Microbiota of infants consuming secretors or non-secretors mothers milk impacts gut and immune system in mice

Authors: Gurung, Manoj; SCHLEGEL, BRENT THOMAS - University Of Pittsburgh; RAJASUNDARAM, DHIVYAA - University Of Pittsburgh; FOX, RENEE - University Arkansas For Medical Sciences (UAMS); BODE, LARS - University Of San Diego; LINDEMANN, STEPHEN - Purdue University; LEROITH, TANYA - Virginia Tech; Read, Quentin; SIMECKA, CHRISTY - University Arkansas For Medical Sciences (UAMS); CAROL, LAURA - University Arkansas For Medical Sciences (UAMS); ANDRES, ALINE - University Arkansas For Medical Sciences (UAMS); Yeruva, Laxmi

Submitted to: mSystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/4/2024
Publication Date: 3/26/2024
Citation: Gurung, M., Schlegel, B., Rajasundaram, D., Fox, R., Bode, L., Lindemann, S.R., Leroith, T., Read, Q.D., Simecka, C., Carol, L., Andres, A., Yeruva, V. 2024. Microbiota of infants consuming secretors or non-secretors mothers milk impacts gut and immune system in mice. mSystems. 9(4). https://doi.org/10.1128/msystems.00294-24.
DOI: https://doi.org/10.1128/msystems.00294-24

Interpretive Summary: Human Milk Oligosaccharides (HMOs) are the carbohydrates that are present in human milk. HMOs have several health benefits for growing infants. However, the composition of HMO could differ among the mothers depending on several factors. One such factor is the mother's genetic background, also known as secretor status. Mothers with a specific gene, FUT2, are known as secretors; those without this gene are called non-secretors. Milk from secretor and non-secretor mothers differs in HMO composition, specifically a major type of HMO named 2-FL. Due to this difference in the composition of HMO, infants consuming human milk have different microbes in their gut. Similarly, infants consuming infant formula also contain different types of gut microbes. However, how these differences in gut microbes impact infant gut morphology and immune cell composition is not explored. Hence, gut microbes from infants consuming milk from secretor or non-secretor mothers or those consuming infant formula were transplanted to mice lacking microbes (i.e., germ-free mice). One group of mice was also supplemented with a mixture of HMOs daily for 14 days to investigate whether adding HMO changes the gut microbes composition and function. Mouse immune cell composition, changes in intestinal gene expression, and antibody responses were measured. The mice receiving microbes from infants consuming milk from secretor or non-secretor mothers or those consuming infant formula had different gut microbes. The addition of HMO did not change the overall composition of gut microbes. However, HMO changed the intestinal gene expression and immune cell composition. Specifically, HMOs increased immunoglobulin A (IgA) in mice transplanted with microbes from infants consuming infant formula. Also, an important regulatory immune cell type, Foxp3, was elevated in these mice. In conclusion, this study provides insights into how microbes from infants consuming milk from secretor or non-secretor mothers or those consuming infant formula impact intestine gene expression and immune cell composition. This study also showed that adding human milk oligosaccharides changes the impact of microbes and could be beneficial, specifically in infants consuming infant formula.

Technical Abstract: Maternal secretor status is one of the determinants of human milk oligosaccharides (HMOs) composition, which in turn changes the gut microbiota composition of infants. Similarly, infants consuming dairy-based formula have distinct gut microbiota. To understand if this change in gut microbiota impacts immune cell composition, intestinal morphology and gene expression, day 21-old germ-free mice were transplanted with fecal microbiota from infants whose mothers were either secretors (SMM, N = 6) or non-secretors (NSM, N = 7) or from infants consuming dairy-based formula (MFM, N = 4). For each group, one set of mice was supplemented with pooled HMOs daily (SMM+HMOs, N = 7, NSM+HMOs, N = 7, MFM+HMOs, N = 4). After 14 days, intestinal tissues were subjected to histomorphometric and transcriptome analysis, spleen and mesenteric lymph nodes (MLN) tissues were used for flow cytometry, serum was separated for immunoglobulin quantification and colon contents were processed for 16s rRNA sequencing. Distinct gut microbiota composition was found in each group and HMO supplementation did not significantly impact the microbiota diversity. SMM mice had higher abundance of genus Bacteroides, Bifidobacterium, and Blautia, whereas, in the NSM group, there was higher abundance of Akkermansia, Enterocloster, and Klebsiella. In MFM, gut microbiota was represented mainly by Parabacteroides, Ruminococcaceae_unclassified, and Clostrodium_sensu_stricto. Distinct immune signature was also found for the supplemented groups (+HMOs). In MLN, Foxp3 +T cells and innate lymphoid cells type 2 (ILC2) were increased in MFM mice supplemented with HMOs (MFM+HMOs) while in the spleen, they were increased in SMM mice supplemented with HMOs (SMM+HMOs). Similarly, serum immunoglobulin A (IgA) was also elevated in MFM+HMOs group. Distinct global gene expression of the distal small intestine and large intestine were present in each group and within each group with supplementation of HMOs. Interestingly, in the SMM group most changes in gene expression due to HMO supplementation were in the distal small intestine while in MFM group changes were observed both in distal small intestine and large intestine. Overall, data shows that distinct infant gut microbiota due to maternal secretor status or consumption of dairy-based formula and HMO supplementation impacts immune cell composition, antibody response and intestinal gene expression.