The long-term goal of this project is to determine the role of viral pathogens in the development of vascular diseases such as atherosclerosis, restenosis, and transplant vascular sclerosis (TVS). All of these diseases are the result of either mechanical or immune-mediated injury followed by inflammation and subsequent smooth muscle cell (SMC) proliferation and migration from the vessel media to the intima, which culminates in vessel narrowing. Clinical studies have directly associated human cytomegalovirus (HCMV) with the acceleration of TVS and vascular restenosis following angioplasty, as well as atherosclerosis. However, the mechanism(s) involved in the acceleration of vascular disease by HCMV is unknown. To address this issue we have developed a rat heart transplant model that exhibits all of the hallmarks of the development of TVS in humans. Studies by our group and others have shown that rat CMV (RCMV) infection significantly accelerates both the development of TVS as well as chronic rejection in the rat heart allotransplant model. We have also shown that both HCMV and RCMV can induce SMC migration that is mediated by virally encoded chemokine receptors US 28 or R33, respectively. Recently we have demonstrated that the insertional deletion of R33 significantly increases the time to chronic rejection, and slows the kinetics of the process of TVS in the rat heart transplant model suggesting that this viral chemokine receptor plays an important role in RCMV acceleration of vascular disease. Accordingly, part of this proposal will continue our examination of this viral chemokine receptor during the development of disease. In addition, using an in vitro model of SMC migration, we will define the chemokines that bind R33, their signaling pathways, as well as their ability to induce SMC migration. We will also determine the critical amino acids of R33 that are involved in ligand binding and signaling. We will then extend these studies to the in vivo rat heart allotransplant model to further characterize the relationship of R33 ligand binding and signaling to TVS acceleration by studying the effects on the development of TVS with appropriate R33 mutations in ligand binding and signaling.
Between 60-90% of the donor and recipient population are latently infected with CMV making the effect of CMV infection on the development of TVS a major concern. Therefore, to avoid the need for retransplantation, and to prolong graft survival, we must understand the pathogenic mechanisms of TVS, and more specifically, the CMV-associated mechanisms of this process. The development of novel therapeutics designed to reduce TVS would benefit all transplant recipients.
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