Polyomavirus reactivation in native kidneys of pancreas alone allograft recipients.

BACKGROUND: Polyomavirus infection is common in childhood, with a seroprevalence of 60% to 100%. These viruses remain latent mostly in the kidney. Impairment in cellular immunity can allow reactivation of the virus. Reactivation can occur in 10% to 45% of renal allografts. A higher intensity of immunosuppression and the allogeneic microenvironment of the graft have been suggested to predispose to reactivation. There are limited data on the status of viral activity in the native kidneys of non-renal solid organ recipients. METHODS: Thirty-eight recipients of pancreas transplant alone were evaluated for evidence of polyomavirus reactivation by urine cytology. All had received induction therapy and were maintained on tacrolimus, mycophenolate mofetil, and prednisone. The renal function and degree of exposure to immunosuppressive agents of patients shedding polyomavirus-infected renal tubular cells were compared with those of patients with negative urine cytology. RESULTS: Screening cytology was performed 16 months (mean) after transplantation. Four subjects (11%) had polyomaviruria. The renal function at baseline and time of screening was comparable between the two groups. The 12-hour trough levels of tacrolimus were significantly higher in patients with positive cytology compared with those without viruria. The doses of mycophenolate mofetil and prednisone were not different between the two groups. CONCLUSION: This study shows that polyomavirus reactivation in native kidneys and urinary tract of pancreas transplant alone patients is not uncommon. In these recipients, viral reactivation was not associated with significant renal functional impairment. The results also suggest that patients who are exposed to higher blood levels of tacrolimus are at higher risk of viral reactivation.

Clinical course of polyoma virus nephropathy in 67 renal transplant patients.

Polyoma virus (PV) can cause interstitial nephritis and lead to graft failure in renal transplant recipients. The clinical course of patients with polyoma virus nephritis (PVN) is not well understood, partially due to its relatively low incidence. This study is a retrospective analysis of our experience over 4 yr. The specific purpose is to outline the clinical course and outcome of patients with PVN and to study the relationship between immunosuppression and the disease process. Between June 1997 and March 2001, 67 patients with graft dysfunction were found to have biopsy-proven PVN. The diagnosis was made at a mean of 12.8 +/- 9.9 mo posttransplantation. The majority of patients were men (79%) with a mean age of 54 +/- 14 yr (range, 28 to 75). All patients received immunosuppression with a calcineurin inhibitor (tacrolimus in 89% of patients). All patients except two received mycophenolate mofetil and prednisone. After the diagnosis of PVN, maintenance immunosuppression was reduced in 52 patients and remained unchanged in 15 patients. After reduction of immunosuppression, eight patients (15.3%) developed acute rejection and six (11.5%) became negative for PV in biopsy and urine. After a mean observation period of 12.6 mo (mean of 26 mo posttransplantation), 16.4% of patients had lost their grafts (8 of 52 in the reduction group and 3 of 15 in the no change group). In comparison to a case-matched polyoma virus-negative control group, the PVN patients were older (P =.0004) and there was a predominance of men (P = 0.02). Kaplan-Meier analysis demonstrated that patients with PVN had reduced graft survival compared with negative controls (P =.0004). It is concluded that PVN is a serious hazard for renal transplant recipients and contributes directly to graft loss. Antiviral drugs are needed, as the reduction of immunosuppression alone may not significantly improve graft function in patients with already established PVN. Although multiple factors probably play a role in the development of PVN, judicious use of immunosuppressive agents is indicated to minimize the occurrence of this infection.