All ETDs from UAB

Advisory Committee Chair

Phillip D Smith

Advisory Committee Members

William J Britt

Lesley E Smythies

Charles O Elson

Louis B Justement

Farah D Lubin

Document Type

Dissertation

Date of Award

2017

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

Cytomegalovirus (CMV) is an opportunistic β-herpesvirus that causes severe mucosal inflammation in recipients of organ and stem cell transplants, HIV-1-infected subjects, and persons with inflammatory bowel disease. The gastrointestinal mucosa is among the most common sites of CMV inflammatory disease, and the inflammatory lesions associated with CMV mucosal infection contain infected macrophages and increased levels of macrophage-derived cytokines, implicating mucosal macrophages in the inflammatory process. Paradoxically, in healthy human intestinal mucosa, macrophages are profoundly down-regulated for pro-inflammatory responses (inflammation anergy) due to stromal TGF-β-induction of Smad signaling and inactivation of NF-κB. To elucidate the mechanism whereby CMV promotes macrophage-mediated mucosal inflammation, despite an abundance of stromal TGF-β, we investigated the effect of CMV infection on inflammation anergy in primary human intestinal macrophages and on the development of stromal TGF-β-induced inflammation anergy in human blood monocytes, the source of intestinal macrophages. We report that CMV infected, but did not replicate in or reverse established inflammation anergy in intestinal macrophages. However, CMV infection of monocytes blocked stromal TGF-β-induced down-regulation of inflammatory responses during monocyte-to-intestinal macrophage differentiation. CMV up-regulated monocyte pro-inflammatory phenotype and function by promoting the maintenance of Toll-Like-Receptors (TLRs) and enhancing expression of MyD88, thus potentiating TLR-inducible, MyD88- and NF-kB-dependent cytokine release. CMV infection also reduced expression of miR-146a, the negative regulator of the NF-kB pathway, promoting prolonged NF-kB activation. Importantly, CMV-infected monocytes retained the capacity to produce cytokines despite the presence of down-regulatory stromal TGF-β due to CMV-induction of TGF-β antagonist, Smad7. Confirming the role of Smad7 in CMVinduced mucosal inflammation, Smad7 expression was markedly elevated in mucosal tissue from subjects with CMV colitis, particularly in areas with an accumulation of CD14+ monocytes, and transfection of a Smad7 antisense oligonucleotide into CMV-infected monocytes reversed CMV blockade of inflammation anergy. Thus, the findings presented in this dissertation indicate that CMV blocks stromal TGF-β-induced differentiation of monocytes into inflammation anergic intestinal macrophages due to induction of Smad7, which enabled MyD88-dependent NF-kB cytokine release despite the presence of stromal TGF-β. These results implicate Smad7 as a key mediator of macrophage-mediated mucosal inflammation and as a potential therapeutic target for CMV mucosal disease.

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