: More than one billion people in developing countries are currently infected with blood feeding hookworms, intestinal nematodes that represent a leading cause of iron deficiency anemia in the world. The pathogenesis of hookworm anemia is a direct result of hemorrhage caused by the adult worm as it attaches to the intestinal mucosa. While it has been appreciated for nearly a century that adult hookworms produce potent inhibitors of thrombosis, only recently have the molecular mechanisms underlying the parasite blood feeding process been elucidated. Potent inhibitors of coagulation and platelet function have been identified in soluble protein extracts and secretory products of the human hookworm parasite Ancylostoma ceylanicum. The anticoagulant has been cloned from adult A. ceylanicum RNA, and the recombinant protein inhibits the activity of coagulation factor Xa by a novel mechanism. The platelet inhibitor blocks the function of two important platelet integrins, glycoprotein Jib/lila (GPIIb/IIIa) and GPIa/Iia, which mediate platelet binding to fibrinogen and collagen, respectively. We hypothesize that these anti-thrombotics play a central role in the pathogenesis of hookworm anemia by facilitating blood feeding and exacerbating gastrointestinal hemorrhage. The mechanism of action of the hookworm factor Xa inhibitor will be characterized using in vitro studies of factor Xa binding, protease mediated inhibitor cleavage, and site directed mutagenesis. The platelet inhibitor will be purified and cloned from A. ceylanicum, and its mechanism of action will be characterized using in vitro assays of GPIa/Iia and GPIJb/iIIa integrin binding. Using a reproducible animal model of A.ceylanicum infection, the role of the anticoagulant and platelet inhibitor in the pathogenesis of hookworm anemia will be characterized using a vaccine-based approach. Animals will be immunized with each recombinant inhibitor, followed by challenge with 50 infectious L3 hookworm larvae. The responses to immunization will be monitored by ELISA, and the degree to which antibodies directed at the anti-thrombotics from A. ceylanicum protect against hookworm anemia and weight loss will be assessed using clinical parameters and worm burden measurements. These studies will ultimately determine the role of blood feeding in the pathogenesis of hookworm disease, as well as identify potential targets for a human vaccine against this globally important parasite.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI047929-02
Application #
6623992
Study Section
Tropical Medicine and Parasitology Study Section (TMP)
Program Officer
Wali, Tonu M
Project Start
2002-04-01
Project End
2006-03-31
Budget Start
2003-04-01
Budget End
2004-03-31
Support Year
2
Fiscal Year
2003
Total Cost
$367,875
Indirect Cost
Name
Yale University
Department
Pediatrics
Type
Schools of Medicine
DUNS #
043207562
City
New Haven
State
CT
Country
United States
Zip Code
06520
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Brown, Allison C; Harrison, Lisa M; Kapulkin, Wadim et al. (2007) Molecular cloning and characterization of a C-type lectin from Ancylostoma ceylanicum: evidence for a role in hookworm reproductive physiology. Mol Biochem Parasitol 151:141-7
Bungiro Jr, Richard D; Cappello, Michael (2005) Detection of excretory/secretory coproantigens in experimental hookworm infection. Am J Trop Med Hyg 73:915-20
Bungiro Jr, Richard D; Solis, Carolina V; Harrison, Lisa M et al. (2004) Purification and molecular cloning of and immunization with Ancylostoma ceylanicum excretory-secretory protein 2, an immunoreactive protein produced by adult hookworms. Infect Immun 72:2203-13
Bungiro, Richard; Cappello, Michael (2004) Hookworm infection: new developments and prospects for control. Curr Opin Infect Dis 17:421-6
Bungiro Jr, Richard D; Anderson, Brett R; Cappello, Michael (2003) Oral transfer of adult Ancylostoma ceylanicum hookworms into permissive and nonpermissive host species. Infect Immun 71:1880-6