Validation of the multiplex ligation-dependent probe amplification assay and its application on the distribution study of the major alleles of 17 blood group systems in Chinese donors from Guangzhou

The study of variant s antigen expression revealing a novel c.160C>T (p.Arg54Cys) variant on GYPB*s allele associated with partial s phenotype

BACKGROUND

Little s antigen is mainly defined by a single nucleotide polymorphism at c.143C (p.Thr48) on the GYPB gene. Several variants on GYPB can alter the expression of s antigen. The aim of this study was to investigate the molecular basis of variant s antigen expression in the Chinese population.

STUDY DESIGN AND METHODS

A total of 4983 whole blood samples were collected to screen the individuals with discrepant s typing results using two different monoclonal anti-s. Then, the sequence of GYPB exon 4 was analyzed by Sanger sequencing. Flow cytometry analysis was performed to quantify s antigen expression on red blood cells (RBCs). In vitro expression study was performed to verify the effect of the GYPB variants identified on the expression of s antigen.

RESULTS

Four donors were identified to have discrepant s typing results. Sanger sequencing showed that three donors carried the c.173C > G variant (p.Pro58Arg) specific for sD antigen, the other one carried a novel GYPB (c.160C > T, p.Arg54Cys) variant. Flow cytometry identified a partial and weak expression of s antigen on the RBCs of the four donors. Furthermore, in vitro expression study confirmed the effect of the two variants on the s antigen expression.

CONCLUSION

The results demonstrated that in addition to p.Thr48, the two extra amino acids p.Arg54 and p.Pro58 are also important for full expression of s antigen. Since the individuals with partial s antigen are at risk for the development of alloanti-s, it is important to select at least two different monoclonal anti-s for correct s typing.

Genotyping Approach to Predict Coa and Cob Antigens in Thai Blood Donor Populations

Purpose

Co^a and Co^b antigens of the Colton (CO) blood group system are implicated in acute and delayed hemolytic transfusion reactions (HTRs). Owing to the inadequate supply of specific antiserum, data on CO phenotypes remain limited. This study aimed to develop genotyping methods to predict Co^a and Co^b antigens and to estimate transfusion-induced alloimmunization risks in three Thai blood donor populations.

Materials and Methods

The study included 2451 blood samples from unrelated healthy Thai blood donors obtained from central, northern, and southern Thailand. DNA sequencing was used to determine the CO*A and CO*B alleles. In-house PCR with sequence-specific primers (PCR-SSP) and high-resolution melting curve (HRM) assays were performed and genotyping results were compared using DNA sequencing. CO*A and CO*B allele frequencies among Thais were determined using PCR-SSP and their frequencies were compared with other populations. The risks of Co^a and Co^b transfusion-induced alloimmunization among Thai donor populations were calculated.

Results

The validated genotyping results by PCR-SSP and HRM assays agreed with DNA sequencing. The CO*A/CO*A was the most common (100.0, 100.0, and 99.3%), followed by CO*A/CO*B (0.0, 0.0, and 0.7%) among central, northern and southern Thais. Homozygous CO*B/CO*B was not found. The CO*A and CO*B allele frequencies among central Thais significantly differed compared among southern Thais (p < 0.01) but not among northern Thais. Those allele frequencies among Thais were similar to those of Taiwanese, Chinese and Malay-Malaysian populations but not to South Asian, Southeast Asian, Korean, Japanese, Filipino, French Basque, and Maltese populations (p < 0.01). A higher risk of anti-Co^b production rather than anti-Co^a production was particularly noted in the southern Thai population.

Conclusion

This study constitutes the first to determine CO*A and CO*B genotypes using PCR-SSP and HRM assays among Thais and this finding would be beneficial in predicting alloimmunization risk and providing safe transfusions among Thais.

Identification of a novel DI*02(2558T) allele associated with weakened expression of DI2 antigen

BACKGROUND

The distribution of DI1/DI2 antigens of the Diego blood group system is polymorphic in Mongoloid populations and the corresponding alloantibodies are clinically significant. Here a novel DI variant was found by donor screening, and the effect of the novel and previously reported mutations on expression of DI1/DI2 antigens and Band 3 protein was explored.

STUDY DESIGN AND METHODS

DNA samples of 1150 Chinese donors were collected. DI*01/DI*02 genotyping was determined by Sanger sequencing. For the carrier of novel allele, the expression of Band 3 and DI1/DI2 antigens on red blood cells (RBCs) was detected by Western blot and flow cytometry, respectively. in vitro expression studies were conducted by transfecting the mutant (including the novel and three reported DI*02(2534T), DI*02(2358_2359insCAC), and DI*02(2572T) alleles) or wild-type DI*02 constructs into HEK 293T cells, the expression of Band 3 and DI1/DI2 antigens was analyzed.

RESULTS

A novel heterozygous mutation (c.2558C>T, p.Thr853Met), which is located near the DI1/DI2 polymorphism site (c.2561T>C), was identified in a donor with DI:-1,2 phenotype. Reduced expression of DI2 antigen was observed on the RBCs, while weakened expression of Band 3 and absence of DI2 antigen were detected in cells transfected with the mutant DI*02(2558T) construct. In addition, absent or decreased expression of Band 3 and DI2 antigen was also detected in cells transfected with three reported mutant constructs.

CONCLUSION

The novel DI*02(2558T) allele and three previously described DI mutations can affect the expression of Band 3 protein and/or DI2 antigen and/or interfere with DI*01/DI*02 genotyping result.

Hybrid glycophorin and red blood cell antigen genotyping in Asian American type O blood donors with Mia phenotype

BACKGROUND

The GP.Mur glycophorin with Mi^a phenotype is relatively common and clinically significant in the Southeast Asian populations. The aim of this study is to genotype Mi^a -positive Asian American type O blood donors. Red blood cell (RBC) minor antigens were also determined in the same cohort.

STUDY DESIGN AND METHODS

Asian American blood donors of the Gulf Coast Regional Blood Center (Houston, TX) were screened using a typing reagent (NOVACLONE Anti-Mi^a Monoclonal IgG Typing Reagent, Dominion Biologicals Ltd) from March 2016 to July 2018. Aliquots of Mi^a -positive blood from type O donors were subjected to serologic confirmation using Mi^a - and/or Mur-specific GAMA210 and 64D6 monoclonal antibodies, and two human antisera. Extracted genomic DNA was amplified by polymerase chain reaction (PCR) using GYP hybrid gene/allele-specific primers followed by bidirectional Sanger sequencing. Zygosity for GYP*Mur and GYP*Bun was determined using TaqMan real-time PCR assay. Phenotypes of 35 RBC antigens and three phenotypic variants were determined with use of an in vitro diagnostic test, PreciseType HEA Molecular BeadChip Test (Immucor).

RESULTS

By screening 4600 blood donations in the Houston metropolitan area, 209 samples from 103 unique donors were identified to be Mi^a -positive. By PCR and sequencing analysis, 97 of the 103 Mi^a -positive donors carried hybrid genes GYP*Mur (89.7% including two homozygotes), GYP*Bun (6.2%), GYP*Vw (3.1%) and GYP*Hut (1.0%). Concordance between serology and DNA analysis was 98%, 99%, and 100% for the GAMA210, 64D6, and human antisera, respectively. Genotyping of RBC antigens showed that the Mi^a -positive donors were predominantly associated M+ N- S- s+ (48.5%) and M+ N+ S- s+ (38.1%) phenotypes.

CONCLUSIONS

The GP.Mur glycophorin is most prevalent in the Mi^a -positive Asian American type O blood donors.

Application of Multiplex Ligation-Dependent Probe Amplification Assay for Genotyping Major Blood Group Systems Including DEL Variants in the D-Negative Korean Population

Background

The DEL blood type, a very weak D variant, is a major concern in the field of transfusion medicine because of its potential to cause anti-D alloimmunization. We investigated the molecular basis of serologically D-negative phenotypes, including the DEL type, and the distribution of other blood group systems in the Korean population using the recently developed multiplex ligation-dependent probe amplification (MLPA) assay.

Methods

Blood group genotyping using the MLPA assay and RhCE phenotyping were performed on randomly selected 95 D-negative red blood cell products. The MLPA results were verified by multiplex PCR for the RHD promoter, exons 4, 7, and 10 and by direct sequencing of RHD exon 9.

Results

Out of 95 cases, total deletion of the RHD was observed in 74 cases (77.9%) and four cases (4.2%) had an RHD-CE-D hybrid allele. The other 17 cases (17.9%) had an RHD(1227G>A) allele, which was further confirmed by sequencing analysis. The RhCE phenotypes of RHD(1227G>A) alleles were composed of 14 Cce and 3 CcEe, and all 60 cases of the ce phenotype were revealed to have a total deletion of the RHD. Genotyping results and allele distribution of the other 17 blood group systems were consistent with previous reports on the East Asian population.

Conclusions

MLPA assay correctly determined RHD genotype, including RHD-CE-D hybrid alleles or RHD(1227G>A) allele, and other clinically relevant blood group genotypes in D-negative Koreans. The use of MLPA assay on serologically D-negative individuals may help improve transfusion safety by preventing anti-D alloimmunization.