High-Throughput Screening of Blood Donors for Twelve Human Platelet Antigen Systems Using Next-Generation Sequencing Reveals Detection of Rare Polymorphisms and Two Novel Protein-Changing Variants.

BACKGROUND

Exposure to non-matching human platelet alloantigens (HPA) may result in alloimmunization. Antibodies to HPA can be responsible for post-transfusion purpura, refractoriness to donor platelets, and fetal and neonatal alloimmune thrombocytopenia. For the supply of compatible apheresis platelet concentrates, the HPA genotypes are determined in a routine manner.

METHODS

Here, we describe a novel method for genotyping twelve different HPA systems simultaneously, including HPA-1 to HPA-5, HPA-9w, HPA-10w, HPA-16w, HPA-19w, HPA-27w, and the novel HPA-34w by means of amplicon-based next-generation sequencing (NGS). Blood donor samples of 757 individuals with a migration background and 547 of Western European ancestry were genotyped in a mass-screening setup. An in-house software was developed for fast and automatic analysis. TaqMan assay and Sanger sequencing results served for validation of the NGS workflow. Finally, blood donors were divided in several groups based on their country of origin and the allele frequencies were compared.

RESULTS

For 1,299 of 1,304 samples (99.6%) NGS was successfully performed. The concordance with TaqMan assay and Sanger sequencing results was 99.8%. Allele-calling dropouts that were observed for two samples with the TaqMan assay caused by rare single nucleotide polymorphisms were resolved by NGS. Additionally, twenty rare and two novel variants in the coding regions of the genes ITGB3, GPB1A, ITGBA2, and CD109 were detected. The determined allele frequencies were similar to those published in the gnomAD database.

CONCLUSIONS

No significant differences were observed in the distribution of allele frequencies of HPA-1 through HPA-5 and HPA-15 throughout the analyzed groups except for a lower allele frequency for the HPA-1b allele in the group of donors with Southern Asian ancestry. In contrast, other nucleotide variants that have not yet been phenotypically characterized occurred three times more often in blood donors with a migration background. High-throughput amplicon-based NGS is a reliable method for screening HPA genotypes in a large sample cohort simultaneously. It is easily upgradeable for genotyping additional targets without changing the setup or the analysis pipeline. Mass-screening methods will help building up blood donor registries to provide matched blood products.