Rachel Hilton

Development of a cross-platform biomarker signature to detect renal transplant tolerance in humans.

Identifying transplant recipients in whom immunological tolerance is established or is developing would allow an individually tailored approach to their posttransplantation management. In this study, we aimed to develop reliable and reproducible in vitro assays capable of detecting tolerance in renal transplant recipients. Several biomarkers and bioassays were screened on a training set that included 11 operationally tolerant renal transplant recipients, recipient groups following different immunosuppressive regimes, recipients undergoing chronic rejection, and healthy controls. Highly predictive assays were repeated on an independent test set that included 24 tolerant renal transplant recipients. Tolerant patients displayed an expansion of peripheral blood B and NK lymphocytes, fewer activated CD4+ T cells, a lack of donor-specific antibodies, donor-specific hyporesponsiveness of CD4+ T cells, and a high ratio of forkhead box P3 to alpha-1,2-mannosidase gene expression. Microarray analysis further revealed in tolerant recipients a bias toward differential expression of B cell-related genes and their associated molecular pathways. By combining these indices of tolerance as a cross-platform biomarker signature, we were able to identify tolerant recipients in both the training set and the test set. This study provides an immunological profile of the tolerant state that, with further validation, should inform and shape drug-weaning protocols in renal transplant recipients.

Predictors of Renal Outcome in HIV-Associated Nephropathy

BACKGROUND Human immunodeficiency virus (HIV)-associated nephropathy (HIVAN) is an important cause of end-stage renal disease among African American patients. This study was performed to study the epidemiology of HIVAN in a predominantly black African population and the impact of highly active antiretroviral therapy and other factors on the development of end-stage renal disease. METHODS We retrospectively identified all patients with HIVAN, defined by biopsy or strict clinical criteria, in 8 clinics in the United Kingdom. Baseline renal function, HIV parameters, renal pathological index of chronic damage, and responses to highly active antiretroviral therapy were analyzed, and factors associated with adverse renal outcome were identified. RESULTS From 1998 through 2004, we studied 16,834 patients, 61 of whom had HIVAN. HIVAN prevalence in black patients was 0.93%, and HIVAN incidence in those without renal disease at baseline was 0.61 per 1000 person-years. After a median of 4.2 years, 34 patients (56%) had developed end-stage renal disease. There were no significant differences in renal function and HIV parameters at baseline, time to initiation of highly active antiretroviral therapy, and rates of HIV RNA suppression between the 20 patients who developed end-stage renal disease >3 months after receiving the HIVAN diagnosis and the 23 patients who maintained stable renal function. However, the index of chronic damage score was significantly higher in those who developed end-stage renal disease (P < .001), and an index of chronic damage score >75 was associated with shorter renal survival (P < .001). CONCLUSIONS Whereas overall patient survival suggested an important benefit of highly active antiretroviral therapy, no additional renal benefit of early initiation of highly active antiretroviral therapy or viral suppression could be demonstrated in this large cohort of patients with established HIVAN. Severity of chronic kidney damage, as quantified by biopsy, was the strongest predictor of renal outcome.

Antiviral therapy for polyomavirus-associated nephropathy after renal transplantation

Polyomavirus-associated nephropathy (PVAN) has recently emerged as an important cause of allograft failure following renal transplantation. The BK virus is the most important polyomavirus associated with this condition. The mainstay of therapy for PVAN is a prompt immunosuppressive dose reduction in conjunction with careful monitoring for BK viraemia. A number of antiviral agents have been tried to help to reduce BK viral replication. So far, there has been only a single randomized controlled study on the use of one of these agents. Pooled data from various small case series did not show significant differences in outcome. Prospective randomized studies with a standardized protocol are urgently required.

Comparison of Regulatory T Cells in Hemodialysis Patients and Healthy Controls: Implications for Cell Therapy in Transplantation

BACKGROUND AND OBJECTIVES Cell-based therapy with natural (CD4(+)CD25(hi)CD127(lo)) regulatory T cells to induce transplant tolerance is now technically feasible. However, regulatory T cells from hemodialysis patients awaiting transplantation may be functionally/numerically defective. Human regulatory T cells are also heterogeneous, and some are able to convert to proinflammatory Th17 cells. This study addresses the suitability of regulatory T cells from hemodialysis patients for cell-based therapy in preparation for the first clinical trials in renal transplant recipients (the ONE Study). DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Healthy controls and age- and sex-matched hemodialysis patients without recent illness/autoimmune disease on established, complication-free hemodialysis for a minimum of 6 months were recruited. Circulating regulatory T cells were studied by flow cytometry to compare the regulatory T cell subpopulations. Regulatory T cells from members of each group were compared for suppressive function and plasticity (IL-17-producing capacity) before and after in vitro expansion with and without Rapamycin, using standard assays. RESULTS Both groups had similar total regulatory T cells and subpopulations I and III. In each subpopulation, regulatory T cells expressed similar levels of the function-associated markers CD27, CD39, HLA-DR, and FOXP3. Hemodialysis regulatory T cells were less suppressive, expanded poorly compared with healthy control regulatory T cells, and produced IL-17 in the absence of Rapamycin. However, Rapamycin efficiently expanded hemodialysis regulatory T cells to a functional and stable cell product. CONCLUSIONS Rapamycin-based expansion protocols should enable clinical trials of cell-based immunotherapy for the induction of tolerance to renal allografts using hemodialysis regulatory T cells.

Biomarkers of Tolerance in Kidney Transplantation: Are We Predicting Tolerance or Response to Immunosuppressive Treatment?

We and others have previously described signatures of tolerance in kidney transplantation showing the differential expression of B cell–related genes and the relative expansions of B cell subsets. However, in all of these studies, the index group—namely, the tolerant recipients—were not receiving immunosuppression (IS) treatment, unlike the rest of the comparator groups. We aimed to assess the confounding effect of these regimens and develop a novel IS‐independent signature of tolerance. Analyzing gene expression in three independent kidney transplant patient cohorts (232 recipients and 14 tolerant patients), we have established that the expression of the previously reported signature was biased by IS regimens, which also influenced transitional B cells. We have defined and validated a new gene expression signature that is independent of drug effects and also differentiates tolerant patients from healthy controls (cross‐validated area under the receiver operating characteristic curve [AUC] = 0.81). In a prospective cohort, we have demonstrated that the new signature remained stable before and after steroid withdrawal. In addition, we report on a validated and highly accurate gene expression signature that can be reliably used to identify patients suitable for IS reduction (approximately 12% of stable patients), irrespective of the IS drugs they are receiving. Only a similar approach will make the conduct of pilot clinical trials for IS minimization safe and hence allow critical improvements in kidney posttransplant management.

Kidney transplantation in HIV-positive adults: the UK experience.

HIV-positive patients are at increased risk of end-stage kidney disease (ESKD). Kidney transplantation (KT) is an established treatment modality for ESKD in the general population. Recent data have confirmed the feasibility of kidney transplantation in HIV-positive patients, and kidney transplantation is increasingly offered to ESKD patients with well-controlled HIV infection. We report clinical outcomes in a national cohort study of kidney transplantation in HIV-positive patients. In all, 35 HIV-positive KT recipients who had undergone KT up to December 2010 (66% male, 74% black ethnicity) were identified; the median CD4 cell count was 366, all had undetectable HIV RNA levels at kidney transplantation, and 44% received a kidney from a live donor. Patient survival at 1 and 3 years was 91.3%, and graft survival 91.3% and 84.7%, respectively. At one-year post-kidney transplantation, the cumulative incidence of acute rejection was 48%, and the median (IQR) eGFR was 64 (46, 78) mL/min/1.73 m2. Although HIV viraemia and HIV disease progression were uncommon, renal complications were relatively frequent. Our study corroborates the feasibility of kidney transplantation in HIV-positive patients. The high rates of acute rejection suggest that the optimal immune suppression strategy in this population remains to be refined.

Incidental renal stones in potential live kidney donors: prevalence, assessment and donation, including role of ex vivo ureteroscopy

Previously, donors with asymptomatic stones found incidentally on CT were not considered ideal donor candidates because of the presumed risk of morbidity to both the donor and recipient. Increasingly, studies show that these risks are low. This study aims to evaluate the long‐term safety of using ex vivo ureteroscopy to remove the stones from the donor kidney on the bench before donation. Outcomes so far suggest that this technique can safely render a kidney stone‐free before transplantation. This has led to 20 more transplants in our institution than would otherwise be possible.

BK virus nephropathy in renal transplant patients in London.

Background. BK nephropathy (BKN) is an important cause of renal transplant dysfunction, believed to be associated with higher levels of immunosuppression. We assessed the experience of BKN in renal transplant patients in the London region. Methods. All six London transplant centers participated and case notes of patients with BKN in 2004 to 2005 were reviewed. Results. There were 17 cases of BKN, giving an incidence of 2.1%. Median time to diagnosis was 9 months. Median baseline creatinine rose from 150 to 196 &mgr;mol/L. At diagnosis, 16 patients were on tacrolimus, 15 on mycophenolate mofetil, and 10 on triple therapy with tacrolimus, mycophenolate mofetil, and prednisolone. Management of BKN involved reducing immunosuppression; cidofovir was used in two patients and methylprednisolone in five for acute rejection. Median follow-up time was 29.2 months. Creatinine returned to baseline in four patients, remained elevated in 12 and one patient lost his graft. The new median baseline creatinine was 216 &mgr;mol/L. Eight patients underwent repeat biopsies of which four became negative for BKV and three subsequently cleared the virus on blood and urine polymerase chain reaction and urine decoy cells. Overall, eight patients cleared the virus. None of age, sex, viral load, or biopsy characteristics (Banff ct score, Drachenberg grade, and number of BKV positive cells) were associated with poorer outcome when patients with increase in creatinine of less than 30% (n=7) or more than 30% (n=10) from baseline were compared. Conclusion. The incidence of BKN in this study is comparable with previous studies, with more favorable outcomes. It supports the association of BKN with potent immunosuppression.

Late low-dose steroid withdrawal in renal transplant recipients increases bone formation and bone mineral density.

Corticosteroids have been the most widely used immunosuppressive agents since the first clinical transplantation in the 1950s. There are few studies of late steroid withdrawal in renal transplantation and none have prospectively assessed bone mineral density (BMD). The study aim was to assess the impact of corticosteroid withdrawal, in stable renal transplant recipients, on BMD and bone turnover.

Mycobacterium abscessus: a cutaneous infection in a patient on renal replacement therapy

We report a 72‐year‐old man on haemodialysis who presented with multiple abscesses on his lower legs. Routine bacterial culture of abscess pus was reported as ‘sterile’ after 48 h, leading to the suspicion of a mycobacterial infection. Skin biopsy taken for mycobacterial microscopy and culture isolated a heavy growth of Mycobacterium abscessus.