Murine Model of Allergen Induced Asthma

Summary

Experimental mouse models of allergic asthma offer new possibilities for studying disease pathogenesis and developing new therapeutics. These models are well suited to measuring factors governing the allergic immune response, airway inflammation, and pulmonary pathophysiology.

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 invasive⁷ and non-invasive⁸ 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.

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 intrap....

Discussion

Animal models of allergic airway disease provide important tools for studies relevant to clinical asthma. A number of different models, employing varying species and antigens, have been developed. The mouse, an attractive and frequently used laboratory species, also offers a number of advantages for models of allergic airway disease.^9,10 Although such models do not mimic asthma in every respect,¹¹ with aspects of chronic disease being particularly difficult to reproduce,^12,13 we confirm h.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Ovalbumin	Sigma-Aldrich	A5503
Aluminum hydroxide	Sigma-Aldrich	239186
Acetyl-β-methylcholine chloride	Sigma-Aldrich	A2251
Pentobarbital sodium salt	Sigma-Aldrich	P3761
Whole body plethysmography (WBP) system	Buxco Research Systems		http://www.buxco.com
FlexiVent	SCIREQ, Inc.		http://www.scireq.com
Light microscope	Leica Microsystems
Cytospin 4	Thermo Fisher Scientific, Inc.
Diff-Quick stain	Siemens AG	B4132-1A
Repetitive pipette	Tridak	STP4001-0025