Human Platelet Antigens Polymorphisms Research Articles

PLT antigen discrepancy pattern among couples with recurrent abortion.

Recurrent abortion refers to a condition of two or more consecutive pregnancies without known etiology affected by miscarriage before the completion of the 20th week of gestational age. However, several hypotheses have been proposed, but not much data are available concerning the relationship between human platelet antigens (HPAs) polymorphisms and recurrent abortion. This study was conducted to evaluate the genetic differences between HPA-1, -2, -3, -5, and - 15 in Iranian couples with a history of recurrent abortion. In this cross-sectional study, a total of 74 couples with at least 2 recurrent abortions without any known specified reasons enrolled in the study. HPA polymorphisms genotyping was performed by single-specific primer PCR. Genotype frequency was calculated using the Hardy-Weinberg equation. A total of 39 couples (52.7%) had HPA genotyping partial mismatches. The most common partial mismatch pairs were found concomitantly on both HPA-15a and HPA-15b in three couples (4%), followed by two (2.7%) on HPA-3a and one (1.3%) in each HPA-2b and HPA-5b. There was a deviation from the Hardy-Weinberg equilibrium in the HPA-2 and -5 systems. The present study declared that partial mismatches of HPA-3 and -15 genotypes were common among Iranian couples due to the history of recurrent abortion and approximately half of the couples carried at least one HPA gene that was absent in their partners. Further studies might be helpful to clarify the association between HPA polymorphisms and recurrent abortion, such as an investigation into the alloantibodies against HPAs.

Association of the human platelet antigens polymorphisms with platelet count in patients with COVID-19.

Polymorphism in human platelet antigen (HPA)-1 and HPA-3 (GPIIb/IIIa), HPA-2 (GPIb/IX), HPA-4 (GPIIIa), HPA-5 (GPIa/IIa), & HPA-15 (CD109) was investigated in 86 COVID-19-infected patients with thrombocytopenia (Group A) and 136 COVID-19-infected patients without thrombocytopenia (Group B). HPA genotyping was done by the sequence-specific primers PCR method. Lower HPA-3a and higher HPA-3b (P = 0.028) allele frequencies were seen in Group A than in Group B, and homozygosity for HPA 3b (P = 0.038) alleles was more prevalent in Group A than in Group B. The allele and genotype distributions of the other HPA polymorphic variants were similar between the two groups. Univariate analysis identified the CCGGGC (P = 0.016) combined genotype to be negatively associated & the TCGGGC (P = 0.003) and CCGGGC (P = 0.003) to be positively associated with thrombocytopenia. The frequency of anti-HPA-1a and anti-HPA-3a antibodies was significantly higher in all patients compared to other anti-HPAs antibodies (P < 0.05). These results highlight the role of HPAs in the thrombocytopenia of COVID-19 infected patients. This is the first evidence demonstrating the differential association of the six common HPA gene variants and specific HPA genotype combinations with thrombocytopenia in COVID-19-infected patients.

Human platelet antigens polymorphisms: Association to primary immune thrombocytopenia in the Iranian patients

Background: Human platelet antigens (HPAs) are part of platelet GP complexes have the potential to contribute to the autoantibody production. Moreover, these antigens demonstrate different patterns of distribution on different ethnic groups and variation in some types of diseases. This study was objected to determine the incidence of HPA-1 to -5 and -15 polymorphisms in the Iranians suffering from primary Immune thrombocytopenic purpura (ITP). &#x0D; Materials and Methods: In this case-control investigation, 30 patients by definite primary ITP were randomly selected and enrolled in the study. HPA genotyping was performed implicating by the Single Specific Primer PCR (SSP-PCR). For the control group, data of recently published gene polymorphism among Iranian Blood donors were deployed for comparison. &#x0D; Results: The incidence of HPA-1 to -5 and -15 polymorphisms in the Iranian patients with primary ITP was found to be: HPA-1a/1a: 0.933, HPA-1a/1b: 0.067, HPA-2a/2a: 0.133, HPA-2a/2b: 0.867, HPA-3a/3a: 0.2, HPA-3a/3b: 0.533, HPA-3b/3b: 0.267, HPA-4a/4a: 1, HPA-5a/5a: 0.967, HPA-5a/5b: 0.330, HPA-15a/15a: 0.166, HPA-15a/15b: 0.667 &amp; HPA-15b/15b: 0.167. &#x0D; Conclusion: This study provides special new data on the distribution of HPA allele among the Iranians ITP patients.Furthermore, it might useful toccharacterize understanding more presizely about ITP and HPA distribution. However, further studies concerning platelet immunology are needed to do help on best practice on management of immune diseases triggered by platelet antibodies.

Association of human platelet antigens polymorphisms with the levels of serum fibrosis marks in chronic hepatitis C patients

BackgroundHost genetic polymorphisms influence the fibrosis progression of chronic hepatitis C (CHC) patients. Previous studies have shown the association of human platelet antigens (HPAs) polymorphisms with CHC. However, little is known regarding the association of HPAs polymorphisms with the fibrosis progression of CHC. The aim of this study was to determine the association of HPA -2, -3, -5 and -15 polymorphisms with the levels of serum fibrosis marks in CHC patients. MethodsThe HPA -2, -3, -5 and -15 were genotyped by 5ˊ-nuclease assay in 211 CHC patients, while the serum concentration of hyaluronic acid (HA), collagen IV (CIV), amino-terminal pro-peptide of type III procollagen (PIIINP), and laminin (LN) from the same samples were measured by time resolved fluorescence immunoassay. ResultsThe level of serum LN was significantly lower in CHC patients with HPA-15aa genotype compared to those with HPA-15ab/bb (P = 0.032) but did not differ among HPA-2, -3 and -5 genotypes. There were no difference in HA, CIV and PIIINP levels among HPA-2, -3,-5 and -15 genotypes. ConclusionsThis study demonstrates that HPA-15 aa polymorphism is associated lower serum LN in CHC, which suggests that HPA -15 aa may be involved in the fibrosis progression of CHC.

Human platelet antigens polymorphisms; association to the development of liver fibrosis in patients with chronic hepatitis C.

Recently, human platelet antigens (HPAs) polymorphisms are found to play a role in susceptibility to hepatitis C virus (HCV) infection and fibrosis progression. The aim of the current study was to evaluate the possible association between the HPAs polymorphisms with liver fibrosis progression in HCV patients. HPAs polymorphisms genotyping was performed in HCV patients (n = 71) by Sequence-specific primers-polymerase chain reaction. Fibrosis progression was evaluated using the Metavir scoring system and liver biopsy, and the patients were assigned to two groups, namely, G1 (n = 35) that included patients with F1 (portal fibrosis without septa) or F2 (few septa) and G2 (n = 36) that comprised patients with F3 (numerous septa) or F4 (cirrhosis). The data analyses were performed using Pearson's χ2 test. The genotype frequency of HPA-3ab was significantly higher in G1 patients than in G2 patients (P = 0.015). No statistically significant differences were found between the patient groups (G1 and G2) regarding the distributions of the allelic and genotypic frequencies of the HPA-1, -2, -4, -5, and -15 systems. Multivariate logistic regression showed an independent association between the genotype HPA-3aa/BB and severe fibrosis (F3-F4), when compared with genotype HPA-3ab, independent of the viral genotype, high alanine transaminase, sex, age, time of infection, diabetes, and high cholesterol as risk factors. The present study suggested that the HPA-3ab genotype could be noticed as a potential protecting factor against hepatic fibrosis. Therefore, the antigenic variation of integrins might be considered as a part of the coordinated inflammatory process involved in the progression of liver fibrosis.

Human platelet antigen polymorphisms and the risk of chronic Chagas disease cardiomyopathy

Human platelet antigen (HPA) polymorphisms are considered to be a risk factor for cardiac and vascular diseases, but the role of HPA in chronic Chagas disease cardiomyopathy (CCC) is not available. Therefore, the aim of this study was to investigate the association of HPA polymorphisms, HPA-1, HPA-2, HPA-3, HPA-5 and HPA-15, in the severity of left ventricular systolic dysfunction (LVSD) in CCC patients. For this, 229 CCC patients were separated into three groups: without LVSD, mild/moderate LVSD and severe LVSD. PCR-SSP was performed for HPA genotyping and the risk was assessed using SNPStats software. HPA-1 allele and genotype frequencies were lower in mild/moderate LVSD patients compared to other groups, without statistical significance. After stratified analyzes, the HPA-3a/3b genotype frequency was lower in women with severe LVSD compared to those without LVSD (OR:0.29; 95% CI: 0.10–0.84). In conclusion, HPA-3 variant could be a protection factor for CCC in the female patients.

Human Platelet Alloantigens (HPA-3) Polymorphism in Sickle Cell Disease Patients with Vaso-Occlusive Crisis

AbstractBackground: Vaso-occlusive crisis (VOC) is a significant cause of morbidity and mortality in sickle cell disease (SCD) patients. As polymorphisms in human platelet antigens (HPA) exhibit a prothrombotic nature, we hypothesized that specific HPA polymorphisms could have a role in the pathogenesis of VOC in SCD.Aim of Study: This study investigated HPA-3 T2622G among Egyptian SCD patients.Patients and Methods: This study included 100 SCD patients and 50 controls. Patients were divided into, VOC group (n=60), and steady-state group (n=40). Genotyping was done using PCR-based Restriction Fragment Length Polymor-phism (RFLP) technique.Results: The HPA-3 mutant genotypes were significantly associated with SCD compared to controls (p=0.001), while no significant difference was observed between VOC and steady-state groups (p=0.169). Regarding the frequency of VOC episodes, the HPA-3 homozygous mutant genotypes showed significant differences (p=0.001). The HPA-3 mutant genotypes were significantly correlated with generalized type of VOC (p=0.006) and need for hospitalization (p=0.003). Regarding VOC complications, the HPA-3b/3b genotype was significantly associated with acute chest syndrome (p=0.008) and stroke (p=0.012).Conclusion: The HPA-3 T2622G is common among SCD patients. Although it is not a major determinant of vasculo-cclusion in SCD, it is significantly associated with VOC complications and may alter their outcome.

Association of human platelet antigen polymorphisms with platelet count and mean platelet volume

ABSTRACTObjectives: Although recent genome-wide association studies have identified a number of single nucleotide polymorphisms associated with platelet count and mean platelet volume (MPV), it is unclear whether polymorphisms in the human platelet antigens (HPA) genes are associated with platelet count and MPV. The aim of this study was to determine the association of the HPA-2, -3, -5 and -15 polymorphisms with platelet count and MPV.Methods: The HPA were genotyped by 5ˊ-nuclease assay in 139 healthy Chinese Han individuals, while platelet count and MPV from the same samples were measured using an hematology cell analyzer.Results: The platelet count was significantly lower in the individuals with the HPA-2aa genotype compared to those with HPA-2ab (P = 0.020), and significantly higher in individuals with HPA-5aa and HPA-15aa genotypes compared to those with HPA-5ab (P = 0.045) and HPA-15ab/bb (P = 0.032), respectively. On the other hand, platelet count of individuals with the HPA-3aa and HPA-3ab/bb genotypes did not differ significantly (P = 0.084). The MPV was significantly lower in individuals with HPA-5aa genotype compared to those with HPA-5ab (P = 0.001) but did not differ among the HPA-2, -3 and -15 genotypes. Furthermore, HPA-2, -5 and -15 polymorphisms were identified as independent factors for the platelet count and HPA-5 polymorphism was shown as an independent factor for MPV.Conclusions: This study demonstrates that HPA-2, -5 and -15 polymorphisms are associated with the platelet count while HPA-5 polymorphism is associated with MPV. This finding will further our understanding of the association of HPA polymorphisms with platelet-related diseases.

Association of human platelet antigens polymorphisms with susceptibility to hepatitis C virus infection in Chinese population.

Hepatitis C virus (HCV) is a major cause of chronic hepatitis. Previous studies have identified a number of single nucleotide polymorphisms that are associated with HCV infection. Human platelet antigens (HPAs) polymorphisms play an important role in several diseases. Here, we demonstrated the association of the HPA-2, HPA-3, HPA-5 and HPA-15 polymorphisms with susceptibility to HCV infection in Chinese population. Overall, 118 patients with HCV and 167 controls were genotyped for HPAs. There were no significant differences in the allele and genotype frequency distribution for the HPA-3, HPA-5 and HPA-15 systems between the patients with chronic HCV infection and the healthy controls (p>.05). However, the genotype frequency of HPA-2aa was significantly lower, while HPA-2ab/bb was significantly higher in patients than that in the controls (p=.006). The allele frequency of HPA-2a in patients was significantly lower than that in the control group (p=.005). In contrast, HPA-2b in patients was significantly higher than that in the control group (p=.005). We conclude that HPA-2 polymorphism is associated with susceptibility to HCV infection, and individuals carrying the HPA-2b allele may have a higher risk of HCV infection compared with individuals carrying HPA-2a.

Simultaneous human platelet antigen genotyping and detection of novel single nucleotide polymorphisms by targeted next‐generation sequencing

Twenty-nine human platelet antigen systems have been described to date, but the majority of current genotyping methods are restricted to the identification of those most commonly associated with alloantibody production in a clinical context. This can result in a protracted investigation if causative human platelet antigens are rare or novel. A targeted next-generation sequencing approach was designed to detect all known human platelet antigens with the additional capability of identifying novel mutations in the encoding genes. A targeted enrichment, high-sensitivity HaloPlex assay was designed to sequence all exons and flanking regions of the six genes known to encode human platelet antigens. Indexed DNA libraries were prepared from 47 previously human platelet antigen-genotyped samples and subsequently combined into one of three pools for sequencing on an Illumina MiSeq platform. The generated FASTQ files were aligned and scrutinized for each human platelet antigen polymorphism using SureCall data analysis software. Forty-six samples were successfully genotyped for human platelet antigens 1 through 29bw, with an average per base coverage depth of 1144. Concordance with historical human platelet antigen genotypes was 100%. A putative novel mutation in Exon 10 of the integrin β-3 (ITGB3) gene from an unsolved case of fetal neonatal alloimmune thrombocytopenia was also detected. A next-generation sequencing-based method that can accurately define all known human platelet antigen polymorphisms was developed. With the ability to sequence up to 96 samples simultaneously, our HaloPlex design could be used for high-throughput human platelet antigen genotyping. This method is also applicable for investigating fetal neonatal alloimmune thrombocytopenia when rare or novel human platelet antigens are suspected.

Analysis of HPA1-16 and HLA-A, B gene polymorphisms among ethnic Han population from Shandong

To study the polymorphisms of human platelet antigen (HPA) 1-16 and human leukocyte antigen (HLA)-A and -B loci among ethnic Han population from Shandong. A total of 588 samples from platelet donors were genotyped for the above loci with sequence-specific primer PCR and sequence-specific oligonucleotide probe PCR. The frequencies of HPA-la, -1b, HPA-2a, -2b, HPA-3a, -3b, HPA-4a, -4b, HPA-5a, -5b, HPA-6a, -6b, HPA-15a, -15b were 0.9974, 0.0026, 0.9456, 0.0544, 0.5417, 0.4583, 0.9983, 0.0017, 0.9889, 0.0111, 0.9903, 0.0097, 0.5434 and 0.4583, respectively. The HPA-7-14 and HPA-16 showed no heterozygosity as the b allele was not detected in such loci. The most common genotypic combination for HPA was HPA-(1,4,7-14,16,17) aa-2aa-3ab-5aa -6aa-15ab (0.1820). HLA-A2 (0.3070) and HLA-B13 (0.1361) demonstrated the highest frequencies at their respective loci. The HPA and HLA loci are highly polymorphic among ethnic Hans from Shandong. The distribution of HPA polymorphisms also shows a great ethnic and territorial difference. It is important to construct regional database for the genotypes of HPA and HLA loci for platelet donors.

The absence of the human platelet antigen polymorphism effect on fibrosis progression in human immunodeficiency virus-1/hepatitis C virus coinfected patients.

Hepatic fibrosis progression in patients with chronic hepatitis C virus infections has been associated with viral and host factors, including genetic polymorphisms. Human platelet antigen polymorphisms are associated with the rapid development of fibrosis in HCV-monoinfected patients. This study aimed to determine whether such an association exists in human immunodeficiency virus-1/hepatitis C virus-coinfected patients. Genomic deoxyribonucleic acid from 36 human immunodeficiency virus-1/hepatitis C virus-coinfected patients was genotyped to determine the presence of human platelet antigens-1, -3, or -5 polymorphisms. Fibrosis progression was evaluated using the Metavir scoring system, and the patients were assigned to two groups, namely, G1 that comprised patients with F1, portal fibrosis without septa, or F2, few septa (n = 23) and G2 that comprised patients with F3, numerous septa, or F4, cirrhosis (n = 13). Fisher's exact test was utilized to determine possible associations between the human platelet antigen polymorphisms and fibrosis progression. There were no deviations from the Hardy-Weinberg equilibrium in the human platelet antigen systems evaluated. Statistically significant differences were not observed between G1 and G2 with respect to the distributions of the allelic and genotypic frequencies of the human platelet antigen systems. The greater stimulation of hepatic stellate cells by the human immunodeficiency virus and, consequently, the increased expression of transforming growth factor beta can offset the effect of human platelet antigen polymorphism on the progression of fibrosis in patients coinfected with the human immunodeficiency virus-1 and the hepatitis C virus.

Genetic polymorphisms of human platelet antigens-1 to -6, and -15 in the Malaysian population.

Human platelet antigens (HPA) are determinant in several platelet-specific alloimmune disorders, such as neonatal alloimmune thrombocytopenia, post-transfusion purpura and platelet transfusion refractoriness. The distribution of HPA systems in the Malaysian population is not known. Defining the patterns of HPA systems provides a basis for risk assessment and management of the above complications. The aim of this study was to investigate the distribution of HPA -1 to -6 and -15 in the three major ethnic groups (Malay, Chinese and Indian) in the Malaysian population. A total of 600 random donor samples, 200 from each of the three ethnic groups, were genotyped by means of real time polymerase chain reaction (PCR) with hydrolysis probes and PCR-restriction fragment length polymorphism (PCR-RFLP). The most common genotype observed in this study was HPA-1a/1a-2a/2a-3a/3b-4a/4a-5a/5a-6a/6a-15a/15b (17%) followed by HPA-1a/1a-2a/2a-3a/3a-4a/4a-5a/5a-6a/6a-15a/15b (14.33%). The allele frequencies of HPA in Malays and Chinese were found to be similar those of other East and South-East Asian populations, while those of Indians were comparable to the frequencies found in Europeans. The results of this study have been useful for determining the distribution of HPA polymorphisms in this region and for potential clinical implications.

Comments on: frequency of human platelet antigens in oncohematological patients with thrombocytopenia and the probability of incompatibility to platelet transfusions

Comments on: frequency of human platelet antigens in oncohematological patients with thrombocytopenia and the probability of incompatibility to platelet transfusions

Human platelet antigen allele frequencies and new mutations on platelet glycoprotein genes in the Chinese Han population

The frequencies of human platelet antigens (HPAs) vary between different populations. In this study, we determined the HPA allele frequencies in the Chinese Han population and identified situation of incompatibility possibly leading to alloimmunisation. A total of 750 volunteer blood donors of the Chinese Han population were genotyped for HPA-1 to -17w systems. HPA genotyping was determined by polymerase chain reaction sequence-based typing. Among the 17 HPA systems, the allele frequency is different from other populations. We noted the absence of HPA-7bw to HPA-14bw, HPA-16bw and HPA-17bw alleles in the population. The estimated incompatibility probabilities regarding platelet antigens 1 to 6w and 15 systems after transfusion of random donor platelet were from 0·004 to 0·373. Thirteen glycoprotein alleles were observed in the population. In addition, we identified 16 novel mutations on the glycoprotein genes separated from HPA polymorphisms, including GP1BA (517-525delAAC), ITGA2B (2722C>T and IVS26+85T>C), ITGA2 (1521C>T, 2474T>G and IVS20+10 G>C), ITGB3 (1476G>A, IVS10+19C>A, 1813G>A, IVS11+21G>A, IVS11+152A>G and IVS11-104T>C), GP1BB (IVS1-79G>A, IVS1-27C>T and 129G>A) and CD109 (2139A>G). Five of them could lead to amino acid deletion, substitution or premature stop codon in corresponding glycoprotein. There was a high degree of polymorphism of the membrane glycoprotein genes related to human platelet alloantigen-1 to -17w systems in the Chinese Han population. These data could have some impact on the diagnosis, prevention and treatment of alloimmune thrombocytopenia.

Molecular testing for platelet and granulocyte antigens

Human platelet antigen (HPA) genotyping is a valuable tool in confirming platelet antigen specificities of alloantibodies detected in patient sera, complementing the clinical history in the diagnosis of alloimmune platelet disorders such as neonatal alloimmune thrombocytopenia (NAIT), post‐transfusion purpura (PTP) and platelet transfusion refractoriness (PR). Likewise, human neutrophil antigen (HNA) typing also plays a critical role in the investigation and diagnosis of some clinical conditions induced by granulocyte alloantibodies, like neonatal alloimmune neutropenia (NAIN) and transfusion‐related acute lung injury (TRALI).Up to now, 27 HPA alloantigens have been described, including the 6 most clinically relevant biallelic systems and a significant number of low‐frequency or rare HPAs, which continues to increase with new reports. The genetic polymorphisms underlying these antigens have been characterized and in all cases but one, are single nucleotide polymorphisms (SNPs) in the coding sequence of the different membrane proteins where the HPA antigens are expressed. In contrast, the molecular basis of the HNA antigens are a little bit more heterogeneous. Within the 5 recognized HNA systems, the first alloantigens to be described, HNA‐1a and HNA‐1b differ in their coding sequence by 5 nucleotides, which result in 4 aminoacid changes in the protein sequence of the FcγRIIIb. Another alloantigen, the HNA‐2a, has been identified on the CD177 glycoprotein but cannot be genotyped, despite knowing the corresponding coding sequence. The HNA‐2a negative phenotype is due to splicing defects in the mRNA and no mutations have been detected in the gene sequence. The remaining HNA alloantigens result from single nucleotide changes, including the clinically relevant HNA‐3a, which has recently been characterized as the result of a single base change in the choline transporter‐like protein (CTL) 2 gene.Currently, genotyping methods are routinely applied to HPA and HNA testing in all laboratories performing platelet and granulocyte immunohematology studies. Many different techniques have been developed for typing these polymorphisms, including PCR with sequence‐specific primers, which is still the most widely used, 5′‐nuclease assays and high‐throughput SNP typing platforms. These latter ones are based on specific hybridization to oligonucleotide probes immobilized in a solid suport, usually a glass slide or beads. Among these, the newest platform developed for HPA typing, ID‐HPA, is based on the xMAP® technology and the beads are analyzed with the Luminex 100/200™ System, which is a robust and convenient system, already implemented in most HLA laboratories. Interestingly, the same technology can recently be used for the detection of HPA and HNA antibodies, which offers the possibility of multiple applications with a unique platform. These features may foster the introduction of such flexible assay systems in the near future. In any case, already at present, different high‐throughput genotyping platforms analyzing HPA polymorphisms are already being used for large‐scale blood or platelet apheresis donor typing, and further automation will probably lead to their final implementation in centralized National Blood Centers, facilitating the provision of antigen‐negative platelets for alloimmunized patients.Finally, it is worth to remark the novel strategies that have been recently developed for the non‐invasive fetal HPA‐1 typing from the maternal plasma DNA. These highly sensitive approaches may be applied in the future to other clinically significant HPA specificities, and will represent a major improvement in the management of pregnancies at risk of NAIT.

Human platelet antigen polymorphisms (HPA-1, -2, -3, -4, -5 and -15) in major ethnic groups of Pakistan

Gene frequencies of human platelet antigens (HPA) determine the magnitude of platelet immunological disorders like neonatal alloimmune thrombocytopenia, platelet refractoriness and ease of availability of particular HPA-typed platelet donors in a given community. However, the pattern of HPA in Pakistani population is not known. The aim of present study was to determine the gene frequencies of HPA (HPA-1 to -5 and -15) in individuals belonging to major ethnic groups and castes of Pakistani population. HPA genotyping was done in 593 individuals belonging to all ethnic groups of Pakistan, by polymerase chain reaction-sequence specific primers with detection on polyacrylamide electrophoresis. The gene frequencies of the 'a' and 'b' alleles of HPA-1 to -5 and -15 in Pakistanis were as follows: HPA-1a/b, 0.885/0.115; HPA-2a/b, 0.92/0.08; HPA-3a/b, 0.69/0.31; HPA-4a/b, 1/0; HPA-5a/b, 0.9/0.1; HPA-15a/b, 0.59/0.41. Except for significant difference regarding gene frequency of HPA-3 between Pathans and Sindhis, there was no significant difference of HPA-1 to -5 and -15 between major ethnic groups of Pakistan. The estimated mismatch probability regarding platelet antigens 1-5 and 15 in Pakistanis, after transfusion of random donor platelets, is from 14 to 37%. The expected incidence of neonatal alloimmune thrombocytopenia due to anti-HPA-1a in Pakistani pregnant females is < 1 of 1000 pregnancies and 8-12 of 1000 in case of anti-HPA-5b. Homozygosity of HPA-1b, -2b and -5b genotypes ranged from 1 to 2% in the Pakistani population, whereas homozygosity of HPA-3b and -15b was 11 and 18%. There is a need to establish donor registries typed for HPA in the transfusion centres of the country.

Human platelet antigens polymorphisms and susceptibility of thrombosis in hemodialysis patients

To investigate the association between the polymorphisms of human platelet antigen (HPA)-1,2,3,4,5 and susceptibility to develop thrombosis accident in arteriovenous fistula (AVF), genomic DNA of 112 hemodialysis (HD) patients and 100 healthy blood donors were genotyped by PCR-SSP. The patients were classified into 2 groups: G1 included 54 HD patients presented at least one thrombotic episode on the level of the AVF, and G2 included 58 HD patients without any episode of thrombosis. The allelic frequencies of HPA-1, 2, 3, and 5 among patients and controls did not reveal significant differences. However, the HPA-4b allele was significantly more frequent in G1 than in controls or in G2 patients (23.1% vs. 11.5% and 0.9%, respectively), p<0.01 and p<0.001. The genotype distribution of HPA-4 polymorphism reveals that the HPA-4a4b genotype was more frequent in G1 patients (23/54: 42.6%) than in all HD patients (25/112: 22.3%) or in G2 patients (1/58: 1.72%) (p<0.001, odds ratio: 45.6). Among 24 HD patients with HPA-4a4b genotype, 23 (96%) developed at least 1 or more thrombotic episode on the level of their AVF. However, 30 patients (34.5%) among 87 HD patients with HPA-4a4a genotype presented thrombotic episode (p<0.001). These results reveal a significant association between HPA-4a4b and thrombosis, and it is likely that HPA polymorphisms could be useful markers for potential risk of thrombosis in hemodialysis.

Gene frequencies of human platelet alloantigens in Bahraini Arabs

Human platelet antigens (HPA) are implicated in the pathophysiology of certain hematological disorders, and as varied distribution of HPA-1 alleles and genotypes were reported fordifferent countries and ethnic populations, we determined the distribution of HPA-1, -2, -3, -4, and -5 alleles, genotypes and haplotypes for 194 healthy Bahraini subjects by polymerase chain reaction with sequence specific primers. The distribution of the HPA polymorphisms was in Hardy-Weinberg equilibrium. Allele frequencies of 0.76 and 0.24 (HPA-1a and -1b), 0.77 and 0.23 (HPA-2a and -2b), 0.57 and 0.43 (HPA-3a and -3b), 0.93 and 0.07 (HPA-4a and -4b), and 0.86 and 0.13 (HPA-5a and -5b) were seen. With the exception of HPA-3a/a (30.4%), the frequencies of homozygous HPA-1a/a (56.8%), 2a/a (60.1%), 4a/a (87.2%), and 5a/a (75.7%) were higher than those of heterozygous (a/b) or homozygous (b/b) variants. Our results provide basic information for further studies of the HPA system polymorphism, which in turn will be instrumental in understanding and treating immune-mediated platelet disorders.

New Method for DNA Microarrays Development: Applied to Human Platelet Antigens Polymorphisms

DNA microarrays are a powerful experimental tool for the detection of specific genomic sequences and are invaluable to a broad array of applications: clinical diagnosis, personalized medicine, drug research and development, gene therapy, food control technologies, and environmental sciences. Alloimmunization to human platelet antigens (HPAs) is commonly responsible for neonatal alloimmune thrombocytopenia, post-transfusional purpura and platelet transfusion refractoriness. Using DNA microarrays, we developed a diagnosis to type the biallelic HPA-1 platelet group. The region for the human genomic DNA sequence that contains the polymorphism responsible for HPA-1 alleles was amplified by polymerase chain reaction (PCR). The expected DNA fragments were hybridized on DNA microarrays, and the data were analyzed using specially developed software. Our initial results show that the two HPA-1 antigens polymorphisms containing a single base difference were detected using DNA microarrays.