BK virus viremia in a well-HLA-matched kidney transplant population mainly on low-dose cyclosporine-based immunosuppression

Allogeneic CD4 T Cells Sustain Effective BK Polyomavirus-Specific CD8 T Cell Response in Kidney Transplant Recipients

Introduction

BK polyomavirus-associated nephropathy (BKPyVAN) is a significant complication in kidney transplant recipients (KTRs), associated with a higher level of plasmatic BK polyomavirus (BKPyV) replication and leading to poor graft survival.

Methods

We prospectively followed-up with 100 KTRs with various degrees of BKPyV reactivation (no BKPyV reactivation, BKPyV-DNAuria, BKPyV-DNAemia, and biopsy-proven BKPyVAN [bp-BKPyVAN], 25 patients per group) and evaluated BKPyV-specific T cell functionality and phenotype.

Results

We demonstrate that bp-BKPyVAN is associated with a loss of BKPyV-specific T cell proliferation, cytokine secretion, and cytotoxic capacities. This severe functional impairment is associated with an overexpression of lymphocyte inhibitory receptors (programmed cell death 1 [PD1], cytotoxic T lymphocyte-associated protein 4, T cell immunoreceptor with Ig and ITIM domains, and T cell immunoglobulin and mucin domain-containing-3), highlighting an exhausted-like phenotype of BKPyV-specific CD4 and CD8 T cells in bp-BKPyVAN. This T cell dysfunction is associated with low class II donor-recipient human leukocyte antigen (HLA) divergence. In contrast, in the context of higher class II donor-recipient HLA (D/R-HLA) divergence, allogeneic CD4 T cells can provide help that sustains BKPyV-specific CD8 T cell responses. In vitro, allogeneic HLA-mismatched CD4 T cells rescue BKPyV-specific CD8 T cell responses.

Conclusion

Our findings suggest that in KTRs, allogeneic CD4 T cells can help to maintain an effective BKPyV-specific CD8 T cell response that better controls BKPyV replication in the kidney allograft and may protect against BKPyVAN.

The Role of HLA and KIR Immunogenetics in BK Virus Infection after Kidney Transplantation

BK virus (BKV) is a polyomavirus with high seroprevalence in the general population with an unremarkable clinical presentation in healthy people, but a potential for causing serious complications in immunosuppressed transplanted patients. Reactivation or primary infection in kidney allograft recipients may lead to allograft dysfunction and subsequent loss. Currently, there is no widely accepted specific treatment for BKV infection and reduction of immunosuppressive therapy is the mainstay therapy. Given this and the sequential appearance of viruria-viremia-nephropathy, screening and early detection are of utmost importance. There are numerous risk factors associated with BKV infection including genetic factors, among them human leukocyte antigens (HLA) and killer cell immunoglobulin-like receptors (KIR) alleles have been shown to be the strongest so far. Identification of patients at risk for BKV infection would be useful in prevention or early action to reduce morbidity and progression to frank nephropathy. Assessment of risk involving HLA ligands and KIR genotyping of recipients in the pre-transplant or early post-transplant period might be useful in clinical practice. This review summarizes current knowledge of the association between HLA, KIR and BKV infection and potential future directions of research, which might lead to optimal utilization of these genetic markers.

BK polyomavirus in solid organ transplantation-Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

The present AST-IDCOP guidelines update information on BK polyomavirus (BKPyV) infection, replication, and disease, which impact kidney transplantation (KT), but rarely non-kidney solid organ transplantation (SOT). As pretransplant risk factors in KT donors and recipients presently do not translate into clinically validated measures regarding organ allocation, antiviral prophylaxis, or screening, all KT recipients should be screened for BKPyV-DNAemia monthly until month 9, and then every 3 months until 2 years posttransplant. Extended screening after 2 years may be considered in pediatric KT. Stepwise immunosuppression reduction is recommended for KT patients with plasma BKPyV-DNAemia of >1000 copies/mL sustained for 3 weeks or increasing to >10 000 copies/mL reflecting probable and presumptive BKPyV-associated nephropathy, respectively. Reducing immunosuppression is also the primary intervention for biopsy-proven BKPyV-associated nephropathy. Hence, allograft biopsy is not required for treating BKPyV-DNAemic patients with baseline renal function. Despite virological rationales, proper randomized clinical trials are lacking to generally recommend treatment by switching from tacrolimus to cyclosporine-A, from mycophenolate to mTOR inhibitors or leflunomide or by the adjunct use of intravenous immunoglobulins, leflunomide, or cidofovir. Fluoroquinolones are not recommended for prophylaxis or therapy. Retransplantation after allograft loss due to BKPyV nephropathy can be successful if BKPyV-DNAemia is definitively cleared, independent of failed allograft nephrectomy.

Archetype JC Polyomavirus (JCPyV) Prevails in a Rare Case of JCPyV Nephropathy and in Stable Renal Transplant Recipients With JCPyV Viruria

Background

JC polyomavirus (JCPyV) is reactivated in approximately 20% of renal transplant recipients, and it may rarely cause JCPyV-associated nephropathy (JCPyVAN). Whereas progressive multifocal leukoencephalopathy of the brain is caused by rearranged neurotropic JCPyV, little is known about viral sequence variation in JCPyVAN owing to the rarity of this condition.

Methods

Using single-molecule real-time sequencing, characterization of full-length JCPyV genomes in urine and plasma samples from 1 patient with JCPyVAN and 20 stable renal transplant recipients with JCPyV viruria was attempted. Sequence analysis of JCPyV strains was performed, with emphasis on the noncoding control region, the major capsid protein gene VP1, and the large T antigen gene.

Results

Exclusively archetype strains were identified in urine from the patient with JCPyVAN. Full-length JCPyV sequences were not retrieved from plasma. Archetype strains were found in urine samples from 19 stable renal transplant recipients, with JCPyV quasispecies detected in 5 samples. In a patient with minor graft dysfunction, a strain with an archetype-like noncoding cont rol region was discovered. Individual point mutations were detected in both VP1 and large T antigen genes.

Conclusions

Archetype JCPyV was dominant in the patient with JCPyVAN and in stable renal transplant recipients. Archetype rather than rearranged JCPyV seems to drive the pathogenesis of JCPyVAN.

High-level JCPyV viruria after kidney transplantation-Clinical and histopathological findings

BACKGROUND

The significance of JC polyomavirus (JCPyV) after kidney transplantation ranges from irrelevant to full-blown nephropathy or PML.

OBJECTIVES

To investigate the clinical significance of high-level JCPyV viruria and JCPyV primary infections after kidney transplantation.

STUDY DESIGN

JCPyV viruria was detected in routine screening by quantitative real-time PCR in 40/238 kidney transplant recipients and was high-level (>10⁷ copies/ml) in 17 patients. A protocol biopsy at the time of JCPyV viruria was available from 10 patients.

RESULTS

Peak urine viral loads were 1.0×10⁷-2.5×10⁹ copies/ml in the 17 high-level viruria patients. 6/15 (40%) patients with high-level JCPyV viruria with pretransplant sera available were JCPyV IgG negative suggesting that JCPyV viruria resulted from the donor graft in most cases. No acute graft dysfunction was associated with JCPyV viruria. No positive SV40 staining was detected in protocol biopsies, and no specific histopathology was associated with high-level viruria; JCPyV nephropathy was not found. No differences were seen in histopathology or graft function at 3 years in patients with high-level viruria compared to non-JCPyV viruric patients transplanted during the same time period, and outcome was similar in patients with presumably primary and reactivated JCPyV. The mean estimated GFR at last follow-up was 44ml/min (range 12-60ml/min). One graft with high-level viruria was lost 9 years posttransplant due to recurrent IgA nephropathy CONCLUSIONS: High-level JCPyV viruria seems to be associated with primary JCPyV infection reflecting the average seroprevalence of 60%, but is not stringently associated with inferior graft function or survival, or histopathological changes.

Simultaneous BK Polyomavirus (BKPyV)-associated nephropathy and hemorrhagic cystitis after living donor kidney transplantation

BK polyomavirus (BKPyV) commonly reactivates after kidney transplantation, and can cause polyomavirus-associated nephropathy (PyVAN), whereas after allogeneic stem cell transplantation the most frequent manifestation of BKPyV is polyomavirus-associated hemorrhagic cystitis (PyVHC). Despite high-level BKPyV replication in both, the pathogenesis and manifestation of both BKPyV entities appears to differ substantially. We describe an unusual case of simultaneous PyVAN and PyVHC presenting with acute symptoms in a BKPyV-IgG positive recipient eight months after kidney transplantation from a haploidentical living donor, who was BKPyV-IgG negative. Symptoms of cystitis and viremia subsided rapidly after reduction of immunosuppression.

BK virus nephropathy in a pediatric patient after hematopoietic stem cell transplantation

We report the case of a seven-yr-old Caucasian girl who presented with progressive deterioration of renal function 13 months after HSCT for myelodysplastic syndrome. BK virus nephropathy was suspected and confirmed. After reduction of immunosuppression and treatment with IVIG, leflunomide, ciprofloxacin, and cidofovir, clearance of BK virus from blood was achieved, and further progression or renal failure was prevented. We believe that BK virus nephropathy should be considered in cases of renal function deterioration in all immunocompromised patients.