The authors wish to acknowledge support relevant to this manuscript from the European Commission Seventh Framework Programme (PIOF-GA-2009-255466) and the Irish Health Research Board (HRA_POR/2010/138). Lux-tagged E. coli was a kind gift from Dr. Cormac Gahan, University College Cork.

1. Tumor Induction
<ol>
 <li>For routine tumor induction, the minimum tumorigenic dose of cells suspended in 200 &mu;l of serum-free culture medium was injected subcutaneously (s.c.) into the flank of infection free 6-8 week old female Balb/C or athymic MF1-nu/nu mice n=6 (Harlan, Oxfordshire, UK) (1 x 106 4T1 cells) using a 21-gauge syringe needle. The viability of cells used for inoculation was greater than 95 % as determined by visual count using a haemocytometer and Trypan Blue Dye Exclusion (Gibco). </li>
 <li>Following tumor establishment, tumors were allowed to grow and develop and were monitored twice weekly. Tumor volume was calculated according to the formula V=(ab2) &Pi;/6, where a is the longest diameter of the tumor and b is the longest diameter perpendicular to diameter a. </li>
</ol>
2. Bacterial Preparation
<ol>
 <li>The bacterial strain used in this protocol was E. coli K-12 MG1655, a non-protein-toxin-expressing strain, harboring a luxABCDE-encoding plasmid that enables the bacteria to be detected by BLI. E. coli MG1655 containing the integrated luxABCDE was grown aerobically at 37 &deg;C in LB medium (Sigma-Aldrich, Ireland) supplemented with 300 &mu;g/ml erythromycin (Em). The bioluminescent derivative of MG1655 was created using the plasmid p16Slux which contains the constitutive PHELPluxABCDE operon 1. </li>
 <li>For preparation for administration to mice, cultures were incubated in LB medium at 37 &deg;C in a shaker at 200 rpm to mid-log phase (optical density at 600 nm). Bacteria were harvested by centrifugation (6,000 &times; g for 5 min), washed with PBS (Sigma), and diluted in PBS 1 &times; 107 colony forming units (cfu) /ml for IV administration, or 1 x 1010 for gavage. </li>
</ol>
3. Bacterial Administration
<ol>
 <li>Mice were randomly divided into experimental groups when tumors reached approximately 100 mm3 in volume. For intravenous administration, restrained mice each received 106 cells in 100 &mu;l, injected directly into the lateral tail vein using a 28G syringe needle. The viable count of each inoculum was determined by retrospective plating. </li>
 <li>For GIT colonization studies, 109 bacterial cells were orally administered in 100 &mu;l per mouse by gavage, on three consecutive days. Pre-existing commensal bacterial levels were decreased prior to feeding by addition of 5 mg/ml streptomycin in mouse drinking water for 7 days prior to commencement of oral gavage 1. </li>
</ol>
4. BioLuminescence Imaging
<ol>
 <li>2D in vivo BLI imaging was performed using the IVIS100 (Caliper). At defined time points post bacterial administration, mice were anesthetized using Caliper's XGI-8 Gas Anesthesia System with 3% Isofluorane, and whole-body image analysis was performed in the IVIS 100 system for 2-5 min at high sensitivity. </li>
 <li>For 3D imaging, anesthetized mice were placed in a mouse imaging shuttle inside of the optical imaging system for dorsal imaging (IVIS Spectrum, Caliper). To acquire images of the bacterial luciferase signal for 3D optical reconstruction, emission filter wavelengths ranging from 500-580 nm were used with bin 16 acquisition times of 3-4 min per filter to maximize the signal to noise ratio. As part of this image acquisition sequence, a structured light image was obtained to define a height map. This map was input diffuse light imaging tomography (DLIT) reconstructions algorithms that were used to form a 3D optical image using a non-negative least squares optimization 2.</li>
 <li>Image Analysis: Regions of interest were identified and quantified using Living Image software (Caliper). </li>
</ol>
5. Representative Results
In this study, the non-pathogenic commensal bacteria E.coli K-12 MG1655 expressing the luxABCDE operon was IV administered to mice bearing s.c. 4T1 xenograft tumors. Bacterial lux signal was detected specifically in tumors of mice post IV-administration (Figure 2). Culture recovery of bacteria from sample mice validates the existence of a linear relationship between viable bacterial numbers and the quantity of light detected (Figure 3). In vivo imaging of orally-administered commensal bacteria in the GIT is also achieved using 3D BLI. 
<img src="/files/ftp_upload/4318/4318fig1.jpg" alt="Figure 1" fo:content-width="4in" fo:src="/files/ftp_upload/4318/4318fig1highres.jpg"/> 
Figure 1. Protocol Timeline. Subcutaneous tumors are induced in mice, and bacteria administered upon tumor development (100 mm3). Live mice are BLI imaged at various time-points post bacterial administration (arrows display typical times). 
<img src="/files/ftp_upload/4318/4318fig2.jpg" alt="Figure 2" /> 
Figure 2. Administration of E. coli MG1655 luxABCDE to tumor bearing mice. Subcutaneous 4T1 tumors were induced in MF1 nu/nu mice and E. coli MG1655 luxABCDE administered upon tumor development. Each animal received 106 cells injected directly into the lateral tail vein. Mice were imaged at four time points during the study (black dots z-axis and images) with subsequent recovery of viable bacteria (cfu) from tumors of sample sacrificed mice (bar graph). Increase in bacterial numbers and plasmid gene expression specifically in tumors was observed over time (representative mouse illustrated per time point). <a href="https://www.jove.com/files/ftp_upload/4318/4318fig2large.jpg" target="_blank"> Click here to view larger figure</a>. 
<img src="/files/ftp_upload/4318/4318fig3.jpg" alt="Figure 3" /> 
Figure 3. Relationship Between Intratumoral Bacterial Numbers And Bioluminescence. Viable bacteria in tumors were enumerated by ex vivo bacterial culture from tumors subsequent to BLI at various time-points post IV administration. Log values of bacterial numbers (cfu) relative to in vivo bioluminesce units are graphed. A robust correlation between bacterial counts and bacterial bioluminescence signals is observed R2=0.97171.
<img src="/files/ftp_upload/4318/4318fig4.jpg" alt="Figure 4" /> 
 Figure 4. 3D IVIS Image Of Murine Gastrointestinal Tract Colonized By E. coli MG1655. The GIT of mice was colonized by oral administration of 109 cfu of E. coli for three consecutive days. A sample isolated image from 3D tomography of the colonized mouse is shown. 3D images show a digital mouse atlas of the skeleton to provide anatomical registration. E. coli MG1655 bioluminescence is visible in green at lower, and purple at higher levels.

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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=Tumor-targeting+prodrug-activating+bacteria+for+cancer+therapy.">Tumor-targeting prodrug-activating bacteria for cancer therapy.</a> Cancer Gene Ther. 15, 393-401 (2008).</li><li>Foucault, M. L., Thomas, L., Goussard, S., Branchini, B. R., Grillot-Courvalin, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+bioluminescence+imaging+for+the+study+of+intestinal+colonization+by+Escherichia+coli+in+mice.">In vivo bioluminescence imaging for the study of intestinal colonization by Escherichia coli in mice.</a> Appl. Environ. Microbiol. 76, 264-274 (2010).</li><li>Collins, S. 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No conflicts of interest declared.

In the context of gene therapy, the use of biological agents for delivery of therapeutic genes to patients has shown great promise 3-5. Like viruses, the innate biological properties of bacteria permit efficient DNA delivery to cells or tissues, particularly in the context of cancer. It has been shown that bacteria are naturally capable of homing to tumors when systemically administered resulting in high levels of replication locally, either external to (non-invasive species) or within tumor cells (pathogens)....

<table border="1">
<tbody>
 <tr>
 <td>Name of the reagent</td>
 <td>Company</td>
 <td>Catalogue number</td>
 <td>Comments </td>
 </tr>
 <tr>
 <td>4T1 cell line</td>
 <td>ATCC</td>
 <td>CRL-2539</td>
 <td>Syngeneic breast cancer model derived from a spontaneously arising BALB/c mammary tumor</td>
 </tr>
 <tr>
 <td>DMEM</td>
 <td>Sigma-Aldrich</td>
 <td>D6429</td>
 <td>Dulbecco's Modified Eagle's Medium</td>
 </tr>
 <tr>
 <td>PBS</td>
 <td>Sigma-Aldrich</td>
 <td>D8537</td>
 <td>Phosphate Buffered Saline</td>
 </tr>
 <tr>
 <td>Xenogen IVIS</td>
 <td>Caliper Life Sciences</td>
 <td>&nbsp;</td>
 <td>IVIS 100 for 2D imaging; IVIS Spectrum for 3D.</td>
 </tr>
 <tr>
 <td>Luria Broth Miller (LB)</td>
 <td>Sigma-Aldrich</td>
 <td>L2542</td>
 <td>Growth medium for E. coli</td>
 </tr>
 <tr>
 <td>Erythromycin</td>
 <td>Sigma-Aldrich</td>
 <td>E5389</td>
 <td>Antibiotic</td>
 </tr>
 <tr>
 <td>Streptomycin</td>
 <td>Sigma-Aldrich</td>
 <td>S9137</td>
 <td>Antibiotic </td>
 </tr>
 <tr>
 <td>MF1nu/nu mice</td>
 <td>Harlan (UK)</td>
 <td>069(nu)/070(nu/+) </td>
 <td>Hsd:Athymic Nude-Foxn1nu </td>
 </tr>
 <tr>
 <td>Balb/c mice</td>
 <td>Harlan (UK)</td>
 <td>066</td>
 <td>Haplotype:&nbsp;H-2d</td>
 </tr>
 <tr>
 <td>Gavage needle </td>
 <td>Vet-tech Solutions (UK)</td>
 <td>DE009</td>
 <td>22G x 38mm straight gavage needle </td>
 </tr>
 <tr>
 <td>Syringe for IV injection </td>
 <td>BD BioSciences</td>
 <td>309309 - 1 ml</td>
 <td>Insulin syringe with 28 G x &frac12; inch micro-fine IV needle.</td>
 </tr>
 <tr>
 <td>Syringe for tumor inoculation</td>
 <td>Braun</td>
 <td>9161376V</td>
 <td>Omnifix 26 G x &frac12; inch needle</td>
 </tr>
 </tbody>
</table>

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.

Watch this Scientific Journal Video about Bioluminescent Bacterial Imaging In Vivo at JoVE.com

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.

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 ...

Research

JoVE Journal

Immunology and Infection

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视频: Bioluminescent Bacterial Imaging In Vivo

In vivo Imaging of Transgenic Leishmania Parasites in a Live Host

Distinct species of Leishmania, a protozoan parasite of the family Trypanosomatidae, typically cause different human disease manifestations. The most common forms of disease are visceral leishmaniasis (VL) and cutaneous leishmaniasis (CL). Mouse models of leishmaniasis are widely used, but quantification of parasite burdens during murine disease requires mice to be euthanized at various times after infection. Parasite loads are then measured either by microscopy, limiting dilution assay, or qPCR amplification of parasite DNA. The in vivo imaging system (IVIS) has an integrated software package that allows the detection of a bioluminescent signal associated with cells in living organisms. Both to minimize animal usage and to follow infection longitudinally in individuals, in vivo models for imaging Leishmania spp. causing VL or CL were established. Parasites were engineered to express luciferase, and these were introduced into mice either intradermally or intravenously. Quantitative measurements of the luciferase driving bioluminescence of the transgenic Leishmania parasites within the mouse were made using IVIS. Individual mice can be imaged multiple times during longitudinal studies, allowing us to assess the inter-animal variation in the initial experimental parasite inocula, and to assess the multiplication of parasites in mouse tissues. Parasites are detected with high sensitivity in cutaneous locations. Although it is very likely that the signal (photons/second/parasite) is lower in deeper visceral organs than the skin, but quantitative comparisons of signals in superficial versus deep sites have not been done. It is possible that parasite numbers between body sites cannot be directly compared, although parasite loads in the same tissues can be compared between mice. Examples of one visceralizing species (L. infantum chagasi) and one species causing cutaneous leishmaniasis (L. mexicana) are shown. The IVIS procedure can be used for monitoring and analyzing small animal models of a wide variety of Leishmania species causing the different forms of human leishmaniasis.

In vivo Imaging of Transgenic Leishmania Parasites in a Live Host

An in vivo imaging system is used to generate quantitative measurements of murine infection with the Trypanosomatid protozoan Leishmania. This is a non-invasive and non-lethal method for detecting parasites expressing luciferase within many tissues throughout the course of chronic Leishmania spp. infection.

Distinct species of Leishmania, a protozoan parasite of the family Trypanosomatidae, typically cause different human disease manifestations. The most ...

Non-invasive Imaging of Leukocyte Homing and Migration in vivo

Two-photon (2P) microscopy is a high resolution imaging technique that has been broadly adapted by biologists. The value of 2P microscopy is that it provides rich spatiotemporal information regarding cell behaviors within intact tissues and in live mice. Leukocyte recruitment plays a significant role in host defense against infection and when unchecked, can contribute to inflammatory and autoimmune diseases. Studying leukocyte recruitment in vivo is technically challenging since cells are moving rapidly within vessels located deep within light scattering tissues. To date, most intravital imaging studies require surgical preparation to expose the blood vessels and tissues. To avoid the tissue damage and inflammation induced by surgery itself, here, we describe a non-invasive single-cell imaging approach that can be used to study leukocyte trafficking in the mouse footpad and phalanges. We discuss the technical aspects of our 2P imaging preparation and walk the reader through a typical experiment from initial set up to execution and data collection.

Non-invasive Imaging of Leukocyte Homing and Migration in vivo

Here, we describe a non-invasive two-photon (2P) microscopy approach to study leukocyte homing in the mouse footpad. We discuss the technical aspects of our tissue imaging preparation and walk the reader through a typical experiment from initial set up to execution and data collection.

Two-photon (2P) microscopy is a high resolution imaging technique that has been broadly adapted by biologists.  The value of 2P microscopy is that it ...

Assessing Stomatal Response to Live Bacterial Cells using Whole Leaf Imaging

Stomata are natural openings in the plant epidermis responsible for gas exchange between plant interior and environment. They are formed by a pair of guard cells, which are able to close the stomatal pore in response to a number of external factors including light intensity, carbon dioxide concentration, and relative humidity (RH). The stomatal pore is also the main route for pathogen entry into leaves, a crucial step for disease development. Recent studies have unveiled that closure of the pore is effective in minimizing bacterial disease development in Arabidopsis plants; an integral part of plant innate immunity. Previously, we have used epidermal peels to assess stomatal response to live bacteria (Melotto et al. 2006); however maintaining favorable environmental conditions for both plant epidermal peels and bacterial cells has been challenging. Leaf epidermis can be kept alive and healthy with MES buffer (10 mM KCl, 25 mM MES-KOH, pH 6.15) for electrophysiological experiments of guard cells. However, this buffer is not appropriate for obtaining bacterial suspension. On the other hand, bacterial cells can be kept alive in water which is not proper to maintain epidermal peels for long period of times. When an epidermal peel floats on water, the cells in the peel that are exposed to air dry within 4 hours limiting the timing to conduct the experiment. An ideal method for assessing the effect of a particular stimulus on guard cells should present minimal interference to stomatal physiology and to the natural environment of the plant as much as possible. We, therefore, developed a new method to assess stomatal response to live bacteria in which leaf wounding and manipulation is greatly minimized aiming to provide an easily reproducible and reliable stomatal assay. The protocol is based on staining of intact leaf with propidium iodide (PI), incubation of staining leaf with bacterial suspension, and observation of leaves under laser scanning confocal microscope. Finally, this method allows for the observation of the same live leaf sample over extended periods of time using conditions that closely mimic the natural conditions under which plants are attacked by pathogens.

We have developed a simple and reproducible protocol to access stomatal response to live bacteria. This method minimizes wounding and manipulation of the leaf as compared to the use of epidermal peels reported previously.

Stomata are natural openings in the plant epidermis responsible for gas exchange between plant interior and environment. They are formed by a pair of ...

Using Bioluminescent Imaging to Investigate Synergism Between Streptococcus pneumoniae and Influenza A Virus in Infant Mice

During the 1918 influenza virus pandemic, which killed approximately 50 million people worldwide, the majority of fatalities were not the result of infection with influenza virus alone. Instead, most individuals are thought to have succumbed to a secondary bacterial infection, predominately caused by the bacterium Streptococcus pneumoniae (the pneumococcus). The synergistic relationship between infections caused by influenza virus and the pneumococcus has subsequently been observed during the 1957 Asian influenza virus pandemic, as well as during seasonal outbreaks of the virus (reviewed in 1, 2). Here, we describe a protocol used to investigate the mechanism(s) that may be involved in increased morbidity as a result of concurrent influenza A virus and S. pneumoniae infection. We have developed an infant murine model to reliably and reproducibly demonstrate the effects of influenza virus infection of mice colonised with S. pneumoniae. Using this protocol, we have provided the first insight into the kinetics of pneumococcal transmission between co-housed, neonatal mice using in vivo imaging 3.

Using Bioluminescent Imaging to Investigate Synergism Between Streptococcus pneumoniae and Influenza A Virus in Infant Mice

A concurrent infection with influenza A virus is one of the factors implicated in the induction of invasive pneumococcal disease during asymptomatic Streptococcus pneumoniae carriage. Here we describe a mixed infection method using infant mice to investigate the synergism between these two respiratory pathogens.

During the 1918 influenza virus pandemic, which killed approximately 50 million people worldwide, the majority of fatalities were not the result of ...

'Bioluminescent' Reporter Phage for the Detection of Category A Bacterial Pathogens

Yersinia pestis and Bacillus anthracis are Category A bacterial pathogens that are the causative agents of the plague and anthrax, respectively 1. Although the natural occurrence of both diseases&#39; is now relatively rare, the possibility of terrorist groups using these pathogens as a bioweapon is real. Because of the disease&#39;s inherent communicability, rapid clinical course, and high mortality rate, it is critical that an outbreak be detected quickly. Therefore methodologies that provide rapid detection and diagnosis are essential to ensure immediate implementation of public health measures and activation of crisis management.
Recombinant reporter phage may provide a rapid and specific approach for the detection of Y. pestis and B. anthracis. The Centers for Disease Control and Prevention currently use the classical phage lysis assays for the confirmed identification of these bacterial pathogens 2-4. These assays take advantage of naturally occurring phage which are specific and lytic for their bacterial hosts. After overnight growth of the cultivated bacterium in the presence of the specific phage, the formation of plaques (bacterial lysis) provides a positive identification of the bacterial target. Although these assays are robust, they suffer from three shortcomings: 1) they are laboratory based; 2) they require bacterial isolation and cultivation from the suspected sample, and 3) they take 24-36 h to complete. To address these issues, recombinant &#34;light-tagged&#34; reporter phage were genetically engineered by integrating the Vibrio harveyi luxAB genes into the genome of Y. pestis and B. anthracis specific phage 5-8. The resulting luxAB reporter phage were able to detect their specific target by rapidly (within minutes) and sensitively conferring a bioluminescent phenotype to recipient cells. Importantly, detection was obtained either with cultivated recipient cells or with mock-infected clinical specimens 7.
For demonstration purposes, here we describe the method for the phage-mediated detection of a known Y. pestis isolate using a luxAB reporter phage constructed from the CDC plague diagnostic phage &#934;A1122 6,7 (Figure 1). A similar method, with minor modifications (e.g. change in growth temperature and media), may be used for the detection of B. anthracis isolates using the B. anthracis reporter phage W&#946;::luxAB 8. The method describes the phage-mediated transduction of a biolumescent phenotype to cultivated Y. pestis cells which are subsequently measured using a microplate luminometer. The major advantages of this method over the traditional phage lysis assays is the ease of use, the rapid results, and the ability to test multiple samples simultaneously in a 96-well microtiter plate format.
<img alt="Figure 1" src="/files/ftp_upload/2740/2740fig1.jpg" /> 
Figure 1. Detection schematic. The phage are mixed with the sample, the phage infects the cell, luxAB are expressed, and the cell bioluminesces. Sample processing is not necessary; the phage and cells are mixed and subsequently measured for light.

&#039;Bioluminescent&#039; Reporter Phage for the Detection of Category A Bacterial Pathogens

A simple method for the identification of priority bacterial pathogens is to use genetically engineered reporter phage. These reporter phage, which are specific to their particular host species, are capable of rapidly transducing a bioluminescent signal response to host cells. Herein, we describe the use of reporter phage for the detection of Yersinia pestis.

Yersinia pestis and Bacillus anthracis are Category A bacterial pathogens that are the causative agents of the plague and anthrax, respectively 1. ...

In Vivo Imaging Systems (IVIS) Detection of a Neuro-Invasive Encephalitic Virus

Modern advancements in imaging technology encourage further development and refinement in the way viral research is accomplished. Initially proposed by Russel and Burch in Hume's 3Rs (replacement, reduction, refinement), the utilization of animal models in scientific research is under constant pressure to identify new methodologies to reduce animal usage while improving scientific accuracy and speed. A major challenge to Hume's principals however, is how to ensure the studies are statistically accurate while reducing animal disease morbidity and overall numbers. Vaccine efficacy studies currently require a large number of animals in order to be considered statistically significant and often result in high morbidity and mortality endpoints for identification of immune protection. We utilized in vivo imaging systems (IVIS) in conjunction with a firefly bioluminescent enzyme to progressively track the invasion of the central nervous system (CNS) by an encephalitic virus in a murine model. Typically, the disease progresses relatively slowly, however virus replication is rapid, especially within the CNS, and can lead to an often, lethal outcome. Following intranasal infection of the mice with TC83-Luc, an attenuated Venezuelan equine encephalitis virus strain modified to expresses a luciferase gene; we are able to visualize virus replication within the brain at least three days before the development of clinical disease symptoms. Utilizing CNS invasion as a key encephalitic disease development endpoint we are able to quickly identify therapeutic and vaccine protection against TC83-Luc infection before clinical symptoms develop. With IVIS technology we are able to demonstrate the rapid and accurate testing of drug therapeutics and vaccines while reducing animal numbers and morbidity.

In Vivo Imaging Systems IVIS Detection of a Neuro-Invasive Encephalitic Virus

Utilizing luciferase and in vivo imaging systems (IVIS) as a novel means to identify disease endpoints before clinical developments occur. IVIS has allowed us to visualize in real time the invasion of encephalitic viruses over multiple days, providing a more accurate disease model for future study. It has also allowed us to identify the potential protective features of antivirals and vaccines faster than currently utilized animal models. The capability to utilize individual animals over multiple time points ensures reduced animal requirements, costs, and overall morbidity to the animals utilized ensuring a more humane and more scientific means of disease study.

Modern advancements in imaging technology encourage further development and refinement in the way viral research is accomplished. Initially proposed by ...

In vivo Imaging Method to Distinguish Acute and Chronic Inflammation

Inflammation is a fundamental aspect of many human diseases. In this video report, we demonstrate non-invasive bioluminescence imaging techniques that distinguish acute and chronic inflammation in mouse models. With tissue damage or pathogen invasion, neutrophils are the first line of defense, playing a major role in mediating the acute inflammatory response. As the inflammatory reaction progresses, circulating monocytes gradually migrate into the site of injury and differentiate into mature macrophages, which mediate chronic inflammation and promote tissue repair by removing tissue debris and producing anti-inflammatory cytokines. Intraperitoneal injection of luminol (5-amino-2,3-dihydro-1,4-phthalazinedione, sodium salt) enables detection of acute inflammation largely mediated by tissue-infiltrating neutrophils. Luminol specifically reacts with the superoxide generated within the phagosomes of neutrophils since bioluminescence results from a myeloperoxidase (MPO) mediated reaction. Lucigenin (bis-N-methylacridinium nitrate) also reacts with superoxide in order to generate bioluminescence. However, lucigenin bioluminescence is independent of MPO and it solely relies on phagocyte NADPH oxidase (Phox) in macrophages during chronic inflammation. Together, luminol and lucigenin allow non-invasive visualization and longitudinal assessment of different phagocyte populations across both acute and chronic inflammatory phases. Given the important role of inflammation in a variety of human diseases, we believe this non-invasive imaging method can help investigate the differential roles of neutrophils and macrophages in a variety of pathological conditions.

In vivo Imaging Method to Distinguish Acute and Chronic Inflammation

We describe a non-invasive imaging method for distinguishing inflammatory stages. Systemic delivery of luminol reveals areas of acute inflammation dependent upon MPO activity in neutrophils. In contrast, injection of lucigenin allows for visualization of chronic inflammation dependent upon Phox activity in macrophages.

Inflammation is a fundamental aspect of many human diseases. In this video report, we demonstrate non-invasive bioluminescence imaging techniques that ...

Generation and Multi-phenotypic High-content Screening of Coxiella burnetii Transposon Mutants

Invasion and colonization of host cells by bacterial pathogens depend on the activity of a large number of prokaryotic proteins, defined as virulence factors, which can subvert and manipulate key host functions. The study of host/pathogen interactions is therefore extremely important to understand bacterial infections and develop alternative strategies to counter infectious diseases. This approach however, requires the development of new high-throughput assays for the unbiased, automated identification and characterization of bacterial virulence determinants. Here, we describe a method for the generation of a GFP-tagged mutant library by transposon mutagenesis and the development of high-content screening approaches for the simultaneous identification of multiple transposon-associated phenotypes. Our working model is the intracellular bacterial pathogen Coxiellaburnetii, the etiological agent of the zoonosis Q fever, which is associated with severe outbreaks with a consequent health and economic burden. The obligate intracellular nature of this pathogen has, until recently, severely hampered the identification of bacterial factors involved in host pathogen interactions, making of Coxiella the ideal model for the implementation of high-throughput/high-content approaches.

Generation and Multi-phenotypic High-content Screening of Coxiella burnetii Transposon Mutants

Coxiella burnetii is an obligate intracellular Gram-negative bacterium responsible for the zoonotic disease Q fever. Here we describe methods for the generation of Coxiella fluorescent transposon mutants as well as the automated identification and analysis of the resulting internalization, replication and cytotoxic phenotypes.

Invasion and colonization of host cells by bacterial pathogens depend on the activity of a large number of prokaryotic proteins, defined as virulence ...

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 ...

Non-invasive In Vivo Fluorescence Optical Imaging of Inflammatory MMP Activity Using an Activatable Fluorescent Imaging Agent

This paper describes a non-invasive method for imaging matrix metalloproteinases (MMP)-activity by an activatable fluorescent probe, via in vivo fluorescence optical imaging (OI), in two different mouse models of inflammation: a rheumatoid arthritis (RA) and a contact hypersensitivity reaction (CHR) model. Light with a wavelength in the near infrared (NIR) window (650 - 950 nm) allows a deeper tissue penetration and minimal signal absorption compared to wavelengths below 650 nm. The major advantages using fluorescence OI is that it is cheap, fast and easy to implement in different animal models.
Activatable fluorescent probes are optically silent in their inactivated states, but become highly fluorescent when activated by a protease. Activated MMPs lead to tissue destruction and play an important role for disease progression in delayed-type hypersensitivity reactions (DTHRs) such as RA and CHR. Furthermore, MMPs are the key proteases for cartilage and bone degradation and are induced by macrophages, fibroblasts and chondrocytes in response to pro-inflammatory cytokines. Here we use a probe that is activated by the key MMPs like MMP-2, -3, -9 and -13 and describe an imaging protocol for near infrared fluorescence OI of MMP activity in RA and control mice 6 days after disease induction as well as in mice with acute (1x challenge) and chronic (5x challenge) CHR on the right ear compared to healthy ears.

Non-invasive In Vivo Fluorescence Optical Imaging of Inflammatory MMP Activity Using an Activatable Fluorescent Imaging Agent

This paper explains the application of fluorescent imaging using an activatable optical imaging probe to visualize the in vivo activity of key matrix metalloproteinases in two different experimental models of inflammation.