Shiga Toxin-induced Hemolytic Uremic Syndrome Research Articles

S1960 Acute Pseudomembranous Colitis, Microangiopathic Hemolytic Anemia, and Renal Injury After Pericardiectomy

Introduction: Acute colonic ischemia following surgery is usually a result of colonic hypoperfusion, particularly in watershed regions; however, it is critical to maintain a broad differential diagnosis for alternate etiologies. Case description/methods: A 57-year-old man with lupus on hydroxychloroquine and prednisone underwent elective pericardiectomy for medically refractory constrictive pericarditis. On post-operative day (POD) 3, he developed abdominal pain, nausea, and non-bloody diarrhea. Hematochezia started on POD 4. Computed tomography showed rectosigmoid thickening and perirectal fat stranding (Figure 1A). Sigmoidoscopy revealed edematous, ulcerated, and discolored mucosa from the anal verge to 30 cm proximally that abruptly normalized thereafter (Figure 1B). Sigmoid histology showed lamina propria hemorrhage with crypt withering and focal pseudomembranes (Figure 1C). Clostridioides difficile testing was negative. Colonic ischemia was favored. Given persistent leukocytosis and low fevers, antibiotics were started. From POD 4 to 8, platelets dropped from 142 to 11 × 109/L, and creatinine rose from 1.1 to 2.0 mg/dL (Figure 2). On POD 6, labs showed lactate dehydrogenase 1,107 U/L, indirect bilirubin 2.7 mg/dL, and undetectable haptoglobin, with hemoglobin dropping from 14.0 to 12.9 g/dL from POD 7 to 8. Peripheral smear on POD 8 showed schistocytes (Figure 3). Serum ADAMTS-13, complement levels, and heparin-induced thrombocytopenia panels were normal. Stool PCR detected shiga-toxin producing E. coli and shiga toxin 2, and stool cultures did not grow the 0157:H7 E. coli strain. Antibiotics were stopped due to the diagnosis of shiga-toxin induced hemolytic uremic syndrome (ST-HUS). The hemolysis, thrombocytopenia, and renal injury resolved after one week of supportive measures. Discussion: Infection by shiga-toxin producing E. coli (STEC), especially with shiga toxin 2 (which disrupts protein synthesis, causing apoptosis), presents with hemorrhagic colitis in 80% of cases and ST-HUS in up to 15% of cases. STEC is often acquired from contaminated food/ water. In this case, a hamburger from an external vendor was the suspected source. After a 3-day incubation period, STEC classically presents with abdominal pain and non-bloody diarrhea, followed by bloody diarrhea 1-3 days later. If it occurs, ST-HUS presents 1-2 weeks later from thrombotic microangiopathy. Antibiotics are linked to shiga toxin production by the encoding bacteriophage in the STEC chromosome.Figure 1.: Acute pseudomembranous colitis. A) Rectosigmoid wall thickening (green arrow) and perirectal fat stranding. B) Rectosigmoid colon was edematous, cyanotic, ulcerated, with luminal narrowing by flexible sigmoidoscopy. There was an abrupt transition to normal sigmoid mucosa at 30 cm from anal verge (not shown). C) Pathologic specimens from sigmoid colon showed crypt withering (blue arrow), lamina propria hemorrhage (orange arrow), and pseudomembrane (yellow arrow).Figure 2.: Clinical course of shiga-toxin induced hemolytic uremic syndrome (ST-HUS). Non-bloody diarrhea started on POD 3, followed by bloody diarrhea on POD 4. The patient’s thrombotic microangiopathy, signified by reduction in platelets and renal injury, began 3-4 days later, illustrating the characteristic delay from diarrhea onset and thrombotic microangiopathy in ST-HUS.Figure 3.: Peripheral smear. Peripheral smear was notable for schistocytes (blue arrow), suggestive of hemolysis, and markedly diminished number of platelets (green arrow). The combination of these features was consistent with thrombotic microangiopathy.

De Novo and Recurrent Thrombotic Microangiopathy After Renal Transplantation: Current Concepts in Management.

Thrombotic microangiopathy is a well-recognized complication of kidney transplantation that leads frequently to allograft failure. This serious outcome can greatly depend on the underlying etiology and on the timing of therapeutic interventions. Thrombotic microangiopathy syndrome may occur with no previous history of thrombotic microangiopathy (that is, de novo thrombotic microangiopathy), mostly due to medica tions or infections. More frequently, it may recur after kidney transplant in patients with endstage renal failure due to atypical hemolytic uremic syndrome. However, for patients with Shiga-toxininduced hemolytic uremic syndrome, particularly pediatric patients, there is a favorable prognosis. A fundamental tool for management of this disease is genetic screening for abnormal mutations; this can recognize the suggested approach of therapy and may determine the outcome of the disease to a large extent. Although patients with complement factor H and I mutations have worse prognosis, other patients with membrane cofactor protein mutations, for example, have a more favorable prognosis. Accordingly, the plan of therapy can be tailored with a better chance of cure. Unfortunately, the successful use of the biological agent eculizumab, an anti-C5 agent, in some of these syndromes is largely impeded by its high cost, which is linked to its use as a life-long therapy. However, newly suggested therapeutic options may ameliorate this drawback.

Tissue-resident macrophages mediate neutrophil recruitment and kidney injury in shiga toxin-induced hemolytic uremic syndrome

Enterohaemorrhagic E.coli cause major epidemics worldwide with significant organ damage and very high percentages of death. Due to the ability of enterohaemorrhagic E.coli to produce shiga toxin these bacteria damage the kidney leading to the hemolytic uremic syndrome. A therapy against this serious kidney disease has not been developed yet and the impact and mechanism of leukocyte activation and recruitment are unclear. Tissue-resident macrophages represent the main leukocyte population in the healthy kidney, but the role of this important cell population in shiga toxin-producing E.coli-hemolytic uremic syndrome is incompletely understood. Using state of the art microscopy and mass spectrometry imaging, our preclinical study demonstrated a phenotypic and functional switch of tissue-resident macrophages after disease induction in mice. Kidney macrophages produced the inflammatory molecule TNFα and depletion of tissue-resident macrophages via the CSF1 receptor abolished TNFα levels in the kidney and significantly diminished disease severity. Furthermore, macrophage depletion did not only attenuate endothelial damage and thrombocytopenia, but also activation of thrombocytes and neutrophils. Moreover, we observed that neutrophils infiltrated the kidney cortex and depletion of macrophages significantly reduced the recruitment of neutrophils and expression of the neutrophil-attracting chemokines CXCL1 and CXCL2. Intravital microscopy revealed that inhibition of CXCR2, the receptor for CXCL1 and CXCL2, significantly reduced the infiltration of neutrophils and reduced kidney injury. Thus, our study shows activation of tissue-resident macrophages during shiga toxin-producing E.coli-hemolytic uremic syndrome leading to the production of disease-promoting TNFα and CXCR2-dependent recruitment of neutrophils.

Absence of interleukin-10 reduces progression of shiga toxin-induced hemolytic uremic syndrome.

Hemolytic Uremic Syndrome (HUS), a disease triggered by Shiga toxin (Stx), is characterized by hemolytic anemia, thrombocytopenia and renal failure. The inflammatory response mediated by polymorphonuclear neutrophils (PMNs) and monocytes is essential to HUS onset. Still, the role of anti-inflammatory cytokines is less clear. The deficiency of IL-10, an anti-inflammatory cytokine, leads to severe pathology in bacterial infections but also to beneficial effects in models of sterile injury. The aim of this work was to analyze the role of IL-10 during HUS. Control and IL-10 lacking mice (IL-10-/-) were intravenously injected with Stx type 2 (Stx2) and survival rate was evaluated. PMN and circulating and renal pro- and anti-inflammatory factors were analyzed by FACS and enzyme-linked immunosorbent assay (ELISA) respectively. IL-10-/- mice showed a higher survival associated with lower renal damage reflected by reduced plasma urea and creatinine levels than control mice. Circulating PMN increased at 72 h in both mouse strains accompanied by an up-regulation of CD11b in control mice. In parallel, renal PMN were significantly increased only in control mice after toxin. Plasma TNF-α, IL-6 and corticosterone levels were higher increased in IL-10-/- than control mice. Simultaneously renal TNF-α raised constantly but was accompanied by increased TGF-β levels in IL-10-/- mice. These results demonstrate that the profile of circulating and renal cytokines after Stx2 differed between strains suggesting that balance of these factors could participate in renal protection. We conclude that IL-10 absence has a protective role in an experimental model of HUS by reducing PMN recruitment into kidney and renal damage, and increasing mice survival.

Activation of the Nlrp3 Inflammasome Contributes to Shiga Toxin-Induced Hemolytic Uremic Syndrome in a Mouse Model

ObjectiveTo explore the role of the Nlrp3 inflammasome activation in the development of hemolytic uremic syndrome (HUS) induced by Stx2 and evaluate the efficacy of small molecule Nlrp3 inhibitors in preventing the HUS.MethodsPeritoneal macrophages (PMs) isolated from wild-type (WT) C57BL/6J mice and gene knockout mice (Nlrc4-/-, Aim2-/-, and Nlrp3-/-) were treated with Stx2 in vitro and their IL-1β releases were measured. WT mice and Nlrp3-/- mice were also treated with Stx2 in vivo by injection, and the biochemical indices (serum IL-1β, creatinine [CRE] and blood urea nitrogen [BUN]), renal injury, and animal survival were compared. To evaluate the effect of the Nlrp3 inhibitors in preventing HUS, WT mice were pretreated with different Nlrp3 inhibitors (MCC950, CY-09, Oridonin) before Stx2 treatment, and their biochemical indices and survival were compared with the WT mice without inhibitor pretreatment.ResultsWhen PMs were stimulated by Stx2 in vitro, IL-1β release in Nlrp3-/- PMs was significantly lower compared to the other PMs. The Nlrp3-/- mice treated by Stx2 in vivo, showed lower levels of the biochemical indices, alleviated renal injuries, and increased survival rate. When the WT mice were pretreated with the Nlrp3 inhibitors, both the biochemical indices and survival were significantly improved compared to those without inhibitor pretreatment, with Oridonin being most potent.ConclusionNlrp3 inflammasome activation plays a vital role in the HUS development when mice are challenged by Stx2, and Oridonin is effective in preventing HUS.

Use of complement monoclonal antibody eculizumab in Shiga toxin producing Escherichia coli associated hemolytic uremic syndrome: A review of current evidence.

Complement activation plays an important role in the pathogenesis of atypical hemolytic uremic syndrome.Eculizumab is a monoclonal antibody that blocks complement activity and has been approved for use in the treatment of atypical hemolytic uremic syndrome (HUS).Less well appreciated is the role of complement in Shiga toxin-induced HUS (Shiga toxin producing Escherichia coli [STEC]-HUS). To a limited extent, eculizumab has been used off label in patients with severe STEC-HUS with neurological involvement.Through a systematic search of available databases, we identified 16 reports describing the use of eculizumab in STEC-HUS (eight case reports/series, seven retrospective studies, and one prospective cohort study). All studies described its use in severe STEC-HUS with neurological or multiorgan dysfunction; none were randomized or blinded. Four studies used the control groups. Although the overall quality of evidence is low, some published studies showed positive clinical improvement after treatment with eculizumab in severe STEC-HUS with progressive neurological involvement.

Phage display and Shiga toxin neutralizers

The current work presents an overview of the use of phage display technology for the identification and characterization of potential neutralizing agents for Shiga toxins. The last major Shiga toxin-associated disease outbreak, which took place in Germany in 2011, showed the international community that Shiga toxins remain a serious threat to public health. This is also demonstrated by the lack of specific therapies against Shiga toxin-induced Hemolytic Uremic Syndrome (HUS). Since its inception, phage display technology has played a key role in the development of antigen-specific (poly)-peptides or antibody fragments with specific biological properties. Herein, we review the current literature regarding the application of phage display to identify novel neutralizing agents against Shiga toxins. We also briefly highlight reported discoveries of peptides and heavy chain antibodies (VHH fragments or nanobodies) that can neutralize the cellular damage caused by these potent toxins.

Thrombotic Microangiopathy (TMA) and Other Severe Systemic Reactions Caused By Quinine-Containing Beverages: Report of a Patient and Review of Published Reports

Case presentation: A 35 year old white female was in excellent health until the sudden onset of fever, chills, headache, myalgias, abdominal and flank pain, nausea and vomiting while driving home from a banquet. She went to an ER the following day; her hematocrit was 39% and platelet count 132,000/µL. She was given IV fluids, antiemetics, and sent home. Two days later, she returned to the ER as her symptoms persisted and she had not urinated since they began; her hematocrit was 32%, platelet count 54,000/µL, creatinine 9.3 mg/dL, AST 350, ALT 274, LDH 2402. Due to anemia, thrombocytopenia, and acute kidney injury (AKI), plasma exchange (PEX) was begun because of suspicion of thrombotic thrombocytopenic purpura; Shiga toxin-induced hemolytic uremic syndrome was also considered. Hemodialysis was begun as her creatinine rose to 10.5 mg/dL and anuria persisted. We saw her the following day; drug-induced TMA was considered to be the most likely etiology because of the very sudden, severe onset with anuric AKI. However her only medicine was Singulair for asthma, which she had taken daily for several years. She had never taken quinine tablets or drunk gin and tonic; then she asked us, "What about vodka and tonic?". She had had "a sip" of vodka and tonic at the banquet; it was a favorite drink. Her previous vodka and tonic was 16 months previously; she had then developed sudden severe headache, neck pain, fever and chills causing suspicion of meningitis. Head CT scan and spinal fluid were normal; blood counts remained normal; creatinine increased transiently to 1.7; an association with vodka and tonic was not suspected. This history confirmed the quinine etiology of her TMA. Subsequently she was demonstrated to have quinine-dependent antibodies reactive with platelets and neutrophils (BloodCenter of Wisconsin). Genetic sequencing (U of Iowa) revealed no mutations associated with complement-mediated TMA. PEX was continued until her platelet count was normal (12 days); hemodialysis was required for 2 months. Five years after TMA, she continues to have hypertension, fatigue and arthralgias. Her creatinine clearance is 54 ml/min/1.73m2, indicating Stage 3A chronic kidney disease.Systematic literature review: A search of 12 databases for reports of adverse reactions to quinine identified 118 patients with definite or probable evidence for a causal association of quinine with idiosyncratic adverse reactions. Most quinine reactions were related to ingestion of tablets, but 24 patients had adverse reactions caused by quinine-containing beverages. Three patients had TMA, similar to our patient; 2 of these 3 patients also had disseminated intravascular coagulation (DIC); one also had liver function abnormalities. Seven patients had isolated severe thrombocytopenia, 1 patient had granulomatous hepatitis, 1 patient had retina toxicity with vision loss; 1 patient had anaphylaxis, and 11 patients had cutaneous reactions (Table). Many patients had multiple recurrent episodes before the quinine etiology was discovered. All patients recovered, but no reports described long-term follow-up.Conclusion: Our patient's experience and our review published reports highlight the potential for severe, systemic adverse reactions caused by quinine-containing beverages. The reactions may involve multiple organ systems. Long-term outcomes are not described in published reports, but our patient has chronic kidney disease 5 years following her acute TMA. The small amounts of quinine in beverages (typically 80 mg/l) are sufficient to cause severe immunologic adverse reactions. Quinine is also added to cocktails to create fluorescence, then described as "Shocktails". A thorough history for exposure to quinine is critical.24 previously published patients with acute quinine-induced reactionsTablePatientsAdverse Events1TMA (3 episodes), also DIC1TMA (6 episodes), also fever, chills, neutropenia, DIC, liver function abnormalities1TMA (1 episode)7Thrombocytopenia (3 patients, multiple episodes), nadir platelet count (median) 2000/µL1Granulomatous hepatitis, neutropenia (multiple episodes)1Retinal toxicity, vision loss1Anaphylactic shock (2 episodes)11Dermatologic disorders: fixed drug eruptions (7), toxic epidermal necrolysis (1), urticaria (1), photosensitivity, erythematous lesions (1), erythematosus rash (1) DisclosuresNo relevant conflicts of interest to declare.

Carboxypeptidase B2 Is Protective in a Mouse Model of Shiga Toxin-Induced Hemolytic Uremic Syndrome

Hemolytic uremic syndrome (HUS) is characterized by a triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure. The most common cause of HUS is Shiga toxin (STX)-producing E. coli, and eculizumab, a monoclonal antibody against complement C5, has shown clinical efficacy in some patients. Carboxypeptidase B2 (CPB2) is a metalloprotease activated by the thrombin/thrombomodulin complex that inactivates a number of inflammatory mediators, including complement C3a, and C5a by removing their C-terminal arginine. We hypothesized that in a murine model of STX-induced HUS, Cpb2-/- mice would have exacerbated disease compared to wild type (WT) mice due to excessive C3a and/or C5a in the absence of CPB2. A mouse model of STX-induced HUS was established by giving STX and LPS toxins intraperitoneally. Cpb2-/- mice had worse survival than WT (37% survival vs. 87% at 48h, p=0.0156). At 48h, severe thrombocytopenia developed in both WT and Cpb2-/- mice (WT: 0.096x106/μL; Cpb2-/-: 0.054x106/μL) compared to controls (1.2x106/μL; p>0.0001 vs. either WT or Cpb2-/-), with Cpb2-/- mice showing worse thrombocytopenia. Renal insufficiency was worse in Cpb2-/- mice than WT mice (BUN at 48h: 85 mg/dL vs. 37 mg/dL, p=0.0074; creatinine: 1.33 mg/dL vs. 0.23 mg/dL; p=0.0112, for Cpb2-/- and WT mice respectively, compared with normal baseline BUN and creatinine of 19 mg/dL and 0.1 mg/dL). Cpb2-/- mice developed worse anemia than WT (hemoglobin 9.8 g/dL vs. 12.4 g/dL, p=0.001 in Cpb2-/- vs. WT mice respectively). At 48h, liver function was worse in Cpb2-/- mice than WT mice, while plasma LDH was increased in Cpb2-/- mice more than WT mice. Using a standardized health score, the Cpb2-/- mice were worse than WT mice at all time points. Thus this model recapitulates STX-induced HUS with the Cpb2-/- mice having worse disease than WT. If the animals were treated with STX alone, there were no deaths in either genotype at 48h and only 37.5% mortality in Cpb2-/- mice by 60h compared with no deaths in WT mice. BUN, creatinine, liver enzymes and LDH were increased in both genotypes treated with STX alone compared to untreated mice, but there was no significant difference between the genotypes. Treatment with LPS alone caused thrombocytopenia in both WT and Cpb2-/- mice and LDH, BUN and creatinine levels were higher in Cpb2-/- mice than in WT mice, but there was no death at 48h and no drop in hemoglobin. Thus while either STX alone or LPS alone caused pathological conditions in the mice, the typical triad of HUS was only present when STX and LPS were given in combination. The Cpb2-/- mice had worse disease than WT mice consistent with our hypothesis on the role of CPB2 in inactivating C3a and/or C5a in STX-induced HUS. The potential efficacy of C3a and/or C5a blockade and anti-thrombotic agents will be tested in this model. DisclosuresNo relevant conflicts of interest to declare.

Quiescent complement in nonhuman primates during E coli Shiga toxin-induced hemolytic uremic syndrome and thrombotic microangiopathy

AbstractEnterohemorrhagic Escherichia coli (EHEC) produce ribosome-inactivating Shiga toxins (Stx1, Stx2) responsible for development of hemolytic uremic syndrome (HUS) and acute kidney injury (AKI). Some patients show complement activation during EHEC infection, raising the possibility of therapeutic targeting of complement for relief. Our juvenile nonhuman primate (Papio baboons) models of endotoxin-free Stx challenge exhibit full spectrum HUS, including thrombocytopenia, hemolytic anemia, and AKI with glomerular thrombotic microangiopathy. There were no significant increases in soluble terminal complement complex (C5b-9) levels after challenge with lethal Stx1 (n = 6) or Stx2 (n = 5) in plasma samples from T0 to euthanasia at 49.5 to 128 hours post-challenge. d-dimer and cell injury markers (HMGB1, histones) confirmed coagulopathy and cell injury. Thus, complement activation is not required for the development of thrombotic microangiopathy and HUS induced by EHEC Shiga toxins in these preclinical models, and benefits or risks of complement inhibition should be studied further for this infection.

Clinical Features of Critically Ill Patients With Shiga Toxin–Induced Hemolytic Uremic Syndrome

In Spring 2011, an unprecedented outbreak of Shiga toxin-producing Escherichia coli serotype O104:H4-associated hemolytic uremic syndrome occurred in Northern Germany. The aim of this study was to describe the clinical characteristics, treatments, and outcomes of critically ill patients with Shiga toxin-producing E. coli-associated hemolytic uremic syndrome during this outbreak. Multicenter, retrospective, observational study of critically ill adult patients with Shiga toxin-producing E. coli-associated hemolytic uremic syndrome in six hospitals in Hamburg, Germany, between May 2011 and August 2011. During the study period, 106 patients with Shiga toxin-producing E. coli-associated hemolytic uremic syndrome were admitted to eight ICUs. The median age was 40 years (range, 18-83) with a female:male ratio of 3:1. The median time from onset of clinical symptoms to hospital admission was 3 days and from hospital to ICU admission an additional 3 days. A total of 101 patients (95.3%) had acute renal failure and 78 (73.6%) required renal replacement therapy. Intubation and mechanical ventilation were required in 38 patients (35.8%) and noninvasive ventilation was required in 17 patients (16.0%). The median duration of invasive ventilation was 7 days (range, 1-32 days) and the median ICU stay was 10 days (range, 1-45 days). Fifty-one patients (48.1%) developed sepsis; of these 51 patients, 27 (25.4%) developed septic shock. Seventy patients (66.0%) developed severe neurological symptoms. Ninety-seven patients (91.5%) were treated with plasma exchange and 50 patients (47.2%) received eculizumab (monoclonal anti-C5 antibody). The mortality rate was 4.7%. Mild residual neurological symptoms were present in 21.7% of patients at ICU discharge, and no patient required renal replacement therapy 6 months after ICU admission. During the 2011 Shiga toxin-producing E. coli-associated hemolytic uremic syndrome outbreak in Germany, critical illness developed rapidly after hospital admission, often in young women. The infection was associated with severe neurological and renal symptoms, requiring mechanical ventilation and renal replacement therapy in a substantial proportion of patients. Overall, recovery was much better than expected.

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.

Pathologic Changes in Mice Induced by Subtilase Cytotoxin, a Potent NewEscherichia coliAB5Toxin That Targets the Endoplasmic Reticulum

Subtilase cytotoxin (SubAB) is the prototype of a recently discovered AB(5) cytotoxin family produced by certain strains of Shiga toxigenic Escherichia coli (STEC). The catalytic A subunit is a highly specific subtilase-like serine protease that cleaves the endoplasmic reticulum chaperone BiP. The toxin is lethal for mice, but the pathology it induces is poorly understood. Here, we show that intraperitoneal injection of SubAB causes microangiopathic hemolytic anemia, thrombocytopenia, and renal impairment in mice--characteristics typical of Shiga toxin-induced hemolytic uremic syndrome. SubAB caused extensive microvascular thrombosis and other histologic damage in the brain, kidneys, and liver, as well as dramatic splenic atrophy. Peripheral blood leukocyte levels were increased at 24 h; there was also significant neutrophil infiltration in the liver, kidneys, and spleen and toxin-induced apoptosis at these sites. These findings raise the possibility that SubAB directly contributes to pathology in humans infected with strains of STEC that produce both Shiga toxin and SubAB.

Antibody therapy in the management of shiga toxin-induced hemolytic uremic syndrome.

Hemolytic uremic syndrome (HUS) is a disease that can lead to acute renal failure and often to other serious sequelae, including death. The majority of cases are attributed to infections with Escherichia coli, serotype O157:H7 strains in particular, which cause bloody diarrhea and liberate one or two toxins known as Shiga toxins 1 and 2. These toxins are thought to directly be responsible for the manifestations of HUS. Currently, supportive nonspecific treatment is the only available option for the management of individuals presenting with HUS. The benefit of antimicrobial therapy remains uncertain because of several reports which claim that such intervention can in fact exacerbate the syndrome. There have been only a few specific therapies directed against neutralizing the activities of these toxins, but none so far has been shown to be effective. This article reviews the literature on the mechanism of action of these toxins and the clinical manifestations and current management and treatment of HUS. The major focus of the article, however, is the development and rationale for using neutralizing human antibodies to combat this toxin-induced disease. Several groups are currently pursuing this approach with either humanized, chimeric, or human antitoxin antibodies produced in transgenic mice. They are at different phases of development, ranging from preclinical evaluation to human clinical trials. The information available from preclinical studies indicates that neutralizing specific antibodies directed against the A subunit of the toxin can be highly protective. Such antibodies, even when administered well after exposure to bacterial infection and onset of diarrhea, can prevent the occurrence of systemic complications.

Protective role of nitric oxide in mice with Shiga toxin-induced hemolytic uremic syndrome

Nitric oxide (NO) is an endogenous vasodilator and platelet inhibitor. An enhanced NO production has been detected in patients with hemolytic uremic syndrome (HUS), although its implication in HUS pathogenesis has not been clarified. A mouse model of Shiga toxin 2 (Stx2)-induced HUS was used to study the role of NO in the development of the disease. Modulation of l-arginine-NO pathway was achieved by oral administration of NO synthase (NOS) substrate or inhibitors, and renal damage, mortality and platelet activity were evaluated. The involvement of platelets was studied by means of a specific anti-platelet antibody. Inhibition of NO generation by the NOS inhibitor L-NAME enhanced Stx2-mediated renal damage and lethality; this effect was prevented by the addition of l-arginine. The worsening effect of L-NAME involved enhanced Stx2-mediated platelet activation, and it was completely prevented by platelet depletion. NO exerts a protective role in the early pathogenesis of HUS, and its inhibition potentiates renal damage and mortality through a mechanism involving enhanced platelet activation.

Protective role of nitric oxide in mice with Shiga toxin-induced hemolytic uremic syndrome

Protective role of nitric oxide in mice with Shiga toxin-induced hemolytic uremic syndrome

Pathogenesis of Shiga toxin-induced hemolytic uremic syndrome.

The term hemolytic uremic syndrome (HUS) was first introduced to describe a heterogeneous group of diseases characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure. Substantial progress has been made in our understanding of the etiology and pathogenesis of HUS. This article reviews some of the classic and new concepts related to the pathogenesis of Shiga toxin (Stx)-HUS and discusses their clinical relevance for the diagnosis and treatment of this syndrome. Infection with Stx-producing bacteria can induce HUS after a prodromal illness with or without diarrhea. Stx-induced renal endothelial injury is the primary pathogenic event. However, Stx also damages mesangial cells, as well as glomerular and renal tubular epithelial cells. Young children are at greatest risk for Stx-HUS because they express high levels of Stx receptors in renal glomeruli. Older children and adults express lower levels of glomerular Stx receptors and may develop Stx-HUS whenever the combined effects of lipopolysaccharide and cytokines upregulate the expression of Stx receptors and sensitize glomerular endothelial cells to Stx-induced injury, activate the coagulation-fibrinolytic system, and induce endothelial injury. Chemokine receptors and cytokines released by inflammatory cells (i.e., monocyte chemoattractant protein-1, interleukin-6, interleukin-8,) or injured endothelial cells (i.e., basic fibrobast growth factor) may play roles in this process. Measurement of the activity of a von Willebrand factor protease in plasma may help distinguish patients with thrombotic thrombocytopenic purpura from those with Stx-HUS.