Dynamic immunoglobulin responses to gut bacteria during inflammatory bowel disease.

Aberrant immune responses against gut microbiota are thought to be key drivers of inflammatory bowel disease (IBD) pathogenesis. However, the extent and targets of immunoglobulin (Ig) A versus IgG responses to gut bacteria in IBD and its association with IBD severity is not well understood. Here, we address this by analyzing fecal samples from Crohn's disease (CD), ulcerative colitis (UC), and Non-IBD patients by flow cytometry for the frequency of bacteria that were endogenously bound with IgA and/or IgG. Assessment of IBD patients from two geographically distinct cohorts revealed increased percentages of IgA- and IgG-bound fecal bacteria compared to non-IBD controls. Notably, the two major subsets of IBD showed distinct patterns of Ig-bound bacteria, with CD activity associated with increases in both IgA and IgG-bound bacteria, whereas UC activity correlated only with increases in IgG-bound bacteria. Analysis of the flow sorted Ig-bound bacterial repertoire by 16S rDNA sequencing revealed taxa that were Ig-bound specifically in IBD. Notably, this included bacteria that are also thought to reside in the oral pharynx, including Gemella, Peptostreptococcus, and Streptococcus species. These data show that the pattern of IgA and IgG binding to fecal bacteria is distinct in UC and CD. In addition, the frequency of Ig-bound fecal bacteria may have potential as a non-invasive biomarker for disease activity. Finally, our results support the hypothesis that immune responses to oral pharyngeal bacteria may play an important role in the pathogenesis of IBD.

Vedolizumab Effectiveness and Safety Over the First Year of Use in an IBD Clinical Practice.

BACKGROUND AND AIMS: Vedolizumab inhibits leucocyte vascular adhesion and migration into the gastrointestinal tract through α4ß7 integrin blockade. This agent became available in mid-2014 for the treatment of moderate to severe Crohn's disease (CD) and UC (UC). The aim of this study was to assess the patterns of use, effectiveness and safety of vedolizumab in an inflammatory bowel disease (IBD) clinical practice. METHODS: Patients beginning vedolizumab were enrolled with informed consent. A prospective cohort was followed with laboratory, disease activity and quality-of-life assessments made during infusion visits up to week 14. Duration of vedolizumab use, mucosal healing and safety were analysed retrospectively for all patients not captured in the prospective component of this study. RESULTS: One hundred and two patients started vedolizumab, with 51 patients (30 CD, 21 UC) followed prospectively. The CD patients exhibited a significant decrease in Crohn's Disease Activity Index (p = 0.04) and Harvey-Bradshaw index (p < 0.01) by week 14. The UC patients demonstrated improved partial Mayo scores at weeks 6 (p < 0.01) and 14 (p < 0.001). Ninety percent of all CD and UC patients remained on vedolizumab up to week 14. IBD-related quality of life was improved by week 6 in CD and UC cohorts (p = 0.02 and p < 0.01 respectively). Colectomy for lack of response and systemic histoplamosis were notable reasons for early discontinuation of vedolizumab, which was otherwise well tolerated. CONCLUSIONS: Vedolizumab was efficacious and a high percentage of patients continued this therapy beyond induction dosing. Observed safety signals may be attributed to the refractory IBD disease state of this early-adopting clinical cohort.