This work was supported by BC Lung Association and Mitacs.

1. Bacterial Strain and Growth Medium
<ol>
	<li>Make albumin dextrose and salt stock solution (ADS) by solubilizing 25 g of bovine serum albumin, 10.0 g of dextrose, and 4.05 g of sodium chloride in 460 mL of deionized water. Filter-sterilize the ADS and store at 4 &#176;C.</li>
	<li>Make 7H9 broth by adding 4.7 g of 7H9 powder and 2 mL of glycerol to 900 mL of purified water. Autoclave the 7H9 broth at 121 &#176;C for 10 min and allow it to cool to room temperature before proceeding. Make 7H9ADST by adding 100 mL of A...

<ol>
	<li>WHO. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Global tuberculosis report 2015. , (2016).</li><li>Yajko, D. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Colorimetric+method+for+determining+MICs+of+antimicrobial+agents+for+Mycobacterium+tuberculosis.">Colorimetric method for determining MICs of antimicrobial agents for Mycobacterium tuberculosis.</a> J Clin Microbiol. 33, 2324-2327 (1995).</li><li>Khare, G., Kumar, P., Tyagi, A. 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A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+high-throughput+screen+to+identify+inhibitors+of+ATP+homeostasis+in+non-replicating+Mycobacterium+tuberculosis.">A high-throughput screen to identify inhibitors of ATP homeostasis in non-replicating Mycobacterium tuberculosis.</a> ACS Chem Biol. 7, 1190-1197 (2012).</li><li>Pethe, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+chemical+genetic+screen+in+Mycobacterium+tuberculosis+identifies+carbon-source-dependent+growth+inhibitors+devoid+of+in+vivo+efficacy.">A chemical genetic screen in Mycobacterium tuberculosis identifies carbon-source-dependent growth inhibitors devoid of in vivo efficacy.</a> Nat Commun. 1, 57 (2010).</li><li>Hmama, Z., Pena-Diaz, S., Joseph, S., Av-Gay, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immunoevasion+and+immunosuppression+of+the+macrophage+by+Mycobacterium+tuberculosis.">Immunoevasion and immunosuppression of the macrophage by Mycobacterium tuberculosis.</a> Immunol Rev. 264, 220-232 (2015).</li><li>Ramon-Garcia, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synergistic+drug+combinations+for+tuberculosis+therapy+identified+by+a+novel+high-throughput+screen.">Synergistic drug combinations for tuberculosis therapy identified by a novel high-throughput screen.</a> Antimicrob Agents Chemother. 55, 3861-3869 (2011).</li><li>Lam, K. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nitazoxanide+stimulates+autophagy+and+inhibits+mTORC1+signaling+and+intracellular+proliferation+of+Mycobacterium+tuberculosis.">Nitazoxanide stimulates autophagy and inhibits mTORC1 signaling and intracellular proliferation of Mycobacterium tuberculosis.</a> PLoS Pathog. 8, e1002691 (2012).</li><li>Sorrentino, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+an+Intracellular+Screen+for+New+Compounds+Able+To+Inhibit+Mycobacterium+tuberculosis+Growth+in+Human+Macrophages.">Development of an Intracellular Screen for New Compounds Able To Inhibit Mycobacterium tuberculosis Growth in Human Macrophages.</a> Antimicrob Agents Chemother. 60, 640-645 (2015).</li><li>Sun, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+broad-range+of+recombination+cloning+vectors+in+mycobacteria.">A broad-range of recombination cloning vectors in mycobacteria.</a> Plasmid. 62, 158-165 (2009).</li><li>. THP-1 (ATCC TIB-202) Available from: <a target="_blank" href="https://www.atcc.org/products/all/TIB-202.aspx">https://www.atcc.org/products/all/TIB-202.aspx</a> (2016)</li><li>Hansen, M. B., Nielsen, S. E., Berg, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Re-examination+and+further+development+of+a+precise+and+rapid+dye+method+for+measuring+cell+growth/cell+kill.">Re-examination and further development of a precise and rapid dye method for measuring cell growth/cell kill.</a> J Immunol Methods. 119, 203-210 (1989).</li><li>Invitrogen. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> AlamarBlue assay. , (2008).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Handbook+of+anti-tuberculosis+agents.+Introduction.">Handbook of anti-tuberculosis agents. Introduction.</a> Tuberculosis (Edinb). 88 (2), 85-86 (2008).</li><li>Riss, T. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Cell Viability Assays. , (2004).</li><li>Meyer, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+efficacy+of+apramycin+in+murine+infection+models.">In vivo efficacy of apramycin in murine infection models.</a> Antimicrob Agents Chemother. 58, 6938-6941 (2014).</li><li>Ballell, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fueling+open-source+drug+discovery:+177+small-molecule+leads+against+tuberculosis.">Fueling open-source drug discovery: 177 small-molecule leads against tuberculosis.</a> ChemMedChem. 8, 313-321 (2013).</li><li>Grundner, C., Cox, J. S., Alber, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protein+tyrosine+phosphatase+PtpA+is+not+required+for+Mycobacterium+tuberculosis+growth+in+mice.">Protein tyrosine phosphatase PtpA is not required for Mycobacterium tuberculosis growth in mice.</a> FEMS Microbiol Lett. 287, 181-184 (2008).</li><li>Wong, D., Bach, H., Sun, J., Hmama, Z., Av-Gay, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mycobacterium+tuberculosis+protein+tyrosine+phosphatase+(PtpA)+excludes+host+vacuolar-H+-ATPase+to+inhibit+phagosome+acidification.">Mycobacterium tuberculosis protein tyrosine phosphatase (PtpA) excludes host vacuolar-H+-ATPase to inhibit phagosome acidification.</a> Proc Natl Acad Sci U S A. 108, 19371-19376 (2011).</li><li>Bach, H., Papavinasasundaram, K. G., Wong, D., Hmama, Z., Av-Gay, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mycobacterium+tuberculosis+virulence+is+mediated+by+PtpA+dephosphorylation+of+human+vacuolar+protein+sorting+33B.">Mycobacterium tuberculosis virulence is mediated by PtpA dephosphorylation of human vacuolar protein sorting 33B.</a> Cell Host Microbe. 3, 316-322 (2008).</li><li>Chanput, W., Peters, V., Wichers, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The Impact of Food Bioactives on Health: in vitro and ex vivo models. , 147-159 (2015).</li><li>Maess, M. B., Wittig, B., Lorkowski, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Highly+efficient+transfection+of+human+THP-1+macrophages+by+nucleofection.">Highly efficient transfection of human THP-1 macrophages by nucleofection.</a> J Vis Exp. , e51960 (2014).</li><li>Ferguson, J. S., Weis, J. J., Martin, J. L., Schlesinger, L. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Complement+protein+C3+binding+to+Mycobacterium+tuberculosis+is+initiated+by+the+classical+pathway+in+human+bronchoalveolar+lavage+fluid.">Complement protein C3 binding to Mycobacterium tuberculosis is initiated by the classical pathway in human bronchoalveolar lavage fluid.</a> Infect Immun. 72, 2564-2573 (2004).</li><li>Andreu, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimisation+of+bioluminescent+reporters+for+use+with+mycobacteria.">Optimisation of bioluminescent reporters for use with mycobacteria.</a> PLoS One. 5, e10777 (2010).</li><li>Queval, C. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+microscopic+phenotypic+assay+for+the+quantification+of+intracellular+mycobacteria+adapted+for+high-throughput/high-content+screening.">A microscopic phenotypic assay for the quantification of intracellular mycobacteria adapted for high-throughput/high-content screening.</a> J Vis Exp. , e51114 (2014).</li><li>Christophe, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+content+screening+identifies+decaprenyl-phosphoribose+2'+epimerase+as+a+target+for+intracellular+antimycobacterial+inhibitors.">High content screening identifies decaprenyl-phosphoribose 2' epimerase as a target for intracellular antimycobacterial inhibitors.</a> PLoS Pathog. 5, e1000645 (2009).</li><li>Pethe, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Discovery+of+Q203,+a+potent+clinical+candidate+for+the+treatment+of+tuberculosis.">Discovery of Q203, a potent clinical candidate for the treatment of tuberculosis.</a> Nat Med. 19, 1157-1160 (2013).</li></ol>

The goal of this study was to create a simple and cost-effective HTS method using a human intracellular infection model for M. tuberculosis. Tuberculosis is a human disease characterized by the infection of alveolar macrophages by M. tuberculosis. Due to biosafety issues, research involving biological models of both the bacterium and the host cells has been used in the past. However, it has been shown that the usage of surrogate bacteria and non-human models are poor predictors of hit-to-lead success in...

Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), is a leading cause of morbidity and mortality worldwide. Drug-sensitive TB is a treatable disease that requires multiple antibiotics for a period of 6 months. Despite being a treatable disease, TB mortality was estimated to be 1.5 million in 20151. In the past 10 years, there have been increasing concerns over the prevalence of drug-resistant M. tuberculosis. Multidrug-resistant TB (MDR-TB) is defined as TB that is resistant to at least Isoniazid (INH) and Rifampicin (RMP), and most MDR-TB strains are also resistant to select second-line TB drugs, thus limiting treatment options. The effects of drug resistance create a greater challenge for treating patients co-infected with Human Immunodeficiency Virus (HIV); 400,000 patients worldwide died of HIV-associated TB in 20151. Disappointingly, the United States Food and Drug Administration has approved only one new TB drug against MDR-TB, bedaquiline, in the past 40 years2. Advances in finding better and shorter TB therapies are urgently needed in order to stay ahead in the fight against TB and MDR-TB.
Traditionally, TB drug screens are performed under in vitro growth conditions in growth medium, whereby compounds are added to a growing culture and their effectiveness in eradicating the microorganisms are determined by counting colony forming units (CFU) on solid medium. As CFU counts are labor intensive, time consuming, and costly, various indirect methods have been developed to alleviate this problem. Such methods include the Alamar Blue viability assay3, the determination of fluorescence4 from green fluorescent protein (GFP) or luminescence5 from luciferase-expressing bacteria, and the estimation of total adenosine triphosphate (ATP)6,7.
Typical TB is characterized by an M. tuberculosis infection of the lung, where the bacteria reside and replicate inside the phagosomes of alveolar macrophages8. The simple in-broth phenotypic screen may suit extracellular pathogens; however, in the historical perspective, hit compounds against M. tuberculosis identified using this method often fail to live up to expectations during downstream validation steps in infection models. We propose that TB drug is best performed in an intracellular host cell infection model. Nevertheless, intracellular models possess many technological and biological barriers to high-throughput screening (HTS) development. A big hurdle is the complexity of the infection process, exemplified by numerous steps and the elaborate removal of extracellular bacteria by in-between washing. A second major hurdle is the lengthy time requirements, as growth detection, normally done by CFU counting on culture plates, is a process that takes over 3 weeks to complete. One solution to replace CFU counts has been provided by automated fluorescent microscopy in combination with fluorescent bacteria. However, this solution requires an initial equipment investment that is out of reach for many research labs. A simple, low-cost, and disease-relevant HTS method would greatly enhance the drug discovery process.
In this study, we report a new, modular HTS system that is aimed at providing a rapid, and highly scalable, yet economical, assay suitable for determining the activity of compounds against intracellular M. tuberculosis. This system is composed of three modules: (i) intracellular, (ii) cytotoxicity, and (iii) in-broth assays. The combined final result provides a comprehensive description of the compound properties, with additional information as to the potential mode of action. This screening system has been used in several projects with various compound libraries that target mode of action, including the analysis of drug synergy9, the stimulation of autophagy10, and the inhibition of M. tuberculosis-secreted virulence factor (unpublished). Compounds of unknown mode of action have also been studied11. A modified version of this method was also adopted by our industrial partner as the primary screening method to identify new compounds against intracellular M. tuberculosis11.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>RPMI 1640</td>
			<td>Sigma-Aldrich</td>
			<td>R5886</td>
			<td></td>
		</tr>
		<tr>
			<td>L-glutamine</td>
			<td>Sigma-Aldrich</td>
			<td>G7513</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal bovine serum (FBS)</td>
			<td>Thermo Fisher Scientific</td>
			<td>12483020</td>
			<td></td>
		</tr>
		<tr>
			<td>Middlebrook 7H9</td>
			<td>Becton, Dickinson and Company</td>
			<td>271210</td>
			<td></td>
		</tr>
		<tr>
			<td>Tween80</td>
			<td>Fisher Scientific</td>
			<td>T164</td>
			<td></td>
		</tr>
		<tr>
			<td>Albumin, Bovine pH7</td>
			<td>Affymetrix</td>
			<td>10857</td>
			<td></td>
		</tr>
		<tr>
			<td>Dextrose</td>
			<td>Fisher Scientific</td>
			<td>BP350</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Chloride</td>
			<td>Fisher Scientific</td>
			<td>BP358</td>
			<td></td>
		</tr>
		<tr>
			<td>kanamycin sulfate</td>
			<td>Fisher Scientific</td>
			<td>BP906</td>
			<td></td>
		</tr>
		<tr>
			<td>PMA</td>
			<td>Sigma-Aldrich</td>
			<td>P8139</td>
			<td></td>
		</tr>
		<tr>
			<td>MTT</td>
			<td>Sigma-Aldrich</td>
			<td>M2128</td>
			<td></td>
		</tr>
		<tr>
			<td>N,N-Dimethylformamide (DMF)</td>
			<td>Fisher Scientific</td>
			<td>D131</td>
			<td></td>
		</tr>
		<tr>
			<td>1M Hydrocholoric acid (HCl)</td>
			<td>Fisher Scientific</td>
			<td>351279212</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetic acid</td>
			<td>Fisher Scientific</td>
			<td>351269</td>
			<td></td>
		</tr>
		<tr>
			<td>SDS</td>
			<td>Fisher Scientific</td>
			<td>BP166</td>
			<td></td>
		</tr>
		<tr>
			<td>Resazurin</td>
			<td>Alfa Aesar</td>
			<td>B21187</td>
			<td></td>
		</tr>
		<tr>
			<td>DMSO</td>
			<td>Sigma-Aldrich</td>
			<td>D5879</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycerol</td>
			<td>Fisher Scientific</td>
			<td>BP229</td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>THP-1</td>
			<td>American Type Culture Collection</td>
			<td>TIB-202</td>
			<td></td>
		</tr>
		<tr>
			<td>M. tuberculosis H37Rv</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>96-well flat bottom white plate</td>
			<td>Corning</td>
			<td>3917</td>
			<td></td>
		</tr>
		<tr>
			<td>95-well flat bottom clear plate</td>
			<td>Corning</td>
			<td>3595</td>
			<td></td>
		</tr>
		<tr>
			<td>Transparent plate sealer</td>
			<td>Thermo Fisher Scientific</td>
			<td>AB-0580</td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Spectrophotometer</td>
			<td>Thermo Fisher Scientific</td>
			<td>Biomate 3</td>
			<td></td>
		</tr>
		<tr>
			<td>Microplate spectrophotometer</td>
			<td>Biotek</td>
			<td>Epoch</td>
			<td></td>
		</tr>
		<tr>
			<td>luminometer</td>
			<td>Applied Biosystems</td>
			<td>Tropix TR717</td>
			<td></td>
		</tr>
	</tbody>
</table>

system for efficacy and cytotoxicity screening of inhibitors targeting intracellular mycobacterium tuberculosis

Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), is a leading cause of morbidity and mortality worldwide. With the increased spread of multi drug-resistant TB (MDR-TB), there is a real urgency to develop new therapeutic strategies against M. tuberculosis infections. Traditionally, compounds are evaluated based on their antibacterial activity under in vitro growth conditions in broth; however, results are often misleading for intracellular pathogens like M. tuberculosis since in-broth phenotypic screening conditions are significantly different from the actual disease conditions within the human body. Screening for inhibitors that work inside macrophages has been traditionally difficult due to the complexity, variability in infection, and slow replication rate of M. tuberculosis. In this study, we report a new approach to rapidly assess the effectiveness of compounds on the viability of M. tuberculosis in a macrophage infection model. Using a combination of a cytotoxicity assay and an in-broth M. tuberculosis viability assay, we were able to create a screening system that generates a comprehensive analysis of compounds of interest. This system is capable of producing quantitative data at a low cost that is within reach of most labs and yet is highly scalable to fit large industrial settings.

High-throughput intracellular screening using M. tuberculosis expressing the luciferase gene
Figure 2A and Table 1 contain the raw data collected by the luminometer, expressed in relative luminescent units (RLU), showing the effect of an increasing concentration of the TB drug rifampicin on M. tuberculosis inside THP-1 cells. Figure 2A is a scatter plot of the raw...

Watch this Scientific Journal Video about System for Efficacy and Cytotoxicity Screening of Inhibitors Targeting Intracellular Mycobacterium tuberculosis at JoVE.com

System for Efficacy and Cytotoxicity Screening of Inhibitors Targeting Intracellular Mycobacterium tuberculosis

We have developed a modular high-throughput screening system for discovering novel compounds against Mycobacterium tuberculosis, targeting intracellular and in-broth growing bacteria as well as cytotoxicity against the mammalian host cell.

System for Efficacy and Cytotoxicity Screening of Inhibitors Targeting Intracellular Mycobacterium tuberculosis

Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), is a leading cause of morbidity and mortality worldwide. With the increased spread ...

The overall goal of this protocol is to provide multidimensional assessment of how compounds affect M.tuberculosis survival inside human macrophages. This method is centered on a Luciferase-based efficacy assay. When combined with cytotoxicity an MIC assay can provide useful information into modification of HIT compounds in TB drug development.The main advantage of our method is that it is time and labor saving. It is replacing a CFU colony forming unit assay with a Luciferase based assay. Generally individuals new to this technique will struggle with consistency with manual pipetting instead of automation.A consistent pipetting technique is crucial. Grow THP1 cells in RPMI in complete medium. While maintaining a cell density of 0.2 to one million cells per milliliter of medium between passages.Use a spectrophotometer to measure the OD600 of an actively growing bacterial suspension. Then calculate the bacterial density using the conversion factor of 0.1 OD600 equals three times 10 to the seventh bacteria per milliliter. Pipette out sufficient bacteria for an MOI of 10 to one into a new centrifuge tube.Then pellet the bacteria at 3, 000 times G for 10 minutes. To opsonize the bacteria, add 50 microliters of human serum to 450 microliters of RPMI 1640 and use it to resuspend the bacterial pellet at a density of one times 10 to the eighth bacteria per 500 microliters of medium. Allow the mixture to incubate at 37 degrees Celsius for 30 minutes.Next, using a hemocytometer and an inverted microscope, determine the THP1 cell culture density. Then, in sterile centrifuge tubes, pellet the cells at 100 times G in 37 degrees Celsius for 10 minutes. Aspirate the supernatant and resuspend the cells in RPMI in complete medium at a density of one million cells per milliliter.Add PMA to a final concentration of 40 nanograms per milliliter. This is differentiation mix. Combined opsonized M.tuberculosis with THP1 differentiation mix at an MOI of 10 to one.And aliquot the final mix at 100 microliters per well in a 96 well white flat bottom plate. Then allow the differentiation and infection to incubate at 37 degrees Celsius in a humidified incubator containing 5%carbon dioxide overnight. The following day, use 100 microliters of RPMI to wash the wells twice.Then add compounds diluted to the desired concentrations and RPMI in complete medium. Incubate the plates for three days. When using multichannel pipettes, remember to practice slow and steady plunger action and always land the pipette tips in the same spot inside each well to minimize disturbance to the THP1 cells.Following the incubation, aspirate the medium from the wells and add 50 microliters of luciferase assay reagent to each well. Then use transparent adhesive plate sealers to seal the plates. Incubate the plates at 22 degrees Celsius for five minutes, then use a luminometer to obtain a readout at one second per well.To differentiate THP1 cells, after preparing differentiation mix as demonstrated earlier in this video, dispense 100 microliters of the differentiation mix into each well of a clear, 96 well plate of cells. Incubate the cells at 37 degrees Celsius in a humidified incubator with 5%carbon dioxide overnight. The following day, aspirate the medium from the wells and use RPMI 1640 to wash them twice.Add 100 microliters of compounds diluted in RPMI incomplete to the wells. Then, incubate the cells for three days. Dissolve 0.5 grams of MTT in 100 milliliters of PBS to make a stock solution of five milligrams per milliliter.Then filter sterilize the solution. Two and a half hours before the end of the three day incubation period, add 25 microliters of MTT solution to each well of cells and complete the incubation period. Prepare 50%NN dimethylformamide or DMF by mixing 250 milliliters of DMF with 250 milliliters of deionized water.Prepare MTT extraction buffer as follows. Lay 100 grams of SDS in a 500 milliliter bottle and add 300 milliliters of 50%DMF. Apply low heat to allow the SDS to dissolve.Add 10 milliliters of pure acetic acid and 12.5 milliliters of one molar hydrochloric acid. Then, use 50%DMF to fill up the bottle to the 500 milliliter mark. At the end of the treatment period, add 100 microliters of extraction buffer to each well.Incubate the mixture at 37 degrees Celsius in a humidified incubator containing 5%carbon dioxide overnight. The following day, read the absorbance at 570 nanometers. To carry out a resazurin assay, grow M.tuberculosis in 7H9 ADST to midlock phase.Dilute the culture with 7H9 ADST to an OD600 of 0.01. Use 7H9 ADST to dilute the compounds to two times the testing concentrations. And aliquot 100 microliters of each diluted compound into each well of a clear 96 well plate.Transfer 100 microliters of the diluted bacterial suspension into each well. Incubate the plates at 37 degrees Celsius in a humidified incubator for five days. Dissolve 10 milligrams of resazurin in 100 milliliters of deionized water.And filter sterilize the solution. Add 30 microliters of resazurin solution to the wells. Then incubate the cells for 48 hours.Bacterial growth is indicated by a color conversion from blue to pink. Carry out quantitative analysis according to the text protocol. This scatterplot shows the raw luminescence data measured in relative luminescence units for the treatment of various concentrations of rifampicin on M.tuberculosis and THP1 cells.In this plot, the percent reduction and luminescence in treated wells compared to untreated wells is shown. Rifampicin is capable of reducing 99.9%of the relative light units, or RLUs from intracellular M.tuberculosis at a concentration of 0.1 micrograms per milliliter. Similar to previously published results determined from CFU.In this figure, the cytotoxicity caused by increasing concentrations of G1-1H used in the MTT assay is illustrated. Concentrations of 10 and three micromolar are clearly below the IC 50 cutoff. This figure shows the effects of various concentrations of the antibiotic apramycin on resazurin conversion by M.tuberculosis.The in-broth MIC90 was between 2.5 and five micrograms per milliliter. This is slightly higher than the previously published value of 1.5 micrograms per milliliter. But it is still well within the acceptable range.As demonstrated here, evaporation becomes significant for all experiments with prolonged incubation times. So care must be taken to keep incubators well humidified to avoid inconsistencies. Once mastered, this technique can provide reliable intracellular data in as little as four days.While attempting this procedure it is important to remember to be gentle with THP1 cells, and be consistent with pipetting if attempting without automation. Following this procedure, other methods like high content screening can be used to determine if hit compounds are bacteriostatic or bactericidal. After its development, this protocol paved the way for researchers in the field of tuberculosis drug discovery to rapidly assess compound efficacy against MTB inside human macrophages.Don't forget that working with microbacterium tuberculosis is dangerous. Use precautions and proper equipment when handling this microorganism.

system-for-efficacy-cytotoxicity-screening-inhibitors-targeting

Research

JoVE Journal

Immunology and Infection

8.4K visualizações.  University of British Columbia. The overall goal of this protocol is to provide multidimensional assessment of how compounds affect M.tuberculosis survival inside human macrophages. This method is centered on a Luciferase-based efficacy assay. When combined with cytotoxicity an MIC assay can provide useful information into modification of HIT compounds in TB drug development.The main advantage of our method is that it is time and labor saving. It is replacing a CFU colony forming unit assay with a Luciferase based as...