No Association between the Plasmodium vivax MS334 or In9 Polymorphisms and Chloroquine Failure in a Pre-Elimination Clinical Cohort from Malaysia with a Large Clonal Expansion.

Increasing reports of resistance to a frontline malaria blood-stage treatment, chloroquine (CQ), raises concerns for the elimination of Plasmodium vivax. The absence of an effective molecular marker of CQ resistance in P. vivax greatly constrains surveillance of this emerging threat.

Genetic Manipulation of Non-Falciparum Human Malaria Parasites.

The development of genetic manipulation of in the 1980s was key to study malaria biology. Genetically modified parasites have been used to study several aspects of the disease, such as red blood cell invasion, drug resistance mechanisms, gametocyte development and mosquito transmission. However, biological and genetic differences between and the other human malaria parasites make a poor model to study different species.

Activity of Plasmodium vivax promoter elements in Plasmodium knowlesi, and a centromere-containing plasmid that expresses NanoLuc throughout the parasite life cycle.

Background: Plasmodium knowlesi is now the major cause of human malaria in Malaysia, complicating malaria control efforts that must attend to the elimination of multiple Plasmodium species. Recent advances in the cultivation of P. knowlesi erythrocytic-stage parasites in vitro, transformation with exogenous DNA, and infection of mosquitoes with gametocytes from culture have opened up studies of this pathogen without the need for resource-intensive and costly non-human primate (NHP) models.

Plasmodium vivax chloroquine resistance links to pvcrt transcription in a genetic cross.

Mainstay treatment for Plasmodium vivax malaria has long relied on chloroquine (CQ) against blood-stage parasites plus primaquine against dormant liver-stage forms (hypnozoites), however drug resistance confronts this regimen and threatens malaria control programs. Understanding the basis of P. vivax chloroquine resistance (CQR) will inform drug discovery and malaria control.

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).

Artemisinin resistance phenotypes and K13 inheritance in a cross and model.

Concerns about malaria parasite resistance to treatment with artemisinin drugs (ARTs) have grown with findings of prolonged parasite clearance s (>5 h) and their association with mutations in Kelch-propeller protein K13. Here, we describe a laboratory cross of K13 C580Y mutant with C580 wild-type parasites to investigate ART response phenotypes in vitro and in vivo. After genotyping >400 isolated progeny, we evaluated 20 recombinants in vitro: IC measurements of dihydroartemisinin were at similar low nanomolar levels for C580Y- and C580-type progeny (mean ratio, 1.

Bone Marrow Is a Major Parasite Reservoir in Plasmodium vivax Infection.

causes heavy burdens of disease across malarious regions worldwide. Mature asexual and transmissive gametocyte stages occur in the blood circulation, and it is often assumed that accumulation/sequestration in tissues is not an important phase in their development. Here, we present a systematic study of stage distributions in infected tissues of nonhuman primate (NHP) malaria models as well as in blood from human infections.

Infection of mosquitoes from in vitro cultivated Plasmodium knowlesi H strain.

In vitro studies of sexual blood stages of the most fatal malaria species, Plasmodium falciparum, have revealed key processes by which gametocytes develop and transmit infection from humans to anopheline mosquitoes. However, most malaria cases outside sub-Saharan Africa are caused by other Plasmodium spp., frequently Plasmodium vivax and Plasmodium knowlesi, a zoonotic parasite of macaque monkeys.

Comparison of two methods for transformation of Plasmodium knowlesi: Direct schizont electroporation and spontaneous plasmid uptake from plasmid-loaded red blood cells.

Human infections from Plasmodium knowlesi present challenges to malaria control in Southeast Asia. P. knowlesi also offers a model for other human malaria species including Plasmodium vivax.

Subtelomeric I-SceI-Mediated Double-Strand Breaks Are Repaired by Homologous Recombination in .

chromosome ends are enriched in surface protein genes and pseudogenes (e.g., trans-sialidases) surrounded by repetitive sequences.

Alternative methods for the Plasmodium falciparum artemisinin ring-stage survival assay with increased simplicity and parasite stage-specificity.

Background: Artemisinin-based combination therapy is recommended to treat Plasmodium falciparum worldwide, but observations of longer artemisinin (ART) parasite clearance times (PCTs) in Southeast Asia are widely interpreted as a sign of potential ART resistance. In search of an in vitro correlate of in vivo PCT after ART treatment, a ring-stage survival assay (RSA) of 0-3 h parasites was developed and linked to polymorphisms in the Kelch propeller protein (K13). However, RSA remains a laborious process, involving heparin, Percoll gradient, and sorbitol treatments to obtain rings in the 0-3 h window.

Editing the Plasmodium vivax genome, using zinc-finger nucleases.

Plasmodium vivax is a major cause of malaria morbidity worldwide yet has remained genetically intractable. To stably modify this organism, we used zinc-finger nucleases (ZFNs), which take advantage of homology-directed DNA repair mechanisms at the site of nuclease action. Using ZFNs specific to the gene encoding P.

Cloning and expression of transgenes using linear vectors in Trypanosoma cruzi.

The identification of new targets for vaccine and drug development for the treatment of Chagas' disease is dependent on deepening our understanding of the parasite genome. Vectors for genetic manipulation in Trypanosoma cruzi basically include those that remain as circular episomes and those that integrate into the parasite's genome. Artificial chromosomes are alternative vectors to overcome problematic transgene expression often occurring with conventional vectors in this parasite.

Interclonal variations in the molecular karyotype of Trypanosoma cruzi: chromosome rearrangements in a single cell-derived clone of the G strain.

Trypanosoma cruzi comprises a pool of populations which are genetically diverse in terms of DNA content, growth and infectivity. Inter- and intra-strain karyotype heterogeneities have been reported, suggesting that chromosomal rearrangements occurred during the evolution of this parasite. Clone D11 is a single-cell-derived clone of the T.

Anatomy and evolution of telomeric and subtelomeric regions in the human protozoan parasite Trypanosoma cruzi.

Background: The subtelomeres of many protozoa are highly enriched in genes with roles in niche adaptation. T. cruzi trypomastigotes express surface proteins from Trans-Sialidase (TS) and Dispersed Gene Family-1 (DGF-1) superfamilies which are implicated in host cell invasion.

Genome size, karyotype polymorphism and chromosomal evolution in Trypanosoma cruzi.

Background: The Trypanosoma cruzi genome was sequenced from a hybrid strain (CL Brener). However, high allelic variation and the repetitive nature of the genome have prevented the complete linear sequence of chromosomes being determined. Determining the full complement of chromosomes and establishing syntenic groups will be important in defining the structure of T.