Inter- and intralaboratory comparison of JC polyomavirus antibody testing using two different virus-like particle-based assays

Pre-Transplantation Assessment of BK Virus Serostatus: Significance, Current Methods, and Obstacles

The immunosuppression required for graft tolerance in kidney transplant patients can trigger latent BK polyomavirus (BKPyV) reactivation, and the infection can progress to nephropathy and graft rejection. It has been suggested that pre-transplantation BKPyV serostatus in donors and recipients is a predictive marker for post-transplantation BKPyV replication. The fact that research laboratories have used many different assay techniques to determine BKPyV serostatus complicates these data analysis. Even studies based on the same technique differed in their standard controls choice, the antigenic structure type used for detection, and the cut-off for seropositivity. Here, we review the different BKPyV VP1 antigens types used for detection and consider the various BKPyV serostatus assay techniques’ advantages and disadvantages. Lastly, we highlight the obstacles in the implementation of a consensual BKPyV serologic assay in clinics (e.g., the guidelines absence in this field).

Progressive multifocal leukoencephalopathy and hematologic malignancies: a single cancer center retrospective review

Progressive multifocal leukoencephalopathy (PML) is an uncommon opportunistic infection with high morbidity and mortality. This is an institutional review board-approved retrospective review of medical records identified by diagnostic coding for PML or John Cunningham virus (JCV) from 2000 to 2015. Inclusion criteria were cerebrospinal fluid (CSF) positive for JCV by polymerase chain reaction or brain biopsy-proven PML in non-HIV patients. There were 16 patients, 12 of whom were men (75%); the median age was 56 years (range, 31-71 years). All had hematologic malignancies (5 [31%] had chronic lymphocytic leukemia, 3 [19%] had acute myeloid leukemia, 3 had [19%] mantle cell lymphoma, and 1 patient each had acute lymphoblastic leukemia, Hodgkin lymphoma, myeloma, or B-cell lymphoma). One patient received no cancer-directed therapy. Of the remaining 15 patients, all received conventional chemotherapy, and 9 (60%) underwent transplant. Thirteen patients (87%) received immunomodulating therapy (predominantly rituximab). The median time from cancer diagnosis to PML diagnosis was 48.5 months. PML was diagnosed a median of 2.1 months from symptom onset; however, the median time to PML diagnosis was 5.4 months for the 4 patients presenting with a cerebellar syndrome. PML was diagnosed by CSF in 12 patients and brain biopsy in 4 following negative CSF test results. Median survival from PML diagnosis was 4.3 months for the 11 patients on treatment and 0.87 months for the 5 without treatment. PML still occurs in patients with hematologic malignancies in the absence of treatment. Twenty-five percent of our patients required brain biopsy for diagnosis, and diagnosis was delayed when the clinical presentation was unusual, such as a cerebellar syndrome.

Multiplex detection in tonsillar tissue of all known human polyomaviruses

BACKGROUND

In the past few years, eleven new human viruses have joined the two previously known members JCPyV and BKPyV of the Polyomaviridae family, by virtue of molecular methods. Serology data suggest that infections with human polyomaviruses (HPyVs) occur since childhood and the viruses are widespread in the general population. However, the viral persistence sites and transmission routes are by and large unknown. Our previous studies demonstrated that the four new HPyVs - KIPyV, WUPyV, MCPyV and TSPyV - were present in the tonsils, and suggested lymphoid tissue as a persistent site of these emerging human viruses. We developed a Luminex-based multiplex assay for simultaneous detection of all 13 HPyVs known, and explored their occurrence in tonsillar tissues of children and adults mostly with tonsillitis or tonsillar hypertrophy.

METHODS

We set up and validated a new Luminex-based multiplex assay by using primer pairs and probes targeting the respective HPyV viral protein 1 (VP1) genes. With this assay we tested 78 tonsillar tissues for DNAs of 13 HPyVs.

RESULTS

The multiplex assay allowed for simultaneous detection of 13 HPyVs with high analytical sensitivity and specificity, with detection limits of 100-102 copies per microliter, and identified correctly all 13 target sequences with no cross reactions. HPyV DNA altogether was found in 14 (17.9%) of 78 tonsils. The most prevalent HPyVs were HPyV6 (7.7%), TSPyV (3.8%) and WUPyV (3.8%). Mixed infection of two HPyVs occurred in one sample.

CONCLUSIONS

The Luminex-based HPyV multiplex assay appears highly suitable for clinical diagnostic purposes and large-scale epidemiological studies. Additional evidence was acquired that the lymphoid system plays a role in HPyV infection and persistence. Thereby, shedding from this site during reactivation might take part in transmission of the newly found HPyVs.

Characterization of Immunodominant BK Polyomavirus 9mer Epitope T Cell Responses

Uncontrolled BK polyomavirus (BKPyV) replication in kidney transplant recipients (KTRs) causes polyomavirus-associated nephropathy and allograft loss. Reducing immunosuppression is associated with clearing viremia and nephropathy and increasing BKPyV-specific T cell responses in most patients; however, current immunoassays have limited sensitivity, target mostly CD4(+) T cells, and largely fail to predict onset and clearance of BKPyV replication. To characterize BKPyV-specific CD8(+) T cells, bioinformatics were used to predict 9mer epitopes in the early viral gene region (EVGR) presented by 14 common HLAs in Europe and North America. Thirty-nine EVGR epitopes were experimentally confirmed by interferon-γ enzyme-linked immunospot assays in at least 30% of BKPyV IgG-seropositive healthy participants. Most 9mers clustered in domains, and some were presented by more than one HLA class I, as typically seen for immunodominant epitopes. Specific T cell binding using MHC class I streptamers was demonstrated for 21 of 39 (54%) epitopes. In a prospective cohort of 118 pediatric KTRs, 19 patients protected or recovering from BKPyV viremia were experimentally tested, and 13 epitopes were validated. Single HLA mismatches were not associated with viremia, suggesting that failing immune control likely involves multiple factors including maintenance immunosuppression. Combining BKPyV load and T cell assays using immunodominant epitopes may help in evaluating risk and reducing immunosuppression and may lead to safe adoptive T cell transfer.

BK Polyomavirus Replication in Renal Tubular Epithelial Cells Is Inhibited by Sirolimus, but Activated by Tacrolimus Through a Pathway Involving FKBP-12

BK polyomavirus (BKPyV) replication causes nephropathy and premature kidney transplant failure. Insufficient BKPyV-specific T cell control is regarded as a key mechanism, but direct effects of immunosuppressive drugs on BKPyV replication might play an additional role. We compared the effects of mammalian target of rapamycin (mTOR)- and calcineurin-inhibitors on BKPyV replication in primary human renal tubular epithelial cells. Sirolimus impaired BKPyV replication with a 90% inhibitory concentration of 4 ng/mL by interfering with mTOR-SP6-kinase activation. Sirolimus inhibition was rapid and effective up to 24 h postinfection during viral early gene expression, but not thereafter, during viral late gene expression. The mTORC-1 kinase inhibitor torin-1 showed a similar inhibition profile, supporting the notion that early steps of BKPyV replication depend on mTOR activity. Cyclosporine A also inhibited BKPyV replication, while tacrolimus activated BKPyV replication and reversed sirolimus inhibition. FK binding protein 12kda (FKBP-12) siRNA knockdown abrogated sirolimus inhibition and increased BKPyV replication similar to adding tacrolimus. Thus, sirolimus and tacrolimus exert opposite effects on BKPyV replication in renal tubular epithelial cells by a mechanism involving FKBP-12 as common target. Immunosuppressive drugs may therefore contribute directly to the risk of BKPyV replication and nephropathy besides suppressing T cell functions. The data provide rationales for clinical trials aiming at reducing the risk of BKPyV replication and disease in kidney transplantation.

Antibody response to BK polyomavirus as a prognostic biomarker and potential therapeutic target in prostate cancer

Infectious agents, including the BK polyomavirus (BKPyV), have been proposed as important inflammatory pathogens in prostate cancer. Here, we evaluated whether the preoperative antibody response to BKPyV large T antigen (LTag) and viral capsid protein 1 (VP1) was associated with the risk of biochemical recurrence in 226 patients undergoing radical prostatectomy for primary prostate cancer. Essentially, the multivariate Cox regression analysis revealed that preoperative seropositivity to BKPyV LTag significantly reduced the risk of biochemical recurrence, independently of established predictors of biochemical recurrence such as tumor stage, Gleason score and surgical margin status. The predictive accuracy of the regression model was denotatively increased by the inclusion of the BKPyV LTag serostatus. In contrast, the VP1 serostatus was of no prognostic value. Finally, the BKPyV LTag serostatus was associated with a peculiar cytokine gene expression profile upon assessment of the cellular immune response elicited by LTag. Taken together, our findings suggest that the BKPyV LTag serology may serve as a prognostic factor in prostate cancer. If validated in additional studies, this biomarker may allow for better treatment decisions after radical prostatectomy. Finally, the favorable outcome of LTag seropositive patients may provide a potential opportunity for novel therapeutic approaches targeting a viral antigen.

Optimizing JC and BK polyomavirus IgG testing for seroepidemiology and patient counseling

BACKGROUND

Polyomavirus JC (JCPyV) and BK (BKPyV) can cause significant diseases in immunocompromised patients including nephropathy, hemorrhagic cystitis, and leukoencephalopathy. Recently, JCPyV and BKPyV IgG have been explored as risk predictors in multiple sclerosis and transplant patients, but sensitivity, specificity and quantification issues limit current performance.

OBJECTIVE

To improve JCPyV and BKPyV-specific antibody testing.

STUDY DESIGN

Healthy blood donor sera (N=400) were tested at dilutions 1:100, 1:200, and 1:400 for JCPyV- and BKPyV-specific IgG using VP1 virus-like particle (VLP)-based ELISAs normalized to a laboratory reference serum. Normalized optical density 492nm greater or equal 0.1 in all 3 dilutions was regarded as reactive. Sera with discordant reactivity in at least one dilution were retested after VLP preadsorption.

RESULTS

At dilutions 1:100, 1:200, and 1:400, IgG reactivity was 74%, 60% and 53% for JCPyV, and 93%, 86% and 74% for BKPyV, respectively. At these dilutions, JCPyV-VLP preadsorption identified 56, 4 and 0 false-positives and 0, 4 and 27 false-negatives, respectively. Dilution-dependent sensitivity was 100%, 98%, and 89%, and specificity 65, 98%, and 100%, respectively. For sera diluted 100-, 200-, and 400-fold, BKPyV-VLP preadsorption identified 28, 1 and 0 false-positives, and 0, 0 and 46 false-negatives, and sensitivity was 100%, 100%, 86%, and specificity 50%, 98%, 100%, respectively.

CONCLUSION

For seroepidemiology studies, normalized JCPyV and BKPyV IgG ELISA at 1:200 serum dilution provides optimal sensitivity and specificity with the lowest false-positive and false-negative rate. For individual risk assessment, dilutions of 100, 200, and 400 combined with preadsorption for low-reactive sera may be most appropriate.

Comparison of Two Commercial Tick-Borne Encephalitis Virus IgG Enzyme-Linked Immunosorbent Assays

Despite the availability of protective vaccines, tick-borne encephalitis virus (TBEV) infections have been increasingly reported to the European Centre for Disease Prevention and Control in the past 2 decades. Since the diagnosis of TBEV exposure relies on serological testing, we compared two commercial enzyme-linked immunosorbent assays (ELISAs), i.e., Immunozym FSME IgG assay (ELISA-1) and Euroimmun FSME Vienna IgG assay (ELISA-2). Both assays use whole TBEV antigens, but they differ in viral strains (Neudoerfl for ELISA-1 and K23 for ELISA-2) and cutoff values. In testing of samples from 398 healthy blood donors, ELISA-1 showed higher reactivity levels than ELISA-2 (P < 0.001), suggesting different assay properties. This finding was supported by Bland-Altman analysis of the optical density at 450 nm (OD450) (mean bias, +0.32 [95% limits of agreement, -0.31 to +0.95]) and persisted after transformation into Vienna units. Concordant results were observed for 276 sera (69%) (44 positive and 232 negative results). Discordant results were observed for 122 sera (31%); 15 were fully discordant, all being ELISA-1 positive and ELISA-2 negative, and 107 were partially discordant (101 being ELISA-1 indeterminate and ELISA-2 negative and 6 having positive or indeterminate reactivity in both ELISAs). Neutralization testing at a 1:10 dilution yielded positive results for 33 of 44 concordant positive sera, 1 of 15 fully discordant sera, and 1 of 33 partially discordant sera. Indirect immunofluorescence testing revealed high antibody titers of ≥100 for yellow fever virus in 18 cases and for dengue virus in one case, suggesting that cross-reactivity contributed to the ELISA-1 results. We conclude that (i) cross-reactivity among flaviviruses remains a limitation of TBEV serological testing, (ii) ELISA-2 revealed reasonable sensitivity and specificity for anti-TBEV IgG population screening of human sera, and (iii) neutralization testing is most specific and should be reserved for selective questions.