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P058 Do circulating exosomes interfere with vedolizumab efficacy in IBD patients?

R. Domenis1, A. Cifu'1, M. Fabris1,2, G. Scardino3, M. Zilli3, M. Marino*3, F. Curcio1,2

1University Hospital of Udine, Dipartimento di Area Medica, Udine, Italy, 2University Hospital of Udine, Istituto di Patologia Clinica, Udine, Italy, 3University Hospital of Udine, Gastroenterology, Udine, Italy

Background

Crohn’s disease (CD) and ulcerative colitis (UC),collectively referred to as the inflammatory bowel diseases (IBDs), are chronic relapsing-remitting inflammatory disorders of the gastrointestinal tract. The attenuation of lymphocyte translocation into the inflamed gut tissue results in a reduction in local inflammation and thus decreases IBD severity. Such mechanism emerged as a new target in IBD therapy. Vedolizumab (VDZ) is a selective monoclonal antibody targeting α4β7 integrin, which is expressed specifically by a subset of gastrointestinal-homing T-lymphocytes. Although VDZ showed promising results in various clinical studies, in common with all existing biological IBD therapies, a significant number of patients either fail to initially respond or lose response with time. Validated markers and mechanistic insights to predict the populations that will derive sustained benefit from VDZ therapies are currently lacking. We hypothesised that circulating exosomes express on their surface high levels of α4β7 integrin, which could bind VDZ and interfere with its activity and therapeutic efficacy.

Methods

Exosomes were isolated from serum of blood donors (BD CTRL) and VDZ-treated patients (IBD) by polymer-based precipitation (Exoquick), analysed for concentration (Exocet) and validated for exosomal markers expression. The surface expression of α4β7 integrin was evaluated by flow cytometry on exosomes-bound beads. The levels of exosome-bound VDZ were investigated by Promonitor-VDZ ELISA kit and western blot analysis. Finally, exosomes isolated from blood donor’s serum were incubated with increasing concentration of VDZ and then exosomal-bound VDZ levels were analysed by immunoblotting analysis.

Results

The number of circulating exosomes was not different between blood donor and IBD patients (A). Flow cytometry analysis revealed that serum exosomes, either from the IBD patients and from the BD donors, express high levels of the VDZ target, α4β7 integrin (B). A significant VDZ levels were measured in exosomes purified from VDZ-treated patient’s serum exosomes (C). Of note, we found that exosomes purified from blood donor’s serum were able to bind VDZ in dose-dependent manner (D).

Conclusion

Our preliminary data suggest that circulating serum exosomes bind VDZ, as they express on the surface the target integrin. Accordingly, exosomes might contribute to drug sequestration, possibly affecting the therapeutic efficacy of VDZ in IBD patients. Further studies are needed to define the possible correlation between VDZ exosomal sequestration and patient’s response.