Genetic variation of the HNA-3a encoding gene

Compound heterozygosity induces a rare Gerbich-negative phenotype in an immunized blood donor

BACKGROUND

Antibodies to Gerbich blood group antigens are exceedingly rare and can cause moderate transfusion reactions. Several deletional variants of the GE-gene, that harbors long sequence repeats, enable alloimmunization and formation of naturally occurring antibodies.

SUBJECT AND METHODS

A female blood donor and soldier of the German Army without history of pregnancy or transfusion showed an antibody reactive with all test cells except for GE:-2-3 RBC. Thus, anti-Ge2 was suspected. Molecular analysis including fragment length specific PCR, Sanger sequencing and NGS should reveal the molecular background of the deficiency. Segregation of the variant alleles should be demonstrated by family analysis.

RESULTS

Compound heterozygosity for GYPC exon 2 (GE*01.-02) and exon 3 (GE*01.-03) deletion was detected in the donor and her sister. The mother had one exon 3 amplicon of reduced length, while the father heterozygously exhibited a truncated GYPC exon 2. NGS clearly demonstrated reduced coverages within the deletional fragments within each family member. The donor and her sister showed the complete absence of a 640 bp fragment.

DISCUSSION AND CONCLUSION

Rare GE deletion variants can induce naturally occurring anti-Ge2 in Caucasians. Because of an enhanced risk of injury as soldier autologous RBC of the donor were cryopreserved. The donor and her sibling can give blood for each other because of identical ABO, Rh, and K antigen blood types.

Occurrence of Rare Deletional Yus and Gerbich Alleles in Syria and Neighbouring Countries

Background

Gerbich-negative phenotypes of the Gerbich Blood Group System (ISBT 020) are very rare (with the exception of Papua New Guinea). The Gerbich-negative phenotypes Yus and Gerbich are negative for the antigens Ge2, and Ge2 and Ge3, respectively. In antigen-negative individuals, anti-Ge2 and anti-Ge3 antibodies can be naturally occurring, or are triggered during pregnancies and after transfusions. Previous studies suggested an elevated frequency of Gerbich-negative phenotypes for the Middle East. In the summer of 2015, a large-scale migration of people from the Middle East to Europe occurred raising the issue of question how to guarantee blood supply for patients and manage antenatal care for pregnant women from these countries.

Materials and Methods

To investigate the frequency of rare Gerbich-negative phenotypes, 1,665 immigrants to Germany originating from the Middle East were genetically tested for the presence of rare Yus, i.e., GE*01.-02, and Gerbich, i.e., GE*01-03, alleles and compared to results obtained from 507 Germans.

Results

Seven Yus GE*01.-02.01 and one Gerbich GE*01.-03.02 alleles were exclusively observed among people from the Middle East, with five of them clustering among 797 Syrians. No such alleles were observed in Germans. A cumulative Yus- and GE*01.-03-type allele frequency of 0.00314 and resultant overall Gerbich-negative phenotype frequency of one among 101,633 Syrians were calculated.

Conclusion

This manuscript describes for the first time an exclusively genetic screening for carriers of Gerbich-negative alleles. In conclusion, the Gerbich blood group system should be considered as one causative agent of unusual antibodies to red cell antigens, in routine patients and pregnant women, especially when originating from the Middle East.

Molecular Genetics of the Human Neutrophil Antigens

BACKGROUND AND OBJECTIVE

Antibodies to human neutrophil antigens (HNAs) have been implicated in transfusion-related acute lung injury and allo- and autoimmune neutropenia. To date, five HNA systems are assigned, and during the last decades enormous efforts have been undertaken to identify the underlying genes and to characterize the antigens. This review of the literature will provide the current genetic, molecular and functional information on HNAs.

RECENT FINDINGS

New information on alleles and antigens has been added to nearly each of the five HNA systems. HNA-1d has been added as the antithetical epitope to HNA-1c that is located on the glycoprotein encoded by FCGR3B*02 but not by FCGR3B. FCGR3B*04 and *05 now are included as new alleles. A CD177*787A>T substitution was demonstrated as the main reason for the HNA-2-negative phenotype on neutrophils. The target glycoprotein of HNA-3 antibodies could be identified as choline transporter-like protein 2 (CTL2) encoded by SLC44A2. The conformation sensitive epitope discriminates between arginine and glutamine at position 152 resulting in HNA-3a and HNA-3b. An additional Leu151Phe substitution can impair HNA-3a antibody binding. Recently an alloantibody against HNA-4b which discriminates from HNA-4a by an Arg61His exchange of the glycoprotein encoded by the ITGAM gene was reported in neonatal alloimmune neutropenia. An update of the current HNA nomenclature based on the new findings was provided in 2016 by the ISBT Granulocyte Immunobiology Working Party nomenclature subcommittee.

CONCLUSIONS

The molecular basis of each of the five HNA antigen systems has been decoded during the past decades. This enables reliable molecular typing strategies, antibody detection and specification as well as development of new assays based on recombinant antigens. However, research on HNA alleles, antigens, and antibodies is not finally terminated and also in the future will add new findings.

A study of human neutrophil antigen genotype frequencies in Hong Kong

BACKGROUND

Alloantibodies against human neutrophil antigens (HNA) are associated with a variety of clinical conditions. Over the past decade, the allelic and genotypic frequencies of the five HNA systems have been evaluated. Although the HNA system is less polymorphic than human leukocyte antigens (HLA), significant differences in the genotypic and allele frequencies still exist in different populations, even those living in close proximity.

OBJECTIVES

To delineate HNA genotypic and allele frequencies to provide vital information on estimating the risk of HNA-associated diseases for our local population.

METHODS

Using a validated, in-house-developed assay, genotyping for HNA-1, HNA-3, HLA-4 and HNA-5 was performed on 300 samples from Chinese blood donors from Hong Kong. In addition, the frequency of the HNA-2 c.843A > T allele was also determined.

RESULTS

The allele frequencies of HNA-1a, -1b and -1c alleles were 67·8, 31·5 and 0%, respectively, whereas the frequencies of HNA-3a and HNA-3b were 71·0 and 29·0%, respectively. The frequencies of HNA-4a and -4b alleles were 99·5 and 0·5%, respectively, and for HNA-5a and -5b, alleles were 85·2 and 14·8%, respectively. Homozygotes for the HNA-2 c.843 TT variant were absent in our population, whereas only <4% of the population were c.843AT heterozygote carriers.

CONCLUSIONS

This is the first study to define HNA genotype and allele frequencies using a validated modified in-house PCR-SSP method in the Hong Kong Chinese blood donor population. Our approach provides a cost-effective assay for conducting routine HNA typing and facilitates the incorporation of these assays into routine clinical service. Our results are comparable with those reported in the Guangzhou Chinese population, but the allele frequencies in our Hong Kong Chinese population are significantly different from the reported European frequencies, confirming that a geographical difference exists for HNA allele frequencies.

Genotype frequencies of human neutrophil antigen-3 in the Chinese Zhuang and Dong populations

Individuals with the human neutrophil antigen (HNA)-3b/3b type can produce HNA-3a antibodies, which have been reported to cause severe, sometimes fatal transfusion-related acute lung injury (TRALI). Our study aimed to determine the genotype frequency of HNA-3a/3b which will be helpful to estimate the potential risk for forming anti-HNA-3a, the clinically relevant antibody linked to TRALI in two different ethnic groups of southern China. Five hundred unrelated and healthy blood donors (284 male, 216 female; 300 Zhuangs, 200 Dongs) from the Guangxi Zhuang Autonomous Region were simultaneously typed for the HNA-3 allele using a polymerase chain reaction sequence-based typing (PCR-SBT) method. Genotype frequencies of HNA-3a/3a, HNA-3a/3b and HNA-3b/3b were 51.7%, 39.7% and 8.6% in the Zhuang population, and 44.0%, 49.0% and 7.0% in the Dong population, respectively. Homozygous HNA-3b/3b genotype frequency among the Zhuang population (8.6%) was significantly higher than previously reported in African Americans (0.4%), Brazilians (3.6%) and English Caucasians (2.9%) (p < .05). And the HNA-3b/3b genotype frequency among the Dong population was higher than African Americans (0.4%) (p < .05). This study showed Chinese Zhuang and Dong populations possessed a higher frequency of HNA-3b/3b genotype, suggesting that they may be at greater risk for developing anti-HNA-3a alloantibodies that may cause severe cases of TRALI. A molecular-based identification of the HNA-3b/3b genotype in all multiparous female blood donors was suggested to reduce the risk of TRALI following plasma and whole blood allogeneic transfusions.

Assessment of HNA alloimmunisation risk in Northeastern Thais, Burmese and Karen

OBJECTIVES

This study aimed to determine human neutrophil antigen (HNA) frequency, estimate possible HNA incompatibilities and predict the risk of HNA alloimmunisation in the Northeastern Thai, Burmese and Karen populations.

BACKGROUND

Alloantibodies against HNA are implicated in a number of clinical conditions, including immune-mediated neutropenia and transfusion reactions.

METHODS

A total of 400 unrelated healthy Thais, 261 Burmese and 249 Karen was included in this study. DNA samples were typed for HNA-1, -3, -4 and -5 systems using polymerase chain reactions with sequence-specific primers (PCR-SSP).

RESULTS

In this cohort, HNA-1a was more prevalent than HNA-1b. Accordingly, the possible risk of HNA-1a alloimmunisation against HNA-1a is lower than HNA-1b (0·0802-0·1351 vs 0·2293-0·2497). This is in contrast to the situation reported in Caucasian and African populations. The predicted risk of HNA-3 incompatibility in Thais, Burmese and Karen were 28·09%, 30·66% and 22·77%, respectively. The possible risks of HNA-3a alloimmunisation were 0·0493 in Thais, 0·0608 in Burmese and 0·0196 in Karen, respectively. No individuals were found to be homozygous for HNA-4bb. The probability of developing alloantibodies against HNA-4a was low in these populations and every population in Asia. In contrast, the overall frequency of HNA-5bb homozygous individuals was high in this study, peaking at 0·192.

CONCLUSIONS

This is the first study that reported the allele frequencies of HNA-1, -3, -4, and -5 in a large sample of healthy unrelated individuals from ethnic Thais, Burmese and Karen. Our results indicated the high possible risk of HNA-1, -3 and -5 alloimmunisation in these populations.

SLC44A2 single nucleotide polymorphisms, isoforms, and expression: Association with severity of Meniere's disease?

SLC44A2 was discovered as the target of an antibody that causes hearing loss. Knockout mice develop age related hearing loss, loss of sensory cells and spiral ganglion neurons. SLC44A2 has polymorphic sites implicated in human disease. Transfusion related acute lung injury (TRALI) is linked to rs2288904 and genome wide association studies link rs2288904 and rs9797861 to venous thromboembolism (VTE), coronary artery disease and stroke. Here we report linkage disequilibrium of rs2288904 with rs3087969 and the association of these SLC44A2 SNPs with Meniere's disease severity. Tissue-specific isoform expression differences suggest that the N-terminal domain is linked to different functions in different cell types. Heterozygosity at rs2288904 CGA/CAA and rs3087969 GAT/GAC showed a trend for association with intractable Meniere's disease compared to less severe disease and to controls. The association of SLC44A2 SNPs with VTE suggests that thrombi affecting cochlear vessels could be a factor in Meniere's disease.

Evaluation of a new microbeads assay for granulocyte antibody detection

BACKGROUND

To reduce the risk of transfusion-associated acute lung injury (TRALI), a high number of plasma donors were tested for human leukocyte antigen (HLA) and human neutrophil antigen (HNA) antibodies. For HNA antibody detection, the gold standard is a combination of the granulocyte immunofluorescence test (GIFT) and the granulocyte agglutination test (GAT). However, these tests are not suitable for a high-throughput of samples.

STUDY DESIGN AND METHODS

To evaluate the new generation of the LABScreen MULTI assay (One Lambda, Inc.), which has special new beads for all the known HNA specificities, including HNA-3a, 97 sera samples containing well-defined HNA antibodies were used. For background testing, we used 91 samples from plasma donors previously identified by GAT, GIFT, and the monoclonal antibody-specific immobilization of granulocyte antigens (MAIGA) assay.

RESULTS

Compared with previous tests, the new LABScreen MULTI assay was highly specific for the HNA-1a, HNA-1b, HNA-2, and HNA-3a antibody specificities required to prevent TRALI. Ninety-eight percent of the HNA-1a, HNA-1b, and HNA-2 antibodies could be detected as true positive; and 90% of the HNA-3a antibodies were recognized correctly as positive. False-positive reactions were identified in 5.5% of samples that previously tested negative.

CONCLUSION

The detection of HNA-3a antibody specificities could be integrated into the new LABScreen MULTI assay; however, we detected only 90%. In addition, we detected further HNA antibodies, such as HNA-1c, HNA-1d, and some HNA-3b and HNA-4a antibodies. The new generation of LABScreen MULTI is a great step toward feasible high-throughput testing for HNA antibodies. Nevertheless, GIFT and GAT remain the gold-standard methods for the differentiation of rare and currently unknown HNA specificities.

Heterogeneity of Human Neutrophil CD177 Expression Results from CD177P1 Pseudogene Conversion

Most humans harbor both CD177neg and CD177pos neutrophils but 1-10% of people are CD177null, placing them at risk for formation of anti-neutrophil antibodies that can cause transfusion-related acute lung injury and neonatal alloimmune neutropenia. By deep sequencing the CD177 locus, we catalogued CD177 single nucleotide variants and identified a novel stop codon in CD177null individuals arising from a single base substitution in exon 7. This is not a mutation in CD177 itself, rather the CD177null phenotype arises when exon 7 of CD177 is supplied entirely by the CD177 pseudogene (CD177P1), which appears to have resulted from allelic gene conversion. In CD177 expressing individuals the CD177 locus contains both CD177P1 and CD177 sequences. The proportion of CD177hi neutrophils in the blood is a heritable trait. Abundance of CD177hi neutrophils correlates with homozygosity for CD177 reference allele, while heterozygosity for ectopic CD177P1 gene conversion correlates with increased CD177neg neutrophils, in which both CD177P1 partially incorporated allele and paired intact CD177 allele are transcribed. Human neutrophil heterogeneity for CD177 expression arises by ectopic allelic conversion. Resolution of the genetic basis of CD177null phenotype identifies a method for screening for individuals at risk of CD177 isoimmunisation.

Genotype frequency of human neutrophil antigen-3 polymorphisms in the Yi, Han, and Tibetan populations of China

BACKGROUND

Human neutrophil antigen-3 (HNA-3) alloantibodies can cause fatal transfusion-related acute lung injury (TRALI). Most frequencies of SLC44A2 alleles encoding the HNA-3a/b antigens have been established in Han individuals by polymerase chain reaction with sequence-specific priming (PCR-SSP). We sequenced SLC44A2 gene fragments and determined allele frequencies in three ethnicities of China.

STUDY DESIGN AND METHODS

Genomic DNA was extracted from 448 samples of 100 blood donors of Yi ethnicity in Xichang, Liangshan; 248 Han in Nanjing, Jiangsu; and 100 Tibetan in Lhasa, Tibet. A PCR-SSP was applied to determine the phase of two single-nucleotide polymorphisms (SNPs); SLC44A2 haplotypes were constructed.

RESULTS

In the 567 nucleotides of the SLC44A2 gene covered by our sequencing approach in Han individuals, we detected the known 331-44G>A (rs12972963) and 461G>A (rs2288904) polymorphisms. In the 243 nucleotides sequenced in Yi and Tibetan populations, we detected the known 461G>A and 503-15T>C (rs1560711) polymorphisms. A PCR-SSP for the common HNA-3a/b SNP was 100% concordant. The frequencies of the HNA-3a allele were 0.58, 0.66, and 0.69 in Yi, Han (Nanjing), and Tibetan, respectively (0.42, 0.34, and 0.31 for HNA-3b).

CONCLUSIONS

The Yi population of China had the highest frequency of blood donors at risk of harboring anti-HNA-3a compared to any population studied so far. We confirmed that the underlying SLC44A2*2 allele is more common in China than in any European or African populations.

Full-length nucleotide sequences of 30 common SLC44A2 alleles encoding human neutrophil antigen-3

BACKGROUND

Human neutrophil antigen-3a (HNA-3a) alloantibodies can cause severe transfusion-related acute lung injury. The frequencies of the single-nucleotide polymorphisms (SNPs) indicative of the two clinically relevant HNA-3a/b antigens are known in many populations. In this study, we determined the full-length nucleotide sequence of common SLC44A2 alleles encoding the choline transporter-like protein-2 that harbors HNA-3a/b antigens.

STUDY DESIGN AND METHODS

A method was devised to determine the full-length coding sequence (CDS) and adjacent intron sequences from genomic DNA by eight polymerase chain reaction amplifications covering all 22 SLC44A2 exons. Samples from 200 African American, 96 Caucasian, two Hispanic, and four Asian blood donors were analyzed. We developed a decision tree to determine alleles (confirmed haplotypes) from the genotype data.

RESULTS

A total of 10 SNPs were detected in the SLC44A2 CDS. The noncoding sequences harbored an additional 28 SNPs (one in the 5'-untranslated region [UTR]; 23 in the introns; and four in the 3'-UTR). No SNP indicative of a nonfunctional allele was detected. The nucleotide sequences for 30 SLC44A2 alleles (haplotypes) were confirmed. There may be 66 haplotypes among the 604 chromosomes screened.

CONCLUSIONS

We found 38 SNPs, including one novel SNP, in 8192 nucleotides covering the CDS of the SLC44A2 gene among 302 blood donors. Population frequencies of these SNPs were established for African Americans and Caucasians. Because alleles encoding HNA-3b are more common than non-functional SLC44A2 alleles, we confirmed our previous postulate that African American donors are less likely to form HNA-3a antibodies compared to Caucasians.

Allelic Discrimination by TaqMan-PCR for Genotyping of Human Neutrophil Antigens

Neutrophil antigens are implicated in a variety of clinical conditions, including neonatal immune neutropenia, transfusion-related acute lung injury, refractoriness to granulocyte transfusions, febrile transfusion reactions, and autoimmune neutropenia. In this report, we describe simultaneous genotyping of human neutrophil antigens (HNA)-1, -3, -4, and -5 using PCR with allele-specific TaqMan probes and end-point fluorescence detection, which is a robust, rapid, and reproducible method, allowing for high-throughput genotyping.

Risk estimation of HNA-3 incompatibility and alloimmunization in Thai populations

Severe transfusion-related acute lung injury (TRALI) is often due to antibodies in blood components directed against human neutrophil antigen (HNA)-3a. This study aimed to report the genotype frequencies of the HNA-3 system and to estimate the potential risk of HNA-3 incompatibility and alloimmunization in two Thai populations. Eight hundred DNA samples obtained from 500 unrelated healthy blood donors at the National Blood Centre, Thai Red Cross Society, Bangkok and 300 samples from the Blood Bank, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand were included. HNA-3 genotyping was performed using an in-house polymerase chain reaction with sequence-specific primer (PCR-SSP) technique. The observed frequencies of the HNA-3a/3a, HNA-3a/3b, and HNA-3b/3b genotypes were 0.528, 0.380, and 0.092 in central Thais and 0.600, 0.350, and 0.050 in northern Thais, respectively. The frequencies were used to estimate HNA-3 incompatibility and risk of HNA-3a alloimmunization. The HNA-3 incompatibility in central Thais (33.28%) was higher than northern Thais (28.75%), corresponding to a significantly higher probability of HNA-3a alloimmunization (P<0.05) similar to Japanese and Chinese populations. This study showed the high risk of HNA-3 incompatibility and alloimmunization, especially in central Thai blood donors. A molecular-based identification of the HNA-3 genotype of female donors is suggested to reduce the risk of TRALI following plasma and whole blood allogeneic transfusion.

Geno- and phenotyping of human neutrophil antigens

For typing of human neutrophil antigens (HNA) usually genotyping techniques are used, except for HNA-2, which-due to a gene expression defect-requires phenotyping. For genotyping, several techniques have been described. Most reference laboratories use variations of the polymerase chain reaction (PCR) for antigen typing which showed good results in international quality assessment exercises. The granulocyte immunofluorescence test has been the gold standard technique for phenotyping for all HNA antigens except for HNA-3a and -3b phenotyping. The expression of the latter antigens on neutrophils is often better shown by the use of the granulocyte agglutination test.

Molecular typing of human platelet and neutrophil antigens (HPA and HNA)

Genotyping is an important tool in the diagnosis of disorders involving allo-immunisation to antigens present on the membranes of platelets and neutrophils. To date 28 human platelet antigens (HPAs) have been indentified on six polymorphic glycoproteins on the surface of platelets. Antibodies against HPAs play a role in foetal and neonatal alloimmune thrombocytopenia (FNAIT), post-transfusion purpura (PTP) and refractoriness to donor platelets. The 11 human neutrophil antigens (HNAs) described to date have been indentified on five polymorphic proteins on the surface of granulocytes. Antibodies to HNAs are implicated with foetal and neonatal alloimmune neutropenia (FNAIN), autoimmune neutropenia (AIN) and transfusion related acute lung injury (TRALI). In this report, we will review the molecular basis and techniques currently available for the genotyping of human platelet and neutrophil antigens.

Genotyping of human neutrophil antigens by polymerase chain reaction sequence-based typing

BACKGROUND

Genotyping for human neutrophil antigen (HNA) systems is required in the investigation of disorders involving alloimmunisation to HNA. We established a polymerase chain reaction sequence-based typing method for genotyping HNA and determined the genotype and allele frequencies of HNA in the Zhejiang Han population of China.

MATERIALS AND METHODS

Four hundred, healthy unrelated Zhejiang Han individuals were recruited. Specific primers for HNA were designed and the polymerase chain reaction amplification conditions were optimised. Amplification amplicons were purified with enzyme digestion and then sequenced.

RESULTS

The frequencies of the FCGR3B*01 and FCGR3B*02 alleles were 0.613 and 0.387; no FCGR3B*03 allele was found. The frequencies of the SLC44A2*1 and SLC44A2*2 alleles were 0.654 and 0.346, respectively, while the frequencies of the ITGAL*1 (HNA-5a) and ITGAL*2 (HNA-5b) alleles were 0.896 and 0.104. Only ITGAM*1 (HNA-4a) allele was found in this study. Six single nucleotide polymorphisms were confirmed on sequenced regions separate from HNA polymorphisms, including FCGR3B (IVS3+39G>A and IVS3+52G>A), CD177(172A>G), SLC44A2 (IVS5-44A>G and IVS7-15T>C) and ITGAM (IVS3+118T>C).

DISCUSSION

The polymerase chain reaction sequence-based typing method for genotyping HNA is reliable. These data of HNA alleles frequencies could contribute to the analysis of alloimmunisation to HNA in China.

The AQP1 mutation c.601delG causes the Co-negative phenotype in four patients belonging to the Romani (Gypsy) ethnic group

BACKGROUND

The Colton blood group antigens Co(a), Co(b) and Co3 are encoded by the AQP1 gene which produces a water channel forming integral protein. The extremely rare Co-deficiency enables immunisation against the Co3 isoantigen.

MATERIALS AND METHODS

Four patients from different regions of Europe who belong to the ethnic minority of Romani (Gypsy) presented with irregular antibodies against a high frequency red blood cell antigen. Positive cross-matches with all red blood cells tested were reported. An Anti-Co3 antibody was identified as the cause of incompatibility in the four cases. The genetic background was determined by polymerase chain reaction typing with sequence-specific primers and by DNA sequencing.

RESULTS

The Co(a-b-) phenotype was confirmed in the four patients despite the fact that genotyping revealed the CO*01 allele of the AQP1 gene. A homozygous AQP1 c.601delG mutation, leading to a frame shift and producing a premature stop in the next codon, was responsible for the Co-negative phenotype in all four cases. While one patient was successfully transfused with blood from his sibling with the identical mutation, another case, a baby affected by haemolytic disease of the newborn, recovered without transfusion.

DISCUSSION

Despite the difficulties in undertaking a population study to determine the prevalence of this AQP1 c.601delG allele in the ethnic minority of Romani, the observations described in this report clearly suggest an accumulation of this mutation, which causes the Co(a-b-) phenotype, in Romani (Gypsy) patients. Further studies are necessary to prove such an accumulation.

HNA-3 gene frequencies in Brazilians and a new polymerase chain reaction-restriction fragment length polymorphism method for HNA-3a/3b genotyping

BACKGROUND

HNA-3 antigens are the result of a rs2288904 single-nucleotide polymorphism (SNP) in the CTL2, and the HNA-3a and HNA-3b variants are encoded by a guanine and adenine at Nucleotide Position 461. Anti-HNA-3 are involved in severe transfusion-related acute lung injury reactions and in neonatal alloimmune neutropenia. Since the distribution of the HNA-3 system was unknown in South Americans, in this study we determined the frequency of the HNA-3 alleles in Brazilians.

STUDY DESIGN AND METHODS

DNA of 500 blood donors, 120 Xikrin Amerindians, 74 Japanese individuals, and 124 African Brazilians were genotyped for rs2288904 by a polymerase chain reaction (PCR)-restriction fragment length polymorphism assay. The PCR product was digested with enzyme Taq(α) 1, specific to nucleotide guanine (HNA-3a).

RESULTS

The results showed that the frequencies of the HNA-3a/HNA-3b alleles were 0.81/0.19 in blood donors, 1.00/0.00 in Amerindians, 0.63/0.37 in Japanese, and 0.85/0.15 in African Brazilians. All 81 individuals genotyped as HNA-3a/a did not present the SNP c.457T by molecular sequencing.

CONCLUSION

The frequencies of HNA-3 genotypes in Brazilian blood donors is similar to that described in Caucasians; however, all Amerindians were HNA-3a/a, African Brazilians showed a lower frequency of HNA-3b/b, and Japanese had a higher prevalence of HNA-3b/b, suggesting that they may be at risk for developing anti-HNA-3a alloantibodies.

The choline transporter-like family SLC44: properties and roles in human diseases

The Na(+)-independent, high affinity choline carrier system proposed to supply choline for the synthesis of cell membrane phospholipids was recently associated with SLC44 family members (SLC44A1-5) also called choline-like transporter family. SLC44A1 is widely expressed throughout the nervous system in both neurons and oligodendrocytes, while SLC44A2-4 are mainly detected in peripheral tissues. The subcellular localization of the proteins was mainly addressed for SLC44A1 through the development of specific antibodies. SLC44A1 is detected in both the plasma and mitochondrial membranes where the protein is able to transport choline at high affinity and in a Na(+)-independent manner. The physiological relevance of SLC44A1 as a choline carrier is indicated by its likely involvement in membrane synthesis for cell growth or repair, and also by its role in phospholipid production for the generation of lung surfactant. Moreover, an autoimmune disease has been related to the blockade of SLC44A2 function, which results in the alteration of hair cells in the inner ear and leads to autoimmune hearing loss. In the alloimmune syndrome called transfusion-related acute lung injury, antibodies to SLC44A2 cause a deleterious aggregation of granulocytes. Therefore transporters of the SLC44 family represent attractive and promising targets for therapeutic and diagnostic applications regarding both immune and degenerative diseases.

External quality assessment of human neutrophil antigen (HNA)-specific antibody detection and HNA genotyping from 2000 to 2012

Since 2000, Quality Assurance (QA) exercises for the detection and identification of granulocyte antibodies and DNA typing for human neutrophil antigens (HNA) have been distributed within the International Granulocyte Immunobiology Workshops, which are linked to International Society of Blood Transfusion. The exercises were standardised at the outset to enable laboratory performance to be monitored. Between 2000 and 2012, nine exercises were distributed to 20 laboratories. Overall, 45 examples of 42 unique samples containing defined granulocyte reactive antibodies were distributed for serological analysis together with 20 samples for HNA genotyping. The level of satisfactory serological performance was initially set at 50% and later increased to 70%, while the 'cut-off' for HNA genotyping was set at 100% after 2008. Failure to achieve the minimum score in the QA exercises in consecutive years resulted in temporary exclusion. In 2000, the 15 participating laboratories had a mean score of 56.1% for serological analysis and 13 laboratories attempted HNA-1a and -1b genotyping, while 11 attempted HNA-1c typing. Steady improvements in proficiency for serological testing and HNA typing occurred in subsequent exercises. In 2012, the mean score for serology was 88.5% and 12/13 laboratories scored 100% for HNA-1a, -1b, -1c, -3a, -3b, -4a, -4bw, -5a and -5bw genotyping. These QA exercises have provided an invaluable tool to monitor and improve the standard of granulocyte immunology investigations for participating laboratories, thereby enhancing performance for both clinical investigations and donor screening programmes to reduce the incidence of TRALI.

Determination of human neutrophil antigen-1, -3, -4 and -5 allele frequencies in English Caucasoid blood donors using a multiplex fluorescent DNA-based assay

BACKGROUND AND OBJECTIVES

A number of DNA-based methods to genotype the alleles coding for HNA have been described, but all require the separate amplification and analysis of each allele. The aim was to develop a DNA-based method for simultaneous detection of HNA-1, HNA-3, HNA-4 and HNA-5 alleles.

MATERIALS AND METHODS

An allele-specific primer extension method was used in combination with magnetic beads from Luminex technology. PCR-sequence-specific primers (SSP) was used to resolve the presence of the HNA-1b allele in samples assigned by the Luminex bead assay as HNA-1a/-1b/-1c or HNA-1b/-1c. HNA allele frequencies were determined in a panel of 140 randomly selected English Caucasoid blood donors.

RESULTS

HNA allelic types were compared with historical results, and 100% concordance was found. Only eight of the 97 samples used in the validation required additional testing by PCR-SSP. Allele frequencies were determined in the blood donor population as follows: 0·318 for HNA-1a, 0·668 for HNA-1b, 0·014 for HNA-1c, 0·768 for HNA-3a, 0·232 for HNA-3b, 0·882 for HNA-4a, 0·118 for HNA-4b, 0·736 for HNA-5a and 0·264 for HNA-5b.

CONCLUSION

A multiplex Luminex bead assay for the simultaneous detection of HNA-1, HNA-3, HNA-4 and HNA-5 alleles is described that enables rapid typing of donors to support HNA alloimmunized patients who require HNA-compatible blood products.

Human neutrophil alloantigen genotype frequencies in Thai blood donors

BACKGROUND

Antibodies to human neutrophil antigens (HNA) can cause transfusion reactions, as well as autoimmune and neonatal neutropenia. This study is the first to report the frequencies of human neutrophil antigen genotypes in the Thai population.

MATERIALS AND METHODS

Three hundred unrelated, healthy Thai blood donors at the National Blood Centre, Thai Red Cross Society, Bangkok, Thailand were typed for HNA-1a, -1b, -1c, -3a, -3b and -4a using polymerase chain reaction with sequence-specific primers. Moreover, HNA-5a genotyping was performed using polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

The gene frequencies of HNA-1a, -1b and -1c were 0.470, 0.530 and 0.005, respectively. The frequencies of HNA-3a and -3b were 0.490 and 0.510, respectively. Additionally, the HNA-4a+/+ and HNA-4a+/- genotype frequencies were 0.947 and 0.053, respectively. The frequencies of HNA-5a+/+, HNA-5a+/- and HNA-5a-/- genotypes were 0.641, 0.297 and 0.062, respectively. Compared with other Asian populations, Thais have higher frequencies of HNA-1b (P<0.001). On the other hand, the frequency of HNA-5a observed in Thais is lower than that reported among Koreans (P<0.001).

DISCUSSION

These findings suggest that Thais would be more susceptible to HNA-1b alloimmunisation. Furthermore, our results could establish a useful human neutrophil antigen donor file to provide more effective transfusion of blood and blood components.

The frequencies of human neutrophil alloantigens among the Japanese population

Human neutrophil antigens (HNAs) play an important role in a variety of clinical conditions including immune-mediated neutropenia, non-hemolytic transfusion reactions, and transfusion-related acute lung injury. The aim of this study was to investigate the frequency distribution of HNAs-1 to -5 among the Japanese population. We analyzed samples from 570 healthy Japanese by molecular and serologic techniques to estimate the gene frequencies of HNAs-1 to -5. DNA samples were obtained and typed for the HNA-1 (n = 523), -3 (n = 570), -4 (n = 570), and -5 (n = 508), by molecular techniques. The HNA-1 genotype was determined by using a commercial polymerase chain reaction-reverse sequence-specific oligonucleotide probes (PCR-rSSOP) kit. The HNA-3 to -5 genotypes were determined by the PCR-sequence specific primer (PCR-SSP), previously described, with a small modification. The HNA-2a phenotype was determined in 301 donors by granulocyte immunofluorescence test. In Japanese, the gene frequencies of HNA-1a, -1b, and -1c were 0.623, 0.377, and 0.000, respectively. The frequency of HNA-2a phenotype was 0.987, and the gene frequencies of HNA-3a and -3b were 0.654 and 0.346, respectively. HNA-4a and -4b were found at 1.000 and 0.000, respectively, and HNA-5a and -5b at 0.840 and 0.160, respectively. We describe, for the first time, the frequencies of all HNAs (HNA-1 to -5) among the Japanese population. This study will be helpful for the prediction of the risk of alloimmunization to HNA, especially to determine the risk of HNA alloantibody production by transfusion of HNA incompatible blood and feto-maternal incompatibility.

Determination of neutrophil antigen HNA-3a and HNA-3b genotype frequencies in six racial groups by high-throughput 5' exonuclease assay

BACKGROUND

People with the human neutrophil antigen (HNA)-3b/3b type can make HNA-3a antibodies, which have been reported to cause immune neutropenia disorders and are especially prone to cause severe cases of transfusion-related acute lung injury. However, knowledge of HNA-3 allele frequencies outside Caucasian populations is limited. We developed a high-throughput genotyping assay and determined the HNA-3a/3b genotype frequencies in six different racial and ethnic groups.

STUDY DESIGN AND METHODS

Genotyping utilized TaqMan 5' exonuclease chemistry and real-time polymerase chain reaction. A total of 742 DNA samples from six different racial and ethnic groups were genotyped for HNA-3a and HNA-3b.

RESULTS

The genotyping assay showed 100% sensitivity and specificity compared to sequencing and phenotyping and had high throughput. A significant percentage of Caucasians (6.5%), Han Chinese (16%), and Asian Indians (6%) typed HNA-3b/3b, but only a small percentage of Hispanics (1%) and no African or Native Americans.

CONCLUSIONS

The HNA-3 genotyping assay had high sensitivity, specificity, and sample throughput. HNA-3b/b genotype results determined for 742 individuals representing six different racial and ethnic groups showed that there could be a significant risk of producing anti-HNA-3a in Chinese, as well as in Caucasian and Asian Indian blood donor populations, but a very low risk in Hispanic, African, or Native American populations.

Detection of HNA-3a and -3b antibodies using transfected cell lines and recombinant proteins

BACKGROUND

HNA-3 is a diallellic system located on choline transporter-like protein 2 (CTL2), defined by a polymorphism at Amino Acid 154. HNA-3a antibodies are of clinical importance in transfusion-related acute lung injury but antibody detection requires labor-intensive granulocyte isolation from HNA-typed donors and the use of techniques such as the granulocyte agglutination test or granulocyte immunofluorescence test. Also, there is no commercial test for detection of HNA-3 antibodies.

STUDY DESIGN AND METHODS

HEK293 cells were transfected to generate stable cell lines expressing CTL2 fragments (Amino Acids 55-230) and full-length membrane bound CTL2 with HNA-3a and -3b epitopes. Soluble fragments were used in enzyme-linked immunosorbent assays to detect HNA-3 antibodies. The cell lines expressing full-length proteins were trypsin treated to remove HLA antigens and frozen at -80°C. Thawed cells were then used to detect HNA-3 antibodies by flow cytometry.

RESULTS

Glycosylated and soluble CTL2 fragments were correctly recognized by 15 of 31 anti-HNA-3a sera and by both available anti-HNA-3b sera. Twenty-one anti-HLA sera reacted variably with untreated cell lines expressing full-length CTL2. After trypsin treatment of the cell lines, reactivity with HLA antisera was abrogated and all 31 anti-HNA-3a and two anti-HNA-3b sera bound to the corresponding cell line.

CONCLUSION

Whereas soluble, glycosylated CTL2 fragments cannot be used for the detection of HNA-3 antibodies, the HEK293 cells expressing full-length CTL2 proteins were useful in the detection of HNA-3 antibodies even in the presence of HLA antibodies. Moreover, the cell lines can be stored for at least 6 months before use.

Frequencies of SLC44A2 alleles encoding human neutrophil antigen-3 variants in the African American population

BACKGROUND

The human neutrophil antigen-3 (HNA-3) epitopes reside on the choline transporter-like protein-2 (CTL2). A single-nucleotide substitution (461G>A; Arg154Gln) on the CTL2 gene (SLC44A2) defines the allele SLC44A2*1, which expresses HNA-3a, and SLC44A2*2, which expresses HNA-3b; an additional substitution (457C>T; Leu153Phe) in SLC44A2*1:2 may impact genotyping systems. People who only express HNA-3b may develop anti-HNA-3a. These alloantibodies have been linked to severe transfusion-related acute lung injury, which may be a reason to screen blood donors for SLC44A2*2 homozygosity. For Caucasian and Asian populations, SLC44A2 allele frequencies are known. Our primary objective was to determine the SLC44A2 allele frequencies in the African American population.

STUDY DESIGN AND METHODS

Purified DNA from 334 individuals (202 male, 132 female; 241 African American, 93 Caucasian) was collected. Two real-time polymerase chain reaction assays were developed to genotype all samples; results were confirmed by nucleotide sequencing.

RESULTS

In 241 African American donors, the allele frequency of SLC44A2*1 was 93% (85%-<100%; 95% confidence intervals, Poisson distribution) while SLC44A2*2 was 7% (5%-10%). In 93 Caucasian donors, the allele frequency of SLC44A2*1 was 83% (71%-98%) and SLC44A2*2 was 17% (11%-24%), matching previously reported data for Caucasians but differing from African Americans (p < 0.001, Fisher's exact test).

CONCLUSIONS

This study describes the allele frequencies of the three known HNA-3 variants in an African American population. We found that African Americans have a significantly lower probability of possessing the SLC44A2*2 allele and may thus be less likely to form the clinically relevant anti-HNA-3a.

Full-length recombinant choline transporter-like protein 2 containing arginine 154 reconstitutes the epitope recognized by HNA-3a antibodies

BACKGROUND

Recent reports have shown that the HNA-3a leukocyte antigen, a target for antibodies that cause severe transfusion-related acute lung injury, correlates with an arginine 154 (rather than glutamine) polymorphism in choline transporter-like protein 2 (CTL2) but did not show directly that R154 determines HNA-3a. CTL2 peptides containing R154 are recognized by only half of HNA-3a antibodies studied to date. Constructs that react with all HNA-3a antibodies are needed to fully define the HNA-3a epitope.

STUDY DESIGN AND METHODS

HEK293 cells were transfected with cDNA encoding full-length CTL2 linked to green fluorescent protein (GFP). Transfectants were selected for GFP expression and tested with antibodies specific for HNA-3a and -3b.

RESULTS

Each of 20 HNA-3a antibodies reacted preferentially with HEK293 cells expressing the R154 CTL2 construct. An HNA-3b antibody reacted only with CTL2 (Q154).

CONCLUSIONS

These findings provide direct evidence that R154 in the context of full-length CTL2 is both necessary and sufficient to create the HNA-3a epitope but suggest that posttranslational modifications of the protein, for example, S-S bonds or addition of glycans, are necessary for recognition of HNA-3a by many antibodies. This could complicate development of an assay for large-scale screening of blood donors to detect anti-HNA-3a.