During 1994 and 1995, the prevalence of hepatitis C virus (HCV) and its genotypes were studied in several rural and urban populations in three West African countries: Guinea, Burkina Faso, and Benin. The following groups were screened for antibodies to HCV (anti-HCV): 459 villagers in the forest region of Guinea; 965 individuals in urban, suburban, and rural populations of the Bobo Dioulasso area, Burkina Faso; and 582 blood donors in Cotonou, Benin. In Benin, 60 patients with sickle cell anemia (30 with and 30 without history of multiple transfusion) and 13 hospital patients with liver disease were also tested. RT-PCR detection of HCV-RNA was carried out on all anti-HCV positive samples, followed by genotyping and sequencing of unrecognized subtypes. The prevalence rates of anti-HCV were 1.1% in the Guinean population group, 1.4% among blood donors in Benin, and 4.9% in residents of Burkina Faso. In patients with sickle cell anemia, five of the 30 polytranfused patients (17%) had anti-HCV, whereas none of the patients without a history of blood transfusion had anti-HCV (P < 0.05). Among the 13 patients with liver disease, five had anti-HCV, of whom four had history of blood transfusion. HCV-RNA was detected in 41 anti-HCV positive sera. All belonged to genotypes 1 or 2, with a high genomic diversity; 18 different subtypes were identified, including 2c, 2d, and 16 new subtypes. Such genetic diversity poses a challenge for vaccine development and also implies that HCV infection is long-established in these West African regions.

The frequency of human platelet antigen-1 (HPA-1) to HPA-11w (excluding HPA-8w) and HPA-15 systems was studied in four sub-Saharan populations: Beninese, Congolese (Democratic Republic of Congo Kinshasa), Cameroonians, and Aka pygmies (Central African Republic). No report of HPA prevalence has previously been published concerning these populations which are characterized by the highest HPA-2b gene frequencies of any reported to date (Aka 0.393, Benin 0.292, Cameroon 0.237, and Congo 0.224) and at lesser degree HPA-5b (Aka 0.405, Congo 0.268, Cameroon 0.254, and Benin 0.182). This study is of great importance (i) particularly in the context of the diversity caused by the population migrations, we may observe today in our hospitals (ii) to confirm that the Pygmy population with distinctive frequencies (absence of the HPA-1b, HPA-2b, and HPA-5b highest frequencies) is an isolated population.

Three new mutations have been identified, two of them potentially immunogenic through their position. Furthermore, the polymorphism found on intron 26, localized in the complementary sequence of the PCR primer, may lead to a false typing assignation. It is therefore important to diversify techniques, both genomic (PCR-RFLP and PCR-SSP), and proteomic monoclonal antibody-specific immobilization of platelets antigen (MAIPA) to ensure accurate HPA antigenic system typing.

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