RHD sequencing: a new tool for decision making on transfusion therapy and provision of Rh prophylaxis

The serological differentiation of weak D from partial D, D-negative and D-positive is not always unequivocal. Therefore, sequencing of the RHD gene is required in some cases. Very recently, several new differences between RHD and RHCE have been identified which permitted us to design primers close to the exon/intron boundaries of the RHD-exons. We evaluated these primers in 83 D-positive and 18 D-negative blood donors and applied the new method for the characterization of the RHD gene in six individuals with weak D phenotype. The amplification reactions were concordant with serological findings in 100 of 101 donors (99.0%). In one D-positive donor the PCR for exons 2 and 5 gave a negative result, while the sequence of the remaining eight exons was unchanged. By sequencing samples with very weak D serological reactions, we identified weak D type 4.2.2 and weak D type 15, both previously reported to be associated with anti-D-alloimmunization. Consequently, we recommended the selection of D-negative blood in the weak D type 4.2.2 patient, and the provision of Rh prophylaxis for pregnant women with weak D type 15. In summary, a new RHD sequencing method was developed which can be applied if serological reactions are inconclusive.     

A D(V)-like phenotype is obliterated by A226P in the partial D DBS

BACKGROUND: In D category V types, the RHD exon 5 or parts thereof are replaced by the corresponding RHCE DNA segments. In D category V types I and II, the amino acid at position 226 is alanine, which is typical of the prevalent RHD allele and is observed in all RHCE alleles encoding the antigen e. A proline at position 226 in RHCE encodes the antigen E. STUDY DESIGN AND METHODS: A blood sample of ccDEe phenotype was referred as suspected D category VI. The RHD nucleotide sequence and the D epitope pattern were determined. RESULTS: A new partial D, DBS, encoded by an RHD-RHcE(5)-RHD hybrid allele, was found. Although it differed from D(Va) type II by an A226P substitution only, it lacked epitopes epD4, epD12, epD17, epD18, and epD22 that were present in D(Va). The 5' breakpoint region was located between the deletion in RHD intron 4 and the first polymorphic nucleotide of DBS exon 5. CONCLUSION: The phenotypes of RHD alleles with gene conversions limited to exon 5 depended critically on the amino acid at position 226. If alanine was present at this position, gene conversions involving E233Q led to a D(Va)-like phenotype. If proline was present, many additional epitopes were lost, and the phenotype became reminiscent of DFR. The 5' breakpoint region is shared by 10 alleles and may represent the most active "hot spot" for gene conversions known in RH.     

Involvement of Ser103 of the Rh polypeptides in G epitope formation

BACKGROUND: Almost all red cells that carry D and/or C antigens also express the G antigen (Rh12). A study was conducted on the molecular background of the G epitope. STUDY DESIGN AND METHODS: Two unrelated donors with the rare ccDEe, G- phenotype and one donor with the ccEe, G+ phenotype were studied. Genomic DNA and cDNA of these donors were studied with polymerase chain reaction, Southern blot, and sequence analysis, with special focus on exon 2, because it is only in this exon that there are supposed to be similarities between RHD and the RHC allele, but not between RHD and the RHc allele. RESULTS: In both ccDEe, G- donors, a nucleotide substitution was found in exon 2 of RHD; T307 was replaced by C307, which predicted a Ser->Pro substitution at amino acid position 103 of the D polypeptide. The ccEe, G+ donor carried the complete exon 2 of RHD. Moreover, despite the absence of all known D epitopes, this donor also carried RHD characteristics in exons 1 to 3 and exon 9 and further downstream. CONCLUSION: Ser103, encoded by exon 2 of the RH genes, is involved in G epitope formation.     

The Dc(G48)e(s) haplotype is frequent among the Dce haplotypes within a white population

BACKGROUND: The absence of hybrid Rhesus boxes denotes an RHD homozygous status and helps to detect the presence of Dce haplotypes instead of dce. RHCE exon 1 C48, characteristic of RHC alleles, and RHCE exon 5 G733, responsible for VS antigenicity, have been noted in many RHce alleles but it was not clearly established whether they occurred in the same allele and/or cosegregate together with RHD. STUDY DESIGN AND METHODS: Samples from 148 white trios (father, mother, and child) were studied. Rh phenotype was performed by hemagglutination. Hybrid Rhesus box, RHCE exon 1 G48C, RHCE exon 5 C733G, and RHC intron 2 polymorphisms were analyzed by polymerase chain reaction. Haplotypes were determined considering serologic, molecular, and segregation data. RESULTS: RHCE exon 1 C48 and RHCE exon 5 G733 were present in RHce alleles that cosegregated with RHD forming Dce haplotypes. Both transversions were not frequently found in the same RHce allele. Of the 33 Dce haplotypes, 16 (48.5%) had a C at position 48 [Dc(C48)e], 11 (33.3%) had a G at position 48 with a G at position 733 [Dc(G48)e(s)], 5 (15.2%) had a G at position 48 [Dc(G48)e], and 1 (3.0%) had a C at position 48 with a G at position 733 [Dc(C48)e(s)]. CONCLUSIONS: The results show four molecular backgrounds for the Dce haplotype and reflect the contribution of African alleles to the genetic pool of the population under study. The molecular characterization of Dce and its frequency distribution may develop a better understanding of the phylogeny of Rh haplotypes.     

1名RhD弱表现型个体携带D~(el)等位基因

目的　探讨 1名RhD弱表现型个体的RH基因型及RHD基因的分子机制。方法　采用常规血清学方法检测RhD、C、c、E和e抗原表型 ,间接抗球蛋白试验确认D抗原 ,用序列特异性引物 聚合酶链反应 (PCR SSP)测定RHD/RHCE基因 ,然后分析RHD编码区全长序列 ,并用PCR检测RhD杂合型。结果　血清学结果显示该个例为D抗原弱表现型 ,Rh因子为D +C +c +E e +,PCR SSP检测RHD/RHCE基因与之相符 ;RHD编码区序列析发现第 9外显子存在 1 2 2 7G→A碱基突变 ,其余外显子序列则与正常RHD基因一致 ,表明该个体携带RHD1 2 2 7A等位基因。RhD合子型鉴定结果为RHD +/RHD -杂合型 ,拟定RHCE和RHD为cis遗传 ,提示该个体基因型为CDe/cde。结论　该RhD弱表现型个体携带RHD 1 2 2 7A等位基因 ,而这一等位基因是Del表型的主要等位基因 ,提示该等位基因在不同个体RhD分子的表达效率不同     

两种技术分析Rh D-先证者形成机制的效果评价

目的 比较和评价血清学和序列特异性引物聚合酶链反应(PCR-SSP)基因分型技术对RhD-先证者及家系成员Rh血型分型和遗传背景分析的效果.方法 对RhD-先证者及其家系成员,采用血清学分型技术检测其RhD、C、c、E、e抗原;采用PCR-SSP基因分型技术检测其RHD、RHCE基因.结果 先证者家系成员Rh表型正常,...     

DCS-1, DCS-2, and DFV share amino acid substitutions at the extracellular RhD protein vestibule

BACKGROUND: RhD and RhCE are structurally related to ammonium transporter proteins, yet their physiologic function remains unclear. Recent three-dimensional homology modeling with Escherichia coli AmtB as a template defined a putative transmembraneous channel. Three RhD variants with amino acid substitutions located at the extracellular channel aperture are described. STUDY DESIGN AND METHODS: Blood samples were selected because of serologic abnormalities. RHD, RHCE, and LW nucleotide sequences were determined from genomic DNA. D epitope patterns were established with monoclonal anti-D panels. Three-dimensional Rh structures were calculated by alignment to AmtB. RESULTS: The RHD allele DCS-1 was found to carry the two amino acid substitutions F223V (667T > G) and A226P (676G > C) caused by missense mutations in RHD exon 5. This study compared DCS-1 with the D variants DFV (F223V) and DCS-2 (A226P), harboring solely one or the other of the two substitutions. All three D variants were associated with a cDE haplotype. The antigen densities were approximately 3,000 D antigens per red blood cell for DCS-1, 800 for DCS-2, and 9,300 for DFV. DCS-1 and DCS-2 were partial D, because they lacked distinct epitopes. DFV presented as an almost normal D phenotype; the sample contained allo-anti-LW(a). The D(w) antigen was absent from DCS-1, DFV, and DAU-4, but expressed by DAU-5. CONCLUSION: DCS-1, DCS-2, and DFV carry amino acid substitutions at the extracellular vestibule, visualized by 3-dimensional modeling. Proline at position 226 greatly influenced the D antigen density and may reduce the RhD membrane integration. Although the F223V substitution is regarded as the initial event in the evolution of the weak D Type 4 cluster, the current DFV allele probably evolved independently, as evident from different RHCE haplotypes.     

1例新的弱D型的鉴定

目的分析1例新的Rh血型弱D型个体的RHD等位基因及其红细胞D抗原表位。方法采用常规血清学方法检测Rh血型D、C、c、E和e抗原表型,间接抗人球蛋白试验(IAT)确认D抗原,并分析D抗原表位;序列特异性引物-聚合酶链反应(PCR-SSP)测定RHD基因,然后分析RHD编码区全长序列,并检测RHD杂合型。结果血清学显示该个例为D抗原弱表现型,Rh因子为D+C+c+E-e+,PCR-SSP检测RHD基因显示与正常Rh(D)阳性对照相同。RHD编码区序列分析发现第9外显子存在1 212C>A碱基突变,其余外显子序列则与正常RHD基因一致(GenBank EF103573),RHD合子型鉴定为RHD+/RHD-杂合型,提示该个体基因型为CDe/cde。红细胞D抗原表位分析显示其具有基本完整D抗原表位。结论该个例为RHD1 212C>A碱基突变形成弱D72型。     

Molecular and serologic characterization of DWI, a novel "high-grade" partial D

BACKGROUND: Accurate D antigen identification is essential for pretransfusion and prenatal evaluation to prevent anti-D alloimmunization. Quantitative and qualitative D variants may pose typing problems and require particular consideration because of differing potential for anti-D induction. STUDY DESIGN AND METHODS: A novel partial D, DWI, was discovered in an anti-D-alloimmunized D+ Austrian woman. This D variant was investigated by RHD genotyping and nucleotide sequencing, as well as characterization of its serologic properties. RESULTS: The proposita exhibited a single-nucleotide exchange in RHD Exon 7 (1073T>C) predicting a Met358Thr substitution in the sixth extracellular loop of the RhD polypeptide. All DWI individuals identified (the proposita and two relatives) were genotyped DWIdCcee, which, together with the family tree, was highly suggestive of a DWICe haplotype association. Epitope mapping studies revealed only minor D antigen modification with weakening but not loss of epitopes D1.1, D9.1, and D16.1. Antigen density varied individually between 8000 and 8600 D sites per erythrocyte. No known low-frequency Rh antigen was detected. Despite the highly retained D epitope composition, the DWI proposita's serum sample contained alloanti-D from an immunization event many years earlier. CONCLUSION: The findings of this investigation emphasize the possible clinical significance of "high-grade" partial D variants that are likely to be missed by routine serology.     

RHD genotyping in weak D phenotypes by multiple polymerase chain reactions

BACKGROUND: Weak D phenotypes involve a quantitative variation of D. The genomic basis in weak D has been disputed, however. STUDY DESIGN AND METHODS: Five sequence-specific polymerase chain reactions (SSP- PCRs) on exons 2, 5, and 7 of the RHD gene were evaluated in 248 white and 98 Japanese blood donors and compared with the results obtained by amplification of intron 4 and serology. All methods and SSP-PCR testing on the 3′ non-coding region of the RHD gene were applied to the genotyping of 94 DNA samples derived from individuals expressing weak D phenotypes. RESULTS: Concordant results were obtained with all genotyping and phenotyping methods in testing 201 D-positive and 145 D- negative donors. Four of 94 weak D samples were typed as D-negative by amplification of intron 4 and SSP-PCR on exon 5. Phenotyping with monoclonal antibodies revealed a DVI category in one of these cases and DFR phenotype in three of these cases. One weak D sample, which reacted like normal D-positive cells with all applied monoclonal antibodies, was typed falsely negative by SSP-PCR on exon 5 because of a point mutation at nucleotide 667 (T–>G) that resulted in a Phe223Val amino acid substitution. In this individual, heterozygosity was found at two other amino acid positions (Glu233Gln and Val238Met) by restriction fragment length polymorphism analysis. CONCLUSION: Genetic diversity in weak D phenotypes is rare. Only 1 of 90 true weak D phenotypes (1.1%) had a genetic variation in testing on seven gene regions of the RHD gene.     

In-frame triplet deletions in RHD alter the D antigen phenotype

BACKGROUND: The deletion of three adjacent nucleotides in an exon may cause the lack of a single amino acid, while the protein sequence remains otherwise unchanged. Only one such in-frame deletion is known in the two RH genes, represented by the RHCE allele ceBP expressing a "very weak e antigen." STUDY DESIGN AND METHODS: Blood donor samples were recognized because of discrepant results of D phenotyping. Six samples came from Switzerland and one from Northern Germany. The molecular structures were determined by genomic DNA nucleotide sequencing of RHD. RESULTS: Two different variant D antigens were explained by RHD alleles harboring one in-frame triplet deletion each. Both single-amino-acid deletions led to partial D phenotypes with weak D antigen expression. Because of their D category V-like phenotypes, the RHD(Arg229del) allele was dubbed DVL-1 and the RHD(Lys235del) allele DVL-2. These in-frame triplet deletions are located in GAGAA or GAAGA repeats of the RHD exon 5. CONCLUSION: Partial D may be caused by a single-amino-acid deletion in RhD. The altered RhD protein segments in DVL types are adjacent to the extracellular loop 4, which constitutes one of the most immunogenic parts of the D antigen. These RhD protein segments are also altered in all DV, which may explain the similarity in phenotype. At the nucleotide level, the triplet deletions may have resulted from replication slippage. A total of nine amino acid positions in an Rhesus protein may be affected by this mechanism.     

DIIIa and DIII Type 5 are encoded by the same allele and are associated with altered RHCE*ce alleles: clinical implications

BACKGROUND: The partial D phenotype DIIIa was originally reported to be associated with 455A>C in Exon 3, 602C>G in Exon 4, and 667T>G in Exon 5. Other alleles with these changes were subsequently identified and designated DIII Types 5, 6, and 7, as they had additional alterations. The observation that DNA samples associated with the DIIIa phenotype had more changes than those originally reported motivated us to reanalyze the DIIIa probands (BP and DJ) from the original study. We also studied additional DIIIa samples to clarify the RHD background and establish the associated RHCE. STUDY DESIGN AND METHODS: Hemagglutination testing was performed by standard methods. RHD and RHCE were analyzed by combinations of polymerase chain reaction–restriction fragment length polymorphism, exon‐specific sequencing, cloning, or direct sequencing of Rh‐cDNAs. RESULTS: The RHD alleles from BP, DJ, and 58 additional DIIIa samples had the three reported nucleotide changes as well as 186G>T, 410C>T, and 819G>A. The DIIIa allele was associated with several altered RHCE*ce‐alleles, the prominent one being ceS (48C, 733G, 1006T). CONCLUSION: The DIIIa phenotype is associated with six RHD changes, five of which encode amino acid changes, and partial DIIIa and DIII Type 5 are encoded by the same RHD allele. In all samples, RHD*DIIIa was inherited with altered RHCE*ce. Patients with partial DIIIa are at risk for production of alloanti‐D, but they are also at risk for alloanti‐e, ‐c, or antibodies to high‐prevalence Rh antigens if there is no conventional RHCE*ce in trans. Among 39 patients studied, 16 had alloanti‐D and 27 had alloanti‐e or anti‐hrB.     

DEL红细胞膜D抗原表位分析

目的分析Rh血型D放散型(DEL)红细胞膜D抗原表位(epitopemapping)。方法采用微量吸收放散技术通过9种抗D抗原不同表位的人抗D单克隆抗体,检测3名已知Rh表型和RH基因型的D放散型个体的红细胞膜D抗原表位,分别以Rh阳性、Rh阴性、部分D表型DVa(Hus)和DVIⅢ型样本作为对照。结果3名携带RHD1227A等位基因的D放散型个体,红细胞膜D抗原9个抗原表位均检测为阳性,而对照样本检测结果各不相同。结论携带RHD1227A等位基因的中国汉族D放散型个体红细胞膜可能表达基本完整D抗原。     

E variants found in Japanese and c antigenicity alteration without substitution in the second extracellular loop

BACKGROUND: The molecular basis of E variants in the Japanese population is poorly understood. In this study, molecular analysis of E variants detected in Japanese by serologic methods was carried out. STUDY DESIGN AND METHODS: E variants from healthy Japanese blood donors were screened by serologic analysis using E MoAbs. Fifteen E variant samples were divided into three types--EFM, EKH, and EKK-on the basis of patterns of reactivity with five distinct E antibodies. The entire coding region of the Rh cDNAs from the E variant samples was analyzed by sequencing. RESULTS: Although the Rh cDNA sequences of the three types were different from each other, those of the EFM-type variants (RHEFM) had a partial DNA exchange in exon 5 between the RHCE and RHD genes, generating an RHcE variant (Gln233Glu, Met238Val). The cDNA of EKH-type variants (RHEKH) exhibited a point mutation (G461C) in exon 3 of the RHcE allele that resulted in an Arg154Thr substitution in the third external loop of the RhcE peptide. The EKK-type variant (RHEKK) carried a hybrid gene structure characterized by replacement of exons 1-3 (or 2-3) of the RHCE gene with those of the RHD gene. The RHD gene of a person possessing an E variant of the EKK type was also a hybrid gene, D-cE(2-3)-D or cE(1-3)-D (RHDKK). The E variants of types EKH and EKK showed weak c antigenicity. CONCLUSION: In serologic screening of 140,723 Japanese blood donors, 15 were found to possess E variants (0.011%). A new RHCE variant, RHEKH, was identified. On the basis of the variants found in this study, the c antigenicity seemed to be determined not only by Pro-103 but also by the structure of the third extracellular loop or the amino acids contained in it.