Development of Multivalent Conjugates with a Single Non-Canonical Amino Acid.

Proteins represent powerful biomacromolecules due to their unique functionality and broad utility both in the cell and in non-biological applications. The genetic encoding of non-canonical amino acids (ncAAs) facilitates functional diversification of these already powerful proteins. Specifically, ncAAs have been demonstrated to provide unique functional handles to bioorthogonally introduce novel functionality via conjugation reactions. Herein we examine the ability of a single ncAA to serve as a handle to generate multivalent bioconjugates to introduce two or more additional components to a protein, yielding a multivalent conjugate. To accomplish this aim, p-bromopropargyloxyphenyalanine (pBrPrF) was genetically encoded into both superfolder green fluorescent protein (sfGFP) and ubiquitin model proteins to serve as a conjugation handle. A sequential bioconjugation sequence involving a copper-assisted cycloaddition reaction coupled with a subsequent Sonogashira cross-coupling was then optimized. The linkage of two additional molecules to the model protein via these reactions yielded the desired multivalent bioconjugate. This domino approach using a single ncAA has a plethora of applications in both therapeutics and diagnostics as multiple unique moieties can be introduced into proteins in a highly controlled fashion.

Survival Benefit of Solid-Organ Transplantation: 10-Year Update.

IMPORTANCE: Transplantation has transformed into a burgeoning field that is rapidly evolving to optimize organ distribution and survival outcomes. The years since 2012 (the last comprehensive study) have seen changes in transplantation, such as advances in immunotherapy and novel indices, that necessitate an updated analysis of survival benefit. DESIGN: Our goal was to determine the survival benefit for solid-organ transplants in the United Network for Organ Sharing (UNOS) database for a three decade period and provide updates on advancements since 2012. Our retrospective analysis examined data containing U.S. patient records from September 1, 1987, to September 1, 2021. RESULTS: We found that 3,430,272 life-years were saved over our transplant period (4.33 life-years saved per patient); kidney-1,998,492 life-years; liver -767,414; heart-435,312; lung-116,625; pancreas-kidney-123,463; pancreas-30,575; intestine-7901. After matching, 3,296,851 life-years were saved. Life-years saved and median survival increased for all organs between 2012 and 2021. Compared to 2012, median survival increased in kidney (from 12.4 to 14.76 years), liver (from 11.6 to 14.59), heart (9.5 to 11.73), lung (5.2 to 5.63), pancreas-kidney (from 14.5 to 16.88), pancreas (from 13.3 to 16.10). When compared to 2012, the percent transplanted increased in kidney, liver, heart, lung, and intestine, while pancreas-kidney and pancreas show decreased percent transplanted. CONCLUSION: Our study underscores the tremendous survival benefits of solid organ transplantation (over 3.4 million life-years saved) and shows improvements since 2012. Our study also highlights areas of transplantation, notably pancreas transplants, that may necessitate reinvigorated attention.

Transplanting hepatitis B surface antigen-positive livers in the United States: Outcomes and opportunities.

Livers from donors with positive hepatitis B surface antigens (HBsAg+) have been used to expand the donor pool; however, outcome data are limited. We aim to evaluate survival following liver transplant (LT) from HBsAg+ donors. Using the United Network for Organ Sharing registry, we identified HBsAg+ donors used for LT from 2009 to 2020. We used Kaplan-Meier survival and Cox proportional hazards regression to compare post-LT survival in hepatitis B virus-negative recipients who utilized HBsAg+ donors to propensity-matched cohorts who utilized other types of donors. From 2009-2020, 70 patients received HBsAg+ livers, and 58 of them did not carry a diagnosis of chronic hepatitis B virus. The 1- and 3-year post-LT survival for hepatitis B virus-negative patients who received livers from HBsAg+ donors were 96.6% and 91.4%, respectively, with no statistical differences compared with patients who received livers from hepatitis C virus viremic donors (96.5%/93.0%, P = .961/.427), donation after cardiac death donors (93.0%/86.0%, P = .651/.598), average-risk donors (89.5%/86.0%, P = 0.264/0.617), and a combination of extended-criteria donors, including donation after cardiac death, donor age over 70, and graft with greater than 30% steatosis (93.0%/91.2%, P = .621/.785). Recipients of HBsAg+ livers have similar post-LT survival compared with those receiving other types of grafts. Increasing the utilization of HBsAg+ livers could safely expand the donor pool.

Disparate Intent-to-Treat Outcomes for Pediatric Liver Transplantation Based on Indication.

Background: The impact of indication for pediatric liver transplantation on waitlist and post-transplant mortality outcomes is well known, but the impact on intent-to-treat outcomes has not been investigated. Intent-to-treat survival analysis is important in this study because it is more comprehensive, combining the transplant outcomes of waitlist mortality, post-transplant mortality, and transplant rate into a single metric to elucidate any disparities in outcomes based on indication. Methods: Cox regression was used to analyze factors impacting survival in 8,002 children listed for liver transplant in the UNOS database between 2006 and 2016. The Kaplan-Meier method and log-rank test were used to assess differences in waitlist, post-transplant, and intent-to-treat mortality among the top 5 indications of biliary atresia, acute hepatic necrosis, metabolic disorders, hepatoblastoma, and autoimmune cirrhosis. Results: When compared to the reference group of biliary atresia, multivariate analyses showed that every indication was associated with inferior intent-to-treat outcomes except for metabolic disorders. Hepatoblastoma (hazard ratio (HR): 3.73), autoimmune cirrhosis (HR: 1.86), and AHN (HR: 1.77) were associated with significantly increased intent-to-treat mortality. Hepatoblastoma was also associated with increased post-transplant mortality (HR: 3.77) and was the only indication significantly associated with increased waitlist mortality (HR: 6.43). Conclusion: Significant disparity exists across all indications with respect to an increased intent-to-treat mortality, along with an increased post-transplant and waitlist mortality, when compared to the biliary atresia reference group. If further studies validate these findings, a reexamination of the equitable distribution of allografts for transplant may be warranted as well as a focus on disparities in survival after transplant.

A modified Kidney Donor Risk Index for pediatric kidney transplant recipients.

BACKGROUND: The Kidney Donor Risk Index (KDRI) by Rao et al. was developed to measure the quality of kidney allografts. While Rao's KDRI has been found to be a robust measure of kidney allograft survival for adult kidney transplant recipients, many studies have indicated the need to create a distinct pediatric KDRI. METHODS: Our retrospective study utilized data from the United Network for Organ Sharing database. We examined 9295 deceased donor recipients' data for age < 18 years from 1990 to 2020. We performed a multivariate Cox regression to determine the significant recipient and transplant factors impacting pediatric kidney allograft survival. RESULTS: Multivariate analysis found 5 donor factors to be independently associated with graft failure or recipient death: age, female sex, anoxia as the cause of death, history of cigarette use, and cold ischemia time. Using receiver operator characteristic (ROC) curve analysis and analyzing the predictive value of each KDRI at 1, 5, and 10 years, the proposed pediatric KDRI had a statistically significant and higher predictive value for pediatric recipients at 5 (0.60 versus 0.57) and 10 years (0.61 versus 0.57) than the Rao KDRI. CONCLUSIONS: The proposed pediatric KDRI may provide a more accurate and simpler index to assess the quality of kidney allografts for pediatric recipients. However, due to the mild increase in predictive capabilities over the Rao index, the study serves as a proof of concept to develop a pediatric KDRI. Further studies should focus on increasing the index's predictive capabilities. A higher resolution version of the Graphical abstract is available as Supplementary information.

Do Patients with Autoimmune Conditions Have Less Access to Liver Transplantation despite Superior Outcomes?

Orthotopic liver transplantation (OLT) is a lifesaving therapy for patients with irreversible liver damage caused by autoimmune liver diseases (AutoD) including autoimmune hepatitis (AIH), primary biliary cholangitis (PBC), and primary sclerosing cholangitis (PSC). Currently, it is unclear how access to transplantation differs among patients with various etiologies of liver disease. Our aim is to evaluate the likelihood of transplant and the long-term patient and graft survival after OLT for each etiology for transplantation from 2000 to 2021. We conducted a large retrospective study of United Network for Organ Sharing (UNOS) liver transplant patients in five 4-year eras with five cohorts: AutoD (PBC, PSC, AIH cirrhosis), alcohol-related liver disease (ALD), hepatocellular carcinoma (HCC), viral hepatitis, and nonalcoholic steatohepatitis (NASH). We conducted a multivariate analysis for probability of transplant. Intent-to-treat (ITT) analysis was performed to assess the 10-year survival differences for each listing diagnosis while accounting for both waitlist and post-transplant survival. Across all eras, autoimmune conditions had a lower adjusted probability of transplant of 0.92 (0.92, 0.93) compared to ALD 0.97 (0.97, 0.97), HCC 1.08 (1.07, 1.08), viral hepatitis 0.99 (0.99, 0.99), and NASH 0.99 (0.99, 1.00). Patients with AutoD had significantly better post-transplant patient and graft survival than ALD, HCC, viral hepatitis, and NASH in each and across all eras (p-values all < 0.001). Patients with AutoD had superior ITT survival (p-value < 0.001, log rank test). In addition, the waitlist survival for patients with AutoD compared to other listing diagnoses was improved with the exception of ALD, which showed no significant difference (p-value = 0.1056, log rank test). Despite a superior 10-year graft and patient survival in patients transplanted for AutoD, patients with AutoD have a significantly lower probability of receiving a liver transplant compared to those transplanted for HCC, ALD, viral hepatitis, and NASH. Patients with AutoD may benefit from improved liver allocation while maintaining superior waitlist and post-transplant survival. Decreased access in spite of appropriate outcomes for patients poses a significant risk for increased morbidity for patients with AutoD.

Marginal allografts in liver transplantation have a limited impact on length of stay.

The study of marginal liver transplant outcomes, including post-transplant length of stay (LOS), is necessary for determining the practicality of their use. 50 155 patients who received transplants from 2012 to 2020 were retrospectively analyzed with data from the Scientific Registry of Transplant Recipients database using Kaplan-Meier survival curves and multivariable Cox regression. Six different definitions were used to classify an allograft as being marginal: 90th percentile Donor Risk Index (DRI) allografts, donation after cardiac death (DCD) donors, national share donors, donors over 70, donors with > 30% macrovesicular steatosis, or 90th percentile Discard Risk Index donors. 24% (n = 12 124) of subjects received marginal allografts. Average LOS was 15.6 days among those who received standard allografts. Among those who received marginal allografts, LOS was found to be highest in those who received 90th percentile DRI allografts at 15.6 days, and lowest in those who received DCD allografts at 12.7 days. Apart from fatty livers (95% CI .86-.98), marginal allografts were not associated with a prolonged LOS. We conclude that accounting for experience and recipient matching, transplant centers may be more aggressive in their use of extended criteria donors with limited fear of increasing LOS and its associated costs.

Photoregulation of PRMT-1 Using a Photolabile Non-Canonical Amino Acid.

Protein methyltransferases are vital to the epigenetic modification of gene expression. Thus, obtaining a better understanding of and control over the regulation of these crucial proteins has significant implications for the study and treatment of numerous diseases. One ideal mechanism of protein regulation is the specific installation of a photolabile-protecting group through the use of photocaged non-canonical amino acids. Consequently, PRMT1 was caged at a key tyrosine residue with a nitrobenzyl-protected Schultz amino acid to modulate protein function. Subsequent irradiation with UV light removes the caging group and restores normal methyltransferase activity, facilitating the spatial and temporal control of PRMT1 activity. Ultimately, this caged PRMT1 affords the ability to better understand the protein's mechanism of action and potentially regulate the epigenetic impacts of this vital protein.

Elevated serum sodium in recipients of liver transplantation has a substantial impact on outcomes.

Dysnatremias are a rare but significant event in liver transplantation. While recipient pre-transplant hypernatremia has been demonstrated to increase post-transplant mortality, the degree of hypernatremia and the impact of its resolution have been less well characterized. Here, we used multivariate Cox regression with a comprehensive list of donor and recipient factors in order to conduct a robust multivariate retrospective database study of 54,311 United Network for Organ Sharing (UNOS) liver transplant patients to analyze the effect of pre-transplant serum sodium on post-transplant mortality, post-transplant length of hospitalization, and post-transplant graft survival. Mortality and graft failure increased in a stepwise fashion with increasing pre-transplant hypernatremia: 145 -150 mEq/L (HR = 1.118 and HR = 1.113), 150-155 mEq/L (HR = 1.324 and HR = 1.306), and > 155 mEq/L (HR = 1.623 and HR = 1.661). Pre-transplant hypo- and hypernatremia also increased length of post-transplant hospitalization: < 125 mEq/L (HR = 1.098), 125-130 mEq/L (HR = 1.060), 145 -150 mEq/L (HR = 1.140), and 150-155 mEq/L (HR = 1.358). Resolution of hypernatremia showed no significant difference in mortality compared with normonatremia, while unresolved hypernatremia significantly increased mortality (HR = 1.254), including a durable long-term increased mortality risk for patients with creatinine < 2 mg/dL and MELD < 25. Pre-transplant hypernatremia serves as a morbid prognostic indicator for post-transplant morbidity and mortality.