Malaria therapy, experimental, and epidemiological studies have shown that erythrocyte Duffy blood group-negative people, largely of African ancestry, are resistant to erythrocyte Plasmodium vivax infection. These findings established a paradigm that the Duffy antigen is required for P. vivax erythrocyte invasion. P. vivax is endemic in Madagascar, where admixture of Duffy-negative and Duffy-positive populations of diverse ethnic backgrounds has occurred over 2 millennia. There, we investigated susceptibility to P. vivax blood-stage infection and disease in association with Duffy blood group polymorphism. Duffy blood group genotyping identified 72% Duffy-negative individuals (FY*B ES /*B ES ) in community surveys conducted at eight sentinel sites. Flow cytometry and adsorption-elution results confirmed the absence of Duffy antigen expression on Duffy-negative erythrocytes. P. vivax PCR positivity was observed in 8.8% (42/476) of asymptomatic Duffy-negative people. Clinical vivax malaria was identified in Duffy-negative subjects with nine P. vivax monoinfections and eight mixed Plasmodium species infections that included P. vivax (4.9 and 4.4% of 183 participants, respectively). Microscopy examination of blood smears confirmed blood-stage development of P. vivax, including gametocytes. Genotyping of polymorphic surface and microsatellite markers suggested that multiple P. vivax strains were infecting Duffy-negative people. In Madagascar, P. vivax has broken through its dependence on the Duffy antigen for establishing human blood-stage infection and disease. Further studies are necessary to identify the parasite and host molecules that enable this Duffyindependent P. vivax invasion of human erythrocytes.erythrocyte | evolution | DARC | Madagascar

Geographic overlap between malaria and the occurrence of mutant hemoglobin and erythrocyte surface proteins has indicated that polymorphisms in human genes have been selected by severe malaria. Deletion of exon 3 in the glycophorin C gene (called GYPCDeltaex3 here) has been found in Melanesians; this alteration changes the serologic phenotype of the Gerbich (Ge) blood group system, resulting in Ge negativity. The GYPCDeltaex3 allele reaches a high frequency (46.5%) in coastal areas of Papua New Guinea where malaria is hyperendemic. The Plasmodium falciparum erythrocyte-binding antigen 140 (EBA140, also known as BAEBL) binds with high affinity to the surface of human erythrocytes. Here we show that the receptor for EBA140 is glycophorin C (GYPC) and that this interaction mediates a principal P. falciparum invasion pathway into human erythrocytes. EBA140 does not bind to GYPC in Ge-negative erythrocytes, nor can P. falciparum invade such cells using this invasion pathway. This provides compelling evidence that Ge negativity has arisen in Melanesian populations through natural selection by severe malaria.

Blood group variants are characteristic of population groups, and can show conspicuous geographic patterns. Interest in the global prevalence of the Duffy blood group variants is multidisciplinary, but of particular importance to malariologists due to the resistance generally conferred by the Duffy-negative phenotype against Plasmodium vivax infection. Here we collate an extensive geo-database of surveys, forming the evidence-base for a multi-locus Bayesian geostatistical model to generate global frequency maps of the common Duffy alleles to refine the global cartography of the common Duffy variants. We show that the most prevalent allele globally was FY*A, while across sub-Saharan Africa the predominant allele was the silent FY*BES variant, commonly reaching fixation across stretches of the continent. The maps presented not only represent the first spatially and genetically comprehensive description of variation at this locus, but also constitute an advance towards understanding the transmission patterns of the neglected P. vivax malaria parasite.