Dietary Intervention in Food Allergy

The goal of this randomized double-blind placebo-controlled clinical study is to determine whether the dietary intervention with pectins leads to food immunomodulation in non-specific lipid transfer proteins (nsLTP) allergic patients. The main question it aims to answer is if the microbiome is a target of intervention against food allergy through the use of prebiotics such as pectins.

Participants will be enrolled to receive a two-month dietary intervention with either two different pectins (citrus or apple pectin) or placebo. Increase in oral tolerance to the peach nsLTP will be measured through a double-blind placebo-controlled food challenge (DBPCFC). Microbiome, proteomic and metabolomic studies will also be performed in blood and stool samples.

DIFAMEM is an original integrative project that aims to use the potential of a pectin-enriched diet to treat food allergy, comprehensively addressing its effects on the epigenome and microbiome, metabolomic modifications and immune modulation. DIFAMEM has been approved by the Regulatory Authorities and Ethics Research Committee of Malaga.

In recent years the microbiome has gained attention as a target of intervention against food allergy, e.g. through the use of prebiotics, which are non-digestible food components that stimulate the growth and activity of certain microorganisms. There is currently great interest in the potential of plant-derived dietary fiber as a protective component against allergies, based on promising results which have been obtained in asthma models. Dietary fibers such as pectin can alter the gut microbiota and lead to increased local and systemic concentrations of gut microbiota-derived short chain fatty acids (SCFAs). SCFAs, including acetate, propionate, and butyrate, can promote the generation of peripheral regulatory T cells by epigenetic modulation, and suppress the inflammatory function of dendritic cells (DC) by transcriptional modulation. It is probable that additional metabolites also play an important role in these processes. Therefore, metabolomics applied in an untargeted approach for food allergy is an attractive option for the discovery of novel metabolites. This technology has been used to show a relationship between the beneficial effects upon using prebiotics and changes in faecal metabolites.

Pectin is a polysaccharide that occurs naturally in fruits, mainly in the peel and core. It has been recently reported that a diet supplemented with pectin alters the ratio of Firmicutes to Bacteroidetes in gut and lung microbiota, increases the concentrations of SCFAs in faeces and sera, and reduces the development of airway inflammation by suppressing DC function via engagement of GPR41 (free fatty acid receptor 3, FFAR3). Notably, natural apple pectin has been shown to have an immunomodulatory effect on allergies, although the mechanisms still need to be elucidated. The dominant component of pectin is a linear chain of galacturonic acid (GalA) in which a proportion of the carboxyl acid groups are present as methylesters. The ratio of esterified GalA groups to total GalA groups is termed the degree of esterification (DE). Two types of pectin exist: high methoxy pectin (HMP) with DE \>50% or low methoxy pectin (LMP) with DE \<50%. The majority of natural pectin is HMP, whereas LMP is more common in processed foods. Both HMP and LMP appear to possess immunomodulatory effects and increase SCFA levels in treated mice. LMP is more efficiently fermented by the microbiota in the ileum whereas HMP is mainly fermented in the proximal colon. These data suggest that the different types of pectin may exert their immunomodulatory effects through different mechanisms, however little is known about the different types of pectin in relation to food allergy.

Food allergy has dramatically increased in prevalence by over 50% during the last decade and is estimated to affect 5% of adults and 8% of children. Fruits are the most frequent triggers in adolescents and adults worldwide. The Rosaceae family contains the most often involved fruits, with non-specific lipid transfer proteins (nsLTPs) the primary sensitizers, such as the major peach allergen Pru p 3. NsLTPs are panallergens associated with sensitization to multiple taxonomically unrelated plant-derived foods. They are very stable and can cause a complex clinical pattern known as LTP-syndrome, which includes life-threatening reactions such as anaphylaxis. This syndrome, even in milder forms, can greatly impact quality of life and causes high socio-economic cost.

The DIFAMEM study is based on the hypothesis that dietary intervention will lead to beneficial effects for food allergic patients, using a natural food constituent with prebiotic properties like pectins. Such an intervention would be safer than specific allergen immunotherapy, avoiding allergic side effects. Studying the mechanisms of this intervention by modern innovative omics technologies will allow us to further optimize the approach in a targeted fashion.

Participants with a confirmed nsLTP allergy from the Allergy Unit of Hospital Regional Universitario de Málaga will be enrolled after informed consent obtention to receive a dietary intervention with two different pectins (citrus low DE or apple high DE) or placebo. DBPCFC with known quantities of Pru p 3 will be performed before and after the dietary intervention to determine improvement in nsLTP oral tolerance. Blood and stool samples will also be collected before and after the intervention to analyze the effects on the epigenome and microbiome, metabolomic modifications and immune modulation.

Eligibility Criteria:
Inclusion Criteria:

* Adults with a clear clinical history of food allergy after eating peach (oral allergy syndrome and/or systemic symptoms)
* Sensitization to Pru p 3 by positive skin prick test (SPT wheal area \>7 mm2) and specific IgE (sIgE \>0.35 kU/L)
* Positive DBPCFC (Sampson 2012) with peach juice
* Signed informed consent

Exclusion Criteria:

* Any clinical condition contraindicating performance of DBPCFC
* A negative result in the DBPCFC
* Lactation
* Active infections
* Acute/chronic inflammatory, autoimmune, and/or oncological diseases
* Diabetes
* Obesity
* Severe immunodeficiency
* Metabolic syndrome
* Alcohol disorder
* Mental illness
* Increased liver parameters and any liver disease
* Smoking habit
* Enzymatic deficiency
* Being vegetarian and taking vitamin supplements, probiotics, prebiotics, antibiotics, metformin, statins, proton pump inhibitors, or corticosteroids in the last three months, and immunomodulators and/or immunotherapy in the last five years.