Name: evaluation of a reliable biomarker in a cecal ligation and puncture-induced mouse model of sepsis
Uploaded: 2022-12-09T12:30:00
Description: Watch this Scientific Journal Video about Evaluation of a Reliable Biomarker in a Cecal Ligation and Puncture-Induced Mouse Model of Sepsis at JoVE.com

We thank Professor Wang Wei and Doctor Liu Shuai for helping with the experiments. This work was funded by grants from the Young Research Funding of Xiangya Hospital, Central South University (No. 2019Q10), From the National and Science Foundation of Hunan Province (No. 2020JJ4902), and from the National Natural Science Foundation of China (No. 82202394).

All animal experiments were performed in accordance with the guidelines approved by theAnimal Review Committee at Xiangya Hospital and Central South University (No. 202103149).
1. Preparation
<ol>
	<li>Select male C57BL/6J mice (weight: 20-25 g; age: 8-12 weeks) and house for 3 days before performing any procedures.</li>
	<li>Weigh the mouse.</li>
	<li>Anesthetize the mouse with 1.5% isoflurane by inhalation and pinch the toes to check the depth of anesthesia.</li>
	<li>Fix ...

<ol>
	<li>Singer, 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+third+international+consensus+definitions+for+sepsis+and+septic+shock+(Sepsis-3).">The third international consensus definitions for sepsis and septic shock (Sepsis-3).</a> JAMA. 315 (8), 801-810 (2016).</li><li>Shankar-Hari, 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=Developing+a+new+definition+and+assessing+new+clinical+criteria+for+septic+shock:+For+the+Third+International+Consensus+Definitions+for+Sepsis+and+Septic+Shock+(Sepsis-3).">Developing a new definition and assessing new clinical criteria for septic shock: For the Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3).</a> JAMA. 315 (8), 775-787 (2016).</li><li>Fleischmann-Struzek, 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=Incidence+and+mortality+of+hospital-+and+ICU-treated+sepsis:+results+from+an+updated+and+expanded+systematic+review+and+meta-analysis.">Incidence and mortality of hospital- and ICU-treated sepsis: results from an updated and expanded systematic review and meta-analysis.</a> Intensive Care Medicine. 46 (8), 1552-1562 (2020).</li><li>Evans, 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=Surviving+sepsis+campaign:+international+guidelines+for+management+of+sepsis+and+septic+shock+2021.">Surviving sepsis campaign: international guidelines for management of sepsis and septic shock 2021.</a> Intensive Care Medicine. 47 (11), 1181-1247 (2021).</li><li>Hughes, J. A., Cabilan, C. J., Williams, J., Ray, M., Coyer, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effectiveness+of+interventions+to+reduce+peripheral+blood+culture+contamination+in+acute+care:+a+systematic+review+protocol.">The effectiveness of interventions to reduce peripheral blood culture contamination in acute care: a systematic review protocol.</a> Systematic Reviews. 7 (1), 216 (2018).</li><li>Kibe, S., Adams, K., Barlow, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diagnostic+and+prognostic+biomarkers+of+sepsis+in+critical+care.">Diagnostic and prognostic biomarkers of sepsis in critical care.</a> The Journal of Antimicrobial Chemotherapy. 66, 33-40 (2011).</li><li>Dejager, L., Pinheiro, I., Dejonckheere, E., Libert, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cecal+ligation+and+puncture:+the+gold+standard+model+for+polymicrobial+sepsis.">Cecal ligation and puncture: the gold standard model for polymicrobial sepsis.</a> Trends in Microbiology. 19 (4), 198-208 (2011).</li><li>Hotchkiss, R., Karl, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+pathophysiology+and+treatment+of+sepsis.">The pathophysiology and treatment of sepsis.</a> The New England Journal of Medicine. 348 (2), 138-150 (2003).</li><li>Madhi, R., Rahman, M., Taha, D., Morgelin, M., Thorlacius, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Targeting+peptidylarginine+deiminase+reduces+neutrophil+extracellular+trap+formation+and+tissue+injury+in+severe+acute+pancreatitis.">Targeting peptidylarginine deiminase reduces neutrophil extracellular trap formation and tissue injury in severe acute pancreatitis.</a> Journal of Cellular Physiology. 234 (7), 11850-11860 (2019).</li><li>Brinkmann, V., 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=Neutrophil+extracellular+traps+kill+bacteria.">Neutrophil extracellular traps kill bacteria.</a> Science. 303 (5663), 1532-1535 (2004).</li><li>Liang, Y., 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=Inhibition+of+peptidylarginine+deiminase+alleviates+LPS-induced+pulmonary+dysfunction+and+improves+survival+in+a+mouse+model+of+lethal+endotoxemia.">Inhibition of peptidylarginine deiminase alleviates LPS-induced pulmonary dysfunction and improves survival in a mouse model of lethal endotoxemia.</a> European Journal of Pharmacology. 833, 432-440 (2018).</li><li>Deng, Q., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Citrullinated+histone+H3+as+a+therapeutic+target+for+endotoxic+shock+in+mice.">Citrullinated histone H3 as a therapeutic target for endotoxic shock in mice.</a> Frontiers in Immunology. 10, 2957 (2019).</li><li>Li, Y. Q., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+citrullinated+histone+H3+as+a+potential+serum+protein+biomarker+in+a+lethal+model+of+lipopolysaccharide-induced+shock.">Identification of citrullinated histone H3 as a potential serum protein biomarker in a lethal model of lipopolysaccharide-induced shock.</a> Surgery. 150 (3), 442-451 (2011).</li><li>Pan, B., 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=CitH3:+a+reliable+blood+biomarker+for+diagnosis+and+treatment+of+endotoxic+shock.">CitH3: a reliable blood biomarker for diagnosis and treatment of endotoxic shock.</a> Scientific Reports. 7 (1), 8972 (2017).</li><li>Park, Y., 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=An+integrated+plasmo-photoelectronic+nanostructure+biosensor+detects+an+infection+biomarker+accompanying+cell+death+in+neutrophils.">An integrated plasmo-photoelectronic nanostructure biosensor detects an infection biomarker accompanying cell death in neutrophils.</a> Small. 16 (1), 1905611 (2020).</li><li>Harikrishnan, V. S., Hansen, A. K., Abelson, K. S. P., Sorensen, D. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+comparison+of+various+methods+of+blood+sampling+in+mice+and+rats:+Effects+on+animal+welfare.">A comparison of various methods of blood sampling in mice and rats: Effects on animal welfare.</a> Laboratory Animals. 52 (3), 253-264 (2018).</li><li>Brook, B., 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=A+controlled+mouse+model+for+neonatal+polymicrobial+sepsis.">A controlled mouse model for neonatal polymicrobial sepsis.</a> Journal of Visualized Experiments. (143), e58574 (2019).</li><li>Rittirsch, D., Huber-Lang, M., Flierl, M., Ward, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immunodesign+of+experimental+sepsis+by+cecal+ligation+and+puncture.">Immunodesign of experimental sepsis by cecal ligation and puncture.</a> Nature Protocols. 4 (1), 31-36 (2009).</li><li>Baker, C. C., Chaudry, I. H., Gaines, H. O., Baue, A. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+factors+affecting+mortality+rate+after+sepsis+in+a+murine+cecal+ligation+and+puncture+model.">Evaluation of factors affecting mortality rate after sepsis in a murine cecal ligation and puncture model.</a> Surgery. 94 (2), 331-335 (1983).</li></ol>

CLP introduces pathogens into the abdomen to create a preclinical model of sepsis. When performing CLP, it is important to use sterile conditions to eliminate the interference of exogenous bacteria and to use accurate dosages of anesthetics16. The three technical aspects of CLP that affect the severity and replicability of the sepsis model are the percentage of the cecum ligated, the size of the needle used for cecal puncture, and the volume of feces squeezed into the abdominal cavity. Ligation of...

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection1, and septic shock is the leading cause of death in severe cases of sepsis2. Sepsis and septic shock cause millions of deaths worldwide each year3. The key to improving the outcome of patients with sepsis is the prompt initiation of treatments such as antibiotics4. The gold standard method for the diagnosis of sepsis is microbial culture; however, microbial culture is time-consuming and can lead to false-positive and false-negative results, which greatly limit the clinical significance5. Thus, it is highly desirable to identify a blood biomarker of sepsis. Procalcitonin is recognized as an ideal sepsis biomarker but has limited diagnostic efficacy because it is unable to distinguish sepsis from sterile diseases6. 
Mouse cecal ligation and puncture (CLP) is commonly used to create a model of sepsis in scientific research. CLP is one of the most widely used sepsis models because it mimics polymicrobial peritonitis, activating both proinflammatory and anti-inflammatory immune responses7. It is well accepted that CLP creates a more clinically relevant sepsis model than alternative techniques, such as the injection of bacterial endotoxin. Therefore, CLP is considered the classical sepsis model for use in research8. However, a major disadvantage of CLP is its reproducibility, as the model severity is affected by several factors such as the percentage of cecum ligated, needle size, number of punctures, and laparotomy technique. Therefore, there is a need to standardize the CLP-induced sepsis model. The present study describes the protocol details of the CLP-induced sepsis model to show the standardized procedure and increase its reproducibility.
The inflammatory response occurs in the early stage of sepsis, with neutrophils releasing excessive amounts of oxidants and proteases that cause organ damage8. A key factor in the pathophysiology of sepsis is the formation of neutrophil extracellular traps (NETs), which release nuclear and cytosolic components such as DNA, citrullinated histones, and antimicrobial proteinases9. Recent studies suggest that excessive generation of NETs mediates the pathology of sepsis; meanwhile, a decrease of NETs, through enzymatic inhibition of peptidyl arginine deiminase (PAD) by chemicals like YW3-56 or Cl-amidine, exerts a pro-survival effect in mouse models of sepsis10,11. Citrullinated histone H3 (CitH3) was identified as a sepsis-specific protein in 201112, and subsequent publications have demonstrated that the circulating CitH3 concentration is a reliable diagnostic biomarker of sepsis13,14. CitH3 is considered a more sensitive and long-lasting biomarker than procalcitonin, and is more specific in distinguishing sepsis than inflammatory cytokines13.
In this study, we have evaluated a reliable diagnostic biomarker of sepsis in a CLP-induced mouse model of sepsis.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>21G needle</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>3,3&#8217;,5,5&#8217;-tetramethylbenzidine&#160;</td>
			<td>R&#38;D Systems Inc</td>
			<td>DY999</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-CitH3 monoclonal antibody</td>
			<td>laboratory self developed</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>anti-CitH3 polyclonal antibody</td>
			<td>Abcam</td>
			<td>ab5103</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-rabbit secondary antibody</td>
			<td>Jackson ImmunoResearch</td>
			<td>111-035-003</td>
			<td></td>
		</tr>
		<tr>
			<td>C57BL/6 mice</td>
			<td>Xiangya School of Medicine, Central South University</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Cl-amidine</td>
			<td>Sigma Aldrich</td>
			<td>SML2250</td>
			<td></td>
		</tr>
		<tr>
			<td>depilatory cream</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dnase I</td>
			<td>Sigma Aldrich</td>
			<td>11284932001</td>
			<td></td>
		</tr>
		<tr>
			<td>isoflurane</td>
			<td>Sigma-Aldrich</td>
			<td>26675-46-7</td>
			<td></td>
		</tr>
		<tr>
			<td>ketoprofen</td>
			<td>Sigma Aldrich</td>
			<td>PHR1375</td>
			<td></td>
		</tr>
		<tr>
			<td>silk sutures (4-0 &#38; 6-0)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>surgical instruments&#160;</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>YW3-56</td>
			<td>GLPBIO</td>
			<td>GC48263</td>
			<td></td>
		</tr>
	</tbody>
</table>

evaluation of a reliable biomarker in a cecal ligation and puncture-induced mouse model of sepsis

Sepsis is a severe life-threatening and rapidly developing disease that causes millions of deaths annually worldwide. Researchers have made tremendous efforts to elucidate the pathophysiology of sepsis using various animal models; the mouse model of sepsis induced by cecal ligation and puncture (CLP) is widely used in laboratories. The three technical aspects that affect the severity and replicability of the CLP model are the percentage of cecum ligated, the size of the needle used for cecal puncture, and the volume of feces squeezed into the abdominal cavity. The rapid and specific diagnosis of sepsis is a crucial factor that affects the outcome. The gold standard for sepsis diagnosis is microbial culture; however, this process is time-consuming and sometimes inaccurate. The detection of sepsis-specific biomarkers is fast, but the existing biomarkers are unsatisfactory due to a short half-life, non-specificity, and insufficient sensitivity. Therefore, there is an urgent need for a reliable biomarker of sepsis in the early stages. Previous publications suggest that excessive neutrophil extracellular traps (NETs) occur in sepsis. Citrullinated histone H3 (CitH3), as a NET component, is elevated both in septic animals and patients, and the presence of CitH3 is a reliable diagnostic biomarker of sepsis. The present study aimed to describe a standardized mouse model of CLP-induced sepsis and establish a reliable blood biomarker of sepsis. Our work may contribute to the early and accurate diagnosis of sepsis in the future.

As shown in Figure 2A, no CitH3 was detected in the sham group by western blotting. The serum CitH3 concentration significantly increased after CLP, and this increase was blocked by the inhibition of NET formation via the administration of YW3-56, a PAD inhibitor10. Figure 2B shows the serumCitH3 concentrations determined by ELISA. At 24 h after CLP, the serum concentration of CitH3 was increased in the CLP groups compared with t...

Watch this Scientific Journal Video about Evaluation of a Reliable Biomarker in a Cecal Ligation and Puncture-Induced Mouse Model of Sepsis at JoVE.com

Evaluation of a Reliable Biomarker in a Cecal Ligation and Puncture-Induced Mouse Model of Sepsis

This protocol presents the operative details of cecal ligation and puncture (CLP) in a mouse model of sepsis. CLP is one of the most widely used techniques to create an animal model of sepsis. Therefore, a standardized CLP protocol is required for the attainment of reliable research results.

Sepsis is a severe life-threatening and rapidly developing disease that causes millions of deaths annually worldwide. Researchers have made tremendous ...

The main purpose of this study is to use mouse model of cecal ligation and puncture-induced sepsis to evaluate reliable blood biomarker of sepsis. Cecal ligation and puncture, or CLP in short, is a clinically-relevant model of sepsis. CLP is commonly used model in sepsis research.Citrullinated histone H3, or CitH3, originates from sepsis-induced NETosis. Our previous study demonstrates that CitH3 is a reliable diagnostic biomarker of sepsis. Select male C57BL/6 mice.Weigh the mouse, and anesthetize the mouse by inhalation of 1.5%isoflurane. Fix the mouse on a heating pad. Apply depilatory cream to the abdomen and leave for no longer than one minute before removing the cream and hair.Prepare sterile surgical instruments suitable for rodent animal surgery. Disinfect the abdominal skin with iodine at least three times. Cover the operative surgical area with the proper sterile surgical drapery.Use sterile surgical scissors to make an approximately two centimeters incision in the abdominal wall, along the linea alba. Identify and isolate the cecum out of the peritoneal cavity with sterile tweezers. Ligate 75 volume of the cecum with 4-0 silk suture.Do not ligate the mesenteric blood vessels. To be noted, different percentage of cecum ligated determines the severity of sepsis. 25%leads to a low-grade sepsis, 50%leads to the mid-grade sepsis, and 75%leads to a high-grade sepsis.Puncture the cecum by one through-and-through perforation with a 21 gauge needle at the midpoint between the tail end and the ligation. Gently squeeze the feces out of the cecum through penetration holes. To be noted, the amount of feces squeezed into the peritoneal cavity should be consistent, since feces also determines the severity of sepsis.Replace the cecum as well as feces into the abdominal cavity gently. Close the abdominal muscle layer and the skin layer with 6-0 silk suture. Disinfect the incision with iodine.Injection of ketoprofen, five milligrams per kilograms, should be performed on the lower left quadrant of the abdomen to avoid the cecum. Place the mouse on a heating pad till full recovery. The mouse is housed in a temperature-controlled room and is given free access to food and water.Animals will be euthanized by carbon dioxide overdose with symptoms of sepsis, relevant to our predefined endpoints based on our study presented. Mice are randomly divided into the sham group, CLP group, and the CLP plus Cl-amidine or YW3-56 treatment group. Mice in sham group receive all CLP procedures except cecum ligation and puncture.Harvest peripheral blood at 24 hours post-operatively and prepare serum through centrifugation. CitH3 concentration was determined by western blotting and a self-developed ELISA kit. As shown in figure two, no CitH3 was detected in sham group.CitH3 levels were elevated after CLP insert, which was attenuated by PAD inhibition significantly. Based on our data, we conclude that circulating CitH3 is a reliable diagnostic biomarker of sepsis.

evaluation-reliable-biomarker-cecal-ligation-puncture-induced-mouse

Research

JoVE Journal

Immunology and Infection

Colon Ascendens Stent Peritonitis (CASP) - a Standardized Model for Polymicrobial Abdominal Sepsis

Sepsis remains a persistent problem on intensive care units all over the world. Understanding the complex mechanisms of sepsis is the precondition for establishing new therapeutic approaches in this field. Therefore, animal models are required that are able to closely mimic the human disease and also sufficiently deal with scientific questions. The Colon Ascendens Stent Peritonitis (CASP) is a highly standardized model for polymicrobial abdominal sepsis in rodents. In this model, a small stent is surgically inserted into the ascending colon of mice or rats leading to a continuous leakage of intestinal bacteria into the peritoneal cavity. The procedure results in peritonitis, systemic bacteraemia, organ infection by gut bacteria, and systemic but also local release of several pro- and anti-inflammatory cytokines. The lethality of CASP can be controlled by the diameter of the inserted stent. A variant of this model, the so-called CASP with intervention (CASPI), raises opportunity to remove the septic focus by a second operation according to common procedures in clinical practice. CASP is an easily learnable and highly reproducible model that closely mimics the clinical course of abdominal sepsis. It leads way to study on questions in several scientific fields e.g. immunology, infectiology, or surgery.

Colon Ascendens Stent Peritonitis CASP - a Standardized Model for Polymicrobial Abdominal Sepsis

The Colon Ascendens Stent Peritonitis (CASP) is a highly standardized model for polymicrobial abdominal sepsis in rodents. This article describes the surgical procedure of CASP. The CASP model and its variants allow the systematic investigation of various problems concerning the subject of sepsis.

Sepsis remains a persistent problem on intensive care units all over the world. Understanding the complex mechanisms of sepsis is the precondition for ...

Cecal Ligation and Puncture-induced Sepsis as a Model To Study Autophagy in Mice

Experimental sepsis can be induced in mice using the cecal ligation and puncture (CLP) method, which causes polymicrobial sepsis. Here, a protocol is provided to induce sepsis of varying severity in mice using the CLP technique. Autophagy is a fundamental tissue response to stress and pathogen invasion. Two current protocols to assess autophagy in vivo in the context of experimental sepsis are also presented here. (I) Transgenic mice expressing green fluorescence protein (GFP)-LC3 fusion protein are subjected to CLP. Localized enhancement of GFP signal (puncta), as assayed either by immunohistochemical or confocal assays, can be used to detect enhanced autophagosome formation and, thus, altered activation of the autophagy pathway. (II) Enhanced autophagic vacuole (autophagosome) formation per unit tissue area (as a marker of autophagy stimulation) can be quantified using electron microscopy. The study of autophagic responses to sepsis is a critical component of understanding the mechanisms by which tissues respond to infection. Research findings in this area may ultimately contribute towards understanding the pathogenesis of sepsis, which represents a major problem in critical care medicine.

Experimental sepsis can be induced in mice using the cecal ligation and puncture (CLP) method. Current protocols to assess autophagy in vivo in the context of CLP-induced sepsis are presented here: A protocol for measuring autophagy using (GFP)-LC3 mice, and a protocol for measuring autophagosome formation by electron microscopy.

Experimental sepsis can be induced in mice using the cecal ligation and puncture (CLP) method, which causes polymicrobial sepsis. Here, a protocol is ...

Influenza A Virus Studies in a Mouse Model of Infection

Influenza viruses cause over 500,000 deaths worldwide1 and are associated with an annual cost of 12 - 14 billion USD in the United States alone considering direct medical and hospitalization expenses and work absenteeism2. Animal models are crucial in Influenza A virus (IAV) studies to evaluate viral pathogenesis, host-pathogen interactions, immune responses, and the efficacy of current and/or novel vaccine approaches as well as antivirals. Mice are an advantageous small animal model because their immune system is evolutionarily similar to that found in humans, they are available from commercial vendors as genetically identical subjects, there are multiple strains that can be exploited to evaluate the genetic basis of infections, and they are relatively inexpensive and easy to manipulate. To recapitulate IAV infection in humans via the airways, mice are first anesthetized prior to intranasal inoculation with infectious IAVs under proper biosafety containment. After infection, the pathogenesis of IAVs is determined by monitoring daily the morbidity (body weight loss) and mortality (survival) rate. In addition, viral pathogenesis can also be evaluated by assessing virus replication in the upper (nasal mucosa) or lower (lungs) respiratory tract of infected mice. Humoral responses upon IAV infection can be rapidly evaluated by non-invasive bleeding and secondary antibody detection assays aimed at detecting the presence of total or neutralizing antibodies. Here, we describe the common methods used to infect mice intranasally (i.n) with IAV and evaluate pathogenesis, humoral immune responses and protection efficacy.

Influenza A viruses (IAVs) are important human respiratory pathogens. To understand the pathogenicity of IAVs and to perform preclinical testing of novel vaccine approaches, animal models mimicking human physiology are required. Here, we describe techniques to evaluate IAV pathogenesis, humoral responses and vaccine efficacy using a mouse model of infection.

Influenza viruses cause over 500,000 deaths worldwide1 and are associated with an annual cost of 12 - 14 billion USD in the United States alone ...

A Controlled Mouse Model for Neonatal Polymicrobial Sepsis

Neonatal sepsis remains a global burden. A preclinical model to screen effective prophylactic or therapeutic interventions is needed. Neonatal mouse polymicrobial sepsis can be induced by injecting cecal slurry intraperitoneally into day of life 7 mice and monitoring them for the following week. Presented here are the detailed steps necessary for the implementation of this neonatal sepsis model. This includes making a homogeneous cecal slurry stock, diluting it to a weight- and litter-adjusted dose, an outline of the monitoring schedule, and a definition of observed health categories used to define humane endpoints. The generation of a homogeneous cecal slurry stock from pooled donors allows for the administration into many litters over time, reducing the variation between donors, and preventing the use of potentially toxic glycerol. The monitoring strategy used allows for the anticipation of survival outcome and the identification of mice that would later progress to death, allowing for an earlier identification of the humane endpoint. Two main behavioral features are used to define the health scores, namely, the ability of the neonatal mice to right themselves when placed on their back and their level of mobility. These criteria could potentially be applied to address humane endpoints in other studies of neonatal disease in mice, as long as a pilot study is performed to confirm accuracy. In conclusion, this approach provides a standardized method to model newborn sepsis in mice, while providing resources to assess animal welfare used to define early humane endpoints for challenged animals.

This protocol provides the necessary steps to establish and evaluate neonatal sepsis in 7-day-old mice.

Neonatal sepsis remains a global burden. A preclinical model to screen effective prophylactic or therapeutic interventions is needed. Neonatal mouse ...

Design of Cecal Ligation and Puncture and Intranasal Infection Dual Model of Sepsis-Induced Immunosuppression

Sepsis, a severe and complicated life-threatening infection, is characterized by an imbalance between pro- and anti-inflammatory responses in multiple organs. With the development of therapies, most patients survive the hyperinflammatory phase but progress to an immunosuppressive phase, which increases the emergence of secondary infections. Therefore, improved understanding of the pathogenesis underlying secondary hospital-acquired infections in the immunosuppressive phase during sepsis is of tremendous importance. Reported here is a model to test infectious outcomes by creating double-hit infections in mice. A standard surgical procedure is used to induce polymicrobial peritonitis by cecal ligation and puncture (CLP) and followed by intranasal infection of Staphylococcus aureus to simulate pneumonia occurring in immune suppression that is frequently seen in septic patients. This dual model can reflect the immunosuppressive state occurring in patients with protracted sepsis and susceptibility to secondary infection from nosocomial pneumonia. Hence, this model provides a simple experimental approach to investigate the pathophysiology of sepsis-induced secondary bacterial pneumonia, which may be used for discovering novel treatments for sepsis and its complications.

This protocol describes techniques to measure infectious outcomes underlying secondary hospital-acquired infections in the immunosuppressive condition, first by establishing cecal ligation/puncture mice then challenging them with intranasal infection to create a clinically relevant model of immunosuppression sepsis.

Sepsis, a severe and complicated life-threatening infection, is characterized by an imbalance between pro- and anti-inflammatory responses in multiple ...

Isolation and Quantitative Evaluation of Brush Cells from Mouse Tracheas

Tracheal brush cells are cholinergic chemosensory epithelial cells poised to transmit signals from the airway lumen to the immune and nervous systems. They are part of a family of chemosensory epithelial cells which include tuft cells in the intestinal mucosa, brush cells in the trachea, and solitary chemosensory and microvillous cells in the nasal mucosa. Chemosensory cells in different epithelial compartments share key intracellular markers and a core transcriptional signature, but also display significant transcriptional heterogeneity, likely reflective of the local tissue environment. Isolation of tracheal brush cells from single cell suspensions is required to define the function of these rare epithelial cells in detail, but their isolation is challenging, potentially due to the close interaction between tracheal brush cells and nerve endings or due to airway-specific composition of tight and adherens junctions. Here, we describe a procedure for isolation of brush cells from mouse tracheal epithelium. The method is based on an initial separation of tracheal epithelium from the submucosa, allowing for a subsequent shorter incubation of the epithelial sheet with papain. This procedure offers a rapid and convenient solution for flow cytometric sorting and functional analysis of viable tracheal brush cells.

Brush cells are rare cholinergic chemosensory epithelial cells found in the na&#239;ve mouse trachea. Due to their limited numbers, ex vivo evaluation of their functional role in airway immunity and remodeling is challenging. We describe a method for isolation of tracheal brush cells by flow cytometry.

Tracheal brush cells are cholinergic chemosensory epithelial cells poised to transmit signals from the airway lumen to the immune and nervous systems. ...

A Neonatal Imaging Model of Gram-Negative Bacterial Sepsis

Neonates are at an increased risk of bacterial sepsis due to the unique immune profile they display in the first months of life. We have established a protocol for studying the pathogenesis of E. coli O1:K1:H7, a serotype responsible for high mortality rates in neonates. Our method utilizes intravital imaging of neonatal pups at different time points during the progression of infection. This imaging, paralleled by measurement of bacteria in the blood, inflammatory profiling, and tissue histopathology, signifies a rigorous approach to understanding infection dynamics during sepsis. In the current report, we model two infectious inoculums for comparison of bacterial burdens and severity of disease. We find that subscapular infection leads to disseminated infection by 10 h post-infection. By 24 h, infection of luminescent E. coli was abundant in the blood, lungs, and other peripheral tissues. Expression of inflammatory cytokines in the lungs is significant at 24 h, and this is followed by cellular infiltration and evidence of tissue damage that increases with infectious dose. Intravital imaging does have some limitations. This includes a luminescent signal threshold and some complications that can arise with neonates during anesthesia. Despite some limitations, we find that our infection model offers an insight for understanding longitudinal infection dynamics during neonatal murine sepsis, that has not been thoroughly examined to date. We expect this model can also be adapted to study other critical bacterial infections during early life.

Infection of neonatal mice with bioluminescent E. coli O1:K1:H7 results in a septic infection with significant pulmonary inflammation and lung pathology. Here, we describe procedures to model and further study neonatal sepsis using longitudinal intravital imaging in parallel with enumeration of systemic bacterial burdens, inflammatory profiling, and lung histopathology.

Neonates are at an increased risk of bacterial sepsis due to the unique immune profile they display in the first months of life. We have established a ...

A Contemporary Warming/Restraining Device for Efficient Tail Vein Injections in a Murine Fungal Sepsis Model

In rodent models, tail vein injections are important methods for intravenous administration of experimental agents. Tail vein injections typically involve warming of the animal to promote vasodilation, which aids in both the identification of the blood vessels and positioning of the needle into the vessel lumen while securely restraining the animal. Although tail vein injections are common procedures in many protocols and are not considered highly technical if performed correctly, accurate and consistent injections are crucial to obtain reproducible results and minimize variability. Conventional methods for inducing vasodilation prior to tail vein injections generally depend on the use of a heat source such as a heat lamp, electrical/rechargeable heat pads, or pre-heated water at 37 &#176;C. Despite being readily accessible in a standard laboratory setting, these tools evidently suffer from poor/limited thermo-regulatory capacity. Similarly, although various forms of restraining devices are commercially available, they must be used carefully to avoid trauma to the animals. These limitations of the current methods create unnecessary variables in experiments or result in varying outcomes between experiments and/or laboratories.
In this article, we demonstrate an improved protocol using an innovative device that combines an independent, thermally regulated, warming device with an adjustable restraining unit into one system for efficient streamlined tail vein injection. The example we use is an intravenous model of fungal bloodstream infection that results in sepsis. The warming apparatus consists of a heat-reflective acrylic box installed with an adjustable automatic thermostat to maintain the internal temperature at a pre-set threshold. Likewise, the width and height of the cone restraining apparatus can be adjusted to safely accommodate various rodent sizes. With the advanced and versatile features of the device, the technique shown here could become a useful tool across a range of research areas involving rodent models that employ tail vein injections.

Here, we present an effective and efficient method for rodent tail vein injections using a uniquely designed warming/restraining device. By streamlining the initiation of vasodilation and restraining processes, this protocol allows accurate and timely intravenous injections of large groups of animals with minimal distress.

In rodent models, tail vein injections are important methods for intravenous administration of experimental agents. Tail vein injections typically involve ...

A Mouse Model of Chronic Liver Fibrosis for the Study of Biliary Atresia

Biliary atresia (BA) is a fatal disease involving obstructive jaundice, and it is the most common indication for liver transplantation in children. Due to the complex etiology and unknown pathogenesis, there are still no effective drug treatments. At present, the classic BA mouse model induced by rhesus rotavirus (RRV) is the most commonly used model for studying the pathogenesis of BA. This model is characterized by growth retardation, jaundice of the skin and mucosa, clay stools, and dark yellow urine. The histopathology shows severe liver inflammation and obstruction of the intrahepatic and extrahepatic bile ducts, which are similar to the symptoms of human BA. However, the livers of end-stage mice in this model lack fibrosis and cannot fully simulate the characteristics of liver fibrosis in clinical BA. The presented study developed a novel BA mouse model of chronic liver fibrosis by injecting 5-10 &#181;g of anti-Ly6G antibody four times, with gaps of 2 days after each injection. The results showed that some of the mice successfully formed chronic BA with typical fibrosis after the time lapse, meaning these mice represent a suitable animal model for the virus-induced liver fibrosis mechanistic study of BA and a platform for developing future BA treatments.

We established a mouse model of chronic liver fibrosis, which provides a suitable animal model for the virus-induced liver fibrosis mechanistic study of biliary atresia (BA) and a platform for future BA treatments.

Biliary atresia (BA) is a fatal disease involving obstructive jaundice, and it is the most common indication for liver transplantation in children. Due to ...

A Mouse Ear Model for Allergic Contact Dermatitis Evaluation

Skin is the human body&#39;s first line of defense and one of the most exposed organs to environmental chemicals. Allergic contact dermatitis (ACD) is a common skin disease that manifests as a local rash, redness, and skin lesions. The occurrence and development of ACD are influenced by both genetic and environmental factors. Although many scholars have constructed a series of models of ACD in recent years, the experimental protocols of these models are all different, which makes it difficult for readers to establish them well. Therefore, a stable and efficient animal model is of great significance to further study the pathogenesis of atopic dermatitis. In this study, we detail a modeling method using 1-fluoro-2,4-dinitrobenzene (DNFB) to induce ACD-like symptoms in the ears of mice and describe several methods for assessing the severity of dermatitis during modeling. This experimental protocol has been successfully applied in some experiments and has a certain promotional role in the field of ACD research.

Here, we describe the methods for inducing allergic contact dermatitis in mouse ears by 1-fluoro-2,4-dinitrobenzene (DNFB) and how to evaluate the severity of allergic contact dermatitis.

Skin is the human body&#39;s first line of defense and one of the most exposed organs to environmental chemicals. Allergic contact dermatitis (ACD) is a ...