells results in localization to lysosomes and abrogation of toxicity

Verotoxins (VTs) are important virulence factors of enterohaemorrhagic Escherichia coli (EHEC), a group of bacteria associated with severe disease sequelae in humans. The potent cytotoxic activity of VTs is important in pathogenicity, resulting in the death of cells expressing receptor Gb3 (globotriaosylceramide). EHEC, particularly serotype O157:H7, frequently colonize reservoir hosts (such as cattle) in the absence of disease, however, the basis to avirulence in this host has been unclear. The objective of this study was assessment of interaction between VT and intestinal epithelium, which represents the major interface between the host and enteric organisms. Bovine intestinal epithelial cells expressed Gb3 in vitro in primary cell cultures, localizing specifically to proliferating crypt cells in corroboration with in situ immunohistological observations on intestinal mucosa. Expression of receptor by these cells contrasts with the absence of Gb3 on human intestinal epithelium in vivo. Despite receptor expression, VT exhibited no cytotoxic activity against bovine epithelial cells. Sub-cellular localization of VT indicated that this toxin was excluded from endoplasmic reticulum but localized to lysosomes, corresponding with abrogation of cytotoxicity. VT intracellular trafficking was unaffected by treatment of primary cell cultures with methyl-beta-cyclodextrin, indicating that Gb3 in these cells is not associated with lipid rafts but is randomly distributed in the membrane. The combination of Gb3 isoform, membrane distribution and VT trafficking correlate with observations of other receptor-positive cells that resist verocytotoxicity. These studies demonstrate that intestinal epithelium is an important determinant in VT interaction with major implications for the differential consequences of EHEC infection in reservoir hosts and humans.

Consequences of EHEC colonisation in humans and cattle

While many factors have been associated with human EHEC infection, the full role these play in both human and ruminant hosts are not yet clear despite much investigation. It is hoped that the continued intense international research effort into EHEC will provide further insights into the commensal versus pathogenic lifestyles of E. coli and lead to approaches to reduce EHEC carriage in ruminants as well as prevent or treat human disease.

Differential tissue targeting and pathogenesis of verotoxins 1 and 2 in the mouse animal model

BACKGROUND

Both verotoxin (VT)1 and VT2 share the same receptor, globotriaosyl ceramide (Gb(3)). Although VT1 is slightly more cytotoxic in vitro and binds Gb(3) with higher affinity, VT2 is more toxic in mice and may be associated with greater pathology in human infections. In this study we have compared the biodistribution of iodine 125 ((125)I)-VT1 and (125)I-VT2 versus pathology in the mouse.

METHODS

(125)I-VT1 whole-body autoradiography defined the tissues targeted. VT1 and VT2 tissue distribution, clearance, and tissue binding sites were compared. The effect of a soluble receptor analogue, adamantylGb(3), on VT2/Gb3 binding and in vivo pathology was assessed.

RESULTS

(125)I-VT1 autoradiography identified the lungs and nasal turbinates as major, previously unrecognized, targets, while kidney cortex and the bone marrow of the spine, long bones, and ribs were also significant targets. VT2 did not target the lung, but accumulated in the kidney to a greater extent than VT1. The serum half-life of VT1 was 2.7 minutes with 90% clearance at 5 minutes, while that of VT2 was 3.9 minutes with only 40% clearance at 5 minutes. The extensive binding of VT1, but not VT2, within the lung correlated with induced lung disease. Extensive hemorrhage into alveoli, edema, alveolitis and neutrophil margination was seen only after VT1 treatment. VT1 targeted lung capillary endothelial cells. Identical tissue binding sites (subsets of proximal/distal tubules and collecting ducts) for VT1 and VT2 were detected by toxin overlay of serial frozen kidney sections. Glucosuria was found to be a new marker of VT1- and VT2-induced renal pathology and positive predictor of outcome in the mouse, consistent with VT-staining of proximal tubules. Lung Gb3 migrated on thin-layer chromatography (TLC) faster than kidney Gb(3), suggesting a different lipid composition. AdamantylGb(3), a soluble Gb(3) analogue, competed effectively for Gb3 binding by VT1 and VT2 in vitro. However, the effect in the mouse model (only measured against VT2, due to the lower LD(50), a concentration required for 50% lethality) was to increase, rather than reduce, pathology and further reduce the VT2 serum clearance rate. Additional renal pathology was seen in VT2 + adamantylGb(3)-treated mice.

CONCLUSIONS

The lung is a preferential (Gb(3)) "sink" for VT1, which explains the relatively slower clearance of VT2 and subsequent increased VT2 renal targeting and VT2 mortality in this animal model.