Name: listeria monocytogenes infection of the brain
Uploaded: 2018-10-02T15:00:00
Description: Watch this Scientific Journal Video about Listeria monocytogenes Infection of the Brain at JoVE.com

This work was supported by U.S. Public Health Service grant AI103806 from the National Institutes of Health.

All animals are to be maintained and handled with maximum care to minimize discomfort during the course of the procedure. The procedure is to be conducted in compliance with the Institutional Animal Care and Use Committee and all federal, state and local laws. Also note that the laboratory experiments are to be conducted in accordance with Biosafety Level 2 guidelines.
1. Growth of L. monocytogenes for Mouse Infection Studies
<ol>
	<li>Autoclave 500 mL of Brain Heart Infusio...

<ol>
	<li>Radoshevich, L., Cossart, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Listeria+monocytogenes:+towards+a+complete+picture+of+its+physiology+and+pathogenesis.">Listeria monocytogenes: towards a complete picture of its physiology and pathogenesis.</a> Nature Reviews Microbiology. 16 (1), 32-46 (2018).</li><li>de Noordhout, C. 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=The+global+burden+of+listeriosis:+a+systematic+review+and+meta-analysis.">The global burden of listeriosis: a systematic review and meta-analysis.</a> The Lancet Infectious Diseases. 14 (11), 1073-1082 (2014).</li><li>Drevets, D. A., Leenen, P. J., Greenfield, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Invasion+of+the+central+nervous+system+by+intracellular+bacteria.">Invasion of the central nervous system by intracellular bacteria.</a> Clinical Microbiology Reviews. 17 (2), 323-347 (2004).</li><li>Huang, S. H., Stins, M. F., Kim, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bacterial+penetration+across+the+blood-brain+barrier+during+the+development+of+neonatal+meningitis.">Bacterial penetration across the blood-brain barrier during the development of neonatal meningitis.</a> Microbes and Infection. 2 (10), 1237-1244 (2000).</li><li>Brouwer, M. C., Tunkel, A. R., van de Beek, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epidemiology,+diagnosis,+and+antimicrobial+treatment+of+acute+bacterial+meningitis.">Epidemiology, diagnosis, and antimicrobial treatment of acute bacterial meningitis.</a> Clinical Microbiology Reviews. 23 (3), 467-492 (2010).</li><li>Thigpen, M. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bacterial+meningitis+in+the+United+States,+1998-2007.">Bacterial meningitis in the United States, 1998-2007.</a> New England Journal of Medicine. 364 (21), 2016-2025 (2011).</li><li>Durand, M. L., 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=Acute+bacterial+meningitis+in+adults.+A+review+of+493+episodes.">Acute bacterial meningitis in adults. A review of 493 episodes.</a> The New England Journal of Medicine. 328 (1), 21-28 (1993).</li><li>Disson, O., Lecuit, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Targeting+of+the+central+nervous+system+by+Listeria+monocytogenes.">Targeting of the central nervous system by Listeria monocytogenes.</a> Virulence. 3 (2), 213-221 (2012).</li><li>Daneman, R., Prat, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+blood-brain+barrier.">The blood-brain barrier.</a> Cold Spring Harbor Perspectives in Biology. 7 (1), a020412 (2015).</li><li>Becavin, C., 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=Comparison+of+widely+used+Listeria+monocytogenes+strains+EGD,+10403S,+and+EGD-e+highlights+genomic+variations+underlying+differences+in+pathogenicity.">Comparison of widely used Listeria monocytogenes strains EGD, 10403S, and EGD-e highlights genomic variations underlying differences in pathogenicity.</a> MBio. 5 (2), e00969-e00914 (2014).</li><li>Kirchner, M., Higgins, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inhibition+of+ROCK+activity+allows+InlF-mediated+invasion+and+increased+virulence+of+Listeria+monocytogenes.">Inhibition of ROCK activity allows InlF-mediated invasion and increased virulence of Listeria monocytogenes.</a> Molecular Microbiology. 68 (3), 749-767 (2008).</li><li>Grubaugh, D., 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+VirAB+ABC+transporter+is+required+for+VirR+regulation+of+Listeria+monocytogenes+virulence+and+resistance+to+nisin.">The VirAB ABC transporter is required for VirR regulation of Listeria monocytogenes virulence and resistance to nisin.</a> Infection and Immunity. 86 (3), 901-917 (2018).</li><li>Vazquez-Boland, J. A., 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=Listeria+pathogenesis+and+molecular+virulence+determinants.">Listeria pathogenesis and molecular virulence determinants.</a> Clinical Microbiology Reviews. 14 (3), 584-640 (2001).</li><li>Ghosh, P., 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=Invasion+of+the+brain+by+Listeria+monocytogenes+is+mediated+by+InlF+and+host+cell+vimentin.">Invasion of the brain by Listeria monocytogenes is mediated by InlF and host cell vimentin.</a> MBio. 9 (1), e00160-e00118 (2018).</li><li>Henke, D., 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=Listeria+monocytogenes+spreads+within+the+brain+by+actin-based+intra-axonal+migration.">Listeria monocytogenes spreads within the brain by actin-based intra-axonal migration.</a> Infection and Immunity. 83 (6), 2409-2419 (2015).</li><li>Maury, M. 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=Uncovering+Listeria+monocytogenes+hypervirulence+by+harnessing+its+biodiversity.">Uncovering Listeria monocytogenes hypervirulence by harnessing its biodiversity.</a> Nature Genetics. 48 (3), 308-313 (2016).</li></ol>

L. monocytogenes is able to cause life-threatening meningoencephalitis in humans. Prior studies have demonstrated the ability of bacteria to cross the blood-brain-barrier (BBB) and to colonize the brain. Three routes of brain invasion have been proposed during infection: direct penetration of the BBB by bacteria, stealth transport by bacteria contained inside of mononuclear cells3, and axonal migration by L. monocytogenes strains that cause rhombencephalitis15</...

The Gram-positive bacterium Listeria monocytogenes is a facultative intracellular pathogen and one of the most deadly food-borne pathogens worldwide. Ingestion of L. monocytogenes contaminated food can lead to listeriosis in humans, a severe invasive disease targeting mostly pregnant women, newborns, the elderly, and immunocompromised individuals1. L. monocytogenes is among the leading causes of death by a food-borne pathogen in the U.S. and case fatality rates from listeriosis are as high as 20&#8211;30%, the highest for all food-borne pathogens2. No vaccine currently exists for L. monocytogenes and the ability of bacteria to effectively spread to distal organs and the brain by crossing the blood-brain barrier (BBB) may lead to life-threatening meningitis and colonization of the brain3,4,5,6. Bacterial meningitis is typically severe; while most people who receive treatment recover, infections can cause serious complications, e.g., brain damage, hearing loss, or learning disabilities in children. L. monocytogenes is predicted to account for at least 10% of all community acquired meningitis in the U.S.7.
A major route for bacterial dissemination to the brain and meninges is through the bloodstream. Bacteria circulating in blood vessels in the brain are able to cross the BBB to cause brain infection. The BBB is a highly vascularized barrier system that protects the brain from foreign particles circulating in the blood. Endothelial cells constitute a layer that lines the interior surface of the blood vessels8,9. In addition to L. monocytogenes, multiple bacterial pathogens such as Neisseria meningitidis, Streptococcus pneumoniae, Escherichia coli, and Haemophilus influenzae type b (Hib) are capable of colonizing the brain by crossing the BBB3,4,5,6. However, when examining bacterial burdens in the brain of infected mice, it is important to determine whether bacteria have crossed the BBB, otherwise the bacterial burden in the brain may represent bacteria that are still in the blood vessels of the brain. Thus, it is necessary to perfuse the mice of all blood prior to determining colony-forming units (CFU) of brain homogenates.
In this study, we describe in vivo methods to examine L. monocytogenes infection of the brain. For the methods described here, we used L. monocytogenes strain 10403S. L. monocytogenes&#160;10403S is one of the most widely used laboratory strains to study systemic listeriosis in the mouse model of infection10. This protocol is based on standard intravenous injection of L. monocytogenes followed by perfusion of the mice. A schematic outline of the infection protocol in mice is shown in Figure 1. L. monocytogenes-infected brains and other organs from non-perfused or perfused mice were collected and the bacterial organ burden determined. These methods are useful for not only determining total bacterial colonization of the brain in infected animals, but are also beneficial for determining whether bacteria have penetrated the BBB in vivo to mediate invasion of the brain. It is important to highlight that this laboratory protocol should be conducted following consultation with the relevant institutional biosafety committee and animal facility management.

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			<td height="21" style="height:21px;width:261px;">Brain Heart Infusion media</td>
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			<td height="42" style="height:42px;width:261px;">IKA T18 ULTRA-TURRAX Basic Homogenizer</td>
			<td>IKA</td>
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			<td>Model: T18BS1</td>
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			<td>Beckman Coulter</td>
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			<td>Jackson Laboratory</td>
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			<td>Becton Dickinson</td>
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			<td height="21" style="height:21px;">26-gauge needles</td>
			<td>Becton Dickinson</td>
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			<td>Becton Dickinson</td>
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			<td>VWR</td>
			<td>21008-918</td>
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			<td>VWR</td>
			<td>60819-546</td>
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			<td height="21" style="height:21px;">Phosphate-buffered saline&#160;</td>
			<td>Corning</td>
			<td>46-013-CM</td>
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			<td height="21" style="height:21px;">Stainless steel spatula</td>
			<td>VWR</td>
			<td>82027-520</td>
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			<td height="21" style="height:21px;">Stainless steel scissors (6.5 in)</td>
			<td>VWR</td>
			<td>82027-592</td>
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			<td height="21" style="height:21px;">Stainless steel scissors (4.5 in)</td>
			<td>VWR</td>
			<td>82027-578</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Stainless steel blunt forceps&#160; (4.5 in)</td>
			<td>VWR</td>
			<td>82027-440</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Stainless steel fine tip forceps&#160; (6 in)</td>
			<td>VWR</td>
			<td>82027-406</td>
			<td></td>
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listeria monocytogenes infection of the brain

Listeria monocytogenes is an intracellular bacterial pathogen that is frequently associated with food-borne infection. The ability of&#160;L. monocytogenes to cross the blood-brain barrier (BBB) is concerning as it can lead to life-threatening meningitis and encephalitis. The BBB protects the brain microenvironment from various toxic metabolites and microbial pathogens found in the blood following infection, and therefore supports brain homeostasis. The mechanisms by which L. monocytogenes present in the bloodstream cross the BBB to cause brain infections are not fully understood and there is also a lack of a robust model system to study brain infections by L. monocytogenes. Here, we present a simple mouse infection model to determine whether bacteria have crossed the BBB and to quantitate the burden of bacteria that have colonized the brain in vivo. In this method, animals were infected intravenously with L. monocytogenes and were humanely euthanized by exposure to CO2 followed by cervical dislocation. Cardiac perfusion of the animals was performed prior to harvesting infected organs. Blood was collected before perfusion and the number of bacteria per organ or mL of blood was determined by plating dilutions of the blood or organ homogenates on agar plates and counting the number of colonies formed. This method can be used to study novel receptor-ligand interactions that enhance infection of the brain by L. monocytogenes and can be easily adapted for the study of multiple bacterial pathogens.

The brain is highly vascularized and L. monocytogenes is known to infect cell types present in the blood3,13. The described protocol is used to demonstrate the ability of L. monocytogenes to cross the blood-brain barrier (BBB) leading to infection of the brain in mice. To determine if bacteria have crossed the BBB in vivo, perfusion of blood in the mouse is performed prior to determining bacterial burden...

Watch this Scientific Journal Video about Listeria monocytogenes Infection of the Brain at JoVE.com

Listeria monocytogenes Infection of the Brain

During infection, Listeria monocytogenes is capable of crossing the blood-brain barrier to colonize the brain. In this protocol, we demonstrate how to assess bacterial colonization of organs following infection of mice. A procedure to perform whole organ perfusion for specific determination of bacterial numbers in the brain parenchyma is provided.

Listeria monocytogenes Infection of the Brain

Listeria monocytogenes is an intracellular bacterial pathogen that is frequently associated with food-borne infection. The ability of&#160;L. ...

This method can help answer key questions in the bacterial pathogenesis field about whether bloodborne bacteria can cross the blood-brain barrier to infect the central nervous system and brain. With this technique, bacterial numbers within the blood and brain tissue of infected animals can be determined while excluding the number of bacteria residing within the blood vessels of the brain. Demonstrating the procedure will be Pallab Ghosh, a research associate from my laboratory.At 72 hours post-infection, set an automated perfusion system to a flow rate of four milliliters of PBS supplemented with 10 millimolar of EDTA per minute. And place the euthanized animal in the supine position in a dissection pan. Confirm euthanization by a lack of response to paw pinch.And wet the abdomen with 75%ethanol. Use scissors to make an abdominal wall incision to just below the rib cage to expose the diaphragm and visceral organs. And cut the diaphragm to open the thoracic cavity.Cut the rub cage bilaterally to expose the left ventricle and use forceps to gently grasp the heart. Insert a 21-gauge butterfly needle connected to the perfusion system into the left ventricle and carefully cut the right atrium to collect about 200 microliters of blood into a two-milliliter tube containing 10 millimolar EDTA to prevent coagulation. Then perfuse the animal for four minutes with 15 to 20 milliliters of PBS plus EDTA.After complete perfusion, the brain and liver will appear blanched ensuring that remaining bacteria are from the harvested organs and not the circulating blood. Following perfusion, carefully transfer the organs of interest into individual sterile, 15-milliliter conical tubes containing five milliliters of sterile four degrees Celsius PBS per tube. To harvest the brain after decapitation, use scissors to cut the scalp skin down the midline between the eyes, keeping the tips pressed against the skull to trim any excess tissue as necessary.Gently insert one tip of the scissors into the foramen magnum and cut laterally into the skull on both sides. Carefully cut the skull between the eyes down the midline in the skull, taking care to apply lateral pressure and to avoid perturbation of the brain. Using forceps, open the skull to expose the brain and place a spatula between the underside of the brain and the base of the skull to carefully transfer the brain into a 15-milliliter tube containing five milliliters of four degrees Celsius PBS.In a biosafety cabinet, insert the tip and run a tissue homogenizer for 10 seconds in sequential 5%bleach, sterile water, 75%ethanol, and sterile water solutions in separate 15-milliliter conical tubes. When the tip has been thoroughly sterilized, homogenize the infected brain in its tube. When no visible tissue fragments remain, re-sterilize the tip to prevent bacterial carryover to the next organ sample, and homogenize the next organ.When all of the organs have been homogenized, prepare 10-fold serial dilutions of each organ homogenate in sterile PBS and plate the dilutions on brain-heart infusion agar plates. Then incubate the homogenate dilution cultures at 37 degrees Celsius overnight and count the number of colonies on each plate to determine the total number of bacteria per organ or milliliter of blood. Calculation of the bacterial burdens in L.monocytogenes-infected mouse organs as just demonstrated suggests that perfusion post-infection does not significantly alter the bacterial burden in the blood or organs of infected mice that were examined in this representative study.Following this procedure, Listeria monocytogenes-infected organs can be further processed for additional analysis such as histopathological processing to answer additional questions about the infiltration of inflammatory cells into infected mouse organs compared to uninfected control animals. While attempting this procedure, it is important to remember to avoid perturbation of the brain and to maintain minimal contact between the scissors and the brain tissue.

listeria-monocytogenes-infection-of-the-brain

Research

JoVE Journal

Immunology and Infection

Measuring Bacterial Load and Immune Responses in Mice Infected with Listeria monocytogenes

Listeria monocytogenes (Listeria) is a Gram-positive facultative intracellular pathogen1. Mouse studies typically employ intravenous injection of Listeria, which results in systemic infection2. After injection, Listeria quickly disseminates to the spleen and liver due to uptake by CD8&alpha;+ dendritic cells and Kupffer cells3,4. Once phagocytosed, various bacterial proteins enable Listeria to escape the phagosome, survive within the cytosol, and infect neighboring cells5. During the first three days of infection, different innate immune cells (e.g. monocytes, neutrophils, NK cells, dendritic cells) mediate bactericidal mechanisms that minimize Listeria proliferation. CD8+ T cells are subsequently recruited and responsible for the eventual clearance of Listeria from the host, typically within 10 days of infection6.
Successful clearance of Listeria from infected mice depends on the appropriate onset of host immune responses6	. There is a broad range of sensitivities amongst inbred mouse strains7,8. Generally, mice with increased susceptibility to Listeria infection are less able to control bacterial proliferation, demonstrating increased bacterial load and/or delayed clearance compared to resistant mice. Genetic studies, including linkage analyses and knockout mouse strains, have identified various genes for which sequence variation affects host responses to Listeria infection6,8-14. Determination and comparison of infection kinetics between different mouse strains is therefore an important method for identifying host genetic factors that contribute to immune responses against Listeria. Comparison of host responses to different Listeria strains is also an effective way to identify bacterial virulence factors that may serve as potential targets for antibiotic therapy or vaccine design.
We describe here a straightforward method for measuring bacterial load (colony forming units [CFU] per tissue) and preparing single-cell suspensions of the liver and spleen for FACS analysis of immune responses in Listeria-infected mice. This method is particularly useful for initial characterization of Listeria infection in novel mouse strains, as well as comparison of immune responses between different mouse strains infected with Listeria. We use the Listeria monocytogenes EGD strain15 that, when cultured on blood agar, exhibits a characteristic halo zone around each colony due to &beta;-hemolysis1 (Figure 1). Bacterial load and immune responses can be determined at any time-point after infection by culturing tissue homogenate on blood agar plates and preparing tissue cell suspensions for FACS analysis using the protocols described below. We would note that individuals who are immunocompromised or pregnant should not handle Listeria, and the relevant institutional biosafety committee and animal facility management should be consulted before work commences.

Measuring Bacterial Load and Immune Responses in Mice Infected with Listeria monocytogenes

Listeria monocytogenes is a model organism for studying immune responses and genetic susceptibility to intracellular bacteria in mice. This method enables one to measure bacterial load and generate single-cell suspensions of the liver and spleen from mice for FACS analysis to determine changes in immune cells due to Listeria infection.

Listeria monocytogenes (Listeria) is a Gram-positive facultative intracellular pathogen1. Mouse studies typically employ intravenous injection of ...

Selection of Plasmodium falciparum Parasites for Cytoadhesion to Human Brain Endothelial Cells

Most human malaria deaths are caused by blood-stage Plasmodium falciparum parasites. Cerebral malaria, the most life-threatening complication of the disease, is characterised by an accumulation of Plasmodium falciparum infected red blood cells (iRBC) at pigmented trophozoite stage in the microvasculature of the brain2-4. This microvessel obstruction (sequestration) leads to acidosis, hypoxia and harmful inflammatory cytokines (reviewed in 5). Sequestration is also found in most microvascular tissues of the human body2, 3. The mechanism by which iRBC attach to the blood vessel walls is still poorly understood.
The immortalized Human Brain microvascular Endothelial Cell line (HBEC-5i) has been used as an in vitro model of the blood-brain barrier6. However, Plasmodium falciparum iRBC attach only poorly to HBEC-5i in vitro, unlike the dense sequestration that occurs in cerebral malaria cases. We therefore developed a panning assay to select (enrich) various P. falciparum strains for adhesion to HBEC-5i in order to obtain populations of high-binding parasites, more representative of what occurs in vivo.
A sample of a parasite culture (mixture of iRBC and uninfected RBC) at the pigmented trophozoite stage is washed and incubated on a layer of HBEC-5i grown on a Petri dish. After incubation, the dish is gently washed free from uRBC and unbound iRBC. Fresh uRBC are added to the few iRBC attached to HBEC-5i and incubated overnight. As schizont stage parasites burst, merozoites reinvade RBC and these ring stage parasites are harvested the following day. Parasites are cultured until enough material is obtained (typically 2 to 4 weeks) and a new round of selection can be performed. Depending on the P. falciparum strain, 4 to 7 rounds of selection are needed in order to get a population where most parasites bind to HBEC-5i. The binding phenotype is progressively lost after a few weeks, indicating a switch in variant surface antigen gene expression, thus regular selection on HBEC-5i is required to maintain the phenotype.
In summary, we developed a selection assay rendering P. falciparum parasites a more "cerebral malaria adhesive" phenotype. We were able to select 3 out of 4 P. falciparum strains on HBEC-5i. This assay has also successfully been used to select parasites for binding to human dermal and pulmonary endothelial cells. Importantly, this method can be used to select tissue-specific parasite populations in order to identify candidate parasite ligands for binding to brain endothelium. Moreover, this assay can be used to screen for putative anti-sequestration drugs7.

Selection of Plasmodium falciparum Parasites for Cytoadhesion to Human Brain Endothelial Cells

An in vitro model for cerebral malaria sequestration is described1. Plasmodium falciparum infected red blood cells are selected for binding to immortalized human brain microvascular endothelial cells. The selected parasites show a distinct phenotype. The selection process can be applied using various P. falciparum strains and endothelial cell lines.

Most human malaria deaths are caused by blood-stage Plasmodium falciparum parasites. Cerebral malaria, the most life-threatening complication of the ...

Introducing Shear Stress in the Study of Bacterial Adhesion

During bacterial infections a sequence of interactions occur between the pathogen and its host. Bacterial adhesion to the host cell surface is often the initial and determining step of the pathogenesis. Although experimentally adhesion is mostly studied in static conditions adhesion actually takes place in the presence of flowing liquid. First encounters between bacteria and their host often occur at the mucosal level, mouth, lung, gut, eye, etc. where mucus flows along the surface of epithelial cells. Later in infection, pathogens occasionally access the blood circulation causing life-threatening illnesses such as septicemia, sepsis and meningitis. A defining feature of these infections is the ability of these pathogens to interact with endothelial cells in presence of circulating blood. The presence of flowing liquid, mucus or blood for instance, determines adhesion because it generates a mechanical force on the pathogen. To characterize the effect of flowing liquid one usually refers to the notion of shear stress, which is the tangential force exerted per unit area by a fluid moving near a stationary wall, expressed in dynes/cm2. Intensities of shear stress vary widely according to the different vessels type, size, organ, location etc. (0-100 dynes/cm2). Circulation in capillaries can reach very low shear stress values and even temporarily stop during periods ranging between a few seconds to several minutes 1. On the other end of the spectrum shear stress in arterioles can reach 100 dynes/cm2 2. The impact of shear stress on different biological processes has been clearly demonstrated as for instance during the interaction of leukocytes with the endothelium 3. To take into account this mechanical parameter in the process of bacterial adhesion we took advantage of an experimental procedure based on the use of a disposable flow chamber 4. Host cells are grown in the flow chamber and fluorescent bacteria are introduced in the flow controlled by a syringe pump. We initially focused our investigations on the bacterial pathogen Neisseria meningitidis, a Gram-negative bacterium responsible for septicemia and meningitis. The procedure described here allowed us to study the impact of shear stress on the ability of the bacteria to: adhere to cells 1, to proliferate on the cell surface 5and to detach to colonize new sites 6 (Figure 1). Complementary technical information can be found in reference 7. Shear stress values presented here were chosen based on our previous experience1 and to represent values found in the literature. The protocol should be applicable to a wide range of pathogens with specific adjustments depending on the objectives of the study.

During the infection process, a key step is the adhesion of pathogens with host cells. In most instances this adhesion step occurs in the presence of mechanical stress generated by flowing liquid. We describe a technique that introduces shear stress as an important parameter in the study of bacterial adhesion.

During bacterial infections a sequence of interactions occur between the pathogen and its host. Bacterial adhesion to the host cell surface is often the ...

Isolation and Analysis of Brain-sequestered Leukocytes from Plasmodium berghei ANKA-infected Mice

We describe a method for isolation and characterization of adherent inflammatory cells from brain blood vessels of P. berghei ANKA-infected mice. Infection of susceptible mouse-strains with this parasite strain results in the induction of experimental cerebral malaria, a neurologic syndrome that recapitulates certain important aspects of Plasmodium falciparum-mediated severe malaria in humans 1,2 . Mature forms of blood-stage malaria express parasitic proteins on the surface of the infected erythrocyte, which allows them to bind to vascular endothelial cells. This process induces obstructions in blood flow, resulting in hypoxia and haemorrhages 3 and also stimulates the recruitment of inflammatory leukocytes to the site of parasite sequestration.
Unlike other infections, i.e neutrotopic viruses4-6, both malaria-parasitized red blood cells (pRBC) as well as associated inflammatory leukocytes remain sequestered within blood vessels rather than infiltrating the brain parenchyma. Thus to avoid contamination of sequestered leukocytes with non-inflammatory circulating cells, extensive intracardial perfusion of infected-mice prior to organ extraction and tissue processing is required in this procedure to remove the blood compartment. After perfusion, brains are harvested and dissected in small pieces. The tissue structure is further disrupted by enzymatic treatment with Collagenase D and DNAse I. The resulting brain homogenate is then centrifuged on a Percoll gradient that allows separation of brain-sequestered leukocytes (BSL) from myelin and other tissue debris. Isolated cells are then washed, counted using a hemocytometer and stained with fluorescent antibodies for subsequent analysis by flow cytometry.
This procedure allows comprehensive phenotypic characterization of inflammatory leukocytes migrating to the brain in response to various stimuli, including stroke as well as viral or parasitic infections. The method also provides a useful tool for assessment of novel anti-inflammatory treatments in pre-clinical animal models.

Isolation and Analysis of Brain-sequestered Leukocytes from Plasmodium berghei ANKA-infected Mice

A method for isolation of adherent inflammatory leukocytes from brain blood vessels of Plasmodium berghei ANKA-infected mice is described. The method allows quantification as well as phenotypic characterization of isolated leukocytes after staining with fluorescent antibodies and subsequent analysis by flow cytometry.

We describe a method for isolation and  characterization of adherent inflammatory cells from brain blood vessels of P. berghei ANKA-infected mice. ...

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 ...

Imaging InlC Secretion to Investigate Cellular Infection by the Bacterial Pathogen Listeria monocytogenes

Bacterial intracellular pathogens can be conceived as molecular tools to dissect cellular signaling cascades due to their capacity to exquisitely manipulate and subvert cell functions which are required for the infection of host target tissues. Among these bacterial pathogens, Listeria monocytogenes is a Gram positive microorganism that has been used as a paradigm for intracellular parasitism in the characterization of cellular immune responses, and which has played instrumental roles in the discovery of molecular pathways controlling cytoskeletal and membrane trafficking dynamics. In this article, we describe a robust microscopical assay for the detection of late cellular infection stages of L. monocytogenes based on the fluorescent labeling of InlC, a secreted bacterial protein which accumulates in the cytoplasm of infected cells; this assay can be coupled to automated high-throughput small interfering RNA screens in order to characterize cellular signaling pathways involved in the up- or down-regulation of infection.

Imaging InlC Secretion to Investigate Cellular Infection by the Bacterial Pathogen Listeria monocytogenes

Listeria monocytogenes is a Gram positive bacterial pathogen frequently used as a major model for the study of intracellular parasitism. Imaging late L. monocytogenes infection stages within the context of small-interfering RNA screens allows for the global study of cellular pathways required for bacterial infection of target host cells.

Bacterial intracellular  pathogens can be conceived as molecular tools to dissect cellular signaling  cascades due to their capacity to exquisitely ...

Assessing Bacterial Invasion of Cardiac Cells in Culture and Heart Colonization in Infected Mice Using Listeria monocytogenes

Listeria monocytogenes is a Gram-positive facultative intracellular pathogen that is capable of causing serious invasive infections in immunocompromised patients, the elderly, and pregnant women. The most common manifestations of listeriosis in humans include meningitis, encephalitis, and fetal abortion. A significant but much less documented sequelae of invasive L. monocytogenes infection involves the heart. The death rate from cardiac illness can be up to 35% despite treatment, however very little is known regarding L. monocytogenes colonization of cardiac tissue and its resultant pathologies. In addition, it has recently become apparent that subpopulations of L. monocytogenes have an enhanced capacity to invade and grow within cardiac tissue. This protocol describes in detail in vitro and in vivo methods that can be used for assessing cardiotropism of L. monocytogenes isolates. Methods are presented for the infection of H9c2 rat cardiac myoblasts in tissue culture as well as for the determination of bacterial colonization of the hearts of infected mice. These methods are useful not only for identifying strains with the potential to colonize cardiac tissue in infected animals, but may also facilitate the identification of bacterial gene products that serve to enhance cardiac cell invasion and/or drive changes in heart pathology. These methods also provide for the direct comparison of cardiotropism between multiple L. monocytogenes strains.

Assessing Bacterial Invasion of Cardiac Cells in Culture and Heart Colonization in Infected Mice Using Listeria monocytogenes

Listeria monocytogenes causes fetal infections in pregnant women and meningitis in susceptible populations. Subpopulations of bacteria can colonize cardiac tissue, causing myocarditis in patients and laboratory animals. Here we present a protocol that describes how to assess L. monocytogenes cardiac cell invasion in vitro and cardiac colonization in infected animals.

Listeria monocytogenes is a Gram-positive facultative intracellular pathogen that is capable of causing serious invasive infections in immunocompromised ...

RNA Purification from Intracellularly Grown Listeria monocytogenes in Macrophage Cells

Analysis of the transcriptome of bacterial pathogens during mammalian infection is a valuable tool for studying genes and factors that mediate infection. However, isolating bacterial RNA from infected cells or tissues is a challenging task, since mammalian RNA mostly dominates the lysates of infected cells. Here we describe an optimized method for RNA isolation of Listeria monocytogenes bacteria growing within bone marrow derived macrophage cells. Upon infection, cells are mildly lysed and rapidly filtered to discard most of the host proteins and RNA, while retaining intact bacteria. Next, bacterial RNA is isolated using hot phenol-SDS extraction followed by DNase treatment. The extracted RNA is suitable for gene transcription analysis by multiple techniques. This method is successfully employed in our studies of Listeria monocytogenes gene regulation during infection of macrophage cells 1-4. The protocol can be easily modified to study other bacterial pathogens and cell types.

RNA Purification from Intracellularly Grown Listeria monocytogenes in Macrophage Cells

Here we describe a method for bacterial RNA isolation from Listeria monocytogenes bacteria growing inside murine macrophages. This technique can be used with other intracellular pathogens and mammalian host cells.

Analysis of the transcriptome of bacterial pathogens during mammalian infection is a valuable tool for studying genes and factors that mediate infection. ...

Experimental Infection with Listeria monocytogenes as a Model for Studying Host Interferon-&#947; Responses

L. monocytogenes is a gram-positive bacterium that is a cause of food borne disease in humans. Experimental infection of mice with this pathogen has been highly informative on the role of innate and adaptive immune cells and specific cytokines in host immunity against intracellular pathogens. Production of IFN-&#947; by innate cells during sublethal infection with L. monocytogenes is important for activating macrophages and early control of the pathogen1-3. In addition, IFN-&#947; production by adaptive memory lymphocytes is important for priming the activation of innate cells upon reinfection4. The L. monocytogenes infection model thus serves as a great tool for investigating whether new therapies that are designed to increase IFN-&#947; production have an impact on IFN-&#947; responses in vivo and have productive biological effects such as increasing bacterial clearance or improving mouse survival from infection. Described here is a basic protocol for how to conduct intraperitoneal infections of C57BL/6J mice with the EGD strain of L. monocytogenes and to measure IFN-&#947; production by NK cells, NKT cells, and adaptive lymphocytes by flow cytometry. In addition, procedures are described to: (1) grow and prepare the bacteria for inoculation, (2) measure bacterial load in the spleen and liver, and (3) measure animal survival to endpoints. Representative data are also provided to illustrate how this infection model can be used to test the effect of specific agents on IFN-&#947; responses to L. monocytogenes and survival of mice from this infection.

This protocol describes how to inoculate C57BL/6J mice with the EGD strain of Listeria monocytogenes (L. monocytogenes) and to measure interferon-&#947; (IFN-&#947;) responses by natural killer (NK) cells, natural killer T (NKT) cells, and adaptive T lymphocytes post-infection. This protocol also describes how to conduct survival studies in mice after infection with a modified LD50 dose of the pathogen.

L. monocytogenes is a gram-positive bacterium that is a cause of food borne disease in humans. Experimental infection of mice with this pathogen has been ...

Evaluation of Host-Pathogen Responses and Vaccine Efficacy in Mice

Vaccines are a 20th century medical marvel. They have dramatically reduced the morbidity and mortality caused by infectious diseases and contributed to a striking increase in life expectancy around the globe. Nonetheless, determining vaccine efficacy remains a challenge. Emerging evidence suggests that the current acellular vaccine (aPV) for Bordetella pertussis (B. pertussis) induces suboptimal immunity. Therefore, a major challenge is designing a next-generation vaccine that induces protective immunity without the adverse side effects of a whole-cell vaccine (wPV). Here we describe a protocol that we used to test the efficacy of a promising, novel adjuvant that skews immune responses to a protective Th1/Th17 phenotype and promotes a better clearance of a B. pertussis challenge from the murine respiratory tract. This article describes the protocol for mouse immunization, bacterial inoculation, tissue harvesting, and analysis of immune responses. Using this method, within our model, we have successfully elucidated crucial mechanisms elicited by a promising, next-generation acellular pertussis vaccine. This method can be applied to any infectious disease model in order to determine vaccine efficacy.

Here we present an elegant protocol for in vivo evaluation of vaccine effectiveness and host immune responses. This protocol can be adapted for vaccine models that study viral, bacterial, or parasitic pathogens.

Vaccines are a 20th century medical marvel. They have dramatically reduced the morbidity and mortality caused by infectious diseases and contributed to a ...