Analysis of platelet-reactive alloantibodies and evaluation of cross-match-compatible platelets for the management of patients with transfusion refractoriness

Detection of alloimmunization in Glanzmann Thrombasthenia and Bernard-Soulier Syndrome: Data from a Brazilian Center

INTRODUCTION

The Glanzmann Thrombasthenia (GT) and Bernard-Soulier Syndrome (BSS) are rare hereditary disorders of platelet function. Their treatment often requires platelet transfusion, which can lead to the development of alloantibodies.

OBJECTIVE

In this study, we aim to develop a strategy for alloantibody detection and to describe the frequency of alloimmunization in a patient population from a single center in southeastern Brazil.

METHODS

Samples from patients with GT or BSS were tested using the Platelet Immunofluorescence Test (PIFT). If a positive result was obtained, a confirmatory step using the Monoclonal Antibody Immobilization of Platelet Antigens (MAIPA) and Luminex bead-based platelet assay (PAKLx) was executed.

MAIN RESULTS

Among 11 patients with GT, we detected the presence of alloantibodies in 5 using PIFT, with confirmation through MAIPA and PAKLx in 2 (1 anti-HLA and 1 anti-HPA), resulting in a frequency of 18.1%. Among 4 patients with BSS, PIFT was positive in 3, with confirmation by MAIPA and PAKLx in 1 (anti-HLA), showing a frequency of 25%. The two patients with anti-HLA antibodies exhibited a panel reactive antibody (PRA-HLA) testing greater than 97%.

CONCLUSION

Our study highlights the importance of identifying platelet alloimmunization in this patient population. The proposed algorithm for platelet alloantibodies detection allows resource optimization.

Evaluation of Platelet Alloimmunization by Filtration Enzyme-Linked Immunosorbent Assay

The current methods for detecting antiplatelet antibodies are mostly manual and labor-intensive. A convenient and rapid detection method is required for effectively detecting alloimmunization during platelet transfusion. In our study, to detect antiplatelet antibodies, positive and negative sera of random-donor antiplatelet antibodies were collected after completing a routine solid-phase red cell adherence test (SPRCA). Platelet concentrates from our random volunteer donors were also prepared using the ZZAP method and then used in a faster, significantly less labor-intensive process, a filtration enzyme-linked immunosorbent assay (fELISA), for detecting antibodies against platelet surface antigens. All fELISA chromogen intensities were processed using ImageJ software. By dividing the final chromogen intensity of each test serum with the background chromogen intensity of whole platelets, the reactivity ratios of fELISA can be used to differentiate positive SPRCA sera from negative sera. A sensitivity of 93.9% and a specificity of 93.3% were obtained for 50 μL of sera using fELISA. The area under the ROC curve reached 0.96 when comparing fELISA with the SPRCA test. We have successfully developed a rapid fELISA method for detecting antiplatelet antibodies.

Anti-HLA Class I alloantibodies in platelet transfusion refractoriness: From mechanisms and determinants to therapeutic prospects

Patients with hematological disorders and severe thrombocytopenia require extensive and iterative platelet transfusion support. In these patients, platelet transfusion refractoriness represents a serious adverse transfusion event with major outcomes for patient care. Recipient alloantibodies against the donor HLA Class I antigens expressed at the cell surface of platelets result in a rapid removal of transfused platelets from the circulation and thus, therapeutic and prophylactic transfusion failure leading to a major bleeding risk. In this case, the only way to support the patient relies on the selection of HLA Class I compatible platelets, an approach restricted by the limited number of HLA-typed donors available and the difficulty of meeting the demand in an emergency. However, not all patients with anti-HLA Class I antibodies develop refractoriness to platelet transfusions, raising the question of the intrinsic characteristics of the antibodies and the immune-mediated mechanisms of platelet clearance associated with a refractory state. In this review, we examine the current challenges in platelet transfusion refractoriness and detail the key features of the antibodies involved that should be considered. Finally, we also provide an overview of future therapeutic strategies.

Role of HLA genes in development of HLA-alloimmunization in blood recipients

A genetically determined predisposition to the development of HLA-alloimmunization as a result of blood transfusions is associated with the presence of HLA-alleles DRB1*04, DQA1*03:01, DQA1*05:01 and HLA-haplotype DRB1*04-DQA1*03:01-DQB1*03:02 in the genotypes of recipients. The risk of antibody production is reduced in patients with HLA-alleles DRB1*16, DQA1*01:02, DQB1*05:02 and HLA-haplotype DRB1*16-DQA1*01:02-DQB1*05:02.

Prozone rates in the solid-phase platelet crossmatch assay and correlation with class I HLA antibody levels

BACKGROUND

Solid-phase platelet crossmatch (PXM) testing is used to help manage patients with platelet transfusion-refractoriness. Recently, we published the first report of false-negative PXM results from prozone effect that was mitigated using sample dilution. This study aimed to describe the prevalence of PXM prozone effect and the levels of class I HLA antibodies (HLA-Abs) associated with positive PXM results and with false-negative PXM results from prozone effect.

STUDY DESIGN AND METHODS

A cross-sectional study of patients undergoing PXM testing from July 2019 through December 2020 was performed. All PXM tests were run simultaneously using undiluted and 1:4 diluted patient plasma. Prozone effect was defined as a negative PXM result using undiluted patient plasma but a positive PXM result using 1:4 diluted patient plasma.

RESULTS

Among 59 patients, 830 individual ABO-compatible PXM results yielded an overall positivity rate of 25.8% (214/830) and a false-negative rate from prozone effect of 4.7% (10/214). Among the 28 patients with class I HLA-Ab testing and no other anti-platelet antibodies, maximum HLA-Ab mean fluorescence intensity (MFI) was significantly associated with a positive PXM result (p < .0001; AUC approx. 0.9) and categorized into negative (<3700), indeterminate (3700-10300), and positive (>10300) maximum HLA-Ab MFI zones. Maximum HLA-Ab MFI, however, was not associated with prozone effect (p = .17; AUC approx. 0.6).

DISCUSSION

While there is a strong predictive association between class I HLA-Ab levels and positive PXM results, PXM prozone effect is a common occurrence not associated with class I HLA-Ab levels, so additional testing with diluted samples should be considered.

The relevance of a bank with genotyped platelets donors

OBJECTIVE

Describe the clinical and laboratory characteristics and the transfusion strategy of patients at Hospital Israelita Albert Einstein with platelet refractoriness and identify their etiological characteristics. Standardize the platelet immunofluorescence technique by flow cytometry as a test for platelet compatibility in immune platelet refractoriness in transfusion support.

METHODS

Review of medical records of refractory platelet patients followed at HIAE from January 2011 to May 2017. Clinical-demographic data, laboratory data and identification of the use of compatible genotyped platelets for patients in need of transfusion therapy were collected. The analyzed patients were classified according to the etiology of their platelet refractoriness. To standardize the FC-PIFT technique, blood group O platelets were incubated with serum from blood group AB donors and anti-IgG monoclonal antibody to determine the negative control. In order to verify the influence of the ABO system, monoclonal anti-IgG antibodies were incubated with blood group A or B platelets and with blood group O donor serum with isohemagglutinins below and above 1/64.

RESULTS

A total of 47 patients were evaluated, a 51% (24/47) preponderance of associated immune and non-immune factors (NIPR + IPR). The most common causes of NIPR + IPR were splenomegaly (54%) and the development of HLA antibodies (88%), consistent with the literature. For patients who required therapeutic transfusion, only a small portion received compatible genotyped platelets.

CONCLUSION

Although 60% of patients could benefit from the therapeutic transfusion of genotyped platelets, only 10% were actually transfused with this type of blood component. This reaffirms the need for investments in a bank of genotyped platelet donors.

Ex Vivo Manufacture of Megakaryocytes and Platelets from Stem Cells: Recent Advances Toward Transfusion in Humans

The generation of ex vivo functional megakaryocytes (MK) and platelets is an important issue in transfusion medicine as donor dependence implies in limitations, such as shortage of eligible volunteers. Indeed, platelet transfusion is still a procedure that saves the lives of patients with defective platelet production. Recent technological development has enabled the isolation and expansion of stem cells that can be used as a source for the production of functional platelets for transfusion. In this review, we discuss recent approaches of in vitro or ex vivo production of MK and platelets, suggesting that, in the near future, donor-independent sources may become a possibility. The feasibility of using these cells in the clinic may be safer, and in vitro manipulation could generate universally compatible products, solving problems related to platelet refractoriness. However, functionality and survival testing of these products in human beings are scarce; therefore, additional studies are needed to consolidate this purpose.

Characterization of glycoprotein IIb/IIIa-specific alloantibodies induced by cross-strain platelet immunization in mice

BACKGROUND

We previously described a mouse model in which platelet immunization between selected strains leads to production of alloantibodies and severe autoimmune thrombocytopenia and mimics the human condition posttransfusion purpura (PTP). This report describes studies defining epitopes recognized by these alloantibodies.

STUDY DESIGN

Hybridomas were produced from spleen cells of immunized mice. Glycoprotein (GP) targets of resulting monoclonal antibodies were characterized by immunoprecipitation using platelets from the immunizing strains. Antigens defined by single amino acid (AA) polymorphisms recognized by monoclonal antibodies were identified by mutagenizing target glycoproteins expressed in Chinese hamster ovary cells and observing the effects on antibody binding.

RESULTS

Three monoclonal antibodies (417.1, 417.3, 425.1) were produced that recognized GPIIb on immunizing platelets. Monoclonal antibodies 417.1 and 417.3 both required G111 and 425.1 required V37, located on the beta propeller domain of GPIIb, for binding to platelets from the immunizing strains C57 and PWK, respectively. Injection of 417.3 and 425.1 into mice caused platelet destruction only in mice with GPIIb containing the targeted AAs.

CONCLUSIONS

Findings made provide evidence that alloantibodies produced by mice experiencing thrombocytopenia in a mouse model of PTP are specific for single AA polymorphisms that differ in GPIIb/IIIa integrin of the immunizing and immunized strains and therefore closely resemble the potent alloantibodies found in patients with PTP. The observations show that naturally occurring single AA differences in GPIIb/IIIa integrin of various mouse strains are highly immunogenic in the mouse strains studied and readily induce antibodies comparable to human platelet antigen-specific antibodies found in transfused and pregnant humans.

The clinical characteristics of patients with acute leukemia or stem cell transplantation exhibiting immune based platelet refractoriness

BACKGROUND

To investigate the related factors influencing immune platelet transfusion refractoriness (PTR) in acute leukemia (AL) from induction to consolidation and compare management for immune PTR, so as to improve the Platelet increment in AL.

METHODS

The primary analysis included 890 patients with AL, 225 of whom were the immune PTR (25 %).They are patients in our center from induction to consolidation or transplantation in the past 10 years. Flow cytometry, karyotype characteristics and other basic information were compared between the immune PTR vs control (no-PTR) groups. We analyzed the treatment outcomes of immune PTR including matched platelets, intravenous immunoglobulin (IVIG), increasing apheresis platelet does.

RESULTS

Immune PTR is more likely to occur in patients with poor prognosis in acute lymphoblastic leukemia (ALL) (P = 0.01).There is a relation between NPM1 mutation and occurrence of immune PTR (P = 0.029).The incidence of PTR at 35-59Y was higher than that at <35Y(OR = 0.68, 95 % CI = 0.48-0.96) and ≥60Y(OR = 0.49,95 % CI = 0.28-0.83), and the difference was statistically significant(P = 0.03, P = 0.01).The Platelet increment with 1 unit (u) was 47.12 %, 2 u increased to 71.14 %, and the matched 2 u (75.11 %) had the best effect. IVIG improved the Platelet increment, but there was no difference between 0.4 g/kg IVIG and 1 g/kg IVIG. Immune PTR is more likely to occur in the ages of 35-60 years.

CONCLUSION

There are specific AL patient characteristics which predispose to the phenomenon of immune based PTR. Meanwhile, increasing the IVIG dose could not improve Platelet increment obviously.

A single-center investigational study of CD36 antigen deficiency and platelet alloantibody distribution in different populations in Northern China as well as platelet alloantibodies effect on pregnancy

BACKGROUND

Platelet antibodies can lead to clinical diseases such as platelet transfusion refractoriness (PTR), fetal/neonatal alloimmune thrombocytopenia (FNAIT), etc. This study is aimed at understanding CD36 expression, platelet alloantibody distribution in different populations in Northern China, and effects of platelet alloantibodies on pregnancy.

STUDY DESIGN AND METHODS

Whole blood samples of 612 subjects including hematological patients, pregnant women, and blood donors were collected at a single center, then CD36 expressions were determined, followed by platelet antibody screening and characterization of platelet antibody specificity. A retrospective analysis was performed in 1552 pregnant women admitted to Department of Obstetrics, in order to investigate FNAIT occurrence.

RESULTS

Rate of CD36 deficiency expression was 2.12% (13/612), all cases exhibited type II deficiency without type I deficiency being detected, and such rate is lower than that in Southern China (3.43%), Japanese (4.87%) and in the black people (4.18%), and higher than that in the White people (0.09%). Positive rates of platelet antibody screening in hematological patient group (6.86%, 14/204) and in pregnant women group (6.31%, 13/206) are higher than that in blood donor group (0.49%, 1/202), P < .01. Out of 1552 pregnant women, there were not children with FNAIT.

CONCLUSION

The frequency of CD36 deficiency in northern China was low, all of them were type II deficiency, and no CD36 antibody was detected. It is speculated that the risk of immune-related thrombocytopenia caused by CD36 deficiency in this population is very low. Platelet antibodies should be monitored early in patients with hematological and multiple miscarriages pregnant.

HLA-Mediated Platelet Refractoriness

OBJECTIVES

To provide an overview of the complexities associated with the human leukocyte antigen (HLA)-mediated platelet refractoriness. HLA antibody detection technologies and limitations associated with methodologies are discussed.

METHODS

A case scenario and review of relevant literature describing platelet refractoriness are presented, followed by a discussion of HLA antibody testing.

RESULTS

Following diagnosis of HLA-mediated refractoriness, a decision is made regarding the approach to obtain the appropriate platelets. The panel reactive antibodies (PRA) % of the patient, HLA typing, and limitations of the HLA testing should be taken into account when deciding which type of product would be the best option for a given patient.

CONCLUSIONS

Following confirmation and review of HLA antibody testing, platelets are ordered based upon the PRA% and approach employed, HLA-matched platelets, antigen restricted platelets, or cross-matched platelets. The platelets are transfused and a posttransfusion increment count is monitored to determine transfusion success.

Allele and haplotype frequencies of human platelet and leukocyte antigens in platelet donors

OBJECTIVE

To described the allele and haplotype frequencies of human leukocyte antigen genes at the -A, -B loci and human platelet antigen genes for human platelet antigen systems 1 to 9, 11 and 15 in blood.

METHODS

We included 867 healthy unrelated volunteer donors who donated platelets between January 2011 and December 2014. Microarray genotyping was performed using a BeadChip microarray. Medium resolution typing of the human leukocyte antigen at loci A and B was carried out using sequence-specific oligonucleotide probe hybridization. We used multivariate analysis and our human leukocyte antigen population was compared to data from the United States national bone marrow donor program. Human platelet antigen results were compared to a literature review and data from around the world.

RESULTS

Our human leukocyte antigen haplotype results were more similar to those of hispanics, followed by caucasians. Likewise, our human platelet antigen sample is more similar to those of Argentina, Rio Grande do Sul and Italy.

CONCLUSION

This was the first article that discusses human platelet antigen and human leukocyte antigen data together. Rare genotypes or antibody associations can make patient management difficult. A blood bank with genotyped donors allows for optimal transfusion and can contribute to better results. Our information can serve as basis for a database of platelet antigen polymorphisms.

Immunological Features in the Process of Blood Platelet-Induced Alloimmunisation, with a Focus on Platelet Component Transfusion

Alloimmunisation to platelet antigens is not uncommon; a large number of females, having had pregnancies, developed antibodies to Human Leukocyte Antigen (HLA) moieties harboured on their foetuses' cells (inherited from the father(s)) that may conflict with further pregnancies and transfused Platelet Components occasionally. This is possible since platelets constitutionally express HLA class I molecules (though in copy numbers that consistently differ among individuals). Platelets also express HPA moieties that are variants of naturally expressed adhesion and aggregation molecules; HPA differences between mothers and foetuses and between donors and recipients explain alloimmune conflicts and consequences. Lastly, platelets express ABO blood group antigens, which are rarely immunising, however transfusion mismatches in ABO groups seem to be related to immunisation in other blood and tissue groups. Transfusion also brings residual leukocytes that may also immunise through their copious copy numbers of HLA class I (rarely class II on activated T lymphocytes, B cells, and dendritic cells). In addition, residual red blood cells in platelet concentrates may induce anti-red blood cell allo-antibodies. This short review aims to present the main mechanisms that are commonly reported in alloimmunisation. It also critically endeavours to examine paths to either dampen alloimmunisation occurrences or to prevent them.

A real-life evaluation of two platelet cross-matching programmes for the treatment of patients refractory to platelet transfusions

BACKGROUND AND OBJECTIVES

Strategies for overcoming alloimmune refractoriness to random donor platelets are based on the use of compatible platelets selected from large panels of HLA-typed donors or cross-matching (XM). The aim of this study was to review the effectiveness of a platelet XM programme for treating refractory haematological patients at Milan's Policlinico Hospital (PHM) 2002-2014 and Spedali Civili in Brescia (SCB) 2013-2016.

MATERIALS AND METHODS

A commercially available solid-phase antibody detection system was used for platelet antibody detection and XM. Forty-nine alloimmune refractory patients at PHM and 13 at SCB, respectively, received a median [IQR] of 12 [6-13] and 18 [13-15] XM compatible platelet transfusions after the detection of refractoriness. The absolute increases in post-transfusion platelet counts obtained using random, and XM platelets were retrieved from the patients' hospital records.

RESULTS

The critical review at SCB showed that the median [IQR] 1 h post-transfusion increase in platelet counts was 3 × 10⁹ /L [1-5] after 47/47 random platelet transfusions, and 10 × 10⁹ /L [2-25] after 325/326 XM compatible platelet transfusions. The documentation concerning the outcomes of XM platelet transfusions at PHM was incomplete, and so the findings of the review were inconclusive.

CONCLUSION

This retrospective analysis confirmed the effectiveness of the XM programme at SCB, but revealed defective data collection and retrieval methods at PHM, thus underlining the importance of such methods. The literature review accompanying this retrospective analysis identified a recently described algorithm for ensuring platelet support in refractory patients that optimally integrates the combined use of XM and HLA typing.

Platelet component transfusion and alloimmunization: Where do we stand?

Platelet transfusion in patients, particularly in onco-haematology, is frequent and can become chronic in some cases. Post-transfusion alloimmunization is often seen, in practice. The risk of this is significantly improved in multitransfused patients. Several classes of antigens binding on platelets (HLA and HPA) are involved and also red blood cell antigens (residual red blood cells in platelet concentrates). Platelet alloimmunization causes a poor transfusion response, refractoriness and, more rarely, post-transfusion purpura. In an alloimmunized recipient, the efficiency of platelet transfusion is based on the selection of compatible products. Significant technical progress means that several methods are currently available to ensure a good post-transfusion platelet count and a satisfactory clinical outcome for the patient.

[Caracterization of HLA allo-immunization and clinical impact in transfusion and organ transplantation]

Allo-immunizations against HLA antigens are known to be deleterious in transfusion and organ transplantation. The development of new tests based on solid phase assays for screening and identification of HLA antibodies in particular those using Luminex^® bead based technology has completely changed the way of allo-immunization monitoring because of their extreme sensitivity. They allow a better characterization of these antibodies, identification of acceptable antigens and the use of virtual cross-matches. All these new possibilities improve the managing of patients before and after platelets transfusion or organ transplantation. However, this technology displays some limits that should be known in order to interpret correctly the results. Beside these bead based assays, cellular cross-matches based on Complement Dependent Cytotoxicity (CDC) and flow cytometry are still used and useful in organ transplantation since beads are produced in vitro and do not reflected exactly what happens physiologically. Moreover, differences of sensitivity between these methods make results interpretation and decision making difficult in some cases.