Blood Group Conversion Research Articles

O232: Enzymatic blood group conversion prevents complement activation in an ABO-incompatible model of human kidney transplantation

Abstract Introduction Recently, enzymatic blood group conversion has been used to convert human kidneys from blood group A to universal blood group O using bacterial enzymes from Flavonifractor plautii. However, little is known about the functional consequences of antigen removal when a treated kidney is transplanted in an ABO-incompatible (ABOi) recipient. Here, we investigated classical complement activation during ABOi conditions in enzyme treated (ABOe) vs control human type A kidneys. Method Three biological pairs of type A human kidneys rejected for transplantation and offered for research were used in this study. One kidney per pair was treated with 1mg/L of FpGalNAc deacetylase and FpGalactosaminidase during 6hrs of hypothermic machine perfusion while the contralateral kidney was perfused without enzymes. Both kidneys were subsequently perfused for 4hrs in ABOi conditions using normothermic machine perfusion (10% AB serum; mouse anti-A IgM titre 1:128; type O red blood cells). Tissue-bound components of classical complement activation were assessed in pre- and post-perfusion biopsies. Results Following ABOi perfusion, control kidneys showed peritubular deposition of the classical complement component C1qA and further complement activation components C4d and C5b-9. The staining directly co-localised with regions of anti-A staining. In ABOe kidneys, no anti-A staining was observed, with no C1qA, C4d, or C5b-9 staining found in post-perfusion biopsies. Conclusions We have shown for the first time that ABOe kidneys do not activate the classical complement pathway in ABOi conditions. This work shows the potential of the enzymatic blood group conversion to evade hyperacute antibody-mediated rejection during renal transplantation.

O042 Enzymatic conversion of human blood group A kidneys to universal blood group O

Abstract Introduction The ABO blood group restriction on allocation of donor organs leads to waiting time disadvantages for individuals of more restrictive blood types. Here, we outline the first preclinical use of two enzymes from Flavonifractor plautii to convert human blood group A kidneys to universal blood group O. Methods Six pairs of human kidneys rejected for transplantation and offered for research were used to in this study with approval from the National Research Ethics committee and Research and Development Office (NRES: 15/NE/0408). Three pairs were perfused for 6 h using normothermic machine perfusion (NMP), and three pairs were perfused for 24 h using hypothermic machine perfusion (HMP), with one kidney per pair randomised to enzyme treatment. Cortical biopsies collected throughout perfusion were examined for antigen loss using immunofluorescence microscopy. Results After 2hrs of NMP, a significant loss of 83.4±10.2% blood group A antigen expression was observed compared to pre-treatment levels (p=0.012), while no significant changes were observed in control kidneys (p=0.999). For HMP, a maximal loss of 71.2±21.9% was observed after 6 h (p=0.066), with no decrease observed in the contralateral controls (p=0.977). Haemodynamic perfusion parameters were stable in both cohorts, with no significant difference between control vs treated kidneys. Conclusion Our results show a loss of 70-80% of blood group A antigens in as little as 2 h of NMP and 6 h of HMP. These approaches pave the way for the first clinical studies that could herald the start of a new era that transforms donor organ allocation in kidney transplantation.

A study of blood group conversion in patients with ABO incompatible hematopoietic stem cell transplantation—A decade survey

BackgroundABO incompatibility is not a contraindication but would affect the prognosis of allogeneic hematopoietic stem cell transplantation (allo-HSCT). The dynamic change of blood phenotype is not only related to the patient's status, but also the basis for the implementation of compatible blood transfusion. The criteria for judging a complete transformation to donor-type and the principle of blood transfusion at relapse need to be unified. We aimed to illustrate the significance of blood group monitoring after allo-HSCT. Material and methodsWe collected 263 patients underwent ABO incompatible allo-HSCT from January 2010 to December 2019, and monitored blood type regularly according to the frequency of the patient's return visits till complete conversion or death. Non-parametric test was used to find differences among incompatible groups. We analyzed factors potentially influence blood type conversion by Binary Logistic model. Cox regression model was used to illustrate the relationship between blood-type conversion and prognosis. ResultsThe median days of conversion were 107, 91 and 108 in major-, minor- and bidirectional groups respectively. Blood type conversion correlated with HLA compatibility (P = 0.012, OR=2.69) and acute graft-versus-host-disease (P = 0.001, OR=0.06). Patients with incomplete blood type conversion had a higher death rate than those with complete blood type conversion(P = 0.003, OR=3.703). DiscussionBlood type monitoring can help to evaluate the prognosis of transplantation and assess the risk of death. It is recommended to monitor the changes of blood group antigens and antibodies, especially within a year after transplantation, to predict the risk of adverse events (such as GVHD, recurrence, death, etc.).

Enzymatic blood group conversion of human kidneys during ex vivo normothermic machine perfusion.

A major restriction to transplantation is the requirement for ABO blood group compatibility between donor and recipient. In this study, an α-galactosidase enzyme from Bacteroides fragilis was used successfully to remove type B blood group antigens enzymatically from human kidneys using ex vivo normothermic machine perfusion. This provides the first step for a strategy to overcome the ABO barrier in kidney transplantation.

A and B antigen levels acquired by group O donor-derived erythrocytes following ABO-non-identical transfusion or minor ABO-incompatible haematopoietic stem cell transplantation.

ABO-incompatible haematopoietic stem cell transplantation (HSCT) presents a challenge to blood component transfusion. The aim of this study was to investigate the weak blood group A or B antigen expression by donor-derived group O red blood cells (RBC) observed following transfusion or minor ABO-incompatible HSCT. In addition, in vitro experiments were performed to elucidate possible mechanisms underlying this phenomenon. A sensitive flow cytometry assay for the semi-quantification of RBC A/B antigen levels was used to assess patient samples and evaluate in vitro experiments. Analysis of blood samples from patients, originally typed as A, B and AB but recently transplanted or transfused with cells from group O donors, revealed the A antigen expression on donor-derived RBC, ranging from very low levels in non-secretor individuals to almost subgroup Ax -like profiles in group A secretors. The B antigen expression was less readily detectable. In vitro experiments, in which group O donor RBC were incubated with (i) group A/B secretor/non-secretor donor plasma or (ii) group A/B donor RBC in the absence of plasma, supported the proposed adsorption of A/B antigen-bearing glycolipids from secretor plasma but also indicated a secretor-independent mechanism for A/B antigen acquisition as well as direct cell-to-cell transfer of ABO antigens. The in vivo conversion of donor-derived blood group O RBC to ABO subgroup-like RBC after transfusion or minor ABO-incompatible HSCT raises the question of appropriate component selection. Based on these data, AB plasma should be transfused following ABO-incompatible HSCT.

Rh D blood group conversion using transcription activator-like effector nucleases.

Group O D-negative blood cells are universal donors in transfusion medicine and methods for converting other blood groups into this universal donor group have been researched. However, conversion of D-positive cells into D-negative is yet to be achieved, although conversion of group A or B cells into O cells has been reported. The Rh D blood group is determined by the RHD gene, which encodes a 12-transmembrane domain protein. Here we convert Rh D-positive erythroid progenitor cells into D-negative cells using RHD-targeting transcription activator-like effector nucleases (TALENs). After transfection of TALEN-encoding plasmids, RHD-knockout clones are obtained. Erythroid-lineage cells differentiated from these knockout erythroid progenitor cells do not agglutinate in the presence of anti-D reagents and do not express D antigen, as assessed using flow cytometry. Our programmable nuclease-induced blood group conversion opens new avenues for compatible donor cell generation in transfusion medicine.

Evaluation of Blood Group Conversion Following ABO-Incompatible Hematopoietic Stem Cell Transplantation (HCT)

Title: Evaluation of blood group conversion following ABO-incompatible Hematopoietic Stem Cell Transplantation (HCT).Background:While there have been a number of reports concerning the influence of AB0 incompatibility on hematopoietic transplantation (HCT) outcomes, data evaluating post-HCT blood group conversions following ABO incompatible transplants remains extremely limited.Methods:We performed a single centre retrospective analysis of 97 patients undergoing major or minor or bidirectional ABO-mismatched bone marrow (BM), peripheral blood (PB), and cord blood (CB) hematopoietic stem cell transplantation (HCT) between January2005 – April 2014, in whom engraftment had occurred and blood group data was available. The aim of the study was to analyse the red cell ABO phenotype (forward grouping) and levels of anti-A/B antibodies (reverse grouping) in these patients following the ABO-mismatched transplants.Results:97 patients transplanted between January 2004 and April 2014 were included in the analysis. There were 40 (41%) matched sibling, 32 (33%) matched unrelated and 25 (26%) CB transplants. Indications for HSCT included both haematological malignancies (n=87) and benign conditions (n=10). Of these donor recipient pairs, there were 44 (45%) minor, 39 (40%) major and 14 (15%) bidirectional ABO mismatches. All patients had achieved full donor type chimerism at the time of analysis.Analysis of post –HCT blood group conversion was performed in each of the three groups. Amongst the major mismatch patients (n=39), all had conversion of RBC phenotype to donor ABO phenotype and loss of their host derived anti-donor ABO antibodies. Interestingly, in the minor mismatch patients who were tested (n=44), all the patients had conversion of their RBC phenotype, but 43 out of 44 patients failed to produce recipient directed anti-ABO antibodies. Similarly in the bidirectional mismatch group, all 14 patients converted to donor ABO phenotype, but none produced recipient directed anti-ABO antibodies.Conclusion:In one of the largest study looking at this issue, our study demonstrated the lack of a development of recipient directed anti A/B antibodies despite complete donor chimerism in the majority (1 out of 58) of patients undergoing minor or bidirectional ABO-mismatched HSCT. We postulate that this phenomenon may be due to the donor B cell tolerance against host ABO antigen due to the presence of host A and B antigens within other body tissues. DisclosuresNo relevant conflicts of interest to declare.

Alanine solution as enzyme reaction buffer used in A to O blood group conversion

The aim of this study was to investigate the effect of alanine solution as α-N-acetylgalactosaminidase enzyme reaction buffer on the enzymatic activity of A antigen. The binding ability of α-N-acetylgalactosaminidase with RBC in different reaction buffer such as alanine solution, glycine solution, normal saline (0.9% NaCl), PBS, PCS was detected by Western blot. The results showed that the efficiency of A to O conversion in alanine solution was similar to that in glycine solution, and Western blot confirmed that most of enzymes blinded with RBC in glycine or alanine solution, but few enzymes blinded with RBC in PBS, PCS or normal saline. The evidences indicated that binding of enzyme with RBC was a key element for A to O blood group conversion, while the binding ability of α-N-acetylgalactosaminidase with RBC in alanine or glycine solution was similar. It is concluded that alanine solution can be used as enzyme reaction buffer in A to O blood group conversion. In this buffer, the α-N-acetylgalactosaminidase is closely blinded with RBC and α-N-acetylgalactosaminidase plays efficient enzymatic activity of A antigen.

Glucose buffer is suitable for blood group conversion with α-N acetylgalactosaminidase and α-galactosidase.

It is well known that the buffer plays a key role in the enzymatic reaction involved in blood group conversion. In previous study, we showed that a glycine buffer is suitable for A to O or B to O blood group conversion. In this study, we investigated the use of 5% glucose and other buffers for A to O or B to O blood group conversion by α-N-acetylgalactosaminidase or α-galactosidase. We compared the binding ability of α-N-acetylgalactosaminidase/α-galactosidase with red blood cells (RBC) in different reaction buffers, such as normal saline, phosphate-buffered saline (PBS), a disodium hydrogen phosphate-based buffer (PCS), and 5% commercial glucose solution. The doses of enzymes necessary for the A/B to O conversion in different reaction buffers were determined and compared. The enzymes' ability to bind to RBC was evaluated by western blotting, and routine blood typing and fluorescence activated cell sorting was used to evaluate B/A to O conversion efficiency. The A to O conversion efficiency in glucose buffer was similar to that in glycine buffer with the same dose (>0.06 mg/mL pRBC). B to O conversion efficiency in glucose buffer was also similar to that in glycine buffer with the same dose (>0.005 mg/mL pRBC). Most enzymes could bind with RBC in glycine or glucose buffer, but few enzymes could bind with RBC in PBS, PCS, or normal saline. These results indicate that 5% glucose solution provides a suitable condition for enzymolysis, especially for enzymes combining with RBC. Meanwhile, the conversion efficiency of A/B to O was similar in glucose buffer and glycine buffer. Moreover, 5% glucose solution has been used for years in venous transfusion, it is safe for humans and its cost is lower. Our results do, therefore, suggest that 5% glucose solution could become a novel suitable buffer for A/B to O blood group conversion.

Properties of a Novel <italic>α</italic>-galactosidase from <italic>B. Fragilis</italic> and Its Potential for Human Blood-type B to O Conversion

Enzymatic removal of blood group B antigen is an effective method to develop universal red blood cells (RBCs) by α-galactosidase. Here we investigated the physicochemical properties of a novel α-galactosidase from B. Fragilis and the optimization of enzymatic conversion for RBC of blood group B to O. The results showed that α-galactosidase exhibited maximum activity at a broad optimal pH of 5.6-6.0 and an optimum temperature of 41°C. Furthermore, the enzyme was efficient in complete removal of B antigen. The conditions for B to O blood group conversion were 26°C, pH 6.8 (250 mmol/L glycine and 3 mmol/L NaCl) for 1 h. The structure and function indexes of the converted red blood cells showed no significant difference from those of normal RBCs. Consequently, the novel α-galactosidase described here was more suitable for enzymatic conversion for achieving the goal of producing universal RBCs, which would improve the blood supply while enhancing the safety of clinical transfusions.

Interaction of Naja naja atra cardiotoxin 3 with H-trisaccharide modulates its hemolytic activity and membrane-damaging activity

To address whether saccharide moieties of blood groups A, B and O antigens modulate hemolytic activity of Naja naja atra cardiotoxins (CTXs), the present study was carried out. Unlike other CTX isotoxins, hemolytic activity of CTX3 toward blood group O cholesterol-depleted red blood cells (RBCs) was notably lower than that of blood groups A and B cholesterol-depleted RBCs. Conversion of blood group B RBCs into blood group O RBCs by α-galactosidase treatment attenuated the susceptibility for hemolytic activity of CTX3, suggesting that H-antigen affected hemolytic potency of CTX3. Pre-incubation with H-trisaccharide reduced hemolytic activity and membrane-damaging activity of CTX3. Moreover, CTX3 showed a higher binding capability with H-trisaccharide than other CTXs did. CD spectra showed that the binding with H-trisaccharide induced changes in gross conformation of CTX3. Self-quenching studies revealed that oligomerization of CTX3 was affected in the presence of H-trisaccharide. Taken together, our data suggest that the binding of CTX3 with H-antigen alters its membrane-bound mode, thus reducing its hemolytic activity toward blood group O cholesterol-depleted RBCs.

Human RBCs blood group conversion from A to O using a novel α-N-acetylgalactosaminidase of high specific activity

α-N-acetylgalactosaminidase (αNAGA) can convert group A human red blood cells (RBCs) to group O. One novel αNAGA gene was cloned by PCR from Elizabethkingia meningosepticum isolated from a domestic clinical sample. Pure recombinant αNAGA was obtained by genetic engineering and protein purification with a calculated molecule of 49.6 kD. αNAGA was selective for terminal α-N-acetylgalactosamine residue with a high specific activity. αNAGA could completely remove A antigens of 1 U (about 100 mL) group A1 or A2 RBCs in 1 h at pH 6.8 and 25°C with a consumption of 1.5 or 0.4 mg recombinant enzyme. Enzyme-converted group A RBCs did not agglutinate after being mixed with monoclonal anti-A or sera of groups A, B, AB and O. Other blood group antigens except ABO had no change. FCM analysis showed that A antigens and A1 antigens disappeared while H antigens increased. It indicated that αNAGA successfully converted human blood group A RBCs to universally transfusable group O RBCs without the risk of ABO-incompatible transfusion reactions. This αNAGA was suitable for producing universal RBCs to increase clinical transfusion safety, improve the RBCs supply, and to decrease transfusion cost and support transfusion service in case of emergency.

Modifying the red cell surface: towards an ABO‐universal blood supply

Eliminating the risk for ABO-incompatible transfusion errors and simplifying logistics by creating a universal blood inventory is a challenging idea. Goldstein and co-workers pioneered the field of enzymatic conversion of blood group A and B red blood cells (RBCs) to O (ECO). Using alpha-galactosidase from coffee beans to produce B-ECO RBCs, proof of principle for this revolutionary concept was achieved in clinical trials. However, because this enzyme has poor kinetic properties and low pH optimum the process was not economically viable. Conversion of group A RBCs was only achieved with the weak A2 subgroup with related enzymes having acidic pH optima. More recently, the identification of entirely new families of bacterial exoglycosidases with remarkably improved kinetic properties for cleaving A and B antigens has reinvigorated the field. Enzymatic conversion of groups A, B and AB RBCs with these novel enzymes resulting in ECO RBCs typing as O can now be achieved with low enzyme protein consumption, short incubation times and at neutral pH. Presently, clinical trials evaluating safety and efficacy of ECO RBCs are ongoing. Here, we review the status of the ECO technology, its impact and potential for introduction into clinical component preparation laboratories.

SI14 Stripped Red Cells–Efforts to Eliminate A and B Antigens from the Blood Supply

Eliminating the risk for ABO‐incompatible transfusion errors and simplifying blood logistics by creating an ABO‐universal blood inventory is a challenging idea but not a new one. In the early 1980s Goldstein and co‐workers at the New York Blood Centre pioneered the field of enzymatic conversion of blood group B red blood cells (RBC) to group O. They used native or recombinant α‐galactosidase from green coffee beans to remove the immunodominant galactose residues terminally located in the carbohydrate chains found on group B RBC. These enzyme‐converted O (ECO) RBC survived normally in the circulation of individuals independent of the blood group of the recipient. Small infusions were escalated to single, multiple and repeated RBC units. A successful phase II clinical trial in patients was reported in 2000 by Kruskall et al. However, economically unfavourable doses of enzyme were required to convert a unit of blood due to the low pH optimum of the enzyme. Conversion of blood group A cells was never achieved due to lack of A‐converting enzymes working at RBC‐friendly conditions. Also, the chemical nature of group A antigens is more complex due to the A1/A2 subgroups. Following screening of >2500 microorganisms we recently identified a novel family of bacterial exoglycosidases with specificities for the blood group A or B antigens and remarkably improved kinetic properties. Enzymatically converted group A and B RBC type as group O and can now be achieved under cost‐efficient and optimised conditions including neutral pH and room temperature incubation. Clinical trials to evaluate the safety and efficacy of ECO RBC are currently ongoing. Of the different strategies envisioned to create a universal blood component supply, the ECO concept is the only one for which clinical trials in humans have been performed. The presentation will review the current status of this exciting technology and its potential for introduction in the clinical component preparation laboratory. The speaker is a Visiting Associate Professor at Harvard Medical School, Boston, MA, USA and also a scientific consultant to the R&D biotech company ZymeQuest, Inc., Beverly, MA, USA. He gratefully acknowledges the significant and dedicated work performed by numerous members of the ECO team at Copenhagen University, Harvard Medical School, Lund University Hospital Blood Centre and the scientific staff at ZymeQuest.

Universal red blood cells—enzymatic conversion of blood group A and B antigens

Accidental transfusion of ABO-incompatible red blood cells (RBCs) is a leading cause of fatal transfusion reactions. To prevent this and to create a universal blood supply, the idea of converting blood group A and B antigens to H using specific exo-glycosidases capable of removing the immunodominant sugar residues was pioneered by Goldstein and colleagues at the New York Blood Center in the early 1980s. Conversion of group B RBCs to O was initially carried out with α-galactosidase extracted from coffee beans. These enzyme-converted O (ECO) RBCs appeared to survive normally in all recipients independent of blood group. The clinical trials moved from small infusions to single RBC units and finally multiple and repeated transfusions. A successful phase II trial utilizing recombinant enzyme was reported by Kruskall and colleagues in 2000. Enzymatic conversion of group A RBCs has lagged behind due to lack of appropriate glycosidases and the more complex nature of A antigens. Identification of novel bacterial glycosidases with improved kinetic properties and specificities for the A and B antigens has greatly advanced the field. Conversion of group A RBCs can be achieved with improved glycosidases and the conversion conditions for both A and B antigens optimized to use more cost-efficient quantities of enzymes and gentler conditions including neutral pH and short incubation times at room temperature. Of the different strategies envisioned to create a universal blood supply, the ECO concept is the only one, for which human clinical trials have been performed. This paper discusses some biochemical and clinical aspects of this developing technology.

Cloning and functional expression of a cDNA encoding coffee bean α-galactosidase

Purified coffee bean α-galactosidase (αGal) has been used for removing terminal α-galactose residues from the glycoconjugates at the red cell surface, in studies of blood group conversion. Here, we report the isolation and sequence of the full-length clone for coffee bean αGal by using the polymerase chain reaction (PCR) and rapid amplification of cDNA ends (RACE) techniques. The cDNA clone (1.4 kb) contains a single open reading frame which encodes a protein of 378 amino acids (aa). Its authenticity is confirmed by perfect alignment of aa sequences obtained from purified coffee bean αGal, and by immune reaction with the antibody raised against the enzyme. Furthermore, the protein produced in insect cells shows enzymatic activity towards a synthetic αGal substrate, p-nitro-phenyl- α-galactopyranoside.

Blood group substabce-degrading enzymes obtained from Streptomyces sp. V. Conversion of human blood group B and AB red blood cells to group O and A cells by Streptomyces enzyme.

Human blood group B and AB cells were converted to O and A active cells, respectively, by treatment with an α-D-galactosidase from Streptomyces 9917 S2. Accompanying these conversions a 2 to 8-fold increase was observed in the group H activity on these cells. The conversion reaction proceeded rapidly in phosphate buffered saline without any supplement. Hemolysis, discoloration, and other visible deterioration of the cell were not observed during the process. Conditions for the optimal conversion as well as the susceptibility to the inhibition by sugars were somewhat different from those for the reaction with soluble substrates.