Denis Bedoret

Lung interstitial macrophages alter dendritic cell functions to prevent airway allergy in mice

The respiratory tract is continuously exposed to both innocuous airborne antigens and immunostimulatory molecules of microbial origin, such as LPS. At low concentrations, airborne LPS can induce a lung DC-driven Th2 cell response to harmless inhaled antigens, thereby promoting allergic asthma. However, only a small fraction of people exposed to environmental LPS develop allergic asthma. What prevents most people from mounting a lung DC-driven Th2 response upon exposure to LPS is not understood. Here we have shown that lung interstitial macrophages (IMs), a cell population with no previously described in vivo function, prevent induction of a Th2 response in mice challenged with LPS and an experimental harmless airborne antigen. IMs, but not alveolar macrophages, were found to produce high levels of IL-10 and to inhibit LPS-induced maturation and migration of DCs loaded with the experimental harmless airborne antigen in an IL-10-dependent manner. We further demonstrated that specific in vivo elimination of IMs led to overt asthmatic reactions to innocuous airborne antigens inhaled with low doses of LPS. This study has revealed a crucial role for IMs in maintaining immune homeostasis in the respiratory tract and provides an explanation for the paradox that although airborne LPS has the ability to promote the induction of Th2 responses by lung DCs, it does not provoke airway allergy under normal conditions.

Dendritic Cells Genetically Engineered to Express IL-10 Induce Long-Lasting Antigen-Specific Tolerance in Experimental Asthma

Dendritic cells (DCs) are professional APCs that have a unique capacity to initiate primary immune responses, including tolerogenic responses. We have genetically engineered bone marrow-derived DCs to express the immunosuppressive cytokine IL-10 and tested the ability of these cells to control experimental asthma. A single intratracheal injection of OVA-pulsed IL-10-transduced DCs (OVA-IL-10-DCs) to naive mice before OVA sensitization and challenge prevented all of the cardinal features of airway allergy, namely, eosinophilic airway inflammation, airway hyperreactivity, and production of mucus, Ag-specific Igs, and IL-4. OVA-IL-10-DCs also reversed established experimental asthma and had long-lasting and Ag-specific effects. We furthermore showed, by using IL-10-deficient mice, that host IL-10 is required for mediating the immunomodulatory effects of OVA-IL-10-DCs and demonstrated a significant increase in the percentage of OVA-specific CD4+CD25+Foxp3+IL-10+ regulatory T cells in the mediastinal lymph nodes of OVA-IL-10-DC-injected mice. Finally, adoptive transfer of CD4+ mediastinal lymph node T cells from mice injected with OVA-IL-10-DCs protected OVA-sensitized recipients from airway eosinophilia upon OVA provocation. Our study describes a promising strategy to induce long-lasting Ag-specific tolerance in airway allergy.

Sirtuin 1 Promotes Th2 Responses and Airway Allergy by Repressing Peroxisome Proliferator-Activated Receptor-γ Activity in Dendritic Cells

Sirtuins are a unique class of NAD+-dependent deacetylases that regulate diverse biological functions such as aging, metabolism, and stress resistance. Recently, it has been shown that sirtuins may have anti-inflammatory activities by inhibiting proinflammatory transcription factors such as NF-κB. In contrast, we report in this study that pharmacological inhibition of sirtuins dampens adaptive Th2 responses and subsequent allergic inflammation by interfering with lung dendritic cell (DC) function in a mouse model of airway allergy. Using genetic engineering, we demonstrate that sirtuin 1 represses the activity of the nuclear receptor peroxisome proliferator-activated receptor-γ in DCs, thereby favoring their maturation toward a pro-Th2 phenotype. This study reveals a previously unappreciated function of sirtuin 1 in the regulation of DC function and Th2 responses, thus shedding new light on our current knowledge on the regulation of inflammatory processes by sirtuins.

Interferon response factor 3 is essential for house dust mite–induced airway allergy

BACKGROUND Pattern-recognition receptors (PRRs) are critically involved in the pathophysiology of airway allergy, yet most of the signaling pathways downstream of PRRs implicated in allergic airway sensitization remain unknown. OBJECTIVE We sought to study the effects of genetic depletion of interferon response factor (IRF) 3 and IRF7, important transcription factors downstream of various PRRs, in a murine model of house dust mite (HDM)-induced allergic asthma. METHODS We compared HDM-induced allergic immune responses in IRF3-deficient (IRF3(-/-)), IRF7(-/-), and wild-type mice. RESULTS Parameters of airway allergy caused by HDM exposure were strongly attenuated in IRF3(-/-), but not IRF7(-/-), mice compared with those in wild-type mice. Indeed, in HDM-exposed IRF3(-/-) mice HDM-specific T(H)2 cell responses did not develop. This correlated with impaired maturation and migration of IRF3(-/-) lung dendritic cells (DCs) on HDM treatment. Furthermore, adoptive transfer of HDM-loaded DCs indicated that IRF3(-/-) DCs had an intrinsic defect rendering them unable to migrate and to prime HDM-specific T(H)2 responses. Intriguingly, we also show that DC function and allergic airway sensitization in response to HDM were independent of signaling by type I interferons, the main target genes of IRF3. CONCLUSION Through its role in DC function, IRF3, mainly known as a central activator of antiviral immunity, is essential for the development of T(H)2-type responses to airway allergens.

ADAM-8, a metalloproteinase, drives acute allergen-induced airway inflammation.

Asthma is a complex disease linked to various pathophysiological events including the activity of proteinases. The multifunctional A disintegrin and metalloproteinases (ADAMs) displaying the ability to cleave membrane‐bound mediators or cytokines appear to be key mediators in various inflammatory processes. In the present study, we investigated ADAM‐8 expression and production in a mouse model of allergen‐induced airway inflammation. In allergen‐exposed animals, increased expression of ADAM‐8 was found in the lung parenchyma and in DC purified from the lungs. The potential role of ADAM‐8 in the development of allergen‐induced airway inflammation was further investigated by the use of an anti‐ADAM‐8 antibody and ADAM‐8 knockout animals. We observed a decrease in allergen‐induced acute inflammation both in BALF and the peribronchial area in anti‐ADAM‐8 antibody‐treated mice and in ADAM‐8‐deficient mice (ADAM‐8−/−) after allergen exposure. ADAM‐8 depletion led to a significant decrease of the CD11c+ lung DC. We also report lower levels of CCL11 and CCL22 production in antibody‐treated mice and ADAM‐8‐ deficient mice that might be explained by decreased eosinophilic inflammation and lower numbers of DC, respectively. In conclusion, ADAM‐8 appears to favour allergen‐induced acute airway inflammation by promoting DC recruitment and CCL11 and CCL22 production.

Pulmonary function and antimicrobial concentration after marbofloxacin inhalation in horses

Injection 15 minutes 1·646 1·348 1·538 1·587 1·792 1·454 1·561 (0·154) Aerosol 15 minutes 0·0706 0·0839 0·0512 0·0383 0·0408 0·0639 0·0581 (0·0179) One hour 0·0395 0·0486 0·0289 0·0299 0·02168 0·0391 0·0346 (0·0096) Three hours 0·0210 0·0251 0·0149 0·0171 0·0110 0·0249 0·0190 (0·0057) Six hours 0·0143 0·0143 0·0083 0·0101 0·0072 0·0170 0·0119 (0·0039) 24 hours 0·0017 0·0015 0·0013 0·0013 0·0013 0·0018 0·0015 (0·0002) TABLE 2: Plasma concentrations of marbofloxacin (μg/ml) in six healthy horses 15 minutes after intravenous administration (2 mg/kg), and 15 minutes, one, three, six and 24 hours after administration by aerosol (300 mg/horse) Pulmonary function and antimicrobial concentration after marbofloxacin inhalation in horses

CD40 triggering induces strong cytotoxic T lymphocyte responses to heat-killed Staphylococcus aureus immunization in mice: a new vaccine strategy for staphylococcal mastitis

Staphylococcus (S.) aureus is a major pathogen involved in chronic bovine mastitis. Staphylococcal mastitis is difficult to control due to the ability of S. aureus to invade and survive within host cells. We therefore postulated that induction of CD8(+) cytotoxic T lymphocyte (CTL) responses leading to destruction of infected cells could help in the control of S. aureus mastitis. We demonstrate that immunization of mice with heat-killed S. aureus together with agonistic anti-CD40 monoclonal antibodies elicits strong CTL responses capable of reducing the severity of subsequent staphylococcal mastitis. Our study shows promise for CTL-dependent vaccination against S. aureus mastitis.