Conversion from mycophenolate mofetil to mizoribine for patients with positive polyomavirus type BK in urine

Conversion from mycophenolate mofetil to mizoribine in the early stages of BK polyomavirus infection could improve kidney allograft prognosis: a single-center study from China

Background

Some studies have suggested mizoribine (MZR) could inhibit the replication of BK polyomavirus (BKPyV). The purpose of this study was to explore whether conversion from mycophenolate mofetil (MMF) to MZR in the early stages of BKPyV infection can improve kidney allograft prognosis.

Methods

Twenty-one kidney transplant recipients with BKPyV viruria/viremia and ten with BK polyomavirus-associated allograft nephropathy (BKPyVAN) received MZR conversion therapy were retrospectively identified. The clearance rate of urine and blood BKPyV DNA, change of serum creatinine (SCr), uric acid (UA), hemoglobin (HB), white blood cell (WBC), lymphocyte ratio, platelet (PLT), routine urinalysis, panel reactive antibody (PRA), and gastrointestinal disorders during follow-up of the 2 groups were evaluated and compared.

Results

After MZR conversion therapy, the clearance rate of urine and blood viral load in BKPyV viruria/viremia group were 85.7 and 100 %, while that in BKPyVAN were 40 and 87.5 %, respectively. Stable SCr were observed in all cases of BKPyV viruria/viremia group, while that of BKPyVAN was only 40 % (P < 0.001) and one even progressed to end-stage renal disease. The results of routine urinalysis in the two groups showed no significant changes before and after MZR conversion therapy. However, in BKPyV viruria/viremia group, four cases developed acute rejection and one had positive PRA-II but no donor specific antibody, requiring conversion back to MMF. Hyperuricemia was the common adverse effect of MZR.

Conclusions

Conversion from MMF to MZR could help clear BKPyV infection. As compared to BKPyVAN, patients who underwent initiation of MZR conversion therapy in the early stages of BKPyV infection maintained stable allograft function. Prospective studies with larger sample size are needed to ascertain this preliminary finding.

BK Virus-Associated Nephropathy after Renal Transplantation

Recent advances in immunosuppressive therapy have reduced the incidence of acute rejection and improved renal transplantation outcomes. Meanwhile, nephropathy caused by BK virus has become an important cause of acute or chronic graft dysfunction. The usual progression of infection begins with BK viruria and progresses to BK viremia, leading to BK virus associated nephropathy. To detect early signs of BK virus proliferation before the development of nephropathy, several screening tests are used including urinary cytology and urinary and plasma PCR. A definitive diagnosis of BK virus associated nephropathy can be achieved only histologically, typically by detecting tubulointerstitial inflammation associated with basophilic intranuclear inclusions in tubular and/or Bowman’s epithelial cells, in addition to immunostaining with anti-Simian virus 40 large T-antigen. Several pathological classifications have been proposed to categorize the severity of the disease to allow treatment strategies to be determined and treatment success to be predicted. Since no specific drugs that directly suppress the proliferation of BKV are available, the main therapeutic approach is the reduction of immunosuppressive drugs. The diagnosis of subsequent acute rejection, the definition of remission, the protocol of resuming immunosuppression, and long-term follow-up remain controversial.

Incidence and risk factors for high-level BK viruria: a single center study in China

Background

BK virus allograft nephropathy is a serious complication after kidney transplantation, and the effect of pre-emptive intervention for high-level BK viruria has been verified, but protocols after kidney transplantation for early identification of high-level viruria are lacking.

Methods

This was a single-center study. The clinical data of the kidney transplant recipients and their donors in our center from January 1, 2015 to December 31, 2018, were collected. The patients were divided into the high-level BK viruria group (Group A) and a non-high-level BK viruria group (Group B) according to the qPCR results of BK virus DNA loads in urine samples. Significant variables were screened out by univariate analysis, and then the results were incorporated into a multivariate logistic regression model to analyze the independent risk factors for high-level BK viruria.

Results

A total of 262 recipients were included in the study. The incidence of high-level BK viruria was 13.4% (n = 35), and the median time of detection was 181 (range 91–1119) days. Univariate analysis showed that donor type (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\chi^{2}$$\end{document}χ2 = 21.770, P < 0.001), history of ATG/ATG-F application (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\chi^{2}$$\end{document}χ2 = 4.543, P = 0.033), acute rejection (AR) (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\chi^{2}$$\end{document}χ2 = 8.313, P = 0.004) and delayed graft function (DGF) (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\chi^{2}$$\end{document}χ2 = 21.170, P < 0.001) were related to high-level BK viruria. After the inclusion of the multivariate logistic regression model, the results showed deceased brain and cardiac donors (P = 0.032, OR = 3.927, 95% CI 1.122–13.746), AR (P = 0.022, OR = 4.709, 95% CI 1.253–17.697) and DGF (P = 0.001, OR = 6.682, 95% CI 2.288–19.518).

Conclusions

Donation by deceased brain and cardiac patients, history of AR and DGF were independent risk factors for high-level BK viruria after kidney transplantation.

Total nephroureterocystectomy and urethrectomy due to urothelial carcinoma associated with the BK polyomavirus infection after kidney transplantation: a case report with literature review

Background

BK polyomavirus (BKPyV) infection after kidney transplantation is an important cause of graft failure among kidney transplant recipient and may cause malignant tumor, although the association between BKPyV infection and malignant tumor has been controversial yet.

Case presentation

We report a case of a 39-year-old-male kidney transplantation (KTx) recipient with urine BKPyV replication who developed a graft pelvic tumor with the positive Simian virus 40 large T antigen (SV40 TAg). The patients received a living-related KTx from his 65-year-old mother. A protocol biopsy at 14 months after KTx showed BKPyV-associated nephropathy. Therefore, the dose of immunosuppressants was reduced, resulting in improved BKPyV viremia, but viruria persisted. About 117 months after KTx, urine cytology showed atypical cells suspicious for malignancy. Cystoscopy revealed a tumor on the neck of the bladder. Transurethral resection of the bladder tumor (TUR-BT) was performed; however, the diagnosis of malignancy was not confirmed at that time. Six months after the TUR-BT, urine cytology showed atypical cells definite for malignancy. Computed tomography and retrograde pyelography showed no evidence of urinary tract tumor and metastasis. Subsequently, total nephroureterocystectomy and urethrectomy were performed. Histological examination of the graft ureter revealed a high-grade urothelial carcinoma, with glandular differentiation, pT1. Immunohistochemically, the tumor showed positivities for SV40 TAg and p53, along with increased Ki67 labeling cells were increased. By contrast, nonneoplastic cells were negative for SV40 TAg. At the time of writing the present manuscript, the patient is free from recurrence or residual tumor and being closely monitored without additional therapy, 32 months after the surgery.

Conclusion

The relationship between BKPyV infection after KTx and bladder carcinogenesis remains to be elucidated. However, when the KTx recipients who continue to have BKPyV infection for a long time are treated, the possibility of risk factors for renourinary carcinoma should always be carefully considered.

Conversion From Mycophenolates to Mizoribine Is Associated With Lower BK Virus Load in Kidney Transplant Recipients: A Prospective Study

BACKGROUND

BK virus allograft nephropathy (BKVAN) is a graft-threatening complication after kidney transplantation. Current consensus regarding the prevention of BKVAN is to screen for BK viremia and to treat sustained BK viremia through reducing immunosuppression. This study assessed the effect of conversion from mycophenolates to mizoribine (MZR) on the prevention of BK viremia in kidney transplant recipients.

METHODS

De novo kidney transplant recipients were screened for BK viruria. Sustained high levels of BK viruria (>10⁷ copies/mL) were treated by switching from mycophenolates to MZR. The reduction and clearance of BK viruria and viremia were evaluated.

RESULTS

Fifty kidney transplant recipients with high levels BK viruria were enrolled, including 11 recipients with BK viremia. After 6 months of MZR therapy, only 3 recipients still had high levels of BK viruria. The clearance rate of BK viremia was 100%. One episode of acute rejection occurred (2.0%) and was reversed by steroid administration. The serum uric acid level of the recipients was similar before and after switching to MZR, but the proportion of recipients receiving uric acid-reducing drugs increased significantly after 3 months of MZR therapy (19/50 vs 31/50; P = .02). No new cases of BK viremia were observed after conversion to MZR.

CONCLUSION

Conversion from mycophenolates to MZR in kidney transplant recipients with sustained high levels of BK viruria was associated with reduction of BK viruria and clearance of BK viremia. This may be an effective approach to prevent BK viremia and BKVAN.

Association Between the Polyomaviruses Titers and Decoy Cell Positivity Rates After Renal Transplantation

BACKGROUND

Urinary decoy cells develop after renal transplantation and their appearance is attributable primarily to the proliferation of polyomavirus types BK and JC. We measured the levels of these 2 viruses that cause decoy cells to appear in the urine.

PATIENTS AND METHODS

BK and JC virus levels were quantified in 1182 urine samples from 335 renal transplant patients using a multiplex Taqman real-time polymerase chain reaction assay. Forty-four samples were excluded from analyses because both viruses were present at ≥10(4) copies/mL. We analyzed the relationship between viral load and the presence of urinary decoy cells.

RESULTS

Decoy cells were observed in 237 of 1138 urine samples (21%) and the BK and JC viruses were positive in 205 (18%) and 455 (40%) samples, respectively. Decoy cells were observed in 0%, 21%, 67%, 87%, 100%, and 96% of urine samples when the BK viral load was <10(4), 10(4)-10(5), 10(5)-10(6), 10(6)-10(7), 10(7)-10(8), and ≥10(8) copies/mL, respectively; and in 1%, 13%, 41%, 59%, 87%, and 97% of urine samples when the JC viral load was <10(4), 10(4)-10(5), 10(5)-10(6), 10(6)-10(7), 10(7)-10(8), and ≥10(8) copies/mL, respectively.

CONCLUSIONS

BK virus more frequently triggered the appearance of decoy cells than did JC virus at equivalent viral titers.

Correlation between urine and serum BK virus levels after renal transplantation

BACKGROUND

Quantification of the serum level of BK virus is used as a surrogate marker for the early onset of BK virus nephropathy. However, little is known about the diagnostic value of the urine level of BK virus for nephropathy or the relationship between the serum and urine viral load. We investigated the correlation between urine and serum BK virus levels after renal transplantation.

METHODS

From November 2008 to August 2013, a total of 270 renal transplant patients who were followed at our institution were included in this study. Urine and serum were collected simultaneously. BK virus levels were quantified in 894 urine and serum samples using a real-time polymerase chain reaction assay.

RESULTS

BK virus was detected in 178 urine samples and 36 serum samples. Among the BK virus-positive urine subjects, the positive predictive value for viral detection in the serum was 9% (13/147) when the urinary virus level was <10(7) copies/mL and 74% (23/31) when the urinary virus was ≥ 10(7) copies/mL. Serum BK viral levels were ∼2-3 log units lower than those in urine.

CONCLUSIONS

BK virus was detected more frequently in serum when present in urine at ≥ 10(7) copies/mL after renal transplantation.

Prevalence of polyomavirus positivity in urine after renal transplantation

BACKGROUND

Little is known about the timing of polyomavirus reactivation and its presence in urine after renal transplantation. The purpose of this study was to investigate the prevalence of positive polyomavirus in urine at various time points after renal transplantation.

METHODS

From November 2008 to August 2013, 279 renal transplant patients from our institution were included in this study. One urine sample was collected at 0-3, 4-6, 7-12, 13-24, 25-60, and ≥ 61 months after renal transplantation. A total of 394 urine samples were assessed for the presence of the BK and JC viruses with the use of a real-time polymerase chain reaction assay.

RESULTS

BK virus was detected in the urine of one-third of patients during the first 6 months. Thereafter, the positivity rate decreased gradually to 12% >5 years after transplantation. The positivity rate for the JC virus in urine was 33%-49% regardless of the post-transplantation phase.

CONCLUSIONS

BK virus was detected more frequently in urine during the early phase after renal transplantation, whereas the JC virus was detected more consistently.