Graduation Year

2015

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Public Health

Major Professor

Thomas R. Unnasch, Ph.D.

Committee Member

Dennis Kyle, Ph.D.

Committee Member

Bill Baker, Ph.D.

Committee Member

Rays Jiang, Ph.D.

Keywords

drug discovery, homology modeling, lymphatic filariasis, proteomics, RNA-seq, transcriptomics

Abstract

Filariasis and onchocerciasis are debilitating diseases affecting 120 million people globally. The massive socio-economic impact of these diseases energized the international community to declare a goal of eliminating filariasis 2020. This resulted in a dramatic increase in the efforts to eliminate filariasis and onchocerciasis, employing a strategy of mass drug administration (MDA). However, these programs rely upon the small arsenal of drugs. This leaves these programs vulnerable to failure in the face of developing resistance and local intolerance to the current drug regimens. Thus, new drugs against these infections are critically needed. A homologue of the ecdysone receptor (EcR), a master regulator of development in insects, has been identified in B. malayi. The potential of the EcR as a drug target has been underscored by work in the agricultural industry, where insecticides targeting the ecdysone developmental pathway are effective and non-toxic to non-target species. As the EcR is absent in humans, it represents an attractive potential chemotherapeutic target. The first study investigates the hypothesis that the ecdysone receptor controls the embryogenesis and molting in the filarial parasite. In-vitro embryogram and in-vivo phenotypic studies were conducted to delineate the effect of 20-hydroxyecdysone on the Brugia malayi parasites. The results suggest that the hormone accelerates embryogenesis and causes precocious molts, resulting in the death of the parasite. Further, transcriptomic and proteomic analysis of the ecdysone treated worms provided evidence that the up-regulated genes participate in embryogenesis. Based upon the validation of the ecdysone receptor as a potential drug target, subsequent studies focused on the development of a drug discovery model to screen for agonists and antagonists of the B. malayi ecdysone receptor. A stable cell line was created to aid the high throughput screening to rapidly identity agonist and antagonist compounds. A total of 7 agonists and 2 antagonists were identified. A homology model of the BmEcR ligand-binding domain was created as an alternate method for virtual screening of small molecules as well as to study the ligand-receptor interactions. The hits identified with the assay were docked in the active site of the BmEcR homology model providing an excellent correspondence of data between the molecular assay and the virtual screening method.

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