The RHD gene is highly detectable in RhD-negative Japanese donors

Guide to Rho(D) Immune Globulin in Women With Molecularly Defined Asian-type DEL (c.1227G>A)

Rh hemolytic disease of the fetus and newborn is a potential risk for D-negative mothers who produce anti-D during pregnancy, which can lead to morbidity and mortality in subsequent pregnancies. To prevent this hemolytic disease, Rho(D) immune globulin (RhIG) is generally administered to D-negative mothers without anti-D at 28 weeks of gestation and shortly after delivery. However, current guidelines suggest that pregnant mothers with molecularly defined weak D types 1, 2, 3, 4.0, and 4.1 do not need RhIG as they are unlikely to produce alloanti-D when exposed to fetuses with D-positive red cells. This issue and the necessity of RHD genotyping have been extensively discussed in Western countries, where these variants are relatively common. Recent evidence indicates that women with Asian-type DEL (c.1227G>A) also do not form alloanti-D when exposed to D-positive red cells. We report that mothers with molecularly defined Asian-type DEL, similar to those with weak D types 1, 2, 3, 4.0, and 4.1, do not require RhIG before and after delivery. Collectively, this review could pave the way for the revision of international guidelines to include the selective use of RhIG based on specific genotypes, particularly in women with the Asian-type DEL.

Molecular basis of RhD-negative phenotype in North Indian blood donor population

Background & objectives

RHD gene typing is highly complex due to homology with RHCE genes. Molecular polymorphism of the RHCE and RHD genes have been characterized among various populations, but no studies have been undertaken among Indians. This study was undertaken to assess the genetic basis of RHD-negative phenotype in Indian blood donor population.

Methods

Sample from a total of 200 phenotypically RhD-negative blood donors were analyzed for presence of RHD gene using polymerase chain reaction (PCR). RHD genotyping was done using three primer sets designed for exons 4 and 10 and one set for identification of pseudo (RHDΨ) gene between introns (int) 3 and 4. Amplified PCR products were analyzed by gel-electrophoresis (XY Loper, Uvitech, Cambridge) and confirmed by nucleotide sequencing (ABI 3730 xl 96 capillary system).

Results

No PCR product was found in 195/200 (97.5%) of study samples indicating homozygous gene deletion. Of the 5/200 (2.5%) showing RHD gene polymorphisms, 4/200 (2%) were positive for presence of exon 10 only (RHD-CE-D hybrid). RHDΨ gene was not detected in any of the samples tested. One sample showed presence of all three tested regions and was negative for RHDΨ gene.

Interpretation & conclusions

RHD gene deletion was found to be the most common cause of an RHD-negative phenotype while RHDΨ gene was, reported to be present in up to 39 per cent of various ethnic populations, but was not detected. RHD-CE-D hybrid gene (found in 2.5% individuals) is important for predicting the requirement of Rh prophylaxis during the antenatal period.

The efficacy of ethnic specific blood groups genotyping for routine donor investigation and rare donor identification in Taiwan

BACKGROUND

Large-scale single nucleotide variation (SNV)-based blood group genotyping assays have been made available for over a decade. Due to differences in ethnic groups, there is much diversity in clinically important blood group antigens and genetic variants. Here, we developed a robust matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF)-based blood group genotyping method on MassARRAY system.

STUDY DESIGN AND METHODS

A total of 1428 donors were enrolled into three groups: (a) reagent red cell donors; (b) rare donor or common antigen-negative donors; and (c) group O, R₁ R₁ /R₂ R₂ donors. Forty-two SNVs were designed for determining nine blood groups, with X/Y chromosome in two multiplex reactions, on MassARRAY 96-well format system. Further targeted sequence analyses were performed by Sanger sequencing.

RESULTS

WHO reference reagent (NIBSC code: 11/214) was tested for concordance with the provided genotype results. Among the donors, concordance rate was over 99%. Alleles of important phenotypes such as Mi(a+), Di(a+), and Asian-type DEL and alleles of rare blood groups such as Fy(a-), Jk(a-b-) and s- were screened. Three types of discrepancies were found. Serologically, the 'N' antigen was expressed on genetically MM with GYP*Mur red blood cells and caused genuine discrepancies (9.5%). Genetically, allele dropout (ADO) was caused by rare SNV in the primer for Ss genotype (2.1%) and partial insertion of RHD genes (0.9%) led to difficulties in predicting phenotypes.

CONCLUSION

Hemo panel module and MassARRAY System in 96-well format showed good performance in terms of large-scale blood group genotyping and phenotype predictions. Implementation of this method is effective for routine blood group genotype screening of donors.

Genotyping of RHD c.1227G>A allele by melting curve analysis

BACKGROUND

DEL is the weakest known D-positive phenotype and is detectable only by adsorption and elution tests. RHD c.1227G>A is an important marker for DEL phenotype in East Asians. The aim of this study was to develop a method for RHD c.1227G>A genotyping by single-tube PCR with melting curve analysis.

METHODS

Two GC-rich tails of different lengths were attached to the 5'-end of allele-specific primers for RHD 1227G and 1227A alleles, such that RHD c.1227G>A could be distinguished by the melting temperature. A total of 145 D-negative Chinese Han blood donors were genotyped for RHD c.1227G>A by melting curve analysis, conventional polymerase chain reaction with sequence-specific primers (PCR-SSP), and sequencing.

RESULTS

In 143 subjects (143/145, 98.6%), PCR-SSP and melting curve analysis produced consistent results with RHD exon 9 sequencings. Two samples were genotyped as RHD 1227G/A by PCR-SSP, but as RHD 1227A/A or A/- by melting curve analysis. These two samples were confirmed to be RHD 1227A/A or A/-. Based on RHD exon 9 sequencing, the accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of the melting curve analysis for detecting both RHD 1227A and 1227G were all 100%. In contrast, the accuracy, specificity and positive predictive value of PCR-SSP for RHD 1227G detection were 98.62%, 98.21% and 94.29%, respectively, which were lower than those observed with the melting curve analysis.

CONCLUSION

Melting curve analysis for RHD c.1227G>A genotyping is a simple, rapid, and reliable method, superior to conventional PCR-SSP.

Molecular and computational analysis of 45 samples with a serologic weak D phenotype detected among 132,479 blood donors in northeast China

Background

RH1 is one of the most clinically important blood group antigens in the field of transfusion and in the prevention of fetal incompatibility. The molecular analysis and characterization of serologic weak D phenotypes is essential to ensuring transfusion safety.

Methods

Blood samples from a northeastern Chinese population were randomly screened for a serologic weak D phenotype. The nucleotide sequences of all 10 exons, adjacent flanking intronic regions, and partial 5′ and 3′ untranslated regions (UTRs) were detected for RHD genes. Predicted deleterious structural changes in missense mutations of serologicl weak D phenotypes were analyzed using SIFT, PROVEAN and PolyPhen2 software. The protein structure of serologic weak D phenotypes was predicted using Swiss-PdbViewer 4.0.1.

Results

A serologic weak D phenotype was found in 45 individuals (0.03%) among 132,479 blood donors. Seventeen distinct RHD mutation alleles were detected, with 11 weak D, four partial D and two DEL alleles. Further analyses resulted in the identification of two novel alleles (RHD weak D 1102A and 399C). The prediction of a three-dimensional structure showed that the protein conformation was disrupted in 16 serologic weak D phenotypes.

Conclusions

Two novel and 15 rare RHD alleles were identified. Weak D type 15, DVI Type 3, and RHD1227A were the most prevalent D variant alleles in a northeastern Chinese population. Although the frequencies of the D variant alleles presented herein were low, their phenotypic and genotypic descriptions add to the repertoire of reported RHD alleles. Bioinformatics analysis on RhD protein can give us more interpretation of missense variants of RHD gene.

Comprehensive Molecular Analysis of Serologically D-Negative and Weak/Partial D Phenotype in Thai Blood Donors

Background

Molecular genetics of the Rh system has been extensively studied in Caucasians, Black Africans, East Asians, and Indians more recently. In this work, we sought to investigate the molecular basis of variant D expression in the Thai population, which remains unknown.

Materials and Methods

Blood samples from 450 Thai donors showing the variant D phenotype were collected. The RHD gene was analyzed by quantitative multiplex polymerase chain reaction of short fluorescent fragments and/or Sanger sequencing.

Results

The most frequent alleles in 200 D-negative and 121 DEL samples were the whole RHD gene deletion and the Asian DEL alleles, respectively. In 129 weak/partial D samples, 36 variant alleles were identified, including eight novel alleles. RHD*06.03, which is common in variant D samples from South China, is the most prevalent variant allele, followed by the recently reported Indian RHD*01W.150 allele.

Discussion

For the first time, a comprehensive overview of the nature and distribution of variant RHD alleles in Thailand is reported. It is a milestone to pave the way towards improvement of the current screening strategy to identify DEL donors accurately. The next step will be the design and implementation of a simple molecular test for screening the most frequent alleles, specifically in this population.

RHD-Positive Alleles among D- C/E+ Individuals from India

Background

Molecular bases of blood group systems, including Rh blood group, have been poorly studied in the Indian population so far, while specificities of Europeans, East Asians and Africans have been well known for years. In order to gain insights into the molecular bases of this population, we sought to characterize the RHD allele in D- Indian donors expressing C and/or E antigen(s).

Methods

RHD gene was analyzed in 171 serologically D-, C/E+ samples by standard molecular methods such as quantitative, multiplex PCR of short fluorescent fragments (QMPSF) and direct sequencing when necessary.

Results

RHD whole gene deletion at the homozygous state was found to be the most common genotype associated with D- phenotype (118/171, 69.0%). Nonfunctional, negative hybrid genes with reported molecular backgrounds were observed in approximately one-third of the samples, while only four samples carry single-nucleotide variations, including one novel nonsense (RHD(Y243X)), one novel frameshift (RHD(c.701delG)), and two missense (RHD(T148R) and RHD(T148R, T195M)) alleles.

Conclusion

Overall we report for the first time the molecular bases of D antigen negativity in the D-, C/E+ Indian population, which appears to be qualitatively similar to other populations, but with a population-specific, quantitative distribution of D-- alleles.

DEL phenotype

DEL red blood cells (RBCs) type as D- by routine serologic methods and are transfused routinely, without being identified as expressing a very weak D antigen, to D- recipients. DEL RBCs are detected only by adsorption and elution of anti-D or by molecular methods. Most DEL phenotypes have been reported in population studies conducted in East Asia, although DEL phenotypes have been detected also among Caucasian individuals. Approximately 98 percent of DEL phenotypes in East Asians are associated with the RHD*DEL1 or RHD*01EL.01 allele. The prevalence of DEL phenotypes has been reported among D- Han Chinese (30%), Japanese (28%), and Korean (17%) populations. The prevalence of DEL phenotypes is significantly lower among D- Caucasian populations (0.1%). Among the 3-5 percent of African individuals who are D-, there are no reports of the DEL phenotype. Case reports from East Asia indicate that transfusion of DEL RBCs to D- recipients has been associated with D alloimmunization. East Asian immigrants constitute 2.1 percent of the 318.9 million persons residing in the United States, and an estimated 2.8 percent are blood donors. Using these statistics, we estimate that 68-683 units of DEL RBCs from donors of East Asian ancestry are transfused as D- annually in the United States. Given the reports from East Asia of D alloimmunization attributed to transfusion of DEL RBCs, one would expect an occasional report of D alloimmunization in the United States following transfusion of DEL RBCs to a D- recipient. If such cases do occur, the most likely reason that they are not detected is the absence of active post-transfusion monitoring for formation of anti-D.

Clinical and laboratory update on the DEL variant

Serological assays for the RhD blood group are based on detection of the RhD antigen on human red blood cells using a specific anti-D antibody. The weak expression of the RhD antigen in the DEL variant hinders the sensitivity of conventional serological assays. Evidence of anti-D immunization in patients with D-negativity who have received DEL-variant blood units has been reported in various populations. This observation has prompted the need for genetic epidemiological and clinical data on the DEL variant in the development of DEL molecular diagnostic testing. This review highlights the molecular features of the DEL variant, the clinical consequences of DEL-blood transfusion, and current approaches for detection of the DEL-variant for donor screening and transfusion.

The association of maternal ABO blood group with gestational diabetes mellitus in Japanese pregnant women

AIMS

To investigated the association between the ABO blood group and gestational diabetes mellitus (GDM).

MATERIALS AND METHODS

A retrospective case-control study was conducted using data from 5424 Japanese pregnancies. GDM screening was performed in the first trimester using a casual blood glucose test and in the second trimester using a 50-g glucose challenge test. If the screening was positive, a 75-g oral glucose tolerance test was performed for a GDM diagnosis, which was defined according to the International Association of Diabetes and Pregnancy Study Groups. Logistic regression was used to obtain the odds ratio (OR) and 95% confidence interval (CI) adjusted for traditional risk factors.

RESULTS

Women with the A blood group (adjusted OR: 0.34, 95% CI: 0.19-0.63), B (adjusted OR: 0.35, 95% CI: 0.18-0.68), or O (adjusted OR: 0.39, 95% CI: 0.21-0.74) were at decreased risk of GDM compared with those with group AB. Women with the AB group were associated with increased risk of GDM as compared with those with A, B, or O (adjusted OR: 2.73, 95% CI: 1.64-4.57).

CONCLUSION

ABO blood groups are associated with GDM, and group AB was a risk factor for GDM in Japanese population.

Intron 4 of the RH Gene in Han Chinese, Tibetan, and Mongol Populations

AIMS

This study aimed to compare the intron 4 sequence of the RHD and RHCE genes from Han Chinese, Tibetans, and Mongols, and explore its polymorphisms.

MATERIALS AND METHODS

To investigate the distinction in the RHD and RHCE intron 4, polymerase chain reaction (PCR) was performed by a set of primers: Intron4F and Intron4R. Primer Intron4F for a sequence located in exon 4 and primer Intron4R for a sequence located in exon 5, respectively. RHD and RHCE intron 4 of all the samples from 26 cases of random unrelated Hans (13 RhD-positive donors and 13 RhD-negative donors), 25 cases of random unrelated Tibetans (18 RhD-positive donors and 7 RhD-negative donors), and 4 cases of random unrelated Mongols (1 RhD-positive donor and 3 RhD-negative donors) were amplified with PCR. The PCR products were then sequenced.

RESULTS

A 576-bp product was detected in all the Han, Tibetan, and Mongol RhD-positive donors, whereas a 1228-bp product was detected in RhD-negative donors. The sequences of RHCE gene intron 4 were identical to each other in all Han, Tibetan, and Mongol RhD-negative donors, including 335 bp of Alu element, with a whole length of 1078 bp. By contrast, a 426-bp product was detected in all Han, Tibetan, and Mongol RhD-positive donors. Compared with the RHCE gene, a 652-bp deletion was noted in the RHD gene of Chinese, including the whole Alu element. The results were similar to the findings of Caucasians, whereas the lengths of RHD gene deletion fragments of Japanese and French were 649 and 654 or 651 bp, respectively.

CONCLUSIONS

The RHCE gene intron 4 of Han Chinese, Tibetans, and Mongols differs from the RHD gene intron 4 in the presence of a 652-bp fragment. The RHCE gene intron 4 in Chinese has its own structural characteristics and differs among various ethnicities and regions.

Rhesus Negative Woman Transfused With Rhesus Positive Blood: Subsequent Normal Pregnancy Without Anti D production

Clinicians sometimes are confronted with the challenge of transfusing haemorrhaging Rhesus (Rh) D negative patients with Rh D positive blood to save their lives. There are concerns about alloimmunization and future haemolytic disease of the newborn in women of the reproductive age. Another fear is transfusion reaction if they receive another Rh D positive blood in future. We present a 32-year-old Rh D negative woman, who had postpartum haemorrhage in her first pregnancy and was transfused with Rh D positive blood because of unavailability of Rh D negative blood. She did not receive anti D immunoglobin but subsequently had a normal term pregnancy of an Rh positive fetus without any detectable anti D antibodies throughout the pregnancy. In life threatening situations from obstetric haemorrhage, transfusion of Rh D negative women with Rh D positive blood should be considered as the last resort.

Characteristics and frequency of DEL phenotype detected by indirect antiglobulin test in Dalmatia county of Croatia

D variants, collectively called DEL, express trace amounts of D antigen which is considered to be serologically detectable only by adsorption-elution techniques. We detected six cases of DEL phenotype by indirect antiglobulin test, in Dalmatia County of Croatia by routine serological testing of D antigen of new blood donors. RH genotyping found that all six donors carry allele RHD(M295I), RH genotype CcDdee. D antigen densities of D variants were very low, between 26 and 44 D antigens per red blood cell. The frequency of D variants detected by IAT allele RHD(M295I) was 1:272 in D negative donors. Obviously, DEL phenotype is more common in some parts of European population than initially thought. In conclusion, our routine serological testing of D antigen can detect extremely weak D antigen, even RBCs with DEL phenotype and antigen density as low as 26 D antigens per RBC.

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.

Weak D types in the Egyptian population

Patients with the most common weak D types 1, 2, and 3 can be safely considered D positive. We evaluated 1,113 Rh-negative Egyptian samples for weak D expression to propose a cost-effective strategy related to D variant testing. D variants were tested using polymerase chain reaction with sequence-specific priming. Fifty samples were D variants (4.5%): weak D type 4.2 (32%), weak D type 4.0/4.1 (16%), and weak D type 15 (2%). Fifteen (62.5%) of 24 samples were identified serologically as partial D. We also studied the probability of the development of anti-D in 52 Rh-negative children with thalassemia who were receiving units for which weak D was not tested. Anti-D alloimmunization was observed in 63.5% of patients with thalassemia. It is prudent to implement weak D typing in Egyptian donors. Weak D variants of Egyptians are significantly different compared with Caucasians. Ethnicity must be taken into consideration when developing clinical and prenatal strategies related to D variants.

RHD PCR of D-Negative Blood Donors

SUMMARY

RHD PCR of blood donors may be used to reveal weak D, partial D, DEL and chimeric D+/D- donors among presumed D-negative blood donors. Units donated by such donors pose a definite yet low risk for anti-D immunization of transfusion recipients. The frequency of DEL donors among D-negative donors is 1:350 to 1:2,000 in Europe and up to 1:5 in Asian countries. Different strategies for RHD PCR of blood donors have been used. Probably, the most cost-efficient implementation is replacement of sensitive D antigen testing with the indirect antiglobulin test by RHD PCR in pools which might even reduce total testing cost.

RhC Phenotyping, Adsorption/Elution Test, and SSP-PCR: The Combined Test for D-Elute Phenotype Screening in Thai RhD-Negative Blood Donors

The Rhesus (Rh) blood group is the most polymorphic human blood group and it is clinically significant in transfusion medicine. Especially, D antigen is the most important and highly immunogenic antigen. Due to anti-D, it is the cause of the hemolytic disease of the newborn and transfusion reaction. About 0.1%–0.5% of Asian people are RhD-negative, whereas in the Thai population, the RhD-negative blood type only occurs in 0.3%. Approximately 10%–30% of RhD-negative in Eastern Asian people actually were D-elute (DEL) phenotype, the very weak D antigen that cannot be detected by indirect antiglobulin test (IAT). There are many reports about anti-D immunization in RhD-negative recipients through the transfusion of red blood cells from individuals with DEL phenotype. D-elute phenotype screening in Thai RhD-negative blood donors was studied to distinguish true RhD-negative from DEL phenotype. A total of 254 Thai serologically RhD-negative blood donors were tested for RhCE phenotypes and anti-D adsorption/elution test. In addition, RhC(+) samples were tested for RHD 1227A allele by SSP-PCR technique. The RhD-negative phenotype samples consisted of 131 ccee, 4 ccEe, 1 ccEE, 101 Ccee, 16 CCee, and 1 CcEe. The 42 Ccee and 8 CCee phenotype samples were typed as DEL phenotype and 96% of DEL samples were positive for RHD 1227A allele. The incidence of RhC(+) was 46.4%, and 48 of the 118 RhC(+) samples were positive for both anti-D adsorption/elution test and SSP-PCR technique for RHD 1227A allele. The sensitivity and specificity were 96% and 100%, respectively, for RHD 1227A detection as compared with the adsorption/elution test. In conclusion, RhC(+) phenotype can combine with anti-D adsorption/elution test and RHD 1227A allele SSP-PCR technique for distinguishing true RhD-negative from DEL phenotype.

DNA-based methods in the immunohematology reference laboratory

Although hemagglutination serves the immunohematology reference laboratory well, when used alone, it has limited capability to resolve complex problems. This overview discusses how molecular approaches can be used in the immunohematology reference laboratory. In order to apply molecular approaches to immunohematology, knowledge of genes, DNA-based methods, and the molecular bases of blood groups are required. When applied correctly, DNA-based methods can predict blood groups to resolve ABO/Rh discrepancies, identify variant alleles, and screen donors for antigen-negative units. DNA-based testing in immunohematology is a valuable tool used to resolve blood group incompatibilities and to support patients in their transfusion needs.

Evidence for maternal-fetal genotype incompatibility as a risk factor for schizophrenia

Prenatal/obstetric complications are implicated in schizophrenia susceptibility. Some complications may arise from maternal-fetal genotype incompatibility, a term used to describe maternal-fetal genotype combinations that produce an adverse prenatal environment. A review of maternal-fetal genotype incompatibility studies suggests that schizophrenia susceptibility is increased by maternal-fetal genotype combinations at the RHD and HLA-B loci. Maternal-fetal genotype combinations at these loci are hypothesized to have an effect on the maternal immune system during pregnancy which can affect fetal neurodevelopment and increase schizophrenia susceptibility. This article reviews maternal-fetal genotype incompatibility studies and schizophrenia and discusses the hypothesized biological role of these ‘‘incompatibility genes”. It concludes that research is needed to further elucidate the role of RHD and HLA-B maternal-fetal genotype incompatibility in schizophrenia and to identify other genes that produce an adverse prenatal environment through a maternal-fetal genotype incompatibility mechanism. Efforts to develop more sophisticated study designs and data analysis techniques for modeling maternal-fetal genotype incompatibility effects are warranted.

Aberrant RNA splicing in RHD 7-9 exons of DEL individuals in Taiwan: a mechanism study

BACKGROUND

The Rh blood D group provides a clinically important model of aberrant splicing with skipped exons. Approximately 30% of serologically D-negative Chinese individuals have an intact RHD gene (DEL phenotype) and induce allo-immunization in transfusions. The RHD1227GNA polymorphism occurs in >95% DEL phenotype of Asian descent. The effects of RHD 1227A and a novel allele on exon 9 splicing were examined.

RESULTS

Amplified DEL RNA products revealed that 3 transcripts involved skipping of exons 8-9, exon 9, or exon 9 with an inserted 170-bp cryptic exon located between exons 7 and 8. A novel, single nucleotide polymorphism was identified in the 7th intron, (IVS7) 923C>T, and present in all DEL patients. The odds ratio of RHD1227G>A allele with DEL phenotype was 2711. Splicing analysis of transcripts from minigenes containing the 1227GNA allele, but not the (IVS7) 923C>T allele, demonstrated aberrant exon 9 skipping.

CONCLUSIONS

A combined haplotype of 1227G>A and IVS7 923C>T alleles was apparent in >95% DEL Chinese individuals. RHD1227A mutation significantly increased aberrant mRNA splicing, producing a hybrid RHD mRNA lacking exon 9. These results provide a molecular basis of the DEL phenotype in the Chinese population.

Primary anti-D immunization by DEL red blood cells

Extremely weak D variants called DEL are serologically detectable only by adsorption-elution techniques. A nucleotide change of exon 9 in RHD gene, RHD (K409K, 1227G>A) allelic variant is present in almost all the DEL individuals of East Asians. No DEL phenotype has yet been shown to induce a primary alloanti-D immunization in East Asia. A 68-yr-old D-negative Korean man was negative for anti-D at admission, and he developed alloanti-D after transfusion of red blood cells (RBC) from 4 apparently D-negative donors. Four donors who typed D-negative by routine serologic test were analyzed by real-time PCR for RHD gene and RHD (K409K). One donor was found to have RHD (K409K). This is the first case in which DEL RBCs with RHD (K409K) induced a primary alloanti-D immunization in Asian population. Because the DEL phenotype can induce an anti-D immunization in D-negative recipients, further discussion is needed whether RhD negative donors should be screened by molecular method and what an efficient genotyping method is for detecting the RHD gene carriers in Korea.

Six years' experience performing RHD genotyping to confirm D- red blood cell units in Germany for preventing anti-D immunizations

BACKGROUND

Red blood cell (RBC) units of D+ donors are falsely labeled D- if regular serologic typing fails to detect low D antigen expression or chimerism. The limitations of serology can be overcome by molecular typing.

STUDY DESIGN AND METHODS

In January 2002, we introduced a polymerase chain reaction (PCR)-based assay for RHD as a routine test for first-time donors who typed D- by serologic methods including the indirect antiglobulin test. Samples were tested in pools of 20 for the RHD-specific polymorphism in Intron 4. RHD alleles were identified by PCR and nucleotide sequencing.

RESULTS

Within 6 years, 46,133 serologically D- first-time donors were screened for the RHD gene. The prevalence of RHD gene carriers detected by this method was 0.21 percent. Twenty-three RHD alleles were found of which 15 were new. Approximately one-half of the RHD gene carriers harbored alleles expressing a DEL phenotype resulting in a prevalence of 0.1 percent.

CONCLUSION

The integration of RHD genotyping into the routine screening program was practical. We report 6 years' experience of this donor testing policy, which is not performed in most transfusion services worldwide. RBC units of donors with DEL phenotype have been reported to anti-D immunize D- recipients. We transferred those donors to the D+ donor pool with the rationale of preventing anti-D immunizations, especially dreaded in pregnancies. For each population, it will be necessary to adapt the RHD genotyping strategy to the spectrum of prevalent alleles.

Applications and Experience with PCR-Based Assays to Predict Blood Group Antigens

DNA-based tests are increasingly being used to predict a blood group phenotype. This is possible because genes encoding 29 of the 30 blood group systems have been cloned and sequenced, and the molecular bases associated with most antigens have been determined. RBCs carrying a particular antigen, if introduced into the circulation of an individual who lacks that antigen, can elicit an immune response. It is the antibody from such an immune response that causes problems in clinical practice and the reason why antigen-negative blood is required for safe transfusion. The classical method of testing for blood group antigens and antibodies is hemagglutination; however, it has certain limitations, some of which can be overcome by testing DNA. Such testing allows conservation of antibodies for confirmation by hemagglutination of predicted antigen-negativity. High-throughput platforms provide a means to test relatively large numbers of donors, thereby opening the door to change the way antigen-negative blood is provided to patients. This chapter discusses how molecular approaches can be applied in transfusion medicine, and summarizes experiences of using laboratory developed tests and DNA arrays at the New York Blood Center.

Molecular genetic blood group typing by the use of PCR-SSP technique

BACKGROUND

DNA-based methods are useful for enhancing immunohematology typings. Ready-to-use Conformité Européenne (CE)-marked test kits based on polymerase chain reaction with sequence-specific priming (PCR-SSP) have been developed, which enable the examination of weak, unexpected, or unclear serologic findings. DEVELOPMENT AND VALIDATION: Primers were designed according to established mutation databases. Proficiency testing for CE marking was performed in accordance with Directive 98/79EC of the European Parliament and of the Council of October 27, 1998 on in vitro diagnostic medical devices using pretyped in-house and external samples. INTENDED USE: BAGene PCR-SSP kits are in vitro diagnostic devices. Genotyping of ABO and RHD/RHCE as well as HPA and KEL, JK, and FY specificities has to be performed after the conclusion of the serologic determination.

APPLICATION

Ready-to-use PCR-SSP typing kits allow the determination of common, rare, or weak alleles of the ABO blood group, Rhesus, and Kell/Kidd/Duffy systems as well as alleles of the human platelet antigens.

RESULTS

The investigations showed clear-cut results in accordance with serology or molecular genetic pretyping.

CONCLUSION

PCR-SSP is a helpful supplementary technique for resolving most of the common problems caused by discrepant or doubtful serologic results, and it is an easy-to-handle robust method. Questionable cases in donor, recipient, and patient typing can be examined with acceptable cost.

Prenatal determination of the fetal RhD blood group by multiplex PCR: a 7-year Portuguese experience

OBJECTIVES

This is a retrospective study to evaluate the efficacy and accuracy of the multiplex polymerase chain reaction (PCR) amplification, for early detection of fetuses at risk for hemolytic disease, in the population living in Portugal, and to characterize the RhD-negative individuals at serologic and molecular level.

METHODS

2030 uncultured amniotic fluid samples and 2012 blood samples from the respective RhD-negative pregnant women were studied by multiplex PCR of intron 3/intron 4, exon 7 and 3'UTR. Amniocentesis was performed for a variety of medical indications. For quality control, serologic RhD blood groups were determined in the cord blood, after birth.

RESULTS

1361 fetal amniotic samples were RhD-positive (67%), 669 were RhD-negative. The average time for diagnosis was 2 days for uncultured amniocytes and the molecular versus serologic RhD typing (n = 809) had 99.5% concordance. Among the 2012 serologic RhD-negative mothers, 26 had an RhD-positive allele.

CONCLUSION

The multiplex PCR amplification used in this study was a rapid and accurate method to determine the RhD blood type in the population living in Portugal, being a great tool for management of pregnancies with fetuses at risk for alloimmune hemolytic disease. In this population, 1.3% of the serologic RhD-negative women have an RHD-positive allele.

An easy RHD genotyping strategy for D- East Asian persons applied to Korean blood donors

BACKGROUND

In East Asian populations RHD alleles are known to occur frequently among D- donors, requiring suitable genotyping strategies. The molecular basis of the "RHD(el)" allele previously reported in Taiwan to harbor a genomic 1013-bp deletion was questioned by several authors.

STUDY DESIGN AND METHODS

The presence of the RHD gene was investigated in 126 random serologic D- blood donors from Gwangju, southwest Korea. Four donors who typed weakly positive for the D antigen were also analyzed. RH alleles were determined by polymerase chain reaction (PCR) with sequence-specific priming (PCR-SSP) or nucleotide sequencing.

RESULTS

Seventy-five percent of the serologically D- samples lacked the RHD gene, 10 percent carried the hybrid RHD-CE(2-9)-D2 or RHD-CE(2-7)-D2 alleles, 13 percent represented the RHD(K409K), and 2 percent were weak D type 15 and type 17. Among the four donors typing weak D, two carried weak D type 15, one RHD(K409K), and one the novel weak D type 43. Critical molecular characteristics of RHD(K409K) and its population frequencies were indistinguishable to those reported for the RHDel allele.

CONCLUSION

Korean RHD allele frequencies are comparable to Chinese and Japanese frequencies. It is concluded that the RHDel allele may actually not exist but is identical to RHD(K409K). A practical RHD genotyping strategy applicable to D- donors in all East Asian populations was devised. The strategy requires four PCR-SSP procedures only for RHD intron 4 and exon 7 as well as RHD(K409K) and non-RHD(K409K).

Prevalence of RHD 1227A and hybrid Rhesus box in the general Chinese population

The Rhesus (Rh) blood group is the most polymorphic blood group system. Serological analyses revealed that only 0.1% to 0.4% of the Chinese population exhibited a D-negative phenotype. In contrast to D-negative Caucasian persons, who are mostly associated with a deletion of RHD between the upstream and downstream Rhesus boxes, approximately 30% of apparently D-negative Chinese were actually DEL, potentially harboring a grossly intact RHD gene. The authors' previous detection of the RHD 1227A allele in all DEL samples prompted the conclusion that the RHD 1227A gene is highly prevalent in DEL populations of Chinese ethnicity, which indicates that it may be a marker for the rapid detection of DEL. Currently, random surveys for RHD 1227 A allele and for hybrid Rhesus box were conducted among 399 Han Chinese in Taiwan. The estimated frequencies of RHD 1227G/G, RHD 1227A/G, RHD A/A, RHD 1227G/-, RHD 1227A/-, and RHD-/- were 0.89054, 0.0118, 0.00016, 0.0414, 0.00055, and 0.00192, respectively. These results were consistent with the prevalence of D-negative and DEL in persons of Chinese ethnicity. The authors conclude that detection of RHD 1227A and hybrid Rhesus box alleles is predictive of Rh phenotypes in the Chinese population.

Taiwan experience suggests that RhD typing for blood transfusion is unnecessary in southeast Asian populations

BACKGROUND

The high frequency of RhD (D) antigen among Taiwanese persons (99.67%) often imposes unnecessary risks of under-transfusion on D- patients awaiting D- blood. Also because of the rare occurrence of anti-D among Taiwanese persons, routine pretransfusion D typing has been discontinued in the Mackay Memorial Hospital since 1988. This report is the retrospective evaluation of the outcome of abolishing RhD typing for Taiwanese.

STUDY DESIGN AND METHODS

More than 10 years of alloantibody data at Mackay Memorial Hospital Blood Bank were reviewed. The cases with anti-D were further used to analyze the potency of D antigen and to observe whether there were differences in the incidence of anti-D before and after discontinuation of routine D typing among Taiwanese individuals.

RESULTS

The incidence of anti-D before and after discontinuation of routine pretransfusion D typing has remained unchanged. The immunogenicity of D and "Mi(a)" in Taiwanese persons is found to be similar. In terms of opportunity for immunization, however, the "Mi(a)" antigen (phenotype frequency 7.3% in Taiwanese persons) has become the most important blood group antigen in Taiwan.

CONCLUSION

The results strongly support the exclusion of D typing from routine compatibility testing for individuals of Taiwanese origin. Because the low incidence of D- and relatively high incidence of "Mi(a)"+ phenotypes are common findings throughout southeast Asia, and because a population genetic study revealed that the Taiwanese people are genetically related to southern Asian populations, it is suggested that RhD typing for blood transfusion is unnecessary among southeast Asian populations.

Detection of RhD(el) in RhD-negative persons in clinical laboratory

The Rhesus (Rh) blood group is the most polymorphic human blood group system, and it is clinically significant in transfusion medicine. About 15% of Caucasoid people are RhD-negative, whereas in the Asian population, the RhD-negative blood type only occurs in 0.1% to 0.5%. However, approximately 30% of apparently RhD-negative Taiwanese people actually were RhD(el). Traditionally, we verify RhD(el) by a serologically adsorption-elution procedure with polyclonal anti-D. In our recent report, RhC phenotype is highly associated with RhD(el), and RHD1227A is a useful genetic marker for RhD(el). For setting up a rapid protocol to detect RhD(el) in clinical laboratory, a total number of 395 Taiwanese serological RhD-negative blood samples, those with RhC (+) phenotypes as selected by serological tests, were further screened by adsorption/elution tests and RHD1227A allele by specific sequence primer-polymerase chain reaction (SSP-PCR) for RhD(el). Among 395 blood samples collected from RhD-negative subjects, the incidence of RhC (+) was 43% (171/395). One hundred and twenty six of the 171 RhC (+) samples were positive for both adsorption/elution for RhD detection and SSP-PCR assay for RHD1227A. The sensitivity and specificity were 96.9% and 97.5%, respectively, for RHD1227A detection as compared with the traditional adsorption/elution test. Our results also indicated that RHD1227A was highly linked to Ce haplotypes (95.2%). In conclusion, combined RhC (+) phenotyping and RHD1227A analysis can be a simple and accurate laboratory screening protocol for RhD(el) detection in RhD-negative population.

Molecular aspects of Rh antigens

Since the cloning of two Rh related cDNAs, several attempts to clarify the molecular basis of Rh system have been performed. The RHD gene is deleted in most Caucasians who lack the D antigen, whereas some Japanese RhD(-) individuals appear to have an intact RHD gene. The expression study in erythroleukemic cells revealed that c and E antigens were expressed on a single polypeptide encoded by a full length cE transcript and RhD transcript give rise to D and G antigens. Recent finishing of human genome euchromatin sequencing confirmed the genomic organization of RH locus in which RHD and CE face each other at their 3' tails, and the gene SMP1 is interspersed between them. Two 9 kb transposon-like DNA segments, called 'rhesus boxes' were identified in both upstream and downstream of the RHD gene. Murine genome sequence of rh locus indicate not only the ancient duplication of RH gene by the mechanism of retro-transposition before hominoids branched off but also the unequal crossing over at the 'rhesus boxes' resulting in an RHD deletion. The macrocomplex formed by Rh, RhAG and band3 is thought contributing for the physiological functions, anchoring lipid bilayer to spectrin-based framework and membrane transportation of CO2 and HCO3-.

Utilisation en routine clinique du génotypage fœtal RHD sur plasma maternel : bilan de deux ans d’activité

OBJECTIVES

To evaluate the predictive value of RHD fetal genotype in maternal plasma of Rh D negative mothers after 10 weeks of gestation in a clinical use.

MATERIAL AND METHOD

Prospective, comparative study between fetal RHD genotyping in maternal plasma, with amplification of exons 4,5,10 of the RHD gene, by real-time multiplex PCR, and Rh D serology at birth, in 218 pregnancy and their 223 babies, between November 2002 and 2004.

RESULTS

Combining the amplification of three exons, the concordance rate of fetal Rh D genotyping in maternal plasma and baby phenotyping at delivery was 100%. Four women whose the babies were Rh D negative were positive for RHD exon 10 during pregnancy. This positivity was, in three cases, correlated with the presence of RHDpsi pseudogene and in last case, with a haplotype Cdes (r's). RHD genotyping was performed for five twin pregnancies.

CONCLUSION

Multiplex PCR using maternal plasma provides perfect prenatal prediction of fetal RHD gene. These results confirm that this non invasive procedure is the preferred method for assessing Rh D fetal status in Rh negative mothers. Using this method for two years in routine practice has led us to modify our management scheme for sensitized Rh D-negative pregnant women.

Systemic analysis and zygosity determination of the RHD gene in a D-negative Chinese Han population reveals a novel D-negative RHD gene

BACKGROUND AND OBJECTIVES

The aim of this study was to systemically analyse the genetic background of D negativity in a Chinese Han population.

MATERIALS AND METHODS

DNA of 74 D-negative samples was analysed by using an RHD multiplex polymerase chain reaction (MPX PCR) for the presence of RHD and by PCR-restriction fragment length polymorphism (PCR-RFLP) for RHD zygosity determination. Sixty-five samples were additionally analysed by using real-time quantitative PCR on RHD exon 7. RHD exon-specific sequencing was performed on discrepant samples.

RESULTS

Forty-six samples (62%) showed the absence of RHD-specific exons by RHD MPX PCR and homozygous RHD negativity by PCR-RFLP. Twenty-two samples (30%) showed a 1227G>A mutation, characteristic for the Del phenotype. Five (7%) samples showed all characteristics of the RHD(1-2)-CE(3-9)-D(10) hybrid gene. One sample (1.4%) showed a novel 933C>A nonsense mutation in RHD exon 6, which resulted in a premature stop codon.

CONCLUSIONS

The RHD gene deletion, RHD-CE-D hybrid genes and one novel 93C>A mutation were found to be the three mechanisms that cause D negativity in our samples. The 1227G>A Del mutation was found to be the major cause of discrepant results between genotyping and phenotyping strategies, favouring genotyping of D-negative samples.

Presence ofRHDin serologically D-, C/E+ individuals: a European multicenter study

BACKGROUND

RHD blood group alleles with reduced or absent antigen expression are a clinically significant and heterogeneous group.

STUDY DESIGN AND METHODS

To detail population genetics data on apparently D- individuals in central Europe, a six-center study was performed with participants from Austria, Germany, Slovenia, Switzerland, and Russia. A total of 1700 serologically D- samples, positive for C and/or E, were investigated.

RESULTS

Observed unexpressed RHD alleles were 59 RHD-CE-D+ hybrid alleles, 9 apparently regular RHD, 1 new RHD(Y401X); DELs were 8 RHD(M295I), 6 RHD(IVS3+1G>A), and 1 new RHD(X418L); and weakly expressed RHDs were 2 weak D type 5, 1 weak D type 1, 1 RHD category VI type 1, and 1 novel weak D type 26. Although weak D type 26 was shown to have one of the lowest D antigen densities ever observed, it gave rise to anti-D immunization in a transfused D- individual.

CONCLUSION

The relative occurrence of RHD among serologically D- samples, positive for C and/or E, differed significantly in the investigated central European regions. Considering the growing use of molecular typing techniques, correct identification of blood group alleles with scarce or missing antigen expression is of utmost clinical importance and requires reliable population-based frequency data.

Molecular characterization of D- Korean persons: development of a diagnostic strategy

BACKGROUND

D- frequencies show wide racial differences: in particular, in Korean persons it is approximately 1/100th of that in Caucasians (0.15% vs. 15%). The molecular mechanisms of D- may be unique to races, and thus specific molecular diagnostic approaches are necessary for individual races. Such marked racial differences have been attributed to the founder effect. It was hypothesized that D- frequencies may be affected by genomic variations of Rhesus boxes, which are instruments of unequal crossing-over.

STUDY DESIGN AND METHODS

First, the molecular basis of D- in Korean donors was characterized. A total of 264 D- persons were analyzed by performing RHD exon polymerase chain reaction (PCR), Rhesus box hybrid PCR-PstI, RHD sequencing, and a novel RHD-CE-D hybrid PCR. Second, with sequencing analysis, Rhesus boxes in Korean and Caucasian persons were compared.

RESULTS

Of 264 D- Korean individuals, 74 percent completely lacked RHD, 9 percent had RHD-CE-D hybrid, and 17 percent had point mutations. Three genetic causes, RHD deletion, RHD-CE(2-9)-D2, and 1227G>A, explained 99.4 percent of D- alleles in Korean persons. Three novel mutations were also found. The identity region of 10 Rhesus boxes in Korean persons was in complete concordance with that in Caucasian persons.

CONCLUSION

In this study, a molecular diagnostic strategy was established and the genetic causes of almost all D- Korean persons was able to be diagnosed with a simple decision tree. The study provides a good example of the molecular diagnosis of D- persons, especially in low-frequency areas. Our hypothesis that D- frequencies are affected by genomic variations in Rhesus boxes was excluded. Rather, racial differences may be influenced by the founder effect.

The highly variable RH locus in nonwhite persons hampers RHD zygosity determination but yields more insight into RH-related evolutionary events

BACKGROUND

Knowledge about paternal RHD hemi- or homozygosity is of clinical interest in alloimmunized pregnant women. D negativity in white persons is usually caused by deletion of the RHD gene. Recently, the physical structure of the RH locus and the mechanism causing the deletion of the RHD gene have been explored, enabling RHD zygosity determination in white persons by specific detection of a hybrid Rhesus box characteristic for the RHD- locus.

STUDY DESIGN AND METHODS

RHD zygosity was determined in 402 samples from five different ethnic groups by polymerase chain reaction (PCR)-restriction fragment length polymorphism and by a newly developed real-time quantitative PCR. The Rhesus boxes of samples showing discrepancies between both tests were cycle sequenced.

RESULTS

In nonwhite persons, several mutated Rhesus boxes exist that hamper zygosity determination by detection of the RHD- locus. Such mutated Rhesus boxes in D+RHD homozygous black persons have a frequency of 0.22. In white persons, no mutated Rhesus boxes were encountered so far.

CONCLUSIONS

Owing to the high frequency of the mutated Rhesus boxes, zygosity determination by detection of the RHD- locus is not feasible in nonwhite persons. The cosegregation of variant RHD genes (RHDpsi and (C)cdes) with specific mutated Rhesus boxes yields more insight into the evolutionary events concerning variant RHD genes and mutated Rhesus boxes.

Non-invasive fetal RHD and RHCE genotyping from maternal plasma in alloimmunized pregnancies

BACKGROUND

In this prospective study, we assessed the feasibility of fetal RH genotyping by analysis of DNA extracted from maternal plasma samples of alloimmunized pregnant women using real-time PCR and primers and probes targeted toward RHD (exon 7 and exon 10) and RHCE (intron 2 and exon 5) genes.

METHODS

We analysed 23 alloimmunized pregnant women (16 anti-D, 5 anti-D + C, 2 anti-E) at risk of haemolytic disease of the newborn (HDN) within 11th and 37th week of pregnancy and correlated the results with serological analysis of cord blood.

RESULTS AND CONCLUSION

Detection of the presence of the RHD gene, the C and/or E alleles of the RHCE gene in maternal plasma samples is highly accurate and enables implementation in a clinical diagnostic algorithm for following pregnancies at risk for HDN. The absence of RHD gene, the C and/or E alleles of RHCE gene in the current pregnancy excludes the risk of HDN caused by anti-D, anti-C and/or anti-E alloantibodies and the performance of invasive fetal-blood sampling.