Autoimmune diseases are the second most common cause of chronic illness in the US. ERAP1 gene polymorphisms have been linked to multiple autoimmune and inflammatory diseases, including ankylosing spondylitis (AS), multiple sclerosis, inflammatory bowel disease, insulin-dependent diabetes mellitus, Bechet’s disease, and others. Understanding how ERAP1 functions contribute to the pathogenesis of autoimmunity will allow us to better understand mechanisms responsible for autoimmunity and will provide new targets for drug development.AS is a prototypic chronic arthritic disease predominantly affecting young individuals, with spinal inflammation and fusions as its key features. In this work we evaluated the intestinal, skeletal and immune systems of ERAP1-/- mice and discovered that they resemble key features of AS. We determined that these mice developed axial spinal ankylosis, sacroiliac erosions, inflammation at the intervertebral discs and systemic osteoporosis. Detailed analysis of the bone remodeling cells showed increased osteoclastogenesis and osteoclast activity, as well as reduced bone formation in vivo. Additionally, ERAP1-/- mice developed spontaneous dysbiosis and had increased susceptibility to chemically induced colitis, closely paralleling intestinal manifestations of AS. Correction of colonic dysbiosis in the ERAP1-/- mice from birth failed to reduce spinal fusions or the osteoporosis of the spine, suggesting that altered microbiome is the result of the disease, rather than its cause. Finally, immunologic analysis of the ERAP1-/- mice revealed a deficiency of type 1 regulatory T (Tr1) cells and tolerogenic dendritic cells, which are important for the development of Tr1 cells. Tr1 cells are thought to be important for tolerance and prevention of autoimmunity. It is possible that Tr1 cell deficiency is responsible for the multiple phenotypes present in the ERAP1-/- mice and ERAP1-associated diseases, including AS.Anti-TNF-α and anti-IL-17A blocking antibodies have been successful in providing symptomatic relief to AS patients. In our work, TNF-α and anti-IL-17A blockade failed to improve osteoporosis and ankylosis in ERAP1-/- mice, downplaying their involvement in the pathogenesis of skeletal abnormalities in these animals.While in autoimmune diseases, the therapeutic strategies involve reduction of the immune responses, there are situations where immune responses need to be strengthened via targeted therapies. For example, strategies targeting immune cell inhibitory and/or co-stimulatory molecules have been successfully used to treat multiple cancer types in humans. There is a need to develop novel cancer immunotherapies. The immune-cell receptor, CD2-like receptor activating cytotoxic cell (CRACC, also known as SLAMF7), is a member of the signaling lymphocytic activation molecules (SLAM) family of receptors which plays a critical role in immunoregulation. In this work, we targeted SLAMF7 signaling by using CRACC-Fc fusion protein expressed on an adenovirus platform (rAd5-mCRACC-Fc) for use as an immunomodulating agent against established CT26 colon adenocarcinoma tumors. We observed enhanced activation of innate and adaptive immunity, increased infiltration of tumors by lymphocytes, and improved tumor killing and survival of CT26 tumor-bearing mice. These data suggest that rAd5-mCRACC-Fc is a promising novel cancer immunotherapy that warrants further testing for clinical application. In summary, the work in this thesis touches upon multiple aspects of genetics and immunology and how the two fields intermingle on a variety of important clinical fronts.
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