COVID-19 and the kidney.

COVID-19 is primarily considered a respiratory illness, but the kidney may be one of the targets of SARS-CoV-2 infection, since the virus enters cells through the angiotensin-converting enzyme 2 receptor, which is found in abundance in the kidney. Information on kidney involvement in COVID-19 is limited but is evolving rapidly. This article discusses the pathogenesis of acute kidney injury (AKI) in COVID-19, its optimal management, and the impact of COVID-19 on patients with chronic kidney disease, patients with end-stage kidney disease on dialysis, and kidney transplant recipients.

The detection of BKPyV genotypes II and IV after renal transplantation as a simple tool for risk assessment for PyVAN and transplant outcome already at early stages of BKPyV reactivation.

BACKGROUND: After reactivation the BK-polyomavirus (BKPyV) associated nephropathy (PyVAN) is observed in 1-10% of renal transplant recipients, of which up to 80% undergo graft failure. BKPyV reactivation after renal transplantation was associated with donor-derived serotypes against which the recipient has no immunological protection. However, PyVAN risk assessment seroactivity testing is a time-consuming and cost intensive process. OBJECTIVES: Since BKPyV serotypes can be attributed to distinct genotypes I to IV, in the present study we retrospectively analyzed whether a simple PCR-based BKPyV genotyping assay might be a fast and inexpensive method to assess the risk for PyVAN and transplant outcome already at early stages of BKPyV reactivation. STUDY DESIGN: 56 patients who were renal transplanted and tested positive for BKPyV viremia were included into the study. The BKPyV-VP1-coding sequences were PCR-amplified, sequenced, and subjected to genotyping. For group specific analysis patients were grouped in genotype I (n = 46) and a second group including genotype II and IV (n = 10) and associated with their clinical outcomes. RESULTS: The most abundant genotype I was detected in 46 of 56 (82%) patients, however, in the genotype II and IV group PyVAN was twice as frequent as compared to the genotype I group 24 months after transplantation (8 of 10 (80%) vs. 17 of 46 (37%); p = 0.001). Accordingly, graft failure was significantly more frequent in the genotype II and IV group (3 of 10 (30%) vs. 2 of 46 (4%); p = 0.007). CONCLUSION: PCR-based BKPyV genotyping might represent a fast and inexpensive method to assess the risk for PyVAN and transplant outcome already at early stages of BKPyV reactivation even if matched samples of the donor are not available.

Comparative evaluation of laboratory developed real-time PCR assays and RealStar(®) BKV PCR Kit for quantitative detection of BK polyomavirus.

BACKGROUND: Quantitative, viral load monitoring for BK virus (BKV) by real-time PCR is an important tool in the management of polyomavirus associated nephropathy in renal transplant patients. However, variability in PCR results has been reported because of polymorphisms in viral genes among different subtypes of BKV, and lack of standardization of the PCR assays among different laboratories. In this study we have compared the performance of several laboratory developed PCR assays that target highly conserved regions of BKV genome with a commercially available, RealStar(®) BKV PCR Kit. METHOD: Three real-time PCR assays (i) VP1 assay: selected from the literature that targets the major capsid protein (VP1) gene (ii) VP1MOD assay: VP1 assay with a modified probe, and (iii) BKLTA assay: newly designed assay that targets the large T antigen gene were assessed in parallel, using controls and clinical specimens that were previously tested using RealStar(®) BKV PCR Kit (Altona Diagnostics GmbH, Hamburg, Germany). Nucleic acid from all samples were extracted using the QIA symphony virus/bacteria kit on an automated DNA extraction platform QIA symphony SP (Qiagen). Primer and probe concentration, and reaction conditions for laboratory developed assays were optimized and the limit of detection of different assays was determined. Positive control for laboratory developed BK assays was prepared through construction of a plasmid carrying respective amplicon sequences. RESULTS: The 95% detection limit of VP1, VP1MOD and BKLTA assays were 1.8×10(2), 3×10(3) and 3.5×10(2) genomic copies/ml, respectively, as determined by Probit regression analysis of data obtained by testing a dilution series of a titered patient specimen, using RealStar(®) BKV PCR Kit. The inter-assay and intra-assay, coefficient of variations of these assays using calibrated, plasmid standards were <1%. All assays, including the RealStar(®) BKV PCR assay, were highly specific when tested against a panel of external proficiency specimens containing both BK and JC viruses. All assays, except the VP1MOD assay determined BK viral load in proficiency specimens within the same log values. With reference to results obtained by RealStar(®) BKV PCR assay, the sensitivity and specificity of different assays tested in 116 serum specimens submitted for BK viral load assay were 91% and 97% for VP1 assay, 88% and 97% for VP1MOD assay, and 97% and 98% for BKLTA assay, respectively. BK Viral load in positive specimens determined by various assays was highly correlated (R(2)>0.97), based on linear regression analysis. CONCLUSIONS: The performance characteristics of the newly designed, BKLTA assay were highly comparable to RealStar(®) BKV PCR assay, and can be used for routine detection and viral load monitoring of BKV in a cost-effective manner.

Clinical usefulness of BK virus plasma quantitative PCR to prevent BK virus associated nephropathy.

The present study investigated the clinical usefulness of plasma real-time polymerase chain reaction (PCR) (plasma-PCR) in the prevention of BK virus-associated nephropathy (BKVAN). First, we investigated the diagnostic value of plasma BK-PCR, urine BK-PCR, and urine cytology for the prediction of BKVAN retrospectively. Then we designed a prospective study of regular plasma-PCR monitoring and pre-emptive immunosuppression (IS) reduction based on the result. In the retrospective cohort, the prevalence of BKVAN was 3.7% (14/379) and the positive rate of decoy cells, urine-PCR (>1 × 10(10) copies/ml), and plasma-PCR (>1 × 10(4) copies/ml) was 18.6%, 11.1%, and 5.5%, respectively. Plasma-PCR was superior to urine-PCR or urine cytology in specificity and positive predictive value for detection of BKVAN. In prospective study, regular monitoring of plasma-PCR detected significant BKV viremia in 8.3% (12/145) and BKVAN in 1 patient (0.6%). After IS reduction, BKV viremia was eliminated in 91.6% (11/12) within 103 days (25-254). In patients with viremia, the frequency of acute rejection did not increase and allograft function did not differ significantly compared with those in patients without viremia during the first year post-transplant (P > 0.05, in both). Plasma-PCR is useful to predict an increased risk for BKVAN, and regular monitoring is effective to prevent the development of BKVAN.

Novel approach for improved assessment of phenotypic and functional characteristics of BKV-specific T-cell immunity.

BACKGROUND: BKV-associated nephropathy represents a serious complication of the posttransplant period in kidney transplant recipients. Monitoring BKV-specific immunity is of a special importance for estimation of clinical course in patients with BKV reactivation. Our recent data demonstrated that all five BKV antigens are immunogenic and elicit T-cell responses varying within patients. Therefore, all five BKV proteins should be evaluated for the assessment of BKV-specific immunity. However, analysis of five proteins performed separately is time- and cost-intensive and requires large amount of blood. METHODS: Using novel approach of a mixture of overlapping peptide pools encompassing all five BKV antigens (viral protein [VP] 1, VP2, VP3, large tumor antigen, and small tumor antigen) and multiparameter flow cytometry, we evaluate BKV-specific T cells in patients with a previous/present severe long-lasting or transient BKV reactivation. Patients without BKV reactivation were used as control. RESULTS: In this study, we show that using mixture of overlapping peptide pool results in the magnitude of CD4- and CD8-positive BKV-specific T-cell response, which is significantly higher compared with any frequencies detected by previously used single BKV antigen stimulation. Of interest, patients with a history of rapid BKV clearance had significantly higher frequency of multifunctional interferon gamma-γ/interleukin (IL)-2/tumor necrosis factor-α and IL-2/tumor necrosis factor-α CD4-positive T cells, suggesting protective potential of polyfunctional T cells. Furthermore, we did not find IL-17-producing BKV-specific memory T cells in patients recovered from BKV reactivation. CONCLUSIONS: Here, we established a fast and sensitive approach allowing the most comprehensive assessment of the total BKV immunity performed to date and offer a new platform for further prospective studies.

Cost-efficient screening for BK virus in pediatric kidney transplantation: a single-center experience and review of the literature.

BKVNP is an increasingly recognized cause of graft dysfunction and loss in kidney transplant recipients. Protocols for BKV screening and for the diagnosis of BKVNP are still evolving. PCR-based BKV detection became available at our institution in 2007, when we began using it according to published guidelines. We subsequently reviewed our experience with urine and plasma BKV PCR testing in our pediatric kidney transplant recipient population. We found rates of viruria, viremia, and BKVNP that were similar to the published literature. We also conducted a cost analysis suggesting that urine PCR testing, as used by us, is not cost efficient in the detection of BKV. We conclude that plasma only-based PCR testing for BKV may be sufficient in most clinical settings.

Screening to prevent polyoma virus nephropathy in kidney transplantation: a cost analysis.

Polyoma virus nephropathy is an important cause of graft dysfunction in kidney transplant recipients and screening to prevent disease has been advocated. Although screening incurs new costs, our hypothesis is that savings from less immunosuppression in those with positive screening tests could pay for overall costs of screening. In 134 consecutive recipients, polyoma virus (positive decoy cells) was detected in the urine of 34 (25.4%) individuals over a 2-year follow-up. Of these 34, 11 had a plasma BK PCR of >7700 copies/mL. Immunosuppression was reduced stepwise in these patients until viral loads fell <1000/mL. Overall screening costs (including extra plasma PCR testing) were estimated at $33,450. Those with positive PCR had greater reductions in annual immunosuppression costs by year 2 ($6452 vs. $2799, p = 0.0015) compared to those with negative screens. At the end of the 2-year period, 61% of the screening costs were covered by less immunosuppressant costs. At the end of 30 months there were net savings. In summary, reductions in immunosuppression cover the cost of screening for polyoma viral infection. Longer-term follow-up is needed to ensure patient outcomes remain acceptable.

A cost too high to bear? Prophylaxis versus preemptive therapy to prevent post-transplantation cytomegalovirus.

Both prophylaxis and preemptive therapy are used to prevent the development of cytomegalovirus (CMV) disease after transplantation. Preemptive therapy exposes the least number of patients to costly and potentially toxic drugs. Prophylaxis is less labor intensive and requires less expensive monitoring. While the overall cost of the two modalities is similar, current literature suggests that prophylaxis has an advantage in avoiding secondary effects of CMV. Randomized comparative trials are imperative.

The use of consensus guidelines for management of cytomegalovirus infection in renal transplantation.

Cytomegalovirus (CMV) infection imposes a significant economic burden on susceptible patients after renal transplantation. Our study was conducted to determine the prediction, probability, consequences, and treatment costs of CMV infection under Canadian consensus guidelines in 270 sequential transplant patients. Transplant patients from donors positive (D(+)) for CMV into recipients negative (R(-)) for CMV received antiviral prophylaxis for 14 weeks and all but donor negative (D(-))/R(-) patients were monitored weekly for the CMVpp65 marker expression. Marker-positive patients and patients with CMV infection or disease received antiviral treatment. Within the first 6 months, 27% of the 270 patients tested had incidences of asymptomatic CMV infection, while 9% had CMV syndrome or disease. Only 1% of patients had infection after 6 months. The CMVpp65 marker levels were significantly greater in patients with syndrome or disease; but post-test probabilities and predictive value of the marker assay were low. Mean direct costs for care were $2256 and ranged from $927 for D(-)/R(-) patients to $7069 in the D(+)/R(-) patients. Extension of antiviral prophylaxis to D(+) or D(+)/R(+) patients significantly increased the estimated mean costs for an absolute reduction to 4% in CMV syndrome or disease. Our studies show that current guidelines for treatment enable effective control of CMV infection; however, alternative strategies have different economic impact.

Case studies in cost effectiveness of molecular diagnostics for infectious diseases: pulmonary tuberculosis, enteroviral meningitis, and BK virus nephropathy.

Pathogen genome amplification is used to detect and identify microorganisms, assess response to therapy, and detect mutations associated with drug resistance. Nucleic acid amplification tests have been shown to be superior to conventional culture-based testing methods in many circumstances. However, the enthusiasm for the technology in clinical laboratories may be decreased by the practical considerations of cost, complexity of the technology, and lack of US Food and Drug Administration-approved tests. The impact of nucleic acid amplification tests on the diagnosis and management of patients with tuberculosis, enteroviral meningitis, and BK virus transplant nephropathy will be examined, with an emphasis on the potential for health care cost savings.

Prophylactic versus preemptive oral valganciclovir for the management of cytomegalovirus infection in adult renal transplant recipients.

Prophylaxis reduces cytomegalovirus (CMV) disease, but is associated with increased costs and risks for side effects, viral resistance and late onset CMV disease. Preemptive therapy avoids drug costs but requires frequent monitoring and may not prevent complications of asymptomatic CMV replication. Kidney transplant recipients at risk for CMV (D+/R-, D+/R+, D-/R+) were randomized to prophylaxis (valganciclovir 900 mg q.d. for 100 days, n=49) or preemptive therapy (900 mg b.i.d. for 21 days, n=49) for CMV DNAemia (CMV DNA level>2000 copies/mL in >or=1 whole blood specimens by quantitative PCR) assessed weekly for 16 weeks and at 5, 6, 9 and 12 months. More patients in the preemptive group, 29 (59%) than in the prophylaxis group, 14 (29%) developed CMV DNAemia, p=0.004. Late onset of CMV DNAemia (>100 days after transplant) occurred in 11 (24%) randomized to prophylaxis, and none randomized to preemptive therapy. Symptomatic infection occurred in five patients, four (3 D+/R- and 1 D+/R+) in the prophylactic group and one (D+/R-) in the preemptive group. Peak CMV levels were highest in the D+/R- patients. Both strategies were effective in preventing symptomatic CMV. Overall costs were similar and insensitive to wide fluctuations in costs of either monitoring or drug.

Periodic assessment of urine and serum by cytology and molecular biology as a diagnostic tool for BK virus nephropathy in renal transplant patients.

OBJECTIVE: To investigate the significance of polyomavirus (PV) viruria and viremia by morphologic, immunohistochemical and molecular analysis (multiplex nested-polymerase chain reaction) in renal transplant patients. STUDY DESIGN: Urine (n=328), serum (n= 53) and renal biopsies (n=24) from renal transplant patients (n=106) were studied. RESULTS: Decoy cells were found in 53 samples (16%) from 19 patients (18%); viral DNA was amplified in all urinary samples and disclosed BK virus (BKV) (n=24), JC virus (JCV) (n=16), and JCV and BKV DNA (n=13). BKV was the prevailing genotype in patients with a high frequency of decoy cell excretion (p = 0.001). JCV excretion correlated with a low number (p = 0.01) and BKV with a high number of decoy cells (p=0.003). PV DNA was amplified from 30/53 serum samples (56.6%); BKV was the prevailing genotype (p = 0.04). On 24 renal biopsies (18 from the decoy cell-negative and 6 from the decoy cell-positive group) PV nephropathy (PVN) was identified and BKV DNA amplified in 4 biopsies, all from the group with a high frequency of decoy cell excretion. PVN was not identified in renal biopsies from the decoy cell-negative group. CONCLUSION: PV infection is frequent in renal transplant patients. The BKV genotype in urine and serum is significantly related to a high frequency and high number of decoy cells. PVN occurs only in patients with BKV viremia and a high number and frequency of decoy cell excretion in urine. In the absence of decoy cells, PVN can be excluded. Cytologic analysis of urine is an important diagnostic tool for screening renal transplant patients at risk of PVN.