Abstract

As specific antiplatelet alloimmunization directed against Human Platelet Antigens (HPA) during pregnancy or after platelet transfusion is not a rare event, this study aims at identifying such a risk in the context of the diversity caused by the population migrations we see today in our hospitals and particularly in the Sub-Saharan African (SSA), south East Asia and Polynesian populations. Samples were collected from 155 Beninese, 118 Cameroonian, 96 Congolese (Kinshasa), 107 Vietnamese and 81 Polynesian Ma’ohis, all unrelated, healthy blood donors. DNA was extracted by salting out method and the platelet genotype was determined by PCR-RFLP. We did not observe any significant deviation from the Hardy-Weinberg equilibrium. As opposed to Caucasian populations, the risk of anti HPA-1a alloimmunization is extremely low, due to the absence, or at least the low frequencies of HPA-1 b homozygous individuals in these populations (Cameroon 0.8 % and Benin 1.3 %). An important risk could be associated with HPA-2 immunization in the SSA population, as we observed a relatively high frequency of HPA-2b homozygous individuals. Moreover we noted the frequency of HPA-3b homozygous to be between 11 and 24%. Given that, as neonatal alloimmune thrombocytopenia (NAIT) caused by anti HPA-3a or 3b is similar in severity to disease caused by incompatibility of HPA-1a, this risk should not be ignored particularly in the Vietnamese population with 24.3 % of HPA3b homozygous. We noted the absence of HPA-4b allele. Finally, in contrast to the frequency of HPA-6 heterozygous in the Polynesian population (17%), we do not observe HPA-6b homozygous individuals, suggesting a small risk for that antigen to be implicated in alloimmunization. The repartition of HPA-15 alleles is heterogeneous in these populations. In conclusion: HPA-2 alloimmunization in SSA populations should be identified for platelet transfusion refractoriness or NAIT, similarly for HPA-3 especially in the Vietnamese population and to a lesser degree, HPA-5 in the Cameroon and in the Congo.

Genotype frequencies

 HPA-1 HPA-2 HPA-3 HPA-5 HPA-6 HPA-15 
 bb ...ab ↑bb ...ab ↑bb ...ab ↑bb ↑ ...ab bb ↑ ...ab bb 
Viet Nam 0.0 ↑ 09.4 0.0 54. ↑24.3 05.6 ↑0.0 02.8 ↑0 ↑ 57.0 24.3 
Polynesia 0.0 ↑ 16.3 0.0 ↑ 37.5 18.7 05. ↑0.0 ↑ 17.1 0 ↑ 52.4 28.4 
Benin 1.3 ↑ 44.8 7.1 42.8 ↑11.1 34.1 ↑0.8 0.00 ↑0 ↑ 41.6 14.1 
Cameroon 0.8 32.7 ↑7.8 ↑ 50.8 13.1 29.8 ↑6.4 ↑ 0.00 0 ↑ 41.2 10.9 
Congo 0.0 40.0 ↑2.5 49. ↑18.6 45.2 ↑4.1 ↑ 0.00 0 ↑ 43.8 05.5 
 HPA-1 HPA-2 HPA-3 HPA-5 HPA-6 HPA-15 
 bb ...ab ↑bb ...ab ↑bb ...ab ↑bb ↑ ...ab bb ↑ ...ab bb 
Viet Nam 0.0 ↑ 09.4 0.0 54. ↑24.3 05.6 ↑0.0 02.8 ↑0 ↑ 57.0 24.3 
Polynesia 0.0 ↑ 16.3 0.0 ↑ 37.5 18.7 05. ↑0.0 ↑ 17.1 0 ↑ 52.4 28.4 
Benin 1.3 ↑ 44.8 7.1 42.8 ↑11.1 34.1 ↑0.8 0.00 ↑0 ↑ 41.6 14.1 
Cameroon 0.8 32.7 ↑7.8 ↑ 50.8 13.1 29.8 ↑6.4 ↑ 0.00 0 ↑ 41.2 10.9 
Congo 0.0 40.0 ↑2.5 49. ↑18.6 45.2 ↑4.1 ↑ 0.00 0 ↑ 43.8 05.5 

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