This study was supported by the Defense Threat Reduction Agency (DTRA) under contract HDTRA1-14-C-0116, and the Center for Excellence in Infection Genomics (DOD #W911NF-11-1-0136).

This work was performed in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. Animal protocols involving rodents were approved by the University of Texas at San Antonio Institutional Animal Care and Use Committee (IACUC) under protocol MU009(RA).
1. Prepare Catheter, Trachea Indicator, and F. tularensis Inoculum
<ol>
	<li>Prepare Catheter (20 G x 2 in)
	<ol>
		<li>Cut the 20 G x 2 ...

<ol>
	<li>Ellis, J., Oyston, P. C. F., Green, M., Titball, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tularemia.">Tularemia.</a> Clin Microbiol Rev. 15 (4), 631-646 (2002).</li><li>Lyons, C. R., Wu, T. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+models+of+Francisella+tularensis+infection.">Animal models of Francisella tularensis infection.</a> Ann N Y Acad Sci. 1105, (2007).</li><li>Hutt, J. A., Lovchik, J. A., Dekonenko, A., Hahn, A. C., Wu, T. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Natural+History+of+Pneumonic+Tularemia+in+Female+Fischer+344+Rats+after+Inhalational+Exposure+to+Aerosolized+Francisella+tularensis+subspecies+tularensis+Strain+Schu+S4.">The Natural History of Pneumonic Tularemia in Female Fischer 344 Rats after Inhalational Exposure to Aerosolized Francisella tularensis subspecies tularensis Strain Schu S4.</a> Am J Pathol. 187 (2), 252-267 (2017).</li><li>Ray, H. J., 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+Fischer+344+rat+reflects+human+susceptibility+to+Francisella+pulmonary+challenge+and+provides+a+new+platform+for+virulence+and+protection+studies.">The Fischer 344 rat reflects human susceptibility to Francisella pulmonary challenge and provides a new platform for virulence and protection studies.</a> PloS one. 5, e9952 (2010).</li><li>Jemski, J. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Respiratory+tularemia:+comparison+of+selected+routes+of+vaccination+in+Fischer+344+rats.">Respiratory tularemia: comparison of selected routes of vaccination in Fischer 344 rats.</a> Infect Immun. 34 (3), 766-772 (1981).</li><li>Wu, T. H., 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=Vaccination+of+Fischer+344+rats+against+pulmonary+infections+by+Francisella+tularensis+type+A+strains.">Vaccination of Fischer 344 rats against pulmonary infections by Francisella tularensis type A strains.</a> Vaccine. 27 (34), 4684-4693 (2009).</li><li>Mara-Koosham, G., Hutt, J. A., Lyons, C. R., Wu, T. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Antibodies+contribute+to+effective+vaccination+against+respiratory+infection+by+type+A+Francisella+tularensis+strains.">Antibodies contribute to effective vaccination against respiratory infection by type A Francisella tularensis strains.</a> Infect Immun. 79 (4), 1770-1778 (2011).</li><li>Oyston, P. C., Sjostedt, A., Titball, R. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tularaemia:+bioterrorism+defence+renews+interest+in+Francisella+tularensis.">Tularaemia: bioterrorism defence renews interest in Francisella tularensis.</a> Nat Rev Microbiol. 2 (12), 967-978 (2004).</li><li>Kingry, L. C., Petersen, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparative+review+of+Francisella+tularensis+and+Francisella+novicida.">Comparative review of Francisella tularensis and Francisella novicida.</a> Front Cell Infect Microbiol. 4, 35 (2014).</li><li>Rohmer, 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=Comparison+of+Francisella+tularensis+genomes+reveals+evolutionary+events+associated+with+the+emergence+of+human+pathogenic+strains.">Comparison of Francisella tularensis genomes reveals evolutionary events associated with the emergence of human pathogenic strains.</a> Genome Biol. 8 (6), R102 (2007).</li><li>Chu, 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=Live+attenuated+Francisella+novicida+vaccine+protects+against+Francisella+tularensis+pulmonary+challenge+in+rats+and+non-human+primates.">Live attenuated Francisella novicida vaccine protects against Francisella tularensis pulmonary challenge in rats and non-human primates.</a> PLoS Pathog. 10 (10), e1004439 (2014).</li><li>Signarovitz, A. 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=Mucosal+Immunization+with+Live+Attenuated+Francisella+novicida+U112&#916;iglB+Protects+against+Pulmonary+F.+tularensis+SCHU+S4+in+the+Fischer+344+Rat+Model.">Mucosal Immunization with Live Attenuated Francisella novicida U112&#916;iglB Protects against Pulmonary F. tularensis SCHU S4 in the Fischer 344 Rat Model.</a> PloS one. 7 (10), e47639 (2012).</li><li>Cunningham, A. 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=Enhancement+of+vaccine+efficacy+by+expression+of+a+TLR5+ligand+in+the+defined+live+attenuated+Francisella+tularensis+subsp.+novicida+strain+U112DiglB::fljB.">Enhancement of vaccine efficacy by expression of a TLR5 ligand in the defined live attenuated Francisella tularensis subsp. novicida strain U112DiglB::fljB.</a> Vaccine. 32 (40), 5234-5240 (2014).</li></ol>

The authors have nothing to disclose

The Fischer 344 rat is becoming an important model for tularemia vaccine development3. Exposure to F. tularensis through the pulmonary route is critical for demonstrating efficacy against weaponized forms of F. tularensis, because these are delivered as aerosols. Intratracheal inoculation of the rat facilitates exposure of the rat lungs to F. tularensis without the need for large, expensive, and complicated aerosol generating equipment. All experiments utilizing select a...

F. tularensis (Ft) causes the human disease, tularemia. When the bacteria are acquired through the pulmonary route, this leads to pneumonic tularemia, which has high morbidity and mortality1. F. tularensis is considered a biothreat agent due to the danger associated with aerosolized forms, and there is currently no vaccine approved for human use in the U.S. An intensive effort is currently underway to develop vaccines and therapeutic measures against pneumonic tularemia, to protect the human population against the illicit use of this bacterial biothreat.
Much of the tularemia research has focused on the mouse model, due to the extreme sensitivity of mice to F. tularensis infection, and the prevalence of reagents. However, mice have proven to be a difficult model for vaccine development, due to the difficulty of demonstrating vaccine efficacy in this model2. Recently, the Fischer 344 rat has been developed as a model for tularemia vaccine development3. The sensitivity of the Fischer 344 rat to various F. tularensis subspecies mimics human sensitivity4, and rats can be protected against F. tularensis pulmonary challenge by vaccination with a live vaccine strain known to protect humans5,6,7. Because the Fischer 344 rat models some features of F. tularensis infection of humans, it may be an extremely useful model for the development of a vaccine that protects against pulmonary F. tularensis exposure.
An effective vaccine needs to protect humans against pulmonary exposure to F. tularensis. The most likely pulmonary exposure from weaponized F. tularensis would be aerosolized bacteria inhaled into the lungs8. However, aerosol generation of F. tularensis is both dangerous and cumbersome, and requires specialized equipment and containment. An alternate route of pulmonary exposure in the rat that is perhaps more adaptable for multiple laboratories lacking specialized equipment is via intratracheal inoculation6. This technique utilizes a laryngoscope for the correct placement of a catheter within the trachea of an anesthetized rat. Placement within the trachea, rather than the esophagus, is verified by a simple device that visualizes airflow from the lungs. F. tularensis is subsequently delivered into the lungs through the catheter by administration with a syringe, followed by the introduction of air into the catheter to ensure pulmonary delivery of the bacteria. In contrast, Jemski5 previously reported that F. tularensis inoculated into Fischer 344 rats via the intranasal route could not be cultured from the lungs until 3 days post-inoculation, indicating that intranasal inoculation in rats does not result in direct delivery of bacteria into the lungs.
Select agent forms of F. tularensis (F. tularensis subsp. tularensis, F. tularensis subsp. holarctica) require Biosafety Level 3 (BSL3) containment procedures, which would prevent videography. However, F. novicida (Fn) is exempt from select agent status due to its avirulence in healthy humans, and can be utilized safely under Biosafety Level 2 (BSL2) conditions9,10. Moreover, Fn serves as the basis for live attenuated vaccines that can protect against F. tularensis pulmonary exposure when delivered via intratracheal inoculation11,12,13. The technique presented here allows for the study of infections that occur through the pulmonary route utilizing rats as a model for humans. This technique can be performed without the need for specialized aerosol-generating equipment. Fn was used for the techniques filmed here.

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intratracheal inoculation of fischer 344 rats with francisella tularensis

Pulmonary infection with the bacterium Francisella tularensis can lead to the serious and potentially fatal disease, tularemia, in humans. Due to the current lack of an approved tularemia vaccine for humans, research is focused on vaccine development utilizing appropriate animal models. The Fischer 344 rat has emerged as a model that reflects human susceptibility to F. tularensis infection, and thus is an attractive model for tularemia vaccine development. Intratracheal inoculation of the Fischer 344 rat with F. tularensis mimics pulmonary exposure in humans. The successful delivery into the rat trachea is critical for pulmonary delivery. A laryngoscope with illumination is used to properly intubate the tracheae of anesthetized rats; the correct placement within the trachea is determined by a simple device to detect breathing. Following intubation, the F. tularensis culture is delivered in a measured dose via syringe. This technique standardizes pulmonary delivery of F. tularensis within the rat trachea to evaluate vaccine efficacy.

The humoral response to intratracheal inoculation of F. tularensis in the rat can be determined by enzyme-linked immunosorbent assay (ELISA) against UV-inactivated bacteria, as described previously11. Total Immunoglobulin G (IgG) response of Fischer 344 rats to inactivated whole cell bacteria was assessed post-intratracheal inoculation with an attenuated strain of Fn (107 CFU inoculum) at day 14 and day 28 (Figure 1...

Watch this Scientific Journal Video about Intratracheal Inoculation of Fischer 344 Rats with Francisella tularensis at JoVE.com

Intratracheal Inoculation of Fischer 344 Rats with Francisella tularensis

This protocol describes intratracheal inoculations of Fischer 344 rats with Francisella tularensis. This procedure mimics pulmonary exposure of humans to this potential biothreat agent and can be used to test vaccine and therapeutic efficacy against pulmonary tularemia.

Intratracheal Inoculation of Fischer 344 Rats with Francisella tularensis

Pulmonary infection with the bacterium Francisella tularensis can lead to the serious and potentially fatal disease, tularemia, in humans. Due to the ...

The overall goal of intratracheal inoculation of Fischer 344 rats with Francisella tularensis is to determine vaccine efficacy against pulmonary tularemia. This method allows us to answer key questions in the development of a tularemia vaccine because we're able to administer the organism through the pulmonary route and therefore test vaccine efficacy against a biothreat agent. And so the main advantage of this technique is the ability to consistently deliver Francisella tularensis into the rat lung without the use of an aerosol-generating equipment.The implications of this technique extend toward therapy and prevention of pulmonary tularemia because the Fischer 344 rat is considered a relevant model for vaccine development against this disease. Though this method can provide insights into vaccines and therapies against tularemia, it can also be applied to other pulmonary infectious disease models utilizing rats such as plague. In general, individuals new to this method will struggle with correct placement of the catheter into the trachea rather than the esophagus.To prepare the catheter, begin by cutting a 20 gauge two inch needle and use a rotary tool to grind the tip of the needle to a blunt and smooth finish. Use 70%ethanol to clean the blunted needles and catheters and sterilize them under UV light for 15 minutes. Trim a 1, 000 microliter pipette tip to allow it to sit into a catheter opening and form an airtight seal.Remove a filter from a 200 microliter aerosol barrier pipette tip and place it inside the trimmed pipette tip. Point the 1, 000 microliter pipette tip downward and ensure the filter can move freely inside the tip downward. After preparing F.tularensis inoculum and anesthetizing a rat according to the text protocol, place the rat dorsally on the rodent intubation stand.Then attach the front teeth of the rat to the holder to keep the rat in place. With the dominant hand, use broad point dressing thumb forceps to move the tongue to the same side as the support hand. Using the support hand, secure the tongue with a laryngoscope against the rat's lower jaw to visualize the trachea and esophagus of the animal.Next, insert the catheter containing the previously prepared 20 gauge blunted needle into the trachea. Remove the blunted needle from the catheter while ensuring the catheter remains in the trachea. Allow a few seconds to pass for the rat to be able to breathe around the catheter.Firmly seat the trachea indicator onto the catheter opening. Movement of the aerosol barrier will indicate the catheter is inserted correctly into the trachea. Ensure that the rat is laying on the intubation stand such that the chest of the animal is facing perpendicular to the plane of the intubation stand.Remove the trachea indicator and with a 200 microliter pipette tip firmly seated against the catheter opening, deliver 100 microliters of the inoculum containing F.tularensis. Attach a one milliliter slip tip tuberculin syringe filled with air and deliver 300 microliters of air to ensure inoculum reaches the lungs of the rat. Remove the catheter from the trachea and take the rat off of the surgical platform.In this experiment, the humoral response to intratracheal inoculation of an attenuated strain of F.tularensis in the rat was determined by ELISA against UV inactivated bacteria. Total IgG response of the Fischer 344 rats to inactivated whole cell bacteria was assessed at days 14 and 28. Mock vaccinated rats received PBS.The red area denotes reactivity of serum from these rats. An increase in serum antibody titers against F.tularensis post inoculation compared to naive mock vaccinated animals indicates the intratracheal vaccination efficacy. Once mastered, the intratracheal inoculation can be done in approximately one minute if it's performed properly.While attempting this procedure, it is important to ensure that the catheter is placed within the trachea and not the esophagus. So, following this method, other procedures such as blood collection can be done to answer additional questions such as antibody response against a vaccine and/or the challenge. After its development, this technique paved the way for researchers in the field of tularemia vaccines to explore the efficacies of different vaccines against pulmonary tularemia.After watching this video, you should have a good understanding of intratracheal delivery of Francisella tularensis in the Fischer 344 rat. So, keep in mind working with live animals and pathogenic agents can be extremely hazardous so it's very important to ensure that animals are anesthetized, properly restrained, and that all properly biocontainment procedures are done.

intratracheal-inoculation-fischer-344-rats-with-francisella

Research

JoVE Journal

Immunology and Infection

7.1K visualizações.  University of Texas San Antonio. The overall goal of intratracheal inoculation of Fischer 344 rats with Francisella tularensis is to determine vaccine efficacy against pulmonary tularemia. This method allows us to answer key questions in the development of a tularemia vaccine because we're able to administer the organism through the pulmonary route and therefore test vaccine efficacy against a biothreat agent. And so the main advantage of this technique is the ability to consistently deliver Francisella tularensis into the r...