Guénolée Prioult

Germ-free status and altered caecal subdominant microbiota are associated with a high susceptibility to cow's milk allergy in mice

Studies suggesting that the development of atopy is linked to gut microbiota composition are inconclusive on whether dysbiosis precedes or arises from allergic symptoms. Using a mouse model of cows milk allergy, we aimed at investigating the link between the intestinal microbiota, allergic sensitization, and the severity of symptoms. Germ-free and conventional mice were orally sensitized with whey proteins and cholera toxin, and then orally challenged with β-lactoglobulin (BLG). Allergic responses were monitored with clinical symptoms, plasma markers of sensitization, and the T-helper Th1/Th2/regulatory-T-cell balance. Microbiota compositions were analysed using denaturing gradient gel electrophoresis and culture methods. Germ-free mice were found to be more responsive than conventional mice to sensitization, displaying a greater reduction of rectal temperature upon challenge, higher levels of blood mouse mast cell protease-1 (mMCP-1) and BLG-specific immunoglobulin G1 (IgG1), and a systemic Th2-skewed response. This may be explained by a high susceptibility to release mMCP-1 even in the presence of low levels of IgE. Sensitization did not alter the microbiota composition. However, the absence of or low Staphylococcus colonization in the caecum was associated with high allergic manifestations. This work demonstrates that intestinal colonization protects against oral sensitization and allergic response. This is the first study to show a relationship between alterations within the subdominant microbiota and severity of food allergy.

Infant gut microbiota is protective against cow's milk allergy in mice despite immature ileal T-cell response

Faecal microbiota of healthy infant displays a large abundance of Bifidobacterium spp. and Bacteroides spp. Although some studies have reported an association between these two genera and allergy, these findings remain a subject of debate. Using a gnotobiotic mouse model of cows milk allergy, we investigated the impact of an infant gut microbiota – mainly composed of Bifidobacterium and Bacteroides spp. – on immune activation and allergic manifestations. The transplanted microbiota failed to restore an ileal T-cell response similar to the one observed in conventional mice. This may be due to the low bacterial translocation into Peyers patches in gnotobiotic mice. The allergic response was then monitored in germ-free, gnotobiotic, and conventional mice after repeated oral sensitization with whey proteins and cholera toxin. Colonized mice displayed a lower drop of rectal temperature upon oral challenge with b-lactoglobulin, lower plasma mMCP-1, and lower anti-BLG IgG1 than germ-free mice. The foxp3 gene was highly expressed in the ileum of both colonized mice that were protected against allergy. This study is the first demonstration that a transplanted healthy infant microbiota mainly composed of Bifidobacterium and Bacteroides had a protective impact on sensitization and food allergy in mice despite altered T-cell response in the ileum.

Lactococcus lactis NCC 2287 Alleviates Food Allergic Manifestations in Sensitized Mice by Reducing IL-13 Expression Specifically in the Ileum

Objective. Utilizing a food allergy murine model, we have investigated the intrinsic antiallergic potential of the Lactococcus lactis NCC 2287 strain. Methods. BALB/c mice were sensitized at weekly intervals with ovalbumin (OVA) plus cholera toxin (CT) by the oral route for 7 weeks. In this model, an oral challenge with a high dose of OVA at the end of the sensitization period leads to clinical symptoms. Lactococcus lactis NCC 2287 was given to mice via the drinking water during sensitization (prevention phase) or after sensitization (management phase). Results. Lactococcus lactis NCC 2287 administration to sensitized mice strikingly reduced allergic manifestations in the management phase upon challenge, when compared to control mice. No preventive effect was observed with the strain. Lactococcus lactis NCC 2287 significantly decreased relative expression levels of the Th-2 cytokine, IL-13, and associated chemokines CCL11 (eotaxin-1) and CCL17 (TARC) in the ileum. No effect was observed in the jejunum. Conclusion/Significance. These results taken together designate Lactococcus lactis NCC 2287 as a candidate probiotic strain appropriate in the management of allergic symptoms.

Immunomodulatory Potential of Partially Hydrolyzed β-Lactoglobulin and Large Synthetic Peptides

The immunomodulatory potential of fragments derived from the cows milk allergen bovine β-lactoglobulin (BLG) was assessed in a mouse model of oral tolerance (OT) [Adel-Patient, K.; Wavrin, S.; Bernard, H.; Meziti, N.; Ah-Leung, S.; Wal, J. M. Oral tolerance and Treg cells are induced in BALB/c mice after gavage with bovine β-lactoglobulin. Allergy 2011, 66 (10), 1312-1321]. Native BLG (nBLG) and chemically denatured BLG (lacking S-S bridges, dBLG), products resulting from their hydrolysis using cyanogen bromide (CNBr) and some synthetic peptides, were produced and precisely characterized. CNBr hydrolysates correspond to pools of peptides of various sizes that are still associated by S-S bridges when derived from nBLG. nBLG, dBLG, and CNBr hydrolysate of nBLG efficiently prevented further sensitization. CNBr hydrolysate of dBLG was less efficient, suggesting that the association by S-S bridges of peptides increased their immunomodulatory potential. Conversely, synthetic peptides were inefficient even if covering 50% of the BLG sequence, demonstrating that the immunomodulatory potential requires the presence of all derived fragments of BLG and further supporting the use of partially hydrolyzed milk proteins to favor OT induction in infants with a risk of atopy.

Bifidobacterium bifidum NCC 453 Promotes Tolerance Induction in Murine Models of Sublingual Immunotherapy

Background:Enhancing clinical efficacy remains a major goal in allergen-specific immunotherapy. In this study, we tested three strains of bifidobacteria as candidate adjuvants for sublingual allergy vaccines. Methods:Probiotic candidates were evaluated in human monocyte-derived dendritic cell (h-DC) maturation and CD4+ T-cell polarization in vitro models and further tested in murine models of sublingual immunotherapy in BALB/c mice sensitized to either ovalbumin or birch pollen. Results:Bifidobacterium adolescentis, B. bifidum and B. longum induced h-DC maturation and polarized naïve CD4+ T cells toward interferon-γ and interleukin-10 production. B. bifidum increased CD25high, Foxp3+ cells within CD4+ T lymphocytes and was the most potent inducer of interferon-γ in Th2-skewed peripheral blood mononuclear cells and h-DC T-cell cocultures. It also induced a significant decrease in airway hyperresponsiveness in BALB/c mice sensitized to ovalbumin. Sublingual administration of B. bifidum together with recombinant Bet v 1 enhanced tolerance induction in BALB/c mice sensitized to birch pollen, with a downregulation of both airway hyperresponsiveness, lung inflammation and Bet v 1-specific Th2 responses. Conclusions: Due to its capacity to reorient established Th2 responses toward Th1/regulatory T-cell profiles, B. bifidum represents a valid candidate adjuvant for specific immunotherapy of type I allergies.

Low-allergenic hydrolyzed egg induces oral tolerance in mice.

Background: Egg allergy is one of the most common food allergies in children. The standard therapy for egg allergy is strict avoidance. Yet, there is considerable clinical and scientific interest in primary or secondary prevention. A major drawback of oral tolerance (OT) induction protocols, however, is the possibility of severe side effects; thus, we have formulated a hypoallergenic egg product and demonstrate its in vivo capacity to modulate the immune system in the current study. Methods: Hydrolyzed egg (HE) was produced using a combination of moderate heat treatment and enzymatic hydrolysis. The capacity of HE to induce OT was tested in experimental models and compared to whole egg (WE). Delayed-type hypersensitivity (DTH) responses, immune markers and potential early markers of OT were analyzed. Results: Allergic responses, assessed by both DTH responses upon OVA challenge and serum OVA-specific IgE and IgG1, were decreased after treatment with HE and WE compared to the control group. Additionally, feeding WE and HE significantly decreased Th2 cytokine induction and cell proliferation, induced the activation of effector CD4+ T cells and increased numbers and percentages of ICOS+CD4+CD25+Foxp3+ cells. Furthermore, DO11.10 mouse experiments showed that HE contains other peptides than the OVA323-339 peptide that are able to induce tolerance to OVA. Conclusions: Altogether, results showed that HE induces OT in mice in a dose-dependent manner. Due to its low allergenicity compared to WE, it may represent a safer alternative for OT induction in at-risk subjects or oral immunotherapy in allergic patients.

Commonly Used Drugs Impair Oral Tolerance in Mice

Abstract: Ibuprofen and antibiotics are commonly prescribed during early childhood. When given to mice at the time at which oral tolerance is induced, both treatments affect either the induction or the maintenance of oral tolerance. These results suggest that the coadministration of these and similarly acting drugs should be considered cautiously for infants at risk of allergy.