עבודה זו נתמכה על ידי מענקים מקרן קנדה עבור חדשנות (CFI), המכון הקנדי לבריאות מחקר (CIHR), ואת למדעי הטבע וההנדסה מועצת המחקר של קנדה (NSERC).

חלק 1: שיבוש של שפעת Virion <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> הוסף 750 μl של חיץ MNT (20 mM MES, 150 mM NaCl, 30 מ&quot;מ טריס, pH 7.5) לתוך הגליל האחד פוליקרבונט צנטריפוגות Beckman (11 מ&quot;מ x 34 מ&quot;מ) נועדה להשתלב הרוטור TLA-120.2 לשימוש אופטימה Beckman Max-E ultracentrifuge. </li><li style=";text-align:right;direction:rtl"> הוסף 500 μl של שפעת וירוס (H3N2 X-31 A/AICHI/68 זן, 2 מ&quot;ג / מ&quot;ל) לתוך הצינור. מערבבים את הנגיף עם למאגר MNT ידי pipetting מעלה ומטה מספר פעמים. </li><li style=";text-align:right;direction:rtl"> צנטריפוגה במשך 10 דקות על 109,000 XG, 4 ° C, צנטריפוגה אופטימה Max-E Beckman באמצעות הרוטור TLA-120.2. </li><li style=";text-align:right;direction:rtl"> הסר את supernatant ו resuspend גלולה במאגר 500 שיבוש μl (100 מ&quot;מ KCl, 5 מ&quot;מ MgCl 2, 5% (w / v) גליצרול, octylglucoside 50 מ&quot;מ, 10 מ&quot;ג / מ&quot;ל lysolecithin, dithiothreitol 1.5 מ&quot;מ, 100 מ&quot;מ MES, pH 5.5). </li><li style=";text-align:right;direction:rtl"> וורטקס במרץ, ולאחר מכן ללחוץ על 31 מעלות צלזיוס למשך 20 דקות thermomixer Eppendorf. </li></ol> חלק 2: צבע גליצרול משקעים צנטריפוגה מהירות <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> הכן שיפוע גליצרול על ידי הצבת את הסכומים הבאים של גליצרול לתוך צינור Beckman צנטריפוגות ultraclear (13 מ&quot;מ x 51 מ&quot;מ): 1 מ&quot;ל 70% (v / v) גליצרול, 0.75 מ&quot;ל גליצרול 50%, 0.375 מ&quot;ל גליצרול 40%, ו - 1.8 מ&quot;ל 33% גליצרול. פתרונות גליצרול מבוצעים על ידי ערבוב גליצרול טהור עם חיץ NM (150 mM NaCl, 50 מ&quot;מ MES, pH 5.5). כמו כן להכין צינור המכיל איזון גם גליצרול חיץ. </li><li style=";text-align:right;direction:rtl"> וורטקס שיבשו מדגם ויראלי שוב, לטעון אותו על השיפוע גליצרול. </li><li style=";text-align:right;direction:rtl"> צנטריפוגה שיפוע עבור 3.75 שעות 217.000 XG, 4 ° C, רוטור MLS-50-Beckman מתנדנד דלי. </li><li style=";text-align:right;direction:rtl"> לאחר צנטריפוגה תושלם, ידני לאסוף 250 aliquots μl של שיפוע החל מהחלק העליון של הצינור. שמור שברים על הקרח או 4 ° C. </li></ol> חלק 3: ניתוח של שברים Gradient גליצרול על ידי ג&#39;ל אלקטרופורזה SDS polyacrylamide <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> הסר 20 μl כל חלק מן לצינור טריים. </li><li style=";text-align:right;direction:rtl"> הוסף 5 μl של חיץ SDS-PAGE 5x המדגם. </li><li style=";text-align:right;direction:rtl"> מחממים עד 95 מעלות צלזיוס למשך 5 דקות. </li><li style=";text-align:right;direction:rtl"> ספין את דגימות בקצרה ומעלים אותם על ג&#39;ל polyacrylamide 10%, והם כוללים סמנים משקל מולקולרי באחת הבארות. </li><li style=";text-align:right;direction:rtl"> הפעל את הדגימות על הג&#39;ל עד לצבוע bromphenol טעינת כחול מגיע קרוב לתחתית הג&#39;ל. </li><li style=";text-align:right;direction:rtl"> הכתם ג&#39;ל עם Coomassie כחול. </li></ol> חלק 4: ריכוז של שברים vRNP <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> בחר את השברים גליצרול המכיל בעיקר NP, לשלב אותם, ולהפיץ אותם לשתי מבחנות צנטריפוגה Beckman פוליקרבונט (11 מ&quot;מ x 34 מ&quot;מ). </li><li style=";text-align:right;direction:rtl"> ממלאים כל צינור עם diethyl pyrocarbonate (DEPC) שטופלו מים ultrapure ו pipet מעלה ומטה מספר פעמים כדי לערבב. </li><li style=";text-align:right;direction:rtl"> צנטריפוגה עבור 4.5 שעות ב 157,000 XG, 4 ° C, רוטור TLA-120.2 Beckman. </li><li style=";text-align:right;direction:rtl"> הסר את supernatant ו resuspend את הכדור ב 50 μl מים DEPC שטופלו. </li><li style=";text-align:right;direction:rtl"> אם תרצה, 280 של vRNPs מרוכז ניתן למדוד. כפי NP היא כיום מרכיב מרכזי אספו את השברים, אומדן molarity של NP יכול להיות מחושב באמצעות מקדם הכחדה של 55,350 M -1 cm -1 (כפי שנקבע באמצעות ProtParam 3). </li><li style=";text-align:right;direction:rtl"> Aliquot vRNPs מטוהרים, ולאחסן אותם קפואים ב -80 ° C לשימוש מאוחר יותר. </li></ol> חלק 5: מכתים שלילי של vRNPs <ol style=";text-align:right;direction:rtl"><li style=";text-align:right;direction:rtl"> מדולל 1 μl של vRNP מטוהרים לתוך μl 9 של טרי מתוצרת מסונן, פעמיים חיץ MNT (20 mM MES, 150 mM NaCl, 30 מ&quot;מ טריס, pH 7.5). מאגרים נוספים הם גם אישור כדי לדלל את vRNPs כדי לשטוף את הרשת הדגימה (שלב 5.5), אבל לא להשתמש PBS אם אצטט uranyl משמש מכתים שלילי. </li><li style=";text-align:right;direction:rtl"> זוהר פריקה טיפוס (TEM נחושת) מצופה בעבר עם parlodion הסרט פחמן למשך 30 שניות רשת. </li><li style=";text-align:right;direction:rtl"> החזק את רשת טרי זוהר משוחררים הדגימה עם פינצטה, ולהחיל על ירידה של 5 μl של vRNP מדולל על הרשת הדגימה. </li><li style=";text-align:right;direction:rtl"> להשאיר את טיפה של הדגימה על רשת במשך 8 דקות. </li><li style=";text-align:right;direction:rtl"> בזמן ההמתנה, במקום רצועה קטנה של Parafilm על הספסל, ולחלק 2 טיפות המכילות 10 μl כל חיץ MNT (כדי לשטוף את הרשת), וירידה של 80 μl של הפתרון מכתים טריים (1% אמוניום molybdate או 1 uranyl אצטט%) על Parafilm. </li><li style=";text-align:right;direction:rtl"> לאחר 8 דקות של ספיחה, הפתיל את חלק מהפתרון מדגם מרשת הדגימה עם פיסת נייר סינון (לחתוך למשולשים). אל תתנו את רשת הדגימה לייבוש. </li><li style=";text-align:right;direction:rtl"> לשטוף רשת הדגימה ב 2 טיפות המכילות 10 μl כל חיץ MNT זמן הכולל של דקה 1. הדבר נעשה על ידי הורדת בזהירות את הרשת הדגימה על ירידה, ולאחר מכן את הפתילה חלק מהפתרון מדגם מרשת הדגימה עם פיסת נייר סינון (בלי לתת את הרשת הדגימה יבש). </li><li style=";text-align:right;direction:rtl"> מיד לאחר הפתילה את הטיפה האחרונה של חיץ מרשת הדגימה, להשליםלצלול ly רשת הדגימה בתוך טיפה את הכתם ולהמתין 1 דקה. </li><li style=";text-align:right;direction:rtl"> הפתיל לחלוטין את פתרון הכתם מן הרשת את הדגימה עם פיסת נייר הסינון. </li><li style=";text-align:right;direction:rtl"> לאפשר את רשת הדגימה לאוויר יבש במשך כמה דקות לפני תצפית במיקרוסקופ אלקטרונים הילוכים. </li></ol> חלק 6: תוצאות נציג: <img src="/files/ftp_upload/old/1105_2009_1_22_1/1105_Figure2.png" alt="איור 2" width="600" height="215" /> איור 1 כמו שפעת A NP (~ 56 KDA) הוא החלבון העיקרי המצוי מתחמי ribonucleoprotein ויראלי, הלהקה NP בדרך כלל היא הלהקה החזקה ביותר שברים המכיל את vRNPs (איור 1). בנוסף NP, כל vRNP שפעת מכיל גם עותק של פולימראז RNA מורכב trimeric (משקולות מולקולרית של kDa 82, 86 ו - 86.5). אלה עשויה או לא עשויה להיות גלוי על ידי מכתים כחול Coomassie בגלל השפע שלהם הוא נמוך בהשוואה לזה של NP. Polymerases, לעומת זאת, ניתן להבחין אם, במקום כחול Commassie כתם, כסף כתם של הג&#39;ל מתבצעת. מטריקס שפעת חלבון M1 (~ 28 KDA) צריכים להיות נוכחים מינימלית של שברים שבו שיא חלבון שברים NP נוכחים. <img src="/files/ftp_upload/old/1105_2009_1_22_2/1105_3.png" alt="איור 3" width="600" height="360" /> איור 2 VRNPs שלילי מוכתם כמו דמיינו תחת מיקרוסקופ אלקטרונים הילוכים אמור להניב vRNPs הדומות מוט בצורת חלקיקים בעלי אורך משתנה, כי הם כ -30 ננומטר עד 120 ננומטר אורך (איור 2 א). NP oligomeric מאורגן כמו שרשרת של מולקולות NP כי הוא מקופל נוספת לתוך מבנה הסליל הכפול לחזור, אז לולאות משני קצותיו של מוט אלה חלקיקים דמויי לפעמים ניתן לראות (איור 2b).

<ol>
	<li>Kemler, I., Whittaker, G., Helenius, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nuclear+import+of+microinjected+influenza+virus+ribonucleoproteins.">Nuclear import of microinjected influenza virus ribonucleoproteins.</a> Virology. 202, 1028-1033 (1994).</li><li>Wu, W. W. H., Weaver, L. L., Pant&#233;, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrastructural+analysis+of+the+nuclear+localization+sequences+on+influenza+a+ribonucleoprotein+complexes.">Ultrastructural analysis of the nuclear localization sequences on influenza a ribonucleoprotein complexes.</a> J Mol Biol. 374, 910-916 (2007).</li><li>Gasteiger, E., Walker, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The Proteomics Protocols Handbook. , 571-607 (2005).</li><li>Wu, W. W. H., Sun, Y. H. B., Pant&#233;, . <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nuclear+import+of+influenza+A+viral+ribonucleoprotein+complexes+is+mediated+by+two+nuclear+localization+sequences+on+viral+nucleoprotein.">Nuclear import of influenza A viral ribonucleoprotein complexes is mediated by two nuclear localization sequences on viral nucleoprotein.</a> Virol J. 4, 49-49 (2007).</li><li>Babcock, H. P., Chen, C., Zhuang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Using+single-particle+tracking+to+study+nuclear+trafficking+of+viral+genes.">Using single-particle tracking to study nuclear trafficking of viral genes.</a> Biophys J. 87, 2749-2758 (2004).</li></ol>

טיהור vRNPs מבוסס על ההליך המתואר על ידי קמלר et al. (1994). 1 אנו ואחרים משמשים גם בפרוטוקול זה על מנת לבודד vRNPs ללמוד לייבא הגרעין שלהם. 2,4,5 אנו ממליצים להשתמש RNase ללא טיפים וצינורות כאשר מניפולציה vRNPs כי הגנום הנגיפי מורכ?...

<table><tbody><tr><td>H3N2 X-31 A/AICHI/68 influenza A</td><td>Charles River Laboratories</td><td>490715</td><td></td></tr><tr><td>Tris</td><td>Sigma-Aldrich</td><td>T1503</td><td></td></tr><tr><td>MES</td><td>Sigma-Aldrich</td><td>M-8250</td><td></td></tr><tr><td>Glycerol</td><td>Fisher Scientific</td><td>G33-1</td><td></td></tr><tr><td>Octylglucoside</td><td>Sigma-Aldrich</td><td>O-8001</td><td></td></tr><tr><td>Lysolecithin</td><td>Sigma-Aldrich</td><td>L-4129</td><td></td></tr><tr><td>Dithiothreitol</td><td>Sigma-Aldrich</td><td>D-9779</td><td></td></tr><tr><td>Coomassie brilliant blue G-250</td><td>Kodak</td><td>1367796</td><td></td></tr><tr><td>diethyl pyrocarbonate (DEPC)-treated water</td><td>Invitrogen</td><td>750024</td><td></td></tr><tr><td>Uranyl Acetate</td><td>Ted Pella, Inc.</td><td>19481</td><td></td></tr><tr><td>Ammonium Molybdate</td><td>Fisher Scientific</td><td>A-674</td><td></td></tr><tr><td>Optima MAX-E Ultracentrifuge</td><td>Beckman Coulter Inc.</td><td>434491</td><td></td></tr><tr><td>MLS-50 Rotor Package, Swinging Bucket</td><td>Beckman Coulter Inc.</td><td>367280</td><td></td></tr><tr><td>TLA-120.2 Rotor Assembly, Fixed-Angle, Titanium</td><td>Beckman Coulter Inc.</td><td>362046</td><td></td></tr><tr><td>Eppendorf Thermomixer</td><td>Lauda Brinkmann</td><td>022670000</td><td></td></tr></tbody></table>

purification and visualization of influenza a viral ribonucleoprotein complexes

שפעת A הגנום הנגיפי מורכב תחושה שלילית ושמונה, יחיד מולקולות RNA תקועים, ארוזים בנפרד עם מספר עותקים של שפעת nucleoprotein (NP) לחלקיקים ribonulceoprotein ויראלי (vRNPs). VRNPs שפעת מוקפים בתוך מעטפת נגיפיים. במהלך כניסה לתא, לעומת זאת, קומפלקסים אלה vRNP משתחררים לתוך הציטופלסמה, שם הם לקבל גישה מכונות התחבורה גרעיני המארח. על מנת ללמוד את הייבוא ​​הגרעין של vRNPs שפעת שכפול של הגנום שפעת, כדאי לעבוד עם vRNPs מבודד כך רכיבים אחרים של הנגיף לא להפריע לתהליכים אלה. כאן אנו מתארים הליך לטהר אלה vRNPs משפעת וירוס. ההליך מתחיל עם הפרעה של שפעת virion עם דטרגנטים על מנת לשחרר את מתחמי vRNP מ virion אפף. VRNPs מופרדים אז מן המרכיבים האחרים של שפעת virion על שיפוע 33-70% גליצרול רציפה על ידי שקיעה מהירות. שברים המתקבל השיפוע גליצרול מנותחים לאחר מכן צביעה עם Coomassie כחול על דרך עמוד SDS. שברים השיא המכיל NP אז הם אספו יחד מרוכז על ידי צנטריפוגה. לאחר ריכוז, שלמות vRNPs הוא מאומת על ידי הדמיה של vRNPs ידי מיקרוסקופית אלקטרונים הילוכים לאחר מכתים שלילי. טיהור הדרגתי גליצרול הוא שינוי כי מן קמלר<em&gt; Et al.</em&gt; (1994)<sup&gt; 1</sup&gt; ו מכתים השלילי שבוצעה על ידי וו<em&gt; Et al.</em&gt; (2007).<sup&gt; 2</sup

Watch this Scientific Journal Video about Purification and Visualization of Influenza A Viral Ribonucleoprotein Complexes at JoVE.com

Purification and Visualization of Influenza A Viral Ribonucleoprotein Complexes

הגנום של שפעת וירוס כוללת שמונה מתחמים נפרדים של רנ&quot;א וחלבונים, כינה מתחמי ribonucleoprotein ויראלי (vRNPs). מאמר זה מתאר את שיפוע גליצרול טיהור במיקרוסקופ אלקטרונים הילוכים להדמיה של שפעת vRNPs.

טיהור ויזואליזציה של שפעת מכלולים Ribonucleoprotein ויראלי

The influenza A viral genome consists of eight negative-sense, single stranded RNA molecules, individually packed with multiple copies of the influenza A ...

purification-visualization-influenza-viral-ribonucleoprotein

Research

JoVE Journal

Biology

12.9K Views.  University of British Columbia - UBC. הגנום של שפעת וירוס כוללת שמונה מתחמים נפרדים של רנ"א וחלבונים, כינה מתחמי ribonucleoprotein ויראלי (vRNPs). מאמר זה מתאר את שיפוע גליצרול טיהור במיקרוסקופ אלקטרונים הילוכים להדמיה של שפעת vRNPs.

Video: Purification and Visualization of Influenza A Viral Ribonucleoprotein Complexes

High-throughput Detection Method for Influenza Virus

Influenza virus is a respiratory pathogen that causes a high degree of morbidity and mortality every year in multiple parts of the world. Therefore, precise diagnosis of the infecting strain and rapid high-throughput screening of vast numbers of clinical samples is paramount to control the spread of pandemic infections. Current clinical diagnoses of influenza infections are based on serologic testing, polymerase chain reaction, direct specimen immunofluorescence and cell culture 1,2.
Here, we report the development of a novel diagnostic technique used to detect live influenza viruses. We used the mouse-adapted human A/PR/8/34 (PR8, H1N1) virus 3 to test the efficacy of this technique using MDCK cells 4. MDCK cells (104 or 5 x 103 per well) were cultured in 96- or 384-well plates, infected with PR8 and viral proteins were detected using anti-M2 followed by an IR dye-conjugated secondary antibody. M2 5 and hemagglutinin 1 are two major marker proteins used in many different diagnostic assays. Employing IR-dye-conjugated secondary antibodies minimized the autofluorescence associated with other fluorescent dyes. The use of anti-M2 antibody allowed us to use the antigen-specific fluorescence intensity as a direct metric of viral quantity. To enumerate the fluorescence intensity, we used the LI-COR Odyssey-based IR scanner. This system uses two channel laser-based IR detections to identify fluorophores and differentiate them from background noise. The first channel excites at 680 nm and emits at 700 nm to help quantify the background. The second channel detects fluorophores that excite at 780 nm and emit at 800 nm. Scanning of PR8-infected MDCK cells in the IR scanner indicated a viral titer-dependent bright fluorescence. A positive correlation of fluorescence intensity to virus titer starting from 102-105 PFU could be consistently observed. Minimal but detectable positivity consistently seen with 102-103 PFU PR8 viral titers demonstrated the high sensitivity of the near-IR dyes. The signal-to-noise ratio was determined by comparing the mock-infected or isotype antibody-treated MDCK cells.
Using the fluorescence intensities from 96- or 384-well plate formats, we constructed standard titration curves. In these calculations, the first variable is the viral titer while the second variable is the fluorescence intensity. Therefore, we used the exponential distribution to generate a curve-fit to determine the polynomial relationship between the viral titers and fluorescence intensities. Collectively, we conclude that IR dye-based protein detection system can help diagnose infecting viral strains and precisely enumerate the titer of the infecting pathogens.

This method describes the use of Infrared dye based imaging system for detection of H1N1 in bronchioalveolar lavage (BAL) fluid of infected mice at a high sensitivity. This methodology can be performed in a 96- or 384-well plate, requires &lt;10 &mu;l volume of test material and has the potential for concurrent screening of multiple pathogens.

תפוקה גבוהה איתור שיטת וירוס השפעת

Influenza virus is a respiratory pathogen that causes a high degree of morbidity and mortality every year in multiple parts of the world. Therefore, ...

Immunology and Infection

Affinity Purification of Influenza Virus Ribonucleoprotein Complexes from the Chromatin of Infected Cells

Like all negative-strand RNA viruses, the genome of influenza viruses is packaged in the form of viral ribonucleoprotein complexes (vRNP), in which the single-stranded genome is encapsidated by the nucleoprotein (NP), and associated with the trimeric polymerase complex consisting of the PA, PB1, and PB2 subunits. However, in contrast to most RNA viruses, influenza viruses perform viral RNA synthesis in the nuclei of infected cells. Interestingly, viral mRNA synthesis uses cellular pre-mRNAs as primers, and it has been proposed that this process takes place on chromatin1. Interactions between the viral polymerase and the host RNA polymerase II, as well as between NP and host nucleosomes have also been characterized1,2.
Recently, the generation of recombinant influenza viruses encoding a One-Strep-Tag genetically fused to the C-terminus of the PB2 subunit of the viral polymerase (rWSN-PB2-Strep3) has been described. These recombinant viruses allow the purification of PB2-containing complexes, including vRNPs, from infected cells. To obtain purified vRNPs, cell cultures are infected, and vRNPs are affinity purified from lysates derived from these cells. However, the lysis procedures used to date have been based on one-step detergent lysis, which, despite the presence of a general nuclease, often extract chromatin-bound material only inefficiently. 
Our preliminary work suggested that a large portion of nuclear vRNPs were not extracted during traditional cell lysis, and therefore could not be affinity purified. To increase this extraction efficiency, and to separate chromatin-bound from non-chromatin-bound nuclear vRNPs, we adapted a step-wise subcellular extraction protocol to influenza virus-infected cells. Briefly, this procedure first separates the nuclei from the cell and then extracts soluble nuclear proteins (here termed the "nucleoplasmic" fraction). The remaining insoluble nuclear material is then digested with Benzonase, an unspecific DNA/RNA nuclease, followed by two salt extraction steps: first using 150 mM NaCl (termed "ch150"), then 500 mM NaCl ("ch500") (Fig. 1). These salt extraction steps were chosen based on our observation that 500 mM NaCl was sufficient to solubilize over 85% of nuclear vRNPs yet still allow binding of tagged vRNPs to the affinity matrix.
After subcellular fractionation of infected cells, it is possible to affinity purify PB2-tagged vRNPs from each individual fraction and analyze their protein and RNA components using Western Blot and primer extension, respectively. Recently, we utilized this method to discover that vRNP export complexes form during late points after infection on the chromatin fraction extracted with 500 mM NaCl (ch500)3.

Influenza viruses replicate their RNA genome in association with host-cell chromatin. Here, we present a method to purify intact viral ribonucleoprotein complexes from the chromatin of infected cells. Purified viral complexes can be analyzed by both Western blot and primer extension of protein and RNA content, respectively.

זיקה טיהור של נגיף השפעת תסביכים Ribonucleoprotein של הכרומטין של תאים נגועים

Like all negative-strand RNA viruses, the genome of influenza viruses is packaged in the form of viral ribonucleoprotein complexes (vRNP), in which the ...

Detection of Viruses from Bioaerosols Using Anion Exchange Resin

This protocol demonstrates a customized bioaerosol sampling method for viruses. In this system, anion exchange resin is coupled with liquid impingement-based air sampling devices for efficacious concentration of negatively-charged viruses from bioaerosols. Thus, the resin serves as an additional concentration step in the bioaerosol sampling workflow. Nucleic acid extraction of the viral particles is then performed directly from the anion exchange resin, with the resulting sample suitable for molecular analyses. Further, this protocol describes a custom-built bioaerosol chamber capable of generating virus-laden bioaerosols under a variety of environmental conditions and allowing for continuous monitoring of environmental variables such as temperature, humidity, wind speed, and aerosol mass concentration. The main advantage of using this protocol is increased sensitivity of viral detection, as assessed via direct comparison to an unmodified conventional liquid impinger. Other advantages include the potential to concentrate diverse negatively-charged viruses, the low cost of anion exchange resin (~$0.14 per sample), and ease of use. Disadvantages include the inability of this protocol to assess infectivity of resin-adsorbed viral particles, and potentially the need for the optimization of the liquid sampling buffer used within the impinger.

An anion exchange resin-based method, adapted to liquid impingement-based bioaerosol sampling of viruses is demonstrated. When coupled with downstream molecular detection, the method allows for facile and sensitive detection of viruses from bioaerosols.

זיהוי של וירוסים Bioaerosols באמצעות אניון Exchange שרף

This protocol demonstrates a customized bioaerosol sampling method for viruses. In this system, anion exchange resin is coupled with liquid ...

Environment

Method for Measurement of Viral Fusion Kinetics at the Single Particle Level

Membrane fusion is an essential step during entry of enveloped viruses into cells. Conventional fusion assays typically report on a large number of fusion events, making it difficult to quantitatively analyze the sequence of the molecular steps involved. We have developed an in vitro, two-color fluorescence assay to monitor kinetics of single virus particles fusing with a target bilayer on an essentially fluid support.
Influenza viral particles are incubated with a green lipophilic fluorophore to stain the membrane and a red hydrophilic fluorophore to stain the viral interior. We deposit a ganglioside-containing lipid bilayer on the dextran-functionilized glass surface of a flow cell, incubate the viral particles on the planar bilayer and image the fluorescence of a 100 x 100 &mu;m2 area, containing several hundreds of particles, on a CCD camera. By imaging both the red and green fluorescence, we can simultaneously monitor the behavior of the membrane dye (green) and the aqueous content (red) of the particles.
Upon lowering the pH to a value below the fusion pH, the particles will fuse with the membrane. Hemifusion, the merging of the outer leaflet of the viral membrane with the outer leaflet of the target membrane, will be visible as a sudden change in the green fluorescence of a particle. Upon the subsequent fusion of the two remaining distal leaflets a pore will be formed and the red-emitting fluorophore in the viral particle will be released under the target membrane. This event will give rise to a decrease of the red fluorescence of individual particles. Finally, the integrated fluorescence from a pH-sensitive fluorophore that is embedded in the target membrane reports on the exact time of the pH drop.
From the three fluorescence-time traces, all the important events (pH drop, lipid mixing upon hemifusion, content mixing upon pore formation) can now be extracted in a straightforward manner and for every particle individually. By collecting the elapsed times for the various transitions for many individual particles in histograms, we can determine the lifetimes of the corresponding intermediates. Even hidden intermediates that do not have a direct fluorescent observable can be visualized directly from these histograms.

We present an in vitro, two-color fluorescence assay to visualize the fusion of single virus particles with a fluid target bilayer. By labeling viral particles with fluorophores that differentially stain the viral membrane and its interior, we are able to monitor the kinetics of hemifusion and pore formation.

שיטת מדידה של קינטיקס Fusion ויראלי ברמה חלקיק יחיד

Membrane fusion is an essential step during entry of enveloped viruses into cells. Conventional fusion assays typically report on a large number of fusion ...

Generation and Assembly of Virus-Specific Nucleocapsids of the Respiratory Syncytial Virus

The use of an authentic RNA template is critical to advance the fundamental knowledge of viral RNA synthesis that can guide both mechanistic discovery and assay development in virology. The RNA template of nonsegmented negative-sense (NNS) RNA viruses, such as the respiratory syncytial virus (RSV), is not an RNA molecule alone but rather a nucleoprotein (N) encapsidated ribonucleoprotein complex. Despite the importance of the authentic RNA template, the generation and assembly of such a ribonucleoprotein complex remain sophisticated and require in-depth elucidation. The main challenge is that the overexpressed RSV N binds non-specifically to cellular RNAs to form random nucleocapsid-like particles (NCLPs). Here, we established a protocol to obtain RNA-free N (N0) first by co-expressing N with a chaperone phosphoprotein (P), then assembling N0 with RNA oligos with the RSV-specific RNA sequence to obtain virus-specific nucleocapsids (NCs). This protocol shows how to overcome the difficulty in the preparation of this traditionally challenging viral ribonucleoprotein complex.

For in-depth mechanistic analysis of the respiratory syncytial virus (RSV) RNA synthesis, we report a protocol of utilizing the chaperone phosphoprotein (P) for coexpression of the RNA-free nucleoprotein (N0) for subsequent in vitro assembly of the virus-specific nucleocapsids (NCs).

יצירה והרכבה של נוקלאוקפסידים ספציפיים לווירוסים של הנגיף הסינכרוני הנשימתי

The use of an authentic RNA template is critical to advance the fundamental knowledge of viral RNA synthesis that can guide both mechanistic discovery and ...

Biochemistry

In Vitro Disassembly of Influenza A Virus Capsids by Gradient Centrifugation

Acid-triggered molecular processes closely control cell entry of many viruses that enter through the endocytic system. In the case of influenza A virus (IAV), virus fusion with the endosomal membrane as well as the subsequent disassembly of the viral capsid, called uncoating, is governed by the ionic conditions inside endocytic vesicles. The early steps in the virus life cycle are hard to study because endosomes cannot be directly accessed experimentally, creating the need for an in vitro approach. Here, we describe a method based on velocity gradient centrifugation of purified virions through a two-layer glycerol gradient, which enables analysis of the IAV core and its stability. The gradient contains a non-ionic detergent (NP-40) in its lower layer to remove the viral membrane by solubilization as the virus sediments toward the bottom. At neutral pH, viral cores are pelleted as stable structures. The major core components, matrix protein (M1) and the viral ribonucleoproteins (vRNPs), can be clearly identified in the pellet fraction by SDS-PAGE. Decreasing the pH to 6.0 or lower in the bottom layer selectively removes M1 from the pellet followed by release of vRNPs at more acidic conditions. Viral protein bands on Coomassie-stained gels can be subjected to densitometric quantification to monitor intermediate states of IAV disassembly. Besides pH, other factors that influence viral core stability can be assessed, such as salt concentration and putative viral uncoating factors, simply by modifying the detergent-containing glycerol layer accordingly. Taken together, the presented technique allows highly reproducible and quantitative analysis of viral uncoating in vitro. It can be applied to other enveloped viruses that undergo complex uncoating processes.

In Vitro Disassembly of Influenza A Virus Capsids by Gradient Centrifugation

Disassembly of influenza A virus cores during virus entry into host cells is a multistep process. We describe an in vitro method to analyze the early stages of viral uncoating. In this approach, velocity gradient centrifugation is used to biochemically dissect the steps that initiate uncoating under defined conditions.

במבחנה פירוק של וירוס שפעת capsids ידי צנטריפוגה שיפוע

Acid-triggered molecular processes closely control cell entry of many viruses that enter through the endocytic system. In the case of influenza A virus ...

Purification of Viral DNA for the Identification of Associated Viral and Cellular Proteins

The goal of this protocol is to isolate herpes simplex virus type 1 (HSV-1) DNA from infected cells for the identification of associated viral and cellular proteins by mass spectrometry. Although proteins that interact with viral genomes play major roles in determining the outcome of infection, a comprehensive analysis of viral genome associated proteins was not previously feasible. Here we demonstrate a method that enables the direct purification of HSV-1 genomes from infected cells. Replicating viral DNA is selectively labeled with modified nucleotides that contain an alkyne functional group. Labeled DNA is then specifically and irreversibly tagged via the covalent attachment of biotin azide via a copper(I)-catalyzed azide-alkyne cycloaddition or click reaction. Biotin-tagged DNA is purified on streptavidin-coated beads and associated proteins are eluted and identified by mass spectrometry. This method enables the selective targeting and isolation of HSV-1 replication forks or whole genomes from complex biological environments. Furthermore, adaptation of this approach will allow for the investigation of various aspects of herpesviral infection, as well as the examination of the genomes of other DNA viruses.

The goal of this protocol is to specifically tag and selectively isolate viral DNA from infected cells for the characterization of viral genome associated proteins.

טיהור של ה-DNA הנגיפי לצורך זיהוי חלבונים הקשורים ויראלי וסלולריות

The goal of this protocol is to isolate herpes simplex virus type 1 (HSV-1) DNA from infected cells for the identification of associated viral and ...

Confocal Imaging of Double-Stranded RNA and Pattern Recognition Receptors in Negative-Sense RNA Virus Infection

Double-stranded (ds) RNA is produced as a replicative intermediate during RNA virus infection. Recognition of dsRNA by host pattern recognition receptors (PRRs) such as the retinoic acid (RIG-I) like receptors (RLRs) RIG-I and melanoma differentiation-associated protein 5 (MDA-5) leads to the induction of the innate immune response. The formation and intracellular distribution of dsRNA in positive-sense RNA virus infection has been well characterized by microscopy. Many negative-sense RNA viruses, including some arenaviruses, trigger the innate immune response during infection. However, negative-sense RNA viruses were thought to produce low levels of dsRNA, which hinders the imaging study of PRR recognition of viral dsRNA. Additionally, infection experiments with highly pathogenic arenaviruses must be performed in high containment biosafety level facilities (BSL-4). The interaction between viral RNA and PRRs for highly pathogenic RNA virus is largely unknown due to the additional technical challenges that researchers need to face in the BSL-4 facilities. Recently, a monoclonal antibody (Mab) (clone 9D5) originally used for pan-enterovirus detection has been found to specifically detect dsRNA with a higher sensitivity than the traditional J2 or K1 anti-dsRNA antibodies. Herein, by utilizing the 9D5 antibody, we describe a confocal microscopy protocol that has been used successfully to visualize dsRNA, viral protein and PRR simultaneously in individual cells infected by arenavirus. The protocol is also suitable for imaging studies of dsRNA and PRR distribution in pathogenic arenavirus infected cells in BSL4 facilities.

Double-stranded RNA produced during RNA virus replication can be recognized by pattern recognition receptors to induce an innate immune response. For negative-sense RNA viruses, the interaction between the low-level dsRNA and PRRs remains unclear. We have developed a confocal microscopy method to visualize arenavirus dsRNA and PRR in individual cells.

הדמיה קונאפוקלית של זוגיות גדילי RNA ודפוס זיהוי רצפטורים להדבקת וירוס RNA שלילי-סנס

Double-stranded (ds) RNA is produced as a replicative intermediate during RNA virus infection. Recognition of dsRNA by host pattern recognition receptors ...

A Liquid Phase Affinity Capture Assay Using Magnetic Beads to Study Protein-Protein Interaction: The Poliovirus-Nanobody Example

In this article, a simple, quantitative, liquid phase affinity capture assay is presented. Provided that one protein can be tagged and another protein labeled, this method can be implemented for the investigation of protein-protein interactions. It is based on one hand on the recognition of the tagged protein by cobalt coated magnetic beads and on the other hand on the interaction between the tagged protein and a second specific protein that is labeled. First, the labeled and tagged proteins are mixed and incubated at room temperature. The magnetic beads, that recognize the tag, are added and the bound fraction of labeled protein is separated from the unbound fraction using magnets. The amount of labeled protein that is captured can be determined in an indirect way by measuring the signal of the labeled protein remained in the unbound fraction. The described liquid phase affinity assay is extremely useful when conformational conversion sensitive proteins are assayed. The development and application of the assay is demonstrated for the interaction between poliovirus and poliovirus recognizing nanobodies1. Since poliovirus is sensitive to conformational conversion2 when attached to a solid surface (unpublished results), the use of ELISA is limited and a liquid phase based system should therefore be preferred. An example of a liquid phase based system often used in polioresearch3,4 is the micro protein A-immunoprecipitation test5. Even though this test has proven its applicability, it requires an Fc-structure, which is absent in the nanobodies6,7. However, as another opportunity, these interesting and stable single-domain antibodies8 can be easily engineered with different tags. The widely used (His)6-tag shows affinity for bivalent ions such as nickel or cobalt, which can on their turn be easily coated on magnetic beads. We therefore developed this simple quantitative affinity capture assay based on cobalt coated magnetic beads. Poliovirus was labeled with 35S to enable unhindered interaction with the nanobodies and to make a quantitative detection feasible. The method is easy to perform and can be established with a low cost, which is further supported by the possibility of effectively regenerating the magnetic beads.

In this article, a simple, quantitative, liquid phase affinity capture assay is presented. It is a reliable technique based on the interaction between magnetic beads and tagged proteins (e.g. nanobodies) on one hand and the affinity between the tagged protein and a second, labeled protein (e.g. poliovirus) on the other.

שלב נוזלי זיקה לכידת Assay באמצעות חרוזים מגנטיים ללמוד חלבונים אינטראקציה: דוגמה poliovirus-Nanobody

In this article, a simple, quantitative, liquid phase affinity capture assay is presented. Provided that one protein can be tagged and another protein ...

Visualization of SARS-CoV-2 using Immuno RNA-Fluorescence In Situ Hybridization

This manuscript provides a protocol for in situ hybridization chain reaction (HCR) coupled with immunofluorescence to visualize severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA in cell line&#160;and three-dimensional (3D) cultures of human airway epithelium. The method allows highly specific and sensitive visualization of viral RNA by relying on HCR initiated by probe localization. Split-initiator probes help amplify the signal by fluorescently labeled amplifiers, resulting in negligible background fluorescence in confocal microscopy. Labeling amplifiers with different fluorescent dyes facilitates the simultaneous recognition of various targets. This, in turn, allows the mapping of the infection in tissues to better understand viral pathogenesis and replication at the single-cell level. Coupling this method with immunofluorescence may facilitate better understanding of host-virus interactions, including alternation of the host epigenome and immune response pathways. Owing to sensitive and specific HCR technology, this protocol can also be used as a diagnostic tool. It is also important to remember that the technique may be modified easily to enable detection of any RNA, including non-coding RNAs and RNA viruses that may emerge in the future.

Here, we describe a simple method that combines RNA fluorescence in situ&#160;hybridization (RNA-FISH) with immunofluorescence to visualize severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA. This protocol may increase understanding of the molecular characteristics of SARS-CoV-2 RNA-host interactions at a single-cell level.

הדמיה של SARS-CoV-2 באמצעות אימונו RNA-פלואורסצנטיות בהכלאה Situ

This manuscript provides a protocol for in situ hybridization chain reaction (HCR) coupled with immunofluorescence to visualize severe acute respiratory ...