UVM Theses and Dissertations
Format:
Print
Author:
Bessoff, Kovi
Dept./Program:
Microbiology and Molecular Genetics
Year:
2013
Degree:
PhD
Abstract:
Cryptosporidiosis is a diarrheal disease that occurs when apicomplexan parasites of the genus Cryptosporidium infect intestinal epithelial cells. In humans, C. parvum and C. hominis account for the majority ofdisease which is typically self-limited in immunocompetent adults, but can result in chronic, fulminant, and sometimes lethal infections in immunocompromised patients. Additionally, susceptibility to and the sequelae of cryptosporidiosis are compounded by malnutrition in children who often develop chronic infections and suffer from stunting. Cryptosporidiosis is a major cause of diarrhea in both the developed and developing world, but concurrent factors including poor sanitation, malnutrition, and the high prevalence of AIDS combined with limited access to highly active antiretroviral therapy (HAAR) places the majority of the disease burden on the developing world.
Despite its prominence as a pressing global health issue, there is no fully effective treatment available for cryptosporidiosis. Nitazoxanide is the current standard of care, but the drug is only partially effective in immunocompetent adults and children, and is no more efficacious than placebo for treating cryptosporidiosis in AIDS patients. Drug development efforts for cryptosporidiosis have been hampered by two major obstacles. The imposing costs of de novo drug development have dissuaded many pharmaceutical firms from undertaking resource intensive drug discovery campaigns, and the inability to propagate and genetically manipulate Cryptosporidium parasites in vitro prevents the application of fundamental drug discovery techniques to this parasite.
In an effort to address both of these issues, we developed a cell-based high throughput screening assay and used it to screen a library of approved drugs. The repurposing of existing drugs permits the leveraging of existing safety data facilitate the rapid and efficient transition of a compound into phase II human clinical trials. Additionally, many of these drugs are well-characterized with respect to their mechanisms of action, providing insights into how they potentially affect the parasite and/or host cell. Our experiences illustrate the potential of cell-based screening of repurposing candidates to identify biological probes that can be useful in elucidating new biology in this difficult to study parasite.
We also screened a collection of small molecules with known activity against Plasmodium falciparum (an etiological agent of malaria), facilitating the application of the vast experience of the malaria drug development field to the study of Cryptosporidium parasites. In addition to identifying novel chemical scaffolds to fuel the development of therapies, the screen identified a panel of potent compounds with varying physiochemical characteristics that will be useful in further understanding the importance of these parameters on the efficacy of a drug to treat cryptosporidiosis. Additional in vitro studies combined with existing knowledge of these molecules facilitated the generation of hypotheses regarding their potential mechanism of action, as well as informed prioritization for future work including in vivo testing in aninlals and ultimately phase II clinical trials in humans.
Despite its prominence as a pressing global health issue, there is no fully effective treatment available for cryptosporidiosis. Nitazoxanide is the current standard of care, but the drug is only partially effective in immunocompetent adults and children, and is no more efficacious than placebo for treating cryptosporidiosis in AIDS patients. Drug development efforts for cryptosporidiosis have been hampered by two major obstacles. The imposing costs of de novo drug development have dissuaded many pharmaceutical firms from undertaking resource intensive drug discovery campaigns, and the inability to propagate and genetically manipulate Cryptosporidium parasites in vitro prevents the application of fundamental drug discovery techniques to this parasite.
In an effort to address both of these issues, we developed a cell-based high throughput screening assay and used it to screen a library of approved drugs. The repurposing of existing drugs permits the leveraging of existing safety data facilitate the rapid and efficient transition of a compound into phase II human clinical trials. Additionally, many of these drugs are well-characterized with respect to their mechanisms of action, providing insights into how they potentially affect the parasite and/or host cell. Our experiences illustrate the potential of cell-based screening of repurposing candidates to identify biological probes that can be useful in elucidating new biology in this difficult to study parasite.
We also screened a collection of small molecules with known activity against Plasmodium falciparum (an etiological agent of malaria), facilitating the application of the vast experience of the malaria drug development field to the study of Cryptosporidium parasites. In addition to identifying novel chemical scaffolds to fuel the development of therapies, the screen identified a panel of potent compounds with varying physiochemical characteristics that will be useful in further understanding the importance of these parameters on the efficacy of a drug to treat cryptosporidiosis. Additional in vitro studies combined with existing knowledge of these molecules facilitated the generation of hypotheses regarding their potential mechanism of action, as well as informed prioritization for future work including in vivo testing in aninlals and ultimately phase II clinical trials in humans.