Ovalbumin-Induced Allergic Airway Inflammation

Reagents and chemicals

• Use ovalbumin as the model antigen, aluminum hydroxide as adjuvant for systemic sensitization, sterile PBS or saline as vehicle, and methacholine for airway-responsiveness testing^[1][2][3][4].

• Published acute models commonly use BALB/c mice sensitized intraperitoneally with OVA plus alum and challenged by aerosol, intranasal, or intratracheal OVA exposure^[1][2][3][4].

Antibodies, probes, dyes, or kits

• Use ELISA kits or validated antibody pairs to measure OVA-specific IgE and cytokines such as IL-4, IL-5, IL-13, IFN-γ, TNF-α, or IL-17 when these endpoints are required^[2][3][6][7].

• Use hematoxylin and eosin staining to assess inflammatory-cell infiltration and periodic acid-Schiff or alcian blue/periodic acid-Schiff staining to assess mucus-producing goblet cells^[3][4][6].

Equipment and instruments

• Required equipment includes animal-housing and procedure equipment suitable for mouse sensitization and airway challenge, an aerosol or intranasal challenge setup, bronchoalveolar lavage collection equipment, a cytospin or equivalent cell-preparation system, microscopy equipment for differential-cell counts and histology, and a system for measuring methacholine-induced airway responsiveness^[2][3][4][6].

Preparation Steps

• Use age-, sex-, and strain-matched mice and randomize animals into at least vehicle control and OVA-sensitized/OVA-challenged groups^[1][2][3][4].

• Prepare OVA/alum sensitization mixtures and OVA challenge solutions under sterile conditions, and keep the same OVA source and endotoxin status within an experiment because LPS contamination in OVA can change the inflammatory profile by adding neutrophilic, Th1, innate, and TLR4-dependent responses^[7].

• Define the protocol as acute or chronic before beginning, because acute OVA protocols typically assess eosinophilic inflammation and airway hyperresponsiveness after short allergen challenge, whereas chronic repeated aerosol exposure can produce airway epithelial lesions, mucus change, and remodeling-like features^[1][2][4][5].

• Include PBS- or saline-challenged controls to distinguish antigen challenge effects from sensitization, handling, or vehicle exposure^[2][3][4].

Operation Steps

• Step 1: Sensitize mice intraperitoneally with OVA plus alum on two occasions separated by one week or two weeks, because published mouse studies used OVA/alum intraperitoneal sensitization as an efficient way to induce asthmatic responses^[1][3].

• Step 2: When using the dose-optimization protocol reported by Chen et al., sensitize BALB/c mice with 0, 10, 20, 50, or 100 µg OVA plus 1 mg alum on days 0 and 7; 50 µg OVA produced the strongest methacholine airway hyperresponsiveness and eosinophil response among the tested doses^[2].

• Step 3: Challenge sensitized mice through the airway with OVA using the selected published route; reported examples include 10 mg/mL OVA aerosol for 30 min on days 14–17, intranasal OVA challenge, and repeated aerosol exposure protocols^[2][4][7].

• Step 4: Use the same challenge route, concentration, duration, and number of exposures for all experimental groups being compared, because airway phenotype differs with challenge route, protocol duration, and timing^[2][4][5][8].

• Step 5: Measure airway responsiveness to methacholine after the final OVA challenge when functional airway reactivity is an endpoint^[2][3][4][6].

• Step 6: Collect bronchoalveolar lavage fluid after functional testing or at a fixed post-challenge time point, count total cells, and prepare differential-cell counts to quantify eosinophils, neutrophils, lymphocytes, and macrophages^[2][3][4][7].

• Step 7: Collect blood for serum OVA-specific IgE and collect lung tissue for histology, cytokine analysis, RNA analysis, or flow cytometry according to the experimental question^{[2][3][4][6][7]}.

Data Acquisition and Analysis

• Interpret successful model induction as a combined phenotype rather than one isolated readout: OVA-challenged mice should show increased BAL eosinophils, airway inflammatory infiltration, mucus-producing goblet cells, Th2 cytokines, OVA-specific IgE, and/or airway hyperresponsiveness compared with vehicle controls^[2][3][4][6].

• BAL eosinophilia alone does not prove airway hyperresponsiveness, because airway function and inflammatory endpoints can dissociate depending on protocol timing and challenge design^[2][5][8].

• Use vehicle-sensitized/vehicle-challenged mice as negative controls and OVA-sensitized/OVA-challenged mice as positive disease controls when testing interventions^[2][3][4][6].

• Report mouse strain, age, sex, OVA grade or endotoxin status, OVA dose, alum dose, sensitization days, challenge route, challenge concentration, challenge duration, endpoint timing, methacholine method, BAL counting method, histology scoring method, biological replicate number, and statistical test^{[2][3][4][7][8]}.

Problem: BAL neutrophilia is unexpectedly high.

• Possible Cause: OVA preparation may contain endotoxin, which can add TLR4-dependent neutrophilic and Th1/innate cytokine responses.
• Literature-supported Solution: Use a consistent OVA preparation within the study and select LPS-free OVA when a cleaner Th2-biased eosinophilic model is required^[7].

Problem: Airway hyperresponsiveness is weak despite OVA sensitization and challenge.

• Possible Cause: Sensitizing OVA dose can affect methacholine responsiveness.
• Literature-supported Solution: Use a dose supported by the selected protocol; in one BALB/c protocol, 50 µg OVA plus 1 mg alum on days 0 and 7 produced stronger AHR than 10, 20, or 100 µg OVA^[2].

Problem: Inflammation is present, but functional airway responsiveness does not match histology.

• Possible Cause: OVA model endpoints can dissociate over time and by protocol design.
• Literature-supported Solution: Analyze BAL inflammation, histology, cytokines, and AHR as separate endpoints and avoid using one endpoint as a substitute for all others^[5][8].

Problem: Results differ between aerosol and intranasal challenge studies.

• Possible Cause: OVA challenge route influences distribution of inflammation and mucus production.
• Literature-supported Solution: Use one challenge route for the entire experiment and report the route explicitly when comparing with published models^[4].