Delayed bacterial colonization of the gut alters the host immune response to oral sensitization against cow's milk proteins.

SCOPE: Cow's milk allergy is the most prevalent food allergy in infants whose immune system development is critically stimulated during postnatal gut colonization by commensal bacteria. Allergenic potential of cow's milk ß-lactoglobulin (BLG) and caseins (CAS) was investigated in germ-free (GF) BALB/c mice and in GF mice conventionalized (CVd) at 6 weeks of age. METHODS AND RESULTS: Oral sensitization to cow's milk in the presence of cholera toxin led to higher BLG-specific IgE, IgG1, and IgG2a responses in GF mice than in conventional (CV) mice. No significant difference was observed for CAS-specific IgE responses although IgG1 responses to αS1- and κ-caseins were higher in GF mice than in CV mice. CVd mice, orally inoculated with fecal preparations from CV mice, also displayed biased antibody responses compared to CV mice. Secretion of Th2 cytokines by BLG- and CAS-reactivated splenocytes of CVd mice was similar to that of GF mice whereas cytokine production by reactivated cells from mesenteric lymph nodes of CVd mice was equivalent to that of CV mice. CONCLUSION: Oral sensitization to BLG and CAS was differentially affected by the absence of gut microbiota and delayed bacterial colonization altered persistently the host immune response to oral sensitization against food antigens.

Allergenic and immunogenic potential of cow's milk ß-lactoglobulin and caseins evidenced without adjuvant in germ-free mice.

SCOPE: In most animal models of allergy, the development of an IgE response requires the use of an adjuvant. Germ-free (GF) mice exhibit Th2-polarized antibody responses combined with defective immunosuppressive mechanisms. The sensitizing potential of milk proteins was investigated in GF mice in the absence of adjuvant. METHODS AND RESULTS: ß-lactoglobulin (BLG) and whole casein (CAS) allergenicity was evaluated by means of intraperitoneal injections without adjuvant. Injections of BLG induced significant IgE and IgG1 responses in GF mice, while CAS injections provoked the production of IgG1 toward κ- and αS1-caseins. No significant antibody response was evidenced in conventional (CV) mice. After in vitro BLG-reactivation, IL-4, IL-5, IL-13 and IFN-γ productions by splenocytes were higher in GF mice than in CV mice. Heat-treatment decreased BLG allergenicity as indicated by the absence of IgE production in GF mice. However, heat-treatment increased protein immunogenicity and led to the production of anti-BLG and anti-κ-casein IgG1 in both GF and CV mice. This correlated with enhanced productions of IL-4, IL-5 and IL-13 in BLG-reactivated splenocytes from CV mice. CONCLUSION: Gut colonization by commensal bacteria appeared then to significantly reduce the susceptibility of mice toward the intrinsic allergenic and immunogenic potential of milk proteins.

Boiling peanut Ara h 1 results in the formation of aggregates with reduced allergenicity.

SCOPE: Roasting rather than boiling and Maillard modifications may modulate peanut allergenicity. We investigated how these factors affect the allergenic properties of a major peanut allergen, Ara h 1. METHODS AND RESULTS: Ara h 1 was purified from either raw (N-Ara h 1) or roasted (R-Ara h 1) peanuts. Boiling (100°C 15 min; H-Ara h 1) resulted in a partial loss of Ara h 1 secondary structure and formation of rod-like branched aggregates with reduced IgE-binding capacity and impaired ability to induce mediator release. Glycated Ara h 1 (G-Ara h 1) formed by boiling in the presence of glucose behaved similarly. However, H- and G-Ara h1 retained the T-cell reactivity of N-Ara h 1. R-Ara h 1 was denatured, comprised compact, globular aggregates, and showed no evidence of glycation but retained the IgE-binding capacity of the native protein. CONCLUSION: Ara h 1 aggregates formed by boiling were morphologically distinct from those formed by roasting and had lower allergenic activity. Glycation had no additional effect on Ara h 1 allergenicity compared with heating alone. Taken together with published data on the loss of Ara h 2/6 from boiled peanuts, this supports the hypothesis that boiling reduces the allergenicity of peanuts.

Effect of heating and glycation on the allergenicity of 2S albumins (Ara h 2/6) from peanut.

BACKGROUND: Peanut allergy is one of the most common and severe food allergies, and processing is known to influence the allergenicity of peanut proteins. We aimed to establish the effect of heating and glycation on the IgE-binding properties and biological activity of 2S albumins (Ara h 2/6) from peanut. METHODOLOGY/PRINCIPAL FINDINGS: Native Ara h 2/6 was purified from raw peanuts and heated in solution (15 min, 110°C) in the presence or absence of glucose. Ara h 2 and 6 were also purified from roasted peanut. Using PBMC and sera from peanut-allergic patients, the cellular proliferative potency and IgE reactivity (reverse EAST inhibition) and functionality (basophil degranulation capacity) of allergens were assessed. Heating Ara h 2/6 at 110°C resulted in extensive denaturation, hydrolysis and aggregation of the protein, whilst Ara h 2 and 6 isolated from roasted peanut retained its native conformation. Allergen stimulation of PBMC induced proliferation and Th2 cytokine secretion which was unaffected by thermal processing. Conversely, IgE reactivity and functionality of Ara h 2/6 was decreased by heating. Whilst heating-glycation further reduced the IgE binding capacity of the proteins, it moderated their loss of histamine releasing capacity. Ara h 2 and 6 purified from roasted peanut demonstrated the same IgE reactivity as unheated, native Ara h 2/6. CONCLUSIONS/SIGNIFICANCE: Although no effect of processing on T-cell reactivity was observed, heat induced denaturation reduced the IgE reactivity and subsequent functionality of Ara h 2/6. Conversely, Ara h 2 and 6 purified from roasted peanut retained the structure and IgE reactivity/functionality of the native protein which may explain the allergenic potency of this protein. Through detailed molecular study and allergenicity assessment approaches, this work then gives new insights into the effect of thermal processing on structure/allergenicity of peanut proteins.

Differential expression of adhesion molecules and chemokines between nasal and small intestinal mucosae: implications for T- and sIgA+ B-lymphocyte recruitment.

Nasal and small intestinal mucosae are the first sites of contact with infectious agents and the sites of T-cell-mediated and secreted immunoglobulin A (IgA)-mediated defences against pathogens. We investigated the factors controlling the infiltration of CD3(+) T lymphocytes and surface IgA(+) (sIgA(+)) B lymphocytes into swine epithelium and lamina propria (LP) within and between these two mucosal effector sites. Vascular addressins, vascular cell adhesion molecule 1 and mucosal addressin cell adhesion molecule-1 were reciprocally expressed in both mucosae. Strong expression of alpha(4)beta(1) relative to alpha(4)beta(7) was characteristic of CD3(+) T cells in nasal mucosa LP and epithelium and of sIgA(+) cells in nasal mucosa epithelium. The same profile was observed on corresponding blood cells. Conversely, higher levels of integrins beta(7) and alpha(4)beta(7) than alpha(4)beta(1) were characteristic of CD3(+) T cells and sIgA(+) cells in the small intestine. However, about 40% of the LP-activated sIgA(+) cells displayed sIgA(high), integrin alpha(4) and integrin alpha(4) expression. Whereas CCL19, CXCL12, CCL21 and CCL28 messenger RNAs were similarly expressed in both mucosae, CCL25 messenger RNA was only expressed in the small intestine. Thus, the nasal and small intestine mucosae represent separate compartments for infiltration by CD3(+) T cells and sIgA(+) effector cells, with the exception of a population of small intestine activated sIgA(+) cells, which may gain access to both mucosae.

Investigation of the hepatotoxicity profile of chemical entities using Liverbeads and WIF-B9 in vitro models.

The cytotoxicity profile of various chemical entities was evaluated using two in vitro hepatocyte models. Liverbeads is a cryopreserved model consisting of primary hepatocytes entrapped in alginate beads. WIF-B9 is a hybrid cell line obtained by fusion of rat hepatoma (Fao) and human fibroblasts (WI38). Various reference hepatotoxicants were tested and ranked according to their equivalent concentration 50 (EC50) for various biochemical endpoints (lactate dehydrogenase (LDH) release, 3-(4,5 dimethylthiazol 2yl)-2,5-diphenyl-2H tetrazolium bromure (MTT) activity, adenosine triphosphate (ATP) and glutathione (GSH) levels). The ranking obtained was comparable in both models and consistent with previously published results on hepatocyte monolayers. Ketoconazole, erythromycin estolate, retinoic acid, telithromycin and alpha-naphthyl-isothiocyanate were among the most toxic chemicals in both models, with an EC50 < 200 microM. Troleandomycin, spiramycin, erythromycin, diclofenac, taurodeoxycholate, warfarin, galactosamine, valproic acid and isoniazid were found to be less toxic. Few marked differences, potentially linked to metabolism pathways, were observed between EC50s in the two models for compounds such as cyclosporine A (10 and > 831 microM) and warfarin (5904 and 1489 microM) in WIF-B9 and Liverbeads, respectively. The results obtained indicate that Liverbeads and WIF-B9 cells are reliable in vitro models to evaluate the hepatotoxic potential of a wide range of chemicals, irrespective of structure and pharmaceutical class.