Changing patterns of clinical decision making: are falling numbers of antibody incompatible transplants related to the increasing success of the UK Living Kidney Sharing Scheme? A national cohort study.

Antibody incompatibility is a barrier to living kidney transplantation; antibody incompatible transplantation (AIT) is an accepted treatment modality, albeit higher risk. This study aims to determine changes to clinical decision making and access to AIT in the UK. An electronic survey was sent to all UK renal transplant centres (n = 24), in 2014, and again in 2018. Questions focused on entry & duration in the UKLKSS for HLA and ABO-incompatible pairs, Can and provision of direct AIT transplantation within those centres. Between 2014 & 2018, the duration recommended for patients in the UKLKSS increased. In 2014, 34.8% of centres reported leaving HLA-i pairs in the UKLKSS indefinitely, or reviewing on a case by case basis, by 2018 this increased to 61%. Centres offering direct HLA-i transplantation reduced from 58% to 37%. For low titre (1:8) ABO-i recipients, 66% of centres recommended at least 9 months (3 matching runs) in the UKLKSS scheme in 2018, compared to 47% in 2014, 50% fewer units consider direct ABO-i transplantation for unsuccessful pairs with high ABO titres (>1:512). Over time, clinicians appear to be facilitating more conservative management of AIT patients, potentially limiting access to living donor transplantation.

Does HLA matching matter in the modern era of renal transplantation?

Children with end-stage kidney disease should be offered the best chance for future survival which ideally would be a well-matched pre-emptive kidney transplant. Paediatric and adult practice varies around the world depending on geography, transplant allocation schemes and different emphases on living (versus deceased) donor renal transplantation. Internationally, paediatric patients often have priority in allocation schemes and younger donors are preferentially allocated to paediatric recipients. HLA matching can be difficult and may result in longer waiting times. Additionally, with improved surgical techniques and modern immunosuppressive regimens, how important is the contribution of HLA matching to graft longevity? In this review, we discuss the relative importance of HLA matching compared with donor quality; and long-term patient outcomes including re-transplantation rates. We share empirical evidence that will be useful for clinicians and families to make decisions about best donor options. We discuss why living donation still provides the best allograft survival outcomes and what to do in the scenario of a highly mismatched living donor.

A Europe wide acceptable mismatch program will enable transplantation of long waiting highly sensitised patients with a compatible donor.

Immunisation against Human Leucocyte Antigens (HLA) can be caused by pregnancy, blood transfusion, or organ transplants. The HLA antibody status of a given patient significantly influences their access and waiting time to transplant. For some highly sensitised patients (HSP) there is hardly any suitable donor available in the deceased donor pool of their allocation organisation and therefore they wait a very long time before being offered a kidney for transplant. Especially patients with rare HLA phenotypes in relation to the actual donor pool are waiting extremely long. As HLA phenotypes are different in the various European populations, we hypothesized that extension of the donor pool outside the respective allocation system will increase the chance of receiving a compatible transplant for this subgroup of highly sensitised patients. One of the objectives of the EUROSTAM project, (a Europe-wide Strategy to enhance Transplantation of highly sensitised patients on the basis of Acceptable HLA Mismatches) was to develop a tool to compare the chance of transplanting HSP in different European populations with donor organs from within and outside their own donor pool. Information on the HLA type and ABO blood group of the actual donor population, as well as the acceptable mismatches of long waiting HSP were obtained from the EUROSTAM partner organizations i.e. Eurotransplant (ET), UK National Health Service Blood and Transplant (NHSBT), Barcelona, Prague and Athens. Results from simulations using the newly developed tool shows that 195 (27%) of the 724 long waiting highly sensitised patients registered at each partner organisation have increased chances of transplant in a different European donor pool. This makes a strong case for sharing kidneys between European countries for selected difficult to transplant patients.

De novo donor-specific HLA antibodies after combined intestinal and vascularized composite allotransplantation - a retrospective study.

Combining vascularized composite allotransplantation (VCA) with intestinal transplantation to achieve primary abdominal closure has become a feasible procedure. Besides facilitating closure, the abdominal wall can be used to monitor intestinal rejection. As the inclusion of a VCA raises the possibility of an enhanced alloimmune response, we investigated the incidence and clinical effect of de novo donor-specific HLA antibodies (dnDSA) in a cohort of patients receiving an intestinal transplant with or without a VCA. The sequential clinical study includes 32 recipients of deceased donor intestinal and VCA transplants performed between 2008 and 2015; eight (25%) modified multivisceral transplants and 24 (75%) isolated small bowel transplants. A VCA was used in 18 (56.3%) cases. There were no episodes of intestinal rejection without VCA rejection. Fourteen patients (14 of 29; 48.3%) developed dnDSA. In the VCA group, fewer patients developed dnDSA; six of 16 (37.5%) VCA vs. eight of 13 (61.5%) non-VCA. There was no statistically significant difference in one- and 3-year overall graft survival stratified for the presence of dnDSA; P = 0.286. In the study, there is no evidence that the addition of a VCA increases the incidence of dnDSA formation compared to transplantation of the intestine alone.

The UK National Registry of ABO and HLA Antibody Incompatible Renal Transplantation: Pretransplant Factors Associated With Outcome in 879 Transplants.

BACKGROUND: ABO and HLA antibody incompatible (HLAi) renal transplants (AIT) now comprise around 10% of living donor kidney transplants. However, the relationship between pretransplant factors and medium-term outcomes are not fully understood, especially in relation to factors that may vary between centers. METHODS: The comprehensive national registry of AIT in the United Kingdom was investigated to describe the donor, recipient and transplant characteristics of AIT. Kaplan-Meier analysis was used to compare survival of AIT to all other compatible kidney transplants performed in the United Kingdom. Cox proportional hazards regression modeling was used to determine which pretransplant factors were associated with transplant survival in HLAi and ABOi separately. The primary outcome was transplant survival, taking account of death and graft failure. RESULTS: For 522 HLAi and 357 ABO incompatible (ABOi) transplants, 5-year transplant survival rates were 71% (95% confidence interval [CI], 66-75%) for HLAi and 83% (95% CI, 78-87%) for ABOi, compared with 88% (95% CI, 87-89%) for 7290 standard living donor transplants, and 78% (95% CI, 77-79%) for 15 322 standard deceased donor transplants (P < 0.0001). Increased chance of transplant loss in HLAi was associated with increasing number of donor specific HLA antibodies, center performing the transplant, antibody level at the time of transplant, and an interaction between donor age and dialysis status. In ABOi, transplant loss was associated with no use of IVIg, cytomegalovirus seronegative recipient, 000 HLA donor-recipient mismatch; and increasing recipient age. CONCLUSIONS: Results of AIT were acceptable, certainly in the context of a choice between living donor AIT and an antibody compatible deceased donor transplant. Several factors were associated with increased chance of transplant loss, and these can lead to testable hypotheses for further improving therapy.

Living Donation Has a Greater Impact on Renal Allograft Survival Than HLA Matching in Pediatric Renal Transplant Recipients.

BACKGROUND: Living donor (LD) kidney transplantation accounts for around half of all pediatric renal transplant recipients and results in improved renal allograft survival. The aim of this study was to determine the effect of HLA matching on deceased and LD renal allograft outcomes in pediatric recipients. METHODS: Data were obtained from the UK Transplant Registry held by NHS Blood and Transplant on all children who received a donation after brain death (DBD) or LD kidney-only transplant between 2000 and 2011. HLA-A, HLA-B and HLA-DR mismatches were categorized into 4 levels and 2 groups. Data were fully anonymized. RESULTS: One thousand three hundred seventy-eight pediatric renal transplant recipients were analyzed; 804 (58%) received a DBD donor kidney, 574 (42%) received an LD kidney. Five-year renal allograft survival was superior for children receiving a poorly HLA-matched LD kidney transplant (88%, 95% confidence interval [95% CI], 84-91%) compared with children receiving a well HLA-matched DBD kidney transplant (83%, 95% CI, 80-86%, log rank test P = 0.03). Five-year renal allograft survival was superior for children receiving an LD kidney with 1 or 2 HLA-DR mismatches (88%, 95% CI, 84-91%) compared with children receiving a DBD kidney with 0 HLA-DR mismatches (83%, 95% CI, 80-86%, log rank test P = 0.03). CONCLUSIONS: In children, poorly HLA-matched LD renal transplant outcomes are not inferior when compared with well HLA-matched DBD renal transplants. It is difficult to justify preferentially waiting for an improved HLA-matched DBD kidney when a poorer HLA-matched LD kidney transplant is available.

Role of anti-vimentin antibodies in renal transplantation.

BACKGROUND: The role of non-HLA antibodies in rejection is not clear. We investigate whether antibodies to vimentin are made after renal transplantation and if production is associated with interstitial fibrosis and tubular atrophy (IFTA). METHODS: In this retrospective study, sera from 70 recipients of renal allografts (40 controls, 30 IFTA) were studied. The biopsy diagnosis of interstitial fibrosis and tubular atrophy (IFTA) was based on random, cause-indicating biopsies. Sera were collected pretransplant and at 3 monthly intervals up to 5 years posttransplant or diagnosis of IFTA and assayed by ELISA for IgM and IgG anti-vimentin antibodies (AVA) and HLA antibodies. RESULTS: Mean titers of IgM AVA were higher at every year after transplantation compared with pretransplant for both IFTA and controls groups (P<0.001). There was no difference in the mean level of IgM AVA achieved by IFTA and control groups. The mean pretransplant levels of IgG AVA in the IFTA and control group were 18.2±11.7 and 11.0±8.1, respectively (P=0.001). There was a significant increase between the pretransplant mean levels of IgG AVA and the levels at years 1 to 4 in the IFTA group (years 1-3, P<0.0001, year 4 P=0.003) but not in the controls. There was no significant difference between the numbers of IFTA or control patients achieving a positive value (mean+2SD of pretransplant antibody titers) of IgM AVA (50% versus 37.5%, respectively) or IgG AVA (26.6% versus 12.5%, respectively). There was no association between production of HLA and AVA antibodies. CONCLUSION: Posttransplant production of IgM AVA is not associated with IFTA. The production of IgG AVA by a minority of IFTA patients suggests that in some individuals, IgG AVA may be involved in the pathology of IFTA.

Consensus guidelines on the testing and clinical management issues associated with HLA and non-HLA antibodies in transplantation.

BACKGROUND: The introduction of solid-phase immunoassay (SPI) technology for the detection and characterization of human leukocyte antigen (HLA) antibodies in transplantation while providing greater sensitivity than was obtainable by complement-dependent lymphocytotoxicity (CDC) assays has resulted in a new paradigm with respect to the interpretation of donor-specific antibodies (DSA). Although the SPI assay performed on the Luminex instrument (hereafter referred to as the Luminex assay), in particular, has permitted the detection of antibodies not detectable by CDC, the clinical significance of these antibodies is incompletely understood. Nevertheless, the detection of these antibodies has led to changes in the clinical management of sensitized patients. In addition, SPI testing raises technical issues that require resolution and careful consideration when interpreting antibody results. METHODS: With this background, The Transplantation Society convened a group of laboratory and clinical experts in the field of transplantation to prepare a consensus report and make recommendations on the use of this new technology based on both published evidence and expert opinion. Three working groups were formed to address (a) the technical issues with respect to the use of this technology, (b) the interpretation of pretransplantation antibody testing in the context of various clinical settings and organ transplant types (kidney, heart, lung, liver, pancreas, intestinal, and islet cells), and (c) the application of antibody testing in the posttransplantation setting. The three groups were established in November 2011 and convened for a "Consensus Conference on Antibodies in Transplantation" in Rome, Italy, in May 2012. The deliberations of the three groups meeting independently and then together are the bases for this report. RESULTS: A comprehensive list of recommendations was prepared by each group. A summary of the key recommendations follows. Technical Group: (a) SPI must be used for the detection of pretransplantation HLA antibodies in solid organ transplant recipients and, in particular, the use of the single-antigen bead assay to detect antibodies to HLA loci, such as Cw, DQA, DPA, and DPB, which are not readily detected by other methods. (b) The use of SPI for antibody detection should be supplemented with cell-based assays to examine the correlations between the two types of assays and to establish the likelihood of a positive crossmatch (XM). (c) There must be an awareness of the technical factors that can influence the results and their clinical interpretation when using the Luminex bead technology, such as variation in antigen density and the presence of denatured antigen on the beads. Pretransplantation Group: (a) Risk categories should be established based on the antibody and the XM results obtained. (b) DSA detected by CDC and a positive XM should be avoided due to their strong association with antibody-mediated rejection and graft loss. (c) A renal transplantation can be performed in the absence of a prospective XM if single-antigen bead screening for antibodies to all class I and II HLA loci is negative. This decision, however, needs to be taken in agreement with local clinical programs and the relevant regulatory bodies. (d) The presence of DSA HLA antibodies should be avoided in heart and lung transplantation and considered a risk factor for liver, intestinal, and islet cell transplantation. Posttransplantation Group: (a) High-risk patients (i.e., desensitized or DSA positive/XM negative) should be monitored by measurement of DSA and protocol biopsies in the first 3 months after transplantation. (b) Intermediate-risk patients (history of DSA but currently negative) should be monitored for DSA within the first month. If DSA is present, a biopsy should be performed. (c) Low-risk patients (nonsensitized first transplantation) should be screened for DSA at least once 3 to 12 months after transplantation. If DSA is detected, a biopsy should be performed. In all three categories, the recommendations for subsequent treatment are based on the biopsy results. CONCLUSIONS: A comprehensive list of recommendations is provided covering the technical and pretransplantation and posttransplantation monitoring of HLA antibodies in solid organ transplantation. The recommendations are intended to provide state-of-the-art guidance in the use and clinical application of recently developed methods for HLA antibody detection when used in conjunction with traditional methods.

Baculovirus as delivery system for gene transfer during hypothermic organ preservation.

Concerns over the safety of conventional viral vectors have limited the translation of gene transfer from an exciting experimental procedure to a successful clinical therapy in transplantation. Baculoviruses are insect viruses, but have the ability to enter mammalian cells and deliver potential therapeutic molecules with no evidence of viral replication. This study provides evidence of the ability of recombinant baculovirus to enter mammalian kidneys and livers during cold preservation. Six kidneys and six liver lobules retrieved from large pigs were perfused with University of Wisconsin (UW) solution containing a baculovirus tagged with green fluorescent protein and preserved for 8 h. In addition, six kidneys were perfused with UW containing a baculovirus expressing red fluorescent protein and preserved for 24 h. Green fluorescent virus particles were detected within transduced kidneys and livers after 8 h standard cold storage and red fluorescent protein mRNA was detected in kidneys after 24 h of cold preservation. There were no significant differences in tissue architecture, cell morphology or ATP content between experimental organs and their controls. Ex vivo transduction of organs with recombinant baculovirus during conventional cold preservation was demonstrated with no evidence of additional injury or reduction in cell viability.

Peripheral blood sampling for the detection of allograft rejection: biomarker identification and validation.

Currently, acute allograft rejection can only be detected reliably by deterioration of graft function confirmed by allograft biopsy. A huge drawback of this method of diagnosis is that substantial organ damage has already taken place at the time that rejection is diagnosed. Discovering and validating noninvasive biomarkers that predict acute rejection, and chronic allograft dysfunction, is of great importance. Many studies have investigated changes in the peripheral blood in an attempt to find biomarkers that reflect changes in the graft directly or indirectly. Herein, we will review the promises and limitations of the peripheral blood biomarkers that have been described in the literature so far.