Murine Model of Allergen Induced Asthma

Abstract

Asthma is a major cause of morbidity and mortality, affecting some 300 million people throughout the world. 1 More than 8% of the US population has asthma, with the prevalence increasing. 2 As with other diseases, animal models of allergic airway disease greatly facilitate understanding of the underlying pathophysiology, help identify potential therapeutic targets, and allow preclinical testing of possible new therapies. Models of allergic airway disease have been developed in several animal species, but murine models are particularly attractive due to the low cost, ready availability, and well-characterized immune systems of these animals. 3 Availability of a variety of transgenic strains further increases the attractiveness of these models. 4 Here we describe two murine models of allergic airway disease, both employing ovalbumin as the antigen. Following initial sensitization by intraperitoneal injection, one model delivers the antigen challenge by nebulization, the other by intratracheal delivery. These two models offer complementary advantages, with each mimicking the major features of human asthma. 5 The major features of acute asthma include an exaggerated airway response to stimuli such as methacholine (airway hyperresponsiveness; AHR) and eosinophil-rich airway inflammation. These are also prominent effects of allergen challenge in our murine models, 5,6 and we describe techniques for measuring them and thus evaluating the effects of experimental manipulation. Specifically, we describe both invasive 7 and non-invasive 8 techniques for measuring airway hyperresponsiveness as well as methods for assessing infiltration of inflammatory cells into the airways and the lung. Airway inflammatory cells are collected by bronchoalveolar lavage while lung histopathology is used to assess markers of inflammation throughout the organ. These techniques provide powerful tools for studying asthma in ways that would not be possible in humans. Video LinkThe video component of this article can be found at http://www.jove.com/video/3771/ Protocol I. Allergen Sensitization and Challenge (see Figure 1) A. For Intratracheal Challenge 1. For initial sensitization, inject male or female C57BL/6 or BALB/c mice (6-8 weeks old) intraperitoneally on day 0 and again on day 7 with 20 μg of ovalbumin (OVA; Sigma-Aldrich, St. Louis, MO) emulsified in 0.2 ml of sterile phosphate buffered saline (PBS) containing 2 mg of aluminum hydroxide (Sigma-Aldrich) or with 2 mg aluminum hydroxide in 0.2 ml of sterile PBS as control. 2. Challenge with antigen as appropriate (e.g., on days 14, 16, 18, and 20). Challenge procedure follows. 3. Anesthetize mouse with an intraperitoneal (i.p.) injection of a mixture of ketamine (90 mg/kg) and xylazine (10 mg/kg). Ensure the mouse is fully anesthetized for at least 10 min. 4. Angle operation surface at 45 degrees or greater. Place mouse on this surface keeping ventral side upward and head at top. 5. Hook thread under front incisors to hold head back. Level the paws with one another to ensure ...

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