Anne-Marie Madore

Food allergy (FA) is a great public health concern with an increased prevalence in the last decades. The underlying development mechanisms of FA and food sensitization (FS), which represents the first stage of development of FA, are influenced by environmental, epigenetic, and genetic factors. DNA methylation is an important epigenetic mediator of gene-environment interactions and key to understanding these mechanisms. Studies have linked whole-genome DNA methylation profile to FA and FS, but they all use methylation arrays. Methylation sequencing captures target regions of methylome with an extensive coverage. Thus, our objective was to identify CpG sites in genome-wide immune regulatory regions associated with FS and test their association with genetic variants using methylation quantitative trait loci (mQTL) analysis in French-Canadian individuals. In 114 individuals from the Saguenay-Lac-Saint-Jean asthma family cohort, a total of 10 CpG sites out of 5,233,004 CpG sites were associated with the FS status (P < 1 × 10^-8). CpG sites were located in 10 genes (ARRDC1, B9D1, CFL1, CROCC, DHX36, DND1, PMS1, RASSF1, TOP2A, and USP21) all of which were associated with immune response and allergic diseases (allergy, asthma, atopic dermatitis, and allergic rhinitis) in the literature. Almost all individuals with FS clustered based on the methylation levels of these CpG sites which reinforces their importance and relevance to discriminate individuals with and without FS in our cohort. Among the top 10 most significant CpG sites, five were associated with 478 genetic variants in trans-mQTL (FDR < 1 × 10^-8). To our knowledge, this is a unique association study between FS and DNA methylation using targeted bisulfite sequencing across the genome. This approach provides high-resolution assessment of genome-wide functional methylome that yields valuable understandings to this field of research. The results reveal potential relationships between FS, CpG sites, and genetic variants located in genes involved in allergic diseases. This provides potential insights on the underlying effects of DNA methylation and genetic variants on FS and possibly the pathogenesis of FA. Further epigenome-wide studies on larger samples combined with genome-wide genotyping are needed to validate the results and verify the biological potential of these CpG sites.

Background: Food allergies (FAs) are an increasing public health concern, particularly in children. Oral immunotherapy (OIT) is an emerging treatment strategy under clinical investigation for desensitization of children with FA to food allergens. Dysbiosis of the gut microbiota has been implicated in FAs, and various factors influence its composition; however, the impact of OIT on the gut microbiota remains largely unexplored. Objective: This study aimed to identify the changes in diversity of the gut microbiota following OIT in children with FA. Methods: Thirty children with FA undergoing oral immunotherapy and seven non-allergic controls participated in this study. Fecal samples were collected before and after OIT from children with FA, and once from controls. The gut microbiota was profiled using 16S rRNA sequencing, followed by diversity and differential abundance analyses. Alpha and beta diversities were compared, and differential abundance was assessed. Results: Beta diversity analysis revealed small but significant differences in microbial composition between children with FA before and after OIT, and between controls and children with FA before OIT. Differential abundance analysis showed that OIT induced a reversion of the abundance levels of Bacteroidota and Verrucomicrobiota towards those observed in controls. Conclusion: To our knowledge, this is the first study to investigate the impact of OIT on the gut microbiota in children with different FAs for identifying potential microbial biomarkers, and convincingly demonstrated their interrelation. These findings may help improve and personalize FA treatment.

Background: Two asthma-associated regions 17q12–q21 and 5q31.1 harbour genes that show strong effect of genotype on expression levels. DNA methylation has an important role in gene regulation; therefore, we examined DNA methylation at promoters of 12 genes from 5q31 and 17q12–q21 regions. Our goal was to determine whether DNA methylation was associated with predisposition to asthma and whether such a relationship was independent from genetic association. Methods: Using sodium bisulfite sequencing and pyrosequencing methylation assays, we examined the effect of genotype on DNA methylation in peripheral blood cells from individuals from the Saguenay-Lac-Saint-Jean asthma familial collection and lymphoblastoid cell lines. Results: The local genotype influenced methylation levels of solute carrier family 22 (organic 3 cation/carnitine transporter) member 5 (SLC22A5), zona pellucida binding protein 2 (ZPBP2) and gasdermin A (GSDMA) promoter regions. The genotype had a dominant effect on ZPBP2 and GSDMA methylation with lower methylation levels in individuals that carry the asthma-predisposing alleles. Males also had lower methylation at the ZPBP2 promoter than females. We did not observe an effect of asthma status that would be independent of the genotype and the sex effects in the GSDMA, ZPBP2 and SLC22A5 regions; however, GSDMA and ZPBP2 data were suggestive of interaction between asthma and methylation levels in females and SLC22A5 in males. Conclusions: The local genotype influences methylation levels at SLC22A5 and ZPBP2 promoters independently of the asthma status. Further studies are necessary to confirm the relationship between GSDMA-ZPBP2 and SLC22A5 methylation and asthma in females and males separately.

Allergic asthma is a complex trait. Several approaches have been used to identify biomarkers involved in this disease. This study aimed at demonstrating the relevance and validity of microarrays in the definition of allergic asthma expression pattern. The authors compared the transcript expressions of bronchial biopsy of 2 different microarray experiments done 2 years apart, both including nonallergic healthy and allergic asthmatic subjects (n = 4 in each experiment). U95Av2 and U133A GeneChips detected respectively 89 and 40 differentially expressed genes. Fifty-five percent of the U133A genes were previously identified with the U95Av2 arrays. The immune signaling molecules and the proteolytic enzymes were the most preserved categories between the 2 experiments, because 3/4 of the genes identified by the U133A were also significant in the U95Av2 study for both categories. These results demonstrate the relevance of microarray experiments using bronchial tissues in allergic asthma. The comparison of these GeneChip studies suggests that earlier microarray results are as relevant as actual ones to target new genes of interest, particularly in function categories linked to the studied disease. Moreover, it demonstrates that microarrays are a valuable technology to target novel allergic asthma pathways as well as biomarkers.