Disruption of a T cell recruitment and retention gradient for the treatment of chronic intestinal inflammation in inflammatory bowel disease

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Inflammatory bowel disease (IBD) is a chronic debilitating disorder requiring lifelong therapeutic intervention and patient monitoring. Currently, the most widely administered immunotherapeutic agents include antibodies targeting single inflammatory factors, or cell adhesion molecules that mediate immune cell trafficking to sites of inflammation. Despite a range of existing therapeutic agents addressing different immune components, a significant proportion of patients suffer from treatment-refractory disease or lose response to treatments within a year, thereby necessitating new treatment options or combination therapies. In our work recently published in Cell, we used state of the art single cell RNA sequencing and mass cytometry technologies to detect pathogenic changes during inflammation. These technologies allowed us to closely examine alterations in cellular gene and protein expression profiles. We used tissue samples from healthy donors and IBD patients with active disease to highlight major drivers of IBD pathology. Important insights derived from these studies have allowed us to select two key functionally-related molecules, CCL19 and CCL21, which display high levels of aberrant expression in inflamed tissues, and have strong chemoattractant properties to recruit immune cells. The secretion of these chemokine molecules therefore perpetuates inflammation by preventing immune homeostasis. In this project we therefore aim to design specific targeted therapeutics that inhibit the actions of these major chemokines. Given the functional redundancy between these targets, we aim to disrupt the signalling activities of these molecules by engineering a neutralising bispecific antibody, which will bind to and antagonise CCL19 and CCL21 functions simultaneously. We will select for antibodies targeting CCL19 and CCL21 with high affinity at the first stage of antibody production. We will then validate the functions of selected antibodies by demonstrating their ability to inhibit a well-characterised cellular signalling pathway in immune cells. The functionality of these antibodies will be further confirmed by chemotaxis assays, in which cells can normally migrate towards a CCL19/CCL21 chemokine gradient, but such an activity will be inhibited in the presence of neutralising antibodies. Identification of an effective therapeutic bispecific antibody will enable subsequent testing of its ability to prevent immune cell migration to areas of mucosal inflammation in colitis models. The therapeutic antibody generated by this project will provide a new type of treatment that differs in its mechanism of action from existing therapies, most of which focus on single molecular targets with a defined biological purpose. By cutting off immune cell recruitment using our strategy, we aim to simultaneously disrupt multiple proinflammatory activities mediated by different subtypes of immune cells. This includes T cells, which are key drivers of chronic intestinal inflammation, and mature dendritic cells, which carry microbial-derived protein fragments to activate T cells. CCL19/CCL21 blockade will therefore directly impede many immune-stimulating pathways responsible for sustaining inflammation in IBD, thereby reducing disease severity and potentially restoring the balance required for immune homeostasis. This therapeutic strategy will potentially benefit patients who fail to respond to conventional therapies, patients who develop resistance to current treatments, and help to prevent disease recurrence in post-operative patients. Targeting these chemokines may also provide much needed opportunities for more personalised therapies for IBD patients, such as those who exhibit high levels of ectopic CCL19/CCL21 production, and may also be useful for the development of combination treatments in order to achieve a better clinical outcome.