We would like to thank Dr. Aaron Brault and Dr. Brandy Russell of the Centers for Disease Control and Prevention (CDC), USA for providing Zika viral strain PRVABC59. We thank Nicholas Ten of Yale University for copy-editing this manuscript. This work was supported by the Cedars-Sinai Medical Center Institutional Programmatic Research Award to V.A.

Note: A schematic outline of the work flow is presented in Figure 1.
1. Cells
<ol>
	<li>Use Vero cells for Zika virus production and analysis of viral replication cycle.</li>
	<li>Prepare complete growth media containing 10% fetal bovine serum (FBS), 2 mM L-glutamine, penicillin (100 units/ml), streptomycin (100 units/ml), and 10 mM HEPES.</li>
	<li>Culture Vero cells with the specified complete growth medium at 37 &#176;C with 5% CO2.</li>
</ol>
2. Zika Virus Production
<ol>
	<li>Harvest the Vero cells at 80% cell density using 0.25% trypsin in T-75 flask and count the cells.
	<ol>
		<li>Aspirate the media from the T-75 culture flask and rinse the cells with 2 ml phosphate buffered saline (PBS).</li>
		<li>Add 2 ml of 0.25% trypsin and incubate the flask at 37 &#176;C for 5 min.</li>
		<li>Add 8 ml of serum containing growth medium to inactivate trypsin. Pipet up and down to suspend cells and transfer the cells to a 15 ml tube.</li>
		<li>Remove 10 &#181;l of cells and mix with equal amount of 0.4% trypan blue. Load the prepared mix to the cell counting chamber slide and obtain viable cell counts using an automated cell counter.</li>
	</ol>
	</li>
	<li>Seed a total of 7 million cells in a 30 ml volume into a T-160 flask.</li>
	<li>The next day, prepare an appropriate multiplicity of infection (0.01 to 0.1 MOI) of Zika virus inoculum in a 10 ml serum free culture media per flask.</li>
	<li>Remove the spent media from the T-160 flask and then add the freshly prepared viral inoculum (10 ml).</li>
	<li>Incubate the inoculated flasks in 37 &#176;C with 5% CO2 for 4-6 hr. Spread the inoculum by gently tilting the flasks sideways at every hr.</li>
	<li>At the completion of incubation, replace the inoculum with warm serum-supplemented growth media (30 ml) for each flask. Then continue the viral culture for next 96 hr.</li>
	<li>Verify the progression of infection by observing the appearance of viral plaques on the cell monolayer using a phase contrast microscope and take images (Figure 2) as needed at 40X and 200X magnifications.</li>
</ol>
<img alt="Figure 2" src="/files/ftp_upload/54767/54767fig2.jpg" /> 
Figure 2: Plaques formed by Zika virus on a monolayer of Vero cells. Bright field images of various magnifications show Zika viral plaques at 48 hpi. Note the presence of rounded cell foci on the monolayer. (Scale bar = 50 &#181;m) <a href="https://www.jove.com/files/ftp_upload/54767/54767fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<ol start="8">
	<li>Harvest cell culture supernatants at the 96 hr time point and centrifuge the supernatant at 300 x g for 10 min at 4 &#176;C to remove cell debris.</li>
	<li>Carefully remove the supernatant without disturbing pelleted debris and transfer to 15 ml tubes. Ultracentrifugation at 24,000 x g can be performed to concentrate the viral particles (optional).</li>
	<li>Store the viral culture supernatants in multiple aliquots at -80 &#176;C.</li>
</ol>
3. Measuring Zika Virus Titer by Plaque Assay
<ol>
	<li>Seed naive Vero cells at 1 x 105 cells per well in 2 ml volume using a 12-well plate.</li>
	<li>The following day, prepare 10-fold serial dilutions of viral culture supernatants collected from the T-160 flask using serum-free media. Remove the spent media from each well and add 400 &#181;l of prepared inoculum onto Vero cells in triplicate.</li>
	<li>Incubate the inoculated flasks in 37 &#176;C with 5% CO2 for 4-6 hr. Spread the inoculum by gently tilting the plate sideways at every one hr.</li>
	<li>At the end of incubation, replace the inoculum with serum supplemented media (2 ml per well).</li>
	<li>At 48 hr post-inoculation, count the viral foci using a phase contrast microscope. Calculate the viral titer as plaque forming units (PFU) per ml. See Figure 3 for plaque assay.</li>
	<li>Fix and stain the cells in 4% formaldehyde and 0.1% crystal violet solution prepared in 20% ethanol for clear visualization of plaques.</li>
</ol>
4. Zika Viral Genome Replication Assay
<ol>
	<li>Seed na&#239;ve Vero cells at 1 x 105 cells per well in 2 ml volumes using a 12-well plate. The following day, prepare viral inocula (MOI of 0.01 and 0.1; 400 &#181;l/well) of low and high titer using serum free media in triplicate. For mock infection, use serum free media (400 &#181;l/well) only.</li>
	<li>Repeat the steps 3.2 to 3.4.</li>
	<li>At the 48 and 96 hr time points, collect the samples for RNA and immunocytochemistry (ICC).
	<ol>
		<li>For harvesting RNA samples, remove the media and then add 400 &#181;l of lysis solution directly to each well and collect the lysates.</li>
		<li>For ICC, remove the media and then fix the cells by adding 1 ml of methanol to each well and incubate the plate at 4&#160;&#176;C for 30 min.</li>
		<li>From the cell lysate, isolate the total RNA using a RNA isolation kit per the manufacturer&#39;s instructions. Quantify the RNA using a spectrophotometer.</li>
	</ol>
	</li>
	<li>Perform a two-step reverse transcription quantitative PCR (RT-qPCR) to determine the ZIKV genome content from harvested RNA.
	<ol>
		<li>To reverse transcribe the RNA, first set up a 13 &#181;l reaction mix comprised of 5 &#181;g of isolated RNA, 1 &#181;l of dNTPs (10 mM), and 1 &#181;l random hexamer (250 ng) in a 0.2 ml tube. Incubate the tube at 65 &#176;C for 5 min and then place it on ice for one minute. Subsequently, add 1 &#181;l of reverse transcriptase, 4 &#181;l of 5x strand synthesis buffer, 1 &#181;l of 0.1 M dithiothreitol, and 1 &#181;l of RNase inhibitor to the reaction mix. Incubate the tube for an additional 5 min at 25 &#176;C, followed by 60 min at 50 &#176;C and inactivate the reaction by heating to 70 &#176;C for 15 min.</li>
		<li>Perform qPCR using 1 &#181;l of the resulting cDNA with 12.5 &#181;l of 2x green dye super mix containing DNA polymerase and 1 &#181;l of 10 mM individual primers specific for Zika virus [Zika virus pan-genotype primers (For: 5&#39;-AARTACACATACCARAACAAAGTGGT-3&#39;; Rev: 5&#39;-TCCRCTCCCYCTYTGGTCTTG-3&#39;), Zika virus Asian genotype PRVABC59 strain primers (5&#39;-AAGTACACATACCAAAACAAAGTGGT-3&#39;; Rev: 5&#39;-TCCGCTCCCCCTTTGGTCTTG-3&#39;)], or hepatitis C virus (JFH RTQ F: 5&#39;CTGGGTCCTTTCTTGGATAA-3; JFH RTQ R: 5&#39;CCTATCAGGCAGTACCACA-3&#39;), or cellular housekeeping gene GAPDH (For: 5&#39;-CCACCTTTGACGCTGGG-3&#39;; Rev: 5&#39;-CATACCAGGAAATGAGCTTGACA-3&#39;) in a 25 &#181;l reaction volume.</li>
		<li>Perform PCR using the run condition 95 &#176;C for 15 sec and 60 &#176;C for 30 sec (40 cycles) in a real-time PCR system.</li>
		<li>Use GAPDH expression level based on cycle threshold (Ct) value to normalize the Zika viral genome measurement. Calculate the delta Ct (&#916;Ct) value of Zika genome compared to that of GAPDH and obtain the 2&#916;Ct value. Then, calculate the fold change by taking the ratio of normalized Zika genome contents between infected and uninfected cells at indicated time points. See Figure 4 for ZIKV genome replication results.</li>
	</ol>
	</li>
	<li>Perform ICC using the methanol fixed cells.
	<ol>
		<li>Wash the fixed cells three times with 1x PBS and block with ICC blocking buffer (3% goat serum, 3% BSA, 0.1% Triton-x 100 in PBS).</li>
		<li>Use mouse monoclonal anti-dsRNA antibody J2 (1 &#181;g/ml) at a dilution of 1:100 in blocking buffer and incubate overnight at 4 &#176;C.</li>
		<li>Wash the cells with 1x PBS and add secondary antibody goat anti-mouse IgG-594 (1 &#181;g/ml) at a 1:1,000 dilution in blocking buffer and incubate for one hour at room temperature.</li>
		<li>Wash cells with 1x PBS and stain for nuclei using Hoechst dye and observe the cells using a fluorescent microscope at 100X magnification (Figure 4).</li>
	</ol>
	</li>
</ol>
5. Screening Cytokine Library against Zika Virus Infection
<ol>
	<li>Seed naive Vero cells at 1 x 105 cells per well using a 12-well plate. Once the cells are attached (6 hr post-seeding), add each cytokine at indicated concentrations in biological duplicates (2 ml volume/well). Include vehicle (PBS) alone control.</li>
	<li>At 12 hr post-treatment, perform Zika viral infection (MOI of 0.1 in 400 &#181;l per well). Include negative control wells without infection (mock).</li>
	<li>At 4 hr post-infection, replace the viral inoculum with cytokine treated media (2 ml). Incubate the cells at 37 &#176;C for additional 44 hr.</li>
	<li>At 48 hr post-infection, count viral plaques using a phase contrast microscope and acquire representative images of infected cells at 40X magnification (Figure 5).</li>
</ol>

<ol><li>Brasil, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Zika+Virus+Infection+in+Pregnant+Women+in+Rio+de+Janeiro+-+Preliminary+Report%5BTitle%5D)+AND+%22N+Engl+J+Med%22%5BJournal%5D)">Zika Virus Infection in Pregnant Women in Rio de Janeiro - Preliminary Report.</a> N Engl J Med. , 1-11 (2016).</li>
<li>Lucey, D. R., Gostin, L. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+Emerging+Zika+Pandemic%3A+Enhancing+Preparedness%5BTitle%5D)+AND+%22JAMA%22%5BJournal%5D)">The Emerging Zika Pandemic: Enhancing Preparedness.</a> JAMA. 315 (9), 865-866 (2016).</li>
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<li>Kuno, G., Chang, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Full-length+sequencing+and+genomic+characterization+of+Bagaza%2C+Kedougou%2C+and+Zika+viruses%5BTitle%5D)+AND+%22Arch+Virol%22%5BJournal%5D)">Full-length sequencing and genomic characterization of Bagaza, Kedougou, and Zika viruses.</a> Arch Virol. 152 (4), 687-696 (2007).</li>
<li>Dick, G. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Zika+virus.+II.+Pathogenicity+and+physical+properties%5BTitle%5D)+AND+%22Trans+R+Soc+Trop+Med+Hyg%22%5BJournal%5D)">Zika virus. II. Pathogenicity and physical properties.</a> Trans R Soc Trop Med Hyg. 46 (5), 521-534 (1952).</li>
<li>Dick, G. W., Kitchen, S. F., Haddow, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Zika+virus.+I.+Isolations+and+serological+specificity%5BTitle%5D)+AND+%22Trans+R+Soc+Trop+Med+Hyg%22%5BJournal%5D)">Zika virus. I. Isolations and serological specificity.</a> Trans R Soc Trop Med Hyg. 46 (5), 509-520 (1952).</li>
<li>Oehler, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Zika+virus+infection+complicated+by+Guillain-Barre+syndrome--case+report%2C+French+Polynesia%5BTitle%5D)+AND+%22Euro+Surveill%22%5BJournal%5D)">Zika virus infection complicated by Guillain-Barre syndrome--case report, French Polynesia.</a> Euro Surveill. 19 (9), 1-3 (2013).</li>
<li>Baronti, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Complete+coding+sequence+of+zika+virus+from+a+French+polynesia+outbreak+in+2013%5BTitle%5D)+AND+%22Genome+Announc%22%5BJournal%5D)">Complete coding sequence of zika virus from a French polynesia outbreak in 2013.</a> Genome Announc. 2 (3), e00500-e00514 (2014).</li>
<li>Lanciotti, R. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Genetic+and+serologic+properties+of+Zika+virus+associated+with+an+epidemic%2C+Yap+State%2C+Micronesia%2C+2007%5BTitle%5D)+AND+%22Emerg+Infect+Dis%22%5BJournal%5D)">Genetic and serologic properties of Zika virus associated with an epidemic, Yap State, Micronesia, 2007.</a> Emerg Infect Dis. 14 (8), 1232-1239 (2008).</li>
<li>Lanciotti, R. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Phylogeny+of+Zika+virus+in+Western+Hemisphere%2C+2015+%5BLetter%5D%5BTitle%5D)+AND+%22Emerg+Infect+Dis%22%5BJournal%5D)">Phylogeny of Zika virus in Western Hemisphere, 2015 [Letter].</a> Emerg Infect Dis. 22 (5), (2016).</li>
<li>Musso, D., Nilles, E. J., Cao-Lormeau, V. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Rapid+spread+of+emerging+Zika+virus+in+the+Pacific+area%5BTitle%5D)+AND+%22Clin+Microbiol+Infect%22%5BJournal%5D)">Rapid spread of emerging Zika virus in the Pacific area.</a> Clin Microbiol Infect. 20 (10), O595-O596 (2014).</li>
<li>Tang, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Zika+Virus+Infects+Human+Cortical+Neural+Progenitors+and+Attenuates+Their+Growth%5BTitle%5D)+AND+%22Cell+Stem+Cell%22%5BJournal%5D)">Zika Virus Infects Human Cortical Neural Progenitors and Attenuates Their Growth.</a> Cell Stem Cell. , 1-5 (2016).</li>
<li>Hamel, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Biology+of+Zika+Virus+Infection+in+Human+Skin+Cells%5BTitle%5D)+AND+%22J+Virol%22%5BJournal%5D)">Biology of Zika Virus Infection in Human Skin Cells.</a> J Virol. 89 (17), 8880-8896 (2015).</li>
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<li>Chu, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Systematic+analysis+of+enhancer+and+critical+cis-acting+RNA+elements+in+the+protein-encoding+region+of+the+hepatitis+C+virus+genome%5BTitle%5D)+AND+%22J+Virol%22%5BJournal%5D)">Systematic analysis of enhancer and critical cis-acting RNA elements in the protein-encoding region of the hepatitis C virus genome.</a> J Virol. 87 (10), 5678-5696 (2013).</li>
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</ol>

The authors have nothing to disclose.

Here, a streamlined protocol for culturing Zika virus in vitro is presented. Critical steps including, identifying optimum end points for expanding virus culture, measuring titer, and quantifying genome replication were provided. Zika virus is a human pathogen, so, while handling infectious agents, biosafety procedures are to be strictly followed. A monkey kidney cell line, Vero, was used for demonstrating various virological assays. Zika viral replication kinetics may differ in cells of various tissues and spec...

Zika Virus (ZIKV) is an important human pathogen associated with microcephaly and poor pregnancy outcomes1,4. ZIKV belongs to the set of medically relevant flaviviruses that can cause neurological defects such as the Dengue, West Nile, and St. Louis encephalitis viruses. The main mode of viral transmission is by the mosquito vector Aedes aegypti, and, in addition, sexual transmission has also been reported5,6. ZIKV has become a major global health issue due to the expanding geographical distribution of the mosquito vector and its strong correlation with birth defects. ZIKV was first isolated in 1947 from a sentinel rhesus monkey in the Zika forest, Uganda and the first human case was reported in 19527,8. Individuals that become infected with ZIKV present with mild symptoms such as fever, rash, headache, conjunctivitis, and muscle/joint pain. Infected pregnant women can transmit ZIKV to the developing fetus1. ZIKV infection has also been linked to Guillain-Barre syndrome, a peripheral nerve auto-immune demyelination disorder9.
The Zika viral genome consists of a positive sense, single-stranded RNA molecule which is about 10.8 kilobases in length. The genome&#39;s structure is organized as 5&#39;NCR-C-prM-E-NS1-NS2A-NS2B-NS3-NS4A-2K-NS4B-NS5-3&#39;NCR, with non-coding regions (NCR) flanking a protein-coding region6. A single polyprotein (3,419 aa) is translated that is co- and post-translationally cleaved into 10 smaller peptides. Both the 5&#39;NCR and 3&#39;NCR RNA stem-loop structures play a critical part in the commencement of viral genome translation and replication. The structural components of the genome are comprised of the capsid, membrane, and envelope proteins. The non-structural proteins are critical for genome replication.
Currently, Zika viral strains are grouped into three main genotypes: West African, East African, and Asian6,10-13. It has been proposed that the East African lineage spread to West Africa and Asia, where it later further evolved12. The Asian genotype is responsible for the current outbreaks in the Americas. Zika virus can be cultured in both mosquito and mammalian cells. Primary dermal fibroblasts, immature dendritic cells, cortical neural progenitor cells, and Vero cells are susceptible to Zika viral infection10,14,15. Both type I and type II interferons have been shown to restrict ZIKV growth in skin fibroblasts15. The objectives of this study are to provide a step-wise, detailed protocol for the production and assaying of the Asian genotype ZIKA viral strain PRVABC59 in a mammalian cell culture system and to demonstrate the utility of this infectious culture system as a drug development platform. This resource has the potential to greatly benefit the Zika viral and neurological research community to further elucidate its mechanisms of viral pathogenesis and evolution of viral virulence.

<table><tbody><tr><td>Dulbecco&amp;rsquo;s modified Eagle&amp;rsquo;s medium (DMEM)</td><td>Sigma Life Science</td><td>D5796</td><td></td></tr><tr><td>HEPES</td><td>Life Technologies</td><td>15630080</td><td></td></tr><tr><td>Glutamax</td><td>Life Technologies</td><td>35050061</td><td></td></tr><tr><td>2.5% Trypsin, 10x [-] Phenol Red&amp;nbsp;&amp;nbsp;</td><td>Corning</td><td>25-054-C1</td><td></td></tr><tr><td>Trypan Blue Stain 0.4%</td><td>Life Technologies</td><td>T10282</td><td></td></tr><tr><td>Countess &amp;ndash; Automated Cell Counter</td><td>ThermoFisher Scientific</td><td>C10227</td><td></td></tr><tr><td>Countess-cell counting&amp;nbsp; chamber slides</td><td>ThermoFisher Scientific</td><td>C10283</td><td></td></tr><tr><td>Rneasy Mini Kit</td><td>Qiagen</td><td>74104</td><td></td></tr><tr><td>Nanodrop 2000</td><td>Thermo Scientific</td><td>Nanodrop 2000</td><td></td></tr><tr><td>mouse monoclonal anti-dsRNA antibody J2&amp;nbsp;</td><td>English &amp;amp; Scientific Consulting Kft.</td><td>10010200</td><td></td></tr><tr><td>Goat anti-rabbit IgG Alexa Fluor 594</td><td>Life Technologies</td><td>A11020</td><td></td></tr><tr><td>SUPERSCRIPT III RT&amp;nbsp;</td><td>Life Technologies</td><td>18080085</td><td></td></tr><tr><td>SYBR QPCR SUPERMIX W/ROX</td><td>Life Technologies</td><td>11744500</td><td></td></tr><tr><td>QuantStudio12K Flex Real-Time PCR System</td><td>Thermo Fischer</td><td>4471088</td><td></td></tr><tr><td>RNase-Free DNase</td><td>Promega</td><td>M6101</td><td></td></tr><tr><td>Vero Cell Line&amp;nbsp;</td><td>ATCC</td><td>CCL-81</td><td></td></tr><tr><td>Zika viral strain PRVABC59</td><td>Centers for Disease Control and Prevention (CDC)</td><td></td><td></td></tr><tr><td>IL-6</td><td>Peprotech</td><td>200-06&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;</td><td></td></tr><tr><td>IL-1 alpha&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;</td><td>Peprotech</td><td>200-01A&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;</td><td></td></tr><tr><td>TNF-alpha</td><td>Peprotech</td><td>300-01A&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;</td><td></td></tr><tr><td>Interferon alpha A&amp;nbsp;&amp;nbsp;</td><td>R &amp;amp; D Systems</td><td>11100-1</td><td></td></tr><tr><td>Interferon beta</td><td>Peprotech</td><td>300-02BC</td><td></td></tr><tr><td>Interferon gamma</td><td>Peprotech</td><td>300-02</td><td></td></tr><tr><td>Centrifuge 5415R</td><td>Eppendorf</td><td>5415R</td><td></td></tr><tr><td>Centrifuge 5810R</td><td>Eppendorf</td><td>5810R</td><td></td></tr><tr><td>Nikon Eclipse Ti Immunofluorescence Microscope with Nikon Intenselight C-HGFI</td><td>Nikon</td><td>Visit Nikon for Request</td><td></td></tr></tbody></table>

zika virus infectious cell culture system and the in vitro prophylactic effect of interferons

Zika Virus (ZIKV) is an emerging pathogen that is linked to fetal developmental abnormalities such as microcephaly, eye defects, and impaired growth. ZIKV is an RNA virus of the Flaviviridae family. ZIKV is mainly transmitted by mosquitoes, but can also be spread by maternal to fetal vertical transmission as well as sexual contact. To date, there are no reliable treatment or vaccine options available to protect those infected by the virus. The development of a reproducible, effective Zika virus infectious cell culture system is critical for studying the molecular mechanisms of ZIKV replication as well as drug and vaccine development. In this regard, a protocol describing a mammalian cell-based in vitro Zika virus culture system for viral production and growth analysis is reported here. Details on the formation of plaques by Zika virus on a cell monolayer and plaque assay for measuring viral titer are presented. Viral genome replication kinetics and double-stranded RNA genome replicatory intermediates are determined. This culture platform was utilized to screen against a library of a small set of cytokines resulting in the identification of interferon-&#945; (IFN-&#945;), IFN-&#946; and IFN-&#947; as potent inhibitors of Zika viral growth. In summary, an in vitro infectious Zika viral culture system and various virological assays are demonstrated in this study, which has the potential to greatly benefit the research community in elucidating further the mechanisms of viral pathogenesis and the evolution of viral virulence. Antiviral IFN-alpha can further be evaluated as a prophylactic, post-exposure prophylactic, and treatment option for Zika virus infections in high-risk populations, including infected pregnant women.

A Zika viral strain (PRVABC59; GenBank accession number KU501215) of the Asian genotype was utilized in this study12. Vero cells at 80% confluency were used for investigating de novo Zika viral infection. For viral production and subsequent virological characterization, an early passage (P3) Zika virus was employed. The viral plaques were observed on the second day of infection. Zika viral progenies released from the initially infected cell can spread to neighboring ce...

Watch this Scientific Journal Video about Zika Virus Infectious Cell Culture System and the In Vitro Prophylactic Effect of Interferons at JoVE.com

Zika Virus Infectious Cell Culture System and the In Vitro Prophylactic Effect of Interferons

Zika Virus (ZIKV), an emerging pathogen, is linked to fetal developmental abnormalities and microcephaly. The establishment of an effective infectious cell culture system is crucial for studies of ZIKV replication as well as vaccine and drug development. In this study, various virological assays pertaining to ZIKV are illustrated and discussed.

Zika Virus Infectious Cell Culture System and the In Vitro Prophylactic Effect of Interferons

Zika Virus (ZIKV) is an emerging pathogen that is linked to fetal developmental abnormalities such as microcephaly, eye defects, and impaired growth. ZIKV ...

zika-virus-infectious-cell-culture-system-vitro-prophylactic-effect

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Immunology and Infection

20.7K Views.  Cedars-Sinai Medical Center. Zika Virus (ZIKV), an emerging pathogen, is linked to fetal developmental abnormalities and microcephaly. The establishment of an effective infectious cell culture system is crucial for studies of ZIKV replication as well as vaccine and drug development. In this study, various virological assays pertaining to ZIKV are illustrated and discussed.

Video: Zika Virus Infectious Cell Culture System and the In Vitro Prophylactic Effect of Interferons

Zika Virus Infection of Cultured Human Fetal Brain Neural Stem Cells for Immunocytochemical Analysis

Human fetal brain neural stem cells are a unique non-genetically modified model system to study the impact of various stimuli on human developmental neurobiology. Rather than use an animal model or genetically modified induced pluripotent cells, human neural stem cells provide an effective in vitro system to examine the effects of treatments, screen drugs, or examine individual differences. Here, we provide the detailed protocols for methods used to expand human fetal brain neural stem cells in culture with serum-free media, to differentiate them into various neuronal subtypes and astrocytes via different priming procedures, and to freeze and recover these cells. Furthermore, we describe a procedure of using human fetal brain neural stem cells to study Zika virus infection.

This article details the methods that are used to expand human fetal brain neural stem cells in culture, as well as how to differentiate them into various neuronal subtypes and astrocytes, with an emphasis on the use of neural stem cells to study Zika virus infection.

Human fetal brain neural stem cells are a unique non-genetically modified model system to study the impact of various stimuli on human developmental ...

Developmental Biology

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 ...

Evaluation of Zika Virus-specific T-cell Responses in Immunoprivileged Organs of Infected Ifnar1-/- Mice

The Zika virus (ZIKV) can induce inflammation in immunoprivileged organs (e.g., the brain and testis), leading to the Guillain-Barr&#233; syndrome and damaging the testes. During an infection with the ZIKV, immune cells have been shown to infiltrate into the tissues. However, the cellular mechanisms that define the protection and/or immunopathogenesis of these immune cells during a ZIKV infection are still largely unknown. Herein, we describe methods to evaluate the virus-specific T-cell functionality in these immunoprivileged organs of ZIKV-infected mice. These methods include a) a ZIKV infection and vaccine inoculation in Ifnar1-/- mice; b) histopathology, immunofluorescence, and immunohistochemistry assays to detect the virus infection and inflammation in the brain, testes, and spleen; c) the preparation of a tetramer of ZIKV-derived T-cell epitopes; d) the detection of ZIKV-specific T cells in the monocytes isolated from the brain, testes, and spleen. Using these approaches, it is possible to detect the antigen-specific T cells that have infiltrated into the immunoprivileged organs and to evaluate the functions of these T cells during the infection: potential immune protection via virus clearance and/or immunopathogenesis to exacerbate the inflammation. These findings may also help to clarify the contribution of T cells induced by the immunization against ZIKV.

Evaluation of Zika Virus-specific T-cell Responses in Immunoprivileged Organs of Infected Ifnar1-/- Mice

A protocol to evaluate antigen-specific T-cell responses in the immunoprivileged organs of the Ifnar1-/- murine model for the Zika virus (ZIKV) infection is described. This method is pivotal for investigating the cellular mechanisms of the protection and immunopathogenesis of ZIKV vaccines and is also valuable for their efficacy evaluation.

The Zika virus (ZIKV) can induce inflammation in immunoprivileged organs (e.g., the brain and testis), leading to the Guillain-Barr&#233; syndrome and ...

Modelling Zika Virus Infection of the Developing Human Brain In Vitro Using Stem Cell Derived Cerebral Organoids

The recent emergence of Zika virus (ZIKV) in susceptible populations has led to an abrupt increase in microcephaly and other neurodevelopmental conditions in newborn infants. While mosquitos are the main route of viral transmission, it has also been shown to spread via sexual contact and vertical mother-to-fetus transmission. In this latter case of transmission, due to the unique viral tropism of ZIKV, the virus is believed to predominantly target the neural progenitor cells (NPCs) of the developing brain.
Here a method for modeling ZIKV infection, and the resulting microcephaly, that occur when human cerebral organoids are exposed to live ZIKV is described. The organoids display high levels of virus within their neural progenitor population, and exhibit severe cell death and microcephaly over time. This three-dimensional cerebral organoid model allows researchers to conduct species-matched experiments to observe and potentially intervene with ZIKV infection of the developing human brain. The model provides improved relevance over standard two-dimensional methods, and contains human-specific cellular architecture and protein expression that are not possible in animal models.

Modelling Zika Virus Infection of the Developing Human Brain In Vitro Using Stem Cell Derived Cerebral Organoids

This protocol describes a technique used to model Zika virus infection of the developing human brain. Using wildtype or engineered stem cell lines, researchers may use this technique to uncover the various mechanisms or treatments that may affect early brain infection and resulting microcephaly in Zika virus-infected embryos.

The recent emergence of Zika virus (ZIKV) in susceptible populations has led to an abrupt increase in microcephaly and other neurodevelopmental conditions ...

Neuroscience

Quantification of Antibody-dependent Enhancement of the Zika Virus in Primary Human Cells

The recent emergence of the flavivirus Zika and neurological complications, such as Guillain-Barr&#233; syndrome and microcephaly in infants, has brought serious public safety concerns. Among the risk factors, antibody-dependent enhancement (ADE) poses the most significant threat, as the recent re-emergence of the Zika virus (ZIKV) is primarily in areas where the population has been exposed and is in a state of pre-immunity to other closely related flaviviruses, especially dengue virus (DENV). Here, we describe a protocol for quantifying the effect of human serum antibodies against DENV on ZIKV infection in primary human cells or cell lines.

We describe a method to evaluate the effect of pre-existing immunity against dengue virus on the Zika virus infection by using human serum, primary human cells, and infection quantification by quantitative real-time polymerase chain reaction.

The recent emergence of the flavivirus Zika and neurological complications, such as Guillain-Barr&#233; syndrome and microcephaly in infants, has brought ...

Isolation and Quantification of Zika Virus from Multiple Organs in a Mouse

The methods being presented demonstrate laboratory procedures for the isolation of organs from Zika virus infected animals and the quantification of viral load. The purpose of the procedure is to quantify viral titers in peripheral and CNS areas of the mouse at different time points post infection or under different experimental conditions to identify virologic and immunological factors that regulate Zika virus infection. The organ isolation procedures demonstrated allow for both focus forming assay quantification and quantitative PCR assessment of viral titers. The rapid organ isolation techniques are designed for the preservation of virus titer. Viral titer quantification by focus forming assay allows for the rapid throughput assessment of Zika virus. The benefit of the focus forming assay is the assessment of infectious virus, the limitation of this assay is the potential for organ toxicity reducing the limit of detection. Viral titer assessment is combined with quantitative PCR, and using a recombinant RNA copy control viral genome copy number within the organ is assessed with low limit of detection. Overall these techniques provide an accurate rapid high throughput method for the analysis of Zika viral titers in the periphery and CNS of Zika virus infected animals and can be applied to the assessment of viral titers in the organs of animals infected with most pathogens, including Dengue virus.

The goal of the protocol is to demonstrate the techniques used to investigate viral disease by isolating and quantifying Zika virus, from multiple organs in a mouse following infection.

The methods being presented demonstrate laboratory procedures for the isolation of organs from Zika virus infected animals and the quantification of viral ...

High-throughput Antiviral Assays to Screen for Inhibitors of Zika Virus Replication

Antiviral drug discovery requires the development of reliable biochemical and cellular assays that can be performed in high-throughput screening (HTS) formats. The flavivirus non-structural (NS) proteins are thought to co-translationally assemble on the endoplasmic reticulum (ER) membranes, forming the replication complex (RC). The NS3 and NS5 are the most studied enzymes of the RC and constitute the main targets for drug development due to their crucial roles in viral genome replication. NS3 protease domain, which requires NS2B as its cofactor, is responsible for the cleavage of the immature viral polyprotein into the mature NS proteins, whereas NS5 RdRp domain is responsible for the RNA replication. Herein, we describe in detail the protocols used in replicon-based screenings and enzymatic assays to test large compound libraries for inhibitors of the Zika virus (ZIKV) replication. Replicons are self-replicating subgenomic systems expressed in mammalian cells, in which the viral structural genes are replaced by a reporter gene. The inhibitory effects of compounds on viral RNA replication can be easily evaluated by measuring the reduction in the reporter protein activity. The replicon-based screenings were performed using a BHK-21 ZIKV replicon cell line expressing Renilla luciferase as a reporter gene. To characterize the specific targets of identified compounds, we established in-vitro fluorescence-based assays for recombinantly expressed NS3 protease and NS5 RdRp. The proteolytic activity of the viral protease was measured by using the fluorogenic peptide substrate Bz-nKRR-AMC, while the NS5 RdRp elongation activity was directly detected by the increase of the fluorescent signal of SYBR Green I during RNA elongation, using the synthetic biotinylated self-priming template 3&#8242;UTR-U30 (5&#39;-biotin-U30-ACUGGAGAUCGAUCUCCAGU-3&#39;).

In this work, we describe the protocols used in replicon-based and viral enzyme-based assays to screen for inhibitors of Zika virus replication in a high-throughput screening format.

Antiviral drug discovery requires the development of reliable biochemical and cellular assays that can be performed in high-throughput screening (HTS) ...

Cell-Based Electrical Impedance Platform to Evaluate Zika Virus Inhibitors in Real Time

Cell-based electrical impedance (CEI)&#160;technology measures changes in impedance caused by a growing or manipulated adherent cell monolayer on culture plate wells embedded with electrodes. The technology can be used to monitor the consequences of Zika virus (ZIKV) infection and adherent cell replication in real time, as this virus is highly cytopathogenic. It is a straightforward assay that does not require the use of labels or invasive methods and has the benefit of providing real-time data. The kinetics of ZIKV infection are highly dependent on the employed cell line, virus strain, and multiplicity of infection (MOI), which cannot be easily studied with conventional endpoint assays. Furthermore, the CEI assay can also be used for the evaluation and characterization of antiviral compounds, which can also have dynamic inhibitory properties over the course of infection. This methods article gives a detailed explanation of the practical execution of the CEI assay and its potential applications in ZIKV research and antiviral research in general.

Here, we demonstrate the use of cell-based electrical impedance (CEI) as a very easy and straightforward method to study Zika virus infection and replication in human cells in real time. Furthermore, the CEI assay is useful for the evaluation of antiviral compounds.

Cell-based electrical impedance (CEI)&#160;technology measures changes in impedance caused by a growing or manipulated adherent cell monolayer on culture ...

An In Vitro Assay for Screening Interferons as Potent Inhibitors of Zika Virus Growth

Source: Contreras, D. et al., <a href="https://app.jove.com/v/54767">Zika Virus Infectious Cell Culture System and the In Vitro Prophylactic Effect of Interferons.</a> J. Vis. Exp. (2016)
The video demonstrates an in vitro assay for screening interferons with antiviral activity against the Zika virus, a human pathogen. Within the host cell, the Zika virus undergoes multiplication upon internalization, infecting neighboring cells and creating distinct zones or viral plaques. Type I interferon, acting as an antiviral agent, hinders virus multiplication, thereby preventing the formation of viral plaques in the host cell monolayer.

1. Screening Cytokine Library against Zika Virus Infection

	Seed naive Vero cells at 1 x 105 cells per well using a 12-well plate. Once the cells are ...

JoVE Encyclopedia of Experiments

Immunology

Immunotherapy

Immunogenics and Vaccine Development

Zika Virus Infection of Fetal Neural Stem Cells

Source: McGrath, E. L., et al., <a href="https://app.jove.com/v/56917">Zika Virus Infection of Cultured Human Fetal Brain Neural Stem Cells for Immunocytochemical Analysis.</a> J. Vis. Exp. (2018)
This video demonstrates a procedure to infect human fetal neural stem cells with Zika virus. The infected cells can be used for further studies.

Source: McGrath, E. L., et al., Zika Virus Infection of Cultured Human Fetal Brain Neural Stem Cells for Immunocytochemical Analysis. J. Vis. Exp. (2018)
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Zika Virus Infectious Cell Culture System and the In Vitro Prophylactic Effect of Interferons

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