Immunoadsorption for removal of anti-A and anti-B blood group antibodies in ABO-incompatible bone marrow transplantation

Combination of hDAF-transgenic pig hearts and immunoadsorption in heterotopic xenotransplantation of immunosuppressed baboons

INTRODUCTION

Hyperacute xenograft rejection (HXR) and acute vascular rejection (AVR) after xenotransplantation are triggered by xenoreactive antibodies (XAb) and an activated complement cascade. In a heterotopic (abdominal) xenotransplantation model we combined immunoadsorption (IA, Ig-Therasorb column) and a quadruple immunosuppressive drug therapy in recipient baboons with donor pig hearts transgenic for human decay accelerating factor (hDAF).

METHODS

According to XAb titers between 6 and 14 cycles of IA were performed preoperatively in 4 recipient baboons (18.6 +/- 2.5 kg). Hearts of hDAF-transgenic donor pigs (6.1 +/- 1.1 kg, Imutran Ltd., a Novartis Pharma AG Company, Basel, Switzerland) were heterotopically transplanted using the abdominal technique in baboons. Immunosuppression consisted of cyclophosphamide (CyP) induction therapy, ERL080 (Novartis Pharma AG), cyclosporin A (CyA, Neoral), and steroids. Blood levels of mycophenolate, CyA, immunoglobulins (Ig), anti-pig-antibodies, complement factors, and cardiac enzymes were determined. Abdominal electrocardiography (ECG), echocardiography, and palpation were used for monitoring of the pig hearts. Myocardial tissue specimens were examined using immunohistochemistry, light microscope (LM), and electron microscope (EM).

RESULTS

Ten cycles of IA alone removed 78% of XAb and accordingly IgM, IgG, IgA, complement C3, and C4. None of the xenografts was hyperacutely rejected, but xenograft failure occurred after 5.0 +/- 1.3 days (range, 2.4-8.0 days) because of an AVR associated with a rapid XAb increase within 24 hours. White blood cell count (10.3 +/- 2.2 G/L) showed a maximum of 13.1 +/- 2.1 (day 1) and constant levels (1.4 +/- 0.3-2.1 +/- 1.3 G/L) between day 3 and 6. Histology (LM/EM) showed massive hemorrhage, necrosis, and vascular thrombi as signs of AVR.

CONCLUSION

Although HXR was prevented by using IA and hDAF-transgenic donor hearts, AVR was not avoided due to insufficient immunosuppressive regimen used and a missed postoperative IA treatment as a result of an inefficient control of XAb production.

ABO-incompatible bone marrow transplantation: a GITMO survey of current practice in Italy and comparison with the literature

ABO incompatibility is not considered a contraindication for allogeneic haematopoietic stem cell transplantation (HSCT) despite its association with several immunohaematological complications. At present, there is no general agreement concerning the best methods to reduce these problems. To survey current practice related to ABO-incompatible HSCT in Italy, a questionnaire was sent to all GITMO centres. Specific questions were addressed for management in pretransplant, peritransplant and post transplant phases. A comparison was made with the experience reported in the literature. In all, 74% of GITMO centres answered the questionnaire. A high degree of heterogeneity concerning the pretransplant tests, methods to overcome infusion of ABO-incompatible marrow and post transplant transfusion policy and monitoring was evident. For many of these aspects the literature does not contain unanimous guidelines. The considerable degree of heterogeneity that reflects, at least partially, the lack of consensus in the literature demonstrates that ABO incompatibility is still an open issue in the setting of HSCT and that further studies are needed for a more rationale approach and for the production of evidence-based guidelines.

In vitro assessment of a new ABO immunosorbent with synthetic carbohydrates attached to sepharose

Transplantation across the ABO barrier is sometimes done in cases of emergency, such as acute liver failure, but is also carried out in elective cases, e.g. kidneys from living donors. Reducing the recipient anti-A/B antibody titres is often necessary in ABO-incompatible kidney transplantation. This is usually done by the use of techniques such as plasmapheresis and protein A- or sepharose-linked anti-human Ig immunoadsorption. A new ABO immunosorbent with synthetic A- or B-trisaccharide carbohydrate epitopes linked to a sepharose matrix has been tested. Columns made of this material have been tested in vitro with plasma from A- and B-individuals, assessed for antibody reduction capacity, flow characteristics, biocompatibility, and unspecific protein adsorption. The columns have a high capacity for ABO antibody removal, reducing titres by three to seven steps in one passage. We noted a high biocompatibility, with no unspecific protein adsorption, no activation of coagulation factors, and a low activation of complement, no immune complex formation and no cytotoxicity towards cultured mammalian L929 cells.

Prolonged red cell aplasia after major ABO-incompatible allogeneic hematopoietic stem cell transplantation: removal of persisting isohemagglutinins with Ig-Therasorb® immunoadsorption

Delayed donor red cell engraftment and prolonged red cell aplasia (PRCA) are well-recognized complications of major ABO-incompatible myeloablative and non-myeloablative hematopoietic stem cell transplantation (HSCT). There is an intense debate about the impact on outcome, severity of hemolysis, association with graft-versus-host disease and survival after blood group-incompatible stem cell transplantation. Therefore, therapeutic strategies should be considered to avoid these possible complications. We present five patients, who received allogeneic HSCT from human leukocyte antigen-identical donors for hematological malignancies, which were treated with Ig-Therasorb immunoadsorption (five treatments/week) to remove persisting incompatible isohemagglutinins. After a median of 17 treatments (range 9-25), all the patients became transfusion independent with the presentation of donor's blood group. No side effects occurred during treatment. Ig-Therasorb immunoadsorption seems to be a promising therapeutic method for rapid, efficient and safe elimination for persisting isohemagglutinins for patients with PRCA after allogeneic hematological stem cell transplantation.

An improved affinity support and immunoadsorbent with a synthetic blood group oligosaccharide and polymer coating for hemoperfusion

An improved affinity support and an immunoadsorbent suitable for extracorporeal perfusion of whole blood (or plasma) are reported. The affinity support consists of calcined diatomite-type silica particles to which a synthetic oligosaccharide hapten, viz. A-trisaccharide representing human blood group A, with a linking spacer-arm is chemically attached. The immunoadsorbent thus obtained is surface-modified with a polymer coating. The modified immunoadsorbent is not hemolytic and shows no loss of biological activity in reducing antibody titers in vitro. An important feature of the improved immunoadsorbent is that the polymer coating provides a better surface resistance and therefore stability to the affinity support to prevent the release of potentially harmful fines. The usefulness of a physically stable support as an affinity adsorbent for the selective removal of specific antibodies or unwanted substances directly from the blood circulation by extracorporeal immunoadsorption has profound medical significance because this would provide an efficient but safe and practical alternative to therapeutic intervention using plasma exchange or plasma perfusion, both of which require plasmapheresis.

A simple technique for red blood cell removal in major ABO-incompatible bone marrow transplantation

A simple technique for red blood cell (RBC) removal in major ABO-incompatible bone marrow transplantation is reported requiring two centrifugation steps, special blood bags and a mechanical device to separate the buffy coat from RBCs within the bag. In 42 transplantations an average of 84% of nucleated cells was recovered with an average contamination of 7.5 ml packed RBCs. The preparations were well tolerated in all patients whose isoagglutinin titers had not been reduced. Bone marrow engraftment was not significantly different from control groups.

Effect of antigen-specific immunoadsorption on antibody kinetics in a rat model

The investigation of antibody kinetics following antigen-specific immunoadsorption in alkaline phosphatase immunized rats revealed significantly lower antibody levels than in untreated controls over a follow-up period of 6 weeks. A rebounding antibody synthesis as a result of specific depletion was not observed. Non-adsorption of specific antiidiotypic antibodies may explain these findings.

Favourable biospecific reactivity of blood group B antigenic trisaccharide chemically attached to poly-N-(2-hydroxyethyl)acrylamide-coated porous glass

Blood group B antigenic trisaccharide-beta-aminopropyl glycoside (B-TSAP) covalently attached to poly-N-(2-hydroxyethyl)acrylamide-coated porous glass interacts with anti-B monoclonal antibodies faster than the ligand coupled to CNBr-activated Sepharose 4B and Affi-Gel 10. Rates of hydrophobic adsorption of antibodies on the butyl derivatives of the same supports were measured to evaluate the diffusion input to overall kinetics. The lowest average affinity adsorption time [t1(aff) = 250 s] observed for polymer-coated glass probably arises because of the flexibility of the extended segments of chemisorbed N-substituted polyacrylamide acting as effective spacer arms.

Biocompatibility of extracorporeal immunoadsorption systems

Following the first publication of a technique aiming for clinical application in 1969, extracorporeal immunoadsorption is increasingly finding a place among haemapheresis techniques. The apparent advantages outweigh the technical difficulties and economical drawbacks still connected with this treatment modality. At present three different developments are under clinical investigation: Staphylococcus Protein-A based immunoadsorption (SpA), the antibody-mediated adsorption (therapeutic affinity chromotography) and hydrophobic interaction-based immunoglobulin adsorption. The exact binding capacity and mechanism has not been completely elucidated for SpA and amino acid-based techniques. The lack of knowledge about pathogenic substrates exclusively responsible for the pathogenicity of many diseases, appears to be the major drawback for the prospective development of affinity chromatography-based extracorporeal systems. The practical application of molecular-biologic diagnostic procedures with a high grade of detection specificity (monoclonal antibodies) appears to be promising for the development of extracorporeal immunoadsorption. The immunomodulatory effect that results from the interaction of blood and plasma with artificial surfaces is an interesting subject of investigation, derived mainly from biocompatibility studies. The careful clinical and laboratory investigation of the biocompatibility of extracorporeal immunoadsorption systems contribute considerably to the prevention of undesired side effects.

Flow Rate Dependence of in vitro Removal of Anti-A and Anti-B Antibodies by Immunoadsorbents with Synthetic Oligosaccharides Representing Blood Group Substances

In vitro removal of anti-A and anti-B antibodies by immunoadsorbents with synthetic oligosaccharide structures representing blood group substances have been studied under controlled and simulated extracorporeal perfusion conditions at different flow rates ranging from 20 to 160 mL/min. There is a gradual decline in antibody titers in the plasma, as it relates to the antibody binding capacity and efficiency of the immunoadsorbents, both as a function of time and plasma volume at any of the flow rates employed. Approximately the same maximal binding capacity is achieved in about 4 hours of perfusion regardless of the flow rate, whereas increased number of plasma volumes are required at higher flow rates to compensate for the appropriate residence times needed in the column to utilize the same capacity. The perfusion time alone appears to be a critical factor which via the flow rate determines the residence time between the plasma and the immobilized hapten in the column. Also, the optimal flow rate at which maximum binding capacity of the immunoadsorbent may be utilized efficiently appears to fall within a range of the flow rate. The factors determining this range and the efficiency of the immunoadsorbents under dynamic conditions are discussed. The results obtained under the controlled conditions and the discussions that follow are expected to be generally useful, at least, as approximate clinical guidelines, for selective removal of specific substances by extracorporeal perfusion techniques utilizing therapeutic intervention with immunoadsorbents in this important area of medical therapy

Transfer of allergen-specific IgE-mediated hypersensitivity with allogeneic bone marrow transplantation

We investigated whether allergen-specific IgE-mediated hypersensitivity is transferred by bone marrow transplantation. Twelve patients, 14 to 47 years of age, undergoing allogeneic bone marrow transplantation for the treatment of hematologic cancer were selected, along with their donors, by a screening questionnaire for a history of atopy in the donor. We evaluated these donor-recipient pairs before transplantation and at several points afterward for immediate skin-test reactivity to 17 allergens. For allergens for which pretransplantation skin tests had been positive in the donors and negative in the recipients, 20 of 46 post-transplantation skin tests were positive in 8 of the 11 recipients who survived for more than one year after transplantation. For allergens for which both donors and recipients had had negative skin tests before transplantation, only 6 of 256 tests (2.3 percent) were positive in the recipients after transplantation. Long-term transfer of donor-derived mite-specific IgE was demonstrated by radioallergosorbent testing in two recipients. Seven recipients either acquired or had an exacerbation of allergic rhinitis, and two recipients without a history of asthma had asthma one year after transplantation. We conclude that allergen-specific IgE-mediated hypersensitivity is adoptively transferred by bone marrow transplantation from donor to recipient by B cells with allergen-specific memory.

Hematological support in patients undergoing allogenetic bone marrow transplantation

Bone marrow transplantation is impossible without effective support with blood components during the period of pancytopenia before graft function appears. We analyzed 39 patients with leukemia and three patients with severe aplastic anemia with regard to the pre- and postgrafting requirements for RBC and PLT transfusions. Overall a median of eight RBC and four PLT concentrates were necessary in all 42 patients after allogeneic BMT (ranges, 1-32 RBC and 1-11 PLT units). Requirements were identical irrespective of the underlying disease (ALL, AML, CML, SAA). Transfusion need for RBC and PLT concentrates increased in patients over 30 years old and with a major red blood group AB0 barrier between marrow donor and recipient. The presence of grade II-IV GvHD increased RBC requirements significantly, but not PLT requirements. In addition these patients were dependent on RBC transfusions for significantly longer periods. Only one patient required therapeutic granulocyte transfusions. In a CMV-negative patient with a CMV-negative marrow donor, who died of veno-occlusive disease, cytomegalovirus was transmitted inadvertently by a seropositive PLT concentrate in his final course. Our transfusion strategy included frozen deglycerolized RBC concentrates and single donor PLT concentrates, collected mainly from the marrow donor by a cell separator. All blood products were irradiated in vitro with 1500 cGy before transfusion. An optimal transfusion policy starting before BMT can contribute to successful bone marrow transplantation.