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.

<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. 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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. 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All authors declare no conflict of interest.

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 ...

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

Research

JoVE Journal

Immunology and Infection

2.8K Views.  National University of Singapore. 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.

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

Quantification of the Respiratory Burst Response as an Indicator of Innate Immune Health in Zebrafish

The phagocyte respiratory burst is part of the innate immune response to pathogen infection and involves the production of reactive oxygen species (ROS). ROS are toxic and function to kill phagocytized microorganisms. In vivo quantification of phagocyte-derived ROS provides information regarding an organism's ability to mount a robust innate immune response. Here we describe a protocol to quantify and compare ROS in whole zebrafish embryos upon chemical induction of the phagocyte respiratory burst. This method makes use of a non-fluorescent compound that becomes fluorescent upon oxidation by ROS. Individual zebrafish embryos are pipetted into the wells of a microplate and incubated in this fluorogenic substrate with or without a chemical inducer of the respiratory burst. Fluorescence in each well is quantified at desired time points using a microplate reader. Fluorescence readings are adjusted to eliminate background fluorescence and then compared using an unpaired t-test. This method allows for comparison of the respiratory burst potential of zebrafish embryos at different developmental stages and in response to experimental manipulations such as protein knockdown, overexpression, or treatment with pharmacological agents. This method can also be used to monitor the respiratory burst response in whole dissected kidneys or cell preparations from kidneys of adult zebrafish and some other fish species. We believe that the relative simplicity and adaptability of this protocol will complement existing protocols and will be of interest to researchers who seek to better understand the innate immune response.

The innate immune response protects organisms against pathogen infection. A critical component of the innate immune response, the phagocyte respiratory burst, generates reactive oxygen species that kill invading microorganisms. We describe a respiratory burst assay that quantifies reactive oxygen species produced when the innate immune response is chemically induced.

The phagocyte respiratory burst is part of the innate immune response to  pathogen infection and involves the production of reactive oxygen species (ROS). ...

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 ...

Generation of Lymph Node-fat Pad Chimeras for the Study of Lymph Node Stromal Cell Origin

The stroma is a key component of the lymph node structure and function. However, little is known about its origin, exact cellular composition and the mechanisms governing its formation. Lymph nodes are always encapsulated in adipose tissue and we recently demonstrated the importance of this relation for the formation of lymph node stroma. Adipocyte precursor cells migrate into the lymph node during its development and upon engagement of the Lymphotoxin-b receptor switch off adipogenesis and differentiate into lymphoid stromal cells (B&#233;n&#233;zech&#160;et al.14). Based on the lymphoid stroma potential of adipose tissue, we present a method using a lymph node/fat pad chimera that allows the lineage tracing of lymph node stromal cell precursors. We show how to isolate newborn lymph nodes and EYFP+ embryonic adipose tissue and make a LN/ EYFP+ fat pad chimera. After transfer under the kidney capsule of a host mouse, the lymph node incorporates local adipose tissue precursor cells and finishes its formation. Progeny analysis of EYFP+ fat pad cells in the resulting lymph nodes can be performed by flow-cytometric analysis of enzymatically digested lymph nodes or by immunofluorescence analysis of lymph nodes cryosections. By using fat pads from different knockout mouse models, this method will provide an efficient way of analyzing the origin of the different lymph node stromal cell populations.

Generation of lymph node/fat pad chimeras for the study of lymph node stromal cell origin is described. The method involves the isolation of lymph nodes from newborn mice and embryonic fat pads, the generation of chimeric lymph node-fat pads, and their transfer under the kidney capsule of a host mouse.

The stroma is a key component of the lymph node structure and function. However, little is known about its origin, exact cellular composition and the ...

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 ...

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 ...

Non-invasive Imaging of the Innate Immune Response in a Zebrafish Larval Model of Streptococcus iniae Infection

The aquatic pathogen, Streptococcus iniae, is responsible for over 100 million dollars in annual losses for the aquaculture industry and is capable of causing systemic disease in both fish and humans. A better understanding of S. iniae disease pathogenesis requires an appropriate model system. The genetic tractability and the optical transparency of the early developmental stages of zebrafish allow for the generation and non-invasive imaging of transgenic lines with fluorescently tagged immune cells. The adaptive immune system is not fully functional until several weeks post fertilization, but zebrafish larvae have a conserved vertebrate innate immune system with both neutrophils and macrophages. Thus, the generation of a larval infection model allows the study of the specific contribution of innate immunity in controlling S. iniae infection.
The site of microinjection will determine whether an infection is systemic or initially localized. Here, we present our protocols for otic vesicle injection of zebrafish aged 2-3 days post fertilization as well as our techniques for fluorescent confocal imaging of infection. A localized infection site allows observation of initial microbe invasion, recruitment of host cells and dissemination of infection. Our findings using the zebrafish larval model of S. iniae infection indicate that zebrafish can be used to examine the differing contributions of host neutrophils and macrophages in localized bacterial infections. In addition, we describe how photolabeling of immune cells can be used to track individual host cell fate during the course of infection.

Non-invasive Imaging of the Innate Immune Response in a Zebrafish Larval Model of Streptococcus iniae Infection

Here, we present a protocol for the generation and imaging of a localized bacterial infection in the zebrafish otic vesicle.

The aquatic pathogen, Streptococcus iniae, is responsible for over 100 million dollars in annual losses for the aquaculture industry and is capable of ...

An Ex Vivo Chicken Primary Bursal-cell Culture Model to Study Infectious Bursal Disease Virus Pathogenesis

Infectious bursal disease virus (IBDV) is a birnavirus of economic importance to the poultry industry. The virus infects B cells, causing morbidity, mortality, and immunosuppression in infected birds. In this study, we describe the isolation of chicken primary bursal cells from the bursa of Fabricius, the culture and infection of the cells with IBDV, and the quantification of viral replication. The addition of chicken CD40 ligand significantly increased cell proliferation fourfold over six days of culture and significantly enhanced cell viability. Two strains of IBDV, a cell-culture adapted strain, D78, and a very virulent strain, UK661, replicated well in the ex vivo cell cultures. This model will be of use in determining how cells respond to IBDV infection and will permit a reduction in the number of infected birds used in IBDV pathogenesis studies. The model can also be expanded to include other viruses and could be applied to different species of birds.

An Ex Vivo Chicken Primary Bursal-cell Culture Model to Study Infectious Bursal Disease Virus Pathogenesis

Here we describe the isolation of chicken primary bursal cells from the bursa of Fabricius, the culture and infection of the cells with infectious bursal disease virus, and the quantification of viral replication.

Infectious bursal disease virus (IBDV) is a birnavirus of economic importance to the poultry industry. The virus infects B cells, causing morbidity, ...

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 ...

A Galleria mellonella Oral Administration Model to Study Commensal-Induced Innate Immune Responses

The investigation of the immunogenic potential of commensal bacteria on the host immune system is one essential component when studying intestinal host-microbe interactions. It is well established that different commensals exhibit a different potential to stimulate the host intestinal immune system. Such investigations involve vertebrate animals, especially rodents. Since increasing ethical concerns are linked with experiments involving vertebrates, there is a high demand for invertebrate replacements models. 
Here, we provide a Galleria mellonella oral administration model using commensal non-pathogenic bacteria and the possible assessment of the immunogenic potential of commensals on the G. mellonella immune system. We demonstrate that G. mellonella is a useful alternative invertebrate replacement model that allows the analysis of commensals with different immunogenic potential such as Bacteroides vulgatus and Escherichia coli. Interestingly, the bacteria exhibited no killing effect on the larvae, which is similar to mammals. The immune responses of G. mellonella were comparable with vertebrate innate immune responses and involve recognition of the bacteria and production of antimicrobial molecules. We propose that G. mellonella was able to restore previous microbiota balance, which is well known from healthy mammalian individuals. Although providing comparable innate immune responses in both G. mellonella and vertebrates, G. mellonella does not harbor an adaptive immune system. Since the investigated components of the innate immune system are evolutionary conserved, the model allows a prescreening and first analysis of bacterial immunogenic properties.

A Galleria mellonella Oral Administration Model to Study Commensal-Induced Innate Immune Responses

Here, we provide a detailed protocol for an oral administration model using Galleria mellonella larvae and how to characterize induced innate immune responses. Using this protocol, researchers without practical experience will be able to use the G. mellonella force-feeding method.

The investigation of the immunogenic potential of commensal bacteria on the host immune system is one essential component when studying intestinal ...

Isolation of Tonsillar Mononuclear Cells to Study Ex Vivo Innate Immune Responses in a Human Mucosal Lymphoid Tissue

Studying isolated cells from mucosa-associated lymphoid tissues (MALT) allows understanding of immune cells response in pathologies involving mucosal immunity, because they can model host-pathogen interactions in the tissue. While isolated cells derived from tissues were the first cell culture model, their use has been neglected because tissue can be hard to obtain. In the present protocol, we explain how to easily process and culture tonsillar mononuclear cells (TMCs) from healthy human tonsils to study innate immune responses upon activation, mimicking viral infection in mucosal tissues. Isolation of TMCs from the tonsils is quick, because the tonsils barely have any epithelium and yield up to billions of all major immune cell types. This method allows detection of cytokine production using several techniques, including immunoassays, qPCR, microscopy, flow cytometry, etc., similar to the use of peripheral mononuclear cells (PBMCs) from blood. Furthermore, TMCs show a higher sensitivity to drug testing than PBMCs, which needs to be considered for future toxicity assays. Thus, ex vivo TMCs cultures are an easy and accessible mucosal model.

In the present protocol, we explain how to easily process and culture tonsillar mononuclear cells from healthy humans undergoing partial surgical tonsillectomy to study innate immune responses upon activation, mimicking viral infection in mucosal tissues.

Studying isolated cells from mucosa-associated lymphoid tissues (MALT) allows understanding of immune cells response in pathologies involving mucosal ...