ABO genotyping by TaqMan assay and allele frequencies in a Japanese population

Allele-specific long-range sequencing as a method for ABO haplotyping in clinical blood group diagnosis and immunohematology research

BACKGROUND

Safe transfusion therapy requires accurate testing of blood donors and recipients to determine their ABO blood group compatibility. Genotyping does not always clarify serological blood typing discrepancies and conventional PCR methods are not suitable to identify ABO haplotypes. Therefore, an allele-specific long-range sequencing-based typing method was established.

METHODS

Study samples (n = 100) and six patient samples were ABO phenotyped and screened for specific single nucleotide polymorphisms (SNP) in the ABO gene. Based on identified heterozygous SNPs in intron 1 (12897G>A), 2 (437C>T) or 4 (102C>A, 1511G>T) both ABO alleles were investigated separately using a high-fidelity long-range PCR system and Sanger sequencing. The alleles were correlated to the ABO phenotypes determined.

RESULTS

Direct sequencing of allelic PCR products up to 6743 bases has been successful in discriminating common combinations of the ABO*A1.01, ABO*A2.01, ABO*B.01, ABO*O.01.01, ABO*O.01.02 and ABO*O.02.01 alleles. 10 out of 64 haplotypes were found to be not previously described. The uncommon ABO*AW.31.01 and the unusual O alleles ABO*O.05 and ABO*O.02.03 alleles were detected in patient samples, resolving the initial inconclusive serologic ABO typing results.

CONCLUSION

This method is an effective tool for analyzing ABO haplotypes. Applicable for ABO molecular diagnostics and immunohematology research it may help to improve pre-transfusion blood type testing.

Safety Profile and Effectiveness of Rivaroxaban for Patients With Venous Thromboembolism in Japan - Results From Post-Marketing Surveillance (XASSENT)

BACKGROUND

The incidence of venous thromboembolism (VTE; pulmonary embolism [PE] and/or deep vein thrombosis [DVT]) in Japan is increasing, but relatively small numbers of patients from Japan have been included in studies investigating rivaroxaban (a direct factor Xa inhibitor) for the treatment of VTE and preventing its recurrence.

METHODS AND RESULTS

An open-label, prospective, observational study (XASSENT [NCT02558465]) investigated the safety profile and effectiveness of rivaroxaban for ≤2 years in the treatment of VTE and prevention of its recurrence in Japanese clinical practice. Primary outcomes were major bleeding and symptomatic recurrent VTE. Statistical analyses were exploratory and descriptive. Overall, 2,540 patients were enrolled (safety analysis population [SAP], n=2,387; effectiveness analysis population [EAP], n=2,386). In the SAP, >80% of patients received the approved rivaroxaban dose, the mean (standard deviation) age was 66.6 (15.0) years, ≈74% were >50 kg, and 43% had a creatinine clearance ≥80 mL/min. PE+DVT, PE only, and DVT only were reported in 42%, 8%, and 50% of patients, respectively, and active cancer in 17% of patients. Major bleeding was reported in 69 patients (2.89%; 3.60%/patient-year; SAP) and symptomatic PE/DVT recurrence in 26 patients (1.09%; 1.36%/patient-year; EAP) during the treatment period.

CONCLUSIONS

XASSENT provided information on the expected proportions of bleeding and VTE recurrence during rivaroxaban treatment in Japanese clinical practice; no new concerns of safety or effectiveness were found.

Detection of five common variants of ABO gene by a triplex probe-based fluorescence-melting-curve-analysis

Current studies have suggested that the ABO blood group system is associated with several clinical conditions. For large-scale genotyping of ABO alleles, we developed a triplex fluorescence melting curve analysis (FMCA) to determine five single nucleotide variants (SNVs), c.261delG, c.796C>A, c.802G>A and c.803G>C and c.1061delC, responsible for common ABO phenotypes using dual-labeled self-quenched (TaqMan) probes in a single tube. We accurately determined c.796C>A, c.802G>A, and c.803G>C genotypes using a FAM-labeled probe, c.261delG using a CAL Fluor Orange 560- labeled probe, and c.1061delC using a Cy5-labeled probe. The present genotyping results of five SNVs in 214 subjects of the 1000 Genomes Project were in full agreement with those of the database sequence. The predicted ABO phenotypes using combinations of these five SNVs by this method in 288 Japanese subjects were in complete agreement with those by hemagglutination assay, although we did not find any A2 (alleles containing c.1061delC) or O.02 (alleles containing c.802G>A) alleles. The present triplex probe-based FMCA is a valid and credible method for a considerably accurate large-scale determination of ABO allele genotypes and estimation of phenotypes.

Mechanism evaluation for an amino acid substitution p.Y246C of B-glycosyltransferase enzyme with Bweak phenotype

BACKGROUND

The amino acid substitutions caused by ABO gene variants are usually predicted to impact the glycosyltransferase function. Here, the effect of an amino acid substitution in the vicinity of the catalytic active region of the B-glycosyltransferase was explored in vitro and in silico study, which is important for further recognizing the ABO subgroup.

METHODS

The ABO serological tests were performed by the routine methods. The ABO genotype was analyzed by polymerase chain reaction and sequenced bidirectionally. The haplotype of the variant allele was separated using single-strand amplification and sequencing with allele-specific primers. Stably expression cell lines with variant were constructed for study in vitro. 3D structure of the B-glycosyltransferase (GTB) variant was simulated by PyMOL software. The free energy change (ΔΔG) was calculated by FoldX.

RESULTS

A variant c.737A > G was identified in a Chinese individual with Bweak phenotype, which led to an amino acid substitution p.Y246C in the vicinity of the catalytic active region of GTB enzyme. The stably expression cell lines with variant and wild type were successfully established and showed that the variant caused a decrease in protein levels and/or enzyme activity. The 3D structural of the GTB modelling found the amino acid substitution p.Y246C caused the hydrogen bond of the protein changes. Meanwhile, the free energy change (ΔΔG) value predicted the destabilizing effect on the variant GTB.

DISCUSSION

The p.Y246C variant in the vicinity of the enzyme active centre reduced the antigen expression because of greatly destabilizing effect on the GTB variant.

The epidemiological characteristics of thromboembolism related to oral contraceptives in Japan: Results of a national survey

AIM

The aim of this study was to reveal the epidemiological characteristics of thromboembolism related to combined oral contraceptives (COCs) in Japan.

METHODS

A survey of confirmed thromboembolism patients among Japanese COC users was conducted at randomly selected hospitals from across Japan. The survey examined six types of venous thromboembolism (VTE) and arterial thromboembolism (ATE) in all COC users: pulmonary embolism, deep vein thrombosis, other venous thrombosis, cerebral infarction, myocardial infarction, and other arterial thrombosis. The survey covered 5 years from 2009 to 2013. This study was approved in an ethical review by Hamamatsu University School of Medicine.

RESULTS

Four hundred and twenty-five cases clearly related to COCs were analyzed. The annual estimated incidence rates per 10 000 person-years of VTE, ATE and all thromboembolisms in all COC users were 1.17, 0.33 and 1.50, respectively. The incidence of thromboembolism was 35.2% within 30 days from the start of COCs, 53.8% within 90 days, 66.9% within 180 days and 78.2% within 360 days regardless of progestin type. Age adjusted odds ratios in the obese and underweight groups were 2.33 and 0.98 for overall thromboembolism, 2.59 and 0.77 for VTE, and 1.11 and 1.28 for ATE compared with the standard group, respectively. Odds ratios for thromboembolism in non-O blood groups were 1.89 for overall thromboembolism, 2.16 for VTE, and 1.35 for ATE, when compared with the O blood group.

CONCLUSION

The epidemiological characteristics of COC-related thromboembolisms were revealed in this national survey covering the years from 2009 to 2013.

ABO blood type compatibility is not a risk factor for gestational trophoblastic neoplasia development from androgenetic complete hydatidiform moles

PROBLEM

Complete hydatidiform moles (CHMs) are allografts to patients in terms of an androgenetic origin. Thus, some immunological reactions may be involved in the development of gestational trophoblastic neoplasia (GTN) from CHMs. This study aimed to evaluate the effect of ABO blood group on the prognosis of androgenetic CHMs.

METHOD OF STUDY

A total of 129 patients who were diagnosed as having CHMs based on multiplex short tandem repeat polymorphism analysis were included. The ABO blood types of molar tissues were determined by single-nucleotide polymorphisms in the ABO gene using a high-resolution melting assay. The incidence of GTN was compared based on ABO compatibility between the patients and their molar tissues.

RESULTS

The overall incidence of GTN was 17.1% (22/129). Gestational trophoblastic neoplasia occurred in 10.8% (4/37), 14.8% (8/54), 22.2% (6/27), and 36.4% (4/11) of type O, A, B, and AB patients, respectively. Type AB patients tended to develop GTN compared with other blood type patients (P = .093). In ABO type of CHMs, GTN occurrence was not significantly different as it was 16.4% (10/64), 16.0% (8/50), and 22.2% (4/18) for types O, A, and B, respectively (P = .854). According to the ABO incompatibility between patients and molar tissues, GTN occurred in 19.1% (18/94) of the compatible cases and 11.4% (4/35) of the incompatible cases; the occurrence was not significantly different (P = .223).

CONCLUSION

Patients with type AB tended to develop GTN. However, ABO compatibility between patients and molar tissues had no relationship with GTN occurrence.

Rapid and Reliable One-Step ABO Genotyping Using Direct Real-Time Allele-Specific PCR and Melting Curve Analysis Without DNA Preparation

ABO genotyping is a molecular diagnostic technique important for transfusion and transplantation in medicine, and human identification in forensic science. Because ABO genotyping are labor intensive and time consuming, the genotyping cannot be firstly used to resolve the serological ABO discrepancy in blood bank. For rapid one-step ABO genotyping, we developed direct, real-time, allele-specific polymerase chain reaction (PCR), and melting curve analysis (DRAM assay) without DNA preparation. In DRAM assay, we used a special PCR buffer for direct PCR, a rapid RBC lysis buffer, white blood cells as template without DNA preparation, allele-specific primers for discriminating three ABO alleles (261G/del, 796C/A, and 803G/C), and melting curve analysis as a detection method. There was 100% concordance among the results of ABO genotyping by the DRAM assay, serologic typing, PCR-RFLP and PCR-direct sequencing of 96 venous blood samples. We were able to reduce the number of manual steps to three and the hands-on time to 12 min, compared to seven steps and approximately 40 min for conventional ABO genotyping using allele-specific PCR with purified DNA and agarose gel electrophoresis. We have established and validated the DRAM assay for rapid and reliable one-step ABO genotyping in a closed system. The DRAM assay with an appropriate number of allele-specific primers could help in resolving ABO discrepancies and should be valuable in clinical laboratory and blood bank.

Frequency of ABO/Rhesus (D) blood groupings and ethnic distribution in the Greater-Accra region of Ghana, towards effective blood bank inventory

Knowledge on blood group phenotypes is of key importance in clinical practice. It used in blood transfusion practice to determine the direction of recruitment of voluntary donors as required for each population within a country, and for disease association and population genetics studies. This study aimed at reporting the frequency of ABO and Rhesus (Rh) groups in the population of the Greater-Accra region of Ghana and amongst their various ethnic groups. A retrospective study in 11 main hospitals within the region was done. Data collected provided information on the blood group status of persons (both blood donors and recipients) who visited the selected hospitals. Medical records used were within the years 2012-2017. A total of 42,317 (26,802 males and 15,515 females) data were retrieved and analysed. The frequencies of the blood groups O, A, B and AB were 50.0%, 24.3%, 20.7% and 5.0%, respectively. Rhesus-positive to negative ratio was 93.2%/6.2%. Frequencies of blood group O was highest (49.1%-53.6%) in all ethnic groups. The second most dominant blood group was B (24.2%-25.4%) in the Ga-Adamgbe, Akan and Ewe ethnic groups, whilst blood group A (25.0%-26.9%) was the second most dominant in the Northerners and non-Ghanaians. Blood group distribution amongst gender and different age groups showed no significant differences but followed the same pattern for the general population. The study provides data on the ethnic distribution and frequency of ABO and Rhesus blood groupings in the Greater-Accra region of Ghana. It also informs the need for blood banks in the region to increase the proportion of stockpiled Rhesus-positive blood groups especially for O, B and A that may be high in demand.

Blood Group Distribution in Switzerland - a Historical Comparison

BACKGROUND

Ethnicities differ in prevalence of blood groups and antigens. Substantial donor-recipient mismatch within mixed-ethnic societies may render certain recipients at higher risk for alloimmunization. Data regarding antigen distribution within Switzerland by ethnicity is limited. We examined immigration patterns against the distribution of ABO blood groups using large cross-sectional Swiss samples spanning 70 years.

METHODS

Historical ABO blood group distribution data (1940-1945) from Swiss army personnel (n = 275,664) were sourced from the literature. Recent blood group phenotypes of 122,925 individuals who presented themselves at army recruitment centers (2004-2015) were obtained, alongside a validation sample of 175,202 patients from a university hospital. Two-sample tests with z-statistics assessing blood groups between samples were used.

RESULTS

The respective proportions of A (47.2% and 45.2%), B (8.4% and 9.8%), and AB (3.0 and 4.1) in the historical and recent army samples were significantly different (p < 0.001), while group O was not. Conclusion: ABO blood groups in Switzerland have remained stable despite substantial immigration with a changing foreign-national profile. Further research is needed to improve the understanding of antigen differences in newly introduced ethnic groups. Blood product requirements and public health initiatives aimed at recruiting blood donors would benefit from this information.

Rapid ABO genotyping by high-speed droplet allele-specific PCR using crude samples

BACKGROUND

ABO genotyping has common tools for personal identification of forensic and transplantation field. We developed a new method based on a droplet allele-specific PCR (droplet-AS-PCR) that enabled rapid PCR amplification. We attempted rapid ABO genotyping using crude DNA isolated from dried blood and buccal cells.

METHODS

We designed allele-specific primers for three SNPs (at nucleotides 261, 526, and 803) in exons 6 and 7 of the ABO gene. We pretreated dried blood and buccal cells with proteinase K, and obtained crude DNAs without DNA purification.

RESULTS

Droplet-AS-PCR allowed specific amplification of the SNPs at the three loci using crude DNA, with results similar to those for DNA extracted from fresh peripheral blood. The sensitivity of the methods was 5%-10%. The genotyping of extracted DNA and crude DNA were completed within 8 and 9 minutes, respectively. The genotypes determined by the droplet-AS-PCR method were always consistent with those obtained by direct sequencing.

CONCLUSION

The droplet-AS-PCR method enabled rapid and specific amplification of three SNPs of the ABO gene from crude DNA treated with proteinase K. ABO genotyping by the droplet-AS-PCR has the potential to be applied to various fields including a forensic medicine and transplantation medical care.

Allelic variance among ABO blood group genotypes in a population from the western region of Saudi Arabia

Background

Characterization of the ABO blood group at the phenotype and genotype levels is clinically essential for transfusion, forensics, and population studies. This study elucidated ABO phenotypes and genotypes, and performed an evaluation of their distribution in individuals from the western region of Saudi Arabia.

Methods

One-hundred and seven samples underwent standard serological techniques for ABO blood group phenotype analysis. ABO alleles and genotypes were identified using multiplex polymerase chain reaction, and electrophoretic analysis was performed to evaluate the highly polymorphic ABO locus.

Results

A phenotype distribution of 37.4%, 30.8%, 24.3%, and 7.5% was found for blood groups O, A, B, and AB respectively in our study cohort. Genotype analysis identified 10 genotype combinations with the O01/O02 and A102/O02 genotypes being the most frequent with frequencies of 33.6% and 14.95%, respectively. Common genotypes such as A101/A101, A101/A102, A101/B101, B101/B101, and O01/O01 were not detected. Similarly, the rare genotypes, cis-AB01/O02, cis-AB01/O01, and cis-AB01/A102 were not found in our cohort. The most frequently observed allele was O02 (35.98%) followed by the A102 allele (17.76%). Furthermore, our findings are discussed in reference to ABO allele and genotype frequencies found in other ethnic groups.

Conclusion

The study has a significant implication on the management of blood bank and transfusion services in Saudi Arabian patients.

ABO Blood Type and Personality Traits in Healthy Japanese Subjects

There is no scientific consensus that a relationship exists between the ABO blood group and personality traits. However, a recent study hypothesized that the dopamine beta-hydroxylase (DBH) gene is in linkage with the ABO gene. The sample population consisted of 1,427 healthy Japanese subjects who completed the Temperament and Character Inventory (TCI). Each subject's ABO blood type was determined by genotyping the rs8176719 and rs8176746 ABO gene single-nucleotide polymorphisms (SNPs) using a TaqMan genotyping assay. The relationships between the six ABO genotypes or four ABO phenotypes and personality traits were examined using a multivariate analysis of covariance (MANCOVA), controlling for age and sex. The MANCOVA data showed a significant difference in TCI scores among the ABO genotype groups (F [7, 1393] = 3.354, p = 0.001). A subsequent univariate analysis showed a significant difference in the mean scores for Persistence among the genotype groups (F = 2.680, partial η2 = 0.010, p = 0.020). Similarly, dividing the ABO blood type into four phenotypes revealed a significant difference among the phenotype groups (F [7, 1397] = 2.529, p = 0.014). A subsequent univariate analysis showed a significant difference among the phenotype groups in the mean scores for Persistence (F = 2.952, partial η2= 0.006, p = 0.032). We observed a significant association between ABO blood group genotypes and personality traits in a large number of healthy Japanese subjects. However, these results should be regarded as preliminary and should be interpreted with caution because it is possible that the association between ABO blood group genotype and the Persistence trait is relatively weak.

A New Method for Analyzing the Duffy Blood Group Genotype by TaqMan Minor Groove Binding Probes

BACKGROUND

Duffy blood group genotyping is useful to ensure transfusion safety and determine the association of Duffy blood group polymorphism with diseases, and therefore has its clinical significance. In order to improve the existing methods for genotyping of Duffy blood group, which normally require post-PCR manipulation, a new method was developed by using 5'-nuclease assay (NA) with TaqMan minor groove binding (MGB) probes.

METHODS

Primers and TaqMan-MGB probes were designed and synthesized to genotype FY*A and FY*B alleles at Duffy blood group locus on a real-time PCR platform. A total of 120 samples were genotyped by using the new 5'-NA and conventional polymerase chain reaction with allele-specific primers (PCR-ASP). The results obtained by the two methods were compared.

RESULTS

There was a complete concordance of results for all samples genotyped by 5'-NA and PCR-ASP. The retesting results of 5'-NA were consistent with those of the initial testing. The detection limit of 5'-NA was determined as 100 pg per reaction. The FY*A and FY*B allelic frequencies were 93.3% and 6.7% respectively in the Chinese Han population in Dalian.

CONCLUSIONS

The 5'-NA for genotyping of Duffy blood group is simple, rapid, reliable, reproducible, sensitive, and high-throughput and is superior to PCR-ASP used in routine genotyping.