Persistent cytomegalovirus infection is associated with increased expression of TGF- 1, PDGF-AA and ICAM-1 and arterial intimal thickening in kidney allografts

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Abstract
Background. Cytomegalovirus (CMV) is a suggested risk factor for the development of chronic allograft nephropathy. Transforming growth factor-β (TGF-β) and platelet-derived growth factor (PDGF) are important molecules in this process. We analysed the impact of persistent CMV infection in kidney allografts on the expression of growth factors, adhesion molecules and inflammation markers. Methods. In a population of 172 renal transplant recipients, CMV was diagnosed in 82 patients by pp65 antigenaemia test and viral cultures. Biopsies taken after CMV infection were available from 48 of the 82 patients for the demonstration of CMV antigens by immunohistochemistry and in situ DNA hybridization. Biopsy material for further analyses was available from 16 CMV patients. Five patients with no previous CMV infection were used as controls. Biopsy histology was scored according to Banff 97 classification. Results. In 11 out of 16 patients, persistent CMV antigens and/or DNA were demonstrated in the biopsy >2 months after the last positive finding in blood or urine. Increased expression of TGF-β1 was recorded in tubuli and in arterial endothelium in biopsies with a positive CMV finding compared with controls. Also, the expression of PDGF-AA was increased in tubuli and somewhat in arterial endothelium in CMV-positive biopsies. The expression of intercellular adhesion molecule-1 (ICAM-1) was increased significantly in peritubular capillary endothelium. Vascular intimal thickening was increased in the biopsies with persistent CMV infection. Conclusions. Persistent CMV infection in kidney allografts was associated with increased vascular changes and increased expression of TGF-β1, PDGF-AA and ICAM-1.