The Role of IL-II in the Development of Autoimmune Response in Multiple Sclerosis

Immunomodulatory therapies are most effective when administered early in the course of relapsing remitting multiple sclerosis (RRMS). Therefore, investigators are seeking biomarkers of the autoimmune response to accurately identify patients with clinically isolated syndrome (CIS), the earliest phase of the disease. Investigators' preliminary studies have identified IL--11 as the most significantly increased cytokine in the serum and cerebrospinal fluid (CSF) of CIS patients. Serum IL--11 and IL--17A levels correlate with brain MRI T2 and T1 lesion load and were significantly increased during clinical exacerbations in comparison to disease remissions in untreated RRMS patients. Investigators also found that IL--11 induces Th17 cell differentiation and expansion in CIS patients. Investigators' human studies have identified that CD4+ cells represent the predominant source of IL--11 within the peripheral circulation. In comparison to healthy controls (HCs), IL--11+CD4+ cells from CIS patients were significantly increased in the peripheral circulation and exhibited the highest CCR6 expression (86 %) among CD4+ T cell subsets. This implied their potential for early migration to the CNS. Indeed, IL-11+CD4+ cells were significantly enriched in the CSF of RRMS patients in comparison to their matched blood samples (40.9 vs. 2.3%), with the most prominent increase in the number of IL--17A+IL--11+CD4+ cells. Immunohistochemistry studies of active brain MS lesion biopsy samples revealed an enrichment of IL--11+ cells within CD4+ infiltrating cells, suggesting their important role in the development of inflammatory CNS lesions. Animal studies have confirmed the causal role of IL--11 in the exacerbation of RR experimental autoimmune encephalomyelitis (EAE), where IL--11 increased the number of central nervous system (CNS)--infiltrating IL-17A+CD4+ cells in comparison to control mice with EAE, reflecting IL--11 induction of CCR6 expression in CD4+ cells. IL--11Ra KO mice had an attenuated EAE clinical course and lower serum IL--17A levels, as well as lower numbers of Il--17A+CD4+ cells in the brain and spinal cord inflammatory infiltrates, similar to the IL23p19 KO mice. Administration of mouse anti IL--11R mAb in the preclinical phase of EAE induced a delayed onset and decreased disease severity, with decreased IL--17A serum levels. The objectives of this study are to (1) identify the molecular mechanisms involved in the IL--11--induced migration of CD4+ cell subsets to the CNS, (2) Functionally characterize CSF--enriched IL--11+CD4+ cells in CIS patients, (3) examine the potential of IL--11 to induce encephalitogenic CD4+ cells, and determine the therapeutic effect of anti IL--11R mAb in RREAE.

Specific Aims:

Aim 1. Characterize the IL--11--induced migration of CD4+ cell subsets in CIS patients.

1.A. Identify signaling pathways involved in the IL--11--induced migration of CD4+ cell subsets to the CNS. Investigators will identify IL--11--stimulated signaling pathways mediating expression of CCR6 and adhesion molecules on CD45RO+ cells.

1. B. Determine direct chemotactic effect of IL--11 in CD4+ cell subsets. In vitro migration assays will determine a direct chemotactic effect of IL--11 on the migration of CD4+ cell subsets through the endothelial cell (EC) barrier.