Hemolytic uremic syndrome (HUS) is a form of thrombotic microangiopathy, characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute renal impairment of varying severity, which may be preceded by an episode of diarrhea with or without blood. Karmali et al. showed the relationship between this syndrome and diarrhea caused by Shiga toxin-producing bacteria such as Escherichia coli. These cytotoxins, called Shiga-like toxins or Shiga toxins (Stx), are also called verotoxins, due to the characteristic cytopathic effect they cause on Vero cell cultures.
HUS is often classified into 3 primary types: 1) HUS due to infections associated with Shiga-toxin producing E. coli (STEC) or Shigella dysenteriae Type 1, often associated with diarrhea, with the rare exception of HUS due to a severe disseminated infection caused by Streptococcus pneumoniae, 2) HUS related to complement abnormalities or related to factor ADAMTS13 deficit, such HUS is also known as "atypical HUS" and is not associated with diarrhea, and 3) HUS of unknown etiology that usually occurs in the course of systemic diseases or physio-pathologic conditions such as pregnancy, after transplantation or after drug use.
E. coli bacteria normally live in the intestines of people and animals. Cattle and sheep are the main reservoirs of STEC, and the major transmission route is believed to be food contaminated with animal feces. Contaminated water has also been recognized as a source, and direct human-to-human and animal-to-human transmission have been reported.
E. coli consists of a diverse group of bacteria. Most of them are harmless and an important part of a healthy human intestinal tract. However, some E. coli are pathogenic, that can cause either diarrhea or illness outside of the intestinal tract. Diarrheagenic E. coli strains are categorized into 6 pathotypes: 1) Enterotoxigenic E. coli, 2) Enteropathogenic E. coli, 3) Enteroaggregative E. coli, 4) Enteroinvasive E. coli, 5) diffusely adherent E. coli, and 6) STEC. STEC may also be referred to as verocytotoxin-producing E. coli (VTEC). This last pathotype is the one most commonly associated with foodborne outbreaks.
Treatment of STEC HUS renal damage caused by Stx is available. The investigational medicinal product (IMP), INM004, proposes to neutralize the toxin in the bloodstream to prevent the interaction of the Stx with the specific receptor, by means of a polyclonal antibody to be administered upon the appearance of symptoms (bloody diarrhea) and diagnosis of infection by STEC, thereby preventing the action of the toxin in the body. Thus, the initial hypothesis for examination is for the prevention of the full expression of HUS, based upon presumptive clinical, biochemical, and other biological evidence suggesting a risk of HUS at the time of treatment application. The polyclonal antibody (F(ab')2 fragment) is obtained by processing the serum of equine animals previously immunized against engineered Stx1B and Stx2B immunogens.
INM004 could be administered at the earlier stages of STEC disease since subjects with STEC diarrhea are more likely to benefit from Stx neutralizing antibodies before the development of extra-intestinal manifestations and HUS. Neutralizing equine anti-Stx F(ab')2 antibodies (INM004) have the objective of preventing the development of HUS by blocking the circulating toxins in patients infected with STEC. Therefore, INM004 may be used in patients with a clinical manifestation of bloody diarrhea and a positive Stx result in feces. Early interruption of the Stx mediated cascade is expected to prevent the development of HUS, alleviate the severity of the illness, the rate of complications and the incidence/duration of hospitalizations. Therefore, patients in the early phases of the disease will be targeted in this study, ie, children who seek medical care due to diarrhea associated with STEC infection before HUS development.
Pediatric subjects between 1 and 10 years (y) of age at the time of screening with an increased risk for development of HUS defined by the presence of bloody diarrhea based upon history or presentation and positive screen for Stx2 in the stool will be enrolled.
Bloody diarrhea and positive screen for Stx2 have been included as inclusion criteria as these factors have been identified as risk factor for HUS development and will serve to enrich the patient population within the study to those most likely to benefit from this therapy.
Case of Bloody Diarrhea Any person with an increase in the number of daily stools and alteration in the stool consistency, with presence of visible blood, which may include episodes of stool formed with blood in the form of streaks on its surface or blood visible only under a microscope, which may be accompanied by other symptoms such as vomiting, nausea, abdominal pain, or fever.
Case of Shiga Toxin producing Escherichia coli Infection
Identification of the etiological agent by at least 1 of the following laboratory criteria:
* Isolation of an E. coli strain that produces Stx or harbors stx1 or stx2 gene(s);
* Direct detection of stx1 or stx2 gene(s) nucleic acid (without strain isolation);
* Direct detection of free Stx in feces (without strain isolation). The surveillance of the STEC strains is performed using subtyping techniques: 1) genotyping of stx and eae by polymerase chain reaction (PCR)-restriction fragment length polymorphism and 2) pulsed-field gel electrophoresis. STEC O157 and non O157 strains are recovered from the clinic, animal, food and environmental samples, and E. coli O157:H7, a Stx2a/Stx2c producer, harboring eae and ehxA genes, is the most common serotype.
Case of Hemolytic Uremic Syndrome Patient of any age who presents in an acute form with microangiopathic hemolytic anemia, thrombocytopenia, and renal compromise.
Case of Hemolytic Uremic Syndrome with Confirmed Diagnosis of Shiga Toxin producing Escherichia coli
Case of HUS with identification of the etiological agent by at least 1 of the laboratory criteria:
* Screening of stx1 and/or stx2 by PCR/isolation of STEC
* Detection of free Stx in stool
* Detection of serogroup-specific O antigen antibodies O157, O145, O121
