Belatacept with time-limited tacrolimus coimmunosuppression modifies the 3-year risk of eplet mismatch in kidney transplantation.

Solid organ transplant donor-recipient eplet mismatch has been correlated with donor-specific antibody (DSA) formation, antibody-mediated rejection, and overall rejection rates. However, studies have been predominantly in patients on tacrolimus-based immunosuppression regimens and have not fully explored differences in ethnically and racially diverse populations. Evidence indicates that patients on belatacept have lower rates of DSA formation, suggesting mediation of the immunogenicity of mismatched human leukocyte antigen polymorphisms. We performed a retrospective, single-center analysis of class II eplet disparity in a cohort of kidney transplant recipients treated using belatacept with tacrolimus induction (Bela/TacTL) or tacrolimus regimens between 2016 and 2019. Bela/TacTL (n = 294) and tacrolimus (n = 294) cohorts were propensity score-matched with standardized difference <0.15. Single-molecule eplet risk level was associated with immune event rates for both groups. In Cox regression analysis stratified by eplet risk level, Bela/TacTL immunosuppression was associated with a decreased rate of DSA (hazard ratio [HR] = 0.4), antibody-mediated rejection (HR = 0.2), and rejection (HR = 0.45). In the low-risk group, cumulative graft failure was lower for patients on Bela/TacTL (P < .02). Analysis of eplet mismatch burden may be a useful adjunct in identifying high-risk populations with increased immunosuppression requirements and should encourage the design of allocation rules to incentivize lower-risk pairings without negatively impacting equity in access.

Three-year Outcomes After Conversion From Monthly to Every 2-month Belatacept Maintenance Therapy in Kidney Transplant Recipients: Results From a Randomized Controlled Trial.

Maintenance immunosuppression with belatacept following kidney transplantation results in improved long-term graft function as compared with calcineurin inhibitors. However, broad application of belatacept has been limited, in part related to logistical barriers surrounding a monthly (q1m) infusion requirement. Methods: To determine whether every 2-mo (q2m) belatacept is noninferior to standard q1m maintenance, we conducted a prospective, single-center randomized trial in low-immunologic-risk, stable renal transplant recipients. Here, post hoc analysis of 3-y outcomes, including renal function and adverse events, are reported. Results: One hundred sixty-three patients received treatment in the q1m control group (n = 82) or q2m study group (n = 81). Renal allograft function as measured by baseline-adjusted estimated glomerular filtration rate was not significantly different between groups (time-averaged mean difference of 0.2 mL/min/1.73 m2; 95% confidence interval: -2.5, 2.9). There were no statistically significant differences in time to death or graft loss, freedom from rejection, or freedom from donor-specific antibodies (DSAs). During the extended 12- to 36-mo follow-up, 3 deaths, 1 graft loss occurred in the q1m group, compared with 2 deaths, and 2 graft losses in the q2m group. In the q1m group, 1 patient developed DSAs and acute rejection. In the q2m group, 3 patients developed DSAs and 2 associated with acute rejection. Conclusions: Based on the similar renal function and survival at 36 mo compared with q1m, q2m belatacept is a potentially viable maintenance immunosuppressive strategy in low immunologic risk kidney transplant recipients that may facilitate increased clinical utilization of costimulation blockade-based immunosuppression.

Persistent SARS-CoV-2-specific immune defects in kidney transplant recipients following third mRNA vaccine dose.

Kidney transplant recipients (KTRs) show poorer response to SARS-CoV-2 mRNA vaccination, yet response patterns and mechanistic drivers following third doses are ill-defined. We administered third monovalent mRNA vaccines to n = 81 KTRs with negative or low-titer anti-receptor binding domain (RBD) antibody (n = 39 anti-RBDNEG; n = 42 anti-RBDLO), compared with healthy controls (HCs, n = 19), measuring anti-RBD, Omicron neutralization, spike-specific CD8+%, and SARS-CoV-2-reactive T cell receptor (TCR) repertoires. By day 30, 44% anti-RBDNEG remained seronegative; 5% KTRs developed BA.5 neutralization (vs 68% HCs, P < .001). Day 30 spike-specific CD8+% was negative in 91% KTRs (vs 20% HCs; P = .07), without correlation to anti-RBD (rs = 0.17). Day 30 SARS-CoV-2-reactive TCR repertoires were detected in 52% KTRs vs 74% HCs (P = .11). Spike-specific CD4+ TCR expansion was similar between KTRs and HCs, yet KTR CD8+ TCR depth was 7.6-fold lower (P = .001). Global negative response was seen in 7% KTRs, associated with high-dose MMF (P = .037); 44% showed global positive response. Of the KTRs, 16% experienced breakthrough infections, with 2 hospitalizations; prebreakthrough variant neutralization was poor. Absent neutralizing and CD8+ responses in KTRs indicate vulnerability to COVID-19 despite 3-dose mRNA vaccination. Lack of neutralization despite CD4+ expansion suggests B cell dysfunction and/or ineffective T cell help. Development of more effective KTR vaccine strategies is critical. (NCT04969263).

Impact of belatacept and tacrolimus on cytomegalovirus viral load control and relapse in moderate and high-risk cytomegalovirus serostatus kidney transplant recipients.

BACKGROUND: Belatacept improves long-term graft survival, but control of some primary viral infections may be impaired. We evaluated the impact of belatacept and tacrolimus on cytomegalovirus (CMV) viral control, remission and relapse in CMV high-risk and moderate-risk recipients. METHODS: Using a multistate Markov model, we evaluated viral load state transitions of 173 kidney transplant recipients with at least one episode of viremia within 1 year after transplant: state 1, undetectable/low viral load; state 2, moderate viremia; and state 3, severe viremia. RESULTS: Among high-risk recipients, belatacept-treated recipients exhibited a significantly higher probability of entering moderate viremia (.36; 95% CI = .31, .41) than tacrolimus-treated recipients (.20; 95% CI = .13, .29). The expected number of days in viremic states differed. High-risk belatacept-treated recipients persisted in moderate viremia for significantly longer (128 days, 95% CI = 110, 146) than did tacrolimus-treated recipients (70.0 days, 95% CI = 45.2, 100) and showed a trend of shorter duration in low/undetectable viral load state (172 days, 95% CI = 148, 195) than did tacrolimus-treated recipients (239 days, 95% CI = 195, 277). Moderate-risk recipients showed better viral load control and with no differences by immunosuppression. CONCLUSION: High-risk belatacept-treated recipients showed defects in sustaining viral control relative to tacrolimus-treated recipients. Avoidance of initial use belatacept in high-risk recipients or development of modified management protocols should be considered.

Longitudinal Evaluation of Cytopenias in the Renal Transplant Population.

Cytopenias, a common complication for immunosuppressed patients, are known to be associated with adverse transplant outcomes. However, there is little information on cytopenias in recipients treated with the costimulation blockade agent, belatacept. Methods: We compared cytopenia incidence and manifestations in patients undergoing kidney transplant at Emory University Hospital on tacrolimus and belatacept. To reduce selection bias, the tacrolimus group was narrowed to include only patients eligible for belatacept. Results: Of 1651 patients transplanted between 2009 and 2019, 187 (11%) experienced severe anemia, 309 (19%) experienced leukopenia, and 62 (4%) thrombocytopenia. On multivariable regressions, deceased-donor transplant, cytomegalovirus viremia, and thymoglobulin treatment were associated with risk of developing leukopenia, anemia, and thrombocytopenia. High-risk cytomegalovirus status was also associated with development of leukopenia and anemia. Additionally, azathioprine was associated with development of anemia, and both tacrolimus therapy and Caucasian race were associated with thrombocytopenia. Longitudinal quantifications of hematologic cell lines over the first-year posttransplant were extracted from generalized linear models fit using splines. Only hemoglobin range was significantly different between groups (greater in belatacept patients). Plots of mean cell count for each group suggest an earlier recovery from posttransplant anemia in belatacept patients. Conclusions: Belatacept patients are not at increased risk of cytopenia but may have improved recovery from posttransplant anemia.

hlaR: A rapid and reproducible tool to identify eplet mismatches between transplant donors and recipients.

Eplet mismatch load, both overall and at the single molecule level, correlates with transplant recipient outcomes. However, precise eplet assessment requires high-resolution HLA typing of both the donor and recipient. Anything less than high-resolution typing requires imputation of HLA types. The currently available methods to identify eplet mismatch are both tedious and demanding. Therefore, we developed a software package and user-friendly web application (hlaR), that simplifies the workflow of eplet analysis, provides functions to impute high-resolution from low-resolution data and calculates both overall and single molecule eplet mismatch for single or multiple donor recipient pairs. Compared to manual assessments using currently available tools (namely, HLAMatchMaker), hlaR resulted in only minimal discrepancy in eplet mismatches (mean absolute difference of 0.56 for class I and 0.86 for class II for unique sum across loci). Additionally, output of the single molecule eplet function compared well to manual calculation, with an average single antigen count increase of 0.19. Importantly, the hlaR tool permits rapid and reproducible imputation and eplet mismatch including comparison between eplet reference tables (e.g. HLAMatchMaker version 2 or 3). Users can import data from a spreadsheet rather than relying on keystroke entry of individual donor and recipient data, thus reducing the risk of data entry errors. The resulting improved scalability of the hlaR tool is highlighted by plotting analysis time against the size of the input dataset. The new hlaR tool can provide eplet mismatch data with a streamlined workflow. With decreased effort from the end user, eplet matching and mismatch load data can be further incorporated into both research and clinical use.

Progress in kidney transplantation: The role for systems immunology.

The development of systems biology represents an immense breakthrough in our ability to perform translational research and deliver personalized and precision medicine. A multidisciplinary approach in combination with use of novel techniques allows for the extraction and analysis of vast quantities of data even from the volume and source limited samples that can be obtained from human subjects. Continued advances in microfluidics, scalability and affordability of sequencing technologies, and development of data analysis tools have made the application of a multi-omics, or systems, approach more accessible for use outside of specialized centers. The study of alloimmune and protective immune responses after solid organ transplant offers innumerable opportunities for a multi-omics approach, however, transplant immunology labs are only just beginning to adopt the systems methodology. In this review, we focus on advances in biological techniques and how they are improving our understanding of the immune system and its interactions, highlighting potential applications in transplant immunology. First, we describe the techniques that are available, with emphasis on major advances that allow for increased scalability. Then, we review initial applications in the field of transplantation with a focus on topics that are nearing clinical integration. Finally, we examine major barriers to adapting these methods and discuss potential future developments.

Is hepatectomy safe following Yttrium-90 therapy? A multi-institutional international experience.

BACKGROUND: Single institution reports demonstrate variable safety profiles when liver-directed therapy with Yttrium-90 (Y-90) is followed by hepatectomy. We hypothesized that in well-selected patients, hepatectomy after Y90 is feasible and safe. METHODS: Nine institutions contributed data for patients undergoing Y90 followed by hepatectomy (2008-2017). Clinicopathologic and perioperative data were analyzed, with 90-day morbidity and mortality as primary endpoints. RESULTS: Forty-seven patients were included. Median age was 59 (20-75) and 62% were male. Malignancies treated included hepatocellular cancer (n = 14; 30%), colorectal cancer (n = 11; 23%), cholangiocarcinoma (n = 8; 17%), neuroendocrine (n = 8; 17%) and other tumors (n = 6). The distribution of Y-90 treatment was: right (n = 30; 64%), bilobar (n = 14; 30%), and left (n = 3; 6%). Median future liver remnant (FLR) following Y90 was 44% (30-78). Resections were primarily right (n = 16; 34%) and extended right (n = 14; 30%) hepatectomies. The median time to resection from Y90 was 196 days (13-947). The 90-day complication rate was 43% and mortality was 2%. Risk factors for Clavien-Dindo Grade>3 complications included: number of Y-90-treated lobes (OR 4.5; 95% CI1.14-17.7; p = 0.03), extent of surgery (p = 0.04) and operative time (p = 0.009). CONCLUSIONS: These data demonstrate that hepatectomy following Y-90 is safe in well-selected populations. This multi-disciplinary treatment paradigm should be more widely studied, and potentially adopted, for patients with inadequate FLR.

A novel, simplified, externally validated staging system for truncal/extremity soft tissue sarcomas: An analysis of the US Sarcoma Collaborative database.

BACKGROUND: The 8th edition AJCC staging system for truncal/extremity soft tissue sarcoma (STS) offers significant changes from the 7th. However the complexity of both limits their clinical utility. METHODS: Patients with truncal/extremity STS undergoing resection from 2000 to 2016 at seven institutions of the US Sarcoma Collaborative were analyzed. The proposed staging system was externally validated using the National Cancer Database (NCDB). RESULTS: Of 1318 patients, mean age was 59 years, and 54% were male. Median tumor size was 9 cm; 72% were high grade. Applying 8th edition staging, there was no differentiation between stages IA/IB ( P = 0.92), and clinically similar outcomes between stages II/IIIA. Receiver operating characteristic (ROC) analysis identified 7.5 cm as the ideal tumor size discriminating 5-year OS for high-grade tumors. Therefore, a simplified staging system defining all low-grade tumors as stage I, high-grade < 7.5 cm as stage II, high-grade > 7.5 cm as stage III, and metastatic disease as stage IV improved stratification (all P < 0.05). The C-statistic was noninferior to the 8th edition. External validation in the NCDB confirmed optimal stratification (all P < 0.01). CONCLUSIONS: Our proposed staging system maintains prognostic significance between stages within a simplified system. For high-grade tumors, a cutoff of 7.5 cm, instead of 5 cm, maintains discrimination for survival and could be a more clinically applicable cutoff for future clinical trials.

Studying a Rare Disease Using Multi-Institutional Research Collaborations vs Big Data: Where Lies the Truth?

BACKGROUND: Multi-institutional collaborations provide granularity lacking in epidemiologic data sets to enable in-depth study of rare diseases. For patients with superficial, high-grade soft tissue sarcomas of the trunk and extremity, the value of radiation therapy (RT) is not clear. We aimed to use the 7-institution US Sarcoma Collaborative (USSC) and the National Cancer Database (NCDB) to investigate this issue. STUDY DESIGN: All adult patients with superficial truncal and extremity high-grade soft tissue sarcomas who underwent primary curative-intent resection from 2000 to 2016 at USSC institutions or were included in the NCDB from 2004 to 2013 were analyzed. Propensity score matching was performed. End points were locoregional recurrence-free survival (LRFS), overall survival (OS), and disease-specific survival (DSS). RESULTS: Of 4,153 patients in the USSC, 169 patients with superficial high-grade tumors underwent primary curative-intent resection, 38% of which received RT. On multivariable Cox-regression analysis, RT was not associated with improved LRFS (p = 0.56), OS (p = 0.31), or DSS (p = 0.20). On analysis of 51 propensity score-matched pairs, RT was still not associated with increased LRFS, OS, or DSS. Analysis of 631 propensity score-matched pairs in the NCDB demonstrated improved 5-year OS rate associated with RT (80% vs 70%; p = 0.02). The LRFS and DSS rates were not evaluable. CONCLUSIONS: Granular data afforded by collaborative research enables in-depth analysis of patient outcomes. The NCDB, although powered with large numbers, cannot assess many relevant outcomes (eg recurrence, DSS, or complications). In this study, the approaches yielded conflicting results. The USSC data suggested no value of radiation and the NCDB demonstrated improved OS, contradicting all randomized controlled trials in sarcoma. The pros and cons of either approach must be considered when applying results to clinical practice, and underscore the importance of randomized controlled trials.

Changing Abdominal Imaging Utilization Patterns: Perspectives From Medicare Beneficiaries Over Two Decades.

PURPOSE: To assess changing utilization patterns of abdominal imaging in the Medicare fee-for-service population over the past two decades. METHODS: Medicare Physician Supplier Procedure Summary master files from 1994 through 2012 were used to study changes in the frequency and utilization rates (per 1,000 Medicare beneficiaries per year) of abdominal CT, MRI, ultrasound, and radiography. RESULTS: In Medicare beneficiaries, the most frequently performed abdominal imaging modality changed from radiography in 1994 (207.4 per 1,000 beneficiaries) to CT in 2012 (169.0 per 1,000). Utilization rates of abdominal MR (1037.5%), CT (197.0%), and ultrasound (38.0%) all increased from 1994-2012 (but declined briefly from 2007 to 2009). A dramatic 20-year utilization rate decline occurred for gastrointestinal fluoroscopic examinations (-91.9% barium enema, -80.0% upper gastrointestinal series) and urologic radiographic examinations (-95.3%). Radiologists were the dominant providers of all modalities, accounting for >90% of CT and MR studies, and >75% of most ultrasound examination types. CONCLUSIONS: Medicare utilization of abdominal imaging has markedly changed over the past two decades, with overall dramatic increases in CT and MRI and dramatic decreases in gastrointestinal fluoroscopic and urologic radiographic imaging. Despite these changes, radiologists remain the dominant providers in all abdominal imaging modalities.

One-carbon chemistry of oxalate oxidoreductase captured by X-ray crystallography.

Thiamine pyrophosphate (TPP)-dependent oxalate oxidoreductase (OOR) metabolizes oxalate, generating two molecules of CO2 and two low-potential electrons, thus providing both the carbon and reducing equivalents for operation of the Wood-Ljungdahl pathway of acetogenesis. Here we present structures of OOR in which two different reaction intermediate bound states have been trapped: the covalent adducts between TPP and oxalate and between TPP and CO2. These structures, along with the previously determined structure of substrate-free OOR, allow us to visualize how active site rearrangements can drive catalysis. Our results suggest that OOR operates via a bait-and-switch mechanism, attracting substrate into the active site through the presence of positively charged and polar residues, and then altering the electrostatic environment through loop and side chain movements to drive catalysis. This simple but elegant mechanism explains how oxalate, a molecule that humans and most animals cannot break down, can be used for growth by acetogenic bacteria.