The role of natural lipids in an in vivo model of sensitisation to Ber e 1

The prevalence of food allergy is increasing in westernized countries, affecting 5-8% of children and 1-3% of adults. Although innumerous proteins are encountered in normal diets, only few proteins are commonly implicated as food allergens. In this vein, the major focus in allergy studies falls into intrinsic features of allergens; however, it is known that extrinsic factors can play a role in allergic processes. The allergenicity of Ber e 1, the major allergen from Brazil nuts, is well established and it has been shown that natural lipids from Brazil nuts are essential for the development of an immune response towards Ber e 1. The present study aimed to characterize the humoral response induced by recombinant (r)Ber e 1 alone or in the presence of lipids, and to investigate the mechanism(s) by which natural lipids influence the development of an immune response. BALB/c mice were sensitised intraperitoneally with rBer e 1 alone or in the presence of different lipid fractions. It was found that rBer e 1 alone did not induce an immune response and only one specific fraction of Brazil nut lipids (SPC fraction C), composed of a mixture of lipid classes, was able to induce a Th2-type humoral response, with the presence of Ber-specific anaphylactic antibodies, high levels of Ber-specific IgG1, and low levels of Ber-specific IgG2a. CD1-restricted natural killer (NK)T cells recognize lipids and therefore to test the hypothesis that NKT cells may be involved in the response, the sensitisation protocol with rBer e 1 and SPC lipid fraction C was tested in mice lacking these cells (J18 KO mice). These animals presented significantly lower titers of Ber-specific anaphylactic antibodies, Ber-specific IgG1, and total IgE than sensitised wild type mice, indicating that one of the pathways by which lipids triggered an immune response involved NKT cells. In conclusion, the present work found that lipids from Brazil nuts were essential for the development of a Th2-type humoral response to rBer e 1 and that the immune response induced by lipids involved NKT cells

Endotoxin exposure during sensitization to Blomia tropicalis allergens shifts TH2 immunity towards a TH17-mediated airway neutrophilic inflammation: role of TLR4 and TLR2

Experimental evidence and epidemiological studies indicate that exposure to endotoxin lipopolysaccharide (eLPS) or other TLR agonists prevent asthma. We have previously shown in the OVA-model of asthma that eLPS administration during alum-based allergen sensitization blocked the development of lung TH2 immune responses via MyD88 pathway and IL-12/IFN-γ axis. In the present work we determined the effect of eLPS exposure during sensitization to a natural airborne allergen extract derived from the house dust mite Blomia tropicalis (Bt). Mice were subcutaneously sensitized with Bt allergens co-adsorbed onto alum with or without eLPS and challenged twice intranasally with Bt. Cellular and molecular parameters of allergic lung inflammation were evaluated 24 h after the last Bt challenge. Exposure to eLPS but not to ultrapure LPS (upLPS) preparation during sensitization to Bt allergens decreased the influx of eosinophils and increased the influx of neutrophils to the airways. Inhibition of airway eosinophilia was not observed in IFN-γdeficient mice while airway neutrophilia was not observed in IL-17RA-deficient mice as well in mice lacking MyD88, CD14, TLR4 and, surprisingly, TLR2 molecules. Notably, exposure to a synthetic TLR2 agonist (PamCSK4) also induced airway neutrophilia that was dependent on TLR2 and TLR4 molecules. In the OVA model, exposure to eLPS or PamCSK4 suppressed OVA-induced airway inflammation. Our results suggest that B. tropicalis allergens engage TLR4 that potentiates TLR2 signaling. This dual TLR activation during sensitization results in airway neutrophilic inflammation associated with increased frequency of lung TH17 cells. Our work highlight the complex interplay between bacterial products, house dust mite allergens and TLR signaling in the induction of different phenotypes of airway inflammation.State of Sao Paulo Foundation for Research Support (FAPESP - 07/03031-3)State of Sao Paulo Foundation for Research Support (FAPESP - 11/17880-8)CAPES, Brazilian Council of Scientific and Technologic Developmen

The role of natural lipids in an in vivo model of sensitisation to Ber e 1

The prevalence of food allergy is increasing in westernized countries, affecting 5-8% of children and 1-3% of adults. Although innumerous proteins are encountered in normal diets, only few proteins are commonly implicated as food allergens. In this vein, the major focus in allergy studies falls into intrinsic features of allergens; however, it is known that extrinsic factors can play a role in allergic processes. The allergenicity of Ber e 1, the major allergen from Brazil nuts, is well established and it has been shown that natural lipids from Brazil nuts are essential for the development of an immune response towards Ber e 1. The present study aimed to characterize the humoral response induced by recombinant (r)Ber e 1 alone or in the presence of lipids, and to investigate the mechanism(s) by which natural lipids influence the development of an immune response. BALB/c mice were sensitised intraperitoneally with rBer e 1 alone or in the presence of different lipid fractions. It was found that rBer e 1 alone did not induce an immune response and only one specific fraction of Brazil nut lipids (SPC fraction C), composed of a mixture of lipid classes, was able to induce a Th2-type humoral response, with the presence of Ber-specific anaphylactic antibodies, high levels of Ber-specific IgG1, and low levels of Ber-specific IgG2a. CD1-restricted natural killer (NK)T cells recognize lipids and therefore to test the hypothesis that NKT cells may be involved in the response, the sensitisation protocol with rBer e 1 and SPC lipid fraction C was tested in mice lacking these cells (J18 KO mice). These animals presented significantly lower titers of Ber-specific anaphylactic antibodies, Ber-specific IgG1, and total IgE than sensitised wild type mice, indicating that one of the pathways by which lipids triggered an immune response involved NKT cells. In conclusion, the present work found that lipids from Brazil nuts were essential for the development of a Th2-type humoral response to rBer e 1 and that the immune response induced by lipids involved NKT cells.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Adsorption of Toll-Like Receptor 4 Agonist to Alum-Based Tetanus Toxoid Vaccine Dampens Pro-T Helper 2 Activities and Enhances Antibody Responses

Aluminum salts gels (alum) are TLR-independent adjuvants and have been used to boost antibody responses in alum-based vaccines such as diphtheria, pertussis, and tetanus toxoid (DPT) triple vaccine. However, the pro-Th2 activity of alum-based vaccine formulations has not been fully appreciated. Here we found that alum-based tetanus toxoid (TT) vaccine was biased toward a Th-2 profile as shown by TT-induced airway eosinophilic inflammation, type 2 cytokine production, and high levels of IgE anaphylactic antibodies. The adsorption into alum of prototypic TLR4 agonists such as lipopolysaccharides (LPS) derived from Escherichia coli consistently dampened TT-induced Th2 activities without inducing IFNγ or Th1-like responses in the lung. Conversely, adsorption of monophosphoryl lipid A (MPLA) extracted from Salmonella minnesota, which is a TIR-domain-containing adapter-inducing interferon-β- (TRIF-) biased TLR4 agonist, was less effective in decreasing Th-2 responses. Importantly, in a situation with antigenic competition (OVA plus TT), TT-specific IgG1 or IgG2a was decreased compared with TT sensitization. Notably, LPS increased the production of IgG1 and IgG2a TT-specific antibodies. In conclusion, the addition of LPS induces a more robust IgG1 and IgG2a TT-specific antibody production and concomitantly decreases Th2-cellular and humoral responses, indicating a potential use of alum/TLR-based vaccines

Food aversion: a critical balance between allergen-specific IgE levels and taste preference

Animals sensitized to allergens change their feeding behavior and avoid drinking the otherwise preferred sweetened solutions containing the allergens. This phenomenon, known as food aversion, appears to be mediated by allergen-specific IgE antibodies. Here we investigated food aversion in BALB/c and C57BL/6 mice, which differ in their allergic responses to the allergen ovalbumin as well as in their preference for sweet taste. BALB/c mice present higher levels of IgE and a natural lower preference for sweet flavors when compared to C57BL/6 mice. Specifically, we studied a conflicting situation in which animals simultaneously experienced the aversive contact with the allergen and the attractive sweet taste of increasing concentrations of sucrose. We found that BALB/c mice were more prone to develop food aversion than C57BL/6 mice and that this aversive behavior could be abolished in both strains by increasing the palatability of the solution containing the allergen. In both strains food aversion was positively correlated with the levels of allergen-specific IgE antibodies and inversely correlated with their preference for sucrose sweetened solution

Dendritic Cells Expressing MyD88 Molecule Are Necessary and Sufficient for CpG-Mediated Inhibition of IgE Production In Vivo

Elevated levels of immunoglobulin E (IgE) are associated with allergies and other immunological disorders. Sensitization with alum adjuvant favours IgE production while CpG-ODN adjuvant, a synthetic toll-like receptor 9 (TLR9) agonist, inhibits it. The cellular mechanisms underlying in vivo TLR regulation of immunoglobulin production, specially IgE, are still controversial. Specifically, TLR-mediated IgE regulation in vivo is not yet known. In this study we showed that augmented levels of IgE induced by sensitizations to OVA with or without alum adjuvant or with OVA-pulsed dendritic cells (DCs) were inhibited by co-administration of CpG. Notably, CpG-mediated suppression of IgE production required MyD88-expression on DCs but not on B-cells. This finding contrasts with previous in vitro studies reporting regulation of IgE by a direct action of CpG on B cells via MyD88 pathway. In addition, we showed that CpG also inhibited IgE production in a MyD88-dependent manner when sensitization was performed with OVA-pulsed DCs. Finally, CpG signalling through MyD88 pathway was also necessary and sufficient to prevent anaphylactic antibody production involved in active cutaneous anaphylaxis