Session: 101. Red Cells and Erythropoiesis, Excluding Iron: Poster I
Hematology Disease Topics & Pathways:
Research, Fundamental Science, Other Pathogens, Diseases, Infectious Diseases
Results: Whole exome sequencing in patient with an alloantibody to a high-prevalence antigen of unknown specificity led to the finding of eight candidate variants including a homozygous 284T>C GYPA mutation resulting in ILE95THR substitution and previously reported only at heterozygous state (frequency 0.0038 % in the Genome Aggregation Database). Others RBCs with rare blood type including Dantu and En(a-) were as reactive as the standard panel cells and the antibody was claimed to be of unknown specificity. Regarding the importance of Ile95 for GYPA dimerization (Trenker et al, JACS, 2015), we analyzed GYPA organization in RBC membranes from the proband and his homozygous brother. Indeed, immunoblotting with a specific anti-GYPA antibody showed the absence of the dimeric form of GYPA in the Ile95Thr and Dantu RBCs. Flow cytometry showed a slight decrease of GYPA but normal expression of Band3 and Wrb antigen in both variants. However, a second anti-GYPA antibody recognizing another epitope of this protein showed a strong decrease of GYPA in these variants. These results indicate a structural alteration of the GYPA in both Ile95Thr and Dantu RBCs. Interestingly, flow cytometry revealed that recombinant PfEBA-175 is able to bind the monomeric form of GYPA in Ile95Thr but not in Dantu RBCs. Finally, ex vivo invasion assays showed a drastic decreased invasion for all Ile95Thr, Dantu, En(a-) and Mk/Mk RBCs, suggesting a crucial role of GYPA dimerization for RBC invasion by P.falciparum.
Conclusion: We reported a new Ile95Thrh variant of GYPA organized in a monomeric form at the RBC membrane. Although EBA-175 binding is normal, this variant seems to be resistant to P. falciparum invasion, as it is the case for Dantu and En(a-) variants. Our findings provide genetic evidence that dimerization of GYPA is critical for RBC invasion by Plasmodium falciparum but not for the binding of EBA-175. This outcome could explain the poorly elucidated mechanism of Dantu RBC resistance to P. falciparum invasion.
Disclosures: No relevant conflicts of interest to declare.
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