Mouse IgA modulates human gut microbiota with inflammatory bowel disease patients

Abstract

Background: The imbalance of commensal bacteria is called dysbiosis in intestinal microflora. Secreted IgA in the intestinal lumen plays an important role in the regulation of microbiota. Although dysbiosis of gut bacteria is reported in IBD patients, it remains unclear what makes dysbiosis of their microflora. The intervention method for remedy of dysbiosis in IBD patients is not well established. In this study, we focused on the quality of human endogenous IgA and investigated whether mouse monoclonal IgA which binds to selectively colitogenic bacteria can modulate human gut microbiota with IBD patients.

Methods: IgA-bound and -unbound bacteria were sorted by MACS and cell sorter. Sorted bacteria were analyzed by 16S rRNA sequencing to investigate what kinds of bacteria endogenous IgA or mouse IgA recognized in human gut microbiota. To evaluate the effect of mouse IgA, gnotobiotic mice with IBD patient microbiota were orally administrated with mouse IgA and analyzed gut microbiota.

Results: We show that human endogenous IgA has abnormal binding activity to gut bacteria in IBD patients. Mouse IgA can bind to human microbiota and bind to selectively colitogenic bacteria. The rW27, especially, has a growth inhibitory activity to human colitogenic bacteria. Furthermore, oral administration of mouse IgA reduced an inflammation biomarker, fecal lipocalin 2, in mice colonized with IBD patient-derived microbiota, and improved dysbiosis of IBD patient sample.

Conclusion: Oral treatment of mouse IgA can treat gut dysbiosis in IBD patients by modulating gut microbiota.

Keywords: Dysbiosis; Gut microbiota; IgA; Inflammatory bowel disease.

Fig. 1

IBD patients have aberrant IgA to gut bacteria. a–d Relative abundances of a Firmicutes, b Verrucomicrobiota, c Proteobacteria, and d Campylobacterota in healthy controls (HC) (n = 12) and IBD patients (n = 20). e–f The concentration of fecal human endogenous IgA and IgG in HC (n = 12) and IBD patients (n = 20, UC: n = 13, CD: n = 7). g Frequency of human endogenous IgA-bound bacteria in gut bacteria of HC (n = 12) and IBD patients (n = 20). h–i Human endogenous IgA index of h HC (n = 12) and i IBD patients (n = 16). Statistical analysis was performed by (a-g) by Mann–Whitney U test. Data are expressed as mean ± s.d. in (a–g), and median ± range in (h–i)

Fig. 2

Mouse IgA antibodies bind to human colitogenic bacteria. a Frequency of mouse IgA-bound gut bacteria in HC (n = 12) and IBD patients (n = 20). b Mouse IgA index of IBD patients (rW27 (n = 16), W37, rPG151A, rPG160A, PGSI1A, and SPFSI12 (n = 12)). Statistical analysis was performed by a Mann–Whitney U test. Data are expressed as mean ± s.d. in (a), and median ± range in (b)

Fig. 3

rW27 inhibits the growth of human colitogenic bacteria. (a-b) Binding analysis of indicated monoclonal IgA to E. coli, E. faecium, G. morbillorum and V. dispar by a ELISA and b FACS. b Grey histogram: unstained bacteria. Red histogram: mouse IgA-bound bacteria. c Growth inhibition of E. coli (n = 6), E. faecium (n = 3), G. morbillorum (n = 3), and V. dispar (n = 6) mediated by rW27. a, b Representative data of repeated experiments. Results of E. coli were same as in Supplementary Fig. 5 a and c. Statistical analysis was performed by c unpaired Student’s t test. Data are expressed as mean ± s.d. in (c)

Fig. 4

The rW27 oral treatment ameliorates gut inflammation in gnotobiotic mice with IBD patients-derived gut bacteria. a Schedule of fecal transplantation, IgA and DSS treatments. b, c b Concentration of fecal lipocalin 2 at day 10 and day 14, c The colon weight/length ratio in gnotobiotic mice with UC10-derived microbiota (n = 4), d, e d Concentration of fecal lipocalin 2 at day 10 and day 14, e The colon weight/length ratio in gnotobiotic mice with CD6-derived microbiota (n = 3). f, g f Concentration of fecal lipocalin 2 at day 10 and day 14, g The colon weight/length ratio in healthy control-derived microbiota (HC5: n = 3, HC8: n = 4, HC10: n = 4). Statistical analysis was performed by b–g Kruskal–Wallis test with Dunn’s multiple comparison test or one-way ANOVA with Tukey's multiple comparisons test. Data are expressed as mean ± s.d. in (b–g)

Fig. 5

Mouse IgA antibodies modulate gut bacteria of gnotobiotic mice with IBD patient-derived gut bacteria. a Relative abundances of bacterial taxa at phylum level in UC10 patient gut microbiota, PBS-, rW27-, and W37-treated mice at day 7 and day 10 (n = 4). Red arrows indicate Fusobacteriaceae. b Shannon index of PBS-, rW27-, and W37-treated mice at day 7 (left bar) and day 10 (right bar) (n = 4). (c) Unweighted unifrac distance of PBS-, rW27-, and W37-treated mice at day 7 (blue circle) and day 10 (red circle) (n = 4). d–f Relative abundance of indicated bacteria of d PBS-, e rW27-, and f W37-treated mice at day 7 and day 10 (n = 4). Statistical analysis was performed by b, d–f by Mann–Whitney U test and c PERMANOVA comparison. Data are expressed as median ± range in (b) and mean ± s.d. in (d–f)