# Cyclic Oligosaccharide-Induced Modulation of Immunoglobulin A Reactivity to Gut Bacteria Contributes to Alterations in the Bacterial Community Structure

## TL;DR

This study shows that cyclic oligosaccharides affect gut bacteria by changing how IgA coats them, which in turn alters the gut bacterial community structure.

## Contribution

The study reveals a novel link between cyclic oligosaccharides, IgA coating of gut bacteria, and bacterial community changes.

## Key findings

- Cyclic oligosaccharides altered gut bacterial composition and IgA coating index (ICI) at phylum and genus levels.
- ICI was positively correlated with bacterial abundance for specific groups like Bacillota and Lachnospiraceae NK4A136 group.
- No significant correlations were observed for other phyla and genera, indicating selective effects of IgA modulation.

## Abstract

Immunoglobulin A (IgA) is a major gut antibody that coats commensal gut bacteria and contributes to shaping a stable gut bacterial composition. Although previous studies have shown that cyclic oligosaccharides, including cyclic nigerosyl-1,6-nigerose (CNN) and cyclodextrins (CDs, including αCD, βCD, and γCD), alter the gut bacterial composition, it remains unclear whether cyclic oligosaccharides modify the IgA coating of gut bacteria, which relates to cyclic oligosaccharide-induced alteration of the gut bacterial composition. To address this issue, mice were maintained for 12 weeks on diets containing CNN, αCD, βCD, or γCD; the animals’ feces were evaluated for their bacterial composition and the IgA coating index (ICI), a measure of the degree of IgA coating of bacteria. We observed that the intake of each cyclic oligosaccharide altered the gut bacterial composition, with changes in the ICI found at both the phylum and genus levels. The ICI for Bacillota, Lachnospiraceae NK4A136 group, UC Lachnospiraceae, and Tuzzerella were significantly and positively correlated with the relative abundance (RA) in total bacteria for these bacteria; in contrast, significant correlations were not seen for other phyla and genera. Our observations suggest that cyclic oligosaccharide-induced modulation of the IgA coating of gut bacteria may partly relate to changes in the community structure of the gut bacteria.