Southern Research's Specialized Biocontainment Screening Center (SRSBSC)
Southern Research Institute (Birmingham, Alabama)
NIH Molecular Libraries Probe Production Centers Network (MLPCN)
Assay Provider: Dong Hoon Chung, University of Louisville
Award: 1 R03 MH087448-01A1

This functional assay was developed for detection of compounds inhibiting Vero 76 cells viability as a secondary screen to the VEEV Inhibition screen.

In this assay, we treated Vero 76 cells with compounds selected as hits in the VEEV Inhibition assay for 72 hours over a 10 point 2-fold dilution series, ranging from 25 uM to 0.05 uM. Following 72 hours of treatment, relative viable cell number was determined using Cell Titer Glo from Promega. Each plate contained 64 replicates of vehicle treated cells which served as negative controls.

Cell Culture: Vero 76 cells obtained from ATCC (CRL-1587) were cultured and maintained in MEM-E (Invitrogen, 10370-088) with 10% Hi-FBS (Invitrogen 16000), 1% Penicillin/Streptomycin/L-glutamine (Invitrogen 10378-024) and 1% HEPES (Invitrogen 15630-080). The cells are maintained at 37C, 5.0% CO2 to 100% confluence being passaged 1:4 every 3-4 days. For cell plating, cells were detached from flask bottom by using Trypsin-EDTA solution and then re-suspended in a growth media. Cells were passaged no more than ten times after being thawed.

Compound Dosing/Plating: Carrier control / compounds were diluted in complete growth medium to prepare a 6X concentrated dosing solution which was dispensed into 384-well black clear-bottom tissue culture treated plates (5 uL volume).

Cell Plating: Twenty-five uL of complete growth medium containing 3000 cells were dispensed per well. Plates were incubated at 37 C, 5% CO2 for 72h prior to endpoint detection.

Endpoint/Detection: At the end of the treatment period, assay plates were removed from the incubator and equilibrated to room temperature for 10 min. Thirty uL of Cell Titer Glo reagent was added and plates were incubated for an additional 10 min in the dark. At the end of the incubation, assay plates were analyzed using a PerkinElmer Envision microplate reader in luminescence mode with an integration time of 0.1 s.

Data Analysis: Sixty-four control wells containing cells treated with DMSO vehicle and were included on each assay plate. Compound data was normalized and reported as % viability which was calculated using the following formula: % viability = 100*(Cmpd Lum-Med background)/(Med Cell Ctrl - Med background). The normalized % viability was plotted against the tested concentrations. The CC50 values were calculated using XLfit formula 205, a 4 parameter Levenburg-Marquardt algorithm with maximum and minimum limits set at 100 and 0, respectively and allowing extrapolation to identify weakly active compounds.

Outcome: Compounds that showed <70% cell viability for at least one concentration were defined as "Active" (toxic). If the % viability at all doses was >70%, the compound was defined as "Inactive" (non-toxic).

The following tiered system has been implemented at Southern Research Institute for use with the PubChem Score: Compounds in the primary screen are scored on a scale of 0-40 based on % activity; a score of 40 corresponds to 100% activity. In the confirmatory dose response screen of primary screen hits, active compounds are scored on a scale of 41-80 based on IC50 result while compounds where activity was not confirmed are given the score 0. Confirmatory dose response and secondary screens of purified and/or resynthesized compounds, indicating the highest degree of confidence) are scored on a scale of 81-100 based on IC50 result. Inactive compounds are given the score 0.

Phenotypic Screen: Yes

Multiplexing: Yes

BSL: BSL2

Screening Concentration
Screening Concentration Range Max: 25

Screening Concentration Range Min: 0.049

Assay Format: Cell-based

Assay Type: Viability/Toxicity

Assay Method: End-point

Assay Detection: Bio-luminescence

Used for Hit Validation?: Yes

Used during SAR?: Yes

Secondary Assay Sub-type: Counter-screen Assay

Grant Number: 1 R03 MH087448-01A1