Intestinal bacteria recognized by serum IgG from patients with Inflammatory bowel disease

Inflammatory bowel disease is associated with intestinal dysbiosis and with elevated antibody production towards microbial epitopes. Based on the induction of antibodies by bacterial glycans, the aim of this study was to address whether changes in antibody profiles can be linked to specific bacterial taxa. To address the antibody reactivity to the gut microbiota, IgG binding to members of a healthy human intestinal microbiota was measured and observed to be increased in sera of patients with Crohn's disease. Based on a high serum IgG reactivity to fucosylated glycans observed in these patients, the same bacteria were tested for recognition by the fucose-binding Aleuria aurantia lectin. Bacteria bound by the lectin or serum IgG from healthy controls or patients were sorted and the composition was determined by 16S rRNA sequencing. Comparison of unsorted and sorted bacteria identified enrichment of Bacteroides stercoris in IgG- and lectin-positive fractions. Recognition of Bacteroides stercoris by Aleuria aurantia lectin and serum IgG, with an increased IgG reactivity for patients with Crohn's disease, was confirmed and additionally shown for other Bacteroides species. This study revealed a link between increased antibody response to fucosylated glycans and Bacteroides species in Crohn's disease.