Effectiveness of a red cell antigen-matching transfusion protocol in sickle cell disease patients

Impact of HLA-G +3142C>G on the development of antibodies to blood group systems other than the Rh and Kell among sensitized patients with sickle cell disease

BACKGROUND

Patients' inflammatory history is an important factor underlying red blood cell (RBC) alloimmunization, which is a frequent transfusion complication among individuals with sickle cell disease (SCD). HLA-G has been associated with different inflammatory and auto - immune diseases. Our goal was to verify whether the HLA-G + 3142 C>G and 14-bp Ins/Del variations are associated with RBC antibody development among SCD patients.

METHODS

This was a single-center case-control study. SCD patients were randomly selected for the study and divided into two groups: 'Alloimmunized' and 'Nonalloimmunized' depending on the presence of irregular antibodies. The 'Alloimmunized'group was further divided into two subgroups according to the presence of only antibodies against the Rh and Kell blood group systems or the existence of antibodies to antigens of the other blood group systems.

RESULTS

A total of 213 patients were included in the study (110 alloimmunized and 103 non-alloimmunized). The 'Alloimmunized' and 'Non-alloimmunized' groups did not differ statistically regarding the HLA-G + 14 bp Ins/Del ( p = 0.494) and + 3142 C>G ( p = 0.334). Individuals who had only antibodies against the Rh and Kell antigens had a frequency of HLA-G + 3142GG genotype almost twice as high compared to the groupwith antibodies against less immunogenic antigens ( p = 0.043).

CONCLUSIONS

The genotype frequency of HLA-G + 3142 C>G differs among alloimmunized SCD patients, depending on the presence of antibodies against low immunogenic RBC antigens. This highlights a possible role played by the HLA-G molecule in the RBC alloimmunization process.

Alloimmunization in transfused patients with constitutional anemias in Norway

BACKGROUND AND OBJECTIVES

The status of red blood cell alloimmunization in patients with constitutional anemias including hemoglobinopathies is not known in Norway. The study objective was to investigate the impact of a strategy based on phenotype-matching for C, c, E, e, K, Jka, Jkb, Fya, Fyb, S and s on alloimmunization.

MATERIALS AND METHODS

We reviewed transfusions of 40 patients retrospectively using the computerized blood bank management system and medical records; including diagnosis, age at start of transfusion therapy, gender, number and age of packed red blood cell units transfused, follow-up time, phenotypes of the donors and patients, antigen-negative patients exposed to antigen-positive packed red blood cell units, transfusion reactions and alloantibody specificities.

RESULTS

Forty patients received 5402 packed red blood cell units. Alloimmunization frequency was 20 % for the whole group, being 7%, 25 % and 30 % in patients with sickle cell disease (n = 14), thalassemia (n = 16) and other conditions (n = 10), respectively. The alloantibodies detected were anti-E, -c, -C, -Cw, -K, -Jka and -Lua.

CONCLUSION

Good communication between the clinicians and the transfusion services is essential for successful management of patients with constitutional anemias. Providing full phenotype-matched units was not always possible. Extended pheno-/genotyping before the first transfusion and providing antigen-negative units for antigen-negative patients for at least C, c, E and K in every red cell transfusion would probably have reduced the alloimmunization rate. Non-phenotype-matched transfusions seem to be the main reason for alloimmunization. Finding markers for identifying responders prone to alloimmunization will ensure targeted transfusion strategies.

Diversity of variant alleles encoding Kidd, Duffy, and Kell antigens in individuals with sickle cell disease using whole genome sequencing data from the NHLBI TOPMed Program

BACKGROUND

Genetic variants in the SLC14A1, ACKR1, and KEL genes, which encode Kidd, Duffy, and Kell red blood cell antigens, respectively, may result in weakened expression of antigens or a null phenotype. These variants are of particular interest to individuals with sickle cell disease (SCD), who frequently undergo chronic transfusion therapy with antigen-matched units. The goal was to describe the diversity and the frequency of variants in SLC14A1, ACKR1, and KEL genes among individuals with SCD using whole genome sequencing (WGS) data.

STUDY DESIGN AND METHODS

Two large SCD cohorts were studied: the Recipient Epidemiology and Donor Evaluation Study III (REDS-III) (n = 2634) and the Outcome Modifying Gene in SCD (OMG) (n = 640). Most of the studied individuals were of mixed origin. WGS was performed as part of the National Heart, Lung, and Blood Institute's Trans-Omics for Precision Medicine (TOPMed) program.

RESULTS

In SLC14A1, variants included four encoding a weak Jka phenotype and five null alleles (JKnull ). JKA*01N.09 was the most common JKnull . One possible JKnull mutation was novel: c.812G>T. In ACKR1, identified variants included two that predicted Fyx (FY*X) and one corresponding to the c.-67T>C GATA mutation. The c.-67T>C mutation was associated with FY*A (FY*01N.01) in four participants. FY*X was identified in 49 individuals. In KEL, identified variants included three null alleles (KEL*02N.17, KEL*02N.26, and KEL*02N.04) and one allele predicting Kmod phenotype, all in heterozygosity.

CONCLUSIONS

We described the diversity and distribution of SLC14A1, ACKR1, and KEL variants in two large SCD cohorts, comprising mostly individuals of mixed ancestry. This information may be useful for planning the transfusion support of patients with SCD.

FcγR2B B2.4 haplotype predicts increased risk of red blood cell alloimmunization in sickle cell disease patients

BACKGROUND

Red blood cell (RBC) alloimmunization is an important transfusion complication which is prevalent among sickle cell disease (SCD) patients. Autoimmune diseases are a known risk factor for RBC alloimmunization, suggesting that autoimmunity and post-transfusion alloantibody development occur through similar physiopathological pathways. Polymorphisms in the FcγR2B gene have already been associated with several autoimmune disorders and hypothetically could be associated with RBC alloimmunization. Our goal was to evaluate if important polymorphisms of FcγR2B have an impact on the risk of RBC alloimmunization among SCD patients.

STUDY DESIGN AND METHODS

This was a case-control study in which alloimmunized and non-alloimmunized SCD patients were compared in terms of the genotype frequency of the FcγR2B polymorphisms -386G/C, -120 T/A, and 695C/T, genotyped through direct Sanger sequencing.

RESULTS

A total of 237 patients met the eligibility criteria, 120 cases (alloimmunized) and 117 controls (non-alloimmunized). RBC alloimmunization was associated with female sex (p < 0.001), lifetime number of RBC units transfused (p = 0.002) and 120 T/A FcγR2B genotype (p = 0.031). The FcγR2B promoter region haplotype 2B.4 (386C120A) was positively associated with RBC alloimunization (p = 0.045). The logistic regression (LR) model identified female sex (OR 10.03, CI 95% 5.16-19.49; p < 0.001) and FcγR2B 2B.4 haplotype (OR 4.55, CI95% 1.1118.65; p = 0.035) as independent predictors of RBC alloimmunization in SCD patients.

CONCLUSION

SCD patients with the FcγR2B 2B.4 haplotype had over a fourfold higher risk for RBC alloimmunization. This highlights the role played by FcγR2B on RBC alloimmunization and may be helpful in identifying the immune responders.

Effectiveness of strategies to screen for blood donors with RH variants in a mixed population

INTRODUCTION

Patients with RH variants presenting antibodies directed to RH high frequency antigens or multiple RH antibodies might, in some occasions, be better served with RH genotype-matched units, requiring screening for RH variants among blood donors. To date, strategies to identify donors with RH variants were restricted to selecting individuals of African descent based on self-reported race, what can be inaccurate in racially mixed population. Our goal was to: 1) Screen for donors with RH variants in a mixed population using self-declared race and Rh phenotype as selection criteria; and 2) Verify if including the Duffy null genotype in the screening algorithm increases its effectiveness.

METHODS

Brazilian donors were included if self-declared as black and phenotyped as R0r or R1r. All individuals were genotyped for RHCE exons 1, 5, 6 and 7 and for the FY*B c.-67 T > C polymorphism in order to determine the Duffy null genotype. RHD variants were searched for in cases of altered RHCE.

RESULTS

Among 2500 blood donors, 217 fulfilled the inclusion criteria and were enrolled. Fifty-three (24.4 %) had a predicted clinically relevant Rh phenotype (partial antigens or lack of high frequency antigens). Twelve donors (5.5 %) had a predicted RhCE phenotype lacking either hrB or hrS. Most cases with predicted lack of high frequency antigens (66.7 %) occurred in donors with the Duffy null genotype.

CONCLUSION

Selecting donors based on self-declared race, Rh phenotype and Duffy null genotype is feasible and effective in identifying RH variants lacking Rh high frequency antigens among racially mixed donors.

Diversity of RH and transfusion support in Brazilian sickle cell disease patients with unexplained Rh antibodies

BACKGROUND

Genetic diversity in the RH genes among sickle cell disease (SCD) patients is well described but not yet extensively explored in populations of racially diverse origin. Transfusion support is complicated in patients who develop unexpected Rh antibodies. Our goal was to describe RH variation in a large cohort of Brazilian SCD patients exhibiting unexpected Rh antibodies (antibodies against RH antigens to which the patient is phenotypically positive) and to evaluate the impact of using the patient's RH genotype to guide transfusion support.

STUDY DESIGN AND METHODS

Patients within the Recipient Epidemiology and Evaluation Donor Study (REDS)-III Brazil SCD cohort with unexpected Rh antibodies were selected for study. RHD and RHCE exons and flanking introns were sequenced by targeted next-generation sequencing.

RESULTS

Fifty-four patients with 64 unexplained Rh antibodies were studied. The majority could not be definitively classified as auto- or alloantibodies using serologic methods. The most common altered RH were RHD*DIIIa and RHD*DAR (RHD locus) and RHCE*ce48C, RHCE*ce733G, and RHCE*ceS (RHCE locus). In 53.1% of the cases (34/64), patients demonstrated only conventional alleles encoding the target antigen: five of 12 anti-D (41.7%), 10 of 12 anti-C (83.3%), 18 of 38 anti-e (47.4%), and one of one anti-E (100%).

CONCLUSION

RHD variation in this SCD cohort differs from that reported for African Americans, with increased prevalence of RHD*DAR and underrepresentation of the DAU cluster. Many unexplained Rh antibodies were found in patients with conventional RH allele(s) only. RH genotyping was useful to guide transfusion to determine which patients could potentially benefit from receiving RH genotyped donor units.

The supply chain of migrant blood donors: an organisational interview study

BACKGROUND AND OBJECTIVES

Migrant blood donors are underrepresented worldwide resulting in shortages of compatible blood products. Prior studies focused on individual barriers and motivators of potential blood donors, but no studies addressed organisational factors of the blood supply chain. This study explored the perceptions and experiences in recruitment and retention of migrant - and potentially rare-blood donors among staff members within the blood supply chain and identified obstacles and solutions in this chain.

MATERIALS AND METHODS

The study was conducted at Sanquin, the national blood supply organisation of the Netherlands. Qualitative in-depth interviews were done among key staff members (N = 17). Expert validity was assessed in three feedback meetings.

RESULTS

Seven staff members believed there is a shortage of migrant blood donors, while five believed there is not. However, there was a consensus that it may become a problem in the future due to demographic changes. The perceived obstacles to recruit and retain migrant donors were difficulties in determining how many migrant donors are needed and recruiting them, excluding potentially rare donors prior to donation, limited use of extended phenotyping and high blood typing and frozen storage costs. The possible solutions to increase blood pool diversity lay in registering donor ethnicity, specialised information provision for donors, reconsidering eligibility criteria and optimising blood typing strategies.

CONCLUSION

Whilst recruitment of migrant blood donors is perceived by staff as difficult, various organisational policies and guidelines seem to hinder retention. Improvements in the blood supply chain may be achieved by addressing logistics, current procedures and registration of ethnicity.

Optimized Antigen-Matched in Sickle Cell Disease Patients: Chances and Challenges in Molecular Times - the Brazilian Way

The development of red blood cell (RBC) alloantibodies and autoantibodies complicates transfusion therapy in sickle cell disease (SCD) patients. In an effort to reduce the risk of alloimmunization, some strategies have been used to provide antigen-matched RBC transfusions to patients with SCD in Brazil, including molecular matching in 3 levels: RH and K matching; extended matching (RH, KEL, FY, JK, MNS, DI), and extended matching including RHD and RHCE variant alleles. Molecular matching has shown clinical benefits to the patients with SCD, contributing significantly to reduce the rates of alloimmunization. Improvements in the clinical outcomes of the patients have also been observed as shown by an increase in their hemoglobin levels and reduction in their percentage of hemoglobin S as well as better in vivo RBC survival and diminished frequency of transfusions. However, prevention of RBC alloimmunization still remains a challenge in Brazil due to the difficulty to fulfill all transfusion requests of the patients with antigen-matching units, inaccuracy of RBC phenotyping, RBC transfusions outside the institution where the patient is treated, advanced age of some patients, the RBC antigen discrepancy between donors and recipients, and the presence of RH variants.

High frequency of variant RHD genotypes among donors and patients of mixed origin with serologic weak-D phenotype

BACKGROUND

The current transfusion policy recommended for individuals with serologic weak-D phenotype is based on data derived from European-descent populations. Data referring to the distribution of RH alleles underlying weak-D phenotype among people of mixed origin are yet incomplete, and the applicability of European-based transfusion guidelines to this specific population is questionable.

GOAL

To evaluate the distribution of RHD variant genotype among individuals with serologic weak-D phenotype of both African and European descent.

METHODS

Donors and patients of mixed origin and with serologic weak-D phenotype were selected for the study. They were investigated using conventional RHD-PCR assays and RHD whole-coding region direct sequencing.

RESULTS

One hundred and six donors and 58 patients were included. There were 47 donors and 29 patients with partial-D genotype (47/106, 44.3%, and 29/58, 50%, respectively). RHD*DAR and RHD*weak D type 38 represented the most common altered RHD alleles among donors (joint frequency of 39.6%), while weak D types 1-3 accounted for 10.4% of the total D variant samples. RHD*DAR was the most common allele identified in the patient group (frequency of 31%), and weak D types 1-3 represented 29.3% of the total.

CONCLUSION

The frequency of partial D among mixed individuals with serologic weak-D phenotype is high. They should be managed as D-negative patients until molecular tests are complete.

-318C/T polymorphism of the CTLA-4 gene is an independent risk factor for RBC alloimmunization among sickle cell disease patients

Cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) molecule is expressed on T-lymphocyte membrane and negatively influences the antigen-presenting process. Reduced expression of CTLA-4 due to gene polymorphisms is associated with increased risk of autoimmune disorders, whose physiopathology is similar to that of post-transfusion red blood cell (RBC) alloimmunization. Our goal was to evaluate if polymorphisms of CTLA-4 gene that affect protein expression are associated with RBC alloimmunization. This was a case-control study in which 134 sickle cell disease (SCD) patients and 253 non-SCD patients were included. All patients were genotyped for the polymorphisms 49A/G and -318C/T of CTLA-4 gene. The genotype frequency of -318C/T differed significantly between alloimmunized and nonalloimmunized SCD patients, irrespective of clinical confounders (p = .016). SCD patients heterozygous for -318T allele presented higher risk of alloantibody development (OR: 5.4, CI: 1.15-25.6). In conclusion, the polymorphism -318C/T of CTLA-4 gene is associated with RBC alloimmunization among SCD patients. This highlights the role played by CTLA-4 on post-transfusion alloantibody development.

RHD and RHCE genotyping by next-generation sequencing is an effective strategy to identify molecular variants within sickle cell disease patients

BACKGROUND

The complexity of Rh genetic variation among sickle cell disease (SCD) patients is high. Conventional molecular assays cannot identify all genetic variants already described for the RH locus as well as foresee novel alleles. Sequencing RHD and RHCE is indicated to broaden the search for Rh genetic variants.

AIMS

To standardize the Next Generation Sequencing (NGS) strategy to assertively identify Rh genetic variants among SCD patients with serologic suspicion of Rh variants and evaluate if it can improve the transfusion support.

METHODS

Thirty-five SCD patients with unexplained Rh antibodies were enrolled. A NGS-based strategy was developed to genotype RHD and RHCE using gene-specific primers. Genotype and serological data were compared.

RESULTS

Data obtained from the NGS-based assay were gene-specific. Ten and 25 variant RHD and RHCE alleles were identified, respectively. Among all cases of unexplained Rh antibodies, 62% had been inaccurately classified by serological analysis and, of these, 73.1% were considered as relevant, as were associated with increased risk of hemolytic reactions and shortage of units suitable for transfusion.

CONCLUSION

The NGS assay designed to genotype RH coding regions was effective and accurate in identifying variants. The proposed strategy clarified the Rh phenotype of most patients, improving transfusion support.