The molecular genetics of blood group polymorphism

Analysis of macular thickness and peripapillary retinal nerve fiber layer thickness in various ABO and Rh blood groups

PURPOSE

To determine the association between ABO and Rh blood groups with retinal structural indices including macular thickness and peripapillary retinal nerve fiber layer (RNFL) thickness.

METHODS

This cross-sectional study was conducted using convenience sampling in a tertiary referral eye hospital in Tehran, Iran. Study participants were referred to the hospital laboratory to test their blood group. Ocular examinations were performed including measurement of visual acuity, auto-refraction, subjective refraction, and slit-lamp biomicroscopy. Retinal imaging was carried out using Spectral-domain OCT under dilated papillary conditions.

RESULTS

Three hundred and twenty-eight individuals were recruited in this study. Of these, 219 (60.7%) were female and the mean age of the participants was 63.29 ± 5.57 years (range: 56 to 83 years). According to the multiple linear regression model, the global peripapillary RNFL thickness [coefficient: -3.05 (95% CI: -5.30 to -0.74); P = 0.010] and peripapillary RNFL thickness in the superior [coefficient: -4.65 (95% CI: -8.40 to -0.89), P < 0.001] and inferior [coefficient: -4.00 (95% CI: -7.81 to -0.19); P = 0.040] quadrants were significantly thinner in individuals with blood type B compared to those with other ABO blood groups. The average [coefficient: 12.69 (95% CI: 4.12-21.64); P = 0.004) and central [coefficient: 16.21 (95%: 6.44-25.97); P = 0.001) macular thicknesses were significantly thicker in AB group compared to other blood groups. The average macular thickness was significantly thinner in Rh + compared to the Rh- group [coefficient: -8.33 (95% CI: -15.4 to -1.25); P = 0.021].

CONCLUSION

Retinal structural indices may be related to blood groups implying a genetic linkage. Considering the lack of consistency among various studies, larger trials are needed to explore the effect of ABO and Rh grouping on peripapillary RNFL and macular thicknesses.

Characterization of Blood Group Variants in an Omani Population by Comparison of Whole Genome Sequencing and Serology

Although blood group variation was first described over a century ago, our understanding of the genetic variation affecting antigenic expression on the red blood cell surface in many populations is lacking. This deficit limits the ability to accurately type patients, especially as serological testing is not available for all described blood groups, and targeted genotyping panels may lack rare or population-specific variants. Here, we perform serological assays across 24 antigens and whole genome sequencing on 100 Omanis, a population underrepresented in genomic databases. We inferred blood group phenotypes using the most commonly typed genetic variants. The comparison of serological to inferred phenotypes resulted in an average concordance of 96.9%. Among the 22 discordances, we identify seven known variants in four blood groups that, to our knowledge, have not been previously reported in Omanis. Incorporating these variants for phenotype inference, concordance increases to 98.8%. Additionally, we describe five candidate variants in the Lewis, Lutheran, MNS, and P1 blood groups that may affect antigenic expression, although further functional confirmation is required. Notably, we identify several blood group alleles most common in African populations, likely introduced to Oman by gene flow over the last thousand years. These findings highlight the need to evaluate individual populations and their population history when considering variants to include in genotype panels for blood group typing. This research will inform future work in blood banks and transfusion services.

Incidence and risk factors for secondary graft failure in uniformly treated patients with severe aplastic anemia receiving fludarabine and cyclophosphamide for conditioning and matched sibling bone marrow graft as stem cell source

BACKGROUND AIMS

Graft failure after allogeneic transplant for aplastic anemia is problematic. The risk of graft failure depends on multiple variables, including the preparative regimen, donor type, stem cell dose and source among other variables.

METHODS

We performed a retrospective analysis of patients with aplastic anemia who underwent matched-sibling allogeneic transplant at a single center.

RESULTS

We identified 82 patients who fit the inclusion criteria. One had primary graft failure and was excluded from this analysis. The recipient median age was 22 years. The donor median age was 23 years. The median time from diagnosis to transplant was 1.6 months. The median number of red cell transfusions before transplant was nine. The median number of platelet transfusions before transplant was 18. Thirteen patients developed secondary graft failure, with a cumulative incidence at 5 years of 16% and median time to develop secondary graft failure of 129 days. All patients engrafted with a median time for neutrophil engraftment of 19 days and a median time for platelet engraftment of 22 days. The survival of patients with or without secondary graft failure was not different. Major or bidirectional ABO incompatibility and older recipient age were statistically significantly associated with greater risk of secondary graft failure.

CONCLUSIONS

Secondary graft failure is a significant complication after allogeneic transplant for SAA. Identification of recipients at risk and mitigating the potential risks of this complication is warranted.

Polymorphisms in the promoter regions of RHD and RHCE genes in the Chinese Han population

BACKGROUND AND OBJECTIVES

The Rh blood group system is the most polymorphic human blood group system. Previous studies have investigated variants in the RHD and RHCE promoter. The relevance of these variants to the Chinese Han population is further clarified in this study.

MATERIALS AND METHODS

In total, 317 donors (223 Rh D-positive [D+], including 20 Del and 94 Rh D-negative [D-]) were randomly selected. The promoter regions and exon 1 of RHD and RHCE were amplified through polymerase chain reaction (PCR) whose products were directly sequenced using forward and reverse primers.

RESULTS

Expected PCR products of the RHD promoter and exon 1 were amplified in 223 D+ individuals, including 20 Del individuals, and were absent in 81 of 94 D- individuals. Expected PCR products of RHCE were observed in all donors. Two single nucleotide variants (SNVs) were observed in the RHD promoter region. Moreover, 11 SNVs were observed in the promoter and exon 1 of RHCE. rs4649082, rs2375313, rs2281179, rs2072933, rs2072932, rs2072931 and rs586178 with strong linkage disequilibria were significantly different between the D+ and D- groups. [A;C] was the most common haplotype in the RHD promoter (NC_000001.11:g.[-1033A>G;-831C>T]). [G;T;T;A;T;A;C;G;A;C;G] was the most predominant haplotype in both total and D- groups. In D+ individuals, [A;C;T;G;C;G;C;G;C;C;C] was the most frequent haplotype in the RHCE promoter (NC_000001.11:g.[-1080A>G;-958C>T;-390T>C;-378G>A;-369C>T;-296G>A;-144C>G;-132G>A;-122C>A;28C>T;48C>G]).

CONCLUSION

We speculate that the SNVs/haplotypes found in this article cannot significantly affect gene expression. The present study findings should help elucidate the molecular basis of the polymorphic expression of RHD and RHCE promoter regions.

Prevalence of blood group antigens among regular blood donors: A single center study from South India with a review of national literature

BACKGROUND AND OBJECTIVES

The antigen frequencies vary across different regions and ethnic groups. Hence, we aimed to study the prevalence of blood group antigens in our population and to systemize the zone-wise prevalence of the same across India.

MATERIALS AND METHODS

Regular voluntary O group blood donors were screened for 21 blood group antigens; C, c, E, e, K, k, Kpa, Kpb, Jka, Jkb, Fya, Fyb, Lea, Leb, Lua, Lub, P1, M, N, S, s, using commercially available monoclonal antisera by column agglutination technology. A literature search was performed to identify all the studies that reported blood group antigens prevalence to estimate the zone-wise prevalence of these antigens in the country.

RESULTS

A total of 521 participants of 9248 O group donors meeting all the inclusion criteria were included. Among the study group, the male-to-female ratio was 9:1 with a mean age of 32.6 years (±10.01) ranging from 18-60 years. The majority of the donors 446 (85.6%) were D positive. The most common phenotypes among Rh, Lewis, Kell, Duffy, Kidd, Lutheran and MNSs were CcDee (34.93%), Le(a-b+) (61.80%), K-k+(98.27%), Fy(a+b-) 43.19%, Jk(a+b+) 42.61%, Lu(a-b+) ( 99.61%), M+N+ (48.17%), S-s+ (45.29%) respectively. The prevalence of D and E antigens was significantly lower in the South zone compared to other zones of India.

CONCLUSION

Significant difference in the prevalence of blood group antigens is observed between the South and other zones of India. Zone-wise prevalence of blood group phenotypes is essential in the timely management of alloimmunized patients.

Investigating the Correlation Between HLA-II Gene Polymorphism and RhE Alloimmunization in Pregnant Chinese Women

The Rhesus (Rh) blood group is a significant and complicated biological system in humans. Incompatible transfusion or pregnancy with Rh antigens can lead to the production of alloantibodies, among which the anti-E antibody is prevalent. The relationship between Anti-E antibody and HLA-II gene polymorphism in Chinese pregnant women is worth exploring. Our aim in this study was to verify the correlation between HLA-II gene polymorphisms and RhE alloimmunization in pregnant Chinese women through HLA-II typing and DR-RhE structural prediction. In total, 94 anti-E-negative pregnant women and 103 anti-E-positive pregnant women were enrolled from Southwest China Second Hospital, and HLA-II genotyping was performed using next-generation sequencing. NetMHCpan software was used to predict the binding of E -derived anchoring peptides to HLA-DRB1 molecules. AlphaFold was used to analyze the differences in antigen presentation based on the structure of major histocompatibility complex peptides. The HLA-DRB1*09:01-DQA1*03:02-DQB1*03:03 haplotype showed a significant positive association with anti-E. One E-derived anchoring peptide (219FWPSVNSPL227) was predicted to bind to the HLA-DRB1*09:01 molecule. The interaction between the 60Ser of DR9 and 226pro of RhE comprised one hydrogen bond. This study demonstrated that HLA-II haplotypes are associated with allo-anti-E antibodies in pregnant women from Sichuan Province, China. The HLA-DRB1*09:01-DQA1*03:02-DQB1*03:03 phenotype may enhance the formation of anti-E alloantibodies, and the HLA-DRB1*09:01 molecule may play a key role in alloimmunity.

Correlation between ABO blood group and prognosis of hepatectomy for hepatitis B virus-associated hepatocellular carcinoma

BACKGROUND

The relationship between ABO blood group and prognosis of patients with hepatocellular carcinoma (HCC) remains unclear. We investigated the relationship between prognosis and ABO blood group in patients with hepatitis B-associated HCC after radical hepatectomy.

METHODS

The medical records of 874 patients with hepatitis B-associated HCC who underwent radical liver tumor resection were retrospectively collected. Cox proportional risk models were constructed for analysis, and the patient data were further balanced using propensity score matching (PSM) analysis to assess the impact of ABO blood group on the prognosis of patients with hepatitis B-associated HCC.

RESULTS

In univariate Cox regression analysis, the overall survival (OS) of non-A blood type group vs. A blood type group [hazard ratio (HR) (95% confidence interval [CI]) = 1.504 (1.003-2.255), P = 0.048], in multivariate Cox regression analysis the OS of non-A blood type group versus A blood type group [HR (95% CI) = 1.596 (1.054-2.417), P = 0.027]. After PSM, the baseline information was more balanced between the two groups, yielding the same results as above [HR (95% CI) = 1.550 (1.012-2.373), P = 0.044].

CONCLUSION

The difference in OS after radical hepatectomy in patients with hepatitis B-associated HCC was statistically significant in terms of ABO blood group, OS was lower in patients with non-A blood group than in patients with A blood group.

Relationship between B-cell epitope structural properties and the immunogenicity of blood group antigens: Outlier properties of the Kell K1 antigen

BACKGROUND

The immunogenicities of polypeptide blood group antigens vary, despite most being created by single amino acid (AA) substitutions. To study the basis of these differences, we employed an immunoinformatics approach to determine whether AA substitution sites of blood group antigens have structural features typical of B-cell epitopes and whether the extent of B-cell epitope properties is positively related to immunogenicity.

STUDY DESIGN AND METHODS

Fifteen structural property prediction programs were used to determine the likelihood of β-turns, surface accessibility, flexibility, hydrophilicity, particular AA composition and AA pairs, and other B-cell epitope properties at AA substitution sites of polypeptide blood group antigens.

RESULTS

AA substitution sites of Lu^a , Jk^a , E, c, M, Fy^a , C, and S were each located in regions with at least two structural features typical of B-cell epitopes. The substitution site of K, the most immunogenic non-ABO/D antigen, scored the lowest for most B-cell epitope properties and was the only one not predicted to be part of a linear B-cell epitope. The most immunogenic antigens studied (K, Jk^a , Lu^a , E) had B-cell epitope structural properties determined by the fewest programs; the least immunogenic antigens (e.g., Fy^a , S, C, c) had B-cell epitope properties according to the most programs.

DISCUSSION

Counter to prediction, the immunogenicity of polypeptide blood group antigens was not positively related to B-cell epitope structural features present at their AA-substitution sites. Instead, it tended to be negatively related. The AA-substitution site of the most immunogenic non-ABO/D antigen, K, had the least B-cell epitope features.

Serological screening and genetic analysis of RhCE variants in the Chinese Southern Han donors

OBJECTIVES

To screen RhCE variants in the Chinese Southern Han donors for molecular genetic analysis.

BACKGROUND

More than hundreds of RhCE variant alleles have been described to resulting in weak and/or partial expression of RhCE antigens, generation of low-prevalence antigens and/or absence of a high-prevalence antigen of Rh system, which mainly reported in the people of African origin. In this study, the serological screening and molecular genetic analysis of RhCE variants were performed in the Chinese Southern Han donors.

METHODS

The blood samples of E(+) donors were preliminarily collected. Then, RhCE antigens of the E(+) samples were further typed by using two sets of monoclonal anti-C, anti-c, anti-e and another anti-E. When weak expression of RhCE antigens was found, direct sequencing for 10 exons of RHCE gene, RH genotyping analysis by using multiplex ligation-dependent probe amplification, flow cytometric analysis and even cDNA sequencing were performed.

RESULTS

A total of 4487 E(+) samples were collected and four samples with weak expression of antigens were detected. RHCE*Ce375G and RHCE*Ce667T variant alleles were identified in two samples with weak expression of e antigen, respectively. But no variant alleles were found in another two samples with weak expression of C antigen.

CONCLUSION

The variant RHCE*Ce375G validated by mRNA sequencing and the deduced RHCE*Ce667T alleles were firstly identified in the Chinese population. The DCE haplotype might account for the weak expression of C antigen in two donors.

Optimization of diagnostic strategy for non-invasive cell-free foetal RHD determination from maternal plasma

BACKGROUND AND OBJECTIVES

The aim of the study was to optimize routine non-invasive prenatal detection of fetal RHD gene from plasma of RhD-negative pregnant women (the median of gestational age was 25 weeks, range 10-38) to detect RhD materno-fetal incompatibility and to avoid the redundant immunoprophylaxis.

MATERIALS AND METHODS

Initially only one exon of RHD gene (exon 10) was investigated in 281 plasma samples (144 verified after delivery), in the second phase three RHD exons (5, 7, 10) were analyzed in 246 samples of plasma and maternal genomic DNA (204 verified) by real-time PCR method. Detection of Y-chromosomal sequence DYS-14 and five X-chromosomal insertion/deletion polymorphisms was used to confirm the fetal cfDNA detectability in plasma. Specific polymorphisms in RHD gene were detected by sequence-specific primer PCR in nine samples.

RESULTS

When only the RHD exon 10 was tested, 2·8% of verified samples were false positive and 3·5% false negative. With three RHD exons (5, 7, 10) and maternal genomic DNA testing, only one case was false negative (0·5%). Nine samples were inconclusive due to RHD-positive results in maternal genomic DNA. These samples were analyzed for specific mutations in RHD gene. Combination of both methods for fetal cfDNA verification succeeded in 75% of tested group.

CONCLUSION

Implementation of analysis of three RHD exons and maternal genomic DNA to routine practice lowers dramatically the ratio of false positive and negative results. This method enables more accurate determination of fetal RHD status with the reduction of unnecessary medical care and RhD immunoprophylaxis.

Non-Invasive Prenatal Fetal Blood Group Genotype and Its Application in the Management of Hemolytic Disease of Fetus and Newborn: Systematic Review and Meta-Analysis

Hemolytic disease of fetus and newborn (HDFN) imposes great healthcare burden being associated with maternal alloimmunization against parental-inherited fetal red blood cell antigens causing fetal anemia or death. Noninvasive prenatal analysis (NIPT) provides safe fetal RHD genotyping for early identification of risk pregnancies and proper management guidance. We aimed to conduct systematic review and meta-analysis on NIPT's beneficial application, in conjunction with quantitative maternal alloantibody analysis, for early diagnosis of pregnancies at risk. Search for relevant articles was done in; PubMed/Medline, Scopus, and Ovid (January 2006April 2020), including only English-written articles reporting reference tests and accuracy data. Nineteen eligible studies were critically appraised. NIPT was estimated highly sensitive/specific for fetal RHD genotyping beyond 11-week gestation. Amplifications from ≥2 exons are optimum to increase accuracy. NIPT permits cost-effectiveness, precious resources sparing, and low emotional stress. Knowledge of parental ethnicity is important for correct NIPT result interpretations and quantitative screening. Cut-off titer ≥8-up-to-32 is relevant for anti-D alloantibodies, while, lower titer is for anti-K. Alloimmunization is influenced by maternal RHD status, gravida status, and history of adverse obstetrics. In conclusion, NIPT allows evidence-based provision of routine anti-D immunoprophylaxis and estimates potential fetal risks for guiding further interventions. Future large-scale studies investigating NIPT's non-RHD genotyping within different ethnic groups and in presence of clinically significant alloantibodies are needed.

The ABO histo-blood group, endothelial activation, and acute respiratory distress syndrome risk in critical illness

BACKGROUNDThe ABO histo-blood group is defined by carbohydrate modifications and is associated with risk for multiple diseases, including acute respiratory distress syndrome (ARDS). We hypothesized that genetically determined blood subtype A1 is associated with increased risk of ARDS and markers of microvascular dysfunction and coagulation.METHODSWe conducted analyses in 3 cohorts of critically ill trauma and sepsis patients (n = 3710) genotyped on genome-wide platforms to determine the association of the A1 blood type genotype with ARDS risk. We subsequently determined whether associations were present in FUT2-defined nonsecretors who lack ABO antigens on epithelium, but not endothelium. In a patient subgroup, we determined the associations of blood type with plasma levels of endothelial glycoproteins and disseminated intravascular coagulation (DIC). Lastly, we tested whether blood type A was associated with less donor lung injury recovery during human ex vivo lung perfusion (EVLP).RESULTSThe A1 genotype was associated with a higher risk of moderate to severe ARDS relative to type O in all 3 populations. In sepsis, this relationship was strongest in nonpulmonary infections. The association persisted in nonsecretors, suggesting a vascular mechanism. The A1 genotype was also associated with higher DIC risk as well as concentrations of thrombomodulin and von Willebrand factor, which in turn were associated with ARDS risk. Blood type A was also associated with less lung injury recovery during EVLP.CONCLUSIONWe identified a replicable association between ABO blood type A1 and risk of ARDS among the critically ill, possibly mediated through microvascular dysfunction and coagulation.FUNDINGNIH HL122075, HL125723, HL137006, HL137915, DK097307, HL115354, HL101779, and the University of Pennsylvania McCabe Fund Fellowship Award.

Phenotype frequencies of Rh (C, c, E, e), M, Mia and Kidd blood group systems among ethnic Thai blood donors from the north-east of Thailand

We here report the first study of antigen and phenotype frequencies of Rh (C, c, E, e), M, Mi^a and Kidd antigens in north-east Thai blood donors. Blood transfusion services aim to ensure availability of adequate and safe blood to minimize the development of transfusion reactions. For pre-transfusion testing, the most important blood group systems are ABO and RhD. The transfusion of ABO-compatible otherwise unknown phenotype blood may result in alloimmunization, especially in multi-transfused patients. Extended red blood cell (RBC) phenotyping and selection of blood negative for specific antigens reduce post-transfusion complications and allow for effective blood transfusion regimens to be achieved. A total of 13,567 regular repeated, voluntary Thai blood donors were included for red-cell antigen typing of Rh (D, C, E, c, e). Samples from 12,768, 9,389 and 13,059 donors were typed for Kidd, M and Mi^a antigens, respectively. Amongst Rh antigens, e was the most common (96.80%) followed by C (95.50%), c (34.40%) and E (32.20%) with CCDee (60.00%) being the most common phenotype. For Kidd phenotypes, Jk(a+b+) was the most common (46.73%) and Jk(a-b-) was rare (0.07%). For the M and Mi^a antigen, M(+) was most frequently found (94.96%) and Mi^a (+) was found in 17.97% of individuals. Knowledge of red-cell antigen phenotype frequencies in a population is helpful for creating a phenotype database of blood donors which can provide antigen-negative compatible blood to patients with multiple alloantibodies. Moreover, provision of antigen-matched blood can prevent alloimmunization in multi-transfused patients.

Noninvasive Antenatal Screening for Fetal RHD in RhD Negative Women to Guide Targeted Anti-D Prophylaxis

RhD negative pregnant women who carry an RhD positive fetus are at risk of immunization against the D antigen, which may result in hemolytic disease of the fetus and the newborn. Predicting the fetal RhD status by noninvasive antenatal screening for the fetal RhD gene (RHD) can guide targeted use of antenatal anti-D prophylaxis.Cell-free fetal DNA is extracted from maternal plasma from RhD negative pregnant women at a gestational age of 25 weeks. A real-time PCR-based detection of two RHD exons enables reliable prediction of the fetal RhD status to determine the administration of antenatal prophylaxis, as well as postnatal prophylaxis.

Relationship of epitope glycosylation and other properties of blood group proteins to the immunogenicity of blood group antigens

BACKGROUND

The intrinsic properties of polypeptide blood group antigens that determine their relative immunogenicities are unknown. Because size, composition, charge, dose, and epitope glycosylation affect the immunogenicity of other polypeptides, we examined whether similar properties were related to the immunogenicity of blood group antigens.

STUDY DESIGN AND METHODS

Amino acid (AA) sequences of antithetical blood group antigens were searched for N- and O-glycosylation sites. Regression analysis was carried out to determine whether blood group protein properties, including total and ectodomain size, red blood cell (RBC) antigen site density, number of mismatched AAs between an antigen and its closest homolog, and differences in mass, charge, and hydrophobicity of the mismatched AAs, were related to immunogenicity.

RESULTS

The immunogenicities of non-RhD polypeptide antigens were directly related to the total and ectodomain sizes of their carrier proteins. A negative power relationship existed between RBC antigen site density and immunogenicity, such that the most immunogenic antigens had the lowest site density. The strong immunogenicity of RhD was related to the number of AA mismatches between RhD and RhCE, to their cumulative hydrophobicity and electrostatic mismatch scores, and the cumulative AA mass difference. No N- or O-glycosylation differences were predicted for antithetical or homologous antigens, other than a previously known N-glycosylation difference between K and k.

CONCLUSION

Epitope glycosylation appeared not to be a determinant of immunogenicity for blood group antigens, except possibly for K. The immunogenicity of blood group antigens was positively related to total and ectodomain sizes of blood group proteins and negatively related to antigen site density. Such findings should be considered hypothesis generating for future, more definitive studies.

Transfusion Medicine and Molecular Genetic Methods

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

Association study of polymorphisms in the ABO gene and their gene-gene interactions with ischemic stroke in Chinese population

AIMS

To investigate the impact of 4 single nucleotide polymorphisms (SNPs) within ABO gene and their gene-gene interactions on ischemic stroke (IS) susceptibility in Chinese Han population.

METHODS

A total of 1993 participants (1375 males, 618 females) were selected, including 991 IS patients and 1002 normal controls. The SNPstats (http://bioinfo.iconcologia.net/SNPstats) was used for Hardy-Weinberg equilibrium (HWE) test. Generalized multifactor dimensionality reduction (GMDR) was used to screen the best interaction combination among 4 SNPs within ABO gene. Logistic regression was performed to calculate the ORs (95%CI) for interaction between SNPs.

RESULTS

Both rs579459 and rs505922 within ABO gene were associated with IS risk in additive and dominant models. IS risks were higher in those with minor alleles of rs579459 and rs505922 than those with wild-type homozygotes, OR (95%CI) were 1.62 (1.19-2.10) and 1.69 (1.23-2.18), respectively. We did not find any relation of rs651007 and rs529565 with IS risk in both additive and dominant models. GMDR model indicated a significant two-locus model (P = .0010) involving rs505922 and rs579459, indicating a potential interaction between rs505922 and rs579459, the cross-validation consistency of the two-locus models was 9/10, and the testing accuracy was 60.72%. We also found that participants with rs505922- TC/CC and rs579459- TC/CC genotype have the highest IS risk, compared to participants with rs505922- TT and rs579459- TT genotype, OR (95%CI) was 2.94 (1.28-4.66).

CONCLUSIONS

We found that rs579459 and rs505922 within ABO gene and their interaction were both associated with increased IS risk in Chinese population.

Structural and functional impacts of amino acid substitutions that create blood group antigens: implications for immunogenicity

BACKGROUND

The immunogenicities of polypeptide blood group antigens vary widely. One possible determinant of immunogenicity is antigenic foreignness. The goal was to employ alternative ways of assessing foreignness and determine whether foreignness was related to immunogenicity.

STUDY DESIGN AND METHODS

Foreignness was assessed as the extent of protein functional disruption caused by the exofacial amino acid (AA) substitutions that create blood group antigens, using AA substitution prediction algorithms such as Meta-SNP and according to whether those substitutions were radical or conservative.

RESULTS

AA substitutions that create the most immunogenic antigens had the highest Meta-SNP scores, predictive of greater protein structure and function changes. Four of the 11 exofacial AAs that distinguish the most immunogenic antigen, RhD, from RhCE, and substitutions creating four of the five next most immunogenic antigens had the highest Meta-SNP scores (0.293-0.649). Excluding the outlier Jk^a , the mean Meta-SNP score of the four most immunogenic non-RhD antigens (K, Lu^a , E, c) was 3.7-fold higher than the mean of the four least immunogenic (M, Fy^a , C, S), 0.459 versus 0.123 (p = 0.0026). Regression analysis revealed a relationship between immunogenicity and Meta-SNP score (R²  = 0.953). Actual protein functional disruption was predicted for the AA substitution creating the E antigen. An AA cluster at Positions 350, 353, and 354 of RhD was unique, containing radical substitutions according to two classification schemes and relatively high Meta-SNP scores (0.351-0.432).

CONCLUSION

The immunogenicity of blood group antigens was related to the functional disruption caused by the AA substitutions that create the antigens, as measured by Meta-SNP score.

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.

Genetic barriers in transplantation medicine

The successful of transplantation is determined by the shared human leukocyte antigens (HLAs) and ABO blood group antigens between donor and recipient. In recent years, killer cell receptor [i.e., killer cell immunoglobulin-like receptor (KIR)] and major histocompatibility complex (MHC) class I chain-related gene molecule (i.e., MICA) were also reported as important determinants of transplant compatibility. At present, several different genotyping techniques (e.g., sequence specific primer and sequence based typing) can be used to characterize blood group, HLA, MICA and KIR and loci. These molecular techniques have several advantages because they do not depend on the availability of anti-sera, cellular expression and have greater specificity and accuracy compared with the antibody-antigen based typing. Nonetheless, these molecular techniques have limited capability to capture increasing number of markers which have been demonstrated to determine donor and recipient compatibility. It is now possible to genotype multiple markers and to the extent of a complete sequencing of the human genome using next generation sequencer (NGS). This high throughput genotyping platform has been tested for HLA, and it is expected that NGS will be used to simultaneously genotype a large number of clinically relevant transplantation genes in near future. This is not far from reality due to the bioinformatics support given by the immunogenetics community and the rigorous improvement in NGS methodology. In addition, new developments in immune tolerance based therapy, donor recruitment strategies and bioengineering are expected to provide significant advances in the field of transplantation medicine.

Profile of Rh, Kell, Duffy, Kidd, and Diego blood group systems among blood donors in the Southwest region of the Paraná state, Southern Brazil

The aim of this study was to assess the distribution of alleles and genotypes of the blood group systems Rh, Kell, Duffy, Kidd, and Diego in 251 regular blood donors registered in the hemotherapy unit of the Southwestern region of Paraná, Southern Brazil. The frequencies were obtained by direct counting on a spreadsheet program and statistical analyses were conducted in order to compare them with other Brazilian populations using chi-squared with Yates correction on OpenEpi software. The frequencies of RHD* negative, RHCE*c/c and RHCE*e/e were higher than expected for the Caucasian population. A difference was also observed for FY alleles, FY*01/FY*01 genotype and FY*02N.01 -67T/C (GATA Box mutation). Two homozygous individuals were defined as a low frequency phenotype K + k- (KEL*01.01/KEL*01.01) and, for Diego blood group system the rare DI*01 allele was found in ten blood donors, of which one was DI*01/DI* 01 (0.4%). The allele and genotype frequencies of Kidd blood group system were similar to expected to Caucasians. The results showed the direction in which to choose donors, the importance of extended genotyping in adequate blood screening and the existence of rare genotypes in Brazilian regular blood donors.

Frequencies of red blood cell major blood group antigens and phenotypes in the Chinese Han population from Mainland China

Alloantibodies directed to red blood cell (RBC) antigens play an important role in alloimmune-mediated haemolytic transfusion reactions and haemolytic disease of the foetus and newborn. The frequencies and phenotypes of RBC antigens are different in populations from different geographic areas and races. However, the data on major blood group antigens in the Chinese Han population from Mainland China are still very limited; thus, we aimed to investigate them in this study. A total of 1412 unrelated voluntary Chinese Han blood donors were randomly recruited. All donors were typed for blood group antigens: D, C, c, E, e, C(w) , Jk(a) , Jk(b) ,M, N, S, s, Le(a) , Le(b) , K, k. Kp(a) , Kp(b) , Fy(a) , Fy(b) , Lu(a) , Lu(b) , P1 and Di(a) using serological technology. Calculations of antigen and phenotype frequencies were expressed as percentages and for allele frequencies under the standard assumption of Hardy-Weinberg equilibrium. Amongst the Rh antigens, D was the most common (98.94%) followed by e (92.28%), C (88.81%), c (58.43%), E (50.78%) and C(w) (0.07%) with DCe/DCe (R1 R1 , 40.72%) being the most common phenotype. In the Kell blood group system, k was present in 100% of the donors and a rare phenotype, Kp (a+b+), was found in 0.28% of the donors. For the Kidd and Duffy blood group systems, Jk (a+b+) and Fy (a+b-) were the most common phenotypes (44.05% and 84.35%, respectively). In the MNS blood group system, M+N+S-s+ (45.54%) was the most common, whereas M+N-S-s- and M-N+S-s- were not found. The rare Lu (a-b-) and Lu (a+b+) phenotypes were identified in 0.43% and 1.13% of the donors, respectively. Le(a) and Le(b) were seen in 17.92% and 63.03% of donors, respectively. The frequency of Di(a) was 4.75%, which was higher than in the Chinese population in Taiwan region or the Caucasian and Black populations (P < 0.0001). This study systematically describes the frequencies of 24 blood group antigens in the Chinese Han population from Mainland China. The data can be helpful in creating a donor database for preparation of indigenous cell panels and providing antigen-negative blood to patients with multiple alloantibodies.

Frequencies of polymorphisms of the Rh, Kell, Kidd, Duffy and Diego systems of Santa Catarina, Southern Brazil

Background

Red blood cell genes are highly polymorphic with the distribution of alleles varying between different populations and ethnic groups. The objective of this study was to investigate gene polymorphisms of blood groups in the state of Santa Catarina, Southern Brazil.

Methods

Three hundred and seventy-three unrelated blood donors and 31 transfusion-dependent patients were evaluated to investigate polymorphisms of the Rh, Kell, Duffy, Kidd, and Diego blood group systems in a population from the state of Santa Catarina. The subjects, from seven regions that comprise the blood-banking network of the state, were assessed between August 2011 and March 2014. The genotypes of the Rh, Kell, Duffy, Kidd, and Diego systems were determined using the restriction fragment length polymorphism-polymerase chain reaction and allele-specific polymerase chain reaction techniques.

Results

The genotype frequencies in this study were significantly different when populations from different regions of Santa Catarina were compared. Furthermore, there were also significant differences in the genetic frequencies compared to other Brazilian states. The genotype frequencies of the Kell and Kidd blood groups are similar to European populations from Naples, Italy and Zurich, Switzerland.

Conclusion

This article reports for the first time the frequency of polymorphisms of blood group systems in blood donors from Santa Catarina, Southern Brazil.

Blood grouping based on PCR methods and agarose gel electrophoresis

The study of erythrocyte antigens continues to be an intense field of research, particularly after the development of molecular testing methods. More than 300 specificities have been described by the International Society for Blood Transfusion as belonging to 33 blood group systems. The polymerase chain reaction (PCR) is a central tool for red blood cells (RBC) genotyping. PCR and agarose gel electrophoresis are low cost, easy, and versatile in vitro methods for amplifying defined target DNA (RBC polymorphic region). Multiplex-PCR, AS-PCR (Specific Allele Polymerase Chain Reaction), and RFLP-PCR (Restriction Fragment Length Polymorphism-Polymerase Chain Reaction) techniques are usually to identify RBC polymorphisms. Furthermore, it is an easy methodology to implement. This chapter describes the PCR methodology and agarose gel electrophoresis to identify the polymorphisms of the Kell, Duffy, Kidd, and MNS blood group systems.

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.

Should cell-free DNA testing be used to target antenatal rhesus immune globulin administration?

OBJECTIVE

To compare the rates of alloimmunization with the use of cell-free DNA (cfDNA) screening to target antenatal rhesus immune globulin (RhIG) prenatally, versus routine administration of RhIG in rhesus D (RhD)-negative pregnant women in a theoretic cohort using a decision-analytic model.

METHODS

A decision-analytic model compared cfDNA testing to routine antenatal RhIG administration. The primary outcome was maternal sensitization to RhD antigen. Sensitivity and specificity of cfDNA testing were assumed to be 99.8% and 95.3%, respectively. Univariate and bivariate sensitivity analyses, Monte Carlo simulation, and threshold analyses were performed.

RESULTS

In a cohort of 10,000 RhD-negative women, 22.6 sensitizations would occur with utilization of cfDNA, while 20 sensitizations would occur with routine RhIG. Only when the sensitivity of the cfDNA test reached 100%, the rate of sensitization was equal for both cfDNA and RhIG. Otherwise, routine RhIG minimized the rate of sensitization, especially given RhIG is readily available in the United States.

CONCLUSIONS

Adoption of cfDNA testing would result in a 13.0% increase in sensitization among RhD-negative women in a theoretical cohort taking into account the ethnic diversity of the United States' population.

Blood group antigen studies using CdTe quantum dots and flow cytometry

New methods of analysis involving semiconductor nanocrystals (quantum dots [QDs]) as fluorescent probes have been highlighted in life science. QDs present some advantages when compared to organic dyes, such as size-tunable emission spectra, broad absorption bands, and principally exceptional resistance to photobleaching. Methods applying QDs can be simple, not laborious, and can present high sensibility, allowing biomolecule identification and quantification with high specificity. In this context, the aim of this work was to apply dual-color CdTe QDs to quantify red blood cell (RBC) antigen expression on cell surface by flow cytometric analysis. QDs were conjugated to anti-A or anti-B monoclonal antibodies, as well as to the anti-H (Ulex europaeus I) lectin, to investigate RBCs of A₁, B, A₁B, O, A₂, and A_weak donors. Bioconjugates were capable of distinguishing the different expressions of RBC antigens, both by labeling efficiency and by flow cytometry histogram profile. Furthermore, results showed that RBCs from A_weak donors present fewer amounts of A antigens and higher amounts of H, when compared to A₁ RBCs. In the A group, the amount of A antigens decreased as A₁ > A₃ > A_X = A_el, while H antigens were A_X = A_el > A₁. Bioconjugates presented stability and remained active for at least 6 months. In conclusion, this methodology with high sensibility and specificity can be applied to study a variety of RBC antigens, and, as a quantitative tool, can help in achieving a better comprehension of the antigen expression patterns on RBC membranes.

Rh D blood group conversion using transcription activator-like effector nucleases

Group O D-negative blood cells are universal donors in transfusion medicine and methods for converting other blood groups into this universal donor group have been researched. However, conversion of D-positive cells into D-negative is yet to be achieved, although conversion of group A or B cells into O cells has been reported. The Rh D blood group is determined by the RHD gene, which encodes a 12-transmembrane domain protein. Here we convert Rh D-positive erythroid progenitor cells into D-negative cells using RHD-targeting transcription activator-like effector nucleases (TALENs). After transfection of TALEN-encoding plasmids, RHD-knockout clones are obtained. Erythroid-lineage cells differentiated from these knockout erythroid progenitor cells do not agglutinate in the presence of anti-D reagents and do not express D antigen, as assessed using flow cytometry. Our programmable nuclease-induced blood group conversion opens new avenues for compatible donor cell generation in transfusion medicine.

Group O/RhD− blood can be safely transfused to any recipient and methods for converting other blood groups into this group hold therapeutic potential. By using programmable nucleases, here the authors edit the gene that determines the RhD blood group and convert the RhD+ into RhD− erythroid progenitor cells.

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.

Screening the expression of ABCB6 in erythrocytes reveals an unexpectedly high frequency of Lan mutations in healthy individuals

Lan is a high-incidence blood group antigen expressed in more than 99.9% of the population. Identification of the human ABC transporter ABCB6 as the molecular basis of Lan has opened the way for studies assessing the relation of ABCB6 function and expression to health and disease. To date, 34 ABCB6 sequence variants have been described in association with reduced ABCB6 expression based on the genotyping of stored blood showing weak or no reactivity with anti-Lan antibodies. In the present study we examined the red blood cell (RBC) surface expression of ABCB6 by quantitative flow cytometry in a cohort of 47 healthy individuals. Sequencing of the entire coding region of the ABCB6 gene in low RBC ABCB6 expressors identified a new allele (IVS9+1G>A, affecting a putative splice site at the boundary of exon 9) and two nonsynonymous SNPs listed in the SNP database (R192Q (rs150221689) and G588 S (rs145526996)). The R192Q mutation showed co-segregation with reduced RBC ABCB6 expression in a family, and we found the G588 S mutation in a compound heterozygous individual with undetectable ABCB6 expression, suggesting that both mutations result in weak or no expression of ABCB6 on RBCs. Analysis of the intracellular expression pattern in HeLa cells by confocal microscopy indicated that these mutations do not compromise overall expression or the endolysosomal localization of ABCB6. Genotyping of two large cohorts, containing 235 and 1039 unrelated volunteers, confirmed the high allele frequency of Lan-mutations. Our results suggest that genetic variants linked to lower or absent cell surface expression of ABCB6/Langereis may be more common than previously thought.

Responder individuality in red blood cell alloimmunization

Many different factors influence the propensity of transfusion recipients and pregnant women to form red blood cell alloantibodies (RBCA). RBCA may cause hemolytic transfusion reactions, hemolytic disease of the fetus and newborn and may be a complication in transplantation medicine. Antigenic differences between responder and foreign erythrocytes may lead to such an immune answer, in part with suspected specific HLA class II associations. Biochemical and conformational characteristics of red blood cell (RBC) antigens, their dose (number of transfusions and pregnancies, absolute number of antigens per RBC) and the mode of exposure impact on RBCA rates. In addition, individual circumstances determine the risk to form RBCA. Responder individuality in terms of age, sex, severity of underlying disease, disease- or therapy-induced immunosuppression and inflammation are discussed with respect to influencing RBC alloimmunization. For particular high-risk patients, extended phenotype matching of transfusion and recipient efficiently decreases RBCA induction and associated clinical risks.

Novel alleles at the Kell blood group locus that lead to Kell variant phenotype in the Dutch population

BACKGROUND

Alloantibodies directed against antigens of the Kell blood group system are clinically significant. In the Netherlands, the KEL1 antigen is determined in all blood donors. In this study, after phenotyping of KEL:1-positive donors, genotyping analysis was conducted in KEL:1,-2 donors to identify possible KEL*02 variant alleles.

STUDY DESIGN AND METHODS

A total of 407 donors with the KEL:1,-2 phenotype were genotyped for the KEL*01/02 polymorphism, followed by direct sequencing of the KEL gene if the KEL*02 allele was detected. Two K0 patients were also included. Transcript analysis was conducted in two probands with the KEL*02. M05 allele defined by a synonymous mutation (G573G). Flow cytometry analysis to determine the expression of Kell antigen was performed.

RESULTS

Thirty KEL:1,-2 individuals (30/407, 7.4%) with discrepant KEL*01/02 genotype were identified. Seven novel alleles were identified: KEL*02(R86Q, R281W)mod, KEL*02(L133P)null, KEL*02(436delG)null, KEL*02(F418S)null, KEL*02(R492X)null, KEL*02(L611R)null, and KEL*02(R700X)null. Nine variant alleles described before were detected: KEL*02N.06, KEL*02N.15, KEL*02N.17, KEL*02N.19, KEL*02N.21, KEL*02M.02, KEL*02M.04, KEL*02M.05, and KEL*02(Q362K)mod. A transcript lacking Exon 16 was identified in two probands with the KEL*02M.05 allele as described before. Finally, flow cytometry analysis showed a decreased total Kell expression and a relatively increased KEL1 expression in individuals with the KEL:1,2null or KEL:1,2mod phenotype, compared to KEL:1,2 controls.

CONCLUSION

In 7.4% of a group of tested KEL:1,-2 Dutch donors, a KEL*02null or KEL*02mod allele was found. A relatively increased KEL1 antigen expression in KEL:1,2null and KEL:1,2mod individuals suggest that the expression of Kell-XK complexes depends on the availability of the XK protein.

Mononuclear cells from a rare blood donor, after freezing under good manufacturing practice conditions, generate red blood cells that recapitulate the rare blood phenotype

BACKGROUND

Cultured red blood cells (cRBCs) from cord blood (CB) have been proposed as transfusion products. Whether buffy coats discarded from blood donations (adult blood [AB]) may be used to generate cRBCs for transfusion has not been investigated.

STUDY DESIGN AND METHODS

Erythroid progenitor cell content and numbers and blood group antigen profiles of erythroblasts (ERYs) and cRBCs generated in human erythroid massive amplification (HEMA) culture by CB (n = 7) and AB (n = 33, three females, three males, one AB with rare blood antigens cryopreserved using CB protocols) were compared.

RESULTS

Variability was observed both in progenitor cell content (twofold) and number of ERYs generated (1 log) by CB and AB in HEMA. The average progenitor cell contents of the subset of AB and CB analyzed were similar. AB generated numbers of ERYs three times lower (p < 0.01) than CB in HEMA containing fetal bovine serum but similar to CB in HEMA containing human proteins. Female AB contained two times fewer (p < 0.05) erythroid progenitor cells but generated numbers of ERYs similar to those generated by male AB. Cryopreserved AB with a rare blood group phenotype and shipped to another laboratory generated great numbers of ERYs, 90% of which matured into cRBCs. Blood group antigen expression was consistent with the donor genotype for ERYs generated both by CB and AB but concordant with that of native RBCs only for cells derived from AB.

CONCLUSION

Buffy coats from regular donors, including a donor with rare phenotypes stored under conditions established for CB, are not inferior to CB for the generation of cRBCs.

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.

(C)ce(s) haplotype screening in Tunisian blood donors

BACKGROUND

The (C)ce(s) haplotype, mainly found in black individuals, contains two altered genes: a hybrid RHD-CE-D(s) gene segregated with a ce(s) allele of RHCE with two single nucleotide polymorphisms, c. 733C>G (p.Leu245Val) in exon 5 and c. 1006G>T (Gly336Cys) in exon 7. This haplotype could be responsible for false positive genotyping results in RhD-negative individuals and at a homozygous level lead to the loss of a high incidence antigen RH34. The aim of this study was to screen for the (C)ce(s) haplotype in Tunisian blood donors, given its clinico-biological importance.

MATERIAL AND METHODS

Blood samples were randomly collected from blood donors in the blood transfusion centre of Sousse (Tunisia). A total of 356 RhD-positive and 44 RhD-negative samples were tested for the (C)ce(s) haplotype using two allele-specific primer polymerase chain reactions that detect c. 733C>G (p.Leu245Val) and c. 1006G>T (p. Gly336Cys) substitutions in exon 5 and 7 of the RHCE gene. In addition, the presence of the D-CE hybrid exon 3 was evaluated using a sequence-specific primer polymerase chain reaction.

RESULTS

Among the 400 individuals only five exhibited the (C)ce(s) haplotype in heterozygosity, for a frequency of 0.625%. On the basis of the allele-specific primer polymerase chain reaction results, the difference in (C)ce(s) haplotype frequency was not statistically significant between RhD-positive and RhD-negative blood donors.

DISCUSSION

These data showed the presence of the (C)ce(s) haplotype at a low frequency (0.625%) compared to that among Africans in whom it is common. Nevertheless, the presence of RHD-CE-D(s) in Tunisians, even at a lower frequency, should be considered in the development of a molecular genotyping strategy for Rh genes, to ensure better management of the prevention of alloimmunisation.

Rh, Kell, Duffy, Kidd and Diego blood group system polymorphism in Brazilian Japanese descendants

Polymorphisms of Rh, Kell, Duffy, Kidd and Diego blood group systems were studied in 209 unrelated Brazilian Japanese descendants from South of Brazil. The methods used were multiplex-PCR, AS-PCR and RFLP-PCR. The differences in frequencies among the populations were evaluated using chi-square test. The frequencies for Rh, Kell, Kidd and Diego system were similar to those of the Japanese. RHCE(*)CC, RHCE(*)EE genotypes and FY(*)01 allele were lower and FY(*)01N.01 was higher than Japanese. These differences in the frequencies between Brazilian Japanese descendants and Japanese could indicate a gene flow in Brazilian population and reinforce the importance of this knowledge to achieve safe red blood cells.

Role of non-HLA gene polymorphisms in graft-versus-host disease

A large number of reports have associated various non-HLA gene polymorphisms with the risk and severity of graft-versus-host disease (GVHD). To date, candidate gene studies and genome-wide association studies have been performed to investigate such non-HLA gene polymorphisms in relation to GVHD. Candidate gene studies are hypothesis-driven and cost-effective, whereas genome-wide association studies have the potential to discover new gene polymorphisms, including possible biomarkers and therapeutic targets. Some gene polymorphisms have the potential to affect protein function or gene expression, or to encode minor histocompatibility antigens. Non-HLA genotyping for genes influencing GVHD prior to transplantation should provide useful information that will facilitate choosing the donor, type of graft, conditioning treatment, and GVHD prophylaxis. However, attention should be paid to the need for validation studies and ethical issues.

Systematic RH genotyping and variant identification in French donors of African origin

BACKGROUND

RH molecular analysis has enabled the documentation of numerous variants of RHD and RHCE alleles, especially in individuals of African origin. The aim of the present study was to determine the type and frequency of D and/or RhCE variants among blood donors of African origin in France, by performing a systematic RH molecular analysis, in order to evaluate the implications for blood transfusion of patients of African origin.

MATERIALS AND METHODS

Samples from 316 African blood donors, whose origin was established by their Fy(a-b-) phenotype, were first analysed using the RHD and RHCE BeadChips Kit (BioArray Solutions, Immucor, Warren, NJ, USA). Sequencing was performed when necessary.

RESULTS

RHD molecular analysis showed that 26.2% of donors had a variant RHD allele. It allowed the prediction of a partial D in 11% of cases. RHCE molecular analysis showed that 14.2% of donors had a variant RHCE allele or RH [RN or (C)ces] haplotype. A rare Rh phenotype associated with the loss of a high-prevalence antigen or partial RhCE antigens were predicted from RHCE molecular analysis in 1 (0.3%) and 17 (5%) cases, respectively.

DISCUSSION

Systematic RHD and RHCE molecular analysis performed in blood donors of African origin provides transfusion-relevant information for individuals of African origin because of the frequency of variant RH alleles. RH molecular analysis may improve transfusion therapy of patients by allowing better donor and recipient matching, based not only on phenotypically matched red blood cell units, but also on units that are genetically matched with regards to RhCE variants.

An easy and efficient strategy for KEL genotyping in a multiethnic population

Background

The Kell blood group system expresses high and low frequency antigens with the most important in relation to transfusion including the antithetic KEL1 and KEL2; KEL3 and KEL4; KEL6 and KEL7 antigens. Kell is a clinically relevant system, as it is highly immunogenic and anti-KEL antibodies are associated with hemolytic transfusion reactions and hemolytic disease of the fetus and newborn. Although required in some situations, Kell antigen phenotyping is restricted due to technical limitations. In these cases, molecular approaches maybe a solution. This study proposes three polymerase chain reaction genotyping protocols to analyze the single nucleotide polymorphisms responsible for six Kell antithetic antigens expressed in a Brazilian population.

Methods

DNA was extracted from 800 blood donor samples and three polymerase chain reaction-restriction fragment length polymorphism protocols were used to genotype the KEL*1/KEL*2, KEL*3/KEL*4 and KEL*6/KEL*7 alleles. KEL*3/KEL*4 and KEL*6/KEL*7 genotyping was standardized using the NlaIII and MnlI restriction enzymes and validated using sequencing. KEL*1/KEL*2 genotyping was performed using a previously reported assay.

Results

KEL genotyping was successfully implemented in the service; the following distribution of KEL alleles was obtained for a population from southeastern Brazil: KEL*1 (2.2%), KEL*2 (97.8%), KEL*3 (0.69%), KEL*4 (99.31%), KEL*6 (2.69%) and KEL*7 (97.31%). Additionally, two individuals with rare genotypes, KEL*1/KEL*1 and KEL*3/KEL*3, were identified.

Conclusion

KEL allele genotyping using these methods proved to be reliable and applicable to predict Kell antigen expressions in a Brazilian cohort. This easy and efficient strategy can be employed to provide safer transfusions and to help in rare donor screening.

A new strategy to identify rare blood donors: single polymerase chain reaction multiplex SNaPshot reaction for detection of 16 blood group alleles

BACKGROUND

As an alternative to phenotyping, large-scale DNA-based assays, which are feasible for high-throughput donor red blood cell typing, were developed for determination of blood group polymorphisms. However, high-throughput genotyping platforms based on these technologies are still expensive and the inclusion of single nucleotide polymorphisms and analysis of the alleles depend on the manufacturer's determination. To overcome this limitation and in order to develop an assay to enable the screening of rare donors, we developed a SNaPshot assay for analysis of nine single nucleotide polymorphisms related to antigens that are difficult to assess using conventional serology.

MATERIALS AND METHODS

The single polymerase chain reaction multiplex SNaPshot reaction was optimized to identify nine single nucleotide polymorphisms determining 16 alleles: KEL*3/KEL*4, KEL*6/KEL*7, DI*1/DI*2, DI*3/DI*4, YT*1/YT*2, CO*1/CO*2, DO*1/DO*2, DO*4, DO*5. We designed a single multiplex PCR with primers encompassing the blood group single nucleotide polymorphisms and performed an internal reaction with probe primers able to discriminate the alleles after fragment analysis. The SNaPshot assay was validated with 140 known alleles previously determined by PCR restriction fragment length polymorphism.

RESULTS

We were able to simultaneous detect nine single nucleotide polymorphisms defining 16 blood group alleles on an assay based on a multiplex PCR combined with a single base extension using genomic DNA.

DISCUSSION

This study demonstrates a robust genotyping strategy for conducting rare donor screening which can be applied in blood centers and could be an important tool for identifying antigen-negative donors and, therefore, for providing rare blood.

Disruption of SMIM1 causes the Vel- blood type

Here, we report the biochemical and genetic basis of the Vel blood group antigen, which has been a vexing mystery for decades, especially as anti-Vel regularly causes severe haemolytic transfusion reactions. The protein carrying the Vel blood group antigen was biochemically purified from red blood cell membranes. Mass spectrometry-based de novo peptide sequencing identified this protein to be small integral membrane protein 1 (SMIM1), a previously uncharacterized single-pass membrane protein. Expression of SMIM1 cDNA in Vel− cultured cells generated anti-Vel cell surface reactivity, confirming that SMIM1 encoded the Vel blood group antigen. A cohort of 70 Vel− individuals was found to be uniformly homozygous for a 17 nucleotide deletion in the coding sequence of SMIM1. The genetic homogeneity of the Vel− blood type, likely having a common origin, facilitated the development of two highly specific DNA-based tests for rapid Vel genotyping, which can be easily integrated into blood group genotyping platforms. These results answer a 60-year-old riddle and provide tools of immediate assistance to all clinicians involved in the care of Vel− patients.