Host immunoglobulin G selectively identifies pathobionts in pediatric inflammatory bowel diseases

BACKGROUND

Inflammatory bowel diseases (IBD) are a group of complex and multifactorial disorders with unknown etiology. Chronic intestinal inflammation develops against resident intestinal bacteria in genetically susceptible hosts. We hypothesized that host intestinal immunoglobulin (Ig) G can be used to identify bacteria involved in IBD pathogenesis.

RESULTS

IgG-bound and -unbound microorganisms were collected from 32 pediatric terminal ileum aspirate washes during colonoscopy [non-IBD (n = 10), Crohn disease (n = 15), and ulcerative colitis (n = 7)], and composition was assessed using the Illumina MiSeq platform. In vitro analysis of invasive capacity was evaluated by fluorescence in situ hybridization and gentamicin invasion assay; immune activation was measured by qPCR. Despite considerable inter-individual variations, IgG binding favored specific and unique mucosa-associated species in pediatric IBD patients. Burkholderia cepacia, Flavonifractor plautii, and Rumminococcus sp. demonstrated increased IgG binding, while Pseudomonas ST29 demonstrated reduced IgG binding, in IBD. In vitro validation confirmed that B. cepacia, F. plautii, and Rumminococcus display invasive potential while Pseudomonas protogens did not.

CONCLUSION

Using IgG as a marker of pathobionts in larger patient cohorts to identify microbes and elucidate their role in IBD pathogenesis will potentially underpin new strategies to facilitate development of novel, targeted diagnostic, and therapeutic approaches. Interestingly, this method can be used beyond the scope of this manuscript to evaluate altered gut pathobionts in a number of diseases associated with altered microbiota including arthritis, obesity, diabetes mellitus, alcoholic liver disease, cirrhosis, metabolic syndrome, and carcinomas.

Respiratory syncytial virus induces indoleamine 2,3-dioxygenase activity: a potential novel role in the development of allergic disease

BACKGROUND

Infants that develop severe bronchiolitis due to respiratory syncytial virus (RSV) are at increased risk of developing asthma later in life. We investigated a potential immunological mechanism for the association between RSV and the development of allergic inflammation. The enzyme indoleamine 2,3-dioxygenase (IDO) has been reported to induce selective apoptosis of T helper 1 (Th1) cells and contributed to Th2-biased immune responses.

OBJECTIVE

To determine whether RSV infection in vitro could induce IDO expression and bioactivity in human dendritic cells, leading to a Th2-biased immune response.

METHODS

Human peripheral blood monocytes from healthy adult donors were isolated, differentiated to dendritic cells (moDC), in vitro. We studied RSV infection and mechanisms of IDO activation in moDC with subsequent effect on T-bet expression.

RESULTS

We found that moDC were infected by RSV and that this induced IDO activation. RSV-induced IDO activity was inhibited by palivizumab, UV inactivation, TL4R inhibition, and ribavirin. However, blocking endosomal TLR function with chloroquine did not inhibit IDO activity. Selective inhibitors suggested that RSV-induced IDO activity was dependent on the retinoic acid-inducible gene-I (RIG-I) related pathway via NF-κB and p38 MAPK. Coculture of RSV-infected moDC with activated T cells, in a transwell system, suppressed expression of T-bet (a Th1-associated factor) but not GATA3 (a Th2 regulator). Inhibition of IDO activity with the competitive inhibitor, 1-methyl tryptophan, blocked the effect on T-bet expression.

CONCLUSION AND CLINICAL RELEVANCE

Our data show for the first time that RSV can induce the expression and bioactivity of IDO in human moDC, in a virus replication-dependant fashion. We suggest that RSV activation of IDO could be a potential mechanism for the development of allergic diseases.

Compound CVT-E002 attenuates allergen-induced airway inflammation and airway hyperresponsiveness, in vivo

Immune modulation has been a sought after means of therapy for atopic diseases. CVT-E002 is an extract derived from North American Ginseng shown to promote T-helper-1-like responses. We determined what effect CVT-E002 could have in a mouse model of atopic asthma. We report that oral CVT-E002 inhibited the development of allergic airway inflammation and airway hyperresponsiveness. This correlated with an increased presence of interferon-γ in the lung, and also increased regulatory T cells and IL-10. The ability of CVT-E002 to induce regulatory T-cell development was also seen in human in vitro co-cultures.

Human dendritic cells promote an antiviral immune response when stimulated by CVT-E002

Objectives

There is interest in developing new compounds to enhance the immune response to airway virus infections. CVT-E002 is a patented ginseng extract shown to decrease symptoms of virus infection in clinical trials. We hypothesized that the mechanism for this antiviral effect could be through modulation of dendritic cells leading to enhanced T-cell activation.

Methods

Human monocyte-derived dendritic cells (moDC) exposed to CVT-E002 (or not) were co-cultured with autologous T cells, with or without virus (respiratory syncytial virus or parainfluenza virus). Effects of CVT-E002 on cell function were determined through flow cytometry, 5-bromo-2′-deoxyuridine (BrdU) incorporation and ELISA.

Key findings

moDC cultured with CVT-E002 or virus induced greater activation of T cells, as measured by CD25 expression and BrdU incorporation, compared with untreated moDC. Responding T cells were CD4+CD45RO+. Co-cultures of CVT-E002 treated moDC with T cells responded with increased release of Th1-type cytokines (interferon-gamma, tumour necrosis factor and interleukin-12). CVT-E002-treated moDC showed increased expression of CD83, CD80 and CD86. Lipopolysaccharide levels were not detected in CVT-E002 and antagonists for Toll-like receptor-4 did not inhibit CVT-E002-induced moDC maturation.

Conclusions

CVT-E002 induced moDC maturation, which caused increased memory T-cell activation and Th1-type cytokine response.

Novel method for the development of regulatory T cells (166.22)

Background: Regulatory T cells (Treg) are important in the inhibition of inflammatory disorders, like asthma. Unfortunately, current protocols used to develop them in vitro for study rely on complicated cloning methods that may not represent biologically relevant Treg. LPS-free ovalbumin (OVA) given intranasal (i.n.) can induce mucosal tolerance in mice. Therefore, we hypothesized that Dendritic cells (DCs) taken from the draining lymph nodes (LNs) of mice given LPS-free OVA would induce Treg in vitro. Methods: Mice were given i.n. LPS-free OVA. 24 h later cervical and bronchial LNs were excised and DCs were isolated (~98% purity). DCs were cultured in vitro with transgenic OVA-specific T cells for four days. The development of Treg was assessed by flowcytometry (Foxp3 expression), ELISA (IL-10 production), and inhibition of T cell proliferation (CFSE staining/BrdU uptake). Finally, we studied the effectiveness of these cells to inhibit the development of AHR in a mouse model of asthma. Results: T cells from mice treated with LPS-free OVA showed high levels of Foxp3 expression, high IL-10 production, and the ability to inhibit OVA specific T cells in vitro. compared to control mice. Furthermore, T cells from LPS-free OVA treated mice prevented the development of AHR when given to mice before OVA challenge (i.n.). Conclusion: We believe our protocol could represent an alternative method to develop Treg cells for study.

Tryptophan catabolites regulate mucosal sensitization to ovalbumin in respiratory airways

BACKGROUND

Indoleamine 2,3 dioxygenase (IDO), the rate-limiting enzyme in tryptophan catabolism, is important in generating tolerance at the foetal-maternal interface. Studies using 1-methyl-tryptophan (1-MT), the specific inhibitor of IDO, showed that this enzyme is important in interferon-gamma (IFN-gamma)-dependent inhibition of allergic inflammation in the respiratory airway during immunotherapy.

AIMS OF STUDY

We investigated the role of IDO in the development of allergic sensitization, leading to allergic inflammation and airway hyper-responsiveness (AHR).

METHODS

We used a mouse model to generate mucosal tolerance to lipopolysaccharide-free ovalbumin (OVA) following repeated intranasal inoculation of OVA over a 3-day period. We tested the successful induction of tolerance by subsequent intraperitoneal (i.p.) sensitization followed by intranasal challenge with OVA. A slow-release pellet of 1-MT implanted into mice was used to block IDO activity prior to repeated intranasal inoculation of OVA. We measured T-cell proliferation in response to OVA, determined airway inflammation, and measured AHR to intranasal methacholine to investigate the role of IDO in sensitization to OVA.

RESULTS

Repeated intranasal administration of OVA generated tolerance and prevented a subsequent sensitization to OVA via the i.p. route. This response was inhibited in mice receiving a slow-release pellet of 1-MT. However, we successfully reconstituted tolerance in mice receiving 1-MT following intra-peritoneal injection of a mixture of kynurenine and hydroxyanthranilic acid.

CONCLUSION

Our data suggest that, in addition to their role in IFN-gamma-mediated inhibition of allergic airway inflammation, products of tryptophan catabolism play an important role in the prevention of sensitization to potential allergens in the respiratory airway.

Proteinase-activated receptor-2 promotes allergic sensitization to an inhaled antigen through a TNF-mediated pathway

The reason why particular inhaled Ags induce allergic sensitization while others lead to immune tolerance is unclear. Along with a genetic predisposition to atopy, intrinsic characteristics of these Ags must be important. A common characteristic of many allergens is that they either possess proteinase activity or are inhaled in particles rich in proteinases. Many allergens, such as house dust mite and cockroach allergens, have the potential to activate the proteinase-activated receptor (PAR)-2. In this study, we report that PAR-2 activation in the airways at the same time as exposure to inhaled Ags induces allergic sensitization, whereas exposure to Ag alone induces tolerance. BALB/c mice were administered OVA with a PAR-2 activating peptide intranasally. Upon allergen re-exposure mice developed airway inflammation and airway hyperresponsiveness, as well as OVA-specific T cells with a Th2 cytokine profile when restimulated with OVA in vitro. Conversely, mice given OVA alone or OVA with a PAR-2 control peptide developed tolerance. These tolerant mice did not develop airway inflammation or airway hyperresponsiveness, and developed OVA-specific T cells that secreted high levels of IL-10 when restimulated with OVA in vitro. Furthermore, pulmonary dendritic cell trafficking was altered in mice following intranasal PAR-2 activation. Finally, we showed that PAR-2-mediated allergic sensitization was TNF-dependent. Thus, PAR-2 activation in the airways could be a critical factor in the development of allergic sensitization following mucosal exposure to allergens with serine proteinase activity. Interfering with this pathway may prove to be useful for the prevention or treatment of allergic diseases.

Proteinase-activated receptor 2 activation in the airways enhances antigen-mediated airway inflammation and airway hyperresponsiveness through different pathways

BACKGROUND

Serine proteinases such as mast cell tryptase, trypsin-like enzymes, and certain allergens are important in the pathogenesis of asthma. These proteinases can activate the proteinase-activated receptor (PAR)-2, which has been shown to be upregulated in the airways of patients with asthma.

OBJECTIVE

The purpose of this study was to investigate PAR-2 activation in the airways during allergen challenge and its effects on the 2 principle features of asthma, airway inflammation and airway hyperresponsiveness (AHR).

METHODS

Proteinase-activated receptor 2 activating peptide SLIGRL-NH2 (PAR-2 activating peptide [ap]) or control peptide LSIGRL-NH2 (PAR-2 control peptide [cp]) was administered alone or in conjunction with ovalbumin intranasally to mice, and AHR and airway inflammation were evaluated.

RESULTS

PAR2ap did not induce AHR or airway inflammation in ovalbumin-sensitized mice that had not been challenged with ovalbumin. When administered with ovalbumin, PAR-2ap enhanced AHR and airway inflammation compared with ovalbumin administered alone or with PAR-2cp. The enhanced AHR persisted for 5 days, whereas the enhancement to airway inflammation dissipated. Mice administered PAR-2ap alone during the 5 days after the final antigen challenge demonstrated an additional enhancement to airway inflammation compared with the control animals. PAR-2ap administered with allergen increased TNF and IL-5 mRNA in lung tissue and IL-13 and TNF in bronchoalveolar lavage fluid.

CONCLUSION

Exogenous PAR-2 activation in parallel with allergen challenge enhances allergen-mediated AHR and airway inflammation through distinct mechanisms. PAR-2 activation can also enhance established airway inflammation even when dissociated from exposure to allergen. Therefore, PAR-2 activation may play a pathogenic role in the development of AHR and airway inflammation.

The Helmholtz Network for Bioinformatics: an integrative web portal for bioinformatics resources

SUMMARY

The Helmholtz Network for Bioinformatics (HNB) is a joint venture of eleven German bioinformatics research groups that offers convenient access to numerous bioinformatics resources through a single web portal. The 'Guided Solution Finder' which is available through the HNB portal helps users to locate the appropriate resources to answer their queries by employing a detailed, tree-like questionnaire. Furthermore, automated complex tool cascades ('tasks'), involving resources located on different servers, have been implemented, allowing users to perform comprehensive data analyses without the requirement of further manual intervention for data transfer and re-formatting. Currently, automated cascades for the analysis of regulatory DNA segments as well as for the prediction of protein functional properties are provided.

AVAILABILITY

The HNB portal is available at http://www.hnbioinfo.de

Opposing effects of short- and long-term stress on airway inflammation

Between 20% and 35% of subjects with asthma experience asthma exacerbations during periods of stress. The biological mechanisms underlying these exacerbations are not clearly understood, and the role of psychologic factors in the pathophysiology of asthma remains controversial. We investigated the ability of psychologic stress to modulate airway inflammation and airway hyperresponsiveness (AHR) to methacholine in a murine model of asthma. Animals were exposed to a stressor daily for 3 (short-term stress) or 7 (long-term stress) days. After allergen challenge, AHR was assessed through plethysmography, and bronchoalveolar lavage cells were counted as a measure of inflammation. After short-term stress, inflammatory cell number was decreased compared with unstressed animals, whereas levels of interleukin (IL)-6, IL-9, and IL-13 were increased. Administration of a corticosteroid receptor antagonist, before stress, prevented the decrease in inflammatory cell numbers. In contrast, animals stressed for 7 consecutive days showed a significant increase in inflammatory cell numbers, which was independent of the glucocorticoid response, but no change in cytokine levels. AHR was not altered in stressed animals. Our results indicate that repeated exposure to stress over the long term engages different mechanisms than short-term stress and can exacerbate the chronic inflammatory responses of the airway.

Sequencing, functional expression and characterization of rat NTPDase6, a nucleoside diphosphatase and novel member of the ecto-nucleoside triphosphate diphosphohydrolase family

We have isolated and characterized the cDNA encoding nucleoside triphosphate diphosphohydrolase 6 (NTPDase6), a novel member of the ecto-nucleoside triphosphate diphosphohydrolase family. The rat-brain-derived cDNA has an open reading frame of 1365 bp encoding a protein of 455 amino acid residues, a calculated molecular mass of 49971 Da and a predicted N-terminal hydrophobic sequence. It shares 86% sequence identity with the human CD39L2 sequence and 48% and 51% identity respectively with sequences of the two related human and murine nucleoside diphosphatases (CD39L4, NTPDase5/ER-UDPase). The mRNA was expressed in all tissues investigated, revealing two major transcripts with differing abundances. PCR analysis suggests a single open reading frame. A Myc-His-tagged NTPDase6 was expressed in Chinese hamster ovary (CHO) and PC12 cells for immunological analysis and protein isolation. The protein was contained in membrane fractions of transfected CHO cells and occurred in a soluble form in the cell culture supernatants. NTPDase6 preferentially hydrolysed nucleoside 5'-diphosphates. With different substrates the order of activity was GDP>IDP>>UDP,CDP>>ADP. Nucleoside 5'-triphosphates were hydrolysed only to a minor extent and no hydrolysis of nucleoside 5'-monophosphates was observed. The enzyme was strongly and equally activated by Ca(2+) and Mg(2+) and had a K(m) for GDP of 211 microM. The immunohistochemical analysis of transfected CHO and PC12 cells suggests that NTPDase6 is associated with the Golgi apparatus and to a small extent also with the plasma membrane. The enzyme might support glycosylation reactions in the Golgi apparatus and, when released from cells, might catalyse the hydrolysis of extracellular nucleotides.

Quantitative trait loci affecting prion incubation time in mice

Although the gene encoding prion protein (PrP) is the major determinant of susceptibility to prion disease, other genes also affect prion incubation time in mice and may be involved in prion replication. Scrapie incubation time was analyzed as a quantitative trait using crosses between SJL/J and CAST/Ei mice; these mouse strains encode identical PrP molecules but have different incubation periods. Our analysis revealed loci on Chromosomes 9 and 11 that affect prion susceptibility.

Abeta 1-40-related reduction in functional hyperemia in mouse neocortex during somatosensory activation

Peptides derived from proteolytic processing of the beta-amyloid precursor protein (APP), including the amyloid-beta peptide (Abeta), play a critical role in the pathogenesis of Alzheimer's dementia. We report that transgenic mice overexpressing APP and Abeta have a profound attenuation in the increase in neocortical blood flow elicited by somatosensory activation. The impairment is highly correlated with brain Abeta concentration and is reproduced in normal mice by topical neocortical application of exogenous Abeta1-40 but not Abeta1-42. Overexpression of M146L mutant presenilin-1 in APP mice enhances the production of Abeta1-42 severalfold, but it does not produce a commensurate attenuation of the hyperemic response. APP and Abeta overexpression do not diminish the intensity of neural activation, as reflected by the increase in somatosensory cortex glucose usage. Thus, Abeta-induced alterations in functional hyperemia produce a potentially deleterious mismatch between substrate delivery and energy demands imposed by neural activity.

The mahogany protein is a receptor involved in suppression of obesity

Genetic studies have shown that mutations within the mahogany locus suppress the pleiotropic phenotypes, including obesity, of the agouti-lethal-yellow mutant. Here we identify the mahogany gene and its product; this study, to our knowledge, represents the first positional cloning of a suppressor gene in the mouse. Expression of the mahogany gene is broad; however, in situ hybridization analysis emphasizes the importance of its expression in the ventromedial hypothalamic nucleus, a region that is intimately involved in the regulation of body weight and feeding. We present new genetic studies that indicate that the mahogany locus does not suppress the obese phenotype of the melanocortin-4-receptor null allele or those of the monogenic obese models (Lep(db), tub and Cpe(fat)). However, mahogany can suppress diet-induced obesity, the mechanism of which is likely to have implications for therapeutic intervention in common human obesity. The amino-acid sequence of the mahogany protein suggests that it is a large, single-transmembrane-domain receptor-like molecule, with a short cytoplasmic tail containing a site that is conserved between Caenorhabditis elegans and mammals. We propose two potential, alternative modes of action for mahogany: one draws parallels with the mechanism of action of low-affinity proteoglycan receptors such as fibroblast growth factor and transforming growth factor-beta, and the other suggests that mahogany itself is a signalling receptor.

Theoretical and empirical issues for marker-assisted breeding of congenic mouse strains

Congenic breeding strategies are becoming increasingly important as a greater number of complex trait linkages are identified. Traditionally, the development of a congenic strain has been a time-consuming endeavour, requiring ten generations of backcrosses. The recent advent of a dense molecular genetic map of the mouse permits methods that can reduce the time needed for congenic-strain production by 18-24 months. We present a theoretical evaluation of marker-assisted congenic production and provide the empirical data that support it. We present this 'speed congenic' method in a user-friendly manner to encourage other investigators to pursue this or similar methods of congenic production.

The physical and genetic map surrounding the Lyst gene on mouse chromosome 13

During the recent cloning of the mouse Lyst gene we developed both a high-resolution genetic map and a complete YAC and BAC contig of the Lyst critical region on mouse Chromosome 13. We also report the mapping of the human homologue of the mouse Lyst gene (LYST) to 1q43. These data are consistent with LYST being the gene for the human Chediak-Higashi Syndrome and strengthen the synteny relationship between MMU13 and human 1q43.

Identification and characterization of the mouse obesity gene tubby: a member of a novel gene family

The mutated gene responsible for the tubby obesity phenotype has been identified by positional cloning. A single base change within a splice donor site results in the incorrect retention of a single intron in the mature tub mRNA transcript. The consequence of this mutation is the substitution of the carboxy-terminal 44 amino acids with 24 intron-encoded amino acids. The normal transcript appears to be abundantly expressed in the hypothalamus, a region of the brain involved in body weight regulation. Variation in the relative abundance of alternative splice products is observed between inbred mouse strains and appears to correlate with an intron length polymorphism. This allele of tub is a candidate for a previously reported diet-induced obesity quantitative trait locus on mouse chromosome 7.

Prion isolate specified allotypic interactions between the cellular and scrapie prion proteins in congenic and transgenic mice

Different prion isolates, often referred to as "strains," present an enigma because considerable evidence argues that prions are devoid of nucleic acid. To investigate prion diversity, we inoculated three "strains" of prions into congenic and transgenic mice harboring variable numbers of two different alleles, designated a and b, of the prion protein (PrP) structural gene, Prn-p. The length of the incubation time was inversely related to the number of Prn-p(a) genes in mice inoculated with the Rocky Mountain Laboratory (RML) prion strain. Results with mice lacking this locus (Prn-p0/0) and transgenic mice argue that long incubation times are not a dominant trait as thought for many years, but rather they are due to reduced levels of the substrate PrPC-A (cellular isoform of PrP, allotype A) in (Prn-p(a) x Prn-pb)F1 mice. In contrast, the Prn-p(a) gene extended incubation times in mice inoculated with the 87V and 22A prion strains, whereas the Prn-pb gene was permissive. Experiments with the 87V isolate suggest that a genetic locus distinct from Prn-p controls deposition of the scrapie isoform of PrP (PrPSc) and attendant neuropathology. Each prion isolate produced distinguishable patterns of PrPSc accumulation in brain; of note, the patterns in Prn-p(a) and Prn-pb congenic mice inoculated with RML prions were more different than those in congenic Prn-pb mice with RML or 22A prions. Our results suggest that scrapie "strain-specific" incubation times can be explained by differences in the relative efficiency of allotypic interactions that lead to conversion of PrPC into PrPSc.

Delimiting the location of the scrapie prion incubation time gene on chromosome 2 of the mouse

Scrapie is a transmissible neurodegenerative disease caused by unusual pathogens called prions. The interval between inoculation and illness for experimental mouse scrapie is dramatically influenced by an incubation time gene (Prn-i) that is linked to Prn-p, the structural gene for prion protein (PrP). Although prion proteins from mouse strains with short and long scrapie incubation times differ by two amino acids, mice with discordant disease phenotype and Prn-p genotype occur in segregating crosses, suggesting recombination between Prn-p and a distinct incubation time locus. In addition, expression of Prn-pb transgenes from long incubation time mice shortened, rather than prolonged, incubation time. In this study, mice carrying chromosomes with meiotic crossovers near Prn-p were analyzed for scrapie incubation time phenotype. The results indicated that Prn-i (should it exist) must lie within an interval 0.67 cM proximal and 0.22 cM distal to Prn-p. The results also suggest that the cumulative effects of other genes, rather than meiotic recombination, were responsible for the putative recombinants of earlier studies. However, the effect of Prn-pb transgene expression in abbreviating scrapie incubation time was mitigated when the transgenes were transferred to mice with an endogenous long incubation time allele. Thus, Prn-pb transgenes and Prn-i may modulate scrapie pathogenesis by different mechanisms.

Paradoxical shortening of scrapie incubation times by expression of prion protein transgenes derived from long incubation period mice

Prolonged incubation times for experimental scrapie in I/LnJ mice are dictated by a dominant gene linked to the prion protein gene (Prn-p). Transgenic mice were analyzed to discriminate between an effect of the I/LnJ Prn-pb allele and a distinct incubation time locus designated Prn-i. Paradoxically, 4 independent Prn-pb transgenic mouse lines had scrapie incubation times shorter than nontransgenic controls, instead of the anticipated prolonged incubation periods. Aberrant or overexpression of the Prn-pb transgenes may dictate abbreviated incubation times, masking genuine Prn-p/Prn-i congruence; alternatively, a discrete Prn-i gene lies adjacent to Prn-p.