We appreciate the help from the Argonne National Laboratory and our collaborating bioinformaticians. This work is supported by various NIH and internal grants.

The Cx3cr1gfp/gfp locus of B6.129P2(Cg)-Cx3cr1tm1Litt/J mice was backcrossed to MRL/MpJ-Faslpr/J (MRL/lpr) for 10 generations to generate MRL/lpr-CX3CR1gfp/gfp mice. Genome screening using single nucleotide polymorphism (SNP) panels confirmed that the genetic background of newly generated mice was more than 97% identical to that of MRL/lpr. After that, mice were bred and maintained in a specific pathogen-free environment following the specific requirements of the Institutional Animal Care and Use Committee (IACUC) at Virginia Tech. Samples were collected when the mice were 13, 14, and 15 weeks old.
1. Collection of microbiota samples from mice
<ol>
	<li>Take each mouse individually out of its cage. Collect a fecal pellet directly from the anus and store it at -80 &#176;C until being processed. Process the samples with sterile and clean forceps, tubes, and gloves. 
	NOTE: A container (e.g., a beaker) can be used to place the mouse while waiting for the fecal sample. Clean the container with ethanol before and after each mouse.</li>
	<li>Add a frozen pellet to a pre-weighed 2 mL screw-cap tube. Record the fecal weight in grams, which should be between 0.02-0.05 g per fecal pellet.</li>
	<li>Add to the pellet a thin layer of 0.1 mm glass beads, 500 &#181;L of lysis buffer (50 mM NaCl, 5 mM Tris, and 50 mM EDTA), and 200 &#181;L of 20% SDS.</li>
	<li>Bead-beat the tube for 4 min in a homogenizer (at maximum power), followed by 3-5 min of vortexing.</li>
	<li>Spin for a short time to eliminate the bubbles and foam (press the button on the centrifuge until it reaches 1,000-1,200 x g, and then release).</li>
</ol>
2. DNA extraction
<ol>
	<li>Transfer 350 &#181;L of supernatant obtained in step 1.5 (ensuring not to carry any debris) to a new 1.5 mL snap cap tube. Add 500 &#181;L of phenol-chloroform-isoamyl alcohol (PCI; 25:24:1, v/v) mixture and vortex for 1 min. 
	NOTE: From now on, samples need to be handled inside a chemical hood. PCI is toxic.</li>
	<li>Spin at 6,000 x g for 3 min at 4 &#176;C. Transfer 180 &#181;L of the aqueous phase (top layer) into a new 1.5 mL snap cap tube. Add 180 &#181;L (1:1) of chloroform, invert, and mix. 
	NOTE: Minimize contamination from the bottom layer when transferring the top layer.</li>
	<li>Spin at 18,400 x g for 3 min at 4 &#176;C. Transfer 180 &#181;L of the aqueous phase into a new snap cap tube. 
	NOTE: After discarding PCI and chloroform, the following steps can be performed in a biological safety cabinet.</li>
	<li>Add 180 &#181;L of cold isopropanol and 36 &#181;L of 5M NH4Ac. Invert a few times to mix, and place the tube on ice for 20 min.</li>
	<li>Spin at 18,400 x g for 20 min at 4 &#176;C. Pour to discard the supernatant. Wash the pellet several times with 500 &#181;L of cold 70% ethanol while inverting. 
	NOTE: Ethanol should be diluted with double deionized sterile water.</li>
	<li>Spin at 18,400 x g for 3 min at 4 &#176;C. Discard the supernatant to remove residual ethanol.</li>
	<li>Air-dry the tube upside down on tissue paper for 20 min, until the pellet becomes clear. Suspend the pellet in 50 &#181;L of molecular-grade water. Heat the liquid at 37 &#176;C for 10 min to fully dissolve large DNA pellets.</li>
	<li>Spin tubes after heating to recover condensation droplets on the lid (3,400 x g for 1 min).</li>
	<li>Measure the concentration and obtain the 260/280 ratio using a spectrophotometer. Use molecular-grade water as a blank. Good quality DNA should have 260/280 ratios ranging between 1.8 and 2. 
	&#8203;NOTE: Expected DNA yield is at least 0.03 g per fecal pellet.</li>
</ol>
3. Sample preparation for 16S rRNA gene sequencing
<ol>
	<li>Send the DNA samples to Argonne National Laboratory, where they undergo library preparation and are sequenced on the Illumina Miseq.
	<ol>
		<li>Send samples in fully-skirted 96-well plates, with samples arranged in rows (A1-A12, B1-B12, etc.), and sealed with foil plate seals.</li>
		<li>Send a final volume of 20 &#181;L per sample per well, ranging in concentration from 1-50 ng/&#181;L. 
		NOTE: Dilutions should be done with molecular-grade water.</li>
		<li>After preparing the samples, spin at 600 x g for 1 min at room temperature before freezing the samples at -80 &#176;C for 24 h.</li>
		<li>Send overnight on dry ice.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Lee, Y. K., Mazmanian, S. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Has+the+microbiota+played+a+critical+role+in+the+evolution+of+the+adaptive+immune+system.">Has the microbiota played a critical role in the evolution of the adaptive immune system.</a> Science. 330 (6012), 1768-1773 (2010).</li><li>Lee, Y. K., Menezes, J. S., Umesaki, Y., Mazmanian, S. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proinflammatory+T-cell+responses+to+gut+microbiota+promote+experimental+autoimmune+encephalomyelitis.">Proinflammatory T-cell responses to gut microbiota promote experimental autoimmune encephalomyelitis.</a> Proceedings of the National Academy of Sciences of the United States of America. 108, 4615-4622 (2011).</li><li>Yeoh, N., Burton, J. P., Suppiah, P., Reid, G., Stebbings, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+the+microbiome+in+rheumatic+diseases.">The role of the microbiome in rheumatic diseases.</a> Current Rheumatology Reports. 15 (3), 314 (2013).</li><li>Larsen, 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=Gut+microbiota+in+human+adults+with+type+2+diabetes+differs+from+non-diabetic+adults.">Gut microbiota in human adults with type 2 diabetes differs from non-diabetic adults.</a> PLoS One. 5 (2), 9085 (2010).</li><li>Alam, M. T., 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=Microbial+imbalance+in+inflammatory+bowel+disease+patients+at+different+taxonomic+levels.">Microbial imbalance in inflammatory bowel disease patients at different taxonomic levels.</a> Gut Pathogens. 12 (1), (2020).</li><li>Vieira, S. M., Pagovich, O. E., Kriegel, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diet,+microbiota+and+autoimmune+diseases.">Diet, microbiota and autoimmune diseases.</a> Lupus. 23 (6), 518-526 (2014).</li><li>Mu, Q., Zhang, H., Luo, X. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=SLE:+another+autoimmune+disorder+influenced+by+microbes+and+diet.">SLE: another autoimmune disorder influenced by microbes and diet.</a> Frontiers of Immunology. 6, 608 (2015).</li><li>Tektonidou, M. G., Wang, Z., Dasgupta, A., Ward, M. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Burden+of+serious+infections+in+adults+with+systemic+lupus+erythematosus:+a+national+population-based+study.">Burden of serious infections in adults with systemic lupus erythematosus: a national population-based study.</a> Arthritis Care &amp; Research. 67 (8), 1078-1085 (2015).</li><li>Mu, Q., 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=Control+of+lupus+nephritis+by+changes+of+gut+microbiota.">Control of lupus nephritis by changes of gut microbiota.</a> Microbiome. 5 (1), 73 (2017).</li><li>Panek, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methodology+challenges+in+studying+human+gut+microbiota+-+effects+of+collection,+storage,+DNA+extraction+and+next+generation+sequencing+technologies.">Methodology challenges in studying human gut microbiota - effects of collection, storage, DNA extraction and next generation sequencing technologies.</a> Scientific Reports. 8 (1), 5143 (2018).</li><li>Fiedorov&#225;, 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=The+impact+of+dna+extraction+methods+on+stool+bacterial+and+fungal+microbiota+community+recovery.">The impact of dna extraction methods on stool bacterial and fungal microbiota community recovery.</a> Frontiers in Microbiology. 10, 821 (2019).</li><li>Gerasimidis, 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=The+effect+of+DNA+extraction+methodology+on+gut+microbiota+research+applications.">The effect of DNA extraction methodology on gut microbiota research applications.</a> BMC Research Notes. 9, 365 (2016).</li><li>Bukin, Y. 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The authors declare that there is no conflict of interest.

Balanced gut microbiota can protect the human body from diseases. Once this balance is disrupted by external or internal triggers, consequences can be devastating. This method presents a way to analyze the dynamics of gut microbiota in murine models. The method is suitable not only for comparisons among groups but also for tracking the gut microbiota over time to better identify time-dependent factors disrupting the gut microbiota.
All the mice in the experiment must be handled in the same environment. One essential matter to consider while collecting fecal samples is to be consistent with the time, day, and place. Mice are coprophagic. This means that they eat their feces or the ones around them to obtain essential nutrients. Therefore, feces cannot be collected from the cage. Samples need to be collected fresh and directly from the anus. The best method is to massage the mouse while holding it or place the mouse in a container. In addition, it is recommended that samples are processed at the same time and frozen at -80 &#176;C while waiting for all the samples to be ready.
DNA extraction is extremely sensitive to pipetting and handling, so all the samples should be processed at the same time. Another consideration is to avoid environmental contamination; therefore, every single step not necessarily performed in the chemical hood due to the toxic reagents should be done in a biological safety cabinet. Even though the chances of environmental contamination are low and there is no step to allow bacteria to grow, this method is extremely sensitive, and avoiding any possible contamination is absolutely recommended. Additionally, weighing the pellets will help to increase consistency among samples. As an advantage over commercially available kits, this method is particularly good for achieving high concentrations of DNA. The DNA yield obtained with this protocol ranges between 0.03 g and 0.07 g depending on the weight of the fecal pellet. In comparison, commercial kits can yield between 0.005 g to 0.05 g, but with a higher chance of saturation as limited by the column retention step.
The bead-beating step is important in breaking the fecal pellet into small pieces so the lysis agent can reach all the bacteria. If this step is not well performed, pellets can be partially disintegrated, and fewer representative bacteria can be reached. In addition, when transferring supernatants, correct pipetting is important, since carrying part of the residual buffer from the previous step would alter the yield and quality of DNA at the end.
When diluting the samples for the 16S ribosomal RNA gene sequencing, it is important to act quickly before the samples are put into the freezer. It is also important to mix samples well prior to performing dilutions. Avoid leaving samples at room temperature for long periods of time. Since the volumes are small, freezing the samples in the plate before shipping them will help to minimize loss.
The Argonne National Laboratory analyses the V4 region of the 16S rRNA gene. The V4 region is better conserved than the other regions and has a better estimation for high-rank taxa13. While the other regions are better for the analysis of quickly evolving species and can help identify and better discriminate genus or species, those regions accumulate mutations faster than V4.
Once results are back and analyzed by a qualified bioinformatician, statistical software can be used to plot the results and compare groups. It is important to understand the limitations of this technique and the results after bioinformatics analysis. The lower the taxonomic level, the lesser the accuracy or greater the variations. From phylum to family, and even the genus level can be analyzed with reliability. However, annotations at the species level are not accurate with this method. Shotgun sequencing, on the other hand, can reach the species level; however, while it can provide more insight into the biological functions of a community, 16S rRNA gene sequencing is still an accurate and cost-efficient method to quantify taxonomical distributions of a microbial community15.
In summary, a cost-efficient protocol has been described to analyze the gut microbiota and study its dynamics with the maximal accuracy that can help to reveal longitudinal changes over time as well as differences among groups.

Humans and bacteria have coexisted for a long time. They have established a codependent relationship with mutual beneficial effects that influences host immune responses in quantitative and qualitative ways1. Recent studies suggest an association between the gut microbiota composition and the pathogenesis of autoimmune diseases that include multiple sclerosis2, rheumatoid arthritis3, type 2 diabetes4, Inflammatory bowel disease5, and systemic lupus erythematosus (SLE)6. However, whether the gut microbiota is the main cause or a secondary effect of these autoimmune diseases is still unclear7. Potentially, gut microbiota could exacerbate the disease during the effector phase of autoimmune disorders or play a role in regulating the induction of these diseases8.
Intestinal dysbiosis has been reported in female lupus-prone MRL/Mp-Faslpr (MRL/lpr) mice, and gut microbiota changes with a significant depletion of Lactobacilli were observed9. When a mixture of five Lactobacillus strains was orally administered, lupus-like symptoms were largely attenuated in these mice, suggesting an essential role of microbiota in regulating SLE pathogenesis.
The following technique of DNA extraction allows to follow microbiota fluctuations and analyze them qualitatively and quantitively during the course of murine SLE-like disease in lupus-prone mice. Whether to examine the healthy gut microbiota or define dysbiosis, it is important to critically examine how data is collected and whether it is accurate and reproducible10. Every step is critical in this process. An appropriate methodology must be used to extract microbial DNA as any possible problem introducing biases during the DNA extraction process could result in inaccurate microbial representation. While the phenol-chloroform method is described here, there are commercially available kits to extract DNA from bacteria that work well in particular cases11. However, their usability is limited by the cost and required sample quantity.
The protocol presented here is cost-effective and requires only a small amount of sample. It works fine with any kind of stool sample and is useful in studying the dynamics of the gut microbiota over time as well as comparisons among groups. DNA is isolated with a method of alcohol purification, which uses phenol, chloroform, and isoamyl alcohol. Alcohol-based extraction helps to clean and remove the sample of proteins and lipids, where DNA is precipitated in the final step. The proposed method has significantly high efficiency and quality and has been proven to be accurate in identifying bacterial populations. One critical note during the procedure is that DNA contamination can occur, and thus appropriate sample handling is required12.
The DNA is then analyzed by the Next Generation Sequencing platforms for the 16S rRNA gene, such as the Illumina MiSeq. In particular, the V4 hyper-variable region is analyzed to provide a better quantification for high-rank taxa13. The subsequent bioinformatics analysis is outsourced, followed by in-house analysis using standard statistical methods. There are numerous open-source bioinformatics software programs available for downstream sequencing, and the type of analyses performed depends heavily on the specific biological question of interest14. This protocol focuses specifically on the experimental steps prior to sequencing and provides a more versatile, cost-effective, comparable, and efficient method to obtain DNA from fecal samples.

<table><tbody><tr><td>0.1 mm glass beads</td><td>BioSpec Products</td><td>11079101</td><td></td></tr><tr><td>2 mL screw cap tubes</td><td>Thermo Fisher Scientific</td><td>3488</td><td></td></tr><tr><td>20% SDS</td><td>FisherScientific</td><td>BP1311-1</td><td>SDS 20%</td></tr><tr><td>96% Ethanol, Molecular Biology Grade</td><td>Thermo Fisher Scientific</td><td>T032021000CS</td><td></td></tr><tr><td>Ammonium Acetate (5 M)</td><td>Thermo Fisher Scientific</td><td>AM9071</td><td>NH4AC 5M</td></tr><tr><td>B6.129P2(Cg)-Cx3cr1tm1Litt/J</td><td>Jackson Laboratory</td><td>005582</td><td></td></tr><tr><td>Bullet Blender storm 24</td><td>Next Advance</td><td>4116-BBY24M</td><td>Homogenizer</td></tr><tr><td>Chloroform</td><td>FisherScientific</td><td>C298-500</td><td></td></tr><tr><td>DEPC-Treated Water</td><td>Thermo Fisher Scientific</td><td>AM9916</td><td></td></tr><tr><td>Ethylenediamine Tetraacetic Acid</td><td>FisherScientific</td><td>BP118-500</td><td>EDTA</td></tr><tr><td>Foil plate seal</td><td>FisherScientific</td><td>NC0302491</td><td></td></tr><tr><td>Kimwipes-Kimtech 34256</td><td>FisherScientific</td><td>06-666C</td><td></td></tr><tr><td>MRL/MpJ-Faslpr/J (MRL/lpr) mice</td><td>Jackson Laboratory</td><td>000485</td><td></td></tr><tr><td>Nanodrop 2000 spectrophotomer</td><td>Thermo Fisher Scientific</td><td>ND2000CLAPTOP</td><td></td></tr><tr><td>Phenol: chloroform: isoamylalchohol (25:24:1)</td><td>FisherScientific</td><td>BP1752I-400</td><td>PCI</td></tr><tr><td>Scale with 4 decimals</td><td>Mettler Toledo</td><td>MS205DU</td><td></td></tr><tr><td>Skirted 96-well plates</td><td>Thermo Fisher Scientific</td><td>AB-0800</td><td></td></tr><tr><td>Sodium chloride</td><td>FisherScientific</td><td>15528154</td><td>NaCl</td></tr><tr><td>Tris Hydrochloride</td><td>FisherScientific</td><td>BP1757-100</td><td></td></tr><tr><td>Vortex</td><td>Scientific Industries</td><td>SI-0236</td><td></td></tr></tbody></table>

analysis of fecal microbiota dynamics in lupus-prone mice using a simple, cost-effective dna isolation method

Gut microbiota has an important role in educating the immune system. This relationship is extremely important for understanding autoimmune diseases that are not only driven by genetic factors, but also environmental factors that can trigger the onset and/or worsen the disease course. A previously published study on the dynamics of the gut microbiota in lupus-prone MRL/lpr female mice showed how changes of the gut microbiota can alter disease progression. Here, a protocol is described for extracting representative samples from the gut microbiota for studies of autoimmunity. Microbiota samples are collected from the anus and processed, from which the DNA is extracted using a phenol-chloroform method and purified by alcohol precipitation. After PCR is performed, purified amplicons are sequenced using a Next Generation Sequencing platform at Argonne National Laboratory. Finally, the 16S ribosomal RNA gene sequencing data is analyzed. As an example, data obtained from gut microbiota comparisons of MRL/lpr mice with or without CX3CR1 are shown. Results showed significant differences in genera containing pathogenic bacteria such as those in the phylum Proteobacteria, as well as the genus Bifidobacterium, which is considered part of the healthy commensal microbiota. In summary, this simple, cost-effective DNA isolation method is reliable and can help the investigation of gut microbiota changes associated with autoimmune diseases.

The results from Argonne National Laboratory are analyzed by a qualified bioinformatician, followed by an in-house analysis of the data using standard statistical methods. Typical microbiome analyses involve clustering of similar sequences into operational taxonomic units (OTUs) or amplicon sequence variants (ASVs) as a proxy for different microorganisms in a sample. Counts of OTUs or ASVs across samples can then be used to test for changes in within-sample (alpha) diversity and between-sample (beta) diversity. They can also be used to test for taxa that are differentially abundant across metadata categories of interest.
As shown in Figure 1, the mouse strain lacking the receptor CX3CR1 has a different gut microbiota composition. Compared to wildtype MRL/lpr, MRL/lpr-CX3CR1gfp/gfp mice (expressing the green fluorescent protein instead of CX3CR1) show significant differences in certain genera relevant to potentially pathogenic bacteria such as those in the phylum Proteobacteria. In addition, some differences were noted for &#34;healthy&#34; commensal bacteria such as Bifidobacterium, but not Lactobacillus.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/63623/63623fig01.jpg" /> 
Figure 1: Comparisons of gut microbiota at the genus level for MRL/lpr and MRL/lpr-CX3CR1 mice. The abundance of different genera at 13, 14, and 15 weeks of age (n = 5 female mice per group). Two-way ANOVA was performed. No significance (&#39;ns&#39;), *P &#60; 0.05, **P &#60; 0.01. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/63623/63623fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Analysis of Fecal Microbiota Dynamics in Lupus-Prone Mice Using a Simple, Cost-Effective DNA Isolation Method at JoVE.com

Analysis of Fecal Microbiota Dynamics in Lupus-Prone Mice Using a Simple, Cost-Effective DNA Isolation Method

This protocol provides a simple, cost-effective DNA isolation method for the analysis of murine gut microbiota alterations during the development of autoimmune disease.

Gut microbiota has an important role in educating the immune system. This relationship is extremely important for understanding autoimmune diseases that ...

analysis-fecal-microbiota-dynamics-lupus-prone-mice-using-simple-cost

Nanyang Technological University

Research

JoVE Journal

Immunology and Infection

2.1K Views.  Virginia Polytechnic Institute and State University. This protocol provides a simple, cost-effective DNA isolation method for the analysis of murine gut microbiota alterations during the development of autoimmune disease.

Video: Analysis of Fecal Microbiota Dynamics in Lupus-Prone Mice Using a Simple, Cost-Effective DNA Isolation Method

A Method to Define the Effects of Environmental Enrichment on Colon Microbiome Biodiversity in a Mouse Colon Tumor Model

Several recent studies have illustrated the beneficial effects of living in an enriched environment on improving human disease. In mice, environmental enrichment (EE) reduces tumorigenesis by activating the mouse immune system, or affects tumor bearing animal survival by stimulating the wound repair response, including improved microbiome diversity, in the tumor microenvironment. Provided here is a detailed procedure to assess the effects of environmental enrichment on the biodiversity of the microbiome in a mouse colon tumor model. Precautions regarding animal breeding and considerations for animal genotype and mouse colony integration are described, all of which ultimately affect microbial biodiversity. Heeding these precautions may allow more uniform microbiome transmission, and consequently will alleviate non-treatment dependent effects that can confound study findings. Further, in this procedure, microbiota changes are characterized using 16S rDNA sequencing of DNA isolated from stool collected from the distal colon following long-term environmental enrichment. Gut microbiota imbalance is associated with the pathogenesis of inflammatory bowel disease and colon cancer, but also of obesity and diabetes among others. Importantly, this protocol for EE and microbiome analysis can be utilized to study the role of microbiome pathogenesis across a variety of diseases where robust mouse models exist that can recapitulate human disease.

Environmental Enrichment (EE) is an animal housing environment that is used to reveal mechanisms that underlie the connections between lifestyle, stress, and disease. This protocol describes a procedure that uses a mouse model of colon tumorigenesis and EE to specifically define alterations in microbiota biodiversity that may impact animal mortality.

Several recent studies have illustrated the beneficial effects of living in an enriched environment on improving human disease. In mice, environmental ...

Cancer Research

Isolation and Flow Cytometric Characterization of Murine Small Intestinal Lymphocytes

The intestines &#8212; which contain the largest number of immune cells of any organ in the body &#8212; are constantly exposed to foreign antigens, both microbial and dietary. Given an increasing understanding that these luminal antigens help shape the immune response and that education of immune cells within the intestine is critical for a number of systemic diseases, there has been increased interest in characterizing the intestinal immune system. However, many published protocols are arduous and time-consuming. We present here a simplified protocol for the isolation of lymphocytes from the small-intestinal lamina propria, intraepithelial layer, and Peyer&#39;s patches that is rapid, reproducible, and does not require laborious Percoll gradients. Although the protocol focuses on the small intestine, it is also suitable for analysis of the colon. Moreover, we highlight some aspects that may need additional optimization depending on the specific scientific question. This approach results in the isolation of large numbers of viable lymphocytes that can subsequently be used for flow cytometric analysis or alternate means of characterization.

There is growing interest in the quantitative characterization of intestinal lymphocytes owing to increasing recognition that these cells play a critical role in a variety of intestinal and systemic diseases. In this protocol, we describe how to isolate single cell populations from different small-intestinal compartments for subsequent flow cytometric characterization.

The intestines &#8212; which contain the largest number of immune cells of any organ in the body &#8212; are constantly exposed to foreign antigens, both ...

The bm12 Inducible Model of Systemic Lupus Erythematosus (SLE) in C57BL/6 Mice

Systemic lupus erythematosus (SLE) is an autoimmune disease with diverse clinical and immunological manifestations. Several spontaneous and inducible animal models mirror common components of human disease, including the bm12 transfer model. Upon transfer of bm12 splenocytes or purified CD4 T cells, C57BL/6 mice rapidly develop large frequencies of T follicular helper cells (Tfh), germinal center (GC) B cells, and plasma cells followed by high levels of circulating anti-nuclear antibodies. Since this model utilizes mice on a pure C57BL/6 background, researchers can quickly and easily study disease progression in transgenic or knockout mouse strains in a relatively short period of time. Here we describe protocols for the induction of the model and the quantitation Tfh, GC B cells, and plasma cells by multi-color flow cytometry. Importantly, these protocols can also be used to characterize disease in most mouse models of SLE and identify Tfh, GC B cells, and plasma cells in other disease models.

The bm12 Inducible Model of Systemic Lupus Erythematosus SLE in C57BL/6 Mice

The transfer of bm12 lymphocytes into a C57BL/6 recipient is an established model of systemic lupus erythematosus. Here we describe how to initiate disease using this model and how to characterize T follicular helper cells, germinal center B cells and plasma cells by flow cytometry.

Systemic lupus erythematosus (SLE) is an autoimmune disease with diverse clinical and immunological manifestations. Several spontaneous and inducible ...

Medicine

Isolating Lymphocytes from the Mouse Small Intestinal Immune System

The intestinal immune system plays an essential role in maintaining the barrier function of the gastrointestinal tract by generating tolerant responses to dietary antigens and commensal bacteria while mounting effective immune responses to enteropathogenic microbes. In addition, it has become clear that local intestinal immunity has a profound impact on distant and systemic immunity. Therefore, it is important to study how an intestinal immune response is induced and what the immunologic outcome of the response is. Here, a detailed protocol is described for the isolation of lymphocytes from small intestine inductive sites like the gut-associated lymphoid tissue Peyer&#39;s patches and the draining mesenteric lymph nodes and effector sites like the lamina propria and the intestinal epithelium. This technique ensures isolation of a large numbers of lymphocytes from small intestinal tissues with optimal purity and viability and minimal cross compartmental contamination within acceptable time constraints. The technical capability to isolate lymphocytes and other immune cells from intestinal tissues enables the understanding of immune responses to gastrointestinal infections, cancers, and inflammatory diseases.

Here we describe a detailed protocol for the isolation of lymphocytes from the inductive sites including the gut-associated lymphoid tissue Peyer&#39;s patches and the draining mesenteric lymph nodes, and the effector sites including the lamina propria and the intestinal epithelium of the small intestinal immune system.

The intestinal immune system plays an essential role in maintaining the barrier function of the gastrointestinal tract by generating tolerant responses to ...

Quantitative Polymerase Chain Reaction-based Analyses of Murine Intestinal Microbiota After Oral Antibiotic Treatment

The gut microbiota has a central influence on human health. Microbial dysbiosis is associated with many common immunopathologies such as inflammatory bowel disease, asthma and arthritis. Thus, understanding the mechanisms underlying microbiota-immune system crosstalk is of crucial importance. Antibiotic administration, while aiding pathogen clearance, also induces drastic changes in the size and composition of intestinal bacterial communities which can have an impact on human health. Antibiotic treatment in mice recapitulates the impact and long-term changes in human microbiota from antibiotic treated patients, and enables investigation of the mechanistic links between changes in microbial communities and immune cell function. While several methods for antibiotic treatment of mice have been described, some of them induce severe dehydration and weight-loss complicating the interpretation of the data. Here, we provide two protocols for oral antibiotic administration which can be used for long-term treatment of mice without inducing major weight-loss. These protocols make use of a combination of antibiotics that target both Gram-positive and Gram-negative bacteria and can be provided either ad libitum in the drinking water or by oral gavage. Moreover, we describe a method for the quantification of microbial density in fecal samples by qPCR which can be used to validate the efficacy of the antibiotic treatment. The combination of these approaches provides a reliable methodology for the manipulation of the intestinal microbiota and the study of the effects of antibiotic treatment in mice.

Here we provide detailed protocols for the oral administration of antibiotics to mice, collection of fecal samples, DNA extraction and quantification of fecal bacteria by qPCR.

The gut microbiota has a central influence on human health. Microbial dysbiosis is associated with many common immunopathologies such as inflammatory ...

Murine Fecal Isolation and Microbiota Transplantation

Gut microbiota dysbiosis plays a role in the pathophysiology of cardiovascular and metabolic disorders, but the mechanisms are not well understood. Fecal microbiota transplantation (FMT) is a valuable approach to delineating a direct role of the total microbiota or isolated species in disease pathophysiology. It is a safe treatment option for patients with recurrent Clostridium difficile infection. Preclinical studies demonstrate that manipulating the gut microbiota is a useful tool to study the mechanistic link between dysbiosis and disease. Fecal microbiota transplantation may help elucidate novel gut microbiota-targeted therapeutics for the management and treatment of cardiometabolic disease. Despite a high success rate in rodents, there remains translational changes associated with the transplantation. The goal here is to provide guidance in studying the effects of gut microbiome in experimental cardiovascular disease. In this study, a detailed protocol for the collection, handling, processing, and transplantation of fecal microbiota in murine studies is described. The collection and processing steps are described for both human and rodent donors. Lastly, we describe using a combination of the Swiss-rolling and immunostaining techniques to assess gut-specific morphology and integrity changes in cardiovascular disease and related gut microbiota mechanisms.

The goal here is to outline a protocol to investigate the mechanisms of dysbiosis in cardiovascular disease. This paper discusses how to aseptically collect and transplant murine fecal samples, isolate intestines, and use the "Swiss-roll" method, followed by immunostaining techniques to interrogate changes in the gastrointestinal tract.

Gut microbiota dysbiosis plays a role in the pathophysiology of cardiovascular and metabolic disorders, but the mechanisms are not well understood. Fecal ...

Preparation and Maintenance of Bioexclusion IsoPositive Cage Experiment for Human Fecal Transplantation into Germ-Free Mice

Germ-free mice are an important investigation tool for understanding the contribution of microorganisms in host health and disease, enabling assessment of the specific role of individuals, defined or complex groups of microorganisms in host response. Traditionally bred and reared in flexible-film or semi-rigid isolators, germ-free mouse husbandry and experimental manipulation are costly and require numerous trained staff and a large space footprint in animal housing facilities. The IsoPositive caging system allows for experimental manipulation of germ-free mice in individual, hermetically-sealed, positive-pressure isolator cages (isocages), reducing cost and enabling greater flexibility in experimental manipulations. 
Here, a protocol is described for transferring germ-free mice from breeding isolators to isocages and subsequent fecal transfer from human donor stool into mice to create stable long-term gut "humanized" mice for future studies. The materials and preparation needed for the utilization of the isocage system are described, including the use of chlorine-dioxide sterilant chemical sterilant to clean cages, supplies, equipment, and personal protective equipment. The methods for confirming the germ-free status of transferred mice and how to determine contamination in the caging system are discussed. The procedure for husbandry, including bedding, food, and water supply, is further discussed. The protocol for human fecal slurry preparation and gavage into germ-free mice to create gut "humanized" mice, along with stool collection to monitor the microbial community composition of these mice, are described. An experiment illustrates that two weeks post-human fecal transplant allows for stable colonization of donor microbiota in the murine hosts, enabling subsequent experimental usage. Furthermore, the collection of humanized mouse feces in viability preservation media, enabling use in further functional experiments, is described. Overall, these methods allow for the safe and effective establishment of humanized mouse communities in experimental gnotobiotic cages for further manipulation.

This protocol describes the best practices for germ-free mouse transfer to and housing in experimental single-cage isolators (isocages) while maintaining sterile conditions. Methods for fecal transplant into germ-free mice and the collection of viable bacteria from these gut "humanized" mice for further applications are discussed.

Germ-free mice are an important investigation tool for understanding the contribution of microorganisms in host health and disease, enabling assessment of ...

A Method to Assess Bacteriocin Effects on the Gut Microbiota of Mice

Very intriguing questions arise with our advancing knowledge on gut microbiota composition and the relationship with health, particularly relating to the factors that contribute to maintaining the population balance. However, there are limited available methodologies to evaluate these factors. Bacteriocins are antimicrobial peptides produced by many bacteria that may confer a competitive advantage for food acquisition and/or niche establishment. Many probiotic lactic acid bacteria (LAB) strains have great potential to promote human and animal health by preventing the growth of pathogens. They can also be used for immuno-modulation, as they produce bacteriocins. However, the antagonistic activity of bacteriocins is normally determined by laboratory bioassays under well-defined but over-simplified conditions compared to the complex gut environment in humans and animals, where bacteria face multifactorial influences from the host and hundreds of microbial species sharing the same niche. This work describes a complete and efficient procedure to assess the effect of a variety of bacteriocins with different target specificities in a murine system. Changes in the microbiota composition during the bacteriocin treatment are monitored using compositional 16S rDNA sequencing. Our approach uses both the bacteriocin producers and their isogenic non-bacteriocin-producing mutants, the latter giving the ability to distinguish bacteriocin-related from non-bacteriocin-related modifications of the microbiota. The fecal DNA extraction and 16S rDNA sequencing methods are consistent and, together with the bioinformatics, constitute a powerful procedure to find faint changes in the bacterial profiles and to establish correlations, in terms of cholesterol and triglyceride concentration, between bacterial populations and health markers. Our protocol is generic and can thus be used to study other compounds or nutrients with the potential to alter the host microbiota composition, either when studying toxicity or beneficial effects.

Bacteriocins are believed to play a key role in defining microbial diversity in different ecological niches. Here, we describe an efficient procedure to assess how bacteriocins affect gut microbiota composition in an animal model.

Very intriguing questions arise with our advancing knowledge on gut microbiota composition and the relationship with health, particularly relating to the ...

Biology

Microbiota Analysis Using Two-step PCR and Next-generation 16S rRNA Gene Sequencing

The human gut is colonized by trillions of bacteria that support physiologic functions such as food metabolism, energy harvesting, and regulation of the immune system. Perturbation of the healthy gut microbiome has been suggested to play a role in the development of inflammatory diseases, including multiple sclerosis (MS). Environmental and genetic factors can influence the composition of the microbiome; therefore, identification of microbial communities linked with a disease phenotype has become the first step towards defining the microbiome&#8217;s role in health and disease. Use of 16S rRNA metagenomic sequencing for profiling bacterial community has helped in advancing microbiome research. Despite its wide use, there is no uniform protocol for 16S rRNA-based taxonomic profiling analysis. Another limitation is the low resolution of taxonomic assignment due to technical difficulties such as smaller sequencing reads, as well as use of only forward (R1) reads in the final analysis due to low quality of reverse (R2) reads. There is need for a simplified method with high resolution to characterize bacterial diversity in a given biospecimen. Advancements in sequencing technology with the ability to sequence longer reads at high resolution have helped to overcome some of these challenges. Present sequencing technology combined with a publicly available metagenomic analysis pipeline such as R-based Divisive Amplicon Denoising Algorithm-2 (DADA2) has helped advance microbial profiling at high resolution, as DADA2 can assign sequence at the genus and species levels. Described here is a guide for performing bacterial profiling using two-step amplification of the V3-V4 region of the 16S rRNA gene, followed by analysis using freely available analysis tools (i.e., DADA2, Phyloseq, and METAGENassist). It is believed that this simple and complete workflow will serve as an excellent tool for researchers interested in performing microbiome profiling studies.

Described here is a simplified standard operating procedure for microbiome profiling using 16S rRNA metagenomic sequencing and analysis using freely available tools. This protocol will help researchers who are new to the microbiome field as well as those requiring updates on methods to achieve bacterial profiling at a higher resolution.

The human gut is colonized by trillions of bacteria that support physiologic functions such as food metabolism, energy harvesting, and regulation of the ...

Fecal Microbiota Transplantation and Detection of Prevalence of IgA-Coated Bacteria in the Gut

Gut microbiota exert pleiotropic roles in human health and disease. Fecal microbiota transplantation (FMT) is an effective method to investigate the biological function of intestinal bacteria as a whole or at the species level. Several different FMT methods have been published. Here, we present an FMT protocol that successfully depletes gut microbiota in a matter of days, followed by transplantation of fecal microbiota from fresh or frozen donor intestinal contents to conventional mice. Real time-PCR is applied to test the efficacy of bacterial depletion. Sequencing of the 16S ribosomal RNA (rRNA) is then applied to test the relative abundance and identity of gut microbiota in recipient mice. We also present a flow cytometry-based detection method of immunoglobulin A (IgA)-coated bacteria in the gut.

We established an efficient way to deplete intestinal bacteria in three days, and subsequently transplant fecal microbiota via gavage of fecal fluid prepared from fresh or frozen intestinal contents in mice. We also present an optimized method to detect the frequency of IgA-coated bacteria in the gut.

Gut microbiota exert pleiotropic roles in human health and disease. Fecal microbiota transplantation (FMT) is an effective method to investigate the ...