Vorremmo ringraziare il Dott. Philippe Erbs per averci fornito la sequenza delle FCU1 genica. Questo lavoro è stato sostenuto da NIH concedere AI 26649.

1. FCU sistema di selezione negativa in Entamoeba histolytica <ol><li> La linea di controllo vettoriale (HM1 / pKT3M) e la linea sperimentale (HM1/pKT3M-FCU1) sono stati generati da 1,2 tecniche descritte in precedenza. Seed le linee oggetto di studio dai tubi magazzino in T-25 palloni e mantenere la selezione con l&#39;aggiunta di antibiotico appropriato (12 mg / mL G418) in TYI-S-33 3 media. I palloni devono essere del 70-80% confluenti dopo 16-18 ore di crescita a 37 ° C. </li><li> Preparare una soluzione fresca magazzino 50mM di 5-fluorocytosine (5-FC, Sigma) nel warm TYI-S-33 di media. Vortex rigorosamente per alcuni minuti per sciogliere 5-FC completamente. Filtro-sterilizzare la soluzione madre facendola passare attraverso un filtro di 0,22 micron. </li><li> Trofozoiti raccolta mettendo i palloni in ghiaccio per 3-5 minuti e raccogliere le cellule per centrifugazione a 200xg per 5 minuti a temperatura ambiente. Risospendere il pellet in acqua dolce di media TYI e contare le cellule. </li><li> Progettazione di un tipico esperimento utilizza 0,5 x 10 4 cellule per pozzetto di una piastra da 48 pozzetti in un volume finale di 1 ml; e ripete tripla per ogni condizione di test. Inoltre, per facilitare le misurazioni fluorescente, un piatto a parte è usata per ogni ceppo per ogni punto del tempo. </li><li> Semi di 0,5 x 10 4 cellule per pozzetto per ogni prova 5-FC concentrazione, in triplice copia. Mantenere la pressione antibiotica selezione nel medio TYI. Ora aggiungete la quantità necessaria di 5-FC soluzione madre e trofozoiti in ciascun pozzetto. </li><li> Incubare le piastre in un sacchetto anaerobica a 37 ° C. </li></ol> 2. Determinazione della efficienza di selezione <ol><li> Preparare 2 mg / ml soluzione stock di Cell Tracker verde CMFDA (Invitrogen) in DMSO. Per rendere la soluzione di lavoro diluire lo stock di 1000 volte in mezzo privo di siero TYI. </li><li> Rimuovere il supporto completamente da piastre di coltura trofozoite e sostituire con 150 microlitri di siero senza CMFDA TYI contiene. Continua incubazione a 37 ° C per 1 ora. </li><li> Rimuovere la soluzione colorante da pozzi e leggere la piastra nella spettrofluorimetro Spectramax M2 micropiastre. La lunghezza d&#39;onda di eccitazione deve essere impostata a 492 nm e l&#39;emissione di fluorescenza leggere a 517 nm. </li><li> Confrontare i valori di fluorescenza per le cellule di controllo rispetto al trasfettate prova. </li><li> Continua a leggere le piastre a ogni intervallo di tempo. Usa positiva appropriata (TYI solo) e negativi (25 mg / ml Hygromycin) pozzetti di controllo in ogni piatto. </li></ol> 3. Rappresentante Risultati La E. trasfettate histolytica ha mostrato l&#39;espressione solida di FCU1 codone ottimizzato ricombinante (Figura 1). Quando questo protocollo è seguita correttamente il risultato è l&#39;eliminazione selettiva di E. cellule che esprimono histolytica FCU1 in presenza di 0,5 mM 5-fluorocytosine. Cellule di controllo, al contrario continuano a crescere normalmente fino a 5 mM concentrazione di 5-FC e raggiungere la confluenza tra il 72 e 96 ore (Figura 2-a). Il FCU1 cellule portando a 48 ore sono completamente lisati, quando i pozzi trattati sono visti al microscopio. Questi mostrano anche diminuito fluorescenza quando colorati con il colorante vitale CMFDA, che viene utilizzato negli studi quantitativi che coinvolgono gran numero di campioni (figura 2-b). Il sistema FCU1/5-FC è uno strumento efficace e potente selezione negativa per E. histolytica trofozoiti. <img src="/files/ftp_upload/2410/2410fig1.jpg" alt="Figura 1" /> Figura 1. Generazione di E. histolytica HM1 trasfettate che esprimono negativo marcatore (A) FCU1 proteina ricombinante è stato rilevato su un Western Blot con anticorpi anti-c Myc (pannello superiore). Come previsto, una band 42kDa poteva essere individuato (indicato da una freccia) nel lisato totale dal trasfettate FCU, ma non nel vettore solo trasfettate controllo. Il pannello in basso mostra la macchia stessa sondato con l&#39;anticorpo contro l&#39;actina come controllo di caricamento. (B) I risultati della PCR in tempo reale quantitativo mostrando FCU1 espressione di mRNA specifico normalizzato a lgl4 controllo. <img src="/files/ftp_upload/2410/2410fig2.jpg" alt="Figura 2" /> Figura 2. Sensibilità ai farmaci in vitro di E. trasfettate histolytica esprimendo negativo marcatore Curve di sopravvivenza di (a) trasfettate controllo e (b) trasfettate FCU1 esprimere coltivate in 48 pozzetti. Le cellule sono state coltivate in presenza di concentrazioni crescenti del profarmaco-5-fluorocytosine; la sopravvivenza delle cellule è stata quantificata colorazione CMFDA ad ogni intervallo di tempo indicato sulla X-asse. L&#39;asse Y rappresenta unità fluorescenza ed è un riflesso diretto della popolazione di cellule sopravvissute. Si prega di notare che la FCU1 trasfettate che esprimono mostrato sensibilità significativa a concentrazione profarmaco 0,5 mm rispetto al controllo. Le cellule non sono stati osservati a punto temporale 120h in questi pozzi come comconfrontato alla crescita confluente visto in pozzetti di controllo corrispondente al microscopio (dati non riportati). Hygro denota 25μg / mL Hygromycin utilizzato come controllo negativo.

<ol>
	<li>Olvera, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stable+transfection+of+Entamoeba+histolytica+trophozoites+by+lipofection.">Stable transfection of Entamoeba histolytica trophozoites by lipofection.</a> Arch. Med. Res. , 49-51 (1997).</li><li>Saito-Nakano, Y., Yasuda, T., Nakada-Tsukui, K., Leippe, M., Nozaki, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rab5-associated+vacuoles+play+a+unique+role+in+phagocytosis+of+the+enteric+protozoan+parasite+Entamoeba+histolytica.">Rab5-associated vacuoles play a unique role in phagocytosis of the enteric protozoan parasite Entamoeba histolytica.</a> J. Biol. Chem. 279, 49497-49507 (2004).</li><li>Diamond, L. S., Harlow, D. R., Cunnick, C. C. <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+medium+for+the+axenic+cultivation+of+Entamoeba+histolytica+and+other+Entamoeba.">A new medium for the axenic cultivation of Entamoeba histolytica and other Entamoeba.</a> Trans. R. Soc. Trop. Med. Hyg. 72, 431-432 (1978).</li><li>Clark, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Anaerobic parasitic protozoa : genomics and molecular biology. , (2010).</li><li>Linford, A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Short+hairpin+RNA-mediated+knockdown+of+protein+expression+in+Entamoeba+histolytica.">Short hairpin RNA-mediated knockdown of protein expression in Entamoeba histolytica.</a> BMC Microbiol. 9, 38-38 (2009).</li><li>Solis, C. F., Guill&#233;n, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Silencing+genes+by+RNA+interference+in+the+protozoan+parasite+Entamoeba+histolytica.">Silencing genes by RNA interference in the protozoan parasite Entamoeba histolytica.</a> Methods Mol. Biol. 442, 113-128 (2008).</li><li>Solis, C. F., Santi-Rocca, J., Perdomo, D., Weber, C., Guill&#233;n, N. <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+bacterially+expressed+dsRNA+to+downregulate+Entamoeba+histolytica+gene+expression.">Use of bacterially expressed dsRNA to downregulate Entamoeba histolytica gene expression.</a> PLoS ONE. 4, e8424-e8424 (2009).</li><li>MacFarlane, R. C., Singh, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Loss+of+dsRNA-based+gene+silencing+in+Entamoeba+histolytica:+implications+for+approaches+to+genetic+analysis.">Loss of dsRNA-based gene silencing in Entamoeba histolytica: implications for approaches to genetic analysis.</a> Exp. Parasitol. 119, 296-300 (2008).</li><li>Dhar, S. K., Vines, R. R., Bhattacharya, S., Petri, W. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ribosomal+DNA+fragments+enhance+the+stability+of+transfected+DNA+in+Entamoeba+histolytica.">Ribosomal DNA fragments enhance the stability of transfected DNA in Entamoeba histolytica.</a> J. Eukaryot. Microbiol. 45, 656-660 (1998).</li><li>Erbs, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+cancer+gene+therapy+by+adenovirus-mediated+transfer+of+a+bifunctional+yeast+cytosine+deaminase/uracil+phosphoribosyltransferase+fusion+gene.">In vivo cancer gene therapy by adenovirus-mediated transfer of a bifunctional yeast cytosine deaminase/uracil phosphoribosyltransferase fusion gene.</a> Cancer Res. 60, 3813-3822 (2000).</li><li>Braks, J. A. M., Franke-Fayard, B., Kroeze, H., Janse, C. J., Waters, A. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+and+application+of+a+positive-negative+selectable+marker+system+for+use+in+reverse+genetics+in+Plasmodium.">Development and application of a positive-negative selectable marker system for use in reverse genetics in Plasmodium.</a> Nucleic Acids Res. 34, e39-e39 (2006).</li><li>Maier, A. G., Braks, J. A. M., Waters, A. P., Cowman, A. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Negative+selection+using+yeast+cytosine+deaminase/uracil+phosphoribosyl+transferase+in+Plasmodium+falciparum+for+targeted+gene+deletion+by+double+crossover+recombination.">Negative selection using yeast cytosine deaminase/uracil phosphoribosyl transferase in Plasmodium falciparum for targeted gene deletion by double crossover recombination.</a> Mol. Biochem. Parasitol. 150, 118-121 (2006).</li></ol>

La produzione di questo video è stato sponsorizzato da Sigma Aldrich, Inc., che produce alcuni dei reagenti utilizzati in questo articolo.

Anche se ci sono stati progressi sostanziali in Entamoeba strumenti molecolari biologici non esistono metodi attualmente disponibili per eliminare o interrompere geni 4. Knockdown di espressione genica specifici è stato raggiunto con l&#39;uso di RNA a gomito 5, piccoli RNA interferenti 6 e batteri espresso dsRNA 7. Tuttavia questi metodi efficaci, mentre per i geni bersaglio rispettivi, hanno diverse limitazioni compreso l&#39;uso di prodotti chimici costosi, selezione continua contro gli antibiotici e la necessità per la convalida costante a causa della elevata incidenza di ritorno che si verificano nel tempo (Alicia Linford, comunicazione personale) 8. Ogni plasmide può replicare in Entamoeba come non c&#39;è a quanto pare un requisito sequenza rigorosa delle origini di replicazione del DNA 9 e così una volta transfettate, di solito è difficile da curare un plasmide. Questo limita la possibilità di usare i plasmidi intatto negli esperimenti di knockout e ricombinazione genica. Marcatori di selezione negativa sono i componenti chiave del gene targeting metodi possono essere utilizzati per eliminare le sottopopolazioni ricombinante. Abbiamo espresso con successo un codone ottimizzato FCU1 gene in Entamoeba histolytica e testato le sue potenzialità come marcatore negativo selezionabile. Questo gene di fusione è stato utilizzato per la terapia genica suicidio delle cellule tumorali umane e metabolizza il profarmaco 5-FC in tossici prodotti a valle con conseguente inibizione della sintesi del DNA e RNA 10. FCU1 è stato recentemente utilizzato come marcatore negativo selezionabile in Plasmodium, un protozoo parassita. Plasmodium cellule che esprimono berghei FCU1 sono risultati essere quasi 1000 volte più sensibili al pro-farmaco in vitro e in vivo, il trattamento con 5-FC ha ucciso oltre il 99,9% del infettare i parassiti ricombinante nella fase eritrocitaria modello murino della malaria 11. E. cellule che esprimono histolytica FCU1 hanno mostrato solo un 30-volte maggiore sensibilità al profarmaco 5-FC in contrasto con la sensibilità osservata in P. berghei. I motivi possibili di questo potrebbe essere grande piscina di nucleotidi disponibili nel terreno di coltura in competizione con i metaboliti tossici. In entrambi i P. berghei e P. falciparum il marcatore FCU1 è stato utilizzato in rottura genica mirata. studi 11,12. Il nostro obiettivo è di manipolare il genoma Entamoeba utilizzando la ricombinazione omologa. La validazione del sistema FCU1/5-FC selezione negativa è un passo significativo verso questo obiettivo.

<table border="1">
<tr>
<td>Material Name</td>
<td>Type</td>
<td>Company</td>
<td>Catalogue Number</td>
<td>Comments</td>
</tr>
<tr>
<td>TYI-S-33 medium</td>
<td>&nbsp;</td>
<td>ATCC</td>
<td>&nbsp;</td>
<td>Reference included in the text</td>
</tr>
<tr>
<td><a href="http://www.sigmaaldrich.com/catalog/ProductDetail.do?lang=en&N4=F7129|SIGMA&N5=SEARCH_CONCAT_PNO|BRAND_KEY&F=SPEC">5-Fluorocytosine</a></td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>F7129</td>
<td>&nbsp;</td>
<tr>
<td>Cell tracker green CMFDA</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>C2925</td>
<td>&nbsp;</td>
<tr>
<td>Spectra Max M2 plate-reader</td>
<td>&nbsp;</td>
<td>Molecular Devices</td>
<td>&nbsp;</td>
<td>&nbsp;</td>		
</table>

development of a negative selectable marker for entamoeba histolytica

Entamoeba histolytica è l&#39;agente eziologico di amebiasi e infetta fino al 10% della popolazione mondiale. Le tecniche molecolari che hanno permesso l&#39;up-e down-regolazione dell&#39;espressione genica contare sulla trasfezione di plasmidi stabilmente mantenuta. Anche se questi hanno aumentato la nostra comprensione dei fattori di virulenza Entamoeba, la capacità di integrare DNA esogeno nel genoma, che consentirebbe invertire esperimenti di genetica, sarebbe un vantaggio significativo nello studio di questo parassita. Le sfide presentate da questo organismo comprendono incapacità di selezionare, per eventi di ricombinazione omologa e la difficoltà di curare episomiale DNA plasmidico da trofozoiti transfettate. I risultati più avanti in un contesto alto di DNA esogeno, un grave problema per l&#39;identificazione di trofozoiti in cui un evento bona fide integrazione genomica si è verificato. Riportiamo lo sviluppo di un sistema di selezione basato sulla negativo espressione transgenica di una citosina deaminasi lievito e uracile fosforibosil transferasi chimera (FCU1) e selezione con profarmaco 5-fluorocytosine (5-FC). L&#39;enzima converte FCU1 non tossico 5-FC in tossico 5-fluorouracile e 5-fluorouridina-5&#39;-monofosfato. E. Linee che esprimono histolytica FCU1 sono risultati essere 30 volte più sensibile alla profarmaco rispetto al ceppo di controllo.

Watch this Scientific Journal Video about Development of a Negative Selectable Marker for Entamoeba histolytica at JoVE.com

Development of a Negative Selectable Marker for Entamoeba histolytica

Riportiamo lo sviluppo di un sistema di selezione negativa<em&gt; E. histolytica</em&gt; Basato sulla espressione transgenica di una proteina chimerica (FCU1) e selezione con il profarmaco 5-fluorocytosine. La proteina FCU1 è una fusione di deaminasi lievito citosina e uracile fosforibosil. Espressione di FCU1 comportato un aumento della<em&gt; E. histolytica</emSensibilità&gt; verso 5-fluorocytosine.

Sviluppo di un marcatore negativo selezionabile per Entamoeba histolytica</em

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 ...

development-of-a-negative-selectable-marker-for-entamoeba-histolytica

Nanyang Technological University

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JoVE Journal

Immunology and Infection

Development of a Negative Selectable Marker for Entamoeba histolytica

12.4K Views.  University of Virginia Health System. Riportiamo lo sviluppo di un sistema di selezione negativa E. histolytica Basato sulla espressione transgenica di una proteina chimerica (FCU1) e selezione con il profarmaco 5-fluorocytosine. La proteina FCU1 è una fusione di deaminasi lievito citosina e uracile fosforibosil. Espressione di FCU1 comportato un aumento della E. histolytica verso 5-fluorocytosine.

Video: Development of a Negative Selectable Marker for Entamoeba histolytica

Biocontained Carcass Composting for Control of Infectious Disease Outbreak in Livestock

Intensive livestock production systems are particularly vulnerable to natural or intentional (bioterrorist) infectious disease outbreaks. Large numbers of animals housed within a confined area enables rapid dissemination of most infectious agents throughout a herd. Rapid containment is key to controlling any infectious disease outbreak, thus depopulation is often undertaken to prevent spread of a pathogen to the larger livestock population. In that circumstance, a large number of livestock carcasses and contaminated manure are generated that require rapid disposal.
Composting lends itself as a rapid-response disposal method for infected carcasses as well as manure and soil that may harbor infectious agents. We designed a bio-contained mortality composting procedure and tested its efficacy for bovine tissue degradation and microbial deactivation. We used materials available on-farm or purchasable from local farm supply stores in order that the system can be implemented at the site of a disease outbreak. In this study, temperatures exceeded 55&deg;C for more than one month and infectious agents implanted in beef cattle carcasses and manure were inactivated within 14 days of composting. After 147 days, carcasses were almost completely degraded. The few long bones remaining were further degraded with an additional composting cycle in open windrows and the final mature compost was suitable for land application. 
Duplicate compost structures (final dimensions 25 m x 5 m x 2.4 m; L x W x H) were constructed using barley straw bales and lined with heavy black silage plastic sheeting. Each was loaded with loose straw, carcasses and manure totaling ~95,000 kg. A 40-cm base layer of loose barley straw was placed in each bunker, onto which were placed 16 feedlot cattle mortalities (average weight 343 kg) aligned transversely at a spacing of approximately 0.5 m. For passive aeration, lengths of flexible, perforated plastic drainage tubing (15 cm diameter) were placed between adjacent carcasses, extending vertically along both inside walls, and with the ends passed though the plastic to the exterior. The carcasses were overlaid with moist aerated feedlot manure (~1.6 m deep) to the top of the bunker. Plastic was folded over the top and sealed with tape to establish a containment barrier and eight aeration vents (50 x 50 x 15 cm) were placed on the top of each structure to promote passive aeration. After 147 days, losses of volume and mass of composted materials averaged 39.8% and 23.7%, respectively, in each structure.

Using readily available materials, this biocontained composting system enables effective on-site disposal of large animal carcasses arising in the event of infectious disease outbreak. This procedure kills most infectious agents in carcasses and contaminated manure. Once infectious agent is confirmed non-viable, mature compost can be spread as fertilizer.

Carcassa di compostaggio Biocontained per il controllo di focolai di malattie infettive del bestiame

Intensive livestock production systems are particularly vulnerable to natural or intentional (bioterrorist) infectious disease outbreaks. Large numbers of ...

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Immunologia e infezioni

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.

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.

Test in vitro Metilazione tRNA con l&#39;Entamoeba histolytica del DNA e Dnmt2 tRNA metiltransferasi (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 ...

Examination of Thymic Positive and Negative Selection by Flow Cytometry

A healthy immune system requires that T cells respond to foreign antigens while remaining tolerant to self-antigens. Random rearrangement of the T cell receptor (TCR) &alpha; and &beta; loci generates a T cell repertoire with vast diversity in antigen specificity, both to self and foreign. Selection of the repertoire during development in the thymus is critical for generating safe and useful T cells. Defects in thymic selection contribute to the development of autoimmune and immunodeficiency disorders1-4. 
T cell progenitors enter the thymus as double negative (DN) thymocytes that do not express CD4 or CD8 co-receptors. Expression of the &alpha;&beta;TCR and both co-receptors occurs at the double positive (DP) stage. Interaction of the &alpha;&beta;TCR with self-peptide-MHC (pMHC) presented by thymic cells determines the fate of the DP thymocyte. High affinity interactions lead to negative selection and elimination of self-reactive thymocytes. Low affinity interactions result in positive selection and development of CD4 or CD8 single positive (SP) T cells capable of recognizing foreign antigens presented by self-MHC5.
Positive selection can be studied in mice with a polyclonal (wildtype) TCR repertoire by observing the generation of mature T cells. However, they are not ideal for the study of negative selection, which involves deletion of small antigen-specific populations. Many model systems have been used to study negative selection but vary in their ability to recapitulate physiological events6. For example, in vitro stimulation of thymocytes lacks the thymic environment that is intimately involved in selection, while administration of exogenous antigen can lead to non-specific deletion of thymocytes7-9. Currently, the best tools for studying in vivo negative selection are mice that express a transgenic TCR specific for endogenous self-antigen. However, many classical TCR transgenic models are characterized by premature expression of the transgenic TCR&alpha; chain at the DN stage, resulting in premature negative selection. Our lab has developed the HYcd4 model, in which the transgenic HY TCR&alpha; is conditionally expressed at the DP stage, allowing negative selection to occur during the DP to SP transition as occurs in wildtype mice10.
Here, we describe a flow cytometry-based protocol to examine thymic positive and negative selection in the HYcd4 mouse model. While negative selection in HYcd4 mice is highly physiological, these methods can also be applied to other TCR transgenic models. We will also present general strategies for analyzing positive selection in a polyclonal repertoire applicable to any genetically manipulated mice.

We present a flow cytometry-based method to examine T cell development in vivo using genetically manipulated mice on a wildtype or T cell receptor transgenic background.

Esame di Selezione timica positivi e negativi per Citometria a Flusso

A healthy immune system requires that T cells respond to foreign  antigens while remaining tolerant to self-antigens. Random rearrangement of the  T cell ...

Using Click Chemistry to Measure the Effect of Viral Infection on Host-Cell RNA Synthesis

Many RNA viruses have evolved the ability to inhibit host cell transcription as a means to circumvent cellular defenses. For the study of these viruses, it is therefore important to have a quick and reliable way of measuring transcriptional activity in infected cells. Traditionally, transcription has been measured either by incorporation of radioactive nucleosides such as 3H-uridine followed by detection via autoradiography or scintillation counting, or incorporation of halogenated uridine analogs such as 5-bromouridine (BrU) followed by detection via immunostaining. The use of radioactive isotopes, however, requires specialized equipment and is not feasible in a number of laboratory settings, while the detection of BrU can be cumbersome and may suffer from low sensitivity.
The recently developed click chemistry, which involves a copper-catalyzed triazole formation from an azide and an alkyne, now provides a rapid and highly sensitive alternative to these two methods. Click chemistry is a two step process in which nascent RNA is first labeled by incorporation of the uridine analog 5-ethynyluridine (EU), followed by detection of the label with a fluorescent azide. These azides are available as several different fluorophores, allowing for a wide range of options for visualization.
This protocol describes a method to measure transcriptional suppression in cells infected with the Rift Valley fever virus (RVFV) strain MP-12 using click chemistry. Concurrently, expression of viral proteins in these cells is determined by classical intracellular immunostaining. Steps 1 through 4 detail a method to visualize transcriptional suppression via fluorescence microscopy, while steps 5 through 8 detail a method to quantify transcriptional suppression via flow cytometry. This protocol is easily adaptable for use with other viruses.

This method describes the use of click chemistry to measure changes in host cell transcription after infection with the Rift Valley fever virus (RVFV) strain MP-12. Results can be visualized qualitatively via fluorescence microscopy or obtained quantitatively through flow cytometry. This method is adaptable for use with other viruses.

Utilizzando Clicca Chimica per misurare l&#39;effetto dell&#39;infezione virale sulla cellula ospite RNA Sintesi

Many RNA viruses have evolved the ability to inhibit host cell transcription as a means to circumvent cellular defenses. For the study of these viruses, ...

Rapid Identification of Gram Negative Bacteria from Blood Culture Broth Using MALDI-TOF Mass Spectrometry

An important role of the clinical microbiology laboratory is to provide rapid identification of bacteria causing bloodstream infection. Traditional identification requires the sub-culture of signaled blood culture broth with identification available only after colonies on solid agar have matured. MALDI-TOF MS is a reliable, rapid method for identification of the majority of clinically relevant bacteria when applied to colonies on solid media. The application of MALDI-TOF MS directly to blood culture broth is an attractive approach as it has potential to accelerate species identification of bacteria and improve clinical management. However, an important problem to overcome is the pre-analysis removal of interfering resins, proteins and hemoglobin&#160;contained in blood culture specimens which, if not removed, interfere with the MS spectra and can result in insufficient or low discrimination identification scores. In addition it is necessary to concentrate bacteria to develop spectra of sufficient quality. The presented method describes the concentration, purification, and extraction of Gram negative bacteria allowing for the early identification of bacteria from a signaled blood culture broth.

The application of matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry (MS) directly to blood culture broth expedites the identification of bacteria. The presented method is a rapid and reliable method for identification of Gram negative bacteria directly from blood culture broth.

Rapida identificazione dei batteri Gram-negativi dal sangue brodo di coltura Uso MALDI-TOF

An important role of the clinical microbiology laboratory is to provide rapid identification of bacteria causing bloodstream infection. Traditional ...

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.

Analisi del danno epiteliale Prodotto da<em&gt; Entamoeba histolytica</em&gt; Infezione

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

Detection of Human Leukocyte Antigen Biomarkers in Breast Cancer Utilizing Label-free Biosensor Technology

According to the American Cancer Society, more than 200,000 women will be diagnosed with invasive breast cancer each year and approximately 40,000 will die from the disease. The human leukocyte antigen (HLA) class I samples peptides derived from proteasomal degradation of cellular proteins and presents these fragments on the cell surface for interrogation by circulating cytotoxic T lymphocytes (CTL). Generation of T-cell receptor mimic (TCRm) monoclonal antibodies (mAbs) which recognize breast cancer specific peptide/HLA-A*02:01 complexes such as those derived from macrophage migration inhibitory factor (MIF19-27) and NY-ESO-1157-165 enable detection and destruction of breast cancer cells in the absence of an effective anti-tumor CTL response. Intact class I HLA/peptide complexes are shed by breast cancer cells and represent potentially relevant cancer biomarkers. In this work, a breakthrough biomarker screening system for cancer diagnostics incorporating T-cell receptor mimic monoclonal antibodies combined with a novel, label-free biosensor utilizing guided-mode resonance (GMR) sensor technology is presented. Detection of shed MIF/HLA-A*02:01 complexes in MDA-MB-231 cell supernatants, spiked human serum, and patient plasma is demonstrated. The impact of this work could revolutionize personalized medicine through development of companion disease diagnostics for targeted immunotherapies.

Intact class I HLA/peptide complexes are shed by cancer cells, representing a potential relevant cancer biomarker. Utilizing label-free sensor technology and T-cell receptor mimicking monoclonal antibodies, detection of shed MIF/HLA-A*02:01 complexes in MDA-MB-231 cell supernatants, spiked human serum, and patient plasma is demonstrated, enabling development of a novel cancer diagnostic platform.

Rilevamento dei leucociti umani Antigen Biomarkers in Breast Cancer Utilizzando libero-Label Biosensor Tecnologia

According to the American Cancer Society, more than 200,000 women will be diagnosed with invasive breast cancer each year and approximately 40,000 will ...

Visualizing the Effects of Sputum on Biofilm Development Using a Chambered Coverglass Model

Biofilms consist of groups of bacteria encased in a self-secreted matrix. They play an important role in industrial contamination as well as in the development and persistence of many health related infections. One of the most well described and studied biofilms in human disease occurs in chronic pulmonary infection of cystic fibrosis patients. When studying biofilms in the context of the host, many factors can impact biofilm formation and development. In order to identify how host factors may affect biofilm formation and development, we used a static chambered coverglass method to grow biofilms in the presence of host-derived factors in the form of sputum supernatants. Bacteria are seeded into chambers and exposed to sputum filtrates. Following 48 hr of growth, biofilms are stained with a commercial biofilm viability kit prior to confocal microscopy and analysis. Following image acquisition, biofilm properties can be assessed using different software platforms. This method allows us to visualize key properties of biofilm growth in presence of different substances including antibiotics.

This protocol describes the visualization of biofilm development following exposure to host-factors using a slide chamber model. This model allows for direct visualization of biofilm development as well as analysis of biofilm parameters using computer software programs.

Visualizzare gli effetti di espettorato su biofilm di sviluppo utilizzando un modello Chambered coprioggetti

Biofilms consist of groups of bacteria encased in a self-secreted matrix. They play an important role in industrial contamination as well as in the ...

Development of a Hepatitis B Virus Reporter System to Monitor the Early Stages of the Replication Cycle

Currently, it is possible to construct recombinant forms of various viruses, such as human immunodeficiency virus 1 (HIV-1) and hepatitis C virus (HCV), that carry foreign genes such as a reporter or marker protein in their genomes. These recombinant viruses usually faithfully mimic the life cycle of the original virus in infected cells and exhibit the same host range dependence. The development of a recombinant virus enables the efficient screening of inhibitors and the identification of specific host factors. However, to date the construction of recombinant hepatitis B virus (HBV) has been difficult because of various experimental limitations. The main limitation is the compact genome size of HBV, and a fairly strict genome size that does not exceed 1.3 genome sizes, that must be packaged into virions. Thus, the size of a foreign gene to be inserted should be smaller than 0.4 kb if no deletion of the genome DNA is to be performed. Therefore, to overcome this size limitation, the deletion of some HBV DNA is required. Here, we report the construction of recombinant HBV encoding a reporter gene to monitor the early stage of the HBV replication cycle by replacing part of the HBV core-coding region with the reporter gene by deleting part of the HBV pol coding region. Detection of recombinant HBV infection, monitored by the reporter activity, was highly sensitive and less expensive than detection using the currently available conventional methods to evaluate HBV infection. This system will be useful for a number of applications including high-throughput screening for the identification of anti-HBV inhibitors, host factors and virus-susceptible cells.

Here we describe a newly developed hepatitis B virus (HBV) reporter system to monitor the early stages of the HBV life cycle. This simplified in vitro system will aid in the screening of anti-HBV agents using a high-throughput strategy.

Sviluppo di un virus System Reporter dell&#39;epatite B per monitorare la fasi iniziali del ciclo di replicazione

Currently, it is possible to construct recombinant forms of various viruses, such as human immunodeficiency virus 1 (HIV-1) and hepatitis C virus (HCV), ...

Utilization of Capsules for Negative Staining of Viral Samples within Biocontainment

Transmission electron microscopy (TEM) is used to observe the ultrastructure of viruses and other microbial pathogens with nanometer resolution. Most biological materials do not contain dense elements capable of scattering electrons to create an image; therefore, a negative stain, which places dense heavy metal salts around the sample, is required. In order to visualize viruses in suspension under the TEM they must be applied to small grids coated with a transparent surface only nanometers thick. Due to their small size and fragility, these grids are difficult to handle and easily moved by air currents. The thin surface is easily damaged, leaving the sample difficult or impossible to image. Infectious viruses must be handled in a biosafety cabinet (BSC) and some require a biocontainment laboratory environment. Staining viruses in biosafety levels (BSL)-3 and -4 is especially challenging because these environments are more turbulent and technicians are required to wear personal protective equipment (PPE), which decreases dexterity. 
In this study, we evaluated a new device to assist in negative staining viruses in biocontainment. The device is a capsule that works as a specialized pipette tip. Once grids are loaded into the capsule, the user simply aspirates reagents into the capsule to deliver the virus and stains to the encapsulated grid, thus eliminating user handling of grids. Although this technique was designed specifically for use in BSL-3 or -4 biocontainment, it can ease sample preparation in any lab environment by enabling easy negative staining of virus. This same method can also be applied to prepare negative stained TEM specimens of nanoparticles, macromolecules and similar specimens.

This protocol provides instruction for negative staining virus samples which can easily be used in BSL-2, -3, or -4 laboratories. It includes the use of an innovative processing capsule, which protects the transmission electron microscopy grid and provides the user easier handling in the more turbulent environments within biocontainment.

Utilizzazione di capsule per la colorazione negativa di campioni virali all&#39;interno del Biocontainment

Transmission electron microscopy (TEM) is used to observe the ultrastructure of viruses and other microbial pathogens with nanometer resolution. Most ...