Recommendation for validation and quality assurance of non-invasive prenatal testing for foetal blood groups and implications for IVD risk classification according to EU regulations.

BACKGROUND AND OBJECTIVES: Non-invasive assays for predicting foetal blood group status in pregnancy serve as valuable clinical tools in the management of pregnancies at risk of detrimental consequences due to blood group antigen incompatibility. To secure clinical applicability, assays for non-invasive prenatal testing of foetal blood groups need to follow strict rules for validation and quality assurance. Here, we present a multi-national position paper with specific recommendations for validation and quality assurance for such assays and discuss their risk classification according to EU regulations. MATERIALS AND METHODS: We reviewed the literature covering validation for in-vitro diagnostic (IVD) assays in general and for non-invasive foetal RHD genotyping in particular. Recommendations were based on the result of discussions between co-authors. RESULTS: In relation to Annex VIII of the In-Vitro-Diagnostic Medical Device Regulation 2017/746 of the European Parliament and the Council, assays for non-invasive prenatal testing of foetal blood groups are risk class D devices. In our opinion, screening for targeted anti-D prophylaxis for non-immunized RhD negative women should be placed under risk class C. To ensure high quality of non-invasive foetal blood group assays within and beyond the European Union, we present specific recommendations for validation and quality assurance in terms of analytical detection limit, range and linearity, precision, robustness, pre-analytics and use of controls in routine testing. With respect to immunized women, different requirements for validation and IVD risk classification are discussed. CONCLUSION: These recommendations should be followed to ensure appropriate assay performance and applicability for clinical use of both commercial and in-house assays.

International Society of Blood Transfusion Working Party on Red Cell Immunogenetics and Blood Group Terminology Report of Basel and three virtual business meetings: Update on blood group systems.

BACKGROUND AND OBJECTIVES: Under the ISBT, the Working Party (WP) for Red Cell Immunogenetics and Blood Group Terminology is charged with ratifying blood group systems, antigens and alleles. This report presents the outcomes from four WP business meetings, one located in Basel in 2019 and three held as virtual meetings during the COVID-19 pandemic in 2020 and 2021. MATERIALS AND METHODS: As in previous meetings, matters pertaining to blood group antigen nomenclature were discussed. New blood group systems and antigens were approved and named according to the serologic, genetic, biochemical and cell biological evidence presented. RESULTS: Seven new blood group systems, KANNO (defined numerically as ISBT 037), SID (038), CTL2 (039), PEL (040), MAM (041), EMM (042) and ABCC1 (043) were ratified. Two (039 and 043) were de novo discoveries, and the remainder comprised reported antigens where the causal genes were previously unknown. A further 15 blood group antigens were added to the existing blood group systems: MNS (002), RH (004), LU (005), DI (010), SC (013), GE (020), KN (022), JMH (026) and RHAG (030). CONCLUSION: The ISBT now recognizes 378 antigens, of which 345 are clustered within 43 blood group systems while 33 still have an unknown genetic basis. The ongoing discovery of new blood group systems and antigens underscores the diverse and complex biology of the red cell membrane. The WP continues to update the blood group antigen tables and the allele nomenclature tables. These can be found on the ISBT website (http://www.isbtweb.org/working-parties/red-cell-immunogenetics-and-blood-group-terminology/).

RH genotyping by nonspecific quantitative next-generation sequencing.

BACKGROUND: Conventional sequencing uses gene-specific primers to determine the location of RH variants and permits a qualitative assessment of zygosity. Whole-genome and whole-exome sequencing determine the genetic location of variants and enable a quantitative assessment of zygosity. Nonspecific sequencing uses RH-consensus primers to detect variants and sequencing-read ratios to quantify their copy number. STUDY DESIGN AND METHODS: Two hundred seventy eight samples with diverse genotypes were analyzed by next-generation sequencing with RH- consensus primers. Custom-developed data analysis software was used to detect individual variants and infer the RH genotype. The method was evaluated for its quantitative nature, its ability to discriminate similar genotypes, its accuracy to detect variants, and its accuracy to assign them to RHD or RHCE. RESULTS: As a measure of balanced amplification of RHD and RHCE sequences, observed ratio medians deviate from expected ratios by 3% or less of the ratio range. As a measure of discriminatory power, contiguous RHCE / [RHD + RHCE] ratio averages are separated by 4 or more standard deviations of the mean. Variants are detected with a sensitivity and specificity greater than 99%, and variants at consensus positions are correctly assigned to RHD vs RHCE with a sensitivity greater than 72% and a specificity greater than 99%. The method is successful in the identification of genotypes with large conversion events and in the detection of copy number variation. CONCLUSION: Nonspecific sequencing of homologous gene sets combines detection and quantification of genetic variation in a single assay. Evidence is provided for the quantitative nature of the method, its sensitivity and specificity, and its ability to identify complex RH genotypes.

Recent advances in non-invasive fetal HPA-1a typing.

Non-invasive fetal HPA-1a typing is a valuable tool to identify the pregnancies at risk of fetal and neonatal alloimmune thrombocytopenia (FNAIT). At present, prenatal determination of the fetus HPA-1a type is performed for diagnostic purposes in pregnancies of HPA-1 alloimmunized women with history of a previous fetus or child with FNAIT. Different approaches have been used to determine the fetal HPA-1a genotype from cell-free fetal DNA (cffDNA) in the mother's plasma, mainly based on real-time PCR. Due to the single nucleotide polymorphism (SNP) between the HPA-1a and HPA-1b allelic sequences, a robust and accurate detection of the fetal genotype is challenging, and the sensitivity of most assays is still limited early in pregnancy. Nowadays, the availability of technologies such as next generation sequencing (NGS) or digital PCR offers unprecedented possibilities of analyzing cell-free DNA (cfDNA)-amplified sequences with very high coverage and high sensitivity. In addition, other interesting approaches using variant sequence enrichment strategies have been recently described. In particular, coamplification at lower denaturation temperature PCR (COLD-PCR) offers a simple and sensitive strategy for noninvasive fetal HPA-1 typing. These novel approaches are explained in more detail in this review. Despite no population-based FNAIT screening programs have so far been implemented, the perspectives in terms of treatment and prevention are changing and less costly high-throughput maternal HPA-1a typing methods have been developed. Altogether, this may lead to the implementation of fetal HPA-1a typing with a broader scope in the future, playing a critical role within FNAIT screening programs.

Multicenter Study on Differential Human Neutrophil Antigen 2 Expression and Underlying Molecular Mechanisms.

BACKGROUND: The human neutrophil antigen 2 (HNA-2), which is expressed on CD177, is undetectable in 3-5% of the normal population. Exposure of these HNA-2null individuals to HNA-2-positive cells can cause immunization and pro-duction of HNA-2 antibodies, which can induce immune neutropenia and transfusion-related acute lung injury. In HNA-2-positive individuals, neutrophils are divided into a CD177pos. and a CD177neg. subpopulation. The molecular background of HNA-2 deficiency and the bimodal expression pattern, however, are not completely decoded. STUDY DESIGN: An international collaboration was conducted on the genetic analysis of HNA-2-phenotyped blood samples, including HNA-2-deficient individuals, mothers, and the respective children with neonatal immune neutropenia and regular blood donors. RESULTS: From a total of 54 HNA-2null individuals, 43 were homozygous for the CD177 *787A>T substitution. Six carried the CD177 *c.1291G>A single nucleotide polymorphism. All HNA-2-positive samples with >40% CD177pos. neutrophils carried the *787A wild-type allele, whereas a lower rate of CD177pos. neutrophils was preferentially associated with *c.787AT heterozygosity. Interestingly, only the *c.787A allele sequence was detected in complementary DNA (cDNA) sequence analysis carried out on all *c.787AT heterozygous individuals. However, cDNA analysis after sorting of CD177pos. and CD177neg. neutrophil subsets from HNA-2-positive individuals showed identical sequences, which makes regulatory elements within the promoter unlikely to affect CD177 gene transcription in different CD177 neutrophil subsets. CONCLUSION: This comprehensive study clearly demonstrates the impact of single nucleotide polymorphisms on the expression of HNA-2 on the neutrophil surface but challenges the hypothesis of regulatory epigenetic effects being implicated in the bimodal CD177 expression pattern.

Characterization of RHD locus polymorphism in D negative and D variant donors from Northwestern Argentina.

BACKGROUND: A notable RHD variability has been observed in Central Argentina's current population attributed to the intermixing of different ethnic groups. The Northwestern region of the country is characterized by a markedly Amerindian genetic contribution. In this sense, the definition of the RHD polymorphism in individuals from this area was lacking. STUDY DESIGN AND METHODS: A total of 757 donors from Northwestern Argentina, with D negative C and/or E positive (n = 526), and D variant (n = 231) phenotype defined by standard hemmaglutination tube techniques were genotyped using in-house PCR strategies, commercial SNP arrays and Sanger sequencing. RESULTS: Among D negative C and/or E positive samples, RHD null (15.40%) and DEL alleles (3.23%) were identified. One unreported SNP c.1001T>A responsible for a null allele was found. RHD*01N.75 (4.18%) and RHD*DEL43 (2.66%) were the most prevalent variants following RHD*03N.01 (8.75%). The characterization of serologic weak D phenotypes showed that RHD*weak D type 1, 2, and 3 variants were found only in 37.24% of the samples, whereas RHD*weak D type 93 was the most prevalent allele (25.11%). Also, a previously unreported missense variation c.764G>A was identified. CONCLUSIONS: A RHD genotyping strategy for patients and donors from Northwestern Argentina must consider the detection of the frequently found RHD*01N.75, RHD*DEL43, and RHD*weak D type 93 variants. Taking into account that RHD*DEL43 has scarcely been found in North Americans and Europeans whereas RHD*01N.75 and RHD*weak D type 93 have never been described in populations other than Argentineans, these RHD variants could be attributed to Native Amerindian genetic influence.

International Society of Blood Transfusion Working Party on Red Cell Immunogenetics and Blood Group Terminology: Report of the Dubai, Copenhagen and Toronto meetings.

BACKGROUND AND OBJECTIVES: The International Society of Blood Transfusion (ISBT) Working Party for Red Cell Immunogenetics and Blood Group Terminology meets in association with the ISBT congress and has met three times since the last report: at the international meetings held in Dubai, United Arab Emirates, September 2016 and Toronto, Canada, June 2018; and at a regional congress in Copenhagen, Denmark, June 2017 for an interim session. METHODS: As in previous meetings, matters pertaining to blood group antigen nomenclature and classification were discussed. New blood group antigens were approved and named according to the serologic and molecular evidence presented. RESULTS AND CONCLUSIONS: Fifteen new blood group antigens were added to eight blood group systems. One antigen was made obsolete based on additional data. Consequently, the current total of blood group antigens recognized by the ISBT is 360, of which 322 are clustered within 36 blood groups systems. The remaining 38 antigens are currently unassigned to a known system. Clinically significant blood group antigens continue to be discovered, through serology/sequencing and/or recombinant or genomic technologies.

Management and outcome of pregnancies in women with red cell isoimmunization: a 15-year observational study from a tertiary care university hospital.

BACKGROUND: The aims of this study were to determine the prevalence of the different anti-erythrocytic alloantibodies, to describe pregnancy outcomes according to a low-risk and high-risk classification for fetal anemia and to determine the factors that influence adverse perinatal outcomes. METHODS: This retrospective observational study included women referred to our center following the identification of maternal anti-erythrocytic alloantibodies between 2002 and 2017. Pregnancies were classified as high risk for fetal anemia in cases with clinically significant antibodies, no fetal-maternal compatibility and titers ≥1:16 or any titration in cases of Kell system incompatibility. In high-risk pregnancies, maternal antibody titration and the fetal middle cerebral artery peak systolic velocity (MCA-PSV) were monitored. Low-risk pregnancies underwent routine pregnancy follow-up. RESULTS: Maternal antibodies were found in 337 pregnancies, and 259 (76.9%) of these antibodies were clinically significant. The most frequent antibodies were anti-D (53%) and anti-K (19%). One hundred forty-three pregnancies were classified as low risk for fetal anemia, 65 (25%) cases were classified as no fetal-maternal incompatibility, 78 had clinically nonsignificant antibodies, 4 (2.8%) resulted in first-trimester pregnancy loss, and 139 (97.2%) resulted in livebirths. Of the 194 high-risk pregnancies, 38 had titers < 1:16 (resulting in 38 livebirths), and 156 had titers ≥1:16 or anti-K antibodies. In the last group, 6 cases miscarried before 18 weeks, 93 had a MCA-PSV < 1.5 multiples of the median (MoM), resulting in 3 perinatal deaths that were unrelated to fetal anemia, one termination and 89 livebirths; and 57 had a MCA-PSV > 1.5 MoM, resulting in 3 intrauterine deaths, 6 terminations and 48 livebirths. Ninety-two intrauterine transfusions were performed in 45 fetuses (87% anti-D). Adverse outcomes were related to a MCA-PSV > 1.5 MoM (p < 0.001), hydrops (p < 0.001) and early gestational age at first transfusion (p = 0.029) CONCLUSION: Anti-D remains the most common antibody in fetuses requiring intrauterine transfusion. A low or high-risk classification for fetal anemia based on the type of antibody, paternal phenotype and fetal antigen allows follow-up of the pregnancy accordingly, with good perinatal outcomes in the low-risk group. In the high-risk group, adverse perinatal outcomes are related to high MCA-PSV, hydrops and early gestational age at first transfusion.

Molecular structures identified in serologically D- samples of an admixed population.

BACKGROUND: The D- phenotype is mainly caused by the complete deletion of the RHD gene in Caucasians. However, a plethora of allelic variants have been described among D- individuals from different ethnic groups. STUDY DESIGN AND METHODS: A cohort of 1314 routine serologically D- samples from white Argentineans was studied by molecular methods. RESULTS: Among the 1314 D- samples, 2.1% showed RHD-specific amplifications. One hybrid Rhesus box was detected in all D-/RHD+ samples, suggesting a hemizygous status. The RHDΨ was found in 0.7% of rr samples while DEL and null variants were detected in 16.7% of the D- samples expressing C and/or E antigens. The variants associated with the C antigen were seven RHD-CE-D(s) , two RHD(1-2)-CE(2-9)-D(10), two previously unreported RHD(329T>C)-CE(3-9)-D null alleles, one RHD(M295I), and one new RHCE(1-2)-RHD(3361del11 -10) null allele whereas those associated with the E antigen were five RHD(46T>C) and one novel RHD(581insG) null allele responsible for a premature stop codon. CONCLUSIONS: The prevalence of D-/RHD+ samples is higher than that observed in Europeans. More than 50% of the RHD alleles found were represented by RHDψ and RHD-CE-D(s) showing the African contribution to the genetic pool of the admixed population analyzed. Interestingly, three new alleles were found, two of them being hybrid structures between previously described RHD variants recombined with RHCE sequences. The knowledge of the RHD allele repertoire in our population allowed the implementation of reliable typing and transfusion strategies for a better management of patients and pregnant women.

Genomic analysis of KEL*03 and KEL*04 alleles among Thai blood donors.

Background: The Kell blood group system is clinically important in transfusion medicine, particularly in patients with antibodies specific to Kell antigens. To date, genetic variations of the Kell metallo-endopeptidase (KEL) gene among Thai populations remain unknown. Objective: This study aimed to determine the frequencies of KEL*03 and KEL*04 alleles among Thai blood donors using an in-house polymerase chain reaction-sequence-specific primer (PCR-SSP) method. Methods: Blood samples obtained from 805 unrelated central Thai blood donors at a blood bank in Pathumthani, Thailand, from March 2023 to June 2023, were typed for Kpa and Kpb antigens using the column agglutination test, and the results for 400 samples were confirmed using DNA sequencing. A PCR-SSP method was developed to detect the KEL*03 and KEL*04 alleles, and genotyping results were validated using known DNA controls. DNA samples obtained from Thai donors in central (n = 2529), northern (n = 300), and southern (n = 427) Thailand were also genotyped using PCR-SSP for comparison. Results: All 805 (100%) donors had the Kp(a-b+) phenotype. The PCR-SSP genotyping results agreed with the column agglutination test and DNA sequencing. All 3256 Thai blood donors had the homozygous KEL*04/KEL*04 genotype. Frequencies of the KEL*03 and KEL*04 alleles among Thai donors differed significantly from those of Japanese, Native American, South African, Brazilian, Swiss, and German populations. Conclusion: This study found a 100% KEL*04 allele frequency in three Thai populations. These data could provide information on KEL*03 and KEL*04 allele frequencies to estimate the risk of alloimmunisation in Thai populations. What this study adds: This study demonstrates that in-house PCR-SSP can be used to determine KEL*03 and KEL*04 alleles to predict Kpa and Kpb antigens. Even though only homozygous KEL*04/KEL*04 genotypes were found among Thai donor populations, the established PCR-SSP method may be useful for estimating the risk of alloimmunisation in other populations.

Noninvasive fetal sex determination in maternal plasma: a prospective feasibility study.

PURPOSE: To prospectively validate a protocol for noninvasive fetal sex determination in maternal plasma and demonstrate its applicability to clinical practice. METHODS: Peripheral blood from 404 pregnant women undergoing prenatal invasive testing was collected from 6 to 23 weeks of gestation. Real-time PCR was performed for the SRY gene and multicopy DYS14 marker sequence located within the TSPY gene by the TaqMan minor groove binder probe assay as a first-line test. Owing to a false-positive result, amplification of repetitive motifs of the DAZ gene region was also tested as a second-line test performed in the last 232 patients enrolled in our series. A diagnostic algorithm was designed using a combination of these three markers. Fetal gender determined by noninvasive prenatal diagnosis (NIPD) was compared with that diagnosed by quantitative fluorescent PCR after invasive testing or ultrasound. RESULTS: A single false-positive result was obtained in the first 172 pregnancies. Reporting criteria were modified in the subsequent 232 pregnancies, giving an overall sensitivity and specificity of 100% (95% CI 99.8-100%) and 99.5% (95% CI 98.1-100%), respectively. Pregnancy outcome was obtained in all cases, including 221 male-bearing and 183 female-bearing pregnancies. CONCLUSION: NIPD for fetal sex determination in maternal plasma is highly accurate and clinically applicable if robust reporting criteria are applied.

Comprehensive analysis of RHD alleles in Argentineans with variant D phenotypes.

BACKGROUND: The serologic assignment of the RhD status may be hindered in patients with weak D expression. A comprehensive study of RHD alleles occurring in the mixed population of Argentina is necessary to evaluate the most suitable DNA typing strategy. STUDY DESIGN AND METHODS: A total of 18,379 patients from two stratified groups, Group 1 (G1; public hospital) and Group 2 (G2; private laboratory), were RhD phenotyped, and 88 samples with reduced D expression underwent molecular characterization. RESULTS: The frequencies of D+, D-, and variant D phenotypes differed significantly (p < 0.001) between G1 and G2 (94.49% vs. 87.66%, 5.15% vs. 11.58%, and 0.36% vs. 0.75%, respectively). Eleven alleles were responsible for the weak D expression. Approximately 60% of the variant D phenotypes from G1 and G2 were weak D Types 1 through 4.0/4.2 and 25% were DVII. RHD alleles associated with African ancestry were encountered in G1. A new -282G>A mutation within the promoter region of DAU-4 and DOL alleles was identified. Three weak D Type 1 samples on R(0) haplotypes were found in G1. CONCLUSIONS: The D phenotype distribution in G2 resembles that in Europeans while the frequencies in G1 account for the Amerindian and African genetic contribution. The genotyping strategy described here is suitable to study D variants in the overall population and could allow a better use of the few available D- units and a rational administration of anti-D immunoprophylaxis. The results also show that weak D Type 1 alleles do not exclusively segregate with a Ce allele, as assumed until present.

ABO gene editing for the conversion of blood type A to universal type O in Rhnull donor-derived human-induced pluripotent stem cells.

The limited availability of red cells with extremely rare blood group phenotypes is one of the global challenges in transfusion medicine that has prompted the search for alternative self-renewable pluripotent cell sources for the in vitro generation of red cells with rare blood group types. One such phenotype is the Rhnull , which lacks all the Rh antigens on the red cell membrane and represents one of the rarest blood types in the world with only a few active blood donors available worldwide. Rhnull red cells are critical for the transfusion of immunized patients carrying the same phenotype, besides its utility in the diagnosis of Rh alloimmunization when a high-prevalence Rh specificity is suspected in a patient or a pregnant woman. In both scenarios, the potential use of human-induced pluripotent stem cell (hiPSC)-derived Rhnull red cells is also dependent on ABO compatibility. Here, we present a CRISPR/Cas9-mediated ABO gene edition strategy for the conversion of blood type A to universal type O, which we have applied to an Rhnull donor-derived hiPSC line, originally carrying blood group A. This work provides a paradigmatic example of an approach potentially applicable to other hiPSC lines derived from rare blood donors not carrying blood type O.

Postnatal treatment for children with fetal and neonatal alloimmune thrombocytopenia: a multicentre, retrospective, cohort study.

BACKGROUND: Children affected by fetal and neonatal alloimmune thrombocytopenia (FNAIT) are at risk of severe intracranial haemorrhage. Management in the postnatal period is based on sparse evidence. We aimed to describe the contemporary management and outcomes of patients with FNAIT in high-income countries. METHODS: In this multicentre, retrospective, cohort study, we set up a web-based registry for the collection of deidentified data on the management and course of neonates with FNAIT. Eight centres from seven countries (Australia, Norway, Slovenia, Spain, Sweden, the Netherlands, and the USA) participated. Eligibility criteria comprised neonates with FNAIT being liveborn between Jan 1, 2010, and Jan 1, 2020; anti-human platelet antigen (HPA) alloantibodies in maternal serum; confirmed maternal and fetal HPA incompatibility; and bleeding detected at antenatal ultrasound, neonatal thrombocytopenia (<150 × 109 platelets per L), or both in the current or previous pregnancy. Clinical data were retrieved from local medical records of the first neonatal admission and entered in the registry. The key outcome was the type of postnatal treatment given to neonates with FNAIT. Other outcomes were daily median platelet counts in the first week of life, median platelet count increment after first unmatched versus first matched transfusions, and the proportion of neonates with mild or severe bleeding. FINDINGS: 408 liveborn neonates with FNAIT were entered into the FNAIT registry, of whom 389 from Australia (n=74), Norway (n=56), Slovenia (n=19), Spain (n=55), Sweden (n=31), the Netherlands (n=138), and the USA (n=16) were included in our analyses. The median follow-up was 5 days (IQR 2-9). More neonates were male (241 [64%] of 379) than female (138 [36%]). Severe thrombocytopenia (platelet count <50 × 109 platelets per L) was reported in 283 (74%) of 380 neonates, and extreme thrombocytopenia (<10 × 109 platelets per L) was reported in 92 (24%) neonates. Postnatal platelet count nadir was higher in the no-treatment group than in all other groups. 163 (42%) of 389 neonates with FNAIT received no postnatal treatment. 207 (53%) neonates received platelet transfusions, which were either HPA-unmatched (88 [43%] of 207), HPA-matched (84 [41%]), or a combination of both (35 [17%]). The proportion of neonates who received HPA-matched platelet transfusions varied between countries, ranging from 0% (Slovenia) to 63% (35 of 56 neonates; Norway). Postnatal intravenous immunoglobulin treatment was given to 110 (28%) of 389 neonates (alone [n=19] or in combination with platelet transfusions [n=91]), with the proportion receiving it ranging from 12% (17 of 138 neonates; the Netherlands) to 63% (ten of 16 neonates; the USA) across countries. The median platelet increment was 59 × 109 platelets per L (IQR 35-94) after HPA-unmatched platelet transfusions and 98 × 109 platelets per L (67-134) after HPA-matched platelet transfusions (p<0·0001). Severe bleeding was diagnosed in 23 (6%) of 389 liveborn neonates, with one having a severe pulmonary haemorrhage and 22 having severe intracranial haemorrhages. Mild bleeding was diagnosed in 186 (48%) neonates. INTERPRETATION: Postnatal management of FNAIT varies greatly between international centres, highlighting the absence of consensus on optimal treatments. Our data suggest that HPA-matched transfusions lead to a larger median platelet count increment than HPA-unmatched transfusions, but whether HPA matching is also associated with a reduced risk of bleeding remains unknown. FUNDING: Sanquin.

Beyond chimerism analysis: methods for tracking a new generation of cell-based medicines.

The analysis of chimerism is crucial to determine the status of patients receiving hematopoietic stem cell transplantation. The variety of relevant techniques available today range from those that analyse nucleic acids (i.e. polymerase chain reaction based, next generation sequencing) and cellular phenotype (i.e. flow cytometry) to sophisticated imaging (particularly multimodal imaging using labelling agents). However, current developments of advanced therapies bring chimerism studies into a new dimension in which methods for detection of donor cells in the patient need to adapt to a wider range of cell- and gene-based medicines, routes of administration, target organs and pathologies. Herein we describe and analyze the toolkit of suitable labelling and detection methodologies with actual examples along with a discussion on challenges ahead and potential solutions. Remarkably, existing methods commonly used in chimerism analysis are suitable for use with new cell- and gene-based medicines. Indeed, new developments may facilitate the evolution and combination of such methodologies to the use of non-invasive and highly informative approaches.

Establishment of the first platelet-donor registry in Argentina.

BACKGROUND: Platelet transfusions are necessary to prevent and treat haemorrhages in thrombocytopenic patients or those with severe platelet dysfunction. In Latin American countries, including Argentina, blood supplies from voluntary non-remunerated blood donors remain dependent on family replacement donors, since altruistic repeat donors are exceptional and platelet donors are very scarce. The aim of this study was to recruit a group of frequent, voluntary, altruistic blood donors and determine their human platelet antigen (HPA)-genotype in order to establish the first registry of HPA-typed voluntary platelet donors in Argentina. MATERIAL AND METHODS: In this study, we invited and recruited voluntary blood donors who attended the Fundación Banco Central de Sangre between July 2016 and July 2017. DNA was extracted from K2EDTA anticoagulated whole blood and genotyping was performed by polymerase chain reaction, using sequence-specific primers to type the HPA-1 to -6, -9 and -15 systems. A subset of samples was also tested using a commercial HPA-TYPE kit. Donors were invited to join the National Register of Haematopoietic Stem Cell Donors of Argentina. RESULTS: A cohort of 500 platelet donors was recruited and characterised and a database with their personal information, including their genotype for the most relevant HPA alloantigens, was created. Eight of the 500 donors (1.6%) were HPA-1a negative. HPA allelic variants -4b, -6b and -9b were detected for the first time in our population. There was 100% concordance between our in-house assay and the commercial kits in the subset of 150 donor samples assayed in parallel. DISCUSSION: The efforts made to recruit, characterise and register voluntary platelet donors will provide the first sustainable source of HPA and human leukocyte antigen-typed platelets for compatible transfusions in the country. Remarkably, we identified a higher percentage of HPA-1a-negative donors than previously detected in the Argentinean population.

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.

Stabilization of Transfected Cells Expressing Low-Incidence Blood Group Antigens: Novel Methods Facilitating Their Use as Reagent-Cells.

BACKGROUND: The identification of erythrocyte antibodies in the serum of patients rely on panels of human red blood cells (RBCs), which coexpress many antigens and are not easily available for low-incidence blood group phenotypes. These problems have been addressed by generating cell lines expressing unique blood group antigens, which may be used as an alternative to human RBCs. However, the use of cell lines implies several drawbacks, like the requirement of cell culture facilities and the high cost of cryopreservation. The application of cell stabilization methods could facilitate their use as reagent cells in clinical laboratories. METHODS: We generated stably-transfected cells expressing low-incidence blood group antigens (Dia and Lua). High-expresser clones were used to assess the effect of TransFix® treatment and lyophilization as cell preservation methods. Cells were kept at 4°C and cell morphology, membrane permeability and antigenic properties were evaluated at several time-points after treatment. RESULTS: TransFix® addition to cell suspensions allows cell stabilization and proper antigen detection for at least 120 days, despite an increase in membrane permeability and a reduction in antigen expression levels. Lyophilized cells showed minor morphological changes and antigen expression levels were rather conserved at days 1, 15 and 120, indicating a high stability of the freeze-dried product. These stabilized cells have been proved to react specifically with human sera containing alloantibodies. CONCLUSIONS: Both stabilization methods allow long-term preservation of the transfected cells antigenic properties and may facilitate their distribution and use as reagent-cells expressing low-incidence antigens, overcoming the limited availability of such rare RBCs.