Transcriptome profiling of in monkeys identifies potential ligands for invasion.

Unlike the case in Asia and Latin America, infections are rare in sub-Saharan Africa due to the absence of the Duffy blood group antigen (Duffy antigen), the only known erythrocyte receptor for the merozoite invasion ligand, Duffy binding protein 1 (DBP1). However, infections have been documented in Duffy-negative individuals throughout Africa, suggesting that may use ligands other than DBP1 to invade Duffy-negative erythrocytes through other receptors. To identify potential ligands, we compared parasite gene expression in and monkey erythrocytes infected with Salvador I (Sal I). DBP1 binds but does not bind to erythrocytes; thus, Sal I must invade erythrocytes independent of DBP1. Comparing RNA sequencing (RNAseq) data for late-stage infections in and erythrocytes when invasion ligands are expressed, we identified genes that belong to tryptophan-rich antigen and merozoite surface protein 3 (MSP3) families that were more abundantly expressed in infections compared with infections. These genes may encode potential ligands responsible for infections of Duffy-negative Africans.