Applying molecular immunohaematology to regularly transfused thalassaemic patients in Thailand

A comparison of serological phenotyping and molecular genotyping for Kell, Kidd, and Duffy antigens in multi-transfused thalassemia patients

BACKGROUND

In multi-transfused thalassemia patients, serological phenotyping fails to test patient's actual blood group antigen profile due to the presence of donor red blood cell (RBC) in the circulation. This limitation of serological tests can be overcome by genotype determination using the polymerase chain reaction (PCR)-based methods. The aim of this study is to compare the serological phenotyping of Kell, Kidd, and Duffy blood group systems with molecular genotyping in the normal blood donors and multi-transfused thalassaemia patients.

MATERIALS AND METHODS

Blood samples from 100 normal blood donors and 50 thalassemia patients were tested using standard serological techniques and PCR-based methods for Kell (K/k), Kidd (Jka/Jkb), and Duffy (Fya/Fyb) blood group systems. The results were compared for concordance.

RESULTS

Genotyping and phenotyping results were 100% concordant for normal blood donors whereas those for thalassemia patients showed 24% discordance. The frequency of alloimmunization in thalassemia patients was 8%. The results of genotyping were used to provide Kell, Kidd, and Duffy matched blood for transfusion therapy to thalassemia patients.

CONCLUSION

The actual antigen profile in multitransfused thalassaemia patients can be reliably determined using genotyping. This would benefit in providing better antigen matched transfusion therapy to such patients hence reducing the rate of alloimmunization.

Kidd Blood Group Genotyping for Thalassemia Patient in Iran

We aimed to determine the JK genotype in thalassemia patients from Iran using different molecular methods to compare with phenotyping results. We also aimed to standardize for the first time, the Tetra-Primer ARMS PCR method for JK genotyping. The serology method cannot correctly determine the phenotype of blood group antigens in patients with multiple blood transfusions. Peripheral blood samples were taken from two hundred alloimmunized thalassemic patients in Tehran Adult Thalassemic Clinic. The samples were tested phenotypically by routine serological methods. After DNA Extraction, SSP-PCR was performed. DNA sequencing and PCR-RFLP were used to confirm the SSP-PCR results. Discrepancies were found between the phenotype and genotype in 32 out of 200 cases. In 16 cases phenotype was determined as Jk (a + b +) but genotype was JK*A/JK*A, in 14 cases phenotype was Jk (a + b +) while the genotype showed JK*B/JK*B, 1 case had been phenotyped as Jk (a + b -) but it was genotyped as JK*A/JK*B and 1 case had been phenotyped as Jk (a - b +) but it was genotyped as JK*A/JK*B. Serological results for a few samples could not be confirmed because of mix-field agglutination. The genotyping however verified the presence of Kidd alleles. Molecular methods are a valuable tool to predict blood group phenotypes in multi-transfused patients in order to select RBC units for a perfect matching improving blood transfusion and preventing alloimmunization. Also Tetra-Primer ARMS PCR is simple and cost effective methods that could be alternative by conventional Molecular methods.

Red Cell Transfusions in the Genomics Era

Red cell genotyping has become widely available and now contributes to support transfusion of patients with hematologic diseases. This technology has facilitated the immunohematologic approach to antibody prevention, detection and identification. Donors, particularly rare donors, are most efficiently screened and identified by red cell genotyping. In transfused patients with challenging serologic reactivity, antibodies are more reliably identified when molecular typing information is available. Red cell genotyping of both donors and patients augments the selection of blood components. This technology, serving at the core of a real-time database inventory, is resulting in blood supply efficiencies. However, there is limited published evidence on the extent to which red cell genotyping has translated into improved clinical outcomes. Red cell alloimmunized patients may benefit the most in enhanced safety. For patients with antibodies to high-prevalence antigens, other than Rh, blood centers realized supply-chain efficiencies in the past decade. Prospective clinical trials and cost-effectiveness studies would contribute to further clarifying the optimal role of molecular testing in providing transfusion support for patients with hematologic diseases.

Molecular genotyping of clinically important blood group antigens in patients with thalassaemia

Background & objectives:

In multitransfused thalassaemic patients, haemagglutination fails to phenotype the patient's blood group antigens due to the presence of donor-derived erythrocytes. DNA-based methods can overcome the limitations of haemagglutination and can be used to determine the correct antigen profile of these patients. This will facilitate the procurement of antigen-matched blood for transfusion to multitransfused patients. Thus, the aim of this study was to compare the serological phenotyping of common and clinically important antigens of Rh, Duffy, Kell, Kidd and MNS blood group systems with molecular genotyping amongst multitransfused thalassaemic patients.

Methods:

Blood samples from 200 patients with thalassaemia and 100 ‘O’ group regular blood donors were tested using standard serological techniques and polymerase chain reaction-based methods for common antigens/alleles (C, c, D, E, e, Fy^a, Fy^b, Jk^a, Jk^b, K, k, M, N, S, s).

Results:

Genotyping and phenotyping results were discordant in 77 per cent of thalassaemic patients for five pairs of antithetical antigens of Rh, Duffy, Kell and Kidd blood group systems. In the MNS blood group system, 59.1 per cent of patients showed discrepancy. The rate of alloimmunization among thalassaemics was 7.5 per cent.

Interpretation & conclusions:

Molecular genotyping enabled the determination of the actual antigen profile in multitransfused thalassaemia patients. This would help reduce the problem of alloimmunization in such patients and would also aid in the better management of transfusion therapy.

How we evaluate red blood cell compatibility and transfusion support for patients with sickle cell disease undergoing hematopoietic progenitor cell transplantation

Multiple hematopoietic progenitor cell (HPC) transplantation options for patients with sickle cell disease (SCD) are currently under investigation. Patients with SCD have a high rate of alloimmunization to red blood cell antigens, often complicating transfusion support. Transfusion reactions, including acute and delayed hemolytic reactions, have been observed despite immunosuppressive regimens. Allogeneic donor transplants have been shown to carry a risk of prolonged reticulocytopenia and acute hemolysis with severe anemia in nonmyeloablative regimens. We discuss our experience providing transfusion support to patients with SCD undergoing HPC transplantation, propose an outline for a complete pretransplantation evaluation, and discuss donor/recipient compatibility issues and their implications.

Rh-Matched Transfusion through Molecular Typing for β-Thalassemia Patients Is Required and Feasible in Chinese

Background

Molecular typing for RHCE blood group alleles has been established in many countries for patients and blood donors. In the Chinese literature nearly 80% of transfused patients with alloimmunization have antibodies specific for antigens of the Rh blood group system. We investigated if it is feasible to match packed red blood cells (RBCs) for Chinese β-thalassemia patients by RHCE genotyping.

Methods

In this study, 481 patients with β-thalassemia were enrolled. They were genotyped for RHCE alleles by a simple PCR method with sequence-specific primers (PCR-SSP). Among these patients, 203 continuously received RBCs of the identical Rh subgroups according to the genotyping results for at least 3 months. Subsequently, their phenotypes were tested through a micro-column gel card method. For validation purposes, 400 donors were serologically typed with the same technology, of which 164 were genotyped too. Finally, the C, c, E, and e frequencies and the feasibility of the simple genotyping method were analyzed.

Results

All patients showed mixed-field agglutination in the Rh subgroup gel cards before the same Rh subgroups in blood donors were selected for blood transfusion. The results, however, lacked mixed-field agglutination in all 203 cases after transfusion with RBC concentrates selected for the patient's C, c, E, and e antigens for at least 3 months. The genotyping results of 164 donors were all consistent with the serological results. Whole coding regions of RHCE were sequenced in 7 individuals with weak c, E, or e antigens. In only one sample we observed a 1059G>A nucleotide mutation coding for a truncated RhCE polypeptide (GenBank KT957625), in the other 6 samples no sequence variant was found. Both patients and donors were predominantly CcEe and CCee, with a prevalence of 55.3% and 24.9% for patients or 49.3% and 31.3% for donors, respectively. It revealed that about 80% of Chinese could receive Rh-matched RBCs easily.

Conclusion

A simple RHCE genotyping technique is safe enough for Rh-matched transfusion of β-thalassemia patients in Chinese Han.

Two large deletions extending beyond either end of the RHD gene and their red cell phenotypes

Only two partial deletions longer than 655 nucleotides had been reported for the RHD gene, constrained within the gene and causing DEL phenotypes. Using a combination of quantitative PCR and long-range PCR, we examined three distinct deletions affecting parts of the RHD gene in three blood donors. Their RHD nucleotide sequences and exact boundaries of the breakpoint regions were determined. DEL phenotypes were caused by a novel 18.4 kb deletion and a previously published 5.4 kb deletion of the RHD gene; a D-negative phenotype was caused by a novel 7.6 kb deletion. Examination of the deletion-flanking regions suggested microhomology-mediated end-joining, replication slippage, and non-homologous end-joining, respectively, as the most likely mechanisms for the three distinct deletions. We described two new deletions affecting parts of the RHD gene, much longer than any previously reported partial deletion: one was the first deletion observed at the 5' end of the RHD gene extending into the intergenic region, and the other the second deletion observed at its 3' end. Large deletions present at either end are a mechanism for a much reduced RhD protein expression or its complete loss. Exact molecular characterization of such deletions is instrumental for accurate RHD genotyping.

Red cell genotyping precision medicine: a conference summary

This review summarizes the salient points of the symposium 'Red Cell Genotyping 2015: Precision Medicine' held on 10 September 2015 in the Masur Auditorium of the National Institutes of Health. The specific aims of this 6th annual symposium were to: (1) discuss how advances in molecular immunohematology are changing patient care; (2) exemplify patient care strategies by case reports (clinical vignettes); (3) review the basic molecular studies and their current implications in clinical practice; (4) identify red cell genotyping strategies to prevent alloimmunization; and (5) compare and contrast future options of red cell genotyping in precision transfusion medicine. This symposium summary captured the state of the art of red cell genotyping and its contribution to the practice of precision medicine.

Red Cell Genotyping by Multiplex PCR Identifies Antigen-Matched Blood Units for Transfusion-Dependent Thai Patients

BACKGROUND

Antigen-negative red cell transfusion is required for transfusion-dependent patients. We developed multiplex PCR for red cell genotyping and calculated the possibility of finding compatible predicted phenotypes in Thai blood donor populations according to red cell alloantibodies found among Thai patients.

METHODS

600 DNA samples obtained from unrelated healthy central and northern Thai blood donors were tested with the newly developed multiplex PCR for FY*A, FY*B, JK*A, JK*B, RHCE*e, RHCE*E, DI*A and GYP*Hut, GYP*Mur, GYP*Hop, GYP*Bun, and GYP*HF allele detections. Additionally, the possibility of finding compatible predicted phenotypes in two Thai blood donor populations was calculated to estimate the minimal number of tests needed to provide compatible blood.

RESULTS

The validity of multiplex PCR using known DNA controls and the phenotyping and genotyping results obtained by serological and PCR-SSP techniques were in agreement. The possibility of finding at least one compatible blood unit for patients with multiple antibodies was comparable in Thai populations.

CONCLUSIONS

The multiplex PCR for red cell genotyping simultaneously interprets 7 alleles and 1 hybrid GP group. Similar strategies can be applied in other populations depending on alloantibody frequencies in transfusion-dependent patients, especially in a country with limited resources.

Molecular typing for blood group antigens within 40 min by direct polymerase chain reaction from plasma or serum

Determining blood group antigens by serological methods may be unreliable in certain situations, such as in patients after chronic or massive transfusion. Red cell genotyping offers a complementary approach, but current methods may take much longer than conventional serological typing, limiting their utility in urgent situations. To narrow this gap, we devised a rapid method using direct polymerase chain reaction (PCR) amplification while avoiding the DNA extraction step. DNA was amplified by PCR directly from plasma or serum of blood donors followed by a melting curve analysis in a capillary rapid-cycle PCR assay. We evaluated the single nucleotide polymorphisms underlying the clinically relevant Fy^a , Fy^b , Jk^a and Jk^b antigens, with our analysis being completed within 40 min of receiving a plasma or serum sample. The positive predictive value was 100% and the negative predictive value at least 84%. Direct PCR with melting point analysis allowed faster red cell genotyping to predict blood group antigens than any previous molecular method. Our assay may be used as a screening tool with subsequent confirmatory testing, within the limitations of the false-negative rate. With fast turnaround times, the rapid-cycle PCR assay may eventually be developed and applied to red cell genotyping in the hospital setting.

A genetic marker of the ACKR1 gene is present in patients with Type II congenital smell loss who have type I hyposmia and hypogeusia

PURPOSE

Our previous study of Type II congenital smell loss patients revealed a statistically significant lower prevalence of an FY (ACKR1, formerly DARC) haplotype compared to controls. The present study correlates this genetic feature with subgroups of patients defined by specific smell and taste functions.

METHODS

Smell and taste function measurements were performed by use of olfactometry and gustometry to define degree of abnormality of smell and taste function. Smell loss was classified as anosmia or hyposmia (types I, II or III). Taste loss was similarly classified as ageusia or hypogeusia (types I, II or III). Based upon these results patient erythrocyte antigen expression frequencies were categorized by smell and taste loss with results compared between patients within the Type II group and published controls.

RESULTS

Comparison of antigen expression frequencies revealed a statistically significant decrease in incidence of an Fy^b haplotype only among patients with type I hyposmia and any form of taste loss (hypogeusia). In all other patient groups erythrocyte antigens were expressed at normal frequencies.

CONCLUSIONS

Data suggest that Type II congenital smell loss patients who exhibit both type I hyposmia and hypogeusia are genetically distinct from all other patients with Type II congenital smell loss. This distinction is based on decreased Fy^b expression which correlated with abnormalities in two sensory modalities (hyposmia type I and hypogeusia). Only patients with these two specific sensory abnormalities expressed the Fy^b antigen (encoded by the ACKR1 gene on the long arm of chromosome 1) at frequencies different from controls.

The DAU cluster: a comparative analysis of 18 RHD alleles, some forming partial D antigens

BACKGROUND

The Rh system is the most complex and polymorphic blood group system in humans with more than 460 alleles known for the RHD gene. The DAU cluster of RHD alleles is characterized by the single-nucleotide change producing the p.Thr379Met amino acid substitution. It is called the DAU-0 allele and has been postulated to be the primordial allele, from which all other alleles of the DAU cluster have eventually evolved.

STUDY DESIGN AND METHODS

For two novel DAU alleles, the nucleotide sequences of all 10 exons as well as adjacent intronic regions, including the 5' and 3' untranslated regions (UTR), were determined for the RHD and RHCE genes. A phylogenetic tree for all DAU alleles was established using the neighbor-joining method with Pan troglodytes as root. Standard hemagglutination and flow cytometry tests were performed.

RESULTS

We characterized two DAU alleles, DAU-11 and DAU-5.1, closely related to DAU-3 and DAU-5, respectively. A phylogenetic analysis of the 18 known DAU alleles indicated point mutations and interallelic recombination contributing to diversification of the DAU cluster.

CONCLUSIONS

The DAU alleles encode a group of RhD protein variants, some forming partial D antigens known to permit anti-D in carriers; all are expected to cause anti-D alloimmunization in recipients of red blood cell transfusions. The DAU alleles evolved through genomic point mutations and recombination. These results suggest that the cluster of DAU alleles represent a clade, which is concordant with our previous postulate that they derived from the primordial DAU-0 allele.

Full-length nucleotide sequence of ERMAP alleles encoding Scianna (SC) antigens

BACKGROUND

Scianna (SC) blood group system comprises two antithetical antigens, Sc1 and Sc2, and five additional antigens. The antigens reside on a glycoprotein encoded by the erythroblast membrane-associated protein (ERMAP) gene. For the common ERMAP alleles, we determined the full-length nucleotide sequence that encodes the Scianna glycoprotein.

STUDY DESIGN AND METHODS

Blood donor samples from five populations were analyzed including 20 African Americans, 10 Caucasians, 10 Thai, five Asians, and five Hispanics for a total of 100 chromosomes. An assay was devised to determine the genomic sequence of the ERMAP gene in one amplicon, spanning 21.4 kb and covering Exons 2 to 12 and the intervening sequence (IVS). All alleles (confirmed haplotypes) were resolved without ambiguity.

RESULTS

Among 50 blood donors, we found 80 single-nucleotide polymorphisms (SNPs), including six novel SNPs, in 21,308 nucleotides covering the coding sequence of the ERMAP gene and including the introns. The noncoding sequences harbored 75 SNPs (68 in the introns and seven in the 3'-UTR). No SNP indicative of a nonfunctional allele was detected. The nucleotide sequences for 48 ERMAP alleles (confirmed haplotypes) were determined by allele-specific polymerase chain reaction and sequencing in 100 chromosomes.

CONCLUSIONS

We documented 48 ERMAP alleles of 21,308 nucleotides each. The two nucleotide sequences available in GenBank for ERMAP alleles of similar length have not been found in our 100 chromosomes. Alleles determined without ambiguity can be used as templates to analyze next generation sequencing data, which will enhance the reliability in clinical diagnostics.

Erythrocyte membrane antigen frequencies in patients with Type II congenital smell loss

OBJECTIVE

The objective of this study was to determine whether there are genetic factors associated with Type II congenital smell loss.

STUDY DESIGN

The expression frequencies of 16 erythrocyte antigens among patients with Type II congenital smell loss were determined and compared to those of a large control group.

METHODS

Blood samples were obtained from 99 patients with Type II congenital smell loss. Presence of the erythrocyte surface antigens A, B, M, N, S, s, Fy(a), Fy(b), D, C, c, E, e, K, Jk(a), and Jk(b) was analyzed by blood group serology. Comparisons of expression frequencies of these antigens were made between the patients and a large control group.

RESULTS

Patients tested for the Duffy b antigen (Fy(b) haplotype) exhibited a statistically significant 11% decrease in expression frequency compared to the controls. There were no significant differences between patients and controls in the expression frequencies for all other erythrocyte antigens (A, B, M, N, S, s, Fy(a), D, C, c, E, e, K, Jk(a), or Jk(b)).

CONCLUSIONS

These findings describe the presence of a previously unrevealed genetic tendency among patients with Type II congenital smell loss related to erythrocyte surface antigen expression. The deviation in expression rate of Duffy b suggests a target gene and chromosome region in which future research into this form of congenital smell loss may reveal a more specific genetic basis for Type II congenital smell loss.