T cell epitopes and specific dietary synbiotics – together towards early life cow’s milk allergy prevention: Takes two to build tolerance

Abstract

Cow’s milk allergy (CMA) is one of the earliest and most common food allergies. It affects approximately 3.5% of children. β-Lactoglobulin (BLG) is one of the main allergenic proteins in cow’s milk. Although many infants spontaneously outgrow CMA throughout childhood, an increasing number of cow’s milk allergic children remain permanently allergic. On the other hand, suffering from CMA in early life is associated with an increased risk of developing asthma later in life. Currently, no treatment is available for CMA and allergen avoidance is the gold standard in the clinic. New preventive and therapeutic approaches are needed to improve the quality of life of patients. Early oral exposure to allergenic foods is important for the development of oral tolerance and is therefore of interest for the primary prevention of food allergies. Protein fragments and peptides are suggested as a safer alternative for the use of the whole protein. Additionally, the use of dietary interventions with specific immunomodulatory components is suggested to beneficially affect the course of allergy development. In this thesis, results are presented on the possibility to induce oral tolerance to the whole whey protein by prior oral exposure to protein fragments or peptides. Furthermore, the possible beneficial effects of a dietary intervention with non-digestible oligosaccharides alone or in combination with health-promoting bacteria on the development of oral tolerance were studied in a mouse model of orally-induced whey allergy. Furthermore, a novel delivery system based on poly(lactic-co-glycolic acid) (PLGA) was used for enhancing the bioavailability of the peptides. The findings of this thesis show that a hydrolyzed whey protein partially prevented the whey-induced allergic response in mice and this was further enhanced when combined with a dietary intervention with non-digestible galacto-, long-chain fructo- and pectin-derived acidic (GFA) oligosaccharides. Similarly, the allergic response was reduced when specific T cell epitope-containing peptides from BLG (PepMix) were administered to mice in parallel with a diet containing short- and long-chain fructo-oligosaccharides and Bifidobacterium breve M-16V (FF/Bb) prior to allergic sensitization. The preventive effect of the PepMix+FF/Bb intervention was associated with enhanced propionate and butyrate concentrations in the cecum and increased markers for regulatory T cells (Tregs) in the Peyer’s patches. Oral exposure to PepMix and FF/Bb before sensitization contributed to an increased percentage of Tregs in the small intestine, enhanced Th1/Th2 ratio in the Peyer’s patches and partial non-responsiveness of splenocytes upon whey sensitization and challenge. Results from in vitro studies with human intestinal epithelial cells (IEC) suggested that IEC-derived galectin-9 is involved in the mechanisms of the non-digestible galacto- and long-chain fructo- (GF) oligosaccharides and a synthetic toll-like receptor 9 ligand by stimulating the activity of the aldehyde dehydrogenase activity in dendritic cells. The use of PLGA nanoparticles for peptide delivery demonstrated partial prevention the whey-induced allergic skin response, suggesting the potential beneficial role of a delivery vehicle in facilitating the tolerogenic capacity of the T cell epitopes. Altogether, this thesis highlights several dietary interventions which might support the development of oral tolerance and contribute to CMA prevention strategies.