This work was supported by the Health Sciences Strategic Investment Fund Faculty Development Grant of Creighton University. The B. burgdorferi RpoC-His10X strain was kindly provided by Dr. D. Scott Samuels of the University of Montana. The E. coli strain harboring the pMAL-C5X plasmid encoding a maltose-binding protein-tagged rpoD allele was kindly provided by Dr. Frank Gherardini of Rocky Mountain Laboratories, NIAID, NIH.

1. Purification of the RNA polymerase and preparation of RNA polymerase stock
<ol>
	<li>Collect the cell pellet from 2-4 L of B. burgdorferi RpoC-His10X cultured in BSKII medium in a microaerophilic environment (34 &#176;C, 5% CO2, 3% O2) to a density of 2-4 x 107 cells/mL using previously described cell collection protocols28,29. Perform centrifugation at 10,000 x g at 4 &#176;C for 30 min in 500 mL centrifugal bottles and pour off the supernatant.</li>
	<li>Resuspend the cells in 30 mL of ice-cold HN buffer (10 mM HEPES, 10 mM NaCl, pH 8.0). Repeat the centrifugation step as described above using a 50 mL centrifuge tube and decant the supernatant. 
	NOTE: Stopping point. Freeze the cell pellet at &#8722;80 &#176;C to store cells for up to 2 weeks or immediately proceed to cell lysis.</li>
	<li>Maintain the cells, lysate, and purified proteins at 4 &#176;C or on ice unless freezing. Keep RNA polymerase in a reducing environment by adding freshly prepared DTT at a concentration of 2 mM to every buffer used in this protocol and maintain pH 8.0.</li>
	<li>Prepare lysate from the B. burgdorferi cell pellet using a commercial bacterial lysis kit following the kit instructions. Resuspend the pellet in 10-15 mL of room temperature (RT) B-PER solution without protease inhibitor and allow lysis to proceed for 5 min on ice. The lysis volume depends on the cell pellet size, as described in the kit instructions.</li>
	<li>Add protease inhibitor cocktail to the lysis solution, followed by three rounds of sonication, as described in the representative results section. 
	NOTE: Alternatively, lyse the cells in a French pressure cell as described previously24. Skip step 1.4. and step 1.5.</li>
	<li>Clarify the cell lysate using centrifugation and filtration using a 50 mL centrifuge tube. Fill the volume of the tube to at least 30 mL total volume by adding cobalt column loading buffer (Table 1) to the solution. Pellet the cell debris by centrifugation at 20,000 x g for 30 min.</li>
	<li>Filter the supernatant using a 0.45 &#181;m syringe filter.</li>
	<li>Dilute the lysate in cobalt column loading buffer (Table 1) using a 1:10 final dilution ratio.</li>
	<li>Perform affinity chromatography on the clarified cell lysate supernatant using a cobalt or nickel-resin column following the manufacturer&#39;s instructions. See the representative results section for an example. Use the buffers listed in Table 1. Collect the flow-through, wash, and elution samples for analysis.</li>
	<li>Immediately exchange the RNA polymerase in the elution buffer solution into RNA polymerase storage buffer solution (Table 1) using a buffer exchange column following the manufacturer&#39;s instructions.</li>
	<li>Prepare the freezer stocks by concentrating the RNA polymerase using 10 kDa-cutoff centrifugal filter units to a concentration of 0.2-0.4 mg/mL determined by spectrophotometry (A280nm without extinction coefficient adjustment [1 abs at 1 cm = 1 mg&#183;mL&#8722;1]).</li>
	<li>Aliquot RNA polymerase freezer stocks in 20-50 &#181;L volumes in PCR tubes and store the RNA polymerase at &#8722;80 &#176;C.</li>
	<li>Determine the quality of the affinity chromatography by SDS-PAGE and measure the total protein yield by spectrophotometry or BCA assay. Run the samples on a 7.5% polyacrylamide gel at 120 V for 50 min for good resolution by SDS-PAGE.</li>
</ol>
2. Purification of recombinant RpoD and preparation of RpoD stock
<ol>
	<li>Culture and induce the expression of Maltose Binding Protein-tagged recombinant B. burgdorferi RpoD (MBP-RpoD) in BL21::MBP-RpoDBb, as described by the protein fusion and purification system instruction manual listed in the Table of Materials, and collect the cells by centrifugation. 
	NOTE: Stopping point. Freeze the cell pellets at &#8722;80 &#176;C to store cells for up to 2 weeks or immediately proceed to cell lysis.</li>
	<li>Perform lysis using a commercial bacterial cell lysis kit or French pressure cell. See the example lysis buffer in Table 1.</li>
	<li>Clarify the cell lysate using centrifugation and filtration. Pellet the cell debris by centrifugation at 20,000 x g for 30 min. Filter the supernatant using a 0.45 &#181;m filter.</li>
	<li>Extract MBP-RpoD using a protein extraction protocol for the expression system. See the representative results section for example implementation details and results.</li>
	<li>Determine the quality of the affinity chromatography process and elution by SDS-PAGE and measure the protein yield by spectrophotometry (A280nm without extinction coefficient adjustment [1 abs at 1 cm = 1 mg&#183;mL&#8722;1]). Use 10% polyacrylamide gel at 200 V for 30 min for separation in SDS-PAGE.</li>
	<li>Concentrate MBP-RpoD using a 10 kDa-cutoff centrifugal filter to a concentration of &#62;2 mg/mL determined by spectrophotometry.</li>
	<li>Cleave MBP from RpoD at the Factor Xa cleavage site. Add CaCl2 to the affinity chromatography elution fractions containing MBP-RpoD at a concentration of 2 mM. Add 200 &#181;g of Factor Xa Protease for every 30 mg of purified protein. Incubate overnight at RT.</li>
	<li>Confirm complete cleavage of MBP from RpoD by SDS-PAGE. Use 10% polyacrylamide gel at 200 V for 30 min for separation in SDS-PAGE.</li>
	<li>Dilute the MBP and RpoD-containing solution at a ratio of 1:10 with a heparin-binding buffer.</li>
	<li>Separate MBP and RpoD on the heparin column by FPLC. See Table 2 for FPLC settings.</li>
	<li>Determine the quality of the affinity chromatography products by SDS-PAGE and measure the protein yield by spectrophotometry. Use 10% polyacrylamide gel at 200 V for 30 min for separation in SDS-PAGE.</li>
	<li>Concentrate the elution fractions containing RpoD using a 10 kDa-cutoff centrifugal filter to a final volume of 2-3 mL.</li>
	<li>Buffer exchange the concentrated RpoD elution fractions to storage buffer using a gel filtration column.</li>
	<li>Concentrate the RpoD stock using a 10 kDa-cutoff centrifugal filter to a concentration of 0.2-0.8 mg/mL as determined by spectrophotometry.</li>
	<li>Aliquot RpoD stock at 20-50 &#181;L volumes in PCR tubes and store at &#8722;80 &#176;C.</li>
</ol>
3. Preparation of DNA template stock
<ol>
	<li>PCR amplify the 500 bp region surrounding an RpoD driven promoter site from B. burgdorferi genomic DNA using a 200 &#181;L reaction (Table 3).</li>
	<li>Purify the PCR products using a commercial PCR purification kit. Elute the DNA in molecular biology grade H2O.</li>
	<li>Adjust the molar concentration of the PCR-generated DNA templates to 100 nM by dilution in molecular biology grade H2O.</li>
</ol>
4. Perform in vitro transcription with the incorporation of radiolabeled nucleotides
<ol>
	<li>Prepare an in vitro transcription experimental plan. Determine the RNA polymerase, RpoD, and DNA template concentrations. Determine the aliquot volumes and pipetting orders for the reaction tubes. See Table 4 and Figure 1 for an example. 
	NOTE: Include controls in the experimental plan, such as reactions containing no RNA polymerase, alternative polymerase, no template, or alternative templates.</li>
	<li>Calculate the volume of &#945;-32P-ATP required for the experiment. Incorporate this into the experimental plan. Typically, include 2 &#181;Ci of activity per in vitro transcription reaction for phosphor screen detection.</li>
	<li>Prepare the work surfaces, including the radiation bench, to reduce the radiation contamination risk.</li>
	<li>Thaw fresh aliquots of RNA polymerase, Rpo, 5x buffer NTP, and template stock solutions on ice. Mix all the thawed frozen stocks thoroughly prior to pipetting.</li>
	<li>Prepare a master reaction mixture and a separate NTP mixture for radiolabeled nucleotides according to the experimental plan.</li>
	<li>Dispense the control reactions and experimental sets into PCR tubes in preparation of adding radiolabel in the reaction. Gently dispense H2O, reaction master mix, RNA polymerase, and RpoD into designated PCR tubes and mix by pipetting.</li>
	<li>Transfer the prepared materials to a radiation bench.</li>
	<li>Add &#945;-32P-ATP to NTP and mix by gentle pipetting. 
	CAUTION: While working with radioactive material, use appropriate protective equipment and handling procedures for radioactive isotopes.</li>
	<li>Add NTP to the tubes containing the in vitro transcription reaction mixtures from step 4.6.</li>
	<li>Start the in vitro transcription reaction with the addition of a DNA template. Mix the reaction volume by gently pipetting.</li>
	<li>Incubate tubes at 37 &#176;C for 5 min in a thermocycler or heat block.</li>
	<li>Remove the reactions from the thermocycler or heat block and add the 2x RNA loading dye containing 50% formamide to an equal reaction volume to stop in vitro transcription reactions.</li>
	<li>Denature the enzymes by incubating reactions at 65 &#176;C for 5 min in a thermocycler or heat block.</li>
	<li>Separate RNA in the in vitro transcription reaction mixture by gel electrophoresis using 10%-15% TBE urea polyacrylamide gels at 180 V for 30-45 min. 
	NOTE: Depending on the gel electrophoresis conditions, the buffer solution may be contaminated with radiolabeled nucleotides or the gel may contain most or all of the radiolabeled nucleotides. Plan for proper radioactivity storage or disposal.</li>
	<li>Image the radiolabeled RNA using phosphoscreen after removing any portion of the gel containing unincorporated radiolabeled ATP. Expose the gel to the phosphoscreen overnight (16 h) and image using a phosphoscreen imager (100 &#181;m resolution, 700 V PMT tube voltage).</li>
	<li>Analyze the data using densitometry methods24.</li>
</ol>

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L., Ryan, K., Kool, E. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rolling-circle+RNA+synthesis:+Circular+oligonucleotides+as+efficient+substrates+for+T7+RNA+polymerase.">Rolling-circle RNA synthesis: Circular oligonucleotides as efficient substrates for T7 RNA polymerase.</a> Journal of the American Chemical Society. 117 (29), 7818-7819 (1995).</li><li>Marras, S. A., Gold, B., Kramer, F. R., Smith, I., Tyagi, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Real-time+measurement+of+in+vitro+transcription.">Real-time measurement of in vitro transcription.</a> Nucleic Acids Research. 32 (9), 72 (2004).</li><li>Chamberlin, M. J., Nierman, W. C., Wiggs, J., Neff, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+quantitative+assay+for+bacterial+RNA+polymerases.">A quantitative assay for bacterial RNA polymerases.</a> Journal of Biological Chemistry. 254 (20), 10061-10069 (1979).</li></ol>

The authors declare no conflicts of interest.

In vitro transcription assays constructed using the presented protocol were recently used to study the role of a transcription factor in B. burgdorferi and can be applied to build similar experiments using other transcription factors, sigma factors, and molecules23. Once active RNA polymerase from B. burgdorferi has been obtained and its activity detected, components and conditions within the in vitro transcription assays can be modified. The assay is highly fle...

Lyme disease and relapsing fever are caused by spirochete pathogens in the genera Borrelia and Borreliella1,2,3. Lyme disease is a prominent vector-borne disease in North America, and, consequently, Borreliella burgdorferi is a prominent model organism to study spirochete biology4,5. Investigations into the B. burgdorferi mechanisms of transcriptional regulation aim to better understand its adaptations to changes in the environment as it cycles between its tick vector and mammalian hosts6,7. Changes in pH, temperature, osmolarity, nutrient availability, short-chain fatty acids, organic acids, and dissolved oxygen and carbon dioxide levels modulate the expression of genes that are important for B. burgdorferi to survive in its arthropod vector and to infect animals8,9,10,11,12,13,14,15,16,17,18. Linking these responses to stimuli with regulatory mechanisms has been an important aspect of B. burgdorferi research19.
Transcription factors and sigma factors control the transcription of genes that carry out cellular processes. Lyme and relapsing fever spirochetes harbor a relatively sparse set of transcription factors and alternative sigma factors. Despite this, there are complex transcriptional changes directing B. burgdorferi responses to the environment20,21,22. The specific mechanisms driving transcriptional changes in B. burgdorferi in response to environmental changes remain unclear. In vitro transcription assays are powerful tools for employing a biochemical approach to assay the function and regulatory mechanisms of transcription factors and sigma factors23,24,25,26.
An in vitro transcription assay system using the B. burgdorferi RNA polymerase was recently established24. As bacteria often have unique cellular physiologies, RNA polymerases of different species and genera respond differently to enzyme purification, enzyme storage, and reaction buffer conditions27. B. burgdorferi is also genetically distant from the many bacterial species in which RNA polymerases have been studied20. Aspects of enzyme preparation such as lysis, wash, and elution buffer conditions, storage buffer, in vitro transcription reaction buffer, and the method of assay construction can all alter RNA polymerase activity. Herein, we provide a protocol for the purification of RNA polymerase and sigma factor RpoD, the production of linear double-stranded DNA template, and the construction of in vitro transcription assays to facilitate reproducibility between laboratories using this system. We detail an example reaction to demonstrate the linear range for RpoD-dependent transcription and discuss limitations and alternatives to this approach.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>0.45 micron syringe filter</td>
			<td>Thermo Scientific</td>
			<td>726-2545</td>
			<td>Step 1.7 and 2.3</td>
		</tr>
		<tr>
			<td>50 mL conical tubes</td>
			<td>MidSci</td>
			<td>C50B</td>
			<td>Step 1.3, and subsequent steps</td>
		</tr>
		<tr>
			<td>50 mL high-speed centrifuge tubes</td>
			<td>Thermo Scientific</td>
			<td>3119-0050PK</td>
			<td>Step 1.2</td>
		</tr>
		<tr>
			<td>500 mL Centrifuge bottles</td>
			<td>Thermo Scientific</td>
			<td>3120-9500PK</td>
			<td>Step 1.1</td>
		</tr>
		<tr>
			<td>B-PER and instruction manual</td>
			<td>Thermo Scientific</td>
			<td>78248</td>
			<td>Step 1.4 and 2.2</td>
		</tr>
		<tr>
			<td>Calcium chloride</td>
			<td>Fisher Scientific</td>
			<td>10035-04-8</td>
			<td>Step 2.6</td>
		</tr>
		<tr>
			<td>Centrifugal filters 10 Kd cutoff</td>
			<td>Millipore Sigma</td>
			<td>UFC8010</td>
			<td>Step 1.11 and 2.11</td>
		</tr>
		<tr>
			<td>Cobalt resin and instruction manual</td>
			<td>Thermo Scientific</td>
			<td>89969</td>
			<td>Step 1.9</td>
		</tr>
		<tr>
			<td>Dithiothreitol</td>
			<td>Acros Organics</td>
			<td>426380500</td>
			<td>Step 1.4 and subsequent steps</td>
		</tr>
		<tr>
			<td>Dnase (Nuclease)</td>
			<td>Millipore Sigma</td>
			<td>70746</td>
			<td>Step 1.4 and 2.2</td>
		</tr>
		<tr>
			<td>Factor Xa Protease&#160;</td>
			<td>Haematologic Technologies</td>
			<td>HCXA-0060</td>
			<td>Step 2.6</td>
		</tr>
		<tr>
			<td>GE Typhoon 5 Phosphoimager</td>
			<td>GE lifesciences</td>
			<td>Multiple</td>
			<td>Step 4.15</td>
		</tr>
		<tr>
			<td>Gel Imager</td>
			<td>Bio-Rad</td>
			<td>Mutiple</td>
			<td>Step 1.13 and subsequent protien quality check steps</td>
		</tr>
		<tr>
			<td>H2O for in vitro transcription</td>
			<td>Fisher Scientific</td>
			<td>7732-18-5</td>
			<td>Step 3.2 and 3.3</td>
		</tr>
		<tr>
			<td>high fidelity PCR kit</td>
			<td>New England Biolabs</td>
			<td>M0530S</td>
			<td>Step 3.1</td>
		</tr>
		<tr>
			<td>High-speed centrifuge</td>
			<td>Eppendorf</td>
			<td></td>
			<td>Step 1.1, and subsequent steps</td>
		</tr>
		<tr>
			<td>HiTrap Heparin HP 5 x 1 mL</td>
			<td>Cytiva Life Sciences</td>
			<td>17040601</td>
			<td>Step 2.8</td>
		</tr>
		<tr>
			<td>Imidazole</td>
			<td>Sigma-Aldrich</td>
			<td>56750-100G</td>
			<td>Step 1.9</td>
		</tr>
		<tr>
			<td>Lysozyme</td>
			<td>Thermo Scientific</td>
			<td>90082</td>
			<td>Step 1.4 and 2.2</td>
		</tr>
		<tr>
			<td>Magnesium chloride&#160;</td>
			<td>Fisher Scientific</td>
			<td>S25401</td>
			<td>Step 4.1</td>
		</tr>
		<tr>
			<td>Manganese chloride</td>
			<td>Fisher Scientific</td>
			<td>S25418</td>
			<td>Step 4.1</td>
		</tr>
		<tr>
			<td>Mini protean tetra cell</td>
			<td>Bio-Rad</td>
			<td>Mutiple</td>
			<td>Step 1.13 and subsequent protien quality check steps</td>
		</tr>
		<tr>
			<td>NP-40</td>
			<td>Thermo Scientific</td>
			<td>85124</td>
			<td>Step 4.1</td>
		</tr>
		<tr>
			<td>NTP mixture</td>
			<td>Thermo Scientific</td>
			<td>R0481</td>
			<td>Step 4.1</td>
		</tr>
		<tr>
			<td>PCR purification kit</td>
			<td>Qiagen</td>
			<td>28506</td>
			<td>Step 3.2</td>
		</tr>
		<tr>
			<td>PCR tubes</td>
			<td>MidSci</td>
			<td>PR-PCR28ACF</td>
			<td>Step 1.12</td>
		</tr>
		<tr>
			<td>PD-10 Sephadex buffer exchange column and instruction manual</td>
			<td>Cytiva</td>
			<td>17085101</td>
			<td>Step 1.10 and 2.10 (gel filtration column)</td>
		</tr>
		<tr>
			<td>pMAL Protein Fusion 
			and Purification System Instruction manual</td>
			<td>New England Biolabs</td>
			<td>E8200S</td>
			<td>Step 2.1</td>
		</tr>
		<tr>
			<td>Polyacrylamide gels AnyKD</td>
			<td>Bio-Rad</td>
			<td>456-8125</td>
			<td>Step 1.13 and subsequent protien quality check steps</td>
		</tr>
		<tr>
			<td>Potassium glutamate</td>
			<td>Sigma-Aldrich</td>
			<td>G1251</td>
			<td>Step 4.1</td>
		</tr>
		<tr>
			<td>Protease inhibitor</td>
			<td>Thermo Scientific</td>
			<td>78425</td>
			<td>Step 1.4 and 2.2</td>
		</tr>
		<tr>
			<td>Radiolabeled ATP</td>
			<td>Perkin Elmer</td>
			<td>BLU503H</td>
			<td>Step 4.2</td>
		</tr>
		<tr>
			<td>RNA Loading Dye, (2x)</td>
			<td>New England Biolabs</td>
			<td>B0363S</td>
			<td>Step 4.13</td>
		</tr>
		<tr>
			<td>Rnase inhibitor</td>
			<td>Thermo Scientific</td>
			<td>EO0381</td>
			<td>Step 4.1</td>
		</tr>
		<tr>
			<td>Spectrophotometer</td>
			<td>Biotek</td>
			<td>Mutiple</td>
			<td>Step 1.13 and subsequent protien quality check steps</td>
		</tr>
		<tr>
			<td>TBE-Urea gels 10 percent</td>
			<td>Bio-Rad</td>
			<td>4566033</td>
			<td>Step 4.14</td>
		</tr>
	</tbody>
</table>

essential components of borreliella (borrelia) burgdorferi in vitro transcription assays

Borreliella burgdorferi is a bacterial pathogen with limited metabolic and genomic repertoires. B. burgdorferi transits extracellularly between vertebrates and ticks and dramatically remodels its transcriptional profile to survive in disparate environments during infection. A focus of B. burgdorferi studies is to clearly understand how the bacteria responds to its environment through transcriptional changes. In vitro transcription assays allow for the basic mechanisms of transcriptional regulation to be biochemically dissected. Here, we present a detailed protocol describing B. burgdorferi RNA polymerase purification and storage, sigma factor purification, DNA template generation, and in vitro transcription assays. The protocol describes the use of RNA polymerase purified from B. burgdorferi 5A4 RpoC-His (5A4-RpoC). 5A4-RpoC is a previously published strain harboring a 10XHis-tag on the rpoC gene encoding the largest subunit of the RNA polymerase. In vitro transcription assays consist of the RNA polymerase purified from strain 5A4-RpoC, a recombinant version of the housekeeping sigma factor RpoD, and a PCR-generated double-stranded DNA template. While the protein purification techniques and approaches to assembling in vitro transcription assays are conceptually well understood and relatively common, handling considerations for RNA polymerases often differ from organism to organism. The protocol presented here is designed for enzymatic studies on the B. burgdorferi RNA polymerase. The method can be adapted to test the role of transcription factors, promoters, and post-translational modifications on the activity of the RNA polymerase.

In an in vitro transcription reaction in which the limiting step of the reaction is sigma factor-mediated transcription initiation, the transcription activity should increase linearly with the amount of sigma factor. We present the preparation of in vitro transcription experiments testing a range of RpoD concentrations along with two concentrations of RNA polymerase to observe the resulting varying signal from radiolabeled nucleotide incorporation into RNA products. Representative results of the prepara...

Watch this Scientific Journal Video about Essential Components of Borreliella Borrelia burgdorferi In Vitro Transcription Assays at JoVE.com

Essential Components of Borreliella Borrelia burgdorferi In Vitro Transcription Assays

In vitro transcription assays can decipher the mechanisms of transcriptional regulation in Borreliella burgdorferi. This protocol describes the steps to purify B. burgdorferi RNA polymerase and perform in vitro transcription reactions. Experimental approaches using in vitro transcription assays require reliable purification and storage of active RNA polymerase.

Essential Components of Borreliella (Borrelia) burgdorferi In Vitro Transcription Assays

Borreliella burgdorferi is a bacterial pathogen with limited metabolic and genomic repertoires. B. burgdorferi transits extracellularly between ...

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Immunology and Infection

1.2K Views.  Creighton University. In vitro transcription assays can decipher the mechanisms of transcriptional regulation in Borreliella burgdorferi. This protocol describes the steps to purify B. burgdorferi RNA polymerase and perform in vitro transcription reactions. Experimental approaches using in vitro transcription assays require reliable purification and storage of active RNA polymerase. 

Video: Essential Components of Borreliella Borrelia burgdorferi In Vitro Transcription Assays

In vitro Uncoating of HIV-1 Cores

The genome of the retroviruses is encased in a capsid surrounded by a lipid envelope. For lentiviruses, such as HIV-1, the conical capsid shell is composed of CA protein arranged as a lattice of hexagon. The capsid is closed by 7 pentamers at the broad end and 5 at the narrow end of the cone1, 2. Encased in this capsid shell is the viral ribonucleoprotein complex, and together they comprise the core.
Following fusion of the viral membrane with the target cell membrane, the HIV-1 is released into the cytoplasm. The capsid then disassembles releasing free CA in the soluble form3 in a process referred to as uncoating. The intracellular location and timing of HIV-1 uncoating are poorly understood. Single amino-acid substitutions in CA that alter the stability of the capsid also impair the ability of HIV-1 to infect cells4. This indicates that the stability of the capsid is critical for HIV-1 infection.
HIV-1 uncoating has been difficult to study due to lack of availability of sensitive and reliable assays for this process. Here we describe a quantitative method for studying uncoating in vitro using cores isolated from infectious HIV-1 particles. The approach involves isolation of cores by sedimentation of concentrated virions through a layer of detergent and into a linear sucrose gradient, in the cold. To quantify uncoating, the isolated cores are incubated at 37&deg;C for various timed intervals and subsequently pelleted by ultracentrifugation. The extent of uncoating is analyzed by quantifying the fraction of CA in the supernatant. This approach has been employed to analyze effects of viral mutations on HIV-1 capsid stability4, 5, 6. It should also be useful for studying the role of cellular factors in HIV-1 uncoating.

In vitro Uncoating of HIV-1 Cores

Uncoating is an essential step in the early phase of the HIV-1 life cycle and is defined as the disassembly of the capsid shell and the release of the viral ribonucleoprotein complex (vRNP). Here, we demonstrate techniques for isolating intact cores from HIV-1 virions and for quantifying their uncoating in vitro.

The genome of the retroviruses is encased in a capsid surrounded by a lipid envelope. For lentiviruses, such as HIV-1, the conical capsid shell is ...

Concurrent Quantification of Cellular and Extracellular Components of Biofilms

Confocal laser scanning microscopy (CLSM) is a powerful tool for investigation of biofilms. Very few investigations have successfully quantified concurrent distribution of more than two components within biofilms because: 1)&#160;selection of fluorescent dyes having minimal spectral overlap is complicated, and 2)&#160;quantification of multiple fluorochromes poses a multifactorial problem. Objectives: Report a methodology to quantify and compare concurrent 3-dimensional distributions of three cellular/extracellular components of biofilms grown on relevant substrates. Methods: The method consists of distinct, interconnected steps involving biofilm growth, staining, CLSM imaging, biofilm structural analysis and visualization, and statistical analysis of structural parameters. Biofilms of Streptococcus mutans (strain UA159) were grown for 48 hr on sterile specimens of Point 4 and TPH3 resin composites. Specimens were subsequently immersed for 60 sec in either Biot&#232;ne PBF (BIO) or Listerine Total Care (LTO) mouthwashes, or water (control group; n=5/group). Biofilms were stained with fluorochromes for extracellular polymeric substances, proteins and nucleic acids before imaging with CLSM. Biofilm structural parameters calculated using ISA3D image analysis software were biovolume and mean biofilm thickness. Mixed models statistical analyses compared structural parameters between mouthwash and control groups (SAS software; &#945;=0.05). Volocity software permitted visualization of 3D distributions of overlaid biofilm components (fluorochromes). Results: Mouthwash BIO produced biofilm structures that differed significantly from the control (p&#60;0.05) on both resin composites, whereas LTO did not produce differences (p&#62;0.05) on either product. Conclusions: This methodology efficiently and successfully quantified and compared concurrent 3D distributions of three major components within S. mutans biofilms on relevant substrates, thus overcoming two challenges to simultaneous assessment of biofilm components. This method can also be used to determine the efficacy of antibacterial/antifouling agents against multiple biofilm components, as shown using mouthwashes. Furthermore, this method has broad application because it facilitates comparison of 3D structures/architecture of biofilms in a variety of disciplines.

A protocol for the concurrent quantification and comparison of three cellular and extracellular components within biofilms is presented. The methodology involves the use of confocal laser scanning microscopy, biofilm structural analysis and visualization software, and statistical analysis software.

Confocal laser scanning microscopy (CLSM) is a powerful tool for investigation of biofilms. Very few investigations have successfully quantified ...

Quantitative In vitro Assay to Measure Neutrophil Adhesion to Activated Primary Human Microvascular Endothelial Cells under Static Conditions

The vascular endothelium plays an integral part in the inflammatory response. During the acute phase of inflammation, endothelial cells (ECs) are activated by host mediators or directly by conserved microbial components or host-derived danger molecules. Activated ECs express cytokines, chemokines and adhesion molecules that mobilize, activate and retain leukocytes at the site of infection or injury. Neutrophils are the first leukocytes to arrive, and adhere to the endothelium through a variety of adhesion molecules present on the surfaces of both cells. The main functions of neutrophils are to directly eliminate microbial threats, promote the recruitment of other leukocytes through the release of additional factors, and initiate wound repair. Therefore, their recruitment and attachment to the endothelium is a critical step in the initiation of the inflammatory response. In this report, we describe an in vitro neutrophil adhesion assay using calcein AM-labeled primary human neutrophils to quantitate the extent of microvascular endothelial cell activation under static conditions. This method has the additional advantage that the same samples quantitated by fluorescence spectrophotometry can also be visualized directly using fluorescence microscopy for a more qualitative assessment of neutrophil binding.

Quantitative In vitro Assay to Measure Neutrophil Adhesion to Activated Primary Human Microvascular Endothelial Cells under Static Conditions

Neutrophil adherence to the activated endothelium at sites of infection is an integral component of the host's inflammatory response. Described in this report is a neutrophil binding assay that allows for the in vitro quantitation of primary human neutrophil binding to endothelial cells activated by inflammatory mediators under static conditions.

The vascular  endothelium plays an integral part in the inflammatory response. During the  acute phase of inflammation, endothelial cells (ECs) are ...

High Yield Purification of Plasmodium falciparum Merozoites For Use in Opsonizing Antibody Assays

Plasmodium falciparum merozoite antigens are under development as potential malaria vaccines. One aspect of immunity against malaria is the removal of free merozoites from the blood by phagocytic cells. However assessing the functional efficacy of merozoite specific opsonizing antibodies is challenging due to the short half-life of merozoites and the variability of primary phagocytic cells. Described in detail herein is a method for generating viable merozoites using the E64 protease inhibitor, and an assay of merozoite opsonin-dependent phagocytosis using the pro-monocytic cell line THP-1. E64 prevents schizont rupture while allowing the development of merozoites which are released by filtration of treated schizonts. &#160;Ethidium bromide labelled merozoites are opsonized with human plasma samples and added to THP-1 cells. Phagocytosis is assessed by a standardized high throughput protocol. Viable merozoites are a valuable resource for assessing numerous aspects of P. falciparum biology, including assessment of immune function. Antibody levels measured by this assay are associated with clinical immunity to malaria in naturally exposed individuals. The assay may also be of use for assessing vaccine induced antibodies. &#160;

High Yield Purification of Plasmodium falciparum Merozoites For Use in Opsonizing Antibody Assays

Measuring antibody function is key to understanding immunity to Plasmodium falciparum malaria. This method describes the purification of viable merozoites, and measurement of opsonization-dependent phagocytosis by flow cytometry.

Plasmodium falciparum merozoite antigens are under development as potential malaria vaccines. One aspect of immunity against malaria is the removal of ...

Assays for Studying the Role of Vitronectin in Bacterial Adhesion and Serum Resistance

Bacteria utilize complement regulators as a means of evading the host immune response. Here, we describe protocols for evaluating the role vitronectin acquisition at the bacterial cell surface plays in resistance to the host immune system. Flow cytometry experiments identified human plasma vitronectin as a ligand for the bacterial receptor outer membrane protein H of Haemophilus influenzae type f. An enzyme-linked immunosorbent assay was employed to characterize the protein-protein interactions between purified recombinant protein H and vitronectin, and binding affinity was assessed using bio-layer interferometry. The biological importance of the binding of vitronectin to protein H at the bacterial cell surface in evasion of the host immune response was confirmed using a serum resistance assay with normal and vitronectin-depleted human serum. The importance of vitronectin in bacterial adherence was analyzed using glass slides with and without vitronectin coating, followed by Gram staining. Finally, bacterial adhesion to human alveolar epithelial cell monolayers was investigated. The protocols described here can be easily adapted to the study of any bacterial species of interest.

This report describes protocols for characterizing interactions between bacterial outer membrane proteins and the human complement regulator vitronectin. The protocols can be used to study the binding reactions and biological function of vitronectin in any bacterial species.

Bacteria utilize complement regulators as a means of evading the host immune response. Here, we describe protocols for evaluating the role vitronectin ...

In Vitro Methods for Comparing Target Binding and CDC Induction Between Therapeutic Antibodies: Applications in Biosimilarity Analysis

Therapeutic monoclonal antibodies (mAbs) are relevant to the treatment of different pathologies, including cancers. The development of biosimilar mAbs by pharmaceutical companies is a market opportunity, but it is also a strategy to increase drug accessibility and reduce therapy-associated costs. The protocols detailed here describe the evaluation of target binding and CDC induction by rituximab in Daudi cells. These two functions require different structural regions of the antibody and are relevant to the clinical effect induced by rituximab. The protocols allow the side-to-side comparison of a reference rituximab and a marketed rituximab biosimilar. The evaluated products showed differences both in target binding and CDC induction, suggesting that there are underlying physicochemical differences and highlighting the need to analyze the impact of those differences in the clinical setting. The methods reported here constitute simple and inexpensive in vitro models for the evaluation of the activity of rituximab biosimilars. Thus, they can be useful during biosimilar development, as well as for quality control in biosimilar production. Furthermore, the presented methods can be extrapolated to other therapeutic mAbs.

In Vitro Methods for Comparing Target Binding and CDC Induction Between Therapeutic Antibodies: Applications in Biosimilarity Analysis

This protocol describes the in vitro comparison of two key functional characteristics of rituximab: target binding and complement-dependent cytotoxicity (CDC) induction. The methods were employed for a side-to-side comparison between reference rituximab and a rituximab biosimilar. These assays can be employed during biosimilar development or as a quality control in their production.

Therapeutic monoclonal antibodies (mAbs) are relevant to the treatment of different pathologies, including cancers. The development of biosimilar mAbs by ...

Screening Assays to Characterize Novel Endothelial Regulators Involved in the Inflammatory Response

The endothelial layer is essential for maintaining homeostasis in the body by controlling many different functions. Regulation of the inflammatory response by the endothelial layer is crucial to efficiently fight against harmful inputs and aid in the recovery of damaged areas. When the endothelial cells are exposed to an inflammatory environment, such as the outer component of gram-negative bacteria membrane, lipopolysaccharide (LPS), they express soluble pro-inflammatory cytokines, such as Ccl5, Cxcl1 and Cxcl10, and trigger the activation of circulating leukocytes. In addition, the expression of adhesion molecules E-selectin, VCAM-1 and ICAM-1 on the endothelial surface enables the interaction and adhesion of the activated leukocytes to the endothelial layer, and eventually the extravasation towards the inflamed tissue. In this scenario, the endothelial function must be tightly regulated because excessive or defective activation in the leukocyte recruitment could lead to inflammatory-related disorders. Since many of these disorders do not have an effective treatment, novel strategies with a focus on the vascular layer must be investigated. We propose comprehensive assays that are useful to the search of novel endothelial regulators that modify leukocyte function. We analyze endothelial activation by using specific expression targets involved in leukocyte recruitment (such as, cytokines, chemokines, and adhesion molecules) with several techniques, including: real-time quantitative polymerase chain reaction (RT-qPCR), western-blot, flow cytometry and adhesion assays. These approaches determine endothelial function in the inflammatory context and are very useful to perform screening assays to characterize novel endothelial inflammatory regulators that are potentially valuable for designing new therapeutic strategies.

Vascular endothelium tightly controls leukocyte recruitment. Inadequate leukocyte extravasation contributes to human inflammatory diseases. Therefore, searching for novel regulatory elements of endothelial activation is necessary to design improved therapies for inflammatory disorders. Here, we describe a comprehensive methodology to characterize novel endothelial regulators that can modify leukocyte trafficking during inflammation.

The endothelial layer is essential for maintaining homeostasis in the body by controlling many different functions. Regulation of the inflammatory ...

High Throughput In Vitro Assessment of Latency Reversing Agents on HIV Transcription and Splicing

HIV remains incurable due to the existence of a reservoir of cells that harbors stable and latent form of the virus, which stays invisible to the immune system and is not targeted by the current antiretroviral therapy (cART). Transcription and splicing have been shown to reinforce HIV-1 latency in resting CD4+ T cells. Reversal of latency by the use of latency reversal agents (LRAs) in the &#34;shock and kill&#34; approach has been studied extensively in an attempt to purge this reservoir but has thus far not shown any success in clinical trials due to the lack of development of adequate small molecules that can efficiently perturb this reservoir. The protocol presented here provides a method for reliably and efficiently assessing latency reversal agents (LRAs) on HIV transcription and splicing. This approach is based on the use of an LTR-driven dual color reporter that can simultaneously measure the effect of an LRA on transcription and splicing by flow cytometry. The protocol described here is adequate for adherent cells as well as the cells in suspension. It is useful for testing a large number of drugs in a high throughput system. The method is technically simple to implement and cost-effective. In addition, the use of flow cytometry allows the assessment of cell viability and thus drug toxicity at the same time.

A high throughput protocol for functional assessment of HIV efficient reactivation and clearance of latent proviruses is described and applied by testing the impact of interventions on HIV transcription and splicing. Representative results of the effect of latency reversing agents on LTR-driven transcription and splicing are provided.

HIV remains incurable due to the existence of a reservoir of cells that harbors stable and latent form of the virus, which stays invisible to the immune ...

Pattern-Triggered Oxidative Burst and Seedling Growth Inhibition Assays in Arabidopsis thaliana

Plants have evolved a robust immune system to perceive pathogens and protect against disease. This paper describes two assays that can be used to measure the strength of immune activation in Arabidopsis thaliana following treatment with elicitor molecules. Presented first is a method for capturing the rapidly-induced and dynamic oxidative burst, which can be monitored using a luminol-based assay. Presented second is a method describing how to measure immune-induced inhibition of seedling growth. These protocols are fast and reliable, do not require specialized training or equipment, and are widely used to understand the genetic basis of plant immunity.

Pattern-Triggered Oxidative Burst and Seedling Growth Inhibition Assays in Arabidopsis thaliana

This paper describes two methods for quantifying defense responses in Arabidopsis thaliana following exposure to immune elicitors: the transient oxidative burst, and the inhibition of seedling growth.

Plants have evolved a robust immune system to perceive pathogens and protect against disease. This paper describes two assays that can be used to measure ...

Tailoring In Vivo Cytotoxicity Assays to Study Immunodominance in Tumor-specific CD8+ T Cell Responses

Carboxyfluorescein succinimidyl ester (CFSE)-based in vivo cytotoxicity assays enable sensitive and accurate quantitation of CD8+ cytolytic T lymphocyte (CTL) responses elicited against tumor- and pathogen-derived peptides. They offer several advantages over traditional killing assays. First, they permit the monitoring of CTL-mediated cytotoxicity within architecturally intact secondary lymphoid organs, typically in the spleen. Second, they allow for mechanistic studies during the priming, effector and recall phases of CTL responses. Third, they provide useful platforms for vaccine/drug efficacy testing in a truly in vivo setting. Here, we provide an optimized protocol for the examination of concomitant CTL responses against more than one peptide epitope of a model tumor antigen (Ag), namely, simian virus 40 (SV40)-encoded large T Ag (T Ag). Like most other clinically relevant tumor proteins, T Ag harbors many potentially immunogenic peptides. However, only four such peptides induce detectable CTL responses in C57BL/6 mice. These responses are consistently arranged in a hierarchical order based on their magnitude, which forms the basis for TCD8 &#8220;immunodominance&#8221; in this powerful system. Accordingly, the bulk of the T Ag-specific TCD8 response is focused against a single immunodominant epitope while the other three epitopes are recognized and responded to only weakly. Immunodominance compromises the breadth of antitumor TCD8 responses and is, as such, considered by many as an impediment to successful vaccination against cancer. Therefore, it is important to understand the cellular and molecular factors and mechanisms that dictate or shape TCD8 immunodominance. The protocol we describe here is tailored to the investigation of this phenomenon in the T Ag immunization model, but can be readily modified and extended to similar studies in other tumor models. We provide examples of how the impact of experimental immunotherapeutic interventions can be measured using in vivo cytotoxicity assays.

Tailoring In Vivo Cytotoxicity Assays to Study Immunodominance in Tumor-specific CD8+ T Cell Responses

We describe here a flow cytometry-based in vivo killing assay that enables examination of immunodominance in cytotoxic T lymphocyte (CTL) responses to a model tumor antigen. We provide examples of how this elegant assay may be employed for mechanistic studies and for drug efficacy testing.

Carboxyfluorescein succinimidyl ester (CFSE)-based in vivo cytotoxicity assays enable sensitive and accurate quantitation of CD8+ cytolytic T lymphocyte ...

Essential Components of Borreliella (Borrelia) burgdorferi In Vitro Transcription Assays

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High Throughput In Vitro Assessment of Latency Reversing Agents on HIV Transcription and Splicing

Pattern-Triggered Oxidative Burst and Seedling Growth Inhibition Assays in Arabidopsis thaliana

Tailoring In Vivo Cytotoxicity Assays to Study Immunodominance in Tumor-specific CD8⁺ T Cell Responses