Project description:Concerns about impending failure of artemisinin compounds (ART) have grown with global use of ART-based combination therapy (ACT) against malaria. WHO has defined Plasmodium falciparum resistance to ART as prolonged parasite clearance half-life in vivo (t1/2) plus the presence of certain K13 Kelch-propeller substitutions, e.g. C580Y. Recrudescences and fever clearance times after ART monotherapy, however, have not correlated well with these criteria. We have crossed K13 C580 wild-type and 580Y-mutant parasites for ART studies in Aotus. Artesunate treated C580- but not 580Y-infections recrudesced requiring retreatment, and K13 type had little or no effect on t1/2. These results challenge K13 and t1/2 variations as markers of increased resistance to ART per se and emphasize the need for effective partner drugs in ACTs.
Project description:Unlike in Asia and Latin America, Plasmodium vivax infections were rare in Sub-Saharan Africa due to the absence of the Duffy blood group antigen (Duffy Antigen), the only known erythrocyte receptor for the P. vivax merozoite invasion ligand, Duffy Binding Protein 1 (DBP1). However, P. vivax infections have been documented in Duffy-negative individuals throughout Africa, suggesting that P. vivax may use ligands other than DBP1 to invade Duffy-negative erythrocytes through other receptors. To identify potential P. vivax ligands, we compared parasite gene expression in Saimiri and Aotus monkey erythrocytes infected with P. vivax Salvador I (Sal I). DBP1 binds Aotus but does not bind to Saimiri erythrocytes, and thus P. vivax Sal I must invade Saimiri erythrocytes independently of DBP1. Comparing RNA sequencing (RNAseq) data for late stage infections in Saimiri and Aotus erythrocytes when invasion ligands are expressed, we identified genes that belong to tryptophan-rich antigen and MSP3 families that were more abundantly expressed in Saimiri infections as compared to Aotus infections. These genes may encode potential ligands responsible for P. vivax infections of Duffy-negative Africans.
Project description:The goal of this study is to identify P. vivax genes whose expression is dependent on the intact spleen in experimental infections in Aotus monkeys.
