This work was supported by the National Science Centre, Poland, grant number 2019/33/B/NZ5/00647. We would like to thank Professor Tomasz Gosiewski and Agnieszka Krawczyk from the Department of Molecular Medical Microbiology, Jagiellonian University Medical College for their invaluable help in the detection of bacterial DNA in EVs.

1. Preparation of ultracentrifuge tubes
<ol>
	<li>Use sterile, single-use tubes. If this is not possible, reuse the ultracentrifuge tubes after washing them with a detergent using a sterile Pasteur pipette or other single-use applicators. Remember that ultracentrifuge tubes should be dedicated to one type of centrifuged material (cell culture supernatant/serum/plasma) and species (human/mouse/etc.).</li>
	<li>After a detergent wash, rinse the ultracentrifuge tubes with deionized, LPS-free water 3x. 
	NOTE: Do not use low-quality water.</li>
	<li>Dry the ultracentrifuge tubes, and then fill them up with 70% ethanol. Leave the tubes with 70% ethanol for overnight disinfection. Remove the ethanol and dry the tubes again.</li>
	<li>Place the tubes and caps in sterilization packaging and close them tightly. Use the plasma or gas (ethylene oxide) sterilization method18,19. Store the ultracentrifuge tubes enclosed in the sterilization packaging in a dry place, and use them before the expiration date. 
	&#8203;NOTE: Perform monthly monitoring of the LPS level in phosphate buffered saline (PBS) and the water used for EVs isolation. Monitoring should include the tubes as well (e.g., by testing the water [wash control] which has been stored in the ultracentrifuge tubes overnight at room temperature [RT]).</li>
</ol>
2. Preparation of EV-depleted low-endotoxin fetal bovine serum (EE-FBS)
<ol>
	<li>Ensure to use ultra-low endotoxin FBS (commercially available; see Table of Materials; &#60;0.1 EU/mL).</li>
	<li>Place a bottle of ultra-low endotoxin FBS in a water bath and incubate at 56 &#176;C for 30 min. This step is required to inactivate the complement system.</li>
	<li>Pipette the inactivated FBS to ultracentrifuge tubes and centrifuge it at 100,000 x g for 4 h at 4 &#176;C. Collect the supernatant into sterile 50 mL tubes, ensuring not to exceed 45 mL per tube to avoid cap contamination and wetting the ring of the tube.</li>
	<li>Store the EE-FBS serum prepared in this manner at -20 &#176;C. Check the concentration of LPS in EE-FBS (step 6). The LPS concentration should be at the same level as before ultracentrifugation.</li>
</ol>
3. Cell culture
<ol>
	<li>For this study, culture SW480 and SW620 cell lines in Dulbecco&#39;s modified Eagle&#39;s medium (DMEM) with 4.5 g/L glucose, L- glutamine, sodium pyruvate, and gentamicin (50 &#181;L/mL) supplemented with 10% EE-FBS accordingly in 75 cm2 culture flasks using aseptic technique. Seed nearly 4.5 x 106 cells&#160;and 6.5 x 106 cells per flask for SW480 and SW620, respectively.</li>
	<li>Collect the supernatants twice a week (~10 mL per flask) when the cells reach full confluency (~13.5 x 106 and 20 x 106 cells per flask for SW480 and SW620, respectively), and split. Ensure that the viability of cells is not less than 99% and that the cells are cultured at 37 &#176;C in a 5% CO2 atmosphere.</li>
	<li>Collect supernatants from the cell culture into appropriately labeled 15 mL tubes. Centrifuge the collected supernatants at 500 x g for 5 min at RT to remove cell debris.</li>
	<li>Collect the supernatants carefully, avoid aspirating debris, place in labeled tubes, and centrifuge again at 3,200 x g for 12 min at 4 &#176;C.</li>
	<li>Collect supernatants from the second centrifugation step into sterile, labeled 50 mL tubes. Avoid wetting the edges of tubes. Ensure that the volume of supernatant does not exceed 45 mL and that the tubes are kept vertically.</li>
	<li>Wrap the tube&#39;s cap with a sterile transparent film and store supernatants in the vertical position at -80 &#176;C. 
	&#8203;NOTE: Perform monthly control of Mycoplasma spp. and LPS contamination in fresh culture supernatants (step 6). If the level of endotoxin in the supernatants exceeds 0.05 EU/mL, verify at which stage contamination might have occurred and restart the process from the beginning. If contamination of the cell culture by Mycoplasma spp. is detected, isolation of the EVs from such supernatants should be discontinued.</li>
</ol>
4. Isolation of EVs from cell culture supernatants
<ol>
	<li>Prepare 0.22 &#181;m syringe filters and syringes of proper volume. Prepare two tubes with culture supernatants (90 mL).</li>
	<li>Fill the syringe with the supernatant and attach the filter to the needle adapter. Place the filled syringe with the filter over a 50 mL tube. Push on the plunger flange and collect ~90 mL of filtrate.</li>
	<li>Pipette the filtrate (7 mL) to the ultracentrifuge tubes (ensuring that the same volume is pipetted to each tube for proper balance) and centrifuge at 100,000 x g for 2 h at 4 &#176;C. 
	NOTE: The efficiency of EVs pelleting depends on many factors (e.g., rotor type, its k-factor, migration path length, the viscosity of the medium, etc.), which need to be optimized for better recovery of EVs20.</li>
	<li>Discard the supernatant using a sterile Pasteur pipette. Collect the remaining pellets using long, filtered pipette tips and pool them into two ultracentrifuge tubes. Fill them up to 7 mL with filtered endotoxin-free PBS to rinse the EVs.</li>
	<li>Centrifuge the PBS-resuspended pellets at 100,000 x g for 2 h at 4 &#176;C. Completely remove the supernatant using a sterile Pasteur pipette, and add 200 &#181;L of filtered, endotoxin-free PBS to both tubes to resuspend the EVs. Gently pipette the EVs pellet to collect all of the EVs.</li>
	<li>Transfer the EVs suspension into a sterile 1.5 mL test tube (if possible, use a low protein binding tube). Retain 10 &#181;L of the EV suspension for preparing a dilution for nanoparticle tracking analysis (NTA) and for other purposes (e.g., protein concentration measurement).</li>
	<li>Dilute the EVs with filtered PBS (1:1,000) for measurements by NTA, according to the manufacturer&#39;s instructions. Secure the EV tubes by wrapping the cap with a sterile transparent film. Store the EVs at -80 &#176;C.</li>
</ol>
5. Specific markers detection by western blotting
<ol>
	<li>Determine the protein level in the samples (e.g., by Bradford assay), and prepare the samples (20 &#181;g) with loading buffer. Prepare the loading buffer by mixing 5 &#181;L of sample buffer (4x) and 2 &#181;L of sample reducing agent (10x) to a total volume of 20 &#181;L. Incubate the samples at 70 &#176;C for 10 min.</li>
	<li>Prepare polyacrylamide gels with SDS (10%-14%) and load the 20 &#181;g of EVs to each well.</li>
	<li>Run the electrophoresis with running buffer (30 g of Tris, 144 g of glycine, 10% SDS per 1 L) for 45 min at 150 V.</li>
	<li>Perform semi-dry transfer of proteins from the gel onto the polyvinylidene difluoride (PVDF) membrane in a transfer machine with Towbin buffer (1.51 g of Tris, 7.2 g of glycine, 10% methanol per 0.5 L) at 25 V for 1 h.</li>
	<li>Place the membrane in TBST buffer (1 mL of Tween, 100 mL of Tris-buffered saline (TBS 10x) per 1 L) for blocking with 1% bovine serum albumin (BSA) in TBST buffer, and incubate for 1 h on the rocker at RT.</li>
	<li>Add diluted (1:1,000) antibodies, anti-CD91 (clone#D8O1A) or anti-Alix1 (clone#3A9), in 1% BSA and incubate with the membrane overnight at 4&#160;&#176;C on the rocker.&#160;Remove antibodies and wash membrane 3x with 10 mL of 1x TBST for 10 minutes.</li>
	<li>Add goat anti-rabbit or goat anti-mouse (dilution: 1:2,000) secondary antibody conjugated with horseradish peroxidase, depending on the primary antibody on the membrane, and incubate for 1 h on the rocker at RT.&#160;Remove antibodies and wash membrane 3x with 10 mL of 1x TBST for 10 minutes.</li>
	<li>Mix the substrate and luminol at a 1:1 ratio to obtain a 1 mL solution. Pour the solution on the membrane. Place the membrane immediately in the measuring chamber of the imaging system, choose the chemiluminescence module, and visualize protein bands on the screen.</li>
</ol>
6. Measurement of endotoxin level by Limulus Amebocyte Lysate test (LAL)
<ol>
	<li>Perform chromogenic LAL measurement of the endotoxin level, according to the manufacturer&#39;s recommendation. Briefly, use the method based on the interaction of the endotoxin with the limulus amebocyte lysate (LAL). The detection limit of this method is 0.005 EU/mL. 
	NOTE: LAL assay, despite its limitations, currently remains the standard method for detecting and quantifying endotoxin contamination in different kinds of solutions and other products used in science or medicine8. The limiting factor of this kit is the stability of the reconstituted amebocyte lysate solution, which is stable for only 1 week at -20 &#176;C if frozen immediately after reconstitution.</li>
	<li>Use a tenfold dilution of EVs and other samples and a 50-fold dilution of serum. For further experiments, use only low-endotoxin reagents such as EE-FBS, DMEM, PBS, RPMI (&#60;0.005 EU/mL), and LPS-free culture supernatants.</li>
</ol>
7. Detection of prokaryotic 16S rRNA gene in EV samples
<ol>
	<li>Isolate DNA from the EV samples. Try to keep the reagents and the site of isolation aseptic. Measure the DNA concentration and quality (e.g., using a spectrophotometer).</li>
	<li>Perform polymerase chain reaction (PCR), as described previously21. Prepare 1.5% agarose gel with ethidium bromide or SYBR green to visualize the PCR products in ultraviolet light (UV).</li>
	<li>Run electrophoresis of the sample and weight marker with TRIS-acetate-EDTA buffer at 75 V for 45 min. Visualize DNA bands using the imaging system.</li>
</ol>
8. Determination of effective LPS concentration for stimulation in human monocyte model
<ol>
	<li>Prepare 2 x 106 monocytes/mL of monocyte suspension in RPMI 1640 supplemented with L-glutamine, glucose, and 2% EE-FBS. Add 50 &#181;L of the suspension per well of a 96-well tissue culture plate22.</li>
	<li>Add a proper volume of LPS or culture medium to obtain the following final concentrations: 0 pg/mL (control), 10 pg/mL, 50 pg/mL, 100 pg/mL, 1 ng/mL, and 100 ng/mL, in 100 &#181;L total volume of cell suspension. Make triplicates of each LPS concentration.</li>
	<li>Culture the cells for 18 h at 37 &#176;C, 5% CO2. Collect the supernatant.</li>
	<li>Spin down the supernatant at 2,000 x g for 5 min. Transfer the supernatants into new tubes. Measure TNF8,23 and IL-1023 concentration in collected supernatants with the cytometric beads array (CBA) human cytokine kit, according to the manufacturer&#39;s procedure, with a flow cytometer.</li>
</ol>

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The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be constructed as a potential conflict of interest.

In the last few years, methods for proper EVs isolation have become increasingly important, enabling their further reliable analyses, for example, in the context of obtaining reliable omics and functional data24. Based on previous research experience, it seems that not only the type of isolation method, but also other conditions during this procedure may be important. The use of EV-depleted FBS is widely recognized as a necessity25,26; how...

Extracellular vesicles (EVs), according to the MISEV 2018 nomenclature, are a collective term describing various subtypes of cell-secreted membranous vesicles that play crucial roles in numerous physiological and pathological processes1,2. Moreover, EVs show promise as novel biomarkers for various diseases, as well as therapeutic agents and drug delivery vehicles. However, realizing their full potential is difficult as there are still many technical obstacles related to their acquisition3. One such challenge is the isolation of endotoxin-free EVs, which has been neglected in many cases. One of the most common endotoxins is lipopolysaccharide (LPS), which is a major component of gram-negative bacterial cell walls and can cause an acute inflammatory response, owing to the release of a large number of inflammatory cytokines by various cells4,5. LPS induces a response by binding to LPS binding protein, followed by interaction with the CD14/TLR4/MD2 complex on myeloid cells. This interaction leads to the activation of MyD88- and TRIF-dependent signaling pathways, which in turn triggers the nuclear factor kappa B (NFkB). Translocation of NFkB to the nucleus initiates the production of cytokines6. Monocytes and macrophages are highly sensitive to LPS, and their exposure to LPS results in a release of inflammatory cytokines and chemokines (e.g., IL-6, IL-12, CXCL8, and TNF-&#945;)7,8. The CD14 structure enables the binding of different LPS species with similar affinity and serves as a co-receptor for other toll-like receptors (TLRs) (TLR1, 2, 3, 4, 6, 7, and 9)6. The number of studies being conducted on the effects of EVs on monocytes/macrophages is still increasing9,10,11. Especially from the perspective of studying the functions of monocytes, their subpopulations, and other immune cells, the presence of endotoxin and even their masked presence in EVs is of great importance12. The overlooked contamination of EVs with endotoxins may lead to misleading conclusions and hide their true biological activity. In other words, working with monocytic cells requires confidence in the absence of endotoxin contamination13. Potential sources of endotoxins can be water, commercially obtained media and sera, media components and additives, laboratory glassware, and plasticware5,14,15.
Therefore, this study aimed to develop a protocol for the isolation of low endotoxin-containing EVs. The protocol provides simple hints on how to avoid endotoxin contamination during EVs isolation instead of removing endotoxins from EVs. Previously, many protocols have been presented on how to remove endotoxins from, for example, engineered nanoparticles used in nanomedicine; however, none of them are useful for biological structures such as EVs. The effective depyrogenation of nanoparticles can be carried out by ethanol or acetic acid rinsing, heating at 175 &#176;C for 3 h, &#947; irradiation, or triton X-100 treatment; however, these procedures lead to the destruction of EVs16,17.
The presented protocol is a pioneering study focused on avoiding endotoxin impurities in EVs, unlike previous studies on the effect of EVs on monocytes9. Applying proposed principles to laboratory practice may help to obtain reliable research results, which can be crucial when considering the potential use of EVs as therapeutic agents in the clinic12.

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	<tbody>
		<tr>
			<td>&#160;Alix (3A9) Mouse mAb&#160;</td>
			<td>Cell Signaling Technology</td>
			<td>2171</td>
			<td></td>
		</tr>
		<tr>
			<td>1250ul Filter Universal Pipette Tips, Clear, Polypropylene, Non-Pyrogenic</td>
			<td>GoogLab Scientific</td>
			<td>GBFT1250-R-NS</td>
			<td></td>
		</tr>
		<tr>
			<td>BD FACSCanto II Flow Cytometr</td>
			<td>BD Biosciences</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>CBA Human Th1/Th2 Cytokine Kit II</td>
			<td>BD Biosciences</td>
			<td>551809</td>
			<td></td>
		</tr>
		<tr>
			<td>CD9 (D8O1A) Rabbit mAb</td>
			<td>Cell Signaling Technology</td>
			<td>13174</td>
			<td></td>
		</tr>
		<tr>
			<td>ChemiDoc Imaging System</td>
			<td>Bio-Rad Laboratories, Inc.&#160;</td>
			<td>17001401</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM (Dulbecco&#8217;s Modified Eagle&#8217;s Medium)&#160;</td>
			<td>Corning</td>
			<td>10-013-CV</td>
			<td></td>
		</tr>
		<tr>
			<td>ELX800NB, Universal Microplate Reader</td>
			<td>BIO-TEK INSTRUMENTS, INC</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum</td>
			<td>Gibco</td>
			<td>16000044</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum South America Ultra Low Endotoxin</td>
			<td>&#160;Biowest</td>
			<td>&#160;S1860-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Gentamicin, 50 mg/mL</td>
			<td>&#160;PAN &#8211; Biotech</td>
			<td>P06-13100</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat anti-Mouse IgG- HRP</td>
			<td>Santa Cruz Biotechnology</td>
			<td>sc-2004</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat anti-Rabbit IgG- HRP</td>
			<td>Santa Cruz Biotechnology</td>
			<td>sc-2005</td>
			<td></td>
		</tr>
		<tr>
			<td>Immun-Blot PVDF Membrane</td>
			<td>Bio-Rad Laboratories, Inc.&#160;</td>
			<td>1620177</td>
			<td></td>
		</tr>
		<tr>
			<td>LPS from Salmonella abortus equi S-form (TLRGRADE)</td>
			<td>&#160;Enzo Life Sciences, Inc.</td>
			<td>ALX-581-009-L002</td>
			<td></td>
		</tr>
		<tr>
			<td>Mini Trans-Blot Electrophoretic Transfer Cell</td>
			<td>Bio-Rad Laboratories, Inc.&#160;</td>
			<td>1703930</td>
			<td></td>
		</tr>
		<tr>
			<td>Nanoparticle Tracking Analysis&#160;</td>
			<td>Malvern Instruments Ltd</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>NuPAGE LDS Sample Buffer (4X)</td>
			<td>&#160;Invitrogen</td>
			<td>&#160;NP0007</td>
			<td></td>
		</tr>
		<tr>
			<td>NuPAGE Sample Reducing Agent (10x)</td>
			<td>&#160;Invitrogen</td>
			<td>NP0004</td>
			<td></td>
		</tr>
		<tr>
			<td>Parafilm</td>
			<td>Sigma Aldrich</td>
			<td>P7793</td>
			<td>transparent film</td>
		</tr>
		<tr>
			<td>Perfect 100-1000 bp DNA Ladder</td>
			<td>EURx</td>
			<td>E3141-01&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>PierceTM Chromogenic Endotoxin Quant Kit</td>
			<td>Thermo Scientific</td>
			<td>A39552</td>
			<td></td>
		</tr>
		<tr>
			<td>PP Oak Ridge Tube with sealing caps</td>
			<td>Thermo Scientific</td>
			<td>3929, 03613</td>
			<td></td>
		</tr>
		<tr>
			<td>RPMI 1640</td>
			<td>RPMI-1640 (Gibco)</td>
			<td>11875093</td>
			<td></td>
		</tr>
		<tr>
			<td>SimpliAmp Thermal Cycler</td>
			<td>Applied Biosystem</td>
			<td>A24811</td>
			<td></td>
		</tr>
		<tr>
			<td>Sorvall wX+ ULTRA SERIES Centrifuge with T-1270 rotor</td>
			<td>Thermo Scientific</td>
			<td>75000100</td>
			<td></td>
		</tr>
		<tr>
			<td>Sub-Cell GT Horizontal Electrophoresis System</td>
			<td>Bio-Rad Laboratories, Inc.&#160;</td>
			<td>1704401</td>
			<td></td>
		</tr>
		<tr>
			<td>SuperSignal West Pico PLUS Chemiluminescent Substrate</td>
			<td>Thermo Scientific</td>
			<td>34577</td>
			<td></td>
		</tr>
		<tr>
			<td>SW480 cell line</td>
			<td>American Type Culture Collection(ATCC)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>SW480 cell line</td>
			<td>American Type Culture Collection (ATCC)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Syringe filter 0.22 um</td>
			<td>TPP</td>
			<td>99722</td>
			<td></td>
		</tr>
		<tr>
			<td>Trans-Blot SD Semi-Dry Transfer Cell</td>
			<td>Bio-Rad Laboratories, Inc.&#160;</td>
			<td>1703940</td>
			<td>Transfer machine</td>
		</tr>
		<tr>
			<td>Transfer pipette, 3.5 mL</td>
			<td>SARSTEDT</td>
			<td>86.1171.001</td>
			<td></td>
		</tr>
	</tbody>
</table>

isolation of low endotoxin content extracellular vesicles derived from cancer cell lines

Extracellular vesicles (EVs) are a heterogeneous population of membrane vesicles released by cells in vitro and in vivo. Their omnipresence and significant role as carriers of biological information make them intriguing study objects, requiring reliable and repetitive protocols for their isolation. However, realizing their full potential is difficult as there are still many technical obstacles related to their research (like proper acquisition). This study presents a protocol for the isolation of small EVs (according to the MISEV 2018 nomenclature) from the culture supernatant of tumor cell lines based on differential centrifugation. The protocol includes guidelines on how to avoid contamination with endotoxins during the isolation of EVs and how to properly evaluate them. Endotoxin contamination of EVs can significantly hinder subsequent experiments or even mask their true biological effects. On the other hand, the overlooked presence of endotoxins may lead to incorrect conclusions. This is of particular importance when referring to cells of the immune system, including monocytes, because monocytes constitute a population that is especially sensitive to endotoxin residues. Therefore, it is highly recommended to screen EVs for endotoxin contamination, especially when working with endotoxin-sensitive cells such as monocytes, macrophages, myeloid-derived suppressor cells, or dendritic cells.

A prerequisite or obligatory step for this protocol is the exclusion of possible endotoxin contamination from reagents. All the reagents being used, such as FBS, DMEM, RPMI, PBS, and even ultracentrifuge tubes, must be endotoxin-free (&#60;0.005 EU/mL). Maintaining the regime of no endotoxin contamination is not easy as, for example, the regular/standard serum for cell culture can be its rich source (0.364 EU/mL; see Table 1).
Although this protocol was developed to isolate EV...

Watch this Scientific Journal Video about Isolation of Low Endotoxin Content Extracellular Vesicles Derived from Cancer Cell Lines at JoVE.com

Isolation of Low Endotoxin Content Extracellular Vesicles Derived from Cancer Cell Lines

The proposed protocol includes guidelines on how to avoid contamination with endotoxin during the isolation of extracellular vesicles from cell culture supernatants, and how to properly evaluate them.

Extracellular vesicles (EVs) are a heterogeneous population of membrane vesicles released by cells in vitro and in vivo. Their omnipresence and ...

isolation-low-endotoxin-content-extracellular-vesicles-derived-from

Research

JoVE Journal

Immunology and Infection

929 Views.  Jagiellonian University Medical College. The proposed protocol includes guidelines on how to avoid contamination with endotoxin during the isolation of extracellular vesicles from cell culture supernatants, and how to properly evaluate them.

Video: Isolation of Low Endotoxin Content Extracellular Vesicles Derived from Cancer Cell Lines

Derivation of Thymic Lymphoma T-cell Lines from Atm-/- and p53-/- Mice

Established cell lines are a critical research tool that can reduce the use of laboratory animals in research. Certain strains of genetically modified mice, such as Atm-/- and p53-/- consistently develop thymic lymphoma early in life 1,2, and thus, can serve as a reliable source for derivation of murine T-cell lines. Here we present a detailed protocol for the development of established murine thymic lymphoma T-cell lines without the need to add interleukins as described in previous protocols 1,3. Tumors were harvested from mice aged three to six months, at the earliest indication of visible tumors based on the observation of hunched posture, labored breathing, poor grooming and wasting in a susceptible strain 1,4. We have successfully established several T-cell lines using this protocol and inbred strains ofAtm-/- [FVB/N-Atmtm1Led/J] 2 and p53-/- [129/S6-Trp53tm1Tyj/J] 5 mice. We further demonstrate that more than 90% of the established T-cell population expresses CD3, CD4 and CD8. Consistent with stably established cell lines, the T-cells generated by using the present protocol have been passaged for over a year.

Derivation of Thymic Lymphoma T-cell Lines from Atm-/- and p53-/- Mice

In this video we demonstrate a protocol to establish mouse thymic lymphoma cell lines. By following this protocol, we have successfully established several T-cell lines from Atm-/- and p53-/- mice with thymic lymphoma.

Established cell lines are a critical research tool that can reduce the use of laboratory animals in research. Certain strains of genetically modified ...

Establishment of Epstein-Barr Virus Growth-transformed Lymphoblastoid Cell Lines

Infection of B cells with Epstein-Barr virus (EBV) leads to proliferation and subsequent immortalization, resulting in establishment of lymphoblastoid cell lines (LCL) in vitro. Since LCL are latently infected with EBV, they provide a model system to investigate EBV latency and virus-driven B cell proliferation and tumorigenesis1. LCL have been used to present antigens in a variety of immunologic assays2, 3. In addition, LCL can be used to generate human monoclonal antibodies4, 5 and provide a potentially unlimited source when access to primary biologic materials is limited6, 7.
A variety of methods have been described to generate LCL. Earlier methods have included the use of mitogens such as phytohemagglutinin, lipopolysaccharide8, and pokeweed mitogen9 to increase the efficiency of EBV-mediated immortalization. More recently, others have used immunosuppressive agents such as cyclosporin A to inhibit T cell-mediated killing of infected B cells7, 10-12.
The considerable length of time from EBV infection to establishment of cell lines drives the requirement for quicker and more reliable methods for EBV-driven B cell growth transformation. Using a combination of high titer EBV and an immunosuppressive agent, we are able to consistently infect, transform, and generate LCL from B cells in peripheral blood. This method uses a small amount of peripheral blood mononuclear cells that are infected in vitroclusters of cells can be demonstrated. The presence of CD23 with EBV in the presence of FK506, a T cell immunosuppressant. Traditionally, outgrowth of proliferating B cells is monitored by visualization of microscopic clusters of cells about a week after infection with EBV. Clumps of LCL can be seen by the naked eye after several weeks. We describe an assay to determine early if EBV-mediated growth transformation is successful even before microscopic clusters of cells can be demonstrated. The presence of CD23hiCD58+ cells observed as early as three days post-infection indicates a successful outcome.

We describe a method for generating transformed B cell lines using Epstein-Barr virus. We also illustrate a novel assay that can identify B cells destined to undergo transformation as early as three days after infection.

Infection of B cells with Epstein-Barr virus (EBV) leads to proliferation and subsequent immortalization, resulting in establishment of lymphoblastoid ...

Isolation of Precursor B-cell Subsets from Umbilical Cord Blood

Umbilical cord blood is highly enriched for hematopoietic progenitor cells at different lineage commitment stages. We have developed a protocol for isolating precursor B-cells at four different stages of differentiation. Because genes are expressed and epigenetic modifications occur in a tissue specific manner, it is vital to discriminate between tissues and cell types in order to be able to identify alterations in the genome and the epigenome that may lead to the development of disease. This method can be adapted to any type of cell present in umbilical cord blood at any stage of differentiation.	
This method comprises 4 main steps. First, mononuclear cells are separated by density centrifugation. Second, B-cells are enriched using biotin conjugated antibodies that recognize and remove non B-cells from the mononuclear cells. Third the B-cells are fluorescently labeled with cell surface protein antibodies specific to individual stages of B-cell development. Finally, the fluorescently labeled cells are sorted and individual populations are recovered. The recovered cells are of sufficient quantity and quality to be utilized in downstream nucleic acid assays.

Here we describe a protocol for isolating subsets of precursor B-cells from umbilical cord blood. A sufficient quantity and quality of nucleic acids may be extracted from the cells and used in subsequent assays utilizing DNA or RNA.

Umbilical cord blood is highly enriched for hematopoietic progenitor cells at different lineage commitment stages. We have developed a protocol for ...

Generation and Multi-phenotypic High-content Screening of Coxiella burnetii Transposon Mutants

Invasion and colonization of host cells by bacterial pathogens depend on the activity of a large number of prokaryotic proteins, defined as virulence factors, which can subvert and manipulate key host functions. The study of host/pathogen interactions is therefore extremely important to understand bacterial infections and develop alternative strategies to counter infectious diseases. This approach however, requires the development of new high-throughput assays for the unbiased, automated identification and characterization of bacterial virulence determinants. Here, we describe a method for the generation of a GFP-tagged mutant library by transposon mutagenesis and the development of high-content screening approaches for the simultaneous identification of multiple transposon-associated phenotypes. Our working model is the intracellular bacterial pathogen Coxiellaburnetii, the etiological agent of the zoonosis Q fever, which is associated with severe outbreaks with a consequent health and economic burden. The obligate intracellular nature of this pathogen has, until recently, severely hampered the identification of bacterial factors involved in host pathogen interactions, making of Coxiella the ideal model for the implementation of high-throughput/high-content approaches.

Generation and Multi-phenotypic High-content Screening of Coxiella burnetii Transposon Mutants

Coxiella burnetii is an obligate intracellular Gram-negative bacterium responsible for the zoonotic disease Q fever. Here we describe methods for the generation of Coxiella fluorescent transposon mutants as well as the automated identification and analysis of the resulting internalization, replication and cytotoxic phenotypes.

Invasion and colonization of host cells by bacterial pathogens depend on the activity of a large number of prokaryotic proteins, defined as virulence ...

Flow Virometry to Analyze Antigenic Spectra of Virions and Extracellular Vesicles

Cells release small extracellular vesicles (EVs) into the surrounding media. Upon virus infection cells also release virions that have the same size of some of the EVs. Both virions and EVs carry proteins of the cells that generated them and are antigenically heterogeneous. In spite of their diversity, both viruses and EVs were characterized predominantly by bulk analysis. Here, we describe an original nanotechnology-based high throughput method that allows the characterization of antigens on individual small particles using regular flow cytometers. Viruses or extracellular vesicles were immunocaptured with 15 nm magnetic nanoparticles (MNPs) coupled to antibodies recognizing one of the surface antigens. The captured virions or vesicles were incubated with fluorescent antibodies against other surface antigens. The resultant complexes were separated on magnetic columns from unbound antibodies and analyzed with conventional flow cytometers triggered on fluorescence. This method has wide applications and can be used to characterize the antigenic composition of any viral- and non-viral small particles generated by cells in vivo and in vitro. Here, we provide examples of the usage of this method to evaluate the distribution of host cell markers on individual HIV-1 particles, to study the maturation of individual Dengue virions (DENV), and to investigate extracellular vesicles released into the bloodstream.

Viruses or extracellular vesicles were immunocaptured with 15 nm magnetic nanoparticles coupled to antibodies recognizing surface antigens. The captured virions or vesicles were labeled with fluorescent antibodies against other surface antigens. The resultant complexes were separated in high magnetic field and analyzed with conventional flow cytometers triggered on fluorescence.

Cells release small extracellular vesicles (EVs) into the surrounding media. Upon virus infection cells also release virions that have the same size of ...

Isolation and Characterization of Extracellular Vesicles from Adult Schistosoma japonicum

Extracellular vesicles (EVs) are membranous vesicles released by a variety of cells into the extracellular microenvironment. EVs represent a population of heterogeneous vesicles, whose size range between 40 and 1,000 nm. Accumulated evidence indicated that EVs play important regulatory roles in pathogen-host interactions. A deep understanding of schistosome EVs should provide insights into the mechanisms underlying schistosome-host interactions, enabling development of novel strategies against schistosomiasis. Here, we aim to further study EVs functions in schistosomes by presenting a protocol for the isolation and characterization of EVs from adult Schistosoma japonicum (S. japonicum). EVs were isolated from in vitro culture medium using centrifugation combined with a commercial exosome isolation kit. The isolated S. japonicum EVs (SjEVs) typically possess a diameter of 100 - 400 nm, and are characterized by transmission electronic microscopy and western blotting. The usage of PKH67 dye-labeled SjEVs has demonstrated that SjEVs are internalized by the recipient cells. Overall, our protocol provides an alternative method for isolating EVs from adult schistosomes; the isolated SjEVs may be suitable for functional analysis.

Isolation and Characterization of Extracellular Vesicles from Adult Schistosoma japonicum

Here, we present a protocol to describe extracellular vesicles (EVs) isolation in in vitro cultured medium from adult Schistosoma japonicum.

Extracellular vesicles (EVs) are membranous vesicles released by a variety of cells into the extracellular microenvironment. EVs represent a population of ...

Isolation of Extracellular Vesicles from Murine Bronchoalveolar Lavage Fluid Using an Ultrafiltration Centrifugation Technique

Extracellular vesicles (EVs) are newly discovered subcellular components that play important roles in many biological signaling functions during physiological and pathological states. The isolation of EVs continues to be a major challenge in this field, due to limitations intrinsic to each technique. The differential ultracentrifugation with density gradient centrifugation method is a commonly used approach and is considered to be the gold standard procedure for EV isolation. However, this procedure is time-consuming, labor-intensive, and generally results in low scalability, which may not be suitable for small-volume samples such as bronchoalveolar lavage fluid. We demonstrate that an ultrafiltration centrifugation isolation method is simple and time- and labor-efficient yet provides a high recovery yield and purity. We propose that this isolation method could be an alternative approach that is suitable for EV isolation, particularly for small-volume biological specimens.

Here, we describe two extracellular vesicle isolation protocols, ultrafiltration centrifugation and ultracentrifugation with density gradient centrifugation, to isolate extracellular vesicles from murine bronchoalveolar lavage fluid samples. The extracellular vesicles derived from murine bronchoalveolar lavage fluid by both methods are quantified and characterized.

Extracellular vesicles (EVs) are newly discovered subcellular components that play important roles in many biological signaling functions during ...

Purification of High Yield Extracellular Vesicle Preparations Away from Virus

One of the major hurdles in the field of extracellular vesicle (EV) research today is the ability to achieve purified EV preparations in a viral infection setting. The presented method is meant to isolate EVs away from virions (i.e., HIV-1), allowing for a higher efficiency and yield compared to conventional ultracentrifugation methods. Our protocol contains three steps: EV precipitation, density gradient separation, and particle capture. Downstream assays (i.e., Western blot, and PCR) can be run directly following particle capture. This method is advantageous over other isolation methods (i.e., ultracentrifugation) as it allows for the use of minimal starting volumes. Furthermore, it is more user friendly than alternative EV isolation methods requiring multiple ultracentrifugation steps. However, the presented method is limited in its scope of functional EV assays as it is difficult to elute intact EVs from our particles. Furthermore, this method is tailored towards a strictly research-based setting and would not be commercially viable.

This protocol isolates extracellular vesicles (EVs) away from virions with high efficiency and yield by incorporating EV precipitation, density gradient ultracentrifugation, and particle capture to allow for a streamlined workflow and a reduction of starting volume requirements, resulting in reproducible preparations for use in all EV research.

One of the major hurdles in the field of extracellular vesicle (EV) research today is the ability to achieve purified EV preparations in a viral infection ...

Isolation and Characterization of Extracellular Vesicles Produced by Iron-limited Mycobacteria

Mycobacteria, including Mycobacterium tuberculosis (Mtb), the causative agent of human tuberculosis, naturally release extracellular vesicles (EVs) containing immunologically active molecules. Knowledge regarding the molecular mechanisms of vesicle biogenesis, the content of the vesicles, and their functions at the pathogen-host interface is very limited. Addressing these questions requires rigorous procedures for isolation, purification, and validation of EVs. Previously, vesicle production was found to be enhanced when M. tuberculosis was exposed to iron restriction, a condition encountered by Mtb in the host environment. Presented here is a complete and detailed protocol to isolate and purify EVs from iron-deficient mycobacteria. Quantitative and qualitative methods are applied to validate purified EVs.

Mycobacterium tuberculosis shows increased production and release of extracellular vesicles in response to low iron conditions. This work details a protocol for generating low iron conditions and methods for the purification and characterization of mycobacterial extracellular vesicles released in response to iron deficiency.

Mycobacteria, including Mycobacterium tuberculosis (Mtb), the causative agent of human tuberculosis, naturally release extracellular vesicles (EVs) ...

Detecting Wolbachia Strain wAlbB in Aedes albopictus Cell Lines

As a maternally harbored endosymbiont, Wolbachia infects large proportions of insect populations. Studies have recently reported the successful regulation of RNA virus transmission using Wolbachia-transfected mosquitoes. Key strategies to control viruses include the manipulation of host reproduction via cytoplasmic incompatibility and the inhibition of viral transcripts via immune priming and competition for host-derived resources. However, the underlying mechanisms of the responses of Wolbachia-transfected mosquitoes to viral infection are poorly understood. This paper presents a protocol for the in vitro identification of Wolbachia infection at the nucleic acid and protein levels in Aedes albopictus (Diptera: Culicidae) Aa23 cells to enhance the understanding of the interactions between Wolbachia and its insect vectors. Through the combined use of polymerase chain reaction (PCR), quantitative PCR, western blot, and immunological analytical methods, a standard morphologic protocol has been described for the detection of Wolbachia-infected cells that is more accurate than the use of a single method. This approach may also be applied to the detection of Wolbachia infection in other insect taxa.

Detecting Wolbachia Strain wAlbB in Aedes albopictus Cell Lines

Four methods were used to detect intracellular Wolbachia, which complemented each other and improved the detection accuracy of Wolbachia infection of Aedes albopictus-derived Aa23 and Aa23-T&#160;cured of native Wolbachia infection using antibiotics.

As a maternally harbored endosymbiont, Wolbachia infects large proportions of insect populations. Studies have recently reported the successful regulation ...