The novel duodenal isolateStreptococcus salivariusAGIRA0003 promotes barrier dysfunction and IgG responses in functional dyspepsia

Abstract

AbstractBackground and aimsFunctional dyspepsia (FD) is a highly prevalent disorder of gut-brain interaction (DGBI) that is associated with an altered duodenal microbiota, unexplained low grade duodenal inflammation and altered intestinal permeability. This study aimed to investigate if novel FD-derived bacterial isolates elicited immune responses in FD and the capacity of an immune-stimulating isolate, AGIRA0003 to breach the duodenal epithelial barrier.MethodsBacterial lysates were investigated for immune reactivity using immunoblotting of patient plasma. Immunoblots were probed with plasma from FD patients (n=44, 46.6±17.5 years, 79.6% female) or controls (n=30, 48.9±15.7 years, 63.3% female). Peripheral gut-homing T cells were quantified by flow cytometry and histological analysis used to investigate duodenal biopsies. Polarised Caco-2 cells and FD duodenal spheroids (n=4 lines) were exposed toStreptococcus salivariusAGIRA0003 at a multiplicity of infection of 10 bacterial cells to 1 mammalian cell for 6 hours.ResultsThe presence of plasma IgG antibodies againstS. salivariusAGIRA0003 was significantly associated with FD (χ215.7, 1,p<0.0001). Patients with these IgG antibodies had increased gut-homing lymphocytes (0.33±0.77% vs 1.00±1.46%,p=0.046). Strain AGIRA0003, but not related commensal strains, disrupted tight junction proteins in Caco-2 monolayers, and decreased claudin 1 (CLDN1; 0.49±0.11,p=0.03), desmocollin 2 (DSC2; 0.64±0.33,p=0.03) and desmoglein 2 (DSG2; 0.30±0.12,p=0.03) in spheroid monolayers. In addition, DSC2 (2.19±0.97 vs 1.48±0.85,p=0.02) and DSG2 (23.22±15.92 vs 12.38±7.34,p=0.04) protein levels were decreased in IgG+FD biopsies compared to controls.ConclusionsS. salivariusAGIRA0003 is a potential pathobiont capable of impairing duodenal epithelial barrier defences that elicits an immune response in FD patients.