Gostaríamos de agradecer Erbs Dr. Philippe por nos fornecer a seqüência de FCU1 gene. Este trabalho foi financiado pelo NIH AI 26649 conceder.

1. FCU Sistema de Seleção Negativa em Entamoeba histolytica <ol><li> A linha de controle de vetores (HM1 / pKT3M) ea linha experimental (HM1/pKT3M-FCU1) foram gerados por técnicas descritas anteriormente 1,2. Sementes das linhas em estudo a partir dos tubos de ações em frascos T-25 e manter a seleção, adicionando antibiótico adequado (12 mcg / mL G418) em TYI-S-33 de médio 3. Os frascos devem ser 70-80% confluentes após 16-18 horas de crescimento a 37 ° C. </li><li> Prepare uma solução estoque 50 mM fresco de 5-fluorocitosina (5-FC, Sigma) em meio TYI-S-33 quente. Vortex rigorosamente por vários minutos para dissolver 5-FC completamente. Filtro de esterilizar a solução de ações por passagem através de um filtro de 0,22 mM. </li><li> Trofozoítos colheita, colocando os frascos no gelo por 3-5 minutos e recolher as células por centrifugação a 200xg por 5 minutos em temperatura ambiente. Ressuspender o sedimento em meio TYI fresco e contar as células. </li><li> Projeto de um experimento típico usa 0,5 x 10 4 células por poço de uma placa de 48 bem em um volume final de 1 mL; e repete em triplicado para cada condição de teste. Além disso, para facilitar as medições fluorescente, um prato separado é usado para cada cepa por ponto de tempo. </li><li> Sementes 0,5 x 10 4 células por poço para cada teste 5-FC concentração, em triplicata. Manter a pressão de seleção de antibióticos no meio TYI. Agora adicione a quantidade necessária de 5-FC solução estoque e trofozoítos a cada poço. </li><li> Incubar as placas em um saco anaeróbica a 37 ° C. </li></ol> 2. Determinação da eficiência da seleção <ol><li> Prepare 2 mg / mL solução estoque de celular rastreador verde CMFDA (Invitrogen) em DMSO. Para fazer a solução de trabalho diluir o estoque 1.000 vezes em meio livre de soro TYI. </li><li> Remova o meio completamente de placas de cultura trofozoíto e substituir com 150 mL CMFDA TYI sem soro contendo. Continue incubação a 37 ° C por 1 hora. </li><li> Remover a solução corante de poços e ler a placa na espectrofluorímetro Spectramax microplaca M2. O comprimento de onda de excitação deve ser fixado em 492 nm ea emissão de fluorescência lida em 517 nm. </li><li> Compare os valores de fluorescência para as células controle versus o transfectants teste. </li><li> Continue a ler as placas em cada intervalo de tempo. Uso positivo apropriado (TYI só) e negativo (25 mcg / mL higromicina) poços de controlo em cada prato. </li></ol> 3. Resultados representante O E. transfectants histolytica mostrou expressão robusta de códon otimizado FCU1 recombinante (Figura 1). Quando este protocolo é seguido corretamente, resulta na eliminação seletiva de E. histolytica células expressando FCU1 na presença de 0,5 mM 5-fluorocitosina. Células controle, em contraste continuar a crescer normalmente em até 5 mM de concentração de 5-FC e chegar a confluência entre 72 e 96 horas (Figura 2-a). O FCU1 células que carregam em 48 horas são completamente lisadas quando os poços tratados são vistos sob um microscópio. Estas também mostram diminuição da fluorescência quando corados com o corante vital CMFDA, que é usado em estudos quantitativos que envolvem grande número de amostras (figura 2-b). O sistema FCU1/5-FC é uma ferramenta eficaz e poderoso de seleção negativa para E. histolytica trofozoítos. <img src="/files/ftp_upload/2410/2410fig1.jpg" alt="Figura 1" /> Figura 1. Geração de E. histolytica HM1 transfectants expressar marcador selecionável negativo (A) FCU1 proteína recombinante foi detectada em um western blot utilizando anticorpo anti-c Myc (painel superior). Como esperado, uma banda de 42kDa pode ser detectado (indicado por uma seta) no lisado total do transfectants FCU, mas não no vetor sozinho transfectants controle. O painel inferior mostra o mesmo sondado blot com anticorpo anti actina como controle de carga. (B) Resultado do quantitativo PCR em tempo real mostrando a expressão de mRNA específicos FCU1 normalizado para lgl4 controle. <img src="/files/ftp_upload/2410/2410fig2.jpg" alt="Figura 2" /> Figura 2. Drogas sensibilidade in vitro de E. transfectants histolytica expressar marcador selecionável negativo Curvas de sobrevivência de transfectants (a) e controle (b) transfectants FCU1 expressar cultivadas em 48 poços da placa. As células foram cultivadas na presença de concentrações crescentes do pró-fármaco-5-fluorocitosina; sobrevivência celular foi quantificada através da coloração CMFDA em cada intervalo de tempo conforme indicado no eixo X. O eixo Y representa unidades de fluorescência e é um reflexo direto da população de células sobreviventes. Por favor, note que o FCU1 transfectants expressar mostrou sensibilidade significativa na concentração de 0,5 mM pró-fármaco em comparação com o controle. Nenhuma célula foi observada no ponto de tempo 120h nestes poços como comcomparação com o crescimento confluente visto nos poços de controle correspondente ao microscópio (dados não mostrados). Higrômetro denota 25μg / mL higromicina usado como um controle 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>

A produção deste vídeo foi patrocinado pela Sigma Aldrich, Inc, que produz alguns dos reagentes utilizados neste artigo.

Embora tenha havido avanços substanciais na Entamoeba molecular ferramentas biológicas não existem métodos atuais disponíveis para eliminar ou interromper genes 4. Knockdown da expressão do gene específico foi alcançado através da utilização de RNAs hairpin 5, pequena interferência RNA 6 e bactérias expressa dsRNA 7. No entanto, estes métodos enquanto eficaz para os genes-alvo respectivos, várias limitações, incluindo o uso de produtos químicos caros, a seleção contínua contra os antibióticos ea necessidade de validação constante devido à alta incidência de reversão que ocorre ao longo do tempo (Alicia Linford, comunicação pessoal) 8. Qualquer plasmídeo pode replicar em Entamoeba como não há, aparentemente, uma exigência estrita seqüência de origens de replicação do DNA 9, e assim uma vez transfectadas, que normalmente é difícil de curar um plasmídeo. Isso limita a possibilidade de utilização de plasmídeos intactos em experimentos knockout recombinação e gene. Marcadores de seleção negativa são componentes-chave de gene targeting métodos como eles podem ser usados ​​para eliminar subpopulações recombinante. Temos expressa com sucesso um códon otimizado FCU1 gene em Entamoeba histolytica e testado o seu potencial como um marcador negativo selecionáveis. Este gene de fusão tem sido utilizado para a terapia de gene do suicídio de células tumorais humanas e metaboliza o pró-fármaco 5-FC em tóxicos produtos a jusante, resultando em inibição da RNA e síntese de DNA 10. FCU1 foi recentemente utilizado como um marcador negativo selecionável em Plasmodium, um outro protozoário. Células Plasmodium berghei expressar FCU1 foram encontrados para ser quase 1000 vezes mais sensíveis ao pró-fármaco in vitro e in vivo do tratamento com 5-FC matou mais de 99,9% do infectando parasitas recombinantes no modelo do rato eritrocítica estágio de malária 11. E. histolytica células expressando FCU1 mostrou apenas uma sensibilidade 30 vezes maior para o pró-fármaco 5-FC, em contraste com a sensibilidade observada em P. berghei. Possíveis razões para isso poderia ser grande pool de nucleotídeos disponível no meio de crescimento competindo com os metabólitos tóxicos. Em ambos os P. berghei e P. falciparum marcador FCU1 tem sido utilizado na interrupção do gene alvo. estudos 11,12. Nosso objetivo é manipular o genoma Entamoeba usando recombinação homóloga. A validação do sistema de seleção FCU1/5-FC negativos é um passo importante para este objectivo.

<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 é o agente causador da amebíase e infecta até 10% da população do mundo. As técnicas moleculares que permitiram a cima e para baixo-regulação da expressão gênica dependem da transfecção de plasmídeos mantida de forma estável. Enquanto estes têm aumentado nossa compreensão de fatores de virulência Entamoeba, a capacidade de integrar DNA exógeno no genoma, o que permitiria experimentos de genética inversa, seria uma vantagem significativa no estudo deste parasita. Os desafios apresentados por este organismo incluem a incapacidade para selecionar para eventos de recombinação homóloga e dificuldade para curar DNA plasmídeo epissomal de trofozoítos transfectadas. Os resultados mais tarde, em um fundo elevado de DNA exógeno, um grande problema na identificação de trofozoítos no qual um evento de integração bona fide genômica ocorreu. Nós relatamos o desenvolvimento de um sistema de seleção negativa baseada em expressão transgênica de uma citosina deaminase fermento e uracil fosforribosil transferase quimera (FCU1) seleção e com o pró-fármaco 5-fluorocitosina (5-FC). A enzima converte FCU1 non-toxic 5-FC em tóxicos 5-fluorouracil e 5-fluorouridina-monofosfato-5&#39;. E. linhas histolytica expressar FCU1 foram encontrados para ser 30 vezes mais sensíveis aos pró-fármaco em comparação com a estirpe de controlo.

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

Nós relatamos o desenvolvimento de um sistema de seleção negativa no<em&gt; E. histolytica</em&gt; Baseada em expressão transgênica de uma proteína quimérica (FCU1) e seleção com o pró-fármaco 5-fluorocitosina. A proteína FCU1 é uma fusão de deaminase levedura citosina e uracil fosforibosiltransferase. Expressão de FCU1 resultou em aumento<em&gt; E. histolytica</em&gt; Sensibilidade para 5-fluorocitosina.

Desenvolvimento de um marcador negativo selecionáveis ​​para 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

Research

JoVE Journal

Immunology and Infection

Development of a Negative Selectable Marker for Entamoeba histolytica

12.4K visualizações.  University of Virginia Health System. Nós relatamos o desenvolvimento de um sistema de seleção negativa no E. histolytica Baseada em expressão transgênica de uma proteína quimérica (FCU1) e seleção com o pró-fármaco 5-fluorocitosina. A proteína FCU1 é uma fusão de deaminase levedura citosina e uracil fosforibosiltransferase. Expressão de FCU1 resultou em aumento E. histolytica Sensibilidade para 5-fluorocitosina.

Vídeo: 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.

Compostagem Carcass Biocontained de Controle de Epidemias de Doenças Infecciosas na Pecuária

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

Imunologia e Infecção

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.

Ensaio in vitro de metilação tRNA com a Entamoeba histolytica DNA e Dnmt2 tRNA metiltransferase (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.

Exame de seleção positiva e negativa Tímico por citometria de fluxo

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.

Usando Click Chemistry medir o efeito da infecção viral sobre a síntese de RNA do Host-Cell

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.

Rápida identificação de bactérias gram-negativas de Sangue Cultura Caldo Usando MALDI-TOF Espectrometria de Massa

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.

Análise do dano epitelial Produzido pela<em&gt; Entamoeba histolytica</em&gt; Infecção

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.

Detecção de Leucócitos Humanos Antigen Biomarkers no cancro da mama Utilizando tecnologia de biossensores livre-Label

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.

Visualizando os Efeitos de escarro no desenvolvimento de biofilmes usando um modelo Chambered lamela

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.

Desenvolvimento de um Sistema Reporter vírus da hepatite B de acompanhar as fases iniciais do ciclo de replicação

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.

Utilização de Cápsulas para Coloração Negativa de Amostras Viral dentro de Biocontenimento

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

Desenvolvimento de um marcador negativo selecionáveis ​​para Entamoeba histolytica

Desenvolvimento de um marcador negativo selecionáveis para Entamoeba histolytica