Vedolizumab is associated with changes in innate rather than adaptive immunity in patients with inflammatory bowel disease.

Objective Vedolizumab, a monoclonal antibody directed against the integrin heterodimer alpha 4 beta 7, is approved for the treatment of Crohn's disease and ulcerative colitis. The efficacy of vedolizumab has been suggested to result from inhibition of intestinal T cell trafficking although human data to support this conclusion are scarce. We therefore performed a comprehensive analysis of vedolizumab-induced alterations in mucosal and systemic immunity in patients with inflammatory bowel disease (IBD), using antiinflammatory therapy with the TNF alpha antibody infliximab as control. Design I mmunophenotyping, immunohistochemistry, T cell receptor profiling and RNA sequencing were performed using blood and colonic biopsies from patients with IBD before and during treatment with vedolizumab (n=18) or, as control, the anti-TNF alpha antibody infliximab (n=20). Leucocyte trafficking in vivo was assessed using single photon emission computed tomography and endomicroscopy. Results Vedolizumab was not associated with alterations in the abundance or phenotype of lamina propria T cells and did not affect the mucosal T cell repertoire or leucocyte trafficking in vivo. Surprisingly, however, alpha 4 beta 7 antibody treatment was associated with substantial effects on innate immunity including changes in macrophage populations and pronounced alterations in the expression of molecules involved in microbial sensing, chemoattraction and regulation of the innate effector response. These effects were specific to vedolizumab, not observed in response to the TNF alpha antibody infliximab, and associated with inhibition of intestinal inflammation. Conclusion Our findings suggest that modulation of innate immunity contributes to the therapeutic efficacy of vedolizumab in IBD.