We thank F. Chisari for providing Huh-7.5.1 cell line. We would like to thank Justine Ho for editing the manuscript. This work was supported by Cedars-Sinai Medical Center Institutional Programmatic Research Award and National Center for Advancing Translational Sciences, Grant UL1TR000124 to V.A.

A general outline of the protocol is illustrated in Figure&#160;1.
1. Cells
<ol>
	<li>Prepare complete growth media that contains 10-15% fetal bovine serum (FBS), 10 mM nonessential amino acids, 10 mM Hepes, penicillin (100 units/ml), streptomycin (100 mg/ml), and 2 mM L-glutamine.</li>
	<li>Maintain Huh-7.5.1 cells13 in complete growth media containing the above supplements for in vitro analysis of hepatitis C viral replication cycle.</li>
	<li>Culture viral strains in Huh-7.5.1 cells with the specified supplemented growth media at 37 &#176;C with 5% CO2.</li>
</ol>
2. Virus and Plasmid Constructs
<ol>
	<li>Generate the complementary DNA (cDNA) form of HCV RNA and clone it into a plasmid vector for ease of genetic manipulation. Note: The discovery of the Japanese fulminant hepatitis 1, JFH-1 (genotype 2a HCV), isolate has been critical for HCV research and is primarily used to study the HCV replication cycle11-13. Inter- and intragenotypic chimeric viruses based on JFH-1 HCV are commonly used in research14-18. Construction of synthetic intragenotype 2a chimeric virus, FNX-HCV, and a monocistronic chimeric reporter strain was described previously19 and construction details are beyond the scope of this protocol.</li>
	<li>Use the pFNX-HCV intragenotype 2a virus as it contains a 5&#8217;NTR, structural regions and p7, and part of the NS2 non-structural regions (nucleotides 1 to 2878) of the J6CF parental strain (NCBI accession no. AF177036), as well as the non-structural components of the JFH-1 viral strain (NCBI accession no. AB047639). Note: FNX-HCV was synthesized based on the sequence of Jc1 intragenotype 2a chimeric HCV reported previously15.</li>
	<li>Generate a monocistronic chimeric reporter viral construct, the pFNX-Rluc, based on the pFNX-HCV strain (above in step 2.2) by inserting a Renilla luciferase gene between the 5&#8217; NTR and core gene (between nt 388 and 389). Subsequently, connect the luciferase gene and core gene of this construct using a foot and mouth disease virus 2A (F2A) peptide sequence, which would work as a cleavage signal.</li>
	<li>Engineer the RNA polymerase-null (Pol-) viral construct using either the pFNX-HCV or the pFNX-Rluc viral background. Replace the NS5B polymerase catalytic residues, GDD (aa 2759-2761; nt 8615-8623), of either of these viral backbones with AAG amino acid residues.</li>
</ol>
3. In Vitro HCV RNA Transcription
<ol>
	<li>Use an intragenotype 2a chimeric virus FNX-HCV and FNX-HCV Pol null (Pol-) HCV for evaluation of viral replication (Figure&#160;2A).</li>
	<li>Linearize the viral plasmids with XbaI restriction enzyme and then treat with mung bean nuclease to generate blunt ends. Purify the digested plasmids by anion-exchange chromatography. Verify the integrity of the linearized plasmid by subjecting DNA to agarose gel electrophoresis (Figure&#160;2B).</li>
	<li>Transcribe the linearized viral plasmids using the T7- RNA polymerase.</li>
	<li>Purify the newly synthesized DNase-treated RNA using an RNA purification kit.</li>
	<li>Verify the RNA production by agarose gel electrophoresis (Figure&#160;2C).</li>
	<li>Quantify the RNA by spectrophotometry.</li>
	<li>Store the generated RNA in -80 &#176;C in 10 &#956;g working aliquots. Note: To minimize variation of RNA quality within each experimental design by transcribing all RNA for each viral sample and control at the same time.</li>
</ol>
4. HCV RNA Transfection and Sample Collection
<ol>
	<li>Harvest the Huh-7.5.1 cells using trypsin.</li>
	<li>To rinse cells, centrifuge and resuspend the suspension twice with cold low serum media. Resuspend the cells in low serum media at 1 x 107cells per ml.</li>
	<li>Mix a total of 10 &#956;g of transcribed viral RNA with 400 &#956;l of resuspended cells (4 x 106 cells) in a 0.4-cm electroporation cuvette. Transfect the cells via electroporation at 270 V, 100 &#937;, and 950 &#956;F.</li>
	<li>Resuspend the electroporated cells in 10 ml complete growth media with 15% FBS. Note: Increased survivability of electroporated cells is seen when the Huh-7.5.1 cells were cultured in 15% Fetal Bovine Serum.</li>
	<li>Plate the cells in both T-25 flasks (~1.2 x 106 cells per flask) and 48-well plates (1 x 104 cells per well) for each of the following time points: 4, 48 and 96 hr.</li>
	<li>Replace the media at 4-8 hr post-transfection with fresh supplemented growth media with 10% FBS to remove dead cell debris from the cultured flasks and plates.</li>
	<li>Harvest cell culture supernatants at the 48, 96 hr time points and remove cellular debris from collected samples by centrifugation of cells at 1,500 rpm for 10 min at 4 &#186;C.</li>
	<li>Store the cell-free supernatants at -80&#160;&#186;C. Lyse the cells for protein and RNA analysis by Western blot and reverse transcription-quantitative PCR at the indicated time points.</li>
</ol>
5. Reverse Transcription-quantitative PCR (RT-qPCR) for Assessing the HCV Genome Copies
<ol>
	<li>Perform a two-step RT-qPCR to determine the HCV genomic RNA copy number.</li>
	<li>Reverse transcribe 1 &#956;g of total cellular RNA using reverse transcriptase and a primer specific for HCV sense strand that binds to 5&#8217;NTR (JFH RTQ R: 5&#8217;CCTATCAGGCAGTACCACA-3&#8217;) or a primer specific for housekeeping gene peptidylprolyl isomerase G (PPIG R: 5&#8217;-GTCTCTCCTCCTTCTCCTCCTATCTTT-3&#8217;). Also reverse transcribe FNX-HCV RNA (generated in Step 3) of known genome copies (101 to 109 standard) using HCV sense strand primer.</li>
	<li>Carry out qPCR by using 50 ng of the resulting transcribed cDNA using specific HCV primers (JFH RTQ F: 5&#8217;CTGGGTCCTTTCTTGGATAA-3; JFH RTQ R: 5&#8217;CCTATCAGGCAGTACCACA-3&#8217;) and DNA binding green dye containing qPCR super mix. Perform qPCR for housekeeping gene PPIG as well (primers PPIG F: 5&#8217;-GAAGAGTGCGATCAAGAACCCATGAC-3&#8217;; PPIG R: 5&#8217;-GTCTCTCCTCCTTCTCCTCCTATCTTT-3&#8217;) Note: For calculating accurate intracellular HCV RNA level across samples, use cellular housekeeping gene, PPIG, expression level (Ct cycle) for normalization. Use the copy number of the FNX-HCV genome as the standard for the copy number determination.</li>
	<li>Use the following conditions when running qPCR to determine HCV RNA copy number: 95&#160;&#186;C for 15 sec and 60&#160;&#186;C for 30 sec (40 cycles) using real-time PCR system.</li>
	<li>See Figures 3A and 3B for genome replication results.</li>
</ol>
6. Western Blotting Analysis for Detecting HCV Protein Expression (Figure 3C)
<ol>
	<li>Use cell lysates from viral RNA transfected at 96 hr post transfection for protein western blotting analysis.</li>
	<li>Resolve the cell lysate using SDS-PAGE and transfer to polyvinylidene difluoride (PVDF) membrane.</li>
	<li>Block the membrane using a blocking solution containing 5% skim milk, 0.2% Tween 20 in phosphate buffered saline (PBS).</li>
	<li>Incubate the membrane with primary mouse monoclonal antibody NS3 (1 in 1,000 dilution) and beta-actin (1 in 5,000 dilution).</li>
	<li>Add goat anti-mouse IgG conjugated to horseradish peroxidase (1 in 5,000 dilution) and detect by chemiluminescence.</li>
</ol>
7. Immunofluorescence Assay (IFA)
<ol>
	<li>Fix the HCV-infected and transfected cells using methanol for 30 min at -20&#160;&#186;C for immunofluorescence assay.</li>
	<li>Wash the cell with PBS three times and block with IFA blocking buffer.</li>
	<li>Use rabbit polyclonal anti-NS5A primarily antibody (kindly provided by Dr. Dasgupta, UCLA) or mouse monoclonal anti-dsRNA antibody J2 at a dilution of 1:200 (1 &#956;g/ml) and incubate for 5 hr to overnight at 4 &#186;C.</li>
	<li>Wash the cells with PBS three times after the primary antibody.</li>
	<li>Add goat anti-rabbit IgG-488 polyclonal secondary antibody or goat anti-mouse IgG-594 polyclonal secondary antibody at a 1:1,000 dilution (1 &#956;g/ml) and incubate for 1 hr at room temperature.</li>
	<li>Wash cells with PBS three times and stain nuclei using Hoechst dye and view using fluorescent microscope (Figure&#160;3D).</li>
</ol>
8. Measuring Virus Titer
<ol>
	<li>Plate na&#239;ve Huh-7.5.1 cells at approximately 3 x 103 cells/well using a 96-well plate. The next day, perform 10-fold serial dilutions of cell-free culture supernatant harvested from HCV RNA transfected cells using growth media and inoculate in triplicate onto Huh-7.5.1 cells.</li>
	<li>Fix cells at 72&#160;hr post-infection using methanol (for 30 min at -20 &#186;C) and immunostain for HCV NS5A protein as stated in the section 7.</li>
	<li>Use the highest dilution to count for the NS5A positive foci and calculate the average number of focus forming unit (FFU) per milliliter. See Figure&#160;4 for HCV titer.</li>
</ol>
9. Renilla Luciferase Reporter Assay for Viral Genome Replication and Infectivity
<ol>
	<li>For evaluating viral genome replication, plate HCV RNA-electroporated Huh-7.5.1 cells in triplicate in 48-well plates (1 x 104 cells/well).</li>
	<li>Lyse the cells with 75 &#956;l of passive lysis buffer at the 6 hr, 48 hr, and 96 hr post-transfection.</li>
	<li>Rock the plates gently for 15 min at room temperature and store at -80&#160;&#186;C.</li>
	<li>To measure the Renilla luciferase enzymatic activity, thaw the protein lysate and Renilla luciferase assay reagents to room temperature.</li>
	<li>Add 20 &#956;l of protein lysate per well of a 96-well white luminescence plate and place the plate in a luminometer.</li>
	<li>Dispense 100 &#956;l of Renilla luciferase assay reagent (coelenterazine substrate + buffer) per well and after a 2 sec pre-read delay; integrate the emitted light for 10 sec.</li>
	<li>Calculate the mean and standard deviation for each sample from the luciferase values of biological triplicates and subject the data to statistical analysis (Figure&#160;5).</li>
	<li>For assessing infectivity, inoculate 500 &#956;l of cell-free supernatant obtained from HCV RNA-transfected cells for the indicated time points (48 hr and 96 hr) in triplicate onto na&#239;ve Huh-7.5.1 cells in 48-well plates.</li>
	<li>Replace the viral inoculum with 500 &#956;l of fresh medium per well after 6&#160;hr post-infection.</li>
	<li>Lyse the cells at 48 hr post-infection and subject to Renilla luciferase assay as described in steps 8.2 to 8.7 (Figure&#160;5).</li>
</ol>
10. Statistical Analysis
<ol>
	<li>The error bars in the graphs indicate standard deviations (SD). The P values were calculated by the unpaired t test.</li>
</ol>

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The authors have nothing to disclose.

This illustration describes a method for analyzing the hepatitis C Virus replication cycle. HCV is a human pathogen and the prescribed biosafety protocol will have to be strictly followed. Infectious HCV cell culture systems have been described previously11-13,16,17. There are few crucial points we implement when following the illustrated protocol. First, it is of high importance to have good quality of intact full length viral genomic RNA for downstream studies. The input plasmid carrying the viral cDNA has t...

Hepatitis C virus (HCV) causes cirrhosis and liver cancer. It affects 170 million people worldwide with 350,000 people dying annually1-3. HCV is a positive strand RNA virus with a genome size of 9.6 kb. The HCV genome is translated as a single polyprotein of ~3,000 amino acid residues that is proteolytically cleaved by various cellular and viral proteases into 10 polypeptides. HCV is the prototype virus in the genus Hepacivirus and belongs to family Flaviviridae4. Upon exposure, HCV establishes chronic infection in 80% of the individuals. The infection is mostly asymptomatic and timely diagnosis can allow therapeutic intervention to prevent liver deterioration. Current treatment is suboptimal and no vaccine is available5,6.
The etiology of hepatitis C was first described in 1989 7. Studying HCV replication is important for hepatitis C vaccine and treatment research, but it had been long hampered by the lack of an efficient viral culture system. A molecular clone of HCV was shown to be infectious in chimpanzees upon intrahepatic inoculation8. Subsequently, HCV sub-genomic replicons were described, which allowed to dissect the viral genome replication stage in a cell culture system9,10. Discovery of a genotype 2a HCV isolate JFH-1 (Japanese Fulminant hepatitis-1), capable of infecting cell culture opened new avenues for HCV replication research11-13. Genotype 2a strain JFH-1 based inter- and intra-genotypic chimeric viruses and genotype 1 HCV based infectious culture systems are available as well14-18.
We have successfully used JFH-1 strain and HCV intragenotype 2a chimeric virus to obtain the high-resolution functional profiling map of protein domains and cis-acting RNA elements19,20. According to this, here we describe an effective culture system routinely used that allows studying various stages of the HCV replication cycle and host-pathogen interaction. We present virological assays to assess viral genome replication and de novo infectivity of intragenotype 2a HCV and a Renilla luciferase based reporter HCV.

<table border="0" cellpadding="0" cellspacing="0" width="1121">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:569px;">Name of Material/ Equipment</td>
			<td style="width:267px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td style="width:167px;">Comments/Description</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dulbecco&#8217;s modified Eagle&#8217;s medium (DMEM)</td>
			<td style="width:267px;">Fisher Scientific</td>
			<td style="width:119px;">10-017-CV</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:569px;">Non essential amino acid</td>
			<td style="width:267px;">Fisher Scientific</td>
			<td style="width:119px;">MT25025CI</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:569px;">HEPES</td>
			<td style="width:267px;">Life Technologies</td>
			<td style="width:119px;">15630080</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:569px;">Glutamax</td>
			<td style="width:267px;">Life Technologies</td>
			<td style="width:119px;">35050061</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:569px;">Opti-MEM Reduced Serum Medium,no Phenol Red</td>
			<td style="width:267px;">Life Technologies</td>
			<td style="width:119px;">11058-021</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:569px;">Huh-7.5.1</td>
			<td style="width:267px;">The Scripps Research Institute</td>
			<td style="width:119px;"></td>
			<td>The cell line was kindly provided by Dr. Francis Chisari to Dr. Arumugaswami under executed MTA between The Scripps Research Institute and Cedars-Sinai Medical Center</td>
		</tr>
		<tr height="23">
			<td height="23" style="height:23px;width:569px;">Plasmids (pFNX-HCV, pFNX-HCV Pol null, pFNX-Rluc, and pFNX-Rluc Pol null)&#160;</td>
			<td style="width:267px;">Cedars-Sinai Medical Center</td>
			<td style="width:119px;"></td>
			<td>The HCV plasmids were synthesized by Dr. Arumugaswami using overlapping oligo-nucleotides.&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:569px;">XbaI</td>
			<td>New England Biolabs Inc.</td>
			<td style="width:119px;">R0145S</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:569px;">Mung Bean Nuclease</td>
			<td>New England Biolabs Inc.</td>
			<td style="width:119px;">M0250S</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:569px;">T7 RiboMAX Express Large Scale RNA Production System</td>
			<td style="width:267px;">Promega</td>
			<td style="width:119px;">P1320</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:569px;">Rneasy Mini Kit</td>
			<td style="width:267px;">Qiagen</td>
			<td style="width:119px;">74104</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:569px;">Nanodrop 2000</td>
			<td style="width:267px;">Thermo Scientific</td>
			<td style="width:119px;">Nanodrop 2000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:569px;">Electroporation Cuvette (4 mm)</td>
			<td style="width:267px;">Bioexpress</td>
			<td>E-5010-4</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:569px;">Gene Pulser Xcell Total System</td>
			<td style="width:267px;">Bio-Rad</td>
			<td style="width:119px;">165-2660</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">mouse monoclonal anti-dsRNA antibody J2&#160;</td>
			<td>English &#38; Scientific Consulting Kft.</td>
			<td style="width:119px;">10010200</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:569px;">Goat anti-rabbit IgG Alexa Fluor 488</td>
			<td style="width:267px;">Life Technologies</td>
			<td>A11008</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:569px;">Goat anti-rabbit IgG Alexa Fluor 594</td>
			<td style="width:267px;">Life Technologies</td>
			<td>A11020</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">PVDF membrane package</td>
			<td style="width:267px;">Bio-Rad</td>
			<td style="width:119px;">162-0263</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:569px;">Blotting Grade Blocker Non Fat Dry Milk</td>
			<td style="width:267px;">Bio-Rad</td>
			<td style="width:119px;">170-6404XTU</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:569px;">Tween-20</td>
			<td style="width:267px;">Bio-Rad</td>
			<td style="width:119px;">170-6531XTU</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Anti-Hepatitis C Virus NS3 antibody [8 G-2]</td>
			<td style="width:267px;">Abcam</td>
			<td style="width:119px;">ab65407</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Anti-Hepatitis C Virus NS3 antibody [H23]</td>
			<td style="width:267px;">Abcam</td>
			<td style="width:119px;">ab13830</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Goat anti-mouse IgG conjugated with horseradish peroxidase (HRP)&#160;</td>
			<td>Jackson ImmunoResearch Laboratories Inc.</td>
			<td style="width:119px;">115-035-003</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Amersham ECL Prime Western Blotting Detection Reagents&#160;</td>
			<td style="width:267px;">GE Healthcare Life Sciences</td>
			<td style="width:119px;">RPN2236</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:569px;">SUPERSCRIPT III RT&#160;</td>
			<td style="width:267px;">Life Technologies</td>
			<td style="width:119px;">18080085</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:569px;">SYBR QPCR SUPERMIX W/ROX</td>
			<td style="width:267px;">Life Technologies</td>
			<td style="width:119px;">11744500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">ViiA 7 real-time PCR system</td>
			<td style="width:267px;">Life Technologies</td>
			<td style="width:119px;">NA</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Renilla Luciferase Assay System kit</td>
			<td style="width:267px;">Promega</td>
			<td style="width:119px;">E2810</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:569px;">RNase-Free DNase</td>
			<td style="width:267px;">Promega</td>
			<td style="width:119px;">M6101</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:569px;">GloMax-Multi Detection System (Luminometer)</td>
			<td style="width:267px;">Promega</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

a protocol for analyzing hepatitis c virus replication

Hepatitis C Virus (HCV) affects 3% of the world&#8217;s population and causes serious liver ailments including&#160;chronic hepatitis, cirrhosis, and hepatocellular carcinoma. HCV is an enveloped RNA virus belonging to the family Flaviviridae. Current treatment is not fully effective and causes adverse side effects. There is no HCV vaccine available. Thus, continued effort is required for developing a vaccine and better therapy. An HCV cell culture system is critical for studying various stages of HCV growth including viral entry, genome replication, packaging, and egress. In the current procedure presented, we used a wild-type intragenotype 2a chimeric virus, FNX-HCV, and a recombinant FNX-Rluc virus carrying a Renilla luciferase reporter gene to study the virus replication. A human hepatoma cell line (Huh-7 based) was used for transfection of in vitro transcribed HCV genomic RNAs. Cell-free culture supernatants, protein lysates and total RNA were harvested at various time points post-transfection to assess HCV growth. HCV genome replication status was evaluated by quantitative RT-PCR and visualizing the presence of HCV double-stranded RNA. The HCV protein expression was verified by Western blot and immunofluorescence assays using antibodies specific for HCV NS3 and NS5A proteins. HCV RNA transfected cells released infectious particles into culture supernatant and the viral titer was measured. Luciferase assays were utilized to assess the replication level and infectivity of reporter HCV. In conclusion, we present various virological assays for characterizing different stages of the HCV replication cycle.

Hepatitis C virus is a RNA virus. Thus for genetic manipulation purpose, the HCV genomic cDNA has been cloned into a bacterial plasmid vector. A T7 RNA polymerase promoter sequence was introduced immediately before the 5&#8217; end of the HCV genome. A general outline of HCV analysis workflow is presented in Figure&#160;1. To generate HCV genomic RNA with precise 3&#8217; end, the HCV genome containing plasmid is cut with XbaI restriction enzyme and the generated single-stranded overhang was blu...

Watch this Scientific Journal Video about A Protocol for Analyzing Hepatitis C Virus Replication at JoVE.com

A Protocol for Analyzing Hepatitis C Virus Replication

Hepatitis C Virus (HCV) is a major human pathogen that causes liver disorders, including cirrhosis and cancer. An HCV infectious cell culture system is essential for understanding the molecular mechanism of HCV replication and developing new therapeutic approaches. Here we describe a protocol to investigate various stages of the HCV replication cycle.

Hepatitis C Virus (HCV) affects 3% of the world&#8217;s population and causes serious liver ailments including&#160;chronic hepatitis, cirrhosis, and ...

a-protocol-for-analyzing-hepatitis-c-virus-replication

Research

JoVE Journal

Immunology and Infection

23.9K Aufrufe.  Cedars-Sinai Medical Center. Hepatitis C Virus (HCV) is a major human pathogen that causes liver disorders, including cirrhosis and cancer. An HCV infectious cell culture system is essential for understanding the molecular mechanism of HCV replication and developing new therapeutic approaches. Here we describe a protocol to investigate various stages of the HCV replication cycle. 

Serie: A Protocol for Analyzing Hepatitis C Virus Replication

Using Bioluminescent Imaging to Investigate Synergism Between Streptococcus pneumoniae and Influenza A Virus in Infant Mice

During the 1918 influenza virus pandemic, which killed approximately 50 million people worldwide, the majority of fatalities were not the result of infection with influenza virus alone. Instead, most individuals are thought to have succumbed to a secondary bacterial infection, predominately caused by the bacterium Streptococcus pneumoniae (the pneumococcus). The synergistic relationship between infections caused by influenza virus and the pneumococcus has subsequently been observed during the 1957 Asian influenza virus pandemic, as well as during seasonal outbreaks of the virus (reviewed in 1, 2). Here, we describe a protocol used to investigate the mechanism(s) that may be involved in increased morbidity as a result of concurrent influenza A virus and S. pneumoniae infection. We have developed an infant murine model to reliably and reproducibly demonstrate the effects of influenza virus infection of mice colonised with S. pneumoniae. Using this protocol, we have provided the first insight into the kinetics of pneumococcal transmission between co-housed, neonatal mice using in vivo imaging 3.

Using Bioluminescent Imaging to Investigate Synergism Between Streptococcus pneumoniae and Influenza A Virus in Infant Mice

A concurrent infection with influenza A virus is one of the factors implicated in the induction of invasive pneumococcal disease during asymptomatic Streptococcus pneumoniae carriage. Here we describe a mixed infection method using infant mice to investigate the synergism between these two respiratory pathogens.

During the 1918 influenza virus pandemic, which killed approximately 50 million people worldwide, the majority of fatalities were not the result of ...

Dissecting Host-virus Interaction in Lytic Replication of a Model Herpesvirus

In response to viral infection, a host develops various defensive responses, such as activating innate immune signaling pathways that lead to antiviral cytokine production1,2. In order to colonize the host, viruses are obligate to evade host antiviral responses and manipulate signaling pathways. Unraveling the host-virus interaction will shed light on the development of novel therapeutic strategies against viral infection.
Murine &gamma;HV68 is closely related to human oncogenic Kaposi's sarcoma-associated herpesvirus and Epsten-Barr virus3,4. &gamma;HV68 infection in laboratory mice provides a tractable small animal model to examine the entire course of host responses and viral infection in vivo, which are not available for human herpesviruses. In this protocol, we present a panel of methods for phenotypic characterization and molecular dissection of host signaling components in &gamma;HV68 lytic replication both in vivo and ex vivo. The availability of genetically modified mouse strains permits the interrogation of the roles of host signaling pathways during &gamma;HV68 acute infection in vivo. Additionally, mouse embryonic fibroblasts (MEFs) isolated from these deficient mouse strains can be used to further dissect roles of these molecules during &gamma;HV68 lytic replication ex vivo.
Using virological and molecular biology assays, we can pinpoint the molecular mechanism of host-virus interactions and identify host and viral genes essential for viral lytic replication. Finally, a bacterial artificial chromosome (BAC) system facilitates the introduction of mutations into the viral factor(s) that specifically interrupt the host-virus interaction. Recombinant &gamma;HV68 carrying these mutations can be used to recapitulate the phenotypes of &gamma;HV68 lytic replication in MEFs deficient in key host signaling components. This protocol offers an excellent strategy to interrogate host-pathogen interaction at multiple levels of intervention in vivo and ex vivo.
Recently, we have discovered that &gamma;HV68 usurps an innate immune signaling pathway to promote viral lytic replication5. Specifically, &gamma;HV68 de novo infection activates the immune kinase IKK&beta; and activated IKK&beta; phosphorylates the master viral transcription factor, replication and transactivator (RTA), to promote viral transcriptional activation. In doing so, &gamma;HV68 efficiently couples its transcriptional activation to host innate immune activation, thereby facilitating viral transcription and lytic replication. This study provides an excellent example that can be applied to other viruses to interrogate host-virus interaction.

We describe a protocol to identify key roles of host signaling molecules in lytic replication of a model herpesvirus, gamma herpesvirus 68 (&gamma;HV68). Utilizing genetically modified mouse strains and embryonic fibroblasts for &gamma;HV68 lytic replication, the protocol permits both phenotypic characterization and molecular interrogation of virus-host interactions in viral lytic replication.

In response to viral infection, a host develops various defensive responses, such as activating innate immune signaling pathways that lead to antiviral ...

High-throughput Assay to Phenotype Salmonella enterica Typhimurium Association, Invasion, and Replication in Macrophages

Salmonella species are zoonotic pathogens and leading causes of food borne illnesses in humans and livestock1. Understanding the mechanisms underlying Salmonella-host interactions are&#160;important to elucidate the molecular pathogenesis of Salmonella infection. The Gentamicin protection assay to phenotype Salmonella association, invasion and replication in phagocytic cells was adapted to allow high-throughput screening to define the roles of deletion mutants of Salmonella enterica serotype Typhimurium in host interactions using RAW 264.7 murine macrophages. Under this protocol, the variance in measurements is significantly reduced compared to the standard protocol, because wild-type and multiple mutant strains can be tested in the same culture dish and at the same time. The use of multichannel pipettes increases the throughput and enhances precision. Furthermore, concerns related to using less host cells per well in 96-well culture dish were addressed. Here, the protocol of the modified in vitro Salmonella invasion assay using phagocytic cells was successfully employed to phenotype 38 individual Salmonella deletion mutants for association, invasion and intracellular replication. The in vitro phenotypes are presented, some of which were subsequently confirmed to have in vivo phenotypes in an animal model. Thus, the modified, standardized assay to phenotype Salmonella association, invasion and replication in macrophages with high-throughput capacity could be utilized more broadly to study bacterial-host interactions.

High-throughput Assay to Phenotype Salmonella enterica Typhimurium Association, Invasion, and Replication in Macrophages

A high-throughput assay to in vitro phenotype Salmonella or other bacterial association, invasion, and replication in phagocytic cells with high-throughput capacity was developed. The method was employed to evaluate Salmonella gene knockout mutant strains for their involvements in host-pathogen interactions.

Salmonella species are zoonotic pathogens and leading causes of food borne illnesses in humans and livestock1. Understanding the mechanisms underlying ...

In Vitro Analysis of Myd88-mediated Cellular Immune Response to West Nile Virus Mutant Strain Infection

An attenuated West Nile virus (WNV), a nonstructural (NS) 4B-P38G mutant, induced higher innate cytokine and T cell responses than the wild-type WNV in mice. Recently, myeloid differentiation factor 88 (MyD88) signaling was shown to be important for initial T cell priming and memory T cell development during WNV NS4B-P38G mutant infection. In this study, two flow cytometry-based methods &#8211; an in vitro T cell priming assay and an intracellular cytokine staining (ICS) &#8211; were utilized to assess dendritic cells (DCs) and T cell functions. In the T cell priming assay, cell proliferation was analyzed by flow cytometry following co-culture of DCs from both groups of mice with carboxyfluorescein succinimidyl ester (CFSE) - labeled CD4+ T cells of OTII transgenic mice. This approach provided an accurate determination of the percentage of proliferating CD4+ T cells with significantly improved overall sensitivity than the traditional assays with radioactive reagents. A microcentrifuge tube system was used in both cell culture and cytokine staining procedures of the ICS protocol. Compared to the traditional tissue culture plate-based system, this modified procedure was easier to perform at biosafety level (BL) 3 facilities. Moreover, WNV- infected cells were treated with paraformaldehyde in both assays, which enabled further analysis outside BL3 facilities. Overall, these in vitro immunological assays can be used to efficiently assess cell-mediated immune responses during WNV infection.

In Vitro Analysis of Myd88-mediated Cellular Immune Response to West Nile Virus Mutant Strain Infection

Two flow cytometry-based methods &#8211; an in vitro T cell priming assay and intracellular cytokine staining were utilized to measure antigen presenting capacity of dendritic cells and antigen-specific T cell responses to a West Nile virus mutant infection in mice.

An attenuated West Nile virus (WNV), a nonstructural (NS) 4B-P38G mutant, induced higher innate cytokine and T cell responses than the wild-type WNV in ...

Immunofluorescence to Monitor the Cellular Uptake of Human Lactoferrin and its Associated Antiviral Activity Against the Hepatitis C Virus

Immunofluorescence is a laboratory technique commonly used to study many aspects of biology. It is typically used to visualize the distribution and/or localization of a target molecule in cells and tissues. Immunofluorescence relies on the specificity of fluorescent-labelled antibodies against their corresponding antigens within a cell. Both direct and indirect immunofluorescence approaches can be used which rely on the use of antibodies linked with a fluorochrome. Direct immunofluorescence is less frequently used because it provides lower signal, involves higher cost and less flexibility. In contrast, indirect immunofluorescence is more commonly used because of its high sensitivity and provides an amplified signal since more than one secondary antibody can attach to each primary antibody. In this manuscript, both epifluorescence microscopy and confocal microscopy were used to monitor the internalization of human lactoferrin, an important component of the immune system, into hepatic cells. Moreover, we monitored the inhibitory potential of hLF on the intracellular replication of the Hepatitis C virus using immunofluorescence. Both the advantages and disadvantages associated with these approaches are discussed.

The human lactoferrin (hLF) is a component of the immune system. In this study, immunofluorescence assays are used to demonstrate both the hepatocellular uptake of hLF and a qualitative reduction in the hepatitis C virus replication upon treatment with hLF.

Immunofluorescence is a laboratory technique commonly used to study many aspects of biology. It is typically used to visualize the distribution and/or ...

A Miniaturized Glycan Microarray Assay for Assessing Avidity and Specificity of Influenza A Virus Hemagglutinins

Influenza A virus (IAV) hemagglutinins recognize sialic acids on the cell surface as functional receptors to gain entry into cells. Wild waterfowl are the natural reservoir for IAV, but IAV can cross the species barrier to poultry, swine, horses and humans. Avian viruses recognize sialic acid attached to a penultimate galactose by a &#945;2-3 linkage (avian-type receptors) whereas human viruses preferentially recognize sialic acid with a &#945;2-6 linkage (human-type receptors). To monitor if avian viruses are adapting to human type receptors, several methods can be used. Glycan microarrays with diverse libraries of synthetic sialosides are increasingly used to evaluate receptor specificity. However, this technique is not used for measuring avidities. Measurement of avidity is typically achieved by evaluating the binding of serially diluted hemagglutinin or virus to glycans adsorbed to conventional polypropylene 96-well plates. In this assay, glycans with &#945;2-3 or &#945;2-6 sialic acids are coupled to biotin and adsorbed to streptavidin plates, or are coupled to polyacrylamide (PAA) which directly adsorb to the plastic. We have significantly miniaturized this assay by directly printing PAA-linked sialosides and their non PAA-linked counterparts on micro-well glass slides. This set-up, with 48 arrays on a single slide, enables simultaneous assays of 6 glycan binding proteins at 8 dilutions, interrogating 6 different glycans, including two non-sialylated controls. This is equivalent to 18x 96-well plates in the traditional plate assay. The glycan array format decreases consumption of compounds and biologicals and thus greatly enhances efficiency.

Using a printed glycan microarray strategy, a conventional 96-well plate assay was miniaturized for analysis of influenza A virus hemagglutinin avidity and specificity for sialic acid containing receptors.

Influenza A virus (IAV) hemagglutinins recognize sialic acids on the cell surface as functional receptors to gain entry into cells. Wild waterfowl are 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.

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

Rescue and Characterization of Recombinant Virus from a New World Zika Virus Infectious Clone

Infectious cDNA clones allow for genetic manipulation of a virus, thus facilitating work on vaccines, pathogenesis, replication, transmission and viral evolution. Here we describe the construction of an infectious clone for Zika virus (ZIKV), which is currently causing an explosive outbreak in the Americas. To prevent toxicity to bacteria that is commonly observed with flavivirus-derived plasmids, we generated a two-plasmid system which separates the genome at the NS1 gene and is more stable than full-length constructs that could not be successfully recovered without mutations. After digestion and ligation to join the two fragments, full-length viral RNA can be generated by in vitro transcription with T7 RNA polymerase. Following electroporation of transcribed RNA into cells, virus was recovered that exhibited similar in vitro growth kinetics and in vivo virulence and infection phenotypes in mice and mosquitoes, respectively.

This protocol describes the recovery of infectious Zika virus from a two-plasmid infectious cDNA clone.

Infectious cDNA clones allow for genetic manipulation of a virus, thus facilitating work on vaccines, pathogenesis, replication, transmission and viral ...

"Liver-on-a-Chip" Cultures of Primary Hepatocytes and Kupffer Cells for Hepatitis B Virus Infection

Despite the exceptional infectivity of the hepatitis B virus (HBV) in vivo, where only three viral genomes can result in a chronicity of experimentally infected chimpanzees, most in vitro models require several hundreds to thousands of viral genomes per cell in order to initiate a transient infection. Additionally, static 2D cultures of primary human hepatocytes (PHH) allow only short-term studies due to their rapid dedifferentiation. Here, we describe 3D liver-on-a-chip cultures of PHH, either in monocultures or in cocultures with other nonparenchymal liver-resident cells. These offer a significant improvement to studying long-term HBV infections with physiological host cell responses. In addition to facilitating drug efficacy studies, toxicological analysis, and investigations into pathogenesis, these microfluidic culture systems enable the evaluation of curative therapies for HBV infection aimed at eliminating covalently closed, circular (ccc)DNA. This presented method describes the set-up of PHH monocultures and PHH/Kupffer cell co-cultures, their infection with purified HBV, and the analysis of host responses. This method is particularly applicable to the evaluation of long-term effects of HBV infection, treatment combinations, and pathogenesis.

&quot;Liver-on-a-Chip&quot; Cultures of Primary Hepatocytes and Kupffer Cells for Hepatitis B Virus Infection

The goal of this protocol is to provide a step-by-step guide to perform 3-D &#34;liver-on-a-chip&#34; infection experiments with the hepatitis B virus.

Despite the exceptional infectivity of the hepatitis B virus (HBV) in vivo, where only three viral genomes can result in a chronicity of experimentally ...

Identification of Coding and Non-coding RNA Classes Expressed in Swine Whole Blood

The advent of innovative and increasingly powerful next generation sequencing techniques has opened new avenues into the ability to examine the underlying gene expression related to biological processes of interest. These innovations not only allow researchers to observe expression from the mRNA sequences that code for genes that effect cellular function, but also the non-coding RNA (ncRNA) molecules that remain untranslated, but still have regulatory functions. Although researchers have the ability to observe both mRNA and ncRNA expression, it has been customary for a study to focus on one or the other. However, when studies are interested in both mRNA and ncRNA expression, many times they use separate samples to examine either coding or non-coding RNAs due to the difference in library preparations. This can lead to the need for more samples which can increase time, consumables, and animal stress. Additionally, it may cause researchers to decide to prepare samples for only one analysis, usually the mRNA, limiting the number of biological questions that can be investigated. However, ncRNAs span multiple classes with regulatory roles that effect mRNA expression. Because ncRNA are important to fundamental biologic processes and disorder of these processes in during infection, they may, therefore, make attractive targets for therapeutics. This manuscript demonstrates a modified protocol for the generation mRNA and non-coding RNA expression libraries, including viral RNA, from a single sample of whole blood. Optimization of this protocol, improved RNA purity, increased ligation for recovery of methylated RNAs, and omitted&#160;size selection, to allow capture of more RNA species.

Here, we present a protocol optimized for the processing of coding (mRNA) and non-coding&#160;(ncRNA) globin reduced RNA-seq libraries from a single whole blood sample.

The advent of innovative and increasingly powerful next generation sequencing techniques has opened new avenues into the ability to examine the underlying ...