ABO-compatible Donor Research Articles

Equity in Kidney Transplant Allocation: Graft Survival Outcomes for Blood Group B Recipients from A2/A2B- and ABO-Compatible Donors

Equity in Kidney Transplant Allocation: Graft Survival Outcomes for Blood Group B Recipients from A2/A2B- and ABO-Compatible Donors

Bloodless Medicine in Patients Undergoing Allogeneic Hematopoietic Stem Cell Transplantation.

Allogeneic hematopoietic stem cell transplantation (alloHSCT) poses challenges for patients who decline blood products because of religious beliefs or other reasons. Despite potential curative prospects, many institutions refrain from offering alloHSCT to patients who decline blood products because of safety concerns associated with cytopenias. This review focuses on one institution's experience of conducting alloHSCT without blood components, emphasizing preparation and supportive care. The approach of conducting alloHSCT without blood components, which involves ABO-compatible donor matching, nonmyeloablative regimens, and pretransplantation optimization of red blood cell production, is discussed. The clinical team can minimize transfusion needs by using erythropoiesis-stimulating agents, thrombopoietin agonists, and peri- and post-transplantation management strategies. These recommendations can ensure patient safety and successful outcomes with bloodless medicine.

ABO Incompatible Kidney Transplantation Without B-cell Depletion is Associated With Increased Early Acute Rejection: A Single-Center Australian Experience.

We performed a single-center retrospective cohort study of 66 consecutive ABO incompatible kidney transplants (ABOiKT) performed without B-cell depleting therapy. Outcomes were compared to an earlier era performed with rituximab (n = 18) and a contemporaneous cohort of ABO compatible live donor transplants (ABOcKT). Acute rejection within 3months of transplant was significantly more common after rituximab-free ABOiKT compared to ABOiKT with rituximab (OR 8.8, p = 0.04) and ABOcKT (OR 2.9, p = 0.005) in adjusted analyses. Six recipients of rituximab-free ABOiKT experienced refractory antibody mediated rejection requiring splenectomy, and a further two incurred early graft loss with no such episodes amongst ABOiKT with rituximab or ABOcKT cohorts. Patient and graft survival were similar between groups over a median follow-up of 3.1years. This observational evidence lends strong support to the continued inclusion of rituximab in desensitization protocols for ABOiKT.

ABO-Incompatible Renal Transplant: A Single-Center Experience from India.

In view of ever-increasing end-stage renal disease (ESRD) population but inadequate availability of suitable donors, ABO-incompatible (ABOi) transplantation can be an important void filler. However, at present, ABOi transplantation is limited to a few centers in India and there is a lack of adequate experience and expertise to guide this program to other centers in the country. Data of all the ABOi transplants performed from 2012 to 2021 in a tertiary care hospital was retrospectively analyzed. The anti-ABO antibody (IgG) titers (≤1:4) were considered safe before transplantation. Desensitization included rituximab, plasma exchange, or selective immunoadsorption column. Tacrolimus and mycophenolate mofetil were initiated at day -7. Induction agents included ATG, ATLG, basiliximab, or no induction. Postoperatively, anti-ABO titers were done daily for 2 weeks. A total of 202 patients underwent transplantation; of these, 195 patients whose data were for available for 12 months were included in the study. Mean duration of follow-up was 28.9 ± 21.7 months. UTI was the most common source of infection, occurring in almost half (46.1%) of the patients. Antibody-mediated rejection (ABMR; 15%) was common in the first year. Patient survival was 86.6% (169/195) at 1 year. Sepsis was the most common of death in more than two-thirds of the population, including coronavirus disease 2019 (COVID-19)-associated mortality in nine patients (4.6%). Death-censored graft survival was 89.3% (174/195). AMR was the leading cause of graft loss in almost half of the patients. ABOi should be considered in ESRD patients for whom suitable ABO-compatible donor is not available. Higher rate of rejection and infection are still a major concern.

Outcomes of keratolimbal allograft from ABO compatible donors for severe bilateral limbal stem cell deficiency.

To report outcomes of keratolimbal allograft (KLAL) compatible for both human leukocyte (HLA) and/or blood type using oral prednisone, mycophenolate, and tacrolimus, with basiliximab if panel reactive antibodies (PRA) are present. Intravenous immunoglobulin (IVIG) was used post-operatively if donor-specific anti-HLA antibodies (DSA) were present. Retrospective interventional series of consecutive patients with KLAL for limbal stem cell deficiency (LSCD) from HLA and/or blood type compatible deceased donors with a minimum follow-up time of 12 months. Main outcome measures were ocular surface stability, visual acuity and systemic immunosuppression (SI) adverse events. Eight eyes of eight patients with mean age of 48.6±10.1 years (range 34-65 years) were included. Mean follow-up time was 37.3±22.7 months (range 12-71 months) following KLAL; four (50%) had combined LR-CLAL surgery. The etiologies of LSCD were Stevens-Johnson Syndrome (n=4/8), aniridia (n=2/8), chemical injury (n=1/8) and atopic eye disease (n=1/8). All patients had PRA present and received basiliximab infusions. 5/8 patients received IVIG based on DSA identified pre-operatively. At last follow-up, 7 eyes (87.5%) had a stable ocular surface; 1 eye (12.5%) developed failure and had keratoprosthesis implantation. There was a significant improvement in visual acuity from 1.65±0.48 to 0.68±0.34 logMAR (p=0.01). SI was tolerated well with minimal adverse events. Preliminary outcomes of KLAL with ABO compatible tissue using the Cincinnati protocol, preoperative basiliximab (when PRA present) and post-operative IVIG (when DSA present) are encouraging. This protocol may allow for utilization of deceased donor tissue with results approximating those of living donor tissue transplanted for severe bilateral LSCD.

P8.093: ABO Incompatible Renal Transplantation in Argentina: Experience in a Tertiary Referral University Hospital

Introduction: ABO-incompatible renal transplant (ABOiTr) is little used in Argentina despite being able to increase the pool of donors. We report our experience with this modality in the period Jul/2014 – Mar/2022. Study population and Methods: 177 living transplant donor were performed in the studied period of which 23 were ABOi (13%). Age of TrABOi: 48 years (20-76), 10 female (43%), second Tr 6/23 (26%), time on dialysis 21.8 months (3-60), preemptive 26%, non-related donor 52%, HLA missmatch 3.7 (0-6), presence of DSA in 22%. Median pre-Tr donor anti-group agglutinins: IgG 1/16 (0-1028), IgM 1/8 (0-256). Pre-Tr conditioning therapy included rituximab in 22/23 and plasmapheresis (PF) in 20/23 with a median of 4 sessions (range 1-9). Two patients received PF post ABOi Tr. All received immunosuppression with tacrolimus and mycophenolate one month pre-Tr and continued post-Tr. Intravenous immunoglobulin (IVIG) was used in all patients post last PF and antithymocyte globulin as induction in 20/23 patients. Results: Mean follow-up post-Tr was 37.4 months (1-92). Six patients developed acute rejection (AMR: 4, TCMR: 2). Rejection treatment included corticosteroids pulses and IVIG in all cases. Bortezomib was used in one case and PF in another. All patients except one responded to treatment. The most frequent post-Tr complications were: urinary tract infections in 7 patients one of them with sepsis, BK reactivation in 2 cases and 1 case of immediate post-Tr hemorrhage. Nine patients developed COVID infection (39%), 3 of them required hospitalization. One graft loss was recorded at 6 months post-Tr due to refractory AMR. Three patients died in the study period, two deaths related to COVID infection (1 and 33 months post-Tr) and one death was related to PTLD (49 months post-Tr), all deaths were with a functioning kidney (median patient survival 89%). Creatinine level in last control was 1.53 mg/dl (0.90-2.70 mg/dl) and P/C 0.18 (0.1-1.0). Conclusion: ABOiTr is a feasible alternative in our country, these preliminary results suggest that it should be offered more extensively to recipients who do not have an ABO compatible donor. Fundación Nefrológica de Córdoba.

O004 Blood group antigen removal of a human kidney using ex-vivo normothermic machine perfusion technology

Abstract Introduction A novel strategy to overcome the constraints of ABO compatibility in solid organ transplantation is the enzymatic removal of blood group antigens using an alpha-galactosidase enzyme from Bacteroides fragilis during ex-vivo normothermic machine perfusion (NMP). Methods Human kidneys rejected for transplantation and offered for research were used in this study which was approved by the National Research Ethics committee and Research and Development office (NRES: 15/NE/0408). Blood group antigen removal using the alpha-galactosidase enzyme GH110B from B. fragilis was first investigated on formalin-fixed paraffin-embedded (FFPE) cortex sections from human kidneys of blood group B (n=5). Immunofluorescence co-staining of the blood group B antigens (isolectin GSIB4) and vascular endothelium (CD-31) was completed. A human kidney of blood group B was then treated with 0.0025mg/ml of alpha-galactosidase during 6hrs of NMP using an acellular perfusate solution. Serial biopsies taken throughout perfusion were stained and analysed for antigen removal. Results Alpha-galactosidase treatment of FFPE sections at all concentrations examined (0.0013mg/ml 0.5mg/ml) caused significant reduction of the Pearson correlation coefficient for B antigen and CD-31 co-localisation compared to the untreated control (p<0.001). Following NMP of the treated B kidney, the Pearson correlation coefficient dropped from 0.182±0.042 (pre-treatment level) to a minimum of 0.017±0.102 after 6hrs (p<0.0001), indicating a near-complete loss of the blood group antigens. Conclusion This is the first example of the enzymatic removal of type B blood group antigens from a human kidney during NMP. This strategy may have the potential to increase the pool of ABO compatible donor kidneys for transplantation. Take-home message We have shown that an alpha-galactosidase enzyme added during ex-vivo normothermic machine perfusion can be used to enzymatically remove the blood group B antigens from human kidneys, providing the first example of whole organ conversion in humans. This strategy has the potential to massively increase the pool of ABO compatible donor kidneys for transplantation.

Experiences of performing ABO-incompatible kidney transplantation in Bangladesh.

BackgroundThe number of end-stage renal disease (ESRD) patients is increasing in Bangladesh. Currently, living kidney donation is the only viable option for transplantation in Bangladesh, and it is further restricted by ABO compatibility issues. We have performed ABO-incompatible kidney transplantations (ABOi KTs) in Bangladesh since 2018. This study examines our experiences with seven cases of ABOi KT.MethodsThe desensitization protocol included low-dose rituximab (100 mg/body) followed by plasma exchange (PEX), which was followed by a 5-g dose of intravenous immunoglobulin. Immunosuppression was undertaken using tacrolimus (0.1 mg/kg/day), mycophenolate mofetil (1,500 mg/day), and prednisolone (0.5 mg/kg/day). All patients received basiliximab for induction therapy.ResultsThe median baseline anti-ABO antibody titer was 164 (range, 132–1128). Transplantation was performed at a titer of ≤18. Our patients attended three to five PEX sessions before transplantation. Graft survival was 100% in the seven cases over a mean period of 22 months. The mean creatinine level was 204.6±47.4 µmol/L. Two patients were suspected of having developed acute rejection and received intravenous methylprednisolone, resulting in improved kidney function. One patient required posttransplant hemodialysis due to delayed graft function and subsequently improved. Infection was the most common complication experienced by ABOi KT patients. Two patients developed severe cytomegalovirus pneumonia and died with functioning grafts.ConclusionsABOi KT in Bangladesh will substantially expand the living kidney donor pool and bring hope to a large number of ESRD patients without ABO-compatible donors. However, the high cost and risk of acute rejection and infection remain major concerns.

Outcome of urgent desensitization in sensitized heart transplant recipients

Sensitization, the presence of preformed anti-human antibody in recipients, restricts access to ABO-compatible donors in heart transplant. Desensitization therapy works by reducing preformed antibodies to increase the chances of a negative crossmatch or permit safe transplantation across positive crossmatch. There is no consensus regarding the desensitization protocol in cardiac patients, and the outcome of desensitization remains under debate. Twenty-five consecutive sensitized heart transplant recipients received perioperative desensitization in our institution from 2012 to 2019. One-year patient survival and graft rejection rate were analyzed and compared between sensitized recipients and non-sensitized recipients. Within the first year after transplant, patient survival in sensitized recipients was 76%. Infection was the major cause of death. The cumulative incidence of rejection was 8% for antibody-mediated rejection and 16% for acute cellular rejection. No significant difference in 1-year survival or rejection rate could be demonstrated between sensitized and nonsensitized recipients. Acceptable early outcomes in patient survival and graft rejection could be anticipated in sensitized heart transplant recipients under a perioperative algorithm using complement-dependent cytotoxicity crossmatch- or panel-reactive antibody-directed urgent immunomodulation strategies, while infection remains the major concern.

Kidney Transplantation with ABO-Incompatible Donors: A Comparison with Matched ABO Compatible Donor Transplants.

Introduction:ABO-incompatible kidney transplantation (ABOiKTx) expands the living donor pool. There is limited long-term outcome data from India especially in comparison with ABO-compatible kidney transplantation (ABOcKTx). Here we report outcomes of the first 100 ABOiKTx compared to ABOcKTx from our center.Methods:Between August 2013 and December 2019, 100 consecutive ABOiKTx were compared with 100 ABOcKTx done during the same period.Controls were matched for age, donor characteristics, HLA mismatches, and date of transplantation.Results:Mean (SD) follow up period was 25.9 ± 20.5 and 27.2 ± 20.6 months in ABOi and ABOcKTx respectively. Patient survival at 1 and 5 years post-transplant was 93.3 and 73.5% vs. 95.4 and 93% (P = 0.03), while graft survival rates were 85 and 60% vs. 93.1 and 83% in ABOi and ABOcKTx respectively (P = 0.03). The incidence of antibody-mediated rejections was 15% vs. 4%, and that of T-cell-mediated rejections was 10 vs. 12% respectively. Infections, malignancies, and surgical complications were similar. Level of anti ABO titers, HLA mismatches, recipient age, donor age, and presence of diabetes did not impact graft survival amongst ABOiKTx. The predicted survival and incidence of acute rejections and infections in the later 50 ABOiKTx transplants were better than the first 50 ABOiKTx when compared to their respective controls.Conclusion:Outcomes of ABOiKTx were inferior to ABOcKTx but tends to improve as more experience is gained. Incidence of ABMR was higher but infections and surgical complications were comparable. This data provides evidence that ABOiKTx is viable option for those without a ABO compatible donor.

ABO-Incompatible Living Donor Liver Transplantation with Reduced Rituximab Dose: A Retrospective Analysis of 65 Patients - Can We Fast-Track Liver Transplant Surgery and Improve Long-Term Survival?

BackgroundABO-incompatible (ABO-i) living donor liver transplantation (LDLT) is a feasible alternative for donor liver allograft in emergency situations, especially in Asia, where deceased-donor organs remain scarce. The reported outcomes of ABO-i LDLT after optimal desensitization are comparable to those of ABO-compatible LDLT. In this retrospective study, we found improved outcomes after ABO-i LDLT with a low-dose rituximab in combination with double-filtration plasmapheresis (DFPP) and prophylactic antibiotic therapy.Material/MethodsBetween January 2006 and December 2018, a total of 65 recipients underwent ABO-i LDLT surgeries at our center. The study cohort consisted of 50 recipients (Era III) who underwent ABO-i LDLT using the recently updated desensitization protocol, which included rituximab 200 mg intravenous injection once a week prior to LDLT, 4 sessions of DFPP in all patients, and prophylactic antibiotics for 3 months.ResultsThe 3-year overall survival rate achieved in ABO-i LDLT patients was 72.7% (66.6% for Era I and 33.3% for Era II patients). In the study population, 11 patients developed complications due to infection. Five of these patients (10%) died due to overwhelming sepsis. Four patients (8%) were diagnosed with multiple strictures and diffusely scattered dilatation of intrahepatic bile ducts on computed tomography, without vascular complications. Three of them had evidence of antibody-mediated rejection (AMR).ConclusionsOur experience shows that the ABO-i LDLT protocol of lowered rituximab combined with pre-transplant sessions of plasmapheresis and a quadruple immunosuppressive regimen can be effective in chronic liver failure patients with clinical urgency in the absence of an ABO-compatible donor. Fast-tracking the use of ABO-i LDLT is feasible in patients with an acute liver failure (ALF) and can safely increase the donor liver pool, with an acceptable outcome.

Impact of ABO incompatibility on outcomes after haploidentical hematopoietic stem cell transplantation for severe aplastic anemia.

The impact of ABO incompatibility on transplantation outcomes in severe aplastic anemia (SAA) patients receiving haploidentical hematopoietic stem cell transplantation (HSCT) remains controversial without published data. A total of 199 SAA patients receiving haploidentical HSCT from ABO-matched (n = 114), minor ABO-incompatible (n = 47), or major ABO-incompatible donors (n = 38) were included in this study. The median time and cumulative incidences of both myeloid and platelet engraftment in the ABO-compatible and ABO-incompatible groups were similar, and pure red cell aplasia was absent. Minor ABO incompatibility increased the rate of grade III-IV acute graft-versus-host disease (aGVHD) (ABO compatible: 6.14 ± 0.05%, minor incompatible: 19.15 ± 0.34%, and major incompatible: 10.53 ± 0.25%; P = 0.051), but did not influence the rates of grade II-IV aGVHD or chronic GVHD (cGVHD). Minor ABO-incompatibility was identified as an independent risk factor for grade III-IV aGVHD by multivariate analysis (hazard ration (HR) = 4.00 (1.48-10.80), P = 0.006). Chronic GVHD, mortality, and treatment failure were not increased in the minor ABO-incompatible group. For SAA patients receiving haploidentical HSCT, ABO compatible donors are better than ABO minor incompatible donors if several haploidentical donors are available.

Cardiac Inotropes Offer Protection of Renal Function in Patients with Kidney Transplantation

Introduction: Impaired cardiac function is one of the most concomitant symptoms in patients with kidney failure after long-term dialysis. In addition, the preservation of adequate perfusion pressure to the graft plays a significant role in the intraoperative management during kidney transplantation, but the use of positive inotropic drugs in kidney transplant patients has been studied less. We investigated the protective effects of renal function by means of cardiac inotropes in kidney transplant patients. Methods: Eighty-nine patients that received kidney transplantation between April 2014 and December 2016 at Qilu Hospital were included and randomly divided into the treatment group receiving levosimendan and a control group. All kidney recipients received ABO-compatible donors. A poor outcome was defined as one of the following: delayed graft function, graft hemorrhage, or nephrectomy. Results: The treatment group had a better composite outcome and the level of neutrophil gelatinase-associated lipocalin was also lower than in the control group. Conclusion: Inotropic drugs may play a protective role in renal function in kidney transplantation.

Efficacy of cross-match compatible platelets in multi transfused haemato-oncology patients refractory to platelet transfusion

BackgroundPlatelet refractoriness, which leads to platelet transfusion failure resulting in significant morbidity and long hospital stay, is routinely not investigated. AimsTo determine the efficacy of cross-match compatible platelets in multi-transfused alloimmunized hemato-oncological patients refractory to platelet transfusion. Materials and method149 ABO compatible single donor apheresis platelet transfusions given to 38 alloimmunized refractory patients. Corrected Count Increment (CCI) <5000 (1 h) was taken to define refractoriness. Solid-phase red cell adherence assay was used to determine the alloimmunization status and platelet cross-matching. Post Transfusion Platelet Increment, CCI and the Percentage Platelet Recovery were used to monitor the effectiveness of platelet transfusion. ANOVA test followed by Post hoc test Tukey HSD used to compare group means and classified into three groups depending upon the cross-matching and compatibility status. Categorical data was analysed for various outcomes using Pearson's chi square test or Fischer exact test. ResultPatients showed statistically significant recovery in terms of PPI, CCI and PPR at 1 h post SDAP transfusions when they received cross-matched compatible platelets. The one-hour CCI was significantly higher for cross-match-compatible platelets (19173 ± 2692) than for incompatible (5888 ± 1526) and for uncross-matched (8140 ± 1480). Forty four (97.8%) of 45 cross-matched compatible platelet transfusion episodes showed a satisfactory response in terms of PPI and CCI values as compared to 50 % and 53.9% in uncross-matched group respectively (p < 0.0001). ConclusionPlatelet cross-matching is an effective intervention in the management of multi-transfused alloimmunized Haemato-oncological patients, refractory to platelet transfusion.

Older Donor Age Is a Risk Factor for Negative Outcomes After Adult Living Donor Liver Transplantation Using Small-for-Size Grafts.

Adult-to-adult living donor liver transplantation (ALDLT) using small-for-size grafts (SFSGs), ie, a graft with a graft-to-recipient weight ratio (GRWR) <0.8%, has been a challenge that should be carefully dealt with, and risk factors in this category are unclear. Therefore, we aimed to examine the risk factors and outcomes of ALDLT using SFSGs over a 13-year period in 121 patients who had undergone their first ALDLT using SFSGs. Small-for-size syndrome (SFSS), early graft loss, and 1-year mortality were encountered in 21.6%, 14.9%, and 18.4% of patients, respectively. By multivariate analysis, older donor age (≥45 years) was an independent risk factor for SFSS (odds ratio [OR], 4.46; P=0.004), early graft loss (OR, 4.11; P=0.02), and 1-year mortality (OR, 3.76; P=0.02). Child-Pugh C class recipients were associated with a higher risk of SFSS development (P=0.013; OR, 7.44). Despite no significant difference between GRWR categories in the multivariate outcome analysis of the whole population, in the survival analysis of the 2 donor age groups, GRWR <0.6% was associated with significantly lower 1-year survival than the other GRWR categories in the younger donor group. Moreover, in the high final portal venous pressure (PVP) group (>15mmHg), younger ABO-compatible donors showed 100% 1-year survival with a significant difference from the group of other donors. Older donor age was an independent risk factor for SFSS, early graft loss, and 1-year mortality after ALDLT using SFSGs. GRWR should not be <0.6%, and PVP modulation is indicated when grafts from older or ABO-incompatible donors are used.

MON-187 EXPERIENCE OF STARTING ABO INCOMPATIBLE RENAL TRANSPLANT IN NEPAL

Because of a strictly related live donor program and lack of effective deceased donor program, only around 5 percent of end stage renal disease patients undergo renal transplantation each year in Nepal. So, to address the growing need for donor, ABO incompatible renal transplantation is a viable option. We present the experience and struggles of starting ABO incompatible renal transplant in a developing country such as Nepal. This is a single center retrospective analysis of renal transplants from March 22nd, 2017 till October 26th, 2018. Pre transplant desensitizing protocol using Rituximab, plasma exchanges and/or immunoadsorption were performed in all the recipients. A titer of <= 1:8 was considered acceptable for transplantation. Post transplant plasma exchanges were done as required according to the level of the antibody titre. A total of 9 ABO incompatible renal transplant were done. Out of 9 Recipients, 5 were males and 4 females. The relationship between donor and recipient were parent to child in 7 cases and spousal in 2 patients. Pre-treatment Anti-A/B antibody titres ranged from 1:32 to 1:1024. In follow up, most of our patients had urinary tract infection and acute gastroenteritis. E. coli was mostly isolated in urine cultures. The longest follow up was 80 weeks. The start of a successful ABO incompatible renal transplant program has given hope to a large number of end stage renal patients who did not have ABO compatible donors. This has shown that even in a developing country like ours, ABO incompatible renal transplantation is a viable option for patients waiting for renal transplant without undue risk to the life of recipient and at reasonable cost.

Older donor age is the risk factor for negative outcomes after adult living donor liver transplantation using small-for-size grafts

Introduction: Adult-to-adult living donor liver transplantation (ALDLT) using small for size grafts (SFSGs) (graft-to-recipient weight ratio (GRWR) < 0.8%) has been a challenge that should be carefully dealt with and risk factors in this category are unclear. Method: We aimed to examine the risk factors and outcomes of ALDLT using SFSGs in 121 patients who had undergone their first ALDLT using SFSGs over a 13-year-period. Result: Small-for-size syndrome (SFSS), early graft loss and 1-year mortality were encountered in 21.6%, 15.1% and 18.4% of patients, respectively. By multivariate analysis, older donor age (≥ 45 years) was an independent risk factor for SFSS, with early graft loss and 1-year mortality P values of 0.004, 0.02 and 0.02 and odds ratios (OR) of 4.46, 4.11 and 3.76, respectively. Child-Pugh C-class recipients were associated with a higher risk of SFSS development (P=0.013, OR 7.44). Despite no significant difference between GRWR% categories in the multivariate outcome analysis of the whole population, in the survival analysis of the two donor age groups, GRWR < 0.6% was associated with significantly lower 1-year survival than the other GRWR% categories in the younger donor group. Moreover, in the high final portal venous pressure (PVP) group (> 15 mmHg), younger ABO compatible donors showed 100% 1-year survival with a significant difference from the group of other donors. Conclusion: Older donor age was an independent risk factor for SFSS, early graft loss and 1-year mortality after ALDLT using SFSGs. GRWR should not be lower than 0.6% and PVP modulation is indicated when grafts from older or ABO incompatible donors are used.

Mechanism Underlying a Role for Factor XIII (FXIII) Polymorphism in Sickle Cell Disease-Associated Priapism

Background: The pathophysiology of priapism in sickle cell disease (SCD) is poorly understood. While blood stasis is essential to tumescence, most research in SCD-associated priapism to date has focused on the potential role of abnormal signaling pathways. We have previously observed that a coding sequence single nucleotide polymorphism (rs5988) of the transglutaminase factor XIII gene (FXIII) is strongly associated with SCD priapism, with an odds ratio of 2.52 [C.I. 1.27 -5.03] for the risk genotype (G/G, expressing only FXIII E652) vs the most common non-risk genotype (G/C, expressing both FXIII E652 and FXIII Q652). We therefore explored the effect of the rs5988 polymorphism on various aspects of FXIII function.Methods: Recombinant FXIII (rFXIII) E652 and rFXIII Q652 were expressed by 293 kidney cells and isolated from serum-free tissue culture supernatant. Before use in assays, activation of rFXIII by thrombin was confirmed by generating activated rFXIII (rFXIIIa) with thrombin (10 U/ml), followed SDS-PAGE, western blotting for FXIII, and densitometry for quantitation. Whole blood samples and plasmas were obtained from previously genotyped subjects with SCD under an IRB-approved protocol. Plasma FXIII and rFXIII transglutaminase activity was measured by the ability to catalyze 5-(biotinamido)pentylamine incorporation into a suitable substrate. Plasma FXIII antigen was assayed by ELISA. Clot contraction was measured after tissue factor-initiated clotting of recalcified whole blood. Clot resistance to lysis was measured after exposure to tissue plasminogen activator (tPA).Results: Transglutaminase activity of each rFXIII was measured using fibrinogen and fibronectin as substrates. At 20 minutes, rFXIIIa E652 showed 1.44-fold more transglutaminase (crosslinking) activity toward fibrin(ogen) than rFXIIIa Q652 (p=0.027), and a nonsignificant trend toward more activity (1.32-fold, p=0.079) toward fibronectin. Kinetic assays also showed that rFXIII E652 had significantly greater activity toward both matrices (p=0.006 and 0.012, respectively), suggesting the risk genotype (homozygosity for the G allele) enhances fibrin(ogen) and/or fibronectin crosslinking. FXIII activity in the plasma of 18 genotyped SCD patients (3 CC, 7 GC, 8 GG) demonstrated a consistent, but not significant, trend toward increased FXIII activity with increasing presence of G alleles (80.01% CC, 98.90% CG, and 107.20% GG). Although results were not adjusted for genotype at other loci reported to affect FXIII expression, there was no significant difference in FXIII antigen among genotypes. Compared to contracted whole blood clots from patients with only one or no risk alleles, clots from SCD patients with two copies of the risk allele (GG, expressing only FXIII E652) did not differ in either RBC retention within clots or clot mass (weight). Moreover, inhibition of transglutaminase activity with T101 significantly increased RBC release and decreased clot weight to a similar degree in contracted clots from patients with either the GC or GG genotype. In clots formed from FXIII-deficient plasma supplemented with rFXIIIa E652 or rFXIIIa Q652 and ABO-compatible donor RBCs, clots containing rFXIIIa E652 were 14% more resistant to lysis than clots containing rFXIIIa Q652 (p=0.016). Parallel studies with SCD patient plasma samples also showed that clots containing only FXIII E652 were more resistant to lysis than clots containing both FXIII E652 and FXIII Q652(p=0.0001).Conclusions: These data suggest the FXIII rs5988 polymorphism does not alter protein expression or clot contraction but may regulate clot stability via slightly increased transglutaminase activity and enhanced resistance to lysis. These effects may predispose patients to formation of microclots during tumescence, thus impairing blood egress and increasing risk of priapism. Further studies should be conducted to determine if anticoagulation or fibrinolytic treatments are viable preventative or treatment strategies for SCD patients with the risk FXIIIGG genotype and recurrent priapism. DisclosuresTelen:Pfizer, Inc.: Consultancy, Research Funding. Wolberg:GlaxoSmithKline: Employment; Novo Nordisk: Research Funding.

Cincinnati Protocol for Preoperative Screening and Donor Selection for Ocular Surface Stem Cell Transplantation.

To describe our process for preoperative screening and donor selection for ocular surface stem cell transplantation (OSST). A 7-year retrospective chart review was performed on limbal stem cell deficiency patients. The inclusion criterion was all patients who underwent an OSST procedure. The exclusion criterion was eyes with unilateral disease in which an autograft was performed. Data for human leukocyte antigen (HLA) typing, virtual crossmatching, donor-specific antibody, and panel reactive antibody level were obtained. Of the included 142 eyes (104 patients), 19 patients had no recorded living donor availability data, and HLA typing was not performed on 16 patients. A total of 94 donors (mean 1.4 donors/patient, range 1-6) were tested for 67 recipients. For 2 patients with graft-versus-host disease, no further HLA typing was needed, as the donors were known HLA-identical donors. For 47 patients, only 1 donor was tested, whereas multiple donors underwent HLA typing for 20 patients. There were 73 ABO (blood group)-compatible matches for the 61 tested recipients, and only 1 recipient did not have any ABO-compatible donor. For the virtual crossmatch, there were 5 patients who did not have a compatible donor (positive virtual crossmatch). The best available donor match was a sibling for 41 recipients (65%), a parent for 19 recipients (30%), and an offspring for 3 recipients (5%). Our protocol for OSST preoperative screening and donor selection minimizes the antigenic burden for transplanted tissue by selecting the best available donor match.

False-negative compatible antiglobulin crossmatches in samples with alloantibodies to cognate red blood cell antigens.

Patient samples showing a positive indirect antiglobulin test are further tested to identify alloantibody specificity using a panel of phenotypically characterized group O reagent red blood cells (RBCs). Donor RBCs phenotypically negative for the antibody specificity are then serologically crossmatched using an antiglobulin reagent. This latter test is performed to identify any incompatibility due to the presence of undetected minor blood group antibodies and considered an important step in patient safety. Samples with well-characterized alloantibodies were intentionally crossmatched against donor RBCs expressing the cognate antigen. In a separate set of specimens, the alloantibody was titered and crossmatched against both heterozygous and homozygous cells. Thirty-five samples containing 10 common alloantibodies crossmatched against 240 ABO-compatible donor cells phenotypically positive for the cognate antigen showed compatible crossmatches in 89 of 240 (37%). Antibody titering of 12 alloantibodies showed that a titer of 2 or more was required for incompatibility of all homozygous cells and a titer of 8 or more for incompatibility of all heterozygous cells. The antiglobulin crossmatch has a high failure rate (false-negatives) related to antibody titer and donor cell zygosity and is not reliable in interdicting incompatibility due to minor blood group antibodies.