Temporal serum creatinine increase and exacerbation of tubulointerstitial inflammation during the first two months in resolving polyomavirus BK nephropathy

Challenges and opportunities in research on BK virus infection after renal transplantation

Renal transplantation is one of the primary approaches for curing end-stage kidney disease. With advancements in immunosuppressive agents, the short-term and long-term survival rates of transplanted kidneys have significantly improved. However, infections associated with potent immunosuppression have remained a persistent challenge. Among them, BK virus (BKV) reactivation following renal transplantation leading to BK virus-associated nephropathy (BKVAN) is a major cause of graft dysfunction. However, we still face significant challenges in understanding the pathogenesis, prevention, diagnosis, and treatment of BKVAN. These challenges include: 1. The mechanism of BKV reactivation under immunosuppressive conditions has not been well elucidated, leading to difficulties in breakthroughs in clinical research on prevention, diagnosis, and treatment. 2. Lack of proper identification of high-risk individuals, and effective personalized clinical management strategies. 3.Lack of early and sensitive diagnostic markers. 4. Lack of direct and effective treatment options due to the absence of specific antiviral drugs. The purpose of this review is to summarize the current status and cutting-edge advancements in BKV-related research, providing new methods and perspectives to address future research challenges.

Peritubular and Tubulointerstitial Inflammation as Predictors of Impaired Viral Clearance in Polyomavirus Nephropathy

Introduction: Polyomavirus-associated nephropathy (BKPyVAN) is a common complication in kidney transplant recipients. The histological changes in the context of BKPyVAN and their association with the viral load and outcomes are still being investigated. Methods: This retrospective study involved 100 adult patients transplanted between 2000 and 2021, with available archived biopsy slides, aiming to analyze associations between viral load clearance in the blood (reduction in BKPyVAN-DNAemia below detection level) and histological features in biopsy-proven BKPyVAN. A kidney pathologist blinded to the clinical data reassessed the BANFF 2019 lesion scores in the BKPyVAN index biopsy. The primary endpoint was viral clearance three months after the diagnosis. Results: The presence of tubulointerstitial inflammation, peritubular capillaritis, and higher PVN Class at the diagnosis was linked to a reduced likelihood of viral clearance three months later (interstitial inflammation OR = 0.2, 95% CI [0.07-0.55], tubulitis OR = 0.39, 95% CI [0.21-0.73], peritubular capillaritis OR = 0.25, 95% CI [0.08-0.82], PVN Score OR = 0.1, 95% CI [0.03-0.4]), independently of other covariates. Combining the four lesions using the ROC analysis enhanced their capability to predict persistent BK viremia after 3 months with an AUC of 0.94. Conclusions: The presence of interstitial inflammation, tubulitis, and peritubular capillaritis, as well as the higher PVN Score, was associated with an up to 90% lower likelihood of viral load clearance three months post-diagnosis. These findings underscore the importance of histological evaluation as a surrogate of subsequent viral clearance and offer valuable insights for the management of BKPyVAN.

Polyomavirus nephropathy: diagnosis, histologic features, and differentiation from acute rejection

Polyomaviruses, particularly BK virus, are ubiquitous latent infections that may reactivate with immunosuppression during kidney transplantation, resulting in polyomavirus nephropathy (PVN). The levels of viruria and viremia serve as tools for screening and making a presumptive diagnosis of PVN, respectively, while a definitive diagnosis requires a kidney biopsy. There are histologic classifications of PVN based on the extent of tubular cell viral infection, interstitial fibrosis, and interstitial inflammation. These classifications correlate to some degree with graft function and loss, aiding in determining treatment efficacy and prognostication. PVN has histologic overlap with acute cell-mediated rejection, making the differential diagnosis challenging, although there are suggestive features for these different causes of graft dysfunction. This article reviews the diagnosis, histologic findings, and classifications of PVN, and discusses how to differentiate viral nephropathy from acute rejection.

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.

Comparison of Immunohistochemical Staining for Large T Antigen and Capsid Protein VP1 in BK Polyomavirus-Associated Nephropathy

AIM

Most transplant centres use SV40 large T antigen (TAg) staining for the diagnosis and assessment of BK polyomavirus-associated nephropathy (BKPyVAN). This study was performed to evaluate the significance of capsid protein VP1 expression in BKPyVAN.

METHODS

We performed immunohistochemical staining using anti-SV40 TAg and anti-BKPyV VP1 antibodies in 16 index biopsies and 12 re-biopsies of BKPyVAN and compared the patterns of positivity and the percentage of positive tubules by counting whole specimens. We investigated the correlation between serum creatinine increase from baseline and the percentage of positive tubules for both markers in 16 index biopsies.

RESULTS

In VP1 staining, positive findings were observed not only in the nuclei of tubular epithelial cells but also in the cytoplasm, cells shedding into the lumen, intra-tubular casts, and in the interstitium. Two of 28 biopsies (7.1%) showed TAg-positive and VP1-negative results, in which TAg-positive cells were detected only in a single tubule. The median (interquartile range) percentage of positive tubules was 2.8% (0.7-9.8%) for TAg and 1.4% (0.5-3.9%) for VP1 staining (p = 0.2). In 16 index biopsies, serum creatinine increases significantly correlated with the percentage of VP1-positive tubules (r = 0.49, p = 0.02), while this correlation revealed borderline significance with TAg-positive tubules.

CONCLUSIONS

VP1 expression showed various patterns, but was detected in half as many tubules as TAg staining, which might lead to false negatives in the samples with minimal viral replication. However, increased VP1-positive tubules indicate advanced tubular damage and possible association with graft dysfunction.

Viral infections directly involved in kidney allograft function

Modern immunosuppressive therapy has dramatically reduced the incidence of acute rejection and improved graft survival in kidney transplant patients. However, infectious complications remain an important issue. Amongst the various pathogens, viruses such as adenovirus and polyomavirus BK can directly cause acute or chronic graft dysfunction. Adenovirus mainly causes haemorrhagic cystitis and tubulointerstitial nephritis in kidney transplant patients. While patients show apparent clinical symptoms such as fever, dysuria, gross haematuria, frequency and urgency of urination, and most patients show acute graft dysfunction, these symptoms and graft dysfunction are reversible. Polyomavirus BK infection, however, is asymptomatic but graft outcome is poor if the patient develops tissue-invasive nephropathy confirmed by graft biopsy. Recently, an attempt to create a pathological classification for predicting the clinical course has been made by the Banff Working Group on Polyomavirus Nephropathy. With regards to treatment, the basic strategy is a reduction of calcineurin inhibitor and/or antimetabolites, and the effectiveness of several adjunct treatments has been investigated in several clinical trials. There are other unresolved issues, such as the diagnosis of subsequent acute rejection, the definition of remission, methods of resuming immunosuppression and long-term follow-up. Most of all, development of effective vaccines and novel drug discovery are necessary to prevent the development and progression of BKV-associated nephropathy.

Histological Evolution of BK Virus-Associated Nephropathy: Importance of Integrating Clinical and Pathological Findings

Long-term clinicopathological studies of BK-associated nephropathy (PyVAN) are not available. We studied 206 biopsies (71 patients), followed 3.09 ± 1.46 years after immunosuppression reduction. The biopsy features (% immunostain for PyV large T ag + staining and inflammation ± acute rejection) were correlated with viral load dynamics and serum creatinine to define the clinicopathological status (PyVCPS). Incidence of acute rejection was 28% in the second biopsy and 50% subsequently (25% mixed T cell-mediated allograft rejection (TCMR) + antibody-mediated allograft rejection (AMR); rejection overall affected 38% of patients (>50% AMR). Graft loss was 15.4% (0.8-5.3 years after PyVAN); 76% had complete viral clearance (mean 28 weeks). The only predictors of graft loss were acute rejection (TCMR p = 0.008, any type p = 0.07), and increased "t" and "ci" in the second biopsy (p = 0.006 and 0.048). Higher peak viremia correlated with poorer viral clearance (p = 0.002). Presumptive and proven PyVAN had similar presentation, evolution, and outcome. Late PyVAN (>2 years, 9.8%) justifies BK viremia evaluation at any point with graft dysfunction and/or biopsy evaluation. This study describes the histological evolution of PyVAN and corresponding clinicopathological correlations. Although the pathological features overall reflect the viral and immunological interactions, the PyVAN course remains difficult to predict based on any single feature. Appropriate clinical management requires repeat biopsies and determination of the PyVCPS at relevant time points, for corresponding personalized immunosuppression adjustment.

Estimated dietary intake and major food sources of polyphenols in elderly of Viçosa, Brazil: a population-based study

PURPOSE

Epidemiological studies have remarked the beneficial role that polyphenols may have in the elderly population such as cancer and cardiovascular disease prevention. This is particularly relevant considering the global tendency of population aging. Data on polyphenol intake in the elderly population are scarce and usually provide partial information-only for some polyphenol classes. The aim of this study was to estimate the intake of polyphenols and its major dietary contributors in the population of Viçosa.

METHODS

A cross-sectional population-based survey including 620 elderly was conducted in Viçosa, Brazil. Food intake was estimated by recall of habitual consumption (RHC). Polyphenol intake was calculated by matching food consumption data from the RHC with the polyphenol content in foods listed in the Phenol-Explorer database.

RESULTS

The average total polyphenol intake was 1198.6 mg/day (533.7 mg/day as aglycone). The main polyphenol classes were phenolic acids (729.5 mg/day) and flavonoids (444.7 mg/day). The main dietary contributors for total polyphenols were coffee (45.8%), beans (32.8%) and polenta (1.3%). A total of 292 polyphenols divided in 14 classes and 23 subclasses were found. The individual compounds with the highest intake were isomers of chlorogenic acid (i.e., 5-caffeoylquinic acid, 4-caffeoylquinic acid and 3-caffeoylquinic acid) among hydroxycinnamic acids that largely originated from coffee.

CONCLUSIONS

The data reported here can be used to evaluate the association between the amount and type of ingested polyphenols and health outcomes in epidemiological studies in order to eventually establish nutritional recommendations.