The authors thank Gary Wong for the English revision. This work was supported by the National Key Research and Development Program of China (grant 2017YFC1200202), the Major Special Projects for Infectious Disease Research of China (grant 2016ZX10004222-003). George F. Gao is a leading principal investigator of the National Natural Science Foundation of China Innovative Research Group (grant 81621091).

Animal experiments were approved by the Institutional Animal Care and Use Committee of National Institute for Viral Disease Control and Prevention, China CDC. All experiments were performed following the Institutional Animal Care and Use Committee-approved animal protocols.
1. Virus Infection
<ol>
	<li>Keep adult (6&#160;to 8 week-old) Ifnar1-/- (50% male and 50% female) mice in standard special pathogen-free (SPF) conditions, and allow them regular access to food and water.</li>
	<li>Infect the Ifnar1-/- mice with the ZIKV via a retro-orbital inoculation of 100 &#181;L of ZIKV in a phosphate-buffered saline (PBS) buffer containing 1 x 104 focus-forming units (FFUs) of the virus. Similarly, provide control mice with an equal volume of PBS. 
	CAUTION: Infect the mice under ABSL2 conditions and perform these procedures with virus-infected mice in the biosafety cabinet.</li>
	<li>Monitor the weight and clinical signs (tremors, staggered march, bilateral flaccid hind limb) of the mice daily for 15 days.</li>
</ol>
2. Immunization with the ZIKV Vaccine
<ol>
	<li>Use Ifnar1-/- (50% male and 50% female) mice between 6 and 8 weeks of age. Keep the mice in standard SPF conditions of 18&#8211;29 &#176;C and a 12 h light/dark cycle with access to food and water.</li>
	<li>Immunize the Ifnar1-/- mice with the ZIKV vaccine: inject 100 &#181;L of AdC7-M/E [4 x 1010 (virus particles)] in PBS buffer via an intramuscular injection (the i.m. route) using a 1 mL syringe with a 23-G needle.</li>
	<li>Similarly, inject control mice with an equal volume of PBS.</li>
</ol>
3. Isolation of the Monocytes from the Spleen
NOTE: The isolation of the monocytes from the spleen is described as mentioned previously16.
<ol>
	<li>Anesthetize the immunized and ZIKV-infected mice 7 d post-inoculation, using a 5% isoflurane concentrationin 100% oxygen (with a flow rate of 1 L/min). Euthanize the mice by cervical dislocation. Then, immediately dip the entire mouse into 75% ethanol. 
	CAUTION:From this step onward, all experimental procedures should be performed aseptically in a biosafety cabinet.</li>
	<li>Using needles, fix the limbs of the (euthanized, previously infected/immunized) mice on the foam plate with the abdomen facing up.</li>
	<li>Cut the skin along the abdominal midline to the thorax with a sterile scalpel, cut the abdominal muscles with scissors, expose the abdominal cavity, and gently remove the liver. 
	NOTE: The long, dark-red organ to the left of the stomach is the spleen.</li>
	<li>Remove the spleen, rinse it 3x in PBS to remove any blood, and place it in 1.5 mL of ice-cold Roswell Park Memorial Institute medium (RPMI). Keep the spleen on ice.</li>
	<li>To generate a single-cell suspension from the spleen, place the organ(s) on a sterile 40 &#181;m-mesh cell strainer on top of a 50 mL tube and add 2 mL of ice-cold RPMI medium containing 10% fetal bovine serum (FBS). Using the plunger of a 5 mL syringe, mechanically mash the organ(s) and add medium until the organ has been fully ground through the mesh.</li>
	<li>Transfer the cell suspension to a 15 mL tube and centrifuge it at 600 x g for 5 min at 4 &#176;C. Remove the supernatant.</li>
	<li>Resuspend the cells with 5 mL of a red blood cell (RBC) lysis buffer (NH4Cl, Na2EDTA, and KHCO3; see the Table of Materials) and incubate the lysis reaction at room temperature for 5&#8211;6 min.</li>
	<li>Stop the RBC lysis with 10 mL of ice-cold RPMI/FBS medium and centrifuge the tube at 600 x g for 5 min at 4 &#176;C. Remove the supernatant.</li>
	<li>Resuspend the cells with 10 mL of complete RPMI medium (RPMI with 10% vol/vol FBS and 100 U/mL penicillin-streptomycin). Transfer 10 &#181;L of the cell suspension to a small tube, mix it with 10 &#181;L of 0.4% wt/vol trypan blue, and count the number of cells using a hemocytometer.</li>
</ol>
4. Isolation of Monocytes from the Brain and Testes
<ol>
	<li>Anesthetize the ZIKV-infected male mice 7 d post-inoculation, using 5% isofluranein 100% oxygen (with a flow rate of 1 L/min). Euthanize the mice by cervical dislocation. Then, immediately dip the entire mouse into 75% ethanol. 
	CAUTION: From this step onwards, all experimental procedures must be performed aseptically in a biosafety cabinet. The isolation of monocytes from the brain and testes is described as mentioned previously17.</li>
	<li>Immobilize a (euthanized, previously infected) male mouse in the prone position on a cutting board.</li>
	<li>Secure the scalp with a straight 1 x 2 teeth forceps, and use Iris scissors to make a midline incision on the scalp to expose the skull.</li>
	<li>Clamp the two sides of the orbits with sharp tweezers and fix the brain. Place one tip of sharp Iris scissors into the foramen magnum and cut laterally into the skull. Repeat this step for the other side.</li>
	<li>Use sharp Iris scissors to carefully cut from the same cavity, up the midline, toward the nose. Try to keep the end of the scissors as superficial as possible to avoid injuring the brain.</li>
	<li>Lift the brain with forceps and use sharp Iris scissors to carefully dissect the cranial nerve fibers. Remove the brain with forceps and place it in a 15 mL tube containing 5 mL of ice-cold RPMI/10% FBS medium.</li>
	<li>Grab the abdominal skin with forceps and use sharp Iris scissors to make a longitudinal incision through the integument and abdominal wall and expose the lowermost part of the abdomen. Push the testes up to the incision. Gently pull the fat layer with tweezers and expose a globular testis on both sides.</li>
	<li>Use sharp Iris scissors to carefully dissect the fat layer and epididymis. Place the testes in a 15 mL tube containing 5 mL of ice-cold RPMI/10% FBS medium with forceps.</li>
	<li>To generate a single-cell suspension from the brain or testes, place the organ on a sterile cell strainer with a 100 &#181;m mesh on top of a 50 mL tube and add 2 mL of ice-cold RPMI/10% FBS medium. Using the plunger of a 5 mL syringe, mash the organ and add medium until the organ has been fully ground through the mesh.</li>
	<li>Transfer the cell suspension to a 15 mL tube and centrifuge it at 600 x g for 5 min at 4 &#176;C. Remove the supernatant.</li>
	<li>Resuspend the cells with 5 mL of 30% density gradient medium and, then, add them very slowly to 2 mL of 70% density gradient medium in a 15 mL tube.</li>
	<li>Switch off the brake and centrifuge the tubes at 4 &#176;C at 800 x g for 30 min. Obtain the lymphocytes from the middle layer.</li>
	<li>Transfer the interphase to a fresh 15-mL tube, add 10 mL of cold RPMI/10% FBS medium, and centrifuge the tube at 300 x&#160;g for 10 min at 4 &#176;C. Remove the supernatant.</li>
	<li>Resuspend the cells with 10 mL of ice-cold RPMI/FBS medium and centrifuge them at 600 x g for 5 min at 4 &#176;C. Remove the supernatant.</li>
	<li>Resuspend the cells with 10 mL of complete RPMI medium and count the number of cells as in step 3.9.</li>
</ol>
5. Tetramer Preparation
<ol>
	<li>Construct plasmids expressing the extracellular domains of H-2Db with a biotinylated site tag on the C-terminus of the &#945;3 domain and the &#946;2m by using the pET28a vector with an NdeI and XohI restriction site18.</li>
	<li>Express and prepare inclusion bodies of H-2Db and &#946;2m as described previously20.</li>
	<li>Renature and purify the MHC/peptide complex H-2Db-E294-302.
	<ol>
		<li>Prepare 200 mL of a refolding solution [100 mM Tris-HCl (pH 8.0), 400 mM L-arginine, 2 mM EDTA-Na, 5 mM GSG, and 0.5 mM GSSG]. Add protease inhibitors: 2 mL of phenylmethylsulphonyl fluoride (PMSF, stock 100 mM), 100 &#181;L of pepstatin (stock 2 mg/mL), and 100 &#181;L of leupeptin (stock 2 mg/mL).Cool the buffer at 4 &#176;C for 30 min.</li>
		<li>Add H-2Db, &#946;2m, and peptide to the refolding solution.
		<ol>
			<li>Inject 500 &#181;L of &#946;2m dissolved in a guanidine solution (30 mg/mL stock) using a syringe. For this, use a 23 G needle with a 5 mL syringe and inject the &#946;2m into the refolding solution drop by drop. Keep the solution constantly and slowly stirring at 150 rpm at 4 &#176;C.</li>
			<li>After &#946;2m has been dissolved in the refolding solution, resolve 2 mg of E294-302 peptide in 200 &#181;L of DMSO and quickly inject it into the refolding solution using a pipette. Slowly stir the solution at 150 rpm at 4 &#176;C for 15 min.</li>
			<li>Inject 1.5 mL of H-2Db dissolved in a guanidine solution. Keep the stir bar rotating at 150 rpm for the refolding of the H-2Db at 4 &#176;C for 8&#8211;10 h. 
			NOTE: The solution was placed in a closed box in a cold room.</li>
		</ol>
		</li>
		<li>Concentrate the refolded protein in a pressurized chamber with a 10 kDa membrane. Exchange the buffer [20 mM Tris-HCl (pH8.0), 50 mM NaCl] to the chamber and concentrate it to a final volume of 30&#8211;50 mL.</li>
		<li>Transfer the refolding solution to a centrifuge tube and spin it at 2,500 x g for 15 min at 4 &#176;C.</li>
		<li>Carefully transfer the supernatant to a 10 kDa centrifugal filter and further concentrate it to a final volume of 500 &#181;L at 2,500 x g for 30 min.</li>
		<li>Transfer the supernatant to a fresh tube and spin it at 12,000 x g for 15 min. Purify the protein with S200 10/300 GL gel &#64257;ltration chromatography.</li>
		<li>Collect the MHC complex peak and concentrate it to a final volume of 350 &#181;L.</li>
	</ol>
	</li>
	<li>To generate a 500-&#181;L reaction volume for biotinylation, add the regents in the following order: 100 &#181;L of solution A [0.5M bicine (pH 8.3)], 100 &#181;L of solution B (100 mM ATP, 100 mM MgOAc, 200 &#181;&#924; biotin), 100 &#181;L of extra d-biotin (500 &#181;&#924; biotin), 20 &#181;L of BirA enzyme (60 &#181;g), 0.5 &#181;L of pepstatin (2 mg/mL), and 0.5 &#181;L of leupeptin (2 mg/mL). Incubate the reaction tube overnight at 4 &#176;C. 
	CAUTION: Do not add any EDTA to the biotinylating reaction.</li>
	<li>Purify the MHC using a S200 10/300 GL gel filtration column to remove any extra biotin.</li>
	<li>Determine the biotinylating efficiency with a streptavidin-shift assay18.
	<ol>
		<li>Prepare three samples, A, B, and C, on ice for 30 min. Then, analyze the results by a 10% SDS-PAGE. Sample A consists of 8 &#181;L of biotinylated MHC molecules and 2 &#181;L of exchange buffer, sample B of 8 &#181;L of biotinylated MHC molecules and 2 &#181;L of streptavidin (20 mg/mL), and sample C of 2 &#181;L of streptavidin (20 mg/mL) and 8 &#181;L exchange buffer. 
		CAUTION: Do not boil the sample.</li>
	</ol>
	</li>
	<li>Form multimers of the biotinylated MHC molecules.
	<ol>
		<li>Produce tetramer by mixing the biotinylated E294-302 peptide-H2Db complex with phycoerythrin-labeled streptavidin at a mole ratio of 1:5 to ensure a complete binding of all the biotinylated MHC molecules.</li>
		<li>Calculate the amount of streptavidin-conjugate needed for tetramerization.
		<ol>
			<li>Determine the moles of the MHC/peptide complexes accounting for the protein concentration and the molar weight (example: 1.8 mg of total protein = 40 nmol).</li>
			<li>Calculate the moles of the streptavidin-conjugate needed by dividing the moles of the MHC/peptide by 5 (example: 40/5 = 8 nmol of streptavidin-conjugate).</li>
			<li>Calculate the amount of streptavidin needed (in &#181;g) depending on the streptavidin-conjugate (example: streptavidin-PE [300,000 g/M] &#8594; 8 nmol needed = 2,400 g).</li>
		</ol>
		</li>
		<li>Divide streptavidin-phycoerythrin into 10 samples. Add each sample to a tube containing the biotinylated E294-302 peptide-H2Db complex, at an interval of 20 min. After loading the last sample, incubate the reaction tube at 4 &#176;C overnight in dark.</li>
	</ol>
	</li>
	<li>Apply the multimerized reagents into a 100 kDa spin tube and concentrate it by centrifugation at 2,000 x g at 4 &#176;C to a volume of &#60;100 &#181;L.</li>
	<li>Dilute the sample in the spin tube to 4 mL using PBS (pH 8.0) and concentrate it again to &#60;100 &#181;L.</li>
	<li>Repeat the buffer exchange step in PBS (pH 8.0) 4x.</li>
	<li>Fill up the total volume again to 500 &#181;L using PBS (pH 8.0). Concentrate the sample to an estimated concentration of 2&#8211;2.5 mg/mL at 2,000 x g at 4 &#176;C. Store the sample in the dark at 4 &#176;C.</li>
</ol>
6. Flow Cytometry
<ol>
	<li>Incubate the cell suspensions (from step 3.9 and/or step 4.15) at 4 &#176;C with 0.1 &#181;L of anti-murine CD16/CD32 Fc-Receptor blocking reagent per 20 &#181;L (dilution factor 1:200) for 10 min, to prevent any unspecific binding.</li>
	<li>Centrifuge the tetramer tube at 20,000 x g for at least 15 min at 4 &#176;C.</li>
	<li>Add 20 &#181;L of the cell suspension to a 96-well platecontaining 1 x 106 cells each well.</li>
	<li>Prepare a sufficient volume of the E294-302 tetramer mix to stain all experimental tubes. Prepare an excess of 15% of the total volume of this mix to account for pipetting errors. Dilute the E294-302 tetramers (2 mg/mL, 1 &#181;L/test) in FACS buffer (PBS, 0.5% FBS)so that 20 &#181;L of the E294-302 tetramer mix is added to each test.</li>
	<li>Add 20 &#181;L of the E294-302 tetramer mix to the 96-well plate. By the end of this step, the final volume in each well should be 40 &#181;L.Incubate the plate in the dark at room temp for 30 min.</li>
	<li>Add primary antibodies (FITC-conjugated or APC-conjugated anti-CD3 (0.2 mg/mL), PerCP-conjugated anti-CD8 (0.2 mg/mL)) at 1 &#181;L/test to the cell suspension and, then, incubate it at 4 &#176;C for 30 min in the dark.</li>
	<li>Wash the cells 2x with 2 mL of FACS buffer and centrifuge them at 600 x g for 5 min. Carefully aspirate the supernatant and resuspend the cells with 200 &#181;L of FACS buffer.</li>
	<li>Store the samples temporarily at 4 &#176;C in the dark until the flow cytometric analysis.</li>
	<li>Use the following gating strategy for the flow cytometric analysis.
	<ol>
		<li>Create a gate on diagonally clustered singlets by plotting a forward scatter (FSC) versus side scatter (SSC) area.</li>
		<li>Then, gate on CD3+ cells by side scatter (SSC) versus CD3; next, gate on CD3+ CD8+ cells; finally, outline CD8+ tetramer+ cells19.</li>
	</ol>
	</li>
</ol>
7. Histopathology, Immunofluorescence, and Immunohistochemistry Assay
<ol>
	<li>Histopathology assay
	<ol>
		<li>Collect the brain and testis tissues of the ZIKV-infected Ifnar1-/- mice 7 d post-inoculation and fix them in 4% neutral-buffered formaldehyde. 
		CAUTION:Paraformaldehyde is toxic; wear appropriate personal protective equipment.</li>
		<li>Embed the tissue in paraffin.</li>
		<li>Section the tissue at 5 mm using a vibratome.</li>
		<li>Stain the tissue with hematoxylin and eosin (H&#38;E).</li>
	</ol>
	</li>
	<li>Immunohistochemistry assay
	<ol>
		<li>Deparaffinize, rehydrate, and antigen-retrieve the tissue sections, based on procedures described previously21.</li>
		<li>Treat the tissue sections with 3% H2O2 in PBS (pH 7.6) for 10 min and block them with 1% bovine serum albumin (BSA) for 10 min.</li>
		<li>Incubate the tissue sections with rat anti-mouse CD3 antibody (dilution: 1/1,000) for 8 h at room temperature and, then, incubate them at 4 &#176;C overnight.</li>
		<li>Rinse the tissues with PBS and, then, incubate them with 3 drops of biotinylated secondary antibody (dilution: 1/1,000) for 2 h at room temperature, followed by 3 drops of avidin-biotin-peroxidase (dilution: 1/200) at room temperature for 30 min.</li>
		<li>Bind, with 3 drops of 30, 30-diaminobenzidine tetrahydrochloride (dilution: 1/1,000), as described previously22.</li>
		<li>Counterstain the tissue sections with Mayer&#39;s hematoxylin.</li>
	</ol>
	</li>
	<li>Immunofluorescence assay
	<ol>
		<li>Air-dry the frozen testis sections (6 mm) for 10 min at room temperature.</li>
		<li>Fix them with ice-cold acetone for 10 min.</li>
		<li>Wash the sections with PBS for 3x and block them with a blocking buffer (1% BSA, 0.3% Triton, 1x PBS) at 37 &#176;C for 30 min.</li>
		<li>Incubate the tissue sections with primary antibody (Z6) (20 &#181;g/mL) at 4 &#176;C overnight.</li>
		<li>Rinse the tissues with PBS and apply the secondary antibody (dilution factor: 1/200) for 1 h at 37 &#176;C.</li>
		<li>Wash the tissue sections with PBS and counterstain them for nuclei using 4&#39;, 6-diamidino-2-phenylindole (DAPI) (dilution factor: 1/1,000), following the manufacturer&#39;s instructions.</li>
	</ol>
	</li>
</ol>

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F., Lifshitz, J., Ziebell, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Primer+for+immunohistochemistry+on+cryosectioned+rat+brain+tissue:+example+staining+for+microglia+and+neurons.">Primer for immunohistochemistry on cryosectioned rat brain tissue: example staining for microglia and neurons.</a> Journal of Visualized Experiments. (99), e52293 (2015).</li><li>Zhou, M., 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=Screening+and+identification+of+severe+acute+respiratory+syndrome-associated+coronavirus-specific+CTL+epitopes.">Screening and identification of severe acute respiratory syndrome-associated coronavirus-specific CTL epitopes.</a> The Journal of Immunology. 177 (4), 2138-2145 (2006).</li><li>Barzon, L., Lavezzo, E., Palu, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zika+virus+infection+in+semen:+effect+on+human+reproduction.">Zika virus infection in semen: effect on human reproduction.</a> The Lancet Infectious Diseases. 17 (11), 1107-1109 (2017).</li><li>Ma, W., 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=Zika+Virus+Causes+Testis+Damage+and+Leads+to+Male+Infertility+in+Mice.">Zika Virus Causes Testis Damage and Leads to Male Infertility in Mice.</a> Cell. 167 (6), 1511-1524 (2016).</li><li>Li, X. F., 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=Characterization+of+a+2016+Clinical+Isolate+of+Zika+Virus+in+Non-human+Primates.">Characterization of a 2016 Clinical Isolate of Zika Virus in Non-human Primates.</a> EBioMedicine. 12, 170-177 (2016).</li></ol>

The authors have nothing to declare.

Immunogenic T-cell epitope plays a significant role in cellular immunity against pathogens23. Thus, the detection of ZIKV-specific T cells in immunoprivileged organs is a critical methodology to understand T-cell responses against the natural ZIKV infection. Meanwhile, T-cell response detection is an excellent tool to investigate the efficacy of the viral vaccine. Here, we show a comprehensive protocol to visualize the experiments, which include the isolation of lymphocytes from the spleen, brain, and testes of ZIKV-infected mice, the preparation of the immunodominant epitope E294-302 tetramer, and the recognition of ZIKV-specific CD8+ T cells in immunoprivileged organs of ZIKV-infected mice.
A previous study showed that a live ZIKV or its RNA can be detected in the semen of male patients, which indicates that the ZIKV can bypass the blood-testis barrier and replicate itself in the reproductive system24. Previously, we also showed that the ZIKV can cause testes damage and lead to male infertility in mice25. ZIKV infection can lead to viremia in rhesus monkeys, and the viral RNA can be detected in the central nervous system (CNS), as well as in the visceral organs. Immunohistochemistry revealed that ZIKV-specific antigens were presented in the CNS and the multiple peripheral organs26. Also, in murine models, ZIKV infection can induce a robust antiviral CD8+ T-cell response in the spleen and CNS26.
Compared to previous work, this study establishes systematic methods to detect ZIKV-specific CD8+ T-cell responses in the brain and testes, which are immunoprivileged sites. It is important to assess the functionality of virus-specific T cells in the immunoprivileged organs of the ZIKV-infected mice. The usage of tetramers to detect ZIKV-specific CD8+ T-cell responses in immunoprivileged organs would greatly enhance our understanding of ZIKV infections and their host immune responses. Using E294-302 tetramer, virus-specific T cells in brain and testis can be isolated by flow cytometry, to investigate the cellular mechanisms of the protection and immunopathogenesis during a ZIKV infection. Meanwhile, it is helpful for researchers to investigate further the functions of the CD8+ T cells to control the ZIKV, or to enhance the immunopathogenesis in these organs during ZIKV infection.
To analyze the antigen-specific murine CD8+ T-cell responses in the immunoprivileged organs, we prepared H-2Db-E294-302 tetramer and detected the CD8+ T cells by flow cytometry. Tetramers are a powerful tool to detect antigen-specific T cells. Here, three types of fluorochrome-conjugated streptavidin (APC, PE, and BV421) were generated. Although there are no statistically significant differences in the APC-, BV421-, and PE-labeled tetramers for detecting antigen-specific T cells, PE-labeled pMHC-I tetramers yielded the best results. Hence, the PE-labeled tetramer was used throughout this study. Interestingly, based on the PE-labeled H-2Db-E294-302 tetramer, we detected high ratios of antigen-specific T cells in both the brain and testes, which indicate the migration ability of the virus-specific T cells from the blood to immunoprivileged organs.
However, there are some limitations to the protocol. The H-2Db-E294-302 tetramer is not useful for human T-cell detection, because tetramer detection is dependent on MHC restriction. The screening of immunodominant HLA-restricted peptides is still needed. Besides, retro-orbital infection is effective for a ZIKV infection but might be not a convenient operation for some investigators. Thus, other routes of infection, including peritoneal, subcutaneous, or intravenous, are also recommended.
In the protocol described here, a critical step is the isolation of monocytes from brain and testis. It is important to acquire high-quality lymphocytes; thus, it is important to pay attention to, for example, the centrifugal speed, the strength of the grinding tissue, and the dissection of the brain and testis tissue. Besides, for tetramer preparation, protease inhibitors (PMSF, pepstatin, leupeptin) are helpful when protecting a protein from being degraded. Therefore, it makes sense to add a protease inhibitor to the refolding buffer and exchange the buffer during the process of the tetramer preparation.
In conclusion, we present the methods of detecting antigen-specific T-cell responses in the immunoprivileged organs of the Ifnar1-/- mouse model for a ZIKV infection. This platform can be widely applied to investigate the immune mechanisms of emerging and re-emerging viruses which can bypass the barriers between the blood and the immunoprivileged organs. Moreover, this study may pave the way for the future development of candidate vaccines and immunotherapies.

The ZIKV is a mosquito-borne flavivirus that was first isolated in 1947 in Uganda from a febrile rhesus macaque. Recently, the ZIKV has become a public health emergency, due to its rapid dissemination in the Americas and its unexpected link to microcephaly and Guillain-Barr&#233; syndrome1,2,3. From epidemiological data, the ZIKV has been suspected to be the cause of the Guillain-Barr&#233; syndrome in around 1 per 4,000 infected adults4. Moreover, a correlation between the ZIKV and testes infection/damage in the mouse model has been demonstrated, suggesting that the ZIKV infection, under certain circumstances, can bypass the blood-testis barrier and eventually lead to male infertility5. These findings highlight the importance of completely understanding the induction of protective or pathologic immune responses during a ZIKV infection.
Much remains to be learned about the cellular immune responses to the ZIKV. CD4+ and CD8+ T-cell responses to the capsid, envelope, and nonstructural protein 1 (NS1) have been observed in ZIKV-infected monkeys and humans6,7,8. In mice, several studies have indicated that CD8+ T cells play a protective role in controlling the ZIKV replication9,10,11. Importantly, Jurado et al. demonstrated that a ZIKV infection results in the breakdown of the blood-brain barrier and perivascular infiltration of CD8+ effector T cells within the testes of Ifnar1-/- mice. Furthermore, they showed that CD8+ T cells instigate ZIKV-associated paralysis and appear to play a role in the neonatal brain immunopathology. In a previous study, we prepared the ZIKV-E294-302 tetramer and showed that ZIKV-specific CD8+ T cells exist in the brains and spinal cords of ZIKV-infected Ifnar1-/- mice, which may have important implications for the design and development of ZIKV vaccines10.
In response to the urgent need for vaccination to prevent ZIKV infection, several vaccines are in the preclinical stages of development, including RNA vaccines, recombinant vector-based vaccines, and purified protein subunit vaccines. The plasmid DNA vaccine is in phase 1 clinical trials12. The evaluation of safety and efficacy of ZIKV vaccines is, therefore, important. One advantage of the vaccines is their ability to elicit specific T-cell responses, which may be important for protection against the ZIKV. By using ZIKV-derived T-cell epitope-related tetramers, the T-cell immunoreactivity induced by an adenovirus-vector-based ZIKV vaccine could be detected in immunized mice, and both M and E glycoproteins were shown to induce robust antigen-specific CD8+ T-cell immunoreactivity13.
During a virus infection, the recognition of peptide antigens presented by major histocompatibility complex (MHC) molecules to the T-cell receptor (TCR) is an important T-cell-mediated mechanism for protecting the host14. Based on this theory, tetramer technology is a unique tool to elucidate the roles that antigen-specific T cells play in regulating the immune responses15. This protocol describes the establishment of the Ifnar1-/- mouse model for ZIKV infections, and the detection of reactive T cells in the spleen, brain, and testes of the mice by using tetramer technology. Additionally, we used the ZIKV-E294-302 tetramer to detect and evaluate T-cell immunoreactivity induced by a ZIKV vaccine (AdC7-M/E) in immunized mice. This study provides guidance for investigating T-cell responses in immunoprivileged organs and provides a reference for the potential applications in the placenta or fetal brain.

<table><tbody><tr><td>Z6</td><td>our lab</td><td></td><td>Ma W, Li S, Ma S, &lt;em&gt;et al.&lt;/em&gt; Zika virus causes testis damage and leads to male infertility in mice. Cell, 2016, 167: 1511-1524 e1510</td></tr><tr><td>CD3</td><td>Santa Cruz</td><td>sc-1127; RRID: AB_631128</td><td></td></tr><tr><td>Fluorescein-Conjuated Affinipure Goat anti-human IgG(H+L)</td><td>ZSGB-BIO</td><td>ZF-0308</td><td></td></tr><tr><td>Rabbit Anti-Goat IgG, FITC Conjugated</td><td>CWBIO</td><td>CW0115</td><td></td></tr><tr><td>FITC anti-mouse CD3</td><td>Biolegend</td><td>17A2</td><td></td></tr><tr><td>APC anti-mouse CD3</td><td>Biolegend</td><td>100236</td><td></td></tr><tr><td>PerCP anti-mouse CD8a</td><td>Biolegend</td><td>100732</td><td></td></tr><tr><td>Percoll</td><td>GE Healthcare</td><td>P8370</td><td></td></tr><tr><td>PMSF</td><td>Ameresco</td><td>0754-5G</td><td>Toxic and corrosive reagent.&lt;br/&gt; Handle with care</td></tr><tr><td>Streptadivin</td><td>BD</td><td>S4762-FZ</td><td>Gives a clear solution at 10mg/ml in PBS and&amp;nbsp; stored at -20 &amp;deg;C</td></tr><tr><td>Pepstatin</td><td>Sigma</td><td>P4265-5MG</td><td>5 mg in 2.5 mL DMSO, aliquots stored at -20 &amp;ordm;C</td></tr><tr><td>Leupeptin</td><td>Sigma</td><td>L8511</td><td>5 mg in 2.5 mL dH&lt;sub&gt;2&lt;/sub&gt;O, aliquots stored at - 20 &amp;ordm;C</td></tr><tr><td>Peptides</td><td>Scilight-peptide</td><td></td><td>Must be resuspended in DMSO and stored at -20 &amp;deg;C</td></tr><tr><td>RPMI 1640</td><td>Hyclone</td><td>SH30809.01</td><td>Must be stored at 4 &amp;deg;C</td></tr><tr><td>DMSO</td><td>MP</td><td>219605590</td><td>Store at room temperature.</td></tr><tr><td>APC-Streptadivin</td><td>BD</td><td>554067</td><td>Must be stored and maintained at&lt;br/&gt; 4 &amp;deg;C. Do not freeze.</td></tr><tr><td>FITC-Streptadivin</td><td>BD</td><td>554060</td><td>Must be stored and maintained at&lt;br/&gt; 4 &amp;deg;C. Do not freeze.</td></tr><tr><td>PE-Streptadivin</td><td>BD</td><td>554061</td><td>Must be stored and maintained at&lt;br/&gt; 4 &amp;deg;C. Do not freeze.</td></tr><tr><td>BV421-Streptadivin</td><td>BD</td><td>563259</td><td>Must be stored and maintained at&lt;br/&gt; 4 &amp;deg;C. Do not freeze.</td></tr><tr><td>PageRuler Unstained Protein Ladder</td><td>Thermo Fisher Scientific&amp;nbsp;</td><td>26614</td><td>Must be stored at 4 &amp;deg;C</td></tr><tr><td>Cell Strainers</td><td>BF</td><td>BF10-5040</td><td>Store at room temperature.</td></tr><tr><td>Amicon Ultra 100 kDa</td><td>Millipore</td><td>UFC510024</td><td>Store at room temperature.</td></tr><tr><td>Ultracentrifuge</td><td>Thermo Fisher Scientific&amp;nbsp;</td><td></td><td></td></tr><tr><td>FACS Cantol</td><td></td><td></td><td>Flow cytometer must contain lasers and filters that are compatible with the staining panel used.</td></tr><tr><td>Superdex 200 Increase 10/300 GL&amp;nbsp;</td><td>GE healthcare</td><td>28990944</td><td></td></tr><tr><td>AKTA PURE</td><td>GE healthcare</td><td></td><td></td></tr><tr><td>red blood cell lysis buffer</td><td>Solarbio</td><td>R1010</td><td>Store at 4 &amp;deg;C.</td></tr></tbody></table>

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.

Following these methods, we have developed a murine model for ZIKV infections. Ifnar1-/- mice at 6&#8211;8 weeks of age were infected with 1 x 104 focus-forming units (FFU) of the ZIKV by retroorbital injection. Pathological symptoms and signs (Figure 1A), as well as weight changes (Figure 1B), were observed in the Ifnar1-/- mice after an infection with the ZIKV. The murine brains showed obvious edema and hyperemia (Figure 1C). Meanwhile, the testes shrank gradually (Figure 1D). Furthermore, pathological changes and the destruction of tissue were found in the brain and testes (Figure 2A). We performed an immunofluorescence assay to detect the ZIKV in the brain and testes (Figure 2B). High viral loads were detected in the brain and testis by immunostaining (Figure 2B). Immunohistochemistry showed a robust infiltration of CD3+ T cells into the mice brain after the infection with the ZIKV (Figure 2C).
To detect and evaluate ZIKV-specific T-cell responses, we prepared a mouse MHC-I H-2Db-E294-302 tetramer. The peptide E294-302 can help the H-2Db renature properly and yield a high amount of the soluble MHC-I (Figure 3A). In the shift assay, a high efficiency in biotinylation could be observed (Figure 3B). Subsequently, three streptavidin fluorescence (APC, PE, and BV421)-tagged pMHC-I tetramers were produced to detect ZIKV-specific T cells (Figure 3C). The PE-labeled tetramer had a higher efficacy to detect the specific CD8+ T cell compared to the APC- and BV421-labeled tetramers, though the difference was not statistically significant.
Using the E294-302 tetramer, we detected ZIKV-specific T lymphocytes in the spleen of the infected mice by flow cytometry at 7 d post-inoculation of the ZIKV (3.49 &#177; 0.45%). Also, similar to the method described in section 3 of this protocol, with 4 weeks post-immunization of AdC7-M/E vaccine, ZIKV-specific T lymphocytes were detected in the spleen (6.89 &#177; 1.36%) (Figure 4).
Furthermore, we detected the lymphocytes infiltrated into the immunoprivileged organs, such as the brain and testes, after the ZIKV infection. The gates were set to select for CD3+CD8+ T cells in total lymphocytes of the brain and testes. A high ratio of the E294-302 tetramer-specific T cells could be detected in the brain (42.2% in CD3+CD8+ T cells) and the testicular (26.4% in CD3+CD8+ T cells) lymphocytes (Figure 5).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/58110/58110fig1.jpg" /> 
Figure 1: Characterization of the ZIKV infection in Ifnar1-/- mice. Ifnar1-/- mice at 6&#8211;8 weeks of age were infected with 104 focus-forming units (FFU) of the ZIKV by retroorbital injection, and mice injected with PBS were used as uninfected controls. The (A) morphology and (B) weight changes of infected Ifnar1-/- mice were monitored. The red arrows indicate Ifnar1-/- mice presented with myeloparalysis and motor paraparesis after the infection. (C) Brains at 7 d post-inoculation and (D) testes at 0, 7, 14, and 30 days post-inoculation were harvested. Representative images of the brain and testes from the mice are shown with a ruler to indicate the sizes. The error bars represent the mean &#177; SEM. n = 10 mice per group per experiment. <a href="https://www.jove.com/files/ftp_upload/58110/58110fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/58110/58110fig2.jpg" /> 
Figure 2: Detection of the ZIKV and lymphocytes in the brain and testis of ZIKV-infected Ifnar1-/- mice. (A) This panel shows histopathological changes in the brain and testes from ZIKV-infected mice compared with negative controls at 7 d post-inoculation. Scale bar = 25 &#181;m (left panel) and 50 &#181;m (right panel). (B) An immunofluorescence assay was performed with the anti-ZIKV Z6 antibody (green). All tissue samples were collected from ZIKV-infected mice at 7 d post-inoculation. The nuclei were stained with DAPI (blue). Scale bar = 50 &#181;m. (C) Immunohistochemistry shows a robust infiltration of CD3+ T cells into the brain and testis. Scale bar = 25 &#181;m (left panel) and 50 &#181;m (right panel). Purple indicates hematoxylin, brown represents the CD3 antibody. <a href="https://www.jove.com/files/ftp_upload/58110/58110fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/58110/58110fig3.jpg" /> 
Figure 3: Preparation of ZIKV-specific pMHC-I tetramers. (A) The binding of E294-302 to H-2Db is elucidated by an in vitro refolding. Blue indicates the H-2Db-E294-302 protein. Orange represents the negative control without peptide. (B) This panel shows the H-2Db-E294-302 shift assay. (C) The mock represents a PBS control. Three streptavidin fluorescence (APC, PE, and BV421)-tagged pMHC-I tetramers were used to detect ZIKV-specific T cells. <a href="https://www.jove.com/files/ftp_upload/58110/58110fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/58110/58110fig4.jpg" /> 
Figure 4:&#160;Flow cytometric analysis of virus-specific CD8+ T cells in the spleen of ZIKV-infected and vaccine-immunized mice. Ifnar1-/- mice at 6-8 weeks of age were either infected with 104 focus-forming units (FFU) of ZIKV or received a single-dose of 4 x 1010 viral particles of AdC7-M/E or PBS as a negative control. After 7 days post-infection or 4 weeks post-vaccination, mouse splenocytes were harvested and analyzed by flow cytometry. The data are shown as mean &#177; SD. Statistical analysis was performed using one-way ANOVA (not significant: P &#62; 0.05; *P &#60; 0.05; **P &#60; 0.01; ***P &#60; 0.001; ****P &#60; 0.0001). <a href="https://www.jove.com/files/ftp_upload/58110/58110fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/58110/58110fig5.jpg" /> 
Figure 5:&#160;Gating strategy and representative results of virus-specific CD8+ T cells in the brain and testes of ZIKV-infected mice.&#160;Representative plots are shown for the infiltrated lymphocytes in (A) the brain and (B) the testis. A succession of gates is set to select lymphoid-scatter+ and CD3+ events. Of these, CD8+ events are gated for the analysis of epitope-specific T cells. <a href="https://www.jove.com/files/ftp_upload/58110/58110fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Evaluation of Zika Virus-specific T-cell Responses in Immunoprivileged Organs of Infected Ifnar1-/- Mice at JoVE.com

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.

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 ...

evaluation-zika-virus-specific-t-cell-responses-immunoprivileged

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JoVE Journal

Immunology and Infection

7.9K Views.  Wenzhou Medical University. Tijdens de Zika-virusinfectie kunnen T-cellen immuunprivilegeerde organen infiltreren voor viruseliminatie, maar kunnen ze ook bijdragen aan immunopathogenese, zoals het Guillain-Barre syndroom of testeenletsel. Het belangrijkste voordeel van deze techniek is dat het de tetramer-gebaseerde detectie van antigeen-specifieke T-cellen in immunoprivileged organen vergemakkelijkt, zowel tijdens zika virusinfectie en na vaccin immunisatie. In dit model wordt Zika-virusinfectie geïnitieerd in interf...

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

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

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 ...

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.

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

Using Zebrafish Models of Human Influenza A Virus Infections to Screen Antiviral Drugs and Characterize Host Immune Cell Responses

Each year, seasonal influenza outbreaks profoundly affect societies worldwide. In spite of global efforts, influenza remains an intractable healthcare burden. The principle strategy to curtail infections is yearly vaccination. In individuals who have contracted influenza, antiviral drugs can mitigate symptoms. There is a clear and unmet need to develop alternative strategies to combat influenza. Several animal models have been created to model host-influenza interactions. Here, protocols for generating zebrafish models for systemic and localized human influenza A virus (IAV) infection are described. Using a systemic IAV infection model, small molecules with potential antiviral activity can be screened. As a proof-of-principle, a protocol that demonstrates the efficacy of the antiviral drug Zanamivir in IAV-infected zebrafish is described. It shows how disease phenotypes can be quantified to score the relative efficacy of potential antivirals in IAV-infected zebrafish. In recent years, there has been increased appreciation for the critical role neutrophils play in the human host response to influenza infection. The zebrafish has proven to be an indispensable model for the study of neutrophil biology, with direct impacts on human medicine. A protocol to generate a localized IAV infection in the Tg(mpx:mCherry) zebrafish line to study neutrophil biology in the context of a localized viral infection is described. Neutrophil recruitment to localized infection sites provides an additional quantifiable phenotype for assessing experimental manipulations that may have therapeutic applications. Both zebrafish protocols described faithfully recapitulate aspects of human IAV infection. The zebrafish model possesses numerous inherent advantages, including high fecundity, optical clarity, amenability to drug screening, and availability of transgenic lines, including those in which immune cells such as neutrophils are labeled with fluorescent proteins. The protocols detailed here exploit these advantages and have the potential to reveal critical insights into host-IAV interactions that may ultimately translate into the clinic.

Systemic and localized zebrafish infection models for human influenza A virus are demonstrated. Using a systemic infection model, zebrafish can be used to screen antiviral drugs. Using a localized infection model, zebrafish can be used to characterize host immune cell responses.

Each year, seasonal influenza outbreaks profoundly affect societies worldwide. In spite of global efforts, influenza remains an intractable healthcare ...

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 ...

Establishing Mouse Models for Zika Virus-induced Neurological Disorders Using Intracerebral Injection Strategies: Embryonic, Neonatal, and Adult

The Zika virus (ZIKV) is a flavivirus currently endemic in North, Central, and South America. It is now established that the ZIKV can cause microcephaly and additional brain abnormalities. However, the mechanism underlying the pathogenesis of ZIKV in the developing brain remains unclear. Intracerebral surgical methods are frequently used in neuroscience research to address questions about both normal and abnormal brain development and brain function. This protocol utilizes classical surgical techniques and describes methods that allow one to model ZIKV-associated human neurological disease in the mouse nervous system. While direct brain inoculation does not model the normal mode of virus transmission, the method allows investigators to ask targeted questions concerning the consequence after ZIKV infection of the developing brain. This protocol describes embryonic, neonatal, and adult stages of intraventricular inoculation of ZIKV. Once mastered, this method can become a straightforward and reproducible technique that only takes a few hours to perform.

Here we describe a method for establishing a model of Zika virus-induced microcephaly in mouse. This protocol includes methods for embryonic, neonatal, and adult-stage intracerebral inoculation of the Zika virus.

The Zika virus (ZIKV) is a flavivirus currently endemic in North, Central, and South America. It is now established that the ZIKV can cause microcephaly ...

Neuroscience

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 ...

Evaluation of T Follicular Helper Cells and Germinal Center Response During Influenza A Virus Infection in Mice

T Follicular Helper (Tfh) cells are an independent CD4+&#160;T cell subset specialized in providing help for germinal center (GC) development and generation of high-affinity antibodies. In influenza virus infection, robust Tfh and GC B cell responses are induced to facilitate effective virus eradication, which confers a qualified mouse model for Tfh-associated study. In this paper, we described protocols in detection of basic Tfh-associated immune response during influenza virus infection in mice. These protocols include: intranasal inoculation of influenza virus; flow cytometry staining and analysis of polyclonal and antigen-specific Tfh cells, GC B cells and plasma cells; immunofluorescence detection of GCs; enzyme-linked immunosorbent assay (ELISA) of influenza virus-specific antibody in serum. These assays basically quantify the differentiation and function of Tfh cells in influenza virus infection, thus providing help for studies in elucidating differentiation mechanism and manipulation strategy.

This paper describes protocols of evaluating Tfh and GC B response in mouse model of influenza virus infection.

T Follicular Helper (Tfh) cells are an independent CD4+&#160;T cell subset specialized in providing help for germinal center (GC) development and ...

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

A Focus-Forming Assay for Quantifying Virus Titers in the Organs of an Infected Mouse

Source: Brien, J. D. et al., <a href="https://app.jove.com/v/59632">Isolation and Quantification of Zika Virus from Multiple Organs in a Mouse.</a> J. Vis. Exp.&#160;(2019)
The video demonstrates a procedure for quantifying the Zika virus in multiple mouse organs via a focus-forming assay. The process involves infecting mammalian cell monolayers with virus-infected tissue homogenates, followed by the use of methyl cellulose to prevent viral spread. Subsequently, immunostaining is employed to enable precise quantification and measurement of organ-specific infectivity.

All procedures involving animal models have been reviewed by the local institutional animal care committee and the JoVE veterinary review board.

1. Organ ...

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

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