Severine Navarro

The oral administration of bacterial extracts prevents asthma via the recruitment of regulatory T cells to the airways

The prevalence of asthma has steadily increased during the last decade, probably as the result of changes in the environment, including reduced microbial exposure during infancy. Accordingly, experimental studies have shown that deliberate infections with live pathogens prevent the development of allergic airway diseases in mice. Bacterial extracts are currently used in children suffering from repeated upper respiratory tract infections. In the present study, we have investigated whether bacterial extracts, commercially available as Broncho-Vaxom (BV), could prevent allergic airway disease in mice. Oral treatment with BV suppressed airway inflammation through interleukin-10 (IL-10)-dependent and MyD88 (myeloid differentiation primary response gene (88))-dependent mechanisms and induced the conversion of FoxP3 (forkhead box P3)− T cells into FoxP3+ regulatory T cells. Furthermore, CD4+ T cells purified from the trachea of BV-treated mice conferred protection against airway inflammation when adoptively transferred into sensitized mice. Therefore, treatment with BV could possibly be a safe and efficient strategy to prevent the development of allergic diseases in children.

Hookworm excretory/secretory products induce interleukin-4 (IL-4)+ IL-10+ CD4+ T cell responses and suppress pathology in a mouse model of colitis.

ABSTRACT Evidence from human studies and mouse models shows that infection with parasitic helminths has a suppressive effect on the pathogenesis of some inflammatory diseases. Recently, we and others have shown that some of the suppressive effects of hookworms reside in their excretory/secretory (ES) products. Here, we demonstrate that ES products of the hookworm Ancylostoma caninum (AcES) suppress intestinal pathology in a model of chemically induced colitis. This suppression was associated with potent induction of a type 2 cytokine response characterized by coexpression of interleukin-4 (IL-4) and IL-10 by CD4+ T cells, downregulation of proinflammatory cytokine expression in the draining lymph nodes and the colon, and recruitment of alternatively activated (M2) macrophages and eosinophils to the site of ES administration. Protease digestion and heat denaturation of AcES resulted in impaired induction of CD4+ IL-4+ IL-10+ cell responses and diminished ability to suppress colitis, indicating that protein component(s) are responsible for some of the immunosuppressive effects of AcES. Identification of the specific parasite-derived molecules responsible for reducing pathology during chemically induced colitis could lead to the development of novel therapeutics for the treatment of human inflammatory bowel disease.

Hookworm recombinant protein promotes regulatory T cell responses that suppress experimental asthma

A secreted hookworm protein in recombinant form acts on dendritic cells to drive the expansion and mucosal homing of regulatory T cells that protect against airway inflammation in mice, and also dampens human dendritic cell and T cell activation. Airway allergy alleviated by hookworm protein One reason for allergy prevalence in the developed world may be a lack of exposure to parasites, which can influence immune development and function. Because administering live parasites to people might pose safety issues, Navarro et al. tested the ability of the hookworm protein AIP-2 to treat airway allergic sensitization. Administration of AIP-2 could prevent or treat asthma symptoms in a mouse model, in a mechanism that was dependent on dendritic cells and regulatory T cells. Encouragingly, AIP-2 also reduced activation of human dendritic cells and T cells, indicating that these findings may readily translate to the clinic. In the developed world, declining prevalence of some parasitic infections correlates with increased incidence of allergic and autoimmune disorders. Moreover, experimental human infection with some parasitic worms confers protection against inflammatory diseases in phase 2 clinical trials. Parasitic worms manipulate the immune system by secreting immunoregulatory molecules that offer promise as a novel therapeutic modality for inflammatory diseases. We identify a protein secreted by hookworms, anti-inflammatory protein-2 (AIP-2), that suppressed airway inflammation in a mouse model of asthma, reduced expression of costimulatory markers on human dendritic cells (DCs), and suppressed proliferation ex vivo of T cells from human subjects with house dust mite allergy. In mice, AIP-2 was primarily captured by mesenteric CD103+ DCs and suppression of airway inflammation was dependent on both DCs and Foxp3+ regulatory T cells (Tregs) that originated in the mesenteric lymph nodes (MLNs) and accumulated in distant mucosal sites. Transplantation of MLNs from AIP-2–treated mice into naïve hosts revealed a lymphoid tissue conditioning that promoted Treg induction and long-term maintenance. Our findings indicate that recombinant AIP-2 could serve as a novel curative therapeutic for allergic asthma and potentially other inflammatory diseases.

Experimental hookworm infection and escalating gluten challenges are associated with increased microbial richness in celiac subjects.

The intestinal microbiota plays a critical role in the development of the immune system. Recent investigations have highlighted the potential of helminth therapy for treating a range of inflammatory disorders, including celiac disease (CeD); however, the mechanisms by which helminths modulate the immune response of the human host and ameliorate CeD pathology are unknown. In this study, we investigated the potential role of alterations in the human gut microbiota in helminth-mediated suppression of an inflammatory disease. We assessed the qualitative and quantitative changes in the microbiota of human volunteers with CeD prior to and following infection with human hookworms, and following challenge with escalating doses of dietary gluten. Experimental hookworm infection of the trial subjects resulted in maintenance of the composition of the intestinal flora, even after a moderate gluten challenge. Notably, we observed a significant increase in microbial species richness over the course of the trial, which could represent a potential mechanism by which hookworms can regulate gluten-induced inflammation and maintain intestinal immune homeostasis.

Effects of TCDD on the Fate of Naive Dendritic Cells

The environmental contaminant, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), causes immune suppression via activation of the aryl hydrocarbon receptor. Dendritic cells (DCs), the professional antigen-presenting cells in the immune system, are adversely affected by TCDD. We hypothesized that TCDD alters DC homeostasis, resulting in a loss of DCs in naive mice. To test this hypothesis, C57Bl/6 mice were gavaged with either vehicle or an immunosuppressive dose of TCDD (15 microg/kg). TCDD exposure decreased the frequency and number of splenic CD11c(high) DCs on day 7 when compared with vehicle-treated controls. TCDD increased the expression of CD86 and CD54, while decreasing the frequency of splenic CD11c(high) DCs expressing CD11a and major histocompatibility complex (MHC) class II. Moreover, TCDD selectively decreased the CD11c(high)CD8alpha(-)33D1(+) splenic DCs specialized at activating CD4(+) T cells but did not affect the regulatory CD11c(high)CD8alpha(+)DEC205(+) splenic DCs. TCDD did not alter the number or frequency of CD11c(low) splenic DCs but decreased their MHC class II and CD11a expression. Loss of splenic CD11c(high) DCs was independent of Fas-mediated apoptosis and was not due to alterations in the numbers of common DC precursors in the bone marrow or their ability to generate steady-state DCs in vitro. Instead, increased CCR7 expression on CD11c(high) DCs suggested involvement of a migratory event. Popliteal and brachial lymph node CD11c(+) cells showed elevated levels of MHC class II and CD40 following TCDD exposure. Collectively, this study shows the presence of a TCDD-sensitive splenic DC subpopulation in naive mice, suggesting that TCDD may induce suppression of T-cell-mediated immunity by disrupting DC homeostasis.

Diterpenoid alkaloids of Aconitum laciniatum and mitigation of inflammation by 14-O-acetylneoline in a murine model of ulcerative colitis

Aconitum laciniatum is used in Bhutanese traditional medicine for treating various chronic infections and inflammatory conditions. We carried out in-depth isolation and characterization of the phytochemicals from the root component and determined the anti-inflammatory effects of the isolated compounds against chemically-induced colitis in mice. Five diterpenoid alkaloids - pseudaconitine, 14-veratroylpseudaconine, 14-O-acetylneoline, neoline, and senbusine A - were isolated from A. laciniatum for the first time. Two of the alkaloids were tested for anti-inflammatory properties in the TNBS-induced colitis model in mice. Various parameters were measured to assess pathology including weight loss, clinical and macroscopic scores, histological structure and IFN-γ production in the gut. Of the two alkaloids tested, 14-O-acetylneoline showed significant protection against different parameters of colitic inflammation. Compared to control mice that received TNBS alone, mice treated with 14-O-acetylneoline experienced significantly less weight loss and had significantly lower clinical scores, macroscopic pathology and grades of histological inflammation. Moreover, colonic IFN-γ mRNA levels were significantly reduced in mice that received 14-O-acetylneoline compared to control mice that received TNBS alone. This alkaloid is now considered a novel anti-colitis drug lead compound.

Identifying the immunomodulatory components of helminths

Immunomodulatory components of helminths offer great promise as an entirely new class of biologics for the treatment of inflammatory diseases. Here, we discuss the emerging themes in helminth‐driven immunomodulation in the context of therapeutic drug discovery. We broadly define the approaches that are currently applied by researchers to identify these helminth molecules, highlighting key areas of potential exploitation that have been mostly neglected thus far, notably small molecules. Finally, we propose that the investigation of immunomodulatory compounds will enable the translation of current and future research efforts into potential treatments for autoimmune and allergic diseases, while at the same time yielding new insights into the molecular interface of host–parasite biology.

Probing of a Human Proteome Microarray With a Recombinant Pathogen Protein Reveals a Novel Mechanism by Which Hookworms Suppress B-Cell Receptor Signaling

Na-ASP-2 is an efficacious hookworm vaccine antigen. However, despite elucidation of its crystal structure and studies addressing its immunobiology, the function of Na-ASP-2 has remained elusive. We probed a 9000-protein human proteome microarray with Na-ASP-2 and showed binding to CD79A, a component of the B-cell antigen receptor complex. Na-ASP-2 bound to human B lymphocytes ex vivo and downregulated the transcription of approximately 1000 B-cell messenger RNAs (mRNAs), while only approximately 100 mRNAs were upregulated, compared with control-treated cells. The expression of a range of molecules was affected by Na-ASP-2, including factors involved in leukocyte transendothelial migration pathways and the B-cell signaling receptor pathway. Of note was the downregulated transcription of lyn and pi3k, molecules that are known to interact with CD79A and control B-cell receptor signaling processes. Together, these results highlight a previously unknown interaction between a hookworm-secreted protein and B cells, which has implications for helminth-driven immunomodulation and vaccine development. Further, the novel use of human protein microarrays to identify host-pathogen interactions, coupled with ex vivo binding studies and subsequent analyses of global gene expression in human host cells, demonstrates a new pipeline by which to explore the molecular basis of infectious diseases.

Current advances of murine models for food allergy

Food allergy affects an increasing population in Western world but also developing countries. Researchers have been taking great efforts in identifying and characterising food allergens using molecular tools. However, there are still many mechanistic hypotheses that need to be tested using an appropriate in vivo experimental platform. To date, a number of mouse models for food allergy have been established and provided valuable insights into food allergenicity, development of therapies and allergic inflammation mechanisms. Nevertheless, a large diversity of protocols have been developed for the establishment of relevant mouse models. As a result, comparisons of outcomes between different models are very difficult to be conducted. The phenotypes of mouse models are greatly influenced by genetic background, gender, route of allergen exposure, the nature and concentration of food allergens, as well as the usage of adjuvants. This review focuses on IgE-mediated food allergy, compares the differential approaches in developing appropriate murine models for food allergy and details specific findings for three major food allergens, peanut, milk and shellfish.

TIMPs of parasitic helminths – a large-scale analysis of high-throughput sequence datasets

BackgroundTissue inhibitors of metalloproteases (TIMPs) are a multifunctional family of proteins that orchestrate extracellular matrix turnover, tissue remodelling and other cellular processes. In parasitic helminths, such as hookworms, TIMPs have been proposed to play key roles in the host-parasite interplay, including invasion of and establishment in the vertebrate animal hosts. Currently, knowledge of helminth TIMPs is limited to a small number of studies on canine hookworms, whereas no information is available on the occurrence of TIMPs in other parasitic helminths causing neglected diseases.MethodsIn the present study, we conducted a large-scale investigation of TIMP proteins of a range of neglected human parasites including the hookworm Necator americanus, the roundworm Ascaris suum, the liver flukes Clonorchis sinensis and Opisthorchis viverrini, as well as the schistosome blood flukes. This entailed mining available transcriptomic and/or genomic sequence datasets for the presence of homologues of known TIMPs, predicting secondary structures of defined protein sequences, systematic phylogenetic analyses and assessment of differential expression of genes encoding putative TIMPs in the developmental stages of A. suum, N. americanus and Schistosoma haematobium which infect the mammalian hosts.ResultsA total of 15 protein sequences with high homology to known eukaryotic TIMPs were predicted from the complement of sequence data available for parasitic helminths and subjected to in-depth bioinformatic analyses.ConclusionsSupported by the availability of gene manipulation technologies such as RNA interference and/or transgenesis, this work provides a basis for future functional explorations of helminth TIMPs and, in particular, of their role/s in fundamental biological pathways linked to long-term establishment in the vertebrate hosts, with a view towards the development of novel approaches for the control of neglected helminthiases.