Le travail a été soutenu par des subventions de la Fondation Bill et Melinda Gates (# 38631) et le NIH, y compris OD004631 DP2 et R01 AI084119.

1. Méthodologie <ol><li> La première étape du protocole consiste à sélectionner la séquence couronne V3 vous voulez suivre in silico. Pour la souche R2, la séquence de ce fragment est KSIPMGPGRAFYT. </li><li> La structure 3D atomique du peptide correspondant à la séquence doit être construit dans l&#39;espace virtuel de l&#39;ordinateur. La commande ICM pour cela est: buildpep &quot;KSIPMGPGRAFYT&quot; ou Fichier: Nouveau: Peptide peut être sélectionné sous le menu déroulant </li><li> Plusieurs paramètres de la procédure sont alors fixés, y compris le nombre d&#39;étapes de recherche (durée de la recherche), la température de la simulation, les paramètres de stratégie de recherche y compris les restrictions variables pour solliciter la recherche vers les domaines de l&#39;énergie, des termes raisonnables, le choix des différentes méthodes de calcul de l&#39;énergie, et des paramètres indiquant comment la recherche sera enregistré comme celles consistant à enregistrer un film et combien de conformations intermédiaires de notation devraient être enregistrées. Tous ces paramètres ont été optimisés par previoNous publications (voir www.molsoft.com). </li><li> Le pliage est alors lancé avec la commande: montecarlo ou Fichier: Nouveau: Peptide peuvent être sélectionnés dans le cadre de la liste déroulante du menu Mécanique Moléculaire: Minimiser: Global Dans le premier cas, les paramètres de l&#39;étape 3 doit être réglé une par une dans la ligne de commande. Dans ce dernier cas, les cases des paramètres les plus couramment sélectionnés sont prévus dans un panneau avant de la commande est exécutée. Pour plus de commodité, le même scénario pliage ICM utilisé pour cette expérience et des expériences déjà publiées est montré ici: <img src="/files/ftp_upload/2118/2118output.jpg" alt="Sortie" /> Ce script peut être sauvegardée dans un fichier texte et exécuté en ligne de l&#39;ordinateur de commande du système d&#39;exploitation (généralement LINUX) rapidement en utilisant la commande: icm _foldingscript </li></ol> 2. Les secrets du succès <ol><li> La boucle V3 est une constante 35 acides aminés de longueur à peu près chaque souche connue, si l&#39;acide aminé positions sont numérotés de 1 à 35 en commençant par le disulfure de cystine originaires lié à 1 et se terminant avec le disulfure de cystine liés correspondant à 35. Comme il fait partie d&#39;une boucle, les limites de la couronne de V3 doit être soigneusement choisi. Si un trop grand fragment est choisie, il est peu probable de se comporter comme un segment librement flexible comme s&#39;il s&#39;agissait d&#39;un peptide libre, de sorte que la simulation de pliage sera pas évalué correctement la structure. Si un trop petit fragment est choisie, la structure informative tertiaire peut pas se former dans la simulation. Notre étude préalable a montré que le fragment de la position 10 à la position 22 en corrélation avec d&#39;anticorps liés conformations cristallographiques, si ce n&#39;est le fragment d&#39;une boucle V3 qui devrait être choisi pour le pliage. </li><li> Bien que l&#39;utilisation de l&#39;interface utilisateur graphique et des menus déroulants est conviviale, le travail préalable avec succès sur le repliement des peptides en général en utilisant l&#39;ICM et la boucle V3 de la couronne déployante en particulier utilisé le script ci-dessus, il suffit de modifier le séquençagee dans la ligne buildpep et l&#39;exécution du script ci-dessus à partir de la ligne de commande est recommandée. </li></ol> 3. Les résultats représentatifs Les résultats pour le pliage R2 sont représentatifs des résultats d&#39;une boucle V3. Pour évaluer les résultats, le fichier projet (il sera nommé &quot;newProject1.icb&quot; dans le script ci-dessus) doit être ouvert et &quot;Mécanique moléculaire, Stack, Voir« choisi. Un tableau des conformations de pile apparaît. Les conformations de pile peut être visualisé graphiquement en cliquant sur l&#39;icône Terrain / histogramme. &quot;Molecular Mechanics, Stack, Lecture&quot; va faire un film sur la pile pour apprécier visuellement les préférences conformationnelles découverts par le pliage. Pour la séquence R2, la conformation est la bêta-épingle à cheveux comme prévu pour V3 boucles 2 - en particulier dans le fragment dans des positions 12 à 14, où une nette préférence β-brin est vu à travers la pile, et très peu de conformations en hélice alpha on voit. En outre,un intervalle d&#39;énergie de près de 3 unités est observée entre la conformation de plus basse énergie et de la conformation de l&#39;énergie le plus bas secondes. D&#39;un point de vue énergétique, cela signifie que la structure ne scintille sur la conformation de plus basse énergie de moins d&#39;un pour cent du temps: les résultats pliantes suggèrent donc que la R2 V3 couronne est une surface rigide, plutôt que flexible, la structure. Il peut y avoir d&#39;autres caractéristiques structurelles importantes dans l&#39;ensemble de conformations, mais ils sont difficiles à apprécier systématiquement. <table border="1"><tbody><tr><td></td><td> JRFL </td><td> SF162_V3JRFL </td><td> SF162_V3R2 </td></tr><tr><td> 447-52D GMT 50 </td><td> 15 </td><td> 0,00061 </td><td> 0,00078 </td></tr></tbody></table> Tableau 1: neutralisation relative des JRFL et R2 V3 boucles en milieu masquées et non masquées. Les données ont été précédemment rapporté dans Cardozo T., et al. ARHR (2008) et Pinter, A., et al. al J. Virol (2004). En bref, une activité neutralisante a été déterminée avec un seul cycle de contrôle de l&#39;infectiosité en utilisant VAL générés avec l&#39;env-défectueuse luciférase exprimant pNL4-3.Luc.RE plasmide pseudotypés avec la Env JRFL ou les variantes SF162 V3 décrites ci-dessus: SF162_V3JRFL contient le JRFL séquence en boucle V3 à la place de la séquence de la boucle V3 SF162. SF162_V3R2 contient la séquence de la boucle V3 R2 à la place de la séquence de la boucle V3 SF162. Les PSV ont été incubées avec des dilutions successives de l&#39;anticorps monoclonal 447-52D pour 1,5 h à 37 ° C, puis ajouté à CD4 + CCR5 + U87 cellules cibles immatriculés dans des plaques 96 puits en présence de polybrène (10 mg = mL). Après 24 heures, les cellules sont réalimentées par du milieu RPMI contenant 10% de FBS et 10 mg = ml de polybrène, suivie par un supplément de 24-48 heures d&#39;incubation. L&#39;activité luciférase a été déterminée 48-72 h après avec un luminomètre plaque de microtitration (HARTA, Inc) en utilisant des réactifs de dosage de Promega, Inc moyenne géométrique des titres pour neutralizat 50%ion (GMT50) 447-52D par ont été déterminées par interpolation à partir des courbes de neutralisation et sont des moyennes d&#39;au moins trois essais indépendants.

<ol>
	<li>Almond, D., Kimura, T., Kong, X., Zolla-Pazner, S. &. a. m. p. ;. a. m. p., Cardozo, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+characterization+of+the+V3+loop+crown.">Dynamic characterization of the V3 loop crown.</a> Antiviral Therapy. 12, 13-31 (2007).</li><li>Almond, D., Kimura, T., Kong, X., Swetnam, J., Zolla-Pazner, S., Cardozo, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+conservation+predominates+over+sequence+variability+in+the+crown+of+HIV+type+1's+V3+loop.">Structural conservation predominates over sequence variability in the crown of HIV type 1's V3 loop.</a> AIDS Res Hum Retroviruses. 26, (2010).</li><li>Abagyan, R., Totrov, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biased+probability+Monte+Carlo+conformational+searches+and+electrostatic+calculations+for+peptides+and+proteins.">Biased probability Monte Carlo conformational searches and electrostatic calculations for peptides and proteins.</a> J Mol Biol. 235, 983-1002 (1994).</li><li>Quinnan, G. V., Zhang, P. F., Fu, D. W., Dong, M., Alter, H. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expression+and+characterization+of+HIV+type+1+envelope+protein+associated+with+a+broadly+reactive+neutralizing+antibody+response.">Expression and characterization of HIV type 1 envelope protein associated with a broadly reactive neutralizing antibody response.</a> AIDS Res Hum Retroviruses. 15, 561-5670 (1999).</li><li>Zhang, P. F., Bouma, P., Park, E. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+variable+region+3+(V3)+mutation+determines+a+global+neutralization+phenotype+and+CD4-independent+infectivity+of+a+human+immunodeficiency+virus+type+1+envelope+associated+with+a+broadly+cross-reactive,+primary+virus-neutralizing+antibody+response.">A variable region 3 (V3) mutation determines a global neutralization phenotype and CD4-independent infectivity of a human immunodeficiency virus type 1 envelope associated with a broadly cross-reactive, primary virus-neutralizing antibody response.</a> J Virol. 76, 644-655 (2002).</li></ol>

Pliage ab initio révèle tertiaires propriétés structurelles, dont les effets peuvent ne pas être évident d&#39;après l&#39;étude individuelle des acides aminés de manière séquentielle. Plusieurs précédemment obscures propriétés structurales de la couronne R2 boucle V3 sont révélées par la simulation de pliage. Ces préférences observées structurelles observées peut corréler avec les propriétés fonctionnelles de la souche R2, à savoir la sensibilité à la neutralisation et hyperinfectiv...

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assessment of immunologically relevant dynamic tertiary structural features of the hiv-1 v3 loop crown r2 sequence by ab initio folding

La diversité antigénique du VIH-1 a longtemps été un obstacle à la conception du vaccin, et cette variabilité est particulièrement prononcé dans la boucle V3 de la glycoprotéine du virus de surface de l&#39;enveloppe. Nous avons déjà proposé que le sommet de la boucle V3, bien que variable dynamique et de la séquence, est contraint toute la population de virus VIH-1 à une immunologiquement pertinente β-épingle structure tertiaire. Surtout, il ya des milliers de séquences V3 différents couronne de boucles en circulation virus VIH-1, faire du 3D, caractérisation structurale des tendances à travers la diversité des virus difficiles, voire impossible, par cristallographie ou RMN. Nos études antérieures réussies avec le pliage de la couronne V3 1, 2 utilisé l&#39;algorithme ab initio 3 accessibles à l&#39;ICM-Pro package logiciel de modélisation moléculaire (Molsoft LLC, La Jolla, CA) et a suggéré que le sommet de la boucle V3, plus précisément de positions 10 à 22, suffisamment avantages de la flexibility et la longueur de ses tiges d&#39;accompagnement de se comporter dans une large mesure comme s&#39;il s&#39;agissait d&#39;un peptide sans contrainte librement pliage en solution. En tant que tel, le pliage rapide ab initio d&#39;un peu de cette partie de la boucle V3 de toute souche individuelle des 60.000 + circulants souches VIH-1 peut être instructif. Ici, nous avons plié la boucle V3 de la souche R2 afin de mieux comprendre la base structurelle de ses propriétés uniques. R2 porte une séquence V3 rare boucle pensé pour être responsable de l&#39;exquise sensibilité de cette souche à la neutralisation par les sérums des patients et les anticorps monoclonaux 4, 5. Les contraintes de médiateur CD4-indépendants infection et semble induire des anticorps neutralisants à large spectre. Nous montrent comment l&#39;évaluation des résultats de pliage peut être informatif pour associer des structures observées dans le pliage des activités immunologiques observées pour R2.

Watch this Scientific Journal Video about Assessment of Immunologically Relevant Dynamic Tertiary Structural Features of the HIV-1 V3 Loop Crown R2 Sequence by ab initio Folding at JoVE.com

Assessment of Immunologically Relevant Dynamic Tertiary Structural Features of the HIV-1 V3 Loop Crown R2 Sequence by ab initio Folding

La région de couronne de différentes séquences de la boucle V3 de la glycoprotéine d&#39;enveloppe de surface (gp120) du VIH-1 peut être structurellement caractérisé dans de nombreux cas dans le repliement in silico des positions 10 à 22 de la boucle à l&#39;aide d&#39;un état-of-the-art<em&gt; Ab initio</emAlgorithme&gt; pliage. Ici nous montrent le pliage et l&#39;évaluation de cette région de la boucle V3 de la souche R2 du VIH-1, d&#39;une souche sensible à la neutralisation de façon unique surprenantes propriétés fonctionnelles.

Évaluation des immunologiquement pertinents dynamiques tertiaires Caractéristiques structurelles de l&#39;épidémie de VIH-1 séquence de la boucle V3 de la Couronne par R2<em&gt; Ab initio</em&gt; Pliante

The antigenic diversity of HIV-1 has long been an obstacle to vaccine design, and this variability is especially pronounced in the V3 loop of the virus' ...

assessment-immunologically-relevant-dynamic-tertiary-structural

Research

JoVE Journal

Immunology and Infection

Assessment of Immunologically Relevant Dynamic Tertiary Structural Features of the HIV-1 V3 Loop Crown R2 Sequence by ab initio Folding

9.5K vues.  School of Medicine, New York University. La région de couronne de différentes séquences de la boucle V3 de la glycoprotéine d'enveloppe de surface (gp120) du VIH-1 peut être structurellement caractérisé dans de nombreux cas dans le repliement in silico des positions 10 à 22 de la boucle à l'aide d'un état-of-the-art Ab initio pliage. Ici nous montrent le pliage et l'évaluation de cette région de la boucle V3 de la souche R2 du VIH-1, d'une souche sensible ...

Vidéo: Assessment of Immunologically Relevant Dynamic Tertiary Structural Features of the HIV-1 V3 Loop Crown R2 Sequence by ab initio Folding

Specific Marking of HIV-1 Positive Cells using a Rev-dependent Lentiviral Vector Expressing the Green Fluorescent Protein

Most of HIV-responsive expression vectors are based on the HIV promoter, the long terminal repeat (LTR). While responsive to an early HIV protein, Tat, the LTR is also responsive to cellular activation states and to the local chromatin activity where the integration has occurred. This can result in high HIV-independent activity, and has restricted the usefulness of LTR-based reporter to mark HIV positive cells 1,2,3. Here, we constructed an expression lentiviral vector that possesses, in addition to the Tat-responsive LTR, numerous HIV DNA sequences that include the Rev-response element and HIV splicing sites 4,5,6. The vector was incorporated into a lentiviral reporter virus, permitting highly specific detection of replicating HIV in living cell populations. The activity of the vector was measured by expression of the green fluorescence protein (GFP). The application of this vector as reported here offers a novel alternative approach to existing methods, such as in situ PCR or HIV antigen staining, to identify HIV-positive cells. The vector can also express therapeutic genes for basic or clinical experimentation to target HIV-positive cells.

We have developed a lentiviral vector that possesses, in addition to the Tat-responsive LTR, the Rev-response element (RRE) that can regulate reporter gene expression in an HIV-1 Tat- and Rev-dependent fashion. The vector permits the specific detection of replicating HIV in living cells via the expression of GFP.

Marquage spécifique du VIH-1 des cellules positives à l&#39;aide d&#39;un vecteur Rev-dépendante lentiviraux exprimant la protéine fluorescente verte

Most of HIV-responsive expression vectors are based on the HIV promoter, the long terminal repeat (LTR). While responsive to an early HIV protein, Tat, ...

Recherche

Immunologie et infection

Genotypic Inference of HIV-1 Tropism Using Population-based Sequencing of V3

Background: Prior to receiving a drug from CCR5-antagonist class in HIV therapy, a patient must undergo an HIV tropism test to confirm that his or her viral population uses the CCR5 coreceptor for cellular entry, and not an alternative coreceptor. One approach to tropism testing is to examine the sequence of the V3 region of the HIV envelope, which interacts with the coreceptor.
Methods: Viral RNA is extracted from blood plasma. The V3 region is amplified in triplicate with nested reverse transcriptase-PCR. The amplifications are then sequenced and analyzed using the software, RE_Call. Sequences are then submitted to a bioinformatic algorithm such as geno2pheno to infer viral tropism from the V3 region. Sequences are inferred to be non-R5 if their geno2pheno false positive rate falls below 5.75%. If any one of the three sequences from a sample is inferred to be non-R5, the patient is unlikely to respond to a CCR5-antagonist.

HIV tropism can be inferred from the V3 region of the viral envelope. V3 is PCR amplified in triplicate using nested RT-PCR, sequenced, and interpreted using bioinformatic software. Samples with with 1 or more sequence(s) with low g2P scores are classified as non-R5 virus.

Inférence génotypique de tropisme du VIH-1 en utilisant la population basée séquençage du V3

Background: Prior to receiving a drug from CCR5-antagonist class in HIV therapy, a patient must undergo an HIV tropism test to confirm that his or her ...

Amplifying and Quantifying HIV-1 RNA in HIV Infected Individuals with Viral Loads Below the Limit of Detection by Standard Clinical Assays

Amplifying viral genes and quantifying HIV-1 RNA in HIV-1 infected individuals with viral loads below the limit of detection by standard assays (below 50-75 copies/ml) is necessary to gain insight to viral dynamics and virus host interactions in patients who naturally control the infection and those who are on combination antiretroviral therapy (cART). 
Here we describe how to amplify viral genomes by single genome sequencing (the SGS protocol) 13, 19 and how to accurately quantify HIV-1 RNA in patients with low viral loads (the single-copy assay (SCA) protocol) 12, 20. 
The single-copy assay is a real-time PCR assay with sensitivity depending on the volume of plasma being assayed. If a single virus genome is detected in 7 ml of plasma, then the RNA copy number is reported to be 0.3 copies/ml. The assay has an internal control testing for the efficiency of RNA extraction, and controls for possible amplification from DNA or contamination. Patient samples are measured in triplicate.
The single-genome sequencing assay (SGS), now widely used and considered to be non-labor intensive 3, 7, 12, 14, 15,is a limiting dilution assay, in which endpoint diluted cDNA product is spread over a 96-well plate. According to a Poisson distribution, when less than 1/3 of the wells give product, there is an 80% chance of the PCR product being resultant of amplification from a single cDNA molecule. SGS has the advantage over cloning of not being subjected to resampling and not being biased by PCR-introduced recombination 19. However, the amplification success of SCA and SGS depend on primer design. Both assays were developed for HIV-1 subtype B, but can be adapted for other subtypes and other regions of the genome by changing primers, probes, and standards.

Quantifying levels of HIV-1 RNA in plasma and sequencing single HIV-1 genomes from individuals with viral loads below the limit of detection (50-75 copies/ml) is difficult. Here we describe how to extract and quantify plasma viral RNA using a real time PCR assay that reliably measures HIV-1 RNA down to 0.3 copies/ml and how to amplify viral genomes by single genome sequencing, from samples with very low viral loads.

Amplifier et quantifier l&#39;ARN VIH-1 chez les individus infectés par le VIH ayant une charge virale sous le seuil de détection par Standard tests cliniques

Amplifying viral genes and quantifying HIV-1 RNA in HIV-1 infected individuals with viral loads below the limit of detection by standard assays (below ...

Structure of HIV-1 Capsid Assemblies by Cryo-electron Microscopy and Iterative Helical Real-space Reconstruction

Cryo-electron microscopy (cryo-EM), combined with image processing, is an increasingly powerful tool for structure determination of macromolecular protein complexes and assemblies. In fact, single particle electron microscopy1 and two-dimensional (2D) electron crystallography2 have become relatively routine methodologies and a large number of structures have been solved using these methods. At the same time, image processing and three-dimensional (3D) reconstruction of helical objects has rapidly developed, especially, the iterative helical real-space reconstruction (IHRSR) method3, which uses single particle analysis tools in conjunction with helical symmetry. Many biological entities function in filamentous or helical forms, including actin filaments4, microtubules5, amyloid fibers6, tobacco mosaic viruses7, and bacteria flagella8, and, because a 3D density map of a helical entity can be attained from a single projection image, compared to the many images required for 3D reconstruction of a non-helical object, with the IHRSR method, structural analysis of such flexible and disordered helical assemblies is now attainable.
In this video article, we provide detailed protocols for obtaining a 3D density map of a helical protein assembly (HIV-1 capsid9 is our example), including protocols for cryo-EM specimen preparation, low dose data collection by cryo-EM, indexing of helical diffraction patterns, and image processing and 3D reconstruction using IHRSR. Compared to other techniques, cryo-EM offers optimal specimen preservation under near native conditions. Samples are embedded in a thin layer of vitreous ice, by rapid freezing, and imaged in electron microscopes at liquid nitrogen temperature, under low dose conditions to minimize the radiation damage. Sample images are obtained under near native conditions at the expense of low signal and low contrast in the recorded micrographs. Fortunately, the process of helical reconstruction has largely been automated, with the exception of indexing the helical diffraction pattern. Here, we describe an approach to index helical structure and determine helical symmetries (helical parameters) from digitized micrographs, an essential step for 3D helical reconstruction. Briefly, we obtain an initial 3D density map by applying the IHRSR method. This initial map is then iteratively refined by introducing constraints for the alignment parameters of each segment, thus controlling their degrees of freedom. Further improvement is achieved by correcting for the contrast transfer function (CTF) of the electron microscope (amplitude and phase correction) and by optimizing the helical symmetry of the assembly.

This article describes a method to obtain a three-dimensional (3D) structure of helically assembled molecules using cryo-electron microscopy. In this protocol, we use HIV-1 capsid assemblies to illustrate the detailed 3D reconstruction procedure for achieving a density map by the iterative helical real-space reconstruction method.

Structure du VIH-1 Assemblées capside par cryo-microscopie électronique et reconstruction itérative hélicoïdal espace réel

Cryo-electron microscopy (cryo-EM), combined with image processing, is an increasingly powerful tool for structure determination of macromolecular protein ...

Prediction of HIV-1 Coreceptor Usage (Tropism) by Sequence Analysis using a Genotypic Approach

Maraviroc (MVC) is the first licensed antiretroviral drug from the class of coreceptor antagonists. It binds to the host coreceptor CCR5, which is used by the majority of HIV strains in order to infect the human immune cells (Fig. 1). Other HIV isolates use a different coreceptor, the CXCR4. Which receptor is used, is determined in the virus by the Env protein (Fig. 2). Depending on the coreceptor used, the viruses are classified as R5 or X4, respectively. MVC binds to the CCR5 receptor inhibiting the entry of R5 viruses into the target cell. During the course of disease, X4 viruses may emerge and outgrow the R5 viruses. Determination of coreceptor usage (also called tropism) is therefore mandatory prior to administration of MVC, as demanded by EMA and FDA. 
The studies for MVC efficiency MOTIVATE, MERIT and 1029 have been performed with the Trofile assay from Monogram, San Francisco, U.S.A. This is a high quality assay based on sophisticated recombinant tests. The acceptance for this test for daily routine is rather low outside of the U.S.A., since the European physicians rather tend to work with decentralized expert laboratories, which also provide concomitant resistance testing. These laboratories have undergone several quality assurance evaluations, the last one being presented in 20111.
For several years now, we have performed tropism determinations based on sequence analysis from the HIV env-V3 gene region (V3)2. This region carries enough information to perform a reliable prediction. 
The genotypic determination of coreceptor usage presents advantages such as: shorter turnover time (equivalent to resistance testing), lower costs, possibility to adapt the results to the patients' needs and possibility of analysing clinical samples with very low or even undetectable viral load (VL), particularly since the number of samples analysed with VL&lt;1000 copies/&mu;l roughly increased in the last years (Fig. 3).
The main steps for tropism testing (Fig. 4) demonstrated in this video: 
1. Collection of a blood sample 
 2. Isolation of the HIV RNA from the plasma and/or HIV proviral DNA from blood mononuclear cells 
 3. Amplification of the env region 
 4. Amplification of the V3 region 
 5. Sequence reaction of the V3 amplicon 
 6. Purification of the sequencing samples 
 7. Sequencing the purified samples 
 8. Sequence editing 
 9. Sequencing data interpretation and tropism prediction

Prediction of HIV-1 Coreceptor Usage Tropism by Sequence Analysis using a Genotypic Approach

The prediction of the coreceptor usage of HIV-1 is required for the administration of a new class of antiretroviral drugs, i.e. coreceptor antagonists. It can be performed by sequence analysis of the env gene and subsequent interpretation through an internet based interpretation system (geno2pheno[coreceptor]).

Prédiction du VIH-1 Utilisation corécepteur (tropisme) par analyse de séquence en utilisant une approche génotypique

Maraviroc (MVC) is the first licensed antiretroviral drug from the class of coreceptor antagonists. It binds to the host coreceptor CCR5, which is used by ...

In vitro Uncoating of HIV-1 Cores

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

In vitro Uncoating of HIV-1 Cores

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

En décapsidation in vitro du VIH-1 Cores

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

Assessing the Innate Sensing of HIV-1 Infected CD4+ T Cells by Plasmacytoid Dendritic Cells Using an Ex vivo Co-culture System.

HIV-1 innate sensing requires direct contact of infected CD4+ T cells with plasmacytoid dendritic cells (pDCs). In order to study this process, the protocols described here use freshly isolated human peripheral blood mononuclear cells (PBMCs) or plasmacytoid dendritic cells (pDCs) to sense infections in either T cell line (MT4) or heterologous primary CD4+ T cells. In order to ensure proper sensing, it is essential that PBMC are isolated immediately after blood collection and that optimal percentage of infected T cells are used. Furthermore, multi-parametric flow cytometric staining can be used to confirm that PBMC samples contain the different cell lineages at physiological ratios. A number of controls can also be included to evaluate viability and functionality of pDCs. These include, the presence of specific surface markers, assessing cellular responses to known agonist of Toll-Like Receptors (TLR) pathways, and confirming a lack of spontaneous type-I interferon (IFN) production. In this system, freshly isolated PBMCs or pDCs are co-cultured with HIV-1 infected cells in 96 well plates for 18-22 hr. Supernatants from these co-cultures are then used to determine the levels of bioactive type-I IFNs by monitoring the activation of the ISGF3 pathway in HEK-Blue IFN-&#945;/&#946; cells. Prior and during co-culture conditions, target cells can be subjected to flow cytometric analysis to determine a number of parameters, including the percentage of infected cells, levels of specific surface markers, and differential killing of infected cells. Although, these protocols were initially developed to follow type-I IFN production, they could potentially be used to study other imuno-modulatory molecules released from pDCs and to gain further insight into the molecular mechanisms governing HIV-1 innate sensing.

Assessing the Innate Sensing of HIV-1 Infected CD4+ T Cells by Plasmacytoid Dendritic Cells Using an Ex vivo Co-culture System.

Unlike cell-free HIV-1 particles, infected CD4+ T cells are effectively sensed by plasmacytoid dendritic cells (pDCs). This manuscript describes a method where peripheral blood mononuclear cells (PBMCs) or isolated pDCs are co-cultured with HIV-1 infected T cells to evaluate innate sensing by pDCs as assessed by release of type-I IFN.

L&#39;évaluation de l&#39;Innate détection du VIH-1 CD4 infectés<sup&gt; +</sup&gt; Cellules T par les cellules dendritiques plasmacytoïdes Utilisation d&#39;un<em&gt; Ex vivo</em&gt; Système de co-culture.

HIV-1 innate sensing requires direct contact of infected CD4+ T cells with plasmacytoid dendritic cells (pDCs). In order to study this process, the ...

Conformational Evaluation of HIV-1 Trimeric Envelope Glycoproteins Using a Cell-based ELISA Assay

HIV-1 envelope glycoproteins (Env) mediate viral entry into target cells and are essential to the infectious cycle. Understanding how those glycoproteins are able to fuel the fusion process through their conformational changes could lead to the design of better, more effective immunogens for vaccine strategies. Here we describe a cell-based ELISA assay that allows studying the recognition of trimeric HIV-1 Env by monoclonal antibodies. Following expression of HIV-1 trimeric Env at the surface of transfected cells, conformation specific anti-Env antibodies are incubated with the cells. A horseradish peroxidase-conjugated secondary antibody and a simple chemiluminescence reaction are then used to detect bound antibodies. This system is highly flexible and can detect Env conformational changes induced by soluble CD4 or cellular proteins. It requires minimal amount of material and no highly-specialized equipment or know-how. Thus, this technique can be established for medium to high throughput screening of antigens and antibodies, such as newly-isolated antibodies.

Understanding viral surface antigens conformations is required to evaluate antibody neutralization and guide the design of effective vaccine immunogens. Here we describe a cell-based ELISA assay that allows the study of the recognition of trimeric HIV-1 Env expressed at the surface of transfected cells by specific anti-Env antibodies.

Évaluation de conformation du VIH-1 trimère glycoprotéines d&#39;enveloppe l&#39;aide d&#39;un base de cellules test ELISA

HIV-1 envelope glycoproteins (Env) mediate viral entry into target cells and are essential to the infectious cycle. Understanding how those glycoproteins ...

Nucleocapsid Annealing-Mediated Electrophoresis (NAME) Assay Allows the Rapid Identification of HIV-1 Nucleocapsid Inhibitors

RNA or DNA folded in stable tridimensional folding are interesting targets in the development of antitumor or antiviral drugs. In the case of HIV-1, viral proteins involved in the regulation of the virus activity recognize several nucleic acids. The nucleocapsid protein NCp7 (NC) is a key protein regulating several processes during virus replication. NC is in fact a chaperone destabilizing the secondary structures of RNA and DNA and facilitating their annealing. The inactivation of NC is a new approach and an interesting target for anti-HIV therapy. The Nucleocapsid Annealing-Mediated Electrophoresis (NAME) assay was developed to identify molecules able to inhibit the melting and annealing of RNA and DNA folded in thermodynamically stable tridimensional conformations, such as hairpin structures of TAR and cTAR elements of HIV, by the nucleocapsid protein of HIV-1. The new assay employs either the recombinant or the synthetic protein, and oligonucleotides without the need of their previous labeling. The analysis of the results is achieved by standard polyacrylamide gel electrophoresis (PAGE) followed by conventional nucleic acid staining. The protocol reported in this work describes how to perform the NAME assay with the full-length protein or its truncated version lacking the basic N-terminal domain, both competent as nucleic acids chaperones, and how to assess the inhibition of NC chaperone activity by a threading intercalator. Moreover, NAME can be performed in two different modes, useful to obtain indications on the putative mechanism of action of the identified NC inhibitors.

Nucleocapsid Annealing-Mediated Electrophoresis NAME Assay Allows the Rapid Identification of HIV-1 Nucleocapsid Inhibitors

This protocol describes NAME, an assay that allows the rapid identification of molecules able to inhibit in vitro the chaperone activities of HIV-1 nucleocapsid protein.

Nucléocapside recuit-Mediated électrophorèse (NOM) Assay permet l&#39;identification rapide des VIH-1 inhibiteurs Nucleocapsid

RNA or DNA folded in stable tridimensional folding are interesting targets in the development of antitumor or antiviral drugs. In the case of HIV-1, viral ...

Isolation of Exosomes from the Plasma of HIV-1 Positive Individuals

Exosomes are small vesicles ranging in size from 30 nm to 100 nm that are released both constitutively and upon stimulation from a variety of cell types. They are found in a number of biological fluids and are known to carry a variety of proteins, lipids, and nucleic acid molecules. Originally thought to be little more than reservoirs for cellular debris, the roles of exosomes regulating biological processes and in diseases are increasingly appreciated.
Several methods have been described for isolating exosomes from cellular culture media and biological fluids. Due to their small size and low density, differential ultracentrifugation and/or ultrafiltration are the most commonly used techniques for exosome isolation. However, plasma of HIV-1 infected individuals contains both exosomes and HIV viral particles, which are similar in size and density. Thus, efficient separation of exosomes from HIV viral particles in human plasma has been a challenge.
To address this limitation, we developed a procedure modified from Cantin et. al., 2008 for purification of exosomes from HIV particles in human plasma. Iodixanol velocity gradients were used to separate exosomes from HIV-1 particles in the plasma of HIV-1 positive individuals. Virus particles were identified by p24 ELISA. Exosomes were identified on the basis of exosome markers acetylcholinesterase (AChE), and the CD9, CD63, and CD45 antigens. Our gradient procedure yielded exosome preparations free of virus particles. The efficient purification of exosomes from human plasma enabled us to examine the content of plasma-derived exosomes and to investigate their immune modulatory potential and other biological functions.

Techniques describing a gradient procedure to separate exosomes from human immunodeficiency virus (HIV) particles are described. This procedure was used to isolate exosomes away from HIV particles in human plasma from HIV-infected individuals. The isolated exosomes were analyzed for cytokine/chemokine content.

Isolement des exosomes dans le plasma du VIH-1 individus positifs

Exosomes are small vesicles ranging in size from 30 nm to 100 nm that are released both constitutively and upon stimulation from a variety of cell types. ...