The risk of polyomavirus-associated graft nephropathy is increased by a combined suppression of CD8 and CD4 cell-dependent immune effects.

Polyomavirus-associated graft nephropathy (PAN) has emerged as a significant risk factor for kidney graft loss. We analyzed intracellular cytokine responses for possible protective versus permissive immunologic effects on BK-virus replication. One hundred five renal transplant patients included in a prospective single-center study were randomized to receive cyclosporine mycophenolate mofetil (MMF) (CM: n = 31), tacrolimus (Tac)/MMF (TM: n = 32) or Tac/MMF with conversion to everolimus (TErl; n = 32). Ten patients were not randomized (NR) due to contraindications to MMF. The immunosuppressive therapy was monitored pre- and posttransplantation at 4, 12, and 24 months using triple fluorescence flow cytometry for intracellular interleukin (Il)-2 Il-4 and interferon (IFN)-γ production in phorbol myristate acetate- and lipopolysaccharide- stimulated lymphocyte cultures. BK viremia screening was performed by reverse-transcriptase polymerase chain reaction testing on days 0, 14, 30, 60, 90, 120, 180, 270, 360, and 720. Seven of 105 (6.7%) patients developed biopsy-proven PAN (CM: n = 1, TM: n = 3, TErl: n = 2, NR: n = 1), among whom 4 lost their grafts (TM: n = 1, TErl: n = 2, NR: n = 1). Twenty-one of 105 (20.0%) patients had documented BK viremia. BK viremia which preceded PAN in all cases, was significantly associated with TM immunosuppression: 4/31 (12.9%) CM: 11/32 (34.4%) TM; 5/32 (15.6%) TErl, and 1/10 (10.0%) NR patients (P = .034). BK-viremic patients showed significantly diminished CD8(+) T-cell Il-2 production at 120 days (P = .011) and 1 year posttransplantation (P = .014) compared with non-BK-viremic patients. Patients with PAN displayed significantly lower CD4(+) T-cell Il-4 responses at 1 and 2 years after transplantation (1 year: P = .007; 2 years: P = .001) with diminished IFN-γ responses at 1 year after transplantation (P = .011). Our analysis showed the incidence of BK viremia to be increased among patients with defective cytotoxic CD8(+) T-cell -dependent immune reactivity. Recipients who progressed from BK viremia to overt PAN showed an additional immunologic defect in CD4(+) T-cell function. Patients on a Tac- plus MMF-based immunosuppression were at higher risk to develop BK viremia.

Renner FC ，Dietrich H ，Bulut N ，Celik D ，Freitag E ，Gaertner N ，Karoui S ，Mark J ，Raatz C ，Weimer R ，Feustel A ... -  《-》

BK viremia surveillance after kidney transplant: single-center experience during a change from cyclosporine-to lower-dose tacrolimus-based primary immunosuppression regimen.

The aim was to report our experience of BK viremia surveillance after kidney transplant during a period of change from cyclosporine (CyA)-to lower-dose tacrolimus (Tac)-based primary immunosuppression regimens. In a prospective single-center observational cohort study, 68 consecutive patients received renal transplant during the period when we used a CyA-based primary immunosuppression regimen and 66 after we changed to a lower-dose Tac-based regimen. Testing for BK viremia by quantitative polymerase chain reaction assay was performed at least monthly for a minimum of 1 year. Thirty-nine (29.1%) patients developed BK viremia and 2 (1.5%) developed BK nephropathy. The actuarial time to BK viremia was shorter in patients receiving CyA/mycophenolate mofetil (MMF)/prednisolone (Pred) compared with Tac/MMF/Pred (P=0.04) and primary immunosuppression with CyA/MMF/Pred was the only independent predictor of BK viremia (hazard ratio 1.95; P=0.047). Comparing patients who experienced BK viremia and those who did not, there was no difference in incidence of acute rejection (20.5% vs. 25.3%; P=0.56) or estimated glomerular filtration rate at 12 months (48.8 vs. 49.9 mL/min/1.73 m(2)), but the incidence of ureteric stenosis was higher (10.3% vs. 1.1%; P=0.01). Our data demonstrate a lower incidence of BK viremia in patients on lower-dose Tac compared with CyA-based primary immunosuppression in contrast to previous studies, and provide further support for the association between BK virus and ureteric complications.

Geddes CC ，Gunson R ，Mazonakis E ，Wan R ，Thomson L ，Clancy M ，Carman WF ... -  《-》

Conversion from tacrolimus-mycophenolate mofetil to tacrolimus-mTOR immunosuppression after kidney-pancreas transplantation reduces the incidence of both BK and CMV viremia.

We sought to determine whether conversion from tacrolimus/mycophenolate mofetil (TAC-MMF) into tacrolimus/mTOR inhibitor (TAC-mTOR) immunosuppression would reduce the incidences of BK and CMV viremia after kidney/pancreas (KP) transplantation. In this single-center review, the TAC-mTOR cohort (n = 39) was converted at 1 month post-transplant to an mTOR inhibitor and reduced-dose tacrolimus. Outcomes were compared to a cohort of KP recipients (n = 40) maintained on TAC-MMF. At 3 years post-transplant, KP survivals and incidences of kidney/pancreas rejection were equivalent between mTOR and MMF-treated cohorts. (P = ns). BK viremia-free survival was better for the mTOR vs MMF-treated group (P = .004). In multivariate analysis, MMF vs mTOR immunosuppression was an independent risk factor for BK viremia (hazard ratio 12.27, P = .02). Similarly, mTOR-treated recipients displayed better CMV infection-free survival compared to the MMF-treated cohort (P = .01). MMF vs mTOR immunosuppression (hazard ratio 18.77, P = .001) and older recipient age (hazard ratio 1.13 per year, P = .006) were independent risk factors for CMV viremia. Mean estimated GFR and HgbA1c levels were equivalent between groups at 1, 2, and 3 years post-transplantation. Conversion from TAC/MMF into TAC/mTOR immunosuppression after KP transplantation reduced the incidences of BK and CMV viremia with an equivalent risk of acute rejection and similar renal/pancreas function.

Knight RJ ，Graviss EA ，Nguyen DT ，Kuten SA ，Patel SJ ，Gaber L ，Gaber AO ... -  《-》

Monitoring of polyomavirus BK replication and impact of preemptive immunosuppression reduction in renal-transplant recipients in China: a 5-year single-center analysis.

This provides the long-term patient/graft survival and outcome of BK viremia and BK virus allograft nephropathy (BKVAN) in renal transplant recipients in the setting of intensive monitoring and preemptive of reduction of immunosuppression. Quantitative BKV DNA PCR and urinary cytology surveillance were performed regularly after transplantation in 229 kidney recipients. Patients with BK viremia and BKVAN were treated with 30-50% reduction in doses of tacrolimus and/or mycophenolate mofetil and were monitored for BKV every 3-6 months. All the patients were followed for 5 years. Overall 5-year patient and graft survival were 95.6% and 92.1%, respectively, and independent of presence of decoy cells, BK viruria, viremia, or BKVAN. After reduction of immunosuppression, BK viremia (n = 38) resolved in 100% of patients, without increased acute rejection. Recurrent BK viremia was not observed in viremic patients without BKVAN (n = 30). All BKVAN patients (n = 7, 3.1%) cleared viremia with a mean time of 5.9 months (range 1-15 months) and manifested no decline in estimated glomerular filtration rate from 1 month to 5 years after transplantation. Viral monitoring and preemptive reduction of immunosuppression resulted in the successful resolution of BK viremia and BKVAN with excellent graft survival and renal function at 5 years.

Huang G ，Wang CX ，Zhang L ，Fei JG ，Deng SX ，Qiu J ，Li J ，Chen GD ，Fu Q ，Chen LZ ... -  《-》

Screening for BK viremia reduces but does not eliminate the risk of BK nephropathy: a single-center retrospective analysis.

Knight RJ ，Gaber LW ，Patel SJ ，DeVos JM ，Moore LW ，Gaber AO ... -  《-》