Intestinal Microbiota in IgE-mediated Cow’s Milk Allergy: microbial dysbiosis and possible modulation through probiotics

Objectives and study: The aim of the study was to evaluate gut microbiota (GM) in infants with cow milk allergy (CMA) compared to food-sensitized and healthy infants. Furthermore, we investigated colonization, persistence and possible effects of a probiotic mixture (B. breve M-16V (BB), B. longum subsp. longum BB536 (BL) and B. longum subsp. infantis M-63 (BI)) in the GM of allergic infants. Methods: We enrolled a total of 40 infants aged 10 to 15 months: 14 CMA patients (Group1); 12 positive IgE and negative food challenge patients (Group2); 14 healthy infants (Group3). For each patient, a stool sample was collected at enrolment (T 0 ). Group1 received probiotic twice per day (3.5×109 UFC/dose) for 30 days. Stool samples, collected at T 1 (7 days from probiotic intake), T2 (30 days from probiotic intake) and T 3 (after 60 day from probiotic discontinuation), were analysed by real-time PCR. The GM profile of groups was characterized by 16S rRNA targeted metagenomics. Data were analysed by QIIME and IBM SPSS Statistic software. Results: At baseline, BB and BL were present in the GM in the three Groups without significant differences. At T 0 , BI median concentration value was 0 in all the three groups, while after probiotics administration, RT-PCR analysis revealed a significant increase, from 0 to 6.4 x 10 1 molecules/l at T 1 (p=0.003) and 1.6 x 10 2 molecules/l at T 2 (p=0.005) with a decreased to 4.56 x 10 1 molecules/l at T 3. From basal microbiota comparison, we demonstrated that allergic patients clustered in Beta- diversity analysis (PERMANOVA test (p=0.019)) and showed a peculiar phylogenetic relatedness. At phylum level, Verrucomicrobia were higher in healthy group and gradually decreased from Group2 to Group1 (pFDR<0.05). Firmicutes resulted more abundant in Group2 and lower in Group3, while Group1 showed an intermediate level (pFDR<0.05). At genus level, Haemophilus, Actinobacillus, Prevotella and Streptococcus resulted associated to allergy, with a significant increase (p<0.05) in Group1 and less in Group2 compared to Group3. Klebsiella showed a higher abundance in Group1 but not in Group2 compared to Group3. Parabacteroides and Granulicatella were instead more abundant in Group3. During probiotic intake, there was an increase of Verrucomicrobia with a peak of abundance at T 2. Proteobacteria showed a gradually increase during probiotic intake and this increment was maintained also at T 3 . On the contrary, Actinobacteria decreased during the time-course, even if there was an increase form point T 1 to point T 2 . At genus level, probiotic intake determined an increase of Akkermansia, Prevotella and Ruminococcus. Actinomyces, Enterococcus, Streptococcus and Sutterella resulted instead diminished after probiotic intervention. Blautia increased during all the period of probiotic intake, until T 2 point, while at T 3 it started to decrease and showed a level of abundances lower than T 0 . Conclusion: GM of CMA infants is different from that of sensitized and healthy infants and BI can colonize and persist in CMA GM. Probiotic administration provoked an increase of anti-inflammatory and a decrease of pro-inflammatory bacteria. In conclusions, early infancy is a window during which gut microbiota may shape food allergy outcomes in childhood and probiotics could be a rational way to modulate it.