Adult female and male
Brugia (
B. malayi and
B. pahangi) were shipped from TRS Labs Inc., Athens, GA and assayed using methods described by Marcellino
et al. (2012) [12 (
link)]. Individual females were placed in each well of a 24-well plate with media (RPMI-1640 with 25 mM HEPES, 2.0 g/L NaHCO
3, 5% heat inactivated FBS, and 1X Antibiotic/Antimycotic solution). Excess media was removed from plates using a Biomek FxP, leaving 500 μL of media per well. Initial screening of a library of FDA-approved compounds, compiled by the Small Molecule Discovery Center at the University of California San Francisco, was conducted at 10 μM per compound, and 1% DMSO was used as a negative control. All drugs including auranofin (Enzo Life Sciences, Farmingdale, NY) were dissolved in DMSO (Sigma-Aldrich, St. Louis, MO) and 10 mM stock solutions were stored at -20°C. Four worms were used as replicates for each concentration and worm plates were kept in a 37°C, 5% CO
2 incubator for four days. Auranofin was also tested against male
Brugia worms under the same conditions after initial screening against female
Brugia revealed its high level of inhibitory activity.
To determine the effect of a compound on worm motility, individual worm movements were counted as the number of pixels displaced per second by each worm in each well using the Worminator. Each plate of worms was video recorded for approximately 60 seconds, and mean movement units (MMUs) were determined for individual worms. Percent inhibition of motility was calculated by dividing the MMUs of the treated worms by the control average MMUs, subtracting the value from 1.0, flooring the values to zero and multiplying by 100%. Videos were recorded for 4 days, including the first day of the assay (Day 0). IC
50 determinations were conducted at 10 μM, 3 μM, 1 μM, 0.3 μM, 0.1 μM and 0.03 μM, with 1% DMSO used as a control. IC
50 assays were repeated at the same concentrations and at six point, three-fold dilutions from 1 μM to 0.003 μM or 3 μM to 0.001 μM to ensure that activity was consistent between assays. Prism 4.0 was used to calculate IC
50 values using a non-linear regression curve fit. The means of all IC
50s with R
2 values greater than or equal to 0.7 are reported.
Bulman C.A., Bidlow C.M., Lustigman S., Cho-Ngwa F., Williams D., Rascón, Jr A.A., Tricoche N., Samje M., Bell A., Suzuki B., Lim K.C., Supakorndej N., Supakorndej P., Wolfe A.R., Knudsen G.M., Chen S., Wilson C., Ang K.H., Arkin M., Gut J., Franklin C., Marcellino C., McKerrow J.H., Debnath A, & Sakanari J.A. (2015). Repurposing Auranofin as a Lead Candidate for Treatment of Lymphatic Filariasis and Onchocerciasis. PLoS Neglected Tropical Diseases, 9(2), e0003534.