HLA class I variation in the West African Pygmies and their genetic relationship with other African populations

We have studied the polymorphism of HLA class I in two West African Pygmy populations, namely, the Bakola from Cameroon and the Mbenzele from the Central African Republic. A unique number of HLA alleles and haplotypes showed specific patterns of these populations. In this study, we identify two alleles (B*37, B*41) and three haplotypes (A*30-B*37, A*66-B*41 and A*68-B*58) that appear to be 'private' or typical of Western Pygmies. These data reflect similarities with the AKA Pygmies from the Central African Republic. On the other hand, we failed to identify alleles that are found at high frequencies among other sub-Saharan populations (B*42, B*51). Allelic and haplotypic frequency distributions show differences between the two Pygmy groups, e.g. B*35 was very common in the Mbenzele but has been found to be absent in the Bakola. In contrast, B*53, which is found in the Bakola, has been found to be rare in the Mbenzele Pygmies. In order to analyse the genetic relationships of the Bakola and Mbenzele Pygmies with other sub-Saharan populations, HLA gene frequencies were subjected to the Neighbour-Joining tree analysis. The Mbenzele, Bakola and AKA were found to be relatively close to each other and isolated from other sub-African populations. However, both the genetic distances and the within-group variation suggests that the Bakola are more admixed with Bantu farmers than Mbenzele.