Large scale blood group genotyping

DEL in China: the D antigen among serologic RhD-negative individuals

BACKGROUND

Providing RhD-negative red cell transfusions is a challenge in East Asia, represented by China, Korea, and Japan, where the frequency of RhD-negative is the lowest in the world.

FINDINGS

Among 56 ethnic groups in China, the RhD-negative frequency in Han, the prevalent ethnicity, is 0.5% or less, similar to most other ethnic groups. The Uyghur ethnic group has the highest reported RhD-negative frequency of up to 4.7%, as compared to 13.9% in the US. However, an estimated 7.15 million RhD-negative people live in China. The RhD-negative phenotype typically results from a loss of the entire RHD gene, causing the lack of the RhD protein and D antigen. The DEL phenotype carries a low amount of the D antigen and types as RhD-negative in routine serology. The DEL prevalence in RhD-negative individuals averages 23.3% in the Han, 17% in the Hui and 2.4% in the Uyghur ethnicities. The Asian type DEL, also known as RHD*DEL1 and RHD:c.1227G > A allele, is by far the most prevalent among the 13 DEL alleles observed in China.

CONCLUSION

The purpose of this review is to summarize the data on DEL and to provide a basis for practical strategy decisions in managing patients and donors with DEL alleles in East Asia using molecular assays.

Optimizing exchange transfusion for patients with severe Babesia divergens babesiosis: Therapeutically-Rational Exchange (T-REX) of M antigen-negative and/or S antigen-negative red blood cells should be evaluated now

Babesia divergens is an intraerythrocytic parasite, which is the major cause of babesiosis in Europe. For years, clinicians have been publishing stunning case reports that describe how some - but not all - conventional red blood cell (RBC) exchange transfusions have saved the lives of severely ill babesiosis patients. Due to markedly different patient outcomes, clinicians agree that new treatments and additional studies are needed. Here we argue that we should evaluate "therapeutically-rational exchange" (T-REX) in which the RBCs used to replace Babesia-parasitized RBCs are special disease-resistant RBC genetic variants (instead of the nondescript, "standard issue" RBCs used in conventional exchanges). T-REX seems prudent because with conventional exchange only some units of "standard issue" RBCs may be disease-resistant, while other units may not protect or may even promote disease. The random selection of RBCs for conventional RBC exchange may explain why clinical outcomes can vary dramatically. Fortunately, researchers have found that M antigen-negative (M-) and S antigen-negative (S-) RBCs resist invasion by B. divergens. Thus, we recommend evaluating T-REX of RBC variants that are B. divergens invasion-resistant: RBCs that are (1) M-, (2) S-, or (3) both M- and S-. By using only Babesia-resistant RBCs, T-REX eliminates the risk of unintentionally infusing Babesia-susceptible RBCs that might increase the severity of babesiosis. Because the T-REX variation of the conventional RBC exchange procedure is feasible, safe, and biologically plausible, we feel T-REX of Babesia-resistant RBCs should now be evaluated.

Extended blood group molecular typing and next-generation sequencing

Several high-throughput multiplex blood group molecular typing platforms have been developed to predict blood group antigen phenotypes. These molecular systems support extended donor/patient matching by detecting commonly encountered blood group polymorphisms as well as rare alleles that determine the expression of blood group antigens. Extended molecular typing of a large number of blood donors by high-throughput platforms can increase the likelihood of identifying donor red blood cells that match those of recipients. This is especially important in the management of multiply-transfused patients who may have developed several alloantibodies. Nevertheless, current molecular techniques have limitations. For example, they detect only predefined genetic variants. In contrast, target enrichment next-generation sequencing (NGS) is an emerging technology that provides comprehensive sequence information, focusing on specified genomic regions. Target enrichment NGS is able to assess genetic variations that cannot be achieved by traditional Sanger sequencing or other genotyping platforms. Target enrichment NGS has been used to detect both known and de novo genetic polymorphisms, including single-nucleotide polymorphisms, indels (insertions/deletions), and structural variations. This review discusses the methodology, advantages, and limitations of the current blood group genotyping techniques and describes various target enrichment NGS approaches that can be used to develop an extended blood group genotyping assay system.

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.

Human platelet antigens - 2013

To date, 33 human platelet alloantigens (HPAs) have been identified on six functionally important platelet glycoprotein (GP) complexes and have been implicated in alloimmune platelet disorders including foetal and neonatal alloimmune thrombocytopenia (FNAIT), posttransfusion purpura (PTP) and multitransfusion platelet refractoriness (MPR). The greatest number of recognized HPA (20 of 33) resides on the GPIIb/IIIa complex, which serves as the receptor for ligands important in mediating haemostasis and inflammation. These include HPA-1a, the most commonly implicated HPA in FNAIT and PTP in Caucasian populations. Other platelet GP complexes, GPIb/V/IX, GPIa/IIa and CD109, express the remaining 13 HPAs. Of the recognized HPAs, 12 occur as six serologically and genetically defined biallelic 'systems' where the -a form designates the higher frequency allele and the -b form, the lower. Twenty-one other HPAs are low-frequency or rare antigens for which postulated higher frequency -a alleles have not yet been identified as antibody specificities. In addition to the HPA markers, platelets also express ABO and human leucocyte antigen (HLA) antigens; antibodies directed at the former are occasionally important in FNAIT, and to the latter, in MPR.

Human platelet antigens frequencies in Maori and Polynesian populations

BACKGROUND

Allele frequencies of human platelet antigens (HPA) reflect population history and possibility of platelet-specific alloimmunization. Here, we report on screening of variants at HPA loci for Polynesian and Maori subjects.

OBJECTIVES

Our aims are to evaluate new HPA genotyping methods, compile and analyse new HPA datasets for these subjects, use HPA data for tracing ancestry, migration patterns, genetic admixture and its potential influence on health.

MATERIALS AND METHODS

A total of 75 Maori and 25 Polynesian DNA samples were genotyped using commercial BAGene HPA-TYPE DNA-SSP kits, BLOODchip hybridization SNP assays and DNA sequence based typing.

RESULTS

Genotyping was successful and cross validation of PCR-SSP and BLOODchip gave 100% agreement. Among the HPA loci tested, only six are dimorphic (HPA-1 to -3, -5, -6 and -15) and all others are monomorphic. The Polynesians and Maori have the 'a' allele form as the most common for all loci except HPA-15.

CONCLUSIONS

The newly observed HPA data as well as principal coordinate analysis clearly indicate genetic contributions from both, Asia and Australasia in Maori and Polynesian populations together with recent admixture with Europeans. In addition, different prevalences of HPA alleles among Polynesian, Maori and European populations contribute towards different risk profiles for platelet-specific alloimmunization. This is the first report for these populations and our findings are of direct practical relevance for blood transfusion centres, the management of pregnancies, assessment of neonatal alloimmune thrombocytopenia and management of multi-transfused patients.

Detection of blood-transmissible agents: can screening be miniaturized?

Transfusion safety relating to blood-transmissible agents is a major public health concern, particularly when faced with the continuing emergence of new infectious agents. These include new viruses appearing alongside other known reemerging viruses (West Nile virus, Chikungunya) as well as new strains of bacteria and parasites (Plasmodium falciparum, Trypanosoma cruzi) and finally pathologic prion protein (variant Creutzfeldt-Jakob disease). Genomic mutations of known viruses (hepatitis B virus, hepatitis C virus, human immunodeficiency virus) can also be at the origin of variants susceptible to escaping detection by diagnostic tests. New technologies that would allow the simultaneous detection of several blood-transmissible agents are now needed for the development and improvement of screening strategies. DNA microarrays have been developed for use in immunohematology laboratories for blood group genotyping. Their application in the detection of infectious agents, however, has been hindered by additional technological hurdles. For instance, the variability among and within genomes of interest complicate target amplification and multiplex analysis. Advances in biosensor technologies based on alternative detection strategies have offered new perspectives on pathogen detection; however, whether they are adaptable to diagnostic applications testing biologic fluids is under debate. Elsewhere, current nanotechnologies now offer new tools to improve the sample preparation, target capture, and detection steps. Second-generation devices combining micro- and nanotechnologies have brought us one step closer to the potential development of innovative and multiplexed approaches applicable to the screening of blood for transmissible agents.

High-throughput red blood cell antigen genotyping using a nanofluidic real-time polymerase chain reaction platform

BACKGROUND

Serologic testing of donors to obtain antigen-negative blood for transfusion is limited by availability and quality of reagents. Where sequence variant information is available, molecular typing platforms can be used to determine the presence of a variant allele and offer a high-throughput format correlated to the blood group antigen. We have investigated a flexible high-throughput platform to screen blood donors for antigen genotypes in the African American population.

STUDY DESIGN AND METHODS

Genomic DNA from 427 African American donors was analyzed for single-nucleotide polymorphisms responsible for red blood cell (RBC) antigens E/e, Fy(a)/Fy(b), Fy gene promoter, Jk(a)/Jk(b), Lu(a)/Lu(b), K/k, Js(a)/Js(b), Do(a)/Do(b), Jo(a), and Hy using primer/probe sets (Taqman, Applied Biosystems) on a high-throughput genotyping platform (OpenArray, BioTrove). Where available, the phenotype obtained by serologic testing was compared to genotype data.

RESULTS

Serologic antigen types were available for 2037 of the 4270 genotypes generated. There were five discordant results. Three resolved with repeat serologic typing, one resolved after repeat genotyping, and one discordance was clarified by confirmation of the BioTrove genotype by Sanger sequencing. Triplicate determinations were made for each sample genotype and the results were identical more than 99% of the time.

CONCLUSIONS

The nanofluidic genotyping platform described here provides an accurate method for predicting blood group phenotypes. The user-specified array layout provides flexibility of target selection and number of replicate determinations and is suitable for screening antigen types.

Blood donation and blood transfusion: special considerations for African Americans

Unique issues in blood donation and blood transfusion regarding African Americans (AA) in the United States span the donation process, manufacturing of products, and hospital transfusion service. As AAs become a growing population, a constant supply of blood donated by AAs is necessary to support this growth. Nationally, AAs are underrepresented in blood collection, which may be secondary to AAs having higher rates of anemia and other deferrable conditions or unique motivators as well as other barriers to blood donation. When investigating blood transfusion practices, blood utilization for different races and ethnicities is unknown. AAs may receive more red blood cell (RBC) transfusions because they have a higher proportion of diseases that require transfusion. Patients with sickle cell disease are at increased risk of RBC alloimmunization likely due to the predominance of RBC units from white donors in the existing blood supply, but it is not known if all AA recipients experience increased alloimmunization rates compared with whites. In conclusion, there is a need to increase donation by AAs, which can only be achieved by conducting studies to understand racial differences in donor recruitment and to better understand blood utilization and adverse events as a factor of race and ethnicity.

Blood group genotyping: from patient to high-throughput donor screening

Blood group antigens, present on the cell membrane of red blood cells and platelets, can be defined either serologically or predicted based on the genotypes of genes encoding for blood group antigens. At present, the molecular basis of many antigens of the 30 blood group systems and 17 human platelet antigens is known. In many laboratories, blood group genotyping assays are routinely used for diagnostics in cases where patient red cells cannot be used for serological typing due to the presence of auto-antibodies or after recent transfusions. In addition, DNA genotyping is used to support (un)-expected serological findings. Fetal genotyping is routinely performed when there is a risk of alloimmune-mediated red cell or platelet destruction. In case of patient blood group antigen typing, it is important that a genotyping result is quickly available to support the selection of donor blood, and high-throughput of the genotyping method is not a prerequisite. In addition, genotyping of blood donors will be extremely useful to obtain donor blood with rare phenotypes, for example lacking a high-frequency antigen, and to obtain a fully typed donor database to be used for a better matching between recipient and donor to prevent adverse transfusion reactions. Serological typing of large cohorts of donors is a labour-intensive and expensive exercise and hampered by the lack of sufficient amounts of approved typing reagents for all blood group systems of interest. Currently, high-throughput genotyping based on DNA micro-arrays is a very feasible method to obtain a large pool of well-typed blood donors. Several systems for high-throughput blood group genotyping are developed and will be discussed in this review.

The Bloodgen Project of the European Union, 2003-2009

The Bloodgen project was funded by the European Commission between 2003 and 2006, and involved academic blood centres, universities, and Progenika Biopharma S.A., a commercial supplier of genotyping platforms that incorporate glass arrays. The project has led to the development of a commercially available product, BLOODchip, that can be used to comprehensively genotype an individual for all clinically significant blood groups. The intention of making this system available is that blood services and perhaps even hospital blood banks would be able to obtain extended information concerning the blood group of routine blood donors and vulnerable patient groups. This may be of significant use in the current management of multi-transfused patients who become alloimmunised due to incomplete matching of blood groups. In the future it can be envisaged that better matching of donor-patient blood could be achieved by comprehensive genotyping of every blood donor, especially regular ones. This situation could even be extended to genotyping every individual at birth, which may prove to have significant long-term health economic benefits as it may be coupled with detection of inborn errors of metabolism.

Molecular Diagnostics in Transfusion Medicine: In Capillary, on a Chip, in Silico, or in Flight?

Serology, defined as antibody-based diagnostics, has been regarded as the diagnostic gold standard in transfusion medicine. Nowadays however the impact of molecular diagnostics in transfusion medicine is rapidly growing. Molecular diagnostics can improve tissue typing (HLA typing), increase safety of blood products (NAT testing of infectious diseases), and enable blood group typing in difficult situations (after transfusion of blood products or prenatal non-invasive RhD typing). Most of the molecular testing involves the determination of the presence of single nucleotide polymorphisms (SNPs). Antigens (e.g. blood group antigens) mostly result from single nucleotide differences in critical positions. However, most blood group systems cannot be determined by looking at a single SNP. To identify members of a blood group system a number of critical SNPs have to be taken into account. The platforms which are currently used to perform molecular diagnostics are mostly gel-based, requiring time-consuming multiple manual steps. To implement molecular methods in transfusion medicine in the future the development of higher-throughput SNP genotyping non-gel-based platforms which allow a rapid, cost-effective screening are essential. Because of its potential for automation, high throughput and cost effectiveness the special focus of this paper is a relative new technique: SNP genotyping by MALDI-TOF MS analysis.

[Genotyping applied to platelet immunology: when? How? Limits]

Platelet alloantigens named Human Platelet Antigens (HPA) are involved in immune conflicts such as post-transfusion purpura, platelet transfusion refractoriness and neonatal alloimmune thrombocytopenia. Biological diagnosis relies on: (1) detection of alloantibodies; (2) identification of the alloantigen involved in the immune conflict. Since the development of methods based on molecular biology, platelet genotyping is preferred to phenotyping. Today, most of the Platelet Immunology Units use PCR-RFLP or PCR-SSP, and few use real-time PCR. An increasing amount of commercial kits based on new technologies is now available, for example microarrays, fluorescent or coloured microbeads, or a combination of both technologies. However, an increasing number of polymorphisms have been discovered that are responsible for erroneous platelet genotypings. Consequently, it would be of interest to develop alternative technologies based on antigen/antibody interaction instead of DNA.

DNA array analysis for red blood cell antigens facilitates the transfusion support with antigen-matched blood in patients with sickle cell disease

BACKGROUND

Blood samples from patients with sickle cell disease (SCD) present to transfusion service with numerous antibodies, making the searching for compatible red blood cells (RBC) a challenge. To overcome this problem we developed an effective strategy to meet needs of supplying RBC-compatible units to SCD patients using DNA arrays.

METHODS

We selected DNA samples from 144 SCD patients with multiple (receiving > 5 units) transfusions previously phenotyped for ABO, Rh(D, C, c, E, e), K1, Fy(a) and Jk(a). We also selected DNA samples from 948 Brazilian blood donors whose ABO/RhD phenotype matched that of the patients. All samples were analysed by DNA array analysis (HEA Beadchip(TM), Bioarray Solutions) to determine polymorphisms associated with antigen expression for 11 blood group systems (Rh, Kell, Kidd, Duffy, MNS, Dombrock, Lutheran, Landsteiner-Wiener, Diego, Colton, Scianna); and one mutation associated with haemoglobinopathies.

RESULTS

Based on genotype results we were able to predict phenotype-compatible donors needed in order to provide compatible units to this group of patients. Based on their ABO/Rh phenotype we were able to find in this pool of donors compatible units for 134 SCD patients.

CONCLUSION

Blood group genotyping by DNA array contributes to the management of transfusions in SCD patients by facilitating the transfusion support with antigen-matched blood. It has the potential to improve the life of thousands of SCD-transfused patients by reducing mortality due to transfusion reactions and immunization.

ABO, D blood typing and subtyping using plug-based microfluidics

A plug-based microfluidic approach was used to perform multiple agglutination assays in parallel without cross-contamination and using only microliter volumes of blood. To perform agglutination assays on-chip, a microfluidic device was designed to combine aqueous streams of antibody, buffer, and red blood cells (RBCs) to form droplets 30-40 nL in volume surrounded by a fluorinated carrier fluid. Using this approach, proof-of-concept ABO and D (Rh) blood typing and group A subtyping were successfully performed by screening against multiple antigens without cross-contamination. On-chip subtyping distinguished common A1 and A2 RBCs by using a lectin-based dilution assay. This flexible platform was extended to differentiate rare, weakly agglutinating RBCs of A subtypes by analyzing agglutination avidity as a function of shear rate. Quantitative analysis of changes in contrast within plugs revealed subtleties in agglutination kinetics and enabled characterization of agglutination of rare blood subtypes. Finally, this platform was used to detect bacteria, demonstrating the potential usefulness of this assay in detecting sepsis and the potential for applications in agglutination-based viral detection. The speed, control, and minimal sample consumption provided by this technology present an advance for point of care applications, blood typing of newborns, and general blood assays in small model organisms.

New technologies to replace current blood typing reagents

PURPOSE OF REVIEW

This review summarizes recent developments in blood grouping and compatibility testing in transfusion medicine.

RECENT FINDINGS

Identification of the molecular characteristics of the major human blood groups has provided an opportunity to develop methods for blood group phenotyping using DNA-based technology. Various studies have demonstrated the feasibility of such an approach and have demonstrated the potential to change current procedures for identifying compatible blood, both in routine settings and in highly immunized patients, for whom compatible blood is difficult to obtain. In the obstetric setting, isolation of cell-free DNA from maternal plasma for fetal blood grouping provides a minimally invasive method for determining the risk for haemolytic disease in the newborn. Recombinant technology for synthesizing blood group proteins, although in its infancy, has the potential to change longstanding antibody identification procedures.

SUMMARY

The molecular revolution occurring throughout medicine is broadly manifest in all areas of transfusion medicine and should contribute to transfusion safety.