Name: design of cecal ligation and puncture and intranasal infection dual model of sepsis-induced immunosuppression
Uploaded: 2019-06-15T15:00:00
Description: Watch this Scientific Journal Video about Design of Cecal Ligation and Puncture and Intranasal Infection Dual Model of Sepsis-Induced Immunosuppression at JoVE.com

This work was supported by National Institutes of Health Grants R01 AI138203-01, AI109317-04, AI101973-01, and AI097532-01A1 to M. W. The University of North Dakota Core Facilities were supported by NIH grants (INBRE P20GM103442 and COBRE P20GM113123). This work was also supported by the Key Program of National Nature Science Foundation of China (81530063) to Jianxin Jiang. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. We thank Marvin Leier (Center for Rural Health, University of North Dakota) for making the video.

All methods described here were performed in accordance with the National Institute of Health Guide for Care and Use of Laboratory Animals and approved by the University of North Dakota Institutional Animal Care and Use Committee (IACUC).
1. Cecal ligation and puncture
NOTE: Female C57BL/6 mice (weight, 18-22 g; age, 6-8 weeks) are randomly divided into six groups: control group (Ctrl), infection group (SA for S. aureus), two sham groups, and two CLP groups. ...

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As the gold standard model for sepsis research, CLP has a combination of three insults, including tissue trauma caused by the laparotomy, necrosis due to ligation of the cecum, and infection as a result of microbial leakage that causes peritonitis with translocation of bacteria into blood8. Therefore, CLP mimics the complexity of human sepsis better than many other models. However, a major limitation of current CLP model is the inability to reflect the more prolonged phase of sepsis seen in patien...

Sepsis initiates a complex interplay of host pro-inflammatory and anti-inflammatory processes and is characterized by a hyperinflammatory response and subsequent immune dysfunction1,2. Sepsis represents a global health priority and causes a high number of deaths in intensive care units (ICUs)3. The incidence of sepsis is estimated to exceed 30 million cases worldwide per year, with mortality rates as high as 30% despite advances in ICU management4,5. In 2017, the World Health Organization adopted a resolution to improve the prevention, diagnosis, and management of this deadly disease5. However, recent studies have illustrated that death does not result from primary infection in severe septic patients but rather from secondary nosocomial infection (particularly pneumonia) that caused by immunosuppression6,7. Therefore, understanding the mechanisms of why septic patients develop secondary infection and discovering more effective treatments are urgently required. Herein, a dual model, also known as a double-hit model, to study the immunosuppressive phenomenon occurring in patients with protracted sepsis is described. 
As the gold standard experimental model in research on polymicrobial sepsis, cecal ligation and puncture (CLP) is a surgery characterized by cecum ligation and perforation, which contributes to polymicrobial peritonitis and sepsis8,9. The pathophysiological process and cytokine profiles, along with the kinetics and magnitude, are similar to clinical sepsis. The position of the ligation, needle size used for the puncture, and number of cecal punctures are major factors that impact the mortality following CLP.
The nosocomial pneumonia is the leading cause of mortality among critically ill patients with sepsis. The major type of organisms causing severe sepsis includes Staphylococcus aureus (20.5%), Pseudomonas species (19.9%), Enterobacteriacae (mainly E. coli, 16.0%), and fungi (19%). Meanwhile, recent studies have suggested an increasing incidence of gram-positive organisms, which are now almost as common as gram-negative infections3.
The method described in this protocol involves CLP, performed as the "first hit" to induce sublethal polymicrobial peritonitis, which manifests an immunosuppression condition. The procedure also involves subsequent intranasal instillation of S. aureus as the "second hit" to provide a clinically relevant research platform.

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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.

Depending on the experimental design and procedures, C57BL/6 mice were subjected to CLP, and after 3 days, they were administered bacteria intranasally (Figure 1). As shown in Figure 2, the mice began to die at ~12 h after induction of peritonitis. Two mice in the CLP+SA group and three mice in the CLP+NS group died before intranasal S. aureus instillation. No mortality was detected in uninfected non- or sham-operated mi...

Watch this Scientific Journal Video about Design of Cecal Ligation and Puncture and Intranasal Infection Dual Model of Sepsis-Induced Immunosuppression at JoVE.com

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

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 ...

Prepare the mouse for surgery. Shave the lower quadrants of the abdomen using a razor and disinfect the area with iodine. Place the mouse onto a clean work surface on its back with the head pointing away from the operator.Make a longitudinal skin incision about a half a centimeter long in the left lower abdomen. Be careful not to penetrate the peritoneal cavity. Use small scissors to extend the incision about one to two centimeters.Make an intramuscular incision to gain access into the peritoneal cavity. In most cases, the cecum is on the left side of the abdomen. Isolate the cecum.Using blunt, anatomical forceps, gently and carefully expose the cecum through the incision. Step four is the ligation. The position of the ligation on the cecum determines the severity level of sepsis.Ligating approximately 75%of the cecum induces severe sepsis. Ligating 50%of the cecum induces mid-level sepsis. Whereas ligating 25%or less of the cecum will result in minor sepsis.Ligate the cecum at the designated position. Make sure not to ligate the ileocecal valve. Step five is to puncture the cecum.Using a needle, perforate the cecum with a single through and through puncture mid-way between the ligation and the tip of the cecum. Make sure you do not puncture any blood vessels. To ensure that there was a complete puncture, extrude a small droplet of feces from both needle holes.Carefully replace the cecum into the abdominal cavity. Close the abdominal musculature by applying simple running sutures and close the skin. Clean the skin with iodine.Inject the mouse with a pre-warmed saline solution to resuscitate. Place the mouse back into the cage with unlimited access to food and water. After about three days from the cecal ligation and puncture or the CLP procedure, we subject the mouse to a second hit with an intranasal infection to stimulate pneumonia that often occurs in sepsis.Approach the neck of the mouse from behind, smoothly and gently. The thumb and index finger of the left hand form a U-shaped position. Hold the neck immediately behind the ears so the mouse head is completely restrained.Introduce the intranasal infection. Using a 100 microliter pipette, instill the staphylococcus aureus strain intranasally. Holding the mouse in an upright position, slowly drop two to three microliters of the bacterial solution into both nostrils of the mouse.Raise the mouse up and down with its head up and tail down to help the bacterial solution enter the trachea. Raise the mouse up quickly while lowering it gently and slowly. Repeat the instillation 15 times or until all the bacterial solution is instilled.The last step is to finish the procedure. Lay the mouse on the angled bedding at about a 35 degree angle to recover. Make sure the mouse is on its back with its head laying up.Watch the mouse to make sure it is completely recovered from the anesthesia and the procedure. After flattening the bedding, place the mouse back in the cage with unlimited access to food and water. Mice began to die at around 12 hours after induction of peritonitis.The mortality was much higher for mice with CLP before a pneumonia. Three days post-surgery, CLP mice had more mortality with an intranasal administration of staphylococcus aureus. The levels of serum pro-inflammatory cytokines significantly increased at 24 hours after bacterial instillation in sepsis mice compared to the mice that had CLP alone or the Sham operated mice with a second hit.However, double-hit mice exhibited significant decrease in BAL fluid cytokine levels compared to both SA and Sham surgery plus SA mice. Hence CLP impairs host defense and increases susceptibility to infection. This dual-hit model is a valuable tool to understand the molecular mechanisms for host-pathogen interaction, which may open the avenue to develop new, effective drugs and other therapeutics for superbug infections.

design-cecal-ligation-puncture-intranasal-infection-dual-model-sepsis

Research

JoVE Journal

Immunology and Infection

Particle Agglutination Method for Poliovirus Identification

In the Global Polio Eradication Initiative, laboratory diagnosis plays a critical role by isolating and identifying PV from the stool samples of acute flaccid paralysis (AFP) cases. In the World Health Organization (WHO) Global Polio Laboratory Network, PV isolation and identification are currently being performed by using cell culture system and real-time RT-PCR, respectively. In the post-eradication era of PV, simple and rapid identification procedures would be helpful for rapid confirmation of polio cases at the national laboratories. In the present study, we will show the procedure of novel PA assay developed for PV identification. This PA assay utilizes interaction of PV receptor (PVR) molecule and virion that is specific and uniform affinity to all the serotypes of PV. The procedure is simple (one step procedure in reaction plates) and rapid (results can be obtained within 2 h of reaction), and the result is visually observed (observation of agglutination of gelatin particles).

A recently developed novel particle agglutination (PA) assay utilizing virus receptor molecule allowed a rapid and easy identification of poliovirus (PV). In this article, we will show the procedure for the PA assay for PV identification.

In the Global Polio Eradication Initiative, laboratory diagnosis plays a critical role by isolating and identifying PV from the stool samples of acute ...

Characterization of Inflammatory Responses During Intranasal Colonization with Streptococcus pneumoniae

Nasopharyngeal colonization by Streptococcus pneumoniae is a prerequisite to invasion to the lungs or bloodstream1. This organism is capable of colonizing the mucosal surface of the nasopharynx, where it can reside, multiply and eventually overcome host defences to invade to other tissues of the host. Establishment of an infection in the normally lower respiratory tract results in pneumonia. Alternatively, the bacteria can disseminate into the bloodstream causing bacteraemia, which is associated with high mortality rates2, or else lead directly to the development of pneumococcal meningitis. Understanding the kinetics of, and immune responses to, nasopharyngeal colonization is an important aspect of S. pneumoniae infection models.
Our mouse model of intranasal colonization is adapted from human models3 and has been used by multiple research groups in the study of host-pathogen responses in the nasopharynx4-7. In the first part of the model, we use a clinical isolate of S. pneumoniae to establish a self-limiting bacterial colonization that is similar to carriage events in human adults. The procedure detailed herein involves preparation of a bacterial inoculum, followed by the establishment of a colonization event through delivery of the inoculum via an intranasal route of administration. Resident macrophages are the predominant cell type in the nasopharynx during the steady state. Typically, there are few lymphocytes present in uninfected mice8, however mucosal colonization will lead to low- to high-grade inflammation (depending on the virulence of the bacterial species and strain) that will result in an immune response and the subsequent recruitment of host immune cells. These cells can be isolated by a lavage of the tracheal contents through the nares, and correlated to the density of colonization bacteria to better understand the kinetics of the infection.

Characterization of Inflammatory Responses During Intranasal Colonization with Streptococcus pneumoniae

Colonization of the murine nasopharynx with Streptococcus pneumoniae and the subsequent extraction of adherent or recruited cells is described. This technique involves flushing the nasopharynx and collection of the fluid through the nares and is adaptable for various readouts, including differential cell quantification and analysis of mRNA expression in situ.

Nasopharyngeal colonization by Streptococcus pneumoniae is a prerequisite to invasion to the lungs or bloodstream1. This organism is capable of colonizing ...

Use of Galleria mellonella as a Model Organism to Study Legionella pneumophila Infection

Legionella pneumophila, the causative agent of a severe pneumonia named Legionnaires&#39; disease, is an important human pathogen that infects and replicates within alveolar macrophages. Its virulence depends on the Dot/Icm type IV secretion system (T4SS), which is essential to establish a replication permissive vacuole known as the Legionella containing vacuole (LCV). L. pneumophila infection can be modeled in mice however most mouse strains are not permissive, leading to the search for novel infection models. We have recently shown that the larvae of the wax moth Galleria mellonella are suitable for investigation of L. pneumophila infection. G. mellonella is increasingly used as an infection model for human pathogens and a good correlation exists between virulence of several bacterial species in the insect and in mammalian models. A key component of the larvae&#39;s immune defenses are hemocytes, professional phagocytes, which take up and destroy invaders. L. pneumophila is able to infect, form a LCV and replicate within these cells. Here we demonstrate protocols for analyzing L. pneumophila virulence in the G. mellonella model, including how to grow infectious L. pneumophila, pretreat the larvae with inhibitors, infect the larvae and how to extract infected cells for quantification and immunofluorescence microscopy. We also describe how to quantify bacterial replication and fitness in competition assays. These approaches allow for the rapid screening of mutants to determine factors important in L. pneumophila virulence, describing a new tool to aid our understanding of this complex pathogen.

Use of Galleria mellonella as a Model Organism to Study Legionella pneumophila Infection

The larva of the wax moth Galleria mellonella was recently established as an in vivo model to study Legionella pneumophila infection. Here, we demonstrate fundamental techniques to characterize the pathogenesis of Legionella in the larvae, including inoculation, measurement of bacterial virulence and replication as well as extraction and analysis of infected hemocytes.

Legionella pneumophila, the causative agent of a severe pneumonia named Legionnaires&#39; disease, is an important human pathogen that infects and ...

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 ...

Methods to Evaluate Cytotoxicity and Immunosuppression of Combustible Tobacco Product Preparations

Among other pathophysiological changes, chronic exposure to cigarette smoke causes inflammation and immune suppression, which have been linked to increased susceptibility of smokers to microbial infections and tumor incidence. Ex vivo suppression of receptor-mediated immune responses in human peripheral blood mononuclear cells (PBMCs) treated with smoke constituents is an attractive approach to study mechanisms and evaluate the likely long-term effects of exposure to tobacco products. Here, we optimized methods to perform ex vivo assays using PBMCs stimulated by bacterial lipopolysaccharide, a Toll-like receptor-4 ligand. The effects of whole smoke-conditioned medium (WS-CM), a combustible tobacco product preparation (TPP), and nicotine were investigated on cytokine secretion and target cell killing by PBMCs in the ex vivo assays. We show that secreted cytokines IFN-&#947;, TNF, IL-10, IL-6, and IL-8 and intracellular cytokines IFN-&#947;, TNF-&#945;, and MIP-1&#945; were suppressed in WS-CM-exposed PBMCs. The cytolytic function of effector PBMCs, as determined by a K562 target cell killing assay was also reduced by exposure to WS-CM; nicotine was minimally effective in these assays. In summary, we present a set of improved assays to evaluate the effects of TPPs in ex vivo assays, and these methods could be readily adapted for testing other products of interest.

Using optimized human peripheral blood mononuclear cell (PBMC) ex vivo assays, we showed that a combustible tobacco product preparation markedly suppresses receptor-mediated intracellularly secreted cytokines and cytolytic ability of effector PBMCs. These rapid assays may be useful in product evaluation and understanding the potential long-term effects of tobacco exposure.

Among other pathophysiological changes, chronic exposure to cigarette smoke causes inflammation and immune suppression, which have been linked to ...

Intranasal Administration of Recombinant Influenza Vaccines in Chimeric Mouse Models to Study Mucosal Immunity

Vaccines are one of the greatest achievements of mankind, and have saved millions of lives over the last century. Paradoxically, little is known about the physiological mechanisms that mediate immune responses to vaccines perhaps due to the overall success of vaccination, which has reduced interest into the molecular and physiological mechanisms of vaccine immunity. However, several important human pathogens including influenza virus still pose a challenge for vaccination, and may benefit from immune-based strategies. 
Although influenza reverse genetics has been successfully applied to the generation of live-attenuated influenza vaccines (LAIVs), the addition of molecular tools in vaccine preparations such as tracer components to follow up the kinetics of vaccination in vivo, has not been addressed. In addition, the recent generation of mouse models that allow specific depletion of leukocytes during kinetic studies has opened a window of opportunity to understand the basic immune mechanisms underlying vaccine-elicited protection. Here, we describe how the combination of reverse genetics and chimeric mouse models may help to provide new insights into how vaccines work at physiological and molecular levels, using as example a recombinant, cold-adapted, live-attenuated influenza vaccine (LAIV). We utilized laboratory-generated LAIVs harboring cell tracers as well as competitive bone marrow chimeras (BMCs) to determine the early kinetics of vaccine immunity and the main physiological mechanisms responsible for the initiation of vaccine-specific adaptive immunity. In addition, we show how this technique may facilitate gene function studies in single animals during immune responses to vaccines. We propose that this technique can be applied to improve current prophylactic strategies against pathogens for which urgent medical countermeasures are needed, for example influenza, HIV, Plasmodium, and hemorrhagic fever viruses such as Ebola virus.

There is an overall lack of knowledge about how vaccines work. Here we propose the combined use of reverse genetics and bone marrow chimeric mice to gain insight into the early host immune responses to vaccines with a special focus on dendritic cells and T cell immunity.

Vaccines are one of the greatest achievements of mankind, and have saved millions of lives over the last century. Paradoxically, little is known about the ...

Protective Efficacy and Pulmonary Immune Response Following Subcutaneous and Intranasal BCG Administration in Mice

Despite global coverage of intradermal BCG vaccination, tuberculosis remains one of the most prevalent infectious diseases in the world. Preclinical data have encouraged pulmonary tuberculosis vaccines as a promising strategy to prevent pulmonary disease, which is responsible for transmission. In this work, we describe the methodology used to demonstrate in the mouse model the benefits of intranasal BCG vaccination when compared to subcutaneous. Our data revealed greater protective efficacy following intranasal BCG administration. In addition, our results indicate that pulmonary vaccination triggers a higher immune response in lungs, including Th1 and Th17 responses, as well as an increase of immunoglobulin A (IgA) concentration in respiratory airways. Our data show correlation between protective efficacy and the presence of IL17-producing cells in lungs post-Mycobacterium tuberculosis challenge, suggesting a role for this cytokine in the protective response conferred by pulmonary vaccination. Finally, we detail the global workflow we have developed to study respiratory vaccination in the mouse model, which could be extrapolated to other tuberculosis vaccines, apart from BCG, targeting the mucosal response or other pulmonary routes of administration such as the intratracheal or aerosol.

We herein detail the methodology followed to compare protective efficacy and lung immune response induced by intranasal and subcutaneous immunization with BCG in mouse model. Our results show the benefits of pulmonary vaccination and suggest a role for IL17-mediated response in vaccine-induced protection.

Despite global coverage of intradermal BCG vaccination, tuberculosis remains one of the most prevalent infectious diseases in the world. Preclinical data ...

A Platform of Anti-biofilm Assays Suited to the Exploration of Natural Compound Libraries

Biofilms are regarded as one of the most challenging topics of modern biomedicine, and they are potentially responsible for over 80% of antibiotic-tolerant infections. Biofilms have displayed an exceptionally high tolerance for chemotherapy, which is thought to be multifactorial. For instance, the matrix provides a physical barrier that decreases the penetration of antibiotics into the biofilm. Also, cells within the biofilms are phenotypically diverse. Likely, biofilm resilience arises from a combination of these and other, yet unknown, mechanisms. All of the currently existing antibiotics have been developed against single-cells (planktonic) bacteria. Therefore, so far, a very limited repertoire of molecules exists that can selectively act on mature biofilms. This situation has driven a progressive paradigm shift in drug discovery, in which searching for anti-biofilms has been urged to occupy a more prominent place. An additional challenge is that there are a very limited number of standardized methods for biofilm research, especially those that can be used for large-throughput screening of chemical libraries. Here, an experimental anti-biofilm platform for chemical screening is presented. It uses three assays to measure biofilm viability (with resazurin staining), total biomass (with crystal violet staining), and biofilm matrix (using a wheat germ agglutinin, WGA-fluorescence-based staining of the poly-N-acetyl-glucosamine, PNAG, fraction). All the assays were developed using Staphylococcus aureus as the model bacteria. Examples of how the platform can be used for primary screening as well as for functional characterization of identified anti-biofilm hits are presented. This experimental sequence further allows for the classification of the hits based upon the measured end-points. It also provides information on their mode of action, especially on long-term versus short-term chemotherapeutic effects. Thus, it is very advantageous for the quick identification of high-quality hit compounds that can serve as starting points for various biomedical applications.

Biofilm infections show high tolerance towards chemotherapy. No single assay captures the complexity of biofilms. Instead, complementary assays are needed. We present a screening platform (developed for S. aureus) that combines assays for viability, biomass, and biofilm matrix. It allows anti-biofilm drug discovery, including the assessment of long-term chemotherapeutic effects.

Biofilms are regarded as one of the most challenging topics of modern biomedicine, and they are potentially responsible for over 80% of ...

Establishment of the Dual Humanized TK-NOG Mouse Model for HIV-associated Liver Pathogenesis

Despite the increased life expectancy of patients infected with human immunodeficiency virus-1 (HIV-1), liver disease has emerged as a common cause of their morbidity. The liver immunopathology caused by HIV-1 remains elusive. Small xenograft animal models with human hepatocytes and human immune system can recapitulate the human biology of the disease&#39;s pathogenesis. Herein, a protocol is described to establish a dual humanized mouse model through human hepatocytes and CD34+ hematopoietic stem/progenitor cells (HSPCs) transplantation, to study liver immunopathology as observed in HIV-infected patients. To achieve dual reconstitution, male TK-NOG (NOD.Cg-Prkdcscid Il2rgtm1Sug Tg(Alb-TK)7-2/ShiJic) mice are intraperitoneally injected with ganciclovir (GCV) doses to eliminate mouse transgenic liver cells, and with treosulfan for nonmyeloablative conditioning, both of which facilitate human hepatocyte (HEP) engraftment and human immune system (HIS) development. Human albumin (ALB) levels are evaluated for liver engraftment, and the presence of human immune cells in blood detected by flow cytometry confirms the establishment of human immune system. The model developed using the protocol described here resembles multiple components of liver damage from HIV-1 infection. Its establishment could prove to be essential for studies of hepatitis virus co-infection and for the evaluation of antiviral and antiretroviral drugs.

This protocol provides a reliable method to establish humanized mice with both human immune system and liver cells. Dual reconstituted immunodeficient mice achieved via intrasplenic injection of human hepatocytes and CD34+ hematopoietic stem cells are susceptible to human immunodeficiency virus-1 infection and recapitulate liver damage as observed in HIV-infected patients.

Despite the increased life expectancy of patients infected with human immunodeficiency virus-1 (HIV-1), liver disease has emerged as a common cause of ...

A Positioning Device for the Placement of Mice During Intranasal siRNA Delivery to the Central Nervous System

Intranasal (IN) drug delivery to the brain has emerged as a promising method to bypass the blood-brain barrier (BBB) for the delivery of drugs into the central nervous system (CNS). Recent studies demonstrate the use of a peptide, RVG9R, incorporating the minimal receptor-binding domain of the Rabies virus glycoprotein, in eliciting the delivery of siRNA into neurons in the brain. In this protocol, the peptide-siRNA formulation is delivered intranasally with a pipette in the dominant hand, while the anesthetized mouse is restrained by the scruff with the nondominant hand in a "head down-and-forward position" to avoid drainage into the lung and stomach upon inhalation. This precise gripping of mice can be learned but is not easy and requires practice and skill to result in effective CNS uptake. Furthermore, the process is long-drawn, requiring about 45 min for the administration of a total volume of ~20-30 &#181;L of solution in 1-2 &#181;L droplet volumes per inhalation, with 3-4 min rest periods between each inhalation. The objective of this study is to disclose a mouse positioning device that enables the appropriate placement of mice for efficient IN administration of the peptide-siRNA formulation. Multiple features are incorporated into the design of the device, such as four or eight positioning chairs with adjustable height and tilt to restrain anesthetized mice in the head down-and-forward position, enabling easy visualization of the mice's nares and a built-in heating pad to maintain the mice's body temperatures during the procedure. Importantly, the ability to treat four or eight mice simultaneously with RVG9R-siRNA complexes in this manner enables studies on a much quicker time scale, for the testing of an IN therapeutic siRNA approach. In conclusion, this device allows for appropriate and controlled mouse head positioning for IN application of RVG9R-siRNA and other therapeutic molecules, such as nanoparticles or antibodies, for CNS delivery.

Here, we present a protocol using a mouse positioning device that enables the appropriate placement of mice for the intranasal administration of a brain-targeting peptide-siRNA formulation enabling effective gene silencing in the central nervous system.

Intranasal (IN) drug delivery to the brain has emerged as a promising method to bypass the blood-brain barrier (BBB) for the delivery of drugs into the ...