Plasmodium falciparum is the causative agent responsible for the most severe form of human malaria, a disease that kills more than a million people a year, mostly young children in Africa. These protozoan parasites invade and ultimately destroy circulating red blood cells (RBCs) of their host, leading to severe anemia and the frequently lethal syndromes of cerebral malaria and pregnancy associated malaria. Over the course of an infection, small sub-populations of parasites arise that have an altered antigenic phenotype, thus avoiding the antibody response of the host. This process is referred to as antigenic variation and is responsible for the persistent nature of the disease as well as the waves of parasitemia frequently observed in P. falciparum infections. Antigenic variation of P. falciparum infected RBCs results from switches in expression between individual members of the multi-copy var gene family. Each var gene encodes a different form of a protein called PfEMP1. This protein is placed on the surface of the infected RBCs and mediates adhesion to specific receptors found on the endothelial surfaces of the blood vessel walls of the infected individual. This adhesion is responsible for many of the disease manifestations of infection with P. falciparum, including both cerebral malaria and pregnancy associated malaria. Only a single var gene is expressed at a time by any given parasite, thus determining both the antigenic phenotype of the infected cells as well as their adhesive properties. Therefore var gene expression is the heart of both antigenic variation and virulence of malaria infections. This project is designed to understand the molecular mechanisms the regulate var gene expression and antigenic variation by malaria parasites. Previous work has demonstrated that mutually exclusive expression of var genes involves specific modifications to the chromatin structure at each var gene, however how these modifications are coordinated to result in expression of only a single gene at a time out of a family of 60 remains unknown.
The specific aims of the project are 1) to identify and characterize chromatin boundary/insulator elements that regulate chromatin assembly at var genes, 2) to determine the role of noncoding RNAs in targeting chromatin assembly to var gene loci, and 3) to investigate the mechanism of translational regulation of a specific var gene implicated in pregnancy associated malaria. The experimental design relies on creating transgenic parasite lines using reporter genes and drug selectable markers to rapidly determine the role of these regulatory elements in controlling var gene expression. The long-term goals are to develop methods to disrupt the process of antigenic variation and thereby shorten the length of an infection and reduce its severity.

Public Health Relevance

Malaria remains one of the most important infectious disease killers in the world today, causing more than a million deaths annually, primarily of young children in sub-Saharan Africa. This project focuses on the ability of malaria parasites to avoid the human immune response and to cause severe disease. A better understanding of these processes will lead to new, novel forms of treatment that will help to relieve the enormous public health burden that malaria inflicts on the developing world.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI052390-12
Application #
8475534
Study Section
Pathogenic Eukaryotes Study Section (PTHE)
Program Officer
Joy, Deirdre A
Project Start
2002-06-01
Project End
2014-05-31
Budget Start
2013-06-01
Budget End
2014-05-31
Support Year
12
Fiscal Year
2013
Total Cost
$340,912
Indirect Cost
$133,620
Name
Weill Medical College of Cornell University
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
060217502
City
New York
State
NY
Country
United States
Zip Code
10065
Kirkman, Laura A; Lawrence, Elizabeth A; Deitsch, Kirk W (2014) Malaria parasites utilize both homologous recombination and alternative end joining pathways to maintain genome integrity. Nucleic Acids Res 42:370-9
Ukaegbu, Uchechi E; Kishore, Sandeep P; Kwiatkowski, Dacia L et al. (2014) Recruitment of PfSET2 by RNA polymerase II to variant antigen encoding loci contributes to antigenic variation in P. falciparum. PLoS Pathog 10:e1003854
Heinberg, Adina; Siu, Edwin; Stern, Chaya et al. (2013) Direct evidence for the adaptive role of copy number variation on antifolate susceptibility in Plasmodium falciparum. Mol Microbiol 88:702-12
Kishore, Sandeep P; Stiller, John W; Deitsch, Kirk W (2013) Horizontal gene transfer of epigenetic machinery and evolution of parasitism in the malaria parasite Plasmodium falciparum and other apicomplexans. BMC Evol Biol 13:37
Bancells, Cristina; Deitsch, Kirk W (2013) A molecular switch in the efficiency of translation reinitiation controls expression of var2csa, a gene implicated in pregnancy-associated malaria. Mol Microbiol 90:472-88
Kirkman, Laura A; Deitsch, Kirk W (2012) Antigenic variation and the generation of diversity in malaria parasites. Curr Opin Microbiol 15:456-62
Swamy, Lakshmi; Amulic, Borko; Deitsch, Kirk W (2011) Plasmodium falciparum var gene silencing is determined by cis DNA elements that form stable and heritable interactions. Eukaryot Cell 10:530-9
Allred, David R; Barbet, Anthony F; Barry, J David et al. (2009) varDB: common ground for a shifting landscape. Trends Parasitol 25:249-52
Deitsch, Kirk W; Lukehart, Sheila A; Stringer, James R (2009) Common strategies for antigenic variation by bacterial, fungal and protozoan pathogens. Nat Rev Microbiol 7:493-503
Kishore, Sandeep P; Perkins, Susan L; Templeton, Thomas J et al. (2009) An unusual recent expansion of the C-terminal domain of RNA polymerase II in primate malaria parasites features a motif otherwise found only in mammalian polymerases. J Mol Evol 68:706-14

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