Name: infection of primary nasal epithelial cells grown at an air-liquid interface to characterize human coronavirus-host interactions
Uploaded: 2023-09-22T13:20:00
Description: Watch this Scientific Journal Video about Infection of Primary Nasal Epithelial Cells Grown at an Air-Liquid Interface to Characterize Human Coronavirus-Host Interactions at JoVE.com

This study has the following funding sources: National Institutes of Health (NIH) R01AI 169537 (S.R.W. and N.A.C.), NIH R01AI 140442 (S.R.W.), VA Merit Review CX001717 (N.A.C.), VA Merit Review BX005432 (S.R.W. and N.A.C.),&#160; Penn Center for Research on Coronaviruses and other Emerging Pathogens (S.R.W.), Laffey-McHugh Foundation (S.R.W. and N.A.C.), T32 AI055400 (CJO), T32 AI007324 (AF).

The use of nasal specimens was approved by the University of Pennsylvania Institutional Review Board (protocol # 800614) and the Philadelphia VA Institutional Review Board (protocol # 00781).
1. Infection of nasal ALI cultures
NOTE: Acquisition of clinical specimens, as well as growth and differentiation of nasal ALI cultures, is outside the scope of this paper. Specific methods for culturing primary nasal epithelial cells can be found in recently pub...

<ol>
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The methods detailed here describe a primary epithelial culture system in which patient-derived nasal epithelial cells are grown at an air-liquid interface and applied to the study of HCoV-host interactions. Once differentiated, these nasal ALI cultures recapitulate many features of the in vivo nasal epithelium, including a heterogeneous cellular population with ciliated, goblet, and basal cells represented, as well as intact mucociliary function with robustly beating cilia and mucus secretion. This heterogeneou...

Seven human coronaviruses (HCoVs) have been identified to date and cause a range of respiratory diseases2. The common or seasonal HCoVs (HCoV-NL63, -229E, -OC43, and -HKU1) are typically associated with upper respiratory tract pathology and cause an estimated 10%-30% of common cold cases annually. Though this is the typical clinical phenotype associated with the common HCoVs, these viruses can cause more significant lower respiratory tract disease in at-risk populations, including children, older adults, and immunocompromised individuals3,4. Three pathogenic HCoVs have emerged and caused significant public health emergencies in the last 20 years, including severe acute respiratory syndrome (SARS)-CoV, Middle East respiratory syndrome (MERS)-CoV, and SARS-CoV-2. Lethal HCoVs are associated with more severe respiratory tract pathology, which is clearly illustrated by the &#62;34% case-fatality rate associated with MERS-CoV cases (894 deaths from over 2,500 cases since its emergence in 2012)5,6. It is important to note that the lethal HCoVs also cause a range of respiratory tract diseases, from asymptomatic infections to lethal pneumonia, as seen with the ongoing COVID-19 pandemic7.
HCoVs, like other respiratory pathogens, enter the respiratory tract and establish a productive infection in the nasal epithelium8. Spread to the lower airway is thought to be associated with aspiration from the oral/nasal cavity to the lung, where HCoVs cause more significant lower respiratory tract pathology9,10,11. Thus, the nose serves as the initial portal for viral entry and is the primary barrier to infection with its robust mucociliary clearance machinery and unique innate immune mechanisms aimed at preventing further viral spread to the lower airway12,13. For example, nasal epithelial cells have been reported to express higher than average basal levels of antiviral interferons and interferon-stimulated genes, indicating that nasal cells may be primed for early responses to respiratory viruses14,15,16.
We have previously utilized patient-derived primary nasal epithelial cells grown at an air-liquid interface (ALI) to model HCoV-host interactions in the nose, where HCoV infections begin. Nasal ALI cultures are permissive to both pathogenic (SARS-CoV-2 and MERS-CoV) and common HCoVs (HCoV-NL63 and HCoV-229E) and offer various advantages over traditional airway epithelial cell lines such as A549 (a lung adenocarcinoma cell line)16,17. After differentiation, nasal ALI cultures contain a heterogeneous cellular population and exhibit many of the functions expected of the in vivo nasal epithelium, such as mucociliary clearance machinery18. Nasal cells also offer advantages over lower airway culture systems (such as human bronchial epithelial cells, HBECs), as the acquisition of nasal epithelial cells via cytologic brushing is significantly less invasive compared with using techniques such as bronchoscopy for attaining HBECs19,20,21.
This paper describes methods for utilizing this nasal ALI culture system to characterize HCoV-host interactions in the nasal epithelium. We have applied these methods in recently published works to compare SARS-CoV-2, MERS-CoV, HCoV-NL63, and HCoV-229E1,16,17. Though these methods and representative results emphasize the study of HCoVs in this nasal cell model, the system is highly adaptable to other HCoVs, as well as other respiratory pathogens. Further, these methods can be applied more broadly to other ALI culture systems in order to investigate viral replication and cellular tropism, as well as cytotoxicity and innate immune induction following infection.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Alexa Fluor secondary antibodies (488, 594, 647)</td>
			<td>Invitrogen</td>
			<td>Various</td>
			<td></td>
		</tr>
		<tr>
			<td>BSA (bovine serum albumin)</td>
			<td>Sigma-Aldrich</td>
			<td>A7906</td>
			<td></td>
		</tr>
		<tr>
			<td>cOmplete mini EDTA-free protease inhibitor</td>
			<td>Roche</td>
			<td>11836170001</td>
			<td></td>
		</tr>
		<tr>
			<td>Cytotoxicity detection kit</td>
			<td>Roche</td>
			<td>11644793001</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM (Dulbecco&#39;s Modified Eagle Media)</td>
			<td>Gibco</td>
			<td>11965-084</td>
			<td></td>
		</tr>
		<tr>
			<td>DPBS (Dulbecco&#39;s Phosphate Buffered Saline)</td>
			<td>Gibco</td>
			<td>14190136</td>
			<td></td>
		</tr>
		<tr>
			<td>DPBS + calcium + magnesium</td>
			<td>Gibco</td>
			<td>14040-117</td>
			<td></td>
		</tr>
		<tr>
			<td>Endohm-6G measurement chamber</td>
			<td>World Precision Instruments</td>
			<td>ENDOHM-6G</td>
			<td></td>
		</tr>
		<tr>
			<td>Epithelial cell adhesion marker (EpCAM; CD326)</td>
			<td>eBiosciences</td>
			<td>14-9326-82</td>
			<td></td>
		</tr>
		<tr>
			<td>Epithelial Volt/Ohm (TEER) Meter (EVOM)</td>
			<td>World Precision Instruments</td>
			<td>300523</td>
			<td></td>
		</tr>
		<tr>
			<td>FBS (Fetal Bovine Serum)</td>
			<td>HyClone</td>
			<td>SH30071.03</td>
			<td></td>
		</tr>
		<tr>
			<td>FV10-ASW software for imaging</td>
			<td>Olympus</td>
			<td>Version 4.02</td>
			<td></td>
		</tr>
		<tr>
			<td>HCoV-NL63 (Human coronavirus, NL63)</td>
			<td>BEI Resources</td>
			<td>NR-470</td>
			<td></td>
		</tr>
		<tr>
			<td>HCoV-NL63 nucleocapsid antibody</td>
			<td>Sino Biological</td>
			<td>40641-V07E</td>
			<td></td>
		</tr>
		<tr>
			<td>Hoescht stain</td>
			<td>Thermo Fisher</td>
			<td>H3570</td>
			<td></td>
		</tr>
		<tr>
			<td>Laemmli sample buffer (4x)</td>
			<td>BIO-RAD</td>
			<td>1610747</td>
			<td></td>
		</tr>
		<tr>
			<td>LLC-MK2 cells</td>
			<td>ATCC</td>
			<td>CCL-7</td>
			<td>To titrate HCoV-NL63</td>
		</tr>
		<tr>
			<td>MERS-CoV (Human coronavirus, Middle East Respiratory Syndrome Coronavirus (MERS-CoV), EMC/2012)</td>
			<td>BEI Resources&#160;</td>
			<td>NR-44260</td>
			<td></td>
		</tr>
		<tr>
			<td>MERS-CoV nucleocapsid antibody</td>
			<td>Sino Biological</td>
			<td>40068-MM10</td>
			<td></td>
		</tr>
		<tr>
			<td>MUC5AC antibody</td>
			<td>Sigma-Aldrich</td>
			<td>AMAB91539</td>
			<td></td>
		</tr>
		<tr>
			<td>Olympus Fluoview confocal microscope</td>
			<td>Olympus</td>
			<td>FV1000</td>
			<td></td>
		</tr>
		<tr>
			<td>Phalloidin-iFluor 647 stain</td>
			<td>Abcam</td>
			<td>ab176759</td>
			<td></td>
		</tr>
		<tr>
			<td>PhosStop easy pack (phosphatase inhibitors)&#160;</td>
			<td>Roche</td>
			<td>PHOSS-RO</td>
			<td></td>
		</tr>
		<tr>
			<td>Plate reader&#160;</td>
			<td>Perkin Elmer</td>
			<td>HH34000000</td>
			<td>Any plate reader or ELISA reader is sufficient; must be able to read absorbance at 492 nm</td>
		</tr>
		<tr>
			<td>RIPA buffer (50 mM Tris pH 8; 150 mM NaCl; 0.5% deoxycholate; 0.1% SDS; 1% NP40)</td>
			<td>Thermo Fisher</td>
			<td>89990</td>
			<td>Can prep in-house or purchase</td>
		</tr>
		<tr>
			<td>RNeasy Plus Kit</td>
			<td>Qiagen</td>
			<td>74134</td>
			<td></td>
		</tr>
		<tr>
			<td>SARS-CoV-2 (SARS-Related Coronavirus 2, Isolate USA-WA1/2020)</td>
			<td>BEI Resources</td>
			<td>NR-52281</td>
			<td></td>
		</tr>
		<tr>
			<td>SARS-CoV-2 nucleocapsid antibody</td>
			<td>Genetex</td>
			<td>GTX135357</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton-X 100</td>
			<td>Fisher Scientific</td>
			<td>BP151100</td>
			<td></td>
		</tr>
		<tr>
			<td>Type IV &#946;- tubulin antibody</td>
			<td>Abcam</td>
			<td>ab11315</td>
			<td></td>
		</tr>
		<tr>
			<td>VeroCCL81 cells</td>
			<td>ATCC</td>
			<td>CCL-81</td>
			<td>To titrate MERS-CoV</td>
		</tr>
		<tr>
			<td>VeroE6 cells</td>
			<td>ATCC</td>
			<td>CRL-1586</td>
			<td>To titrate SARS-CoV-2</td>
		</tr>
	</tbody>
</table>

infection of primary nasal epithelial cells grown at an air-liquid interface to characterize human coronavirus-host interactions

Three highly pathogenic human coronaviruses (HCoVs) - SARS-CoV (2002), MERS-CoV (2012), and SARS-CoV-2 (2019) - have emerged and caused significant public health crises in the past 20 years. Four additional HCoVs cause a significant portion of common cold cases each year (HCoV-NL63, -229E, -OC43, and -HKU1), highlighting the importance of studying these viruses in physiologically relevant systems. HCoVs enter the respiratory tract and establish infection in the nasal epithelium, the primary site encountered by all respiratory pathogens. We use a primary nasal epithelial culture system in which patient-derived nasal samples are grown at an air-liquid interface (ALI) to study host-pathogen interactions at this important sentinel site. These cultures recapitulate many features of the in vivo airway, including&#160;the cell types present, ciliary function, and mucus production. We describe methods to characterize viral replication, host cell tropism, virus-induced cytotoxicity, and innate immune induction in nasal ALI cultures following HCoV infection, using recent work comparing lethal and seasonal HCoVs as an example1. An increased understanding of host-pathogen interactions in the nose has the potential to provide novel targets for antiviral therapeutics against HCoVs and other respiratory viruses that will likely emerge in the future.

The representative figures are partially adapted from data that can be found in the manuscript Otter et al.1. Nasal ALI cultures derived from four or six donors were infected with one of four HCoVs (SARS-CoV-2, MERS-CoV, HCoV-NL63, and HCoV-229E) according to the protocols described above, and the average apically shed viral titers for each virus are depicted in Figure 1A. While all four of these HCoVs replicate productively in nasal ALI cultures, SARS-CoV-2 and HCoV-...

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Infection of Primary Nasal Epithelial Cells Grown at an Air-Liquid Interface to Characterize Human Coronavirus-Host Interactions

The nasal epithelium is the primary barrier site encountered by all respiratory pathogens. Here, we outline methods to use primary nasal epithelial cells grown as air-liquid interface (ALI) cultures to characterize human coronavirus-host interactions in a physiologically relevant system.

Three highly pathogenic human coronaviruses (HCoVs) - SARS-CoV (2002), MERS-CoV (2012), and SARS-CoV-2 (2019) - have emerged and caused significant public ...

The protocols described here address key questions such as replication kinetics, host cell tropism, innate immune induction, and cytotoxicity induction in the nasal epithelium during infections with human coronaviruses. This protocol enables the study of human coronavirus host interactions in an organoid microenvironment that closely recapitulates features of the in vivo nasal epithelium, including its heterogeneous cellular population and mucociliary functions. This technique can be applied to other ALI culture systems such as those derived from the lower airway.Additionally, the system can be used to mimic clinical disease states like asthmatic or cystic fibrosis airways. Grow and differentiate the nasal air-liquid interface, or ALI cultures, in transwells having a basal and an apical chamber. Expand the dissociated human sinonasal cells under submerged condition, following which, remove the media from the apical chamber to allow differentiation of the cultures in an air-liquid interface.On the day prior to infection, wash the ALI cultures apically with phosphate-buffered saline, or PBS. To do so, add 200 microliters of warmed PBS into the apical compartment of each transwell and incubate the plate at 37 degrees Celsius for five minutes. Aspirate the PBS and repeat the washing process twice.Then, replace the basal medium with 500 microliters of fresh medium per well and equilibrate the culture overnight at the intended infection temperature. On the next day, dilute the virus in serum-free DMEM to achieve the desired multiplicity of infection in a total inoculum volume of 50 microliters. Add the viral inoculum apically to the culture and place it back in the incubator for one hour.Every 15 minutes during incubation, gently rock the plate forward and backward as well as side to side by holding it firmly with both hands to ensure a uniform adsorption of the viral inoculum. After incubation, aspirate the viral inoculum and ensure its complete removal by washing each infected culture three times with PBS as described previously. If desired, collect the third PBS wash to confirm adequate removal of the input virus.Replace the basal medium on the infected ALIs every 72 hours. At predetermined time points after the infection, add 200 microliters of PBS to the apical chamber of each infected transwell. Pipette the PBS up and down five times to ensure maximum apically-shed virus collection, and transfer the entire volume into a microcentrifuge tube to collect the apical surface liquid, or ASL sample.Next, serially dilute the sample to quantify the concentration of viral particles in the ASL using a standard viral plaque assay. As outlined on the screen, select the cell type depending on the human coronavirus, or HCoV, being titrated. If desired, confirm the absence of basally-released virus by plaque assay of undiluted basal medium collected at various time points post-infection.To measure TEER on nasal ALI cultures, clean, equilibrate, and blank the EVOM instrument per the manufacturer's instructions. Use an empty transwell with no nasal cells for blanking and record the blank measurement. To wash residual basal medium, transfer each infected transwell to a pre-labeled, clean, 24-well plate containing 500 microliters of PBS with calcium and magnesium in each well.Then, add 200 microliters of PBS containing calcium and magnesium to the apical compartment of each transwell. Add one milliliter of PBS containing calcium and magnesium to the Endohm-6 measurement chamber. Place each transwell into the Endohm-6 measurement chamber using forceps and close the chamber by replacing the lid.Ensure that the apical electrode is submerged in the 200 microliters of PBS in the apical compartment. The basal electrode remains at the bottom of the chamber. Once the EVOM reading stabilizes, record the raw TEER measurement.If titering is desired, collect the ASL sample after TEER measurement. Convert the raw TEER readings to final measurements in ohms per centimeter squared using the equation shown on the screen. For human coronaviruses, or HCoVs, assess the TEER at 24-or 48-hour intervals post-infection.Ensure to include a negative control at each time point. For the medium or background control, use PBS with the same composition as the one used for collecting the ASL sample. For the positive control, treat the control ALA cultures apically with 200 microliters of 2%Triton X-100.After incubating for 10 to 15 minutes, collect the entire volume as a Triton sealing sample, following the plate layout consisting of Triton-positive control samples, mock background control samples, PBS control samples, and experimental samples. Load the lactate dehydrogenase, or LDH plate, in triplicate. Finally, calculate the percentage cytotoxicity relative to the Triton sealing value using the displayed equation, The average apically-shed viral titers from nasal ALI cultures infected with four HCoVs revealed that each of the viruses replicated productively, though SARS-CoV-2 and HCoV-229E replicated most efficiently.MERS-CoV intracellular and apically-shed viral titers were approximately the same at 48 hours post-infection, or HPI. Co-staining of the infected cultures with antibodies specific to viral antigens and markers for ciliated or goblet cells showed that SARS-CoV-2 and HCoV-NL63 primarily infected ciliated cells, but MERS-CoV predominantly infected non-ciliated goblet cells. The difference in TEER from baseline to a given post-infection time point or delta-TEER for both SARS-CoV-2 and HCoV-NL63 infections were negative at 192 HPI, unlike MERS-CoV infection, which resulted in no significant change in TEER.Negative delta-TEER values indicate damage to epithelial barrier integrity. HCoV-229E caused epithelial barrier dysfunction at an earlier time point of 96 HPI, but recovered to mock levels later in the infection. TEER traces depicting raw TEER data for each infected transwell over time allowed for the visualization of TEER trends over the course of infection.Quantification of apically-released LDH during infection revealed that SARS-CoV-2, HCoV-NL63, and HCoV-229E caused significant cytotoxicity in nasal cultures, while MERS-CoV did not. It's crucial to understand viral replication kinetics in nasal cultures, as these determine the optimal time points for other downstream analysis such as cytotoxicity and innate immune induction. TEER measurements are most informative if taken sequentially on the same cultures, both prior to infection and then at various times post-infection in order to monitor changes in TEER over the course of infection.Our current research applies RNA sequencing approaches to the described system to understand transcriptional changes during human coronavirus infections, as well as ELISA techniques to measure cytokine and other protein production.

infection-primary-nasal-epithelial-cells-grown-at-an-air-liquid

Research

JoVE Journal

Immunology and Infection

Application of a Mouse Ligated Peyer&#x2019;s Patch Intestinal Loop Assay to Evaluate Bacterial Uptake by M cells

The inside of our gut is inhabited with enormous number of commensal bacteria. The mucosal surface of the gastrointestinal tract is continuously exposed to them and occasionally to pathogens. The gut-associated lymphoid tissue (GALT) play a key role for induction of the mucosal immune response to these microbes1, 2. To initiate the mucosal immune response, the mucosal antigens must be transported from the gut lumen across the epithelial barrier into organized lymphoid follicles such as Peyer's patches. This antigen transcytosis is mediated by specialized epithelial M cells3, 4. M cells are atypical epithelial cells that actively phagocytose macromolecules and microbes. Unlike dendritic cells (DCs) and macrophages, which target antigens to lysosomes for degradation, M cells mainly transcytose the internalized antigens. This vigorous macromolecular transcytosis through M cells delivers antigen to the underlying organized lymphoid follicles and is believed to be essential for initiating antigen-specific mucosal immune responses. However, the molecular mechanisms promoting this antigen uptake by M cells are largely unknown. We have previously reported that glycoprotein 2 (Gp2), specifically expressed on the apical plasma membrane of M cells among enterocytes, serves as a transcytotic receptor for a subset of commensal and pathogenic enterobacteria, including Escherichia coli and Salmonella enterica serovar Typhimurium (S. Typhimurium), by recognizing FimH, a component of type I pili on the bacterial outer membrane 5. Here, we present a method for the application of a mouse Peyer's patch intestinal loop assay to evaluate bacterial uptake by M cells. This method is an improved version of the mouse intestinal loop assay previously described 6, 7. The improved points are as follows: 1. Isoflurane was used as an anesthetic agent. 2. Approximately 1 cm ligated intestinal loop including Peyer's patch was set up. 3. Bacteria taken up by M cells were fluorescently labeled by fluorescence labeling reagent or by overexpressing fluorescent protein such as green fluorescent protein (GFP). 4. M cells in the follicle-associated epithelium covering Peyer's patch were detected by whole-mount immunostainig with anti Gp2 antibody. 5. Fluorescent bacterial transcytosis by M cells were observed by confocal microscopic analysis. The mouse Peyer's patch intestinal loop assay could supply the answer what kind of commensal or pathogenic bacteria transcytosed by M cells, and may lead us to understand the molecular mechanism of how to stimulate mucosal immune system through M cells.

Application of a Mouse Ligated Peyer&amp;#8217;s Patch Intestinal Loop Assay to Evaluate Bacterial Uptake by M cells

M cells in a specialized follicle-associated epithelium covering Peyer&#x2019;s patches play an important role for the mucosal immunosurveillance in gut-associated lymphoid tissue. Here we described the evaluation method for bacterial transcytosis by M cells in vivo. This method provides a method to understand M-cell function in the immune system.

The inside of our gut is inhabited with enormous number of commensal bacteria. The mucosal surface of the gastrointestinal tract is continuously exposed ...

An In vitro Co-infection Model to Study Plasmodium falciparum-HIV-1 Interactions in Human Primary Monocyte-derived Immune Cells

Plasmodium falciparum, the causative agent of the deadliest form of malaria, and human immunodeficiency virus type-1 (HIV-1) are among the most important health problems worldwide, being responsible for a total of 4 million deaths annually1. Due to their extensive overlap in developing regions, especially Sub-Saharan Africa, co-infections with malaria and HIV-1 are common, but the interplay between the two diseases is poorly understood. Epidemiological reports have suggested that malarial infection transiently enhances HIV-1 replication and increases HIV-1 viral load in co-infected individuals2,3. Because this viremia stays high for several weeks after treatment with antimalarials, this phenomenon could have an impact on disease progression and transmission.
The cellular immunological mechanisms behind these observations have been studied only scarcely. The few in vitro studies investigating the impact of malaria on HIV-1 have demonstrated that exposure to soluble malarial antigens can increase HIV-1 infection and reactivation in immune cells. However, these studies used whole cell extracts of P. falciparum schizont stage parasites and peripheral blood mononuclear cells (PBMC), making it hard to decipher which malarial component(s) was responsible for the observed effects and what the target host cells were4,5. Recent work has demonstrated that exposure of immature monocyte-derived dendritic cells to the malarial pigment hemozoin increased their ability to transfer HIV-1 to CD4+ T cells6,7, but that it decreased HIV-1 infection of macrophages8. To shed light on this complex process, a systematic analysis of the interactions between the malaria parasite and HIV-1 in different relevant human primary cell populations is critically needed.
Several techniques for investigating the impact of HIV-1 on the phagocytosis of micro-organisms and the effect of such pathogens on HIV-1 replication have been described. We here present a method to investigate the effects of P. falciparum-infected erythrocytes on the replication of HIV-1 in human primary monocyte-derived macrophages. The impact of parasite exposure on HIV-1 transcriptional/translational events is monitored by using single cycle pseudotyped viruses in which a luciferase reporter gene has replaced the Env gene while the effect on the quantity of virus released by the infected macrophages is determined by measuring the HIV-1 capsid protein p24 by ELISA in cell supernatants.

An In vitro Co-infection Model to Study Plasmodium falciparum-HIV-1 Interactions in Human Primary Monocyte-derived Immune Cells

We have developed an in vitro malaria-HIV-1 co-infection model to study the impact of Plasmodium falciparum on the HIV-1 replicative cycle in human primary monocyte-derived macrophages. This versatile system can easily be adapted to other primary cell types susceptible to HIV-1 infection.

Plasmodium falciparum, the causative agent  of the deadliest form of malaria, and human immunodeficiency virus type-1 (HIV-1) are among the most important ...

Flow Cytometric Isolation of Primary Murine Type II Alveolar Epithelial Cells for Functional and Molecular Studies

Throughout the last years, the contribution of alveolar type II epithelial cells (AECII) to various aspects of immune regulation in the lung has been increasingly recognized. AECII have been shown to participate in cytokine production in inflamed airways and to even act as antigen-presenting cells in both infection and T-cell mediated autoimmunity 1-8. Therefore, they are especially interesting also in clinical contexts such as airway hyper-reactivity to foreign and self-antigens as well as infections that directly or indirectly target AECII. However, our understanding of the detailed immunologic functions served by alveolar type II epithelial cells in the healthy lung as well as in inflammation remains fragmentary. Many studies regarding AECII function are performed using mouse or human alveolar epithelial cell lines 9-12. Working with cell lines certainly offers a range of benefits, such as the availability of large numbers of cells for extensive analyses. However, we believe the use of primary murine AECII allows a better understanding of the role of this cell type in complex processes like infection or autoimmune inflammation. Primary murine AECII can be isolated directly from animals suffering from such respiratory conditions, meaning they have been subject to all additional extrinsic factors playing a role in the analyzed setting. As an example, viable AECII can be isolated from mice intranasally infected with influenza A virus, which primarily targets these cells for replication 13. Importantly, through ex vivo infection of AECII isolated from healthy mice, studies of the cellular responses mounted upon infection can be further extended.
Our protocol for the isolation of primary murine AECII is based on enzymatic digestion of the mouse lung followed by labeling of the resulting cell suspension with antibodies specific for CD11c, CD11b, F4/80, CD19, CD45 and CD16/CD32. Granular AECII are then identified as the unlabeled and sideward scatter high (SSChigh) cell population and are separated by fluorescence activated cell sorting 3.
In comparison to alternative methods of isolating primary epithelial cells from mouse lungs, our protocol for flow cytometric isolation of AECII by negative selection yields untouched, highly viable and pure AECII in relatively short time. Additionally, and in contrast to conventional methods of isolation by panning and depletion of lymphocytes via binding of antibody-coupled magnetic beads 14, 15, flow cytometric cell-sorting allows discrimination by means of cell size and granularity. Given that instrumentation for flow cytometric cell sorting is available, the described procedure can be applied at relatively low costs. Next to standard antibodies and enzymes for lung disintegration, no additional reagents such as magnetic beads are required. The isolated cells are suitable for a wide range of functional and molecular studies, which include in vitro culture and T-cell stimulation assays as well as transcriptome, proteome or secretome analyses 3, 4.

We describe the rapid isolation of primary murine type II alveolar epithelial cells (AECII) by flow cytometric negative selection. These AECII show high viability and purity and are suitable for a wide range of functional and molecular studies regarding their role in respiratory conditions such as autoimmune or infectious diseases.

Throughout  the last years, the contribution of alveolar type II epithelial cells (AECII)  to various aspects of immune regulation in the lung has been ...

Biomimetic Materials to Characterize Bacteria-host Interactions

Bacterial attachment to host cells is one of the earliest events during bacterial colonization of host tissues and thus a key step during infection. The biochemical and functional characterization of adhesins mediating these initial bacteria-host interactions is often compromised by the presence of other bacterial factors, such as cell wall components or secreted molecules, which interfere with the analysis. This protocol describes the production and use of biomimetic materials, consisting of pure recombinant adhesins chemically coupled to commercially available, functionalized polystyrene beads, which have been used successfully to dissect the biochemical and functional interactions between individual bacterial adhesins and host cell receptors. Protocols for different coupling chemistries, allowing directional immobilization of recombinant adhesins on polymer scaffolds, and for assessment of the coupling efficiency of the resulting &#8220;bacteriomimetic&#8221; materials are also discussed. We further describe how these materials can be used as a tool to inhibit pathogen mediated cytotoxicity and discuss scope, limitations and further applications of this approach in studying bacterial - host interactions.

Bacterial attachment to host cells is a key step during host colonization and infection. This protocol describes the generation of polymer-coupled recombinant adhesins as biomimetic materials which allow analysis of the contribution of individual adhesins to these processes, independent of other bacterial factors.

Bacterial attachment to host cells is one of the earliest events during bacterial colonization of host tissues and thus a key step during infection. The ...

Human Placental and Decidual Organ Cultures to Study Infections at the Maternal-fetal Interface

The placenta shows a large degree of interspecies anatomic variability. To best understand biology and pathophysiology of the human placenta, it is imperative to design experiments using human cells and tissues. An advantage of organ culture is maintenance of three-dimensional (3D) structural organization and extracellular matrix. The goal of the method described here is successful establishment of ex vivo human gestational tissue organ cultures and their healthy culture maintenance for 72-96 hr. The protocol details the immediate processing of research-consented, placental and decidual specimens fresh from the operating suite. These are abundant specimens that would otherwise be discarded. Detailed instructions on the sterile collection of these samples, including morphologic details on how to select appropriate tissues to establish 3D organ cultures, is provided. Placental villous and decidual tissues are microdissected into 2-3 mm3 pieces and placed separately on matrix-lined transwell filters and cultured for several days. Villous and decidual organ cultures are well suited for the study of human host-pathogen interaction. As compared to other model organisms, these human cultures are particularly advantageous to examine mechanism of infection for pathogens that demonstrate variable patterns of host specificity. As an example, we demonstrate infection of placental and decidual organ cultures with the clinically relevant, facultative intracellular bacterial pathogen Listeria monocytogenes.

A simple method to establish primary human placental (villous) and decidual organ cultures is described. Villous and decidual organ cultures are invaluable tools for studying pathogenesis at the human maternal-fetal interface. Infection with the facultative intracellular bacterium Listeria monocytogenes is demonstrated.

The placenta shows a large degree of interspecies anatomic variability. To best understand biology and pathophysiology of the human placenta, it is ...

Assessment of the Synaptic Interface of Primary Human T Cells from Peripheral Blood and Lymphoid Tissue

The current understanding of the dynamics and structural features of T-cell synaptic interfaces has been largely determined through the use of glass-supported planar bilayers and in vitro-derived T-cell clones or lines1,2,3,4. How these findings apply to the primary human T cells isolated from blood or lymphoid tissues is not known, partly due to significant difficulties in obtaining a sufficient number of cells for analysis5. Here we address this through the development of a technique exploiting multichannel flow slides to build planar lipid bilayers containing activating and adhesion molecules. The low height of the flow slides promotes rapid cell sedimentation in order to synchronize cell:bilayer attachment, thereby allowing researchers to study the dynamic of the synaptic interface formation and the kinetics of the granules release. We apply this approach to analyze the synaptic interface of as few as 104 to 105 primary cryopreserved T cells isolated from lymph nodes (LN) and peripheral blood (PB). The results reveal that the novel planar lipid bilayer technique enables the study of the biophysical properties of primary human T cells derived from blood and tissues in the context of health and disease.

The protocol describes a technique to study the ability of primary polyclonal human T cells to form synaptic interfaces using planar lipid bilayers. We use this technique to show the differential synapse formation capability of human primary T cells derived from lymph nodes and peripheral blood.

The current understanding of the dynamics and structural features of T-cell synaptic interfaces has been largely determined through the use of ...

High-Efficiency Generation of Antigen-Specific Primary Mouse Cytotoxic T Cells for Functional Testing in an Autoimmune Diabetes Model

Type 1 Diabetes (T1D) is characterized by islet-specific autoimmunity leading to beta cell destruction and absolute loss of insulin production. In the spontaneous non-obese diabetes (NOD) mouse model, insulin is the primary target, and genetic manipulation of these animals to remove a single key insulin epitope prevents disease. Thus, selective elimination of professional antigen presenting cells (APCs) bearing this pathogenic epitope is an approach to inhibit the unwanted insulin-specific autoimmune responses, and likely has greater translational potential.
Chimeric antigen receptors (CARs) can redirect T cells to selectively target disease-causing antigens. This technique is fundamental to recent attempts to use cellular engineering for adoptive cell therapy to treat multiple cancers. In this protocol, we describe an optimized T-cell retrovirus (RV) transduction and in vitro expansion protocol that generates high numbers of functional antigen-specific CD8 CAR-T cells starting from a low number of naive cells. Previously multiple CAR-T cell protocols have been described, but typically with relatively low transduction efficiency and cell viability following transduction. In contrast, our protocol provides up to 90% transduction efficiency, and the cells generated can survive more than two weeks in vivo and significantly delay disease onset following a single infusion. We provide a detailed description of the cell maintenance and transduction protocol, so that the critical steps can be easily followed. The whole procedure from primary cell isolation to CAR expression can be performed within 14 days. The general method may be applied to any mouse disease model in which the target is known. Similarly, the specific application (targeting a pathogenic peptide/MHC class II complex) is applicable to any other autoimmune disease model for which a key complex has been identified.

This article describes a protocol for the generation of antigen-specific CD8 T cells, and their expansion in vitro, with the aim of yielding high numbers of functional T cells for use in vitro and in vivo.

Type 1 Diabetes (T1D) is characterized by islet-specific autoimmunity leading to beta cell destruction and absolute loss of insulin production. In the ...

Pneumococcus Infection of Primary Human Endothelial Cells in Constant Flow

Interaction of Streptococcus pneumoniae with the surface of endothelial cells is mediated in blood flow via mechanosensitive proteins such as the Von Willebrand Factor (VWF). This glycoprotein changes its molecular conformation in response to shear stress, thereby exposing binding sites for a broad spectrum of host-ligand interactions. In general, culturing of primary endothelial cells under a defined shear flow is known to promote the specific cellular differentiation and the formation of a stable and tightly linked endothelial layer resembling the physiology of the inner lining of a blood vessel. Thus, the functional analysis of interactions between bacterial pathogens and the host vasculature involving mechanosensitive proteins requires the establishment of pump systems that can simulate the physiological flow forces known to affect the surface of vascular cells.
The microfluidic device used in this study enables a continuous and pulseless recirculation of fluids with a defined flow rate. The computer-controlled air-pressure pump system applies a defined shear stress on endothelial cell surfaces by generating a continuous, unidirectional, and controlled medium flow. Morphological changes of the cells and bacterial attachment can be microscopically monitored and quantified in the flow by using special channel slides that are designed for microscopic visualization. In contrast to static cell culture infection, which in general requires a sample fixation prior to immune labeling and microscopic analyses, the microfluidic slides enable both the fluorescence-based detection of proteins, bacteria, and cellular components after sample fixation; serial immunofluorescence staining; and direct fluorescence-based detection in real time. In combination with fluorescent bacteria and specific fluorescence-labeled antibodies, this infection procedure provides an efficient multiple component visualization system for a huge spectrum of scientific applications related to vascular processes.

This study describes the microscopic monitoring of pneumococcus adherence to von Willebrand factor strings produced on the surface of differentiated human primary endothelial cells under shear stress in defined flow conditions. This protocol can be extended to detailed visualization of specific cell structures and quantification of bacteria by applying differential immunostaining procedures.

Interaction of Streptococcus pneumoniae with the surface of endothelial cells is mediated in blood flow via mechanosensitive proteins such as the Von ...

P. aeruginosa Infected 3D Co-Culture of Bronchial Epithelial Cells and Macrophages at Air-Liquid Interface for Preclinical Evaluation of Anti-Infectives

fDrug research for the treatment of lung infections is progressing towards predictive in vitro models of high complexity. The multifaceted presence of bacteria in lung models can re-adapt epithelial arrangement, while immune cells coordinate an inflammatory response against the bacteria in the microenvironment. While in vivo models have been the choice for testing new anti-infectives in the context of cystic fibrosis, they still do not accurately mimic the in vivo conditions of such diseases in humans and the treatment outcomes. Complex in vitro models of the infected airways based on human cells (bronchial epithelial and macrophages) and relevant pathogens could bridge this gap and facilitate the translation of new anti-infectives into the clinic. For such purposes, a co-culture model of the human cystic fibrosis bronchial epithelial cell line CFBE41o- and THP-1 monocyte-derived macrophages has been established, mimicking an infection of the human bronchial mucosa by P. aeruginosa at air-liquid interface (ALI) conditions. This model is set up in seven days, and the following parameters are simultaneously assessed: epithelial barrier integrity, macrophage transmigration, bacterial survival, and inflammation. The present protocol describes a robust and reproducible system for evaluating drug efficacy and host responses that could be relevant for discovering new anti-infectives and optimizing their aerosol delivery to the lungs.

P. aeruginosa Infected 3D Co-Culture of Bronchial Epithelial Cells and Macrophages at Air-Liquid Interface for Preclinical Evaluation of Anti-Infectives

We describe a protocol for a three-dimensional co-culture model of infected airways, using CFBE41o- cells, THP-1 macrophages, and Pseudomonas aeruginosa, established at the air-liquid interface. This model provides a new platform to simultaneously test antibiotic efficacy, epithelial barrier function, and inflammatory markers.

fDrug research for the treatment of lung infections is progressing towards predictive in vitro models of high complexity. The multifaceted presence of ...

Co-Culture of Murine Small Intestine Epithelial Organoids with Innate Lymphoid Cells

Complex co-cultures of organoids with immune cells provide a versatile tool for interrogating the bi-directional interactions that underpin the delicate balance of mucosal homeostasis. These 3D, multi-cellular systems offer a reductionist model for addressing multi-factorial diseases and resolving technical difficulties that arise when studying rare cell types such as tissue-resident innate lymphoid cells (ILCs). This article describes a murine system that combines small intestine organoids and small intestine lamina propria derived helper-like type-1 ILCs (ILC1s), which can be readily extended to other ILC or immune populations. ILCs are a tissue-resident population that is particularly enriched in the mucosa, where they promote homeostasis and rapidly respond to damage or infection. Organoid co-cultures with ILCs have already begun shedding light on new epithelial-immune signaling modules in the gut, revealing how different ILC subsets impact intestinal epithelial barrier integrity and regeneration. This protocol will enable further investigations into reciprocal interactions between epithelial and immune cells, which hold the potential to provide new insights into the mechanisms of mucosal homeostasis and inflammation.

This protocol offers detailed instructions for establishing murine small intestine organoids, isolating type-1 innate lymphoid cells from the murine small intestine lamina propria, and establishing 3-dimensional (3D) co-cultures between both cell types to study bi-directional interactions between intestinal epithelial cells and type-1 innate lymphoid cells.

Complex co-cultures of organoids with immune cells provide a versatile tool for interrogating the bi-directional interactions that underpin the delicate ...