Molecular typing of human platelet and neutrophil antigens (HPA and HNA)

Severe Platelet Transfusion Refractoriness in Association with Antibodies Against CD36

Platelet-transfusion refractoriness (PTR) is common in patients with hematological malignancies. The etiology of immune PTR is typically human leukocyte antigen (HLA) antibodies (Abs) from pregnancy or previous transfusion. Herein, we report PTR in the setting of induction chemotherapy for acute myelogenous leukemia (AML) from Abs against CD36/glycoprotein (GP)IV. A 66-year-old African American woman presented with anemia and thrombocytopenia. She was found to have transfusion-dependent AML, and a 7 + 3 regimen (7 days of standard-dose cytarabine and 3 days of an anthracycline antibiotic or an anthracenedione, most often daunorubicin) was initiated. The patient developed profound thrombocytopenia, with platelet nadir of 0 by day 13. The results of HLA antibody screening were negative. However, the results of a screening test for platelet-specific antibodies screen showed Abs against cluster of differentiation (CD)36. The platelets of the patient lacked expression of CD36, and DNA analysis showed mutations in the CD36 gene. HLA Ab-mediated PTR is common in patients with hematological malignancies. However, once HLA Abs are excluded, other less-frequent Abs should be considered, particularly in patient populations of Asian, African, or Middle Eastern descent.

Diagnosis of autoimmune neutropenia in a 10-month-old boy - a case report

Neutropenia, congenital or acquired, is related to impaired granulocyte production in the bone marrow or increased destruction by antibodies. Autoimmune neutropenia of infancy (AIN) is associated with the occurrence of antineutrophil antibodies. AIN is the most common cause of neutropenia in infants and young children. However, its incidence is low. Detection of anti-neutrophil antibodies is an important step in confirming the diagnosis of AIN, although their detection is difficult due to low titer and poor avidity. In differential diagnosis, another cause of neutropenia should be considered, such as a drug-induced mechanism, viral infection, autoimmune and metabolic disease, hematological conditions or immune deficiency syndromes. Despite the benign course of AIN, serious infectious complications can occur. Spontaneous remission of neutropenia was observed in 95% of patients during 24 months of follow-up. We present a case of a 10-month-old boy with deafness, heart defect and Morgagni-Larrey hernia diagnosed in our department because of formation of a skin abscess due to autoimmune neutropenia.

Human neutrophil antigens: Nature, clinical significance and detection

Granulocytes are an essential part of both the innate and adaptive immune systems. Human neutrophil antigens (HNAs) are a family of epitopes that are located on glycoproteins that are mostly expressed on human granulocytes. Antibodies that recognize these epitopes have been associated with neutropenia, transfusion complications, haematopoietic stem cell transplant nonengraftment and renal transplant rejection. Currently, there are fourteen recognized HNA alleles across five antigen systems (HNA-1 through HNA-5), the molecular basis of which are located on the genes FCGR3B, CD177, SLC44A2, ITGAM and ITGAL, respectively. Elucidation of the associated genes has permitted the development of testing strategies for HNA typing and aided understanding of the associated epitopes. This review will outline the associated clinical conditions that require HNA investigation and how these are performed in specialized laboratories. Investigations provided are both reactive for patients with a variety of existing or suspected neutropenias and proactive in the testing of blood component donors in order to reduce the potential risk to patients who require transfusion.

Targeted exome sequencing designed for blood group, platelet, and neutrophil antigen investigations: Proof-of-principle study for a customized single-test system

BACKGROUND

Immunohematology reference laboratories provide red blood cell (RBC), platelet (PLT), and neutrophil typing to resolve complex cases, using serology and commercial DNA tests that define clinically important antigens. Broad-range exome sequencing panels that include blood group targets provide accurate blood group antigen predictions beyond those defined by serology and commercial typing systems and identify rare and novel variants. The aim of this study was to design and assess a panel for targeted exome sequencing of RBC, PLT, and neutrophil antigen-associated genes to provide a comprehensive profile in a single test, excluding unrelated gene targets.

STUDY DESIGN AND METHODS

An overlapping probe panel was designed for the coding regions of 64 genes and loci involved in gene expression. Sequencing was performed on 34 RBC and 17 PLT/neutrophil reference samples. Variant call outputs were analyzed using software to predict star allele diplotypes. Results were compared with serology and previous sequence genotyping data.

RESULTS

Average coverage exceeded 250×, with more than 94% of targets at Q30 quality or greater. Increased coverage revealed a variant in the Scianna system that was previously undetected. The software correctly predicted allele diplotypes for 99.5% of RBC blood groups tested and 100% of PLT and HNA antigens excepting HNA-2. Optimal throughput was 12 to 14 samples per run.

CONCLUSION

This single-test system demonstrates high coverage and quality, allowing for the detection of previously overlooked variants and increased sample throughput. This system has the potential to integrate genomic testing across laboratories within hematologic reference settings.

High-Throughput Screening of Blood Donors for Twelve Human Platelet Antigen Systems Using Next-Generation Sequencing Reveals Detection of Rare Polymorphisms and Two Novel Protein-Changing Variants

Background

Exposure to non-matching human platelet alloantigens (HPA) may result in alloimmunization. Antibodies to HPA can be responsible for post-transfusion purpura, refractoriness to donor platelets, and fetal and neonatal alloimmune thrombocytopenia. For the supply of compatible apheresis platelet concentrates, the HPA genotypes are determined in a routine manner.

Methods

Here, we describe a novel method for genotyping twelve different HPA systems simultaneously, including HPA-1 to HPA-5, HPA-9w, HPA-10w, HPA-16w, HPA-19w, HPA-27w, and the novel HPA-34w by means of amplicon-based next-generation sequencing (NGS). Blood donor samples of 757 individuals with a migration background and 547 of Western European ancestry were genotyped in a mass-screening setup. An in-house software was developed for fast and automatic analysis. TaqMan assay and Sanger sequencing results served for validation of the NGS workflow. Finally, blood donors were divided in several groups based on their country of origin and the allele frequencies were compared.

Results

For 1,299 of 1,304 samples (99.6%) NGS was successfully performed. The concordance with TaqMan assay and Sanger sequencing results was 99.8%. Allele-calling dropouts that were observed for two samples with the TaqMan assay caused by rare single nucleotide polymorphisms were resolved by NGS. Additionally, twenty rare and two novel variants in the coding regions of the genes ITGB3, GPB1A, ITGBA2, and CD109 were detected. The determined allele frequencies were similar to those published in the gnomAD database.

Conclusions

No significant differences were observed in the distribution of allele frequencies of HPA-1 through HPA-5 and HPA-15 throughout the analyzed groups except for a lower allele frequency for the HPA-1b allele in the group of donors with Southern Asian ancestry. In contrast, other nucleotide variants that have not yet been phenotypically characterized occurred three times more often in blood donors with a migration background. High-throughput amplicon-based NGS is a reliable method for screening HPA genotypes in a large sample cohort simultaneously. It is easily upgradeable for genotyping additional targets without changing the setup or the analysis pipeline. Mass-screening methods will help building up blood donor registries to provide matched blood products.

Towards a Regional Registry of Extended Typed Blood Donors: Molecular Typing for Blood Group, Platelet and Granulocyte Antigens

BACKGROUND

The provision of compatible blood products to patients is the most essential task of transfusion medicine. Besides ABO and Rh, a number of additional blood group antigens often have to be considered for the blood supply of immunized or chronically transfused patients. It also applies for platelet antigens (HPA) and neutrophil antigens (HNA) for patients receiving platelet or granulocyte concentrates. Here, we describe the molecular screening for a number of blood group, HPA, and HNA alleles. Based on the screening results we are building up a regional blood donor registry to provide extended matched blood products on demand.

METHODS

We developed and validated TaqMan™ PCR and PCR-SSP methods for genetic markers defining 37 clinically relevant blood group antigens (beyond ABO and Rh), 10 HPA, and 11 HNA. Furthermore, we describe a feasible method for fast molecular screening of the HNA-2null phenotype. All data were statistically evaluated regarding genotype distribution. Allele frequencies were compared to ExAC data from non-Finnish Europeans.

RESULTS

Up to now more than 2,000 non-selected regular blood donors in south-west Germany have been screened for blood group, HPA, and HNA alleles. The screening results were confirmed by serology and PCR-SSP methods for selected numbers of samples. The allele frequencies were similar to non-finnish Europeans in the ExAC database except for the alleles encoding the S, HPA-3b and HNA-4b antigens, with significantly lower prevalence in our cohort, as well as the LU14 and the HNA-3b antigens, with a higher frequency compared to the ExAC data. We identified 71 donors with rare blood groups such as Lu(a+b-), Kp(a+b-), Fy(a-b-) and Vel-, and 169 donors with less prevalent HPA or HNA types.

CONCLUSION

Molecular screening for blood group alleles by using TaqMan™ PCR is an effective and reliable high-throughput method for establishing a rare donor registry.

Neonatal Alloimmune Neutropenia

Neonatal alloimmune neutropenia (NAIN, NAIN or NIN) is a neutrophil blood group antagonism, analogous to hemolytic disease of the fetus and newborn (HDFN) and fetal/neonatal alloimmune thrombocytopenia (FNAIT). A limited number of prospective screening studies showed that granulocyte-specific antibodies were detectable in 0.35-1.1% of random postnatal maternal samples and that the incidence of NAIN was below 0.1%. Symptoms vary from none to mild skin infections, omphalitis or more severe infections like pneumonia, sepsis, and meningitis. Treatment of neonatal infection with antibiotics and granulocyte-colony stimulating factor is advised.

Noninvasive prenatal diagnosis by cell-free DNA screening for fetomaternal HPA-1a platelet incompatibility

BACKGROUND

The development of new noninvasive approaches for the diagnosis of human platelet antigen (HPA)-1 fetomaternal incompatibility has become of great interest. These approaches allow determination of whether the fetus is incompatible or not with the mother and a decision on antenatal therapy to avoid fetal or neonatal alloimmune thrombocytopenia (FNAIT). The objective of this work was to perform rapid, noninvasive prenatal test for HPA-1ab fetal antigen detection after the detection of an HPA-1-homozygous mother by using plasma cell-free DNA (cfDNA).

STUDY DESIGN AND METHODS

The HPA-1 genotypes of 142 pregnant women and 17 nonpregnant controls were retrospectively determined by high-resolution melting (HRM) polymerase chain reaction (PCR). Coamplification at lower denaturation temperature (COLD) HRM PCR was performed to determine the fetal genotype analyzing cfDNA from all HPA-1bb pregnant women.

RESULTS

After the HRM analysis, the following genotypes were identified: HPA-1aa (71.13%), HPA-1bb (2.8%), and HPA-1ab (26.06%). Four HPA-1bb-homozygous pregnant women were carrying an incompatible fetus. Plasma samples from these mothers were analyzed by HRM COLD-PCR. Homozygous HPA-1bb pregnant women carrying an HPA-1ab-heterozygous fetus did not group with either the HPA-1ab or the HPA-1bb controls. Thus, COLD-PCR analysis allows the detection of HPA-1ab-heterozygous fetuses carried by homozygous mothers during first weeks of pregnancy.

CONCLUSION

The fetal genotype from HPA-1bb-homozygous women was detected by a noninvasive prenatal test as soon as 12 weeks of gestation.

Transfusion Medicine and Molecular Genetic Methods

Transfusion procedures are always complicated by potential genetic mismatching between donor and recipient. Compatibility is determined by several major antigens, such as the ABO and Rhesus blood groups. Matching for other blood groups (Kell, Kidd, Duffy, and MNS), human platelet antigens, and human leukocyte antigens (HLAs) also contributes toward the successful transfusion outcomes, especially in multitransfused or highly immunized patients. All these antigens of tissue identity are highly polymorphic and thus present great challenges for finding suitable donors for transfusion patients. The ABO blood group and HLA markers are also the determinants of transplant compatibility, and mismatched antigens will cause graft rejection or graft-versus-host disease. Thus, a single and comprehensive registry covering all of the significant transfusion and transplantation antigens is expected to become an important tool in providing an efficient service capable of delivering safe blood and quickly locating matching organs/stem cells. This review article is intended as an accessible guide for physicians who care for transfusion-dependent patients. In particular, it serves to introduce the new molecular screening methods together with the biology of these systems, which underlies the tests.

Prolonged neutropenia due to antihuman neutrophil antigen 2 (CD177) antibody after bone marrow transplantation

We describe a patient who presented with prolonged neutropenia due to anti-human neutrophil antigen (HNA)-2 (CD177) antibody after allogeneic bone marrow transplantation. A granulocyte immunofluorescence test showed bimodal expression of antineutrophil antibody that resulted from specific binding of anti-HNA-2 to CD177⁺ neutrophils from healthy donors. The patient did not respond to granulocyte colony stimulating factor, which is able to upregulate CD177 expression on neutrophils. The low percentage of CD177⁺ cells in the few remaining neutrophils supports the possibility of elimination of CD177-upregulated neutrophils. These findings might explain an inferior response to neutrophil growth factors in neutropenia secondary to anti-HNA-2 antibody.

Human neutrophil antigen profiles in Banjar, Bugis, Champa, Jawa and Kelantan Malays in Peninsular Malaysia

BACKGROUND

Human neutrophil antigens (HNA) are polymorphic and immunogenic proteins involved in the pathogenesis of neonatal alloimmune neutropenia, transfusion-related acute lung injury (TRALI) and transfusion-related alloimmune neutropenia. The characterisation of HNA at a population level is important for predicting the risk of alloimmunisation associated with blood transfusion and gestation and for anthropological studies.

MATERIALS AND METHODS

Blood samples from 192 healthy, unrelated Malays were collected and genotyped using polymerase chain reaction-sequence specific primers (HNA-1, -3, -4) and polymerase chain reaction-restriction fragment length polymorphisms (HNA-5). The group comprised 30 Banjar, 37 Bugis, 51 Champa, 39 Jawa and 35 Kelantan Malays.

RESULTS

The most common HNA alleles in the Malays studied were HNA-1a (0.641-0.765), -3a (0.676-0.867), -4a (0.943-1.000) and -5a (0.529-0.910). According to principal coordinate plots constructed using HNA allele frequencies, the Malay sub-ethnic groups are closely related and grouped together with other Asian populations. The risks of TRALI or neonatal neutropenia were not increased for subjects with HNA-1, -3 and -4 loci even for donor and recipient or pairs from different Malay sub-ethnic groups. Nonetheless, our estimates showed significantly higher risks of HNA alloimmunisation during pregnancy and transfusion between Malays and other genetically differentiated populations such as Africans and Europeans.

DISCUSSION

This study reports HNA allele and genotype frequencies for the five Malay sub-ethnic groups living in Peninsular Malaysia for the first time. These Malay sub-ethnic groups show closer genetic relationships with other Asian populations than with Europeans and Africans. The distributions of HNA alleles in other lineages of people living in Malaysia (e.g. Chinese, Indian and Orang Asli) would be an interesting subject for future study.

Platelet reactive alloantibodies responsible for immune thrombocytopenia in Malay population

Background: Alloantibodies against human platelet alloantigens (HPAs) are responsible for the development of platelet transfusion refractoriness (PTR) in patients receiving random platelets and bleeding disorder in babies with fetal neonatal alloimmune thrombocytopenia (FNAIT). Recently, our results based on the analysis of the allelic distribution of HPAs indicated that immunization may occur among Malay. In this study, we sought to analyze the frequencies of platelet reactive alloantibodies responsible for FNAIT and PTR in Malaysia.Methods: Sera from suspected FNAIT (n = 295) and PTR (n = 74) were collected in five years period (2008-2013) and tested for the presence of platelet reactive antibodies by the use of antigen capture assay.Results: In 5/74 (5.41%) platelet specific antibodies against HPA-2b (n = 1), HPA-5a (n = 1), HPA-5b (n = 1), HPA-15b (n = 2) could be identified in our PTR cohort. In FNAIT cohort, platelet specific alloantibodies could be detected in 18 sera (6.10%) consisting anti-HPA-1a (n = 1), anti-HPA-3a (n = 3), anti-HPA-5a (n = 6), anti-HPA-5b (n = 6), anti-HPA-15a (n = 1), and anti-HPA-15b (n = 1).Conclusion: Our study indicates that anti-HPA-3, -HPA-5 and -HPA-15 antibodies seems to be the most platelet specific antibodies involved in FNAIT and PTR cases in Malaysian population. Since similar HPA allelic distribution among Malaysian and Indonesian populations have been observed, immunization against these three HPA systems are expected to be the most potential risk of alloimmune mediated platelet disorders in Indonesia.

Platelets: still a therapeutical target for haemostatic disorders

Platelets are cytoplasmatic fragments from bone marrow megakaryocytes present in blood. In this work, we review the basis of platelet mechanisms, their participation in syndromes and in arterial thrombosis, and their potential as a target for designing new antithrombotic agents. The option of new biotechnological sources is also explored.