Polyomavirus replicates in differentiating but not in proliferating tubules of adult mouse polycystic kidneys

Biopsy-proven BK virus nephropathy in kidney transplant patients: risk factors, prevalence and treatment approach

Purpose: BK virus nephropathy (BKVN) is a latent infection and it is closely associated with immunsuppressive therapy. We aimed in this study to evaluate biopsy-proven BKVN and investigate frequency, risk factors and treatment management. Materials and Methods: In this study, 422 kidney transplant recipients were analysed retrospectively between April 2014 and April 2020 for biopsy-proven BK virus nephropathy. Group I included 16 kidney transplant patients with biopsy-proven BK nephropathy and group II included 36 kidney transplant patients with negative BK virus nephropathy. We aimed demographic, clinical features of kidney transplant recipients with BKVN (group I, n: 16 ) and non-BKVN (group II, n:36) were compared and the factors affecting of BKVN. Results: The mean age of grup I and group II were were 41±14.8 years and 39±15.2 respectively. The patients mean follow-up period of 43±11.2 months. Serum creatinine and proteinuria degree were significantly higher in the group with BKVN. In order to reduce the dose of immunosuppression in patients with BKVN, tacrolimus treatment was discontinued in 8 patients, and they were switched to everolimus + MMF + prednisone treatment, leflunamide + MMF + prednisone treatment in 4 patients, and sirolimus + MMF + prednisone treatment in 4 patients. The mean serum creatinine level of the patients who were followed up were observed as 1.78±0.98 mg/dl in group I. Conclusion: In our center, the prevalance of BKVN was found 3.92% during the study period. Reduction of dose immunosuppressive therapy is the most effective treatment. It is thought that there was no differences between Leflunamide and other approaches for treatment. Early diagnosis and screening (frequently intervals) seems to be most effective way for BKVN.

Comparison of BK virus nephropathy risk between double-J-stent with anti-reflux mechanism and standart double-J-stent: single-center experience

Aim: Ureteral stend use is a risk factor for BK nephropathy (BKVN). In 2015, we compared the patients with anti-reflux mechanism DJS (ARD-DJS) and those used standard DJS (st-DJS) in terms of BKV and BKVN frequency in 90 kidney transplant patients in two centers. With the increase in the number of our patients over time and lengthening of the follow-up duration, we needed to re-evaluate the data in one center. Material and Method: We retrospectively evaluated 211 patients who underwent kidney transplantation at Gazi Yaşargil Training and Research Hospital between September 2012 and September 2019. The following parameters were recorded, demographic data, immunosuppression protocols, presence of rejection, graft loss, plasma BKV levels, and presence of BKVN. Median and IQR follow-up time for ARD-DJS and St-DJS patients was 72 months (62,5-80,3 months) and 27,8 months (17,4-39,6 months) respectively. Results: Thirteen patients (6,1%) had BKV viremia. BKVN was revealed by kidney biopsy in 3 of 13 patients. However, graft loss due to BKVN was observed in only one patient. ARD-DJS was used in 4 of these cases and standard DJS was used in 9 of these cases. Patients in whom BKV revealed in the first 3 months were compared in the aspect of DJS technique, BKV was significantly less observed in the ARD-DJS group (ARD-DJS: 2 patients; St-DJS:9 patients), (p=0,046). Conclusion: In our study, BKV was observed less in patients with ARD-DJS that were clinically significant but not statistically significant. Therefore, prospective randomized studies with high patient numbers are needed to determine the effectiveness of ARD-DJS.

The impact of prophylactic ureteral stenting during kidney transplantation on postoperative surgical outcomes

Background

The aim of this study was to evaluate the safety and feasibility of prophylactic ureteric stenting during kidney transplantation (KT).

Methods

The authors retrospectively reviewed patients who underwent KT between June 2016 and June 2019. The prophylactic ureteral stenting group (double-J [DJ]) and no-stent group (no-DJ) were compared with respect to the clinical data and surgical outcomes.

Results

A total of 42 patients underwent KT; 17 patients were classified into the DJ group and 25 patients into the no-DJ group. Antithymocyte globulin induction and donor-specific antibody positivity were significantly higher in the DJ group. There were no significant differences between the groups in terms of symptomatic urinary tract infection (UTI). The time to postoperative UTI was significantly shorter in the DJ group than in the no-DJ group (33.5±7.8 vs. 105.3±71.6 days, P=0.013). The development of postoperative BK viremia was significantly higher in the no-DJ group (0.0% vs. 16.0%, P=0.035). Urologic complications were significantly higher in the no-DJ group (0.0% vs. 16.0%, P=0.035). In the no-DJ group, urologic complications occurred in four patients ureteroneocystostomy stenosis in three patients and ureteroneocystostomy leakage in one patient. Percutaneous ureteral interventions were performed for all patients using percutaneous nephrostomy and reno-uretero-vesical stenting. However, there were no postoperative urologic complications in the DJ group.

Conclusions

Prophylactic ureteric stenting during KT may be safe and feasible without significantly increasing the incidence of UTI and BK viremia. Additionally, prophylactic ureteric stenting may reduce urologic complications after KT.

Externalized Percutaneous Stent Versus Internal Double J Stent: Short- and Long-term Complications After Kidney Transplantation

BACKGROUND

In patients undergoing kidney transplantation, ureteral stents are an established technique to reduce major urologic complications such as leakage and stenosis of the ureter. However, the best technique for ureteral stenting remains unclear. The aim of this study was to compare the outcome of percutaneous ureteral stents (PS) with internal double J stents (JJS) after kidney transplantation.

METHODS

All patients undergoing kidney transplantation between 2005 and 2014 were retrospectively analyzed. After excluding patients <18 years old, patients without stenting, and patients who underwent multiorgan transplantation, a total of 308 patients were included in the study. Two consecutive cohorts of patients were compared. In the cohort transplanted between 2005 and 2010, stenting was routinely performed using PS (216 patients), and in the second cohort, those transplanted after 2011, stenting was routinely performed using JJS (92 patients). For ureteric anastomosis, the Lich-Grégoir technique was used in all patients.

RESULTS

There was no statistical difference in postoperative urinary tract infections (P = .239) between the 2 cohorts. In patients with PS, the incidence of major urologic complications (11.6% vs 3.3%; P = .018), vesicoureteral reflux (14.3% vs 2.2%; P < .001), and urologic reinterventions (14.4% vs 5.4%; P = .031) was significantly higher when compared with JJS patients. Multivariable logistic regression revealed increased incidence of major urologic complications (odds ratio [OR] 3.66, 95% confidence interval [CI] 1.07-12.55, P = .039) and vesicoureteral reflux (OR 5.29, 95% CI 1.21-23.10, P = .027) in patients with PS compared with JJS.

CONCLUSION

Stenting of ureterovesical anastomosis using JJS is associated with reduced complications compared with PS after kidney transplantation.

Kidney transplant recipients with polycystic kidney disease have a lower risk of post-transplant BK infection than those with end-stage renal disease due to other causes

BACKGROUND

Polyomavirus-associated nephropathy is associated with high risk of kidney allograft loss. Whether the cause of native end-stage renal disease influences the risk of BK infection is unclear.

METHODS

A retrospective, single-center study of 2741 adult kidney transplant recipients between 1994 and 2014 was performed. Recipients had end-stage renal disease due to polycystic kidney disease (PKD, n = 549), diabetes mellitus (DM, n = 947), hypertension (HTN, n = 442), or glomerulonephritis (GN, n = 803).

RESULTS

A total of 327 recipients (12%) developed post-transplant BK viremia over a median follow-up time of 5 years. The incidence rate of BK viremia was lowest in patients with PKD (1.46 per 100 person-years) compared to other causes of ESRD (DM = 2.06, HTN = 2.65, and GN = 2.01 per 100 person-years). A diagnosis of PKD was associated with a lower risk of post-transplant BK viremia (adjusted HR (95% CI) = 0.67 (0.48-0.95), P = 0.02). BK nephropathy was significantly less common in patients with PKD (0.21 per 100 person-years) compared to those with HTN (0.80 per 100 person-years, P ≤ 0.001). Among patients with PKD, the risk of BK viremia was lower in patients with nephrectomy, compared to those without nephrectomy (adjusted HR (95% CI) = 0.42 (0.19-0.92), P < 0.05).

CONCLUSION

ESRD due to PKD is associated with a lower risk of post-transplant BK infection. The renal tubular epithelial cells in PKD are unique; they are in a proliferative but non-differentiated state. Whether this characteristic of renal tubular epithelial cells alters the BK viral reservoir or replication in PKD patients warrants further study.

Polyomavirus Persistence

Mammalian polyomaviruses are characterized by establishing persistent infections in healthy hosts and generally causing clinical disease only in hosts whose immune systems are compromised. Despite the fact that these viruses were discovered decades ago, our knowledge of the mechanisms that govern viral persistence and reactivation is limited. Whereas mouse polyomavirus has been studied in a fair amount of detail, our understanding of the human viruses in particular is mostly inferred from experiments aimed at addressing other questions. In this review, we summarize the state of our current knowledge, draw conclusions when possible, and suggest areas that are in need of further study.

Ureteral stent placement and BK viremia in kidney transplant recipients

INTRODUCTION

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.

METHODS

Data were collected on consecutive kidney-only transplant recipients between December 1, 2006 and June 30, 2010. All patients had at least 12 months of follow-up.

RESULTS

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 46 days (range: 11-284) post transplantation; removals occurred within 0-30, 30-60, 60-90, 90-120, 120-150, and >150 days 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 >46 days (P = 0.70) or by the 6-level groupings (P = 0.92).

CONCLUSIONS

Although we observed a significant association of BK viremia with stent placement, no dose-dependent effect was seen.

Lessons in signaling and tumorigenesis from polyomavirus middle T antigen

The small DNA tumor viruses have provided a very long-lived source of insights into many aspects of the life cycle of eukaryotic cells. In recent years, the emphasis has been on cancer-related signaling. Here we review murine polyomavirus middle T antigen, its mechanisms, and its downstream pathways of transformation. We concentrate on the MMTV-PyMT transgenic mouse, one of the most studied models of breast cancer, which permits the examination of in situ tumor progression from hyperplasia to metastasis.

Restriction of human polyomavirus BK virus DNA replication in murine cells and extracts

BK virus (BKV) causes persistent and asymptomatic infections in most humans and is the etiologic agent of polyomavirus-associated nephropathy (PVAN) and other pathologies. Unfortunately, there are no animal models with which to study activation of BKV replication in the human kidney and the accompanying PVAN. Here we report studies of the restriction of BKV replication in murine cells and extracts and the cause(s) of this restriction. Upon infection of murine cells, BKV expressed large T antigen (TAg), but viral DNA replication and progeny were not detected. Transfection of murine cells with BKV TAg expression vectors also caused TAg expression without accompanying DNA replication. Analysis of the replication of DNAs containing chimeric BKV and murine polyomavirus origins revealed the importance of BKV core origin sequences and TAg for DNA replication. A sensitive assay was developed with purified BKV TAg that supported TAg-dependent BKV DNA replication with human but not with murine cell extracts. Addition of human replication proteins, DNA polymerase alpha-primase, replication protein A, or topoisomerase I to the murine extracts with BKV TAg did not rescue viral DNA replication. Notably, addition of murine extracts to human extracts inhibited BKV TAg-dependent DNA replication at a step prior to or during unwinding of the viral origin. These findings and differences in replication specificity between BKV TAg and the TAgs of simian virus 40 (SV40) and JC virus (JCV) and their respective origins implicate features of the BKV TAg and origin distinct from SV40 and JCV in restriction of BKV replication in murine cells.

Ureteral stents: a novel risk factor for polyomavirus nephropathy

Polyomavirus virus nephropathy (PVN) is an important cause of renal allograft dysfunction. The risk factors for the development of PVN have not been completely elucidated. We investigated the hypothesis that ureteral trauma caused by placement of indwelling stents is an independent risk factor for PVN. Twenty cases of PVN were compared with 46 controls. Logistic regression was used to calculate odds ratios and to construct multivariate models. A total of 75% of cases and 35% of controls had stents placed during renal transplantation. In both univariate and multivariate logistic regression analyses adjusting for age, gender, deceased donor transplant, delayed graft function, tacrolimus and exposure to antibodies, the placement of a ureteral stent at the time of kidney transplantation was found to have a statistically significant association with developing PVN. Our findings reveal that the presence of a ureteral stent is associated with an increase in the risk of PVN.

How viruses shape the tree of life

Consideration of virus evolution only from a disease perspective has provided a limited view of virus–host evolution. Such views assume all viruses fit predator/prey models for replication, but fail to explain the origin of disease or how viruses might make significant contributions to host evolution. On a long evolutionary time scale, the ability of a virus to persist in an individual host is a much more prevalent life strategy. Persistence can explain both origins of most viral disease and virus–host evolutionary stability. However, persistence (both genomic and epigenomic) is a much more complex and demanding virus–host relationship that is difficult to study. We must change our attitudes towards persistence if we are to understand how viruses shape the tree of life.

Natural biology of polyomavirus middle T antigen

"It has been commented by someone that 'polyoma' is an adjective composed of a prefix and suffix, with no root between--a meatless linguistic sandwich" (C. J. Dawe). The very name "polyomavirus" is a vague mantel: a name given before our understanding of these viral agents was clear but implying a clear tumor life-style, as noted by the late C. J. Dawe. However, polyomavirus are not by nature tumor-inducing agents. Since it is the purpose of this review to consider the natural function of middle T antigen (MT), encoded by one of the seemingly crucial transforming genes of polyomavirus, we will reconsider and redefine the virus and its MT gene in the context of its natural biology and function. This review was motivated by our recent in vivo analysis of MT function. Using intranasal inoculation of adult SCID mice, we have shown that polyomavirus can replicate with an MT lacking all functions associated with transformation to similar levels to wild-type virus. These observations, along with an almost indistinguishable replication of all MT mutants with respect to wild-type viruses in adult competent mice, illustrate that MT can have a play subtle role in acute replication and persistence. The most notable effect of MT mutants was in infections of newborns, indicating that polyomavirus may be highly adapted to replication in newborn lungs. It is from this context that our current understanding of this well-studied virus and gene is presented.

Ubiquitous human adeno-associated virus type 2 autonomously replicates in differentiating keratinocytes of a normal skin model

Since its discovery in 1966, adeno-associated virus type 2 (AAV) has been described as a helper-dependent parvovirus. However, in this study we demonstrate that AAV undergoes its complete life cycle, devoid of helper viruses or genotoxic agents, in the organotypic epithelial raft tissue culture system, a model of normal skin. AAV progeny production directly correlated with epithelial differentiation, as nondifferentiating keratinocytes were defective for this activity. Large nuclear virus arrays of particles of approximately 26 nm (parvovirus size) were observed in the granular layers of the raft epithelium by electron microscopy. Additionally, dosage-dependent histologic changes, some of which might be interpreted as cytopathology, were induced in the AAV-infected epithelial tissues. These data suggest a new biological model for AAV; that is, AAV is an epithelial-tropic autonomous parvovirus that can alter normal squamous differentiation.

The distribution and kinetics of polyomavirus in lungs of intranasally infected newborn mice

The primary cell types that sustain polyomavirus (Py) replication following intranasal infection as well as the nature of the host cellular response to Py were unknown. As this is an essential and specific site for virus entry, it seems likely that viral gene function must be adapted to these mucosal tissues. Using immunohistochemistry and in situ hybridization, we determined the cell types in the lung that support Py gene expression and replication following intranasal inoculation of newborn mice within 24 h of birth. Lungs were collected daily from days 1 to 10 postinfection for Py DNA and early T antigen analysis and for histological examination by H&E staining, using methods that preserve the delicate newborn lung architecture. Viral DNA was present in increasing quantities from 2 to 6 dpi in a subset of the Clara cells lining the inner lumen of the bronchi and bronchioles, while T antigen expression was present in a majority of the cells in the bronchi and bronchiole lumen. A distinct and transient pattern of hyperplasia was observed among the cells expressing T antigen and was present from 3 through 6 dpi. Py DNA-containing cells exfoliated into the bronchiole lumen and alveolar ducts, but Py T antigen was not detected in these cells. Py DNA was first detected at 2 dpi, increased through 6 dpi, and abruptly declined through 9 dpi at which time there was no sign of viral DNA in the lungs by in situ hybridization. An unusual infiltration of neutrophils began before the presence of exfoliated cells or Py replication and continued for 2-3 days and was followed by a lymphocytic infiltration at 8-10 dpi lasting 2-3 days. Neither the hyperplasia nor the neutrophil infiltration occurred following infection with the MOP1033 MT-Ag or RB1 LT-Ag mutants of Py. In addition, both the neutrophil infiltration and the transient hyperplasia are in stark contrast to the heavy macrophage infiltration that follows infection of lungs with mouse adenovirus. Thus it appears that Py elicits a distinct host response pattern not seen with other DNA viral infections.

Synthesis of infectious human papillomavirus type 18 in differentiating epithelium transfected with viral DNA

The lack of a permissive system for the propagation of viral stocks containing abundant human papillomavirus (HPV) particles has hindered the study of infectivity and the early stages of HPV replication. The organotypic (raft) culture system has permitted the study of a number of the differentiation-specific aspects of HPV, including amplification of viral DNA, expression of late genes, and viral morphogenesis. However, these investigations have been limited to a single virus type, namely, HPV type 31 (HPV31). We have artificially introduced linearized HPV18 genomic DNA into primary keratinocytes by electroporation, followed by clonal expansion and induction of epithelial stratification and differentiation in organotypic culture. We report the synthesis of infectious HPV18 virions. Virus particles approximately 50 nm in diameter were observed by electron microscopy. HPV18 virions purified by isopycnic gradient were capable of infecting keratinocytes in vitro, as shown by the expression of multiple HPV18-specific, spliced transcripts.

Potential role of DNA polymerase beta in gene therapy against cancer: a case for colorectal cancer

Genetic instability characterized by the accumulation of mutations of tumor suppressor genes and oncogenes appears to be associated with carcinogenesis in colorectal and other cancers. Mutations of DNA polymerase beta (pol beta) and related chromosomal alterations appear to be consistent with the causal role of a "mutator phenotype' in carcinogenesis. However, homozygous knockout pol beta mutations appear to interfere with embryogenesis. Increased pol beta activity (i.e. relative to pol alpha activity) has been associated with cell cycle arrest. The related aphidicolin-resistant DNA replication has been observed primarily in differentiating cells, including the mammalian blastocyst, adrenal cortex, thyroid, anterior pituitary, and the mechanism of endoreduplication (amitotic over-replication of DNA) can be traced to lower eukaryotes. This increased activity in relation to terminal commitment is inconsistent with a simple "DNA repair' view of pol beta. It is therefore proposed that pol beta may play a more fundamental role in cellular differentiation through involvement in a putative subgenomic DNA replication-based model of terminal gene expression. Thus genetic instability, loss of differentiation, and carcinogenesis may result from aberration(s) or "derailment' of such replication-based mechanism of terminal gene expression. It is suggested to examine the relationship of DNA pol beta to genomic instability and carcinogenesis using genetic analyses and antisense technology with possible applications for gene therapy against colorectal cancer.

Differentiation-dependent up-regulation of the human papillomavirus E7 gene reactivates cellular DNA replication in suprabasal differentiated keratinocytes

mRNA transcription, DNA amplification, and progeny production of human papillomaviruses (HPVs) are closely linked to squamous epithelial differentiation in patient papillomas. Because suprabasal, differentiated keratinocytes have exited the cell cycle for days or weeks and because viral DNA synthesis requires the host DNA replication machinery, HPVs must have a mechanism to reactivate the essential host genes. In this study, we show via acute recombinant retrovirus infection that an intact E7 gene of either high-risk or of low-risk HPV genotypes, under the control of its respective native enhancer-promoter, induced proliferating cell nuclear antigen (PCNAs) expression in the suprabasal cells of epithelial raft cultures of primary human foreskin keratinocytes (PHK). The cellular differentiation program was unaltered by the viral oncoprotein; it was essential for high HPV promoter activity. Furthermore, extensive host chromosomal DNA replication took place in differentiated cells of HPV-18 E7-expressing raft cultures and of patient laryngeal papillomas caused by HPV-6. These results indicate that the main function of the E7 protein is to reactivate host DNA replication machinery to support viral replication in differentiated, noncycling cells.

The evolution of small DNA viruses of eukaryotes: past and present considerations

Historically, viral evolution has often been considered from the perspective of the ability of the virus to maintain viral pathogenic fitness by causing disease. A predator-prey model has been successfully applied to explain genetically variable quasi-species of viruses, such as influenza virus and human immunodeficiency virus (HIV), which evolve much faster rates than the host. In contrast, small DNA viruses (polyomaviruses, papillomaviruses, and parvoviruses) are species specific but are stable genetically, and appear to have co-evolved with their host species. Genetic stability is attributable primarily to the ability to establish and maintain a benign persistent state in vivo and not to the host DNA proofreading mechanisms. The persistent state often involves a cell cycle-regulated episomal state and a tight linkage of DNA amplification mechanisms to cellular differentiation. This linkage requires conserved features among viral regulatory proteins, with characteristic host-interactive domains needed to recruit and utilize host machinery, thus imposing mechanistic constrains on possible evolutionary options. Sequence similarities within these domains are seen amongst all small mammalian DNA viruses and most of the parvo-like viruses, including those that span the entire spectrum of evolution of organisms from E. coli to humans that replicate via a rolling circle-like mechanism among the entire spectrum of organisms throughout evolution from E. coli to humans. To achieve benign inapparent viral persistence, small DNA viruses are proposed to circumvent the host acute phase reaction (characterized by minimal inflammation) by mechanisms that are evolutionarily adapted to the immune system and the related cytokine communication networks. A striking example of this is the relationship of hymenoptera to polydnaviruses, in which the crucial to the recognition of self, development, and maintenance of genetic identity of both the host and virus. These observations in aggregate suggest that viral replicons are not recent "escapies" of host replication, but rather provide relentless pressure in driving the evolution of the host through cospeciation.