Prevalence of platelet-specific antibodies and efficacy of crossmatch-compatible platelet transfusions in refractory patients

Divergent CD4+ T-cell profiles are associated with anti-HLA alloimmunization status in platelet-transfused AML patients

Introduction

Acute myeloid leukemia (AML) is one of the commonest hematologic disorders. Due to the high frequency of disease- or treatment-related thrombocytopenia, AML requires treatment with multiple platelet transfusions, which can trigger a humoral response directed against platelets. Some, but not all, AML patients develop an anti-HLA immune response after multiple transfusions. We therefore hypothesized that different immune activation profiles might be associated with anti-HLA alloimmunization status.

Methods

We tested this hypothesis, by analyzing CD4+ T lymphocyte (TL) subsets and their immune control molecules in flow cytometry and single-cell multi-omics.

Results

A comparison of immunological status between anti-HLA alloimmunized and non-alloimmunized AML patients identified differences in the phenotype and function of CD4+ TLs. CD4+ TLs from alloimmunized patients displayed features of immune activation, with higher levels of CD40 and OX40 than the cells of healthy donors. However, the most notable differences were observed in non-alloimmunized patients. These patients had lower levels of CD40 and OX40 than alloimmunized patients and higher levels of PD1. Moreover, the Treg compartment of non-alloimmunized patients was larger and more functional than that in alloimmunized patients. These results were supported by a multi-omics analysis of immune response molecules in conventional CD4+ TLs, Tfh circulating cells, and Tregs.

Discussion

Our results thus reveal divergent CD4+ TL characteristics correlated with anti-HLA alloimmunization status in transfused AML patients. These differences, characterizing CD4+ TLs independently of any specific antigen, should be taken into account when considering the immune responses of patients to infections, vaccinations, or transplantations.

Three patients highlighting potential pitfalls in platelet refractory testing

BACKGROUND

Platelet-transfusion refractory (PR) patients do not achieve expected post-transfusion platelet counts. We investigate suspected PR patients with post-transfusion platelet counts, indirect platelet antibody screens (ind-PAS), Class I HLA antibody tests (HLA-Scr), and physical platelet crossmatch (PXM) studies.

STUDY DESIGN AND METHODS

The three following cases describe possible pitfalls of laboratory tests used in PR workup and management.

RESULTS

Case #1: Antibody testing detected antibodies to only HLA-B13, corresponding to a 4% calculated panel reactive antibodies (CPRA; 96% predicted donor compatibility). However, PXM showed the patient compatible with 11/14 (79%) donors; two of the PXM-incompatible units were ABO-incompatible. Case #2: PXM revealed compatibility with 1/14 screened donors; however, the patient did not respond to the product from the compatible donor. The patient did respond to HLA-matched product. Dilution studies provided evidence of the prozone effect, which caused negative PXM despite clinically relevant antibodies. Case #3: There was a discrepancy between the ind-PAS and HLA-Scr. Ind-PAS was negative for HLA antibodies, while HLA-Scr was positive and specificity testing corresponded to 38% CPRA. Per the package insert, the sensitivity of ind-PAS is ~85% compared to HLA-Scr.

DISCUSSION

These cases highlight the importance of investigating incongruent results. Cases #1 and #2 demonstrate PXM pitfalls: ABO incompatibility can result in positive PXM and false-negative PXM can occur in the setting of the prozone effect. Case #3 reveals the importance of knowing a test's sensitivity. Centers that only perform ind-PAS may fail to detect HLA antibodies.

Phagocytosis of platelets opsonized with differently glycosylated anti-HLA hIgG1 by monocyte-derived macrophages

Immune-mediated platelet refractoriness (PR) remains a significant problem in the setting of platelet transfusion and is predominantly caused by the presence of alloantibodies directed against class I human leukocyte antigens (HLA). Opsonization of donor platelets with these alloantibodies can result in rapid clearance after transfusion via multiple mechanisms, including antibody dependent cellular phagocytosis (ADCP). Interestingly, not all alloimmunized patients develop PR to unmatched platelet transfusions, suggesting variation in HLA-specific IgG responses between patients. Previously, we observed that the glycosylation profile of anti-HLA antibodies was highly variable between PR patients, especially with respect to Fc galactosylation, sialylation and fucosylation. In the current study, we investigated the effect of different Fc glycosylation patterns, with known effects on complement deposition and FcγR binding, on phagocytosis of opsonized platelets by monocyte-derived human macrophages. We found that the phagocytosis of antibody- and complement-opsonized platelets, by monocyte derived M1 macrophages, was unaffected by these qualitative IgG-glycan differences.

Evaluation of the effectiveness of platelet crossmatching by the solid‐phase red cell adherence assay in adult patients of a tertiary care hospital in Thailand: A retrospective study

Background and Aims

Platelet transfusion refractoriness is well aware to be associated with poor clinical outcomes. Patients with the alloantibody causing refractoriness required cross‐matched compatible products to improve the platelet number. This study aims to evaluate the effectiveness and availability of platelet crossmatching provided by the solid‐phase red cell adherence (SPRCA) technique in the context of a tertiary university hospital.

Methods

A retrospective chart review was performed of the records of 214 patients with platelet refractoriness in Siriraj Hospital, a tertiary university hospital in Thailand, between January 1, 2017, and December 31, 2020.

Results

The SPRCA technique successfully provided cross‐matched compatible platelets to 114 patients (69.7%). Platelet crossmatching significantly improved the platelet counts, as shown by the increased 1‐ and 24‐h corrected‐count increments (p< 0.0001). No acute transfusion reactions were observed in these patients. Of the 114 patients who received cross‐matched platelets, 82 patients (71.9%) survived at 30‐day posttransfusion; whereas, 16 patients (14.0%) died within 7‐day posttransfusion.

Conclusion

The SPRCA method can provide a high availability rate of cross‐matched platelets, which is effective at stopping and preventing clinical bleeding conditions. This method is appropriate to apply for platelet crossmatching in the context of a hospital blood bank.

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.

Cytokine Release Syndrome Is an Independent Risk Factor Associated With Platelet Transfusion Refractoriness After CAR-T Therapy for Relapsed/Refractory Acute Lymphoblastic Leukemia

Background: Chimeric antigen receptor T cell (CAR-T) therapy is successful in improving treatment outcomes for relapsed/refractory acute lymphoblastic leukemia (R/R ALL). However, toxicities associated with CAR-T therapy are being increasingly identified. Pancytopenia is one of the most common complications after CAR-T therapy, and platelet transfusions are an essential part of its supportive care. Study Design and Methods: This study aimed to assess the effectiveness of platelet transfusions for R/R ALL patients at our single center and identify associated risk factors. Overall, 44 R/R ALL patients were enrolled in this study, of whom 26 received CAR-T therapy and 18 received salvage chemotherapy. Result: Patients in the CAR-T group had a higher incidence of platelet transfusion refractoriness (PTR) (15/26, 57.7%) than those in the chemotherapy group (3/18, 16.7%) (p = 0.007). For patients receiving CAR-T therapy, multivariate analysis showed that the grade of cytokine release syndrome (CRS) was the only independent risk factor associated with PTR (p = 0.007). Moreover, higher peak serum IL-6 and IFN-γ levels suggested a higher risk of PTR (p = 0.024 and 0.009, respectively). Patients with PTR received more platelet infusion doses than those without PTR (p = 0.0426). Patients with PTR had more grade 3-4 bleeding events than those without PTR (21.4 vs. 0%, p = 0.230), and the cumulative incidence of grade 3-4 bleeding event was different (p = 0.023). Conclusion: We found for the first time that PTR is associated with the CRS grade. Improved knowledge on the mechanisms of PTR after CAR-T therapy is needed to design a rational therapeutic strategy that aims to improve the efficiency of transfusions.

Development and validation of a universal blood donor genotyping platform: a multinational prospective study

Each year, blood transfusions save millions of lives. However, under current blood-matching practices, sensitization to non-self-antigens is an unavoidable adverse side effect of transfusion. We describe a universal donor typing platform that could be adopted by blood services worldwide to facilitate a universal extended blood-matching policy and reduce sensitization rates. This DNA-based test is capable of simultaneously typing most clinically relevant red blood cell (RBC), human platelet (HPA), and human leukocyte (HLA) antigens. Validation was performed, using samples from 7927 European, 27 South Asian, 21 East Asian, and 9 African blood donors enrolled in 2 national biobanks. We illustrated the usefulness of the platform by analyzing antibody data from patients sensitized with multiple RBC alloantibodies. Genotyping results demonstrated concordance of 99.91%, 99.97%, and 99.03% with RBC, HPA, and HLA clinically validated typing results in 89 371, 3016, and 9289 comparisons, respectively. Genotyping increased the total number of antigen typing results available from 110 980 to >1 200 000. Dense donor typing allowed identification of 2 to 6 times more compatible donors to serve 3146 patients with multiple RBC alloantibodies, providing at least 1 match for 176 individuals for whom previously no blood could be found among the same donors. This genotyping technology is already being used to type thousands of donors taking part in national genotyping studies. Extraction of dense antigen-typing data from these cohorts provides blood supply organizations with the opportunity to implement a policy of genomics-based precision matching of blood.

KDIGO Clinical Practice Guideline on the Evaluation and Management of Candidates for Kidney Transplantation

The 2020 Kidney Disease: Improving Global Outcomes (KDIGO) Clinical Practice Guideline on the Evaluation and Management of Candidates for Kidney Transplantation is intended to assist health care professionals worldwide who evaluate and manage potential candidates for deceased or living donor kidney transplantation. This guideline addresses general candidacy issues such as access to transplantation, patient demographic and health status factors, and immunological and psychosocial assessment. The roles of various risk factors and comorbid conditions governing an individual's suitability for transplantation such as adherence, tobacco use, diabetes, obesity, perioperative issues, causes of kidney failure, infections, malignancy, pulmonary disease, cardiac and peripheral arterial disease, neurologic disease, gastrointestinal and liver disease, hematologic disease, and bone and mineral disorder are also addressed. This guideline provides recommendations for evaluation of individual aspects of a candidate's profile such that each risk factor and comorbidity are considered separately. The goal is to assist the clinical team to assimilate all data relevant to an individual, consider this within their local health context, and make an overall judgment on candidacy for transplantation. The guideline development process followed the Grades of Recommendation Assessment, Development, and Evaluation (GRADE) approach. Guideline recommendations are primarily based on systematic reviews of relevant studies and our assessment of the quality of that evidence, and the strengths of recommendations are provided. Limitations of the evidence are discussed with differences from previous guidelines noted and suggestions for future research are also provided.

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.

REFRACTORINESS TO DONOR PLATELETS TRANSFUSION IN PATIENTS WITH APLASTIC ANEMIA AND HEMOBLASTOSIS

Refractoriness to transfusions of platelet concentrates (PC) adversely affects the conduct of complex therapy in hematological patients. Individual selection of platelets is recommended for such patients. In cases of high degree of alloimmunization with the formation of polyspecific antibodies, when individual selection is difficult, procedures plasmapheresis (PPs) is included in the treatment program.

Aims: to evaluate the effectiveness of PC transfusions by individual selection in patients refractory to transfusions and the use of PPs as a second line therapy in combination with individual platelet selection.

Materials and methods: from September 2015 to December 2017, 91 patients with refractory to PC transfusions from 1263 patients who received PC transfusion were observed in the center’s clinics. The median age was 43 (18–71) years. M/F – 38/53. Patients: 20 – aplastic anemia (AA), 17 – myelodysplastic syndrome (MDS), 45 – acute myeloid leukemia (AML), 9 – acute lymphoblastic leukemia (ALL). All patients underwent PC transfusion by individual selection (HLA/HPA) Immucor’s Capture-P solid phase technology. In 28 (30 %) of 91 patients, due to the inability to select, there was a need for PP as a second line therapy. Patients: AA – 4 (20 %); MDS – 8 (47 %); AML – 12 (26 %); ALL– 4 (44 %). The median age was 48 (23–71) years. M/F – 8/20. From 2 to 15 procedures were performed (on average – 6) for each patient. All patients received PC transfusions by individual selection by cross-matching immediately after the PP procedure. The efficacy of PC transfusions was assessed by Absolute Platelet Increment (API) and Corrected Count Increment (CCI), relief of hemorrhagic syndrome.

Results: in 26 of 28 refractory to PC transfusions patients, in the absence of compatible donor platelets, carrying out PPs in combination with subsequent individual platelet selection promoted relief of hemorrhagic syndrome, increase in API from 3.3 × 109/L at 29.5 × 109/L and CCI from 1.3 to 10.7. Against the background of PPs, combined with individual selection, the degree of alloimmunization (the percentage of incompatible pairs) decreased on average: AA (n = 4) – from 91.7 to 50.2 %; MDS (n = 8) – from 89.6 to 31.6 %; AML (n = 12) – 86.0 to 40.5 % and ALL (n = 4) – from 91.7 to 37.7 %. In 2 patients with a high degree of alloimmunization and after carrying out PPs, it was not possible to select compatible platelets, PC transfusions were ineffective (API = 5 × 109/L, CCI = 1), and hemorrhagic syndrome was not completely managed, but its severity was reduced.

Conclusions. With the development of refractoriness to PC transfusions and the ineffectiveness of individual platelet selection, PPs should be used as the second line of therapy, which, combined with individual selection, increases the likelihood of compatible donor-recipient pairs and increases the clinical efficacy of PC transfusions. When PPs is ineffective in combination with individual selection, it is necessary to exclude the syndrome of increased consumption and other mechanisms of refractoriness.

Storage-Induced Platelet Apoptosis Is a Potential Risk Factor for Alloimmunization Upon Platelet Transfusion

Platelet transfusion can elicit alloimmune responses leading to alloantibody formation against donor-specific polymorphic residues, ultimately resulting in platelet transfusion refractoriness. Universal leukoreduction significantly reduced the frequency of alloimmunization after platelet transfusion, thereby showing the importance of white blood cells (WBCs) in inducing this alloresponse. It is, however, unknown if the residual risk for alloimmunization is caused by WBCs remaining after leukoreduction or if alloimmunization can be induced by platelets themselves. This study investigated the capacity of platelets to induce alloimmunization and identified potential product-related risk factors for alloimmunization. First, internalization of allogeneic platelets by dendritic cells (DCs) was demonstrated by confocal microscopy. Second, after internalization, presentation of platelet-derived peptides was shown by mass spectrometry analysis of human leukocytes antigen (HLA)-DR eluted peptides. Third, platelet-loaded DCs induced platelet-specific CD4 T cell responses. Altogether, this indicates a platelet-specific ability to induce alloimmunization. Therefore, factors enhancing platelet internalization may be identified as risk factor for alloimmunization by platelet concentrates. To investigate if storage of platelets is such a risk factor, internalization of stored platelets was compared with fresh platelets and showed enhanced internalization of stored platelets. Storage-induced apoptosis and accompanied phosphatidylserine exposure seemed to be instrumental for this. Indeed, DCs pre-incubated with apoptotic platelets induced the strongest IFN-γ production by CD4 T cells compared with pre-incubation with untreated or activated platelets. In conclusion, this study shows the capacity of platelets to induce platelet-specific alloimmune responses. Furthermore, storage-induced apoptosis of platelets is identified as potential risk factor for alloimmunization after platelet transfusions.

A subset of anti-HLA antibodies induces FcγRIIa-dependent platelet activation

HLA antibodies are associated with refractoriness to platelet transfusion, leading to rapid platelet clearance, sometimes coinciding with clinical side effects such as fever and chills. The presence of HLA antibodies is not always manifested by clinical symptoms. It is currently unclear why refractoriness to platelet transfusion is only observed in a subset of patients. Here, we utilized the availability of a unique panel of human monoclonal antibodies to study whether these were capable of activating platelets. Three out of eight human HLA-specific monoclonal antibodies induced activation of HLA-matched platelets from healthy donors as evidenced by enhanced α-granule release, aggregation, and α_IIbb₃ activation. The propensity of HLA monoclonal antibodies to activate platelets was independent of the HLA subtype to which they were directed, but was dependent on the recognized epitope. Activation was fully inhibited either by blocking FcγRIIa, or by blocking FcγRIIa-dependent signaling with Syk inhibitor IV. Furthermore, activation required the presence of the IgG-Fc part, as F(ab’)₂ fragments of HLA monoclonal antibodies were unable to induce platelet activation. Mixing experiments revealed that activation of platelets occurred in an intra-platelet dependent manner. Accordingly, a proportion of sera from refractory patients with HLA antibodies induced FcγRIIa-dependent platelet activation. Our data show that a subset of HLA antibodies is capable of crosslinking HLA and FcγRIIa thereby promoting platelet activation and enhancing these cells’ phagocytosis by macrophages. Based on these findings we suggest that FcγRIIa-dependent platelet activation may contribute to the decreased platelet survival in platelet-transfusion-dependent patients with HLA antibodies.

"In vitro" correction of the severe factor V deficiency-related coagulopathy by a novel plasma-derived factor V concentrate

INTRODUCTION

Severe congenital factor V (FV) deficiency is a rare bleeding disorder characterized by very low/undetectable levels of FV. Fresh frozen plasma is the standard treatment for bleeding manifestations. Recently, a novel plasma-derived FV concentrate has been developed.

AIM

To evaluate the "in vitro" ability of the novel FV concentrate to normalize clotting times and generate normal amount of thrombin in plasma collected from patients with severe FV deficiency.

METHODS

Prothrombin time (PT), activated partial thromboplastin time (aPTT), FV activity and antigen levels and thrombin generation were measured pre- and postspiking of plasma samples of 10 patients with increasing doses of FV concentrate (from 0 to 100 IU/dL).

RESULTS

Prothrombin time and activated partial thromboplastin time ratios as well as all thrombin generation parameters were fully corrected by the addition of FV concentrate at a final concentration of 25 IU/dL. However, the addition of FV at a concentration of 1-3 IU/dL was already sufficient to correct peak height and endogenous thrombin potential (but not lag time and time to peak) after activation with 5 pmol/L tissue factor. FV activity and antigen levels showed a linear response to supplementation with the novel FV concentrate.

CONCLUSION

The novel plasma-derived FV concentrate was effective to correct "in vitro" severe FV deficiency in patients. The optimal FV concentration to fully normalize both global clotting times and thrombin generation parameters using the novel plasma-derived FV concentrate was 25 IU/dL.

Platelet Transfusion for Patients With Cancer: American Society of Clinical Oncology Clinical Practice Guideline Update

Purpose

To provide evidence-based guidance on the use of platelet transfusion in people with cancer. This guideline updates and replaces the previous ASCO platelet transfusion guideline published initially in 2001.

Methods

ASCO convened an Expert Panel and conducted a systematic review of the medical literature published from September 1, 2014, through October 26, 2016. This review builds on two 2015 systematic reviews that were conducted by the AABB and the International Collaboration for Transfusion Medicine Guidelines. For clinical questions that were not addressed by the AABB and the International Collaboration for Transfusion Medicine Guidelines (the use of leukoreduction and platelet transfusion in solid tumors or chronic, stable severe thrombocytopenia) or that were addressed partially (invasive procedures), the ASCO search extended back to January 2000.

Results

The updated ASCO review included 24 more recent publications: three clinical practice guidelines, eight systematic reviews, and 13 observational studies.

Recommendations

The most substantial change to a previous recommendation involved platelet transfusion in the setting of hematopoietic stem-cell transplantation. Based on data from randomized controlled trials, adult patients who undergo autologous stem-cell transplantation at experienced centers may receive a platelet transfusion at the first sign of bleeding, rather than prophylactically. Prophylactic platelet transfusion at defined platelet count thresholds is still recommended for pediatric patients undergoing autologous stem-cell transplantation and for adult and pediatric patients undergoing allogeneic stem-cell transplantation. Other recommendations address platelet transfusion in patients with hematologic malignancies or solid tumors or in those who undergo invasive procedures. Guidance is also provided regarding the production of platelet products, prevention of Rh alloimmunization, and management of refractoriness to platelet transfusion ( www.asco.org/supportive-care-guidelines and www.asco.org/guidelineswiki ).

Adverse Reactions to Transfusion of Blood Products and Best Practices for Prevention

Transfusion, a common practice in critical care, is not without complication. Acute adverse reactions to transfusion occur within 24 hours and include acute hemolytic transfusion reaction, febrile nonhemolytic transfusion reaction, allergic and anaphylactic reactions, and transfusion-related acute lung injury, transfusion-related infection or sepsis, and transfusion-associated circulatory overload. Delayed transfusion adverse reactions develop 48 hours or more after transfusion and include erythrocyte and platelet alloimmunization, delayed hemolytic transfusion reactions, posttransfusion purpura, transfusion-related immunomodulation, transfusion-associated graft versus host disease, and, with long-term transfusion, iron overload. Clinical strategies may reduce the likelihood of reactions and improve patient outcomes.