Regulation of human neutrophil IL-1ß secretion induced by Escherichia coli O157:H7 responsible for hemolytic uremic syndrome.

Shiga-toxin producing Escherichia coli (STEC) infections can cause from bloody diarrhea to Hemolytic Uremic Syndrome. The STEC intestinal infection triggers an inflammatory response that can facilitate the development of a systemic disease. We report here that neutrophils might contribute to this inflammatory response by secreting Interleukin 1 beta (IL-1ß). STEC stimulated neutrophils to release elevated levels of IL-1ß through a mechanism that involved the activation of caspase-1 driven by the NLRP3-inflammasome and neutrophil serine proteases (NSPs). Noteworthy, IL-1ß secretion was higher at lower multiplicities of infection. This secretory profile modulated by the bacteria:neutrophil ratio, was the consequence of a regulatory mechanism that reduced IL-1ß secretion the higher were the levels of activation of both caspase-1 and NSPs, and the production of NADPH oxidase-dependent reactive oxygen species. Finally, we also found that inhibition of NSPs significantly reduced STEC-triggered IL-1ß secretion without modulating the ability of neutrophils to kill the bacteria, suggesting NSPs might represent pharmacological targets to be evaluated to limit the STEC-induced intestinal inflammation.

Shiga toxin targets the podocyte causing hemolytic uremic syndrome through endothelial complement activation.

BACKGROUND: Shiga toxin (Stx)-producing Escherichia coli hemolytic uremic syndrome (STEC-HUS) is the leading cause of acute kidney injury in children, with an associated mortality of up to 5%. The mechanisms underlying STEC-HUS and why the glomerular microvasculature is so susceptible to injury following systemic Stx infection are unclear. METHODS: Transgenic mice were engineered to express the Stx receptor (Gb3) exclusively in their kidney podocytes (Pod-Gb3) and challenged with systemic Stx. Human glomerular cell models and kidney biopsies from patients with STEC-HUS were also studied. FINDINGS: Stx-challenged Pod-Gb3 mice developed STEC-HUS. This was mediated by a reduction in podocyte vascular endothelial growth factor A (VEGF-A), which led to loss of glomerular endothelial cell (GEnC) glycocalyx, a reduction in GEnC inhibitory complement factor H binding, and local activation of the complement pathway. Early therapeutic inhibition of the terminal complement pathway with a C5 inhibitor rescued this podocyte-driven, Stx-induced HUS phenotype. CONCLUSIONS: This study potentially explains why systemic Stx exposure targets the glomerulus and supports the early use of terminal complement pathway inhibition in this devastating disease. FUNDING: This work was supported by the UK Medical Research Council (MRC) (grant nos. G0901987 and MR/K010492/1) and Kidney Research UK (grant nos. TF_007_20151127, RP42/2012, and SP/FSGS1/2013). The Mary Lyon Center is part of the MRC Harwell Institute and is funded by the MRC (A410).

Shiga Toxin 2 Triggers C3a-Dependent Glomerular and Tubular Injury through Mitochondrial Dysfunction in Hemolytic Uremic Syndrome.

Shiga toxin (Stx)-producing Escherichia coli is the predominant offending agent of post-diarrheal hemolytic uremic syndrome (HUS), a rare disorder of microvascular thrombosis and acute kidney injury possibly leading to long-term renal sequelae. We previously showed that C3a has a critical role in the development of glomerular damage in experimental HUS. Based on the evidence that activation of C3a/C3a receptor (C3aR) signaling induces mitochondrial dysregulation and cell injury, here we investigated whether C3a caused podocyte and tubular injury through induction of mitochondrial dysfunction in a mouse model of HUS. Mice coinjected with Stx2/LPS exhibited glomerular podocyte and tubular C3 deposits and C3aR overexpression associated with cell damage, which were limited by C3aR antagonist treatment. C3a promoted renal injury by affecting mitochondrial wellness as demonstrated by data showing that C3aR blockade reduced mitochondrial ultrastructural abnormalities and preserved mitochondrial mass and energy production. In cultured podocytes and tubular cells, C3a caused altered mitochondrial fragmentation and distribution, and reduced anti-oxidant SOD2 activity. Stx2 potentiated the responsiveness of renal cells to the detrimental effects of C3a through increased C3aR protein expression. These results indicate that C3aR may represent a novel target in Stx-associated HUS for the preservation of renal cell integrity through the maintenance of mitochondrial function.

Citrobacter rodentium(ϕStx2dact), a murine infection model for enterohemorrhagic Escherichia coli.

The formation of attaching and effacing (A/E) lesions on intestinal epithelium, combined with Shiga toxin production, are hallmarks of enterohemorrhagic Escherichia coli (EHEC) infection that can lead to lethal hemolytic uremic syndrome. Although an animal infection model that fully recapitulates human disease remains elusive, mice orally infected with Citrobacter rodentium(ϕStx2dact), a natural murine pathogen lysogenized with an EHEC-derived Shiga toxin 2-producing bacteriophage, develop intestinal A/E lesions and toxin-dependent systemic disease. This model has facilitated investigation of how: (A) phage gene expression and prophage induction contribute to disease and are potentially triggered by antibiotic treatment; (B) virulence gene expression is altered by microbiota and the colonic metabolomic milieu; and (C) innate immune signaling is affected by Stx. Thus, the model provides a unique tool for accessing diverse aspects of EHEC pathogenesis.

Shiga Toxins: An Update on Host Factors and Biomedical Applications.

Shiga toxins (Stxs) are classic bacterial toxins and major virulence factors of toxigenic Shigella dysenteriae and enterohemorrhagic Escherichia coli (EHEC). These toxins recognize a glycosphingolipid globotriaosylceramide (Gb3/CD77) as their receptor and inhibit protein synthesis in cells by cleaving 28S ribosomal RNA. They are the major cause of life-threatening complications such as hemolytic uremic syndrome (HUS), associated with severe cases of EHEC infection, which is the leading cause of acute kidney injury in children. The threat of Stxs is exacerbated by the lack of toxin inhibitors and effective treatment for HUS. Here, we briefly summarize the Stx structure, subtypes, in vitro and in vivo models, Gb3 expression and HUS, and then introduce recent studies using CRISPR-Cas9-mediated genome-wide screens to identify the host cell factors required for Stx action. We also summarize the latest progress in utilizing and engineering Stx components for biomedical applications.

Citrobacter rodentium Lysogenized with a Shiga Toxin-Producing Phage: A Murine Model for Shiga Toxin-Producing E. coli Infection.

Shiga toxin-producing E. coli (STEC) is a common foodborne pathogen in developed countries. STEC generates "attaching and effacing" (AE) lesions on colonic epithelium, characterized by effacement of microvilli and the formation of actin "pedestals" beneath intimately attached bacteria. In addition, STEC are lysogenized with a phage that, upon induction, can produce potent Shiga toxins (Stx), potentially leading to both hemorrhagic colitis and hemolytic uremic syndrome. Investigation of the pathogenesis of this disease has been challenging because STEC does not readily colonize conventional mice.Citrobacter rodentium (CR) is a related mouse pathogen that also generates AE lesions. Whereas CR does not produce Stx, a murine model for STEC utilizes CR lysogenized with an E. coli-derived Stx phage, generating CR(Φstx), which both colonizes conventional mice and readily gives rise to systemic disease. We present here key methods for the use of CR(Φstx) infection as a highly predictable murine model for infection and disease by STEC. Importantly, we detail CR(Φstx) inoculation by feeding, determination of pathogen colonization, production of phage and toxin, and assessment of intestinal and renal pathology. These methods provide a framework for studying STEC-mediated systemic disease that may aid in the development of efficacious therapeutics.

Nephrotic-range proteinuria and central nervous involvement in typical hemolytic uremic syndrome: a case report.

BACKGROUND: Hemolytic uremic syndrome (HUS), a common subtype of thrombotic microangiopathy (TMA), is characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. Shiga toxin-producing Escherichia coli infection is the most common cause of post-diarrheal HUS. Kidney and central nervous system are the primary target organs. CASE PRESENTATION: A 64-year-old male presented with HUS following bloody diarrhea. Nephrotic-range proteinuria and hypoalbuminemia were present at the acute stage and renal histology revealed common TMA features. Neurological involvement presented as confusion and impaired cognitive function. Cranial magnetic resonance imaging demonstrated bilateral T2 hyperintensities in the brainstem and insula. The patient received plasma exchange and supportive care. Both the renal and neurological impairments were completely recovered 3 months after the onset. CONCLUSION: We report an adult patient presenting with nephrotic-range proteinuria and central nervous system involvement at the acute phase of post-diarrheal HUS. The reversibility of the organ damages might predict a favorable outcome.

Shiga Toxin Selectively Upregulates Expression of Syndecan-4 and Adhesion Molecule ICAM-1 in Human Glomerular Microvascular Endothelium.

Hemolytic uremic syndrome (HUS) is a severe renal disease that is often preceded by infection with Shiga toxin (Stx)-producing Escherichia coli (STEC). The exact mechanism of Stx-mediated inflammation on human glomerular microvascular endothelial cells (HGMVECs) during HUS is still not well understood. In this study, we investigated the effect of Stx1 on the gene expression of proteins involved in leucocyte-mediated and complement-mediated inflammation. Our results showed that Stx1 enhances the mRNA and protein expression of heparan sulfate proteoglycan (HSPG) syndecan-4 in HGMVECs pre-stimulated with tumor necrosis factor α (TNFα). CD44 was upregulated on mRNA but not on protein level; no effect on the mRNA expression of other tested HSPGs glypican-1 and betaglycan was observed. Furthermore, Stx1 upregulated the mRNA, cell surface expression, and supernatant levels of the intercellular adhesion molecule-1 (ICAM-1) in HGMVECs. Interestingly, no effect on the protein levels of alternative pathway (AP) components was observed, although C3 mRNA was upregulated. All observed effects were much stronger in HGMVECs than in human umbilical endothelial cells (HUVECs), a common model cell type used in endothelial studies. Our results provide new insights into the role of Stx1 in the pathogenesis of HUS. Possibilities to target the overexpression of syndecan-4 and ICAM-1 for STEC-HUS therapy should be investigated in future studies.

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.

Heme as Possible Contributing Factor in the Evolvement of Shiga-Toxin Escherichia coli Induced Hemolytic-Uremic Syndrome.

Shiga-toxin (Stx)-producing Escherichia coli hemolytic-uremic syndrome (STEC-HUS) is one of the most common causes of acute kidney injury in children. Stx-mediated endothelial injury initiates the cascade leading to thrombotic microangiopathy (TMA), still the exact pathogenesis remains elusive. Interestingly, there is wide variability in clinical presentation and outcome. One explanation for this could be the enhancement of TMA through other factors. We hypothesize that heme, as released during extensive hemolysis, contributes to the etiology of TMA. Plasma levels of heme and its scavenger hemopexin and degrading enzyme heme-oxygenase-1 (HO-1) were measured in 48 STEC-HUS patients. Subsequently, the effect of these disease-specific heme concentrations, in combination with Stx, was assessed on primary human glomerular microvascular endothelial cells (HGMVECs). Significantly elevated plasma heme levels up to 21.2 µM were found in STEC-HUS patients compared to controls and were inversely correlated with low or depleted plasma hemopexin levels (R2 -0.74). Plasma levels of HO-1 are significantly elevated compared to controls. Interestingly, especially patients with high heme levels (n = 12, heme levels above 75 quartile range) had high plasma HO-1 levels with median of 332.5 (86-720) ng/ml (p = 0.008). Furthermore, heme is internalized leading to a significant increase in reactive oxygen species production and stimulated both nuclear translocation of NF-κB and increased levels of its target gene (tissue factor). In conclusion, we are the first to show elevated heme levels in patients with STEC-HUS. These increased heme levels mediate endothelial injury by promoting oxidative stress and a pro-inflammatory and pro-thrombotic state. Hence, heme may be a contributing and driving factor in the pathogenesis of STEC-HUS and could potentially amplify the cascade leading to TMA.

Particulate Shiga Toxin 2 in Blood is Associated to the Development of Hemolytic Uremic Syndrome in Children.

Hemolytic uremic syndrome (HUS), the leading cause of acute renal failure in children (< 3 years), is mainly related to Shiga toxins (Stx)-producing Escherichia coli (STEC) infections. STEC are confined to the gut resulting in hemorrhagic colitis, whereas Stx are delivered in blood to target kidney and brain, with unclear mechanisms, triggering HUS in 5 to 15% of infected children. Stx were found on circulating cells, free in sera (soluble Stx) or in blood cell-derived microvesicles (particulate Stx), whereby the relationship between these forms of circulating toxins is unclear. Here, we have examined 2,846 children with bloody diarrhea and found evidence of STEC infection in 5%. Twenty patients were enrolled to study the natural course of STEC infections before the onset of HUS. In patients, Stx were found to be associated to circulating cells and/or free and functionally active in sera. In most children, Stx were bound to neutrophils when high amounts of toxins were found in feces. Time-course analysis showed that Stx increased transiently in patients' sera while the decrease of toxin amount on leukocytes was observed. Notably, patients who recovered (85%) displayed different settings than those who developed HUS (15%). The distinctive feature of the latter group was the presence in blood of particulate Stx2 (Stx2 sedimented at g-forces corresponding to 1 µm microvesicles) the day before diagnosis of HUS, during the release phase of toxins from circulating cells. This observation strongly suggests the involvement of blood cell-derived particulate Stx2 in the transition from hemorrhagic colitis to HUS.

Platelet thrombus formation in eHUS is prevented by anti-MBL2.

E. coli associated Hemolytic Uremic Syndrome (epidemic hemolytic uremic syndrome, eHUS) caused by Shiga toxin-producing bacteria is characterized by thrombocytopenia, microangiopathic hemolytic anemia, and acute kidney injury that cause acute renal failure in up to 65% of affected patients. We hypothesized that the mannose-binding lectin (MBL) pathway of complement activation plays an important role in human eHUS, as we previously demonstrated that injection of Shiga Toxin-2 (Stx-2) led to fibrin deposition in mouse glomeruli that was blocked by co-injection of the anti-MBL-2 antibody 3F8. However, the markers of platelet thrombosis in affected mouse glomeruli were not delineated. To investigate the effect of 3F8 on markers of platelet thrombosis, we used kidney sections from our mouse model (MBL-2+/+ Mbl-A/C-/-; MBL2 KI mouse). Mice in the control group received PBS, while mice in a second group received Stx-2, and those in a third group received 3F8 and Stx-2. Using double immunofluorescence (IF) followed by digital image analysis, kidney sections were stained for fibrin(ogen) and CD41 (marker for platelets), von-Willebrand factor (marker for endothelial cells and platelets), and podocin (marker for podocytes). Electron microscopy (EM) was performed on ultrathin sections from mice and human with HUS. Injection of Stx-2 resulted in an increase of both fibrin and platelets in glomeruli, while administration of 3F8 with Stx-2 reduced both platelet and fibrin to control levels. EM studies confirmed that CD41-positive objects observed by IF were platelets. The increases in platelet number and fibrin levels by injection of Stx-2 are consistent with the generation of platelet-fibrin thrombi that were prevented by 3F8.

Complement dysregulation in glomerulonephritis.

Glomerulonephritis (GN) refers to a group of renal diseases affecting the glomeruli due to the damage mediated by immunological mechanisms. A large proportion of the disease manifestations are caused by disturbances in the complement system. They can be due to genetic errors, autoimmunity, microbes or abnormal immunoglobulins, like modified IgA or paraproteins. The common denominator in most of the problems is an overactive or misdirected alternative pathway complement activation. An assessment of kidney function, amount of proteinuria and hematuria are crucial elements to evaluate, when glomerulonephritis is suspected. However, the cornerstones of the diagnoses are renal biopsy and careful examination of the complement abnormality. Differential diagnostics between the various forms of GN is not possible based on clinical features, as they may vary greatly. This review describes the known mechanisms of complement dysfunction leading to different forms of primary GN (like IgA glomerulonephritis, dense deposit disease, C3 glomerulonephritis, post-infectious GN, membranous GN) and differences to atypical hemolytic uremic syndrome. It also covers the basic elements of etiology-directed therapy and prognosis of the most common forms of GN. Common principles in the management of GN include treatment of hypertension and reduction of proteinuria, some require immunomodulating treatment. Complement inhibition is an emerging treatment option. A thorough understanding of the basic disease mechanism and a careful follow-up are needed for optimal therapy.

Tamoxifen blocks retrograde trafficking of Shiga toxin 1 and 2 and protects against lethal toxicosis.

Shiga toxin 1 (STx1) and 2 (STx2), produced by Shiga toxin-producing Escherichia coli, cause lethal untreatable disease. The toxins invade cells via retrograde trafficking. Direct early endosome-to-Golgi transport allows the toxins to evade degradative late endosomes. Blocking toxin trafficking, particularly at the early endosome-to-Golgi step, is appealing, but transport mechanisms of the more disease-relevant STx2 are unclear. Using data from a genome-wide siRNA screen, we discovered that disruption of the fusion of late endosomes, but not autophagosomes, with lysosomes blocked the early endosome-to-Golgi transport of STx2. A subsequent screen of clinically approved lysosome-targeting drugs identified tamoxifen (TAM) to be a potent inhibitor of the trafficking and toxicity of STx1 and STx2 in cells. The protective effect was independent of estrogen receptors but dependent on the weak base property of TAM, which allowed TAM to increase endolysosomal pH and alter endosomal dynamics. Importantly, TAM treatment enhanced survival of mice injected with a lethal dose of STx1 or STx2. Thus, it may be possible to repurpose TAM for treating Shiga toxin-producing E. coli infections.

Star-shaped polypeptides exhibit potent antibacterial activities.

Peptide-based biomaterials are a promising class of antimicrobial agents that work by physically damaging bacterial cell membranes rather than targeting intracellular factors, resulting in less susceptibility to drug resistance. Herein we report the synthesis of cationic, star-shaped polypeptides with 3 to 8 arms and their evaluation as antimicrobial agents against different types of bacteria. The effects of the arm number and side chain group on their antimicrobial activities were systematically investigated. Compared to their linear counterparts, these star-shaped polypeptides exhibited potent antibacterial activity (which may involve adhesion and disruption processes). The increase of the arm number can efficiently increase the antibacterial activities up until 8 arms, which did not exhibit further improvement of antibacterial activities. Poly(l-lysine) (PLL) modified with an indole group (PLL-g-indo) exhibited the best antibacterial activity among all grafted copolypeptides and improved cytotoxic selectivity towards pathogens over mammalian cells without compromising their hemolytic activities. In vivo studies showed that the star-shaped PLL-g-indo can effectively suppress Enterohaemorrhagic E. coli (EHEC) infection and attenuate the clinical symptoms in mice, suggesting that they are promising antimicrobial agents.

Rab7b participation on the TLR4 (Toll-like receptor) endocytic pathway in Shiga toxin-associated Hemolytic Uremic Syndrome (HUS).

BACKGROUND: The inflammatory response of the host to Shiga toxin and/or lipopolysaccharide (LPS) of Escherichia coli (E. coli) is included in (HUS). The TLR4-LPS complex is internalized and TLR4 induced inflammatory signaling is stopped by targeting the complex for degradation. Rab7b, a small guanosine triphosphatase (GTPase) expressed in monocytes, regulates the later stages of the endocytic pathway. OBJECTIVE: we studied the Rab7b participation on the TLR4 endocytic pathway and its effect on monocyte cytokine production along the acute course of pediatric Shiga toxin-associated HUS. METHODS AND RESULTS: Monocytes were identified according to their positivity in CD14 expression. Surface TLR4 expression in monocytes from 18 HUS patients significantly increased by day 1 to 6, showing the highest increase on day 4 compared to monocytes of 10 healthy children. Significant higher surface TLR4 expression was accompanied by increased proinflammatory intracellular cytokines, tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6). In contrast, after these time points, surface TLR4 expression and intracellular TNF-α levels, returned to near control levels after 10 days. Furthermore, confocal immunofluorescence microscopy proved colocalization of increased intracellular TLR4/Rab7b determined by Pearson's coefficient in monocytes from HUS patients from day 1 on the highest colocalization of both proteins by day 4. Decreased TLR4/Rab7b colocalization was shown 10 days after HUS onset. CONCLUSION: The colocalization of TLR4 and Rab7b allows us to suggest Rab7b participation in the control of the TLR4 endocytic pathway in HUS patient monocytes. A consequential fall in cytokine production throughout the early follow up of HUS is demonstrated.

Interleukin-33/ST2 signaling contributes to the severity of hemolytic uremic syndrome induced by enterohemorrhagic Escherichia coli.

OBJECTIVES: Interleukin (IL)-33 plays an important role in host defense, immune regulation, and inflammation. This study assessed IL-33's role in the pathogenesis of severe hemolytic uremic syndrome (HUS) induced by enterohemorrhagic Escherichia coli (EHEC). We also investigated the clinical significance of IL-33 and soluble ST2 (soluble form of IL-33 receptor) serum levels in patients with EHEC-induced HUS. METHODS: The role of IL-33 in Shiga toxin (STx)-2-induced endothelial injury was studied in human umbilical vein endothelial cells (HUVECs) in vitro. Blood samples were obtained from 21 HUS patients and 15 healthy controls (HC). The IL-33 and sST2 serum levels were quantified using an enzyme-linked immunosorbent assay. The results were compared to HUS' clinical features. RESULTS: Cytotoxic assays indicated that IL-33 enhanced STx2 toxicity in HUVECs. Serum IL-33 levels in most HUS patients were below the lowest detection limit. On the other hand, serum sST2 levels in patients during the HUS phase were significantly higher than those in HC and showed a correlation with disease severity. Serum sST2 levels in patients with encephalopathy were significantly higher than those in patients without it. A serum sST2 level > 63.2 pg/mL was associated with a high risk of encephalopathy. Serum sST2 levels significantly correlated with serum levels of inflammatory cytokines related to the development of HUS. CONCLUSIONS: Our results indicate that IL-33 contributes to the severity of EHEC-induced HUS. Serum sST2 level in HUS patients correlated with disease activity, which suggests its potential role as a marker for disease activity and development of encephalopathy in patients with EHEC-induced HUS.

Shiga toxin-glycosphingolipid interaction: Status quo of research with focus on primary human brain and kidney endothelial cells.

Shiga toxin (Stx)-mediated injury of the kidneys and the brain represent the major extraintestinal complications in humans upon infection by enterohemorrhagic Escherichia coli (EHEC). Damage of renal and cerebral endothelial cells is the key event in the pathogenesis of the life-threatening hemolytic uremic syndrome (HUS). Stxs are AB5 toxins and the B-pentamers of the two clinically important Stx subtypes Stx1a and Stx2a preferentially bind to the glycosphingolipid globotriaosylceramide (Gb3Cer, Galα4Galß4Glcß1Cer) and to less extent to globotetraosylceramide (Gb4Cer, GalNAcß3Galα4Galß4Glcß1), which are expected to reside in lipid rafts in the plasma membrane of the human endothelium. This review summarizes the current knowledge on the Stx glycosphingolipid receptors and their lipid membrane ensemble in primary human brain microvascular endothelial cells (pHBMECs) and primary human renal glomerular endothelial cells (pHRGECs). Increasing knowledge on the precise initial molecular mechanisms by which Stxs interact with cellular targets will help to develop specific therapeutics and/or preventive measures to combat EHEC-caused diseases.

Complement depletion and Coombs positivity in pneumococcal hemolytic uremic syndrome (pnHUS). Case series and plea to revisit an old pathogenetic concept.

Hemolytic uremic syndrome is a rare complication of invasive pneumococcal infection (pnHUS). Its pathogenesis is poorly understood, and treatment remains controversial. The emerging role of complement in various forms of HUS warrants a new look at this "old" disease. We performed a retrospective analysis of clinical and laboratory features of three sequential cases of pnHUS since 2008 associated with pneumonia/pleural empyema, two due to Streptococcus pneumoniae serotype 19 A. Profound depletion of complement C3 (and less of C4) was observed in two patients. One patient was Coombs test positive. Her red blood cells (RBCs) strongly agglutinated with blood group compatible donor serum at 0 °C, but not at 37 °C. All three patients were treated with hemodialysis, concentrated RBCs, and platelets. Patient 2 received frozen plasma for hepatic failure with coagulation factor depletion. Intravenous immunoglobulin infusion, intended to neutralize pneumococcal neuraminidase in patient 3, was associated with rapid normalization of platelets and cessation of hemolysis. Two patients recovered without sequelae or disease recurrence. Patient 2 died within 2½ days of admission due to complicating Pseudomonas aeruginosa sepsis and multiorgan failure. Our observations suggest that pnHUS can be associated with dramatic, transient complement consumption early in the course of the disease, probably via the alternative pathway. A critical review of the literature and the reported cases argue against the postulated pathological role of preformed antibodies against the neuraminidase-exposed Thomsen-Friedenreich neoantigen (T antigen) in pnHUS. The improved understanding of complement regulation and bacterial strategies of complement evasion allows to propose a testable, new pathogenetic model of pnHUS. This model shifts emphasis from the action of natural anti-T antibodies toward impaired Complement Factor H (CFH) binding and function on desialylated membranes. Removal of neuraminic acid residues converts (protected) self to non-self surfaces that supports membrane attack complex (MAC) assembly. Complement activation is potentially exacerbated by decreased CFH availability following tight CFH binding to pneumococcal evasion proteins and/or by the presence of genetic variants of complement regulator proteins. Detailed clinical and experimental investigations are warranted to better understand the role of unregulated complement activation in pnHUS. Instead of avoidance of plasma, a new, integrated model is evolving, which may include short-term therapeutic complement blockade, particularly where genetic or functional APC dysregulation is suspected, in addition to bacterial elimination and, potentially, neuraminidase neutralization.

L-FABP and IL-6 as markers of chronic kidney damage in children after hemolytic uremic syndrome.

BACKGROUND: Hemolytic-uremic syndrome (HUS) is a form of thrombotic microangiopathy, in the course of which some patients may develop chronic kidney disease (CKD). From a clinical point of view, it is important to search for markers that allow for early identification of patients at risk of a poor prognosis. OBJECTIVES: The study evaluated the serum and urine levels of liver-type fatty acid binding protein (L-FABP) and interleukin 6 (IL-6). MATERIAL AND METHODS: The study was conducted in 29 children with a history of HUS. The relationship between L-FABP and IL-6 and anthropometric measurements, the value of estimated glomerular filtration rate (eGFR) and albuminuria were additionally evaluated. RESULTS: In children after HUS, L-FABP and IL-6 concentration in both serum and urine was significantly higher in comparison to the control group. No differences in L-FABP and IL-6 concentration in serum and urine depending on the type of HUS and gender were noted. Correlation between L-FABP and IL-6 in serum and urine with eGFR and urine albumin-creatinine ratio (ACR) in the total group of patients after HUS was not detected. In the group of children after 6 month observation after HUS, a negative correlation of L-FABP concentration with eGFR was found. CONCLUSIONS: The results indicate that the higher concentration of L-FABP in serum and urine of children with a history of HUS can be the result of protracted injury initiated during the acute phase of the disease. Lack of correlation of L-FABP concentration with the ACR may be associated with a short (less than 6 months) observation after acute renal failure or merely temporary renal tubular damage in the acute phase of the disease. In contrast, higher levels of IL-6 in serum and urine in children after HUS compared to healthy children and the negative correlation of L-FABP concentration and eGFR in children after 6 month observation after HUS may confirm their participation in CKD. Thus, L-FABP and IL-6 seem to be good biomarkers of chronic kidney damage in survivors of the acute phase of HUS.