Our goal is to combat filarial diseases by screening for compounds that target Wolbachia, an intracellular bacterium that iso symbiotic with filarial nematodes. Filarial diseases include Elephantiasis and River Blindness, affecting over 140 million people in tropical areas. Current anti-filarial medications eliminate juvenile nematodes, but do not kill the long-lived (5-15 years) adult nematodes. The recent discovery that most parasitic nematodes require the bacterial symbiont Wolbachia for embryonic and larval development, as well as for adult survival, creates an entirely new avenue for antibiotic-based treatment of these diseases. In addition, many disease symptoms are a direct result of the patient's immune response against the Wolbachia that are re- leased from the nematodes. Therefore an antibiotic approach will have two advantages over current treatments: it will induce the death of the long-lived adult nematodes and eliminate the symptoms created by the destructive immune response upon release of Wolbachia from the nematodes. Presently available antibiotics require daily doses for 4 to 6 weeks, which is impractical for mass drug administration in the afflicted areas. Consequently, there is an urgent need to identify more potent anti-Wolbachia compounds that work in shorter treatment regimens with fewer contraindications. Our laboratory is uniquely situated to achieve this goal, because we have developed a high-throughput screening system using Drosophila cell lines. In addition, we are very experienced in analyzing and imaging Wolbachia-infected Drosophila (a natural Wolbachia host) and have developed an efficient whole-organism secondary screen for compounds that reduce Wolbachia titer. Finally, our lab has developed a set of techniques and reagents to examine Wolbachia population dynamics in Brugia malayi, a large filarial nematode that causes Elephantiasis. Our new whole-mount immunnofluorescent techniques allow us to directly assay the effects of promising new compounds on Wolbachia titer and morphology. For our high-throughput primary screen we have generated a Wolbachia-infected cell line from Drosophila that expresses fluorescing proteins to facilitate image-based screening.
In Aim 1, we will use these cell lines to per- form high-throughput screens for small-molecule Wolbachia inhibitors. Currently, we have the capacity to screen 30 384-well plates per week. In collaboration with the Genomics Institute of the Novartis Research Foundation, we will screen their 600,000-compound small-molecule library at their San Diego facility. In addition to novel compounds, we will also screen a newly established comprehensive collection of FDA-approved drugs to improve Doxycycline efficacy in targeting Wolbachia.
In Aim 2, we will use our efficient secondary screen in which we determine the effect of candidate compounds on Wolbachia titer in Drosophila oocytes. This screen is has been successfully used to identify the promising anti-Wolbachia compounds from our pilot screen {Serbus, 2012 #893}. This approach will test if candidate drugs from the first screen are active when administered orally, passing through the insect gut and crossing cell barriers. Compounds that significantly re- duce titer in these secondary and tertiary screens will then be tested in the whole animal filarial nematode (L. sigmodontis)/Mouse model system. Finally in Aim 3, compounds that reduce Wolbachia titer in the cell lines and Drosophila oocytes will be tested for their affects on Wolbachia titer in culturd B. malayi filarial nematodes using whole-mount immunofluorescence. Known anti-Wolbachia compounds will be used to perform a de- tailed cellular analysis to determine Wolbachia replication and turnover rates in developing and mature nematodes. With this information, we will define the effects of our most promising compounds on Wolbachia replication and turnover in B. malayi.

Public Health Relevance

Filarial diseases afflict around 140 million people with over 1.3 billion people at risk. Filarial nematodes depend on a bacterial symbiont, Wolbachia, which also contributes to disease symptoms (Elephantiasis and River Blindness). The goal of our high- throughput screen is to find compounds that eliminate Wolbachia and that can be developed into drugs that are amenable to mass-drug-administrations. Achieving this goal will significantly contribute to the elimination of these devastating diseases, a major goal of the World Health Organization and their Global Program to Eliminate Lymphatic Filariasis.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Special Emphasis Panel (ZRG1-BST-U (55))
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Fabian, Miles
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University of California Santa Cruz
Schools of Arts and Sciences
Santa Cruz
United States
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