This work was supported by NIH grants to T.W. (R01AI072060 and R01AI099123). G. Xie was supported by a Sealy Center for Vaccine Development Predoctoral Fellowship. We thank Dr. Richard Flavell (Howard Hughes Medical Institute, Yale University School of Medicine, New Haven) and Dr. Shizuo Akira (Osaka University, Japan) for providing the MyD88&#8211;/&#8211; mice and Dr. Y Cong (UTMB, Galveston) for providing OTII transgenic mice.

All animal experiments were approved by the Animal Care and Use Committee at the University of Texas Medical Branch.
1. Isolation of DCs from Non-infected and WNV-infected Mice
<ol>
	<li>Age- and sex- match 6-10 week-old, wild-type C57BL/6 (B6) and MyD88&#8722;/&#8722;mice. Inoculate intraperitoneally (i.p.) with 500 plaque forming unit (PFU) of WNV NS4B- P38G mutant. At day 3 post-infection, euthanize B6 and MyD88&#8722;/&#8722; mice with CO2. Use non-infected mice of both groups as controls. Use three mice from each group.</li>
	<li>Wet fur on left side of sacrificed mouse using 70% ethanol and cut away the fur along the left side of the mouse, about half-way between the front and back legs. Cut open the body cavity. Remove the spleen by using the forceps. Place the spleen in a Petri dish with RPMI.</li>
	<li>Isolate splenic DCs by using anti-CD11c magnetic beads according to the manufacturer&#8217;s instructions.</li>
</ol>
2. Purification and Labeling of T Cells of OTII Transgenic Mice
<ol>
	<li>Harvest one spleen from a na&#239;ve OTII mouse as described in step 1.2 above and homogenize the spleen between the frosted ends of two slides. Transfer the cell suspension to a 15 ml conical tube, add RPMI medium up to 14 ml. Let the suspension sit for 5 min and transfer 13 ml of it to a new 15 ml conical tube.</li>
	<li>Isolate splenic CD4+ T cells by using a CD4+ T cell isolation kit according to the manufacturer&#8217;s instructions.</li>
	<li>Transfer cells into a 50 ml conical tube, wash twice with PBS. Resuspend cells in PBS with 0.5% bovine serum albumin (BSA) at 1 x 106 cells per ml, and add 0.5 &#181;mol/ml of CFSE. Incubate at 37 &#176;C for 10 min, protected from light.</li>
	<li>Add 5 ml cold complete medium (RPMI-1640 with 10% heat-inactivated fetal bovine serum, 1/100 vol antibiotics/antimycotics, 1/100 vol L-glutamine and 1/1,000 vol of 1,000 x 2-mercaptoethanol).</li>
	<li>Incubate on ice for 5 min. Wash cells once with PBS, fix 0.2 x 106 labeled CD4+ T cells in 2% PFA and acquire on a flow cytometer. Use this sample to determine the basal level of CFSE. Re-suspend the rest of labeled cells in complete medium.</li>
</ol>
3. Co-culture OTII T cells with DCs of WNV-infected Mice
<ol>
	<li>Culture 2 x 105 purified CD4+ T cells of OTII mice alone or with purified DCs of wild-type or MyD88&#8722;/&#8722; mice (2 x 104) in a 24 well plate with or without OVA residue 323-339 (1 g/ml) in 1 ml complete medium per well.</li>
	<li>Incubate cells at 37 &#176;C for 5 days. Harvest cells, wash twice in FACS buffer (PBS with 1% FBS) and fix in 0.25 ml 2% PFA. Vortex immediately.</li>
</ol>
4. Flow Cytometry Analysis of In Vitro T Cell Priming
<ol>
	<li>For acquisition, double click the flow cytometry software icon. For a density plot of linear FSC-A vs. linear SSC-A, select channels 0 to 200,000 on FSC-A and 0 to 200,000 on SSC-A. Then create a gate on live cells (P2; see Figure 1A).</li>
	<li>To analyze the fluorescence intensity of CFSE, open the histogram for the FL1 channel and acquire 20,000 events on the gated population. Set up a marker on samples for OTII cells cultured alone (Figure 1A).</li>
	<li>Acquire samples for OTII cells co-cultured with wild-type DCs (Figure 1B) or MyD88&#8722;/&#8722; DCs (Figure 1C) in a similar way.</li>
</ol>
5. Isolation and Stimulation of Splenocytes for Cytokine Assays
<ol>
	<li>Infect B6 and MyD88&#8722;/&#8722;mice with WNV NS4B-P38G mutant using the same procedure as described in step 1.1. At day 30 post-infection, re-challenge surviving mice with 2000 PFU of the wild-type WNV strain i.p. At days 8 and 21 post-primary WNV infection or at day 4 following secondary infection, euthanize mice with CO2 for collection of spleens. 
	NOTE: We used 2-3 mice per group for each time point.</li>
	<li>Make a single cell suspension of splenocytes as described above in step 1.2 &#38; step 2.2. Count cells using a hemocytometer and re-suspend them in 10 ml complete medium.</li>
	<li>Dilute cells with complete medium to 2.5 x 106 cells/ml. Add 1 ml of splenocytes in a 1.5 ml micro-centrifuge tube.</li>
	<li>To simulate CD8+ T cells, dilute WNV-specific NS4B and E peptides (SSVWNATTA and IALTFLAV) to 1 mg/ml in DMSO. For stimulation of CD4+ T cells, dilute WNV-specific NS3 and E peptides (RRWCFDGPRTNTILE and PVGRLVTVNPFVSVA) to 1 mg/ml in DMSO. Add 10 &#181;l of peptides to the cells followed by 1 &#181;l of Brefeldin A solution. Use cells without peptides treatment as controls. Mix the cells.</li>
	<li>Punch two holes with an 18 G needle in the cap of the tube. Incubate cells at 37 &#176;C for 5 hr.</li>
</ol>
6. Intracellular Cytokine Staining
<ol>
	<li>Transfer cells to a new micro-centrifuge tube. Spin cells for 5 min at 300-400 x g and pour off supernatant. Add 1 ml FACS buffer, spin 5 min at 300-400 x g and re-suspend cells by pipetting with 120 &#181;l FACS buffer.</li>
	<li>Add 2 &#181;l Fc blocker and incubate cells at room temperature for 10 min. Add 1 ml FACS buffer to each tube. Spin 5 min at 300 - 400 x g.</li>
	<li>Re-suspend cells in 300 &#181;l FACS buffer and split them into three tubes (about 0.8 x 106 cells per tube). As shown in Table 1, reserve the first tube of each culture condition for rat IgG-PE staining. For the second tube, add 3 &#181;l of anti-CD4 APC to CD4 peptides-treated cells, 3 &#181;l of anti-CD8 FITC to CD8 peptides-treated cells or both antibodies to cells without peptides treatment. Use the third tube for compensation staining. For each culture condition, use three tubes of cells stained with APC-conjugated CD4, FITC-conjugated CD8 or PE- labeled CD3 antibodies alone (3 &#181;l per tube) as compensation controls for FL1, FL2 and FL4 channels.</li>
	<li>Vortex cells briefly. Leave on ice for 20 min and protect from light. Add 1.4 ml FACS buffer. Spin 5 min at 300-400 x g and pour off supernatant.</li>
	<li>Agitate to disrupt cell pellet (or briefly vortex). Re-suspend cell pellet in 250 &#181;l fixation/permeabilization solutionby pipetting. Incubate at room temperature for 20 min and protect from light.</li>
	<li>Add 1.2 ml FACS buffer. Spin 5 min at 300-400 x g and resuspend cells in 300 &#181;l FACS buffer. 
	NOTE: At this point, cells can be transferred to a BL2 laboratory for further processing or stored in a refrigerator and protected from light for up to three days.</li>
	<li>Add 500 &#181;l FACS buffer. Spin 5 min at 300-400 x g and resuspend cells in 500 &#181;l of 1x permeabilization/wash buffer. Spin 5 min at 300-400 x g.</li>
	<li>Re-suspend cells in 100 &#181;l 1x Perm/Wash, add 3.5 &#181;l anti-IFN&#947;-PE to the tube previously added with antibodies for CD4 and/or CD8 T cell markers in step 6.3 and 3.5 &#181;l rat IgG-PE in the tube reserved for IgG control for 25 min on ice and protect from light. Wash cells by adding 1.4 ml of 1x permeabilization/wash buffer. Spin 5 min at 300-400 x g. Repeat the washing step by adding 1.4 ml 1x permeabilization/wash buffer.</li>
	<li>Spin 5 min at 300-400 x g and decant supernatant. Wash cells by adding 1.4 ml of FACS buffer and re-suspend in 400 &#181;l of FACS buffer for final acquisition.</li>
</ol>
7. Flow Cytometry Analysis of Intracellular Cytokine Staining
<ol>
	<li>Use the same acquisition settings as in step 4.1. Create a gate on live cells (P2; see Figure 2A). Adjust the voltages using the compensation tubes for each group.</li>
	<li>Open two new dot plots, one to display data collected for FL1 vs. FL2 (CD8 vs. IFN-&#947;), and the other one is to display data collected for FL4 vs. FL2 (CD4 vs. IFN-&#947;). Acquire 50,000 events for the gated population of each sample.</li>
</ol>

<ol>
	<li>Campbell, G. L., Marfin, A. A., Lanciotti, R. S., Gubler, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=West+Nile+virus.">West Nile virus.</a> Lancet Infect. Dis. 2, 519-529 (2002).</li><li>Welte, T., 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=Immune+responses+to+an+attenuated+West+Nile+virus+NS4B-P38G+mutant+strain.">Immune responses to an attenuated West Nile virus NS4B-P38G mutant strain.</a> Vaccine. 29, 4853-4861 (2011).</li><li>Iwasaki, A., Medzhitov, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Toll-like+receptor+control+of+the+adaptive+immune+responses.">Toll-like receptor control of the adaptive immune responses.</a> Nat. Immunol. 5, 987-995 (2004).</li><li>Akira, S., Hemmi, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recognition+of+pathogen-associated+molecular+patterns+by+TLR+family.">Recognition of pathogen-associated molecular patterns by TLR family.</a> Immunol. Lett. 85, 85-95 (2003).</li><li>Xie, G., 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=A+West+Nile+virus+NS4B-P38G+mutant+strain+induces+adaptive+immunity+via+TLR7-MyD88-dependent+and+independent+signaling+pathways.">A West Nile virus NS4B-P38G mutant strain induces adaptive immunity via TLR7-MyD88-dependent and independent signaling pathways.</a> Vaccine. 31 (38), 4143-4151 (2013).</li><li>Fang, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=gammadelta+T+cells+promote+the+maturation+of+dendritic+cells+during+West+Nile+virus+infection.">gammadelta T cells promote the maturation of dendritic cells during West Nile virus infection.</a> FEMS Immunol. Med. Microbiol. 59, 71-80 (2010).</li><li>Silva, M. C., Guerrero-Plata, A., Gilfoy, F. D., Garofalo, R. P., Mason, P. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differential+activation+of+human+monocyte-derived+and+plasmacytoid+dendritic+cells+by+West+Nile+virus+generated+in+different+host+cells.">Differential activation of human monocyte-derived and plasmacytoid dendritic cells by West Nile virus generated in different host cells.</a> J. Virol. 81, 13640-13648 (2007).</li><li>Shrestha, B., Samuel, M. A., Diamond, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CD8++T+Cells+Require+Perforin+To+Clear+West+Nile+Virus+from+Infected+Neurons.">CD8+ T Cells Require Perforin To Clear West Nile Virus from Infected Neurons.</a> J. Virol. 80, 119-129 (2006).</li><li>Wang, Y., Lobigs, M., Lee, E., Mullbacher, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CD8++T+cells+mediate+recovery+and+immunopathology+in+West+Nile+virus+encephalitis.">CD8+ T cells mediate recovery and immunopathology in West Nile virus encephalitis.</a> J. Virol. 77, 13323-13334 (2003).</li><li>Plebanski, M., Katsara, M., Sheng, K. C., Xiang, S. D., Apostolopoulos, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methods+to+measure+T-cell+responses.">Methods to measure T-cell responses.</a> Expert Rev. Vaccines. 9, 595-600 (2010).</li><li>Lyons, A. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysing+cell+division+in+vivo+and+in+vitro+using+flow+cytometric+measurement+of+CFSE+dye+dilution.">Analysing cell division in vivo and in vitro using flow cytometric measurement of CFSE dye dilution.</a> J. Immunol. Methods. 243, 147-154 (2000).</li><li>Kraus, A. A., Priemer, C., Heider, H., Kruger, D. H., Ulrich, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inactivation+of+Hantaan+virus-containing+samples+for+subsequent+investigations+outside+biosafety+level+3+facilities.">Inactivation of Hantaan virus-containing samples for subsequent investigations outside biosafety level 3 facilities.</a> Intervirology. 48, 255-261 (2005).</li><li>Saxena, V., 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=A+hamster-derived+west+nile+virus+isolate+induces+persistent+renal+infection+in+mice.">A hamster-derived west nile virus isolate induces persistent renal infection in mice.</a> PLoS Negl. Trop. Dis. 7, 2275 (2013).</li><li>Welte, T., 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=Vgamma4++T+cells+regulate+host+immune+response+to+West+Nile+virus+infection.">Vgamma4+ T cells regulate host immune response to West Nile virus infection.</a> FEMS Immunol. Med. Microbiol. 63, 183-192 (2011).</li></ol>

The authors have nothing to disclose.

WNV is a BL3 pathogen. Due to safety regulations, immunological assays with WNV-infected samples are often restricted by the availability of equipment at BL3 facilities or more lengthy and tedious to perform. In a recent study, we used two flow cytometry-based methods to study cell mediated immune responses during WNV infection5. In both assays, WNV-infected cells were treated with 1-2% PFA directly or with fixation/permeabilization solution containing 4% PFA. It is known that 1% PFA fixation of virus-infected...

West Nile virus (WNV), a neurotropic, plus-sensed flavivirus, is an emerging public health threat. Currently, no vaccines have been approved for human use1. An attenuated WNV strain, which has a P38G substitution in the nonstructural (NS)4B protein, is known to induce no lethality in mice but higher innate cytokines and T cell responses in mice than wild-type WNV NY99 strain2. Mice immunized with the NS4B-P38G mutant were all protected from a secondary challenge with lethal wild-type WNV. This suggests that the NS4B-P38G mutant has suitable features for an ideal vaccine candidate. The mechanisms by which the NS4B-P38G mutant induces high protective adaptive immunity are not clearly understood yet. Toll-like receptors (TLRs), which recognize pathogen-associated molecular patterns, play an essential role in the initiation of innate immunity to viral infection. The core TLR signaling pathway utilizes myeloid differentiation primary response gene 88 (MyD88) as the primary adaptor3,4. In a recent study, MyD88 signaling was shown to play an important role in development of cell mediated immunity during WNV NS4B- P38G mutant infection in mice5. Dentritic cells (DCs) are one of the most important antigen-presenting cells exhibiting the unique capacity to initiate primary T cell responses during viral infection6,7. CD4+ and CD8+ T-cells both contribute to long-lasting protective immunity and are important for host survival following wild-type WNV infection8,9. Two immunological assays were used in this study to assess the functions of these cells in the NS4B-P38G mutant infected mice.
First, an in vitro T cell priming assay was utilized to compare the antigen-presenting capability of DCs of WNV-infected wild-type and MyD88&#8722;/&#8722; mice. To increase sensitivity of the assay, na&#239;ve CD4+ T cells were isolated from OTII transgenic mice, which express a V&#945;2/V&#946;5 TCR specific for the chicken ovalbumin (OVA) peptide 323 - 339. DCs of WNV infected mice were purified, and co-cultured with carboxyfluorescein succinimidyl easter (CFSE)-labeled CD4+ T cells in the presence of OVA peptide. After 5 days of co-culture, cells were harvested and fixed with paraformaldehyde (PFA) and analyzed by flow cytometry. Proliferative assays have been traditionally carried out through incorporation of 5-bromo-2&#8217;-deoxyuridine (BrdU) or tritiated thymine deoxyriboside (3HTdr)10. Nevertheless, these assays are either radioactive and/or in need of special equipments at biosafety level (BL) 3 facilities, where WNV studies are conducted. The flow cytometric analysis of lymphocyte proliferation by serial halving of the fluorescence intensity of the vital dye CFSE has become more commonly used in immunological assays as the dye is more stably and evenly incorporated into cells, detected easily by flow cytometry, and is nonradioactive11. The assay also has the ability to assess the number of cell divisions. One major advantage of using this assay in WNV studies is that fixation of the infected cells with 1-2% PFA could inactivate WNV12, which will enable sample acquisition with a flow cytometer in a BL2 laboratory.
Next, a modified intracellular cytokine staining (ICS) procedure was used to study the role of MyD88 signaling in regulation of WNV specific T cell responses in NS4B-P38G mutant-infected mice. In this assay, splenocytes isolated from infected mice were treated in vitro with WNV specific peptides. Brefeldin A was added to retain the cytokines within the cell. After 5 hr incubation, cells were harvested, washed and stained for T cell subsets. Cells were then fixed in PFA, permeabilized and stained for interferon (IFN)-&#947; and analyzed by flow cytometry. As with other flow cytometry-based assay, once the cells are treated with fixation and permeabilization buffer containing PFA, infected samples can be transferred to a BL2 laboratory for further processing and analysis. In several published studies, we have used ICS to measure T cell effector functions in WNV-infected mice13,14. Although it&#8217;s well established, one major drawback of this assay is that the procedure is very lengthy and could be more time consuming when performed inside BL3 facilities. Here, a micro-centrifuge tube-based ICS method was shown to be more feasible, easier to proceed and less time consuming when performed within a BL3 laboratory.

<table border="0" cellpadding="0" cellspacing="0" width="655">
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Name of Material/ Equipment</td>
			<td style="width:153px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td style="width:167px;">Comments/Description</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;"></td>
			<td style="width:153px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">RPMI 1640</td>
			<td style="width:153px;">Invitrogen</td>
			<td align="right" style="width:119px;">11875</td>
			<td>warm up at 37C</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">anti-CD11c magnetic beads&#160;</td>
			<td>Miltenyi Biotec</td>
			<td>130-052-001</td>
			<td>follow the manufacturer&#8217;s instructions</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">anti-CD4 magnetic beads&#160;</td>
			<td>Miltenyi Biotec</td>
			<td>130-095-248</td>
			<td>follow the manufacturer&#8217;s instructions</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">CFSE</td>
			<td style="width:153px;">Invitrogen</td>
			<td>C34554</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">OVA residue 323-339</td>
			<td>Genscript Corporation</td>
			<td>RP10610</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;"></td>
			<td style="width:153px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="39">
			<td height="39" style="height:39px;width:216px;">Peptides</td>
			<td style="width:153px;">Proimmune</td>
			<td>PC0AD-D</td>
			<td></td>
		</tr>
		<tr height="58">
			<td height="58" style="height:58px;">Brefeldin A solution</td>
			<td style="width:153px;">BD Bioscience</td>
			<td align="right">555029</td>
			<td></td>
		</tr>
		<tr height="58">
			<td height="58" style="height:58px;width:216px;">Mouse Fc Blocker</td>
			<td style="width:153px;">e-Bioscience</td>
			<td>14-0161-85</td>
			<td></td>
		</tr>
		<tr height="58">
			<td height="58" style="height:58px;">APC-conjugated CD4&#160;</td>
			<td style="width:153px;">e-Bioscience</td>
			<td>17-0041-81</td>
			<td></td>
		</tr>
		<tr height="58">
			<td height="58" style="height:58px;">FITC-conjugated CD8&#160;</td>
			<td style="width:153px;">e- bioscience</td>
			<td>11-0081-82</td>
			<td></td>
		</tr>
		<tr height="58">
			<td height="58" style="height:58px;">Fixation/Permeabilization Solution</td>
			<td style="width:153px;">BD- Bioscience</td>
			<td align="right" style="width:119px;">554722</td>
			<td></td>
		</tr>
		<tr height="58">
			<td height="58" style="height:58px;">Permeabilization/wash buffer</td>
			<td style="width:153px;">BD- Bioscience</td>
			<td align="right">554723</td>
			<td></td>
		</tr>
		<tr height="58">
			<td height="58" style="height:58px;">anti-IFNg-PE&#160;</td>
			<td style="width:153px;">e-Bioscience</td>
			<td>12-7311-82</td>
			<td></td>
		</tr>
		<tr height="58">
			<td height="58" style="height:58px;width:216px;">Accuri flow cytometer</td>
			<td style="width:153px;">BD Bioscience</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

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 the T cell priming assay, CFSE labeled CD4+ T cells were cultured with purified DCs from the NS4B-P38G mutant-infected wild-type and MyD88&#8722;/&#8722; mice in the presence or absence of OVA peptides. Labeled T cells cultured alone with or without OVA for 5 days were used as negative controls. As shown in Figure 1A, total T cells were gated for analysis of fluorescence intensity on the FL1 channel. The marker was set up based on the freshly labeled CD4<sup...

Watch this Scientific Journal Video about In Vitro Analysis of Myd88-mediated Cellular Immune Response to West Nile Virus Mutant Strain Infection at JoVE.com

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.

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 ...

in-vitro-analysis-myd88-mediated-cellular-immune-response-to-west

Research

JoVE Journal

Immunology and Infection

8.1K Views.  The University of Texas Medical Branch. Two flow cytometry-based methods – 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.

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

Multicolor Flow Cytometry Analyses of Cellular Immune Response in Rhesus Macaques

The rhesus macaque model is currently the best available model for HIV-AIDS with respect to understanding the pathogenesis as well as for the development of vaccines and therapeutics1,2,3. Here, we describe a method for the detailed phenotypic and functional analyses of cellular immune responses, specifically intracellular cytokine production by CD4+ and CD8+ T cells as well as the individual memory subsets. We obtained precise quantitative and qualitative measures for the production of interferon gamma (INF-) and interleukin (IL) -2 in both CD4+ and CD8+ T cells from the rhesus macaque PBMC stimulated with PMA plus ionomycin (PMA+I). The cytokine profiles were different in the different subsets of memory cells. Furthermore, this protocol provided us the sensitivity to demonstrate even minor fractions of antigen specific CD4+ and CD8+ T cell subsets within the PBMC samples from rhesus macaques immunized with an HIV envelope peptide cocktail vaccine developed in our laboratory. The multicolor flow cytometry technique is a powerful tool to precisely identify different populations of T cells 4,5 with cytokine-producing capability6 following non-specific or antigen-specific stimulation 5,7.

We demonstrate the utility of multicolor flow cytometry for detailed phenotypic and functional characterization of total as well as memory subsets of CD4+ and CD8+ T cells in rhesus macaques, the ideal model for HIV/AIDS vaccine studies.

The rhesus macaque model is currently the best available model for HIV-AIDS with respect to understanding the pathogenesis as well as for the development ...

Seven Steps to Stellate Cells

Hepatic stellate cells are liver-resident cells of star-like morphology and are located in the space of Disse between liver sinusoidal endothelial cells and hepatocytes1,2. Stellate cells are derived from bone marrow precursors and store up to 80% of the total body vitamin A1, 2. Upon activation, stellate cells differentiate into myofibroblasts to produce extracellular matrix, thus contributing to liver fibrosis3. Based on their ability to contract, myofibroblastic stellate cells can regulate the vascular tone associated with portal hypertension4. Recently, we demonstrated that hepatic stellate cells are potent antigen presenting cells and can activate NKT cells as well as conventional T lymphocytes5. 

 Here we present a method for the efficient preparation of hepatic stellate cells from mouse liver. Due to their perisinusoidal localization, the isolation of hepatic stellate cells is a multi-step process. In order to render stellate cells accessible to isolation from the space of Disse, mouse livers are perfused in situ with the digestive enzymes Pronase E and Collagenase P. Following perfusion, the liver tissue is subjected to additional enzymatic treatment with Pronase E and Collagenase P in vitro. Subsequently, the method takes advantage of the massive amount of vitamin A-storing lipid droplets in hepatic stellate cells. This feature allows the separation of stellate cells from other hepatic cell types by centrifugation on an 8% Nycodenz gradient. The protocol described here yields a highly pure and homogenous population of stellate cells. Purity of preparations can be assessed by staining for the marker molecule glial fibrillary acidic protein (GFAP), prior to analysis by fluorescence microscopy or flow cytometry. Further, light microscopy reveals the unique appearance of star-shaped hepatic stellate cells that harbor high amounts of lipid droplets. 


 Taken together, we present a detailed protocol for the efficient isolation of hepatic stellate cells, including representative images of their morphological appearance and GFAP expression that help to define the stellate cell entity.

Here we describe a method for the isolation of hepatic stellate cells from mouse liver. For stellate cell purification, mouse livers are digested in situ and in vitro by pronase-collagenase treatment prior to density gradient centrifugation. This technique yields highly pure hepatic stellate cells.

Hepatic stellate cells are liver-resident  cells of star-like morphology and are located in the space of Disse between  liver sinusoidal endothelial cells ...

An Introduction to Parasitic Wasps of Drosophila and the Antiparasite Immune Response

Most known parasitoid wasp species attack the larval or pupal stages of Drosophila. While Trichopria drosophilae infect the pupal stages of the host (Fig. 1A-C), females of the genus Leptopilina (Fig. 1D, 1F, 1G) and Ganaspis (Fig. 1E) attack the larval stages. We use these parasites to study the molecular basis of a biological arms race. Parasitic wasps have tremendous value as biocontrol agents. Most of them carry virulence and other factors that modify host physiology and immunity. Analysis of Drosophila wasps is providing insights into how species-specific interactions shape the genetic structures of natural communities. These studies also serve as a model for understanding the hosts' immune physiology and how coordinated immune reactions are thwarted by this class of parasites.
The larval/pupal cuticle serves as the first line of defense. The wasp ovipositor is a sharp needle-like structure that efficiently delivers eggs into the host hemocoel. Oviposition is followed by a wound healing reaction at the cuticle (Fig. 1C, arrowheads). Some wasps can insert two or more eggs into the same host, although the development of only one egg succeeds. Supernumerary eggs or developing larvae are eliminated by a process that is not yet understood. These wasps are therefore referred to as solitary parasitoids.
Depending on the fly strain and the wasp species, the wasp egg has one of two fates. It is either encapsulated, so that its development is blocked (host emerges; Fig. 2 left); or the wasp egg hatches, develops, molts, and grows into an adult (wasp emerges; Fig. 2 right). L. heterotoma is one of the best-studied species of Drosophila parasitic wasps. It is a "generalist," which means that it can utilize most Drosophila species as hosts1. L. heterotoma and L. victoriae are sister species and they produce virus-like particles that actively interfere with the encapsulation response2. Unlike L. heterotoma, L. boulardi is a specialist parasite and the range of Drosophila species it utilizes is relatively limited1. Strains of L. boulardi also produce virus-like particles3 although they differ significantly in their ability to succeed on D. melanogaster1. Some of these L. boulardi strains are difficult to grow on D. melanogaster1 as the fly host frequently succeeds in encapsulating their eggs. Thus, it is important to have the knowledge of both partners in specific experimental protocols.
In addition to barrier tissues (cuticle, gut and trachea), Drosophila larvae have systemic cellular and humoral immune responses that arise from functions of blood cells and the fat body, respectively. Oviposition by L. boulardi activates both immune arms1,4. Blood cells are found in circulation, in sessile populations under the segmented cuticle, and in the lymph gland. The lymph gland is a small hematopoietic organ on the dorsal side of the larva. Clusters of hematopoietic cells, called lobes, are arranged segmentally in pairs along the dorsal vessel that runs along the anterior-posterior axis of the animal (Fig. 3A). The fat body is a large multifunctional organ (Fig. 3B). It secretes antimicrobial peptides in response to microbial and metazoan infections.
Wasp infection activates immune signaling (Fig. 4)4. At the cellular level, it triggers division and differentiation of blood cells. In self defense, aggregates and capsules develop in the hemocoel of infected animals (Fig. 5)5,6. Activated blood cells migrate toward the wasp egg (or wasp larva) and begin to form a capsule around it (Fig. 5A-F). Some blood cells aggregate to form nodules (Fig. 5G-H). Careful analysis reveals that wasp infection induces the anterior-most lymph gland lobes to disperse at their peripheries (Fig. 6C, D).
We present representative data with Toll signal transduction pathway components Dorsal and Sp&auml;tzle (Figs. 4,5,7), and its target Drosomycin (Fig. 6), to illustrate how specific changes in the lymph gland and hemocoel can be studied after wasp infection. The dissection protocols described here also yield the wasp eggs (or developing stages of wasps) from the host hemolymph (Fig. 8).

An Introduction to Parasitic Wasps of Drosophila and the Antiparasite Immune Response

Parasitoid (parasitic) wasps constitute a major class of natural enemies of many insects including Drosophila melanogaster. We will introduce the techniques to propagate these parasites in Drosophila spp. and demonstrate how to analyze their effects on immune tissues of Drosophila larvae.

Most known parasitoid wasp species attack the larval or pupal stages of Drosophila. While Trichopria drosophilae infect the pupal stages of the host (Fig. ...

PRP as a New Approach to Prevent Infection: Preparation and In vitro Antimicrobial Properties of PRP

Implant-associated infection is becoming more and more challenging to the healthcare industry worldwide due to increasing antibiotic resistance, transmission of antibiotic resistant bacteria between animals and humans, and the high cost of treating infections.
In this study, we disclose a new strategy that may be effective in preventing implant-associated infection based on the potential antimicrobial properties of platelet-rich plasma (PRP). Due to its well-studied properties for promoting healing, PRP (a biological product) has been increasingly used for clinical applications including orthopaedic surgeries, periodontal and oral surgeries, maxillofacial surgeries, plastic surgeries, sports medicine, etc.
PRP could be an advanced alternative to conventional antibiotic treatments in preventing implant-associated infections. The use of PRP may be advantageous compared to conventional antibiotic treatments since PRP is less likely to induce antibiotic resistance and PRP's antimicrobial and healing-promoting properties may have a synergistic effect on infection prevention. It is well known that pathogens and human cells are racing for implant surfaces, and PRP's properties of promoting healing could improve human cell attachment thereby reducing the odds for infection. In addition, PRP is inherently biocompatible, and safe and free from the risk of transmissible diseases.
For our study, we have selected several clinical bacterial strains that are commonly found in orthopaedic infections and examined whether PRP has in vitro antimicrobial properties against these bacteria. We have prepared PRP using a twice centrifugation approach which allows the same platelet concentration to be obtained for all samples. We have achieved consistent antimicrobial findings and found that PRP has strong in vitro antimicrobial properties against bacteria like methicillin-sensitive and methicillin-resistant Staphylococcus aureus, Group A Streptococcus, and Neisseria gonorrhoeae. Therefore, the use of PRP may have the potential to prevent infection and to reduce the need for costly post-operative treatment of implant-associated infections.

PRP as a New Approach to Prevent Infection: Preparation and In vitro Antimicrobial Properties of PRP

Implant-associated infection is a significant clinical complication. This study describes an approach using platelet-rich plasma (PRP) to prevent implant-associated infections, presents the protocol for preparing PRP with constant platelet concentration, and reports the newly identified antimicrobial properties of PRP and related protocols for examining such antimicrobial properties in vitro.

Implant-associated infection is becoming more and more challenging to the healthcare industry worldwide due to increasing antibiotic resistance, ...

An In vitro Model to Study Immune Responses of Human Peripheral Blood Mononuclear Cells to Human Respiratory Syncytial Virus Infection

Human respiratory syncytial virus (HRSV) infections present a broad spectrum of disease severity, ranging from mild infections to life-threatening bronchiolitis. An important part of the pathogenesis of severe disease is an enhanced immune response leading to immunopathology.	Here, we describe a protocol used to investigate the immune response of human immune cells to an HRSV infection. First, we describe methods used for culturing, purification and quantification of HRSV. Subsequently, we describe a human in vitro model in which peripheral blood mononuclear cells (PBMCs) are stimulated with live HRSV. This model system can be used to study multiple parameters that may contribute to disease severity, including the innate and adaptive immune response. These responses can be measured at the transcriptional and translational level. Moreover, viral infection of cells can easily be measured using flow cytometry. Taken together, stimulation of PBMC with live HRSV provides a fast and reproducible model system to examine mechanisms involved in HRSV-induced disease.

An In vitro Model to Study Immune Responses of Human Peripheral Blood Mononuclear Cells to Human Respiratory Syncytial Virus Infection

Human respiratory syncytial virus (HRSV) can cause severe bronchiolitis in young infants. Part of the pathogenesis of severe HRSV disease is caused by the host immune response. Stimulation of primary human immune cells with HRSV provides a fast and reproducible model system to study activation of inflammatory pathways and infection.

Human respiratory syncytial  virus (HRSV) infections present a broad spectrum of disease severity, ranging  from mild infections to life-threatening ...

Using RNA-interference to Investigate the Innate Immune Response in Mouse Macrophages

Macrophages are key phagocytic innate immune cells. When macrophages encounter a pathogen, they produce antimicrobial proteins and compounds to kill the pathogen, produce various cytokines and chemokines to recruit and stimulate other immune cells, and present antigens to stimulate the adaptive immune response. Thus, being able to efficiently manipulate macrophages with techniques such as RNA-interference (RNAi) is critical to our ability to investigate this important innate immune cell. However, macrophages can be technically challenging to transfect and can exhibit inefficient RNAi-induced gene knockdown. In this protocol, we describe methods to efficiently transfect two mouse macrophage cell lines (RAW264.7 and J774A.1) with siRNA using the Amaxa Nucleofector 96-well Shuttle System and describe procedures to maximize the effect of siRNA on gene knockdown. Moreover, the described methods are adapted to work in 96-well format, allowing for medium and high-throughput studies. To demonstrate the utility of this approach, we describe experiments that utilize RNAi to inhibit genes that regulate lipopolysaccharide (LPS)-induced cytokine production.

In this protocol, we describe methods to efficiently transfect murine macrophage cell lines with siRNAs using the Amaxa Nucleofector 96-well Shuttle System, stimulate the macrophages with lipopolysaccharide, and monitor the effects on inflammatory cytokine production.

Macrophages are key phagocytic innate immune cells.  When macrophages encounter a pathogen, they produce antimicrobial proteins and compounds to kill the ...

An In Vitro Model for Measuring Immune Responses to Malaria in the Context of HIV Co-infection

Malaria and HIV co-infection is a growing health priority. However, most research on malaria or HIV currently focuses on each infection individually. Although understanding the disease dynamics for each of these pathogens independently is vital, it is also important that the interactions between these pathogens are investigated and understood. 
We have developed a versatile in vitro model of HIV-malaria co-infection to study host immune responses to malaria in the context of HIV infection. Our model allows the study of secreted factors in cellular supernatants, cell surface and intracellular protein markers, as well as RNA expression levels. The experimental design and methods used limit variability and promote data reliability and reproducibility. 
All pathogens used in this model are natural human pathogens (Plasmodium falciparum and HIV-1), and all infected cells are naturally infected and used fresh. We use human erythrocytes parasitized with P. falciparum and maintained in continuous in vitro culture. We obtain freshly isolated peripheral blood mononuclear cells from chronically HIV-infected volunteers. Every condition used has an appropriate control (P. falciparum parasitized vs. normal erythrocytes), and every HIV-infected donor has an HIV uninfected control, from which cells are harvested on the same day. This model provides a realistic environment to study the interactions between malaria parasites and human immune cells in the context of HIV infection.

An In Vitro Model for Measuring Immune Responses to Malaria in the Context of HIV Co-infection

Human co-infection is difficult to replicate in vitro. However, human malaria parasites can readily be cultured in vitro, as can freshly isolated human peripheral blood mononuclear cells naturally infected with HIV. This provides an excellent model for studying early immune responses to malaria parasites in the context of HIV co-infection.

Malaria and HIV co-infection is a growing health priority. However, most research on malaria or HIV currently focuses on each infection individually. ...

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

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

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

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

A Simple and Efficient Approach to Construct Mutant Vaccinia Virus Vectors

The CRISPR-associated endonuclease Cas9 can edit particular genomic loci directed by a single guide RNA (gRNA). The CRISPR/Cas9 system has been successfully employed for editing genomes of various organisms. Here we describe a protocol for editing the vaccinia virus (VV) genome in the cytoplasm of VV-infected CV-1 cells using the RNA-guided Cas9. RNA-guided Cas9 induces double-stranded DNA breaks facilitating homologous recombination efficiently and specifically in the targeted site of VV and a transgene can be incorporated into these sites by homologous recombination. By using a site-specific homologous vector with transgene(s), a N1L gene-deleted VV with the red fluorescence protein (RFP) gene incorporated in this region was generated with a successful recombination efficiency 10 times greater than that obtained from the conventional homologous recombination method. This protocol demonstrates successful use of RNA-guided Cas9 system to generate mutant VVs with enhanced efficiency.

Vaccinia virus (VV) has been widely used in biomedical research and the improvement of human health. This article describes a simple, highly efficient method to edit the VV genome using a CRISPR-Cas9 system.

The CRISPR-associated endonuclease Cas9 can edit particular genomic loci directed by a single guide RNA (gRNA). The CRISPR/Cas9 system has been ...

A Mouse Model to Assess Innate Immune Response to Staphylococcus aureus Infection

Staphylococcus aureus (S. aureus)&#160;infections, including methicillin resistant stains, are an enormous burden on the healthcare system. With incidence rates of S. aureus infection climbing annually, there is a demand for additional research in its&#160;pathogenicity. Animal models of infectious disease advance our understanding of the host-pathogen response and lead to the development of effective therapeutics. Neutrophils play a primary role in the innate immune response that controls S. aureus infections by forming an abscess to wall off the infection and facilitate bacterial clearance; the number of neutrophils that infiltrate an S. aureus skin infection often correlates with disease outcome. LysM-EGFP mice, which possess the enhanced green fluorescent protein (EGFP) inserted in the Lysozyme M (LysM) promoter region (expressed primarily by neutrophils), when used in conjunction with in vivo whole animal fluorescence imaging (FLI) provide&#160;a means of quantifying neutrophil emigration noninvasively and longitudinally into wounded skin. When combined with a bioluminescent S. aureus strain and sequential in vivo whole animal bioluminescent imaging (BLI), it is possible to longitudinally monitor both the neutrophil recruitment dynamics and in vivo bacterial burden at the site of infection in anesthetized mice from onset of infection to resolution or death. Mice are more resistant to a number of virulence factors produced by S. aureus that facilitate effective colonization and infection in humans. Immunodeficient mice provide a more sensitive animal model to examine persistent S. aureus infections and the ability of therapeutics to boost innate immune responses. Herein, we characterize responses in LysM-EGFP mice that have been bred to MyD88-deficient mice (LysM-EGFP&#215;MyD88-/- mice) along with wild-type LysM-EGFP mice to investigate S. aureus skin wound infection. Multispectral simultaneous detection enabled study of neutrophil recruitment dynamics by using in vivo FLI, bacterial burden by using in vivo BLI, and wound healing longitudinally and noninvasively over time.

A Mouse Model to Assess Innate Immune Response to Staphylococcus aureus Infection

An approach is described for real-time detection of the innate immune response to cutaneous wounding and Staphylococcus aureus infection of mice. By comparing LysM-EGFP mice (which possess fluorescent neutrophils) with a LysM-EGFP crossbred immunodeficient mouse strain, we advance our understanding of infection and the development of approaches to combat infection.

Staphylococcus aureus (S. aureus)&#160;infections, including methicillin resistant stains, are an enormous burden on the healthcare system. With incidence ...