1. Virus Inoculation and VLPs Purification from Nicotiana benthamiana Plants
<ol>
	<li>Produce capped T7-RNA transcripts from Potato virus X (PVX)-based vector plasmids carrying MRFV wild-type (wt) and Cys-mutated coat protein (CP) genes 12, using Ambion's T7-mMessage mMachine Kit.</li>
	<li>For each T7 transcript reaction, inoculate two fully expanded leaves of N. benthamiana with 10 &mu;l reactions and incubate the plants for 10 days in greenhouse, at 60% humidity for 16 hr with light (25,000-30,000 lux) at 25 &deg;C and 8 hr dark at 20 &deg;C.</li>
	<li>Harvest N. benthamiana virus-infected leaves 10 days post inoculation (dpi), weigh the plant tissue (50 grams) and place on ice.</li>
	<li>Homogenize the plant material in a blender in presence of 100 ml of a chilled solution of 0.5 M Na-Citrate buffer, pH 5.5 (use 2 ml of buffer per gram of plant tissue).</li>
	<li>Filter homogenate through 3 layers of cheesecloth and clarify by centrifugation at 27,000 x g for 30 min. Transfer the supernatant into a chilled graduated cylinder, measure the volume, and then transfer to a chilled sterile beaker. Discard the pellet.</li>
	<li>Process the supernatant by adding 10% polyethylene glycol 8,000 (PEG 8,000), stir for 15 min at 4 &deg;C, and incubate for an additional 45 min at 4 &deg;C to precipitate the virus-like particles (VLPs)-PEG matrix.</li>
	<li>Centrifuge the sample at 27,000 x g for 20 min at 4 &deg;C and remove the supernatant.</li>
	<li>Process the pellet by adding 8 ml of 0.05 M Na-Citrate buffer, pH 5.5 containing 2% Triton X-100. Swirl the centrifuge tubes well to release the pellet. Transfer the pellet and buffer to a chilled sterile beaker. Rinse the tubes immediately with 2 ml of the same buffer and add to the beaker. Stir the suspension at 4 &deg;C until the pellets are dissolved (generally 1 hr).</li>
	<li>Clarify by centrifugation for 5 min at 27,000 x g, discard the pellet, and process the supernatant by centrifugation at 140,000 x g for 2 hr at 4 &deg;C.</li>
	<li>Resuspend the pellet in 1 ml 0.05 M Na-Citrate buffer, pH 5.5 and place the suspension on top of a 10-40% sucrose gradient made in 0.05 M Na-Citrate buffer, pH 5.5.</li>
	<li>Centrifuge the gradient for 3 hr at 140,000 x g at 4 &deg;C.</li>
	<li>Shine a light over the top of the centrifuge tube and collect the light-scattering upper band at 4 cm from the top of the tube, dilute with 0.05 M Na-Citrate buffer, pH 5.5, and centrifuge for 3 hr at 140,000 x g at 4 &deg;C.</li>
	<li>Resuspend the pellet in 0.5 ml of sterile water and store at 4 &deg;C for up to six months.</li>
	<li>Quantitate the VLPs concentration by performing a Bradford protein assay. The yield of VLPs is between 1 and 3 &mu;g/g of plant tissue.</li>
</ol>
2. Fluorescein-5-maleimide-labeling Reactions of VLPs
<ol>
	<li>Prepare a 1 mM solution of fluorescein-5-maleimide (427.37 g/mole) in 50 mM sodium phosphate buffer, pH 7.0; 1 mM EDTA. Mix using the vortex and verify complete dissolution. Protect the tube from light using aluminum foil.</li>
	<li>Add fluorescein-5-maleimide to VLPs produced in step 1 and mix. Use a 25-fold molar excess of fluorescein-5-maleimide for molar amount of sulfhydryls. Generally, using 30 &mu;l of VLPs at the concentration of 1 &mu;g/&mu;l and 60 &mu;l of the fluorescein-5-maleimide solution produces acceptable results.</li>
	<li>Incubate the reaction for 2 hr at room temperature or overnight at 4 &deg;C.</li>
	<li>Terminate the reaction by adding dithiothreitol (DTT) to a final concentration of 50 mM.</li>
	<li>Remove non-reacted fluorescein using a desalting spin column (Thermo Scientific Inc, Rockford IL) and centrifugation for 2 min at 1,500 x g at room temperature.</li>
	<li>For SDS-PAGE analysis, add 10 &mu;l of 2 x SDS-PAGE Laemmli sample buffer to 10 &mu;l of each reaction. Store the labeled protein protected from light at 4 &deg;C for up to one month or in single-use aliquots at -20 &deg;C up to 3 months.</li>
</ol>
3. Labeling Reaction and Determination of Biotin Incorporation
<ol>
	<li>Use desalting spin columns (Thermo Scientific Inc., Rockford IL) to perform a buffer exchange from water to phosphate-buffered saline (PBS), pH 7.0 of the VLPs produced in step 1.</li>
	<li>Prepare a 20 mM stock solution of maleimide-PEG2-biotin by adding 190 &mu;l of PBS in No-Weigh maleimide-PEG2-biotin and mix by pipetting up and down.</li>
	<li>Add maleimide-PEG2-biotin to the VLPs and mix. Use a 10-fold molar excess of reagent for VLPs solutions &le; 2 mg/ml.</li>
	<li>Incubate the reaction at room temperature for 4 hr.</li>
	<li>Remove non-reacted maleimide-PEG2-biotin using a desalting spin column (Thermo Scientific Inc, Rockford IL) and centrifugation for 2 min at 1,500 x g at room temperature.</li>
	<li>Determine the moles of biotin per moles of VLPs using the Pierce Biotin Quantitation Kit (Thermo Scientific) and following manufacturer's instructions.</li>
</ol>
4. Cross-linking of Cys 2-VLPs and F Peptide
<ol>
	<li>VLPs which resulted in available cysteine residues for cross-linking in step 2 (Cys 2-VLPs) are used in the following step. Prepare a fresh cross-linking stock solution (28.63 mM) by dissolving 10 mg of NHS-PEG4-maleimide cross-linker in 680 &mu;l of dimethyl sulfoxide.</li>
	<li>Dissolve a 17 (F)-amino acid long peptide (LLPNMOKDKEACAKAPL) in 50 &mu;l of conjugation buffer (1 x PBS, pH 7.2; 1 mM EDTA) at a concentration of 0.1 mM.</li>
	<li>Add 4 &mu;l of cross-linker to 50 &mu;l of the dissolved peptide (protein-NH2) at 1 mM final concentration (which is a 10-fold molar excess for 0.1 mM of peptide solution).</li>
	<li>Incubate the reaction for 2 hr at 4 &deg;C.</li>
	<li>Purify cross-linked peptide using a desalting column (Thermo Scientific Inc., Rockford IL) equilibrated with conjugation buffer (1 x PBS, pH 7.2; 1 mM EDTA) by centrifugation at 1,500 x g for 1 min at room temperature.</li>
	<li>Set up a reaction mix combining VLPs (protein-SH) and cross-linked peptide (protein-NH2) in a molar ratio determined by the number of thiols and activated amines involved in the reaction and the difference in molecular weight between VLPs and peptide.</li>
	<li>Incubate the reaction mixture at room temperature for 2 hr at 4 &deg;C.</li>
	<li>For Western blot analysis, mix the resulting conjugated product 1:1 with Laemmli buffer, boil for 10 min, and proceed with SDS-PAGE on a pre-cast 10-20% Tris-Glycine gel (Invitrogen), followed by electroblotting onto a nitrocellulose membrane (Invitrogen). Block the membranes with 1 x PBS, pH 7.2 containing 0.05% Tween-20 (PBS-Tween) and 5% skim milk powder and probe with peptide-specific antibodies followed by the appropriate phosphatase-labeled secondary antibody.</li>
</ol>

<ol>
	<li>Barnhill, H., Reuther, R., Ferguson, P. L., Dreher, T. W., Wang, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Turnip+yellow+mosaic+virus+as+a+chemoaddressable+bionanoparticle.">Turnip yellow mosaic virus as a chemoaddressable bionanoparticle.</a> Bioconj. Chem. 18, 852-859 (2007).</li><li>Chapman, S., Kavanagh, T., Baulcombe, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Potato+virus+X+as+a+vector+for+gene+expression+in+plants.">Potato virus X as a vector for gene expression in plants.</a> Plant J. 2, 549-557 (1992).</li><li>Chen, C., Kwak, E. S., Stein, B., Kao, C. C., Dragnea, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Packaging+of+gold+particles+in+viral+capsids.">Packaging of gold particles in viral capsids.</a> J. Nanosci. Nanotechnol. 5, 2029-2033 (2005).</li><li>Fowler, C. E., Shenton, W., Stubbs, G., Mann, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tobacco+mosaic+virus+liquid+crystals+as+templates+for+the+interior+design+of+silica+mesophases+and+nanoparticles.">Tobacco mosaic virus liquid crystals as templates for the interior design of silica mesophases and nanoparticles.</a> Advanced Materials. 13, 1266-1269 (2001).</li><li>Gazit, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+biomolecular+templates+for+the+fabrication+of+metal+nanowires.">Use of biomolecular templates for the fabrication of metal nanowires.</a> FEBS. J. 274, 317-322 (2007).</li><li>Gillitzer, E., Wilts, D., Young, M., Douglas, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemical+modification+of+a+viral+cage+for+multivalent+presentation.">Chemical modification of a viral cage for multivalent presentation.</a> Chem. Commun. , 2390-2391 (2002).</li><li>Hammond, R. W., Hammond, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Maize+rayado+fino+virus+capsid+proteins+assemble+into+virus-like+particles+in+Escherichia+coli.">Maize rayado fino virus capsid proteins assemble into virus-like particles in Escherichia coli.</a> Virus Res. 147, 208-215 (2010).</li><li>Hermamson, G. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Bioconjugate techniques. , (1991).</li><li>Kaiser, C. R., Flenniken, M. L., Gillitzer, E., Harmsen, A. L., Harmsen, A. G., Jutila, M. A., Douglas, T., Young, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biodistribution+studies+of+protein+cage+nanoparticles+demonstrate+broad+tissue+distribution+and+rapid+clearance+in+vivo.">Biodistribution studies of protein cage nanoparticles demonstrate broad tissue distribution and rapid clearance in vivo.</a> Int. J. Nanomed. 2, 715-733 (2007).</li><li>Knez, M., Bittner, A. M., Boes, F., Wege, C., Jeske, H., Maisse, E., Kern, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biotemplate+synthesis+of+3-nm+nickel+and+cobalt+nanowires.">Biotemplate synthesis of 3-nm nickel and cobalt nanowires.</a> Nano Lett. 3, 1079-1082 (2003).</li><li>Lee, S. Y., Culver, J. N., Harris, M. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+CuCl2+concentration+on+the+aggregation+and+mineralization+of+Tobacco+mosaic+virus+biotemplate.">Effect of CuCl2 concentration on the aggregation and mineralization of Tobacco mosaic virus biotemplate.</a> J. Colloid. Interface. Sci. 297, 554-560 (2006).</li><li>Lvov, Y., Haas, H., Decher, G., Mohwald, H., Mikhailov, A., Mtchedlishvily, B., Morgunova, E., Vainshtein, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Successive+deposition+of+alternate+layers+of+polyelectrolytes+and+a+charged+virus.">Successive deposition of alternate layers of polyelectrolytes and a charged virus.</a> Langmuir. 10, 4232-4236 (1994).</li><li>Natilla, A., Hammond, R. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Maize+rayado+fino+virus+virus-like+particles+expressed+in+tobacco+plants:+a+new+platform+for+cysteine+selective+bioconjugation+peptide+display.">Maize rayado fino virus virus-like particles expressed in tobacco plants: a new platform for cysteine selective bioconjugation peptide display.</a> J. Virol. Methods. 178, 209-215 (2011).</li><li>Rae, C. S., Khor, I. W., Wang, Q., Destito, G., Gonzalez, M. J., Singh, P., Thomas, D. M., Estrada, M. N., Powell, E., Finn, M. G., Manchester, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Systemic+trafficking+of+plant+virus+nanoparticles+in+mice+via+the+oral+route.">Systemic trafficking of plant virus nanoparticles in mice via the oral route.</a> Virology. 343, 2224-2235 (2005).</li><li>Raja, K. S., Wang, Q., Gonzalez, M. J., Manchester, M., Johnson, J. E., Finn, M. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hybrid+virus-polymer+materials.+Synthesis+and+properties+of+PEG-decorated+Cowpea+mosaic+virus.">Hybrid virus-polymer materials. Synthesis and properties of PEG-decorated Cowpea mosaic virus.</a> Biomacromolecules. 4, 472-476 (2003).</li><li>Royston, E., Lee, S. Y., Culver, J. N., Harris, M. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+silica-coated+Tobacco+mosaic+virus.">Characterization of silica-coated Tobacco mosaic virus.</a> J. Colloid Interface Sci. 298, 706-712 (2006).</li><li>Schlick, T. L., Ding, Z., Kovacs, E. W., Francis, M. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dual-surface+modification+in+the+Tobacco+mosaic+virus.">Dual-surface modification in the Tobacco mosaic virus.</a> J. Am. Chem. Soc. 127, 3718-3723 (2005).</li><li>Young, M., Willits, D., Uchida, M., Douglas, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plant+viruses+as+biotemplates+for+materials+and+their+use+in+nanotechnology.">Plant viruses as biotemplates for materials and their use in nanotechnology.</a> Annu. Rev. Phytopathol. 46, 361-384 (2008).</li></ol>

Mention of the trade names of commercial products in the publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.

The method presented here enables a very sensitive and rapid analysis of reactive cysteines present on the surface of plant-produced VLPs as well as on other protein complexes. Maleimides are thiol-specific reagents, which react with free sulfhydryl-containing molecules to form stable thioether bonds. This method draws on the specificity of the maleimides to react with sulfhydryl groups not involved in interactions with other amino acids. Preserving the native structure of the VLPs is very important through the en...

<table border="1">
	<tbody>
		<tr>
			<td>Name of the reagent</td>
			<td>Company</td>
			<td>Catalog number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Thinwall, Ultra-Clear Tubes</td>
			<td>Beckman</td>
			<td>344059</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>mMESSAGE mMACHINE T7 Kit</td>
			<td>Life Tecnologies</td>
			<td>AM1344M</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Fluorescein-5-Maleimide</td>
			<td>Thermo Scientific Life Technologies</td>
			<td>46130 F150</td>
			<td>46130 is out of order substitute with F150</td>
		</tr>
		<tr>
			<td>Pierce Biotin Quantitation Kit</td>
			<td>Thermo Scientific</td>
			<td>28005</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>EZ-Link Maleimide-PEG2-Biotin, No-Weigh Format</td>
			<td>Thermo Scientific</td>
			<td>21901</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>SM(PEG)n Crosslinkers</td>
			<td>Thermo Scientific</td>
			<td>22107</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>10-20% Tris-Glycine gel</td>
			<td>Invitrogen</td>
			<td>EC61352</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Laemmli Buffer</td>
			<td>Bio-Rad</td>
			<td>1610737</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Tris Glycine SDS Running Buffer</td>
			<td>Invitrogen</td>
			<td>LC2675</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Tris Glycine Transfer Buffer</td>
			<td>Invitrogen</td>
			<td>LC3675</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Nitrocellulose Membrane Filter Paper Sandwich</td>
			<td>Invitrogen</td>
			<td>LC2001</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Phosphatase Labeled Affinity Purified Antibody to Rabbit IgG</td>
			<td>Kirkegaard and Perry Laboratories</td>
			<td>0751516</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>NBT/BCIP Phosphatase Substrate</td>
			<td>Kirkegaard and Perry Laboratories</td>
			<td>508107</td>
			<td>&nbsp;</td>
		</tr>
	</tbody>
</table>

analysis of the solvent accessibility of cysteine residues on maize rayado fino virus virus-like particles produced in nicotiana benthamiana plants and cross-linking of peptides to vlps

Mimicking and exploiting virus properties and physicochemical and physical characteristics holds promise to provide solutions to some of the world's most pressing challenges. The sheer range and types of viruses coupled with their intriguing properties potentially give endless opportunities for applications in virus-based technologies. Viruses have the ability to self- assemble into particles with discrete shape and size, specificity of symmetry, polyvalence, and stable properties under a wide range of temperature and pH conditions. Not surprisingly, with such a remarkable range of properties, viruses are proposed for use in biomaterials 9, vaccines 14, 15, electronic materials, chemical tools, and molecular electronic containers4, 5, 10, 11, 16, 18, 12.
In order to utilize viruses in nanotechnology, they must be modified from their natural forms to impart new functions. This challenging process can be performed through several mechanisms including genetic modification of the viral genome and chemically attaching foreign or desired molecules to the virus particle reactive groups 8. The ability to modify a virus primarily depends upon the physiochemical and physical properties of the virus. In addition, the genetic or physiochemical modifications need to be performed without adversely affecting the virus native structure and virus function. Maize rayado fino virus (MRFV) coat proteins self-assemble in Escherichia coli producing stable and empty VLPs that are stabilized by protein-protein interactions and that can be used in virus-based technologies applications 8. VLPs produced in tobacco plants were examined as a scaffold on which a variety of peptides can be covalently displayed 13. Here, we describe the steps to 1) determine which of the solvent-accessible cysteines in a virus capsid are available for modification, and 2) bioconjugate peptides to the modified capsids. By using native or mutationally-inserted amino acid residues and standard coupling technologies, a wide variety of materials have been displayed on the surface of plant viruses such as, Brome mosaic virus 3, Carnation mottle virus 12, Cowpea chlorotic mottle virus 6, Tobacco mosaic virus 17, Turnip yellow mosaic virus 1, and MRFV 13.

Transient expression of mutant MRFV coat protein (CP) genes in N. benthamiana plants in a PVX-based vector producing VLPs is described in Figure 1. The modified MRFV coat protein gene is amplified by PCR and then placed under the transcriptional control of the duplicated subgenomic CP promoter in a PVX-based vector, pP2C2S 2, (a gift of D. Baulcombe, Sainsbury Laboratories, Norwich, England). In vitro RNA transcription produces RNA transcripts that are then used to ino...

Watch this Scientific Journal Video about Analysis of the Solvent Accessibility of Cysteine Residues on Maize rayado fino virus Virus-like Particles Produced in Nicotiana benthamiana Plants and Cross-

Analysis of the Solvent Accessibility of Cysteine Residues on Maize rayado fino virus Virus-like Particles Produced in Nicotiana benthamiana Plants and Cross-linking of Peptides to VLPs

A method to analyze the solvent accessibility of the thiol group of cysteine residues of Maize rayado fino virus (MRFV)-virus-like particles (VLPs) followed by a peptide cross-linking reaction is described. The method takes advantage of the availability of several chemical groups on the surface of the VLPs that can be targets for specific reactions.

Analysis of the Solvent Accessibility of Cysteine Residues on Maize rayado fino virus Virus-like Particles Produced in Nicotiana benthamiana Plants and Cross-linking of Peptides to VLPs

Mimicking  and exploiting virus properties and physicochemical and physical  characteristics holds promise to provide solutions to some of  the world's ...

analysis-solvent-accessibility-cysteine-residues-on-maize-rayado-fino

Research

JoVE Journal

Immunology and Infection

11.0K visualizações.  Agricultural Research Service, United States Department of Agriculture. Um método para analisar a acessibilidade do solvente do grupo tiol de resíduos de cisteína de Milho rayado fino vírus (MRFV)-partículas semelhantes a vírus (VLPs), seguido por uma reacção de ligação cruzada de péptidos é descrito. O método tira partido da existência de grupos químicos sobre a superfície das partículas VLP, que podem ser alvos para as reacções específicas.

Vídeo: Analysis of the Solvent Accessibility of Cysteine Residues on Maize rayado fino virus Virus-like Particles Produced in Nicotiana benthamiana Plants and Cross-linking of Peptides to VLPs

Isolation and Genome Analysis of Single Virions using 'Single Virus Genomics'

Whole genome amplification and sequencing of single microbial cells enables genomic characterization without the need of cultivation 1-3. Viruses, which are ubiquitous and the most numerous entities on our planet 4 and important in all environments 5, have yet to be revealed via similar approaches. Here we describe an approach for isolating and characterizing the genomes of single virions called 'Single Virus Genomics' (SVG). SVG utilizes flow cytometry to isolate individual viruses and whole genome amplification to obtain high molecular weight genomic DNA (gDNA) that can be used in subsequent sequencing reactions.

Isolation and Genome Analysis of Single Virions using &#039;Single Virus Genomics&#039;

Single Virus Genomics (SVG) is a method to isolate and amplify the genomes of single virons. Viral suspensions of a mixed assemblage are sorted using flow cytometry onto a microscope slide with discrete wells containing agarose, thereby capturing the virion and reducing genome shearing during downstream processing. Whole genome amplification is achieved using multiple displacement amplification (MDA) resulting in genomic material that is suitable for sequencing.

Whole genome amplification and sequencing of single microbial cells enables genomic characterization without the need of cultivation 1-3. Viruses, which ...

Analysis of the Epithelial Damage Produced by Entamoeba histolytica Infection

Entamoeba histolytica is the causative agent of human amoebiasis, a major cause of diarrhea and hepatic abscess in tropical countries. Infection is initiated by interaction of the pathogen with intestinal epithelial cells. This interaction leads to disruption of intercellular structures such as tight junctions (TJ). TJ ensure sealing of the epithelial layer to separate host tissue from gut lumen. Recent studies provide evidence that disruption of TJ by the parasitic protein EhCPADH112 is a prerequisite for E. histolytica invasion that is accompanied by epithelial barrier dysfunction. Thus, the analysis of molecular mechanisms involved in TJ disassembly during E. histolytica invasion is of paramount importance to improve our understanding of amoebiasis pathogenesis. This article presents an easy model that allows the assessment of initial host-pathogen interactions and the parasite invasion potential. Parameters to be analyzed include transepithelial electrical resistance, interaction of EhCPADH112 with epithelial surface receptors, changes in expression and localization of epithelial junctional markers and localization of parasite molecules within epithelial cells.

Analysis of the Epithelial Damage Produced by Entamoeba histolytica Infection

Human infection by Entamoeba histolytica leads to amoebiasis, a major cause of diarrhea in tropical countries. Infection is initiated by pathogen interactions with intestinal epithelial cells, provoking the opening of cell-cell contacts and consequently diarrhea, sometimes followed by liver infection. This article provides a model to assess the early host-pathogen interactions to improve our understanding of amoebiasis pathogenesis.

Entamoeba histolytica is the causative agent of human amoebiasis, a major cause of diarrhea and hepatic abscess in tropical countries. Infection is ...

In Vitro Analysis of Myd88-mediated Cellular Immune Response to West Nile Virus Mutant Strain Infection

An attenuated West Nile virus (WNV), a nonstructural (NS) 4B-P38G mutant, induced higher innate cytokine and T cell responses than the wild-type WNV in mice. Recently, myeloid differentiation factor 88 (MyD88) signaling was shown to be important for initial T cell priming and memory T cell development during WNV NS4B-P38G mutant infection. In this study, two flow cytometry-based methods &#8211; an in vitro T cell priming assay and an intracellular cytokine staining (ICS) &#8211; were utilized to assess dendritic cells (DCs) and T cell functions. In the T cell priming assay, cell proliferation was analyzed by flow cytometry following co-culture of DCs from both groups of mice with carboxyfluorescein succinimidyl ester (CFSE) - labeled CD4+ T cells of OTII transgenic mice. This approach provided an accurate determination of the percentage of proliferating CD4+ T cells with significantly improved overall sensitivity than the traditional assays with radioactive reagents. A microcentrifuge tube system was used in both cell culture and cytokine staining procedures of the ICS protocol. Compared to the traditional tissue culture plate-based system, this modified procedure was easier to perform at biosafety level (BL) 3 facilities. Moreover, WNV- infected cells were treated with paraformaldehyde in both assays, which enabled further analysis outside BL3 facilities. Overall, these in vitro immunological assays can be used to efficiently assess cell-mediated immune responses during WNV infection.

In Vitro Analysis of Myd88-mediated Cellular Immune Response to West Nile Virus Mutant Strain Infection

Two flow cytometry-based methods &#8211; an in vitro T cell priming assay and intracellular cytokine staining were utilized to measure antigen presenting capacity of dendritic cells and antigen-specific T cell responses to a West Nile virus mutant infection in mice.

An attenuated West Nile virus (WNV), a nonstructural (NS) 4B-P38G mutant, induced higher innate cytokine and T cell responses than the wild-type WNV in ...

Modeling The Lifecycle Of Ebola Virus Under Biosafety Level 2 Conditions With Virus-like Particles Containing Tetracistronic Minigenomes

Ebola viruses cause severe hemorrhagic fevers in humans and non-human primates, with case fatality rates as high as 90%. There are no approved vaccines or specific treatments for the disease caused by these viruses, and work with infectious Ebola viruses is restricted to biosafety level 4 laboratories, significantly limiting the research on these viruses. Lifecycle modeling systems model the virus lifecycle under biosafety level 2 conditions; however, until recently such systems have been limited to either individual aspects of the virus lifecycle, or a single infectious cycle. Tetracistronic minigenomes, which consist of Ebola virus non-coding regions, a reporter gene, and three Ebola virus genes involved in morphogenesis, budding, and entry (VP40, GP1,2, and VP24), can be used to produce replication and transcription-competent virus-like particles (trVLPs) containing these minigenomes. These trVLPs can continuously infect cells expressing the Ebola virus proteins responsible for genome replication and transcription, allowing us to safely model multiple infectious cycles under biosafety level 2 conditions. Importantly, the viral components of this systems are solely derived from Ebola virus and not from other viruses (as is, for example, the case in systems using pseudotyped viruses), and VP40, GP1,2 and VP24 are not overexpressed in this system, making it ideally suited for studying morphogenesis, budding and entry, although other aspects of the virus lifecycle such as genome replication and transcription can also be modeled with this system. Therefore, the tetracistronic trVLP assay represents the most comprehensive lifecycle modeling system available for Ebola viruses, and has tremendous potential for use in investigating the biology of Ebola viruses in future. Here, we provide detailed information on the use of this system, as well as on expected results.

Work with infectious Ebola viruses is restricted to biosafety level 4 laboratories. Tetracistronic minigenome-containing replication and transcription-competent virus like particles (trVLPs) represent a lifecycle modeling system that allows us to safely model multiple infectious cycles under biosafety level 2 conditions, relying exclusively on Ebola virus components.

Ebola viruses cause severe hemorrhagic fevers in humans and non-human primates, with case fatality rates as high as 90%. There are no approved vaccines or ...

Neutrophil Isolation and Analysis to Determine their Role in Lymphoma Cell Sensitivity to Therapeutic Agents

Neutrophils are the most abundant (40% to 75%) type of white blood cells and among the first inflammatory cells to migrate towards the site of inflammation. They are key players in the innate immune system and play major roles in cancer biology. Neutrophils have been proposed as key mediators of malignant transformation, tumor progression, angiogenesis and in the modulation of the antitumor immunity; through their release of soluble factors or their interaction with tumor cells. To characterize the specific functions of neutrophils, a fast and reliable method is coveted for in vitro isolation of neutrophils from human blood. Here, a density gradient separation method is demonstrated to isolate neutrophils as well as mononuclear cells from the blood. The procedure consists of layering the density gradient solution such as Ficoll carefully above the diluted blood obtained from patients diagnosed with chronic lymphocytic leukemia (CLL), followed by centrifugation, isolation of mononuclear layer, separation of neutrophils from RBCsby dextran then lysis of residual erythrocytes. This method has been shown to isolate neutrophils &#8805; 90 % pure. To mimic the tumor microenvironment, 3-dimensional (3D) experiments were performed using basement membrane matrix such as Matrigel. Given the short half-life of neutrophils in vitro, 3D experiments with fresh human neutrophils cannot be performed. For this reason promyelocytic HL60 cells are differentiated along the granulocytic pathway using the differentiation inducers dimethyl sulfoxide (DMSO) and retinoic acid (RA). The aim of our experiments is to study the role of neutrophils on the sensitivity of lymphoma cells to anti-lymphoma agents. However these methods can be generalized to study the interactions of neutrophils or neutrophil-like cells with a large range of cell types in different situations.

Neutrophils are the most abundant type of white blood cells. The isolation of neutrophils from human blood by density gradient separation method and the differentiation of human promyelocytic (HL60) cells along the granulocytic pathway are described here; to test their role on sensitivity of lymphoma cells to anti-lymphoma agents.

Neutrophils are the most abundant (40% to 75%) type of white blood cells and among the first inflammatory cells to migrate towards the site of ...

Development of Stem Cell-derived Antigen-specific Regulatory T Cells Against Autoimmunity

Autoimmune diseases arise due to the loss of immunological self-tolerance. Regulatory T cells (Tregs) are important mediators of immunologic self-tolerance. Tregs represent about 5 - 10% of the mature CD4+ T cell subpopulation in mice and humans, with about 1 - 2% of those Tregs circulating in the peripheral blood. Induced pluripotent stem cells (iPSCs) can be differentiated into functional Tregs, which have a potential to be used for cell-based therapies of autoimmune diseases. Here, we present a method to develop antigen (Ag)-specific Tregs from iPSCs (i.e., iPSC-Tregs). The method is based on incorporating the transcription factor FoxP3 and an Ag-specific T cell receptor (TCR) into iPSCs and then differentiating on OP9 stromal cells expressing Notch ligands delta-like (DL) 1 and DL4. Following in vitro differentiation, the iPSC-Tregs express CD4, CD8, CD3, CD25, FoxP3, and Ag-specific TCR and are able to respond to Ag stimulation. This method has been successfully applied to cell-based therapy of autoimmune arthritis in a murine model. Adoptive transfer of these Ag-specific iPSC-Tregs into Ag-induced arthritis (AIA)-bearing mice has the ability to reduce joint inflammation and swelling and to prevent bone loss.

We present here a method to develop functional antigen (Ag)-specific regulatory T cells (Tregs) from induced pluripotent stem cells (iPSCs) for immunotherapy of autoimmune arthritis in a murine model.

Autoimmune diseases arise due to the loss of immunological self-tolerance. Regulatory T cells (Tregs) are important mediators of immunologic ...

Use of the Soft-agar Overlay Technique to Screen for Bacterially Produced Inhibitory Compounds

The soft-agar overlay technique was originally developed over 70 years ago and has been widely used in several areas of microbiological research, including work with bacteriophages and bacteriocins, proteinaceous antibacterial agents. This approach is relatively inexpensive, with minimal resource requirements. This technique consists of spotting supernatant from a donor strain (potentially harboring a toxic compound(s)) onto a solidified soft agar overlay that is seeded with a bacterial test strain (potentially sensitive to the toxic compound(s)). We utilized this technique to screen a library of Pseudomonas syringae strains for intraspecific killing. By combining this approach with a precipitation step and targeted gene deletions, multiple toxic compounds produced by the same strain can be differentiated. The two antagonistic agents commonly recovered using this technique are bacteriophages and bacteriocins. These two agents can be differentiated using two simple additional tests. Performing a serial dilution on a supernatant containing bacteriophage will result in individual plaques becoming less in number with greater dilution, whereas serial dilution of a supernatant containing bacteriocin will result a clearing zone that becomes uniformly more turbid with greater dilution. Additionally, a bacteriophage will produce a clearing zone when spotted onto a fresh soft agar overlay seeded with the same strain, whereas a bacteriocin will not produce a clearing zone when transferred to a fresh soft agar lawn, owing to the dilution of the bacteriocin.

We describe a simple method for screening bacterial cultures for the production of compounds inhibitory towards other bacteria.

The soft-agar overlay technique was originally developed over 70 years ago and has been widely used in several areas of microbiological research, ...

Combining Analysis of DNA in a Crude Virion Extraction with the Analysis of RNA from Infected Leaves to Discover New Virus Genomes

This metagenome approach is used to identify plant viruses with circular DNA genomes and their transcripts. Often plant DNA viruses that occur in low titers in their host or cannot be mechanically inoculated to another host are difficult to propagate to achieve a greater titer of infectious material. Infected leaves are ground in a mild buffer with optimal pH and ionic composition recommended for purifying most bacilliform Para retroviruses. Urea is used to break up inclusion bodies that trap virions and to dissolve cellular components. Differential centrifugation provides further separation of virions from plant contaminants. Then proteinase K treatment removes the capsids. Then the viral DNA is concentrated and used for next-generation sequencing (NGS). The NGS data are used to assemble contigs which are submitted to NCBI-BLASTn to identify a subset of virus sequences in the generated dataset. In a parallel pipeline, RNA is isolated from infected leaves using a standard column-based RNA extraction method. Then ribosome depletion is carried out to enrich for a subset of mRNA and virus transcripts. Assembled sequences derived from RNA sequencing (RNA-seq) were submitted to NCBI-BLASTn to identify a subset of virus sequences in this dataset. In our study, we identified two related full-length badnavirus genomes in the two datasets. This method is preferred to another common approach which extracts the aggregate population of small RNA sequences to reconstitute plant virus genomic sequences. This latter metagenomic pipeline recovers virus related sequences that are retro-transcribing elements inserted into the plant genome. This is coupled to biochemical or molecular assays to further discern the actively infectious agents. The approach documented in this study, recovers sequences representative of replicating viruses that likely indicate active virus infection.

Here we present a new approach to identify plant viruses with double-strand DNA genomes. We use standard methods to extract DNA and RNA from infected leaves and carry out next-generation sequencing. Bioinformatic tools assemble sequences into contigs, identify contigs representing virus genomes and assign genomes to taxonomic groups.

This metagenome approach is used to identify plant viruses with circular DNA genomes and their transcripts. Often plant DNA viruses that occur in low ...

Establishment of Viral Infection and Analysis of Host-Virus Interaction in Drosophila Melanogaster

Virus spreading is a major cause of epidemic diseases. Thus, understanding the interaction between the virus and the host is very important to extend our knowledge of prevention and treatment of viral infection. The fruit fly Drosophila melanogaster has proven to be one of the most efficient and productive model organisms to screen for antiviral factors and investigate virus-host interaction, due to powerful genetic tools and highly conserved innate immune signaling pathways. The procedure described here demonstrates a nano-injection method to establish viral infection and induce systemic antiviral responses in adult flies. The precise control of the viral injection dose in this method enables high experimental reproducibility. Protocols described in this study include the preparation of flies and the virus, the injection method, survival rate analysis, the virus load measurement, and an antiviral pathway assessment. The influence effects of viral infection by the flies' background were mentioned here. This infection method is easy to perform and quantitatively repeatable; it can be applied to screen for host/viral factors involved in virus-host interaction and to dissect the crosstalk between innate immune signaling and other biological pathways in response to viral infection.

Establishment of Viral Infection and Analysis of Host-Virus Interaction in Drosophila Melanogaster

This protocol describes how to establish viral infection in vivo in Drosophila melanogaster using the nano-injection method and basic techniques to analyze virus-host interaction.

Virus spreading is a major cause of epidemic diseases. Thus, understanding the interaction between the virus and the host is very important to extend our ...

Flow Cytometric Measurement Of ROS Production In Macrophages In Response To Fc&#947;R Cross-linking

The oxidative or respiratory burst is used to describe the rapid consumption of oxygen and generation of reactive oxygen species (ROS) by phagocytes in response to various immune stimuli. ROS generated during immune activation exerts potent antimicrobial activity primarily through the ability of ROS to damage DNA and proteins, causing death of microorganisms. Being able to measure ROS production reproducibly and with ease is necessary in order to assess the contribution of various pathways and molecules to this mechanism of host defense. In this paper, we demonstrate the use of fluorescent probes and flow cytometry to detect ROS production. Although widely used, fluorescent measurement of ROS is notoriously problematic, especially with regards to measurement of ROS induced by specific and not mitogenic stimuli. We present a detailed methodology to detect ROS generated as a result of specific Fc&#947;R stimulation beginning with macrophage generation, priming, staining, Fc&#947;R cross-linking, and ending with flow cytometric analysis.

Flow Cytometric Measurement Of ROS Production In Macrophages In Response To Fc&amp;#947;R Cross-linking

This study demonstrates the use of flow cytometry to detect reactive oxygen species (ROS) production resulting from activation of the Fc&#947;R. This method can be used to assess changes in the antimicrobial and redox signaling function of phagocytes in response to immune complexes, opsonized microorganisms, or direct Fc&#947;R cross-linking.

The oxidative or respiratory burst is used to describe the rapid consumption of oxygen and generation of reactive oxygen species (ROS) by phagocytes in ...