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Judith Van den Bosch,1 D Simone Warren,1 Peter A Rutherford21Pallas Health Research and Consultancy BV, Rotterdam, the Netherlands; 2Baxter Healthcare SA, Zürich, SwitzerlandAbstract: To make an informed decision on renal replacement therapy, patients should receive education about dialysis options in a structured program covering all modalities. Many patients do not receive such education, and there is disparity in the information they receive. This review aims to compile evidence on effective components of predialysis education programs as related to modality choice and outcomes. PubMed MEDLINE, Cochrane Library, and Ovid searches (from January 1, 1995 to December 31, 2013) with the main search terms of “predialysis”, “peritoneal dialysis”, “home dialysis”, “education”, “information”, and “decision” were performed. Of the 1,005 articles returned from the initial search, 110 were given full text reviews as they potentially met inclusion criteria (for example, they included adults or predialysis patients, or the details of an education program were reported). Only 29 out of the 110 studies met inclusion criteria. Ten out of 13 studies using a comparative design, showed an increase in home dialysis choice after predialysis education. Descriptions of the educational process varied and included individual and group education, multidisciplinary intervention, and varying duration and frequency of sessions. Problem-solving group sessions seem to be an effective component for enhancing the proportion of home dialysis choice. Evidence is lacking for many components, such as timing and staff competencies. There is a need for a standardized approach to evaluate the effect of predialysis educational interventions.Keywords: dialysis, end-stage renal disease, informed decision, modality choice

Neutralizing antibody (nAb) responses are attenuated in solid organ transplant recipients (SOTRs) despite severe acute respiratory syndrome-coronavirus-2 vaccination. Preexposure prophylaxis (PrEP) with the antibody combination tixagevimab and cilgavimab (T+C) might augment immunoprotection, yet in vitro activity and durability against Omicron sublineages BA.4/5 in fully vaccinated SOTRs have not been delineated. Vaccinated SOTRs, who received 300 + 300 mg T+C (ie, full dose), within a prospective observational cohort submitted pre and postinjection samples between January 31, 2022, and July 6, 2022. The peak live virus nAb was measured against Omicron sublineages (BA.1, BA.2, BA.2.12.1, and BA.4), and surrogate neutralization (percent inhibition of angiotensin-converting enzyme 2 receptor binding to full length spike, validated vs live virus) was measured out to 3 months against sublineages, including BA.4/5. With live virus testing, the proportion of SOTRs with any nAb increased against BA.2 (47%-100%; P < .01), BA.2.12.1 (27%-80%; P < .01), and BA.4 (27%-93%; P < .01), but not against BA.1 (40%-33%; P = .6). The proportion of SOTRs with surrogate neutralizing inhibition against BA.5, however, fell to 15% by 3 months. Two participants developed mild severe acute respiratory syndrome-coronavirus-2 infection during follow-up. The majority of fully vaccinated SOTRs receiving T+C PrEP achieved BA.4/5 neutralization, yet nAb activity commonly waned by 3 months postinjection. It is critical to assess the optimal dose and interval of T+C PrEP to maximize protection in a changing variant climate., (Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.)

Heterologous vaccination ("mixing platforms") for the third (D3) dose of SARS-CoV-2 vaccine is a potential strategy to improve antibody responses in solid organ transplant recipients (SOTRs), but data are mixed regarding potential differential immunogenicity. We assessed for differences in immunogenicity and tolerability of homologous (BNT162b2 or mRNA-1273; D3-mRNA) versus heterologous (Ad.26.COV2.S; D3-JJ) D3 among 377 SARS-CoV-2-infection naïve SOTRs who remained seronegative after two mRNA vaccines. We measured anti-spike titers and used weighted Poisson regression to evaluate seroconversion and development of high-titers, comparing D3-JJ to D3-mRNA, at 1-, 3-, and 6 month post-D3. 1-month post-D3, seroconversion (63% vs. 52%, p = .3) and development of high-titers (29% vs. 25%, p = .7) were comparable between D3-JJ and D3-mRNA recipients. 3 month post-D3, D3-JJ recipients were 1.4-fold more likely to seroconvert (80% vs. 57%, weighted incidence-rate-ratio: wIRR =  1.10 1.40 1.77 , p = .006) but not more likely to develop high-titers (27% vs. 22%, wIRR =  0.44 0.92 1.93 , p = .8). 6 month post-D3, D3-JJ recipients were 1.41-fold more likely to seroconvert (88% vs. 59%, wIRR =  1.04 1.41 1.93 , p = .029) and 2.63-fold more likely to develop high-titers (59% vs. 21%, wIRR =  1.38 2.63 5.00 , p = .003). There was no differential signal in alloimmune events or reactogenicity between platforms. SOTRs without antibody response after two mRNA vaccines may derive benefit from heterologous Ad.26.COV2.S D3., (© 2022 The Authors. American Journal of Transplantation published by Wiley Periodicals LLC on behalf of The American Society of Transplantation and the American Society of Transplant Surgeons.)

Vaccine-induced SARS-CoV-2 antibody responses are attenuated in solid organ transplant recipients (SOTRs) and breakthrough infections are more common. Additional SARS-CoV-2 vaccine doses increase anti-spike IgG in some SOTRs, but it is uncertain whether neutralization of variants of concern (VOCs) is enhanced. We tested 47 SOTRs for clinical and research anti-spike IgG, pseudoneutralization (ACE2 blocking), and live-virus neutralization (nAb) against VOCs before and after a third SARS-CoV-2 vaccine dose (70% mRNA, 30% Ad26.COV2.S) with comparison to 15 healthy controls after two mRNA vaccine doses. We used correlation analysis to compare anti-spike IgG assays and focused on thresholds associated with neutralization. A third SARS-CoV-2 vaccine dose increased median total anti-spike (1.6-fold), pseudoneutralization against VOCs (2.5-fold vs. Delta), and neutralizing antibodies (1.4-fold against Delta). However, neutralization activity was significantly lower than healthy controls (p < .001); 32% of SOTRs had zero detectable nAb against Delta after third vaccination compared to 100% for controls. Correlation with nAb was seen at anti-spike IgG >4 Log 10 (AU/ml) on the Euroimmun ELISA and >4 Log 10 (AU/ml) on the MSD research assay. These findings highlight benefits of a third vaccine dose for some SOTRs and the need for alternative strategies to improve protection in a significant subset of this population., (© 2021 The American Society of Transplantation and the American Society of Transplant Surgeons.)

Fibrosis refers to the accumulation of excess extracellular matrix (ECM) components and represents a key feature of many chronic inflammatory diseases. Unfortunately, no currently available treatments specifically target this important pathogenic mechanism. MicroRNAs (miRNAs) are short, non-coding RNAs that post-transcriptionally repress target gene expression and the development of miRNA-based therapeutics is being actively pursued for a diverse array of diseases. Because a single miRNA can target multiple genes, often within the same pathway, variations in the level of individual miRNAs can potently influence disease phenotypes. Members of the miR-29 family, which include miR-29a, miR-29b and miR-29c, are strong inhibitors of ECM synthesis and fibrosis-associated decreases in miR-29 have been reported in multiple organs. We observed downregulation of miR-29a/b/c in fibrotic livers of carbon tetrachloride (CCl4) treated mice as well as in isolated human hepatocytes exposed to the pro-fibrotic cytokine TGF-β. Importantly, we demonstrate that a single systemic injection of a miR-29a expressing adeno-associated virus (AAV) can prevent and even reverse histologic and biochemical evidence of fibrosis despite continued exposure to CCl4. The observed therapeutic benefits were associated with AAV transduction of hepatocytes but not hepatic stellate cells, which are the main ECM producing cells in fibroproliferative liver diseases. Our data therefore demonstrate that delivery of miR-29 to the hepatic parenchyma using a clinically relevant gene delivery platform protects injured livers against fibrosis and, given the consistent fibrosis-associated downregulation of miR-29, suggests AAV-miR-29 based therapies may be effective in treating a variety of fibroproliferative disorders.

Current methods to remove donor-specific HLA antibody (DSA) from sensitized patients remain imperfect. We tested novel approaches to desensitization using an animal model of allogeneic sensitization with skin grafts from dark agouti (DA) to Lewis rats. At the peak IgG alloantibody response we transplanted DA kidneys into nephrectomized Lewis recipients (n = 6) and all died within 10 days from antibody-mediated rejection (AMR). Allogeneic hematopoietic stem cell transplants (HSCT) from DA donors failed to engraft after lethal or sub-lethal irradiation. Sensitized rats given lethal irradiation plus syngeneic green fluorescent protein (GFP) + HSCT had repopulation of blood, spleen, thymus and lymph nodes by GFP+ cells. At 2 months after HSCT, serum DSA levels were reduced 60-70% and DSA (IgG) production in cultured splenocytes was also significantly decreased. However, there was only a modest improvement in graft survival from an average of 6.5 to 13.9 (n = 9) days. Adding seven daily doses of fludarabine to the preconditioning regimen resulted in long-term survival (>90 days) in 7 out of 10 rat kidney allografts. We conclude that syngeneic HSCT performed after preconditioning with irradiation and fludarabine can reduce DSA, prevent DSA rebound and AMR, enabling successful transplantation in animals with strong antibody reactivity to the donor MHC., (© Copyright 2014 The American Society of Transplantation and the American Society of Transplant Surgeons.)

Background and Objectives: Use of incompatible kidney transplantation (IKT) is growing as a response to the organ shortage and the increase in sensitization among candidates. However, recent regulatory mandates possibly threaten IKT, and the potential effect of these mandates cannot be estimated because dissemination of this modality remains unknown. The goal of this study was to better understand practice patterns of IKT in the United States., Design, Setting, Participants, & Measurements: Directors from all 187 unique active adult kidney transplant programs were queried about transplantation across the following antibody barriers: positive Luminex, negative flow crossmatch (PLNF); positive flow, negative cytotoxic crossmatch (PFNC); positive cytotoxic crossmatch (PCC); and ABO incompatible (ABOi)., Results: Responses from 125 centers represented 84% of the live-donor transplant volume in the United States. Barriers of PLNF, PFNC, PCC, and ABOi are being crossed in 70%, 51%, 18%, and 24%, respectively, of transplant centers that responded. Desensitization was performed in 58% of PLNF, 76% of PFNC, 100% of PCC, and 80% of ABOi using plasmapheresis and low-dose intravenous Ig (IVIg) in 71% to 83% and high-dose IVIg in 29% to 46%., Conclusions: A higher proportion of centers perform IKT than might be inferred from the literature. The rapid dissemination of these protocols despite adequate evidence of a clear advantage of IKT transplants argues for the creation of a national registry and randomized studies.

The random nature of T-cell receptor-β (TCR-β) recombination needed to generate immunological diversity dictates that two-thirds of alleles will be out-of-frame. Transcripts derived from nonproductive rearrangements are cleared by the nonsense-mediated mRNA decay (NMD) pathway, the process by which cells selectively degrade transcripts harboring premature termination codons. Here, we demonstrate that the fetal thymus in transgenic mice that ubiquitously express a dominant-negative form of Rent1/hUpf1, an essential trans-effector of NMD, shows decreased cell number, reduced CD4CD8 double-positive thymocytes, diminished expression of TCR-β, and increased expression of CD25, suggesting a defect in pre-TCR signaling. Transgenic fetal thymocytes also demonstrated diminished endogenous Vβ-to-DβJβ rearrangements, whereas Dβ-to-Jβ rearrangements were unperturbed, suggesting that inhibition of NMD induces premature shut-off of TCR-β rearrangement. Developmental arrest of thymocytes is prevented by the introduction of a fully rearranged TCR-β transgene that precludes generation of out-of-frame transcripts, suggesting direct mRNA-mediated trans-dominant effects. These data document that NMD has been functionally incorporated into developmental programs during eukaryotic evolution.

Identification of factors responsible for an increase in the breadth or strength of HLA-specific antibody (HSA) is critical to the continued successful management and transplantation of sensitized patients. A retrospective review of our HLA registry identified 107 patients with known HSA and sufficient information in their electronic patient record to determine the presence or absence of a proinflammatory event. The patients were stratified according to transplant status [sensitized and on the transplant waitlist (n = 65); immunosuppressed recipients of a positive crossmatch (+XM) transplant (n = 42)]. Eighty-three percent of waitlist candidates and 55% of sensitized kidney transplant recipients with a documented proinflammatory event had an associated increase in HSA. Interestingly, among patients with a culture-proven infection, 97% of the waitlist patients and 54.8% of +XM recipients had an associated rise in HSA. Overall, proinflammatory events were associated with a greater increase among waitlist patients than +XM recipients, 5.3-fold [IRR 5.25, (95% CI 4.03-6.85), p < 0.001] versus 2.5-fold [IRR 2.54, (95% CI 1.64-3.95), p < 0.001] increase in HSA. Therefore, sensitized patients known to have an infection or undergoing surgery should be monitored for expansion of HSA.

We reviewed 116 surveillance biopsies obtained approximately 1, 3, 6 and 12 months posttransplantation from 50 +XM live donor kidney transplant recipients to determine the frequency of subclinical cell-mediated rejection (CMR) and antibody-mediated rejection (AMR). Subclinical CMR was present in 39.7% of the biopsies at 1 month and >20% at all other time points. The presence of diffuse C4d on biopsies obtained at each time interval ranged from 20 to 30%. In every case, where histological and immunohistological findings were diagnostic for AMR, donor-specific antibody was found in the blood, challenging the long-held belief that low-level antibody could evade detection due to absorption on the graft. Among clinical factors, only recipient age was associated with subclinical CMR. Clinical factors associated with subclinical AMR were recipient age, positive cytotoxic crossmatch prior to desensitization and two mismatches of HLA DR 51, 52 and 53 alleles. Surveillance biopsies during the first year post-transplantation for these high-risk patients uncover clinically occult processes and phenotypes, which without intervention diminish allograft survival and function.

Single-center studies have reported equivalent outcomes of kidney allografts recovered with histidine-tryptophan-ketoglutarate (HTK) or University of Wisconsin (UW) solution. However, these studies were likely underpowered and often unadjusted, and multicenter studies have suggested HTK preservation might increase delayed graft function (DGF) and reduce graft survival of renal allografts. To further inform clinical practice, we analyzed the United Network for Organ Sharing (UNOS) database of deceased donor kidney transplants performed from July 2004 to February 2008 to determine if HTK (n = 5728) versus UW (n = 15 898) preservation impacted DGF or death-censored graft survival. On adjusted analyses, HTK preservation had no effect on DGF (odds ratio [OR] 0.99, p = 0.7) but was associated with an increased risk of death-censored graft loss (hazard ratio [HR] 1.20, p = 0.008). The detrimental effect of HTK was a relatively late one, with a strong association between HTK and subsequent graft loss in those surviving beyond 12 months (HR 1.43, p = 0.007). Interestingly, a much stronger effect was seen in African-American recipients (HR 1.55, p = 0.024) than in Caucasian recipients (HR 1.18, p = 0.5). Given recent studies that also demonstrate that HTK preservation reduces liver and pancreas allograft survival, we suggest that the use of HTK for abdominal organ recovery should be reconsidered.

Outcomes after heart and lung transplants have improved, and many recipients survive long enough to develop secondary renal failure, yet remain healthy enough to undergo kidney transplantation. We used national data reported to United Network for Organ Sharing (UNOS) to evaluate outcomes of 568 kidney after heart (KAH) and 210 kidney after lung (KAL) transplants performed between 1995 and 2008. Median time to kidney transplant was 100.3 months after heart, and 90.2 months after lung transplant. Renal failure was attributed to calcineurin inhibitor toxicity in most patients. Outcomes were compared with primary kidney recipients using matched controls (MC) to account for donor, recipient and graft characteristics. Although 5-year renal graft survival was lower than primary kidney recipients (61% KAH vs. 73.8% MC, p < 0.001; 62.6% KAL vs. 82.9% MC, p < 0.001), death-censored graft survival was comparable (84.9% KAH vs. 88.2% MC, p = 0.1; 87.6% KAL vs. 91.8% MC, p = 0.6). Furthermore, renal transplantation reduced the risk of death compared with dialysis by 43% for KAH and 54% for KAL recipients. Our findings that renal grafts function well and provide survival benefit in KAH and KAL recipients, but are limited in longevity by the general life expectancy of these recipients, might help inform clinical decision-making and allocation in this population.

C4d deposition in peritubular capillaries is a specific marker for the presence of antidonor antibodies in renal transplant recipients and is usually associated with antibody-mediated rejection (AMR) in conventional allografts. In ABO-incompatible grafts, however, peritubular capillary C4d is often present on protocol biopsies lacking histologic features of AMR; the significance of C4d in this setting remains unclear. For addressing this, data from 33 patients who received ABO-incompatible renal allografts (after desensitization) were retrospectively reviewed. Protocol biopsies were performed at 1 and/or 3 and 6 mo after transplantation in each recipient and at 12 mo in 28 recipients. Twenty-one patients (group A) had strong, diffuse peritubular capillary C4d staining without histologic evidence of AMR or cellular rejection on their initial protocol biopsies. The remaining 12 patients (group B) had negative or weak, focal peritubular capillary C4d staining. Three grafts (two in group B) were lost but not as a result of AMR. Excluding these three patients, serum creatinine levels were similar in the two groups at 6 and 12 mo after transplantation and at last follow-up; however, recipients in group A developed significantly fewer overall chronic changes, as scored by the sum of Banff chronic indices, than group B during the first year after transplantation. These results suggest that diffuse peritubular capillary C4d deposition without rejection is associated with a lower risk for scarring in ABO-incompatible renal allografts; the generalizability of these results to conventional allografts remains unknown.

Desensitized patients are at high risk of developing acute antibody-mediated rejection (AMR). In most cases, the rejection episodes are mild and respond to a short course of plasmapheresis (PP) / low-dose IVIg treatment. However, a subset of patients experience severe AMR associated with sudden onset oliguria. We previously described the utility of emergent splenectomy in rescuing allografts in patients with this type of severe AMR. However, not all patients are good candidates for splenectomy. Here we present a single case in which eculizumab, a complement protein C5 antibody that inhibits the formation of the membrane attack complex (MAC), was used combined with PP/IVIg to salvage a kidney undergoing severe AMR. We show a marked decrease in C5b-C9 (MAC) complex deposition in the kidney after the administration of eculizumab.

Although the majority of deceased-donor kidneys are donated after brain death, increased recovery of kidneys donated after cardiac death could reduce the organ shortage and is now a national priority. Racial disparities in donations after brain death have been well described for renal transplantation, but it is unknown whether similar disparities occur in donations after cardiac death. In this study, outcomes of adult deceased-donor renal transplant recipients included in the United Network for Organ Sharing database (1993 through 2006) were analyzed. Among black recipients of kidneys obtained after cardiac death, those who received kidneys from black donors had better long-term graft and patient survival than those who received kidneys from white donors. In addition, compared with standard-criteria kidneys from white donors after brain death, kidneys from black donors after cardiac death conferred a 70% reduction in the risk for graft loss (adjusted hazard ratio 0.30; 95% confidence interval 0.14 to 0.65; P = 0.002) and a 59% reduction in risk for death (adjusted hazard ratio 0.41; 95% confidence interval 0.2 to 0.87; P = 0.02) among black recipients. These findings suggest that kidneys obtained from black donors after cardiac death may afford the best long-term survival for black recipients.

We have used attenuated total reflection infrared (ATR-IR) spectroscopy to study the model compound perfluoro(2-ethoxyethane) sulfonic acid (PES) and the spectral changes induced by humidity variations to improve understanding of the IR spectrum of Nafion. This work was supported by density functional theory (DFT) calculations of the PES molecule and ion complexes to confirm assignments and determine local modes that contributed to specific absorptions in the IR spectrum. The work illustrates the difficulties of interpreting the spectrum of Nafion with several mixed modes being present. However, the loss of degeneracy in the -SO3- asymmetric stretching mode is clearly observed in difference spectra, and the use of DFT calculations provides an insight into changes induced by the variation in humidity.

Current billing practices and mandates to report surgical outcomes are disincentives to surgical treatment of obese patients, who are at increased risk for longer hospital stays and higher complication rates. The objective of this study was to quantify the independent association between body mass index (BMI) and waiting time for kidney transplantation to identify potential provider bias against surgical treatment of the obese. A secondary data analysis was performed of a prospective cohort of 132,353 patients who were registered for kidney transplantation in the United States between 1995 and 2006. Among all patients awaiting kidney transplantation, the likelihood of receiving a transplant decreased with increasing degree of obesity, categorized by ranges of BMI (adjusted hazard ratios 0.96 for overweight, 0.93 for obese, 0.72 for severely obese, and 0.56 for morbidly obese, compared with a reference group of patients with normal BMI). Similarly, the likelihood of being bypassed when an organ became available increased in a graded manner with category of obesity (adjusted incidence rate ratio 1.02 for overweight, 1.05 for obese, 1.11 for severely obese, and 1.22 for morbidly obese). Although matching an available organ with an appropriate recipient requires clinical judgment, which could not be fully captured in this study, the observed differences are dramatic and warrant further studies to understand this effect better and to design a system that is less susceptible to unintended bias.

Although donation after cardiac death (DCD) kidneys have a high incidence of delayed graft function (DGF) and have been considered marginal, no tool for stratifying risk of graft loss nor a specific policy governing their allocation exist. We compared outcomes of 2562 DCD, 62,800 standard criteria donor (SCD) and 12,812 expanded criteria donor (ECD) transplants reported between 1993 and 2005, and evaluated factors associated with risk of graft loss and DGF in DCD kidneys. Donor age was the only criterion used in the definition of ECD kidneys that independently predicted graft loss among DCD kidneys. Kidneys from DCD donors <50 had similar long-term graft survival to those from SCD (RR 1.1, p = NS). While DGF was higher among DCD compared to SCD and ECD, limiting cold ischemia (CIT) to <12 h decreased the rate of DGF 15% among DCD <50 kidneys. These findings suggest that DCD <50 kidneys function like SCD kidneys and should not be viewed as marginal or ECD, and further, limiting CIT <12 h markedly reduces DGF.

Biopsies of ABO-incompatible and positive crossmatch (HLA-incompatible) renal allografts were retrospectively examined to compare results of C4d and C3d staining, and the correlation between such staining and histologic findings suggestive of antibody-mediated rejection (AMR). A total of 75 biopsies (55 protocol, 17 for graft dysfunction, 3 for other indications) of 24 ABO-incompatible grafts and 244 biopsies (103 protocol, 129 for graft dysfunction, 12 for other indications) of 66 HLA-incompatible grafts were examined; all were stained for C4d and approximately 40% for C3d. In ABO-incompatible grafts, 80% of protocol biopsies and 59% performed for graft dysfunction showed C4d staining in peritubular capillaries (PTC); this staining was not correlated with neutrophil margination in PTC. In HLA-incompatible grafts, PTC C4d was present in 26% of protocol biopsies and 60% of biopsies for graft dysfunction; 92% of biopsies with >1+ (0-4+ scale), diffuse PTC C4d had > or =1+ margination and/or thrombotic microangiopathy (TMA), compared with 12% of C4d-negative biopsies. C3d was somewhat more predictive of margination than C4d in ABO-incompatible, but not HLA-incompatible, grafts. In summary, while PTC C4d deposition indicates probable AMR in biopsies of HLA-incompatible grafts, including protocol biopsies, there is no histologic evidence that C4d deposition is correlated with injury in most ABO-incompatible grafts.

Most successful protocols for renal transplantation across ABO incompatible (ABOi) barriers have utilized splenectomy as part of the pre-conditioning process. We recently described successful ABOi transplantation using anti-CD20 monoclonal antibody in lieu of splenectomy. In the current study, we hypothesized that plasmapheresis (PP) and low dose CMV hyper-immunoglobulin (CMVIg) alone would be sufficient to achieve successful engraftment of ABOi kidneys. We describe four blood type incompatible patients who received live donor renal transplants from A1 (two patients), A2 (one patient), and B (one patient) donors. All patients started with antihuman globulin (AHG) phase titers of 64 or higher and were pre-conditioned with PP/CMVIg but not splenectomy or anti-CD20. All 4 patients underwent successful transplantation and have a mean current serum creatinine of 1.1 (range: 0.9-1.2). There were no episodes of antibody mediated rejection. Rapid allograft accommodation may limit the need for long-term antibody suppression provided by splenectomy or anti-CD20, thereby eliminating the added infectious risk of these modalities and removing another disincentive to ABOi transplantation.

The majority of preconditioning protocols developed to allow ABO-incompatible (ABOi) renal transplantation include concurrent splenectomy as a prerequisite to successful engraftment. Our center has developed a preconditioning protocol that includes plasmapheresis (PP), low-dose CMV hyperimmune globulin (CMVIg), and anti-CD20 monoclonal antibody (rituximab) to allow ABOi renal transplantation without splenectomy. Our initial experience has included treatment of six recipients and successful transplantation from blood group A(1), A(2), and group B living donors. Mean (+/- SD) serum creatinine was 1.3 +/- 0.1 mg/dL among the six recipients and no episodes of antibody-mediated rejection (AMR) occurred at a median follow-up of 12 months. ABO antibody titers have remained below pretreatment levels. The absence of AMR and stable allograft function in this series show the potential of this preconditioning protocol to increase ABOi renal transplantation. The use of rituximab, allowing avoidance of splenectomy, may further remove one of the significant disincentives to ABOi transplantation, and eliminate the risk of post-splenectomy infections.

ABO incompatibility and human leukocyte antigen (HLA) sensitization remain the two largest barriers to optimal utilization of kidneys from live donors. Here we describe the first successful transplantation of patients who were both ABO incompatible and crossmatch positive with their only available donor. A preconditioning regimen of plasmapheresis (PP) and low-dose CMV hyperimmune globulin (CMVIg) was delivered every other day until donor-specific antibody (DSA) titers were reduced to a safe level and isoagglutinin titers were < or =16. Each patient received quadruple sequential immunosuppression, splenectomy and three protocol post-transplant PP/CMVIg treatments. There was no hyperacute rejection. Two of the three patients had a persistent positive cytotoxic crossmatch on the day of transplant and eliminated their DSA subsequently. Antibody-mediated rejection (AMR) in one patient was reversed by reinitiating PP/CMVIg and anti-CD20. The patients are more than 9 months post-transplant with excellent graft function. Preconditioning with PP/CMVIg results in a durable suppression of DSA and permits accommodation of the allograft to a discordant blood type. The ability to cross these two barriers simultaneously is clinically important as sensitized patients have often exhausted their blood type compatible living donors during previous transplants.

Peroxisomal matrix protein import requires PEX12, an integral peroxisomal membrane protein with a zinc ring domain at its carboxy terminus. Mutations in human PEX12 result in Zellweger syndrome, a lethal neurological disorder, and implicate the zinc ring domain in PEX12 function. Using two-hybrid studies, blot overlay assays, and coimmunoprecipitation experiments, we observed that the zinc-binding domain of PEX12 binds both PEX5, the PTS1 receptor, and PEX10, another integral peroxisomal membrane protein required for peroxisomal matrix protein import. Furthermore, we identified a patient with a missense mutation in the PEX12 zinc-binding domain, S320F, and observed that this mutation reduces the binding of PEX12 to PEX5 and PEX10. Overexpression of either PEX5 or PEX10 can suppress this PEX12 mutation, providing genetic evidence that these interactions are biologically relevant. PEX5 is a predominantly cytoplasmic protein and previous PEX5-binding proteins have been implicated in docking PEX5 to the peroxisome surface. However, we find that loss of PEX12 or PEX10 does not reduce the association of PEX5 with peroxisomes, demonstrating that these peroxins are not required for receptor docking. These and other results lead us to propose that PEX12 and PEX10 play direct roles in peroxisomal matrix protein import downstream of the receptor docking event.

The peroxisome-biogenesis disorders (PBDs) are a group of genetically heterogeneous, lethal diseases that are characterized by neuronal, hepatic, and renal abnormalities; severe mental retardation; and, in their most severe form, death within the 1st year of life. Cells from all PBD patients exhibit decreased import of one or more classes of peroxisome matrix proteins, a phenotype shared by yeast pex mutants. We identified the human orthologue of yeast PEX10 and observed that its expression rescues peroxisomal matrix-protein import in PBD patients' fibroblasts from complementation group 7 (CG7). In addition, we detected mutations on both copies of PEX10 in two unrelated CG7 patients. A Zellweger syndrome patient, PBD100, was homozygous for a splice donor-site mutation that results in exon skipping and loss of 407 bp from the PEX10 open reading frame. A more mildly affected neonatal adrenoleukodystrophy patient was a compound heterozygote for a missense mutation in the PEX10 zinc-binding domain, H290Q, and for a nonsense mutation, R125ter. Although all three mutations attenuate PEX10 activity, the two alleles detected in the mildly affected patient, PBD052, encode partially functional PEX10 proteins. PEX10-deficient PBD100 cells contain many peroxisomes and import peroxisomal membrane proteins but do not import peroxisomal matrix proteins, indicating that loss of PEX10 has its most pronounced effect on peroxisomal matrix-protein import.