BK Virus Polymerase Chain Reaction Research Articles

Effects of Induction Therapy on Graft Functions in Terms of Immunologic Risk

Advances in immunosuppressive therapies and surgical techniques have led to a significant reduction in the incidence of rejection within 1 year after kidney transplantation. Immunologic risk is an important factor affecting graft functions and guiding the clinician in the selection of induction therapy. The aim of this study was to investigate graft functions based on serum creatinine levels, Chronic Kidney Disease Epidemiology Collaboration (CKD- EPI) and proteinuria levels, frequency of leukopenia, cytomegalovirus (CMV) and BK virus polymerase chain reaction (PCR) positivity in patients with low and high immunologic risk. This retrospective study included 80 renal recipients. Recipients were divided into 2 groups: patients at low immunologic risk who received basiliximab only and those with high immunologic risk who received low-dose (1.5 mg/kg for 3 days) antithymocyte globulin and basiliximab. No significant differences were observed between the 2 risk groups in terms of first, third, sixth, and 12th-month creatinine levels, CKD-EPI, proteinuria levels, leukopenia frequency, and CMV and BK virus PCR positivity. One-year graft survivals did not differ significantly between these 2 treatment modalities. The combined use of low-dose antithymocyte globulin and basiliximab in the induction treatment of patients with high immunologic risk seems promising in terms of graft survival, leukopenia frequency, and CMV and BK virus PCR positivity.

Native BK virus nephropathy in lung transplant: a case report and literature review.

ABSTRACTClassically described in renal allografts, BK virus nephropathy is increasingly recognized in native kidneys of other non-renal solid organ transplants. We discuss a 68-year-old woman with a history of bilateral lung transplant referred for worsening renal function, confirmed to have BK virus nephropathy by biopsy with a serum BK virus polymerase chain reaction of over 59 million copies/mL. She was managed with a reduction in immunosuppression and intravenous cidofovir with no improvement in her clinical parameters. The seven prior reported cases of polyoma virus nephropathy in lung transplant recipients are reviewed, and the challenges of screening and management are discussed.

Prospective Analysis of Hemorrhagic Cystitis and BK Viremia in Allogeneic Hematopoietic Stem Cell Transplantation

Objective:BK virus (BKV) infection has been shown to be related to hemorrhagic cystitis (HC) in allogeneic hematopoietic stem cell transplantation (allo-HSCT). There are conflicting data regarding the association between BKV titers in plasma and clinical disease as well as the risk factors for BKV-related HC. Our aim is to study the risk factors and relationship with plasma BK viral load for development of HC in a prospective analysis.Materials and Methods:We prospectively evaluated 59 patients who received allo-HSCT between 2014 and 2016 by quantitative BK virus polymerase chain reaction (PCR) (Altona Diagnostics, Germany) from blood samples at days 0, 30, 60, and 90 after allo-HSCT. The patients were monitored for signs and symptoms of HC.Results:HC was diagnosed in 22 patients (37%) at a mean of 100 days (range: 0-367 days). In multivariate analysis, the usage of cyclophosphamide (sub-distribution hazard ratio [sdHR]: 7.82, confidence interval [CI]: 1.375-39.645, p=0.02), reactivated CMV (sdHR: 6.105, CI: 1.614-23.094, p=0.008), and positive BKV viremia (sdHR: 2.15, CI: 1.456-22.065, p=0.01) significantly increased the risk of developing HC. Patients with higher viral loads at day 30 and day 60 were diagnosed with more severe HC (p<0.001). Median BK viral loads of >101.5 copies/mL at day 0 (sensitivity 0.727, specificity 0.875), >98.5 copies/mL at day 30 (sensitivity 0.909, specificity 0.875), and >90.0 copies/mL at day 60 (sensitivity 0.909, specificity 0.875) were indicative of HC.Conclusion:Our study showed that administration of cyclophosphamide, CMV reactivation, and BK virus positivity were associated with HC. Plasma BK virus PCR titers at days 0, 30, and 60 after transplant were sensitive tools for predicting clinically proven HC.

BK virus nephropathy and multiorgan involvement in a child with heart transplantation

BK virus is a known cause of renal failure in kidney transplant recipients, but there is little data regarding its effect on native kidneys in heart transplant patients. Here, we describe the case of a child who underwent heart transplantation and was later diagnosed with BK virus with multiorgan involvement. This patient was diagnosed with dilated cardiomyopathy at 4 months of age and underwent heart transplantation at the age of 5 years. Before transplantation, the patient suffered from cardiac arrest and fungal pyelonephritis. The patient had no evidence of azotemia. Ten months after transplantation, the patient was diagnosed with diffuse large B-cell lymphoma associated with Epstein-Barr virus infection. She underwent chemotherapy, and later developed azotemia and BK viremia. The findings on renal biopsy were compatible with BK nephropathy. After the biopsy, she was treated with intravenous cidofovir, immunoglobulins, and oral leflunomide. The tacrolimus dose was also reduced. However, the patient's renal function continued to worsen. She developed end-stage renal disease and started peritoneal dialysis. After experiencing a seizure, the patient was found to have positive BK virus polymerase chain reaction in the cerebrospinal fluid. Brain magnetic resonance image revealed a new white matter lesion in the splenium. On immunohistochemistry, there was SV40-positive staining in gastric and heart biopsy specimens. Therefore, BK virus enteropathy and cardiac involvement were suspected. This case suggests that BK virus infection can lead to systemic involvement and can be fatal. .

The clinical significance of BK viremia and the effect of cyclosporine and/or mizoribine on BK virus infection

IntroductionThe diagnosis of BK virus nephropathy is based on renal biopsy findings, and the diagnosis of presumptive BK virus nephropathy is made by sustained plasma BK virus DNA loads of > 4 log10 copies/ml. However, the BK virus plasma viral load cutoff of 4 log10 copies/ml may underestimate the diagnosis of BK virus nephropathy. In this study, we evaluated the clinical significance of BK viremia in kidney transplant recipients. Patients and MethodsFrom January 2010 to November 2015, we experienced 8 kidney transplant recipients who developed BK viremia. We retrospectively analyzed these recipients, focusing on the plasma BK viral load at onset of BK viremia, time to BK viremia after transplantation, frequency of BK virus nephropathy, and our treatment for BK viremia. ResultsThe median plasma BK virus polymerase chain reaction at the diagnosis of BK viremia was 1600 copies/ml (370–9400 copies/ml). The median time to BK viremia after transplantation was 10.9 months (1.4–67.9 months). Three patients were associated with BK virus nephropathy on biopsy. Clearance of BK viremia was observed in all of these cases after intervention. ConclusionsOur study demonstrated that intervention in BK viremia with a viral load of < 4 log10 copies/ml may be needed to prevent the development of graft dysfunction and BK virus nephropathy in kidney transplant recipients.

Diagnostic utility of urine cytology in early detection of polyomavirus in transplant patients

Polyomavirus-associated nephropathy (PVAN) is one of the most common disease affecting transplant patients, mainly caused by BK polyomavirus (BKV) and with <5% of the cases caused by JC polyomavirus (JCV). Screening and early intervention, including appropriate reduction in immunosuppressive therapy, are critical to reduce allograft loss. The presence of decoy cells in the urine is a characteristic cytopathic effect of polyomavirus. The goal of this study was to investigate the significance of decoy cells in urine cytology in transplant patients, comparing with the plasma viral replication level detected by the real-time quantitative BK virus polymerase chain reaction test (Qt-BK PCR). A cohort of post-transplantation patients with serum BKV level monitored by Qt-BK PCR from 2008 to 2013 was studied. Among them, 35 patients had both urine cytology (UC) analysis and Qt-BK PCR performed. The clinical presentation along with the available UC slides were retrieved and reviewed. Compared with Qt-BK PCR, the sensitivity, specificity, positive predictive value, and negative predictive value of urine cytology analyzed within one week apart were 92%, 71%, 85%, and 83%, respectively. The accuracy of the UC was 84%. More interestingly, UC played a key role in identifying a case of JCV associated PVAN whereas Qt-BK PCR from both urine and plasma failed to detect this virus. Our data suggests that urine cytology is a sensitive surveillance test for early detection of polyomavirusin transplant patients, and it is particularly useful to screen for rare JC polyomavirus.

Prevalence of Polyomavirus Among United Arab Emirates Kidney Transplant Recipients: Results From a Single Center

BackgroundBK viremia and nephropathy are increasing problems in renal transplant recipients. The absence of a safe and effective antiviral therapy made screening-based prevention a recommended strategy. The prevalence of its reactivation among recipients of kidney transplants in the Middle East has not been well established. Our objective was to determine the prevalence of BK virus (BKV) infection for renal transplant recipients at our medical center. MethodsAll renal transplant recipients followed up in our transplantation clinic between 2012 and 2013 (n = 116) were screened. Urine and blood quantitative real-time polymerase chain reaction (PCR) for the BKV were performed in all of the study patients. Renal biopsy was performed only in patients with deteriorating renal function associated with positive PCR. Patients who showed positive BKV PCR were followed up for 6 to 12 months. This included clinical and kidney function assessment along with BKV PCR viral load. ResultsAmong the 116 kidney transplant recipients studied, 65 (56%) were male, age 51 ± 15 years, with a transplantation vintage of 131 ± 61 months; 17 (14.7%) were positive for BKV PCR. Three (2.7%) showed viremia; 2 of them had deterioration of kidney function, renal biopsy confirmed the diagnosis of BK nephropathy (NP) in both cases. The 3 cases were managed by reducing the immunosuppressive treatment with stabilization of their kidney function. Cases with stable renal function and positive urine for BKV cleared the virus spontaneously during follow-up after minor reduction of the immunosuppressive treatment or without any intervention. None of our patients lost the graft due to BK NP. ConclusionOur study suggests that BKV is not uncommon in our kidney transplant recipients. Routine screening suggested by the KDIGO Guidelines could help minimize its detrimental impact on the transplant outcome.

Occurrence of the polyomavirus among kidney transplant recipients: A single-center study

Polyoma virus-associated nephropathy is an increasingly recognized cause of graft dysfunction among kidney transplant recipients and could be the result of use of potent immunosuppression following transplantation. Because there is no safe and effective anti-viral therapy available presently, screening-based prevention and pre-emptive strategy are recommended. This study, which was conducted at the Nephrology Unit, Internal Medicine Department, Alexandria University, consisted of two phases: Phase 1 was a cross-sectional study and phase 2 was a 6-month follow-up study only for polyoma virus-positive cases. Phase 1 included 75 renal allograft recipients from living donors. Urine cytology for decoy cells and quantitative real-time blood polymerase chain reaction (PCR) for the BK virus (BKV) were performed on all the study patients. Renal biopsy was performed only in patients with deteriorating renal function associated with positive urine cytology. Patients who showed positive urine cytology for decoy cells and/or positive quantitative BKV PCR assay were followed-up for six months. During follow-up, the serum creatinine level, with or without urine cytology for decoy cells, and BKV PCR viral load assay were performed. Among the 75 kidney transplant recipients studied, eight were positive for decoy cells (11%), three showed viremia by quantitative PCR for BKV (4.1%), while two others showed nephropathy (2.7%) in the form of tubulointerstitial nephritis with intra-nuclear inclusions in the tubular cells. Cases with stable renal function and positive decoy cells or viremia cleared the virus spontaneously during follow-up without any intervention. Only one case with biopsyproven nephropathy and deteriorating graft function, with undetectable BKV in blood, lost the graft while another case with viremia died during follow-up due to septicemia. Our study suggests that polyoma virus should be considered as a cause of nephropathy in renal transplant recipients. Further research is required to understand this entity better.

CMV Viremia Is Associated With a Decreased Incidence of BKV Reactivation after Kidney and Kidney-Pancreas Transplantation

Cytomegalovirus (CMV) and BK virus (BKV) infections can cause significant morbidity after kidney and kidney-pancreas transplant. There are limited data on the epidemiology and interactions between these two viral pathogens. We prospectively screened 609 kidney or kidney-pancreas transplant recipients from January 2007 to June 2011 for BKV and/or CMV viremia. This included 7453 quantitative BKV polymerase chain reaction and 15,496 quantitative CMV polymerase chain reaction tests. We evaluated risk factors and timing of these infections and the impact of treatment of one infection on the other. Among 609 recipients, 108 (17.7%) developed CMV viremia, of which 95 (88%) were asymptomatic, 5 (5%) had CMV syndrome, and 8 (7%) developed CMV tissue invasive disease at a median of 5.6 months after transplantation. Risk factors for CMV infection using multivariable analysis were D+R- serogroup (P≤0.0001), donor age >50 years (P=0.013), and higher mean tacrolimus (P=0.0009) and mycophenolate mofetil (P=0.01) blood levels. The incidence of BKV infection in the total population was 163 of 609 (26.7%), of which 150 (92%) occurred in patents without antecedent CMV viremia. Such patients demonstrated a higher rate of subsequent BKV viremia than patients with antecedent CMV viremia (P=0.003; hazard ratio, 2.05; 95% confidence interval, 1.2-3.4). Moreover, we found that only symptomatic CMV viremia had a significant negative impact on graft survival when compared with asymptomatic CMV viremia and those without CMV viremia (relative risk, 3.5; 95% confidence interval, 1.06-8.9; P=0.04). CMV viremia may indirectly protect against subsequent BK viremia possibly due to a reduction of intensity of immunosuppression after diagnosis of CMV viremia.

Ureteral stent placement and BK viremia in kidney transplant recipients

BK virus (BKV) infection is an important cause of kidney transplant dysfunction. A possible association of double-J ureteral stent placement and BK viremia has been suggested in previous studies; however, risk factors for BK are incompletely understood. We aimed to determine if stent placement is an independent risk factor for BK viremia. Data were collected on consecutive kidney-only transplant recipients between December 1, 2006 and June 30, 2010. All patients had at least 12months of follow-up. Of 600 consecutive kidney transplants, BK viremia within the first post-transplant year was detected in 93 patients (15.5%); in 70 of these cases, the peak BKV polymerase chain reaction was ≥10,000 copies/mL. By multivariate analysis, significant risk factors for BK viremia were recipient age (P=0.02) and stent placement (P=0.03). Stents were placed in 49.2% and removed at a median of 46days (range: 11-284) post transplantation; removals occurred within 0-30, 30-60, 60-90, 90-120, 120-150, and >150days post transplantation in 18.4%, 67.2%, 10.5%, 2.4%, 1.0%, and 0.3% of cases, respectively. No association was found of BK viremia with stent duration >46days (P=0.70) or by the 6-level groupings (P=0.92). Although we observed a significant association of BK viremia with stent placement, no dose-dependent effect was seen.

Trends in immune function assay (ImmuKnow; Cylex ) results in the first year post-transplant and relationship to BK virus infection

The ImmuKnow assay is a functional T-cell assay (TCA) that may quantify cellular immune responsiveness following renal transplantation. Using a standard protocol of TCA sampling in the first year post-transplant, we examined changes in TCA values over time and tested for an association between TCA and BK virus (BKV) infection as a marker of over-immunosuppression. We performed a single-center retrospective analysis of 897 TCA results in 414 renal transplant recipients obtained at 0 (N = 122), 1 (N = 316), 6 (N = 258) and 12 (N = 201) months post-transplant from May 2005 to July 2009 with concurrent urine and blood BKV polymerase chain reaction measurements. Nearly 40% of patients experienced a decrease in TCA of >150 ng/mL from 1 to 6 months (mean 466-356 ng/mL, P < 0.0001) and remained stable from 6 to 12 months (mean 357 versus 370 ng/mL, P = 0.33). Neither a change in TCA of >150 ng/mL nor a TCA value of ≤ 225 ng/mL were associated with a diagnosis of BKV infection at 1 or 6 months, while TCA ≤ 225 ng/mL was associated with BKV infection at 12 months (P = 0.005). A reduction in TCA from 1 to 6 months post-transplant is common and is not associated with conditions of over-immunosuppression, rendering the interpretation of changes in TCA during this time period difficult. BKV infection is associated with low TCA values at 12 months, suggesting that patients with low TCA values after 6 months may benefit from potential tailoring of immunosuppression or more aggressive monitoring to prevent subsequent BKV infection.

BK Virus Infection and Its Effect on Renal Function in Pediatric Liver-Transplant Recipients: A Cross-Sectional, Longitudinal, Prospective Study

Chronic renal failure (CRF) is a well-documented complication of liver transplantation. BK virus (BKV) is a common cause of CRF in renal-transplant recipients and has been sporadically associated with renal failure after nonrenal solid-organ transplantation. The aims of the study were to determine the prevalence of BK viruria and viremia in pediatric liver-transplant recipients, assess the natural course of BKV infection over time, and examine the association between BKV positivity and renal function. A prospective, cross-sectional study of 59 pediatric liver-transplant recipients. Blood and urine samples were collected at enrollment for creatinine level and BKV polymerase chain reaction test. BKV-positive patients underwent repeated testing and follow-up. The medical files were reviewed for clinical data. Median age at enrollment was 11.5 years, and median time from transplantation was 61 months. One child (1.7%) had viremia, and nine children (15.3%) had viruria (median: 610 copies/mL). All cases of viruria/viremia resolved spontaneously, nine of them within 10 months. There were no significant differences in demographic or clinical variables between the BKV-positive and BKV-negative children. None of the BKV-positive patients had evidence of renal dysfunction. Pediatric liver-transplant recipients have a low prevalence of BK viruria/viremia. BKV infection is associated with low viral loads and resolves spontaneously within a relatively short period, without residua. BKV is not associated with CRF postliver transplantation. BKV testing should not be part of the routine follow-up of children after liver transplantation.

Routine BK Virus Surveillance in Renal Transplantation - A Single Center's Experience

Background We started a universal screening of all our kidney transplant recipients for BK virus in 2005. This review of our experience includes patients with ≥6 months' posttransplantation follow-up. Methods We performed a retrospective chart evaluation of all kidney transplants from January 2005 to February 2010. Urine polymerase chain reaction (PCR) for BK virus was done on all patients starting from 4 weeks after transplantation. If negative, it was repeated monthly for the first 6 months and then every 3–4 months. If the test was positive, a urine and blood BK virus PCR done on the next visit was repeated every 2–4 weeks with a slow reduction in immunosuppression. Results From January 2005 to February 2010 we performed 173 kidney transplantations with 12 graft losses within the first 6 weeks which were excluded from the analysis. Induction immunosuppression consisted of anti–interleukin-2 receptor antibody (n = 102) or antithymoglobulin (ATG; n = 59). In 112 patients (70%), the urine BK virus PCR remained negative; 18 (11%) only the urine was positive and among an additional 31 (19%) BK virus PCR was positive in blood. There was no difference in incidence according to induction therapy. Delayed graft function was observed among 39 patients (24%); there was no difference in the incidence of BK virus with versus without DGF. The mean time to first detection was shorter with ATG induction (mean, 199 days; median, 90 days; range, 26–1198 days) compared with anti–IL-2 (mean, 321 days; median, 195 days; range, 23–1077 days). Urine-only positivity was first detected from 37 to 1198 days (mean, 366 days; median, 227 days) and blood positivity from 23 to 1069 days (mean, 216 days; median, 90 days). Among BK-positive patients, 26 (53%) were detected within the first 6 months and 38 (76%) within the first year. With reduction in immunosuppression, there was gradual reduction or elimination of positive PCR tests in all cases except one, which resulted in graft failure. Conclusions Routine BK virus surveillance is effective; it tends to detect BK virus replication early, allowing reduction of immunosuppression, which results in good outcomes with renal preservation.

Preemptive Retransplant for BK Virus Nephropathy Without Concurrent Transplant Nephrectomy

Preemptive Retransplant for BK Virus Nephropathy Without Concurrent Transplant Nephrectomy

Bone marrow aplasia and graft loss in a pediatric renal transplant patient with polyomavirus nephropathy

Sirs, BK-virus nephropathy (BKN) is an important cause of graft dysfunction in kidney transplant recipients. Severe allograft dysfunction and graft loss are well-known complications [1–3]. However, pancytopenia caused by an infection of the bone marrow is thus far an unknown complication of BK virus (BKV) infection. We report a 17-year-old boy with end-stage renal disease due to peripartal asphyxia who was transplanted with a cadaveric kidney. Posttransplantation immunosuppressive therapy (IS) consisted of tacrolimus, mycophenolate mofetil (MMF), prednisolone, and basiliximab (Simulect ®) as induction therapy. Eighteen months after transplantation, IS was diminished because of detection of BK viruria and viremia. As this could not improve the number of BKV copies and serum creatinine increased, cidofovir (Vistide ® 1 mg/kg) was administered IV weekly (four times). A graft biopsy 4 months later showed a BKN Drachenberg B1 [3] without signs of acute humoral or cellular rejection. MMF was discontinued, and tacrolimus was diminished until trough levels of 4–5 μg/l were achieved. Despite these interventions, our patient was hospitalized 2 months later because of high and recurrent fever, pancytopenia, and deterioration of renal function. BKV polymerase chain reaction (PCR) in plasma at that time was strongly elevated: >5,000,000 copies/ml (7.7 log copies/ml), and hemoglobin, white blood cell, and thrombocyte count were unacceptably low. Adjunctive therapy was started: six extra doses of cidofovir and five of immunoglobulin (Multigam ® 2 g/kg) were administrated IV over a period of 4 weeks. A bone marrow biopsy showed global aplasia, and PCR was positive for BKV (>5,000,000 copies/ml). All other causes of pancytopenia, such as Epstein-Barr virus (EBV), cytomegalovirus (CMV), Parvovirus B19, human herpes virus-6 (HHV-6), malignancy, or hemophagocytic syndrome were excluded; tacrolimus and prednisolone were discontinued, and treatment with granulocyte colony stimulating factor (GCS) and erythropoietin was started. As the boy’s condition was life threatening due to persistent pancytopenia, deterioration of renal function, and systemic aspergillosis, and as severe BKN with BKV infection of the bone marrow seemed to be the cause of this, it was decided to remove the graft 2.5 months after the initial biopsy. The nephrectomy specimen showed BKN Drachenberg grade B3 [3], without signs of acute rejection. After removal of the graft, the patient’s general condition improved quickly: fever disappeared, and plasma BKV PCR copies decreased rapidly. BKV was no longer detectable in plasma after 11 days and in urine 3 months after transplantectomy. The bone marrow recovered very slowly over several months. Figure 1 shows the evolution of hemoglobin (Hb), white blood cell count (WBC), creatinine, and polyomavirus (BK) copy numbers after discovery of BK shedding in urine. S. H. M. Gardeniers :D. Mekahli : E. Levtchenko : R. Van Damme-Lombaerts Department of Pediatric Nephrology, UZ Leuven, Leuven, Belgium

Hydronephrosis Resulting from Bilateral Ureteral Stenosis: A Late Complication of Polyoma BK Virus Cystitis?

We report here a case of acute lymphoblastic leukemia in remission presenting a late-onset bilateral hydronephrosis probably due to polyoma BK virus-induced proliferation of bladder endothelium on both ostii. The diagnosis was made virologically by BK virus Polymerase Chain Reaction (PCR) detection in the absence of any other bladder disease. Awareness of this late complication is necessary not only in patients after renal transplantation but also in patients after hematopoietic stem cell transplantation from matched unrelated donor.

Active Management of Post–Renal Transplantation BK Virus Nephropathy: Preliminary Report

To assess the efficacy of leflunomide, intravenous immunoglobulins, and ciprofloxacin as active treatment of postrenal transplant BK virus nephropathy (BKVN) in graft outcome at 1 year. Renal transplant recipients with positive results of 2 BK virus polymerase chain reaction tests of urine and blood underwent graft biopsy to confirm BKVN. If BKVN was diagnosed, antimetabolite therapy (mycophenolate mofetil or azathioprine) was changed to leflunomide therapy accompanied by a course of immunoglobulin and oral ciproflxacin. Of 18 patients evaluated, 72% were men. Nine patients received cadaveric organs, with a mean of 3.6 HLA mismatches. All patients received induction thereapy (61% thymoglobulin), and 61% received antirejection therapy before BKVN was diagnosed. Maintenance immunosuppression therapy was primarily with prednisolone (94%); mycophenolate mofetil, 2 g/d (94%); and tacrolimus (61%). At baseline, mean (SD) creatinine clearance was 35.6 (11.5) mL/min/1.73(2), which decreased to 29.3 (17.3) mL/min/1.73(2) at 1 year (P = .01). Patients were divided into 2 groups of 9 each according to creatinine clearance values. In group 1, baseline value was 44.5 (6.6) mL/min/1.73(2), compared with 25.36 (7.8) mL/min/1.73(2) in group 2, which decreased to 42.66 (12.8) mL/min/1.73(2) (P = .23) and 16.76 (9.0) mL/min/1.73(2) (P = .009), respectively, at 1 year. Three grafts (16.7%) were lost by the end of the study, all in group 2 (P = .03). Late diagnosis and intensive immunosuppression predispose to BKVN. Early active treatment of BKVN may improve graft outcome at 1 year posttransplantation.

Integrated wavelength-selective optical waveguides for microfluidic-based laser-induced fluorescence detection

We demonstrate the fabrication and characterization of a novel, inexpensive microchip capable of laser induced fluorescence (LIF) detection using integrated waveguides with built-in optical filters. Integrated wavelength-selective optical waveguides are fabricated by doping poly(dimethysiloxane) (PDMS) with dye molecules. Liquid-core waveguides are created within dye-doped PDMS microfluidic chips by filling channels with high refractive index liquids. Dye molecules are allowed to diffuse into the liquid core from the surrounding dye-doped PDMS. The amount of diffusion is controlled by choosing either polar (low diffusion) or apolar (high diffusion) liquid waveguide cores. The doping dye is chosen to absorb excitation light and to transmit fluorescence emitted by the sample under test. After 24 h, apolar waveguides demonstrate propagation losses of 120 dB cm(-1) (532 nm) and 4.4 dB cm(-1) (633 nm) while polar waveguides experience losses of 8.2 dB cm(-1) (532 nm) and 1.1 dB cm(-1) (633 nm) where 532 and 633 nm light represent the excitation and fluorescence wavelengths, respectively. We demonstrate the separation and detection of end-labelled DNA fragments using polar waveguides for excitation light delivery and apolar waveguides for fluorescence collection. We demonstrate that the dye-doped waveguides can provide performance comparable to a commercial dielectric filter; however, for the present choice of dye, their ultimate performance is limited by autofluorescence from the dye. Through the detection of a BK virus polymerase chain reaction (PCR) product, we demonstrate that the dye-doped PDMS system is an order of magnitude more sensitive than a similar undoped system (SNR: 138 vs. 9) without the use of any external optical filters at the detector.

BK Virus–Associated Nephropathy in Sirolimus-Treated Renal Transplant Patients: Incidence, Course, and Clinical Outcomes

Because the course of polyoma virus-associated nephropathy (PVAN) has not been evaluated in a large cohort of patients receiving sirolimus (SRL)-based regimens, we have herein presented the incidence, clinical characteristics, and outcomes of 378 renal transplant recipients treated with SRL-based immunosuppression. This retrospective single center study evaluated 344 kidney alone (KTX) and 34 simultaneous pancreas-kidney (SPK) transplantations performed between June 2000 and December 2004. At a mean follow-up of 43.3 months, six kidney (1.7%) and three kidney-pancreas (9.0%) transplanted patients displayed biopsy-proven PVAN. The mean time to diagnosis after transplantation was 18.2 months (range: 3.5-31.1 months), with a higher incidence among patients exposed (4.23%) versus not exposed to rabbit antithymocyte globulin (rATG; 0.53%; P=0.019) or SPK (9.0%) versus KTX (1.7%) recipients (odds ratio: 5.43; confidence interval: 1.29-22.8; P=0.038). Despite treatment with cidofovir, reduced immunosuppression and maintenance therapy with no agents other than SRL (C0=10.2+/-2.7 ng/dL) plus modest doses of prednisone (< or =5 mg), five patients (55.5%) experienced renal allograft failure. No rejection episodes were documented during the PVAN treatment and pancreatic function continued to be excellent among the SPK patients. Patients treated with SRL-based immunosuppression showed an incidence at the lower end of the range described with various other contemporaneous immunosuppressive regimens and with other cohorts not undergoing BK virus polymerase chain reaction surveillance. Exposure to rATG and SPK transplantation represented risk factors for the occurrence of PVAN, which showed a pernicious course despite withdrawal of calcineurin antagonists and/or mycophenolate mofetil.