Thalamic involvement in patients with neurologic impairment due to Shiga toxin 2

Cytokines expression from altered motor thalamus and behavior deficits following sublethal administration of Shiga toxin 2a involve the induction of the globotriaosylceramide receptor

Encephalopathy associated with hemolytic uremic syndrome is produced by enterohemorrhagic E. coli (EHEC) infection, which releases the virulence factors Shiga toxin (Stx) and lipopolysaccharide (LPS). Neurological compromise is a poor prognosis and mortality factor of the disease, and the thalamus is one of the brain areas most frequently affected. We have previously demonstrated the effectiveness of anti-inflammatory drugs to ameliorate the deleterious effects of these toxins. However, the thalamic production of cytokines involved in pro-inflammatory processes has not yet been acknowledged. The aim of this work attempts to determine whether systemic sublethal Stx2a or co-administration of Stx2a with LPS are able to rise a proinflammatory profile accompanying alterations of the neurovascular unit in anterior and lateral ventral nuclei of the thalamus (VA-VL) and motor behavior in mice. After 4 days of treatment, Stx2a affected the lectin-bound microvasculature distribution while increasing the expression of GFAP in reactive astrocytes and producing aberrant NeuN distribution in degenerative neurons. In addition, increased swimming latency was observed in a motor behavioral test. All these alterations were heightened when Stx2a was co-administered with LPS. The expression of pro-inflammatory cytokines TNFα, INF-γ and IL-2 was detected in VA-VL. All these effects were concomitant with increased expression of the Stx receptor globotriaosylceramide (Gb3), which hints at receptor involvement in the neuroinflammatory process as a key finding of this study. In conclusion, Stx2a to Gb3 may be determinant in triggering a neuroinflammatory event, which may resemble clinical outcomes and should thus be considered in the development of preventive strategies.

Roles of Shiga Toxins in Immunopathology

Shigella species and Shiga toxin-producing Escherichia coli (STEC) are agents of bloody diarrhea that may progress to potentially lethal complications such as diarrhea-associated hemolytic uremic syndrome (D+HUS) and neurological disorders. The bacteria share the ability to produce virulence factors called Shiga toxins (Stxs). Research over the past two decades has identified Stxs as multifunctional toxins capable of inducing cell stress responses in addition to their canonical ribotoxic function inhibiting protein synthesis. Notably, Stxs are not only potent inducers of cell death, but also activate innate immune responses that may lead to inflammation, and these effects may increase the severity of organ injury in patients infected with Stx-producing bacteria. In the intestines, kidneys, and central nervous system, excessive or uncontrolled host innate and cellular immune responses triggered by Stxs may result in sensitization of cells to toxin mediated damage, leading to immunopathology and increased morbidity and mortality in animal models (including primates) and human patients. Here, we review studies describing Stx-induced innate immune responses that may be associated with tissue damage, inflammation, and complement activation. We speculate on how these processes may contribute to immunopathological responses to the toxins.

Postinfectious Hemolytic Uremic Syndrome

Post-infectious hemolytic uremic syndrome (HUS) is caused by specific pathogens in patients with no identifiable HUS-associated genetic mutation or autoantibody. The majority of episodes is due to infections by Shiga toxin (Stx) producing Escherichia coli (STEC). This chapter reviews the epidemiology and pathogenesis of STEC-HUS, including bacterial-derived factors and host responses. STEC disease is characterized by hematological (microangiopathic hemolytic anemia), renal (acute kidney injury) and extrarenal organ involvement. Clinicians should always strive for an etiological diagnosis through the microbiological or molecular identification of Stx-producing bacteria and Stx or, if negative, serological assays. Treatment of STEC-HUS is supportive; more investigations are needed to evaluate the efficacy of putative preventive and therapeutic measures, such as non-phage-inducing antibiotics, volume expansion and anti-complement agents. The outcome of STEC-HUS is generally favorable, but chronic kidney disease, permanent extrarenal, mainly cerebral complication and death (in less than 5 %) occur and long-term follow-up is recommended. The remainder of this chapter highlights rarer forms of (post-infectious) HUS due to S. dysenteriae, S. pneumoniae, influenza A and HIV and discusses potential interactions between these pathogens and the complement system.

Role of Shiga/Vero toxins in pathogenesis

Shiga toxin (Stx) is the primary cause of severe host responses including renal and central nervous system (CNS) disease in Shiga toxin-producing E. coli (STEC) infections. The interaction of Stx with different eukaryotic cell types is described. Host responses to Stx and bacterial lipopolysaccharide (LPS) are compared as related to the features of the STEC-associated Hemolytic Uremic Syndrome (HUS). Data derived from animal models of HUS and CNS disease, in vivo, and eukaryotic cells, in vitro, are evaluated in relation to HUS disease of humans.

Recovery of thalamic microstructural damage after Shiga toxin 2-associated hemolytic-uremic syndrome

INTRODUCTION

The underlying pathophysiology of neurological complications in patients with hemolytic-uremic syndrome (HUS) remains unclear. It was recently attributed to a direct cytotoxic effect of Shiga toxin 2 (Stx2) in the thalamus. Conventional MRI of patients with Stx2-caused HUS revealed - despite severe neurological symptoms - only mild alterations if any, mostly in the thalamus. Against this background, we questioned: Does diffusion tensor imaging (DTI) capture the thalamic damage better than conventional MRI? Are neurological symptoms and disease course better reflected by thalamic alterations as detected by DTI? Are other brain regions also affected?

METHODS

Three women with serious neurological deficits due to Stx2-associated HUS were admitted to MRI/DTI at disease onset. Two of them were longitudinally examined. Fractional anisotropy (FA) and mean diffusivity were computed to assess Stx2-caused microstructural damage.

RESULTS

Compared to 90 healthy women, all three patients had significantly reduced thalamic FA. Thalamic mean diffusivity was only reduced in two patients. DTI of the longitudinally examined women demonstrated slow normalization of thalamic FA, which was paralleled by clinical improvement.

CONCLUSION

Whereas conventional MRI only shows slight alterations based on subjective evaluation, DTI permits quantitative, objective, and longitudinal assessment of cytotoxic cerebral damage in individual patients.

Neurological involvement in children with E. coli O104:H4-induced hemolytic uremic syndrome

BACKGROUND

The aim of this study was to analyze the neurological involvement and outcome in pediatric patients with hemolytic uremic syndrome (HUS) during the 2011 epidemic caused by Escherichia coli O104:H4.

METHODS

Clinical data and data from magnetic resonance imaging (MRI) scans and electroencephalography (EEG) during the acute phase of the disease and during follow-up at 3 and 6 months were analyzed in 50 patients. Twenty-five of these patients underwent neuropsychological testing (WISC IV) during follow-up.

RESULTS

Neurological involvement (stupor or coma, seizures, visual disturbances, paresis, myocloni) was initially observed in 14/50 (28%) patients. One patient died. EEG abnormalities were more frequent in patients with neurological involvement than in those without (12/14 vs. 13/25, respectively). Cranial MRI scans were analyzed in nine patients with neurological involvement, of whom five showed abnormal findings. At the 3- and 6-month follow-ups, EEG abnormalities were found in 14/40 (35%) and 7/36 (19%) patients, respectively, whereas 28/42 (67%) and 17/39 (44%) patients, respectively, complained about on-going reduced performance. Neuropsychological testing showed a slightly lower global intelligence quotient in patients with neurological involvement versus those without (113.4 ± 2.8 vs. 119.4 ± 1.8, respectively).

CONCLUSIONS

Neurological involvement was frequent in our cohort. Accordingly, the incidence of pathological EEG findings was high, even in patients without clinical signs of neurological involvement. Nevertheless, major neurological sequelae were rare, and neuropsychological outcome was favorable after 6 months.

Psychiatric symptoms in patients with Shiga toxin-producing E. coli O104:H4 induced haemolytic-uraemic syndrome

Background

In May 2011 an outbreak of Shiga toxin-producing enterohaemorrhagic E. coli (STEC) O104:H4 in Northern Germany led to a high number of in-patients, suffering from post-enteritis haemolytic-uraemic syndrome (HUS) and often severe affection of the central nervous system. To our knowledge so far only neurological manifestations have been described systematically in literature.

Aim

To examine psychiatric symptoms over time and search for specific symptom clusters in affected patients.

Methods

31 in-patients suffering from E. coli O104:H4 associated HUS, were examined and followed up a week during the acute hospital stay. Psychopathology was assessed by clinical interview based on the AMDP Scale, the Brief Symptom Inventory and the Clinical Global Impressions Scale.

Results

At baseline mental disorder due to known physiological condition (ICD-10 F06.8) was present in 58% of the examined patients. Patients suffered from various manifestations of cognitive impairment (n = 27) and hallucinations (n = 4). Disturbances of affect (n = 28) included severe panic attacks (n = 9). Psychiatric disorder was significantly associated with higher age (p<0.0001), higher levels of C-reactive protein (p<0.05), and positive family history of heart disease (p<0.05). Even within the acute hospital stay with a median follow up of 7 days, symptoms improved markedly over time (p <0.0001).

Conclusions

Aside from severe neurological symptoms the pathology in E.coli O104:H4 associated HUS frequently includes particular psychiatric disturbances. Long term follow up has to clarify whether or not these symptoms subside.

Cerebral magnetic resonance imaging findings in adults with haemolytic uraemic syndrome following an infection with Escherichia coli, subtype O104:H4

PURPOSE

Infections with Enterohaemorrhagic Escherichia coli typically occur in children causing haemolytic uraemic syndrome (HUS) and neurological symptoms in 20-50 %. Little information is available on the morphology of brain manifestations in adults. The purpose of this study was to identify a characteristic magnetic resonance imaging (MRI) pattern during the outbreak of a novel mutation of Escherichia coli O104:H4.

METHODS

Patients were recruited from two hospitals between May and July 2011. The MRI protocol included standard anatomical, diffusion-weighted, and susceptibility-sensitive sequences.

RESULTS

A total of 104 MRIs of 57 (32 female, 25 male) patients (mean 45.5 ± 18.4 years) showed abnormal signal intensity on 51 MRIs (49 %). Bilateral thalamus (39 %), bilateral pons (35 %), centrum semiovale and splenium of corpus callosum (33 %) were most often involved. Acute lesions were reversible in 81 % of cases. There was no statistically significant association between symptom onset and the MRI findings (P = 0.2).

CONCLUSIONS

Neuroimaging findings in this adult patient cohort were non-specific and similar to previous findings in children. A characteristic neuroimaging pattern of an infection with Escherichia coli O104:H4 was not identified. However, bilateral symmetric T2 hyperintense lesions of the thalami and dorsal pons characterized by restricted diffusion suggest a metabolic toxic effect of the disease on the brain.