This study was supported by grants from the Israel Science Foundation and the Rappaport Family Institute for Research in the Medical Sciences, and the Deutsche Forschungsgemeinschaft (DFG).

<ol>
	<li>Banerjee, S., Fisher, O., Lohia, A., Ankri, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Entamoeba+histolytica+DNA+methyltransferase+(Ehmeth)+is+a+nuclear+matrix+protein+that+binds+EhMRS2,+a+DNA+that+includes+a+scaffold/matrix+attachment+region+(S/MAR).">Entamoeba histolytica DNA methyltransferase (Ehmeth) is a nuclear matrix protein that binds EhMRS2, a DNA that includes a scaffold/matrix attachment region (S/MAR).</a> Mol Biochem Parasitol. 139, 91-97 (2005).</li><li>Fisher, O., Siman-Tov, R., Ankri, S. <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+cytosine+methylated+regions+and+5-cytosine+DNA+methyltransferase+(Ehmeth)+in+the+protozoan+parasite+Entamoeba+histolytica.">Characterization of cytosine methylated regions and 5-cytosine DNA methyltransferase (Ehmeth) in the protozoan parasite Entamoeba histolytica.</a> Nucleic Acids Res. 32, 287-297 (2004).</li><li>Harony, H., Bernes, S., Siman-Tov, R., Ankri, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=DNA+methylation+and+targeting+of+LINE+retrotransposons+in+Entamoeba+histolytica+and+Entamoeba+invadens.">DNA methylation and targeting of LINE retrotransposons in Entamoeba histolytica and Entamoeba invadens.</a> Mol Biochem Parasitol. 147, 55-63 (2006).</li><li>Kuhlmann, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Silencing+of+retrotransposons+in+Dictyostelium+by+DNA+methylation+and+RNAi.">Silencing of retrotransposons in Dictyostelium by DNA methylation and RNAi.</a> Nucleic Acids Res. 33, 6405-6417 (2005).</li><li>Katoh, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Developmentally+regulated+DNA+methylation+in+Dictyostelium+discoideum.">Developmentally regulated DNA methylation in Dictyostelium discoideum.</a> Eukaryot Cell. 5, 18-25 (2006).</li><li>Phalke, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retrotransposon+silencing+and+telomere+integrity+in+somatic+cells+of+Drosophila+depends+on+the+cytosine-5+methyltransferase+DNMT2.">Retrotransposon silencing and telomere integrity in somatic cells of Drosophila depends on the cytosine-5 methyltransferase DNMT2.</a> Nat Genet. 41, 696-702 (2009).</li><li>Tovy, A., Siman Tov, R., Gaentzsch, R., Helm, M., Ankri, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+nuclear+function+of+the+Entamoeba+histolytica+glycolytic+enzyme+enolase:+the+metabolic+regulation+of+cytosine-5+methyltransferase+2+(Dnmt2)+activity.">A new nuclear function of the Entamoeba histolytica glycolytic enzyme enolase: the metabolic regulation of cytosine-5 methyltransferase 2 (Dnmt2) activity.</a> PLoS Pathog. 6, e1000775-e1000775 (2010).</li><li>Jeltsch, A., Nellen, W., Lyko, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two+substrates+are+better+than+one:+dual+specificities+for+Dnmt2+methyltransferases.">Two substrates are better than one: dual specificities for Dnmt2 methyltransferases.</a> Trends Biochem Sci. 31, 306-308 (2006).</li><li>Fechter, P., Rudinger, J., Giege, R., Theobald-Dietrich, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ribozyme+processed+tRNA+transcripts+with+unfriendly+internal+promoter+for+T7+RNA+polymerase:+production+and+activity.">Ribozyme processed tRNA transcripts with unfriendly internal promoter for T7 RNA polymerase: production and activity.</a> FEBS Lett. 436, 99-103 (1998).</li><li>Hermann, A., Schmitt, S., Jeltsch, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+human+Dnmt2+has+residual+DNA-(Cytosine-C5)-methyltransferase+activity.">The human Dnmt2 has residual DNA-(Cytosine-C5)-methyltransferase activity.</a> J Biol Chem. 278, 31717-31721 (2003).</li><li>Narsa Reddy, M., Tang, L. Y., Lee, T. L., &amp;amp, T. L., James Shen, C. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+candidate+gene+for+Drosophila+genome+methylation.">A candidate gene for Drosophila genome methylation.</a> Oncogene. 22, 6301-6303 (2003).</li></ol>

No conflicts of interest declared.

In this presentation, we illustrated how to prepare active components for the measure of the tRNA methyltransferase activity of E. histolytica Ehmeth enzyme. This procedure can serve as a starting point and be easily adapted for the measure of other tRNA methyltransferases. It is important to follow the procedures that preserve the quality and the integrity of the tRNA substrate and of the tRNA methyltransferase protein to insure an optimal measure of the enzymatic activity.

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		<div>
		<table border="1">
		<thead>
		<tr>
		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
		</tr>
		</thead>
		<tbody>
		
<tr>
<td>Taq Polymerase (5 U/&mu;l)</td>
<td>&nbsp;</td>
<td>Rapidozym, Berlin</td>
<td>GEN-003-1000</td>
<td>&nbsp;</td>
<tr>
<td>10X Gentherm PCR Buffer</td>
<td>&nbsp;</td>
<td>Rapidozym, Berlin</td>
<td>With GEN-003-1000</td>
<td>&nbsp;</td>
<tr>
<td>MgCl2 (50 mM)</td>
<td>&nbsp;</td>
<td>Rapidozym, Berlin</td>
<td>With GEN-003-1000</td>
<td>&nbsp;</td>
<tr>
<td>dNTP mix (10 mM)</td>
<td>&nbsp;</td>
<td>Fermentas, St. Leon-Rot</td>
<td>R0191</td>
<td>&nbsp;</td>
<tr>
<td>Oligo nucleotides</td>
<td>&nbsp;</td>
<td>IBA, G&ouml;ttingen</td>
<td>Customized</td>
<td>&nbsp;</td>
<tr>
<td>NTP mix (25mM)</td>
<td>&nbsp;</td>
<td>Fermentas, St. Leon-Rot</td>
<td>R0481</td>
<td>&nbsp;</td>
<tr>
<td>GelRed Nucleic Acid Stain 3X in water</td>
<td>&nbsp;</td>
<td>Biotium</td>
<td>41001</td>
<td>&nbsp;</td>
<tr>
<td>Dithiotreitol</td>
<td>&nbsp;</td>
<td>Fermentas, St. Leon-Rot</td>
<td>R0861</td>
<td>&nbsp;</td>
<tr>
<td>Spermidine</td>
<td>&nbsp;</td>
<td>Sigma, Germany</td>
<td>S0266</td>
<td>&nbsp;</td>
<tr>
<td>Pall Nanosep 0.45 &mu;m</td>
<td>&nbsp;</td>
<td>Sigma, Germany</td>
<td>Z722014</td>
<td>&nbsp;</td>
<tr>
<td>Dichlorodimethylsilane</td>
<td>&nbsp;</td>
<td>Sigma, Germany</td>
<td>40140</td>
<td>&nbsp;</td>
<tr>
<td>Ethanol (Ph. Eur.)</td>
<td>&nbsp;</td>
<td>Roth, Karlsruhe</td>
<td>5054.3</td>
<td>&nbsp;</td>
<tr>
<td>Tris HCl</td>
<td>&nbsp;</td>
<td>Roth, Karlsruhe</td>
<td>9090.3</td>
<td>&nbsp;</td>
<tr>
<td>Tris</td>
<td>&nbsp;</td>
<td>Roth, Karlsruhe</td>
<td>AE15.1</td>
<td>&nbsp;</td>
<tr>
<td>BSA</td>
<td>&nbsp;</td>
<td>Fermentas, St. Leon-Rot</td>
<td>B14</td>
<td>&nbsp;</td>
<tr>
<td>Triton X-100</td>
<td>&nbsp;</td>
<td>Sigma, Germany</td>
<td>T8787</td>
<td>&nbsp;</td>
<tr>
<td>TEMED</td>
<td>&nbsp;</td>
<td>Roth, Karlsruhe</td>
<td>2367.1</td>
<td>&nbsp;</td>
<tr>
<td>Ammonium Peroxodisulfate</td>
<td>&nbsp;</td>
<td>Roth, Karlsruhe</td>
<td>9592.2</td>
<td>&nbsp;</td>
<tr>
<td>Rotiphorese Sequencing gel concentrate</td>
<td>&nbsp;</td>
<td>Roth, Karlsruhe</td>
<td>3043.1</td>
<td>&nbsp;</td>
<tr>
<td>Rotiphorese Sequencing gel diluent</td>
<td>&nbsp;</td>
<td>Roth, Karlsruhe</td>
<td>3047.1</td>
<td>&nbsp;</td>
<tr>
<td>Rotiphorese Sequencing gel buffer concentrate</td>
<td>&nbsp;</td>
<td>Roth, Karlsruhe</td>
<td>3050.1</td>
<td>&nbsp;</td>
<tr>
<td>Rotiphorese 10X TBE-buffer</td>
<td>&nbsp;</td>
<td>Roth, Karlsruhe</td>
<td>3061.2</td>
<td>&nbsp;</td>
<tr>
<td>DEPC</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>D5758</td>
<td>&nbsp;</td>
<tr>
<td>RNAse ExTERMINATOR</td>
<td>&nbsp;</td>
<td>Biological Industry Beit Haemek</td>
<td>01-895-1B</td>
<td>&nbsp;</td>
<tr>
<td>Ampicillin</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>A0166</td>
<td>&nbsp;</td>
<tr>
<td>IPTG</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>I6758</td>
<td>&nbsp;</td>
<tr>
<td>PMSF</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>P7626</td>
<td>&nbsp;</td>
<tr>
<td>Lysozyme</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>L7651</td>
<td>&nbsp;</td>
<tr>
<td>Leupeptine</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>L2884</td>
<td>&nbsp;</td>
<tr>
<td>Benzonase Nuclease</td>
<td>&nbsp;</td>
<td>Novagen</td>
<td>70746-3</td>
<td>&nbsp;</td>
<tr>
<td>BugBuster protein extraction reagent</td>
<td>&nbsp;</td>
<td>Novagen</td>
<td>70921-3</td>
<td>&nbsp;</td>
<tr>
<td>Glutathione-agarose resin</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>G4510</td>
<td>&nbsp;</td>
<tr>
<td>L-glutathione reduced</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>G4251</td>
<td>&nbsp;</td>
<tr>
<td>AdoMet</td>
<td>&nbsp;</td>
<td>New England Biolabs</td>
<td>B9003</td>
<td>&nbsp;</td>
<tr>
<td>AdoMet 3H</td>
<td>&nbsp;</td>
<td>PerkinElmer</td>
<td>NET155250UC</td>
<td>&nbsp;</td>
<tr>
<td>Scintillation Cocktail</td>
<td>&nbsp;</td>
<td>CytoScint</td>
<td>882453</td>
<td>&nbsp;</td>		</tbody>
		</table>
		</div>

in vitro trna methylation assay with the entamoeba histolytica dna and trna methyltransferase dnmt2 (ehmeth) enzyme

Protozoan parasites are among the most devastating infectious agents of humans responsible for a variety of diseases including amebiasis, which is one of the three most common causes of death from parasitic disease. The agent of amebiasis is the amoeba parasite Entamoeba histolytica that exists under two stages: the infective cyst found in food or water and the invasive trophozoite living in the intestine. The clinical manifestations of amebiasis range from being asymptomatic to colitis, dysentery or liver abscesses. E. histolytica is one of the rare unicellular parasite with 5-methylcytosine (5mC) in its genome. 1, 2 It contains a single DNA methyltransferase, Ehmeth, that belongs to the Dnmt2 family. 2 A role for Dnmt2 in the control of repetitive elements has been established in E. histolytica, 3 Dictyostelium discoideum 4,5 and Drosophila. 6 Our recent work has shown that Ehmeth methylates tRNAAsp, and this finding indicates that this enzyme has a dual DNA/tRNAAsp methyltransferase activity. 7 This observation is in agreement with the dual activity that has been reported for D. discoideum and D. melanogaster. 8 The functional significance of the DNA/tRNA specificity of Dnmt2 enzymes is still unknown. To address this question, a method to determine the tRNA methyltransferase activity of Dnmt2 proteins was established. In this video, we describe a straightforward approach to prepare an adequate tRNA substrate for Dnmt2 and a method to measure its tRNA methyltransferase activity.

Watch this Scientific Journal Video about In vitro tRNA Methylation Assay with the Entamoeba histolytica DNA and tRNA Methyltransferase Dnmt2 Ehmeth Enzyme at JoVE.com

In vitro tRNA Methylation Assay with the Entamoeba histolytica DNA and tRNA Methyltransferase Dnmt2 Ehmeth Enzyme

This protocol describes the preparation of a synthetic tRNA substrate for the Entamoeba histolytica DNA/tRNA methyltransferase 2 (Dnmt2) homolog Ehmeth and the measure of its methyltransferase activity. This experimental approach can be used for investigating the activity of other Dnmt2 proteins.

In vitro tRNA Methylation Assay with the Entamoeba histolytica DNA and tRNA Methyltransferase Dnmt2 (Ehmeth) Enzyme

Protozoan parasites are among the most devastating infectious agents of humans responsible for a variety of diseases including amebiasis, which is one of ...

in-vitro-trna-methylation-assay-with-entamoeba-histolytica-dna-trna

Research

JoVE Journal

Immunology and Infection

14.3K Views.  Technion - Israel Institute of Technology. Этот протокол описывает подготовку синтетический субстрат для тРНК Entamoeba histolytica ДНК / тРНК метилтрансферазы 2 (Dnmt2) Ehmeth гомолога и мера ее метилтрансферазы деятельности. Этот экспериментальный подход может быть использован для исследования деятельнос...

Video: In vitro tRNA Methylation Assay with the Entamoeba histolytica DNA and tRNA Methyltransferase Dnmt2 Ehmeth Enzyme

Development of a Negative Selectable Marker for Entamoeba histolytica

Entamoeba histolytica is the causative agent of amebiasis and infects up to 10% of the world's population. The molecular techniques that have enabled the up- and down-regulation of gene expression rely on the transfection of stably maintained plasmids. While these have increased our understanding of Entamoeba virulence factors, the capacity to integrate exogenous DNA into genome, which would allow reverse genetics experiments, would be a significant advantage in the study of this parasite. The challenges presented by this organism include inability to select for homologous recombination events and difficulty to cure episomal plasmid DNA from transfected trophozoites. The later results in a high background of exogenous DNA, a major problem in the identification of trophozoites in which a bona fide genomic integration event has occurred. We report the development of a negative selection system based upon transgenic expression of a yeast cytosine deaminase and uracil phosphoribosyl transferase chimera (FCU1) and selection with prodrug 5-fluorocytosine (5-FC). The FCU1 enzyme converts non-toxic 5-FC into toxic 5-fluorouracil and 5-fluorouridine-5'-monophosphate. E. histolytica lines expressing FCU1 were found to be 30 fold more sensitive to the prodrug compared to the control strain.

Development of a Negative Selectable Marker for Entamoeba histolytica

We report development of a negative selection system in E. histolytica based upon transgenic expression of a chimeric protein (FCU1) and selection with the prodrug 5-fluorocytosine. The FCU1 protein is a fusion of yeast cytosine deaminase and uracil phosphoribosyltransferase. Expression of FCU1 resulted in increased E. histolytica sensitivity towards 5-fluorocytosine.

Entamoeba histolytica is the causative agent of amebiasis and infects up to 10% of the world's population. The molecular techniques that have enabled the ...

In Vitro Assay of Bacterial Adhesion onto Mammalian Epithelial Cells

To cause infections, bacteria must colonize their host. Bacterial pathogens express various molecules or structures able to promote attachment to host cells1. These adhesins rely on interactions with host cell surface receptors or soluble proteins acting as a bridge between bacteria and host. Adhesion is a critical first step prior to invasion and/or secretion of toxins, thus it is a key event to be studied in bacterial pathogenesis. Furthermore, adhered bacteria often induce exquisitely fine-tuned cellular responses, the studies of which have given birth to the field of 'cellular microbiology'2. Robust assays for bacterial adhesion on host cells and their invasion therefore play key roles in bacterial pathogenesis studies and have long been used in many pioneer laboratories3,4. These assays are now practiced by most laboratories working on bacterial pathogenesis.
Here, we describe a standard adherence assay illustrating the contribution of a specific adhesin. We use the Escherichia coli strain 27875, a human pathogenic strain expressing the autotransporter Adhesin Involved in Diffuse Adherence (AIDA). As a control, we use a mutant strain lacking the aidA gene, 2787&Delta;aidA (F. Berthiaume and M. Mourez, unpublished), and a commercial laboratory strain of E. coli, C600 (New England Biolabs). The bacteria are left to adhere to the cells from the commonly used HEp-2 human epithelial cell line. This assay has been less extensively described before6.

In Vitro Assay of Bacterial Adhesion onto Mammalian Epithelial Cells

This protocol is a simple bacterial adhesion assay consisting in counting the numbers of bacterial colony forming units that are adhered onto cultured cells. The assay is robust, independent of the adhesin studied, and numerous variations are used in most laboratories working on bacterial pathogenesis.

To cause infections, bacteria must colonize their host. Bacterial pathogens express various molecules or structures able to promote attachment to host ...

Establishment of an In vitro System to Study Intracellular Behavior of Candida glabrata in Human THP-1 Macrophages

A cell culture model system, if a close mimic of host environmental conditions, can serve as an inexpensive, reproducible and easily manipulatable alternative to animal model systems for the study of a specific step of microbial pathogen infection. A human monocytic cell line THP-1 which, upon phorbol ester treatment, is differentiated into macrophages, has previously been used to study virulence strategies of many intracellular pathogens including Mycobacterium tuberculosis. Here, we discuss a protocol to enact an in vitro cell culture model system using THP-1 macrophages to delineate the interaction of an opportunistic human yeast pathogen Candida glabrata with host phagocytic cells. This model system is simple, fast, amenable to high-throughput mutant screens, and requires no sophisticated equipment. A typical THP-1 macrophage infection experiment takes approximately 24 hr with an additional 24-48 hr to allow recovered intracellular yeast to grow on rich medium for colony forming unit-based viability analysis. Like other in vitro model systems, a possible limitation of this approach is difficulty in extrapolating the results obtained to a highly complex immune cell circuitry existing in the human host. However, despite this, the current protocol is very useful to elucidate the strategies that a fungal pathogen may employ to evade/counteract antimicrobial response and survive, adapt, and proliferate in the nutrient-poor environment of host immune cells.

Establishment of an In vitro System to Study Intracellular Behavior of Candida glabrata in Human THP-1 Macrophages

The current article outlines a protocol to establish an in vitro cell culture model system to study the interaction of a facultative intracellular human fungal pathogen Candida glabrata with human macrophages which will be a useful tool to advance our knowledge of fungal virulence mechanisms.

A cell culture model system, if a close mimic of host environmental conditions, can serve as an inexpensive, reproducible and easily manipulatable ...

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 ...

Investigating the Effects of Probiotics on Pneumococcal Colonization Using an In Vitro Adherence Assay

Adherence of Streptococcus pneumoniae (the pneumococcus) to the epithelial lining of the nasopharynx can result in colonization and is considered a prerequisite for pneumococcal infections such as pneumonia and otitis media. In vitro adherence assays can be used to study the attachment of pneumococci to epithelial cell monolayers and to investigate potential interventions, such as the use of probiotics, to inhibit pneumococcal&#160;colonization.&#160;The protocol described here is used to investigate the effects of the probiotic Streptococcus salivarius on the adherence of pneumococci to the human epithelial cell line CCL-23 (sometimes referred to as HEp-2 cells). The assay involves three main steps: 1) preparation of epithelial and bacterial cells, 2) addition of bacteria to epithelial cell monolayers, and 3) detection of adherent pneumococci by viable counts (serial dilution and plating) or quantitative real-time PCR (qPCR). This technique is relatively straightforward and does not require specialized equipment other than a tissue culture setup. The assay can be used to test other probiotic species and/or potential inhibitors of pneumococcal colonization and can be easily modified to address other scientific questions regarding pneumococcal adherence and invasion.

Investigating the Effects of Probiotics on Pneumococcal Colonization Using an In Vitro Adherence Assay

In vitro adherence assays can be used to study the attachment of Streptococcus pneumoniae to epithelial cell monolayers and to investigate potential interventions such as the use of probiotics for inhibiting pneumococcal colonization.

Adherence of Streptococcus pneumoniae (the pneumococcus) to the epithelial lining of the nasopharynx can result in colonization and is considered a ...

A Restriction Enzyme Based Cloning Method to Assess the In vitro Replication Capacity of HIV-1 Subtype C Gag-MJ4 Chimeric Viruses

The protective effect of many HLA class I alleles on HIV-1 pathogenesis and disease progression is, in part, attributed to their ability to target conserved portions of the HIV-1 genome that escape with difficulty. Sequence changes attributed to cellular immune pressure arise across the genome during infection, and if found within conserved regions of the genome such as Gag, can affect the ability of the virus to replicate in vitro. Transmission of HLA-linked polymorphisms in Gag to HLA-mismatched recipients has been associated with reduced set point viral loads. We hypothesized this may be due to a reduced replication capacity of the virus. Here we present a novel method for assessing the in vitro replication of HIV-1 as influenced by the gag gene isolated from acute time points from subtype C infected Zambians. This method uses restriction enzyme based cloning to insert the gag gene into a common subtype C HIV-1 proviral backbone, MJ4. This makes it more appropriate to the study of subtype C sequences than previous recombination based methods that have assessed the in vitro replication of chronically derived gag-pro sequences. Nevertheless, the protocol could be readily modified for studies of viruses from other subtypes. Moreover, this protocol details a robust and reproducible method for assessing the replication capacity of the Gag-MJ4 chimeric viruses on a CEM-based T cell line. This method was utilized for the study of Gag-MJ4 chimeric viruses derived from 149 subtype C acutely infected Zambians, and has allowed for the identification of residues in Gag that affect replication. More importantly, the implementation of this technique has facilitated a deeper understanding of how viral replication defines parameters of early HIV-1 pathogenesis such as set point viral load and longitudinal CD4+ T cell decline.

A Restriction Enzyme Based Cloning Method to Assess the In vitro Replication Capacity of HIV-1 Subtype C Gag-MJ4 Chimeric Viruses

HIV-1 pathogenesis is defined by both viral characteristics and host genetic factors. Here we describe a robust method that allows for reproducible measurements to assess the impact of the gag gene sequence variation on the in vitro replication capacity of the virus.

The protective effect of many HLA class I alleles on HIV-1 pathogenesis and disease progression is, in part, attributed to their ability to target ...

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 ...

Development of an in vitro model system for studying the interaction of Equus caballus IgE with its high-affinity receptor Fc&#949;RI

The interaction of IgE with its high-affinity Fc receptor (Fc&#949;RI) followed by an antigenic challenge is the principal pathway in IgE mediated allergic reactions. As a consequence of the high affinity binding between IgE and Fc&#949;RI, along with the continuous production of IgE by B cells, allergies usually persist throughout life, with currently no permanent cure available. Horses, especially race horses, which are commonly inbred, are a species of mammals that are very prone to the development of hypersensitivity responses, which can seriously affect their performance. Physiological responses to allergic sensitization in horses mirror that observed in humans and dogs. In this paper we describe the development of an in situ assay system for the quantitative assessment of the release of mediators of the allergic response pertaining to the equine system. To this end, the gene encoding equine Fc&#949;RI&#945; was transfected into and expressed onto the surface of parental Rat Basophil Leukemia (RBL-2H3.1) cells. The gene product of the transfected equine &#945;-chain formed a functional receptor complex with the endogenous rat &#946;- and &#947;-chains 1. The resultant assay system facilitated an assessment of the quantity of mediator secreted from equine Fc&#949;RI&#945; transfected RBL-2H3.1 cells following sensitization with equine IgE and antigenic challenge using &#946;-hexosaminidase release as a readout 2, 3. Mediator release peaked at 36.68% &#177; 4.88% at 100 ng ml-1 of antigen. This assay was modified from previous assays used to study human and canine allergic responses 4, 5. We have also shown that this type of assay system has multiple applications for the development of diagnostic tools and the safety assessment of potential therapeutic intervention strategies in allergic disease 6, 2, 3.

Development of an &lt;em&gt;in vitro&lt;/em&gt; model system for studying the interaction of &lt;em&gt;Equus&lt;/em&gt; &lt;em&gt;caballus&lt;/em&gt; IgE with its high-affinity receptor Fc&amp;#949;RI

The current study describes the development and applications of a genetically engineered assay system based on the transfection of rat basophilic leukemia cells with the equine Fc&#949;RI&#945; gene. Transfected cells express a functional receptor where the release of mediators of the allergic response can be activated by IgE and antigen.

The interaction of IgE with its high-affinity Fc receptor (Fc&#949;RI) followed by an antigenic challenge is the principal pathway in IgE mediated ...

Measuring Influenza Neuraminidase Inhibition Antibody Titers by Enzyme-linked Lectin Assay

Antibodies to neuraminidase (NA), the second most abundant surface protein on influenza virus, contribute toward protection against influenza. Traditional methods to measure NA inhibiting (NI) antibody titers are not practical for routine serology. This protocol describes the enzyme-linked lectin assay (ELLA), a practical alternative method to measure NI titers that is performed in 96 well plates coated with a large glycoprotein substrate, fetuin. NA cleaves terminal sialic acids from fetuin, exposing the penultimate sugar, galactose. Peanut agglutinin (PNA) is a lectin with specificity for galactose and therefore the extent of desialylation can be quantified using a PNA-horseradish peroxidase conjugate, followed by addition of a chromogenic peroxidase substrate. The optical density that is measured is proportional to NA activity. To measure NI antibody titers, serial dilutions of sera are incubated at 37 &#176;C O/N on fetuin-coated plates with a fixed amount of NA. The reciprocal of the highest serum dilution that results in &#8805;50% inhibition of NA activity is designated as the NI antibody titer. The ELLA provides a practical format for routine evaluation of human antibody responses following influenza infection or vaccination.

We describe the enzyme-linked lectin assay (ELLA) for measuring influenza neuraminidase (NA)-inhibition antibody titers in sera. The assay uses peanut agglutinin to quantify galactose residues that become accessible when NA removes sialic acid from fetuin-coated, 96-well plates.

Antibodies to neuraminidase (NA), the second most abundant surface protein on influenza virus, contribute toward protection against influenza. Traditional ...

Analysis of Lymphocyte Extravasation Using an In Vitro Model of the Human Blood-brain Barrier

Lymphocyte extravasation into the central nervous system (CNS) is critical for immune surveillance. Disease-related alterations of lymphocyte extravasation might result in pathophysiological changes in the CNS. Thus, investigation of lymphocyte migration into the CNS is important to understand inflammatory CNS diseases and to develop new therapy approaches. Here we present an in vitro model of the human blood-brain barrier to study lymphocyte extravasation. Human brain microvascular endothelial cells (HBMEC) are confluently grown on a porous polyethylene terephthalate transwell insert to mimic the endothelium of the blood-brain barrier. Barrier function is validated by zonula occludens immunohistochemistry, transendothelial electrical resistance (TEER) measurements as well as analysis of evans blue permeation. This model allows investigation of the diapedesis of rare lymphocyte subsets such as CD56brightCD16dim/- NK cells. Furthermore, the effects of other cells, cytokines and chemokines, disease-related alterations, and distinct treatment regimens on the migratory capacity of lymphocytes can be studied. Finally, the impact of inflammatory stimuli as well as different treatment regimens on the endothelial barrier can be analyzed.

Analysis of Lymphocyte Extravasation Using an In Vitro Model of the Human Blood-brain Barrier

Here, we describe a human blood-brain barrier model enabling to investigate lymphocyte transmigration into the central nervous system in vitro.