Molecular analysis of inactive and active RHD alleles in native Congolese cohorts

In Africa, RHD alleles have not been fully characterized. The purpose of this study was to identify inactive and active RHD alleles at the molecular level in Congolese cohorts.

Blood samples were collected from people living in central Congo populated by Teke ethnic group. A total of 110 D- and 40 D+ samples from Congo-Brazzaville and Teke groups, respectively, were selected for RHD genotyping using allele-specific primer polymerase chain reaction and sequencing.

In the 110 D- samples, RHD exon amplifications were observed in 7 samples that were subsequently identified by sequencing as weak D type 4 variants. In the remaining 103 D- samples, the frequencies of RHD gene deletion, RHDpsi pseudogene, and RHD-CE-D(s) hybrid gene were 0.75685, 0.20560, and 0.04468, respectively. In the D+ samples, 26 individuals carried at least a regular RHD gene; 9 carried aberrant RHD alleles belonging to the African D clusters, that is, DAU, DIVa, and weak D type 4; 3 carried RHDpsi in trans with a DAU allele including one novel RHD allele (V279M, S333N, T379M) named DAU-7; and 2 others were partially determined.

This study revealed a high frequency of weak D type 4 alleles that confirmed the need to use indirect antiglobulin test to improve transfusion safety in the Congo and in countries hosting Congolese people. Findings also indicated that there is a geographic variation in RHD allele distribution and showed that RHD gene deletion is the most prevalent cause of the D- phenotype in the Congolese population.