The immunoregulatory role of CD4⁺ FoxP3⁺ CD25⁻ regulatory T cells in lungs of mice infected with Bordetella pertussis

The identification of regulatory T (Treg) cells was originally based on CD25 expression; however, CD25 is also expressed by activated effector T cells. FoxP3 is a more definitive marker of Treg cells, and CD4(+) FoxP3(+) CD25(+) T cells are considered the dominant natural Treg (nTreg) population. It has been suggested that certain CD4(+) FoxP3(+) Treg cells do not express CD25. In this study, we used a murine model of respiratory infection with Bordetella pertussis to examine the role of Treg cells in protective immunity in the lung. We first demonstrated that CD4(+) FoxP3(+) CD25(-) cells are the dominant Treg population in the lung, gut and liver. Pre-activated lung CD4(+) FoxP3(+) CD25(-) cells suppressed CD4(+) effector T cells in vitro, which was partly mediated by IL-10 and not dependent on cell contact. Furthermore, CD4(+) FoxP3(+) CD25(-) IL-10(+) T cells were found in the lungs of mice at the peak of infection with B. pertussis. The rate of bacterial clearance was not affected by depletion of CD25(+) cells or in IL-10-deficient (IL-10(-/-) ) mice, but was compromised in CD25-depleted IL-10(-/-) mice. Our findings suggest that IL-10-producing CD4(+) FoxP3(+) CD25(-) T cells represent an important regulatory cell in the lung.     

Quantitative Proteomic Analysis of Type III Secretome of Enteropathogenic Escherichia coli Reveals an Expanded Effector Repertoire for Attaching/Effacing Bacterial Pathogens

Type III secretion systems are central to the pathogenesis and virulence of many important Gram-negative bacterial pathogens, and elucidation of the secretion mechanism and identification of the secreted substrates are critical to our understanding of their pathogenic mechanisms and developing potential therapeutics. Stable isotope labeling with amino acids in cell culture-based mass spectrometry is a quantitative and highly sensitive proteomics tool that we have previously used to successfully analyze the type III secretomes of Citrobacter rodentium and Salmonella enterica serovar Typhimurium. In this report, stable isotope labeling with amino acids in cell culture was used to analyze the type III secretome of enteropathogenic Escherichia coli (EPEC), an important human pathogen, which, together with enterohemorrhagic E. coli and C. rodentium, represents the family of attaching and effacing bacterial pathogens. We not only confirmed all 25 known EPEC type III-secreted proteins and effectors previously identified by conventional molecular and bioinformatical techniques but also identified several new type III-secreted proteins, including two novel effectors, C_0814/NleJ and LifA, that were shown to be translocated into host cells. LifA is a known virulence factor believed to act as a toxin as well as an adhesin, but its mechanism of secretion and function is not understood. With a predicted molecular mass of 366 kDa, LifA is the largest type III effector identified thus far in any pathogen. We further demonstrated that Efa1, ToxB, and Z4332 (homologs of LifA in enterohemorrhagic E. coli) are also type III effectors. This study has comprehensively characterized the type III secretome of EPEC, expanded the repertoire of type III-secreted effectors for the attaching and effacing pathogens, and provided new insights into the mode of function for LifA/Efa1/ToxB/Z4332, an important family of virulence factors.     

Computer-based assessment of movement difficulties in Parkinson's disease

The prevalence of Parkinson's disease (PD) is increasing due to an ageing population. It is an unpredictable disease which requires regular assessment and monitoring. Current techniques used to assess PD are subjective. Clinicians observe movements made by a patient and subsequently rate the level of severity of, for example tremor or slowness of movement. Within this work, we have developed and evaluated a prototype computer-based assessment tool capable of collecting information on the movement difficulties present in PD. Twenty participants took part in an assessment of the tool, 10 of whom were diagnosed with PD and 10 were without the disease. Following the usage of the tool, it was found that there was a significant difference (p?=?0.038) in the speed of movement between the two groups. We envisage that this tool could have the potential to enable more objective clinical conclusions to be made.     

Oxysterol-binding protein (OSBP) enhances replication of intracellular Salmonella and binds the Salmonella SPI-2 effector SseL via its N-terminus

Effectors translocated into the host cell by Salmonella enterica serovar Typhimurium are critical for bacterial virulence. For many effectors, the mechanisms of their interactions with host pathways are not yet understood. We have recently found an interaction between the SPI-2 effector SseL and oxysterol-binding protein (OSBP). We show here that SseL binds the N-terminus of OSBP and that S. Typhimurium infection results in redistribution of OSBP. We furthermore demonstrate that OSBP is required for efficient replication of intracellular S. Typhimurium. This suggests that S. Typhimurium hijacks OSBP-dependent pathways to benefit its intracellular life-style, possibly by SseL- and OSBP-mediated manipulation of host lipid metabolism.     

Early life antibiotic-driven changes in microbiota enhance susceptibility to allergic asthma

Allergic asthma rates have increased steadily in developed countries, arguing for an environmental aetiology. To assess the influence of gut microbiota on experimental murine allergic asthma, we treated neonatal mice with clinical doses of two widely used antibiotics--streptomycin and vancomycin--and evaluated resulting shifts in resident flora and subsequent susceptibility to allergic asthma. Streptomycin treatment had little effect on the microbiota and on disease, whereas vancomycin reduced microbial diversity, shifted the composition of the bacterial population and enhanced disease severity. Neither antibiotic had a significant effect when administered to adult mice. Consistent with the 'hygiene hypothesis', our data support a neonatal, microbiota-driven, specific increase in susceptibility to experimental murine allergic asthma.     

Ecological aspects of mycorrhizal symbiosis: with special emphasis on the functional diversity of interactions involving the extraradical mycelium

Different symbiotic mycorrhizal associations between plantsand fungi occur, almost ubiquitously, in a wide range of terrestrialecosystems. Historically, these have mainly been consideredwithin the rather narrow perspective of their effects on theuptake of dissolved mineral nutrients by individual plants.More recent research has placed emphasis on a wider, multifunctionalperspective, including the effects of mycorrhizal symbiosison plant and microbial communities, and on ecosystem processes.This includes mobilization of N and P from organic polymers,release of nutrients from mineral particles or rock surfacesvia weathering, effects on carbon cycling, interactions withmyco-heterotrophic plants, mediation of plant responses to stressfactors such as drought, soil acidification, toxic metals, andplant pathogens, as well as a range of possible interactionswith groups of other soil micro-organisms. Mycorrhizal fungiconnect their plant hosts to the heterogeneously distributednutrients required for their growth, enabling the flow of energy-richcompounds required for nutrient mobilization whilst simultaneouslyproviding conduits for the translocation of mobilized productsback to their hosts. In addition to increasing the nutrientabsorptive surface area of their host plant root systems, theextraradical mycelium of mycorrhizal fungi provides a directpathway for translocation of photosynthetically derived carbonto microsites in the soil and a large surface area for interactionwith other micro-organisms. The detailed functioning and regulationof these mycorrhizosphere processes is still poorly understoodbut recent progress is reviewed and potential benefits of improvedunderstanding of mycorrhizosphere interactions are discussed. Key words: Arbuscular mycorrhiza, biotic interactions, carbon flow, ectomycorrhiza, ericoid mycorrhiza, mycelium, nutrient uptake, symbiosis, weathering Received 22 January 2008; Revised 7 February 2008 Accepted 7 February 2008     

Molecular analysis as an aid to assess the public health risk of non-O157 Shiga toxin-producing Escherichia coli strains

Shiga toxin-producing Escherichia coli (STEC) strains are commensal bacteria in cattle with high potential for environmental and zoonotic transmission to humans. Although O157:H7 is the most common STEC serotype, there is growing concern over the emergence of more than 200 highly virulent non-O157 STEC serotypes that are globally distributed, several of which are associated with outbreaks and/or severe human illness such as hemolytic-uremic syndrome (HUS) and hemorrhagic colitis. At present, the underlying genetic basis of virulence potential in non-O157 STEC is unknown, although horizontal gene transfer and the acquisition of new pathogenicity islands are an expected origin. We used seropathotype classification as a framework to identify genetic elements that distinguish non-O157 STEC strains posing a serious risk to humans from STEC strains that are not associated with severe and epidemic disease. We report the identification of three genomic islands encoding non-LEE effector (nle) genes and 14 individual nle genes in non-O157 STEC strains that correlate independently with outbreak and HUS potential in humans. The implications for transmissible zoonotic spread and public health are discussed. These results and methods offer a molecular risk assessment strategy to rapidly recognize and respond to non-O157 STEC strains from environmental and animal sources that might pose serious public health risks to humans.     

Community analysis of arbuscular mycorrhizal fungi and bacteria in the maize mycorrhizosphere in a long-term fertilization trial

In this study, we investigated the impact of organic and mineral fertilizers on the community composition of arbuscular mycorrhizal (AM) fungi and bacteria in the mycorrhizosphere of maize in a field experiment established in 1956, in south-east Sweden. Roots and root-associated soil aggregates were sampled four times during the growing season in 2005, in control plots and in plots amended with calcium nitrate, ammonium sulphate, green manure, farmyard manure or sewage sludge. Fungi in roots were identified by cloning and sequencing, and bacteria in soil aggregates were analysed by terminal-restriction fragment length polymorphism, cloning and sequencing. The community composition of AM fungi and bacteria was significantly influenced by the different fertilizers. Changes in microbial community composition were mainly correlated with changes in pH induced by the fertilization regime. However, other factors, including phosphate and soil carbon content, also contributed significantly to these changes. Changes in bacterial community composition and a reduction in bacterial taxon richness throughout the growing season were also manifest. The results of this study highlight the importance and significant effects of the long-term application of different fertilizers on edaphic factors and specific groups of fungi and bacteria playing a key role in arable soils.     

Glycogen Synthase Kinase-3 regulates IGFBP-1 gene transcription through the Thymine-rich Insulin Response Element

Background  

Hepatic expression of several gene products involved in glucose metabolism, including phosphoenolpyruvate carboxykinase (PEPCK), glucose-6-phosphatase (G6Pase) and insulin-like growth factor binding protein-1 (IGFBP-1), is rapidly and completely inhibited by insulin. This inhibition is mediated through the regulation of a DNA element present in each of these gene promoters, that we call the Thymine-rich Insulin Response Element (TIRE). The insulin signalling pathway that results in the inhibition of these gene promoters requires the activation of phosphatidylinositol 3-kinase (PI 3-kinase). However, the molecules that connect PI 3-kinase to these gene promoters are not yet fully defined. Glycogen Synthase Kinase 3 (GSK-3) is inhibited following activation of PI 3-kinase. We have shown previously that inhibitors of GSK-3 reduce the activity of two TIRE-containing gene promoters (PEPCK and G6Pase), whose products are required for gluconeogenesis.