Gene frequencies of human platelet antigens in the Macedonian population

Genotyping of Eight Human Platelet Antigen Systems in Serbian Blood Donors: Foundation for Platelet Apheresis Registry

Introduction

The aim of this study was to investigate the allele and genotype frequencies of 8 human platelet antigen (HPA) systems among blood donors from the Blood Transfusion Institute of Serbia and to compare them with published studies. These data would be useful to establish the basis for a platelet apheresis donor registry.

Material and Methods

Seventy-two unrelated male platelet apheresis/blood donors from Serbia were typed for 8 HPA systems (HPA-1 to HPA-6, HPA-9, and HPA-15) via the FluoGene method, based on polymerase chain reaction-sequence-specific amplification (PCR-SSP; PCR using sequence-specific primers) with fluorometric signal detection. Allele and genotype frequencies were estimated by direct counting and compared to the expected genotype frequencies according to the Hardy-Weinberg principle. The transfusion mismatch probability was calculated for every HPA specificity.

Results

The allele frequencies were: HPA-1a, 0.868; HPA-1b, 0.132; HPA-2a, 0.917; HPA-2b, 0.083; HPA-3a, 0.611; HPA-3b, 0.389; HPA-5a, 0.903; HPA-5b, 0.097; HPA-9a, 0.993; HPA-9b, 0.007; HPA-15a, 0.472; and HPA-15b, 0.528. For HPA-4 and HPA-6 only allele a was detected.

Discussion

The HPA allele frequencies of European populations showed no significant differences in comparison with our results. Statistically significant differences were revealed in comparison with some populations of non-European origin. In the tested donors no HPA-2 bb genotype was detected, but we found 1 donor with the rare HPA-9b allele. The biggest transfusion mismatch probability in the Serbian population is for systems HPA-15 (37.4%) and HPA-3 (36.2%), which means that more than a third of random transfusions could cause mismatch in these systems. This study was enabled by the introduction of molecular HPA typing, and it provides initial results of the HPA allele and genotype frequencies in the population of blood donors in Serbia. They will be used to provide a compatible blood supply on demand for treating patients with alloimmune thrombocytopenic disorders. The successful implementation of PCR-SSP with fluorometric signal detection could be further complemented in the future by the introduction of high-throughput methods, which will largely depend on the available financial resources.

[Polymorphism of human platelet antigens in Tunisian population: Clinical and anthropological interests]

OBJECTIVES

Human Platelet Antigens (HPA) are of considerable interest in obstetric transfusion medicine and anthropological genetics. This study aims to provide clinicians with a detailed database of HPA antigenic variants, which allows them to estimate the probability of allo-immunisation of each antigen. In addition, it aims to make an interethnic comparison of the Tunisian population with other populations.

METHODS

The target population consists of 324 healthy and unrelated Tunisian blood donors recruited from the National Blood Transfusion Center in Tunis. DNA extraction was performed by the Salting Out method and molecular genotyping was performed by the PCR-SSP technique. The statistical analysis was performed using two approaches: manual calculation and computerized calculation. Phylogenetic trees were constructed through the use of Standard Genetic Distances that were calculated from allelic frequencies.

RESULTS

With the exception of the HPA-4 system, statistical analysis showed that all HPA systems are polymorphic especially the two systems HPA-3 and HPA-15. The inter-ethnic analysis showed that Tunisians are closer to North Africans and Caucasians than Sub-Saharan and Asian populations, which shows genetic mixing between Tunisians, Arabs, Europeans and Africans.

CONCLUSION

The results of this study could be exploited to prepare a ready-to-use genotyping plate dedicated to HPA antigens, with the aim of ensuring better management, especially for polytransfused patients.

Human platelet antigen 1, 2 and 5 gene polymorphisms in Egyptians and their potential association with susceptibility to immune thrombocytopenic purpura in Egyptian patients

OBJECTIVES

This study determined the incidence of HPA1, HPA2 and HPA5 polymorphisms in 120 Egyptian immune thrombocytopenic purpura (ITP) patients and 120 healthy Egyptian subjects.

METHODS

Human platelet antigen (HPA) genotyping was done using the polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

The frequency of HPA1 allele a and b was 78.75 and 21.25% in controls, 80.8 and 19.2% in ITP, respectively. HPA2 allele a and b frequency was 86.25 and 13.75% in controls and of 74.6 and 25.4% in patients, respectively. HPA5 allele a and b frequency was 87.5 and 12.5% in controls, in patients it was 85 and 15%, respectively. With the exception of HPA2, no other significant difference was encountered in HPA allele frequency between controls and ITP patients.

DISCUSSION

Egyptian HPA profile is closely linked to Middle East and neighboring Arabs. The current study noted that in all the studied HPA systems 1, 2 and 5, the 'a' allele is more prevalent than the b allele; the most frequent genotype was the homozygous a/a genotype. HPA2b frequency, homo- and hetero-zygous HPA2b genotype frequencies were significantly higher in ITP patients compared to controls.

CONCLUSION

HPA 2b are 2.37 times more likely to develop ITP compared to those without this allele. The relatively high allele frequency of the HPA-1b in the Egyptian population suggests that this ethnic group has a higher risk of alloimmunization.

The allele frequencies of HPA 1-16 determined by PCR-SSP in Chinese Cantonese donors

BACKGROUND

Typing of human platelet antigens (HPA) has proven to be useful in some clinical situations related to platelet alloimmunization.

OBJECTIVE

The objective of this study was to investigate HPA 1-16 and to determine genotype and allele frequencies by polymerase chain reaction-sequence specific primer (PCR-SSP) in apheresis platelet donors in Guangzhou Blood Center.

METHODS

A total of 200 random samples from donors were involved in the study. Genotype and allele frequencies of HPA 1 to 16 were detected by PCR-SSP method.

RESULTS

The frequencies obtained from these donors were 99·50 and 0·50% for HPA-1a and -1b; 96·25 and 3·75% for HPA-2a and -2b; 54·25 and 45·75% for HPA-3a and -3b; 99·50 and 0·50% for HPA-4a and -4b; 99·00 and 1·00% for HPA-5a and -5b; 97·00 and 3·00% for HPA-6a and -6b and 42·25 and 57·75% for HPA-15a and -15b. There is only a/a homozygosis detected in HPA-7, -8, -9, -10, -11, -12, -13, -14 and -16. In this study, none of HPA-1b/ 1b, -2b/2b, -5b/5b homozygosis were detected which were found in other racial groups. One homozygosis of HPA-6b/6b in 200 individuals was detected which was not found in a study involving 1000 Chinese (Feng et al., 2006).

CONCLUSION

The HPA-3 and -15 appear to the highest priority and HPA-2, -6, -5 -1 and -4 to be the second priority in Chinese Cantonese when it comes to the diagnosis of neonatal alloimmune thrombocytopenia and to provide the HPA-matched platelet for patients with platelet transfusion refractoriness. The PCR-SSP method makes it possible to detect genotype of HPA-1 to -16 in less than 4 h and to establish a donor database for HPA genotype in a blood bank.

Platelet-specific alloantigens and antibodies in Tunisian women after three or more pregnancies

Pregnancy may allow alloimmunization against human platelet antigens (HPA), which can lead to neonatal alloimmune thrombocytopenia (NAIT). The specificities of alloantibodies are closely related to the distribution of the HPA systems. A total of 281 Tunisian multiparous women (mean number of pregnancies: 4.5) were phenotyped for the HPA-1, -3 and -5 systems, by monoclonal antibody immobilization of platelet antigens (MAIPA). We searched for antibodies against HPA-1a, HPA-3a, HPA-5b and HPA-5a in HPA-1b1b, HPA-3b3b, HPA-5a5a and HPA-5b5b individuals, respectively. The gene frequencies were: 0.83 for HPA-1a, 0.17 for HPA-1b, 0.78 for HPA-3a, 0.22 for HPA-3b, 0.82 for HPA-5a and 0.18 for HPA-5b. Anti-HPA-5b antibodies were present in eight sera and anti-HPA-3a antibodies were present in one serum. The anti-HPA-5b system is the most frequently involved in platelet alloimmunization in Tunisian multiparous women. However, prospective trials are required to confirm this result and to determine the exact frequencies and clinical relevance of platelet alloantibodies in pregnant Tunisian women.