Grantee Research Project Results
2007 Progress Report: Improved Animal Model for Assessment of Allergenic Potential of Foods Through Selective Deletion of T Cells and Global Gene Expression Analysis
EPA Grant Number: R833134Title: Improved Animal Model for Assessment of Allergenic Potential of Foods Through Selective Deletion of T Cells and Global Gene Expression Analysis
Investigators: HogenEsch, Harm , Muir, William
Institution: Purdue University
EPA Project Officer: Aja, Hayley
Project Period: November 1, 2006 through October 31, 2009 (Extended to November 30, 2010)
Project Period Covered by this Report: November 1, 2006 through October 31,2007
Project Amount: $398,497
RFA: Biotechnology: Potential Allergenicity of Genetically Engineered Foods (2006) RFA Text | Recipients Lists
Research Category: Human Health
Objective:
To develop a new animal model to test for allergenic potential of foods that requires a short duration of testing; has increased sensitivity and discriminatory power over existing models; and is relatively easy to use.
Progress Summary:
The first aim of the project was to determine if T cell receptor (TCR) γδ-deficient mice are more susceptible to the induction of food allergy through oral exposure than mice with normal numbers of TCRγδ+ T cells. The rationale was that increased susceptibility would allow the induction of food allergy without the use of (mucosal) adjuvants and enhance the ability to discriminate between allergic and non-allergic foods. Two complementary approaches were used to address this aim of the research. TCRγδ+-deficient mice (B6.129P2-Tcrdtm1Mom/J, backcrossed onto a C57BL/6J background) were obtained and bred. Wild type C57BL/6J mice were used as controls. As an alternative, female C3H/HeJ mice were injected with 300 μg of the anti-TCRγδ antibody GL3 or hamster IgG. The TCRγδ-deficient and control mice were fed 2.5 mg or 0.25 mg peanut protein extract (PPE) or ovalbumin (OVA) via oral gavage each day for 5 consecutive days. Serum was collected 2 weeks after the last dosing and tested for antigen-specific IgG and IgE. The data indicate that feeding of either 0.25 or 2.5 mg/day induced a modest increase of antigen-specific IgG, but no detectable IgE. There was marked variability among the individual mice and no difference in response between the control and TCRγδ-deficient mice. Extending the feeding period to 10 days (2 x 5 days of feeding) slightly increased the antibody response, but the variability remained and there was no difference between control and TCRγδ-deficient mice. We conclude from these experiments that the absence of TCRγδ+ T cells by itself is not sufficient to overcome oral tolerance and to induce food allergy.
The addition of cholera toxin to orally administer proteins has been used for many years as a method to break oral tolerance. A potential drawback of the use of cholera toxin would be that it may enhance the immune response to both allergenic and non-allergenic food proteins. The ability of mice to discriminate between allergenic and non-allergenic proteins mixed with cholera toxin was determined in three different strains of mice. The mice were fed PPE or spinach protein extract mixed with 10 μg cholera toxin twice a week for 3 weeks. Serum was collected 2 weeks after the last feeding and analyzed for antigen-specific IgG and IgE. The data indicate that A/J mice had a significantly greater IgE response than BALB/c and C3H/HeJ mice. In addition, the IgE response to PPE was significantly greater than the response to spinach extract.
These experiments were repeated in A/J mice with PPE and OVA as model allergenic proteins and potato protein extract as a non-allergenic protein. The mice had a significantly greater IgE response to PPE and OVA than to potato protein extract. These results suggest that feeding of A/J mice with protein antigens in combination with cholera toxin can distinguish between allergenic and non-allergenic proteins.
Future Activities:
The A/J model will be used to identify novel biomarkers for early detection of food allergy. For this purpose, mice will be fed allergenic and non-allergenic proteins and RNA will be extracted from tissues and compared for gene expression using DNA microarrays.
Journal Articles:
No journal articles submitted with this report: View all 2 publications for this projectSupplemental Keywords:
food allergy, animal model, biomarkersProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.