AUTHOR=Li Shuo , Li Na , Wang Chenwei , Zhao Yi , Cao Jie , Li Xuejing , Zhang Ziyi , Li Yue , Yang Xin , Wang Xiaoxin , Che Chuanyan , Zhao Yufeng , Wang Linghua , Zhao Liping , Shen Jian 

TITLE=Gut Microbiota and Immune Modulatory Properties of Human Breast Milk Streptococcus salivarius and S. parasanguinis Strains

JOURNAL=Frontiers in Nutrition

VOLUME=9

YEAR=2022

URL=https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2022.798403

DOI=10.3389/fnut.2022.798403

ISSN=2296-861X

ABSTRACT=<p>Human breast milk <italic>Streptococcus</italic> spp. are transferred to infant guts via breast feeding, but their effects on the gut microbiota and immunity remain unclear. In this study, we characterized gut microbiota and immune modulatory properties of human breast milk <italic>S. salivarius</italic> F286 and <italic>S. parasanguinis</italic> F278 that had been shown to be able to colonize gut. The two <italic>Streptococcus</italic> strains were orally administered to mouse pups individually at 1 × 10<sup>7</sup> cells/day from postnatal Days 1 to 21. At postnatal week 3 (the weaning period), <italic>S. salivarius</italic> F286 reduced the colonic microbiota α-diversity, increased 21 amplicon sequence variants (ASVs), including bacteria from <italic>Akkermansia, Intestinimonas</italic>, and Lachnospiraceae, and decreased 52 ASVs, including bacteria from <italic>Eubacterium, Bifidobacterium, Escherichia</italic>-<italic>Shigella</italic>, and <italic>Turicibacter</italic>; however, <italic>S. parasanguinis</italic> F278 didn't change the colonic microbiota. Both <italic>Streptococcus</italic> strains reduced the ileal mRNA expression of cytokine/transcription factor representatives of T helper (Th) cells, including IFN-γ (Th1), Gata3 (Th2), and TGF-β (Treg) in 2-week-old suckling mice, and promoted the ileal expression of Foxp3 and TGF-β, which are representatives of anti-inflammatory Treg cells, in 3-week-old weaning mice. The two <italic>Streptococcus</italic> strains exhibited anti-inflammatory potential when incubated <italic>in vitro</italic> with human peripheral blood mononuclear cells and TNF-α-treated gut epithelial HT29 cells. In <italic>C. elegans</italic>, both strains activated immune response genes, which was associated with their lifespan-prolonging effects. Our results suggest that <italic>S. salivarius</italic> F286 and <italic>S. parasanguinis</italic> F278 may exert regulatory (anti-inflammatory) roles in gut immunity and <italic>S. salivarius</italic> F286 can modulate gut microbiota, and highlight the probiotic potential of milk <italic>S. salivarius</italic> and <italic>S. parasanguinis</italic> strains.</p>