Name: system for efficacy and cytotoxicity screening of inhibitors targeting intracellular mycobacterium tuberculosis
Uploaded: 2017-04-05T14:30:00
Description: Watch this Scientific Journal Video about System for Efficacy and Cytotoxicity Screening of Inhibitors Targeting Intracellular Mycobacterium tuberculosis at JoVE.com

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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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

Sample Preparation of Mycobacterium tuberculosis Extracts for Nuclear Magnetic Resonance Metabolomic Studies

Mycobacterium tuberculosis is a major cause of mortality in human beings on a global scale. The emergence of both multi- (MDR) and extensively-(XDR) drug-resistant strains threatens to derail current disease control efforts. Thus, there is an urgent need to develop drugs and vaccines that are more effective than those currently available. The genome of M. tuberculosis has been known for more than 10 years, yet there are important gaps in our knowledge of gene function and essentiality. Many studies have since used gene expression analysis at both the transcriptomic and proteomic levels to determine the effects of drugs, oxidants, and growth conditions on the global patterns of gene expression. Ultimately, the final response of these changes is reflected in the metabolic composition of the bacterium including a few thousand small molecular weight chemicals. Comparing the metabolic profiles of wild type and mutant strains, either untreated or treated with a particular drug, can effectively allow target identification and may lead to the development of novel inhibitors with anti-tubercular activity. Likewise, the effects of two or more conditions on the metabolome can also be assessed. Nuclear magnetic resonance (NMR) is a powerful technology that is used to identify and quantify metabolic intermediates. In this protocol, procedures for the preparation of M. tuberculosis cell extracts for NMR metabolomic analysis are described. Cell cultures are grown under appropriate conditions and required Biosafety Level 3 containment,1 harvested, and subjected to mechanical lysis while maintaining cold temperatures to maximize preservation of metabolites. Cell lysates are recovered, filtered sterilized, and stored at ultra-low temperatures. Aliquots from these cell extracts are plated on Middlebrook 7H9 agar for colony-forming units to verify absence of viable cells. Upon two months of incubation at 37 &deg;C, if no viable colonies are observed, samples are removed from the containment facility for downstream processing. Extracts are lyophilized, resuspended in deuterated buffer and injected in the NMR instrument, capturing spectroscopic data that is then subjected to statistical analysis. The procedures described can be applied for both one-dimensional (1D) 1H NMR and two-dimensional (2D) 1H-13C NMR analyses. This methodology provides more reliable small molecular weight metabolite identification and more reliable and sensitive quantitative analyses of cell extract metabolic compositions than chromatographic methods. Variations of the procedure described following the cell lysis step can also be adapted for parallel proteomic analysis.

Sample Preparation of Mycobacterium tuberculosis Extracts for Nuclear Magnetic Resonance Metabolomic Studies

The metabolomic profile of Mycobacterium tuberculosis is determined after growth in broth cultures. Conditions can be varied to test the effects of nutritional supplements, oxidants, and anti-tuberculosis agents on the metabolic profile of this microorganism. Procedure for extract preparation is applicable for both 1D 1H and 2D 1H-13C NMR analyses.

Mycobacterium tuberculosis is a major cause of mortality in human beings on a global scale. The emergence of both multi- (MDR) and extensively-(XDR) ...

Growth of Mycobacterium tuberculosis Biofilms

Mycobacterium tuberculosis, the etiologic agent of human tuberculosis, has an extraordinary ability to survive against environmental stresses including antibiotics. Although stress tolerance of M. tuberculosis is one of the likely contributors to the 6-month long chemotherapy of tuberculosis 1, the molecular mechanisms underlying this characteristic phenotype of the pathogen remain unclear. Many microbial species have evolved to survive in stressful environments by self-assembling in highly organized, surface attached, and matrix encapsulated structures called biofilms 2-4. Growth in communities appears to be a preferred survival strategy of microbes, and is achieved through genetic components that regulate surface attachment, intercellular communications, and synthesis of extracellular polymeric substances (EPS) 5,6. The tolerance to environmental stress is likely facilitated by EPS, and perhaps by the physiological adaptation of individual bacilli to heterogeneous microenvironments within the complex architecture of biofilms 7.
In a series of recent papers we established that M. tuberculosis and Mycobacterium smegmatis have a strong propensity to grow in organized multicellular structures, called biofilms, which can tolerate more than 50 times the minimal inhibitory concentrations of the anti-tuberculosis drugs isoniazid and rifampicin 8-10. M. tuberculosis, however, intriguingly requires specific conditions to form mature biofilms, in particular 9:1 ratio of headspace: media as well as limited exchange of air with the atmosphere 9. Requirements of specialized environmental conditions could possibly be linked to the fact that M. tuberculosis is an obligate human pathogen and thus has adapted to tissue environments. In this publication we demonstrate methods for culturing M. tuberculosis biofilms in a bottle and a 12-well plate format, which is convenient for bacteriological as well as genetic studies. We have described the protocol for an attenuated strain of M. tuberculosis, mc27000, with deletion in the two loci, panCD and RD1, that are critical for in vivo growth of the pathogen 9. This strain can be safely used in a BSL-2 containment for understanding the basic biology of the tuberculosis pathogen thus avoiding the requirement of an expensive BSL-3 facility. The method can be extended, with appropriate modification in media, to grow biofilm of other culturable mycobacterial species.
Overall, a uniform protocol of culturing mycobacterial biofilms will help the investigators interested in studying the basic resilient characteristics of mycobacteria. In addition, a clear and concise method of growing mycobacterial biofilms will also help the clinical and pharmaceutical investigators to test the efficacy of a potential drug.

Growth of Mycobacterium tuberculosis Biofilms

Mycobacterium tuberculosis forms drug tolerant biofilms when cultured in certain conditions. Here we describe methods for culturing M. tuberculosis biofilms and determining the frequency of drug tolerant persisters. These protocols will be useful for further studies into the mechanisms of drug tolerance in M. tuberculosis.

Mycobacterium tuberculosis, the etiologic agent of human tuberculosis, has an extraordinary ability to survive against environmental stresses including ...

An Experimental Model to Study Tuberculosis-Malaria Coinfection upon Natural Transmission of Mycobacterium tuberculosis and Plasmodium berghei

Coinfections naturally occur due to the geographic overlap of distinct types of pathogenic organisms. Concurrent infections most likely modulate the respective immune response to each single pathogen and may thereby affect pathogenesis and disease outcome. Coinfected patients may also respond differentially to anti-infective interventions. Coinfection between tuberculosis as caused by mycobacteria and the malaria parasite Plasmodium, both of which are coendemic in many parts of sub-Saharan Africa, has not been studied in detail. In order to approach the challenging but scientifically and clinically highly relevant question how malaria-tuberculosis coinfection modulate host immunity and the course of each disease, we established an experimental mouse model that allows us to dissect the elicited immune responses to both pathogens in the coinfected host. Of note, in order to most precisely mimic naturally acquired human infections, we perform experimental infections of mice with both pathogens by their natural routes of infection, i.e. aerosol and mosquito bite, respectively.

An Experimental Model to Study Tuberculosis-Malaria Coinfection upon Natural Transmission of Mycobacterium tuberculosis and Plasmodium berghei

Tuberculosis and malaria are two of the most prevalent infections in humans and major causes of morbidity and mortality in impoverished populations in the tropics. We established an experimental model system to study outcome of malaria-tuberculosis coinfection in mice after challenge with both pathogens via their natural route of infection.

Coinfections naturally occur due to the geographic overlap of distinct types of pathogenic organisms. Concurrent infections most likely modulate the ...

High-throughput Screening for Broad-spectrum Chemical Inhibitors of RNA Viruses

RNA viruses are responsible for major human diseases such as flu, bronchitis, dengue, Hepatitis C or measles. They also represent an emerging threat because of increased worldwide exchanges and human populations penetrating more and more natural ecosystems. A good example of such an emerging situation is chikungunya virus epidemics of 2005-2006 in the Indian Ocean. Recent progresses in our understanding of cellular pathways controlling viral replication suggest that compounds targeting host cell functions, rather than the virus itself, could inhibit a large panel of RNA viruses. Some broad-spectrum antiviral compounds have been identified with host target-oriented assays. However, measuring the inhibition of viral replication in cell cultures using reduction of cytopathic effects as a readout still represents a paramount screening strategy. Such functional screens have been greatly improved by the development of recombinant viruses expressing reporter enzymes capable of bioluminescence such as luciferase. In the present report, we detail a high-throughput screening pipeline, which combines recombinant measles and chikungunya viruses with cellular viability assays, to identify compounds with a broad-spectrum antiviral profile.

In vitro assays to measure virus replication have been greatly improved by the development of recombinant RNA viruses expressing luciferase or other enzymes capable of bioluminescence. Here we detail a high-throughput screening pipeline that combines such recombinant strains of measles and chikungunya viruses to isolate broad-spectrum antivirals from chemical libraries.

RNA viruses are responsible for major human diseases such as flu, bronchitis, dengue, Hepatitis C or measles. They also represent an emerging threat ...

Demonstrating a Multi-drug Resistant Mycobacterium tuberculosis Amplification Microarray

Simplifying microarray workflow is a necessary first step for creating MDR-TB microarray-based diagnostics that can be routinely used in lower-resource environments. An amplification microarray combines asymmetric PCR amplification, target size selection, target labeling, and microarray hybridization within a single solution and into a single microfluidic chamber. A batch processing method is demonstrated with a 9-plex asymmetric master mix and low-density gel element microarray for genotyping multi-drug resistant Mycobacterium tuberculosis (MDR-TB). The protocol described here can be completed in 6 hr and provide correct genotyping with at least 1,000 cell equivalents of genomic DNA. Incorporating on-chip wash steps is feasible, which will result in an entirely closed amplicon method and system. The extent of multiplexing with an amplification microarray is ultimately constrained by the number of primer pairs that can be combined into a single master mix and still achieve desired sensitivity and specificity performance metrics, rather than the number of probes that are immobilized on the array. Likewise, the total analysis time can be shortened or lengthened depending on the specific intended use, research question, and desired limits of detection. Nevertheless, the general approach significantly streamlines microarray workflow for the end user by reducing the number of manually intensive and time-consuming processing steps, and provides a simplified biochemical and microfluidic path for translating microarray-based diagnostics into routine clinical practice.

Demonstrating a Multi-drug Resistant Mycobacterium tuberculosis Amplification Microarray

An amplification microarray combines asymmetric PCR amplification and microarray hybridization into a single chamber, which significantly streamlines microarray workflow for the end user. Simplifying microarray workflow is a necessary first step for creating microarray-based diagnostics that can be routinely used in lower-resource environments.

Simplifying microarray workflow is a necessary first step for creating MDR-TB microarray-based diagnostics that can be routinely used in lower-resource ...

Rapid Screening of HIV Reverse Transcriptase and Integrase Inhibitors

Although a number of anti HIV drugs have been approved, there are still problems with toxicity and drug resistance. This demonstrates a need to identify new compounds that can inhibit infection by the common drug resistant HIV-1 strains with minimal toxicity. Here we describe an efficient assay that can be used to rapidly determine the cellular cytotoxicity and efficacy of a compound against WT and mutant viral strains.
The desired target cell line is seeded in a 96-well plate and, after a 24 hr incubation, serially dilutions of the compounds to be tested are added. No further manipulations are necessary for cellular cytotoxicity assays; for anti HIV assays a predetermined amount of either a WT or drug resistant HIV-1 vector that expresses luciferase is added to the cells. Cytotoxicity is measured by using an ATP dependent luminescence assay and the impact of the compounds on infectivity is measured by determining the amount of luciferase in the presence or the absence of the putative inhibitors.
This screening assay takes 4 days to complete and multiple compounds can be screened in parallel. Compounds are screened in triplicate and the data are normalized to the infectivity/ATP levels in absence of target compounds. This technique provides a quick and accurate measurement of the efficacy and toxicity of potential anti HIV compounds.

Here we describe cellular cytotoxicity and single round infectivity assays that allow for the rapid and accurate screening of compounds to determine their cellular cytotoxicity (CC50) and IC50 values against WT and drug resistant HIV-1.

Although a number of anti HIV drugs have been approved, there are still problems with toxicity and drug resistance. This demonstrates a need to identify ...

A 3D Human Lung Tissue Model for Functional Studies on Mycobacterium tuberculosis Infection

Tuberculosis (TB) still holds a major threat to the health of people worldwide, and there is a need for cost-efficient but reliable models to help us understand the disease mechanisms and advance the discoveries of new treatment options. In vitro cell cultures of monolayers or co-cultures lack the three-dimensional (3D) environment and tissue responses. Herein, we describe an innovative in vitro model of a human lung tissue, which holds promise to be an effective tool for studying the complex events that occur during infection with Mycobacterium tuberculosis (M. tuberculosis). The 3D tissue model consists of tissue-specific epithelial cells and fibroblasts, which are cultured in a matrix of collagen on top of a porous membrane. Upon air exposure, the epithelial cells stratify and secrete mucus at the apical side. By introducing human primary macrophages infected with M. tuberculosis to the tissue model, we have shown that immune cells migrate into the infected-tissue and form early stages of TB granuloma. These structures recapitulate the distinct feature of human TB, the granuloma, which is fundamentally different or not commonly observed in widely used experimental animal models. This organotypic culture method enables the 3D visualization and robust quantitative analysis that provides pivotal information on spatial and temporal features of host cell-pathogen interactions. Taken together, the lung tissue model provides a physiologically relevant tissue micro-environment for studies on TB. Thus, the lung tissue model has potential implications for both basic mechanistic and applied studies. Importantly, the model allows addition or manipulation of individual cell types, which thereby widens its use for modelling a variety of infectious diseases that affect the lungs.

A 3D Human Lung Tissue Model for Functional Studies on Mycobacterium tuberculosis Infection

Human tuberculosis infection is a complex process, which is difficult to model in vitro. Here we describe a novel 3D human lung tissue model that recapitulates the dynamics that occur during infection, including the migration of immune cells and early granuloma formation in a physiological environment.

Tuberculosis (TB) still holds a major threat to the health of people worldwide, and there is a need for cost-efficient but reliable models to help us ...

A High-throughput Compatible Assay to Evaluate Drug Efficacy against Macrophage Passaged Mycobacterium tuberculosis

The early drug development process for anti-tuberculosis drugs is hindered by the inefficient translation of compounds with in vitro activity to effectiveness in the clinical setting. This is likely due to a lack of consideration for the physiologically relevant cellular penetration barriers that exist in the infected host. We recently established an alternative infection model that generates large macrophage aggregate structures containing densely packed M. tuberculosis (Mtb) at its core, which was suitable for drug susceptibility testing. This infection model is inexpensive, rapid, and most importantly BSL-2 compatible. Here, we describe the experimental procedures to generate Mtb/macrophage aggregate structures that would produce macrophage-passaged Mtb for drug susceptibility testing. In particular, we demonstrate how this infection system could be directly adapted to the 96-well plate format showing throughput capability for the screening of compound libraries against Mtb. Overall, this assay is a valuable addition to the currently available Mtb drug discovery toolbox due to its simplicity, cost effectiveness, and scalability.

A High-throughput Compatible Assay to Evaluate Drug Efficacy against Macrophage Passaged Mycobacterium tuberculosis

New models and assays that would improve the early drug development process for next-generation anti-tuberculosis drugs are highly desirable. Here, we describe a quick, inexpensive, and BSL-2 compatible assay to evaluate drug efficacy against Mycobacterium tuberculosis that can be easily adapted for high-throughput screening.

The early drug development process for anti-tuberculosis drugs is hindered by the inefficient translation of compounds with in vitro activity to ...

Imaging Mycobacterium tuberculosis in Mice with Reporter Enzyme Fluorescence

Reporter enzyme fluorescence (REF) utilizes substrates that are specific for enzymes present in target organisms of interest for imaging or detection by fluorescence or bioluminescence. We utilize BlaC, an enzyme expressed constitutively by all M. tuberculosis strains. REF allows rapid quantification of bacteria in lungs of infected mice. The same group of mice can be imaged at many time points, greatly reducing costs, enumerating bacteria more quickly, allowing novel observations in host-pathogen interactions, and increasing statistical power, since more animals per group are readily maintained. REF is extremely sensitive due to the catalytic nature of the BlaC enzymatic reporter and specific due to the custom flourescence resonance energy transfer (FRET) or fluorogenic substrates used. REF does not require recombinant strains, ensuring normal host-pathogen interactions. We describe the imaging of M. tuberculosis infection using a FRET substrate with maximal emission at 800 nm. The wavelength of the substrate allows sensitive deep tissue imaging in mammals. We will outline aerosol infection of mice with M. tuberculosis, anesthesia of mice, administration of the REF substrate, and optical imaging. This method has been successfully applied to evaluating host-pathogen interactions and efficacy of antibiotics targeting M. tuberculosis.

Imaging Mycobacterium tuberculosis in Mice with Reporter Enzyme Fluorescence

We describe the optical imaging of mice infected with Mycobacterium tuberculosis (M. tuberculosis) using reporter enzyme fluorescence (REF). This protocol facilitates the sensitive and specific detection of M. tuberculosis in pre-clinical animal models for pathogenesis, therapeutics and vaccine research.

Reporter enzyme fluorescence (REF) utilizes substrates that are specific for enzymes present in target organisms of interest for imaging or detection by ...

Identification of Virulence Markers of Mycobacterium abscessus for Intracellular Replication in Phagocytes

What differentiates Mycobacterium abscessus from other saprophytic mycobacteria is the ability to resist phagocytosis by human macrophages and the ability to multiply inside such cells. These virulence traits render M. abscessus pathogenic, especially in vulnerable hosts with underlying structural lung disease, such as cystic fibrosis, bronchiectasis or tuberculosis. How patients become infected with M. abscessus remains unclear. Unlike many mycobacteria, M. abscessus is not found in the environment but might reside inside amoebae, environmental phagocytes that represent a potential reservoir for M. abscessus. Indeed, M. abscessus is resistant to amoebal phagocytosis and the intra-amoeba life seems to increase M. abscessus virulence in an experimental model of infection. However, little is known about M. abscessus virulence in itself. To decipher the genes conferring an advantage to M. abscessus intracellular life, a screening of a M. abscessus transposon mutant library was developed. In parallel, a method of RNA extraction from intracellular Mycobacteria after co-culture with amoebae was developed. This method was validated and allowed the sequencing of whole M. abscessus transcriptomes inside the cells; providing, for the first time, a global view on M. abscessus adaptation to intracellular life. Both approaches give us an insight into M. abscessus virulence factors that enable M. abscessus to colonize the airways in humans.

Identification of Virulence Markers of Mycobacterium abscessus for Intracellular Replication in Phagocytes

Here, we present two protocols to study Phagocyte-Mycobacterium abscessus interactions: the screening of a transposon mutant library for bacterial intracellular deficiency and the determination of bacterial intracellular transcriptome from RNA sequencing. Both approaches provide insight into the genomic advantages and transcriptomic adaptations enhancing intracellular bacteria fitness.

What differentiates Mycobacterium abscessus from other saprophytic mycobacteria is the ability to resist phagocytosis by human macrophages and the ability ...