Determining the frequency of human platelet antigen-1 polymorphisms in the Maltese population

Abstract

Platelets bear the fibrinogen receptor αIIbβ3, an integrin which is required for normal haemostasis. The human platelet antigen 1 (HPA-1) system is located at residue 33 of the αIIb component of this integrin. An amino acid change from a leucine (Leu) to a proline (Pro) occurs at this position due to a single nucleotide substitution (SNP) of a T to a C at base 196 of the ITGB3 gene coding for the αIIb protein. This results in the HPA-1a (Leu33) and HPA-1b (Pro33) alloantigens, which constitute the HPA-1 system. In the sample population studied which represented the Maltese population, the HPA-1b allele frequency was found to be 15.6 % and the HPA-1a allele frequency was found to be 84.4 %. The presence of the HPA-1b allele has been associated with myocardial infarction (MI), whilst the presence of the HPA-1a allele has been associated with autism. In rare cases in pregnancy or a blood transfusion, platelet incompatibility due to the HPA-1a and HPA-1b antigens occurs, resulting in alloantibody production against foreign HPA-1 antigens. Conditions associated with platelet incompatibility include neonatal alloimmune thrombocytopenia (NAIT), complications of NAIT, platelet transfusion refractoriness, post-transfusion purpura (PTP), and recurrent miscarriages. Thus, since the HPA-1a and HPA-1b allele frequencies of the Maltese population are similar to other European Caucasian population frequencies and African population frequencies, they may indicate similar polymorphism-associated diseases which may be studied alongside this polymorphism in the future.