Cytomegalovirus infection in vascular diseases and transplant rejection

Abstract

Human cytomegalovirus (HCMV) infects 60-100% of the adult population. It belongs to the Herpesviridae family and establishes latency within its host post primary infection. HCMV reactivation is dependent on inflammation and the virus has evolved numerous mechanisms to sustain an inflammatory process and thus prolong its replication period. This has led to the hypothesis that HCMV may contribute to the pathogenesis of various inflammatory diseases. Our studies herein focus on further elucidating the role of HCMV in vascular diseases and transplant rejection.

We found that: I) HCMV is present in a vast majority of abdominal aortic aneurysms where it predominantly infects the intimal smooth muscle cells. The infected cells showed an increased migratory capacity that was in part dependent on basic fibroblast growth factor. Furthermore, in the vascular lesions where HCMV was present there was an induced expression of 5-lipoxygenase, a key enzyme in the synthesis of the potent proinflammatory leukotriene B4. Thus, our study supports previous findings that HCMV is found in abdominal aortic aneurysm, and that it has the potential to contribute to the pathogenesis of abdominal aortic aneurysm.

II) Native arteriovenous fistula (AVF) is the preferred form of haemodialysis vascular access however dysfunction due to neointimal hyperplasia, vascular stenosis and thrombosis is a major cause of morbidity in this patient population. In a prospective cohort study we sought to identify novel prognostic factors for failure of native AVF. Numerous biochemical and patient characteristics were analysed just prior to construction of the AVF. We identified white blood cell count, monocyte count and red blood cell distribution width as independent prognostic factors for AVF failure. Red blood cell distribution width is a novel prognostic factor and was also the most optimal. The mechanistic link between high red blood cell distribution width and AVF failure is yet to be elucidated.

III) Using the patient cohort described in (II) we investigated the potential role of HCMV in the failure of AVF. In contrary to previous reports, high anti-HCMV IgG levels were not associated with reduced AVF patency in our study. HCMV proteins could be located in the vessels of 46% of patients at the time of AVF construction but presence of HCMV proteins was not associated with reduced AVF patency. Our study does not support the hypothesis that HCMV has a role in the failure of AVF.

IV) HCMV has been associated with chronic transplant rejection however the virus has been difficult to detect in the affected organs and thus the effects of HCMV have been defined as indirect. In this retrospective cohort study we evaluated the presence of HCMV in chronic renal allograft dysfunction, in early as well as end-stage biopsies. We found that HCMV is present in a majority of grafts early post transplantation and that the HCMV levels increase as the graft deteriorates. Furthermore, high HCMV intragraft protein expression in the early biopsy is associated with reduced allograft survival. Our study provides further support for a role of HCMV in allograft rejection and suggests that direct effects of the virus are involved in chronic allograft dysfunction.