The emergence and spread of drug-resistant Plasmodium falciparum poses an immense global health threat. While we understand much about the selection of drug resistant malaria in populations, little is known about in- host evolution. Most individuals infected with falciparum malaria carry multiple genetically distinct variants ("genotypes", "strains") which continually evolve and compete for resources. This within-host competition could be as important as competition within populations. Many of the variants are present at low levels and undetectable by older genotyping technologies. In order to measure within-host competition, we propose to employ a new method uniquely capable of identifying and quantitating genotypes in a single host - Massively Parallel Pyrosequencing (MPP). With this technology, we will measure, within individual hosts, the true diversity of falciparum infections and the selective pressure of antimalarials. Specifically, we will: i) sequence and quantitate merozoite surface protein-2 (msp2) genotypes within individual subjects from two areas of different transmission intensity: Tanzania (high transmission) and Thailand (low intensity), ii) measure the rate of change in frequency (selection coefficients) for individual parasite variants from Tanzanian patients treated with Coartem and determine the effect of competing variants on frequency, and iii) measure up-selection for individual parasite variants from Thai patients treated with Artesunate-Mefloquine to define selection coefficients and better define the phenotype used to study drug resistance to artemisinins. This novel approach of quantitatively studying variant diversity within individuals will i) allow accurate measurement of within-host selection and dynamics of variants in mixed infections, ii) provide new tools for testing hypotheses about the genetic basis of low- and high-level resistance, and iii) define the factors that allow the development and spread drug resistant parasites in populations.
Malaria remains the most important vector borne parasitic infection in the world today, causing nearly a million deaths annually. This project focuses on understanding the factors involved in the evolution of drug resistance within individual hosts and improving the methods for early detection of drug resistant parasites. A better understanding of these evolutionary processes will augment resistance management strategies, assist malaria control efforts, and help alleviate malaria's public health burden in the developing world.
|Bowman, Natalie M; Juliano, Jonathan J; Snider, Cynthia J et al. (2016) Longevity of Genotype-Specific Immune Responses to Plasmodium falciparum Merozoite Surface Protein 1 in Kenyan Children from Regions of Different Malaria Transmission Intensity. Am J Trop Med Hyg 95:580-7|
|Parobek, Christian M; Lin, Jessica T; Saunders, David L et al. (2016) Selective sweep suggests transcriptional regulation may underlie Plasmodium vivax resilience to malaria control measures in Cambodia. Proc Natl Acad Sci U S A 113:E8096-E8105|
|Parr, Jonathan B; Belson, Connor; Patel, Jaymin C et al. (2016) Estimation of Plasmodium falciparum Transmission Intensity in Lilongwe, Malawi, by Microscopy, Rapid Diagnostic Testing, and Nucleic Acid Detection. Am J Trop Med Hyg 95:373-7|
|Spring, Michele D; Lin, Jessica T; Manning, Jessica E et al. (2015) Dihydroartemisinin-piperaquine failure associated with a triple mutant including kelch13 C580Y in Cambodia: an observational cohort study. Lancet Infect Dis 15:683-91|
|Juliano, Jonathan J; Barnett, Eric; Parobek, Christian M et al. (2015) Use of Oropharyngeal Washes to Diagnose and Genotype Pneumocystis jirovecii. Open Forum Infect Dis 2:ofv080|
|Lin, Jessica T; Hathaway, Nicholas J; Saunders, David L et al. (2015) Using Amplicon Deep Sequencing to Detect Genetic Signatures of Plasmodium vivax Relapse. J Infect Dis 212:999-1008|
|Taylor, Steve M; Parobek, Christian M; DeConti, Derrick K et al. (2015) Absence of putative artemisinin resistance mutations among Plasmodium falciparum in Sub-Saharan Africa: a molecular epidemiologic study. J Infect Dis 211:680-8|
|Pollitt, Laura C; Sim, Derek; SalathÃ©, Rahel et al. (2015) Understanding genetic variation in in vivo tolerance to artesunate: implications for treatment efficacy and resistance monitoring. Evol Appl 8:296-304|
|Parobek, Christian M; Jiang, Linda Y; Patel, Jaymin C et al. (2014) Multilocus microsatellite genotyping array for investigation of genetic epidemiology of Pneumocystis jirovecii. J Clin Microbiol 52:1391-9|
|Givens, Matthew B; Lin, Jessica T; Lon, Chanthap et al. (2014) Development of a capillary electrophoresis-based heteroduplex tracking assay to measure in-host genetic diversity of initial and recurrent Plasmodium vivax infections in Cambodia. J Clin Microbiol 52:298-301|
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