Human Platelet Antigens in Brazilian Multiethnic Populations: Occurrence of Regional Variation and Frequency in a Large Urban Center (Belo Horizonte)

Abstract

Background: The frequency of human platelet antigens (HPA) varies according to ethnicity, which causes differences in the morbidity of alloimmune and autoimmune thrombocytopenic disorders in different populations. Studies on HPA frequencies in Brazil have reported differences among Brazilian populations produced by the diverse degrees of admixture throughout the country. Methods: In the present study, we investigated the variation of HPA distribution in Brazil, compared with worldwide populations, and describe the frequencies of HPA-1, -2, -3, -5, and -15 in a large urban center in Southern Brazil (Belo Horizonte) based on a sample of blood donors. Results: The principal component analysis and the dendrogram based on genetic distance revealed a clear relationship between Brazilian populations and the groups formed by European and African populations. The coefficients of variation for HPA allele frequencies suggest that Brazilian populations presented variations for HPA alleles comparable with the populations from continental groups. In Belo Horizonte, the allele a frequencies for HPA-1, -2, -3, -5 and -15 were 0.8575, 0.8400, 0.6225, 0.8525 and 0.5825 respectively. The genotypes with higher frequencies were a/a (72-74%), except for HPA-3 and -15, whose heterozygous a/b genotypes were shown to be more prevalent (43.5 and 44.5%, respectively). Conclusion: We confirmed the heterogeneity of HPA antigens in Brazilian populations, reinforcing the importance of HPA panels composed of regional blood donors, or a national panel that contemplates the specificities of the different regions of the country, in order to provide support in platelet transfusions and to minimize the risks associated with HPA alloimmunization. The evaluation of HPA data from Belo Horizonte represents the initial step toward the development of a genotyped platelet donor registry in order to treat HPA alloimmunized patients in this region.

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

“…Research of HPA allele frequencies and study of HPA antigen distribution differences between various ethnic populations are conducted to better understand the association between alloimmunization to these antigens and their clinical importance [8]. There are a number of studies reporting distributions of HPA gene frequencies in worldwide populations, which exhibit great variations between different ethnic and geographic groups [10]. The HPA antigens are expressed not only on platelet glycoproteins but also on other cells such as endothelial cells and monocytes, and they probably behave as histocompatibility antigens in organ transplantation [15, 16].…”

“…Platelet genotyping is currently considered the gold standard for HPA typing and it is useful when correlated with the results of antiplatelet antibody testing to determine alloimmunization and to measure the risk of AIT [10, 19].…”

“…HPA allele frequencies in populations of Slovenia (HPA-1 to HPA-5) [16], North Macedonia (HPA-1 to HPA-3 and HPA-5) [20], and Croatia (HPA-1 to HPA-3, HPA-5, and HPA-15) [21, 22], as shown in Table 3, all showed no significant differences in comparison with our results ( p > 0.05 for all populations and HPA systems that were tested in these studies). Similarly, statistically significant differences were not encountered between the Serbian population and data from non-Finnish European populations from the gnomAD database [23], or other European populations [10]. There are, however, significant differences between the Serbian population and some populations of non-European origin, as exemplified by populations from Asia [10, 14], Africa [8, 10], and South America [10].…”

“…Similarly, statistically significant differences were not encountered between the Serbian population and data from non-Finnish European populations from the gnomAD database [23], or other European populations [10]. There are, however, significant differences between the Serbian population and some populations of non-European origin, as exemplified by populations from Asia [10, 14], Africa [8, 10], and South America [10].…”

“…This study was conducted in a cohort of 72 unrelated healthy male platelet apheresis/blood donors from the city of Belgrade, Serbia. It is expected that there are no differences in the frequencies of HPA between men and women; therefore, we considered this sample to represent the general population [10].…”