Name: modeling hepatitis b virus infection in non-hepatic 293t-ne-3nrs cells
Uploaded: 2020-06-05T14:30:00
Description: Watch this Scientific Journal Video about Modeling Hepatitis B Virus Infection in Non-Hepatic 293T-NE-3NRs Cells at JoVE.com

This work was supported by the National Natural Science Foundation of China (No. 81870432 and 81570567 to X.L.Z.), (No. 81571994 to P.N.S.), Research Fund for International Young Scientists (No. 81950410640 to W.I.); The Li Ka Shing Shantou University Foundation (No. L1111 2008 to P.N.S.). We would like to thank Prof. Stanley Lin from Shantou University Medical College for useful advice.

Culture, collection of supernatants from HepG2.2.15 cells and HBV infection should be performed in biosafety level II (P2) or biosafety level III (P3) laboratory according to the biosafety guidance in the country. Laboratory safety practices should be followed to ensure the safety of laboratory personnel, and all should be vaccinated and detected HBsAb positive before performing HBV experiments. Observe the state of the cells at every step before proceeding to the next step. Human serum samples were used in accordance wi...

<ol>
	<li>World Health Organization. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Global+hepatitis+report,+2017.">Global hepatitis report, 2017.</a> World Health Organization. , (2017).</li><li>Yoffe, B., Burns, D. K., Bhatt, H. S., Combes, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extrahepatic+hepatitis+B+virus+DNA+sequences+in+patients+with+acute+hepatitis+B+infection.">Extrahepatic hepatitis B virus DNA sequences in patients with acute hepatitis B infection.</a> Hepatology. 12, 187-192 (1990).</li><li>Mason, A., Wick, M., White, H., Perrillo, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hepatitis+B+virus+replication+in+diverse+cell+types+during+chronic+hepatitis+B+virus+infection.">Hepatitis B virus replication in diverse cell types during chronic hepatitis B virus infection.</a> Hepatology. 18, 781-789 (1993).</li><li>Yan, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sodium+taurocholate+cotransporting+polypeptide+is+a+functional+receptor+for+human+hepatitis+B+and+D+virus.">Sodium taurocholate cotransporting polypeptide is a functional receptor for human hepatitis B and D virus.</a> eLife. 1, 00049 (2012).</li><li>Tang, H., McLachlan, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transcriptional+regulation+of+hepatitis+B+virus+by+nuclear+hormone+receptors+is+a+critical+determinant+of+viral+tropism.">Transcriptional regulation of hepatitis B virus by nuclear hormone receptors is a critical determinant of viral tropism.</a> Proceedings of the National Academy of Sciences of the United States of America. 98, 1841-1846 (2001).</li><li>Sells, M. A., Chen, M. L., Acs, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Production+of+hepatitis+B+virus+particles+in+Hep+G2+cells+transfected+with+cloned+hepatitis+B+virus+DNA.">Production of hepatitis B virus particles in Hep G2 cells transfected with cloned hepatitis B virus DNA.</a> Proceedings of the National Academy of Sciences of the United States of America. 84, 1005-1009 (1987).</li><li>Sells, M. A., Zelent, A. Z., Shvartsman, M., Acs, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Replicative+intermediates+of+hepatitis+B+virus+in+HepG2+cells+that+produce+infectious+virions.">Replicative intermediates of hepatitis B virus in HepG2 cells that produce infectious virions.</a> Journal of Virology. 62, 2836-2844 (1988).</li><li>Watashi, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cyclosporin+A+and+its+analogs+inhibit+hepatitis+B+virus+entry+into+cultured+hepatocytes+through+targeting+a+membrane+transporter,+sodium+taurocholate+cotransporting+polypeptide+(NTCP).">Cyclosporin A and its analogs inhibit hepatitis B virus entry into cultured hepatocytes through targeting a membrane transporter, sodium taurocholate cotransporting polypeptide (NTCP).</a> Hepatology. 59, 1726-1737 (2014).</li><li>Yang, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Defined+host+factors+support+HBV+infection+in+non-hepatic+293T+cells.">Defined host factors support HBV infection in non-hepatic 293T cells.</a> Journal of Cell and Molecular Medicine. 24, 2507-2518 (2020).</li><li>Xia, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+stem+cell-derived+hepatocytes+as+a+model+for+hepatitis+B+virus+infection,+spreading+and+virus-host+interactions.">Human stem cell-derived hepatocytes as a model for hepatitis B virus infection, spreading and virus-host interactions.</a> Journal of Hepatology. 66, 494-503 (2017).</li><li>Ortega-Prieto, A. M., Cherry, C., Gunn, H., Dorner, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+Vivo+Model+Systems+for+Hepatitis+B+Virus+Research.">In Vivo Model Systems for Hepatitis B Virus Research.</a> ACS Infectious Diseases. 5, 688-702 (2019).</li><li>Liang, T. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hepatitis+B:+the+virus+and+disease.">Hepatitis B: the virus and disease.</a> Hepatology. 49, 13-21 (2009).</li><li>Nie, Y. Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recapitulation+of+hepatitis+B+virus-host+interactions+in+liver+organoids+from+human+induced+pluripotent+stem+cells.">Recapitulation of hepatitis B virus-host interactions in liver organoids from human induced pluripotent stem cells.</a> EBioMedicine. 35, 114-123 (2018).</li><li>Nishinakamura, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+kidney+organoids:+progress+and+remaining+challenges.">Human kidney organoids: progress and remaining challenges.</a> Nature Reviews Nephrology. 15, 613-624 (2019).</li></ol>

Here, we introduce protocols for HBV infection in non-hepatic 293T-NE-3NRs and hepatoma-based HepG2-NE cells. 293T-NE-3NRs were suitable for HBV infection at both high and low GEq. The following critical steps need to be taken into consideration while using our protocol. The cell status is an important factor for a successful infection. The infection medium must be changed timely after the initial period of HBV infection. 293T-NE-3NRs cells are typically fragile following infection with high viral titers. Therefore, thes...

Hepatitis B affects the lives of more than 2 billion people and is one of the major threats to public health. Approximately 257 million people are chronically infected with hepatitis B virus (HBV) worldwide, causing a big burden to the society1. Hepatocytes are not the only cells infected by HBV and other cells in non-hepatic tissue, such as kidney and testis, are also infected by this virus2,3. Currently, HBV infection cell models are limited to human hepatocytes with only few non-hepatic cell line models. This hampers the study of HBV infection and HBV-related pathology of non-hepatic tissues. Here we present protocols to study HBV infection in non-hepatic 293T cells as well as in hepatoma-based cells.
Sodium taurocholate co-transporting polypeptide (NTCP) is a functional receptor for human hepatitis B and hepatitis D virus4. Hepatocyte nuclear factor 4&#945; (HNF4&#945;), retinoid X receptor &#945; (RXR&#945;) and peroxisome proliferator-activated receptor &#945; (PPAR&#945;) are liver-enriched transcription factors restricting viral tropism of HBV. They have been verified to promote HBV pregenomic RNA synthesis and support HBV replication in a nonhepatoma cell line5. We constructed three different cell lines, HepG2 cell lines expressing NTCP (HepG2-NE), 293T cell line expressing NTCP (293T-NE) and 293T cell line expressing four host genes; NTCP, HNF4&#945;, RXR&#945; and PPAR&#945; (293T-NE-3NRs). Two methods for HBV infection were developed based on 293T-NE-3NRs (Figure 1). The first method uses inoculation in 293T-NE-3NRs with high viral genome equivalence (high GEq (150), DMSO and PEG8000) for 24 h. The second method employs co-culturing 293T-NE-3NRs with HepG2.2.15, which can produce HBV particles (low GEq (about 1.83) without DMSO and PEG8000), thus closely emulating natural conditions.
HepG2.2.15 cells are derived from the HepG2 line and chronically secrete infectious HBV, as well as subviral particles into the culture medium6,7. Cyclosporin A (CsA) is an immunosuppressant clinically used for the suppression of xenograft rejection. Studies have shown that CsA inhibits HBV entry into cultured hepatocytes by inhibiting the transporter activity of NTCP and blocking the binding of NTCP to large envelope proteins8.
HepG2-NE cells were used as positive control whereas CsA treated cells were used as negative control. By comparing with the positive and negative control groups, we can find out which host genes play a critical role in HBV infection. Additionally, through this mode of HBV infection, we can also find other novel mechanisms or host genes involved in HBV infection.

<table>
	<tbody>
		<tr>
			<td>0.45&#956;m membrane filter</td>
			<td>Millex-HV</td>
			<td>SLHU033RB</td>
			<td>Filter for HepG 2.2.15 supernatant</td>
		</tr>
		<tr>
			<td>293T-NE</td>
			<td>Laboratory construction</td>
			<td>&#8212;&#8212;</td>
			<td>Cell model for HBV infection</td>
		</tr>
		<tr>
			<td>293T-NE-3NRs</td>
			<td>Laboratory construction</td>
			<td>&#8212;&#8212;</td>
			<td>Cell model for HBV infection</td>
		</tr>
		<tr>
			<td>594 labeled goat against rabbit IgG</td>
			<td>ZSGB-BIO</td>
			<td>ZF-0516</td>
			<td>For immunofluorescence assay,second antibody</td>
		</tr>
		<tr>
			<td>6-well plate</td>
			<td>BIOFIL</td>
			<td>TCP010006</td>
			<td>For co-culture</td>
		</tr>
		<tr>
			<td>Amicon Ultra 15 ml</td>
			<td>Millipore</td>
			<td>UFC910008</td>
			<td>For concentration of HepG 2.2.15 supernatant</td>
		</tr>
		<tr>
			<td>BSA</td>
			<td>Beyotime</td>
			<td>ST023</td>
			<td>For immunofluorescence assay</td>
		</tr>
		<tr>
			<td>Cyclosporin A</td>
			<td>Sangon biotech</td>
			<td>59865-13-3</td>
			<td>inhibitor of HBV infection</td>
		</tr>
		<tr>
			<td>DAPI</td>
			<td>Beyotime</td>
			<td>C1006</td>
			<td>For nuclear staining</td>
		</tr>
		<tr>
			<td>Diagnostic kit for Quantification of Hepatitis B Virus DNA(PCR-Fluorescence Probing)</td>
			<td>DAAN GENE</td>
			<td>7265-2013</td>
			<td>For HBV DNA detection</td>
		</tr>
		<tr>
			<td>DMEM</td>
			<td>HyClong</td>
			<td>SH30243.01</td>
			<td>For culture medium</td>
		</tr>
		<tr>
			<td>DMSO</td>
			<td>Sigma-Aldrich</td>
			<td>D5879</td>
			<td>For improvement of infection efficiency</td>
		</tr>
		<tr>
			<td>Fetal bovine serum&#65288;FBS&#65289;</td>
			<td>CLARK Bioscience</td>
			<td>FB25015</td>
			<td>For culture medium</td>
		</tr>
		<tr>
			<td>Fluorescence microscope</td>
			<td>ZEISS</td>
			<td>Axio observer Z1</td>
			<td>For immunofluorescence assay</td>
		</tr>
		<tr>
			<td>HepG2-NE</td>
			<td>Laboratory construction</td>
			<td>&#8212;&#8212;</td>
			<td>Cell model for HBV infection</td>
		</tr>
		<tr>
			<td>HBcAg antibody</td>
			<td>ZSGB-BIO</td>
			<td>ZA-0121</td>
			<td>For immunofluorescence assay, primary antibody</td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>ZSGB-BIO</td>
			<td>ZLI-9062</td>
			<td>For cell wash</td>
		</tr>
		<tr>
			<td>PEG8000</td>
			<td>Merck</td>
			<td>P8260</td>
			<td>For infection medium</td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin-Glutamine</td>
			<td>Thermo Fisher</td>
			<td>10378016</td>
			<td>For culture medium</td>
		</tr>
		<tr>
			<td>Transwell</td>
			<td>CORNING</td>
			<td>3412</td>
			<td>For co-culture</td>
		</tr>
		<tr>
			<td>Tween 20</td>
			<td>sigma-Aldrich</td>
			<td>WXBB7485V</td>
			<td>For PBST</td>
		</tr>
		<tr>
			<td>Virkon</td>
			<td>Douban</td>
			<td>6971728840012</td>
			<td>Viruside</td>
		</tr>
	</tbody>
</table>

modeling hepatitis b virus infection in non-hepatic 293t-ne-3nrs cells

HBV mainly infects human hepatocytes, but it has also been found to infect extrahepatic tissues such as kidney and testis. Nonetheless, cell-based HBV models are limited to hepatoma cell lines (such as HepG2 and Huh7) overexpressing a functional HBV receptor, sodium taurocholate co-transporting polypeptide (NTCP). Here, we used 293T-NE-3NRs (293T&#160;overexpressing human NTCP, HNF4&#945;, RXR&#945; and PPAR&#945;) and HepG2-NE (HepG2 overexpressing NTCP) as model cell lines.&#160;HBV infection in these cell lines was performed either by using concentrated HBV virus particles from HepG2.2.15 or co-culturing HepG2.2.15 with the target cell lines. HBcAg immunofluorescence for HBcAg was performed to confirm HBV infection. The two methods presented here will help us study HBV infection in non-hepatic cell lines.&#160;&#160;

We constructed pSIN-NTCP-EGFP plasmid expressing NTCP and EGFP fusion and with puromycin resistance. The plasmid was transfected into HepG2 and 293T cells to construct stable cell lines HepG2-NE and 293T-NE expressing NTCP and EGFP. Plasmids (pSIN-HNF4&#945;, pSIN-RXR&#945;, pLV-PPAR&#945;-puro-flag) with puromycin resistance and expression were transfected into 293T-NE cells to construct a stable cell line expressing 4 host genes9. The expression of NTCP-EGFP can be observed by green fluorescence...

Watch this Scientific Journal Video about Modeling Hepatitis B Virus Infection in Non-Hepatic 293T-NE-3NRs Cells at JoVE.com

Modeling Hepatitis B Virus Infection in Non-Hepatic 293T-NE-3NRs Cells

This manuscript describes a detailed protocol for Hepatitis B virus (HBV) infection in novel engineered 293T cells (293T-NE-3NRs, expressing human NTCP, HNF4&#945;, RXR&#945; and PPAR&#945;) and traditional hepatic cells (HepG2-NE, expressing human NTCP).

HBV mainly infects human hepatocytes, but it has also been found to infect extrahepatic tissues such as kidney and testis. Nonetheless, cell-based HBV ...

HBV viral replication in extrahepatic plays an important role in the pathogenesis of extrahepatic syndromes. Currently, cell culture models for starting extrahepatic HBV infection are limited. We present an in vitro non-hepatic infection model to help identify novel host factors which affect HBV replication and investigate HBV-related kidney diseases.Compared to traditional HBV infection models, we adopted and engineered 293T cell line, 293T-NE-3NR, and co-cultured it with HepG2.2.15. HBV infection should be performed in a biosafety level two or biosafety level three laboratory. Laboratory safety practices should be followed to ensure the safety of laboratory personnel and all researchers should be vaccinated and detect HBS antibody positive before performing HBV experiments.Begin by culturing the HepG2.2.15 cells keeping in mind that the cell supernatant as well as all the tips, flasks, plates, and tubes that come in contact with HepG2.2.15 should be soaked in 2%virucide overnight prior to disposal. Remove the vial containing HepG2.2.15 cells from liquid nitrogen and thaw it in gentle swirling in a 37 degree Celsius water bath. Transfer the cells to a 25 centimeter square tissue culture flask and add four milliliters of complete culture medium.Culture the HepG2.2.15 cells at 37 degrees Celsius and 5%carbon dioxide in a humidified incubator. Change the medium every three days. When ready, collect the cell supernatant in a 50 milliliter centrifuge tube.Close the lid firmly and wrap it with paraffin film. To remove the cell fragments, filter the HepG2.2.15 supernatant with a 0.45 micrometer membrane into a new 50 milliliter centrifuge tube. Then add 14 milliliters of filtered supernatant to a virus concentrator column and close the lid.Centrifuge the column at 3, 200 times g for 35 minutes in a horizontal spinning centrifuge and collect the HepG2.2.15 supernatant concentrate into a 1.5 milliliter tube. Run real-time PCR to ensure that the concentration if HBV DNA in the HepG2.2.15 supernatant concentrate is within the standard curve range. Dilute the concentrate 20-fold by adding 10 microliters to 190 microliters of DMEM in a 1.5 milliliter microcentrifuge tube.Along with the supernatant concentrate, prepare a negative control, positive control, and four dilutions of the quantitative reference. Add 450 microliters of HBV DNA extraction buffer to each sample and centrifuge them at 12, 000 times g for five minutes at room temperature. Combine 27 microliters of PCR master mix and three microliters of Taq polymerase enzyme per sample in PCR tubes placed on ice.Then add 20 microliters of the centrifuged sample to each tube. Perform real-time PCR according to manuscript directions and export the CT values to obtain a standard curve. Divide the HepG2.2.15 supernatant concentrate into aliquots and store it at minus 80 degrees Celsius until ready to use.Prepare infection medium according to manuscript directions. Then seed HepG2-NE in two wells, 293T-NE-3NR cells in two wells, and 293T-NE in one well. Incubate the cells at 37 degrees Celsius and 5%carbon dioxide in a humidified incubator for 24 hours.After the incubation, observe the cells and proceed with infection if they're healthy. Add 500 microliters of the infection complex to each well and incubate the cells for another 24 hours. Wash the cells twice with 500 microliters of PBS.Then add one milliliter of medium to each well. Change the medium gently every two days. On day 11, gently wash the cells twice with 500 microliters of PBS and fix the cells with ice cold methanol for immunofluorescence.Seed 100, 000 cells per well of HepG-NE into two wells, 293T-NE-3NRs into two wells, and 293T-NE into one well of the plate. Seed 100, 000 cells per well of HepG2.2.15 into five membrane inserts in a separate six-well plate. Incubate the cells for 24 hours.After the incubation, ensure that the cells are all adherent and in good state. Discard the medium in the six-well plate and the cell membrane inserts. Then place the membrane inserts with HepG2.2.15 into the six-well plate seeded with HepG-NE, 293T-NE-3NRs, and 293T-NE.Incubate the cells at 37 degrees Celsius and 5%carbon dioxide in a humidified incubator, changing the medium every three to four days. After 10 days, remove the membrane inserts, gently wash the cells with PBS twice, and fix the cells with ice cold methanol for immunofluorescence. Incubation with the HBcAg primary antibody and DAPI resulted in a distinct staining when observed with a 10X objective on a fluorescent inverted microscope.Nuclear localization was confirmed by staining with DAPI and NTCP-EGFP expression was identified with green fluorescence. The expression sites of HBcAg were located with red fluorescence. When DAPI, NTCP and HBcAg are in the same cell, the cell has been successfully infected with HBV.The Cyclosporin A group was the negative control because it prevents HBV from entering cells by blocking NTCP. HBcAg was detected in 293T-NE-3NRs, but not in 293T-NE cells indicating NTCP is not the only factor essential for HBV infection in 293T. Good cell status and efficient operation are the key points to getting successful infection results.Gentle washing and changing the media after infection is also important. As an alternative, HBV infection method with hepatoma-based HepG2-NE cells has higher infection efficiency than this method and is suitable for anti-HBV drug screening. Modeling HBV infection in 293T-NE-3NR is a useful compliment to the traditional cell model due to the non-hepatic background of these cells.This method will facilitate the study of HBV infection in non-hepatic cells as well as host factors required for liver of HBV.

modeling-hepatitis-b-virus-infection-in-non-hepatic-293t-ne-3nrs-cells

Research

JoVE Journal

Immunology and Infection

Murine Model of CD40-activation of B cells

Research on B cells has shown that CD40 activation improves their antigen presentation capacity. When stimulated with interleukin-4 and CD40 ligand (CD40L), human B cells can be expanded without difficulties from small amounts of peripheral blood within 14 days to very large amounts of highly-pure CD40-B cells (&gt;109 cells per patient) from healthy donors as well as cancer patients1-4. CD40-B cells express important lymph node homing molecules and can attract T cells in vitro5. Furthermore they efficiently take up, process and present antigens to T cells6,7. CD40-B cells were shown to not only prime na&iacute;ve, but also expand memory T cells8,9. Therefore CD40-activated B cells (CD40-B cells) have been studied as an alternative source of immuno-stimulatory antigen-presenting cells (APC) for cell-based immunotherapy1,5,10. In order to further study whether CD40-B cells induce effective T cell responses in vivo and to study the underlying mechanism we established a cell culture system for the generation of murine CD40-activated B cells. Using splenocytes or purified B cells from C57BL/6 mice for CD40-activation, optimal conditions were identified as follows: Starting from splenocytes of C57BL/6 mice (haplotype H-2b) lymphocytes are purified by density gradient centrifugation and co-cultured with HeLa cells expressing recombinant murine CD40 ligand (tmuCD40L HeLa)11. Cells are recultured every 3-4 days and key components such as CD40L, interleukin-4, -Mercaptoethanol and cyclosporin A are replenished. In this protocol we demonstrate how to obtain fully activated murine CD40-B cells (mCD40B) with similar APC-phenotype to human CD40-B cells (Fig 1a,b). CD40-stimulation leads to a rapid outgrowth and expansion of highly pure (&gt;90%) CD19+ B cells within 14 days of cell culture (Fig 1c,d). To avoid contamination with non-transfected cells, expression of the murine CD40 ligand on the transfectants has to be controlled regularly (Fig 2). Murine CD40-activated B cells can be used to study B-cell activation and differentiation as well as to investigate their potential to function as APC in vitro and in vivo. Moreover, they represent a promising tool for establishing therapeutic or preventive vaccination against tumors and will help to answer questions regarding safety and immunogenicity of this approach12.

In this video, we demonstrate the procedure of CD40-activation and expansion of murine B cells from splenocytes of C57BL/6 mice, which can be used as a model antigen-presenting cell (APC) to study induction of immunity.

Research on B cells has shown that CD40 activation improves their antigen presentation capacity. When stimulated with interleukin-4 and CD40 ligand ...

RNAi Screening for Host Factors Involved in Vaccinia Virus Infection using Drosophila Cells

Viral pathogens represent a significant public health threat; not only can viruses cause natural epidemics of human disease, but their potential use in bioterrorism is also a concern. A better understanding of the cellular factors that impact infection would facilitate the development of much-needed therapeutics. Recent advances in RNA interference (RNAi) technology coupled with complete genome sequencing of several organisms has led to the optimization of genome-wide, cell-based loss-of-function screens. Drosophila cells are particularly amenable to genome-scale screens because of the ease and efficiency of RNAi in this system 1. Importantly, a wide variety of viruses can infect Drosophila cells, including a number of mammalian viruses of medical and agricultural importance 2,3,4. Previous RNAi screens in Drosophila have identified host factors that are required for various steps in virus infection including entry, translation and RNA replication 5. Moreover, many of the cellular factors required for viral replication in Drosophila cell culture are also limiting in human cells infected with these viruses 4,6,7,8, 9. Therefore, the identification of host factors co-opted during viral infection presents novel targets for antiviral therapeutics. Here we present a generalized protocol for a high-throughput RNAi screen to identify cellular factors involved in viral infection, using vaccinia virus as an example.

RNAi Screening for Host Factors Involved in Vaccinia Virus Infection using Drosophila Cells

Novel host factors involved in viral infection can be identified through cell-based genome-wide loss of function RNAi screening. A Drosophila cell culture model is particularly amenable to this approach due to the ease and efficiency of RNAi. Here we demonstrate this technique using vaccinia virus as an example.

Viral pathogens represent a significant public health threat; not only can viruses cause natural epidemics of human disease, but their potential use in ...

Recombinant Retroviral Production and Infection of B Cells

The transgenic expression of genes in eukaryotic cells is a powerful reverse genetic approach in which a gene of interest is expressed under the control of a heterologous expression system to facilitate the analysis of the resulting phenotype. This approach can be used to express a gene that is not normally found in the organism, to express a mutant form of a gene product, or to over-express a dominant-negative form of the gene product. It is particularly useful in the study of the hematopoetic system, where transcriptional regulation is a major control mechanism in the development and differentiation of B cells 1, reviewed in 2-4.
Mouse genetics is a powerful tool for the study of human genes and diseases. A comparative analysis of the mouse and human genome reveals conservation of synteny in over 90% of the genome 5. Also, much of the technology used in mouse models is applicable to the study of human genes, for example, gene disruptions and allelic replacement 6. However, the creation of a transgenic mouse requires a great deal of resources of both a financial and technical nature. Several projects have begun to compile libraries of knock out mouse strains (KOMP, EUCOMM, NorCOMM) or mutagenesis induced strains (RIKEN), which require large-scale efforts and collaboration 7. Therefore, it is desirable to first study the phenotype of a desired gene in a cell culture model of primary cells before progressing to a mouse model. 
Retroviral DNA integrates into the host DNA, preferably within or near transcription units or CpG islands, resulting in stable and heritable expression of the packaged gene of interest while avoiding transcriptional silencing 8 9. The genes are then transcribed under the control of a high efficiency retroviral promoter, resulting in a high efficiency of transcription and protein production. Therefore, retroviral expression can be used with cells that are difficult to transfect, provided the cells are in an active state during mitosis. Because the structural genes of the virus are contained within the packaging cell line, the expression vectors used to clone the gene of interest contain no structural genes of the virus, which both eliminates the possibility of viral revertants and increases the safety of working with viral supernatants as no infectious virions are produced 10. 
Here we present a protocol for recombinant retroviral production and subsequent infection of splenic B cells. After isolation, the cultured splenic cells are stimulated with Th derived lymphokines and anti-CD40, which induces a burst of B cell proliferation and differentiation 11. This protocol is ideal for the study of events occurring late in B cell development and differentiation, as B cells are isolated from the spleen following initial hematopoetic events but prior to antigenic stimulation to induce plasmacytic differentiation.

An efficient system of structure and function analysis of a gene in an ex vivo culture of splenic B-lymphocytes is described. This method takes advantage of recombinant retroviral production in a helper free, ecotrophic packaging cell line. Stable, heritable expression of a gene of interest within primary lymphocytes is achieved leading to generation of surface antibodies on B cells undergoing class switch recombination.

The transgenic expression of genes in eukaryotic cells is a powerful reverse genetic approach in which a gene of interest is expressed under the control ...

Visualizing Dengue Virus through Alexa Fluor Labeling

The early events in the interaction between virus and cell can have profound influence on the outcome of infection. Determining the factors 
that influence this interaction could lead to improved understanding of disease pathogenesis and thus influence vaccine or therapeutic design. Hence, the development 
of methods to probe this interaction would be useful. Recent advancements in fluorophores development1-3 and imaging technology4 can be exploited to 
improve our current knowledge on dengue pathogenesis and thus pave the way to reduce the millions of dengue infections occurring annually.

The enveloped dengue virus has an external scaffold consisting of 90 envelope glycoprotein (E) dimers protecting the nucleocapsid shell, 
which contains a single positive strand RNA genome5. The identical protein subunits on the virus surface can thus be labeled with an amine reactive dye and visualized 
through immunofluorescent microscopy. Here, we present a simple method of labeling of dengue virus with Alexa Fluor succinimidyl ester dye dissolved directly in a sodium 
bicarbonate buffer that yielded highly viable virus after labeling. There is no standardized procedure for the labeling of live virus and existing manufacturer&#x2019;s protocol 
for protein labeling usually requires the reconstitution of dye in dimethyl sulfoxide. The presence of dimethyl sulfoxide, even in minute quantities, can block 
productive infection of virus and also induce cell cytotoxicity6. The exclusion of the use of dimethyl sulfoxide in this protocol thus reduced this possibility. 
Alexa Fluor dyes have superior photostability and are less pH-sensitive than the common dyes, such as fluorescein and rhodamine2, making them ideal for 
studies on cellular uptake and endosomal transport of the virus. The conjugation of Alexa Fluor dye did not affect the recognition of labeled dengue 
virus by virus-specific antibody and its putative receptors in host cells7. This method could have useful applications in virological studies.

Taking advantage of the advancements in fluorophore development and imaging technology, a simple method of Alexa Fluor labeling of dengue virus was devised to visualize the early interactions between virus and cell.

The early events in the interaction between virus and cell can have profound influence on the outcome of infection. Determining the factors 
that ...

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 (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 ...

Modeling The Lifecycle Of Ebola Virus Under Biosafety Level 2 Conditions With Virus-like Particles Containing Tetracistronic Minigenomes

Ebola viruses cause severe hemorrhagic fevers in humans and non-human primates, with case fatality rates as high as 90%. There are no approved vaccines or specific treatments for the disease caused by these viruses, and work with infectious Ebola viruses is restricted to biosafety level 4 laboratories, significantly limiting the research on these viruses. Lifecycle modeling systems model the virus lifecycle under biosafety level 2 conditions; however, until recently such systems have been limited to either individual aspects of the virus lifecycle, or a single infectious cycle. Tetracistronic minigenomes, which consist of Ebola virus non-coding regions, a reporter gene, and three Ebola virus genes involved in morphogenesis, budding, and entry (VP40, GP1,2, and VP24), can be used to produce replication and transcription-competent virus-like particles (trVLPs) containing these minigenomes. These trVLPs can continuously infect cells expressing the Ebola virus proteins responsible for genome replication and transcription, allowing us to safely model multiple infectious cycles under biosafety level 2 conditions. Importantly, the viral components of this systems are solely derived from Ebola virus and not from other viruses (as is, for example, the case in systems using pseudotyped viruses), and VP40, GP1,2 and VP24 are not overexpressed in this system, making it ideally suited for studying morphogenesis, budding and entry, although other aspects of the virus lifecycle such as genome replication and transcription can also be modeled with this system. Therefore, the tetracistronic trVLP assay represents the most comprehensive lifecycle modeling system available for Ebola viruses, and has tremendous potential for use in investigating the biology of Ebola viruses in future. Here, we provide detailed information on the use of this system, as well as on expected results.

Work with infectious Ebola viruses is restricted to biosafety level 4 laboratories. Tetracistronic minigenome-containing replication and transcription-competent virus like particles (trVLPs) represent a lifecycle modeling system that allows us to safely model multiple infectious cycles under biosafety level 2 conditions, relying exclusively on Ebola virus components.

Ebola viruses cause severe hemorrhagic fevers in humans and non-human primates, with case fatality rates as high as 90%. There are no approved vaccines or ...

Neutrophil Isolation and Analysis to Determine their Role in Lymphoma Cell Sensitivity to Therapeutic Agents

Neutrophils are the most abundant (40% to 75%) type of white blood cells and among the first inflammatory cells to migrate towards the site of inflammation. They are key players in the innate immune system and play major roles in cancer biology. Neutrophils have been proposed as key mediators of malignant transformation, tumor progression, angiogenesis and in the modulation of the antitumor immunity; through their release of soluble factors or their interaction with tumor cells. To characterize the specific functions of neutrophils, a fast and reliable method is coveted for in vitro isolation of neutrophils from human blood. Here, a density gradient separation method is demonstrated to isolate neutrophils as well as mononuclear cells from the blood. The procedure consists of layering the density gradient solution such as Ficoll carefully above the diluted blood obtained from patients diagnosed with chronic lymphocytic leukemia (CLL), followed by centrifugation, isolation of mononuclear layer, separation of neutrophils from RBCsby dextran then lysis of residual erythrocytes. This method has been shown to isolate neutrophils &#8805; 90 % pure. To mimic the tumor microenvironment, 3-dimensional (3D) experiments were performed using basement membrane matrix such as Matrigel. Given the short half-life of neutrophils in vitro, 3D experiments with fresh human neutrophils cannot be performed. For this reason promyelocytic HL60 cells are differentiated along the granulocytic pathway using the differentiation inducers dimethyl sulfoxide (DMSO) and retinoic acid (RA). The aim of our experiments is to study the role of neutrophils on the sensitivity of lymphoma cells to anti-lymphoma agents. However these methods can be generalized to study the interactions of neutrophils or neutrophil-like cells with a large range of cell types in different situations.

Neutrophils are the most abundant type of white blood cells. The isolation of neutrophils from human blood by density gradient separation method and the differentiation of human promyelocytic (HL60) cells along the granulocytic pathway are described here; to test their role on sensitivity of lymphoma cells to anti-lymphoma agents.

Neutrophils are the most abundant (40% to 75%) type of white blood cells and among the first inflammatory cells to migrate towards the site of ...

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), ...

Detection of Low Copy Number Integrated Viral DNA Formed by In Vitro Hepatitis B Infection

Hepatitis B Virus (HBV) is a common blood-borne pathogen causing liver cancer and liver cirrhosis resulting from chronic infection. The virus generally replicates through an episomal DNA intermediate; however, integration of HBV DNA fragments into the host genome has been observed, even though this form is not necessary for viral replication. The exact purpose, timing, and mechanism(s) by which HBV DNA integration occurs is not yet clear, but recent data show that it occurs very early after infection. Here, the in vitro generation and detection of HBV DNA integrations are described in detail. Our protocol specifically amplifies single copies of virus-cell DNA integrations and allows both absolute quantification and single-base pair resolution of the junction sequence. This technique has been applied to various HBV-susceptible cell types (including primary human hepatocytes), to various HBV mutants, and in conjunction with various drug exposures. We foresee this technique becoming a key assay to determine the underlying molecular mechanisms of this clinically relevant phenomenon.

Detection of Low Copy Number Integrated Viral DNA Formed by In Vitro Hepatitis B Infection

We describe here the in vitro generation of HBV DNA via a Hepatitis B virus infection system and the highly sensitive detection of its (1&#8211;2 copies) integration using inverse nested PCR.

Hepatitis B Virus (HBV) is a common blood-borne pathogen causing liver cancer and liver cirrhosis resulting from chronic infection. The virus generally ...

"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 ...