Duffy Antigen Expression in Erythroid Bone Marrow Precursor Cells of Genotypically Duffy Negative Individuals

Abstract

Tel : +33 (0)1 44 49 31 47 (Dial 0 only within France) SignificanceDuffy blood group negativity results from a single nucleotide polymorphism (SNP) in the gene promoter, and reaches genetic fixation in many African ethnicities. Because the Duffy protein (Fy) is an important contact point during Plasmodium vivax human red blood cell invasion, Fy-negativity is considered to confer resistance to P. vivax malaria.With recent studies in African countries reporting P. vivax infection in Fy-negative people, we studied Fy expression across erythroid development. Here we report that the FY promoter SNP does not abolish Fy protein expression in erythroid progenitors developing in the bone marrow. These results further emphasizes the importance of reticulocytes as targets for P. vivax blood stage infection and propose a mechanism for P. vivax infections in Fy-negative people. Abstract The gene encoding the Duffy blood group protein (Fy, CD234; additional designations Duffy Antigen Receptor of Chemokines [DARC] and Atypical Chemokine Receptor 1 [ACKR1]) is characterized by a SNP in a GATA-1 transcription factor binding site associated with the erythrocyte silent (ES) phenotype. FY ES homozygous people are viewed to be highly resistant to blood stage infection with Plasmodium vivax. Increasingly, however, studies are reporting P.vivax infections in Fy-negative individuals across malarious African countries where FY ES approaches genetic fixation. This suggests that P. vivax has evolved a Fy-independent RBC invasion pathway, or that the GATA-1 SNP does not abolish Fy expression. Here, we tested the second hypothesis through binding studies to erythroid lineage cells using recombinant P. vivax Duffy binding protein, the parasite's invasion ligand and Fy6-specific antibodies. We first observed variable Fy expression on circulating RBCs, irrespective of FY genotype; FY ES RBCs were periodically Fy-positive. Furthermore, during the in vitro erythroid differentiation of CD34+ cells and on ex vivo bone marrow samples, we observed Fy expression on erythroid precursor cells from FY ES people. Finally, the Fy6-specific nanobody, CA111 was used to capture Fy from the surface of FY ES RBCs. Our findings reveal that the GATA-1 SNP does not fully abolish Fy expression and provide insight on potential susceptibility of Fy-negative people to vivax malaria.

Home Sweet Home: Plasmodium vivax-Infected Reticulocytes—The Younger the Better?

“…Some DARCindividuals may not be fully Duffynull, as residual RNA transcription may still happen marginally (Popovici et al, 2020). This phenomenon has recently been described in bone marrow-derived DARC -RBC progenitors (Dechavanne et al, 2018). The possibility that some very immature DARCreticulocytes in the bone marrow, but also in peripheral blood (Thomson-Luque et al, 2018), harbor marginal expression of DARC tempts us to speculate that they may be the explanation behind the possibility of transmission between Duffyindividuals infected with P. vivax.…”

The epidemiology of Plasmodium vivax among adults in the Democratic Republic of the Congo

“…Although there are numerous other explanations, all three of these explanations are consistent with previous work that suggests P. vivax infections among Duffy-negative individuals are frequently mild and asymptomatic compared with Duffy-positive individuals 5,6 . Finally, emerging research suggests that genotypically Duffy-negative hosts express the Duffy antigen among erythroid progenitors in the bone marrow and that P. vivax gametocytes are able to mature and proliferate in the bone marrow of non-human primate animal models 30,31 . Collectively, this suggests that P. vivax in SSA may be persisting as low parasitemic, asymptomatic infections, by hiding in the bone marrow or other tissues containing early progenitor red blood cells of Duffy-negative hosts [30][31][32] .…”

The enigmatic mechanisms by which Plasmodium vivax infects Duffy-negative individuals

“…Indeed, it can be speculated that although the −67 T to C mutation reduces the binding of the GATA-1 transcription factor and therefore transcription of the gene, this reduction might not be complete and RNA transcription could still be occurring at very low levels, leading to an amount of Duffy protein below the limit of detection of current analytical tools. Some recent data suggest that Duffy protein is notably detectable in erythroid precursor cells typically found in the bone marrow where P. vivax invasion is believed to occur to some extent [85][86][87]. It is worth mentioning here that Duffy-negative people do express the Duffy protein in other cell types such as in endothelial cells, indicating that the expression of Duffy is not intrinsically abolished by the −67 T to C mutation [23,88].…”

“…However, what has not been definitely ruled out and is perhaps the most parsimonious explanation for the mechanisms of Duffy-negative invasion is that the Duffy-negative phenotype is not Duffy null [85]. Indeed, it can be speculated that although the −67 T to C mutation reduces the binding of the GATA-1 transcription factor and therefore transcription of the gene, this reduction might not be complete and RNA transcription could still be occurring at very low levels, leading to an amount of Duffy protein below the limit of detection of current analytical tools.…”