Ubiquitous, interspersed repeated sequences in mammalian genomes

DNA base sequence comparisons demonstrate that the principal family of 300-nucleotide interspersed human DNA sequences, the repetitive double-strand regions of HeLa cell heterogeneous nuclear RNA, and specific RNA polymerase III in vitro transcripts of cloned human DNA sequences are all representatives of a closely related family of sequences. A segment of approximately 30 residues of these sequences is highly conserved in mammalian evolution because it is also present in the interspersed repeated DNA sequences of Chinese hamsters. Further DNA sequence comparisons demonstrate that a portion of this highly conserved segment of repetitive mamalian DNA sequence is similar to a sequence found within a low molecular weight RNA that hydrogen-bonds to poly(A)-terminated RNA molecules of Chinese hamsters and a sequence that forms half of a perfect inverted repeat near the origin of DNA replication in papovaviruses.

Persistence of DNA sequences of BK virus and JC virus in normal human tissues and in diseased tissues

Available evidence suggests that BK virus (BKV) and JC virus (JCV) persist in the kidneys of healthy individuals after primary infection and may reactivate when the host's immune response is impaired. Data supporting this hypothesis are presented. A previous study had shown BKV to be present in the kidneys of eight (57%) of 14 subjects. In the present study, which extended the investigation to a total of 30 subjects, BKV DNA was found in the renal tissues of 10 (33%) subjects, and JCV DNA was found in the renal tissues of three (10%) subjects. The viral DNA detected appeared not to be integrated with host DNA and to be isolated in foci. Investigation of normal and diseased brain tissue, including tissue from six subjects with multiple sclerosis, failed to reveal the presence of either JCV DNA or BKV DNA.

Testing for polyomavirus type BK DNA in plasma to identify renal-allograft recipients with viral nephropathy

BACKGROUND

Reactivation of polyomavirus type BK (BK virus) is increasingly recognized as a cause of severe renal-allograft dysfunction. Currently, patients at risk for nephropathy due to infection with the BK virus are identified by the presence of cells containing viral inclusion bodies ("decoy cells") in the urine or by biopsy of allograft tissue.

METHODS

In a retrospective analysis, we performed polymerase-chain-reaction assays for BK virus DNA in plasma samples from 9 renal-allograft recipients with BK virus nephropathy; 41 renal-allograft recipients who did not have signs of nephropathy, 16 of whom had decoy cells in the urine; and as immunocompromised controls, 17 patients who had human immunodeficiency virus type 1 (HIV-1) infection (stage C3 according to the classification of the Centers for Disease Control and Prevention) and who had not undergone transplantation.

RESULTS

In all nine patients with BK virus nephropathy, BK virus DNA was detected in the plasma at the time of the initial histologic diagnosis (a mean [+/-SD] of 46+/-28 weeks after transplantation) and during the course of histologically diagnosed, persistent BK virus disease. In three of the six patients with nephropathy who were studied serially after transplantation, BK virus DNA was initially undetectable but was detected 16 to 33 weeks before nephropathy became clinically evident and was confirmed by biopsy. Tests for BK virus DNA in plasma became negative and the nephropathy resolved after the doses of immunosuppressive drugs were decreased in two patients and after removal of the renal allograft in three patients. BK virus DNA was found in the plasma of only 2 of the 41 renal-allograft recipients who had no signs of nephropathy and in none of the patients with HIV-1 infection.

CONCLUSIONS

Testing for BK virus DNA in plasma from renal-allograft recipients with use of the polymerase chain reaction is a sensitive and specific method for identifying viral nephropathy.

The genome of human papovavirus BKV

The complete DNA sequence of human papovavirus BKV(Dun), consisting of 5153 nucleotide pairs, is presented. We describe the segments of the genome which correspond to the replication origin, the tandem repeated sequences, the 5' and 3' ends of the mRNAs, the splice sites, the early and late viral proteins and the putative viral polypeptides. These BKV DNA sequences are compared with analogous regions in the SV40 and Py virus genomes in an attempt to localize viral functions for lytic growth and transformation.

DNA sequences similar to those of simian virus 40 in ependymomas and choroid plexus tumors of childhood

BACKGROUND

Ependymomas and papillomas of the choroid plexus occur in early childhood. The ubiquitous human polyomaviruses, BK virus and JC virus, have been associated with the induction of these neoplasms in animal models. A related monkey polyomavirus, simian virus 40 (SV40), is highly tumorigenic in rodents and also induces choroid plexus papillomas.

METHODS

We tested the possibility that polyomaviruses were associated with these tumors in humans. Tumors from 31 children--20 with choroid plexus neoplasms and 11 with ependymomas--were evaluated for the presence of polyomavirus T-antigen gene sequences by means of amplification with the polymerase chain reaction.

RESULTS

Ten of the 20 choroid plexus tumors and 10 of the 11 ependymomas contained amplification products that preferentially hybridized to probes specific for SV40 viral DNA rather than BK or JC viral DNA. In two specimens, DNA sequencing demonstrated that the amplified sequence was identical to the sequence of that region of the SV40 gene. In three other specimens, amplification with SV40-specific primers revealed a 574-bp segment of the SV40 viral gene. In 7 of 11 tumors examined by immunohistochemical staining, viral T antigen was expressed in the nuclei of the neoplastic cells.

CONCLUSIONS

Half of the choroid plexus tumors and most of the ependymomas that we studied contained and expressed a segment of T-antigen gene related to SV40. These results suggest that SV40 or a closely related virus may have an etiologic role in the development of these neoplasms during childhood, as in animal models.

Seroepidemiology of the human polyomaviruses

To assess the stability of polyomavirus antibodies in serial samples over time and the incidence and age-specific prevalence of polyomavirus infections, we established enzyme immunoassays (EIAs) using purified yeast-expressed virus-like particles (VLPs) containing the VP1 major capsid proteins of JC virus (JCV) and the AS and SB strains of BK virus (BKV). A random subsample of 150 Finnish women who had serum samples taken during the first trimester of pregnancy and had a second pregnancy during a 5 year follow-up period was selected, grouped by age of first pregnancy. The polyomavirus antibody levels were similar in samples taken during the first and second pregnancies (correlation coefficient 0.93 for BKV SB and 0.94 for JCV). Analysis of serum samples from 290 Swedish children aged 1-13 years, grouped by age in 2 year intervals, demonstrated that BKV seropositivity increased rapidly with increasing age of the children, reaching 98 % seroprevalence at 7-9 years of age, followed by a minor decrease. JCV seroprevalence increased only slowly with increasing age and reaching 72 % positivity among mothers >25 years of age. The age-specific seroprevalence of the human polyomaviruses measured using this VLP-based EIA was similar to previous serosurveys by other methods. The stability of the antibodies over time indicates that polyomavirus seropositivity is a valid marker of cumulative virus exposure, and polyoma VLP-based EIAs may therefore be useful for epidemiological studies of these viruses.

Discovery and epidemiology of the human polyomaviruses BK virus (BKV) and JC virus (JCV)

Although discovered over thirty years ago, many aspects of the epidemiology of BKV and JCV in the general population, such as the source of infectious virus and the mode of transmission, are still unknown. Primary infection with both BKV and JCV is usually asymptomatic, and so age seroprevalence studies have been used to indicate infection. BKV commonly infects young children in all parts of the world, with the exception of a few very isolated communities, adult seroprevalence rates of 65-90% being reached by the age of ten years. In contrast, the pattern of JCV infection appears to vary between populations; in some anti-JCV antibody is acquired early as for BKV, but in others anti-JCV antibody prevalence continues to rise throughout life. This indicates that the two viruses are probably transmitted independently and by different routes. Whilst BKV DNA is found infrequently in the urine of healthy adults, JCV viruria occurs universally, increasing with age, with adult prevalence rates often between 20% and 60%. Four antigenic subtypes have been described for BKV and eight genotypes are currently recognized for JCV. The latter have been used to trace population movements and to reconstruct the population history in various communities.

Detection of BK virus and JC virus in urine and brain tissue by the polymerase chain reaction

DNAs of the human polyomaviruses BK virus (BKV) and JC virus (JCV) were amplified by the polymerase chain reaction (PCR) by using a single pair of 20-base oligonucleotide primers that were complementary to the same regions of both viruses. The sequences flanked by the primers were unique for each virus and could be differentiated by hybridization with 40-base, 32P-labeled oligonucleotide probes or by cleavage with BamHI. The DNA fragments resulting from amplification of BKV and JCV were 176 and 173 nucleotide pairs, respectively. The sensitivities of PCR for amplification of cloned BKV and JCV DNAs were 10 and 100 copies, respectively. Hybridization with the oligonucleotide probes was specific for each virus. A total of 57 urine samples from three groups of subjects were processed by DNA extraction or boiling and were tested by PCR. Urine samples collected from immunosuppressed patients (n = 11) and previously documented to be positive for BKV, JCV, or both were positive by PCR. Ten percent of urine samples from healthy adults (n = 30) that were previously negative for BKV and JCV were positive for one or both viruses by PCR. Urine samples (n = 16) from four seronegative bone marrow transplant recipients were uniformly negative for BKV. JCV was detected in deparaffinized brain tissue from a patient with progressive multifocal leukoencephalopathy. Specific diagnosis of virus in clinical specimens could be made within 1 day of receipt of the specimens. The PCR method is attractive for use in diagnosing polyomavirus infections because of its sensitivity, specificity, and rapid turnaround time.

Polyomavirus BK versus JC replication and nephropathy in renal transplant recipients: a prospective evaluation

BACKGROUND

JC virus (JCV) viruria is more common than BK virus (BKV) viruria in healthy individuals but in kidney transplants (KT), polyomavirus nephropathy (PVAN) is primarily caused by BKV. Few cases of PVAN have been attributed to JCV. Systematic studies on JCV replication in KT are lacking.

METHODS

Out of a cohort of KT patients screened with urine cytology, patients shedding decoy cells were studied (n=103). Molecular studies demonstrated BKV, JCV, or BKV+JCV shedding in 58 (56.3%), 28 (27.2%), and 17 (16.5%), respectively. Biopsy was performed when decoy cells persisted 2 months or serum creatinine increased >20%.

RESULTS

BKV viruria was strongly associated with BKV viremia (93%), PVAN (48%, P=0.01) and graft loss (P=0.03). Higher BKV viremia correlated with graft dysfunction (P=0.01), more advanced histological pattern of PVAN (P<0.0001), and more infected cells in biopsy (P=0.0001). BKV viremia of > or =10,000 copies/mL was significantly associated with histologically confirmed PVAN (P=0.0001). Reduction of immunosuppression lead to disappearance of decoy cells in patients shedding BK (>93%). JCV viruria, was more often asymptomatic (P=0.002) and affected older patients (P=0.02). JCV PVAN was less common (21.4%) and was characterized by sparse cytopathic changes but significant inflammation and fibrosis. JCV viremia was rare (14.2%), transient, and low (mean 2.0E+03/mL). After reduction of immunosuppression decoy cells persisted in >50% of patients with JCV (P=0.0001), but no graft loss occurred. During the period of the current study, the incidence of BKV-PVAN was 5.5% and the incidence of JCV-PVAN was 0.9%.

CONCLUSIONS

The data point to significant differences of BKV and JCV biology regarding replication and disease in KT patients, with important implications for screening and management.

Prospective monitoring of polyomavirus BK replication and impact of pre-emptive intervention in pediatric kidney recipients

Polyoma BK virus (BKV)-associated nephropathy (PVAN) is a relevant cause of poor renal allograft survival. In a prospective analysis, we monitored BKV DNA in blood and urine samples from 62 consecutive pediatric kidney recipients. In patients with BKV replication, we analyzed the impact of reduction of maintenance immunosuppression on viral load kinetics and PVAN in patients with BKV replication. BKV-specific immunity was concomitantly evaluated on blood samples of viremic patients, by measuring the frequency of BKV-specific interferon-gamma-producing and cytotoxic T cells, and BKV IgG antibody levels. At a median follow-up of 24 months, BK viruria was observed in 39 of 62 patients, while BK viremia developed in 13 patients (21%). In all viremic patients, immunosuppression reduction resulted in the clearance of viremia, and prevented development of PVAN, without increasing the rate of acute rejection or causing graft dysfunction. As a consequence of immunosuppression adjustment, an expansion of BKV-specific cellular immunity was observed that coincided with viral clearance. We conclude that treating pediatric kidney transplant patients pre-emptively with immunosuppression reduction guided by BKV DNA in blood is safe and effective to prevent onset of PVAN. BKV-specific cellular immunity may be useful to guide this intervention.

Correlates of quantitative measurement of BK polyomavirus (BKV) DNA with clinical course of BKV infection in renal transplant patients

BK virus-allograft nephropathy (BKVAN) is an increasingly recognized complication after kidney transplantation. Quantitative tests have been advocated to monitor patients, but data demonstrating their efficacy are relatively limited. We developed a real-time PCR assay to quantitate BK virus loads in the setting of renal transplantation, and we correlated the BK virus load with clinical course and with the presence of BK virus in renal biopsy specimens. BK virus loads were measured in urine, plasma, and kidney biopsy samples in three clinical settings: (i) patients with asymptomatic BK viruria, (ii) patients with active BKVAN, and (iii) patients with resolved BKVAN. Active BKVAN was associated with BK viremia greater than 5 x 103 copies/ml and with BK viruria greater than 107 copies/ml in all cases. Resolution of nephropathy led to resolution of viremia, decreased viruria levels, and disappearance of viral inclusions, but low-level viral DNA persisted in biopsy specimens even for patients whose viruria was cleared. All but one patient in the resolved BKVAN group carried a urinary viral load below 107 copies/ml. Viral loads in patients with asymptomatic viruria were generally lower but in some cases overlapped with levels more typical of BKVAN. One patient with asymptomatic viruria and with a viral load overlapping values seen in BKVAN had developed nephropathy by the time of follow-up. In conclusion, serial measurement of viral loads by quantitative PCR is a useful tool in monitoring the course of BK virus infection. The results should be interpreted in conjunction with the clinical picture and biopsy findings.

Documenting the epidemiologic patterns of polyomaviruses in human populations by studying their presence in urban sewage

This is the first description, to our knowledge, of the distribution of human polyomavirus and simian virus 40 (SV40) in urban sewage. Using a nested-PCR procedure, we report the detection of human polyomaviruses JC virus (JCV) and BK virus (BKV) but not SV40 in a high percentage of urban sewage samples obtained from widely divergent geographical areas in Europe and Africa. For a total of 28 samples analyzed, JCV was detected in 26, BKV was detected in 22, and none was positive for SV40. All geographical areas showed a high prevalence of these viruses with mean estimated values of JC viral particles per ml on the order of 10(3) in Barcelona (Spain) and Nancy (France) and 10(2) in Pretoria (South Africa) and Umeå (Sweden) and mean values of BK viral particles on the order of 10(2) in Pretoria and Barcelona and 10(1) in Nancy and Umeå. This compares with estimated mean values of 10(2) to 10(3) for human adenovirus that was evaluated as a control. Nucleotide sequence analysis of the amplified DNA from some of the samples is also presented and represents the sequence of the most abundant JC and BK viral strains in these samples. The nucleotide sequence of the JCV detected was also analyzed in a phylogenetic study and for genomic characterization in the regulatory region. This study has shown that human polyomaviruses are spread in high concentrations in the sewage of different geographical areas and are present in contaminated environments. The frequency and concentration of JCV detected in the environment and the absence of described animal hosts suggest that JCV may be useful as a marker for fecal pollution of anthropogenic origin. The results also support the idea previously described that the strains of JCV are closely related to the ethnic origin of the population studied. The procedure applied should also be useful in future studies of population patterns of viral excretion and as a tool in epidemiological studies for the detection of changes in the prevalence of specific viral pathogens.

BK virus DNA: complete nucleotide sequence of a human tumor virus

The complete DNA sequence of the human papovavirus BK is presented. From the 4963 base-pair sequence of BK virus (MM strain), the amino acid sequence of at least five proteins can be deduced: a T antigen and a t antigen, which share amino terminal peptides; proteins VP2 and VP3, which share 232 amino acids; and protein VP1, whose coding sequence overlaps those for VP2 and VP3 by 113 nucleotides but is read in a different frame. The gene loci and the arrangement of genes are strikingly similar in BK virus and simian virus 40 (SV40). The sequence of the deduced proteins in BK virus shares 73 percent amino acid homology with those in SV40, whereas the DNA sequence of the two viruses shares 70 percent homology, suggesting close evolutionary relationship. However, the repeated DNA sequences in the noncoding regions of these viruses are different.

Quantification of polyoma BK viruria in hemorrhagic cystitis complicating bone marrow transplantation

Polyoma BK virus (BKV) is frequently identified in the urine of bone marrow transplantation (BMT) patients with hemorrhagic cystitis (HC). However, viruria is common even in asymptomatic patients, making a direct causative role of BKV difficult to establish. This study prospectively quantified BK viruria and viremia in 50 BMT patients to define the quantitative relationship of BKV reactivation with HC. Adenovirus (ADV) was similarly quantified as a control. More than 800 patient samples were quantified for BKV VP1 gene with a real-time quantitative polymerase chain reaction. Twenty patients (40%) developed HC, 6 with gross hematuria (HC grade 2 or higher) and 14 with microscopic hematuria (HC grade 1). When compared with asymptomatic patients, patients with HC had significantly higher peak BK viruria (6 x 10(12) versus 5.7 x 10(7) genome copies/d, P <.001) and larger total amounts of BKV excreted during BMT (4.9 x 10(13) versus 7.7 x 10(8) genome copies, P <.001). There was no detectable increase in BK viremia. Binary logistic regression analysis showed that BK viruria was the only risk factor, with HC not related to age, conditioning regimen, type of BMT, and graft-versus-host disease. Furthermore, the levels of ADV viruria in patients with or without HC were similar and comparable with those of BK viruria in patients without HC, suggesting that the significant increase in BK viruria in HC patients was not due to background viral reactivation or damage to the urothelium. BK viruria was quantitatively related to the occurrence of HC after BMT.

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.

The TGGCA protein binds to the MMTV-LTR, the adenovirus origin of replication, and the BK virus enhancer

TGGCA-binding proteins are nuclear proteins with high affinity for double-stranded DNA homologous to the prototype recognition sequence 5'YTGGCANNNTGCCAR 3'. Their ubiquitous tissue distribution in higher vertebrates characterizes them as a class of highly conserved proteins which may exert a basic function. To obtain clues to this function, specific binding sites were mapped on three viral genomes. Recognition sites were identified in the enhancer region of the BK virus, in the LTR of the mouse mammary tumor virus, and in the origin of replication of adenovirus 12. The TGGCA-binding protein from HeLa cells appears to be identical to nuclear factor I described by others, which stimulates initiation of adenovirus DNA replication in vitro. However, data from MMTV, BKV, and from cellular genes suggest that this specific protein-DNA interaction may also be involved in the control of gene activity.

Infection of human polyomaviruses JC and BK in peripheral blood leukocytes from immunocompetent individuals

Widely disseminated infection with the human polyomaviruses JC and BK is followed by lifelong asymptomatic viral persistence that can be reactivated under prolonged immunosuppression to fatal CNS and urogenital disease. In an attempt to understand the pathogenesis of polyomavirus diseases, we asked whether leukocytes are involved in polyomavirus infection in the immunocompetent host. Peripheral blood leukocytes from 29 immunocompetent individuals and umbilical cord blood from 10 newborn children were analyzed for the presence of polyomavirus DNA. Southern blot analysis demonstrated the presence of JCV-specific full-length virus genomes and indicated involvement of the second human polyomavirus BK. In contrast to specimens from newborn children, PCR amplification of target DNA in the adult age group followed by species-specific hybridization provided evidence of concomitant JCV and BKV infection in almost all specimens. Nucleotide sequencing of virus-specific products representing DNA segments essential for virus multiplication confirmed presence of both virus species in leukocytes. The detection of a new virus subtype and single base changes or deletions in the noncoding DNA region from individual cases suggested widespread heterogeneity in the circulating virus population, although the structure of the transcriptional control elements in all cases was comparable to highly active elements found in lytically infected cells. Those findings and the localization of both virus types in the nuclei of blood cells by in situ hybridization demonstrate that JCV and BKV frequently infect peripheral leukocytes and give strong evidence that leukocytes are common sites of polyomavirus persistence in healthy individuals.

Quantitation of BK virus load in serum for the diagnosis of BK virus-associated nephropathy in renal transplant recipients

BK virus-associated nephropathy is an increasingly recognized cause of graft dysfunction among kidney transplant recipients, and definitive diagnosis requires renal biopsy. By using a newly developed, quantitative, real-time polymerase chain reaction (PCR) assay for BK virus DNA, a retrospective analysis was done of sequential serum samples (n=28) from 4 transplant recipients with histopathologically documented BK virus nephropathy and from samples (n=76) from 16 transplant recipient control patients. BK virus DNA was detected in serum samples from all 4 case patients versus 0 of 16 control patients (P< .0001, Fisher's exact test) at a median of 32 weeks (range, 17-61 weeks) before the diagnosis of BK virus nephropathy. BK virus load decreased in 3 of 3 patients after the reduction of immunosuppression and/or nephrectomy. It is concluded that quantitative PCR for BK virus DNA in serum is useful both for identifying transplant recipients at risk for BK virus nephropathy and for monitoring the response to therapy.

Incidence of BK virus and JC virus viruria in human immunodeficiency virus-infected and -uninfected subjects

BK virus (BKV) and JC virus (JCV) are present within the renal system of most adults. Reactivation may be linked to immunodeficiency, since many of the extant virus strains have been isolated from urine or kidney tissue of patients who were receiving immunosuppressive therapy or who had disorders of the immune system. To more critically evaluate the relationship between immunodeficiency and viruria, urine samples from individuals infected with human immunodeficiency virus (HIV) with various degrees of immunodeficiency were screened for the presence of viral DNA. JCV viruria occurred in 24%-27% of immunocompetent control subjects and was not increased with immunodeficiency. By contrast, there were both qualitative and quantitative changes in BKV viruria in immunodeficient subjects. The incidence of BKV viruria was increased, and some immunodeficient subjects shed BKV at levels up to 3000 times greater than levels shed by any of the nonimmunodeficient controls. DNA sequence rearrangements in the viral regulatory region did not appear to be required for shedding of virus, although they were present in approximately 20% of samples.

Evolutionarily conserved function of a viral microRNA

MicroRNAs (miRNAs) are potent RNA regulators of gene expression. Some viruses encode miRNAs, most of unknown function. The majority of viral miRNAs are not conserved, and whether any have conserved functions remains unclear. Here, we report that two human polyomaviruses associated with serious disease in immunocompromised individuals, JC virus and BK virus, encode miRNAs with the same function as that of the monkey polyomavirus simian virus 40 miRNAs. These miRNAs are expressed late during infection to autoregulate early gene expression. We show that the miRNAs generated from both arms of the pre-miRNA hairpin are active at directing the cleavage of the early mRNAs. This finding suggests that despite multiple differences in the miRNA seed regions, the primary target (the early mRNAs) and function (the downregulation of early gene expression) are evolutionarily conserved among the primate polyomavirus-encoded miRNAs. Furthermore, we show that these miRNAs are expressed in individuals diagnosed with polyomavirus-associated disease, suggesting their potential as targets for therapeutic intervention.

Quantification of human polyomaviruses JC Virus and BK Virus by TaqMan quantitative PCR and comparison to other water quality indicators in water and fecal samples

In the United States, total maximum daily load standards for bodies of water that do not meet bacterial water quality standards are set by each state. The presence of human polyomaviruses (HPyVs) can be used as an indicator of human-associated sewage pollution in these waters. We have developed and optimized a TaqMan quantitative PCR (QPCR) assay based on the conserved T antigen to both quantify and simultaneously detect two HPyVs; JC virus and BK virus. The QPCR assay was able to consistently quantify > or =10 gene copies per reaction and is linear over 5 orders of magnitude. HPyVs were consistently detected in human waste samples (57 of 64) and environmental waters with known human fecal contamination (5 of 5) and were not amplified in DNA extracted from 127 animal waste samples from 14 species. HPyV concentrations in sewage decreased 81.2 and 84.2% over 28 days incubation at 25 and 35 degrees C, respectively. HPyVs results were compared to Escherichia coli, fecal coliform, and enterococci concentrations and the presence of three other human-associated microbes: Bacteroidetes, Methanobrevibacter smithii, and adenovirus. HPyVs were the most frequently detected of these in human and contaminated environmental samples and were more human specific than the Bacteroidetes (HF183) or M. smithii. HPyVs and M. smithii more closely mimicked the persistence of adenovirus in sewage than the other microbes. The use of this rapid and quantitative assay in water quality research could help regulatory agencies to identify sources of water pollution for improved remediation of contaminated waters and ultimately protect humans from exposure to pathogens.

BK viral enhancer element and a human cellular homolog

Comparison of two closely related primate papovaviruses, simian virus 40 (SV40) and human BK virus (BKV), reveals that the only region of extensive divergence, the tandem sequences adjacent to the origins of DNA replication, is responsible in SV40 for enhancing early gene expression. This study demonstrates a similar enhancer function for the analogous repeated region in BKV. The dissimilarity in sequence of the BKV and SV40 enhancer elements suggests that they may have been acquired since SV40 and BKV diverged. A locus cloned from the human genome homologous to the BKV tandem repeats has been shown to function as low level enhancer element in mammalian cells. These data support the hypothesis that viral enhancer sequences may be evolutionarily related to host cell sequences.

High incidence of urinary JC virus excretion in nonimmunosuppressed older patients

Urine specimens from 120 patients attending urologic clinics were screened by blot hybridization for the presence of a polyomavirus DNA. Detected viral DNA was then identified as BK or JC by fine restriction enzyme analysis. BK and JC viral DNA was found in 5 (4%) and 35 (29%) patients, respectively. Detection rates were compared among three age groups: 0-29, 30-59, and 60-89 years. Detection of JC viral DNA increased with age and reached the highest value (45%) in the group aged 60-89 years. For BK viral DNA a correlation between detection and age was not clear because the rate of detection was low, although the highest rate (9%) occurred in the oldest group. To confirm the active urinary excretion of polyomavirus DNA in older patients, urine specimens from 23 patients (60-90 years) treated at an internal medicine clinic were examined for viral DNA. BK and JC viral DNA were in 2 (9%) and 12 patients (52%), respectively. These results suggest that JC virus is frequently reactivated in older individuals.

BK virus nephritis after renal transplantation

BK viremia and nephritis are increasing problems in renal transplant recipients. The exact cause of the increasing prevalence of this condition remains poorly understood. Increasing prevalence has been correlated with newer immunosuppressive agents and the decline in acute rejection rates in recent years. The clinical manifestation varies from the asymptomatic state of viremia and nephritis to clinical renal dysfunction. The diagnosis of this infection is based on the combination of the presence of urinary decoy cells, virus in the urine/blood, and typical renal histological findings of interstitial nephritis. Routine post-transplant screening for BK viremia and viruria prior to the occurrence of nephritis and the reduction in immunosuppressive therapy for subjects with viremia appear to be attractive approaches. The treatment of BKV nephritis (BKVN) consists of reduction in immunosuppressive therapy and antiviral therapy with cidofovir or leflunomide or a combination of both. Approximately 30-60% of subjects with BKVN experienced irreversible graft failure. However, in recent years, the combinations of early detection, prompt diagnosis, and appropriate reduction in immunosuppressive therapy have been associated with better outcome. The pathogenesis of BK virus infection in renal transplant recipients needs to be explored. The source of BKV infection (donor as opposed to recipient), the role of host humoral, and cellular immunity to BKV, and the role of alloimmune activation in renal graft to the occurrence of nephritis are discussed in this review.