We would like to thank the research staff in NUS Department of Otolaryngology and Department of Microbiology and Immunology for their help with the hNEC culture- and viral-culture-related work. We would also like to thank the surgeons and surgical team in National University Hospital, Department of Otolaryngology, for their assistance in providing the cell and blood samples required for the study. 
This study was funded by National Medical Research Council, Singapore No. NMRC/CIRG/1458/2016 (to De Yun Wang) and MOH-OFYIRG19may-0007 (to Kai Sen Tan). Kai Sen Tan is a recipient of fellowship support from European Allergy and Clinical Immunology (EAACI) Research Fellowship 2019.

NOTE: Refer to Table 1 for recipes of media used in this protocol. 
NOTE: hNECS grown on 12-well transwell have been found to grow into more optimal thickness for soluble factors to reach the basal chamber readily when infected with Influenza virus. Hence use of 12-well sized transwell for co-culture is recommended.&#160;
1. Establishment of the 3T3 feeder layer
<ol>
	<li>Establishment from frozen stocks
	<ol>
		<li>Thaw a cryovial of NIH/3T3 fibroblasts from frozen sto...

<ol>
	<li>Monto, A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vaccines+and+antiviral+drugs+in+pandemic+preparedness.">Vaccines and antiviral drugs in pandemic preparedness.</a> Emerging Infectious Diseases. 12 (1), 55-60 (2006).</li><li>Lightfoot, N., Rweyemamu, M., Heymann, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparing+for+the+next+pandemic.">Preparing for the next pandemic.</a> The British Medical Journal. 346, 364 (2013).</li><li>Gerdil, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+annual+production+cycle+for+influenza+vaccine.">The annual production cycle for influenza vaccine.</a> Vaccine. 21 (16), 1776-1779 (2003).</li><li>Putri, W., Muscatello, D. J., Stockwell, M. S., Newall, A. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Economic+burden+of+seasonal+influenza+in+the+United+States.">Economic burden of seasonal influenza in the United States.</a> Vaccine. 36 (27), 3960-3966 (2018).</li><li>Mas-Coma, S., Jones, M. K., Marty, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=COVID-19+and+globalization.">COVID-19 and globalization.</a> One Health. 9, 100132 (2020).</li><li>Guo, Y. R., 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=The+origin,+transmission+and+clinical+therapies+on+coronavirus+disease+2019+(COVID-19)+outbreak+-+an+update+on+the+status.">The origin, transmission and clinical therapies on coronavirus disease 2019 (COVID-19) outbreak - an update on the status.</a> Military Medical Research. 7 (1), 11 (2020).</li><li>Guan, W. J., 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=Clinical+characteristics+of+coronavirus+disease+2019+in+China.">Clinical characteristics of coronavirus disease 2019 in China.</a> New England Journal of Medicine. 382, 1708-1720 (2020).</li><li>van Wilgenburg, B., 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=MAIT+cells+are+activated+during+human+viral+infections.">MAIT cells are activated during human viral infections.</a> Nature Communications. 7, 11653 (2016).</li><li>Chien, Y. H., Meyer, C., Bonneville, M. <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:+first+line+of+defense+and+beyond.">Gammadelta T cells: first line of defense and beyond.</a> Annual Review of Immunology. 32, 121-155 (2014).</li><li>van Wilgenburg, B., 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=MAIT+cells+contribute+to+protection+against+lethal+influenza+infection+in+vivo.">MAIT cells contribute to protection against lethal influenza infection in vivo.</a> Nature Communications. 9 (1), 4706 (2018).</li><li>Dias, J., Leeansyah, E., Sandberg, J. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multiple+layers+of+heterogeneity+and+subset+diversity+in+human+MAIT+cell+responses+to+distinct+microorganisms+and+to+innate+cytokines.">Multiple layers of heterogeneity and subset diversity in human MAIT cell responses to distinct microorganisms and to innate cytokines.</a> Proceedings of the National Academy of Sciences of the United States of America. 114 (27), 5434-5443 (2017).</li><li>Yan, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+nasal+epithelial+cells+derived+from+multiple+individuals+exhibit+differential+responses+to+H3N2+influenza+virus+infection+in+vitro.">Human nasal epithelial cells derived from multiple individuals exhibit differential responses to H3N2 influenza virus infection in vitro.</a> Journal of Allergy and Clinical Immunology. 138 (1), 276-281 (2016).</li><li>Luukkainen, A., 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+co-culture+model+of+PBMC+and+stem+cell+derived+human+nasal+epithelium+reveals+rapid+activation+of+NK+and+innate+T+cells+upon+Influenza+A+virus+infection+of+the+nasal+epithelium.">A co-culture model of PBMC and stem cell derived human nasal epithelium reveals rapid activation of NK and innate T cells upon Influenza A virus infection of the nasal epithelium.</a> Frontiers in Immunology. 9, 2514 (2018).</li><li>Tan, K. S., 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=RNA+sequencing+of+H3N2+influenza+virus-infected+human+nasal+epithelial+cells+from+multiple+subjects+reveals+molecular+pathways+associated+with+tissue+injury+and+complications.">RNA sequencing of H3N2 influenza virus-infected human nasal epithelial cells from multiple subjects reveals molecular pathways associated with tissue injury and complications.</a> Cells. 8 (9), 986 (2019).</li><li>Kim, N., 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=Effect+of+lipopolysaccharide+on+diesel+exhaust+particle-induced+junctional+dysfunction+in+primary+human+nasal+epithelial+cells.">Effect of lipopolysaccharide on diesel exhaust particle-induced junctional dysfunction in primary human nasal epithelial cells.</a> Environmental Pollution. 248, 736-742 (2019).</li><li>Tan, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vitro+model+of+fully+differentiated+human+nasal+epithelial+cells+infected+with+rhinovirus+reveals+epithelium-initiated+immune+responses.">In vitro model of fully differentiated human nasal epithelial cells infected with rhinovirus reveals epithelium-initiated immune responses.</a> Journal of Infectious Diseases. 217 (6), 906-915 (2018).</li><li>Tan, K. S., 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=Comparative+transcriptomic+and+metagenomic+analyses+of+influenza+virus-infected+nasal+epithelial+cells+from+multiple+individuals+reveal+specific+nasal-initiated+signatures.">Comparative transcriptomic and metagenomic analyses of influenza virus-infected nasal epithelial cells from multiple individuals reveal specific nasal-initiated signatures.</a> Frontiers in Microbiology. 9, 2685 (2018).</li><li>Cytokine /Chemokine Panel II 96 Well Plate Assay. Millipore Corporation Available from: <a target="_blank" href="https://www.merckmillipore.com/SG/en/product/MILLIPLEX-MAP-Human-Cytokine-Chemokine-Magnetic-Bead-Panel-II-Premixed-23-Plex-Immunology-Multiplex-Assay">https://www.merckmillipore.com/SG/en/product/MILLIPLEX-MAP-Human-Cytokine-Chemokine-Magnetic-Bead-Panel-II-Premixed-23-Plex-Immunology-Multiplex-Assay</a> (2020)</li><li>Gamage, A. 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=Infection+of+human+nasal+epithelial+cells+with+SARS-CoV-2+and+a+382-nt+deletion+isolate+lacking+ORF8+reveals+similar+viral+kinetics+and+host+transcriptional+profiles.">Infection of human nasal epithelial cells with SARS-CoV-2 and a 382-nt deletion isolate lacking ORF8 reveals similar viral kinetics and host transcriptional profiles.</a> PLoS Pathogens. 16 (12), 1009130 (2020).</li><li>Zhao, X. N., 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=The+use+of+nasal+epithelial+stem/progenitor+cells+to+produce+functioning+ciliated+cells+in+vitro.">The use of nasal epithelial stem/progenitor cells to produce functioning ciliated cells in vitro.</a> American Journal of Rhinology &amp; Allergy. 26 (5), 345-350 (2012).</li></ol>

Innate immune responses against viruses are an under-investigated field of study in antiviral management. The airway epithelial cells and innate immune cells work in concert to suppress viral replication during an infection, besides serving as a determinant of overactive adaptive response if the viral load is not kept in check12,13,17. However, the development of a relevant human model for the study of epithelial-innate immune c...

Respiratory viruses are perhaps amongst the most widespread pathogens causing severe healthcare and economic burden. From the periodic global outbreaks of emerging epidemic strains (e.g., H1N1, H5N1, H3N2, MERS, COVID-19) to the seasonal strains of influenza every year, viruses are a constant threat to public health. Although vaccines form the main bulk of the response to these global public health challenges, it is sobering to note that these countermeasures are merely responsive1,2. Furthermore, a delay between the emergence of a new infectious strain and the successful development of its vaccine is inevitable3, leading to a period when measures available to curb the spread of the virus are highly limited.
These delays are further emphasized by the costs that are inflicted upon society-economically and socially. The seasonal flu alone is responsible for approximately $8 billion in indirect costs, $3.2 billion in medical costs, and 36.3 thousand deaths in the United States of America annually4. This is before consideration of the research costs that are necessary to fund vaccine development. Epidemic outbreaks have even more severe effects on society, compounded by the increasing rate of globalization every year, as evidenced by the global disruptions caused by the emergence and rapid spread of severe acute respiratory syndrome coronovirus 2 (SARS-CoV-2)5,6,7.
Recent studies have shown that infected patients having a greater population of activated innate T cells tend to have a better disease outcome8,9,10. Furthermore, the innate T cell population is categorized into multiple subgroups: the mucosal-associated invariant T (MAIT) cells, V&#948;1 &#947;&#948; T cells, V&#948;2 &#947;&#948; T cells, and the natural killer T (NKT) cells. These subgroups of innate T cells also exhibit heterogeneity within their populations, increasing the complexity of the interactions between the cell populations involved in the innate immune response11. Hence, the mechanism that activates these innate T cells and the knowledge of the specific subgroups of innate T cells may provide a different avenue of research to curtail the infectious effects of these viruses on the human host, especially during the period of vaccine development.
Epithelial cells infected by influenza produce factors that activate innate T cells rapidly12,13,14. Building upon that finding, this contact-free Air-Liquid Interface (ALI) co-culture model aims to mimic the early chemical interactions (mediated by soluble factors released by the infected epithelial layer) between the infected nasal epithelial layer and the PBMCs during early infection. The physical separation between the nasal epithelial layer (cultured on membrane inserts) and the PBMCs (in the chamber underneath) and the epithelial integrity prevent direct infection of the PBMCs by the virus, allowing a detailed study of the effects of epithelial-derived soluble factors on the PBMCs. The identified factors can therefore be further investigated for their therapeutic potential in inducing the appropriate innate T cell population that may protect against influenza infection. This paper therefore has detailed the methods of establishing a co-culture for the study of innate T-cell activation from epithelium-derived soluble factors.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>0.5% Trypsin-EDTA</td>
			<td>Gibco</td>
			<td>15400-054</td>
			<td></td>
		</tr>
		<tr>
			<td>0.5 M Ethylenediaminetetraacetic acid (EDTA), pH 8.0, RNase-free</td>
			<td>Thermofisher</td>
			<td>AM9260G</td>
			<td>0.5M EDTA</td>
		</tr>
		<tr>
			<td>1.5 mL SafeLock Tubes</td>
			<td>Eppendorf</td>
			<td>0030120086</td>
			<td>1.5mL Centrifuge Tube</td>
		</tr>
		<tr>
			<td>10 mL K3EDTA Vacutainer Tubes</td>
			<td>BD</td>
			<td>366643</td>
			<td>10mL Blood Collection Tubes</td>
		</tr>
		<tr>
			<td>10x dPBS</td>
			<td>Gibco</td>
			<td>14200-075</td>
			<td></td>
		</tr>
		<tr>
			<td>10x PBS</td>
			<td>Vivantis</td>
			<td>PC0711</td>
			<td></td>
		</tr>
		<tr>
			<td>12-well Plate</td>
			<td>Corning&#160;</td>
			<td>3513</td>
			<td></td>
		</tr>
		<tr>
			<td>12-well Transwell Insert</td>
			<td>Corning&#160;</td>
			<td>3460</td>
			<td>membrane insert</td>
		</tr>
		<tr>
			<td>1x FACS Lysing Solution</td>
			<td>BD</td>
			<td>349202</td>
			<td></td>
		</tr>
		<tr>
			<td>2.0 mL SafeLock Tubes</td>
			<td>Eppendorf</td>
			<td>0030120094</td>
			<td>2 mL centrifuge tube</td>
		</tr>
		<tr>
			<td>24-well Plate</td>
			<td>Corning&#160;</td>
			<td>3524</td>
			<td></td>
		</tr>
		<tr>
			<td>24-well Transwell Insert</td>
			<td>Corning&#160;</td>
			<td>3470</td>
			<td></td>
		</tr>
		<tr>
			<td>3% Acetic Acid with Methylene Blue</td>
			<td>STEMCELL Technologies</td>
			<td>07060</td>
			<td></td>
		</tr>
		<tr>
			<td>3,3&#39;,5-triiodo-l-thyronine</td>
			<td>Sigma</td>
			<td>T-074</td>
			<td></td>
		</tr>
		<tr>
			<td>37% Formaldehyde Solution w 15% Methanol as Stabilizer in H2O</td>
			<td>Sigma</td>
			<td>533998</td>
			<td></td>
		</tr>
		<tr>
			<td>5810R Centrifuge</td>
			<td>Eppendorf</td>
			<td>5811000320</td>
			<td></td>
		</tr>
		<tr>
			<td>5 mL polypropylene tubes (flow tubes)</td>
			<td>BD</td>
			<td>352058</td>
			<td></td>
		</tr>
		<tr>
			<td>70 &#181;m Cell Strainer</td>
			<td>Corning&#160;</td>
			<td>431751</td>
			<td></td>
		</tr>
		<tr>
			<td>A-4-62 Rotor</td>
			<td>Eppendorf</td>
			<td>5810709008</td>
			<td></td>
		</tr>
		<tr>
			<td>Accutase</td>
			<td>Gibco</td>
			<td>A1110501</td>
			<td>Cell Dissociation Reagent</td>
		</tr>
		<tr>
			<td>Antibiotic-Antimycotic</td>
			<td>Gibco</td>
			<td>15240-062</td>
			<td></td>
		</tr>
		<tr>
			<td>Avicel CL-611</td>
			<td>FMC Biopolymer</td>
			<td>NA</td>
			<td>Liquid Overlay</td>
		</tr>
		<tr>
			<td>Bio-Plex Manager 6.2 Standard Software</td>
			<td>Bio-Rad Laboratories, Inc</td>
			<td>171STND01</td>
			<td>Multiplex Manager Software</td>
		</tr>
		<tr>
			<td>Butterfly Needle 21 G</td>
			<td>BD</td>
			<td>367287</td>
			<td></td>
		</tr>
		<tr>
			<td>Cholera Toxin</td>
			<td>Sigma</td>
			<td>C8052</td>
			<td></td>
		</tr>
		<tr>
			<td>Crystal Violet&#160;</td>
			<td>Merck</td>
			<td>C6158</td>
			<td></td>
		</tr>
		<tr>
			<td>Cytofix/Cytoperm Solution</td>
			<td>BD</td>
			<td>554722</td>
			<td>Fixation and Permeabilization Solution</td>
		</tr>
		<tr>
			<td>Dispase II</td>
			<td>Sigma</td>
			<td>D4693</td>
			<td>Neutral Protease</td>
		</tr>
		<tr>
			<td>DMEM/High Glucose</td>
			<td>GE Healthcare Life Sciences</td>
			<td>SH30243.01</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM/Nutrient Mixture F-12</td>
			<td>Gibco-Invitrogen</td>
			<td>11320033</td>
			<td></td>
		</tr>
		<tr>
			<td>dNTP Mix</td>
			<td>Promega</td>
			<td>U1515</td>
			<td>dNTP Mix</td>
		</tr>
		<tr>
			<td>EMEM (w L-Glutamine)</td>
			<td>ATCC</td>
			<td>30-2003</td>
			<td></td>
		</tr>
		<tr>
			<td>EVOM voltohmmeter device</td>
			<td>WPI, Sarasota, FL, USA</td>
			<td>300523</td>
			<td></td>
		</tr>
		<tr>
			<td>FACS Lysing Solution</td>
			<td>BD</td>
			<td>349202</td>
			<td>1x Lysing Solution</td>
		</tr>
		<tr>
			<td>Falcon tube 15 mL</td>
			<td>CellStar</td>
			<td>188271</td>
			<td>15 mL tube</td>
		</tr>
		<tr>
			<td>Falcon tube 50 mL</td>
			<td>CellStar</td>
			<td>227261</td>
			<td>50 mL Tube</td>
		</tr>
		<tr>
			<td>Fast Start Essential DNA Probes Master</td>
			<td>Roche</td>
			<td>6402682001</td>
			<td>qPCR Master Mix</td>
		</tr>
		<tr>
			<td>Ficoll Paque Premium</td>
			<td>Research Instruments</td>
			<td>17544203</td>
			<td>Density Gradient Media</td>
		</tr>
		<tr>
			<td>H3N2 (A/Aichi/2/1968)&#160;</td>
			<td>ATCC</td>
			<td>VR547</td>
			<td></td>
		</tr>
		<tr>
			<td>H3N2 M1 Forward Primer Sequence</td>
			<td>Sigma</td>
			<td colspan="2">5&#39;- ATGGTTCTGGCCAGCACTAC-3&#39;</td>
		</tr>
		<tr>
			<td>H3N2 M1 Reverse Primer Sequence</td>
			<td>Sigma</td>
			<td colspan="2">5&#39;- ATCTGCACCCCCATTCGTTT-3&#39;</td>
		</tr>
		<tr>
			<td>H3N2 NS1 Forward Primer Sequence</td>
			<td>Sigma</td>
			<td colspan="2">5&#39;- ACCCGTGTTGGAAAGCAGAT-3&#39;</td>
		</tr>
		<tr>
			<td>H3N2 NS1 Reverse Primer Sequence</td>
			<td>Sigma</td>
			<td colspan="2">5&#39;- CCTCTTCGGTGAAAGCCCTT-3&#39;</td>
		</tr>
		<tr>
			<td>Heat Inactivated Fetal Bovine Serum</td>
			<td>Gibco</td>
			<td>10500-064</td>
			<td></td>
		</tr>
		<tr>
			<td>hNESPCs</td>
			<td>Human Donors</td>
			<td>NA</td>
			<td></td>
		</tr>
		<tr>
			<td>Human Epithelial Growth Factor</td>
			<td>Gibco-Invitrogen</td>
			<td>PHG0314</td>
			<td></td>
		</tr>
		<tr>
			<td>Hydrocortisone</td>
			<td>STEMCELL Techonologies</td>
			<td>7925</td>
			<td>Collected from nasal biopsies during septal deviation surgeries</td>
		</tr>
		<tr>
			<td>Insulin</td>
			<td>Sigma</td>
			<td>I3536</td>
			<td></td>
		</tr>
		<tr>
			<td>Lightcycler 96</td>
			<td>Roche</td>
			<td>5815916001</td>
			<td>qPCR Instrument</td>
		</tr>
		<tr>
			<td>Live/DEAD Blue Cell Stain Kit *for UV Excitation</td>
			<td>Thermofisher</td>
			<td>L23105</td>
			<td>Viability Stain</td>
		</tr>
		<tr>
			<td>MILLIPLEX MAP Human Cytokine/Chemokine Magnetic Bead Panel II - Premixed 23 Plex</td>
			<td>Merck Pte Ltd</td>
			<td>HCP2MAG-62K-PX23</td>
			<td>Immunology Multiplex Assay</td>
		</tr>
		<tr>
			<td>Mitomycin C</td>
			<td>Sigma</td>
			<td>M4287</td>
			<td></td>
		</tr>
		<tr>
			<td>M-MLV 5x Buffer</td>
			<td>Promega</td>
			<td>M1705</td>
			<td>RT-PCR 5x Buffer</td>
		</tr>
		<tr>
			<td>M-MLV Reverse Transcriptase</td>
			<td>Promega</td>
			<td>M1706</td>
			<td>Reverse Transcriptase</td>
		</tr>
		<tr>
			<td>N-2 supplement</td>
			<td>Gibco-Invitrogen</td>
			<td>17502-048</td>
			<td></td>
		</tr>
		<tr>
			<td>NIH/3T3</td>
			<td>ATCC</td>
			<td>CRL1658</td>
			<td></td>
		</tr>
		<tr>
			<td>Perm/Wash Buffer</td>
			<td>BD</td>
			<td>554723</td>
			<td>Permeabilization Wash Buffer</td>
		</tr>
		<tr>
			<td>PneumaCult-ALI 10x Supplement</td>
			<td>STEMCELL Techonologies</td>
			<td>5001</td>
			<td></td>
		</tr>
		<tr>
			<td>PneumaCult-ALI Basal Medium</td>
			<td>STEMCELL Techonologies</td>
			<td>5001</td>
			<td></td>
		</tr>
		<tr>
			<td>PneumaCult-ALI Maintenance Supplement (100x)</td>
			<td>STEMCELL Techonologies</td>
			<td>5001</td>
			<td></td>
		</tr>
		<tr>
			<td>Random Primers</td>
			<td>Promega</td>
			<td>C1181</td>
			<td>Random Primers</td>
		</tr>
		<tr>
			<td>Recombinant Rnasin Rnase Inhibitor</td>
			<td>Promega</td>
			<td>N2511</td>
			<td>RNase Inhibitor</td>
		</tr>
		<tr>
			<td>RNA Lysis Buffer</td>
			<td>Qiagen</td>
			<td>Part of 52904</td>
			<td></td>
		</tr>
		<tr>
			<td>RPMI 1640 (w L-Glutamine)</td>
			<td>ATCC</td>
			<td>30-2001</td>
			<td></td>
		</tr>
		<tr>
			<td>STX2 electrodes</td>
			<td>WPI, Sarasota, FL, USA</td>
			<td>STX2</td>
			<td>Electrode</td>
		</tr>
		<tr>
			<td>T25 Flask</td>
			<td>Corning</td>
			<td>430639</td>
			<td></td>
		</tr>
		<tr>
			<td>T75 Flask</td>
			<td>Corning</td>
			<td>430641U</td>
			<td></td>
		</tr>
		<tr>
			<td>TPCK Trypsin</td>
			<td>Sigma</td>
			<td>T1426</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypan Blue</td>
			<td>Hyclone</td>
			<td>SV30084.01</td>
			<td></td>
		</tr>
		<tr>
			<td>Viral RNA Extraction Kit</td>
			<td>Qiagen</td>
			<td>52904</td>
			<td>Viral RNA Extraction Kit</td>
		</tr>
		<tr>
			<td>V-Shaped 96-well Plate</td>
			<td>Corning</td>
			<td>3894</td>
			<td></td>
		</tr>
	</tbody>
</table>

contact-free co-culture model for the study of innate immune cell activation during respiratory virus infection

The early interactions between the nasal epithelial layer and the innate immune cells during viral infections remains an under-explored area. The significance of innate immunity signaling in viral infections has increased substantially as patients with respiratory infections who exhibit high innate T cell activation show a better disease outcome. Hence, dissecting these early innate immune interactions allows the elucidation of the processes that govern them and may facilitate the development of potential therapeutic targets and strategies for dampening or even preventing early progression of viral infections. This protocol details a versatile model that can be used to study early crosstalk, interactions, and activation of innate immune cells from factors secreted by virally infected airway epithelial cells. Using an H3N2 influenza virus (A/Aichi/2/1968) as the representative virus model, innate cell activation of co-cultured peripheral blood mononuclear cells (PBMCs) has been analyzed using flow cytometry to investigate the subsets of cells that are activated by the soluble factors released from the epithelium in response to the viral infection. The results demonstrate the gating strategy for differentiating the subsets of cells and reveal the clear differences between the activated populations of PBMCs and their crosstalk with the control and infected epithelium. The activated subsets can then be further analyzed to determine their functions as well as molecular changes specific to the cells. Findings from such a crosstalk investigation may uncover factors that are important for the activation of vital innate cell populations, which are beneficial in controlling and suppressing the progression of viral infection. Furthermore, these factors can be universally applied to different viral diseases, especially to newly emerging viruses, to dampen the impact of such viruses when they first circulate in na&#239;ve human populations.

Although conventional T cells form the main repertoire of adaptive immune response against viral infection to facilitate viral clearance, the innate T cell population works across a broader spectrum to suppress the viral load for effective clearance at a later stage. Therefore, this protocol specifically creates a robust condition to study innate T cells, their activation, and their functional population following influenza infection, without needing epithelial and immune cell samples fro...

Watch this Scientific Journal Video about Contact-Free Co-Culture Model for the Study of Innate Immune Cell Activation During Respiratory Virus Infection at JoVE.com

Contact-Free Co-Culture Model for the Study of Innate Immune Cell Activation During Respiratory Virus Infection

This protocol details an investigation of the early interactions between virally infected nasal epithelial cells and innate cell activation. Individual subsets of immune cells can be distinguished based on their activation in response to viral infections. They can then be further investigated to determine their effects on early antiviral responses.

The early interactions between the nasal epithelial layer and the innate immune cells during viral infections remains an under-explored area. The ...

This protocol is designed to investigate crosstalk of epithelial cells and first-line innate immune cells, specifically innate T cells, which is our interest. Primary cells from human sources are used in this technique, allowing individual investigation of physiological crosstalk relevant to what is happening in humans. Innate T cells have been implicated in improving the survival of influenza-infected patients.Knowing how they get activated could help in developing anti-influenza and antiviral therapy. This method is designed to identify factors that can activate the innate T cells, which may help in developing preventive measures against respiratory virus infection. At day zero, infect human nasal epithelial cells, or HNECs.First, count cells by adding 150 microliters of 1x trypsin EDTA to the apical chamber of the membrane insert and 350 microliters of 1x trypsin EDTA to the basal chamber of the representative well. Incubate the cells at 37 degrees Celsius for 10 minutes or until the cells detach from the membrane. Flush the cells on the membrane by pipetting up and down and collect the suspension in a 1.5-milliliter centrifuge tube.Add 200 microliters of DMEM to quench trypsin activity. Then, count cells via trypan blue staining. Calculate the required multiplicity of infection, or MOI, of the virus based on the cell count per well.Dilute the virus stock accordingly with complete RPMI on ice. For the remaining wells for the infection experiment, add one 1x DPBS into the apical chambers of the membrane inserts. Incubate at 37 degrees Celsius for 10 minutes and remove the 1x DPBS.Change the basal medium in the membrane inserts to complete RPMI medium by transferring the inserts to a new plate with complete RPMI added to the wells. Add the prepared virus inoculum into the apical chamber of the membrane insert. Incubate at 35 degrees Celsius in a 5%carbon dioxide atmosphere for one hour and remove the viral inoculum from the apical chamber.Change the basal medium of the membrane insert to fresh RPMI medium and incubate at 35 degrees Celsius in a 5%carbon dioxide atmosphere for 24 to 72 hours. Seed the required number of peripheral blood mononuclear cells, or PBMCs, in complete RPMI medium by directly adding the PBMC suspension into the basal chamber of each well of infected HNECs from day zero. Incubate at 37 degrees Celsius for 24 to 48 hours.To collect the apical supernatant, add 1x DBPS to each apical chamber and incubate at 37 degrees Celsius for 10 minutes. Then, collect the DPBS in 1.5-milliliter tubes. Aliquot the supernatant for the plaque assay in a new 1.5-milliliter tube and immediately freeze both the stock and the aliquots at minus 80 degrees Celsius.To collect RNA-form HNECs, transfer the membrane insert to a clean well. Add RNA lysis buffer to the apical chamber and incubate at room temperature for five minutes. Collect the supernatant in a 1.5-milliliter centrifuge tube and store it at minus 80 degrees Celsius until RNA extraction for molecular analysis.Finally, harvest PBMCs by gently scraping the surface of the well with the broad base of a sterile pipette tip to dislodge the activated PBMCs that may be adherent to the well surface. Collect the basal medium containing PBMCs in a two-milliliter centrifuge tube. Flush the wells twice with 300 microliters of 1x DPBS and collect the wash in the same two-milliliter tube.Centrifuge the two-milliliter tube and collect the supernatant in a fresh two-milliliter tube without disturbing the cell pellet. Store the aspirated supernatant at minus 80 degrees Celsius for cytokine and chemokine analysis. Resuspend the remaining cell pellet in 200 microliters of 1x DPBS.This protocol can be used to study innate T cells following influenza infection without the need for epithelial and immune cells from the same donor. A sample of the expected progression of the HNESPCs as they grow on the 3T3 feeder layer is shown here. These were used for differentiation in the air/liquid interface culture to obtain multi-layered HNECs with functional, ciliated, and goblet cells.Using the HNECs, innate T cell activation can be investigated using flow cytometry. These results show the detection of mucosal-associated invariant T, or MAIT cells, V delta one, gamma delta T cells, and the natural killer T, or NKT cells. These cells were significantly increased in co-culture involving HNECs infected with influenza virus.This setup can then be applied to other influenza virus strains, or innate immune cell populations to observe their respective activation under co-culture conditions with infected epithelial cells. Accurate calculation of the number of the human nasal epithelial cells to ensure that the right multiplicity of infection is used is important for optimal levels and timing of activation. Crosstalk between epithelial cells and innate immune cells are increasingly gaining attention, and this can be applied further to any other methods involving acute or chronic respiratory immunology.

contact-free-co-culture-model-for-study-innate-immune-cell-activation

Research

JoVE Journal

Immunology and Infection

2.7K Views.  National University of Singapore. This protocol is designed to investigate crosstalk of epithelial cells and first-line innate immune cells, specifically innate T cells, which is our interest. Primary cells from human sources are used in this technique, allowing individual investigation of physiological crosstalk relevant to what is happening in humans. Innate T cells have been implicated in improving the survival of influenza-infected patients.Knowing how they get activated could help in developing anti-influenza and ...