BALB/c mice can be used to evaluate allergenicity of different food protein extracts(1)
The United States Food and Drug Administration (USFDA) reports the eight most common allergenic foods including milk, eggs, fish, crustacean/shellfish, tree nuts, peanuts, wheat, and soybeans, and these accounted for 90% of all reported clinical allergic reactions. The foundation for the analysis and determi- nation of the original structure of allergens and antigenic determinants to characterize the allergenic risk of an allergen. Many studies have also examined differences in the allergenicity of proteins through animal models, such as C3H/HeJ and BALB/C mice.
Sensitization of the mice was achieved by the oral administration (gavage) of 1 mg OVA, 5 mg PPE, 1 mg CME/g BW, 1 mg PAPE, or 200 μl saline vehicle (control) on Days 1, 7, 21, and 28 of the experiment. Subsequently, the mice were challenged (by gavage) with a 5-fold dose of protein extract on Day 42.
OVA-specific IgE and IgG1, histamine, and albumin levels in OVA- treated mice were significantly higher than those in saline-treated mice, suggesting the BALB/c hosts exhibited clear humoral and cellular immune responses to OVA.
Mice produced the highest levels of sIgE in response to the PPE, followed by the CME, and the lowest levels in response to PAPE mice. The CME-treated hosts produced significantly higher levels of sIgG1 than did mice in the other two groups. In addition, histamine levels (30 min after challenge) in PPE-treated mice were significantly higher than those in the CME and PAPE hosts.
Toluidine blue-stained spleen sections revealed that most of the recruited mast cells were degranulated and had apparently released their histamine in the PPE-treated mice.
Oral administration of PPE increased the relative number of effector TH1 and TH2 cells compared to levels seen in spleens of saline-treated mice, but not compared to those in CME- and PAPE-treated hosts. In contrast, the numbers of Foxp3+ Treg cells were significantly increased in PAPE-treated mice compared to those in spleens of saline-, CME-, or PPE-treated mice.
Levels of formation/release of the TH2 cytokine IL-4 by isolated splenocytes were higher in samples of cells from the PPE-treated mice compared with that by cells obtained from any of the other three test groups.
Intake of allergenic proteins often disrupts the dynamic balance between T-helper Type 1 (TH1) and Type 2 (TH2) cells, increases the number of TH-cells, and alters the circulating levels of antigen-specific IgE and IgG1. The Ara h 1, Ara h 5, Ara h 7, and Ara h 8 proteins in PPE belonged to four of the above five protein families, for example, the cupin superfamily, prolamin superfamily, and the profilin and pathogenesis-related protein Bet v I family. In addition, these allergens had a typical aller- gen structure and exhibited many of the antigen epitopes that were characteristic of their protein families. The proliferation of TH cells and the secretion of key cytokines, including interferon (IFN)-γ, interleukin (IL)-4, and IL-5, promote B-cell secretion of IgE. The results of the in vivo experiments and bioinformatics analyses revealed that the allergenic strength of the foods was peanut > milk > potato and this is consistent with a sensitization food-map obtained in previous studies.