BINDING OF ALLERGENS TO LIPOSOMES FOR IMMUNOTHERAPY

在过去的25年里，研究人员试图开发提取物

Within the last 25 years, researchers have attempted to develop extracts that would require less frequent immunization. The idea is to modify the chemical structure of the allergen in such a manner that reduces the allergenicity but promotes the immunogenicity. Recently, pliposomes and immune potentiators have been used to enhance the immune system in general and to promote the immunogenicity of many antigens in particular. Since for modification of allergens this approach has not yet been used by other investigators, in this study our major goal is to encapsulate standardized allergens and biological response modifiers (BRMs) to different liposomes and study the effect of this modification on their allergenicity and antigenicity using in vitro techniques. It is hoped that modification of allergen by binding to liposomes with or without BRMs will correct the faulty regulation in T cell function and may lead to production of IgG blocking antibodies but not IgE. To test this hypothesis, in Phase I it is planned to: 1. Encapsulate ragweed or June grass to different phospholipid composition (liposome) 2. Encapsulate ragweed or June grass and an immune potentiator such as acylated muramyl dipeptide (MDP) to liposomes. 3. Check the stability of the liposome encapsulated allergen and/or MDP by preparation of radiolabeled products and measuring radioactivity in the supermutants. These modified allergens will be examined in an in vitro model system developed for this purpose. Mononuclear cells from control and atopic patients will be incubated in tissue culture system with different concentrations of soluble ragweed, June grass or liposome encapsulated allergen with or without MDP, for up to 12 days. At different intervals (Day 1, 7, 12), samples from the supernatant will be measured for the level of histamine released from the basophils and for the amount of allergen specific IgG or IgE, by RIA or EIA respectively. In addition, mononuclear cells will be counted for the numbers of lymphocytes, basophils and for antigen-specific IgE-plaque forming cells. Decrease in the numbers of IgE plaque forming cells and IgE content with an increase in allergen specific blocking IgG antibodies in the culture system containing liposome encapsulated allergens, will be indicative of reduced allergenicity but enhanced antigenicity. During Phase II additional allergens by both encapsulation as well as cross linking to liposomes will be tested.