Development of a Germ-Free Murine Model for Prediction of Food Allergen Potency: Preliminary Studies Using Peanut Ara h1 and Ara h2 As Model Food Allergens

Rationale: Novel food or protein sources are becoming increasingly common in our diets but have potential to sensitize consumers.  A germ-free C3H/HeN mouse model for food allergy has shown promise for differentiating sensitization and elicitation profiles of known allergenic food proteins.  The aim of this study was to determine if this mouse model can predict the potential potency of allergenic food proteins.  Known peanut allergens, Ara h1 and h2, were used as model allergenic proteins with varying potency as reported by in vitro sera or basophil analysis from peanut-allergic individuals.

Methods: Germ-free C3H/HeN mice were sensitized with 60μg Ara h1 (n=20) or h2 (n=18) by three weekly intraperitoneal injections (IP) with alum adjuvant, followed by IP challenge of 500μg of indicated protein.  Thirty minutes post-challenge clinical scores were graded (0=no symptoms to 5=death) and body temperatures recorded.  ELISA was used to measure presence of protein-specific IgE and mast cell protease in sera.

Results: Germ-free mice sensitized with Ara h1 exhibited significantly less-severe clinical scores (mean=2) compared to mice sensitized with Ara h2 (mean=4) (p<0.05).  Hypothermic responses post-challenge [average -2.5(SD=1.6) and -8.8(SD=0.9)°C, respectively (p<0.05)] correlated well with clinical scores.

Conclusions: Preliminary results based on clinical scores and hypothermia confirm that the germ-free C3H/HeN mouse model can differentiate between the potency of Ara h1 and h2 as reported in previous in vitro and in vivo analyses of human subjects.  While further analysis of additional known allergens is needed, this model shows promise as a risk assessment tool for prediction of allergenicity of novel food proteins.