Single cell transcriptomic analysis of renal allograft rejection reveals insights into intragraft TCR clonality

Bulk analysis of renal allograft biopsies (rBx) identified RNA transcripts associated with acute cellular rejection (ACR); however, these lacked cellular context critical to mechanistic understanding of how rejection occurs despite immunosuppression (IS). We performed combined single cell RNA transcriptomic and TCRα/β sequencing on rBx from patients with ACR under differing IS: tacrolimus, iscalimab, and belatacept. We found distinct CD8+ T cell phenotypes (e.g., effector, memory, exhausted) depending upon IS type, particularly within clonally expanded cells (CD8EXP). Gene expression of CD8EXP identified therapeutic targets that were influenced by IS type. TCR analysis revealed a highly restricted number of CD8EXP, independent of HLA mismatch or IS type. Subcloning of TCRα/β cDNAs from CD8EXP into Jurkat76 cells (TCR-/-) conferred alloreactivity by mixed lymphocyte reaction. Analysis of sequential rBx samples revealed persistence of CD8EXP that decreased, but were not eliminated, after successful anti-rejection therapy. In contrast, CD8EXP were maintained in treatment-refractory rejection. Finally, most rBx-derived CD8EXP were also observed in matching urine samples, providing precedent for using urine-derived CD8EXP as a surrogate for those found in the rejecting allograft. Overall, our data define the clonal CD8+ T cell response to ACR, paving the next steps to improve detection, assessment, and treatment of rejection.

Single cell transcriptomic analysis of renal allograft rejection reveals novel insights into intragraft TCR clonality

Bulk analysis of renal allograft biopsies (rBx) identified RNA transcripts associated with acute cellular rejection (ACR); however, these lacked cellular context critical to mechanistic understanding. We performed combined single cell RNA transcriptomic and TCRα/β sequencing on rBx from patients with ACR under differing immunosuppression (IS): tacrolimus, iscalimab, and belatacept. TCR analysis revealed a highly restricted CD8 ⁺ T cell clonal expansion (CD8 _EXP ), independent of HLA mismatch or IS type. Subcloning of TCRα/β cDNAs from CD8 _EXP into Jurkat76 cells (TCR ^-/- ) conferred alloreactivity by mixed lymphocyte reaction. scRNAseq analysis of CD8 _EXP revealed effector, memory, and exhausted phenotypes that were influenced by IS type. Successful anti-rejection treatment decreased, but did not eliminate, CD8 _EXP , while CD8 _EXP were maintained during treatment-refractory rejection. Finally, most rBx-derived CD8 _EXP were also observed in matching urine samples. Overall, our data define the clonal CD8 ⁺ T cell response to ACR, providing novel insights to improve detection, assessment, and treatment of rejection.

Belatacept-based immunosuppression with simultaneous calcineurin inhibitor avoidance and early corticosteroid withdrawal: A prospective, randomized multicenter trial

Simultaneous calcineurin inhibitor avoidance (CNIA) and early corticosteroid withdrawal (ESW) have not been achieved primarily due to excessive acute rejection. This trial compared 2 belatacept-based CNIA/ESW regimens with a tacrolimus-based ESW regimen. Kidney transplant recipients were randomized to receive alemtuzumab/belatacept, rabbit anti-thymocyte globulin (rATG)/belatacept, or rATG/tacrolimus. The combinatorial primary endpoint consisted of patient death, renal allograft loss, or a Modification of Diet in Renal Disease-calculated eGFR of <45 mL/min/1.73 m² at 12 months. Results are reported by treatment group (alemtuzumab/belatacept, rATG/belatacept, and rATG/tacrolimus). Superiority was not observed at 1 year for the primary endpoint (9/107 [8.4%], 15/104 [14.4%], and 14/105 [13.3%], respectively; P = NS) for either belatacept-based regimen. Differences were not observed for secondary endpoints (death, death-censored graft loss, or estimated glomerular filtration rates < 45 mL/min/1.73 m² ). Differences were observed in biopsy-proved acute cellular rejection (10.3%, 18.3%, and 1.9%, respectively) (P < .001), but not in antibody-mediated rejection, mixed acute rejection, or de novo donor-specific anti-HLA antibodies. Neurologic and electrolyte abnormality adverse events were less frequent under belatacept. Belatacept-based CNIA/ESW regimens did not prove to be superior for the primary or secondary endpoints. Belatacept-treated patients demonstrated an increase in biopsy-proved acute cellular rejection and reduced neurologic and metabolic adverse events. These results demonstrate that simultaneous CNIA/ESW is feasible without excessive acute rejection.

Laparoscopic sleeve gastrectomy improves renal transplant candidacy and posttransplant outcomes in morbidly obese patients

Morbid obesity is a barrier to kidney transplantation due to inferior outcomes, including higher rates of new-onset diabetes after transplantation (NODAT), delayed graft function (DGF), and graft failure. Laparoscopic sleeve gastrectomy (LSG) increases transplant eligibility by reducing BMI in kidney transplant candidates, but the effect of surgical weight loss on posttransplantation outcomes is unknown. Reviewing single-center medical records, we identified all patients who underwent LSG before kidney transplantation from 2011-2016 (n = 20). Post-LSG kidney recipients were compared with similar-BMI recipients who did not undergo LSG, using 2:1 direct matching for patient factors. McNemar's test and signed-rank test were used to compare groups. Among post-LSG patients, mean BMI ± standard deviation (SD) was 41.5 ± 4.4 kg/m² at initial encounter, which decreased to 32.3 ± 2.9 kg/m² prior to transplantation (P < .01). No complications, readmissions, or mortality occurred following LSG. After transplantation, one patient (5%) experienced DGF, and no patients experienced NODAT. Allograft and patient survival at 1-year posttransplantation was 100%. Compared with non-LSG patients, post-LSG recipients had lower rates of DGF (5% vs 20%) and renal dysfunction-related readmissions (10% vs 27.5%) (P < .05 each). Perioperative complications, allograft survival, and patient survival were similar between groups. These data suggest that morbidly obese patients with end-stage renal disease who undergo LSG to improve transplant candidacy, achieve excellent posttransplantation outcomes.

Contrast-Induced Nephropathy in Renal Transplant Recipients: A Single Center Experience

BACKGROUND

Contrast-induced nephropathy (CIN) in native kidneys is associated with a significant increase in mortality and morbidity. Data regarding CIN in renal allografts are limited, however. We retrospectively studied CIN in renal allografts at our institution: its incidence, risk factors, and effect on long-term outcomes including allograft loss and death.

METHODS

One hundred thirty-five renal transplant recipients undergoing 161 contrast-enhanced computed tomography (CT) scans or coronary angiograms (Cath) between years 2000 and 2014 were identified. Contrast agents were iso- or low osmolar. CIN was defined as a rise in serum creatinine (SCr) by >0.3 mg/dl or 25% from baseline within 4 days of contrast exposure. After excluding 85 contrast exposures where patients had no SCr within 4 days of contrast administration, 76 exposures (CT: n = 45; Cath: n = 31) in 50 eligible patients were analyzed. Risk factors assessed included demographics, comorbid conditions, type/volume of contrast agent used, IV fluids, N-acetylcysteine administration, and calcineurin inhibitor use. Bivariate and multivariable analyses were used to assess the risk of CIN.

RESULTS

Incidence of CIN was 13% following both, CT (6 out of 45) and Cath (4 out of 31). Significant bivariate predictors of CIN were IV fluid administration (p = 0.05), lower hemoglobin (p = 0.03), and lower albumin (p = 0.02). In a multivariable model, CIN was predicted by N-acetylcysteine (p = 0.03) and lower hemoglobin (p = 0.01). Calcineurin inhibitor use was not associated with CIN. At last follow-up, CIN did not affect allograft or patient survival.

CONCLUSION

CIN is common in kidney transplant recipients, and there is room for quality improvement with regards to careful renal function monitoring post-contrast exposure. In our study, N-acetylcysteine exposure and lower hemoglobin were associated with CIN. Calcineurin inhibitor use was not associated with CIN. Our sample size is small, however, and larger prospective studies of CIN in renal allografts are needed.

Pharmacokinetic and pharmacogenetic analysis of immunosuppressive agents after laparoscopic sleeve gastrectomy

BACKGROUND

Severe obesity has been shown to limit access to renal transplantation in patients with end-stage renal disease (ESRD). Laparoscopic sleeve gastrectomy (LSG) has been performed in the ESRD population to assist in achieving waitlist and transplant eligibility. Little is known about how LSG impacts the bioequivalence of tacrolimus products and immunosuppression pharmacokinetics.

METHODS

This was a prospective, open-label, single-dose, crossover, two-period pharmacokinetic (PK) study. The purpose of this study was to assess single-dose PK of immediate-release tacrolimus (IR-TAC), extended-release tacrolimus (ER-TAC), and mycophenolic acid (MPA) in adult ESRD patients post-LSG.

RESULTS

Twenty-three subjects were included in the 24-hour PK assessments. The ratio of geometric means between ER-TAC and IR-TAC was 103.5% (90% CI; 89.6%-119.6%) for AUC_0-24 and 92.5% (90% CI; 80.4%-106.4%) for C_max . PK parameters were similar between ER-TAC and IR-TAC, except for C_min (P=.004) and C_max (P=.04). MPA AUC_0-24 was similar when given with either ER-TAC or IR-TAC (P=.32). Patients expressing CYP3A5*1 genotypes had lower tacrolimus AUC_0-24 values vs those with CYP3A5*3/*3 (IR-TACP<.001; ER-TACP=.008). Genotype did not impact MPA PK.

CONCLUSION

Dose modification of immunosuppressants post-LSG may not be necessary aside from standard therapeutic drug monitoring.

Prospective iterative trial of proteasome inhibitor-based desensitization

A prospective iterative trial of proteasome inhibitor (PI)-based therapy for reducing HLA antibody (Ab) levels was conducted in five phases differing in bortezomib dosing density and plasmapheresis timing. Phases included 1 or 2 bortezomib cycles (1.3 mg/m(2) × 6-8 doses), one rituximab dose and plasmapheresis. HLA Abs were measured by solid phase and flow cytometry (FCM) assays. Immunodominant Ab (iAb) was defined as highest HLA Ab level. Forty-four patients received 52 desensitization courses (7 patients enrolled in multiple phases): Phase 1 (n = 20), Phase 2 (n = 12), Phase 3 (n = 10), Phase 4 (n = 5), Phase 5 (n = 5). iAb reductions were observed in 38 of 44 (86%) patients and persisted up to 10 months. In Phase 1, a 51.5% iAb reduction was observed at 28 days with bortezomib alone. iAb reductions increased with higher bortezomib dosing densities and included class I, II, and public antigens (HLA DRβ3, HLA DRβ4 and HLA DRβ5). FCM median channel shifts decreased in 11/11 (100%) patients by a mean of 103 ± 54 mean channel shifts (log scale). Nineteen out of 44 patients (43.2%) were transplanted with low acute rejection rates (18.8%) and de novo DSA formation (12.5%). In conclusion, PI-based desensitization consistently and durably reduces HLA Ab levels providing an alternative to intravenous immune globulin-based desensitization.

Randomized controlled pilot study of B cell-targeted induction therapy in HLA sensitized kidney transplant recipients

Optimal induction regimens for patients at high risk for antibody and/or cell-mediated rejection have not been established. This pilot, prospective, randomized study evaluated addition of B cell/plasma cell-targeting agents to T cell-based induction with rabbit antithymocyte globulin (rATG) in high immunologic risk renal transplant recipients. Patients were randomized to induction with rATG, rATG + rituximab, rATG + bortezomib or rATG + rituximab + bortezomib. Inclusion criteria were: (1) current cytotoxic panel reactive antibody (PRA) ≥20% or peak cytotoxic PRA ≥50% or (2) T or B cell positive flow crossmatch with donor-specific antibody (DSA) or (3) historical positive serologic or cytotoxic crossmatch or DSA to donor or (4) prior allograft loss with more than one acute rejection. Median overall follow-up was 496 days: 1-year and overall acute rejection were 25% and 27.5%, and 25% of patients developed de novo DSA within 1 year. One-year and overall patient survival were 97.5% and 92.5%, and 1-year and overall death-censored allograft survival were 97.5% and 95%. Renal allograft function posttransplant was similar among all arms. Eight of nine cases of peripheral neuropathy were mild, whereas one case was moderate and required a narcotic prescription. In conclusion, addition of rituximab and/or bortezomib to rATG induction has an acceptable safety/toxicity profile in a high immunologic risk renal transplant population.

Magnetically actuated nanorod arrays as biomimetic cilia

We present a procedure for producing high-aspect-ratio cantilevered micro- and nanorod arrays of a PDMS-ferrofluid composite material. The rods have been produced with diameters ranging from 200 nm to 1 mum and aspect ratios as high as 125. We demonstrate actuation of these superparamagnetic rod arrays with an externally applied magnetic field from a permanent magnet and compare this actuation with a theoretical energy-minimization model. The structures produced by these methods may be useful in microfluidics, photonic, and sensing applications.

Outcomes analysis for hearing conservation programs

In health care, an increasing interest in accountability for outcomes, proof of quality care, and cost effectiveness is forcing many practitioners, including audiologists, in the direction of using outcomes analysis to provide proof of performance in their practices. Critical to the conduct of outcomes analysis are the selection of valid outcomes metrics and application of appropriate statistical processes. Modeling of clinical protocols is a useful exercise for developing outcomes data and data management standards. The authors describe the implications for wider use of outcomes modeling once the Health Insurance Portability and Accountability Act (HIPAA) administrative simplification law is implemented. This legislation will set up a wholly new administrative data set that has strong potential to provide outcomes metrics to a variety of Audiology practices. The modeling exercise described here was originally intended to derive assessment outcomes for evaluating hearing conservation program effectiveness in military populations from an administrative database implemented within the Military Health System starting in 1997. The outcomes modelers, however, soon realized the broader applicability of modeling techniques for other special populations and Audiology practices, particularly with the oncoming startup of HIPAA legislative mandates. The modeling exercise demonstrates a process of structuring standard health-care codes to produce outcomes data for epidemiologic and cost analyses, thereby providing better information to guide health-care practices toward improving quality and cost effectiveness. This information in time series should also provide a record of continuous quality improvement. The authors present a general hearing surveillance protocol for evaluating occupational hearing loss. The protocol is used as a specific instance to demonstrate the shaping of an outcomes metrics model. This same process can be applied more generally when used to model outcomes data from other audiology practices. Implementation of the administrative data model described here began at more than 400 Department of Defense (DOD) medical treatment facilities worldwide as of October 1, 1999. The exercise of developing similar outcomes metrics for newborn hearing screening programs, school hearing conservation programs, and other clinical and rehabilitative audiology practices in the civilian sector remains to be done.