E. histolytica is a cytopathic enteric protozoan that infects nearly 10% of the world's population. Invasion of the colonic epithelium manifests as colitis or liver abscess resulting in an estimated 40-110 thousand deaths annually. Currently no protective vaccine is available. Adherence to the colonic mucosa is an important first step in the pathogenesis of colitis. The 170 kDa subunit of the galactose lectin which mediates adherence to colonic mucins in vitro, has been cloned and appears to be encoded by a gene family. The goals of this proposal are; to determine the copy number and linkage of the members of the 170 kDa gene family, to identify the adherence-inhibitory and enhancing domains of the 170 kDa subunit, and to evaluate the immunoprotective potential of recombinant 170 kDa subunit in an animal model of amebiasis. The molecular organization and copy number of the genes encoding the 170 kDa subunit will first be characterized in order to understand the complexity of the lectin gene family. To identify adherence domains, DNA clones encoding specific portions of the 170 kDa will be expressed individually in E. coli, purified, and used to raise antibody. The region-specific antisera will be tested for the ability to block or enhance amebic adherence to target cells and thus identify the regions of the protein involved in this activity. The amebic liver abscess model developed in the gerbil will be used to evaluate the immunoprotective potential of recombinant 170 kDa subunit. Gerbils will be immunized with the complete subunit or portions thereof. The anti-170 kDa antibody titer and antigen-specific response of immune T cells will be measured. The gerbils will then be challenged intrahepatically with amebic trophozoites and protection against challenge will be analyzed by inspecting the liver for abscesses. The characterization of the 170 kDa subunit of the galactose lectin will be important for understanding the adherence mechanisms of E. histolytica and will assist in the design of protective vaccine against amebiasis which could eventually lead to the prevention of disease and would reduce the global suffering caused by this parasite.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI032615-04
Application #
2003785
Study Section
Tropical Medicine and Parasitology Study Section (TMP)
Project Start
1993-12-01
Project End
1997-11-30
Budget Start
1996-12-01
Budget End
1997-11-30
Support Year
4
Fiscal Year
1997
Total Cost
Indirect Cost
Name
University of Virginia
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
001910777
City
Charlottesville
State
VA
Country
United States
Zip Code
22904
Okada, Mami; Huston, Christopher D; Oue, Miho et al. (2006) Kinetics and strain variation of phagosome proteins of Entamoeba histolytica by proteomic analysis. Mol Biochem Parasitol 145:171-83
McCoy, James J; Mann, Barbara J (2005) Proteomic analysis of Gal/GalNAc lectin-associated proteins in Entamoeba histolytica. Exp Parasitol 110:220-5
Okada, Mami; Huston, Christopher D; Mann, Barbara J et al. (2005) Proteomic analysis of phagocytosis in the enteric protozoan parasite Entamoeba histolytica. Eukaryot Cell 4:827-31
Hughes, Molly A; Lee, Constance W; Holm, Christopher F et al. (2003) Identification of Entamoeba histolytica thiol-specific antioxidant as a GalNAc lectin-associated protein. Mol Biochem Parasitol 127:113-20
Teixeira, Jose E; Mann, Barbara J (2002) Entamoeba histolytica-induced dephosphorylation in host cells. Infect Immun 70:1816-23
Petri Jr, William A; Haque, Rashidul; Mann, Barbara J (2002) The bittersweet interface of parasite and host: lectin-carbohydrate interactions during human invasion by the parasite Entamoeba histolytica. Annu Rev Microbiol 56:39-64
Godbold, Gene D; Corbett, Kevin D; Mann, Barbara J (2002) A Rho-like small GTPase of Entamoeba histolytica contains an unusual amino acid residue in a conserved GDP-stabilization region and is not a substrate for C3 exoenzyme. Exp Parasitol 101:107-10
Cheng, X J; Hughes, M A; Huston, C D et al. (2001) Intermediate subunit of the Gal/GalNAc lectin of Entamoeba histolytica is a member of a gene family containing multiple CXXC sequence motifs. Infect Immun 69:5892-8
Godbold, G D; Mann, B J (2000) Cell killing by the human parasite Entamoeba histolytica is inhibited by the rho-inactivating C3 exoenzyme. Mol Biochem Parasitol 108:147-51
Hughes, M A; Reed, S L; Mann, B J (2000) Role of the Entamoeba histolytica Gal/GalNAc lectin in recruiting proteins to the host:parasite interface. Arch Med Res 31:S229-30

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