Bifidobacteria infantis and human milk oligosaccharides have independent and synergistic effects on immune response and amino acid metabolism in germ-free mouse models

Authors: MULAKALA, BHARATH - University Of Arkansas; SALINAS, MICHAEL - Texas A&M University; DAVIDSON, LAURIE - Texas A&M University; ROMERO, SELIM - Texas A&M University; Read, Quentin; FOX, RENEE - Arkansas Children'S Nutrition Research Center (ACNC); LEROITH, TANYA - Virginia Tech; CAI, JAMES - Texas A&M University; CHAPKIN, ROBERT - Texas A&M University; DONOVAN, SHARON - University Of Illinois Urbana-Champaign; Yeruva, Venkat

Submitted to: mSystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/13/2026
Publication Date: 6/15/2026
Citation: Mulakala, B., Salinas, M.L., Davidson, L.A., Romero, S., Read, Q.D., Fox, R., Leroith, T., Cai, J.J., Chapkin, R.S., Donovan, S.M., Yeruva, V. 2026. Bifidobacteria infantis and human milk oligosaccharides have independent and synergistic effects on immune response and amino acid metabolism in germ-free mouse models. mSystems. https://doi.org/10.1128/msystems.00392-26.
DOI: https://doi.org/10.1128/msystems.00392-26

Interpretive Summary: Background: Diet and the gut microbiome interaction plays a major role in early infant growth and development. However, studies on the interactive effects of bioactives such as human milk oligoscharides (HMO) and the predominant gut microbe [Bifidobacteria infantis (BI)] in human milk fed infants shaping the immune system and metabolic functions during early life are lacking. To address the knowledge gap we investigated individual and combined effects of BI colonization and HMO supplementation on host physiology using germ-free mouse model. Findings: Data revealed that BI and HMO exert distinct individual effects on the immune cell composition of the MLN and spleen, the large intestinal transcriptome, and the cecal and serum metabolic profiles. Interestingly, we observed unique BI × HMO interactions in each of these compartments that differed from individual effects. Specifically, BI influenced the genes in colonocytes and modulated serum metabolites involved in regulating circadian rhythms, amino acid metabolism, increased proportion of immune cells (B cells) while in the presence of HMOs metabolism shifted to fermentation pathways. Impact: Results indicate that host-microbe-diet interactions are complex and highlight that to modulate infant health during early life these interactions need to be taken into consideration.

Technical Abstract: Early-life microbial colonization is essential for gut and immune development. Human milk oligosaccharides (HMO) support the growth of Bifidobacterium infantis (BI), a keystone infant species. Herein, we studied the individual and combined effects of BI and HMO on immune and colon transcriptomes, and the serum metabolome. Germ-free mice were randomly assigned to four groups [10-14/group: HMO, BI, BI+HMO and control (no HMO or BI)]. HMO and BI+HMO groups received 5 mg/d each of 2'-fucosyllactose, lacto-N-tetraose and 3'-sialyllactose for 14 d. BI and BI+HMO received B. infantis ATCC 15697 (1x10^9 CFU/d) on days 1, 4, and 9. Mono-colonization with BI increased monocytes, macrophages, B cells, CD4+ T cells, and Treg cells in mesenteric lymph nodes (MLN) relative to control. In the spleen, BI alone increased B cells, dendritic cells, Th17 cells, and ILC3 cells, and enriched serum amino acid metabolism pathways. Additionally, BI influenced colonocyte gene expression, and modulated serum metabolites regulating circadian rhythms. BI+HMO increased MLN Th17 cells and spleen monocytes compared to HMO alone. Collectively, the results of this study highlight the complex interplay between host-microbe-diet interactions and emphasize the importance of considering these interactions when designing strategies to modulate infant health during early life.