Name: establishing a porcine ex vivo cornea model for studying drug treatments against bacterial keratitis
Uploaded: 2020-05-12T13:30:00
Description: Watch this Scientific Journal Video about Establishing a Porcine Ex Vivo Cornea Model for Studying Drug Treatments against Bacterial Keratitis at JoVE.com

The authors would like to thank Elliot Abattoir in Chesterfield for providing porcine eyes. The glass rings were made based on our design by the glass blower Dan Jackson from the Department of Chemistry at the University of Sheffield. The authors would like to thank the Medical Research Council (MR/S004688/1) for funding. The authors would like to also thank Mrs Shanali Dikwella for technical help with cornea preparation. The authors would like to thank Mr Jonathan Emery for help with formatting pictures.

Albino laboratory rabbits were sacrificed in the laboratory for other planned experimental work under home office approved protocols. The eyes were not required for experimental use in those studies so they were used for this protocol.
1. Sterilization
<ol>
	<li>CRITICAL STEP: Disinfect all forceps and scissors by soaking for 1 h in 5% (v/v) solution of Distel in distilled water, clean with a brush, rinse with tap water and sterilize in an oven at 185 &#176;C for a minimum of 2 h.</li>
	<li>...

<ol>
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R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Establishment+and+Characterization+of+an+Air-Liquid+Canine+Corneal+Organ+Culture+Model+To+Study+Acute+Herpes+Keratitis.">Establishment and Characterization of an Air-Liquid Canine Corneal Organ Culture Model To Study Acute Herpes Keratitis.</a> Journal of Virology. 88 (23), 13669-13677 (2014).</li><li>Madhu, S. N., Jha, K. K., Karthyayani, A. P., Gajjar, D. U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ex+vivo+Caprine+Model+to+Study+Virulence+Factors+in+Keratitis.">Ex vivo Caprine Model to Study Virulence Factors in Keratitis.</a> Journal of Ophthalmic &amp; Vision Research. 13 (4), 383-391 (2018).</li><li>Vermeltfoort, P. B. J., van Kooten, T. G., Bruinsma, G. M., Hooymans, A. M. M., vander Mei, H. C., Busscher, H. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bacterial+transmission+from+contact+lenses+to+porcine+corneas:+An+ex+vivo+study.">Bacterial transmission from contact lenses to porcine corneas: An ex vivo study.</a> Investigative Ophthalmology &amp; Visual Science. 46 (6), 2042-2046 (2005).</li><li>Duggal, 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=Zinc+oxide+tetrapods+inhibit+herpes+simplex+virus+infection+of+cultured+corneas.">Zinc oxide tetrapods inhibit herpes simplex virus infection of cultured corneas.</a> Molecular Vision. 23, 26-38 (2017).</li><li>Brothers, 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=Bacterial+Impediment+of+Corneal+Cell+Migration.">Bacterial Impediment of Corneal Cell Migration.</a> Investigative Ophthalmology &amp; Visual Science. 56 (7), (2015).</li><li>Alekseev, O., Tran, A. H., Azizkhan-Clifford, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ex+vivo+Organotypic+Corneal+Model+of+Acute+Epithelial+Herpes+Simplex+Virus+Type+I+Infection.">Ex vivo Organotypic Corneal Model of Acute Epithelial Herpes Simplex Virus Type I Infection.</a> Journal of Visualized Experiments. (69), (2012).</li><li>Sack, R. A., Nunes, I., Beaton, A., Morris, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Host-Defense+Mechanism+of+the+Ocular+Surfaces.">Host-Defense Mechanism of the Ocular Surfaces.</a> Bioscience Reports. 21 (4), 463-480 (2001).</li><li>Kunzmann, B. 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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=Protectively+Decellularized+Porcine+Cornea+versus+Human+Donor+Cornea+for+Lamellar+Transplantation.">Protectively Decellularized Porcine Cornea versus Human Donor Cornea for Lamellar Transplantation.</a> Advanced Functional Materials. 29, 1902491-1902503 (2019).</li><li>Menduni, F., Davies, L. N., Madrid-Costa, D., Fratini, A., Wolffsohn, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterisation+of+the+porcine+eyeball+as+an+in-vitro+model+for+dry+eye.">Characterisation of the porcine eyeball as an in-vitro model for dry eye.</a> Contact Lens &amp; Anterior Eye. 41 (1), 13-17 (2018).</li><li>Castro, N., Gillespie, S. R., Bernstein, A. 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The main driver behind the development of this keratitis model using ex vivo porcine cornea is to provide researchers developing novel antimicrobials with a representative in vitro model to more accurately determine antimicrobial efficacy at the preclinical stages. This will provide researchers involved in developing new antimicrobials greater control over drug design and formulation at the pre-clinical stages, increase success at clinical trials, reduce use of animals by enabling targeted studies and result in faster tr...

Corneal infections are important causes of blindness and occur in epidemic proportions in low- and mid-income countries. The etiology of the disease varies from region to region but bacteria account for a large majority of these cases. Pseudomonas aeruginosa is an important pathogen that causes a rapidly progressive disease. In many cases, patients are left with stromal scarring, irregular astigmatism, require transplant or in the worst case scenario, lose an eye1,2.
Bacterial keratitis caused by P. aeruginosa is a difficult eye infection to treat particularly due to the increasing emergence of antimicrobial resistant strains of P. aeruginosa. Within the last decade, it has become apparent that testing and developing new treatments for corneal infections, in general, and those caused by Pseudomonas sp., in particular, are essential to combat the current trend in antibiotic resistance3.
For testing the efficacy of new treatments for corneal infections, conventional in vitro microbiological methods are a poor surrogate due to the difference in bacterial physiology during laboratory culture and during infections in vivo as well as due to the lack of the host interface4,5. In vivo animal models, however, are expensive, time-consuming, can only deliver a small number of replicates and raise concerns about animal welfare.
In this article, we demonstrate a simple and reproducible organotypic ex vivo porcine model of keratitis that can be used to test various treatments for acute and chronic infections. We have used P. aeruginosa for this experiment but the model also works well with other bacteria, and organisms such as fungi and yeast which cause keratitis.

<table>
	<tbody>
		<tr>
			<td>50 mL Falcon tube</td>
			<td>SLS</td>
			<td>352070</td>
			<td></td>
		</tr>
		<tr>
			<td>Amphotericin B</td>
			<td>Sigma</td>
			<td>A2942</td>
			<td></td>
		</tr>
		<tr>
			<td>Cellstar 12 well plate</td>
			<td>Greiner Bio-One</td>
			<td>665180</td>
			<td></td>
		</tr>
		<tr>
			<td>Dextran</td>
			<td>Sigma</td>
			<td>31425-100mg-F</td>
			<td></td>
		</tr>
		<tr>
			<td>Distel</td>
			<td>Fisher Scientific</td>
			<td>12899357</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM + glutamax</td>
			<td>SLS</td>
			<td>D0819</td>
			<td></td>
		</tr>
		<tr>
			<td>Dual Oven Incubator</td>
			<td>SLS</td>
			<td>OVe1020</td>
			<td>Sterilising oven</td>
		</tr>
		<tr>
			<td>Epidermal growth factor</td>
			<td>SLS</td>
			<td>E5036-200UG</td>
			<td></td>
		</tr>
		<tr>
			<td>F12 HAM</td>
			<td>Sigma</td>
			<td>N4888</td>
			<td></td>
		</tr>
		<tr>
			<td>Foetal calf serum</td>
			<td>Labtech International</td>
			<td>CA-115/500</td>
			<td></td>
		</tr>
		<tr>
			<td>Forceps</td>
			<td>Fisher Scientific</td>
			<td>15307805</td>
			<td></td>
		</tr>
		<tr>
			<td>Handheld homogeniser 220</td>
			<td>Fisher Scientific</td>
			<td>15575809</td>
			<td>Homogeniser</td>
		</tr>
		<tr>
			<td>Heracell VIOS 160i</td>
			<td>Thermo Scientific</td>
			<td>15373212</td>
			<td>Tissue culture incubator</td>
		</tr>
		<tr>
			<td>Heraeus Megafuge 16R</td>
			<td>VWR</td>
			<td>521-2242</td>
			<td>Centrifuge</td>
		</tr>
		<tr>
			<td>Insulin, recombinant Human</td>
			<td>SLS</td>
			<td>91077C-1G</td>
			<td></td>
		</tr>
		<tr>
			<td>LB agar</td>
			<td>Sigma</td>
			<td>L2897</td>
			<td></td>
		</tr>
		<tr>
			<td>Multitron</td>
			<td>Infors</td>
			<td>Not appplicable</td>
			<td>Bacterial incubator</td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>SLS</td>
			<td>P4417</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin</td>
			<td>SLS</td>
			<td>P0781</td>
			<td></td>
		</tr>
		<tr>
			<td>Petri dish</td>
			<td>Fisher Scientific</td>
			<td>12664785</td>
			<td></td>
		</tr>
		<tr>
			<td>Petri dish 35x10mm CytoOne</td>
			<td>Starlab</td>
			<td>CC7672-3340</td>
			<td></td>
		</tr>
		<tr>
			<td>Povidone iodine</td>
			<td>Weldricks pharmacy</td>
			<td>2122828</td>
			<td></td>
		</tr>
		<tr>
			<td>Safe 2020</td>
			<td>Fisher Scientific</td>
			<td>1284804</td>
			<td>Class II microbiology safety cabinet</td>
		</tr>
		<tr>
			<td>Scalpel blade number 15</td>
			<td>Fisher Scientific</td>
			<td>O305</td>
			<td></td>
		</tr>
		<tr>
			<td>Scalpel Swann Morton</td>
			<td>Fisher Scientific</td>
			<td>11849002</td>
			<td></td>
		</tr>
	</tbody>
</table>

establishing a porcine ex vivo cornea model for studying drug treatments against bacterial keratitis

When developing novel antimicrobials, the success of animal trials is dependent on accurate extrapolation of antimicrobial efficacy from in vitro tests to animal infections in vivo. The existing in vitro tests typically overestimate antimicrobial efficacy as the presence of host tissue as a diffusion barrier is not accounted for. To overcome this bottleneck, we have developed an ex vivo porcine corneal model of bacterial keratitis using Pseudomonas aeruginosa as a prototypic organism. This article describes the preparation of the porcine cornea and protocol for establishment of the infection. Bespoke glass molds enable straightforward setup of the cornea for infection studies. The model mimics in vivo infection as bacterial proliferation is dependent on the ability of the bacterium to damage corneal tissue. Establishment of infection is verified as an increase in the number of colony forming units assessed via viable plate counts. The results demonstrate that infection can be established in a highly reproducible fashion in the ex vivo corneas using the method described here. The model can be extended in the future to mimic keratitis caused by microorganisms other than P. aeruginosa. The ultimate aim of the model is to investigate the effect of antimicrobial chemotherapy on the progress of bacterial infection in a scenario more representative of in vivo infections. In so doing, the model described here will reduce the use of animals for testing, improve success rates in clinical trials and ultimately enable rapid translation of novel antimicrobials to the clinic.

The design of the glass molds are an innovative and original idea, the use of which allowed us to set up the model in a consistent fashion with minimal/no issues with contamination. The molds were prepared by a glass blower at the University of Sheffield based on a design (Figure 1A). The experimental setup maintains the convex shape of the cornea and holds bacteria on the top of the epithelium where infection takes place (Figure 1B).
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Watch this Scientific Journal Video about Establishing a Porcine Ex Vivo Cornea Model for Studying Drug Treatments against Bacterial Keratitis at JoVE.com

Establishing a Porcine Ex Vivo Cornea Model for Studying Drug Treatments against Bacterial Keratitis

This article describes a step-by-step protocol to set up an ex vivo porcine model of bacterial keratitis. Pseudomonas aeruginosa is used as a prototypic organism. This innovative model mimics in vivo infection as bacterial proliferation is dependent on the ability of the bacterium to damage corneal tissue.

When developing novel antimicrobials, the success of animal trials is dependent on accurate extrapolation of antimicrobial efficacy from in vitro tests to ...

The ex vivo porcine keratitis model presented here provides researchers developing novel antimicrobials with a representative in vitro model to more accurately determine antimicrobial efficacy at the preclinical stages. We have used Pseudomonas aeruginosa for this experiment, but the model also works well with other bacteria and organisms such as fungi and yeast. Use sterile forceps to transfer the eyeball to a Petri dish.Remove the conjunctiva and muscle tissue around the eyeball using a scalpel blade number 15 and forceps. Then while holding the optic nerve with the forceps, gently lift the eyeball and transfer it to a half liter jar filled with sterile PBS. Once all eyeballs are cleared of surrounding tissue, use sterile forceps to move them to another half liter jar filled with 3%povidone iodine in PBS.After the eyeballs have been in the jar for one minute, transfer them to a third jar containing sterile PBS. Place an eyeball on a clean Petri dish and use the forceps to hold it steady. With a number 10A scalpel blade, make a cut near the cornea.Use scissors to excise the cornea leaving about three millimeters of sclera surrounding it. Ensure the sharp end of the scissors is in the suprachoroidal space and does not pierce the iris. Hold the corneoscleral button with forceps and use another pair of pointed end forceps to gently separate the uveal tissue.Then lift the corneoscleral button to separate it from the remainder of the eyeball. Briefly rinse the button in a 1.5%solution of povidone iodine in PBS. Then place the button in sterile PBS in a 12-well plate.After processing no more than 40 eyeballs, place each corneoscleral button in its own 34 millimeter Petri dish with the epithelial side up. To each dish, add three milliliters of culture medium pre-warmed to 37 degrees Celsius. Incubate the Petri dishes for 24 hours at 37 degrees Celsius in a humidified tissue culture incubator.Use aseptic technique to remove the media from the Petri dishes and replace it with three milliliters of fresh pre-warmed culture media containing antibiotics. After incubating the corneas for 48 hours, remove the media again and rinse the corneas with two milliliters of PBS. Then add antibiotic-free media and incubate for two to three days to remove residual antibiotics from the tissue.Change the media at least one more time within these three days. Discard corneas if any turbidity develops in the antibiotic-free medium. Add 10 milliliters of LB to a 50 milliliter conical flask with a foam stopper.Inoculate the broth with a colony of P.aeruginosa from a fresh agar plate and incubate at 37 degrees Celsius for three to four hours until the bacteria are in mid log phase. Transfer the bacterial culture to a 50 milliliter tube and centrifuge it at 3, 000 times G for five minutes. Remove the supernatant and resuspend the cell pellet in PBS.After washing the cells two more times and resuspending them in PBS, adjust the optical density of the suspension at 600 nanometers to approximately 0.6 using sterile PBS as a blank. Remove the media from the Petri dish and rinse the corneas twice with one milliliter of sterile PBS. Hold the cornea with forceps and squeeze gently.Use a 10A scalpel to make four cuts, two vertical, two horizontal in the central section of the corneoscleral button through the epithelial layer to the underlying stroma. Place a sterile glass mold in a six-well plate with the wide part up. Then place the cornea in the middle of the glass mold with the epithelium side facing down and the wounded part of the cornea centered in the glass mold.Fill the glass mold completely by adding one milliliter of agar solution. After allowing the agar to set, invert the glass mold so that the corneal epithelium is facing upwards. The glass mold has to be sealed with agar up to the brim to prevent leaking of the inoculum or drug solution.Pipette 200 microliters of the bacterial culture directly into a cut area. Also for each experiment, set up a control by adding 200 microliters of sterile PBS to one cornea instead of adding the bacterial culture. Next, add 185 microliters of PBS to the top of each cornea to keep the epithelium moist.Then add one milliliter of DMEM without antibiotics to the bottom of each well. Incubate the six-well plate at 37 degrees Celsius with humidity and 5%carbon dioxide for up to 24 hours. Discard the DMEM from the six-well plate and one milliliter of sterile PBS to each well to rinse it.Remove the PBS gently without touching the central part of the corneoscleral button. Remove the glass mold using sterile forceps and place it in 5%Distel. Gently rinse the top of the corneoscleral button twice with one milliliter of PBS.Use fine tip forceps to lift the edge of the corneoscleral button, detach it from the agar underneath and transfer it to a 50 milliliter tube filled with one to two milliliters of ice cold PBS. To help detach bacteria from the corneal epithelium and the cut area, add PBS to the tube and use a fine tip homogenizer to shear the top of the infected cornea. The tissue does not have to be completely liquidized.Vortex to resuspend settled bacteria and add 20 microliters of the homogenized cornea to 180 microliters of PBS. Then perform serial dilutions of the homogenate in a 96-well plate. Pipette 10 microliters of the diluted homogenate onto a blood agar plate.After incubating the plate for 16 hours, count the number of colony forming units. Porcine corneas usually swell after a few days in medium. There was no significant difference in colony forming units obtained from corneas with and without addition of dextran, which is usually added to prevent swelling of the cornea.Corneas are typically wounded to help the bacteria penetrate the epithelium. Although there was no significant difference in the progress of infection between wounded and unwanted corneas, there was more variation among replicates in wounded corneas. Washing the corneas twice with PBS removes excess bacteria that did not attach to the epithelium.There is a significant difference in CFU between washed and unwashed porcine corneas infected with P.aeruginosa PAO1 for 24 hours. There was no significant difference in CFU counts between porcine and rabbit corneas infected with PA14 and PAO1. The results for both models were reproducible.After 24 hours, the corneas infected with either Pseudomonas strain always developed opacity and the cut area becomes more visible and open in comparison to the uninfected cornea. Infected and treated corneas that were processed with this method can be further used for waxing, cryopreservation, sectioning, staining with hematoxylin and Olsen, immunostaining, and confocal microscopy. The protocol contributes to greater control over drug design and formulation at the preclinical stages, which would increase success at clinical trials, reduce the use of animals, and result in faster translation of new antimicrobials to the clinic.

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Research

JoVE Journal

Immunology and Infection

Recurrent Herpetic Stromal Keratitis in Mice, a Model for Studying Human HSK

Herpetic eye disease, termed herpetic stromal keratitis (HSK), is a potentially blinding infection of the cornea that results in over 300,000 clinical visits each year for treatment. Between 1 and 2 percent of those patients with clinical disease will experience loss of vision of the infected cornea. The vast majority of these cases are the result of reactivation of a latent infection by herpes simplex type I virus and not due to acute disease. Interestingly, the acute infection is the model most often used to study this disease. However, it was felt that a recurrent model of HSK would be more reflective of what occurs during clinical disease. The recurrent animal models for HSK have employed both rabbits and mice. The advantage of rabbits is that they experience reactivation from latency absent any known stimulus. That said, it is difficult to explore the role that many immunological factors play in recurrent HSK because the rabbit model does not have the immunological and genetic resources that the mouse has. We chose to use the mouse model for recurrent HSK because it has the advantage of there being many resources available and also we know when reactivation will occur because reactivation is induced by exposure to UV-B light. Thus far, this model has allowed those laboratories using it to define several immunological factors that are important to this disease. It has also allowed us to test both therapeutic and vaccine efficacy.

Most studies of herpetic corneal disease use a primary infection model. However, primary infection with HSV-1 does not typically lead to human disease. Here we describe a recurrent model of herpetic corneal disease, which more closely mimics human disease.

Herpetic eye disease, termed herpetic stromal keratitis (HSK), is a potentially blinding infection of the cornea that results in over 300,000 clinical ...

Bioluminescent Bacterial Imaging In Vivo

This video describes the use of whole body bioluminesce imaging (BLI) for the study of bacterial trafficking in live mice, with an emphasis on the use of bacteria in gene and cell therapy for cancer. Bacteria present an attractive class of vector for cancer therapy, possessing a natural ability to grow preferentially within tumors following systemic administration. Bacteria engineered to express the lux gene cassette permit BLI detection of the bacteria and concurrently tumor sites. The location and levels of bacteria within tumors over time can be readily examined, visualized in two or three dimensions. The method is applicable to a wide range of bacterial species and tumor xenograft types. This article describes the protocol for analysis of bioluminescent bacteria within subcutaneous tumor bearing mice. Visualization of commensal bacteria in the Gastrointestinal tract (GIT) by BLI is also described. This powerful, and cheap, real-time imaging strategy represents an ideal method for the study of bacteria in vivo in the context of cancer research, in particular gene therapy, and infectious disease. This video outlines the procedure for studying lux-tagged E. coli in live mice, demonstrating the spatial and temporal readout achievable utilizing BLI with the IVIS system.

Bioluminescent Bacterial Imaging In Vivo

This article describes the administration of lux-tagged bacteria to mice and subsequent in vivo analysis using IVIS bioluminescence imaging.

This video describes the use of whole body bioluminesce imaging (BLI) for the study of bacterial trafficking in live mice, with an emphasis on the use of ...

Assays for the Identification of Novel Antivirals against Bluetongue Virus

To identify potential antivirals against BTV, we have developed, optimized and validated three assays presented here. The CPE-based assay was the first assay developed to evaluate whether a compound showed any antiviral efficacy and have been used to screen large compound library. Meanwhile, cytotoxicity of antivirals could also be evaluated using the CPE-based assay. The dose-response assay was designed to determine the range of efficacy for the selected antiviral, i.e. 50% inhibitory concentration (IC50) or effective concentration (EC50), as well as its range of cytotoxicity (CC50). The ToA assay was employed for the initial MoA study to determine the underlying mechanism of the novel antivirals during BTV viral lifecycle or the possible effect on host cellular machinery. These assays are vital for the evaluation of antiviral efficacy in cell culture system, and have been used for our recent researches leading to the identification of a number of novel antivirals against BTV.

Three assays, including the cytopathic effect (CPE)-based assay, dose-response assay and Time-of-Addition (ToA) assay have been developed, optimized, validated and utilized to identify novel antivirals against Bluetongue virus (BTV), as well as to determine the possible Mechanism-of-Action (MoA) for newly identified antivirals.

To identify potential antivirals against BTV, we have  developed, optimized and validated three assays presented here. The CPE-based  assay was the first ...

An Ex vivo Model of an Oligodendrocyte-directed T-Cell Attack in Acute Brain Slices

Death of oligodendrocytes accompanied by destruction of neurons and axons are typical histopathological findings in cortical and subcortical grey matter lesions in inflammatory demyelinating disorders like multiple sclerosis (MS). In these disorders, mainly CD8+ T-cells of putative specificity for myelin- and oligodendrocyte-related antigens are found, so that neuronal apoptosis in grey matter lesions may be a collateral effect of these cells. Different types of animal models are established to study the underlying mechanisms of the mentioned pathophysiological processes. However, although they mimic some aspects of MS, it is impossible to dissect the exact mechanism and time course of &#8216;&#8216;collateral&#8217;&#8217; neuronal cell death. To address this course, here we show a protocol to study the mechanisms and time response of neuronal damage following an oligodendrocyte-directed CD8+ T cell attack. To target only the myelin sheath and the oligodendrocytes, in vitro activated oligodendrocyte-specific CD8+ T-cells are transferred into acutely isolated brain slices. After a defined incubation period, myelin and neuronal damage can be analysed in different regions of interest. Potential applications and limitations of this model will be discussed.

An Ex vivo Model of an Oligodendrocyte-directed T-Cell Attack in Acute Brain Slices

To address mechanisms of demyelination and neuronal apoptosis in cortical lesions of inflammatory demyelinating disorders, different animal models are used. We here describe an ex vivo approach by using oligodendrocyte-specific CD8+ T-cells on brain slices, resulting in oligodendroglial and neuronal death. Potential applications and limitations of the model are discussed.

Death of oligodendrocytes accompanied by destruction of neurons and axons are typical histopathological findings in cortical and subcortical grey matter ...

In Vitro and In Vivo Model to Study Bacterial Adhesion to the Vessel Wall Under Flow Conditions

In order to cause endovascular infections and infective endocarditis, bacteria need to be able to adhere to the vessel wall while being exposed to the shear stress of flowing blood.
To identify the bacterial and host factors that contribute to vascular adhesion of microorganisms, appropriate models that study these interactions under physiological shear conditions are needed. Here, we describe an in vitro flow chamber model that allows to investigate bacterial adhesion to different components of the extracellular matrix or to endothelial cells, and an intravital microscopy model that was developed to directly visualize the initial adhesion of bacteria to the splanchnic circulation in vivo. These methods can be used to identify the bacterial and host factors required for the adhesion of bacteria under flow. We illustrate the relevance of shear stress and the role of von Willebrand factor for the adhesion of Staphylococcus aureus using both the in vitro and in vivo model.

In Vitro and In Vivo Model to Study Bacterial Adhesion to the Vessel Wall Under Flow Conditions

To study the interaction of bacteria with the blood vessels under shear stress, a flow chamber and an in vivo mesenteric intravital microscopy model are described that allow to dissect the bacterial and host factors contributing to vascular adhesion.

In order to cause endovascular infections and infective endocarditis, bacteria need to be able to adhere to the vessel wall while being exposed to the ...

A High-throughput Compatible Assay to Evaluate Drug Efficacy against Macrophage Passaged Mycobacterium tuberculosis

The early drug development process for anti-tuberculosis drugs is hindered by the inefficient translation of compounds with in vitro activity to effectiveness in the clinical setting. This is likely due to a lack of consideration for the physiologically relevant cellular penetration barriers that exist in the infected host. We recently established an alternative infection model that generates large macrophage aggregate structures containing densely packed M. tuberculosis (Mtb) at its core, which was suitable for drug susceptibility testing. This infection model is inexpensive, rapid, and most importantly BSL-2 compatible. Here, we describe the experimental procedures to generate Mtb/macrophage aggregate structures that would produce macrophage-passaged Mtb for drug susceptibility testing. In particular, we demonstrate how this infection system could be directly adapted to the 96-well plate format showing throughput capability for the screening of compound libraries against Mtb. Overall, this assay is a valuable addition to the currently available Mtb drug discovery toolbox due to its simplicity, cost effectiveness, and scalability.

A High-throughput Compatible Assay to Evaluate Drug Efficacy against Macrophage Passaged Mycobacterium tuberculosis

New models and assays that would improve the early drug development process for next-generation anti-tuberculosis drugs are highly desirable. Here, we describe a quick, inexpensive, and BSL-2 compatible assay to evaluate drug efficacy against Mycobacterium tuberculosis that can be easily adapted for high-throughput screening.

The early drug development process for anti-tuberculosis drugs is hindered by the inefficient translation of compounds with in vitro activity to ...

Opsonophagocytic Killing Assay to Assess Immunological Responses Against Bacterial Pathogens

A key aspect of the immune response to bacterial colonization of the host is phagocytosis. An opsonophagocytic killing assay (OPKA) is an experimental procedure in which phagocytic cells are co-cultured with bacterial units. The immune cells will phagocytose and kill the bacterial cultures in a complement-dependent manner. The efficiency of the immune-mediated cell killing is dependent on a number of factors and can be used to determine how different bacterial cultures compare with regard to resistance to cell death. In this way, the efficacy of potential immune-based therapeutics can be assessed against specific bacterial strains and/or serotypes. In this protocol, we describe a simplified OPKA that utilizes basic culture conditions and cell counting to determine bacterial cell viability after co-culture with treatment conditions and HL-60 immune cells. This method has been successfully utilized with a number of different pneumococcal serotypes, capsular and acapsular strains, and other bacterial species. The advantages of this OPKA protocol are its simplicity, versatility (as this assay is not limited to antibody treatments as opsonins), and minimization of time and reagents to assess basic experimental groups.

This opsonophagocytic killing assay is used to compare the ability of phagocytic immune cells to respond to and kill bacteria based on different treatments and/or conditions. Classically, this assay serves as the gold&#160;standard for assessing effector functions of antibodies raised against a bacterium as opsonin.

A key aspect of the immune response to bacterial colonization of the host is phagocytosis. An opsonophagocytic killing assay (OPKA) is an experimental ...

Assessment of Lymphocyte Migration in an Ex Vivo Transmigration System

Herein, we present an efficient method that can be executed with basic laboratory skills and materials to assess lymphocyte chemokinetic movement in an ex vivo transmigration system. Group 2 innate lymphoid cells (ILC2) and CD4+ T helper cells were isolated from spleens and lungs of chicken egg ovalbumin (OVA)-challenged BALB/c mice. We confirmed the expression of CCR4 on both CD4+ T cells and ILC2, comparatively. CCL17 and CCL22 are the known ligands for CCR4; therefore, using this ex vivo transmigration method we examined CCL17- and CCL22-induced movement of CCR4+ lymphocytes. To establish chemokine gradients, CCL17 and CCL22 were placed in the bottom chamber of the transmigration system. Isolated lymphocytes were then added to top chambers and over a 48 h period the lymphocytes actively migrated through 3 &#181;m pores towards the chemokine in the bottom chamber. This is an effective system for determining the chemokinetics of lymphocytes, but, understandably, does not mimic the complexities found in the in vivo organ microenvironments. This is one limitation of the method that can be overcome by the addition of in situ imaging of the organ and lymphocytes under study. In contrast, the advantage of this method is that is can be performed by an entry-level technician at a much more cost-effective rate than live imaging. As therapeutic compounds become available to enhance migration, as in the case of tumor infiltrating cytotoxic immune cells, or to inhibit migration, perhaps in the case of autoimmune diseases where immunopathology is of concern, this method can be used as a screening tool. In general, the method is effective if the chemokine of interest is consistently generating chemokinetics at a statistically higher level than the media control. In such cases, the degree of inhibition/enhancement by a given compound can be determined as well.

In this protocol, lymphocytes are placed in the top chamber of a transmigration system, separated from the bottom chamber by a porous membrane. Chemokine is added to the bottom chamber, which induces active migration along a chemokine gradient. After 48 h, lymphocytes are counted in both chambers to quantitate transmigration.

Herein, we present an efficient method that can be executed with basic laboratory skills and materials to assess lymphocyte chemokinetic movement in an ex ...

Multi-scale Analysis of Bacterial Growth Under Stress Treatments

Analysis of the bacterial ability to grow and survive under stress conditions is essential for a wide range of microbiology studies. It is relevant to characterize the response of bacterial cells to stress-inducing treatments such as exposure to antibiotics or other antimicrobial compounds, irradiation, non-physiological pH, temperature, or salt concentration. Different stress treatments might disturb different cellular processes, including cell division, DNA replication, protein synthesis, membrane integrity, or cell cycle regulation. These effects are usually associated with specific phenotypes at the cellular scale. Therefore, understanding the extent and causality of stress-induced growth or viability deficiencies requires a careful analysis of several parameters, both at the single-cell and at the population levels. The experimental strategy presented here combines traditional optical density monitoring and plating assays with single-cell analysis techniques such as flow cytometry and real time microscopy imaging in live cells. This multiscale framework allows a time-resolved description of the impact of stress conditions on the fate of a bacterial population.

This protocol allows a time-resolved description of bacterial growth under stress conditions at the single-cell and the cell population levels.

Analysis of the bacterial ability to grow and survive under stress conditions is essential for a wide range of microbiology studies. It is relevant to ...

Visualization of Bacterial Resistance using Fluorescent Antibiotic Probes

Fluorescent antibiotics are multipurpose research tools that are readily used for the study of antimicrobial resistance, due to their significant advantage over other methods. To prepare these probes, azide derivatives of antibiotics are synthesized, then coupled with alkyne-fluorophores using azide-alkyne dipolar cycloaddition by click chemistry. Following purification, the antibiotic activity of the fluorescent antibiotic is tested by minimum inhibitory concentration assessment. In order to study bacterial accumulation, either spectrophotometry or flow cytometry may be used, allowing for much simpler analysis than methods relying on radioactive antibiotic derivatives. Furthermore, confocal microscopy can be used to examine localization within the bacteria, affording valuable information about mode of action and changes that occur in resistant species. The use of fluorescent antibiotic probes in the study of antimicrobial resistance is a powerful method with much potential for future expansion.

Fluorescently tagged antibiotics are powerful tools that can be used to study multiple aspects of antimicrobial resistance. This article describes the preparation of fluorescently tagged antibiotics and their application to studying antibiotic resistance in bacteria. Probes can be used to study mechanisms of bacterial resistance (e.g., efflux) by spectrophotometry, flow cytometry, and microscopy.