A screening system to determine the effect of bacterial metabolites on MAdCAM-1 expression by transformed endothelial sinusoidal cells.

Mucosal addressin cell adhesion molecule 1 (MAdCAM-1) expression in high endothelial venules is regulated by bacterial metabolites emanating from the gut and the interaction of MAdCAM-1 with α4β7 integrin mediates lymphocyte diapedesis into gut-associated secondary lymphoid tissues. MAdCAM-1 thus controls the abundance of circulating immunosuppressive T cells that can reach malignant tissue and compromise the therapeutic efficacy of anticancer immunotherapy. Here we describe a biosensor-based phenotypic assessment that facilitates the high throughput screening (HTS)-compatible assessment of MAdCAM-1 regulation in response to exposure to bacterial metabolites. This screening routine encompasses high endothelial venule cells expressing green fluorescent protein (GFP) under the control of the MAdCAM-1 promoter combined with robot-assisted bioimaging and a multistep image analysis pipeline. Altogether this system facilitates the discovery of bacterial composites that control anticancer immunity via the sequestration of Th17-specific regulatory T cells (Treg17) in the gut.