Determination of 24 minor red blood cell antigens for more than 2000 blood donors by high-throughput DNA analysis

Multiplex-PCR technique to predict polymorphic antigens - M, N, S and s - and associations between their alleles and Mia-associated hybrid glycophorins

Serological typing of MNS polymorphic antigens - M, N, S and s - remains a fundamental technique in transfusion medicine and prenatal care, providing essential information for matching blood donors and recipients and managing haemolytic disease. Although this method is well proven and routinely used, it is not a comprehensive solution, as it has several weaknesses. Alternatively, multiplex polymerase chain reaction (PCR) is a commonly used genotyping tool due to its potency and ability to amplify several DNA targets simultaneously in a single reaction. In this work, we aimed to develop multiplex PCR and evaluate its performance for GYPA*M, GYPA*N, GYPB*S, and GYPB*s allele identification using serological and DNA sequencing methods. We also aimed to investigate the correlation between these alleles and Mia-associated hybrid glycophorins (GPs). Remarkably, multiplex PCR was well optimised, and the results aligned with serological phenotyping and DNA sequencing data with maximum accuracy and reliability; this confirmed our findings on its validity in predicting MNSs phenotypes. In addition, this work strongly demonstrates, for the first time, a moderate correlation between the GYPA*M/M and GYPB*s/s genotypes and Mia-associated hybrid GPs among Thai donors. Individuals with the GYPA*M/M and GYPB*s/s genotypes, predicted M + N - S- s + phenotypes, will thus most likely to express the Mi(a+) antigen. Nevertheless, further studies are required to validate these results and elucidate the underlying correlations.

Genetic profile of RHCE, Kell, Duffy, Kidd, Diego and MNS hybrid glycophorins blood groups in ethnic northeastern Thais: Alleles, genotypes and risk of alloimmunisation

BACKGROUND

Antibodies against blood group antigens play a key role in the pathophysiology of haemolytic transfusion reactions (HTRs) and haemolytic disease of the fetus and newborn (HDFN). This study aimed to determine the frequencies of alleles, genotypes, and risk of alloimmunisation of clinically significant blood group systems in ethnic northeastern Thais.

METHODS

In total, 345 unrelated, healthy, ethnic northeastern Thais were tested using the in-house PCR-sequence specific primers (PCR-SSP) method for simultaneously genotyping of RHCE, Kell, Duffy, Kidd, Diego and MNS glycophorin hybrids and results confirmed by Sanger sequencing.

RESULTS

In this cohort, the alleles RHCE*C (81.0%) and RHCE*e (84.8%) were more prevalent than RHCE*c (19.0%) and RHCE*E (15.2%). The most common predicted haplotype combinations of the RHCE alleles were C+c-E-e+(R1R1) (59.4%) followed by the C+c+E+e+ (R1R2) (20.6%) and C+c+E-e+ (R1r) (11.3%). The KEL*01 allele was not found in this study. The frequencies of FY*01 and FY*02 were 88.3% and 11.7%, respectively. The genotype FY*02/02 was found in four samples (1.2%). The frequencies of JK*01 and JK*02 were 52.5% and 47.5%, respectively. Homozygous JK*02/02 was found in 81 samples (23.5%). The frequencies of DI*01 and DI*02 were 0.6% and 99.4%, respectively. In total, 64 samples (18.6%) were found to carry the MNS glycophorin hybrids.

CONCLUSIONS

Our results indicated a possible high risk of c, E, Fyb, Jka, Jkb and Mia alloimmunisation in these populations. Moreover, methods established for genotyping clinically significant blood groups in this study can now be utilised in routine clinical application.

[Genotyping and its applications, a look to the future]

The detection of the most significant erythrocyte antigens present in each one of the individuals is fundamental when carrying out a transfusion or a transplant. Detection to date is performed by conventional serological methods through the antigen-antibody reaction. But several drawbacks may arise depending on the pathology under study, limiting the availability of blood components. Molecular methods such as genotyping is a tool that complements sensitivity and specificity and has come to revolutionize immunohematology in the blood bank, allowing not only the detection of erythrocyte antigens but also platelet antigens. These methodologies are applicable in patients and in large-scale donors, starting from the allelic variants present in each of the genes that code for the antigens of clinical interest, using microarray systems or systems based on particles labeled with specific probes or their variants that allow an analysis from the immunohematological point of view.

Mapping anticipated advantages and disadvantages of implementation of extensive donor genotyping: A focus group approach

BACKGROUND AND OBJECTIVES

Current genotyping techniques allow typing of all relevant red cell, human leukocyte and platelet antigens in a single analysis. Even genetic markers related to donor health can be added. Implementation of this technology will affect various stakeholders within the transfusion chain. This study aims to systematically map the anticipated advantages and disadvantages of a national rollout of blood group genotyping of donors, which will affect the availability of rare donors and the implementation of an extensively typed blood transfusion policy.

MATERIALS AND METHODS

Two focus-group sessions were held with a wide representation of stakeholders, including representatives of donor and patient organisations. A dedicated software tool was used to collect the reflections of participants on genotyping for blood group antigens and extensive matching. Additionally, stakeholders and experts discussed various prepared propositions. All information collected was categorised.

RESULTS

From 162 statements collected, 59 statements (36%) were labelled as 'hopes' and 77 (48%) as 'fears'. Twenty-six (16%) statements remained unlabelled. The statements were divided in 18 categories under seven main themes: patient health, genotyping, privacy issues and ethical aspects, donor management, inventory management and logistics, hospital and transfusion laboratory and general aspects. The discussion on the propositions was analysed and summarised.

CONCLUSION

Stakeholders believe that a genotyped donor pool can result in a reduction of alloimmunization and higher availability of typed blood products. There are concerns regarding logistics, costs, consent for extended typing, data sharing, privacy issues and donor management. These concerns need to be carefully addressed before further implementation.

Application of Blood Group Genotyping by Next-Generation Sequencing in Various Immunohaematology Cases

BACKGROUND

Next-generation sequencing (NGS) technology has been recently introduced into blood group genotyping; however, there are few studies using NGS-based blood group genotyping in real-world clinical settings. In this study, we applied NGS-based blood group genotyping into various immunohaematology cases encountered in routine clinical practice.

METHODS

This study included 4 immunohaematology cases: ABO subgroup, ABO chimerism, antibody to a high-frequency antigen (HFA), and anti-CD47 interference. We designed a hybridization capture-based NGS panel targeting 39 blood group-related genes and applied it to the 4 cases.

RESULTS

NGS analysis revealed a novel intronic variant (NM_020469.3:c.29-10T>G) in a patient with an Ael phenotype and detected a small fraction of ABO*A1.02 (approximately 3-6%) coexisting with the major genotype ABO*B.01/O.01.02 in dizygotic twins. In addition, NGS analysis found a homozygous stop-gain variant (NM_004827.3:c.376C>T, p.Gln126*; ABCG2*01N.01) in a patient with an antibody to an HFA; consequently, this patient's phenotype was predicted as Jr(a-). Lastly, blood group phenotypes predicted by NGS were concordant with those determined by serology in 2 patients treated with anti-CD47 drugs.

CONCLUSION

NGS-based blood group genotyping can be used for identifying ABO subgroup alleles, low levels of blood group chimerism, and antibodies to HFAs. Furthermore, it can be applied to extended blood group antigen matching for patients treated with anti-CD47 drugs.

Extended red blood cell matching for all transfusion recipients is feasible

OBJECTIVE

To demonstrate the feasibility and effectiveness of extended matching of red blood cells (RBC) in practice.

BACKGROUND

At present, alloimmunisation preventing matching strategies are only applied for specific transfusion recipient groups and include a limited number of RBC antigens. The general assumption is that providing fully matched RBC units to all transfusion recipients is not feasible. In this article we refute this assumption and compute the proportion of alloimmunisation that can be prevented, when all donors and transfusion recipients are typed for A, B, D plus twelve minor blood group antigens (C, c, E, e, K, Fy^a , Fy^b , Jk^a , Jk^b , M, S and s).

METHODS

We developed a mathematical model that determines the optimal sequence for antigen matching. The model allows for various matching strategies, issuing policies and inventory sizes.

RESULTS

For a dynamic inventory composition (accounting for randomness in the phenotypes supplied and requested) and an antigen identical issuing policy 97% and 94% of alloimmunisation events can be prevented, when respectively one and two RBC units per recipient are requested from an inventory of 1000 units. Although this proportion decreases with smaller inventory sizes, even for an inventory of 60 units almost 50% of all alloimmunisation events can be prevented.

CONCLUSION

In case antigen of both donors and recipients are comprehensively typed, extended preventive matching is feasible for all transfusion recipients in practice and will significantly reduce transfusion-induced alloimmunisation and (alloantibody-induced) haemolytic transfusion reactions.

Multiple GYPB gene deletions associated with the U- phenotype in those of African ancestry

BACKGROUND

The MNS blood group system is defined by three homologous genes: GYPA, GYPB, and GYPE. GYPB encodes for glycophorin B (GPB) carrying S/s and the "universal" antigen U. RBCs of approximately 1% of individuals of African ancestry are U- due to absence of GPB. The U- phenotype has long been attributed to a deletion encompassing GYPB exons 2 to 5 and GYPE exon 1 (GYPB*01N).

STUDY DESIGN AND METHODS

Samples from two U-individuals underwent Illumina short read whole genome sequencing (WGS) and Nanopore long read WGS. In addition, two existing WGS datasets, MedSeq (n = 110) and 1000 Genomes (1000G, n = 2535), were analyzed for GYPB deletions. Deletions were confirmed by Sanger sequencing. Twenty known U- donor samples were tested by a PCR assay to determine the specific deletion alleles present in African Americans.

RESULTS

Two large GYPB deletions in U- samples of African ancestry were identified: a 110 kb deletion extending left of GYPB (DEL_B_LEFT) and a 103 kb deletion extending right (DEL_B_RIGHT). DEL_B_LEFT and DEL_B_RIGHT were the most common GYPB deletions in the 1000 Genomes Project 669 African genomes (allele frequencies 0.04 and 0.02). Seven additional deletions involving GYPB were seen in African, Admixed American, and South Asian samples. No samples analyzed had GYPB*01N.

CONCLUSIONS

The U- phenotype in those of African ancestry is primarily associated with two different complete deletions of GYPB (with intact GYPE). Seven additional less common GYPB deletion backgrounds were found. GYPB*01N, long assumed to be the allele commonly encoding U- phenotypes, appears to be rare.

Blood group antigen and phenotype prevalence in the Korean population compared to other ethnic populations and its association with RBC alloantibody frequency

OBJECTIVES

This study aimed to analyse the allele frequency of blood group antigens in the Korean population and other ethnic populations and the association of blood group antigens with red blood cell (RBC) alloantibodies.

BACKGROUND

Blood group antigen genotyping can support patients undergoing frequent transfusions who have alloantibodies and antibodies against high-prevalence blood group antigens.

METHODS

Twenty-nine single nucleotide variations and 37 blood group antigens were tested. Samples requested for routine blood typing were collected from Jan to Apr 2016. Genotyping was performed on 145 Korean samples and was confirmed by bidirectional sequencing and serologic tests. The allele frequency data were compared with previous genotyping datasets (three datasets from Korea and one each from China, Europe, Asia, and the USA). Alloantibody frequencies and blood group antigens from the electronic medical record of 1772 cases were examined.

RESULTS

E antigen was higher in the Korean population compared to that of Asian and European populations. K, Kp^a , Fy^b and Do^a allele frequencies were lower compared to other ethnic populations. RBC alloantibodies with frequencies (%) greater than 1% from the 1772 cases were as follows: anti-E, 36·7%, anti-C, 17·7%; anti-c 7·39%; anti-M, 5·9%; anti-e, 5·2%; anti-Jk^a , 2·9%; and anti-Fy^a , 1·1%. Blood group antigens and alloantibody frequencies revealed inverse trends that did not reach statistical significance.

CONCLUSION

The allele frequency of blood group antigens assessed by high-throughput methods provided reliable and valuable information that could be used for maintaining donor pools and providing compatible blood for genotyped patients.

Blood group genotyping

Genomics is affecting all areas of medicine. In transfusion medicine, DNA-based genotyping is being used as an alternative to serological antibody-based methods to determine blood groups for matching donor to recipient. Most antigenic polymorphisms are due to single nucleotide polymorphism changes in the respective genes, and DNA arrays that target these changes have been validated by comparison with antibody-based typing. Importantly, the ability to test for antigens for which there are no serologic reagents is a major medical advance to identify antibodies and find compatible donor units, and can be life-saving. This review summarizes the evolving use and applications of genotyping for red cell and platelet blood group antigens affecting several areas of medicine. These include prenatal medicine for evaluating risk of fetal or neonatal disease and candidates for Rh-immune globulin; transplantation for bone marrow donor selection and transfusion support for highly alloimmunized patients and for confirmation of A2 status of kidney donors; hematology for comprehensive typing for patients with anemia requiring chronic transfusion; and oncology for patients receiving monoclonal antibody therapies that interfere with pretransfusion testing. A genomics approach allows, for the first time, the ability to routinely select donor units antigen matched to recipients for more than ABO/RhD to reduce complications. Of relevance, the growth of whole-genome sequencing in chronic disease and for general health will provide patients' comprehensive extended blood group profile as part of their medical record to be used to inform selection of the optimal transfusion therapy.

Assessment of common red blood cell pretreatments to yield an accurate serologic antigen phenotype compared with genotype-predicted phenotype

For patients requiring multiple transfusions and patients with positive direct antiglobulin tests (DATs), an extended red blood cell (RBC) phenotype can provide valuable information and help to determine the risk of forming alloantibodies. In some instances, the phenotype may be used for prophylactic matching. Phenotyping in this patient population is often hindered by the presence of circulating donor cells and/or by a positive DAT. Several methods, such as EDTA glycine acid (EGA) treatment to remove IgG, hypotonic saline wash to separate autologous RBCs, or reticulocyte separation, are often used in these situations to isolate patient RBCs for serologic phenotyping. This study aimed to determine the accuracy of each RBC pretreatment method by comparing serologically determined antigen types with those predicted by RBC genotyping. Forty-eight peripheral blood samples from recently transfused patients were phenotyped for selected antigens in the Rh, Kell, MNS, Duffy, and Kidd systems. Treatment methods for the sample sets were reticulocyte separation (N = 12), EGA (N = 16), and hypotonic saline wash (N = 20). DNA was extracted using standard methods, and genotyping was performed using the HEA BeadChip panel. In addition, 21 samples positive for RBC-bound IgG were EGA-treated up to two times. These samples were analyzed pre- and post-EGA treatment for RBC-bound IgG by tube DAT and by flow cytometry with fluorescein isothiocyanate-labeled anti-human IgG. After reticulocyte separation, 3 of the 12 samples had discordant types with one antigen each: Fy^b, N, and K; serologic results were negative compared with genotype-predicted positive phenotype results. The EGA-treated sample set showed one discordant type: Fy^b; serologic results were negative compared with genotype-predicted positive phenotype results. Four of the 20 samples had discordant types involving the following antigens: Fy^b, N, e, and M; serologic results were negative compared with genotype-predicted positive phenotype results. After EGA treatment of 21 samples, 14 (67%) were negative for RBC-bound IgG by tube DAT, and 7 remained positive. Using flow cytometry, EGA treatment rendered only 4 samples negative, and 17 remained positive. In the antigen testing sample set of 48 samples, 10 of 511 total antigen types tested were discordant. Discordant types were most frequent in the hypotonic saline wash sample set (N = 6). In the flow cytometry sample set, 48 percent of the samples negative by tube DAT after EGA elution had detectable RBC-bound IgG by flow cytometry. These findings suggest that caution should be taken when using phenotype results from all pretreated RBCs and support the use of RBC genotyping to predict RBC antigen expression in samples from recently transfused patients.

For patients requiring multiple transfusions and patients with positive direct antiglobulin tests (DATs), an extended red blood cell (RBC) phenotype can provide valuable information and help to determine the risk of forming alloantibodies. In some instances, the phenotype may be used for prophylactic matching. Phenotyping in this patient population is often hindered by the presence of circulating donor cells and/or by a positive DAT. Several methods, such as EDTA glycine acid (EGA) treatment to remove IgG, hypotonic saline wash to separate autologous RBCs, or reticulocyte separation, are often used in these situations to isolate patient RBCs for serologic phenotyping. This study aimed to determine the accuracy of each RBC pretreatment method by comparing serologically determined antigen types with those predicted by RBC genotyping. Forty-eight peripheral blood samples from recently transfused patients were phenotyped for selected antigens in the Rh, Kell, MNS, Duffy, and Kidd systems. Treatment methods for the sample sets were reticulocyte separation (N = 12), EGA (N = 16), and hypotonic saline wash (N = 20). DNA was extracted using standard methods, and genotyping was performed using the HEA BeadChip panel. In addition, 21 samples positive for RBC-bound IgG were EGA-treated up to two times. These samples were analyzed pre- and post-EGA treatment for RBC-bound IgG by tube DAT and by flow cytometry with fluorescein isothiocyanate–labeled anti-human IgG. After reticulocyte separation, 3 of the 12 samples had discordant types with one antigen each: Fy^b, N, and K; serologic results were negative compared with genotype-predicted positive phenotype results. The EGA-treated sample set showed one discordant type: Fy^b; serologic results were negative compared with genotype-predicted positive phenotype results. Four of the 20 samples had discordant types involving the following antigens: Fy^b, N, e, and M; serologic results were negative compared with genotype-predicted positive phenotype results. After EGA treatment of 21 samples, 14 (67%) were negative for RBC-bound IgG by tube DAT, and 7 remained positive. Using flow cytometry, EGA treatment rendered only 4 samples negative, and 17 remained positive. In the antigen testing sample set of 48 samples, 10 of 511 total antigen types tested were discordant. Discordant types were most frequent in the hypotonic saline wash sample set (N = 6). In the flow cytometry sample set, 48 percent of the samples negative by tube DAT after EGA elution had detectable RBC-bound IgG by flow cytometry. These findings suggest that caution should be taken when using phenotype results from all pretreated RBCs and support the use of RBC genotyping to predict RBC antigen expression in samples from recently transfused patients.

Methods for blood group antigens detection: cost-effectiveness analysis of phenotyping and genotyping

Background

Alloimmunization is a major problem in transfusion practice due to the clinical complications of the patients and the difficulty of choosing a unit of compatible blood product. Serological methods are widely used in blood banks, but they not always determine the phenotype. Thus, genotyping is an important complement to the serology tool as it allows one to predict the phenotype from deoxyribonucleic acid (DNA) with high accuracy.

Objective

To compare the centrifugation gel, microarray, Restriction Fragment Length Polymorphismone PCR (PCR-RFLP) and Sequence-Specific Primer PCR (PCR-SSP) techniques, in terms of cost, reaction time and reliability of the results.

Methods

The RHCE, Kidd, Kell and Duffy blood group systems were chosen to determine the approximate cost of each technique, considering the reagents used in both methods and considering only one sample. The time required for the development of each reaction was obtained at the Maringa Regional Blood Center and Immunogenetics Laboratory at the State University of Maringa. Data from Microarray reactions were obtained at the Campinas Blood Center. The results of phenotyping and genotyping of the 16 samples were compiled in a spreadsheet and compared.

Results

The PCR-SSP was more economical compared to other methods, and the serological method was faster than the molecular methods. However, all methods proved to be effective and safe in the detection of erythrocyte antigens.

Conclusion

Analyzing the advantages and limitations of the molecular and serological methods tested in this study, we note that both are important and complementary. However, the choice of a methodology depends on the reality and needs of each health service.

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.

Massively parallel and multiplex blood group genotyping using next-generation-sequencing

OBJECTIVES

Thirty-six blood group systems are listed by the International Society of Blood Transfusion, containing almost 350 antigens. Most of these result from a single nucleotide polymorphism (SNP). Serology is the standard method for blood group typing. However, this technique has some limitations and cannot respond to the growing demand of blood product typing for a large number of antigens. Here we describe a blood group genotyping assay directly from whole blood samples using Next-Generation Sequencing (NGS), allowing the simultaneous identification of 15 SNPs associated with the blood group systems of 95 patients in a single run.

DESIGN AND METHOD

After an automated DNA extraction, targets are amplified by multiplex polymerase chain reaction (PCRm). Two panels addressing 9 groups have been developed (MNS, Lutheran, Kell, Duffy, Kidd, Diego, Yt, Dombrock, and Colton), one for 8 SNPs, the other for 7 SNPs. For each sample, both panels corresponding to 14 amplicons (1 amplicon containing 2 SNPs) are pooled. Then a dual-indexed library is generated from each pool by linking Illumina adaptors directly onto amplicons, followed by sequencing using the MiSeq platform (Illumina).

RESULTS

In a single experiment, 95 blood donor samples have been sequenced for the genes of interest. Among the 1425 targeted single nucleotide polymorphisms, 1420 were identified by sequencing, reflecting a coverage of 99.65%. The obtained data shows a good correlation (99% for all SNPs) with other blood group typing methods. Depending on the allele pairs analyzed, correlations vary between 97.12 and 100%.

CONCLUSION

Next-Generation sequencing would supplement serological and molecular techniques and, in the near future, could replace it with complete and fast results acquisition for pre-screening and identification of rare blood bags.

Predicted S and s phenotypes from genotyping results among Thai populations to prevent transfusion-induced alloimmunization risks

BACKGROUND

S and s antigens of the MNS system are of clinical importance because alloanti-S and -s have usually caused delayed hemolytic transfusion reactions and hemolytic disease of the fetus and newborn. Various red cell genotyping has been established to predict the phenotypes to solve serological test limitations.

OBJECTIVES AND METHODS

This study aimed to determine S and s genotype frequencies and to estimate the alloimmunization risks among central, northern and southern Thai populations. Altogether, 1237 blood samples from Thai blood donors were included. Only 150 samples were tested with anti-S and anti-s by indirect antiglobulin test. All samples were genotyped for GYPB*S and GYPB*s alleles using inhouse PCR with sequence-specific primer. Additionally, the allele frequencies were used to estimate alloimmunization risks and compare with other populations.

RESULTS

The phenotyping and genotyping results in 150 samples were in 100% concordance. The allele frequencies of GYPB*S in central, northern and southern Thais were 0.061, 0.040 and 0.097, and GYPB*s were 0.939, 0.960 and 0.903, respectively. The frequencies among central Thais were similar to those among northern Thai and Korean populations (P > 0.05) but significantly differed from those of Asian, Caucasian African American and Hispanic populations (P < 0.05). In addition, the risk of S alloimmunization among southern Thais (0.1566) was higher than those among central (0.1038) and northern Thais (0.0736).

CONCLUSION

This was the first study to report S and s predicted phenotypes and estimate alloimmunization risks among Thais, which is beneficial to prevent transfusion-induced alloimmunization among donors and patients.

Extended Donor Typing by Pooled Capillary Electrophoresis: Impact in a Routine Setting

Background

PCR with sequence-specific priming using allele-specific fluorescent primers and analysis on a capillary sequencer is a standard technique for DNA typing. We aimed to adapt this method for donor typing in a medium-throughput setting.

Methods

Using the Extract-N-Amp PCR system, we devised a set of eight multiplex allele-specific PCR with fluorescent primers for Fy^a/Fy^b, Jk^a/Jk^b, M/N, and S/s. The alleles of a gene were discriminated by the fluorescent color; donor and polymorphism investigated were encoded by product length. Time, cost, and routine performance were collated. Discrepant samples were investigated by sequencing. The association of new alleles with the phenotype was evaluated by a step-wise statistical analysis.

Results

On validation using 312 samples, for 1.1% of antigens (in 5.4% of samples) no prediction was obtained. 99.96% of predictions were correct. Consumable cost per donor were below EUR 2.00. In routine use, 92.2% of samples were successfully predicted. Discrepancies were most frequently due to technical reasons. A total of 11 previously unknown alleles were detected in the Kell, Lutheran, and Colton blood group systems. In 2017, more than 20% of the RBC units prepared by our institution were from donors with predicted antigen status. A steady supply of Yt(a-), Co(a-) and Lu(b-) RBC units was ensured.

Conclusions

Pooled capillary electrophoresis offers a suitable alternative to other methods for extended donor DNA typing. Establishing a large cohort of typed donors improved transfusion support for patients.

Multiplex Lateral Flow Assay for Rapid Visual Blood Group Genotyping

Conventional blood group phenotyping by hemagglutination assays, carried out pretransfusion, is unsuitable in certain clinical situations. Molecular typing offers an alternative method, allowing the deduction of blood group phenotype from genotype. However, current methods require a long turnaround time and are not performed on-site, limiting their application in emergency situations. Here, we report the development of a novel, rapid multiplex molecular method to identify seven alleles in three clinically relevant blood group systems (Kidd, Duffy, and MNS). Our test, using a dry-reagent allele-specific lateral flow biosensor, does not require DNA extraction and allows easy visual determination of blood group genotype. Multiplex linear-after-the-exponential (LATE)-PCR and lateral flow parameters were optimized with a total processing time of 1 h from receiving the blood sample. Our assay had a 100% concordance rate between the deduced and the standard serological phenotype in a sample from 108 blood donors, showing the accuracy of the test. Owing to its simple handling, the assay can be operated by nonskilled health-care professionals. The proposed assay offers the potential for the development of other relevant single nucleotide polymorphism (SNP) panels for immunohematology and new applications, such as for infectious diseases, in the near future.

Automated typing of red blood cell and platelet antigens: a whole-genome sequencing study

BACKGROUND

There are more than 300 known red blood cell (RBC) antigens and 33 platelet antigens that differ between individuals. Sensitisation to antigens is a serious complication that can occur in prenatal medicine and after blood transfusion, particularly for patients who require multiple transfusions. Although pre-transfusion compatibility testing largely relies on serological methods, reagents are not available for many antigens. Methods based on single-nucleotide polymorphism (SNP) arrays have been used, but typing for ABO and Rh-the most important blood groups-cannot be done with SNP typing alone. We aimed to develop a novel method based on whole-genome sequencing to identify RBC and platelet antigens.

METHODS

This whole-genome sequencing study is a subanalysis of data from patients in the whole-genome sequencing arm of the MedSeq Project randomised controlled trial (NCT01736566) with no measured patient outcomes. We created a database of molecular changes in RBC and platelet antigens and developed an automated antigen-typing algorithm based on whole-genome sequencing (bloodTyper). This algorithm was iteratively improved to address cis-trans haplotype ambiguities and homologous gene alignments. Whole-genome sequencing data from 110 MedSeq participants (30 × depth) were used to initially validate bloodTyper through comparison with conventional serology and SNP methods for typing of 38 RBC antigens in 12 blood-group systems and 22 human platelet antigens. bloodTyper was further validated with whole-genome sequencing data from 200 INTERVAL trial participants (15 × depth) with serological comparisons.

FINDINGS

We iteratively improved bloodTyper by comparing its typing results with conventional serological and SNP typing in three rounds of testing. The initial whole-genome sequencing typing algorithm was 99·5% concordant across the first 20 MedSeq genomes. Addressing discordances led to development of an improved algorithm that was 99·8% concordant for the remaining 90 MedSeq genomes. Additional modifications led to the final algorithm, which was 99·2% concordant across 200 INTERVAL genomes (or 99·9% after adjustment for the lower depth of coverage).

INTERPRETATION

By enabling more precise antigen-matching of patients with blood donors, antigen typing based on whole-genome sequencing provides a novel approach to improve transfusion outcomes with the potential to transform the practice of transfusion medicine.

FUNDING

National Human Genome Research Institute, Doris Duke Charitable Foundation, National Health Service Blood and Transplant, National Institute for Health Research, and Wellcome Trust.

Evolution of technology for molecular genotyping in blood group systems

The molecular basis of the blood group antigens was identified first in the 1980s and 1990s. Since then the importance of molecular biology in transfusion medicine has been described extensively by several investigators. Molecular genotyping of blood group antigens is one of the important aspects and is successfully making its way into transfusion medicine. Low-, medium- and high-throughput techniques have been developed for this purpose. Depending on the requirement of the centre like screening for high- or low-prevalence antigens where antisera are not available, correct typing of multiple transfused patients, screening for antigen-negative donor units to reduce the rate of alloimmunization, etc. a suitable technique can be selected. The present review discusses the evolution of different techniques to detect molecular genotypes of blood group systems and how these approaches can be used in transfusion medicine where haemagglutination is of limited value. Currently, this technology is being used in only a few blood banks in India. Hence, there is a need for understanding this technology with all its variations.

Red blood cell minor antigen mismatches during chronic transfusion therapy for sickle cell anemia

BACKGROUND

Red blood cell (RBC) alloimmunization occurs at a high frequency in sickle cell anemia (SCA) despite serologic matching for Rh (C/c, E/e) and K antigens. RBC minor antigen genotyping allows for prediction of antigens and RH variants that may lead to alloimmunization.

STUDY DESIGN AND METHODS

RBC antigen genotyping was performed on chronically transfused pediatric SCA patients, using PreciseType human erythrocyte antigen (HEA), RHCE, and RHD BeadChip arrays. All patients received C/c, E/e, and K serologically matched units (Category 1); patients with prior RBC antibodies were also matched for Fy^a , Jk^b , and any antibodies (Category 2). The RBC genotypes of all leukoreduced (LR) units transfused over a 12-month period were determined by the prototype HEA-LR BeadChip assay.

RESULTS

There were 2320 RBC units transfused to 90 patients in 1135 transfusion episodes. Thirty-five (38.9%) patients had homozygous or compound heterozygous RH variants. Seven new alloantibodies were detected, with alloantibody incidence of 0.706 in 100 units for Category 2 transfusions and 0.068 in 100 units for Category 1 (p = 0.02). Three patients on Category 2 transfusions formed new anti-Js^a and had a higher rate of exposure to Js^a than those who did not form anti-Js^a (20.4 vs. 8.33 exposures/100 units, p = 0.02). The most frequent mismatches were S (43.9%), Do^a (43.9%), Fy^a (29.2%), M (28.4%), and Jk^b (28.1%).

CONCLUSIONS

Alloimmunization incidence was higher in those with prior RBC antibodies, suggesting that past immunologic responders are at higher risk for future alloimmunization and therefore may benefit from more extensive antigen matching beyond C/c, E/e, K, Fy^a , and Jk^b .

Rapid RHD Zygosity Determination Using Digital PCR

BACKGROUND

Paternal zygosity testing is used for determining homo- or hemizygosity of RHD in pregnancies that are at a risk of hemolytic disease of the fetus and newborn. At present, this is achieved by using real-time PCR or the Rhesus box PCR, which can be difficult to interpret and unreliable, particularly for black African populations.

METHODS

DNA samples extracted from 53 blood donors were analyzed using 2 multiplex reactions for RHD-specific targets against a reference (AGO1)² to determine gene dosage by digital PCR. Results were compared with serological data, and the correct genotype for 2 discordant results was determined by long-range PCR (LR-PCR), next-generation sequencing, and conventional Sanger sequencing.

RESULTS

The results showed clear and reliable determination of RHD zygosity using digital PCR and revealed that 4 samples did not match the serologically predicted genotype. Sanger sequencing and long-range PCR followed by next-generation sequencing revealed that the correct genotypes for samples 729M and 351D, which were serologically typed as R₁R₂ (DCe/DcE), were R₂r' (DcE/dCe) for 729M and R₁r″ (DCe/dcE), R₀r^y (Dce/dCE), or R_Zr (DCE/dce) for 351D, in concordance with the digital PCR data.

CONCLUSIONS

Digital PCR provides a highly accurate method to rapidly define blood group zygosity and has clinical application in the analysis of Rh phenotyped or genotyped samples. The vast majority of current blood group genotyping platforms are not designed to define zygosity, and thus, this technique may be used to define paternal RH zygosity in pregnancies that are at a risk of hemolytic disease of the fetus and newborn and can distinguish between homo- and hemizygous RHD-positive individuals.

Red Cell Genotyping by Multiplex PCR Identifies Antigen-Matched Blood Units for Transfusion-Dependent Thai Patients

BACKGROUND

Antigen-negative red cell transfusion is required for transfusion-dependent patients. We developed multiplex PCR for red cell genotyping and calculated the possibility of finding compatible predicted phenotypes in Thai blood donor populations according to red cell alloantibodies found among Thai patients.

METHODS

600 DNA samples obtained from unrelated healthy central and northern Thai blood donors were tested with the newly developed multiplex PCR for FY*A, FY*B, JK*A, JK*B, RHCE*e, RHCE*E, DI*A and GYP*Hut, GYP*Mur, GYP*Hop, GYP*Bun, and GYP*HF allele detections. Additionally, the possibility of finding compatible predicted phenotypes in two Thai blood donor populations was calculated to estimate the minimal number of tests needed to provide compatible blood.

RESULTS

The validity of multiplex PCR using known DNA controls and the phenotyping and genotyping results obtained by serological and PCR-SSP techniques were in agreement. The possibility of finding at least one compatible blood unit for patients with multiple antibodies was comparable in Thai populations.

CONCLUSIONS

The multiplex PCR for red cell genotyping simultaneously interprets 7 alleles and 1 hybrid GP group. Similar strategies can be applied in other populations depending on alloantibody frequencies in transfusion-dependent patients, especially in a country with limited resources.

Emerging strategies of blood group genotyping for patients with hemoglobinopathies

Red cell alloimmunization is a serious problem in chronically transfused patients. A number of high-throughput DNA assays have been developed to extend or replace traditional serologic antigen typing. DNA-based typing methods may be easily automated and multiplexed, and provide reliable information on a patient. Molecular genotyping promises to become cheaper, being not dependent on serologic immunoglobulin reagents. Patients with hemoglobinopathies could benefit from receiving extended genomic typing. This could limit post transfusional complications depending on subtle antigenic differences between donors and patients. Patient/donor compatibility extended beyond the phenotype Rh/Kell may allows improved survival of transfused units of red blood cells (RBC) and lead to reduced need for blood transfusion and leading to less iron overload and reduced risk of alloimmunization. Here we discuss the advantages and limitations of current techniques, that detect only predefined genetic variants. In contrast, target enrichment next-generation sequencing (NGS) has been used to detect both known and de novo genetic polymorphisms, including single-nucleotide polymorphisms, indels (insertions/deletions), and structural variations. NGS approaches can be used to develop an extended blood group genotyping assay system.

Advances in Blood Typing

The clinical importance of blood group antigens relates to their ability to evoke immune antibodies that are capable of causing hemolysis. The most important antigens for safe transfusion are ABO and D (Rh), and typing for these antigens is routinely performed for patients awaiting transfusion, prenatal patients, and blood donors. Typing for other blood group antigens, typically of the Kell, Duffy, Kidd, and MNS blood groups, is sometimes necessary, for patients who have, or are likely to develop antibodies to these antigens. The most commonly used typing method is serological typing, based on hemagglutination reactions against specific antisera. This method is generally reliable and practical for routine use, but it has certain drawbacks. In recent years, molecular typing has emerged as an alternative or supplemental typing method. It is based on detecting the polymorphisms and mutations that control the expression of blood group antigens, and using this information to predict the probable antigen type. Molecular typing methods are useful when traditional serological typing methods cannot be used, as when a patient has been transfused and the sample is contaminated with red blood cells from the transfused blood component. Moreover, molecular typing methods can precisely identify clinically significant variant antigens that cannot be distinguished by serological typing; this capability has been exploited for the resolution of typing discrepancies and shows promise for the improved transfusion management of patients with sickle cell anemia. Despite its advantages, molecular typing has certain limitations, and it should be used in conjunction with serological methods.

Comprehensive red blood cell and platelet antigen prediction from whole genome sequencing: proof of principle

BACKGROUND

There are 346 serologically defined red blood cell (RBC) antigens and 33 serologically defined platelet (PLT) antigens, most of which have known genetic changes in 45 RBC or six PLT genes that correlate with antigen expression. Polymorphic sites associated with antigen expression in the primary literature and reference databases are annotated according to nucleotide positions in cDNA. This makes antigen prediction from next-generation sequencing data challenging, since it uses genomic coordinates.

STUDY DESIGN AND METHODS

The conventional cDNA reference sequences for all known RBC and PLT genes that correlate with antigen expression were aligned to the human reference genome. The alignments allowed conversion of conventional cDNA nucleotide positions to the corresponding genomic coordinates. RBC and PLT antigen prediction was then performed using the human reference genome and whole genome sequencing (WGS) data with serologic confirmation.

RESULTS

Some major differences and alignment issues were found when attempting to convert the conventional cDNA to human reference genome sequences for the following genes: ABO, A4GALT, RHD, RHCE, FUT3, ACKR1 (previously DARC), ACHE, FUT2, CR1, GCNT2, and RHAG. However, it was possible to create usable alignments, which facilitated the prediction of all RBC and PLT antigens with a known molecular basis from WGS data. Traditional serologic typing for 18 RBC antigens were in agreement with the WGS-based antigen predictions, providing proof of principle for this approach.

CONCLUSION

Detailed mapping of conventional cDNA annotated RBC and PLT alleles can enable accurate prediction of RBC and PLT antigens from whole genomic sequencing data.

Development and Validation of a Fully Automated Platform for Extended Blood Group Genotyping

Thirty-five blood group systems, containing >300 antigens, are listed by the International Society of Blood Transfusion. Most of these antigens result from a single nucleotide polymorphism. Blood group typing is conventionally performed by serology. However, this technique has some limitations and cannot respond to the growing demand of blood products typed for a large number of antigens. The knowledge of the molecular basis of these red blood cell systems allowed the implementation of molecular biology methods in immunohematology laboratories. Here, we describe a blood group genotyping assay based on the use of TKL immobilization support and microarray-based HIFI technology that takes approximately 4 hours and 30 minutes from whole-blood samples to results analysis. Targets amplified by multiplex PCR were hybridized on the chip, and a revelation step allowed the simultaneous identification of up to 24 blood group antigens, leading to the determination of extended genotypes. Two panels of multiplex PCR were developed: Panel 1 (KEL1/2, KEL3/4; JK1/2; FY1/2; MNS1/2, MNS3/4, FY*Fy et FY*X) and Panel 2 (YT1/2; CO1/2; DO1/2, HY+, Jo(a+); LU1/2; DI1/2). We present the results of the evaluation of our platform on a panel of 583 and 190 blood donor samples for Panel 1 and 2, respectively. Good correlations (99% to 100%) with reference were obtained.

A model for integrating molecular-based testing in transfusion services

BACKGROUND

Molecular-based laboratory tests can predict blood group antigens and supplement serological methods, adding a unique technology to assist in resolving discrepant or incomplete blood group typing or antibody identification. Hospital transfusion services have options for integrating molecular-based methods in their routine operations. We describe here the model of a hospital-reference laboratory partnership.

MATERIALS AND METHODS

Blood samples for compatibility testing were obtained from patients in a 609-bed hospital serving an urban multiethnic and multiracial population. When results of blood group phenotyping by serological methods were inconclusive, samples were referred for molecular-based testing. The reference laboratory used several methods for genotyping, including polymerase chain reaction followed by restriction enzyme-linked polymorphism analysis, sequence-specific primer polymerase chain reaction and array-based approaches. Human erythrocyte antigen, RHCE and RHD single nucleotide polymorphism arrays were integrated into the laboratory as they became commercially available.

RESULTS

The hospital-reference laboratory model made it possible to integrate blood group genotyping promptly by current technology without the expense of new laboratory equipment or adding personnel with technical expertise. We describe ten cases that illustrate the categories of serological problems that were resolved by molecular methods.

DISCUSSION

In-hospital molecular testing for transfusion services has logistical advantages, but is financially impractical for most hospitals. Our model demonstrates the advantages of a hospital-reference laboratory partnership. In conclusion, hospital transfusion services can integrate molecular-based testing in their routine services without delay by establishing a partnership with a molecular blood group reference laboratory. The hospital reference-laboratory model promotes genomic medicine without the expense of new equipment and skilled personnel, while supporting the economy of centralised large-scale laboratory operations.

Insights into RHCE Molecular Analysis in Samples with Partial D Variants: the Experience of Western France

BACKGROUND

Although systematic blood group genotyping of patients/donors is virtually possible, serological studies remain the gold standard to identify samples of clinical interest that may be further genotyped. In this context, we sought to identify variant D alleles that are likely to be clinically relevant in terms of other Rh antigens in a subset of population genotyped in Western France.

METHODS

Samples presenting with the RHD*weak D type 4.2.2 allele (n = 47) were selected for the study. RHCE exons 1-7 were directly sequenced, and expression of Rh antigens was predicted on the basis of the molecular data.

RESULTS

Of the 47 samples tested, 19 (40.4%) were predicted to be of potential clinical interest. Moreover, we could show that selecting the samples to be genotyped by the nature of their variant D allele (i.e., RHD*weak D type 4.2.2 allele) rather than by their Duffy-null status appears to increase significantly the likelihood of identifying clinically relevant individuals for Rh status.

CONCLUSION

On the basis of our findings we suggest that all individuals genotyped as weak D type 4.2.2 should be systematically screened for RHCE variants by molecular analysis on a routine basis.

Molecular identification of rare FY*Null and FY*X alleles in Caucasian thalassemic family from Sardinia

Molecular genetic studies on Duffy blood group antigens have identified mutations underlying rare FY*Null and FY*X alleles. FY*Null has a high frequency in Blacks, especially from sub-Saharan Africa, while its frequency is not defined in Caucasians. FY*X allele, associated with Fy(a-b+w) phenotype, has a frequency of 2-3.5% in Caucasian people while it is absent in Blacks. During the project of extensive blood group genotyping in patients affected by hemoglobinopathies, we identified FY*X/FY*Null and FY*A/FY*Null genotypes in a Caucasian thalassemic family from Sardinia. We speculate on the frequency of FY*X and FY*Null alleles in Caucasian and Black people; further, we focused on the association of FY*X allele with weak Fyb antigen expression on red blood cells and its identification performing high sensitivity serological typing methods or genotyping.

A simple genotyping procedure without DNA extraction to identify rare blood donors

BACKGROUND

Transfusion-induced alloimmunization has severe clinical consequences including haemolytic transfusion reactions, impaired transfused RBCs longevity and greater difficulty in finding compatible blood. Molecular analysis of genomic DNA now permits prediction of blood group phenotypes based on identification of single nucleotide polymorphisms. Implementation of molecular technologies in donor centres would be helpful in finding RBC units for special patient populations, but DNA extraction remains an obstacle to donor genotyping.

MATERIALS AND METHODS

We propose a simple method compatible with high throughput that allows blood group genotyping using a multiplex commercial kit without the need for DNA extraction. The principle relies on pre-PCR treatment of whole blood using heating/cooling procedure in association with a recombinant hotstart polymerase.

RESULTS

In a prospective analysis, we yielded 5628 alleles identification and designated 63 donors with rare blood, that is either negative for a high-frequency antigen or with a rare combination of common antigens.

CONCLUSION

The procedure was optimized for simplicity of use in genotyping platform and would allow not only to supply antigen-matched products to recipients but also to find rare phenotypes. This methodology could also be useful for establishing a donor repository for human platelet antigens (HPA)-matched platelets since the same issues are involved for patients with neonatal alloimmune thrombocytopenia or post-transfusion purpura.

Erythrocyte genotyping for transfusion-dependent patients at the Azienda Universitaria Policlinico of Naples

BACKGROUND AND OBJECTIVES

Although minor erythrocyte antigens are not considered clinically significant in sporadic transfusions, they may be relevant for multi-transfusion patients. When serological assay is not conceivable, molecular genotyping allows predicting the red blood cell phenotype, extending the typing until minor blood groups. The aim of this study was to evaluate the utility of blood group genotyping and compare the molecular typing of erythrocyte antigens with the established serological methods.

MATERIALS AND METHODS

We selected 225 blood donors and 50 transfusion-dependent patients at the Division of Immunohematology of the Second University of Naples. Blood samples were analyzed with NEO Immucor automated system and genotyped for 38 red blood cell antigens and phenotypic variants with the kit HEA BeadChip™. The comparative study was conducted for RhCE and Kell antigens whose typing is available with both methods.

RESULTS

We observed a good correlation between serological and molecular methods for donors that were concordant for 99.5% (224/225) and discordant for 0.5% (1/225). Patients resulted concordant only for 46.0% (23/50) and discordant for 54.0% (27/50); discrepancies were 46.0% (23/50) and 8.0% (4/50) for RhCE and Kell systems respectively. Through molecular genotyping we also identified polymorphisms in RhCE, Kell, Duffy, Colton, Lutheran and Scianna loci in donors and patients.

CONCLUSIONS

Blood group genotyping is particularly useful for poly-transfused patients. Molecular analysis confirms and extends serological test data and then allows us to obtain a better match. This molecular assay can be used in the future to prevent alloimmunization in transfusion-dependent patients.

Changing practice: red blood cell typing by molecular methods for patients with sickle cell disease

BACKGROUND

Extended red blood cell (RBC) antigen matching is recommended to limit alloimmunization in patients with sickle cell disease (SCD). DNA-based testing to predict blood group phenotypes has enhanced availability of antigen-negative donor units and improved typing of transfused patients, but replacement of routine serologic typing for non-ABO antigens with molecular typing for patients has not been reported.

STUDY DESIGNS AND METHODS

This study compared the historical RBC antigen phenotypes obtained by hemagglutination methods with genotype predictions in 494 patients with SCD. For discrepant results, repeat serologic testing was performed and/or investigated by gene sequencing for silent or variant alleles.

RESULTS

Seventy-one typing discrepancies were identified among 6360 antigen comparisons (1.1%). New specimens for repeat serologic testing were obtained for 66 discrepancies and retyping agreed with the genotype in 64 cases. One repeat Jk(b-) serologic phenotype, predicted Jk(b+) by genotype, was found by direct sequencing of JK to be a silenced allele, and one N typing discrepancy remains under investigation. Fifteen false-negative serologic results were associated with alleles encoding weak antigens or single-dose Fy(b) expression.

CONCLUSIONS

DNA-based RBC typing provided improved accuracy and expanded information on RBC antigens compared to hemagglutination methods, leading to its implementation as the primary method for extended RBC typing for patients with SCD at our institution.

A comparison of methods for the detection of the r'(s) haplotype

BACKGROUND

The r'(s) haplotype is found in 5% to 15% of individuals of African descent. Persons with this haplotype have a partial C antigen and weakened e and can produce anti-C or other "e-like" alloantibodies. Thus, for these chronically transfused patients, accurate detection of the r'(s) haplotype is important for selection of matched units.

STUDY DESIGN AND METHODS

African-American donors were genotyped using the human erythrocyte antigen (HEA) microarray. Samples (n = 125) identified as "possible r'(s) " were then tested by IDCORE XT and RHD and RHCE microarrays. DNA sequencing was used to resolve discordant samples. The genotyping results were compared to serologic testing using a monoclonal anti-C reagent (Clone MS24).

RESULTS

Of the 125 possible r'(s) samples identified by HEA, only 94 (75%) were confirmed by both RHD and RHCE microarrays. The IDCORE XT accurately detected 93 of 94 (99%) of the confirmed r'(s) and had no false positives. DNA sequencing of the one discordant sample revealed the presence of a compound heterozygote with RHD* DIII.4/RHCE*ceVS.02 as one haplotype and r'(s) Type 2 as the other. The 31 unconfirmed r'(s) samples carried RHCE*ceVS.03 not linked to the hybrid RHD-CE-D. This occurred most often with RHD*DIIIa (55%) or RHD*01 (19%) and rarely with DIII.4, DIII.6, DAU3, and weak D Type 14. Serologic testing with anti-C gave 100% concordance with the r'(s) samples.

CONCLUSIONS

The predominant type of r'(s) in African-Americans is Type 1, which can be detected either by a reagent anti-C containing Clone MS24 or by IDCORE XT. However, serology cannot differentiate between a normal C allele and the hybrid.

Approaches to determination of a full profile of blood group genotypes: single nucleotide variant mapping and massively parallel sequencing

The number of blood group systems, currently 35, has increased in the recent years as genetic variations defining red cell antigens continue to be discovered. At present, 44 genes and 1568 alleles have been defined as encoding antigens within the 35 blood group systems. This paper provides a brief overview of two genetic technologies: single nucleotide variant (SNV) mapping by DNA microarray and massively parallel sequencing, with respect to blood group genotyping. The most frequent genetic change associated with blood group antigens are SNVs. To predict blood group antigen phenotypes, SNV mapping which involves highly multiplexed genotyping, can be performed on commercial microarray platforms. Microarrays detect only known SNVs, therefore, to type rare or novel alleles not represented in the array, further Sanger sequencing of the region is often required to resolve genotype. An example discussed in this article is the identification of rare and novel RHD alleles in the Australian population. Massively parallel sequencing, also known as next generation sequencing, has a high-throughput capacity and maps all points of variation from a reference sequence, allowing for identification of novel SNVs. Examples of the application of this technology to resolve the genetic basis of orphan blood group antigens are presented here. Overall, the determination of a full profile of blood group SNVs, in addition to serological phenotyping, provides a basis for provision of compatible blood thus offering improved transfusion safety.

Molecular matching for Rh and K reduces red blood cell alloimmunisation in patients with myelodysplastic syndrome

BACKGROUND

Matching for Rh and K antigens has been used in an attempt to reduce antibody formation in patients receiving chronic transfusions but an extended phenotype matching including Fy(a) and Jk(a) antigens has also been recommended. The aim of this study was to identify an efficient transfusion protocol of genotype matching for patients with myelodysplastic syndrome (MDS) or chronic myelomonocytic leukaemia. We also examined a possible association of HLA class II alleles with red blood cell (RBC) alloimmunisation.

MATERIALS AND METHODS

We evaluated 43 patients with MDS undergoing transfusion therapy with and without antibody formation. We investigated antigen-matched RBC units for ABO, D, C, c, E, e, K, Fy(a), Fy(b), Jk(a), Jk(b), S, s, Do(a), Do(b) and Di(a) on the patients' samples and on the donor units serologically matched for them based on their ABO, Rh and K phenotypes and presence of antibodies. We also determined the frequencies of HLA-DRB1 alleles in the alloimmunised and non-alloimmunised patients.

RESULTS

Seventeen of the 43 patients had discrepancies or mismatches for multiple antigens between their genotype-predicted profile and the antigen profile of the units of blood serologically matched for them. We verified that 36.8% of patients had more than one RBC alloantibody and 10.5% of patients had autoantibodies. Although we were able to find a better match for the patients in our extended genotyped/phenotyped units, we verified that matching for Rh and K would be sufficient for most of the patients. We also observed an over-representation of the HLA-DRB1*13 allele in the non-alloimmunised group of patients with MDS.

DISCUSSION

In our population molecular matching for C, c, E, e, K was able to reduce RBC alloimmunisation in MDS patients. An association of HLA-DRB1*13 and protection from RBC alloimmunisation should be confirmed.

Flexible automated platform for blood group genotyping on DNA microarrays

The poor suitability of standard hemagglutination-based assay techniques for large-scale automated screening of red blood cell antigens severely limits the ability of blood banks to supply extensively phenotype-matched blood. With better understanding of the molecular basis of blood antigens, it is now possible to predict blood group phenotype by identifying single-nucleotide polymorphisms in genomic DNA. Development of DNA-typing assays for antigen screening in blood donation qualification laboratories promises to enable blood banks to provide optimally matched donations. We have designed an automated genotyping system using 96-well DNA microarrays for blood donation screening and a first panel of eight single-nucleotide polymorphisms to identify 16 alleles in four blood group systems (KEL, KIDD, DUFFY, and MNS). Our aim was to evaluate this system on 960 blood donor samples with known phenotype. Study data revealed a high concordance rate (99.92%; 95% CI, 99.77%-99.97%) between predicted and serologic phenotypes. These findings demonstrate that our assay using a simple protocol allows accurate, relatively low-cost phenotype prediction at the DNA level. This system could easily be configured with other blood group markers for identification of donors with rare blood types or blood units for IH panels or antigens from other systems.

How do we use molecular red blood cell antigen typing to supplement pretransfusion testing?

The molecular basis of many blood group antigens is known, and it provides a means for predicting the red blood cell phenotype. Molecular typing methods are useful when serologic typing cannot be performed, due to sample or reagent limitations. We discuss the implementation of a commercial molecular typing assay at our Transfusion Service, the indications for testing, and the advantages and drawbacks of the assay. We also present our algorithm for selecting candidates for testing.

Establishing an antigen-negative red blood cell inventory in a hospital-based blood bank

BACKGROUND

Our blood bank is part of a large academic institution with an active sickle cell anemia program. We provide sickle patients with blood phenotypically matched for C/c, E/e, and K antigens. Since licensed reagents are available for phenotyping C/c, E/e, and K on an automated blood analyzer, we decided to evaluate whether establishing our own inventory of blood negative for those antigens would result in cost savings and decreased turnaround time (TAT).

STUDY DESIGN AND METHODS

Antigen typing of blood units for C/c, E/e, and K was validated. From March 1, 2012, to August 31, 2012, a total of 1033 units from our own donor center and from our suppliers were phenotyped. We compared direct cost savings and TAT for blood availability with historical data before we began phenotyping.

RESULTS

Thirty-eight percent of typed antigen-negative (AG-) units were transfused to sickle patients. An additional 35% were transfused to nonsickle patients needing AG- blood. Twenty-one percent were used by patients without antibodies to prevent outdating. The remaining 6% had not yet been transfused by the end of the study period. From March 1, 2011, to August 31, 2011, we spent almost $200,000 on obtaining AG- blood. In the 6 months since we started antigen typing, we have saved approximately $110,000, the majority of which resulted from AG- blood provided to sickle patients. In addition, TAT for AG- units from our inventory significantly improved to 1 to 2 hours versus approximately 6 hours when obtained from our suppliers.

CONCLUSION

Establishing an AG- inventory in a hospital-based blood bank is cost-effective and time-efficient.

Genomic analyses of RH alleles to improve transfusion therapy in patients with sickle cell disease

BACKGROUND

Red cell (RBC) blood group alloimmunization remains a major problem in transfusion medicine. Patients with sickle cell disease (SCD) are at particularly high risk for developing alloantibodies to RBC antigens compared to other multiply transfused patient populations. Hemagglutination is the classical method used to test for blood group antigens, but depending on the typing methods and reagents used may result in discrepancies that preclude interpretation based on serologic reactivity alone. Molecular methods, including customized DNA microarrays, are increasingly used to complement serologic methods in predicting blood type. The purpose of this study was to determine the diversity and frequency of RH alleles in African Americans and to assess the performance of a DNA microarray for RH allele determination.

MATERIAL AND METHODS

Two sets of samples were tested: (i) individuals with known variant Rh types and (ii) randomly selected African American donors and patients with SCD. Standard hemagglutination tests were used to establish the Rh phenotype, and cDNA- and gDNA-based analyses (sequencing, PCR-RFLP, and customized RHD and RHCE microarrays were used to predict the genotype).

RESULTS

In a total of 829 samples (1658 alleles), 72 different alleles (40 RHD and 32 RHCE) were identified, 22 of which are novel. DNA microarrays detected all nucleotides probed, allowing for characterization of over 900 alleles.

CONCLUSIONS

High-throughput DNA testing platforms provide a means to test a relatively large number of donors and potentially prevent immunization by changing the way antigen-negative blood is provided to patients. Because of the high RH allelic diversity found in the African American population, determination of an accurate Rh phenotype often requires DNA testing, in conjunction with serologic testing. Allele-specific microarrays offer a means to perform high-throughput donor Rh typing and serve as a valuable adjunct to serologic methods to predict Rh type. Because DNA microarrays test for only a fixed panel of allelic polymorphisms and cannot determine haplotype phase, alternative methods such as Next Generation Sequencing hold the greatest potential to accurately characterize blood group phenotypes and ameliorate the clinical course of multiply-transfused patients with sickle cell disease.

Molecular approaches to transfusion medicine in Polynesians and Maori in New Zealand

In recent years, with the application of genotyping technology, there has been a substantial increase in the number of reported blood group alleles. This survey was designed to evaluate new molecular blood group genotyping methods and compile reference blood group data sets for Polynesian and Maori subjects. Subsequent analyses of these results were used to calculate probability of random match, to trace Polynesian ancestry and migration patterns and to reveal past and present episodes of genetic admixture. Genomic DNA samples from Maori and Polynesian subjects were drawn from the Victoria University of Wellington DNA Bank and genotyped using combination of commercial PCR-SSP kits, hybridization SNP assay services or sequence-based typing. This survey also involves compilation of serological ABO and Rhesus blood group data from RakaiPaaka Iwi tribal members for comparison with those generated during our molecular blood group study. We observed perfect consistency between results obtained from all molecular methods for blood group genotyping. The A, O, DCcEe, DCCee, MNs, K-k+, Jk(a+b-), Jk(a+b+), Fy(a+b-), Fy(a+b+), Di(a+b-), Co(a+b-) and Do(a-b+) were predominant blood group phenotypes in both Polynesians and Maori. Overall, our survey data show only small differences in distributions of blood group phenotypes between Polynesian and Maori groups and their subgroups. These differences might be associated with selection, population history and gene flow from Europeans. In each case, we estimate that patients with certain blood groups have a very low probability of an exact phenotypic match, even if the patients were randomly transfused with blood from donors of their own ethnicity. The best way to avoid haemolytic transfusion reaction in such cases is to perform a pretransfusion cross-match and recruit increased numbers of donors with rare phenotype profiles. The conclusion of this study is that application of molecular method covering as many known variants as possible may help to improve the accuracy blood group genotyping and potentially conserve the routine requirements of transfusion centres.

DNA biosensor/biochip for multiplex blood group genotyping

At present, 33 blood groups representing over 300 antigens are listed by the International Society of Blood Transfusion (ISBT). Most of them result from a single nucleotide polymorphism (SNP) in the corresponding DNA sequence, i.e. approx. 200 SNPs. In immunohematology laboratories, blood group determination is classically carried out by serological tests, but these have some limitations, mostly in term of multiplexing and throughput. Yet, there is a growing need of extended blood group typing to prevent alloimmunization in transfused patients and transfusion accidents. The knowledge of the molecular bases of blood groups allows the use of molecular biology methods within immunohematology laboratories. Numerous assays focused on blood group genotyping were developed and described during the last 10 years. Some of them were real biochips or biosensors while others were more characterized by the particular molecular biology techniques they used, but all were intending to produce multiplex analysis. PCR techniques are most of the time used followed by an analytical step involving a DNA biosensor, biochip or analysis system (capillary electrophoresis, mass spectrometry). According to the method used, the test can then be classified as low-, medium- or high-throughput. There are several companies which developed platforms dedicated to blood group genotyping able to analyze simultaneously various SNPs or variants associated with blood group systems. This review summarizes the characteristics of each molecular biology method and medium-/high-throughput platforms dedicated to the blood group genotyping.

Heterogeneity of alleles encoding high- and low-prevalence red blood cell antigens across Africa: useful data to facilitate transfusion in African patients

Ethnic variations in red blood cell (RBC) antigens can be a source of alloimmunization, especially in migrant populations. To improve transfusion safety in continental Africa and countries with African migrants, we performed RBC genotyping to determine allele frequencies coding for high- and low-prevalence antigens. A total of 481 blood samples were collected in ethnic groups from West, Central and East Africa. Molecular typing was performed using a polymerase chain reaction - reverse sequence specific oligonucleotide method. Results demonstrated no DI*1, DI*3, YT*2, SC*2, LW*7, KN*2 alleles in any sample and the CO*2 allele was rare. The frequency of LU*1 was comparable to that of European-Caucasians (2%) except in Biaka pygmies (8%). The frequency of CROM*-1 was high in Mbuti pygmies (13%). High frequency of KN*7 and KN*6 may reflect selection pressure in the countries investigated. Analysis of Dombrock allele patterns confirmed uneven distribution of the DO*1 and DO*2 alleles with high frequencies of DO*-4 and DO*-5 in all groups. Altogether, findings demonstrated extensive allele-frequency heterogeneity across Africa and suggested that knowledge of patient ethnicity gives information about the high-prevalence antigens that may be lacking. These data are medically useful to support transfusion care of African migrants living in countries where the majority of the population is from a different ethnical background.

Comprehensive genotyping for 18 blood group systems using a multiplex ligation-dependent probe amplification assay shows a high degree of accuracy

BACKGROUND

In recent years genotyping methods have been implemented in blood banks as alternative to comprehensive serologic typing. We evaluated a newly developed assay for convenient and comprehensive genotyping of blood group alleles based on multiplex ligation-dependent probe amplification (MLPA) technology.

STUDY DESIGN AND METHODS

We analyzed 103 random and 150 selected samples to validate the specificity of the blood-MLPA assay that is able to determine the presence, absence, and copy number of 48 blood group and 112 variant alleles of 18 blood group systems. A total of 4038 serologic typing results, including 52 different antigens, were available for these samples.

RESULTS

In 4018 (99.5%) of the 4038 serologic typing results the predicted phenotypes by the blood-MLPA were in concordance with serologic typing. Twenty discordant results were due to false-positive serologic results (n = 2), false-negative serologic results (n = 1), inability of routine serologic typing to detect variant antigens (n = 14), or false-positive prediction from the blood-MLPA due to the presence of a null allele (n = 3).

CONCLUSION

The blood-MLPA reliably predicts the presence or absence of blood group antigens, including almost all clinically relevant blood group antigens, except ABO, in patients and donors. Furthermore, it is the first assay that determines copy numbers of blood group alleles in the same test. It even provides more detailed and accurate information than serologic typing, because most variant alleles are immediately recognized. Since only standard laboratory equipment is needed, this assay finally offers the possibility to comprehensively type recipients and makes extensive matching for selected patients groups more feasible.

Identification of novel silent KEL alleles causing KEL:-5 (Ko) phenotype or discordance between KEL:1,-2 phenotype/KEL*01/02 genotype

BACKGROUND

The Kell system, encoded by the KEL gene, is one of the most clinically important blood group systems. Molecular defects may lead to the absence of Kell antigen expression. The very rare KEL:5 results from silent KEL genes, also called KELnull alleles. In a few cases, the rare KEL:1,-2 phenotype may be associated with silent KEL*02 alleles.

STUDY DESIGN AND METHODS

The aim of this study was to perform DNA investigations to identify silent KEL alleles among 10 KEL:-5 patients and 121 individuals presenting the rare KEL:1,-2 phenotype. Serologic investigations were performed on patients' red blood cells and serum. The KEL gene analysis was done by using a BeadChip assay (HEA Version, 1.2, Immucor), real-time polymerase chain reaction, and/or sequencing of all 19 exons of the KEL gene.

RESULTS

In KEL:-5 patients, two novel KELnull alleles were described: 821G>A being the second described KELnull allele on a KEL*01 backbone and 184Tdel. In the 121 KEL:1,-2 individuals, nine (7.4%) were found to display a discordant KEL:1,-2 phenotype and KEL*01/KEL*02 genotype. Three novel silent KEL*02 alleles were described: 1084C>A, 1708G>A, and IVS11+5g>a.

CONCLUSION

The number of silent KEL alleles and the notion that KEL null alleles are on a KEL*02 background may evolve in the coming years. Systematic DNA analysis showed that the number of discordant phenotype/genotype results, related to silent KEL*02 alleles was higher than expected in France. These data emphasize that clinical practice based on DNA analysis for blood group antigens requires caution and should improve the performance of the blood group phenotype prediction.

Emily Cooley lecture 2012: Emily Cooley and techniques that have been applied to characterize DO and JR blood groups

Emily Cooley was a well-respected medical technologist and morphologist with a remarkable skill set. She was highly regarded both professionally and personally. The "Emily Cooley Lectureship and Award" was established to honor her in particular and medical technologists in general. This article first reviews the history of the Emily Cooley award and provides some of the reasons why it carries her name. Then, using two blood group systems, DO and JR, it illustrates how many discoveries regarding blood groups were dependent on access to techniques.