EXPERIMENTAL AND CLINICAL TRANSPLANTATION

Objectives: Thus far, there is no active treatment for BK virus-associated nephropathy after a kidney transplant that has proven to be effective. We sought to assess the effectiveness of treatment with leflunomide, intravenous immunoglobulin, and ciprofloxacin on graft outcome after 1 year compared with a historical group treated with reduced immunosuppressive medications strategy.

Materials and Methods: Group 1 (n = 19) was composed of kidney transplant recipients with twice positive BK virus-polymerase chain reaction in urine and blood who underwent graft biopsy to confirm BK virus-associated nephropathy. Once BK virus-associated nephropathy was diagnosed, antimetabolite (mycophenolate mofetil or azathioprine) was changed to leflunomide, and intravenous immunoglobulin and oral ciprofloxacin were given. Group 2 (n = 14) was composed of BK virus-associated nephropathy patients treated conventionally with reduced immunosuppressive medications.

Results: Thirty-three patients were treated, 23 were males (70%), there were 15 were deceased donors (45.5%), 15 were diabetics (45.5%), mean human leukocyte antigen mismatches were 3.76, seven had a zero DR mismatch (21.2%), and 8 were CW7 negative (24.2%). All patients received induction therapy (thymoglobulin in 22 [66.6%]), 7 had delayed graft function (21.2%) and 18 received antirejection therapy before receiving BK virus-associated nephropathy diagnosis (52.9%). Main-tenance immunosuppression was prednisolone and mycophenolate mofetil (2 g/d) in 31 patients (94%), and tacrolimus in 13 (39.4%). Tacrolimus was given to 12 patients in group 1 (63.1%), while sirolimus was given to 7 patients in group 2 (50%). One graft was lost in each group by the end of the study, and 1 patient died with functioning graft in group 2.

Conclusions: No significant difference existed in 1-year graft outcomes between treatment of BK virus-associated nephropathy by reduction of immunosuppressive medications or actively by leflunomide, intravenous immunoglobulin, and ciprofloxacin.

Key words : Polyomavirus, Renal transplant, Allograft rejection, Immunosuppression

BK virus (BKV) is a polyomavirus highly sero-prevalent in humans; however, it may cause clinical disease in immunocompromised patients only. In kidney transplant recipients, BK virus primarily causes tubulointerstitial nephritis, hemorrhagic cystitis, and ureteral stenosis.¹ BK virus-associated nephropathy is a serious complication of a renal transplant that leads to graft dysfunction and loss.^1-5 The prevalence of BK virus-associated nephropathy (BKVAN) in kidney transplant recipients is estimated to between 1% and 10%.^1,2 BK virus infection directly correlates with the intensity of immunosuppression, although no specific immuno-suppressive drug or combination has been shown to be associated with BKVAN owing to the paucity of randomized controlled trials.^1,2,4 Other potential risk factors include older and younger age, male gender, white ethnicity, total HLA mismatch, absence of HLA-CW7, zero HLA-DR mismatch, an earlier tubular injury, ureteral trauma, diabetes mellitus, delayed graft function, cytomegalovirus infection, treatment for acute rejection, and treatment with tacrolimus or mycophenolate mofetil.^1,5,6

Quantitative or real-time polymerase chain reaction (PCR) for BK viral DNA of serum and urine are useful in diagnosing and monitoring kidney transplant recipients for BK infection.⁵ A definitive diagnosis of BKVAN is made by renal allograft biopsy. The histologic diagnosis requires characteristic cytopathic changes and positive immunohistochemistry tests using antibodies specifically directed against BK virus or against the cross-reacting SV40 large T antigen.^7-10 In the absence of definite histologic evidence obtained by biopsy, findings of sustained urine viral replication (> 2 wk) and significant BK replication (plasma DNA PCR load > 10 000 copies/mL) (with or without kidney dysfunction) defines presumptive BK nephropathy.⁷

The 2 principal approaches to preventing and managing BK-induced nephritis in kidney transplant recipients are a screening and preemptive strategy (which involve periodic monitoring for viremia to allow a decrease in immunosuppressive medications and/or administering antiviral agents after detecting early systemic infection; and treatment involves decreasing immunosuppressive medications and administering antiviral agents to patients with only biopsy-proven or presumptive diagnosis of BK-induced nephritis.^8-11 The rationale is to allow host immunity to combat BKV; however, the risks include increased acute and subclinical rejection. Better therapies are warranted for controlling BK virus reactivation and improving graft outcome.

Leflunomide, intravenous immunoglobulin (IVIG), ciprofloxacin, and cidofovir are being sought as treatment for BKVAN.^12-16 Unlike cytomegalovirus, where potent and specific antivirals exist, with BKV, there have been no randomized controlled trials to assess treatment.¹⁷ Current practice includes reducing dosage of immunosuppressive agents, but the risks and benefits have not been well studied because of the small numbers of patients treated.^8,10 There is potential to inhibit BKV by manipulating the host intracellular signaling pathways that the virus triggers to facilitate its replication. Using drugs that specifically target the Akt and mTOR pathway may reduce BKV pathogenesis. Because both sirolimus and leflunomide possess immunosuppressive activity; treatment of BK reactivation using this combination may control BK replication.¹⁸ Our patients with BKVAN were initially treated with a reduction of immunosuppressives.

We sought to assess the short-term effectiveness regarding graft/patient outcomes of active management of BKVAN with combined leflunomide, IVIG, and ciprofloxacin compared with minimization of immunosuppressive drugs. Cidofovir was not included because of its nephrotoxicity and adverse events.

Materials and Methods

Between 2004 and 2009, our kidney transplant recipients were screened for possible BKVAN by PCR in urine and blood. Of 345 patients screened, 33 patients (9.5%) were diagnosed and treated as BKVAN. All patients were prospectively observed for 1 year. Fourteen patients were conventionally treated with immunosuppressive dosage reduction (group 2) and subsequently, 19 patients received active treatment with IVIG, leflunomide, and ciprofloxacin (group 1). Group 1 was actively managed by changing antimetabolites (myco-phenolate mofetil or azathioprine) to leflunomide (100 mg daily for 3-5 days, followed by 20-40 mg daily), giving a concurrent course of IVIG (2 g/kg, maximum 120 g, divided over 5 d) and oral ciprofloxacin (500 mg twice daily for 4 wk) (Figure 1). Group 2 was conventionally managed by gradual immunosuppressive drug reduction (historical control group). This was applied by reducing the antimetabolite dosage by 50%. In addition, calcineurin inhibitors and sirolimus were maintained at low therapeutic trough blood levels in both groups.

Our immunosuppression protocol consisted of inducing antilymphocyte antibody with 5 dosages of antithymocyte globulin (Sanofi US, Bridgewater, NJ, USA) or 2 dosages of IL-2 receptor blocker (basiliximab; Novartis, Inc., Basel, Switzerland) based on immunologic risk stratification. Maintenance therapy consisted of prednisone, mycophenolate mofetil, and a calcineurin inhibitor. Maintenance immunosuppression with sirolimus was given to stable patients with low immunologic risk, and when the conversion from a calcineurin inhibitor was applicable. Acute cellular rejection was treated with intravenous bolus methylprednisolone sodium succinate (1 g daily for 3 d) and/or thymoglobulin (1 mg/kg daily for 7-10 d) for steroid-resistant rejection. Antibody-mediated rejection was treated with plasma exchange, IVIG 2 g/kg, and rituximab. All rejection episodes were diagnosed by biopsies and treated according to the Banff criteria and a gradual reduction of immunosuppressive drugs if BK-PCR remained positive. The study was approved by the Ethical Review Committee of the Institute. All of the protocols conformed with the ethical guidelines of the 1975 Helsinki Declaration. Written informed consent was obtained from all subjects.

Our kidney transplant recipients were screened for BKV by urine and blood PCR after renal transplant when unexplained graft dysfunction was noticed (> 20% of basal serum creatinine) or whenever graft biopsy was indicated. There was no facility to do a regular screening of our kidney transplant recipients. BK viremia was considered significantly positive when it exceeded 10 000 copies/mL. Kidney transplant recipients with twice-positive viremia underwent graft biopsy to confirm BKVAN. Histopathologically, BKVAN was classified into 3 patterns. Pattern A, evidence of BKVAN with minimal inflammation; pattern B, BKVAN with focal or diffuse interstitial fibrosis and tubular atrophy; and pattern C, BKVAN with significant graft sclerosis. Serial monitoring of graft function, blood counts, drug levels, and urine and blood BKV-PCR were done after 2 weeks, and at 1, 2, 3, 6, and 12 months of starting a treatment regimen. Repeat urine and blood BKV-PCR and a graft biopsy were used when an unexplained rise of serum creatinine (> 20% above baseline) was observed. Follow-up was 1 year.

Data analyses
Statistical analyses were performed with SPSS software (SPSS: An IBM Company, version 17.0, IBM Corporation, Armonk, NY, USA). Means were compared using paired sample t test, independent sample t test, chi-square test, and the Fisher exact test. Results are expressed as means ± standard deviation, and differences are considered significant when P is ≤ .05.

Table 1 shows the demographic features. The 2 groups were comparable in their demographic data (P > .05). Odds ratio with 95% confidence interval (OR, 95% CI) was > 1 for male gender, thymoglobulin induction, prednisolone, and mycophenolate mofetil mainte-nance therapy, and antirejection therapy before diagnosis of BKVAN. Most patients had positive viruria and viremia when BKVAN diagnosis was established (Table 2). Diagnosis of BKVAN was confirmed histopathologically in most patients, and different patterns are demonstrated in Table 3. The 2 groups are comparable regarding histopathologic pattern of BKVAN (P > .05). Pattern B was the most common among the biopsies of both groups (51.5%).

Although viremia was positive at 1 year for most cases but the viral load was not significant (< 2000 copies/mL) for 22 patients (81.8%), the 2 groups were comparable (P > .05). Mean time from transplant until established BKVAN diagnosis was 25.6 ± 35.9 months. Mean time from first viremia and viruria until the diagnosis of BKVAN was established was 2.7 ± 8 months. Basal mean estimated glomerular filtration rate was 36.9 ± 15.1, which was reduced to 35.4 ± 18.8 mL/min/1.73 m² at 1 year (P > .05). Basal mean estimated glomerular filtration rate was lower in group 1 (35.7 ± 11.2 mL/min/1.73 m²) compared with group 2 (38.4 ± 19.5 mL/min/1.73 m²; P = .64). Mean estimated glomerular filtration rate was reduced to 33.4 ± 15.7 mL/min/1.73 m² in group 1 (P = .75) and 38.3 ± 23.1 mL/min/1.73 m² in group 2 (P = .97) after 1 year.

Table 4 shows that the 2 groups were comparable regarding rejection episodes before and after diagnosis of BKVAN (P > .05). Cytomegalovirus infection and other infections requiring hos-pitalization also were comparable between the groups (Table 2). One graft failed in each group by the end of the study, and 1 cardiovascular mortality with a functioning graft was reported in group 2. Mean time from established diagnosis of BKVAN until graft failure was 8.0 ± 1.7 months.

Our kidney transplant recipients receiving the diagnosis of BKVAN were at higher risk for BKV infection because they were mainly men with a greater mean HLA mismatch requiring thymoglobulin induction and full-dose mycophenolate mofetil maintenance therapy (OR, 95% CI > 1 in Table 1). Moreover, nearly half the patients received grafts from deceased donors, adding to antirejection therapy before diagnosis with BKVAN (OR, 95% CI > 1). Intensive maintenance immunosuppression predis-posed to BKVAN in most patients, as many of them received antithymocyte antibody induction therapy maintained on tacrolimus and received grafts from deceased donors. More kidney transplant recipients on sirolimus were managed with immuno-suppressive drug minimization than by converting them from calcineurin inhibitors. Our immuno-suppression protocol has changed with time to use more tacrolimus, which is evident in group 1. BK virus-associated nephropathy occurs soon after transplant, and it is standard to screen for the virus for the first 1 to 2 years after transplant.³ BK virus-associated nephropathy is responsible for a significant number of renal graft losses. Early management of BKVAN is the cornerstone in managing this infection to save the graft.^1,19

In our study, delayed management (owing to the lack of mass screening facilities) was apparent, as the mean duration since transplant until established diagnosis of BKVAN was 25.6 ± 35.9 months, and from the first viremia/viruria was 2.7 ± 8 months. These times exceed published values, which result in a negative effect on graft outcomes.³ Although there was no significant deterioration of the estimated glomerular filtration rate, subsequent histologic changes show that damage was obvious in 11 of 35 follow-up biopsies (> 30%). This shows the natural progression of disease, even when not reflected by estimated glomerular filtration rate at 1 year. Additionally, this significant histopathologic deterioration supports regular screening for 1 year after transplant to have early diagnosis and management of BKVAN.

The small number of patients diagnosed with BKVAN reduced the power of the study, which is a known problem in most clinical studies of BKVAN in kidney transplant recipients. Significant graft dysfunction when diagnosing BKVAN is a major risk factor for graft failure.^1,20 Basal graft function (as represented by estimated glomerular filtration rate) is comparable across the groups, and the graft outcome is similar after 12 months. Both management strategies were effective and resulted in reducing viral load to acceptable levels at 1 year. Tailoring the intensity of immunosuppression to immunologic risk of the patient facilitates induction of tolerance, and thus less maintenance immuno-suppressive agents and fewer incidences of infection including with BKV.^1,8,21 Regular screening and less intensive immunosuppression (according to the immunologic risk and protocol biopsies) are advisable to acquire an early diagnosis and receive a better evaluation of actively managing BKVAN.^5,8,19,21

In conclusion, there was no significant difference in 1-year graft outcomes between actively treating BKVAN with leflunomide, IVIG, and ciprofloxacin or by minimizing immunosuppressive drugs. Early diagnosis and tailoring of immunosuppressive therapy may reduce the incidence of BKVAN and improve the clinical response to treatment.

Volume: 12 Issue: 6 December 2014

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