Annual meeting, Ottawa, October 21-24, 2004.

"Background: Mouse models of allergic asthma with ovalbumin (OVA) in alum have been used for many years. However, OVA is not a common allergen to humans and using alum for mouse sensitization is not close to human allergic diseases. Objective: To evaluate the effect of different antigens and the use of natural allergens without alum in the induction of IgE and IgG responses and airway inflammation in mice. Methods: Mice were intraperitoneal (i.p.) sensitized and intranasal (i.n.) challenged as below: A: sensitized twice with 2 μg of OVA in alum at weeks 0 and 2 and challenged (50 μg of OVA) at week 4; B: sensitized with 10 μg of OVA twice a week for 4 weeks, and challenged at week 5; C: the same as protocol "A," except that OVA was replaced with 100 μg of ragweed; D: the same as protocol "B," expect that OVA was replaced with ragweed. Sera were obtained every 2 weeks, and bronchoalveolar lavage fluids (BALFs) were collected 1 week after the nasal challenge. Serum total IgE, OVA- or ragweed-specific IgE and IgG2a levels were measured by ELISAs. BALF eosinophils were stained and counted. Results: Mice sensitized with OVA in alum had the highest total IgE level followed by groups B, C and D (mean OD410 = 3.39, 2.11, 1.42, and 1.12 for groups A, B, C, and D, respectively). Antigen-specific IgE levels were higher and specific IgG2a levels were lower in groups with alum than groups without alum (p < .01). There is no significant difference of eosinophilic percentages in OVA groups with or without alum (60% for A and 59% for B), which were higher than ragweed groups (24% for C and 41% for D). Conclusion: OVA induces higher IgE and eosinophilic responses in BALB/c mice than ragweed. Injections of natural antigens without alum are able to induce IgE and airway inflammation responses. This study was supported by The Hospital for Sick Children Foundation (Toronto)."