We would like to acknowledge support from the College of Veterinary Medicine and Biomedical Sciences Experiential Award and College Research Council Shared Research Program to NKG and funding by ATCC (award # 2016-0550-0002) to KMD. We would also like to acknowledge Anne Simpson for technical support and BEI Resources, NIAID, NIH for the following reagents: Monoclonal Anti-Mycobacterium tuberculosis LpqH (Gene Rv3763), IT-54 (produced in vitro), NR-13792, Monoclonal Anti-Mycobacterium tuberculosis GroES (Gene Rv3418c), Clone IT-3 (SA-12) (produced in vitro), NR-49223, and Monoclonal Anti-Mycobacterium tuberculosis LAM, Clone CS-35 (produced in vitro), NR-13811.

The Colorado State University Institutional Biosafety Committee approved the present study (19-046B). Cultivation of Mycobacterium tuberculosis and harvesting of EV-rich culture supernatants were performed by trained personnel in a high-containment laboratory. The materials were moved out of the high-containment area after a valid inactivation method was performed, confirmed, and approved by institutional biosafety policies. While replicating the protocol, if validated inactivation or sterile filtration method is not feasible, the following procedures need to be performed in a high-containment laboratory.
1. Preparation of crude Mtb EV concentrate
NOTE: For detailed procedures on the cultivation of Mtb and preparation of culture filtrate protein (CFP), see References11,12. It is recommended that bacterial culture media is free from growth supplements with EV-containing or proteinaceous components, such as Oleic Albumin Dextrose Catalase (OADC), and detergents such as Tween. It is also recommended that the bacterial culture&#39;s quality and harvested CFP be screened to ensure limited cell death and lysis13,14.
<ol>
	<li>Prepare a 100 kDa molecular weight cut-off (MWCO) centrifugal filter (see Table of Materials) by adding the full volume capacity of phosphate-buffered saline (1x PBS). Centrifuge for 5 min at 2,800 x g at 4 &#176;C. 
	NOTE: If using a filter with no dead stop volume, care must be taken to ensure the sample volume does not reduce below the filter level, resulting in complete filter drying during centrifugation.</li>
	<li>Discard the flow-through and any remaining PBS before filling the sample chamber with Mtb CFP to its maximum capacity. Centrifuge at 2,800 x g at 4 &#176;C until the volume has reduced to the minimum volume of the ultrafiltration device. Repeat as necessary, adding more CFP to the unit until the entire sample has been reduced sufficiently. 
	NOTE: Retain a portion of the 100 kDa flow-through (100F) material for downstream qualification if desired. Store at 4 &#176;C.</li>
	<li>Add 1x PBS to the filter unit containing the concentrate up to the total device capacity. Reduce the volume as described in 1.2. Repeat this step five times to ensure complete washing and buffer exchange.</li>
	<li>Recover the 100 kDa concentrated CFP retentate (100R) according to the ultrafiltration device specifications (see Table of Materials). Once the 100R is recovered, wash the filter with a minimal volume of 1x PBS at least three times, and pool the wash with the 100R to maximize the recovery.</li>
	<li>Quantitate the 100R material with a bicinchoninic assay (BCA) following the manufacturer&#39;s instructions (see Table of Materials). To perform the assay, use several dilutions of samples 1:2, 1:5, and 1:10 in PBS. Test the sample in triplicate. 
	&#8203;NOTE: Retain a portion of the 100R material for downstream qualification if desired. Store at 4 &#176;C.</li>
</ol>
2. Size exclusion chromatography for the enrichment of Mtb EVs from CFP
NOTE: The following procedure is specific for using 3 mg of 100R Mtb CFP with SEC column and automatic fraction collector (AFC, see Table of Materials). It can be adapted for other starting concentrations and column types by following the manufacturer&#39;s specifications. Additionally, the users are recommended to read and understand the automatic fraction collector user manual.
<ol>
	<li>Allow the SEC column to equilibrate to room temperature.</li>
	<li>Turn on the AFC using the power switch on the back of the tower unit and adjust the settings for the load cell, if necessary, by pressing SETUP on the main menu touchscreen. The load cell must only be calibrated upon first use, after every software update, and if inconsistency in fraction collection volumes is noticed.</li>
	<li>From the SETUP screen, align the carousel by selecting CAROUSEL &#62; CALIBRATE. Insert the carousel with the 13 small holes facing up into the AFC tower, and adjust the carousel so that the fluid nozzle is directly above the flush position by pressing the - and/or + buttons.</li>
	<li>Remove the caps from the equilibrated SEC column. Slide the SEC column into the appropriate column mount and carefully install it on the AFC tower. Ensure the radio frequency identification (RFID) tag on the column faces the AFC, and check that the connection between the column and the valve is secure. Place the waste outlet tubing in a collection container.</li>
	<li>From the SETUP screen, select Collection Schedule and set the count to 13 and the size to 0.5 mL by pressing the - and/or + buttons. Leave the &#34;Buffer Volume&#34; setting as the default of 2.7 mL, and then close the &#34;Collection Schedule&#34; window by pressing X.</li>
	<li>Select START COLLECTION from the home screen and confirm the collection parameters by selecting YES. Load 13 labeled 1.7 mL microcentrifuge tubes with the lids open and pointing toward the carousel center.</li>
	<li>Advance the AFC by selecting OK, then mount the column reservoir and advance again by pressing OK. Select the option to flush the column by pressing YES, and add one column volume of 0.2 &#181;m filtered PBS to remove any storage buffer. Once the flush is complete, advance the AFC by pressing OK.</li>
	<li>Place the carousel cover over the AFC and press OK. Prepare one column volume of 0.2 &#181;m filtered PBS. Use a pipette to remove any excess buffer from the column.</li>
	<li>Bring 3 mg of 100R sample as quantified in step 1.5 to 500 &#181;L with 1x PBS. Add the 3 mg sample to the top of the column. Advance the AFC and allow the sample to run into the frit. Once the sample has fully entered the column, add the PBS prepared in step 2.6 to the reservoir.</li>
	<li>Monitor the run of the AFC while it collects first the void volume and then the specified fractions. After the run completes and the carousel returns to waste position, remove the cover, and remove the fraction tubes from the carousel. Store the fractions at 4 &#176;C prior to quantification (step 3) and qualification (step 4).</li>
	<li>If the column is to be reused, select the option to clean the column by pressing YES; otherwise, press NO. Follow the instructions on the AFC. 
	&#8203;NOTE: Once the column is washed and the storage buffer has run through, it can be removed, capped, and stored at 4 &#176;C.</li>
</ol>
3. Quantification of the Mtb EVs
<ol>
	<li>Measure the protein concentration for each fraction using BCA and micro BCA12.
	<ol>
		<li>For 0.5 mL fractions collected from 3 mg of 100R Mtb CFP, use the micro BCA with a 1:3 dilution for fractions numbered 1-7 of each sample in triplicate.</li>
		<li>For 0.5 mL fractions numbered 5-13, use the BCA with no dilution for each sample in triplicate. 
		NOTE: Overlapping the assays for fractions 5-7 will help ensure all fractions have a readable output.</li>
	</ol>
	</li>
	<li>Quantitate the particle concentration for each fraction using nanoparticle tracking analysis (NTA).
	<ol>
		<li>Dilute the samples in 1 mL of 1x PBS using the following suggested starting ratios; for fractions 1-3, use 1:100, and then for the remaining fractions, use a 1:10 dilution.</li>
		<li>Vortex the diluted solutions and then draw the sample into a 1 mL disposable syringe. Set the syringe in an automatic syringe pump if available.</li>
		<li>Set the syringe pump to 30 &#181;L/min and use the video capture settings with a screen gain of 10-12 and a camera level of 10-12. Adjust the focus for each sample.</li>
		<li>Collect a minimum of three videos at 30 s each using a constant flow.</li>
		<li>Perform the analysis with the software detection threshold set to five. 
		&#8203;NOTE: It may not be possible to obtain NTA data for the latest fractions (&#62;7) without sacrificing significant sample volume.</li>
	</ol>
	</li>
</ol>
4. Qualification of Mtb EVs
<ol>
	<li>Visualize the general protein profile of each fraction using a silver-stained protein gel. 
	NOTE: Detailed procedures for SDS-PAGE and silver stain can be found in Reference15.
	<ol>
		<li>Add SDS sample buffer to 10 &#181;L of each fraction and 5 &#181;g of CFP, 100R, and 100F. Boil for 5 min at 100 &#176;C, then load on a 4%-12% Bis-Tris Gel with a molecular weight ladder for polyacrylamide gel electrophoresis (PAGE) (see Table of Materials).</li>
		<li>Run the gel using 1x 2-[N-morpholino]ethanesulfonic acid (MES) running buffer (see Table of Materials) and a 200 V current for 35 min.</li>
		<li>Remove the gel from the cassette and proceed with silver staining15.</li>
	</ol>
	</li>
	<li>Evaluate the presence or absence of EV markers in each fraction by Western blot. 
	NOTE: Detailed procedures for Western blotting can be found in Reference15.
	<ol>
		<li>Run an SDS-PAGE gel as described in steps 4.1.1-4.1.2.</li>
		<li>Remove the gel from the cassette and transfer the resolved proteins to a 0.2 &#181;m nitrocellulose membrane (see Table of Materials) by applying a 50 V current for a minimum of 1 h.</li>
		<li>Perform Western blot analysis to evaluate proteins of interest. Primary antibodies against LpqH, lipoarabinomannan (LAM), and GroES (see Table of Materials) are recommended.</li>
		<li>Pool fractions based on the presence or absence of markers as applicable for the downstream application.</li>
	</ol>
	</li>
	<li>Confirm the presence of intact vesicles by transmission electron microscopy (TEM).
	<ol>
		<li>Fix 15 &#181;L of the vesicle sample by adding 15 &#181;L of 4% EM grade paraformaldehyde and store at 4 &#176;C overnight.</li>
		<li>Prepare a 200 mesh formvar-carbon coated copper TEM grid by cleaning the surface and making a hydrophilic substrate. 
		NOTE: Plasma cleaning with 95% argon, 5% oxygen, and 30% plasma power for 1 min is recommended.</li>
		<li>Drop 10 &#181;L of the fixed sample onto the grid and allow the sample to adhere for 10 min, then blot away the excess liquid with filter paper.</li>
		<li>Float the grid on a drop of ultrapure water for 30 s, then blot away excess liquid.</li>
		<li>Float the grid on a d% EM grade uranyl acetate drop for 2 min, then blot away the excess liquid.</li>
		<li>Allow the grid to air dry completely.</li>
		<li>Image using a TEM (see Table of Materials) at 100 kV or similar. 
		NOTE: Other EV quantitation and characterization methods should be used based on downstream applications. The Minimal Information for Studies of Extracellular Vesicles18 should be consulted for guidelines to ensure the rigor and reproducibility of all EV studies.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Gill, S., Catchpole, R., Forterre, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extracellular+membrane+vesicles+in+the+three+domains+of+life+and+beyond.">Extracellular membrane vesicles in the three domains of life and beyond.</a> FEMS Microbiology Reviews. 43 (3), 273-303 (2019).</li><li>World Health Organization. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=GLOBAL+TUBERCULOSIS+REPORT+2021.">GLOBAL TUBERCULOSIS REPORT 2021.</a> World Health Organization. , (2021).</li><li>Prados-Rosales, R., 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=Mycobacteria+release+active+membrane+vesicles+that+modulate+immune+responses+in+a+TLR2-dependent+manner+in+mice.">Mycobacteria release active membrane vesicles that modulate immune responses in a TLR2-dependent manner in mice.</a> Journal of Clinical Investigation. 121 (4), 1471-1483 (2011).</li><li>Prados-Rosales, R., 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=Mycobacterial+membrane+vesicles+administered+systemically+in+mice+induce+a+protective+immune+response+to+surface+compartments+of+mycobacterium+tuberculosis.">Mycobacterial membrane vesicles administered systemically in mice induce a protective immune response to surface compartments of mycobacterium tuberculosis.</a> mBio. 5 (5), 01921 (2014).</li><li>Prados-Rosales, R., 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=Role+for+mycobacterium+tuberculosis+membrane+vesicles+in+iron+acquisition.">Role for mycobacterium tuberculosis membrane vesicles in iron acquisition.</a> Journal of Bacteriology. 196 (6), 1250-1256 (2014).</li><li>Lee, 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=Proteomic+analysis+of+extracellular+vesicles+derived+from+Mycobacterium+tuberculosis.">Proteomic analysis of extracellular vesicles derived from Mycobacterium tuberculosis.</a> Proteomics. 15 (19), 3331-3337 (2015).</li><li>Athman, J. 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A., Kennedy, M. T., Zasadzinski, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Encapsulation+of+bilayer+vesicles+by+self-assembly.">Encapsulation of bilayer vesicles by self-assembly.</a> Nature. 387 (6628), 61-64 (1997).</li><li>Edwards, D. 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=Spontaneous+vesicle+formation+at+lipid+bilayer+membranes.">Spontaneous vesicle formation at lipid bilayer membranes.</a> Biophysical Journal. 71 (3), 1208 (1996).</li><li>. Production Manuals &amp; SOPs. SP007: Running of polyacrylamide gels, SP011: Western blot, and SP0012: Silver staining protocols Available from: <a target="_blank" href="https://labs.vetmebiosci.colostate.edu/dobos/bei-resources/">https://labs.vetmebiosci.colostate.edu/dobos/bei-resources/</a> (2022)</li><li>Engers, H. D., 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=Results+of+a+World+Health+Organization-sponsored+workshop+to+characterize+antigens+recognized+by+mycobacterium-specific+monoclonal+antibodies.">Results of a World Health Organization-sponsored workshop to characterize antigens recognized by mycobacterium-specific monoclonal antibodies.</a> Infection and Immunity. 51 (2), 718-720 (1986).</li><li>Chatterjee, D., Lowell, K., Rivoire, B., McNeil, M. R., Brennan, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lipoarabinomannan+of+Mycobacterium+tuberculosis.+Capping+with+mannosyl+residues+in+some+strains.">Lipoarabinomannan of Mycobacterium tuberculosis. Capping with mannosyl residues in some strains.</a> Journal of Biological Chemistry. 267 (9), 6234-6239 (1992).</li><li>Th&#233;ry, C., 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=Minimal+information+for+studies+of+extracellular+vesicles+2018+(MISEV2018):+a+position+statement+of+the+International+Society+for+Extracellular+Vesicles+and+update+of+the+MISEV2014+guidelines.">Minimal information for studies of extracellular vesicles 2018 (MISEV2018): a position statement of the International Society for Extracellular Vesicles and update of the MISEV2014 guidelines.</a> Journal of Extracellular Vesicles. 7 (1), 1535750 (2018).</li><li>Palacios, 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=Mycobacterium+tuberculosis+extracellular+vesicle-associated+lipoprotein+LpqH+as+a+potential+biomarker+to+distinguish+paratuberculosis+infection+or+vaccination+from+tuberculosis+infection.">Mycobacterium tuberculosis extracellular vesicle-associated lipoprotein LpqH as a potential biomarker to distinguish paratuberculosis infection or vaccination from tuberculosis infection.</a> BMC Veterinary Research. 15 (1), 1-9 (2019).</li><li>Ziegenbalg, 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=Immunogenicity+of+mycobacterial+vesicles+in+humans:+Identification+of+a+new+tuberculosis+antibody+biomarker.">Immunogenicity of mycobacterial vesicles in humans: Identification of a new tuberculosis antibody biomarker.</a> Tuberculosis. 93 (4), 448-455 (2013).</li><li>Chiplunkar, S. 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The authors have nothing to disclose.

Mycobacterium tuberculosis extracellular vesicles are highly antigenic reservoirs, which present them as an attractive avenue for developing diagnostic tools and future vaccines4,19,20. Historically, density gradient ultracentrifugation has been used to separate Mtb EVs from other soluble, secreted material8. While this process is effective, it is also time-consuming, technically challenging, and...

Extracellular vesicle (EV) release by pathogens may be the key to unlocking new technologies to control infectious diseases1. Mycobacterium tuberculosis (Mtb) is a pathogen of high consequence, infecting approximately one-third of the world&#39;s population and claiming the lives of millions of people each year2. EV production by Mtb is well documented yet elusive in the biogenesis and varied roles (i.e., immunostimulatory, immunosuppressive, iron and nutrient acquisition) of these EVs in the context of infection3,4,5. Efforts to understand the composition of Mtb EVs revealed 50-150 nm lipid membrane-enclosed spheres derived from the plasma membrane containing lipids and proteins of immunological significance3,6. Investigation of the role of Mtb EVs in bacterial physiology has revealed the importance of bacterial EV modulation in response to environmental stress for survival5. Host-pathogen interaction studies have been more complicated to interpret, but evidence indicates that Mtb EVs can influence the immune response of the host and may potentially serve as an effective vaccination component3,4,7.
Most studies of Mtb EVs thus far have relied on density gradient ultracentrifugation for vesicle enrichment8. This has been effective for small-scale studies; however, this technique has several technical and logistical challenges. Alternate workflows couple multistep centrifugation, for the removal of whole cells and large debris, with a final ultracentrifugation step to pellet EVs. This methodology can vary in efficiency, and often results in low yield and co-purification of soluble non-vesicle associated biomolecules while also impacting vesicle integrity9. Additionally, this process is time-consuming, manually intensive, and very limited in throughput due to equipment constraints.
The present protocol describes an alternative technique to density gradient ultracentrifugation: size exclusion chromatography (SEC). This method has been demonstrated for environmental mycobacteria, and in the current work, it has been extrapolated to Mtb10. A commercially available column and automatic fraction collector can improve consistency in vesical preparation and reduce the necessity for specific, expensive equipment. It is also possible to complete this protocol in a fraction of the time compared to density gradient ultracentrifugation, increasing the throughput. This technique is less technically challenging, making it easier to master, and can increase inter/intra-laboratory reproducibility. Finally, SEC has high separation efficiency and is gentle, preserving the integrity of the vesicles.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>20x MES SDS Running Buffer</td>
			<td>ThermoFisher Scientific</td>
			<td>NP0002</td>
			<td></td>
		</tr>
		<tr>
			<td>96 well plate</td>
			<td>Corning</td>
			<td>15705-066</td>
			<td></td>
		</tr>
		<tr>
			<td>Automatic Fraction Collector</td>
			<td>IZON Science</td>
			<td>AFC-V1-USD</td>
			<td></td>
		</tr>
		<tr>
			<td>BenchMark Pre-stained Protein Ladder</td>
			<td>Invitrogen</td>
			<td>10748010</td>
			<td></td>
		</tr>
		<tr>
			<td>Benchtop centrifuge</td>
			<td>Beckman Coulter</td>
			<td>Allegra 6R</td>
			<td></td>
		</tr>
		<tr>
			<td>Centricon Plus - 70 Centrifugal filter, 100 kDa cutoff</td>
			<td>Millipore Sigma</td>
			<td>UFC710008</td>
			<td>Ultrafiltration device used in step 1.1</td>
		</tr>
		<tr>
			<td>Electroblotting System</td>
			<td>ThermoFisher Scientific</td>
			<td>09-528-135</td>
			<td></td>
		</tr>
		<tr>
			<td>EM Grade Paraformaldehyde</td>
			<td>Electron Microscopy Sciences</td>
			<td>15714-S</td>
			<td></td>
		</tr>
		<tr>
			<td>Formvar/Carbon 200 mesh Cu Grids</td>
			<td>Electron Microscopy Sciences</td>
			<td>FCF200H-Cu-TA</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat Anti-Mouse IgG H&#38;L (Alkaline Phosphatase), whole molecule, 1 mL</td>
			<td>AbCam</td>
			<td>ab6790</td>
			<td>Secondary antibody</td>
		</tr>
		<tr>
			<td>JEM-1400 Transmission Electron Microscope</td>
			<td>JOEL</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Micro BCA Protein Assay Kit</td>
			<td>ThermoFisher Scientific</td>
			<td>23235</td>
			<td></td>
		</tr>
		<tr>
			<td>Microplate reader</td>
			<td>BIOTEK</td>
			<td>Epoch</td>
			<td></td>
		</tr>
		<tr>
			<td>Monoclonal Anti-Mycobacterium tuberculosis GroES (Gene Rv3814c)</td>
			<td>BEI Resources</td>
			<td>NR-49223</td>
			<td>Primary antibody</td>
		</tr>
		<tr>
			<td>Monoclonal Anti-Mycobacterium tuberculosis LpqH (Gene Rv3763)</td>
			<td>BEI Resources</td>
			<td>NR-13792</td>
			<td>Primary antibody</td>
		</tr>
		<tr>
			<td>Monocolonal Anti-Mycobacterium tuberculosis LAM, Clone CS-35</td>
			<td>BEI Resources</td>
			<td>NR-13811</td>
			<td>Primary antibody</td>
		</tr>
		<tr>
			<td>NanoClean 1070</td>
			<td>Fischione Instruments</td>
			<td></td>
			<td>For plasma cleaning of the TEM grid</td>
		</tr>
		<tr>
			<td>Nanosight equipped with syringe pump and computer with NanoSight NTA software</td>
			<td>Malvern Panalytical</td>
			<td>NS300</td>
			<td></td>
		</tr>
		<tr>
			<td>Nitrocellulose membrane, Roll, 0.2 &#956;m</td>
			<td>BioRad</td>
			<td>1620112</td>
			<td></td>
		</tr>
		<tr>
			<td>NuPAGE 4-12% Bis-Tris Protein Gels</td>
			<td>ThermoFisher Scientific</td>
			<td>NP0323BOX</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate-buffered Saline, 1X without calcium and magnesium</td>
			<td>Corning</td>
			<td>21-040-CV</td>
			<td></td>
		</tr>
		<tr>
			<td>Pierce BCA Protein Assay Kit</td>
			<td>ThermoFisher Scientific</td>
			<td>23225</td>
			<td></td>
		</tr>
		<tr>
			<td>PowerPac Basic Power Supply</td>
			<td>BioRad</td>
			<td>1645050</td>
			<td></td>
		</tr>
		<tr>
			<td>qEV Original 35 nm 5/pk</td>
			<td>IZON Science</td>
			<td>SP5-USD</td>
			<td>SEC column</td>
		</tr>
		<tr>
			<td>SDS sample buffer</td>
			<td>Boster</td>
			<td>AR1112</td>
			<td>In-house recipe used in this procedure, however this product is equivalent</td>
		</tr>
		<tr>
			<td>SDS-PAGE gel chamber</td>
			<td>ThermoFisher Scientific</td>
			<td>EI0001</td>
			<td></td>
		</tr>
		<tr>
			<td>Sigmafast BCIP/NBT</td>
			<td>Millipore Sigma</td>
			<td>B5655</td>
			<td></td>
		</tr>
		<tr>
			<td>Silver Stain Plus Kit</td>
			<td>BioRad</td>
			<td>1610449</td>
			<td>In-house protocol used in this procedure, however this kit is equivalent</td>
		</tr>
		<tr>
			<td>Uranyl Acetate</td>
			<td>Electron Microscopy Sciences</td>
			<td>22400</td>
			<td></td>
		</tr>
	</tbody>
</table>

mycobacterium tuberculosis extracellular vesicle enrichment through size exclusion chromatography

The role of extracellular vesicles (EVs) in the context of bacterial infection has emerged as a new avenue for understanding microbial physiology. Specifically, Mycobacterium tuberculosis (Mtb) EVs play a role in the host-pathogen interaction and response to environmental stress. Mtb EVs are also highly antigenic and show potential as vaccine components. The most common method for purifying Mtb EVs is density gradient ultracentrifugation. This process has several limitations, including low throughput, low yield, reliance on expensive equipment, technical challenges, and it can negatively impact the resulting preparation. Size exclusion chromatography (SEC) is a gentler alternative method that combats many of the limitations of ultracentrifugation. This protocol demonstrates that SEC is effective for Mtb EV enrichment and produces high-quality Mtb EV preparations of increased yield in a rapid and scalable manner. Additionally, a comparison to density gradient ultracentrifugation by quantification and qualification procedures demonstrates the benefits of SEC. While the evaluation of EV quantity (nanoparticle tracking analysis), phenotype (transmission electron microscopy), and content (Western blotting) is tailored to Mtb EVs, the workflow provided can be applied to other mycobacteria.

Culture filtrate protein (CFP) from Mycobacterium tuberculosis (Mtb) was concentrated, quantified, and then 3 mg of material was applied to a size exclusion chromatography (SEC) column. The protein and particle concentrations were enumerated by BCA and NTA, respectively. Expected ranges for protein and particle recovery plus the exact values obtained for these results are reported in Table 1. Values much higher than these ranges may indicate contamination or column integrity issues. Values signi...

Watch this Scientific Journal Video about Mycobacterium tuberculosis Extracellular Vesicle Enrichment through Size Exclusion Chromatography at JoVE.com

Mycobacterium tuberculosis Extracellular Vesicle Enrichment through Size Exclusion Chromatography

This protocol describes size exclusion chromatography, a facile and reproducible technique for enriching Mycobacterium tuberculosis extracellular vesicles from culture supernatants.

Mycobacterium tuberculosis Extracellular Vesicle Enrichment through Size Exclusion Chromatography

The role of extracellular vesicles (EVs) in the context of bacterial infection has emerged as a new avenue for understanding microbial physiology. ...

mycobacterium-tuberculosis-extracellular-vesicle-enrichment-through

Research

JoVE Journal

Immunology and Infection

2.3K Views.  Colorado State University. This protocol describes size exclusion chromatography, a facile and reproducible technique for enriching Mycobacterium tuberculosis extracellular vesicles from culture supernatants. 

Video: Mycobacterium tuberculosis Extracellular Vesicle Enrichment through Size Exclusion Chromatography

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 ...

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 ...

A Novel Microdissection Approach to Recovering Mycobacterium tuberculosis Specific Transcripts from Formalin Fixed Paraffin Embedded Lung Granulomas

Microdissection has been used for the examination of tissues at DNA, RNA, and protein levels for over a decade. Laser capture microscopy (LCM) is the most common microdissection technique used today. In this technique, a laser is used to focally melt a thermoplastic membrane that overlies a dehydrated tissue section1. The tissue section composite is then lifted and separated from the membrane. Although this technique can be used successfully for tissue examination, it is time consuming and expensive. Furthermore, the successful completion of procedures using this technique requires the use of a laser, thus limiting its use. A new more affordable and practical microdissection approach called mesodissection is a possible solution to the pitfalls of LCM. This technique employs the MESO-1/MeSectr system to mill the desired tissue from a slide mounted tissue sample while concurrently dispensing and aspirating fluid to recover the desired tissue sample into a consumable mill bit. Before the dissection process begins, the user aligns the formalin fixed paraffin embedded (FFPE) slide with a hematoxylin and eosin stained (H&#38;E) reference slide. Thereafter, the operator annotates the desired dissection area and proceeds to dissect the appropriate segment. The program generates an archived image of the dissection. The main advantage of mesodissection is the short duration needed to dissect a slide, taking an average of ten minutes from set up to sample generation in this experiment. Additionally, the system is significantly more cost effective and user friendly. A slight disadvantage is that it is not as precise as laser capture microscopy. In this article we demonstrate how mesodissection can be used to extract RNA from slides from FFPE granulomas caused by Mycobacterium tuberculosis (Mtb).

A Novel Microdissection Approach to Recovering Mycobacterium tuberculosis Specific Transcripts from Formalin Fixed Paraffin Embedded Lung Granulomas

Microdissection has been extensively employed for the examination of DNA, RNA, and protein within tissue. Laser capture microscopy (LCM) is the most commonly used method, but a new milling technique, mesodissection, is recently available. We demonstrate RNA extraction from mesodissected formalin fixed paraffin embedded tissue slides of Mycobacterium tuberculosis granulomas.

Microdissection has been used for the examination of tissues at DNA, RNA, and protein levels for over a decade. Laser capture microscopy (LCM) is the most ...

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 ...

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.

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.

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

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 ...

Evaluation of Extracellular Vesicle Function During Malaria Infection

Malaria is a life-threatening disease caused by Plasmodium parasites, with P. falciparum being the most prevalent on the African continent and responsible for most malaria-related deaths globally. Several factors including parasite sequestration in tissues, vascular dysfunction, and inflammatory responses influence the evolution of the disease in malaria-infected people. P. falciparum-infected red blood cells (iRBCs) release small extracellular vesicles (EVs) containing different kinds of cargo molecules that mediate pathogenesis and cellular communication between parasites and host. EVs are efficiently taken up by cells in which they modulate their function. Here we discuss strategies to address the role of EVs in parasite-host interactions. First, we describe a straightforward method for labeling and tracking EV internalization by endothelial cells, using a green cell linker dye. Second, we report a simple way to measure permeability across an endothelial cell monolayer by using a fluorescently labeled dextran. Finally, we show how to investigate the role of small non-coding RNA molecules in endothelial cell function.

In this work, we describe protocols to investigate the role of extracellular vesicles (EVs) released by Plasmodium falciparum infected erythrocytes. In particular, we focus on the interactions of EVs with endothelial cells.

Malaria is a life-threatening disease caused by Plasmodium parasites, with P. falciparum being the most prevalent on the African continent and responsible ...