BK virus-induced tubulo-interstitial nephritis in a renal transplant recipient

We present a case of renal BK virus infection with renal allograft dysfunction. Renal allograft biopsy showed mononuclear infiltrates in the interstitium and viral inclusions in the tubular epithelial cells. Infected cells were stained with an anti-polyomavirus antibody. The polymerase chain reaction (PCR) performed on blood, urine, and on the DNA extracted from renal tissue showed the presence of the BK virus DNA sequence. The immunosuppressive therapy including tacrolimus, prednisone, and mycophenolate mofetil was reduced leading to an improvement of the renal function. BK virus infection is now recognized as a cause of renal allograft dysfunction, and has been observed with increasing frequency in recent years. Reactivation of the latent virus occurs in immunocompromised hosts such as organ recipients with immunosuppressive treatment. Histologically, renal BK virus infection is characterized by a lymphocytic interstitial infiltrate, and could mimic acute rejection. The pathologist should diagnose the viral infection and may be helped by urine cytology and immunohistochemistry. An accurate diagnosis is important because antirejection therapy favors the decline of the renal function. Enhanced new immunotherapy protocols seem to be the main risk factor for this infection. The response to reduced immunosuppression is variable with reports of an end stage renal failure in 70% of the patients after 18 months.     

Polyomavirus BK DNA quantification assay to evaluate viral load in renal transplant recipients.

BACKGROUND: Several studies have disclosed a correlation between polyomavirus BK (BKV) and interstitial nephritis in renal transplant recipients and its quantification in urine and serum is therefore required to assess the role of BKV infection in nephropathy. OBJECTIVE: This paper describes a urine and serum BKV-DNA quantification protocol devised to evaluate the viral load. STUDY DESIGN: Screening of samples containing > or =10(3)/ml viral genome copies by a semi-quantitative polymerase chain reaction (PCR) assay is followed by precise quantification of the samples containing a high number of viral genomes in a quantitative-competitive (QC)-PCR assay. Generation of the competitor construct relied on the different sizes of wild-type and competitor amplicons. RESULTS AND CONCLUSIONS: Screening by semi-quantitative PCR selects samples with a high number of viral genomes for use in the more labor-intensive and -expensive QC-PCR assay and thus provides a handy means for quantitative DNA analysis of large numbers of samples. The results obtained in BKV-DNA quantification in urine and serum samples from 51 renal transplant recipients (22 on treatment with tacrolimus (FK506) and 29 on cyclosporine A (Cy A)) are interesting: BKV-DNA findings (43.1%) in urine samples are in agreement with the BKV urinary shedding reported in literature (5-45%). With regard to immunosuppressive treatment, the percentage of activation of the infection (revealed by BKV-DNA detection in urine samples) in the two groups of therapy is similar (40.9% vs 44.8%). The observation that the viral load in urine is dissociated with that of serum suggests that both parameters should be investigated in evaluation of the pathogenetic role of BKV reactivation in renal transplant recipients. Moreover, our BKV-DNA quantification protocol could be used to monitor viral load in urine and serum samples from renal transplant recipients so as to detect those at risk of nephropathy and monitor their response to immunosuppression reduction therapy if it occurs.     

Real-time polymerase chain reaction and laser capture microdissection for the diagnosis of BK virus infection in renal allografts

We used real-time polymerase chain reaction (PCR) technology to detect BK virus (BKV) in H and E-stained kidney biopsy sections, using laser capture microdissection. Renal allograft biopsy specimens from 4 patients with the histopathologic diagnosis of BKV-associated nephropathy (BKVAN; group 1) and 3 patients suspected to have BKVAN but without diagnostic histologic features (group 2) were retrieved. Diagnostic inclusion-bearing cells were microdissected by laser capture microscopy from group 1. Renal tubular epithelial cells were microdissected randomly in group 2. DNA was extracted and real-time amplification performed using primers targeting the large "T" and small "t" regions of the BKV and JC virus genomes. Tubular epithelial cells from a case without evidence of BKV infection were used as negative controls in a similar reaction. BKV presence was demonstrated only in epithelial cells containing typical viral inclusions. Group 2 and negative control samples were confirmed as negative for BKVAN. Real-time PCR technology can be used to detect BKV in H and E-stained, paraffin-embedded tissue sections. This technique detected BKV in tubular epithelial cells of renal allografts. To our knowledge, this is the first report of detecting BKV in laser capture microdissected renal biopsy specimens using real-time PCR.     

Analysis of polyomavirus-infected renal transplant recipients' urine specimens: correlation of routine urine cytology, fluorescence in situ hybridization, and digital image analysis

Urinary polyomavirus subtype BK (BKV)-infected urothelial and renal tubular cells, "decoy cells," have been shown to be aneuploid with digital image analysis (DIA). We wanted to determine whether decoy cells cause false-positive fluorescence in situ hybridization (FISH) results in BKV-infected urine samples. Urine samples from 38 renal transplant recipients were split 3 ways and evaluated for number of decoy cells per 10 high-power fields by routine cytology, total nuclear DNA content by DIA, and chromosomal abnormalities by FISH. For DIA, Feulgen-stained cells were quantified with a CAS 200 image analyzer (Bacus Laboratories, Lombard, IL), and for FISH, the UroVysion probe set (Vysis, Downers Grove, IL) consisting of chromosome enumeration probes 3, 7, 17, and locus-specific identifier probe 9p21 (p16 gene) was used. Of the 38 specimens, 32 (84.2%) had evidence of BKV infection by routine cytology. DIA and FISH results were aneuploid/aneusomic in 30 (93.8%) and 4 (12.5%) cases, respectively. All aneusomic FISH specimens occurred in men older than 52 years of age and who also had 4 of the 6 highest PCR-BKV titers. To date, no patient has clinical evidence of malignancy. The 6 specimens without decoy cells were DNA diploid/disomic by DIA and FISH. Abnormal FISH results of urinary decoy cells occur much less frequently than aneuploidy by DIA in renal transplant recipients and might merit close follow-up in some transplant recipients.     

BK virus infection in human immunodeficiency virus-infected patients

The aim of this study is to evaluate the prevalence of BK virus (BKV) infection in HIV-positive patients receiving highly active antiretroviral therapy (HAART) in our hospital. The presence of BKV was analysed in urine and plasma samples from 78 non-selected HIV-infected patients. Clinical data were recorded using a pre-established protocol. We used a nested PCR to amplify a specific region of the BKV T-large antigen. Positive samples were quantified using real-time PCR. Mean CD4 count in HIV-infected patients was 472 cells/mm3 and median HIV viral load was <50 copies/mL. BKV viraemia was detected in only 1 HIV-positive patient, but 57.7% (45 out of 78) had BKV viruria, which was more common in patients with CD4 counts>500 cells/mm3 (74.3% vs 25.7%; p=0.007). Viruria was present in 21.7% of healthy controls (5 out of 23 samples, p=0.02). All viral loads were low (<100 copies/mL), and we could not find any association between BKV infection and renal or neurological manifestations. We provide an update on the prevalence of BKV in HIV-infected patients treated with HAART. BKV viruria was more common in HIV-infected patients; however, no role for BKV has been demonstrated in this population.     

Mechanisms of BK virus infection of renal cells and therapeutic implications

BK virus (BKV) causes BKV nephritis in renal transplant patients and contributes significantly to the increase of probability of graft loss. BKV, being latent in the urogenital tract, is likely to be transported with the donor kidney to recipients and following reactivation replicates in the nucleus of renal epithelial tubular cells. BKV daughter viruses are released and enter other renal epithelial cells to spread infection. There are still a lot of unknown factors about the mechanism and kinetics of BKV infection. The treatment of BKV infection, with exception of reduction in immunosuppression which increases the risk of allograft rejection, is almost exclusively limited to application of anti-viral drugs with rather inconsistent results. The shortcomings of anti-viral therapies demand the understanding of early steps of infection of permissive cells by BK virus in hope that adequate interventional therapies preventing infection of cells with BK virus could be developed. This review describes the BKV entry in target human cells, intracellular trafficking pathways of BKV particles and potential therapeutic implications based on understanding of mechanisms of BKV infection of renal cells.     

Viral infections of renal allografts--an immunohistochemical and ultrastructural study

Viral infections have been recognized as an integral part of both graft injury and rejection. On routine histology, viral infections are diagnosed only when fully established, by the presence of viral inclusions or cytopathic effect. Although renal transplants are routinely done in many centres in India, the incidence of viral infections is largely unkown. This study was aimed at detecting 5 viral infections namely, cytomegalovirus (CMV), BK polyoma Virus (BKV), Herpes Simplex Virus1 and 2 (HSV1 and 2) and Epstein Barr Virus (EBV) in renal biopsies from 321 renal allograft patients, using immunohistochemical and electron microscopic studies. Sixty two biopsies were selected from a total of 414 (belonging to 321 patients) for immunostaining on the basis of features suspicious of viral infections in hematoxylin and eosin stained sections. Immunostaining confirmed CMV infection in 8 biopsies, BKV infection in 31 biopsies and HSV1 in only 2 biopsies. HSV2 and EBV were not detected in any biopsy. Two biopsies showing CMV immunopositivity and 5 of BKV were further processed for electron microscopy, which supported the diagnoses. Thus, the study highlights the prevalence of BKV and CMV infections in renal transplant patients having graft dysfunction, to be 9.3% and 1.9%, respectively. Besides, only one case each was diagnosed as CMV infection and BKV infection in routine histopathological reporting, establishing the importance of immunohistochemical studies in early diagnosis of these viral infections.     

JC virus DNA in the peripheral blood of renal transplant patients: a 1-year prospective follow-up in France

There is little information on JC virus (JCV) infection in renal transplant patients. A long-term prospective follow-up study was conducted to assess the incidence of JCV DNA in the blood of 103 adult renal transplant patients enrolled prospectively between 1 January and 31 December 2006. Patients were monitored until April 2008. JCV DNA was quantified by a real-time polymerase chain reaction in whole blood samples collected regularly for at least 1 year post-transplant. JCV was detected in seven patients (6.8%) (31/1,487 whole blood samples) at a median time of 139 days post-transplant. The median JC virus load of the first positive DNA blood sample was 3.4 log(10) copies/ml (1.9-5.7 log(10) copies/ml). Induction therapy were either anti-CD25 monoclonal antibodies (n = 5) or antithymocyte globulins (n = 2). Post-transplant immunosuppressive treatment included steroids with tacrolimus/mycophenolate mofetil (MMF) (n = 2), or ciclosporin/MMF (n = 1), or belatacept/MMF (n = 4). Two patients were also treated with rituximab. All seven patients infected with JCV had other viral infections(s): BK virus (3), Epstein-Barr virus (2), Cytomegalovirus (1) or both BK virus and Epstein-Barr virus (1). Three patients had BKV-associated nephropathy and decoy cells shedding. JCV infection was not associated with acute rejection episodes or nephropathy, regardless of the virus load. No patient developed progressive multifocal leukoencephalopathy during follow-up. Thus the incidence of JCV infection in renal transplant patients was low and not associated with any specific clinical manifestations. JCV replication must still be diagnosed and differentiated from BK virus infection because of its non-aggressive course.     

The high incidence of JC virus infection in urothelial carcinoma tissue in Taiwan

Human polyomaviruses, JC virus (JCV) and BK virus (BKV), usually remain latent in kidney and urothelial tissue after primary infection. Infection with human polyomavirus has still not been correlated conclusively with malignancy of kidney and urothelial tissue. The present study investigated further the possible relationship between JCV/BKV infection and urothelial carcinoma. Tissue samples were examined from 33 urothelial carcinomas and 5 renal cell carcinomas for JCV/BKV infection, using nested PCR with primers common to both JCV and BKV. The viral genotypes were further verified by endonuclease digestion and DNA sequencing following the PCR. In addition, immunohistochemistry and Western blotting were also performed to detect viral large tumor protein (LT) and the late capsid protein (VP1) in the tissue samples. The results from nested PCR showed that 90.1% (30/33) of the urothelial carcinomas samples and all of the renal cell carcinomas samples (5/5) were JCV DNA positive. Both archetypal and re-arranged JCV genotypes were detected. On the other hand, BKV DNA was detected in only one (3%) of the urothelial carcinoma tissue samples. The immunohistochemical results showed that 30% (10/33) of urothelial carcinoma tissues was stained positive for large tumor antigen (LT). However, the structural protein VP1 was not detectable in any of the tissue samples examined. The present study demonstrated that JCV is highly prevalent in urothelial carcinoma tissue as is the expression of large tumor antigen. Therefore, the findings support the hypothesis that JCV infection is associated with urothelial carcinoma.     

Transforming growth factor-beta-mediated regulation of BK virus gene expression

The increasing prevalence of BK virus (BKV)-associated diseases in immunosuppressed patients has prompted an investigation of the immune response to BKV, especially the role of cytokines in regulating viral replication. We examined the effect of TGF-beta, a cytokine that is stimulated by certain immunosuppressive therapies, on BKV gene expression during lytic infection of renal proximal tubule epithelial cells. Viral gene expression, and specifically the activity of the BKV early promoter, is regulated by TGF-beta in a strain-dependent manner. Promoter activity is upregulated in the presence of TGF-beta for the TU strain of BKV, and not for the Dik, Dunlop, or Proto-2 strains. Using site-directed mutagenesis, we have identified a small segment of the TU promoter that is required for stimulation in response to TGF-beta. These results demonstrate that BKV strains can respond differently to cytokine treatment and suggest that TGF-beta may play a role in the reactivation of BKV.     

Intracellular trafficking pathway of BK Virus in human renal proximal tubular epithelial cells

Intracellular trafficking of BK Virus (BKV) in human renal proximal tubular epithelial cells (HRPTEC) is critical for BKV nephritis. However, the major trafficking components utilized by BKV remain unknown. Coincubation of HRPTEC with BKV and microtubule disrupting agents prevented BKV infection as detected by immunofluorescence and western blot analysis with antibodies which recognize BKV large T antigen. However, inhibition of a dynein, cellular motor protein, did not interfere with BKV infection in HRPTEC. A colocalization study of BKV with the markers of the endoplasmic reticulum (ER) and the Golgi apparatus (GA), indicated that BKV reached the ER from 6 to 10 h, while bypassing the GA or passing through the GA too transiently to be detected. This study contributes to the understanding of mechanisms of intracellular trafficking used by BKV in the infection of HRPTEC.     

Antigen-specific T cell responses to BK polyomavirus antigens identify functional anti-viral immunity and may help to guide immunosuppression following renal transplantation

Infection with the polyoma virus BK (BKV) is a major cause of morbidity following renal transplantation. Limited understanding of the anti-viral immune response has prevented the design of a strategy that balances treatment with the preservation of graft function. The proven utility of interferon-gamma enzyme-linked immunospot (ELISPOT) assays to measure T cell responses in immunocompetent hosts was the basis for trying to develop a rational approach to the management of BKV following renal transplantation. In a sample of transplant recipients and healthy controls, comparisons were made between T cell responses to the complete panel of BKV antigens, the Epstein-Barr virus (EBV) antigens, BZLF1 and EBNA1, and the mitogen phytohaemagglutinin (PHA). Correlations between responses to individual antigens and immunosuppressive regimens were also analysed. Antigen-specific T cell responses were a specific indicator of recent or ongoing recovery from BKV infection (P < 0·05), with responses to different BKV antigens being highly heterogeneous. Significant BKV immunity was undetectable in transplant patients with persistent viral replication or no history of BKV reactivation. Responses to EBV antigens and mitogen were reduced in patients with BKV reactivation, but these differences were not statistically significant. The T cell response to BKV antigens is a useful and specific guide to recovery from BKV reactivation in renal transplant recipients, provided that the full range of antigenic responses is measured.     

BK Polyomavirus Interstitial Nephritis in a Renal Allograft Recipient

Human polyomavirus (PV) interstitial nephritis has recently been recognized as a cause of severe renal allograft dysfunction. It occurs in immunosuppressed patients after reactivation of the latent virus PV type BK (BK virus) in the renal epithelium. BK disease is defined as a morphologically manifest renal infection with cytopathic signs accompanied by varying degrees of interstitial inflammatory cell infiltrates and functional impairment. It is also identified by the presence of cells containing viral inclusion bodies (decoy cells) in the urine. The authors report a case of BK PV interstitial nephritis in a 36-year-old renal allograft recipient. Under light microscopy the chief diagnostic indicator was detection of intranuclear viral inclusions, which were found exclusively in tubular epithelial cells. Cells with viral changes were often enlarged with nuclear atypia and chromatin basophilia. Widespread interstitial plasma cell infiltrates associated with tubulitis were present. Intranuclear paracrystalline arrays of virus particles 35-38 nm in diameter were present as characteristic ultrastructural indicators. Urine samples revealed decoy cells with ground-glass-type intranuclear inclusions positive for BK virus by electron microcopy.     

BK polyomavirus interstitial nephritis in a renal allograft recipient

Human polyomavirus (PV) interstitial nephritis has recently been recognized as a cause of severe renal allograft dysfunction. It occurs in immunosuppressed patients after reactivation of the latent virus PV type BK (BK virus) in the renal epithelium. BK disease is defined as a morphologically manifest renal infection with cytopathic signs accompanied by varying degrees of interstitial inflammatory cell infiltrates and functional impairment. It is also identified by the presence of cells containing viral inclusion bodies (decoy cells) in the urine. The authors report a case of BK PV interstitial nephritis in a 36-year-old renal allograft recipient. Under light microscopy the chief diagnostic indicator was detection of intranuclear viral inclusions, which were found exclusively in tubular epithelial cells. Cells with viral changes were often enlarged with nuclear atypia and chromatin basophilia. Widespread interstitial plasma cell infiltrates associated with tubulitis were present. Intranuclear paracrystalline arrays of virus particles 35-38 nm in diameter were present as characteristic ultrastructural indicators. Urine samples revealed decoy cells with ground-glass-type intranuclear inclusions positive for BK virus by electron microcopy.     

Tubulointerstitial Nephritis Due to a Mutant Polyomavirus BK Virus Strain, BKV(Cin), Causing End-Stage Renal Disease

A renal biopsy from a 36-year-old man with AIDS showed a severe tubulointerstitial nephritis with intranuclear inclusions in epithelial cells. Electron microscopy revealed the characteristic findings of a polyomavirus (PyV) infection, and immunofluorescence indicated the presence of BK virus (BKV) antigen. Inoculation of rhesus monkey kidney cell cultures both with urine and with buffy coat blood cells resulted in a cytopathic response which was subsequently confirmed to be due to BKV. Further characterization of the viral DNA from the kidney by PCR amplification and Southern blot analysis with PyV and strain-specific primers and probes indicated that the virus was closely related to the BK(Dun) strain but different in its apparent sequence arrangement. Subsequent cycle sequencing showed a dinucleotide mutation of TG→AA which substitutes hydrophilic Gln for hydrophobic Leu in a sequence homologous to an origin DNA-binding domain of simian virus 40 T antigen. It is suggested that the mutation and a coding region rearrangement of this strain of BKV designated BKV(Cin) has the potential to alter viral DNA replication and enhance pathogenicity.     

Update on human polyomavirus BK nephropathy

Polyomavirus BK (BKV) has ebeen identified as the main cause of polyomavirus‐associated nephropathy, a major cause of renal allograft failure. Although BKV‐associated nephropathy develops in only 2% to 5% of renal transplant recipients, its prognosis when present is very poor, with irreversible graft failure developing in 45% of affected patients. While the use of urine cytology for the detection of decoy cells has been in use for decades, other diagnostic modalities to detect BKV have emerged, including tissue biopsy, polymerase chain reaction, viral culture, and serology. Currently, there is no consensus regarding the laboratory technique best suited for clinical monitoring. This review article will discuss essential and clinical features of polyomavirus, followed by a discussion pertaining to the various diagnostic modalities that contribute to detecting polyomavirus‐associated nephropathy. Diagn. Cytopathol. 2009. © 2009 Wiley‐Liss, Inc.     

Functional analysis of polyomavirus BK non‐coding control region quasispecies from kidney transplant recipients

Replication of the human polyomavirus BK (BKV) in renal tubular epithelial cells causes viruria and BKV‐nephropathy in kidney transplant recipients. Following prolonged high‐level BKV replication, rearrangement of the archetype non‐coding control region (NCCR) leads to a mixture of BKV variants. The aim of this study was to compare potential functional differences of 12 rearranged (rr)‐NCCR variants with the archetype (ww)‐NCCR (WWT) found in allograft biopsies or urine from three kidney transplant recipients including two with BKV‐nephropathy. Twelve different rr‐NCCRs and one archetype ww‐NCCR were inserted between the early and late protein coding region of BKV(Dunlop) to make recombinant BKV genomes for transfection into Vero cells. Immunoblotting, immunofluorescence staining, and quantitative PCR demonstrated that viral protein expression and extracellular BKV loads of 10 rr‐NCCR variants were similar or higher than observed for the ww‐NCCR BKV. Two rr‐NCCR variants (RH‐2 and RH‐19) were non‐functional. The functional rr‐NCCRs produced infectious progeny successfully infecting primary renal proximal tubular epithelial cells. The number of infected cells and extracellular BKV loads corresponded to the activity seen in Vero cells. Three rr‐NCCR variants (RH‐1, RH‐10, RH‐13) only gave rise to a few infected cells similar to ww‐NCCR, whereas seven variants had intermediate activity (RH‐5, RH‐6, RH‐8, RH‐9, RH‐11) or high replication activity (RH‐7 and RH‐18) with several hundred infected cells per well. The results indicate that both functional and non‐functional BKV rr‐NCCR variants arise during BKV replication in kidney transplant recipients and that most functional rr‐NCCR variants confer a higher replication capacity than archetype ww‐NCCR. J. Med. Virol. 81:1959–1967, 2009. © 2009 Wiley‐Liss, Inc.     

BK virus renal infection in a patient with the acquired immunodeficiency syndrome.

BACKGROUND: We describe herein a patient with the acquired immunodeficiency syndrome and renal failure due to biopsy-proven BK virus (BKV) infection. Three months after the diagnosis of the renal viral infection, his condition remained unchanged. Although BKV has previously been shown to be associated with ureteral stenosis and renal damage in renal transplant patients, to our knowledge, the literature contains only 3 cases describing the presence of BKV lesions in the kidneys of immunosuppressed patients who had not undergone transplantation. METHODS: The presence of BKV infection was demonstrated by means of histology, immunohistochemistry with polyclonal anti-SV40 antibody, immunoelectron microscopy, polymerase chain reaction, and enzymatic cleavage with BamHI. RESULTS: Histologic examination revealed interstitial inflammatory infiltrates and tubules with enlarged and eosinophilic nuclei. CONCLUSIONS: The high frequency of latent BKV infection and its reactivation during immunosuppression suggest that the possibility of its involvement in renal damage should be considered in immunocompromised patients.     

Molecular characterization and sequence analysis of polyomavirus strains isolated from needle biopsy specimens of kidney allograft recipients

We retrospectively examined 29 renal allograft biopsy specimens from 42 kidney transplant recipients by means of molecular biologic techniques (nested polymerase chain reaction), immunohistochemical analysis (anti-SV40 antibody), and histologic examination to evaluate the presence of polyomaviruses (PVs), viral genotypes, genomic mutations, and their pathologic significance. PV genomes were found in six cases (21%); restriction fragment length polymorphism analysis characterized 4 as JC virus (JCV) and 2 as BK virus (BKV). The latter also were positively stained immunohistochemically and showed histologically typical intranuclear viral inclusions; JCV cases were negative. DNA sequence analysis revealed only minor changes in the 4 JCV cases (3 archetypes and 1 JCV type 3, not associated with a known pathogenic genotype) but identified 2 specific variants in the BKV isolates (AS and WW strains). Given the different histologic findings (mixed inflammatory infiltration in the AS and no inflammation in the WW strain), we speculate that different BKV strains may cause differential damage in transplanted kidneys. Finally, the negative histologic and immunohistochemical JCV results, as well as the absence of viral mutations, indicate that JCV renal infection is latent in transplant recipients.