Name: transformation of probiotic yeast and their recovery from gastrointestinal immune tissues following oral gavage in mice
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Description: Watch this Scientific Journal Video about Transformation of Probiotic Yeast and Their Recovery from Gastrointestinal Immune Tissues Following Oral Gavage in Mice at JoVE.com

The authors acknowledge funding through the Children&#39;s Center for Immunology and Vaccines and an NIH New Innovator Award (1DP2AI112242-01) awarded to Tracey J. Lamb. The authors also thank Natalya P. Degtyareva for the generous contribution of rad1 S. cerevisiae.

1. UV Mutagenesis to Generate Auxotrophic Yeast Strains
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	<li>Generate survival curves to determine needed doses of UV irradiation
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		<li>Prepare YPD (yeast extract peptone dextrose) media and other reagents listed in Table 1 according to standard procedures26 and inoculate single colonies into 5-10 ml of YPD media. Incubate cultures on a roller drum at 30 &#176;C O/N&#160;to saturation for at least 8 hr.</li>
		<li>Determine the cell concentration of O/N cultures using a spectropho...

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Together, the protocols herein describe the essential steps necessary for the development and testing of auxotrophic probiotic yeast strains for delivery of heterologous therapeutic protein to the intestine. This manipulation and testing of recombinant probiotic yeast requires techniques and resources with which any individual laboratory may not currently be familiar. Thus, although numerous previous studies have described the above protocols for multiple yeast and mouse strains, these methods have not to the authors&#39...

Probiotic microorganisms are an intriguing potential means of efficiently and economically delivering heterologous proteins to the gastrointestinal tract. These organisms are capable of surviving passage through the gastrointestinal tract yet do not colonize it1, enabling controlled dosing and limiting exposure to the drug expressed. Furthermore, the ability to easily engineer these organisms to produce heterologous protein on a large scale renders them an economical alternative to synthetic delivery particles. However, development of such an approach, as recently demonstrated using an auxotrophic strain of the probiotic yeast Saccharomyces boulardii2, requires knowledge of laboratory techniques not traditionally combined within a given study, ranging from yeast and molecular biology to animal handling techniques and immunological methods. Thus although the individual procedures described herein are not in themselves novel laboratory protocols, the goal of this manuscript is to present a unified introduction to techniques needed for experimental testing of probiotic yeast as drug delivery vehicles to the murine gastrointestinal tract. Provided is a compilation of essential protocols for: 1) generation of auxotrophic mutant strains of yeast that can easily be genetically manipulated; 2) transformation of yeast cultures to express heterologous protein; 3) administration of recombinant yeast to the intestine via oral gavage; and 4) recovery of viable recombinant probiotic yeast from the murine intestine and assessment of their heterologous protein expression.
First, although numerous positive and negative selection methods exist for the manipulation of yeast species, negative selection such as through the use of auxotrophic markers increases both the efficiency and ease with which yeast can be transformed and selected. Positive selection of transformants using antibiotics, in contrast, significantly increases the cost of yeast manipulation. Furthermore, selection of yeast on antibiotic-containing solid media can allow for increased growth of untransformed background colonies relative to selection of auxotrophic yeast on synthetic drop out solid media (unpublished observations). Auxotrophic yeast is strains which lack enzymes critical for the synthesis of essential amino acids or uracil. Such yeast can grow only if supplemented with the missing metabolite or metabolic gene, thus enabling negative selection when yeast is plated onto synthetic drop out media that lacks the essential metabolite. Many commonly used Saccharomyces cerevisiae laboratory strains are in fact already auxotrophic mutants3. Industrial, clinical, and probiotic yeast strains, however, are typically prototrophic with the ability to synthesize all required nutrients. To enable more efficient genetic manipulation of such yeast, auxotrophic genes can be selectively targeted to generate strains that can be selected without antibiotics. Specific targeting of auxotrophic marker genes can be achieved through PCR-mediated gene disruption relying on homologous recombination or more recently through CRISPR/Cas9 targeting4-6. Alternatively, UV mutagenesis can quickly generate auxotrophic mutants even in yeast strains for which transformation with multiple plasmids is technically difficult7. While PCR targeting and CRISPR/Cas9 have been described extensively elsewhere, presented in part one of this manuscript is a detailed protocol describing a UV mutagenesis approach to create auxotrophic strains that will allow for negative selection rather than positive antibiotic selection of yeast transformants.
The next necessary step in the use of such auxotrophic strains for oral delivery of heterologous protein is yeast transformation with plasmid DNA. Since the first successful transformation of yeast spheroplasts reported for Saccharomyces cerevisiae in 19788, numerous modifications have been characterized to increase the efficiency and ease with which yeast species can be genetically modified. Use of electroporation for the successful transformation of DNA into S. cerevisiae was first described in 19859 and has since been improved via the addition of 1 M sorbitol incubation to osmotically support cells10. Electroporation efficiency has furthermore been shown to depend on the yeast species and strain, cell number and phase of growth, electroporation volume, field strength, and specific buffers11. Lithium acetate (LiOAc) transformation, originally described by Ito et al.12, is among the most commonly used transformation protocols as it requires no special equipment. Additional analyses showed that the efficiency of LiOAc yeast transformation greatly increases when cells are collected in mid-log phase of growth and are heat shocked in the presence of polyethylene glycol (PEG) and DNA at 42 &#176;C12. Incubation of whole intact yeast with PEG is essential for efficient transformation, possibly through improving attachment of DNA to the cell membrane as well as via other effects on the membrane13. Lithium itself also increases the permeability of intact cells14. Although most laboratory S. cerevisiae strains can easily be transformed using LiOAc transformation3, other yeast species may be more efficiently transformed using alternative protocols. Pichia pastoris, for example, is most efficiently transformed via electroporation rather than LiOAc transformation13. It is crucial, therefore, to test multiple methods of transformation and to optimize incubation periods and reagent concentrations when attempting to genetically modify an uncharacterized yeast strain. This manuscript thus describes both LiOAc transformation and electroporation as techniques for the transformation of auxotrophic mutant and wild type S. boulardii. Interested readers are directed to recent reviews for thorough descriptions of the evolution of yeast transformation, alternative protocols, and further discussions of possible mechanisms of action13,15. Transformation of yeast with plasmid encoding an easily detectable protein is furthermore essential for downstream testing in order to ensure proper expression and function of heterologous protein. Myriad different proteins may be selected depending on the ultimate purpose of the therapeutic study and the antibodies available for protein detection by immunoblotting, ELISA, and other techniques. Protocols for these techniques have been thoroughly described elsewhere16,17, and can be used to determine levels of heterologous protein production from transformed yeast by comparison to standard curves. For purposes of demonstration and to show successful production of a very commonly used protein in yeast biology, this manuscript presents transformation with plasmid encoding green fluorescent protein (GFP), which allows for subsequent detection using fluorescence microscopy.
Equally important to the production of probiotic organisms that express heterologous protein is the proper administration and detection of these microorganisms within gastrointestinal tissues, as described in parts three and four. Administration of recombinant yeast via oral gavage allows for delivery of controlled quantities of yeast directly into the stomach, from which C57BL/6 mice are naturally incapable of vomiting18. However, improper animal handling and gavage can lead to esophageal damage and perforation, gastric perforation, tracheal administration, and aspiration pneumonia19,20. Poor technique and inexperience can furthermore increase variability in murine immune responses and experimental results, which have been attributed to animal stress upon oral gavage21,22. Practice in the proper technique can thus not only attenuate animal discomfort, but can also increase precision of experimental results. This manuscript describes and demonstrates animal handling and oral gavage for the administration of controlled doses of recombinant yeast.
Finally, it is vital to confirm successful delivery of recombinant yeast by analyzing lymphoid tissues for the presence of yeast and heterologous protein. The gastrointestinal immune tissues which can most easily and predictably be examined for the presence of yeast are the Peyer&#39;s patches. Peyer&#39;s patches are secondary lymphoid organs along the small intestine that are key sites of mucosal immune response induction23. Antigens from the lumen are transferred transcellularly through microfold (M) cells in the epithelium and are released into the Peyer&#39;s patches, thus exposing enclosed antigen presenting cells to intestinal luminal contents. Although particle uptake across the intestinal epithelium can also be achieved by goblet cells, these cells have been shown to only take up particles less than 0.02 &#181;m in diameter24. Transepithelial dendrites extended from CD103+ dendritic cells (DC) also take up small particles from the intestinal lumen25; however, there are currently no reports demonstrating that CD103+ DCs take up particles larger than bacteria. Thus, intact probiotic yeast, of average size between 3-6 &#181;m in diameter, are most likely to be taken up by M cells and transferred to the Peyer&#39;s patches. Described here is a protocol for collection and screening of Peyer&#39;s patches for viable recombinant yeast, although this procedure can also be easily adapted for evaluating uptake of probiotic bacteria.
In summary, assessing recombinant probiotic yeast for the delivery of therapeutic proteins to the intestine requires proficiency in laboratory techniques spanning molecular biology to animal handling and immunology. Presented here are protocols for 1) the generation and screening of auxotrophic yeast strains which can be easily negatively selected without antibiotics, 2) alternative protocols to transform yeast and enable expression of heterologous protein, 3) demonstrations of proper animal handling techniques and oral gavage for intragastric delivery of recombinant yeast, and 4) protocols for Peyer&#39;s patch dissection and screening for viable recombinant yeast and functional heterologous protein. Combined, these protocols will allow for the generation and testing of a probiotic yeast strain capable of delivering heterologous therapeutic protein to the gastrointestinal tract.

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			<td height="63" style="height:63px;width:216px;">SmartSpec 3000 Spectrophotometer</td>
			<td style="width:107px;">BioRad</td>
			<td style="width:107px;">170-2501</td>
			<td style="width:275px;">Example of spectrophotometer for determining cell concentration and OD600 of yeast cultures</td>
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			<td height="42" style="height:42px;width:216px;">New Brunswick Roller Drum</td>
			<td style="width:107px;">Eppendorf</td>
			<td style="width:107px;">M1053-4004</td>
			<td style="width:275px;">Example of roller drum for yeast culture incubation</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">UV Stratalinker 2400</td>
			<td style="width:107px;">Stratagene</td>
			<td style="width:107px;">400075-03</td>
			<td style="width:275px;">Example stratalinker</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Stuart Colony Counter SC6PLUS</td>
			<td style="width:107px;">11983044</td>
			<td style="width:107px;">Fisher Scientific</td>
			<td style="width:275px;">Plate stand with magnification records colony count upon sensing pressure from pen</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Scienceware Colony Counter&#160;</td>
			<td style="width:107px;">F378620002</td>
			<td style="width:107px;">Bel-Art Scienceware</td>
			<td style="width:275px;">Hand held colony counter pen</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Replica plating device</td>
			<td style="width:107px;">Fisherbrand</td>
			<td>09-718-1</td>
			<td rowspan="2" style="width:275px;">Example of replica plating stand and pads&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Velveteen squares</td>
			<td style="width:107px;">Fisherbrand</td>
			<td>09-718-2</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">&#160;L shaped sterile cell spreaders&#160;</td>
			<td style="width:107px;">Fisherbrand</td>
			<td style="width:107px;">14665230</td>
			<td style="width:275px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Deoxyribonucleic acid, single stranded from salmon testes</td>
			<td style="width:107px;">Sigma-Aldrich</td>
			<td style="width:107px;">D7656-1ML</td>
			<td style="width:275px;">Example carrier DNA for yeast LiOAc transformation</td>
		</tr>
		<tr height="126">
			<td height="126" style="height:126px;width:216px;">Gavage needles</td>
			<td style="width:107px;">Braintree Scientific</td>
			<td style="width:107px;">N-PK&#160;002</td>
			<td style="width:275px;">For mice 15-20 g, the suggested needle is a 22 gauge (1.25 mm ball), 1 in long, straight reusable gavage needle. For mice weighing greater than 20 g, 20 gauge or larger straight or curved gavage needles may be used</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">1mL sterile slip-tip disposable tuberculin syringe&#160;</td>
			<td style="width:107px;">Becton Dickinson</td>
			<td style="width:107px;">BD 309659</td>
			<td style="width:275px;"></td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">Blunt forceps such as Electron Microscopy Sciences 7&#34; (178 mm) serrated tip, broad grip forceps</td>
			<td style="width:107px;">Electron Microscopy Sciences</td>
			<td style="width:107px;">77937-28</td>
			<td style="width:275px;">Example of blunt forceps needed for dissection&#160;</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Straight and curved dissection scissors&#160;</td>
			<td style="width:107px;">Electron Microscopy Sciences&#160;</td>
			<td style="width:107px;">72966-02 and 72966-03</td>
			<td style="width:275px;">Examples of scissors needed for dissection&#160;</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">IMDM</td>
			<td style="width:107px;">Life technologies</td>
			<td style="width:107px;">12440053</td>
			<td style="width:275px;"></td>
		</tr>
	</tbody>
</table>

transformation of probiotic yeast and their recovery from gastrointestinal immune tissues following oral gavage in mice

Development of recombinant oral therapy would allow for more direct targeting of the mucosal immune system and improve the ability to combat gastrointestinal disorders. Adapting probiotic yeast in particular for this approach carries several advantages. These strains have not only the potential to synthesize a wide variety of complex heterologous proteins but are also capable of surviving and protecting those proteins during transit through the intestine. Critically, however, this approach requires expertise in many diverse laboratory techniques not typically used in tandem. Furthermore, although individual protocols for yeast transformation are well characterized for commonly used laboratory strains, emphasis is placed here on alternative approaches and the importance of optimizing transformation for less well characterized probiotic strains. Detailing these methods will help facilitate discussion as to the best approaches for testing probiotic yeast as oral drug delivery vehicles and indeed serve to advance the development of this novel strategy for gastrointestinal therapy.

Generation of a survival curve following UV irradiation requires plating of diluted yeast cells such that distinct colony forming units (CFU) are able to form. Each 500 &#181;l sample collected as described above contains approximately 5 x 106 cells; however, greater than 100 colonies per plate are difficult to accurately distinguish. Plating undiluted sample as well as serial 1:10 dilutions of irradiated cells thus ensures that CFU can be enumerated at each UV dose, as demonst...

Watch this Scientific Journal Video about Transformation of Probiotic Yeast and Their Recovery from Gastrointestinal Immune Tissues Following Oral Gavage in Mice at JoVE.com

Transformation of Probiotic Yeast and Their Recovery from Gastrointestinal Immune Tissues Following Oral Gavage in Mice

Presented here is a unified description of techniques that can be used to develop, transform, administer, and test heterologous protein expression of the probiotic yeast Saccharomyces boulardii.

Development of recombinant oral therapy would allow for more direct targeting of the mucosal immune system and improve the ability to combat ...

The overall goal of these procedures is to develop a strain of probiotic yeast that can be easily transformed to express and deliver heterologous protein to the murine gastrointestinal tract. The main advantage of these techniques is that they allow for rapid generation of oxytrophic strains of probiotic yeast. These mutant yeasts can then be genetically manipulated without relying on antibiotic selection.Oral gavage of mice and harvest of Peyer's patches also allows for verification of mutant yeast adherence to the gastrointestinal immune tissues. These methods will help answer key questions in the field of oral vaccination and facilitate experiments testing probiotics for the delivery of gastrointestinal therapeutics. After preparing YPD medium and growing yeast overnight to saturation, dilute cells one to ten in water in a plastic cuvette.Then, lank a spectrophotometer and determine the optical density of the overnight culture. With 20 milliliters of sterile distilled water, dilute the cells to a concentration of 10 to the seventh cells per milliliter. Then, pour the diluted cells into a sterile plastic petri dish, and with the lid removed, place the plate into a UV crosslinker.Next, expose the cell solution to cumulative incremental doses of UV irradiation, extracting 500 microliter aliquots following each increment to establish a killing curve, and identify the optimal percent survival for screening. Use sterile water to serially dilute the cells at one to ten increments. Then, pellet the cells from each dilution by centrifugation at maximum speed for one minute.Aspirate the supernatant, and resuspend the cells in a 100 microliter volume of sterile water appropriate for plating yeast cells. Then, pipette the full volume of resuspended cells onto plates containing YPD solid medium, and use a sterile spreader to evenly distribute cells across each plate. Plot a survival curve, and determine the dose of UV irradiation to be used for screening according to the text protocol.After exposing yeast to the dose of UV irradiation selected for screening, pellet the full volume of irradiated cells, and use 100 microliters of sterile water to resuspend the pellet. Plate onto minimal medium containing 5-FOA according to the text protocol, in order to select your three minus oxytrophic newtons. Confirm the URA3 minus phenotype by using the tip of a sterile toothpick to collect part of a single colony on the 5-FOA plate, and restreak it onto YPD, 5-FOA, and uracil minus plates.Wrap the plates, and incubate upside down at 30 degrees Celsius for two to four days. Confirm oxytrophic status by verifying growth of colonies on YPD and 5-FOA, but not Uracil minus plates. After confirming the URA-3 minus status of irradiated yeast, set up an overnight filter for lithium acetate transformation, by inoculating 10 milliliters of YPD with a single mutant colony, and incubate in a warm room at 30 degrees Celsius.The following day, use 50 milliliters of fresh, warm YPD to dilute the overnight cultures to an OD600 of 0.16 to 0.2, and incubate the cells on an orbital platform shaker set to 200 RPM, until the culture reaches approximately one times 10 to the seventh cells per mill, usually around four hours. After washing the cells with water and lithium acetate according to the protocol, add 50 microliters of resuspended cells to a transformation mixture of plasmid and carrier DNA. Then, add 300 microliters of PEG, TE, and lithium acetate and vortex.Incubate the preparations at 30 degrees Celsius on an orbital platform shaker at 200 RPM for 30 minutes. Continue with the transformation as described in the text protocol. After preparing yeast cultures according to the text protocol, use a hemocytometer to determine the cell concentration, and adjust to 10 to the ninth cells per milliliter.Pellet the cells by centrifugation at 2500 times G for three minutes. Then, pour off the supernatant and resuspend the cells by adding the appropriate volume of sterile water, and gently pipetting up and down. Fix an appropriate gauge gavage needle onto a one milliliter sterile syringe, and load the yeast sample, eliminating any air bubbles.Load an additional syringe with sterile water to gavage control mice. Using the non-dominant hand, pick up the mouse to be gavaged and, with the index finger and thumb, tightly grasp the skin around the neck. Tuck the tail under the small finger.Be sure the grip is secure and prohibits the mouse from moving its head. Next, gently insert the gavage needle into the mouse's esophagus by angling the needle along the roof of the mouth and back of the throat, keeping slightly to the left of center. Wait for the mouse to swallow the bulb of the needle.If resistance is felt or the mouse gasps, gently remove the needle, and try again to find the esophagus. After the mouse has swallowed the bulb of the gavage needle, gently depress the syringe plunger to administer the yeast directly into the mouse stomach. Gently remove the gavage needle from the mouse stomach and esophagus, and return the mouse to the cage.Check that the mouse is breathing and moving normally to ensure the gavage was performed properly. After sacrificing the mouse according to the text protocol, position it with the abdomen fully exposed and use 70%ethanol to spray the abdominal area. With scissors, make a transverse incision through the fur and skin.Then manually pry the incision open to further expose the peritoneum, the thin serosal lining that covers the abdominal organs. Gently lift the peritoneum, and make a transverse incision to expose the intestines. Then, use blunt forceps to carefully tease the small intestine away from the mesenteric arteries, fat, and other tissues.Expose the small intestine from the stomach in the upper left quadrant of the mouse abdomen to the cecum, the large pocket of intestinal tissue at the start of the large intestine. Next, isolate Peyer's patches by looking for one to two millimeter roughly circular patches of opaque tissue along the small intestine. Then, using curved dissection scissors, cut away the dome of the Peyer's patch, leaving margins to ensure that none of the surrounding tissue is collected.Transfer the dissected Peyer's patches into complete IMDM. Then, pour the solution with suspended Peyer's patches onto a 40 micrometer cell strainer. After washing the Peyer's patches with complete IMDM, use a plunger from a one milliliter syringe to gently break up the tissue, and collect the cells in a 50 milliliter tube.Pellet the strained cells at 1800 RPM for seven minutes. Then, plate and analyze the cells according to the text protocol. This figure shows a plating from a serial dilution of irradiated S Boulardii cells.The serial dilution ensures that the CF use could be enumerated at each UV dose. From these images of yeast plates, the consistent growth of mutant colonies on YPD and 5-FOA, but not Uracil minus plates, indicates a Uracil minus oxytrophic phenotype. This graph illustrates the transformation efficiency for wild type S Boulardii, compared to S Cerevisiae, using both lithium acetate and electroporation techniques.Although lithium acetate transformation is very efficient for S Cerevisiae, transformation efficiency for S Boulardii is greatly improved using electroporation. In these Brightfield and Fluorescence images, S Cerevisiae transformed with a URA3 plasmid encoating GFE demonstrates a functional expression of heterologous protein. In this figure, an example of viable CF use detected from Peyer's patches after animal dissection is shown.A typical yield of CF use recovered per mouse is less than 10. You should now have a good understanding of how to generate oxytrophic mutant strains of probiotic yeast, using UV mutogenesis. We have also described how to test the ability of these yeasts to express heterologous protein and adhere to Peyer's patches of the mouse small intestine.Following these procedures, other methods, such as ELISA and fluorescence microscopy can be used to evaluate proper folding and function of heterologous proteins expressed.

transformation-probiotic-yeast-their-recovery-from-gastrointestinal

Research

JoVE Journal

Immunology and Infection

Seven Steps to Stellate Cells

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

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


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

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

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

Oral Transmission of Listeria monocytogenes in Mice via Ingestion of Contaminated Food

L. monocytogenes are facultative intracellular bacterial pathogens that cause food borne infections in humans. Very little is known about the gastrointestinal phase of listeriosis due to the lack of a small animal model that closely mimics human disease. This paper describes a novel mouse model for oral transmission of L. monocytogenes. Using this model, mice fed L. monocytogenes-contaminated bread have a discrete phase of gastrointestinal infection, followed by varying degrees of systemic spread in susceptible (BALB/c/By/J) or resistant (C57BL/6) mouse strains. During the later stages of the infection, dissemination to the gall bladder and brain is observed. The food borne model of listeriosis is highly reproducible, does not require specialized skills, and can be used with a wide variety of bacterial isolates and laboratory mouse strains. As such, it is the ideal model to study both virulence strategies used by L. monocytogenes to promote intestinal colonization, as well as the host response to invasive food borne bacterial infection.

Oral Transmission of Listeria monocytogenes in Mice via Ingestion of Contaminated Food

This paper describes a novel method for oral infection of mice using Listeria monocytogenes-contaminated food. The protocol can readily be adapted for use with other food borne bacterial pathogens.

L. monocytogenes are facultative intracellular bacterial pathogens that cause food borne infections in humans. Very little is known about the ...

Induction of Murine Intestinal Inflammation by Adoptive Transfer of Effector CD4+CD45RBhigh T Cells into Immunodeficient Mice

There are many different animal models available for studying the pathogenesis of human inflammatory bowel diseases (IBD), each with its own advantages and disadvantages. We describe here an experimental colitis model that is initiated by adoptive transfer of syngeneic splenic CD4+CD45RBhigh T cells into T and B cell deficient recipient mice. The CD4+CD45RBhigh T cell population that largely consists of na&#239;ve effector cells is capable of inducing chronic intestinal inflammation, closely resembling key aspects of human IBD. This method can be manipulated to study aspects of disease onset and progression. Additionally it can be used to study the function of innate, adaptive, and regulatory immune cell populations, and the role of environmental exposures, i.e., the microbiota, in intestinal inflammation. In this article we illustrate the methodology for inducing colitis with a step-by-step protocol. This includes a video demonstration of key technical aspects required to successfully develop this murine model of experimental colitis for research purposes.

Induction of Murine Intestinal Inflammation by Adoptive Transfer of Effector CD4+CD45RBhigh T Cells into Immunodeficient Mice

Here, we present a protocol to induce colonic inflammation in mice by adoptive transfer of syngeneic CD4+CD45RBhigh T cells into T and B cell deficient recipients. Clinical and histopathological features mimic human inflammatory bowel diseases. This method allows the study of the initiation of colonic inflammation and progression of disease.

There are many different animal models available for studying the pathogenesis of human inflammatory bowel diseases (IBD), each with its own advantages ...

In Situ Detection of Bacteria within Paraffin-embedded Tissues Using a Digoxin-labeled DNA Probe Targeting 16S rRNA

The presence of bacteria within the pocket epithelium and underlying connective tissue in gingival biopsies from patients with periodontitis has been reported using various methods, including electron microscopy, immunohistochemistry or immunofluorescence using bacteria-specific antibodies, and fluorescent in situ hybridization (FISH) using a fluorescence-labeled oligonucleotide probe. Nevertheless, these methods are not widely used due to technical limitation or difficulties. Here a method to localize bacteria within paraffin-embedded tissues using DIG-labeled DNA probes has been introduced. The paraffin-embedded tissues are the most common form of biopsy tissues available from pathology banks. Bacteria can be detected either in a species-specific or universal manner. Bacterial signals are detected as either discrete forms (coccus, rod, fusiform, and hairy form) of bacteria or dispersed forms. The technique allows other histological information to be obtained: the epithelia, connective tissue, inflammatory infiltrates, and blood vessels are well distinguished. This method can be used to study the role of bacteria in various diseases, such as periodontitis, cancers, and inflammatory immune diseases.

In Situ Detection of Bacteria within Paraffin-embedded Tissues Using a Digoxin-labeled DNA Probe Targeting 16S rRNA

Here a method to localize bacteria within paraffin-embedded tissues using DIG-labeled 16S rRNA-targeting DNA probes has been described. This protocol can be applied to study the role of bacteria in various diseases such as periodontitis, cancers, and inflammatory immune diseases.

The presence of bacteria within the pocket epithelium and underlying connective tissue in gingival biopsies from patients with periodontitis has been ...

Isolation, Characterization and Functional Examination of the Gingival Immune Cell Network

Immune cell networks in tissues play a vital role in mediating local immunity and maintaining tissue homeostasis, yet little is known of the resident immune cell populations in the oral mucosa and gingiva. We have established a technique for the isolation and study of immune cells from murine gingival tissues, an area of constant microbial exposure and a vulnerable site to a common inflammatory disease, periodontitis. Our protocol allows for a detailed phenotypic characterization of the immune cell populations resident in the gingiva, even at steady state. Our procedure also yields sufficient cells with high viability for use in functional studies, such as the assessment of cytokine secretion ex vivo. This combination of phenotypic and functional characterization of the gingival immune cell network should aid towards investigating the mechanisms involved in oral immunity and periodontal homeostasis, but will also advance our understanding of the mechanisms involved in local immunopathology.

We have established a technique for the isolation, phenotypic characterization and functional analysis of immune cells from murine gingiva.

Immune cell networks in tissues play a vital role in mediating local immunity and maintaining tissue homeostasis, yet little is known of the resident ...

Induction of Experimental Autoimmune Encephalomyelitis in Mice and Evaluation of the Disease-dependent Distribution of Immune Cells in Various Tissues

Multiple sclerosis is presumed to be an inflammatory autoimmune disease, which is characterized by lesion formation in the central nervous system (CNS) resulting in cognitive and motor impairment. Experimental autoimmune encephalomyelitis (EAE) is a useful animal model of MS, because it is also characterized by lesion formation in the CNS, motor impairment and is also driven by autoimmune and inflammatory reactions. One of the EAE models is induced with a peptide derived from the myelin oligodendrocyte protein (MOG)35-55 in mice. The EAE mice develop a progressive disease course. This course is divided into three phases: the preclinical phase (day 0 - 9), the disease onset (day 10 - 11) and the acute phase (day 12 - 14). MS and EAE are induced by autoreactive T cells that infiltrate the CNS. These T cells secrete chemokines and cytokines which lead to the recruitment of further immune cells. Therefore, the immune cell distribution in the spinal cord during the three disease phases was investigated. To highlight the time point of the disease at which the activation/proliferation/accumulation of T cells, B cells and monocytes starts, the immune cell distribution in lymph nodes, spleen and blood was also assessed. Furthermore, the levels of several cytokines (IL-1&#946;, IL-6, IL-23, TNF&#945;, IFN&#947;) in the three disease phases were determined, to gain insight into the inflammatory processes of the disease. In conclusion, the data provide an overview of the functional profile of immune cells during EAE pathology.

This manuscript describes the methods for induction and scoring of the experimental autoimmune encephalomyelitis (EAE) model, together with the assessment of immune cell distribution and mRNA cytokine levels in lymph nodes, spleen, blood and spinal cord using flow cytometry and quantitative PCR, respectively, at various disease phases.

Multiple sclerosis is presumed to be an inflammatory autoimmune disease, which is characterized by lesion formation in the central nervous system (CNS) ...

Protective Efficacy and Pulmonary Immune Response Following Subcutaneous and Intranasal BCG Administration in Mice

Despite global coverage of intradermal BCG vaccination, tuberculosis remains one of the most prevalent infectious diseases in the world. Preclinical data have encouraged pulmonary tuberculosis vaccines as a promising strategy to prevent pulmonary disease, which is responsible for transmission. In this work, we describe the methodology used to demonstrate in the mouse model the benefits of intranasal BCG vaccination when compared to subcutaneous. Our data revealed greater protective efficacy following intranasal BCG administration. In addition, our results indicate that pulmonary vaccination triggers a higher immune response in lungs, including Th1 and Th17 responses, as well as an increase of immunoglobulin A (IgA) concentration in respiratory airways. Our data show correlation between protective efficacy and the presence of IL17-producing cells in lungs post-Mycobacterium tuberculosis challenge, suggesting a role for this cytokine in the protective response conferred by pulmonary vaccination. Finally, we detail the global workflow we have developed to study respiratory vaccination in the mouse model, which could be extrapolated to other tuberculosis vaccines, apart from BCG, targeting the mucosal response or other pulmonary routes of administration such as the intratracheal or aerosol.

We herein detail the methodology followed to compare protective efficacy and lung immune response induced by intranasal and subcutaneous immunization with BCG in mouse model. Our results show the benefits of pulmonary vaccination and suggest a role for IL17-mediated response in vaccine-induced protection.

Despite global coverage of intradermal BCG vaccination, tuberculosis remains one of the most prevalent infectious diseases in the world. Preclinical data ...

Probiotic Studies in Neonatal Mice Using Gavage

Adult mouse models have been widely used to understand the mechanism behind disease progression in humans. The applicability of studies done in adult mouse models to neonatal diseases is limited. To better understand disease progression, host responses and long-term impact of interventions in neonates, a neonatal mouse model likely is a better fit. The sparse use of neonatal mouse models can in part be attributed to the technical difficulties of working with these small animals. A neonatal mouse model was developed to determine the effects of probiotic administration in early life and to specifically assess the ability to establish colonization in the newborn mouse intestinal tract. Specifically, to assess probiotic colonization in the neonatal mouse, Lactobacillus plantarum (LP) was delivered directly into the neonatal mouse gastrointestinal tract. To this end, LP was administered to mice by feeding through intra-esophageal (IE) gavage. A highly reproducible method was developed to standardize the process of IE gavage that allows an accurate administration of probiotic dosages while minimizing trauma, an aspect particularly important given the fragility of newborn mice. Limitations of this process include possibilities of esophageal irritation or damage and aspiration if gavaged incorrectly. This approach represents an improvement on current practices because IE gavage into the distal esophagus reduces the chances of aspiration. Following gavage, the colonization profile of the probiotic was traced using quantitative polymerase chain reaction (qPCR) of the extracted intestinal DNA with LP specific primers. Different litter settings and cage management techniques were used to assess the potential for colonization-spread. The protocol details the intricacies of IE neonatal mouse gavage and subsequent colonization quantification with LP.

This study details the process of gavaging precise amounts of probiotics to neonatal mice. The experimental set-up was optimized to include but is not limited to probiotic dosing, methods of administration, and quantification of bacteria in the intestines.

Adult mouse models have been widely used to understand the mechanism behind disease progression in humans. The applicability of studies done in adult ...

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 ...

Quantification of three DNA Lesions by Mass Spectrometry and Assessment of Their Levels in Tissues of Mice Exposed to Ambient Fine Particulate Matter

DNA adducts and oxidized DNA bases are examples of DNA lesions that are useful biomarkers for the toxicity assessment of substances that are electrophilic, generate reactive electrophiles upon biotransformation, or induce oxidative stress. Among the oxidized nucleobases, the most studied one is 8-oxo-7,8-dihydroguanine (8-oxoGua) or 8-oxo-7,8-dihydro-2&#39;-deoxyguanosine (8-oxodGuo), a biomarker of oxidatively induced base damage in DNA. Aldehydes and epoxyaldehydes resulting from the lipid peroxidation process are electrophilic molecules able to form mutagenic exocyclic DNA adducts, such as the etheno adducts 1,N2-etheno-2&#39;-deoxyguanosine (1,N2-&#949;dGuo) and 1,N6-etheno-2&#39;-deoxyadenosine (1,N6-&#949;dAdo), which have been suggested as potential biomarkers in the pathophysiology of inflammation. Selective and sensitive methods for their quantification in DNA are necessary for the development of preventive strategies to slow down cell mutation rates and chronic disease development (e.g., cancer, neurodegenerative diseases). Among the sensitive methods available for their detection (high performance liquid chromatography coupled to electrochemical or tandem mass spectrometry detectors, comet assay, immunoassays, 32P-postlabeling), the most selective are those based on high performance liquid chromatography coupled to tandem mass spectrometry (HPLC-ESI-MS/MS). Selectivity is an essential advantage when analyzing complex biological samples and HPLC-ESI-MS/MS evolved as the gold standard for quantification of modified nucleosides in biological matrices, such as DNA, urine, plasma and saliva. The use of isotopically labeled internal standards adds the advantage of corrections for molecule losses during the DNA hydrolysis and analyte enrichment steps, as well as for differences of the analyte ionization between samples. It also aids in the identification of the correct chromatographic peak when more than one peak is present.
We present here validated sensitive, accurate and precise HPLC-ESI-MS/MS methods that were successfully applied for the quantification of 8-oxodGuo, 1,N6-dAdo and 1,N2-dGuo in lung, liver and kidney DNA of A/J mice for the assessment of the effects of ambient PM2.5 exposure.

We describe here methods for sensitive and accurate quantification of the lesions 8-oxo-7,8-dihydro-2&#39;-deoxyguanosine (8-oxodGuo), 1,N6-etheno-2&#39;-deoxyadenosine (1,N6-dAdo) and 1,N2-etheno-2&#39;-deoxyguanosine (1,N2-dGuo) in DNA. The methods were applied to the assessment of the effects of ambient fine particulate matter (PM2.5) in tissues (lung, liver and kidney) of exposed A/J mice.