Immune monitoring of allograft status in kidney transplant recipients.

Kidney transplant patients require careful management of immunosuppression to avoid rejection while minimizing the risk of infection and malignancy for the best long-term outcome. The gold standard for monitoring allograft status and immunosuppression adequacy is a kidney biopsy, but this is invasive and costly. Conventional methods of allograft monitoring, such as serum creatinine level, are non-specific. Although they alert physicians to the need to evaluate graft dysfunction, by the time there is a clinical abnormality, allograft damage may have already occurred. The development of novel and non-invasive methods of evaluating allograft status are important to improving graft outcomes. This review summarizes the available conventional and novel methods for monitoring allograft status after kidney transplant. Novel and less invasive methods include gene expression, cell-free DNA, urinary biomarkers, and the use of artificial intelligence. The optimal method to manage patients after kidney transplant is still being investigated. The development of less invasive methods to assess allograft function has the potential to improve patient outcomes and allow for a more personalized approach to immunosuppression management.

Urinary Cell mRNA Profiles Predictive of Human Kidney Allograft Status.

Immune monitoring of kidney allograft recipients and personalized therapeutics may help reach the aspirational goal of "one transplant for life." The invasive kidney biopsy procedure, the diagnostic tool of choice, has become safer and the biopsy classification more refined. Nevertheless, biopsy-associated complications, interobserver variability in biopsy specimen scoring, and costs continue to be significant concerns. The dynamics of the immune repertoire make frequent assessments of allograft status necessary, but repeat biopsies of the kidney are neither practical nor safe. To address the existing challenges, we developed urinary cell mRNA profiling and investigated the diagnostic, prognostic, and predictive accuracy of absolute levels of a hypothesis-based panel of mRNAs encoding immunoregulatory proteins. Enabled by our refinements of the PCR assay and by investigating mechanistic hypotheses, our single-center studies identified urinary cell mRNAs associated with T cell-mediated rejection, antibody-mediated rejection, interstitial fibrosis and tubular atrophy, and BK virus nephropathy. In the multicenter National Institutes of Health Clinical Trials in Organ Transplantation-04, we discovered and validated a urinary cell three-gene signature of T-cell CD3 ε chain mRNA, interferon gamma inducible protein 10 (IP-10) mRNA, and 18s ribosomal RNA that is diagnostic of subclinical acute cellular rejection and acute cellular rejection and prognostic of acute cellular rejection and graft function. The trajectory of the signature score remained flat and below the diagnostic threshold for acute cellular rejection in the patients with no rejection biopsy specimens, whereas a sharp rise was observed during the weeks before the biopsy specimen that showed acute cellular rejection. Our RNA sequencing and bioinformatics identified kidney allograft biopsy specimen gene signatures of acute rejection to be enriched in urinary cells matched to acute rejection biopsy specimens. The urinary cellular landscape was more diverse and more enriched for immune cell types compared with kidney allograft biopsy specimens. Urinary cell mRNA profile-guided clinical trials are needed to evaluate their value compared with current standard of care.

Influence of Cold Ischemia Time in Combination with Donor Acute Kidney Injury on Kidney Transplantation Outcomes.

BACKGROUND: Deceased-donor kidneys are often exposed to ischemic events from donor instability, as evidenced by acute kidney injury (AKI). Clinicians may be reluctant to transplant kidneys with AKI that also have prolonged cold ischemia time (CIT) for fear of an additional deleterious effect. STUDY DESIGN: We evaluated national data between 1998 and 2013 of adult first-time kidney-only recipients of paired kidneys from donors with AKI (terminal serum creatinine ≥ 2 mg/dL), in which the CIT difference between recipients was ≥1, 5, 10, or 15 hours. RESULTS: On multivariate analysis of AKI kidney recipients, overall death-censored graft survival (DCGS) was comparable between recipients with higher CIT relative to paired donor recipients with lower CIT when the CIT difference was at least 1 hour (adjusted hazard ratio [aHR] 0.98, 95% CI 0.85 to 1.13, n = 4,458), 5 hours (aHR 0.97, 95% CI 0.79 to 1.18, n = 2,412), 10 hours (aHR 0.82, 95% CI 0.59 to 1.15, n = 922), or 15 hours (aHR 0.94, 95% CI 0.57 to 1.58, n = 442). Overall patient survival of the longer CIT groups was comparable or protective with delta CIT of ≥1 (aHR 0.94, 95% CI 0.83 to 1.06), 5 (aHR 0.80, 95% CI 0.68 to 0.94), 10 (aHR 0.70, 95% CI 0.53 to 0.91), and 15 (aHR 0.64, 95%CI 0.43 to 0.95) hours. Between each of the 4 delta-CIT levels of shorter and longer CIT, there were no statistically significant differences in the proportion of acute rejection at delta ≥1, 5, 10, or 15 hours. CONCLUSIONS: These results suggest that in the setting of a previous ischemic donor event, prolonged CIT has limited bearing on long-term outcomes. This may be important evidence that despite the occurrence of other ischemic events, kidneys with prolonged CIT offer acceptable outcomes to recipients and are a potential source to expand the donor pool.

Campath induction in HCV and HCV/HIV-seropositive kidney transplant recipients.

Alemtuzumab (AZ) induction in hepatitis C-seropositive (HCV+) kidney transplant (KTX) recipients may negatively affect patient survival; however, available information is scant. Using US registry data from 2003 to 2010 of adult HCV+ deceased-donor KTXs (n = 4910), we examined outcomes by induction agent - AZ (n = 294), other T cell-depleting agents, (n = 2033; T cell), IL-2 receptor blockade (n = 1135; IL-2RAb), and no induction (n = 1448). On multivariate analysis, induction therapy was associated with significantly better overall patient survival with AZ [adjusted hazards ratio (aHR) 0.64, 95% confidence interval (CI) 0.45, 0.92], T cell (aHR 0.52, 95% CI 0.41, 0.65) or IL-2RAb (aHR 0.67, 95% CI 0.53, 0.87), compared to no induction. A significant protective effect was also seen with AZ (aHR 0.63, 95% CI 0.40, 0.99), T cell (aHR 0.62, 95% CI 0.49, 0.78), and IL2R-Ab (aHR 0.62, 95% CI 0.47, 0.82) in terms of death-censored graft survival relative to no induction. There were 88 HIV+/HCV+ coinfected recipients. Compared to noninduction, any induction (i.e. three induction groups combined) was associated with similar overall patient survival (P = 0.2255) on univariate analysis. Induction therapy with AZ, other T cell-depleting agents, or IL-2RAb in HCV+ KTX is associated with better patient and death-censored graft survival compared to noninduction. In HCV/HIV coinfected patients, induction is not contraindicated.