Novel insights into mechanisms of food allergy and allergic airway inflammation using experimental mouse models

Over the last decades, considerable efforts have been undertaken in the development of animal models mimicking the pathogenesis of allergic diseases occurring in humans. The mouse has rapidly emerged as the animal model of choice, due to considerations of handling and costs and, importantly, due to the availability of a large and increasing arsenal of genetically modified mouse strains and molecular tools facilitating the analysis of complex disease models. Here, we review latest developments in allergy research that have arisen from in vivo experimentation in the mouse, with a focus on models of food allergy and allergic asthma, which constitute major health problems with increasing incidence in industrialized countries. We highlight recent novel findings and controversies in the field, most of which were obtained through the use of gene-deficient or germ-free mice, and discuss new potential therapeutic approaches that have emerged from animal studies and that aim at attenuating allergic reactions in human patients.

Eosinophilic esophagitis: analysis of food impaction and perforation in 251 adolescent and adult patients

BACKGROUND ; AIMS: Eosinophilic esophagitis is a rapidly emerging, chronic inflammatory disorder. Prolonged inflammation evokes structural alterations and a fragile esophageal wall prone to perforation/rupture and food impaction. This report assesses the risk of spontaneously arising and procedure-induced complications and proposes practical recommendations. METHODS: The Swiss Esophageal Esophagitis Database documented 251 confirmed cases. A chart review identified which patients had required endoscopic bolus removal and/or experienced transmural esophageal perforation/rupture. In addition, a MEDLINE search for "eosinophilic esophagitis" with "esophageal perforation" or "esophageal rupture" was undertaken. RESULTS: During an 18-year period, 87 patients (34.7%) experienced 134 food impactions requiring flexible (124, 92.5%) or rigid (10, 7.5%) endoscopic bolus removal. Transmural perforation occurred in 20% (2/10) of rigid procedures, and 1 esophageal rupture (Boerhaave's syndrome) was observed. CONCLUSIONS: Bolus removal by rigid endoscopy is a high-risk procedure and should be avoided in eosinophilic esophagitis patients who require a gentler approach. Whether food impaction and esophageal wall remodeling can be prevented with anti-inflammatory medication is still undetermined. All Boerhaave's syndrome cases should be evaluated for underlying eosinophilic esophagitis.

Target genes for virulence assessment of Escherichia coli isolates from water, food and the environment

The widespread species Escherichia coli includes a broad variety of different types, ranging from highly pathogenic strains causing worldwide outbreaks of severe disease to avirulent isolates which are part of the normal intestinal flora or which are well characterized and safe laboratory strains. The pathogenicity of a given E. coli strain is mainly determined by specific virulence factors which include adhesins, invasins, toxins and capsule. They are often organized in large genetic blocks either on the chromosome ('pathogenicity islands'), on large plasmids or on phages and can be transmitted horizontally between strains. In this review we summarize the current knowledge of the virulence attributes which determine the pathogenic potential of E. coli strains and the methodology available to assess the virulence of E. coli isolates. We also focus on a recently developed procedure based on a broad-range detection system for E. coli-specific virulence genes that makes it possible to determine the potential pathogenicity and its nature in E. coli strains from various sources. This makes it possible to determine the pathotype of E. coli strains in medical diagnostics, to assess the virulence and health risks of E. coli contaminating water, food and the environment and to study potential reservoirs of virulence genes which might contribute to the emergence of new forms of pathogenic E. coli.

Public health risks of enterobacterial isolates producing extended-spectrum β-lactamases or AmpC β-lactamases in food and food-producing animals: an EU perspective of epidemiology, analytical methods, risk factors, and control options

The blaESBL and blaAmpC genes in Enterobacteriaceae are spread by plasmid-mediated integrons, insertion sequences, and transposons, some of which are homologous in bacteria from food animals, foods, and humans. These genes have been frequently identified in Escherichia coli and Salmonella from food animals, the most common being blaCTX-M-1, blaCTX-M-14, and blaCMY-2. Identification of risk factors for their occurrence in food animals is complex. In addition to generic antimicrobial use, cephalosporin usage is an important risk factor for selection and spread of these genes. Extensive international trade of animals is a further risk factor. There are no data on the effectiveness of individual control options in reducing public health risks. A highly effective option would be to stop or restrict cephalosporin usage in food animals. Decreasing total antimicrobial use is also of high priority. Implementation of measures to limit strain dissemination (increasing farm biosecurity, controls in animal trade, and other general postharvest controls) are also important.

Thiazolides, a Novel Class of Anti-Infective Drugs, Effective Against Viruses, Bacteria, Intracellular and Extracellular Protozoan Parasites and Proliferating Mammalian Cells

The thiazolide nitazoxanide (2-acetolyloxy-N-(5-nitro 2-thiazolyl) benzamide; NTZ) is composed of a nitrothiazole- ring and a salicylic acid moiety, which are linked together through an amide bond. NTZ exhibits a broad spectrum of activities against a wide range of helminths, protozoa, enteric bacteria, and viruses infecting animals and humans. Since the first synthesis of the drug, a number of derivatives of NTZ have been produced, which are collectively named thiazolides. These are modified versions of NTZ, which include the replacement of the nitro group with bromo-, chloro-, or other functional groups, and the differential positioning of methyl- and methoxy-groups on the salicylate ring. The presence of a nitro group seems to be the prerequisite for activities against anaerobic or microaerophilic parasites and bacteria. Intracellular parasites and viruses, however, are susceptible to non-nitro-thiazolides with equal or higher effectiveness. Moreover, nitro- and bromo-thiazolides are effective against proliferating mammalian cells. Biochemical and genetic approaches have allowed the identification of respective targets and the molecular basis of resistance formation. Collectively, these studies strongly suggest that NTZ and other thiazolides exhibit multiple mechanisms of action. In microaerophilic bacteria and parasites, the reduction of the nitro group into a toxic intermediate turns out to be the key factor. In proliferating mammalian cells, however, bromo- and nitro-thiazolides trigger apoptosis, which may also explain their activities against intracellular pathogens. The mode of action against helminths may be similar to mammalian cells but has still not been elucidated.

Effects of Habitat Fragmentation on Abundance, Larval Food and Parasitism of a Spider-Hunting Wasp.

Habitat fragmentation strongly affects species distribution and abundance. However, mechanisms underlying fragmentation effects often remain unresolved. Potential mechanisms are (1) reduced dispersal of a species or (2) altered species interactions in fragmented landscapes. We studied if abundance of the spider-hunting and cavity-nesting wasp Trypoxylon figulus Linnaeus (Hymenoptera: Crabronidae) is affected by fragmentation, and then tested for any effect of larval food (bottom up regulation) and parasitism (top down regulation). Trap nests of T. figulus were studied in 30 agricultural landscapes of the Swiss Plateau. The sites varied in the level of isolation from forest (adjacent, in the open landscape but connected, isolated) and in the amount of woody habitat (from 4 % to 74 %). We recorded wasp abundance (number of occupied reed tubes), determined parasitism of brood cells and analysed the diversity and abundance of spiders that were deposited as larval food. Abundances of T. figulus were negatively related to forest cover in the landscape. In addition, T. figulus abundances were highest at forest edges, reduced by 33.1% in connected sites and by 79.4% in isolated sites. The mean number of spiders per brood cell was lowest in isolated sites. Nevertheless, structural equation modelling revealed that this did not directly determine wasp abundance. Parasitism was neither related to the amount of woody habitat nor to isolation and did not change with host density. Therefore, our study showed that the abundance of T. figulus cannot be fully explained by the studied trophic interactions. Further factors, such as dispersal and habitat preference, seem to play a role in the population dynamics of this widespread secondary carnivore in agricultural landscapes.

Action of food preservatives on 14-days dental biofilm formation, biofilm vitality and biofilm-derived enamel demineralisation in situ

AIMS The aims of this double-blind, controlled, crossover study were to assess the influence of food preservatives on in situ dental biofilm growth and vitality, and to evaluate their influence on the ability of dental biofilm to demineralize underlying enamel over a period of 14 days. MATERIALS AND METHODS Twenty volunteers wore appliances with six specimens each of bovine enamel to build up intra-oral biofilms. During four test cycles of 14 days, the subjects had to place the appliance in one of the assigned controls or active solutions twice a day for a minute: negative control 0.9 % saline, 0.1 % benzoate (BA), 0.1 % sorbate (SA) and 0.2 % chlorhexidine (CHX positive control). After 14 days, the biofilms on two of the slabs were stained to visualize vital and dead bacteria to assess biofilm thickness (BT) and bacterial vitality (BV). Further, slabs were taken to determine mineral loss (ML), by quantitative light-induced laser fluorescence (QLF) and transversal microradiography (TMR), moreover the lesion depths (LD). RESULTS Nineteen subjects completed all test cycles. Use of SA, BA and CHX resulted in a significantly reduced BV compared to NaCl (p < 0.001). Only CHX exerted a statistically significant retardation in BT as compared to saline. Differences between SA and BA were not significant (p > 0.05) for both parameters. TMR analysis revealed the highest LD values in the NaCl group (43.6 ± 44.2 μm) and the lowest with CHX (11.7 ± 39.4 μm), while SA (22.9 ± 45.2 μm) and BA (21.4 ± 38.5 μm) lay in between. Similarly for ML, the highest mean values of 128.1 ± 207.3 vol% μm were assessed for NaCl, the lowest for CHX (-16.8 ± 284.2 vol% μm), while SA and BA led to values of 83.2 ± 150.9 and 98.4 ± 191.2 vol% μm, respectively. With QLF for both controls, NaCl (-33.8 ± 101.3 mm(2) %) and CHX (-16.9 ± 69.9 mm(2) %), negative values were recorded reflecting a diminution of fluorescence, while positive values were found with SA (33.9 ± 158.2 mm(2) %) and BA (24.8 ± 118.0 mm(2) %) depicting a fluorescence gain. These differences were non-significant (p > 0.05). CONCLUSION The biofilm model permited the assessment of undisturbed oral biofilm formation influenced by antibacterial components under clinical conditions for a period of 14 days. An effect of BA and SA on the demineralization of enamel could be demonstrated by TMR and QLF, but these new findings have to be seen as a trend. As part of our daily diet, these preservatives exert an impact on the metabolism of the dental biofilm, and therefore may even influence demineralization processes of the underlying dental enamel in situ.

Genetic and functional analyses of cell division proteins FtsZ and FtsA in Escherichia coli

In the current model for bacterial cell division, the FtsZ protein forms a ring that marks the division plane, creating a cytoskeletal framework for the subsequent action of other essential division proteins such as FtsA and ZipA. The putative protein complex ultimately generates the division septum. The essential cell division protein FtsZ is a functional and structural homolog of eukaryotic tubulin, and like tubulin, FtsZ hydrolyzes GTP and self-assembles into protein filaments in a strictly GTP-dependent manner. FtsA shares sequence similarity with members of the ATPase superfamily that include actin, but its actual function remains unknown. To test the division model and elucidate functions of the division proteins, this dissertation primarily focuses on the analysis of FtsZ and FtsA in Escherichia coli. ^ By tagging with green fluorescent protein, we first demonstrated that FtsA also exhibits a ring-like structure at the potential division site. The localization of FtsA was dependent on functional FtsZ, suggesting that FtsA is recruited to the septum by the FtsZ ring. In support of this idea, we showed that FtsA and FtsZ directly interact. Using a novel E. coli in situ assay, we found that the FtsA-FtsZ interaction appears to be species-specific, although an interspecies interaction could occur between FtsA and FtsZ proteins from two closely related organisms. In addition, mutagenesis of FtsA revealed that no single domain is solely responsible for its septal localization or interaction with FtsZ. To explore the function of FtsA, we purified FtsA protein and demonstrated that it has ATPase activity. Furthermore, purified FtsA stimulates disassembly of FtsZ polymers in a sedimentation assay but does not affect GTP hydrolysis of FtsZ. This result suggests that in the cell, FtsA may function similarly in regulating dynamic instability of the FtsZ ring during the cell division process. ^ To elucidate the structure-function relationship of FtsZ, we carried out thorough genetic and functional analyses of the mutagenized FtsZ derivatives. Our results indicate that the conserved N-terminal domain of FtsZ is necessary and sufficient for FtsZ self-assembly and localization. Moreover, we discovered a critical role for an extreme C-terminal domain of FtsZ that consists of only 12 residues. Truncated FtsZ derivatives lacking this domain, though able to polymerize and localize, are defective in ring formation in vivo as well as interaction with FtsA and ZipA. Alanine scanning mutagenesis of this region pinpointed at least five residues necessary for the function of FtsZ. Studies of protein levels and protein-protein interactions suggested that these residues may be involved in regulating protein stability and/or FtsZ-FtsA interactions. Interestingly, two of the point mutants exhibited dominant-negative phenotypes. ^ In summary, results from this thesis work have provided additional support for the division machinery model and will contribute to a better understanding of the coordinate functions of FtsA and FtsZ in the cell division process. ^

Effects of Food Primes and Thought Suppression on Eating Habits

Food primes and thought suppression have been identified as factors influencing poor eating choices. Primes affect people non-consciously by activating thoughts of food. Suppression of food thoughts leads to a preoccupation with food that is often followed by a hyperaccessibility of food thoughts and increased binging. The current study paired these two processes to examine their interactional effects. We manipulated exposure to food primes and instructions to suppress thoughts of a tasty snack food (M&Ms) for 76 college-aged women. We hypothesized that participants both primed with food images and asked to suppress would consume the most M&Ms at the end of the study. Contrary to predictions, results showed no effects for the manipulations. Perceived weight category, however, did interact with the manipulations, with overweight participants eating more when they got either the food prime or the suppression (but not both together). These findings have important implications for weight-loss strategies.