Cell fusion assay for clade C HIV-1ZM109 Env Measured in Cell-Based System Using Plate Reader - 7013-05_Inhibitor_Dose_CherryPick_Activity
This is a cell-cell fusion assay that mimics the process whereby HIV-1 enters cells. The assay employs HeLa effector cells, in which the clade C HIV-1 Env protein (HIV-1ZM109) expression is driven by a promoter responsive to a tetracycline-controlled transactivator (tTA) protein. HIV-1ZM109 is a different Env protein from clade C with 74% identity to HIV-1JRFL Env. The tTA protein is more ..
BioActive Compounds: 871
Keywords: HIV, viral entry, clade C, ZM109, luciferase
This is a cell-cell fusion assay that mimics the process whereby HIV-1 enters cells. The assay employs HeLa effector cells, in which the clade C HIV-1 Env protein (HIV-1ZM109) expression is driven by a promoter responsive to a tetracycline-controlled transactivator (tTA) protein. HIV-1ZM109 is a different Env protein from clade C with 74% identity to HIV-1JRFL Env. The tTA protein is constitutively expressed in the effector cells. The tTA protein is inactive in the presence of the tetracycline analogue Doxycycline (Dox) and activates HIV-1 Env expression in the absence of Dox. The CEM lymphoblast target cells express the HIV-1 receptors, CD4 and CCR5, and were stably transduced with a Firefly Luciferase (F-luc) gene under the control of the tTA-responsive promoter. During the co-cultivation of effector and target cells, HIV-1 Envs that are expressed on the effector cell surface bind receptor-bearing target cells and fuse the cell membranes. Cell-cell fusion allows tTA to diffuse from the effector cells to the target cells and activate F-luc expression. F-luc activity is proportionate to the number of cell-cell fusion events and measured with the SteadyGlo (Promega) reagent.
Expected Outcome: If a compound prevents cell-cell fusion mediated by the Env protein, a decrease in luciferase signal will be seen. A decrease in luciferase signal could also be caused by cytotoxic compounds or compounds that prevent cell fusion.
ZM109 Env Fusion Assay Protocol
1.Grow ZM109 effector cells in DMEM passage medium with Doxycycline. Split 1:3 or 1:4 for passing. For HTS: 4 days prior to plating, thaw 3 vials (1.0 x 10;7 cells/ vial) into 4 triple flasks with 120 mL DMEM passage medium/flask. After 3 days, transfer to 3 Hyperflasks (HF) with ~550 mL RPMI induction media (~33 million cells per HF)
2.Day 0: Pass ZM109 cells to DoxFree media. Wash cells 2x with PBS & add 15 ml Accutase per triple to detach cells. Stop Accutase by adding RPMI induction media. Spin down cells & seed 9-10 x10;6 cells in 120 ml of RPMI induction medium in triple flask.
3.Day 1: Plating of CTL cells. Wash cells with PBS & add 15 ml Accutase for triple or 50 ml for HF to detach cells (@ 37 degrees C). Stop by adding RPMI induction medium. Spin down the cells at 1200 rpm for 5 min & re-suspend in phenol red-free RPMI induction medium (with Puromycin).
4.Count cells, adjust to 1.25 x10;5 cells/mL & seed 2,500 cells per well in 20 microl of RPMI (no Phenol Red) induction medium in Aurora white, opaque 384 well plates.
5.Day 2: Pinning & adding CEM21 cells Spin down & count CEM21 cells. Adjust to 5.0x105 cells/ml in RPMI fusion medium. Dispense 5,000 cells at 10 microl/well in RPMI induction media. Pin transfer compounds to the plate. Positive control is Maraviroc to a final concentration of 300 nM. Incubate the plate 37 degrees C overnight.
6.Day 3: SteadyGlo & Read. Add 10 microl of room temperature Steady-Glo substrate. Shake plate with Big Bear plate shaker. Incubate at room temperature for 10 minutes & read luminescence on a Perkin-Elmer EnVIsion with ultrasensitive luminescence settings for 0.5 seconds per well.
DMEM passage medium (1 L):
DMEM 882 mL
Heat Inactivated-FBS 100 mL
Pen-Strep-L-Glu 10 mL
*Doxycycline (1 mg/mL)2 mL
Puromycin (10 mg/mL)100 microL
Geniticin (50 mg/mL)4 mL
RPMI induction medium (DoxFree) (1 L):
RPMI (-Phenol red)890 mL
10 % Tet approved HI-FBS 100 mL
Pen-Strep-L-Glu 10 mL
Puromycin (10 mg/mL)100 microL
.*Doxycycline is light sensitive, minimize light exposure
.All cells have to be in exponential growth phase. Hela-F-Luc cells are usually split 1:3 every 2-3 days, CEM#21 are split 1:10 every 3 days. Cells should not be allowed to overgrow in the flasks.
.CEM21 cells take 1-2 weeks after thawing to grow at an optimal rate
.Cells must be spun down after dissociation to remove StemPro Accutase from the medium.
.Cells can be allowed to fuse 16 to 24 hours.
.Effector (ZM109) cells should be propagated for no more than 30 passages or 3 months whichever is sooner.
PRESENCE OF CONTROLS: Neutral control wells (NC; n=36) and positive control wells (PC; n=36) were included on every plate.
EXPECTED OUTCOME: Active compounds result in decreasing readout signal.
The compounds were assayed in multiple independent instances using an identical protocol; each instance is called a 'test'. For each test, the following analysis was applied:
ACTIVE CONCENTRATION LIMIT:
For each sample, the highest valid tested concentration (Max_Concentration) was determined and the active concentration limit (AC_limit) was set to equal (2)(Max_Concentration).
The raw signals of the plate wells were normalized using the 'Neutral Controls Minus Inhibitors' method in Genedata Assay Analyzer (v10.0.2):
The median raw signal of the intraplate neutral control wells was set to a normalized activity value of 0.
The median raw signal of the intraplate positive control wells was set to a normalized activity value of -100.
Experimental wells values were scaled to this range.
PATTERN CORRECTION: No plate pattern correction algorithm from Genedata Condoseo (v.10.0.2) was applied.
MEASUREMENT USED TO DETERMINE ACTIVE CONCENTRATION (AC): AC50
AC values were calculated using the curve fitting strategies in Genedata Screener Condoseo (7.0.3).
AC values were calculated up to the active concentration limit described for each sample.
pAC was set to equal -1*log10(AC)
Activity_Outcome = 1 (inactive) when:
a) compound shows activity but in a direction opposite to the expected outcome
in these cases, values describing curve fitting parameters (Sinf, S0, Hill Slope, log_AC50, log_AC50_SE) are set to null
b) curve fit is constant where activity is > -30% and < 30% at all tested concentrations, or
c) AC > AC_limit
Activity_Outcome = 2 (active) when:
AC <= AC_limit
Activity_Outcome = 3 (inconclusive) when:
a) Curve fitting strategy resulted in a constant fit with activity >= -70% but <= -30%, or
b) The fit was deemed not valid due to poor fit quality.
If PUBCHEM_ACTIVITY_OUTCOME = 1 (inactive) or 3 (inconclusive),
then PUBCHEM_ACTIVITY_SCORE = 0
If PUBCHEM_ACTIVITY_OUTCOME = 2 (active)
then PUBCHEM_ACTIVITY_SCORE = (10)(pAC)
Scores relate to AC in this manner:
120 = 1 pM
90 = 1 nM
60 = 1 uM
30 = 1 mM
0 = 1 M
When the active concentration (AC) is calculated to be greater than the highest valid tested concentration (Max_Concentration), the PUBCHEM_ACTIVITY_SCORE is calculated using Max_Concentration as the basis.
When the active concentration (AC) is calculated to be less than the lowest tested concentration, the PUBCHEM_ACTIVITY_SCORE is calculated using the lowest tested concentration as the basis.
Once the data for each test was processed, the test number was appended to all column headers in that test's data set. The individual test results were then aggregated as follows:
1. The final PUBCHEM_ACTIVITY_OUTCOME was set to:
a. '2' (active) when all test outcomes were '2' (active), or
b. '1' (inactive) when all test outcomes were '1' (inactive), or
c. '3' (inconclusive) when the test outcomes were mixed.
2. The final ACTIVE_CONCENTRATION (AC) was set as follows:
a. If the final PUBCHEM_ACTIVITY_OUTCOME = 2, AC was set as the mean of the constituent test active concentrations;
b. If the final PUBCHEM_ACTIVITY_OUTCOME = 1 or 3, AC was left empty.
3. The final PUBCHEM_ACTIVITY_SCORE was calculated based on the aggregated ACTIVE_CONCENTRATION, using the same logic described above for individual test scores.
The individual dose data point columns ('Activity_at_xxuM') reported here represent the median of valid (unmasked) replicate observations at each concentration. These values are the inputs to a curve fitting algorithm.
All other data columns represent values which are derived during the curve fitting algorithm; this may sometimes include automatic further masking of some replicate data points.
Occasionally this results in perceived inconsistencies: for example, between the derived 'Maximal_Activity' and the apparent most active data point.
Categorized Comment - additional comments and annotations
Assay Format: Cell-based
Assay Cell Type: HeLa
Assay Format: Cell-based
Assay Type: Functional
* Activity Concentration. ** Test Concentration.
Data Table (Concise)