Detection of BK virus DNA in nasopharyngeal aspirates from children with respiratory infections but not in saliva from immunodeficient and immunocompetent adult patients

Frequent detection of polyomaviruses in stool samples from hospitalized children

BACKGROUND

Infection with BK virus (BKV) generally occurs early during life, but its mode of transmission has not been clearly defined. We tested the hypothesis that polyomavirus shedding in stool may be a source of BKV exposure.METHODS. Pediatric stool and rectal swab samples were tested for the presence of polyomavirus DNA by a polymerase chain reaction (PCR) assay that could detect a conserved region in the large T antigen gene of BKV, JC virus (JCV), and simian virus 40 (SV40). The specific viruses detected by this assay were confirmed by DNA sequence analysis of the PCR amplicons.Results. Of 120 samples collected from 99 patients, 54 (45.0%) were positive for polyomavirus DNA. Of the 99 patients, 46 (46.5%) had at least 1 positive sample, with 38 (38.4%) positive for BKV and 8 (8.1%) positive for SV40. JCV was not detected. There was no association between polyomavirus fecal shedding and age, sex, race/ethnicity, immune status, or symptoms of gastrointestinal disease in the children studied. The BKV strains detected displayed polymorphisms in the T antigen sequence.Conclusions. Polyomaviruses are frequently present in stool samples from hospitalized children. These findings suggest that fecal-oral transmission of BKV may play a role in the ubiquity of infection.

Polymorphism in the genome of non-passaged human polyomavirus BK: implications for cell tropism and the pathological role of the virus

Worldwide studies have demonstrated that the human polyomavirus BK resides ubiquitously in the human population. After primary infection, which occurs mainly during childhood, the virus seems to establish a life-long harmless infection in the host. However, impaired immune functions may lead to reactivation of BK virus. The recent findings that associate BK virus with an increasing number of clinical conditions, including renal, pulmonary, ophthalmologic, hepatic, neurological, and autoimmune diseases, has resuscitated the interest in this virus as a pathogenic agent. This review focuses on polymorphisms in the genomes of non-passaged BK virus isolates from nonneoplastic tissues, with special focus on the transcriptional control region, the regulatory proteins large T-antigen and agnoprotein, and the major capsid protein VP1. The possible implications of genome diversity with respect to cell tropism, pathogenicity, and therapeutic strategies are discussed.

Leucoencéphalopathie multifocale progressive à BK virus chez un patient immunodéprimé par une corticothérapie

INTRODUCTION

BK virus has been described previously in renal transplant patients, but has also been reported in cases of progressive multifocal leukoencephalopathy.

METHOD

A case of progressive BK virus multifocal leukoencephalopathy induced by long-term corticosteroid therapy is reported.

RESULTS

In our case, BK virus was detected in cerebrospinal fluid by polymerase chain reaction (PCR). A detailed review of similar cases in the literature showed most of them occurred in AIDS patients, but four involved immunocompetent patients.

CONCLUSION

Though BK virus infection usually leads to urinary tract symptoms in immunologically suppressed patients, it is important to be aware of its neurological manifestations and to recognize BK infections that can occur in immunocompetent patients.

Detection of BK virus and simian virus 40 in the urine of healthy children

Seroprevalence studies indicate that most primary infections with BK virus (BKV) and JC virus (JCV) occur in the first and second decades of life, respectively. Relatively little is known about the transmission of these agents, including the primary source of human exposure, the portal of entry, and the pathophysiology of life-long viral persistence. We sought to determine if simian virus 40 (SV40) excretion could be detected in the urine of healthy children and to define the age-related prevalence of polyomavirus shedding in this population. A point prevalence study of polyomavirus shedding was conducted in healthy children using rigorous enrollment criteria. Urine samples were collected from healthy children, age from 3 to 18 years, during routine evaluation at two urban pediatric clinics. Qualitative PCR analysis was performed using primers that detect a conserved region of the T-antigen gene of BKV, JCV, and SV40. The identity of polyomaviruses detected was determined by DNA sequence analysis and/or PCR amplification of other regions of the viral genomes. Seven of 72 (9.7%) urine samples were positive for polyomaviruses: three with BKV (ages 4, 6, 13), two with SV40 (ages 6, 16), two with BKV and SV40 co-excretion (ages 6, 15), and none with JCV. DNA sequence analysis confirmed the identity of viruses detected. These results suggest that the timing of SV40 infections in humans may be similar to that of BKV and that urine from healthy children could contribute to the ubiquity of BKV infection early in life.

Use of cidofovir in polyomavirus BK viral nephropathy in two renal allograft recipients

Polyomavirus BK viral allograft nephropathy is a potentially reversible cause of deteriorating function of kidney allografts. Initial treatment involves reducing immunosuppressive medications, with low-dose cidofovir an effective alternative in refractory cases. We describe two cases of BK viral allograft nephropathy responding to low-dose cidofovir after a reduction in immunosuppressive medications failed to clear the virus or stabilize the deterioration in renal function. There were no significant side-effects from this treatment in either patient.

Polyomavirus BK

Polyomavirus hominis 1, better known as BK virus (BKV), infects up to 90% of the general population. However, significant clinical manifestations are rare and limited to individuals with impaired immune functions. BKV has been associated with diverse entities such as haemorrhagic cystitis, ureteric stenosis, vasculopathy, pneumonitis, encephalitis, retinitis, and even multi-organ failure. In addition, BKV has been implicated in autoimmune disease and possibly cancer. Due to high prevalence and frequent reactivation, the role of BKV in some of these pathologies has been difficult to define. Development of BKV diseases is likely to require complementing determinants in the host, the target organ, and possibly the virus, that are subject to modulators such as immunosuppression. These complex aspects are highlighted in polyomavirus-associated nephropathy (PAN), an emerging disease in renal allograft recipients that may jeopardise the progress in renal transplantation accomplished in the past 10 years. Intervention is difficult due to the lack of specific antivirals and relies mostly on improving immune control. Diagnostic strategies using urine cytology and BKV load measurements in plasma have led to earlier diagnosis of PAN, which increased the success rate of intervention. Case series suggest that cidofovir might be effective, especially when combined with reduced immunosuppression.

Population-based study of antibody to the human polyomaviruses BKV and JCV and the simian polyomavirus SV40

Molecular studies suggest that the simian polyomavirus SV40 is present in the human population, possibly introduced in contaminated polio vaccine. However, no recent seroepidemiological data exist in England on SV40 or on the two human polyomaviruses, BKV and JCV. A comparative age seroprevalence study was undertaken on 2,435 residual sera from 1991 by haemagglutination inhibition (HI) for BKV and JCV, and virus neutralisation for SV40. The overall rates of seropositivity for BKV and JCV were 81% and 35%, respectively, and each was significantly related to age (P < 0.001). BKV seroprevalence reached 91% at 5-9 years of age, but JCV seroprevalence reached only 50% by age 60-69 years. There was a highly significant association between BKV antibody titre and age (P < 0.001), titres decreasing linearly at a rate of 8.7% per 10 years (95% CI = 7.4-10% drop). Significantly more males than females had antibody to JCV (P = 0.013). In individuals under 40 years of age there was a significant negative association between the presence of antibody to BKV and JCV (P < 0.001). By contrast, the antibody prevalence to SV40 remained at 1.3-5% throughout all age groups and titres were low. There was a significant positive association between the presence of antibody to SV40 and antibody to both BKV (P < 0.001) and JCV (P = 0.009), and also to the geometric mean titre (GMT) of BKV antibody (P = 0.011). The results indicate that BKV and JCV are transmitted by different routes. There is no serological evidence that SV40 entered the human population during the past 80 years, and the possibility of cross-reaction with BKV or JCV antibody must be considered.

Analysis of the excreted JC virus strains and their potential oral transmission

JC virus (JCV) particles have been detected in urban sewage of divergent geographical areas. In this study, the authors evaluate the genetic characteristics and the infective capabilities of JCV strains in relation to the potential oral transmission of JCV in the population. JCV strains excreted in urine and detected in sewage have been described as presenting archetypal structure of the regulatory region of the viral genome. The regulatory region of JCV viral particles detected in two urban sewage samples have been cloned and characterized. From a total of 40 clones tested, 39 presented archetypal-like regulatory regions, whereas 1 of the clones analyzed presented a tandem repeated structure. Archetypal strains present in the urine of a pregnant woman were able to infect SVG cells, producing infectious virions, as demonstrated by confirmative cell culture, electron microscopy, and in situ DNA hybridization. This is the first description of archetypal JCV productive infection of SVG cells. SVG cells were also successfully infected with Mad-4 JCV viral particles subjected to pH 3 for 1 h at 37 degrees C and to 10 microg/ml of trypsin in the same conditions. A decrease in the viral progeny production was observed when Mad-4 was subjected to acidic pH. Mad-4 did not produce any detectable infection in the enteric cell line CaCo-2. The oral route could represent a significant route of transmission of JCV infections because JCV virions have demonstrated relative resistance in the environment and to some of the conditions present in the gastrointestinal tract. The archetypal strains commonly detected in the environment may be implicated in the transmission of JCV among the population. Sporadic infection with strains presenting tandem repeated structures may have implications in pathogenicity.

Potential transmission of human polyomaviruses through the gastrointestinal tract after exposure to virions or viral DNA

The mechanism of human-to-human transmission of the polyomaviruses JC virus (JCV) and BK virus (BKV) has not been firmly established with regard to possible human exposure. JCV and BKV have been found in sewage samples from different geographical areas in Europe, Africa, and the United States, with average concentrations of 10(2) to 10(3) JCV particles/ml and 10(1) to 10(2) BKV particles/ml. Selected polyomavirus-positive sewage samples were further characterized. The JCV and BKV present in these samples were identified by sequencing of the intergenic region (the region found between the T antigen and VP coding regions) of JCV and the VP1 region of BKV. The regulatory region of the JCV and BKV strains found in sewage samples presented archetypal or archetype-like genetic structures, as described for urine samples. The stability (the time required for a 90% reduction in the virus concentration) of the viral particles in sewage at 20 degrees C was estimated to be 26.7 days for JCV and 53.6 days for BKV. The presence of JCV in 50% of the shellfish samples analyzed confirmed the stability of these viral particles in the environment. BKV and JCV particles were also found to be stable at pH 5; however, treatment at a pH lower than 3 resulted in the detection of free viral DNA. Since most humans are infected with JCV and BKV, these data indicate that the ingestion of contaminated water or food could represent a possible portal of entrance of these viruses or polyomavirus DNA into the human population.

Bk virus: a clinical review

We present a review of the clinically oriented literature about BK virus, a relative of JC virus, which is the etiologic agent of progressive multifocal leukoencephalopathy (PML). The kidney, lung, eye, liver, and brain have been proposed as sites of BK virus-associated disease, both primary and reactivated. BK virus has also been detected in tissue specimens from a variety of neoplasms. We believe that BK virus is most often permissively present in sites of disease in immunosuppressed patients, rather than being an etiologic agent that causes symptoms or pathologic findings. There is, however, strong evidence for BK virus-associated hemorrhagic cystitis and nephritis, especially in recipients of solid organ or bone marrow transplants. Now that BK virus can be identified by use of specific and sensitive techniques, careful evaluation of the clinical and pathologic presentations of patients with BK virus will allow us to form a clearer picture of viral-associated pathophysiology in many organ systems.

BK virus as the cause of meningoencephalitis, retinitis and nephritis in a patient with AIDS

BACKGROUND

The two widely spread human polyomaviruses, BK virus (BKV) and JC virus (JCV) establish latency in the urinary tract, and can be reactivated in AIDS. JCV might cause progressive multifocal leucoencephalopathy, but although up to 60% of AIDS patients excrete BKV in the urine there have been few reports of BKV-related renal and/or neurological disease in AIDS.

OBJECTIVE

To report on an AIDS patient with progressive renal and neurological symptoms involving the retina.

DESIGN

Case report.

SETTING

Venhälsan, Söder Hospital, Stockholm, Sweden.

METHODS

The brain, eye tissue, cerebrospinal fluid, urine and peripheral blood mononuclear cells were analysed by nested PCR for polyoma-virus DNA. Macroscopical and microscopical examination were performed of the kidney and brain post mortem. Immunohistochemical stainings for the two BKV proteins, the VP1 and the agnoprotein, were performed on autopsy material and virus infected tissue culture cells.

RESULTS

BKV could be demonstrated in the brain, cerebrospinal fluid, eye tissues, kidneys and peripheral blood mononuclear cells.

CONCLUSION

During 6 years, approximately 400 cerebrospinal fluid samples from immunosuppressed individuals with neurological symptoms have been investigated by PCR for the presence of polyomaviruses. BKV DNA has, so far, only been found in the case reported here. Although reports of BKV infections in the nervous system are rare, there is now evidence for its occurrence in immunocompromised patients and the diagnosis should be considered in such patients with neurological symptoms and signs of renal disease. The diagnosis is simple to verify and is important to establish.

Human polyoma virus-associated interstitial nephritis in the allograft kidney

BACKGROUND

Asymptomatic polyoma virus infection documented by urine cytology or serology is well known, but the clinical course of biopsy-proven interstitial nephritis is not well defined.

METHODS

Twenty-two cases were identified by histology, immunostaining, in situ hybridization, electron microscopy, or polymerase chain reaction.

RESULTS

The clinical features mimicked acute rejection (n=19), chronic rejection with incidental diagnosis at nephrectomy (n=2), or drug toxicity (n=1). Histology showed homogenous intranuclear inclusions. In situ hybridization showed BK virus (BKV) to be the predominant species, but polymerase chain reaction documented JC virus co-infection in one of five cases so tested. Electron microscopy in seven cases showed 20-51-nm virions. The two cases diagnosed at nephrectomy received no therapy. Initial antirejection therapy in 12 cases led to clearance of the virus in 1/12 (8%), partial therapeutic response in 3/12 (25%), and graft loss in 8/12 (67%) cases. The last recorded creatinine in patients with functional grafts ranged from 1.9 to 7.0 (median: 4.5) mg/dl, 0.4-45 (median: 4.0) months after initial diagnosis. The remaining eight cases treated by reduction of immunosuppression at the outset have been free of graft loss for 0.2-10.0 (median: 4.8) months since diagnosis, and clearance of virus has been documented in three of six (50%) cases. The serum creatinine in these patients is 1.7-6.0 (median: 2.4) mg/dl, 0.2-10 (median: 4.8) months after diagnosis. Follow-up biopsies performed 1-23.5 months after diagnosis show chronic allograft nephropathy.

CONCLUSIONS

Polyoma virus tubulo-interstitial nephritis-associated graft dysfunction usually calls for judicious decrease in immunosuppression and monitoring for acute rejection. Development of methods to serially quantify the viral load in individual patients could potentially improve clinical outcome.

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.

Experimental expression in mice and spontaneous expression in human SLE of polyomavirus T-antigen. A molecular basis for induction of antibodies to DNA and eukaryotic transcription factors

We have previously demonstrated that experimental expression of the polyomavirus transcription factor T-antigen has the potential to induce anti-DNA antibodies in mice. Two sets of independent evidences are presented here that demonstrate a biological relevance for this model. First, we describe results demonstrating that mice inoculated with T-antigen-expressing plasmids produced antibodies, not only to T-antigen and DNA, but also to the DNA-binding eukaryotic transcription factors TATA-binding protein (TBP), and to the cAMP-response-element-binding protein (CREB). Secondly, we investigated whether polyomavirus reactivation occurs in SLE patients, and whether antibodies to T-antigen, DNA, and to TBP and CREB are linked to such events. Both within and among these SLE patients, frequent polyomavirus reactivations were observed that could not be explained by certain rearrangements of the noncoding control regions, nor by corticosteroid treatment. Linked to these events, antibodies to T-antigen, DNA, TBP, and CREB were detected, identical to what we observed in mice. Antibodies recognizing double-stranded DNA were confined to patients with frequent polyomavirus reactivations. The results described here indicate that cognate interaction of B cells recognizing DNA or DNA-associated proteins and T cells recognizing T antigen had taken place as a consequence of complex formation between T ag and DNA in vivo in the context of polyomavirus reactivations.

Noncoding control region of naturally occurring BK virus variants: sequence comparison and functional analysis

The human polyomavirus BK (BKV) has a proven oncogenic potential, but its contribution to tumorigenesis under natural conditions remains undetermined. As for other primate polyomaviruses, the approximately 5.2 kbp double-stranded circular genome of BKV has three functional regions: the coding regions for the two early (T, t antigens) and four late (agno, capsid proteins; VP1-3) genes separated by a noncoding control region (NCCR). The NCCR contains the origin of replication as well as a promoter/enhancer with a mosaic of cis-acting elements involved in the regulation of both early and late transcription. Since the original isolation of BKV in 1971, a number of other strains have been identified. Most strains reveal a strong sequence conservation in the protein coding regions of the genome, while the NCCR exhibits considerable variation between different BKV isolates. This variation is due to deletions, duplications, and rearrangements of a basic set of sequence blocks. Comparative studies have proven that the anatomy of the NCCR may determine the transcriptional activities governed by the promoter/enhancer, the host cell tropism and permissivity, as well as the oncogenic potential of a given BKV strain. In most cases, however, the NCCR sequence of new isolates was determined after the virus had been passaged several times in more or less arbitrarily chosen cell cultures, a process known to predispose for NCCR rearrangements. Following the development of the polymerase chain reaction (PCR), it has become feasible to obtain naturally occurring BKV NCCRs, and their sequences, in samples taken directly from infected human individuals. Hence, the biological significance of BKV NCCR variation may be studied without prior propagation of the virus in cell culture. Such variation has general interest, because the BKV NCCRs represent typical mammalian promoter/enhancers, with a large number of binding motifs for cellular transacting factors, which can be conveniently handled for experimental purposes. This communication reviews the naturally occurring BKV NCCR variants, isolated and sequenced directly from human samples, that have been reported so far. The sequences of the different NCCRs are compared and analyzed for the presence of proven and putative cellular transcription factor binding sites. Differences in biological properties between BKV variants are discussed in light of their aberrant NCCR anatomies and the potentially modifying influence of transacting factors.